Endoplasmic Reticulum Stress Regulates Cardiomyocyte Apoptosis in Myocardial Fibrosis Development via PERK-Mediated Autophagy.

Endoplasmic reticulum stress (ERS) is involved in a variety of diseases. Recently, it was found that ERS induces not only apoptosis but also autophagy. Previous studies showed that inhibition of autophagy alleviates cell injury. The purpose of our study was to investigate the involvement of the R-like ER kinase (PERK) in ERS-induced autophagy in H9c2 cardiomyoblasts. To address this aim, therefore, H9c2 cells were treated with PERK agonist and inhibitor after establishment of rapamycin-induced ERS models in H9c2 cardiomyoblasts. Transmission electron microscopy and immunofluorescence staining were used to detect degrees of ERS-induced autophagy, apoptosis and myocardial fibrosis. Western blotting was employed to detect the levels of total and phosphorylated PERK, light chain 3 (LC3), P62, Caspase3, Bcl2 and Bax. Immunofluorescence staining was used to assess α-SMA density. TGF-β induced H9c2 cardiomyoblasts time-dependently upregulated col I, col III, FN, and LC3 expressions, PERK phosphorylation and α-SMA density, and downregulated P62 level compared with control cells. Treatment with PERK agonist and inhibitor respectively increased and decreased LC3 expression, conversely in P62 level, which is consistent with effect of ERS agonists and inhibitors. And a PERK inhibitor upregulated the expressions of Caspase3 and Bax, and downregulated Bcl2 level, which developed H9c2 cardiomyoblasts. Moreover, siRNA-mediated knockdown of PERK reduced ERS mediated autophagy activity and increased cells apoptosis. On the other hand, elevated autophagy activity could downregulated PERK level. Our finding showed that PERK activity mediates upregulation of ERS-induced autophagy and regulation of cardiomyocyte apoptosis in H9c2 cardiomyoblasts.