New Viral Diseases and New Possible Remedies by Means of the Pharmacology of the Renin-Angiotensin System

Abstract

All strains of SARS-CoV-2, as well as previously described SARS-CoV and MERS-CoV, bind to ACE2, the cell membrane receptor of β-coronaviruses. Monocarboxypeptidase ACE2 activity stops upon viral entry into cells, leading to inadequate tissue production of angiotensin 1-7 (Ang1-7). Acute lung injury due to the human respiratory syncytial virus (hRSV) or avian influenza A H7N9 and H5N1 viruses is also characterized by significant downregulation of lung ACE2 and increased systemic levels of angiotensin II (Ang II). Restoration of Ang1-7 anti-inflammatory, antifibrotic, vasodilating, and natriuretic properties was attempted at least in some COVID-19 patients through i.v. infusion of recombinant human ACE2 or intranasal administration of the modified ACE2 protein, with inconsistent clinical results. Conversely, use of ACE inhibitors (ACEis), which increase ACE2 cell expression, seemed to improve the prognosis of hypertensive patients with COVID-19. To restore Ang1-7 tissue levels in all these viral diseases and avoid the untoward effects frequently seen with ACE2 systemic administration, a different strategy may be hypothesized. Experimentally, when metallopeptidase inhibitors block ACE2, neprilysin (NEP), highly expressed in higher and lower airways, starts cleaving angiotensin I (Ang I) into Ang1-7. We suggest a discerning use of ACEis in normohypertensive patients with β-coronavirus disease as well as in atypical pneumonia caused by avian influenza viruses or hRSV to block the main ACE-dependent effects: Ang II synthesis and Ang1-7 degradation into angiotensin 1-5. At the same time, i.v.-infused Ang I, which is not hypertensive provided ACE is inhibited, may become the primary substrate for local Ang1-7 synthesis via ubiquitous NEP; i.e., NEP could replace inadequate ACE2 function if Ang I was freely available. Moreover, inhibitors of chymase, a serine endopeptidase responsible for 80% of Ang II-forming activity in tissues and vessel walls, could protect patients with atypical pneumonia from Ang II-mediated microvascular damage without reducing arterial blood pressure.

1. Introduction

Three species of genus β-coronavirus (SARS-CoV, MERS-CoV, and SARS-CoV-2) have caused atypical pneumonia in humans, called severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and coronavirus disease of 2019 (COVID-19), respectively. The SARS outbreak first occurred in China in 2002 and the MERS outbreak in Saudi Arabia in 2012. They led to hundreds of deaths with a fatality rate of 10% and 37%, respectively [1]. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection arrived on the medical scene in December 2019, and in less than 3 months, it was declared a pandemic. To date, COVID-19 has been diagnosed in more than 760 million people worldwide, and more than 6.8 million patients have died from the illness.

Approved vaccines against SARS-CoV-2 are being administered, but a significant number of infections still occur in people who are not vaccinated or, most dramatically, because of the progressive appearance of immune-evasive viral variants often characterized by increased infectivity but seldom by increased morbidity and mortality rates [2, 3]. Immunocompromised patients, who may not be able to mount an appropriate response to vaccines, have monoclonal antibodies as the only prophylactic agents, which may not work because of the propensity of the viral spike to evolve and escape neutralization [4, 5]. When it comes to the treatment of COVID-19, besides necessary ventilatory support, dexamethasone, remdesivir, molnupiravir, nirmatrelvir, and monoclonal antibodies, such as the REGN-CoV-2 cocktail, do not significantly improve the survival rate of severe patients with acute respiratory distress syndrome (ARDS) caused by SARS-CoV-2 [6–8]. Nonetheless, remdesivir treatment within two days of admission, with or without dexamethasone, reduces in-hospital mortality due to COVID-19, at least among elderly patients receiving supplemental oxygen on the day of admission [9, 10].

It is well known that an exuberant cytokine release and the consequential inappropriate hyperinflammatory reaction fuel the most severe cases of COVID-19 [11]. A dramatic consequence of this “cytokine storm” is invariably acute lung injury (ALI), clinically characterized by ARDS with exponentially elevated systemic levels of tumour necrosis factor-α (TNF-α) and interleukin-1 (IL-1), along with a systemic inflammatory response characterized by hypotension, organ hypoperfusion, fever with increased heart rate, and altered mental status [12, 13].

All genus β-coronaviruses so far described use the metallopeptidase angiotensin-converting enzyme type 2 (ACE2) as the cell membrane receptor to enter human cells [14, 15], a process that leads to annihilation of the key functions of ACE2: control of hemodynamics and systemic inflammation. ACE2 functionally belongs to the so-called nonclassical local/tissue renin-angiotensin system (RAS), where it is primarily involved in the conversion of angiotensin II (Ang II) into angiotensin 1-7 (Ang1-7). Nonclassical RAS itself (Figure 1) is an extremely complex and adaptable network of enzymes and active peptides that is involved in the regulation of extracellular fluid volume, arterial pressure, tissue blood perfusion, and inflammation.

Figure 1

Diagram depicting pathways of synthesis and degradation of angiotensins in classical and nonclassical local/tissue RAS, with respective receptors for each bioactive peptide. ACE: angiotensin-converting enzyme; ACE2: angiotensin-converting enzyme type 2; AT_1-2-4Rs: angiotensin type 1-2-4 receptors; MasR: Mas receptor; MRGD: Mas-related G protein-coupled receptor member D; PCP: prolyl carboxypeptidase; PEP: prolyl endopeptidase. The main degradative pathway for Ang II in normal humans is through the sequential actions of plasma aminopeptidases A and N, not through ACE2; serine endopeptidase chymase, in the heart, renal tubules, and ubiquitous mast cells, converts Ang I into Ang II as efficiently as ACE does in the vascular endothelium; Zn-metalloendopeptidase neprilysin cleaves angiotensin I into Ang1-7. Neprilysin, based on the occasional substrate available, generates Ang1-7 from Ang I but may metabolize Ang1-7 to form Ang1-4.

It is to be remembered also that human respiratory syncytial virus (hRSV) and avian influenza A H7N9 and H5N1 viruses may cause ALI characterized by significant downregulation of lung ACE2 and increased systemic levels of Ang II [16–18]. As for coronaviruses, it is worth mentioning that another component of nonclassical RAS (i.e., aminopeptidase N, in part responsible for Ang II catabolism) (Figure 1) is the human cell membrane receptor of coronavirus hCoV-229E, which circulates worldwide and causes just mild respiratory disease (i.e., the common cold) [19].

For these reasons, maybe the most sensible clinical answer to all these viral illnesses, which have much in common, i.e., considerable damage to tissue ACE2 activity, should be sought in the intricate links between RAS malfunction and inflammatory cytokine release.

2. Classical and Nonclassical RAS (Figure 1)

The classical RAS is controlled by renin, which cleaves the decapeptide angiotensin I (Ang I) from plasma angiotensinogen. In turn, angiotensin-converting enzyme (ACE) converts Ang I into Ang II, the octapeptide that essentially stimulates angiotensin type 1 receptors (AT1Rs), leading to increased cardiac inotropism, arterial vasoconstriction, catecholamine release, aldosterone secretion, and renal sodium retention (the so-called ACE-Ang II-AT1R pathway) [20].

The nonclassical RAS is a further network of enzymes and angiotensins derived from Ang II. ACE2 is a transmembrane protein with an extracellular N-terminal domain, which contains a monocarboxypeptidase site and the SARS-CoV, MERS-CoV, and SARS-CoV-2 binding sites [14, 15], and a transmembrane C-terminal tail. ACE2 is a key player of the nonclassical RAS. Donoghue et al. [21] and Tipnis et al. [22] identified ACE2 from the complementary DNA library of heart failure and lymphoma patients in 2000 and inaugurated a new wave of studies of the real and expanded RAS.

ACE2, by cleaving the Pro7-Phe8 bond of Ang II, leads to the generation of the vasodilator and natriuretic peptide Ang1-7. ACE2 also cleaves Ang I into angiotensin 1-9 (Ang1-9) [20, 23], catabolizes other non-RAS peptides (apelin, kinins, and endorphins), and regulates the absorption of tryptophan in the intestine [24].

ACE2 is mainly located in the epithelial lining of the upper airways, in alveolar type II pneumocytes and pulmonary macrophages [25], as well as in the upper esophagus, colon, and surface enterocytes of the small intestine [26, 27]. Moreover, endothelial cells, testis, liver, kidney, and cardiac pericytes express ACE2 [28].

In the brain, ACE2 is expressed in astrocytes and astrocytic foot processes, pericytes and endothelial cells in the olfactory bulb, the hypothalamic nuclei, the midbrain substantia nigra, and the hindbrain pontine nucleus. Discrete neuronal groups express ACE2 in brainstem respiratory rhythm-generating centers (e.g., the pontine nucleus), in the arousal-related pontine reticular nucleus, and in the hippocampus [29].

Along with ACE2, three more enzymes play key roles in the nonclassical RAS [24, 30, 31] (Figure 1): (i)

ACE is a dicarboxypeptidase that notoriously cuts the Phe8-His9 bond of Ang I and generates Ang II in the ACE-Ang II-AT1R pathway. ACE has supporting roles also in the nonclassical RAS: it cleaves angiotensin 1-12 (Ang1-12) into Ang I, Ang1-9 into Ang1-7, and, finally, Ang1-7 into angiotensin 1-5 (Ang1-5) [20, 23]. Moreover, ACE catabolizes enkephalins, substance P, and luteinizing hormone-releasing hormone [24]. Most renal tubular cells and glomerular mesangial cells contain ACE. Finally, ACE is found in endothelial cells, especially in the blood vessels of the lung [20, 23, 24].

(ii)

Chymase is a serine endopeptidase found in the heart, liver, renal tubules, and mast cells. Chymase converts Ang I into Ang II in tissues the same as ACE in the vascular endothelium [24]. In areas of chronic inflammation, chymase also converts big endothelin-1 (big ET-1) into endothelin-1 (ET-1) [32] and releases transforming growth factor-β (TGF-β) through Ang II-dependent mechanisms [33]. 80% of Ang II synthesized in the blood vessel walls is dependent on chymase [34], but chymase inhibitors, unlike ACE inhibitors (ACEis), do not affect blood pressure and renin levels because ACE is located in endothelial cells and chymase in mast cells of the vascular adventitia of arterial vessel walls. Moreover, plasma contains serine endopeptidase (chymase) inhibitors [35]. Finally, chymase also cleaves Ang1-12 into Ang II

(iii)

Neprilysin (NEP) is a membrane-bound Zn-metalloendopeptidase also called atriopeptidase because neprilysin cleaves urodilatin, atrial, brain-derived, and C-type natriuretic peptides mostly in the kidneys, lung, brain, and heart [36]. NEP catabolizes opioid peptides, bradykinin, bombesin-like peptide, substance P, and adrenomedullin [37]. Inside pathways of nonclassical RAS, NEP cleaves Ang II into Ang1-5, Ang I into Ang1-7, and Ang1-7 into angiotensin 1-4 (Ang1-4) [20, 38]. This means that, based on the available precursor, NEP both generates and degrades Ang1-7

These enzymes, including ACE2, are anchored to the membranes of cells and orient their active sites on the extracellular cell surface to process substrates within the blood, glomerular filtrate, and interstitial fluids.

