Up regulation of isoleucyl-tRNA synthetase promotes vascular smooth muscle cells dysfunction via p38 MAPK/PI3K signaling pathways.

ABSTRACT

The pathogenesis of abdominal aortic aneurysm remains unclear. The aim of the present study was to establish whether isoleucyl-tRNA synthetase (Iars) regulates the differentiation and apoptosis of vascular smooth muscle cells (VSMCs) during the development of abdominal aortic aneurysm (AAA). In addition, the contribution of various signaling pathways towards this process was ascertained. The study demonstrated that the expression of Iars, p-p38, osteopontin (OPN) and Bcl-2-associated X protein (Bax) clearly increased, while levels of p-PI3K and smooth muscle 22 alpha (SM22α) decreased significantly in AAA tissues. Inhibition of Iars significantly reduced the incidence of angiotensin II (AngII)-induced AAA in mice, coincident with decreased activity of the p38 MAPK pathway and increased PI3K pathway activity. AngII-induced phenotypic switching and apoptosis of VSMCs decreased following the inhibition of Iars in vitro. Upregulation of the IARS gene induced phenotypic switching and apoptosis in VSMCs in addition to increased p38 MAPK pathway activation and reduced PI3K pathway activation. Following pretreatment with an activator of the PI3K pathway, expression of Iars and the phenotypic markers of VSMCs were not affected, while apoptosis of VSMCs decreased. Similarly, inhibition of the p38 MAPK pathway in VSMCs did not affect the expression of Iars or the degree of cell apoptosis, but reduced phenotypic switching was observed. Conclusively, upregulation of Iars regulates the phenotypic switching and apoptosis of VSMCs. Targeting Iars may be a promising strategy to prevent abdominal aortic aneurysm.