TGF-beta(1) modulates NOS expression and phosphorylation of Akt/PKB in ratmyocytes exposed to hypoxia-reoxygenation

Myocardial hypoxia-reoxygenation (H-R) is associated with upregulation of i nducible nitric oxide synthase (iNOS), decrease in endothelial NOS (eNOS), and increase in protein kinase B (PYB). Previous work also shows that trans forming growth factor-beta (1) (TGF-beta (1)) can attenuate myocardial inju ry induced by H-R. We examined the modulation of NOS and PKB expression in response to H-R by TGF- beta (1). Myocytes from Sprague-Dawley rat hearts w ere cultured and exposed to hypoxia (95% N-2-5% CO2, PO2 similar to 30 mmHg ) for 24 h and reoxygenation (95% air-5% CO2) for 3 h. Myocytes were then e xamined for lactate dehydrogenase (LDH) release, iNOS activity (conversion Of L-[H-3]arginine to L-[H-3]citrulline), iNOS and eNOS expression, and PKB phosphorylation. H-R alone resulted in myocyte injury, upregulation of iNO S activity and expression, decrease in eNOS expression, and increase in PKB phosphorylation (all P < 0.05 vs. cells cultured in normoxic conditions). Treatment of myocytes with TGF-beta (1) (1 ng/ml) resulted in a reduction i n LDH release, attenuation of the alterations in NOS expression (both iNOS and eNOS), and PKB phosphorylation in response to H-R (all P < 0.05 vs. H-R alone). These observations suggest that TGF-beta (1) decreases H-R injury and attenuates alterations in NOS and PKB phosphorylation in myocytes expos ed to H-R.