Ang1-7, the product of ACE2 action on Ang II, binds to cell membrane G protein-coupled receptors called Mas receptors (MasRs). MasR stimulation leads to enhanced phosphorylation of protein kinase B and nitric oxide production, to increased cell levels of cyclic GMP, and to increased production of prostaglandins G2, H2, and prostacyclins [20, 24, 38]. Natriuretic and vasodilator MasRs are ubiquitous but show the highest expression in the brain and testis [39].

The nonclassical RAS encompasses much more than this ACE2-Ang1-7-MasR axis. For instance, Ang1-7 may be transformed into the heptapeptide alamandine by an aspartate decarboxylase that converts Asp1 of Ang1-7 into Ala1. In turn, alamandine binds to the so-called Mas-related G protein-coupled receptor member D (MRGD), leads to vasodilatation, and has several health benefits owing to its antithrombogenic, anti-inflammatory, and antifibrotic characteristics [23, 40].

To sum up, Ang1-7 may be generated from Ang II through ACE2, from Ang I through NEP, and from Ang1-9 through ACE. This same heptapeptide may be metabolized to alamandine through aspartate decarboxylases or degraded to Ang1-5 through ACE or to Ang1-4 through NEP.

RAS peptidases behaviour is also versatile because their activity is strictly linked to the available substrate: monocarboxypeptidase ACE2 converts Ang I into Ang1-9 or Ang II into Ang1-7; dicarboxypeptidase ACE converts Ang I into Ang II or Ang1-7 into Ang1-5; NEP can remove three C-terminal amino acid residues from Ang I to form Ang1-7 or catabolizes Ang1-7 to form Ang1-4.

3. Links among Infectious Agents, a Complex Metabolic System, and an Inflammatory Cascade

Let us take β-coronaviruses as a paradigm of RAS involvement in viral infectious diseases.

These viruses express a glycoprotein called spike (S glycoprotein) on the viral coat. S glycoprotein contains two functional domains: an S1 ACE2-binding domain and an S2 domain necessary for fusion of the viral envelope and cell membranes. Host trypsin-like serine protease TMPRSS2 cuts between S1 and S2, and this process of spike priming is essential to allow viral entry into cells [26]. It is just the higher affinity of the SARS-CoV-2 S-protein for cell membrane ACE2 that explains why SARS-CoV-2 is far more infectious than SARS-CoV [7].

Beside TMPRSS2, two further serine proteases, furin and plasmin, may prime the SARS-CoV-2 S glycoprotein by cleaving it differently from TMPRSS2. High plasmin levels occur in cirrhotic patients because of increased activity of tissue-type plasminogen activator and decreased alpha 2-antiplasmin [41]. Therefore, the coexistence of liver cirrhosis aggravates the COVID-19 clinical syndrome [23]. As for furin, this serine protease of the subtilisin-like proprotein convertase family exerts priming effects on the receptor-binding domain (RBD) of different viruses: the human immunodeficiency virus (HIV), the influenza virus, the dengue fever virus, and several filoviruses, including the Ebola virus (EBOV). Therefore, inhibitors of furin are under consideration as therapeutic agents [18].

Following S glycoprotein priming, however determined, clathrin-dependent endocytosis of the parent virions, tightly bound to ACE2, into cells occurs and infection starts [23].

In patients with COVID-19, internalization and the subsequent proteasomal degradation of ACE2 reduce its availability and function on the cell surface. Moreover, unknown SARS-CoV-2 components induce gene expression of a disintegrin and metalloproteinase domain-17 (ADAM-17) [23]. ADAM-17 is a membrane-bound zinc endopeptidase related to a family of enzymes known as sheddases or secretases. Sheddase ADAM-17 releases anchored ACE2 (Figure 2), interleukin-4 (IL-4), interferon γ (IFNγ), TNF-α, and IL-1 from human cell membranes. In turn, free IL-4 and TNF-α further downregulate the expression of membrane-bound ACE2 (Figure 3). TMPRSS2, beyond priming SARS-CoV-2 spikes, also cleaves ACE2 and competes with ADAM-17 for ACE2 extracellular shedding [26] (Figure 2). Inhibition of ADAM-17 with the vitamin D analog paricalcitol [42] or through knockdown by short interfering RNA (siRNA) successfully suppresses cellular infection by SARS-CoV-2 in vitro [43].

Figure 2

Left-hand side of the picture: soluble ACE2 (sACE2), obtained through the action of ADAM-17 on cellular ACE2, is the complete N-terminal ectodomain of the enzyme, which is still able to bind SARS-CoV-2 and convert Ang II into Ang1-7 in the extracellular space. Right-hand side of the picture: C-terminal ACE2 fragments of 13 kDa results from TMPRSS2 processing of cellular ACE2. Arginine and lysine residues within ACE2 amino acids 697 to 716 are essential for ACE2 cleavage by TMPRSS2; ADAM-17 requires arginine and lysine residues within ACE2 amino acids 652 to 659 for cleavage.

Figure 3

SARS-CoV-2 causes cell membrane ACE2 depletion through cellular internalization and subsequent proteasomal degradation once the enzyme is bound to infecting virions, but also through ADAM-17 upregulation. Ang II contributes to ADAM-17 upregulation. Upregulated ADAM-17 causes shedding of ACE2, interleukin-4, IFNγ, and TNF-α into extracellular fluids. In turn, free interleukin-4 and IFNγ further downregulate ACE2 cellular expression, while free TNF-α starts the inflammatory cascade.

The degree of ACE2 extracellular shedding by ADAM-17 in the form of soluble ACE2 (sACE2, the complete N-terminal ectodomain of the enzyme) revealed a significant association with acute myocardial infarction and circulatory shock in COVID-19 patients, because elevation in sACE2 reflects cellular depletion of ACE2 and diminished tissue protection against Ang II-mediated microvascular damage [43].

The release of TNF-α through ADAM-17 is essential to COVID-19 pathogenesis (Figure 3). Two related forms of this cytokine have been described: a soluble form, sTNF-α, and a membrane-bound form, mTNF-α. There are two membrane receptors which sTNF-α interacts with to generate its pathological responses: these cell surface receptors are called TNFR-1 and TNFR-2 [44]. TNF-α starts the cytokine release required to initiate the inflammatory response in the lungs [45], which is characterized by increased vascular permeability and accumulation of pulmonary inflammatory fluid [46]. TNF-α also leaves the primary site of infection, reaches different target tissues as a systemic messenger of inflammation, and causes a generalized systemic inflammatory response [47]. TNF-α is thought to be the key mediator of the systemic inflammatory response syndrome.

Since ACE2 metabolizes also des-arginine bradykinin (des-Arg1-BK), this peptide, when ACE2 is lacking, becomes a promoter of pulmonary inflammation via stimulation of bradykinin B1 receptors in lung endothelial cells [48].

Finally, lack of ACE2 promotes considerable oxidative stress. The ACE2/Ang1-7/Mas axis counterregulates oxidative damage in the vascular system by reducing reactive oxygen species (ROS) production by NADPH-oxidase (NOX) [49]. Infusion of recombinant human ACE2 (rhACE2) in patients with pulmonary hypertension is associated with increased plasma levels of superoxide dismutase 2 (SOD2) and reduced oxidative stress [50] (Table 1).

Table 1

Opposing effects of Ang II and Ang1-7.

Ang II leads to:

NADPH-oxidase-mediated reactive oxygen species production

Increased collagenolytic activity of MMP-9

Reduced ACE2 cell expression

Induction of the enzymatic activity of ADAM-17, leading to increased circulating levels of TNF-α

NLRP3 inflammasome activation

High transcription of NF-κB leading to production of proinflammatory cytokines

Ang1-7 leads to:

Increased plasma levels of superoxide dismutase 2 and reduced oxidative stress

Reduced ACE function

Increased production of the vasodilator NO, prostaglandins H2 and G2, and prostacyclin

Inhibition of NADPH-oxidase-mediated reactive oxygen species production

Inhibition of NLRP3 inflammasome activation

Neutrophils recruited in the lungs of patients with atypical viral pneumonia are a key source of matrix metalloproteinase 9 (MMP-9), which is a matrixin, a class of enzymes that belong to the zinc-metalloproteinase family involved in the degradation of the extracellular matrix [47]. ROS, which are released after the binding of Ang II to AT1Rs followed by NOX activation, increase the collagenolytic activity of MMP-9 and extracellular matrix degradation [51] (Table 1). TNF-α and MMP-9 are interrelated, and both stimulate the release of the other during inflammation [47].

Loss of ACE2 leads to a general shift of the RAS to a higher Ang II and lower Ang1-7 tone. Ang1-7 binds to the C-terminal domain of ACE and reduces Ang II generation. Conversely, Ang II can trigger the phosphorylation of the microtubule-associated protein (MAP) kinases and the activation of extracellular signal-regulated kinase (ERK) 1 and 2 pathways, thus reducing ACE2 cell expression and upregulating transcription of profibrogenic genes such as TGF-β, plasminogen activator inhibitor-1, fibrillar collagens, and fibronectin [23] (Table 1). Therefore, ACE inhibitors (ACEis) and AT1R blockers (ARBs) increase ACE2 activity, as shown experimentally [15]. The conundrum is that ACEis and ARBs, through increased ACE2 expression and reduced Ang II function, may improve outcomes in patients with ARDS but may theoretically increase susceptibility to SARS-CoV-2 infection through increased expression of the viral receptor [15]. Recent meta-analyses demonstrate that RAS inhibitors are associated with a better prognosis in hypertensive patients with COVID-19 [52] and should not be discontinued in these subjects [53]. Inhibition of Ang1-7 clearance by ACEis may in part explain this finding (Figure 1). Moreover, reduced Ang II production decreases the enzymatic activity of ADAM-17 and, indirectly, the circulating levels of TNF-α [47] (Table 1). Finally, a study from the United Kingdom that included more than 15,000 patients with COVID-19 and 70,000 controls showed that ACEIs and ARBs did not increase but actually decreased the risk of SARS-CoV-2 infection in treated hypertensive subjects [54].

