Calcitonin Gene-related Peptide Inhibits the Cardiac Fibroblasts Senescence in Cardiac Fibrosis Via Up-regulating Klotho Expression

It has been documented cardiac fibroblasts as the predominant cell population undergoing senescence in heart. Calcitonin gene-related peptide (CGRP) exhibits a wide range of cardiovascular protective effects. Whether CGRP protects against cardiac fibroblasts senescence in cardiac fibrosis remains unknown. Here, we detected the down-regulation of CGRP concomitant with senescence in fibrotic myocardium, both hypertension- induced left ventricular fibrosis in SHR rats and hypoxia-induced right ventricular fibrosis in pulmonary artery hypertension rats. Exogenous CGRP inhibited the cardiac fibroblasts senescence and senescence-associated secretory phenotype (SASP) induced by TGF-β1, which was abolished by CGRP, a selective CGRP receptor antagonist. Moreover, the expression of klotho, an anti-senescence protein, was down-regulated in fibrotic myocardium, and CGRP up-regulated the klotho expression in TGF-β1-treated cardiac fibroblasts. Klotho knockdown by siRNA reversed the inhibition of CGRP on senescence and SASP induced by TGF-β1 in cardiac fibroblasts. These results suggested that CGRP inhibited the cardiac fibroblasts senescence and SASP in cardiac fibrosis via up-regulating klotho expression.