Ischemic stroke is a devastating neurological disease. Brain ischemia impairs systemic immune responses and heightens susceptibility to infections, though the underlying mechanisms remain incompletely understood. Natural killer (NK) cells exhibited decreased frequency and compromised function after acute stage of stroke, resulting in NK cell-associated immune deficiency and increased risk of infection. MicroRNAs (miRNAs) are post-transcriptional molecular modulators. Our previous study revealed a significant upregulation of miR-451a in circulating NK cells from patients with ischemic stroke, but its effects and precise mechanism on immune defense remain elusive. In this study, we observed a substantial elevation of miR-451a level in brain and splenic NK cells in murine model of ischemic stroke miR-451a mimics suppressed NK cell activation and cytotoxicity within the ischemic brain and periphery, including a downregulation of activation marker CD69, and reduced production of effector molecules IFN-γ and perforin. Conversely, miR-451a inhibitor preserved NK cell activation and cytotoxicity, rescuing local inflammation, and reducing bacterial burden in the lung. Pharmacological inhibition of Akt-mTOR pathway with AZD8055 effectively blocked the impacts of miR-451a on NK cell functions. Collectively, these findings suggest miR-451a negatively regulates NK cell cytotoxicity in both the brain and periphery, which could be re-addressed by modulating the Akt-mTOR signaling pathway.
GoASMozaffarianDRogerVL, et al.
Executive summary: heart disease and stroke statistics–2014 update: a report from the American Heart Association. Circulation2014;
129: 399–410.
2.
FeiginVLForouzanfarMHKrishnamurthiR, et al.
Global and regional burden of stroke during 1990–2010: findings from the global burden of disease study 2010. Lancet2014;
383: 245–254.
3.
GongSZhouZZhouM, et al.
Validation of risk scoring models for predicting stroke-associated pneumonia in patients with ischaemic stroke. Stroke Vasc Neurol2016;
1: 122–126.
4.
KwanJPickeringRMKunkelD, et al.
Impact of stroke-associated infection on long-term survival: a cohort study. J Neurol Neurosurg Psychiatry2013;
84: 297–304.
5.
WestendorpWFNederkoornPJVermeijJD, et al.
Post-stroke infection: a systematic review and meta-analysis. BMC Neurol2011;
11: 110.
6.
KalraLIrshadSHodsollJ, et al.
Prophylactic antibiotics after acute stroke for reducing pneumonia in patients with dysphagia (STROKE-INF): a prospective, cluster-randomised, open-label, masked endpoint, controlled clinical trial. Lancet2015;
386: 1835–1844.
7.
WestendorpWFVermeijJ-DZockE, PASS investigatorset al.
The preventive antibiotics in stroke study (PASS): a pragmatic randomised open-label masked endpoint clinical trial. Lancet2015;
385: 1519–1526.
8.
FuYLiuQAnratherJ, et al.
Immune interventions in stroke. Nat Rev Neurol2015;
11: 524–535.
9.
LiuQJinWNLiuY, et al.
Brain ischemia suppresses immunity in the periphery and brain via different neurogenic innervations. Immunity2017;
46: 474–487.
10.
MeiselCSchwabJMPrassK, et al.
Central nervous system injury-induced immune deficiency syndrome. Nat Rev Neurosci2005;
6: 775–786.
11.
KellyPLemmensRWeimarC, et al.
Long-term colchicine for the prevention of vascular recurrent events in non-cardioembolic stroke (CONVINCE): a randomised controlled trial. Lancet2024;
404: 125–133.
12.
LiJMengXShiFD, et al.
Colchicine in patients with acute ischaemic stroke or transient ischaemic attack (CHANCE-3): multicentre, double blind, randomised, placebo controlled trial. BMJ2024;
385: e079061.
13.
HorowitzAStegmannKARileyEM.Activation of natural killer cells during microbial infections. Front Immunol2011;
2: 88.
LongEOKimHSLiuD, et al.
Controlling natural killer cell responses: integration of signals for activation and inhibition. Annu Rev Immunol2013;
31: 227–258.
