Abstract
AIM: Endoplasmic reticulum stress (ERS) and inflammation participate in cardiac fibrosis. Importantly, a novel paracrine/autocrine peptide intermedin(1-53) (IMD(1-53)) in the heart inhibits myocardial fibrosis in rats. However, the mechanisms are yet to be fully elucidated. METHODS: Myocardial fibrosis in apolipoprotein E-deficient (ApoE -/-) mice and neonatal rat cardiac fibroblasts (CFs) were induced using homocysteine (Hcy). RESULTS: IMD(1-53) inhibited myocardial fibrosis in vivo and in vitro. Picrosirius red staining showed that IMD(1-53) reduced myocardial interstitial collagen deposition in ApoE-/- mice treated with Hcy and decreased the expression of myocardial collagen I and III, which was further verified in rat CFs. IMD(1-53) attenuated myocardial hypertrophy, as shown by cardiomyocyte cross-sectional area, ratio of heart weight to body weight, and mRNA levels of atrial natriuretic peptide and brain natriuretic peptide. IMD(1-53) inhibited the upregulation of ERS hallmarkers such as glucose-regulated protein 78 (GRP78), GRP94, activating transcription factor 6 (ATF6), ATF4, inositol-requiring enzyme 1α, spliced-X-box-binding protein-1, protein kinase receptor-like ER kinase, and eukaryotic translation initiation factor 2α in mouse myocardium and rat CFs treated with Hcy. In addition, IMD(1-53) decreased the production of inflammatory factors such as tumor necrosis factor-α, monocyte chemotactic protein-1, interleukin-6 (IL-6), and IL-1β in the mouse myocardium and rat CFs treated with Hcy. Concurrently, IMD(1-53) ameliorated the expression of nuclear factor-κB, transforming growth factor-β1, and c-Jun N-terminal kinase in the mouse myocardium and rat CFs treated with Hcy. CONCLUSIONS: IMD potentially protects against myocardial fibrosis induced by Hcy in ApoE-/- mice, possibly via attenuating myocardial ERS and inflammation.