Melatonin and aqueous curry leaf extract in combination protects against lead induced oxidative stress mediated injury to rat heart: a new approach

Objective(s): The objective(s) of the present study was to investigate whether a combination of melatonin and aqueous curry leaf extract is capable of providing protection against lead acetate induced oxidative stress mediated injury to cardiac tissue of experimental rats. Methods: Male Wistar rats were used as an animal model for the present study. After acclimatization to laboratory condition, in the first set of experiments rats were divided in to different groups. In the second, rats were divided in to four groups, i.e., control, positive control, lead acetate treated and melatonin + curry leaf extract in combination protected. Rats were treated intraperitoneally (i.p.) with lead acetate (15 mg / kg body weight) for a period of seven consecutive days. Rats of the protected group were pre-treated with melatonin also for seven days. The control rats were treated with vehicle only while the positive control rats were treated with melatonin + aqueous curry leaf extract only. After the treatment period, rats were sacrificed; blood and cardiac tissue collected and processed for analysis. Results: Treatment of rats with lead acetate caused accumulation of lead in the cardiac tissue and alterations in the biomarkers of organ damage and oxidative stress. It caused deteriorative changes to the cardiac tissue morphology and collagen content which were evaluated using light microscopy, electron microscopy and confocal microscopy. Involvement of oxidative stress is evident from the alterations in the level of lipid peroxidation and protein carbonyl content, activities of the antioxidant as well as pro-oxidant enzymes and some of the enzymes of the citric acid cycle and Electron Transport Chain (ETC) following lead acetate treatment. All changes were protected when the rats were pre-treated (fed orally) with melatonin (10 mg / kg body weight) and aqueous extract of curry leaves (50 mg/kg body weight) in combination for seven days. Conclusion: The results of the current studies indicate protective effect of the combination of melatonin (a natural antioxidant in pure form) and the aqueous extract of curry leaves to mitigate lead acetate-induced oxidative stress in experimental rats possibly through their synergistic antioxidant mechanism(s) .This study opens up avenues for development of an effective drug formulation against lead induced oxidative stress mediated cardiac damage in people who get environmentally or occupationally exposed to lead.