16.
ShiFDLjunggrenHGLa CavaA, et al.
Organ-specific features of natural killer cells. Nat Rev Immunol2011;
11: 658–671.
17.
VivierERauletDHMorettaA, et al.
Innate or adaptive immunity? The example of natural killer cells. Science2011;
331: 44–49.
18.
ChenCAiQDChuSF, et al.
NK cells in cerebral ischemia. Biomed Pharmacother2019;
109: 547–554.
19.
GanYLiuQWuW, et al.
Ischemic neurons recruit natural killer cells that accelerate brain infarction. Proc Natl Acad Sci U S A2014;
111: 2704–2709.
20.
ZhangYGaoZWangD, et al.
Accumulation of natural killer cells in ischemic brain tissues and the chemotactic effect of IP-10. J Neuroinflammation2014;
11: 79.
21.
MacrezRAliCToutiraisO, et al.
Stroke and the immune system: from pathophysiology to new therapeutic strategies. Lancet Neurol2011;
10: 471–480.
22.
FabianMRSonenbergN.The mechanics of miRNA-mediated gene silencing: a look under the hood of miRISC. Nat Struct Mol Biol2012;
19: 586–593.
23.
StarkABrenneckeJBushatiN, et al.
Animal MicroRNAs confer robustness to gene expression and have a significant impact on 3′UTR evolution. Cell2005;
123: 1133–1146.
24.
BartelDP.MicroRNAs: genomics, biogenesis, mechanism, and function. Cell2004;
116: 281–297.
25.
KrolJLoedigeIFilipowiczW.The widespread regulation of microRNA biogenesis, function and decay. Nat Rev Genet2010;
11: 597–610.
26.
JeyaseelanKLimKYArmugamA.MicroRNA expression in the blood and brain of rats subjected to transient focal ischemia by middle cerebral artery occlusion. Stroke2008;
39: 959–966.
27.
SaugstadJA.MicroRNAs as effectors of brain function with roles in ischemia and injury, neuroprotection, and neurodegeneration. J Cereb Blood Flow Metab2010;
30: 1564–1576.
28.
SunPLiuDZJicklingGC, et al.
MicroRNA-based therapeutics in central nervous system injuries. J Cereb Blood Flow Metab2018;
38: 1125–1148.
29.
KongYLiSChengX, et al.
Brain ischemia significantly alters microRNA expression in human peripheral blood natural killer cells. Front Immunol2020;
11: 759.
30.
FengYLiaoSWeiC, et al.
Infiltration and persistence of lymphocytes during late-stage cerebral ischemia in middle cerebral artery occlusion and photothrombotic stroke models. J Neuroinflammation2017;
14: 248.
31.
JinWNGonzalesRFengY, et al.
Brain ischemia induces diversified neuroantigen-specific T-cell responses that exacerbate brain injury. Stroke2018;
49: 1471–1478.
32.
ChrestaCMDaviesBRHicksonI, et al.
AZD8055 is a potent, selective, and orally bioavailable ATP-competitive mammalian target of rapamycin kinase inhibitor with in vitro and in vivo antitumor activity. Cancer Res2010;
70: 288–298.
33.
KleinertMSylowLFazakerleyDJ, et al.
Acute mTOR inhibition induces insulin resistance and alters substrate utilization in vivo. Mol Metab2014;
3: 630–641.
34.
YatesJWTHoltSVLogieA, et al.
A pharmacokinetic-pharmacodynamic model predicting tumour growth inhibition after intermittent administration with the mTOR kinase inhibitor AZD8055. Br J Pharmacol2017;
174: 2652–2661.
35.
YouWWangZLiH, et al.
Inhibition of mammalian target of rapamycin attenuates early brain injury through modulating microglial polarization after experimental subarachnoid hemorrhage in rats. J Neurol Sci2016;
367: 224–231.
36.
JinWNShiSXLiZ, et al.