Ang II binding to AT1Rs prompts RhoA/Rock-1 complex activation, which leads to NOX-dependent ROS production [55] (Table 1 and Figure 4). In turn, ROS lessen nitric oxide (NO) bioavailability with subsequent endothelial dysfunction [47] (Figure 4). Conversely, activation of the ACE2/Ang1-7/Mas axis in the vascular endothelium increases production of vasodilators NO and prostacyclin by vascular smooth muscle cells [56]. The transcription level of the inflammatory inducer NF-κB highly increases upon stimulation of AT1Rs by Ang II [55]: AT1R stimulation leads to phosphorylation of serine residues on IκBα by the IκB kinase. This results in the degradation of IκBα, a natural inhibitor of NF-κB. This way, NF-κB is free to move into the cell nucleus and interact with proinflammatory target genes (e.g., the TNF-α gene), leading to their transcription [24, 47].

Figure 4

Schematic depiction of intracellular NRLP3 inflammasome activation due to SARS-CoV-2 and Ang II excess, and its consequences. Internalized ACE2 bound to virions undergoes proteasomal degradation. Intracellular SARS-CoV-2 N protein leads to direct NRLP3 inflammasome activation.

The COVID-19 prognosis is related to age and sex. Nonetheless, the expression of ACE2 decreases with increasing age: the ACE2 expression is higher in young people than in elderly individuals and higher in females than in males [57, 58]. This pattern does not match the characteristics of severely ill COVID-19 patients, being mostly elderly males. These findings underline that the patients endowed with a more developed “anti-inflammatory” ACE2 system do better, once infected by SARS-CoV-2, despite ACE2 being the cell receptor of the virus. In other words, patients at increased susceptibility to COVID-19 complications may have reduced baseline ACE2 [59].

The above findings do not seem to support the newly proposed use of ursodeoxycholate (UDCA) as the primary prophylaxis of COVID-19 [60]. In fact, UDCA and phytosteroid z-guggulsterone have been proposed to decrease the risk of the SARS-CoV-2 primary infection because both drugs, by inhibiting the activity of the bile acid receptor and transcription factor FXR, decrease ACE2 expression on the plasma membrane of cells in the gastrointestinal tract, pharynx, bronchi, lungs, and systemic circulation. And this treatment, at least in human organoids and perfused human lungs ex vivo, seems to reduce the rate of infection by SARS-CoV-2. Admittedly, the authors of such studies do not hide the fact that depriving the ACE2 body pool with UDCA to prevent dissemination of SARS-CoV-2 infection (secondary prophylaxis) might pose risks for patients already infected. In effect, the FXR (and, therefore, ACE2) activator obeticholic acid, despite the upregulation of ACE2, may paradoxically reduce COVID-19 disease severity and ameliorate cholestasis [60].

4. RAS and Inflammasome Activation (Figure 4)

Inflammasomes are multiprotein cytosolic complexes that assemble in monocytes, macrophages, and barrier epithelial cells in response to pathogen- or damage-associated molecular patterns. Upon activation, inflammasome sensors oligomerize to form mature inflammasomes, within which caspase 1 is activated. In turn, a proinflammatory lytic cell death called pyroptosis may occur [61], because caspase 1 processes pro-interleukin-1β (pro-IL-1β) and pro-interleukin-18 (pro-ΙL-18) into their active forms, which are also released into extracellular fluids along with alarmins such as lactate dehydrogenase (LDH).

NLRP3, a member of the nucleotide-binding domain- and leucine-rich repeat-containing protein (NLRP) family, responds to an array of insults to the cell that cause cytosolic K⁺ efflux, Ca²⁺ cytosolic influx, or release of mitochondrial ROS [61, 62].

Inflammasome activation in COVID-19 is testified by studies that revealed serum LDH concentration as the strongest predictor of severe disease [11]. Inflammasome activation is also accompanied by a release of serum markers of inflammation such as the interleukin-6-inducible C-reactive protein and ferritin, both associated with a severe prognosis of COVID-19 [63, 64]. Finally, interleukin-18 is a highly predictive biomarker of death by COVID-19 [65], and measurements in bronchoalveolar lavage fluid (BALF) showed a significant increase in the interleukin-1β (IL-1β) level in patients with moderate to severe COVID-19 [66]. Postmortem histological sections from lung parenchyma also showed broadly elevated staining of IL-1β compared with control sections [67].

Another strong indicator of inflammasome involvement in COVID-19 has been conclusively demonstrated: the N protein of SARS-CoV-2 directly induces NRLP3 inflammasome activation [11].

Generally, both NOX-derived ROS and mitochondrial ROS contribute to NLRP3 inflammasome activation. For instance, Ang II induces liver fibrosis in chronic liver diseases by NLRP3 inflammasome activation through a NADPH-oxidase 4- (NOX4-) and H₂O₂-dependent mechanism. Conversely, in hepatic stellate cells, Ang1-7 inhibits the Ang II-induced activation of the NLRP3 inflammasome [68]. In addition, in vivo activation of the NLRP3 inflammasome parallels an increase in the AT1R protein level and ROS production, as shown in human oral fibrosis tissues. Once again, Ang1-7 improves arecoline-induced rat oral submucosal fibrosis through reduction of protein levels of NOX4 and the NLRP3 inflammasome [69] (Table 1).

5. Restoration of ACE2 Function as a Suitable Clinical Answer

Several studies have shown that Ang1-7, through stimulation of MasRs, reduces the release of proinflammatory TNF-α, interleukin-6, and TGF-β, which trigger cell apoptosis and necrosis followed by tissue fibrosis. For instance, experimental liver fibrosis is aggravated by MasR antagonists [70] and relieved by recombinant ACE2 [71]. Thus, it appears that having excess ACE2 is beneficial to the patient with acute or chronic inflammation.

RAS imbalance, i.e., increase in ACE and decrease in ACE2 activities, contributes to ARDS development. In the rat model of ARDS caused by lipopolysaccharides, ACE activity and the Ang II content of the bronchoalveolar lavage fluid increase significantly, while the corresponding expression of ACE2 and Ang1-7 decreases [72]. Another study showed that in the mouse model of ARDS caused by bleomycin, the ACE2 gene-deficient mice had the most severe symptoms, which were relieved by treatment with rhACE2. ARDS symptoms were also relieved when applying AT1R blockers (ARBs), and the lung injury in mice with AT1R deletion was less severe [73].

During the outbreak of SARS in 2002, many patients developed ARDS and died. In those patients, the Ang II plasma levels increased significantly, and the expression of ACE2 was downregulated, resulting in lung injuries [74]. In human trials, patients with ARDS of different etiologies treated with i.v. rhACE2 showed reduction in Ang II and increase in Ang1-7 levels, although rhACE2 failed to improve significantly the clinical indicators of ARDS but, at least, was well tolerated [75].

Based on the above evidence, it can be concluded that ACE2 has a protective effect on lung injury and that ACE2 downregulation aggravates lung damage but that rhACE2 exogenous administration does not improve significantly the prognosis of patients with ARDS [73].

Finally, ACE2 exerts potent antithrombotic, anti-inflammatory, and antioxidant effects through cleavage of Ang II into the beneficial Ang1-7 [43]. Loss of ACE2 increases monocyte-endothelial adhesion, macrophage activation, vascular permeability, and oxidative stress, which exacerbate endothelial dysfunction [56]. Moreover, interleukin-6, whose secretion is blunted by Ang1-7, promotes the release of α-defensin, a prothrombotic peptide released by human neutrophils [76]. Not unexpectedly, the COVID-19 clinical profile includes coagulopathy, thrombosis, and endotheliitis in the microvasculature [77].

Once verified that atypical viral pneumonia and most experimental models of ARDS are indeed characterized by downregulation or, in the case of β-coronaviruses, actual annihilation of ACE2 everywhere this enzyme is located (i.e., lungs, heart, brain, blood vessels, kidney, and liver), how does the ACE/ACE2 imbalance manifest itself?

One study showed very low plasma levels of Ang1-7 and its catabolite Ang1-5 and even of Ang I, in patients with COVID-19 vs. healthy controls. Unexpectedly, lower, not higher, serum levels of Ang II were found in those same COVID-19 patients as compared with matched healthy controls [78]. Of course, serum levels of Ang II may not represent the actual tissue levels of the octapeptide. Moreover, it has to be stressed that the main degradative pathway of Ang II is not effected by ACE2, whose function is clearly damaged by SARS-CoV-2 infection, but through the sequential actions of aminopeptidases A and N, which lead to the production of angiotensin 2-8 (Ang2-8) and then angiotensin 3-8 (Ang3-8) [23] (Figure 1). This means that lack of ACE2, by itself, may not necessarily increase the serum levels of Ang II. The uncertainties about relative excess or lack of RAS peptides recently arrived at such a point that infusion of Ang II itself was taken into consideration to treat the most severe patients with COVID-19: of course, the results of such attempts were disappointing [79].

Another study compared prolonged viral shedders (nasopharyngeal positive SARS-CoV-2 $PCR \geq 10 days$ from the first consultation) to short viral shedders (nasopharyngeal positive SARS-CoV-2 $PCR < 10 days$ from the first consultation) and showed that Ang II serum concentrations were significantly higher in prolonged viral shedders than in healthy controls or short viral shedders [80].

The last word came from a large cohort of Chinese patients with COVID-19, where plasma Ang II levels were found increased, and these hormonal levels correlated with the viral load in the bronchoalveolar lavage fluid [81].

Therefore, due to the ACE/ACE2 imbalance occurring in atypical viral pneumonia, we do find definitely increased Ang II and dramatically decreased Ang1-7 levels mostly in tissues but also in extracellular fluids.

Atypical viral pneumonia, even when unrelated to the β-coronavirus infection, is frequently characterized by a lack of tissue ACE2. In summary, severe inflammatory reactions with a local and systemic release of TNF-α and interleukin-4 or activation of ADAM-17 lead to ACE2 downregulation and extracellular shedding (Figure 3). In turn, lack of cell membrane ACE2 brings about ACE/ACE2 imbalance, increased Ang II, and decreased Ang1-7 tissue levels, fuelling further local inflammation and oxidative stress (Figure 4).

Not unexpectedly, patients with acute lung injury due to avian influenza A H7N9 and H5N1 viruses or hRSV show significant downregulation of lung ACE2 and elevated Ang II serum levels [16, 17]. In these cases, since the cell receptor of hRSV and influenza viruses is not ACE2 and ACE2 therefore does not get internalized into cells attached to these infecting agents, it is the intrinsic mechanism of inflammation ignited by these viral agents that leads to the secondary depletion of tissue ACE2, through TNF-α, interleukin-4, or ADAM-17 activation. A further proof of this mechanism comes from the study of cell infection by hepatitis C virus or cytomegalovirus: these two viral agents do not decrease but actually increase cell expression of ACE2 in in vitro infected epithelial cells but, nonetheless, cause significant local and systemic inflammation [82, 83].

6. New Treatment Strategies Provided by Nonclassical RAS Functioning

It is reasonable that if we could in some way replace ACE2 that is primarily or secondarily lost in infected tissues, we would potentially decrease the extent of systemic inflammation and local damage in patients with atypical viral pneumonia of different etiologies [84]. Restoring the Ang1-7 content in tissues despite inadequate ACE2 function might be an alternative novel strategy. Notably, the latter metabolic approach would be eligible in every clinical case of COVID-19, irrespective of the genetic variant of SARS-CoV-2 involved, and in ALI due to hRSV and avian influenza viruses.

