Myofibroblast apoptosis is essential for normal resolution of wound repair, including cardiac infarction repair. Impaired cardiac myofibroblast (CMF) apoptosis is associated with excessive extracellular matrix (ECM) deposition, which could be responsible for pathological cardiac fibrosis. Conventionally, angiotensin II (Ang II), a soluble peptide, is implicated in fibrogenesis because it induces cardiac fibroblast (CFb) proliferation, differentiation, and collagen synthesis. However, the role of Ang II in regulation of CMF survival and apoptosis has not been fully clarified. In this report, we cultured neonatal rat CFbs, which transform into CMFs after passage 3 (6-8 days), and investigated the effects of Ang II on CMFs challenged by TNF-α combined with cycloheximide and the underlying mechanisms. Here, we show that Ang II rapidly activates MAPKs but not AKT in CMFs and confers apoptosis resistance, as evidenced by the inhibition of caspase-3 cleavage, early apoptotic cells and late apoptotic cells. This inhibitory effect of Ang II was reversed by blockade of AT1 or inactivation of ERK1/2 or RSK1 but not AT2, indicating that activation of the prosurvival AT1/ERK1/2/RSK1 signaling pathway mediates apoptosis resistance. TGF-β, a latent fibrotic factor, was found to have no relation to Ang II-induced apoptosis resistance in our study. Furthermore, Ang II-mediated apoptosis resistance, which was conferred by activation of the AT1/ERK1/2/RSK1 signaling pathway, was also confirmed in human adult ventricular cardiac myofibroblasts. Collectively, our findings suggest a novel profibrotic mechanism of Ang II in which it promotes myofibroblast resistance to apoptosis in addition to classical mechanisms, providing a potential novel therapeutic approach by targeting prosurvival signaling pathways. © 2018 IUBMB Life, 71(1):261-276, 2019.
Keywords: ERK1/2; angiotensin II; apoptosis; cardiac fibrosis; myofibroblast.
© 2018 International Union of Biochemistry and Molecular Biology.