Dose-dependent actions of curcumin in experimentally induced myocardial necrosis: a biochemical, histopathological, and electron microscopic evidence.

Curcumin, an active component of turmeric, is a well-known antioxidant due to its reactive oxygen species (ROS) scavenging property. However, some in vitro studies have suggested that curcumin induces generation of ROS at higher doses and thus exerts pro-oxidant effect. We demonstrate, for the first time, the dose-dependent effects of curcumin in isoprenaline-induced model of myocardial necrosis in rats. The animals were assigned to control, isoprenaline and three curcumin treatment groups. Curcumin (100, 200, and 400 mg/kg) and vehicle (dimethyl sulfoxide) were administrated orally for 15 days and isoprenaline (85 mg/kg, s.c.) was given to curcumin treated and isoprenaline group on 13th and 14th day, respectively. Thereafter, on 15th day, the animals were sacrificed for biochemical analysis along with histopathological and ultrastructural examination. There was an increase in glutathione, superoxide dismutase (SOD), creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) levels, decrease in thiobarbituric acid reactive substances (TBARS), and preservation of myocardial architecture in the curcumin (100 and 200 mg/kg) treated groups. However, at 400 mg/kg dose there was ineffectual protection against isoprenaline-induced myocardial damage. Instead, there was significant lipid peroxidation as evident by increased levels of TBARS (93.87 +/- 9.93, p < 0.0001) and decrease in CK-MB (206.32 +/- 13.54, p < 0.0001) and LDH (134.26 +/- 9.13, p < 0.01) as compared to the two lower doses. Hence, it can be concluded that curcumin augments endogenous antioxidant system at lower doses but mediates ROS induction at higher concentration leading to myocardial damage.