In COVID-19, it was initially thought that rhACE2 systemic administration would either prevent viral spread or inhibit the secretion of proinflammatory mediators [85].

Endogenous plasma levels of soluble ACE2 are almost undetectable and unable to sequester SARS-CoV-2 in the circulation to prevent viral dissemination. Six months after the onset of the pandemic, the first COVID-19 patient treated with intravenous rhACE2 was described [86, 87]. Nine days after the onset of COVID-19 symptoms, the patient received rhACE2 twice daily for seven days by intravenous infusion: a marked reduction in serum Ang II levels with concomitant increases in Ang1-7, Ang1-9, and their by-product Ang1-5 was promptly observed. The copy number of SARS-CoV-2 decreased dramatically, as well as the systemic levels of cytokines interleukin-6 and interleukin-8. The patient survived. This initial enthusiasm raised by i.v. rhACE2 was rapidly blunted: a clinical trial of infused rhACE2 was proposed and subsequently withdrawn in China because ACE2 infusion, decreasing Ang II and increasing Ang1-7 systemic levels too much, caused considerable arterial hypotension and cardiovascular side effects in patients with advanced stages of COVID-19 [7, 15].

Since soluble ACE2 may at least act as bait to neutralize the spike protein on the surface of SARS-CoV-2, a fusion protein containing a modified ACE2 enzyme with a low catalytic activity bound to the Fc region of IgG1 was produced. This compound showed a good binding affinity for the receptor-binding domain (RBD) of SARS-CoV and SARS-CoV-2 in infected mice [88].

Intranasal delivery of ACE2 has also been proposed. In this case, modified ACE2 molecules were administered by an inhaler during the early phases of the COVID-19 infection. This approach should reduce the number of virions that infect the nasal mucosa. Consequently, there should be fewer virions that can reach the lungs, and by this route, a portion of drugs could also reach the brain from the nasal cavity [89, 90]. This way, adverse cardiovascular events should not occur, even if some of the drug enters the circulation [90].

A further strategy implies a soluble ACE2 variant fused with an albumin-binding domain (ABD) (ACE2–1-618-DDC-ABD). This drug was administered intranasally and intraperitoneally to mice before and after intranasal inoculation of SARS-CoV-2: untreated animals died by day 7 due to pulmonary alveolar hemorrhage with mononuclear infiltrates; in contrast, almost all mice infected with a lethal dose of SARS-CoV-2 that received ACE2–1-618-DDC-ABD survived [91].

ACE2-derived peptides potentially neutralizing the RBD of the SARS-CoV-2 S1 domain have also been identified. It was shown that amino acid sequences placed at the 21-57 and 351-357 positions of the N-terminal helix of ACE2 allow the interaction with SARS-CoV-2 RBD [87, 92].

Finally, extracellular vesicles that express ACE2 (evACE2) were isolated from the plasma of patients with COVID-19. evACE2 neutralizes SARS-CoV-2 infection by competing with cellular ACE2 and protects human ACE2 transgenic mice from SARS-CoV-2-induced lung injury [93].

When it comes to the atypical viral pneumonia of different etiologies but characterized by tissue ACE2 loss, a completely different approach may be hypothesized. Provided by the functional flexibility of RAS peptidases, this approach consists in replacing defective Ang1-7 production without resorting to systemic administration of exogenous ACE2, which otherwise would cause Ang1-7 production inside blood vessels, arterial hypotension, and cardiovascular complications.

Flexibility of RAS means that the same component can produce opposite physiological effects through different pathways (e.g., Ang II may be antinatriuretic when bound to AT1Rs or natriuretic when bound to Ang II type 2 receptors [AT2Rs]), and different components can have the same physiological effect by different pathways (e.g., Ang1-7 is produced from Ang II by ACE2 or from Ang I by NEP). Moreover, when a branch of RAS is blocked, synthesis of angiotensins may find its way along another path of the RAS metabolism that is still practicable (Figure 1). For instance, when ACEis are used, a quota of aldosterone is still released by the adrenals due to Ang II being newly produced by chymase and cathepsin G [94]. Another example is as follows: when ACE2 is blocked by specific metallopeptidase inhibitors, NEP starts cleaving Ang I into Ang1-7, provided enough substrate for the reaction is available [95]. In addition, it was shown that Ang1-7 is the most common metabolite of Ang I in certain areas of the brain (i.e., the hippocampus) where thimet oligopeptidase and prolyl endopeptidase (PEP) are the enzymes involved in the generation of the heptapeptide [96]. Finally, even carboxypeptidase A and prolyl carboxypeptidase (PCP) may generate Ang1-7 from Ang II [56].

Understanding this flexibility of nonclassical RAS suggests the following strategy.

Captopril can reduce pulmonary hypertension, delay the progression of ARDS, and protect lung vascular endothelial cells in rat models of oleic acid-induced ARDS or endotoxin-induced lung injury [97], and it was shown that even ARBs have a therapeutic effect in human ARDS [77]. Mostly because ACEis inhibit clearance of Ang1-7 into inactive Ang1-5 (Figure 1), while ARBs do not, ACEis should be administered to normo-hypertensive patients affected by atypical viral pneumonia due to ACE2 loss; what is more, concurrent i.v. infusion of Ang I, which does show very low serum concentrations at least in COVID-19 patients [70], should be associated. This decapeptide is not hypertensive, provided ACE is inhibited, and is the substrate for Ang1-7 synthesis by NEP in the lung. This strategy would possibly lead to increased tissue production of Ang1-7 by NEP, without significant spillover of this hypotensive heptapeptide into the systemic circulation.

Previous experiments seem to support this atypical strategy, which involves ACEis and Ang I administration at the same time.

Firstly, when the rat cirrhotic liver was perfused with metallopeptidase inhibitors, ACE2 inhibition dramatically increased hepatic Ang1-7 production from Ang I, an effect abolished by NEP inhibitors. This means that ACE2 inhibition unleashed Ang I cleavage into Ang1-7 by hepatic NEP [95]. The authors of this review had previously described the overexpression of NEP inside the cirrhotic liver [37].

Secondly, since NEP mRNA and NEP-immunoreactive material are largely detected in the bronchial epithelial cells, submucosal glands, smooth muscle, and endothelium [98], NEP could replace inadequate ACE2 function at least in the lung if its occasional substrate Ang I was freely available.

Thirdly, in a recent review, it was postulated that increasing NEP activity might mitigate by itself COVID-19 severity [99]. NEP seems to play a protective role in the lung since, in the experimental model of mice with acute lung injury, a significant decrease in NEP enzymatic activity occurs. This leads to defective tachykinin clearance and Ang1-7 synthesis and uncontrolled lung inflammation [100].

Finally, it is important to remember that NEP may also degrade Ang1-7, but this peptidase is reported to be involved in the catabolism of Ang1-7 into Ang1-4 within tissues other than the lung, mostly in the renal cortex [101, 102]. Indeed, the major enzyme responsible for Ang1-7 catabolism (into Ang1-5) in the pulmonary tissue is ACE [101].

A strategy pursued against diseases caused by genus β-coronaviruses is the attempt to modify the host cell membrane ACE2, the viral receptor.

After the SARS-CoV outbreak of 2002, metallopeptidase inhibitors (e.g., MLN-4760) were produced to alter the physical conformation of ACE2, thereby preventing the coronavirus from binding to cell membranes. Unfortunately, those drugs led to further inhibition of ACE2-dependent Ang1-7 production [103].

Recently, novel pyrazolone-based compounds derived from edaravone, a vasodilator of brain and coronary arteries, were designed as potential inhibitors that would interrupt the interaction between the SARS-CoV-2 S protein and the host cell receptor (ACE2). Notably, these new molecules do not alter the structural integrity of cell membrane ACE2, prevent attachment of the coronavirus spike to its receptor, and may not inhibit ACE2-driven production of Ang1-7 [104].

Serine protease inhibitors might prevent the host serine protease TMPRSS2 from priming the spike (S glycoprotein) of the SARS-CoV-2 viral coat prior to viral entry into human cells. With this aim, i.v. serine protease inhibitors camostat mesylate and nafamostat mesylate were administered to symptomatic patients with confirmed COVID-19 infection. In two different randomized clinical trials, camostat mesylate did not affect the time to clinical improvement or mortality, without significant adverse events [105, 106]. In a retrospective clinical study, nafamostat mesylate was ineffective against COVID-19 and, on top of this, frequently caused hyperkalemia due to unwanted inhibition of amiloride-sensitive sodium channels in the kidney [107].

These discouraging results must be balanced by the knowledge that 80% of Ang II-forming activity in kidney, heart, and blood vessels is dependent on another human serine protease: chymase [34] (Figure 1). Moreover, unlike ACE inhibitors, chymase inhibitors do not lower blood pressure because chymase is found in mast cells of the vascular adventitia [35]. Both chymase and TMPRSS2 are trypsin-like serine proteases belonging to family F1 and subfamily A of serine proteases, according to the MEROPS peptidase database. Therefore, the chymase inhibitor SF2809E would warrant consideration in COVID-19 because chymase is a ubiquitous serine protease quite like TMPRSS2, it is a source of detrimental peptides Ang II and ET-1 in human tissues and not in the systemic circulation [108], and SF2809E might also inhibit TMPRSS2. Moreover, SF2809E does not cause hyperkalemia and relieves sodium retention in a model of experimental liver cirrhosis with ascites [108]. It is not known whether chymase inhibitors affect cellular ACE2 expression as ACEis do.

Finally, serine protease (chymase) inhibitors circulate freely in the blood of otherwise healthy humans. These physiological serine protease inhibitors (serpins and α1-antitrypsin) have potent anti-inflammatory effects [109].

Therefore, efforts should be made to assess the ability of serpins, α1-antitrypsin, and, mostly, chymase inhibitors to block the host serine protease TMPRSS2 [26, 35].

7. Conclusions

Local and systemic loss of ACE2 is a key trigger of severe inflammatory syndromes caused by genus β-coronaviruses, avian influenza viruses, and the human respiratory syncytial virus and of almost every case of ARDS. It is known that attempts at restoring the ACE2 body content in these cases through systemic administration of this peptidase may lead to excessive intravascular production of the vasodilator Ang1-7 and intolerable side effects. The way nonclassical RAS works provides suggestions for restoring tissue Ang1-7 levels, the true target of therapies, without resorting to ACE2 administration.

In general, when key mechanisms of inflammation are recruited, i.e., ADAM-17 releasing soluble ACE2 from cell membranes and, mostly, TNF-α downregulating cell membrane ACE2, the strategy of replacing the Ang1-7 tissue production through ACEis, NEP, and its substrate Ang I, as we illustrate in this paper, might be of some use and is worth being evaluated through trials in human patients, not only in COVID-19 but also in acute lung injury due to hRSV and avian influenza viruses.

