Protection of Myocytes From Hypoxia-Reoxygenation Injury by Nitric Oxide Is Mediated by Modulation of Transforming Growth

Background—Reoxygenation injury is a result of several complex events, including release of reactive oxygen species, protein kinase C (PKC) activation, and altered expression of transforming growth factor1 (TGF1). Nitric oxide (NO) generally protects tissues from reperfusion injury. Methods and Results—We examined the modulation of TGF1 expression and activity and PKC activation in cultured rat heart myocytes exposed to a brief period of hypoxia-reoxygenation (H-R) by NO donor 3-morpholino-sydnonimine (SIN-1). H-R resulted in an increased expression of total TGF1 (mRNA and protein) but a decrease in the release of active TGF1. Myocyte PKCprotein level was not altered by H-R, but its phosphorylation was augmented. Pretreatment of myocytes with SIN-1 diminished myocyte injury quantified as lactate dehydrogenase release. Simultaneously, release of active TGF1 increased and total TGF1 expression decreased (all P 0.05 versus H-R alone). PKCphosphorylation increased further in cells treated with SIN-1. The effects of SIN-1 were blocked by the NO scavenger phenyl-tetramethyl-imidazoline-oxyl-oxide as well as by the PKC inhibitor staurosporine. To examine if another NO donor would have a similar effect, cardiomyocytes were treated with nitroglycerin before H-R. With nitroglycerin treatment, similar to SIN-1 treatment, myocyte injury was diminished, TGF1 release increased, and total TGF1 expression decreased. Conclusions—These observations suggest modulation of TGF1 expression as a novel mechanism of salutary effect of NO donors. PKCactivation may play an important role in the protective effect of NO against H-R injury. (Circulation. 2002;105:2206-2211.)