Depletion of microglia exacerbates postischemic inflammation and brain injury. J Cereb Blood Flow Metab2017;
37: 2224–2236.
37.
LiZLiMShiSX, et al.
Brain transforms natural killer cells that exacerbate brain edema after intracerebral hemorrhage. J Exp Med2020;
217: 2020.
38.
JinWNDucruetAFLiuQ, et al.
Activation of JAK/STAT3 restores NK-cell function and improves immune defense after brain ischemia. FASEB J2018;
32: 2757–2767.
39.
LiuQLiMWhiteakerP, et al.
Attenuation in nicotinic acetylcholine receptor α9 and α10 subunit double knock-out mice of experimental autoimmune encephalomyelitis. Biomolecules2019;
9: 827.
40.
FengYLiYZhangY, et al.
miR-1224 contributes to ischemic stroke-mediated natural killer cell dysfunction by targeting Sp1 signaling. J Neuroinflammation2021;
18: 133.
41.
PlanasAM.Role of immune cells migrating to the ischemic brain. Stroke2018;
49: 2261–2267.
42.
PrassKMeiselCHoflichC, et al.
Stroke-induced immunodeficiency promotes spontaneous bacterial infections and is mediated by sympathetic activation reversal by poststroke T helper cell type 1-like immunostimulation. J Exp Med2003;
198: 725–736.
43.
XieRChengMLiM, et al.
Akt isoforms differentially protect against stroke-induced neuronal injury by regulating mTOR activities. J Cereb Blood Flow Metab2013;
33: 1875–1885.
44.
ZhaoHSapolskyRMSteinbergGK.Phosphoinositide-3-kinase/akt survival signal pathways are implicated in neuronal survival after stroke. Mol Neurobiol2006;
34: 249–270.
45.
AliAKNandagopalNLeeSH.IL-15-PI3K-AKT-mTOR: a critical pathway in the life journey of natural killer cells. Front Immunol2015;
6: 355.
46.
MaoYvan HoefVZhangX, et al.
IL-15 activates mTOR and primes stress-activated gene expression leading to prolonged antitumor capacity of NK cells. Blood2016;
128: 1475–1489.
47.
ChenWSinhaBLiY, et al.
Monogenic, polygenic, and MicroRNA markers for ischemic stroke. Mol Neurobiol2019;
56: 1330–1343.
48.
KhoshnamSEWinlowWFarboodY, et al.
Emerging roles of microRNAs in ischemic stroke: As possible therapeutic agents. J Stroke2017;
19: 166–187.
49.
LiGMorris-BlancoKCLopezMS, et al.
Impact of microRNAs on ischemic stroke: from pre- to post-disease. Prog Neurobiol2018;
163–164: 59–78.
50.
LianLZhangYLiuL, et al.
Neuroinflammation in ischemic stroke: focus on MicroRNA-mediated polarization of microglia. Front Mol Neurosci2020;
13: 612439.
51.
EdbauerDNeilsonJRFosterKA, et al.
Regulation of synaptic structure and function by FMRP-associated microRNAs miR-125b and miR-132. Neuron2010;
65: 373–384.
52.
HarrazMMEackerSMWangX, et al.
MicroRNA-223 is neuroprotective by targeting glutamate receptors. Proc Natl Acad Sci U S A2012;
109: 18962–18967.
53.
YangZBZhangZLiTB, et al.
Up-regulation of brain-enriched miR-107 promotes excitatory neurotoxicity through down-regulation of glutamate transporter-1 expression following ischaemic stroke. Clin Sci (Lond)2014;
127: 679–689.
54.
Hamzei TajSKhoWRiouA, et al.
MiRNA-124 induces neuroprotection and functional improvement after focal cerebral ischemia. Biomaterials2016;
91: 151–165.
55.
SongYLiZHeT, et al.
M2 microglia-derived exosomes protect the mouse brain from ischemia-reperfusion injury via exosomal miR-124. Theranostics2019;
9: 2910–2923.
56.