Finally, attempts at inhibiting host serine proteases that prime coronaviruses prior to cell infection, albeit initially discouraging, must not be abandoned. Instead, this effort should be renewed employing serine proteinase inhibitors capable of blocking both nonclassical RAS serine peptidase chymase (the main source of Ang II in tissues and vessel walls) and hopefully even serine peptidase TMPRSS2. Once again, clinical trials in humans are warranted.

Footnotes

Abbreviations

Data Availability

This review includes data from all the cited references. This is not a clinical trial.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Authors’ Contributions

GS and MA were both responsible for the drafting of the article, critical revision of the article for important intellectual content, and final approval of the article.

Acknowledgments

This review was funded through the RILO 2021 DSCB Aragno contribution by the University of Turin.

References

WHO

Clinical management of severe acute respiratory infection when Middle East respiratory syndrome coronavirus (MERS-CoV) infection is suspected: interim guidance 2019

World Health Organization

Papanikolaou

Chrysovergis

Tsiambas

V. R. E.

Katsinis

Manoli

Papouliakos

Roukas

Mastronikolis

Peschos

Batistatou

Kyrodimos

Mastronikolis

From delta to omicron: S1-RBD/S2 mutation/deletion equilibrium in SARS-CoV-2 defined variants

Gene 2022 814, article 146134

3362391

10.1016/j.gene.2021.146134

34990799

Thomson

E. C.

Rosen

L. E.

Shepherd

J. G.

Spreafico

Filipe

A. d. S.

Wojcechowskyj

J. A.

Davis

Piccoli

Pascall

D. J.

Dillen

Lytras

Czudnochowski

Shah

Meury

Jesudason

De Marco

Bassi

O'Toole

Pinto

Colquhoun

R. M.

Culap

Jackson

Zatta

Rambaut

Jaconi

Sreenu

V. B.

Nix

Zhang

Jarrett

R. F.

Glass

W. G.

Beltramello

Nomikou

Pizzuto

Tong

Cameroni

Croll

T. I.

Johnson

Di Iulio

Wickenhagen

Ceschi

Harbison

A. M.

Mair

Ferrari

Smollett

Sallusto

Carmichael

Garzoni

Nichols

Galli

Hughes

Riva

Schiuma

Semple

M. G.

Openshaw

P. J. M.

Fadda

Baillie

J. K.

Chodera

J. D.

ISARIC4C Investigators COVID-19 Genomics UK (COG-UK) Consortium Rihn

S. J.

Lycett

S. J.

Virgin

H. W.

Telenti

Corti

Robertson

D. L.

Snell

Circulating SARS-CoV-2 spike N439K variants maintain fitness while evading antibody-mediated immunity

Cell 2021 184

3362391

5 1171 1187.e20

10.1016/j.cell.2021.01.037

33621484

Cao

Wang

Jian

Xiao

Song

Yisimayi

Huang

Wang

Niu

Yang

Liang

Sun

Cui

Liu

Yang

Zhang

Hao

Shao

Jin

Wang

Xiao

Wang

Xie

X. S.

Omicron escapes the majority of existing SARS-CoV-2 neutralizing antibodies

Nature 2022 602

3362391

7898 657 663

10.1038/s41586-021-04385-3

35016194

World Health Organization

WHO guidelines: drugs to prevent COVID-19

World Health Organization Guidelines 2021 53

3362391

1689 1699

Kumar Singh

Singh

Misra

Molnupiravir in COVID-19: a systematic review of literature

Diabetes & Metabolic Syndrome 2021 15

3362391

6, article 102329

10.1016/j.dsx.2021.102329

34742052

Zhang

Niu

ACE2 and COVID-19 and the resulting ARDS

Postgraduate Medical Journal 2020 96

3362391

1137 403 407

10.1136/postgradmedj-2020-137935

32522846

Collier

D. A.

De Marco

Ferreira

I. A. T. M.

Meng

Datir

R. P.

Walls

A. C.

Kemp

S. A.

Bassi

Pinto

Silacci-Fregni

Bianchi

Tortorici

M. A.

Bowen

Culap

Jaconi

Cameroni

Snell

Pizzuto

M. S.

Pellanda

A. F.

Garzoni

Riva

CITIID-NIHR BioResource COVID-19 Collaboration Elmer

Kingston

Graves

McCoy

L. E.

Smith

K. G. C.

Bradley

J. R.

Temperton

Ceron-Gutierrez

Barcenas-Morales

COVID-19 Genomics UK (COG-UK) Consortium Harvey

Virgin

H. W.

Lanzavecchia

Piccoli

Doffinger

Wills

Veesler

Corti

Gupta

R. K.

Sensitivity of SARS-CoV-2 B.1.1.7 to mRNA vaccine-elicited antibodies

Nature 2021 593

3362391

7857 136 141

10.1038/s41586-021-03412-7

33706364

Breskin

Wiener

Adimora

A. A.

Brown

R. S.

Jr. Landis

Reddy

K. R.

Verna

E. C.

Crawford

J. M.

Mospan

Fried

M. W.

Brookhart

M. A.

Effectiveness of remdesivir treatment protocols among patients hospitalized with COVID-19: a target trial emulation

Epidemiology 2023 34

3362391

3 365 375

10.1097/EDE.0000000000001598

36719738

10.

Leding

Bodilsen

Brieghel

Barrella Harboe

Helleberg

Holm

Bastrup Israelsen

Jensen

T. Ø.

Johansen

I. S.

Johnsen

Kirk

Lindegaard

Meyer

C. N.

Mohey

Pedersen

Nielsen

Lønberg Nielsen

Omland

L. H.

Podlekareva

Ravn

Starling

Storgaard

Søborg

Schmeltz Søgaard

Tranborg

Wiese

Westring Worm

S. H.

Rolighed Christensen

Benfield

Treatment effect modifiers in hospitalised patients with COVID-19 receiving remdesivir and dexamethasone

Infectious Diseases 2023 55

3362391

5 351 360

10.1080/23744235.2023.2187081

36905638

11.

Vora

S. M.

Lieberman

Inflammasome activation at the crux of severe COVID-19

Nature Reviews. Immunology 2021 21

3362391

11 694 703

10.1038/s41577-021-00588-x

34373622

12.

Pugin

Ricou

Steinberg

K. P.

Suter

P. M.

Martin

T. R.

Proinflammatory activity in bronchoalveolar lavage fluids from patients with ARDS, a prominent role for interleukin-1

American Journal of Respiratory and Critical Care Medicine 1996 153

3362391

6 1850 1856

10.1164/ajrccm.153.6.8665045

2-s2.0-0029892565

8665045

13.

Levy

M. M.

Fink

M. P.

Marshall

J. C.

Abraham

Angus

Cook

Cohen

Opal

S. M.

Vincent

J. L.

Ramsay

SCCM/ESICM/ACCP/ATS/SIS

2001 SCCM/ESICM/ACCP/ATS/SIS international sepsis definitions conference

Critical Care Medicine 2003 31

3362391

4 1250 1256

10.1097/01.CCM.0000050454.01978.3B

2-s2.0-0037389094

12682500

14.

Abassi

Z. A.

Assady

Khoury

E. E.

Heyman

S. N.

Angiotensin-converting enzyme 2: an ally or a Trojan horse? Implications to SARS-CoV-2-related cardiovascular complications

American Journal of Physiology-Heart and Circulatory Physiology 2020 318

3362391

5 H1080 H1083

10.1152/ajpheart.00215.2020

32223552

15.

South

A. M.

Diz

D. I.

Chappell

M. C.

COVID-19, ACE2, and the cardiovascular consequences

American Journal of Physiology-Heart and Circulatory Physiology 2020 318

3362391

5 H1084 H1090

10.1152/ajpheart.00217.2020

32228252

16.

Yang

Zhao

Wang

Cao

Lai

Yang

Zhang

Duan

Zhang

Chen

Zhen

Cai

Penninger

J. M.

Jiang

Wang

Angiotensin-converting enzyme 2 (ACE2) mediates influenza H7N9 virus-induced acute lung injury

Scientific Reports 2014 4

3362391

1 7027

10.1038/srep07027

2-s2.0-84922551964

25391767

17.

Xie

Zhang

Lai

Zhu

Wang

Han

Duan

Zhao

Yang

Xing

Zhang

Wang

J. J.

Wang

Yang

Angiotensin-converting enzyme 2 inhibits lung injury induced by respiratory syncytial virus

Scientific Reports 2016 6

3362391

1, article 19840

10.1038/srep19840

2-s2.0-84955512711

26813885

18.

Hatmal

M. M.

Alshaer

Al-Hatamleh

M. A. I.

Hatmal

Smadi

Taha

M. O.

Oweida

A. J.

Boer

J. C.

Mohamud

Plebanski

Comprehensive structural and molecular comparison of spike proteins of SARS-CoV-2, SARS-CoV and MERS-CoV, and their interactions with ACE2

Cell 2020 9

3362391

12 2638

10.3390/cells9122638

19.

Yeager

C. L.

Ashmun

R. A.

Williams

R. K.

Cardellichio

C. B.

Shapiro

L. H.

Look

A. T.

Holmes

K. V.

Human aminopeptidase N is a receptor for human coronavirus 229E

Nature 1992 357

3362391

6377 420 422

10.1038/357420a0

2-s2.0-0026693135

1350662

20.

Chappell

M. C.

Nonclassical renin-angiotensin system and renal function

Comprehensive Physiology 2012 2

3362391

4 2733 2752

10.1002/cphy.c120002

23720263

21.

Donoghue

Hsieh

Baronas

Godbout

Gosselin

Stagliano

Donovan

Woolf

Robison

Jeyaseelan

Breitbart

R. E.

Acton

A novel angiotensin-converting enzyme-related carboxypeptidase (ACE2) converts angiotensin I to angiotensin 1-9

Circulation Research 2000 87

3362391

5 E1 E9

10.1161/01.RES.87.5.e1

10969042

22.

Tipnis

S. R.

Hooper

N. M.

Hyde

Karran

Christie

Turner

A. J.

A human homolog of angiotensin-converting enzyme:

The Journal of Biological Chemistry 2000 275

3362391

43 33238 33243

10.1074/jbc.M002615200

2-s2.0-0034721906

23.

Sansoè

Aragno

Wong

COVID-19 and liver cirrhosis: focus on the nonclassical renin-angiotensin system and implications for therapy

Hepatology 2021 74

3362391

2 1074 1080

10.1002/hep.31728

33524188

24.

Sansoè

Aragno

Wong

Pathways of hepatic and renal damage through non-classical activation of the renin-angiotensin system in chronic liver disease

Liver International 2020 40

3362391

1 18 31

10.1111/liv.14272

31580514

25.

