Abstract
Recent progress suggests that caveolins are cardiac protective molecules in regulating apoptotic cell death during myocardial ischemia-reperfusion injury. To understand the mechanisms of caveolins in cardiac protection, we investigated the expressions of caveolin-1(cav-1), caveolin-2 (cav-2) and caveolin-3 (cav-3) proteins in the isolated cultured hypoxia-reoxygenated cardiomyocytes. Neonatal rat cardiomyocytes were subjected to 4 h hypoxia and 24 h reoxygenation by exposed to 1% [O2] and replaced with normal air respectively. The expression of cav-3, instead of cav-1 and cav-2, was down-regulated by hypoxiareoxygenation. Pre-treatments of superoxide dismutase and catalase (SOD/CAT) or peroxynitrite decomposition catalyst FeTMPyP prevented the down-regulation of cav-3. We then investigated the effects of extraneous free radicals on regulating the expression of cav-3 by incubating with xanthine/xanthine oxidase (X/XO), H2O2, 1-[N, N-di-(2-aminoethyl) amino] diazen-1-ium-1, 2-diolate (DETA/NO, NO donor) or 3-morpholinosydnonimine (SIN-1, peroxynitrite donor) respectively. Treatments of X/XO, H2O2, DETA/NO and SIN-1 significantly induced the down-regulation of cav-3 protein. The results indicate that the productions of free radicals contribute to the down-regulation of cav-3 protein in the hypoxiareoxgenated cardiomyocytes. Moreover, our data showed that cav-3 peptide significantly enhanced the expression and the activity of SOD, inhibited O2 .- production and caspase 3 activity, and reduced the rates of early and late apoptotic cell death, whereas cav-1 peptide had no effect on SOD, but slightly reduced O2 .production and decreased the rates of apoptotic cell death in the hypoxia-reoxygenated cardiomyocytes. Taken together, we conclude that caveolin-1 and caveolin-3 could ameliorate free radicals-induced oxidative injury via diverse mechanisms in hypoxia-reoxygenated cardiomyocytes.
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