Selective Inhibition of Protein Kinase C β2 Attenuates Inducible Nitric Oxide Synthase-Mediated Cardiovascular Abnormalities in Streptozotocin-Induced Diabetic Rats

OBJECTIVE-Impaired cardiovascular function in diabetes is partially attributed to pathological overexpression of inducible nitric oxide synthase (iNOS) in cardiovascular tissues. We examined whether the hyperglycemia-induced increased expression of iNOS is protein kinase C-beta(2) (PKC beta(2)) dependent and whether selective inhibition of PKC beta reduces iNOS expression and corrects abnormal hemodynamic function in streptozotocin (STZ)-induced diabetic rats. RESEARCH DESIGN AND METHODS-Cardiomyocytes and aortic vascular smooth muscle cells (VSMC) from nondiabetic rats were cultured in low (5.5 mmol/l) or high (25 mmol/l) glucose or mannitol (19.5 mmol/l mannitol + 5.5 mmol/l glucose) conditions in the presence of a selective PKC beta inhibitor, LY333531 (20 nmol/l). Further, the in vivo effects of PKC beta inhibition on iNOS-mediated cardiovascular abnormalities were tested in STZ-induced diabetic rats. RESULTS-Exposure of cardiomyocytes to high glucose activated PKC beta(2) and increased iNOS expression that was prevented by LY333531. Similarly, treatment of VSMC with LY333531 prevented high glucose-induced activation of nuclear factor kappa B, extracellular signal-related kinase, and iNOS overexpression. Suppression of PKC beta(2) expression by small interference RNA decreased high-glucose-induced nuclear factor kappa B and extracellular signal-related kinase activation and iNOS expression in VSMC. Administration of LY333531 (1 mg/kg/day) decreased iNOS expression and formation of peroxynitrite in the heart and superior mesenteric arteries and corrected the cardiovascular abnormalities in STZ-induced diabetic rats, an action that was also observed with a selective iNOS inhibitor, L-NIL. CONCLUSIONS-Collectively, these results suggest that inhibition of PKC beta(2) may be a useful approach for correcting abnormal hemodynamics in diabetes by preventing iNOS mediated nitrosative stress. Diabetes 58:2355-2364, 2009