XiangBZhongPFangL, et al.
miR-183 inhibits microglia activation and expression of inflammatory factors in rats with cerebral ischemia reperfusion via NF-kappaB signaling pathway. Exp Ther Med2019;
18: 2540–2546.
57.
NiJWangXChenS, et al.
MicroRNA let-7c-5p protects against cerebral ischemia injury via mechanisms involving the inhibition of microglia activation. Brain Behav Immun2015;
49: 75–85.
58.
LaterzaOFLimLGarrett-EngelePW, et al.
Plasma MicroRNAs as sensitive and specific biomarkers of tissue injury. Clin Chem2009;
55: 1977–1983.
59.
LiSLuGWangD, et al.
MicroRNA-4443 regulates monocyte activation by targeting tumor necrosis factor receptor associated factor 4 in stroke-induced immunosuppression. Eur J Neurol2020;
27: 1625–1637.
60.
MracskoELieszAKarcherS, et al.
Differential effects of sympathetic nervous system and hypothalamic-pituitary-adrenal axis on systemic immune cells after severe experimental stroke. Brain Behav Immun2014;
41: 200–209.
61.
WongCHJenneCNLeeWY, et al.
Functional innervation of hepatic iNKT cells is immunosuppressive following stroke. Science2011;
334: 101–105.
62.
IwasakiAFoxmanEFMolonyRD.Early local immune defences in the respiratory tract. Nat Rev Immunol2017;
17: 7–20.
63.
MujalAMDelconteRBSunJC.Natural killer cells: from innate to adaptive features. Annu Rev Immunol2021;
39: 417–447.
64.
SeifertHACollierLAChapmanCB, et al.
Pro-Inflammatory interferon gamma signaling is directly associated with stroke induced neurodegeneration. J Neuroimmune Pharmacol2014;
9: 679–689.
65.
ZhaoYZhangXChenX, et al.
Neuronal injuries in cerebral infarction and ischemic stroke: from mechanisms to treatment (review). Int J Mol Med2022;
49: 15.
66.
MaoRZongNHuY, et al.
Neuronal death mechanisms and therapeutic strategy in ischemic stroke. Neurosci Bull2022;
38: 1229–1247.
67.
EndresMMoroMANolteCH, et al.
Immune pathways in etiology, acute phase, and chronic sequelae of ischemic stroke. Circ Res2022;
130: 1167–1186.
68.
FauraJBustamanteAMiró-MurF, et al.
Stroke-induced immunosuppression: implications for the prevention and prediction of post-stroke infections. J Neuroinflammation2021;
18: 127.
69.
ShiKWoodKShiFD, et al.
Stroke-induced immunosuppression and poststroke infection. Stroke Vasc Neurol2018;
3: 34–41.
70.
de JongeJCvan de BeekDLydenP, et al.
Temporal profile of pneumonia after stroke. Stroke2022;
53: 53–60.
71.
StreleckieneGInciuraiteRJuzenasS, et al.
miR-20b and miR-451a are involved in gastric carcinogenesis through the PI3K/AKT/mTOR signaling pathway: Data from gastric cancer patients, cell lines and Ins-Gas mouse model. Int J Mol Sci2020;
21: 877.
72.
TianYNanYHanL, et al.
MicroRNA miR-451 downregulates the PI3K/AKT pathway through CAB39 in human glioma. Int J Oncol2012;
40: 1105–1112.
73.
ChenJZhangXLiuX, et al.
Ginsenoside Rg1 promotes cerebral angiogenesis via the PI3K/akt/mTOR signaling pathway in ischemic mice. Eur J Pharmacol2019;
856: 172418.
74.
HouYWangKWanW, et al.
Resveratrol provides neuroprotection by regulating the JAK2/STAT3/PI3K/AKT/mTOR pathway after stroke in rats. Genes Dis2018;
5: 245–255.
75.
GuanYTMaoLLJiaJ, et al.
Postischemic administration of a potent PTEN inhibitor reduces spontaneous lung infection following experimental stroke. CNS Neurosci Ther2013;
19: 990–993.