Abassi

Knaney

Karram

Heyman

S. N.

The lung macrophage in SARS-CoV-2 infection: a friend or a foe?

Frontiers in Immunology 2020 11

3362391

1312

10.3389/fimmu.2020.01312

26.

Hoffmann

Kleine-Weber

Schroeder

Krüger

Herrler

Erichsen

Schiergens

T. S.

Herrler

N. H.

Nitsche

Müller

M. A.

Drosten

Pöhlmann

SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor

Cell 2020 181

3362391

2 271 280.e8

10.1016/j.cell.2020.02.052

32142651

27.

Han

Wang

COVID-19: gastrointestinal manifestations and potential fecal-oral transmission

Gastroenterology 2020 158

3362391

6 1518 1519

10.1053/j.gastro.2020.02.054

28.

Chen

Feng

Xiong

The ACE2 expression in human heart indicates new potential mechanism of heart injury among patients infected with SARS-CoV-2

Cardiovascular Research 2020 116

3362391

6 1097 1100

10.1093/cvr/cvaa078

32227090

29.

Hernandez

V. S.

Zetter

M. A.

Guerra

E. C.

Hernández-Araiza

Karuzin

Hernández-Pérez

O. R.

Eiden

L. E.

Zhang

ACE2 expression in rat brain: implications for COVID-19 associated neurological manifestations

Experimental Neurology 2021 345, article 113837

3362391

10.1016/j.expneurol.2021.113837

34400158

30.

Souza Santos

R. A.

Oudit

G. Y.

Verano-Braga

Canta

Steckelings

Bader

The renin-angiotensin system: going beyond the classical paradigms

American Journal of Physiology-Heart and Circulatory Physiology 2019 316

3362391

5 H958 H970

10.1152/ajpheart.00723.2018

2-s2.0-85064938928

30707614

31.

Paz Ocaranza

Riquelme

J. A.

Garcia

Jalil

J. E.

Chiong

Santos

R. A. S.

Lavandero

Counter-regulatory renin-angiotensin system in cardiovascular disease

Nature Reviews Cardiology 2020 17

3362391

2 116 129

10.1038/s41569-019-0244-8

2-s2.0-85071099405

31427727

32.

Simard

Jin

Takai

Miyazaki

Brochu

D'Orléans-Juste

Chymase-dependent conversion of big endothelin-1 in the mouse in vivo

The Journal of Pharmacology and Experimental Therapeutics 2009 328

3362391

2 540 548

10.1124/jpet.108.142992

2-s2.0-59649085140

18987301

33.

Takai

Jin

Miyazaki

Multiple mechanisms for the action of chymase inhibitors

Journal of Pharmacological Sciences 2012 118

3362391

3 311 316

10.1254/jphs.11R11CP

2-s2.0-84859510328

22333480

34.

Takai

Sakaguchi

Jin

Yamada

Kirimura

Miyazaki

Different angiotensin II-forming pathways in human and rat vascular tissues

Clinica Chimica Acta 2001 305

3362391

1-2 191 195

10.1016/S0009-8981(01)00379-5

2-s2.0-0035106195

11249939

35.

Miyazaki

Takai

Local angiotensin II-generating system in vascular tissues: the roles of chymase

Hypertension Research 2001 24

3362391

3 189 193

10.1291/hypres.24.189

2-s2.0-0034967798

36.

Wilkins

R. M.

Redondo

Brown

L. A.

The natriuretic-peptide family

The Lancet 1997 349

3362391

9061 1307 1310

10.1016/S0140-6736(96)07424-7

2-s2.0-0030891703

37.

Sansoè

Aragno

Mastrocola

Restivo

Mengozzi

Smedile

Rosina

Danni

Parola

Rizzetto

Neutral endopeptidase (EC 3.4.24.11) in cirrhotic liver: a new target to treat portal hypertension?

Journal of Hepatology 2005 43

3362391

5 791 798

10.1016/j.jhep.2005.04.017

2-s2.0-26244439679

16085334

38.

Berard

Niel

Rubio

Is the renin-angiotensin system actually hypertensive?

Pediatric Nephrology 2014 29

3362391

6 951 960

10.1007/s00467-013-2481-0

2-s2.0-84901586605

39.

Singh

K. D.

Karnik

S. S.

Angiotensin receptors: structure, function signaling and clinical application

Journal of Cellular Signaling 2016 1

3362391

111

40.

Hekmat

A. S.

Javanmardi

Alamandine: potential protective effects in SARS-CoV-2 patients

Journal of the Renin-Angiotensin-Aldosterone System 2021 2021, article 6824259

3362391

10.1155/2021/6824259

34853605

41.

Leebeek

F. W.

Kluft

Knot

E. A. R.

de Maat

M. P. M.

Wilson

J. H. P.

A shift in balance between profibrinolytic and antifibrinolytic factors causes enhanced fibrinolysis in cirrhosis

Gastroenterology 1991 101

3362391

5 1382 1390

10.1016/0016-5085(91)90092-Y

2-s2.0-0026080024

1718809

42.

Riera

Anguiano

Clotet

Roca-Ho

Rebull

Pascual

Soler

M. J.

Paricalcitol modulates ACE2 shedding and renal ADAM17 in NOD mice beyond proteinuria

American Journal of Physiology. Renal Physiology 2016 310

3362391

6 F534 F546

10.1152/ajprenal.00082.2015

2-s2.0-84980350558

26697977

43.

Wang

Gheblawi

Nikhanj

Munan

MacIntyre

O'Neil

Poglitsch

Colombo

Del Nonno

Kassiri

Sligl

Oudit

G. Y.

Dysregulation of ACE (angiotensin-converting enzyme)-2 and renin-angiotensin peptides in SARS-CoV-2 mediated mortality and end-organ injuries

Hypertension 2022 79

3362391

2 365 378

10.1161/HYPERTENSIONAHA.121.18295

34844421

44.

Zhao

Forward and reverse signaling mediated by transmembrane tumor necrosis factor-alpha and TNF receptor 2: potential roles in an immunosuppressive tumor microenvironment

Frontiers in Immunology 2017 8

3362391

1675

10.3389/fimmu.2017.01675

2-s2.0-85035329372

45.

Strieter

R. M.

Kunkel

S. L.

Bone

R. C.

Role of tumor necrosis factor-α in disease states and inflammation

Critical Care Medicine 1993 21

3362391

Supplement S447 S463

10.1097/00003246-199310001-00006

46.

Semenzato

Tumour necrosis factor: a cytokine with multiple biological activities

British Journal of Cancer 1990 61

3362391

3 354 361

10.1038/bjc.1990.78

2-s2.0-0025247919

2183871

47.

Moftah

M. B.

Eswayah

Intricate relationship between SARS-CoV-2-induced shedding and cytokine storm generation: a signaling inflammatory pathway augmenting COVID-19

Health Sciences Review 2022 2, article 100011

3362391

10.1016/j.hsr.2021.100011

35013738

48.

Van de Veerdonk

F. L.

Netea

M. G.

van Deuren

van der Meer

J. W.

de Mast

Brüggemann

R. J.

van der Hoeven

Kallikrein-kinin blockade in patients with COVID-19 to prevent acute respiratory distress syndrome

eLife 2020 9

3362391

10.7554/eLife.57555

49.

Zhang

Liu

Luo

J. Y.

Tian

X. Y.

Cheang

W. S.

Lau

C. W.

Wang

Wong

W. T.

Wong

C. M.

Lan

H. Y.

Yao

Raizada

M. K.

Huang

Upregulation of angiotensin (1-7)-mediated signaling preserves endothelial function through reducing oxidative stress in diabetes

Antioxidants & Redox Signaling 2015 23

3362391

11 880 892

10.1089/ars.2014.6070

2-s2.0-84944871698

25867182

50.

Hemnes

A. R.

Rathinasabapathy

Austin

E. A.

Brittain

E. L.

Carrier

E. J.

Chen

Fessel

J. P.

Fike

C. D.

Fong

Fortune

Gerszten

R. E.

Johnson

J. A.

Kaplowitz

Newman

J. H.

Piana

Pugh

M. E.

Rice

T. W.

Robbins

I. M.

Wheeler

Loyd

J. E.

West

A potential therapeutic role for angiotensin-converting enzyme 2 in human pulmonary arterial hypertension

The European Respiratory Journal 2018 51

3362391

6, article 1702638

10.1183/13993003.02638-2017

2-s2.0-85050351547

29903860

51.

Siwik

D. A.

Pagano

P. J.

Colucci

W. S.

Oxidative stress regulates collagen synthesis and matrix metalloproteinase activity in cardiac fibroblasts

American Journal of Physiology. Cell Physiology 2001 280

3362391

1 C53 C60

10.1152/ajpcell.2001.280.1.C53

11121376

52.

Pirola

C. J.

Sookoian

Estimation of renin-angiotensin-aldosterone-system (RAAS)-inhibitor effect on COVID-19 outcome: a meta-analysis

The Journal of Infection 2020 81

3362391

2 276 281

10.1016/j.jinf.2020.05.052

32474043

53.

Flacco

M. E.

Acuti Martellucci

Bravi

Parruti

Cappadona

Mascitelli

Manfredini

Mantovani

L. G.

Manzoli

Treatment with ACE inhibitors or ARBs and risk of severe/lethal COVID-19: a meta-analysis

Heart 2020 106

3362391

19 1519 1524

10.1136/heartjnl-2020-317336

32611676

54.

Rezel-Potts

Douiri

Chowienczyk

P. J.

Gulliford

M. C.

Antihypertensive medications and COVID-19 diagnosis and mortality: population-based case-control analysis in the United Kingdom

British Journal of Clinical Pharmacology 2021 87

3362391

12 4598 4607

10.1111/bcp.14873

33908074

55.

Suzuki

Ruiz-Ortega

Lorenzo

Ruperez

Esteban

Egido

Inflammation and angiotensin II

The International Journal of Biochemistry & Cell Biology 2003 35

3362391

6 881 900

10.1016/S1357-2725(02)00271-6

2-s2.0-0037409417

56.

Kuriakose

Montezano

A. C.

Touyz

R. M.

ACE2/Ang-(1-7)/Mas1 axis and the vascular system: vasoprotection to COVID-19-associated vascular disease

Clinical Science 2021 135

3362391

2 387 407

10.1042/CS20200480

33511992

57.

Shi

Wang

Zhang

Huang

Zhang

Liu

Zhao

Liu

Zhu

Tai

Bai

Gao

Song

Xia

Dong

Zhao

Wang

F. S.

Pathological findings of COVID-19 associated with acute respiratory distress syndrome

Respiratory Medicine 2020 8

3362391

4 420 422

10.1016/S2213-2600(20)30076-X

32085846

58.

Cheng

Wang

G. Q.

Organ-protective effect of angiotensin-converting enzyme 2 and its effect on the prognosis of COVID-19

Journal of Medical Virology 2020 92

3362391

7 726 730

10.1002/jmv.25785

32221983

59.

