M3-mAChR Stimulation Exerts Anti-apoptotic Effect Via Activating the HIF-1α/HO-1/VEGF Signaling Pathway in H9c2 Rat Ventricular Cells

The protective role of M(3)-mAChR against apoptosis has been identified previously. However, the underlying mechanisms remain unclear. This study was performed to clarify the signaling pathways of the anti-apoptotic effect mediated by activation of M(3)-mAChR in cultured cardiac H9c2 cells.Both H9c2 rat ventricular cells and H9c2 cells with stable expression of M(3)-mAChR were used.Activation of M(3)-mAChR by cabarchol produced protective effect on etoposide-induced apoptosis in H9c2 cells. Forced overexpression of M(3)-mAChR in H9c2 cells further enhanced this effect. Application of 4-diphenyl-acetoxy-N-methyl-piperidine methiodide (inhibitor of M(3)-mAChR), YC-1 [inhibitor of hypoxia-inducible factor 1, (HIF-1], or ZnPP (inhibitor of heme oxygenase-1)abrogated carbacol-induced cardioprotection, respectively. Moreover, the expression of HIF-1α, HO-1, and vascular endothelial growth factor (VEGF) were enhanced after the activation of M3-mAChR, and the induction of HO-1 and VEGF was reversed by HIF-1α inhibitor YC-1.These findings indicated that M(3)-mAChR upregulates HO-1 and VEGF expression likely through induction of HIF-1α, which at least partly underlies the cytoprotection of M(3)-mAChR activation in H9c2 cells.