Abstract: Objective To investigate whether Calcitonin Gene-Related Peptide (CGRP) plays a protective role in cardiomyocytes against hypoxia-induced apoptosis via an NO-mediated pathway. Methods H9c2 cardiac cells were exposed to hypoxia for 2 h to establish a model of myocardial hypoxic-ischemic injury. The cells were pretreated with either CGRP or an NOS inhibitor (L-NAME) before being exposed to hypoxia for 30 min. Cell viability was analyzed using a cell counter kit 8 (CCK-8). The expression levels of several apoptosis proteins (p53, caspase-3, cytochrome C) and nitric oxide synthase (NOS) were detected via a Western blot assay. An NO kit was used to evaluate the production of NO. Results Our studies demonstrated that pretreatment of H9c2 cardiac cells with CGRP for 30 min prior to exposure to hypoxia markedly improved cell viability; the same effect was observed following pretreatment with the NOS inhibitor, L-NAME. Additionally, CGRP enhanced the expression of both eNOS and p-eNOS; the application of both L-NAME and CGRP attenuated the hypoxia-induced expression of iNOS and enhanced the hypoxia-mediated decrease in NO. Furthermore, CGRP significantly decreased the hypoxia-induced overexpression of several apoptotic proteins, p53, caspase-3 and cyto C. Interestingly, the expression levels of cell death, NOS and apoptotic factors were slightly attenuated in the presence of L-NAME and CGRP co-working 2 hours of acute hypoxia. Conclusion CGRP protects cardiomyocytes from hypoxia-induced apoptosis via the modulation of the production of NO.

Key words: hypoxia, apoptosis, calcitonin gene-related peptide, nitric oxide, H9c2