Chaudry

Lavandero

Xie

Sabharwal

Zheng

Y. Y.

Correa

Narula

Levy

Manipulation of ACE2 expression in COVID-19

Open Heart 2020 7

3362391

2, article e001424

10.1136/openhrt-2020-001424

33443121

60.

Brevini

Maes

Webb

G. J.

John

B. V.

Fuchs

C. D.

Buescher

Wang

Griffiths

Brown

M. L.

Scott

W. E.

3rd Pereyra-Gerber

Gelson

W. T. H.

Brown

Dillon

Muraro

Sharp

Neary

Box

Tatham

Stewart

Curley

Pertinez

Forrest

Mlcochova

Varankar

S. S.

Darvish-Damavandi

Mulcahy

V. L.

Kuc

R. E.

Williams

T. L.

Heslop

J. A.

Rossetti

Tysoe

O. C.

Galanakis

Vila-Gonzalez

Crozier

T. W. M.

Bargehr

Sinha

Upponi

S. S.

Fear

Swift

Saeb-Parsy

Davies

S. E.

Wester

Hagström

Melum

Clements

Humphreys

Herriott

Kijak

Cox

Bramwell

Valentijn

Illingworth

C. J. R.

UK-PBC Consortium Dahman

Bastaich

D. R.

Ferreira

R. D.

Marjot

Barnes

Moon

A. M.

Barritt

A. S.

4th Gupta

R. K.

Baker

Davenport

A. P.

Corbett

Gorgoulis

V. G.

Buczacki

S. J. A.

Lee

J. H.

Matheson

N. J.

Trauner

Fisher

A. J.

Gibbs

Butler

A. J.

Watson

C. J. E.

Mells

G. F.

Dougan

Owen

Lohse

A. W.

Vallier

Sampaziotis

FXR inhibition may protect from SARS-CoV-2 infection by reducing ACE2

Nature 2023 615

3362391

7950 134 142

10.1038/s41586-022-05594-0

36470304

61.

Broz

Dixit

V. M.

Inflammasomes: mechanism of assembly, regulation and signalling

Nature Reviews. Immunology 2016 16

3362391

7 407 420

10.1038/nri.2016.58

2-s2.0-84976516826

62.

Munoz-Pianillo

Kuffa

Martínez-Colón

Smith

B. L.

Rajendiran

T. M.

Núñez

K⁺ efflux is the common trigger of NLRP3 inflammasome activation by bacterial toxins and particulate matter

Immunity 2013 38

3362391

6 1142 1153

10.1016/j.immuni.2013.05.016

2-s2.0-84879596906

23809161

63.

Del Valle

D. M.

Kim-Schulze

Huang

H. H.

Beckmann

N. D.

Nirenberg

Wang

Lavin

Swartz

T. H.

Madduri

Stock

Marron

T. U.

Xie

Patel

Tuballes

Van Oekelen

Rahman

Kovatch

Aberg

J. A.

Schadt

Jagannath

Mazumdar

Charney

A. W.

Firpo-Betancourt

Rao Mendu

Jhang

Reich

Sigel

Cordon-Cardo

Feldmann

Parekh

Merad

Gnjatic

An inflammatory cytokine signature predicts COVID-19 severity and survival

Nature Medicine 2020 26

3362391

10 1636 1643

10.1038/s41591-020-1051-9

32839624

64.

Chen

Zheng

K. I.

Liu

Yan

Qiao

Plasma CRP level is positively associated with the severity of COVID-19

Annals of Clinical Microbiology and Antimicrobials 2020 19

3362391

1 18

10.1186/s12941-020-00362-2

65.

Satıs

Selçuk Özger

Aysert Yıldız

Hızel

Gulbahar

Ö.

Erbaş

Aygencel

Tunccan

Öztürk

M. A.

Dizbay

Tufan

Prognostic value of interleukin-18 and its association with other inflammatory markers and disease severity in COVID-19

Cytokine 2021 137, article 155302

3362391

10.1016/j.cyto.2020.155302

33002740

66.

Yang

Wang

Liu

Zhao

Liao

Liu

Zhang

The differential immune responses to COVID-19 in peripheral and lung revealed by single-cell RNA sequencing

Cell Discovery 2020 6

3362391

1 73

10.1038/s41421-020-00225-2

67.

Zhang

Yao

X. H.

Zhang

Zhou

Wang

Ren

Sun

Tian

Bian

Wei

Pyroptotic macrophages stimulate the SARS-CoV-2-associated cytokine storm

Cellular & Molecular Immunology 2021 18

3362391

5 1305 1307

10.1038/s41423-021-00665-0

33742186

68.

Zhang

Huang

X. X.

Zhang

W. Y.

Wang

Jin

S. Y.

Zhang

Y. P.

Angiotensin(1-7) attenuated angiotensin II-induced hepatocyte EMT by inhibiting NOX-derived H₂O₂-activated NLRP3 inflammasome/IL-1β/Smad circuit

Free Radical Biology & Medicine 2016 97

3362391

531 543

10.1016/j.freeradbiomed.2016.07.014

2-s2.0-84979223426

69.

You

Huang

Wang

Jin

Zhu

Angiotensin (1–7) inhibits arecoline-induced migration and collagen synthesis in human oral myofibroblasts via inhibiting NLRP3 inflammasome activation

Journal of Cellular Physiology 2019 234

3362391

4 4668 4680

10.1002/jcp.27267

2-s2.0-85053734735

30246378

70.

Warner

F. J.

Rajapaksha

Shackel

Herath

C. B.

ACE2: from protection of liver disease to propagation of COVID-19

Clinical Scence 2020 134

3362391

23 3137 3158

10.1042/CS20201268

33284956

71.

Osterreicher

C. H.

Taura

K. K.

De Minicis

Seki

Penz-Osterreicher

Kodama

Kluwe

Schuster

Oudit

G. Y.

Penninger

J. M.

Brenner

D. A.

Angiotensin-converting-enzyme 2 inhibits liver fibrosis in mice

Hepatology 2009 50

3362391

3 929 938

10.1002/hep.23104

2-s2.0-70349229376

19650157

72.

Wösten-van Asperen

R. M.

Lutter

Specht

P. A.

Moll

G. N.

van Woensel

J. B.

van der Loos

C. M.

van Goor

Kamilic

Florquin

Bos

A. P.

Acute respiratory distress syndrome leads to reduced ratio of ACE/ACE2 activities and is prevented by angiotensin-(1–7) or an angiotensin II receptor antagonist

The Journal of Pathology 2011 225

3362391

4 618 627

10.1002/path.2987

2-s2.0-81355146424

73.

Imai

Kuba

Rao

Huan

Guo

Guan

Yang

Sarao

Wada

Leong-Poi

Crackower

M. A.

Fukamizu

Hui

C. C.

Hein

Uhlig

Slutsky

A. S.

Jiang

Penninger

J. M.

Angiotensin-converting enzyme 2 protects from severe acute lung failure

Nature 2005 436

3362391

7047 112 116

10.1038/nature03712

2-s2.0-21844460785

16001071

74.

Kuba

Imai

Rao

Gao

Guo

Guan

Huan

Yang

Zhang

Deng

Bao

Zhang

Liu

Wang

Chappell

Liu

Zheng

Leibbrandt

Wada

Slutsky

A. S.

Liu

Qin

Jiang

Penninger

J. M.

A crucial role of angiotensin converting enzyme 2 (ACE2) in SARS coronavirus-induced lung injury

Nature Medicine 2005 11

3362391

8 875 879

10.1038/nm1267

2-s2.0-23844463115

16007097

75.

Khan

Benthin

Zeno

Albertson

T. E.

Boyd

Christie

J. D.

Hall

Poirier

Ronco

J. J.

Tidswell

Hardes

Powley

W. M.

Wright

T. J.

Siederer

S. K.

Fairman

D. A.

Lipson

D. A.

Bayliffe

A. I.

Lazaar

A. L.

A pilot clinical trial of recombinant human angiotensin-converting enzyme 2 in acute respiratory distress syndrome

Critical Care 2017 21

3362391

1 234

10.1186/s13054-017-1823-x

2-s2.0-85028931663

28877748

76.

Abdeen

Abu-Fanne

Bdeir

Maraga

Higazi

Cines

D. B.

Heyman

S. N.

Al-Roof Higazi

Divergent impacts of tocilizumab and colchicine in COVID-19-associated coagulopathy: the role of alpha-defensins

British Journal of Haematology 2022 196

3362391

4 923 927

10.1111/bjh.17885

34622440

77.

Varga

Flammer

A. J.

Steiger

Haberecker

Andermatt

Zinkernagel

A. S.

Mehra

M. R.

Schuepbach

R. A.

Ruschitzka

Endothelial cell infection and endotheliitis in COVID-19

The Lancet 2020 395

3362391

1417 1418

78.

Kutz

Conen

Gregoriano

Haubitz

Koch

Domenig

Bernasconi

Mueller

Schuetz

Renin-angiotensin-aldosterone system peptide profiles in patients with COVID-19

European Journal of Endocrinology 2021 184

3362391

543 553

79.

Ofosu-Barko

Liu

Tamimi

F. A.

Al Husami

Ganatra

Resnic

Shah

S. P.

Angiotensin II administration in patients With COVID-19 shock

Critical Pathways in Cardiology 2021 20

3362391

2 100 102

10.1097/HPC.0000000000000246

33031192

80.

Osman

I. O.

Melenotte

Brouqui

Million

Lagier

J. C.

Parola

Stein

La Scola

Meddeb

Mege

J. L.

Raoult

Devaux

C. A.

Expression of ACE2, soluble ACE2, angiotensin I, angiotensin II and angiotensin-(1-7) is modulated in COVID-19 patients

Frontiers in Immunology 2021 12 3362391 article 625732

10.3389/fimmu.2021.625732

81.

Guan

W. J.

Z. Y.

Liang

W. H.

Liu

Shan

Lei

Hui

D. S. C.

Zeng

Yuen

Chen

Tang

Wang

Chen

Xiang

Wang

Liang

Peng

Wei

Liu

Peng

Wang

Liu

Chen

Zheng

Qiu

Luo

Zhu

Zhong

China Medical Treatment Expert Group for Covid-19

Clinical characteristics of coronavirus disease 2019 in China

The New England Journal of Medicine 2020 382

3362391

18 1708 1720

10.1056/NEJMoa2002032

32109013

82.

Perera

M. R.

Greenwood

E. J. D.

Crozier

T. W. M.

Elder

Schmitt

Crump

C. M.

Lehner

P. J.

Wills

M. R.

Sinclair

Cambridge Institute of Therapeutic Immunology and Infectious Disease-National Institute of Health Research COVID BioResource Collaboration

Human cytomegalovirus infection of epithelial cells increases SARS-CoV-2 superinfection by upregulating the ACE2 receptor

The Journal of Infectious Diseases 2023 227

3362391

4 543 553

10.1093/infdis/jiac452

36408607

83.

