Calcitonin gene-related peptide partly protects cultured smooth muscle cells from apoptosis induced by an oxidative stress via activation of ERK1/2 MAPK.

Oxidative stress induced by a glucose/glucose oxidase (G/GO) generator system dose-dependently decreased the viability of cultured vascular smooth muscle cells (VSMC) as estimated by MTT assay. Cell death was induced in 40% of cells exposed to 0.2 IU/ml of the free radical generating mixture. Annexin-V labeling, Hoechst staining together with DNA laddering demonstrated that apoptosis was responsible for this cell loss. Pretreatment of the cells with 10(-8) M calcitonin gene-related peptide (CGRP) significantly attenuated the damaging effect of the oxidative stress. Indeed, cell viability was estimated to be 80% in CGRP-treated group, instead of 60% in absence of CGRP treatment. This protective effect of CGRP was antagonized by 8-37 CGRP, an antagonist of CGRP-1 receptors, whereas it was not reproduced by amylin, a CGRP analogue. As indicated by the reduction in Hoechst staining and in DNA laddering, CGRP prevented the onset of apoptosis. We also demonstrated that the peptide significantly up-regulated the activation of ERK1/2 and P38 kinases. Inhibitors of the kinases prevented the protective effect of CGRP. We conclude that CGRP antagonizes oxidative stress-induced apoptosis by up-regulating MAP kinase activation and that activation of these kinases was necessary to protection.