Valsartan ameliorates high glucose-induced peritoneal fibrosis by blocking mTORC1 signaling

Abstract

Our previous study demonstrated that the mammalian target of rapamycin complex 1 (mTORC1) pathway is activated in peritoneal fibrosis under high glucose condition. This study aimed to investigate whether valsartan inhibits high glucose-induced peritoneal fibrosis via decreasing the activity of the mTORC1 pathway. We used high glucose peritoneal dialysis solution in a mouse peritoneal dialysis model to induce peritoneal fibrosis in vivo and high glucose in human peritoneal mesothelial cells (HPMCs) to stimulate extracellular matrix accumulation in vitro. After injections of peritoneal dialysis solution containing 4.25% glucose for four weeks, mice showed typical features of peritoneal fibrosis, including markedly increased peritoneal thickness, excessive matrix deposition, increased peritoneal permeability, and higher expression of extracellular matrix proteins, such as α-smooth muscle actin (α-SMA) and collagen I. Oral gavage of valsartan significantly ameliorated these pathological changes at both week 6 and week 8. These effects of valsartan were closely correlated with a decrease in the activation of the mTORC1 signal, which was mediated by the downregulation of the protein expression of phosphorylated (p)-mTOR, p-eukaryotic initiation factor 4E-binding protein 1, and p-p70 S6 kinase 1. Further research showed that the protein expression of mTORC1 signal was positively correlated with the expression of both α-SMA and collagen I in the peritoneum. In vitro, high glucose increased the protein expression of α-SMA and collagen I in a dose-dependent manner, while valsartan significantly inhibited high glucose-induced extracellular matrix accumulation in HPMCs. The effect was also accompanied by a decrease in the activation of the mTORC1 signal. Furthermore, the mTOR agonist MHY1485 reversed the downregulation of extracellular matrix components in HPMCs, even in the presence of valsartan. We conclude that valsartan exerts a protective effect against high glucose-induced peritoneal fibrosis via suppressing the activity of the mTORC1 pathway.

Impact statement

Our study provided new insight into the mechanism underlying the preservation of the peritoneum by valsartan. The results demonstrated that the mice receiving chronic high glucose (HG) peritoneal dialysis solution infusion showed a typical feature of peritoneal fibrosis (PF), as well as higher expression of α-smooth muscle actin (α-SMA) and collagen I. In vitro, HG increased the protein expression of α-SMA and collagen I in a dose-dependent manner, while valsartan significantly ameliorated these pathological changes. Interestingly, there was a parallel decrease in the activity of mammalian target of rapamycin complex 1 (mTORC1) and the protein expression levels of α-SMA and collagen I upon treatment with valsartan in vivo and in vitro. Moreover, the mTOR agonist MHY1485 reversed the downregulation of α-SMA and collagen I in vitro, even in the presence of valsartan. Altogether, our findings reported for the first time that valsartan exerts a protective effect against HG-induced PF by inhibiting the activity of the mTORC1 pathway.