Domovitz

Ayoub

Werbner

Alter

Tavor

L. I.

Yahalom-Ronen

Tikhonov

Meirson

Maman

Para

Israely

Dessau

Gal-Tanamy

HCV infection increases the expression of ACE2 receptor, leading to enhanced entry of both HCV and SARS-CoV-2 into hepatocytes and a coinfection state

Microbiology Spectrum 2022 10

3362391

6, article e0115022

10.1128/spectrum.01150-22

36314945

84.

Heyman

S. N.

Walther

Abassi

Angiotensin-(1-7) – a potential remedy for AKI: insights derived from the COVID-19 pandemic

Journal of Clinical Medicine 2021 10

3362391

6 1200

10.3390/jcm10061200

85.

Talotta

Roberston

E. S.

Perspectives: potential therapeutic approach with inhalation of ACE2-derived peptides for SARS-CoV-2 infection

American Journal of Clinical and Experimental Immunology 2020 9

3362391

5 73 80

33489475

86.

Zoufaly

Poglitsch

Aberle

J. H.

Hoepler

Seitz

Traugott

Grieb

Pawelka

Laferl

Wenisch

Neuhold

Haider

Stiasny

Bergthaler

Puchhammer-Stoeckl

Mirazimi

Montserrat

Zhang

Slutsky

A. S.

Penninger

J. M.

Human recombinant soluble ACE2 in severe COVID-19

The Lancet Respiratory Medicine 2020 8

3362391

11 1154 1158

10.1016/S2213-2600(20)30418-5

33131609

87.

Abd El-Aziz

T. M.

Al-Sabi

Stockand

J. D.

Human recombinant soluble ACE2 (hrsACE2) shows promise for treating severe COVID19

Signal Transduction and Targeted Therapy 2020 5

3362391

1 258

10.1038/s41392-020-00374-6

33144565

88.

Chan

K. K.

Dorosky

Sharma

Abbasi

S. A.

Dye

J. M.

Kranz

D. M.

Herbert

A. S.

Procko

Engineering human ACE2 to optimize binding to the spike protein of SARS coronavirus 2

Science 2020 369

3362391

6508 1261 1265

10.1126/science.abc0870

32753553

89.

Ameratunga

Woon

S. T.

Steele

Snell

Medlicott

Mears

Leung

Lehnert

Jordan

Das

Abbott

Longhurst

Quiñones-Mateu

M. E.

Perspective: the nose and the stomach play a critical role in the NZACE2-Pātari

*

(modified ACE2) drug treatment project of SARS-CoV-2 infection

Expert Review of Clinical Immunology 2021 17

3362391

6 553 560

10.1080/1744666X.2021.1912596

33792473

90.

Wang

Xiong

Tsang

W. C.

Schätzlein

A. G.

Uchegbu

I. F.

Nose-to-brain delivery

The Journal of Pharmacology and Experimental Therapeutics 2019 370

3362391

3 593 601

10.1124/jpet.119.258152

2-s2.0-85071711892

91.

Hassler

Wysocki

Gelarden

Sharma

Tomatsidou

Gula

Nicoleascu

Randall

Pshenychnyi

Khurram

Kanwar

Missiakas

Henkin

Yeldandi

Batlle

A novel soluble ACE2 protein provides lung and kidney protection in mice susceptible to lethal SARS-CoV-2 infection

Journal of the American Society of Nephrology 2022 33

3362391

7 1293 1307

10.1681/ASN.2021091209

35236774

92.

Han

Kral

Computational design of ACE2-based peptide inhibitors of SARS-CoV-2

ACS Nano 2020 14

3362391

4 5143 5147

10.1021/acsnano.0c02857

32286790

93.

El-Shennawy

Hoffmann

A. D.

Khund Dashzeveg

McAndrews

Mehl

Cornish

Tokars

Nicolaescu

Tomatsidou

Mao

Felicelli

Tsai

Ostiguin

Jia

Furlong

Wysocki

Luo

Ruivo

C. F.

Batlle

Hope

Shen

Chae

Y. K.

Zhang

LeBleu

Shi

Swaminathan

Luo

Missiakas

Randall

Demonbreun

Ison

Kalluri

Fang

Liu

Circulating ACE2-expressing extracellular vesicles block broad strains of SARS-CoV-2

Nature Communications 2022 13

3362391

1 405

10.1038/s41467-021-27893-2

35058437

94.

Huang

Kahng

K. W.

Noble

N. A.

Border

W. A.

Huang

Aldosterone and TGF-β1 synergistically increase PAI-1 and decrease matrix degradation in rat renal mesangial and fibroblast cells

American Journal of Physiology. Renal Physiology 2008 294

3362391

6 F1287 F1295

10.1152/ajprenal.00017.2008

2-s2.0-48249139468

18367662

95.

Herath

C. B.

Lubel

J. S.

Jia

Velkoska

Casley

Brown

Tikellis

Burrell

L. M.

Angus

P. W.

Portal pressure responses and angiotensin peptide production in rat liver are determined by relative activity of ACE and ACE2

American Journal of Physiology. Gastrointestinal and Liver Physiology 2009 297

3362391

1 G98 G106

10.1152/ajpgi.00045.2009

2-s2.0-67650074511

96.

Pereira

M. G.

Souza

L. L.

Becari

Duarte

D. A.

Camacho

F. R. B.

Oliveira

J. A. C.

Gomes

M. D.

Oliveira

E. B.

Salgado

M. C.

Garcia-Cairasco

Costa-Neto

C. M.

Angiotensin II–independent angiotensin-(1–7) formation in rat hippocampus

Hypertension 2013 62

3362391

5 879 885

10.1161/HYPERTENSIONAHA.113.01613

2-s2.0-84886390176

24041943

97.

Neyrinck

A. P.

Matthay

M. A.

The role of angiotensin-converting enzyme inhibition in endotoxin-induced lung injury in rats

Critical Care Medicine 2009 37

3362391

2 776 777

10.1097/CCM.0b013e318194cfa6

2-s2.0-67650355432

19325385

98.

Baraniuk

J. N.

Ohkubo

Kwon

O. J.

Mak

Ali

Davies

Twort

Kaliner

Letarte

Barnes

P. J.

Localization of neutral endopeptidase (NEP) mRNA in human bronchi

The European Respiratory Journal 1995 8

3362391

9 1458 1464

10.1183/09031936.95.08091458

8575569

99.

El Tabaa

M. M.

El Tabaa

M. M.

Targeting neprilysin (NEP) pathways: a potential new hope to defeat COVID-19 ghost

Biochemical Pharmacology 2020 178, article 114057

3362391

10.1016/j.bcp.2020.114057

100.

Hashimoto

Amaya

Oh-Hashi

Kiuchi

Hashimoto

Expression of neutral endopeptidase activity during clinical and experimental acute lung injury

Respiratory Research 2010 11

3362391

1 164

10.1186/1465-9921-11-164

2-s2.0-78649378111

101.

Allred

A. J.

Diz

D. I.

Ferrario

C. M.

Chappell

M. C.

Pathways for angiotensin-(1–7) metabolism in pulmonary and renal tissues

American Journal of Physiology. Renal Physisology 2000 279

3362391

5 F841 F850

10.1152/ajprenal.2000.279.5.F841

11053044

102.

Sansoè

Aragno

Mastrocola

Cutrin

J. C.

Silvano

Mengozzi

Smedile

Rosina

Danni

Rizzetto

Overexpression of kidney neutral endopeptidase (EC 3.4.24.11) and renal function in experimental cirrhosis

American Journal of Physiology. Renal Physiology 2006 290

3362391

6 F1337 F1343

10.1152/ajprenal.00435.2005

2-s2.0-33744812413

16449355

103.

Towler

Staker

Prasad

S. G.

Menon

Tang

Parsons

Ryan

Fisher

Williams

Dales

N. A.

Patane

M. A.

Pantoliano

M. W.

ACE2 X-ray structures reveal a large hinge-bending motion important for inhibitor binding and catalysis

The Journal of Biological Chemistry 2004 279

3362391

17 17996 18007

10.1074/jbc.M311191200

2-s2.0-2342418543

14754895

104.

Obakachi

V. A.

Kushwaha

N. D.

Kushwaha

Mahlalela

M. C.

Shinde

S. R.

Kehinde

Karpoormath

Design and synthesis of pyrazolone-based compounds as potent blockers of SARS-CoV-2 viral entry into the host cells

Journal of Molecular Structure 2021 1241, article 130665

3362391

10.1016/j.molstruc.2021.130665

34007088

105.

Gunst

J. D.

Staerke

N. B.

Pahus

M. H.

Kristensen

L. H.

Bodilsen

Lohse

Dalgaard

L. S.

Brønnum

Fröbert

Hønge

Johansen

I. S.

Monrad

Erikstrup

Rosendal

Vilstrup

Mariager

Bove

D. G.

Offersen

Shakar

Cajander

Jørgensen

N. P.

Sritharan

S. S.

Breining

Jespersen

Mortensen

K. L.

Jensen

M. L.

Kolte

Frattari

G. S.

Larsen

C. S.

Storgaard

Nielsen

L. P.

Tolstrup

Sædder

E. A.

Østergaard

L. J.

Ngo

Jensen

M. H.

Højen

J. F.

Kjolby

Søgaard

O. S.

Efficacy of the TMPRSS2 inhibitor camostat mesilate in patients hospitalized with COVID-19-a double-blind randomized controlled trial

EClinicalMedicine 2021 35

3362391

100849

10.1016/j.eclinm.2021.100849

106.

Tobback

Degroote

Buysse

Delesie

Van Dooren

Vanherrewege

Barbezange

Hutse

Romano

Thomas

Padalko

Callens

De Scheerder

M. A.

Efficacy and safety of camostat mesylate in early COVID-19 disease in an ambulatory setting: a randomized placebo-controlled phase II trial

International Journal of Infectious Diseases 2022 122

3362391

628 635

10.1016/j.ijid.2022.06.054

35803469

107.

Kodama

Imai

Asai

Kozu

Hayashi

Shimizu

Gon

Ootsuka

Incidence and risk factors for hyperkalaemia in patients treated for COVID-19 with nafamostat mesylate

Journal of Clinical Pharmacy and Therapeutics 2022 47

3362391

7 1070 1078

10.1111/jcpt.13646

35313385

108.

Sansoè

Aragno

Mastrocola

Mengozzi

Novo

Parola

Role of chymase in the development of liver cirrhosis and its complications: experimental and human data

PLoS One 2016 11

3362391

10.1371/journal.pone.0162644

2-s2.0-84992359664

109.

Gettins

P. G. W.

Serpin structure, mechanism, and function

Chemical Reviews 2002 102

3362391

12 4751 4804

10.1021/cr010170+

2-s2.0-0036882395