3-Integrin Inhibits Lipopolysaccharide-Induced Autophagy in Cardiomyocytes via the Akt Signaling Pathway

Objective: To investigate the role of β3-integrin in lipopolysaccharide (LPS)-induced autophagy in cardiomyocytes and its underlying mechanism. Methods: β3-Integrin expression in cardiomyocytes was up- or downregulated by adenovirus transfection or cyclic arginine-glycine-aspartic acid (cRGD) peptide treatment before LPS stimulation. The expression of autophagy-associated proteins (LC3-II, Beclin-1 and Bcl-2) and the activation of Akt were determined using Western blotting. Autophagosomes and autophagic vacuoles were observed using monodansylcadaverine (MDC) dye and transmission electron microscopy, respectively. Results: Downregulation of β3-integrin with cRGD peptide resulted in enhanced LC3-II and Beclin-1 and decreased Bcl-2 expression. Low Beclin-1 levels were detected after LPS stimulation in adenovirus β3-integrin-transfected cardiomyocytes. There was no significant difference in LC3-II levels between control and adenovirus β3-integrin-transfected cardiomyocytes. Enhanced accumulation of MDC dye and autophagosomes, which were inhibited by β3-integrin overexpression, were detected after LPS treatment. The increased phosphorylation of Akt after LPS stimulation was inhibited by cRGD and enhanced by β3-integrin overexpression. Furthermore, the Akt inhibitor triciribine inhibited the negative effect of β3-integrin on autophagy, as shown by LC3-II and Beclin-1 upregulation. Conclusions: β3-Integrin inhibits LPS-induced autophagy in cardiomyocytes. The inhibition of Akt signaling might be an important mechanism in this process. © 2015 S. Karger AG, Basel