Azelnidipine prevents cardiac dysfunction in streptozotocin-diabetic rats by reducing intracellular calcium accumulation, oxidative stress and apoptosis

BACKGROUND: Numerous evidences suggest that diabetic heart is characterized by compromised ventricular contraction and prolonged relaxation attributable to multiple causative factors including calcium accumulation, oxidative stress and apoptosis. Therapeutic interventions to prevent calcium accumulation and oxidative stress could be therefore helpful in improving the cardiac function under diabetic condition. METHODS: This study was designed to examine the effect of long-acting calcium channel blocker (CCB), Azelnidipine (AZL) on contractile dysfunction, intracellular calcium (Ca(2+)) cycling proteins, stress-activated signaling molecules and apoptosis on cardiomyocytes in diabetes. Adult male Wistar rats were made diabetic by a single intraperitoneal (IP) injection of streptozotocin (STZ). Contractile functions were traced from live diabetic rats to isolated individual cardiomyocytes including peak shortening (PS), time-to-PS (TPS), time-to-relengthening (TR(90)), maximal velocity of shortening/relengthening (± dL/dt) and intracellular Ca(2+ )fluorescence. RESULTS: Diabetic heart showed significantly depressed PS, ± dL/dt, prolonged TPS, TR(90 )and intracellular Ca(2+ )clearing and showed an elevated resting intracellular Ca(2+). AZL itself exhibited little effect on myocyte mechanics but it significantly alleviated STZ-induced myocyte contractile dysfunction. Diabetes increased the levels of superoxide, enhanced expression of the cardiac damage markers like troponin I, p67(phox )NADPH oxidase subunit, restored the levels of the mitochondrial superoxide dismutase (Mn-SOD), calcium regulatory proteins RyR2 and SERCA2a, and suppressed the levels of the anti-apoptotic Bcl-2 protein. All of these STZ-induced alterations were reconciled by AZL treatment. CONCLUSION: Collectively, the data suggest beneficial effect of AZL in diabetic cardiomyopathy via altering intracellular Ca(2+ )handling proteins and preventing apoptosis by its antioxidant property.