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

Abstract

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-β₂ (PKCβ₂) dependent and whether selective inhibition of PKCβ 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 PKCβ inhibitor, LY333531 (20 nmol/l). Further, the in vivo effects of PKCβ inhibition on iNOS-mediated cardiovascular abnormalities were tested in STZ-induced diabetic rats.

RESULTS Exposure of cardiomyocytes to high glucose activated PKCβ₂ and increased iNOS expression that was prevented by LY333531. Similarly, treatment of VSMC with LY333531 prevented high glucose–induced activation of nuclear factor κB, extracellular signal–related kinase, and iNOS overexpression. Suppression of PKCβ₂ expression by small interference RNA decreased high-glucose–induced nuclear factor κB 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 PKCβ₂ may be a useful approach for correcting abnormal hemodynamics in diabetes by preventing iNOS mediated nitrosative stress.