Arnab Kumar Ghosh

Protective effect of aqueous Curry leaf (Murraya koenigii) extract against cadmium-induced oxidative stress in rat heart

Treatment of rats with a low dose of cadmium chloride caused a significant damage in the rat cardiac tissue indicated by the increase in the level of serum glutamate oxaloacetate transaminase and lactate dehydrogenase1 activities. Histological studies confirmed the damage due to cadmium. That cadmium-induced tissue damage was caused due to oxidative stress was evident from the changes observed in the levels of lipid peroxidation and reduced glutathione, the protein carbonyl content, and the alterations in the activities of cardiac antioxidant and pro-oxidant enzymes. Treatment of rats with cadmium also caused alterations in the activities of mitochondrial Krebs cycle as well as respiratory chain enzymes. All these changes were ameliorated when the rats were pre-treated with an aqueous extract of Curry leaf (Murraya koenigii). The studies indicated that the aqueous extract of Curry leaf protects the rat cardiac tissue against cadmium-induced oxidative stress possibly through its antioxidant activity. As curry leaf is consumed by people as part of their diet in India and South-East Asian and some European countries as well, and, as it has no reported side-effects, the results seem to have relevance at places where humans are exposed to cadmium environmentally or occupationally.

High fat diet aggravates arsenic induced oxidative stress in rat heart and liver

Arsenic is a well known global groundwater contaminant. Exposure of human body to arsenic causes various hazardous effects via oxidative stress. Nutrition is an important susceptible factor which can affect arsenic toxicity by several plausible mechanisms. Development of modern civilization led to alteration in the lifestyle as well as food habits of the people both in urban and rural areas which led to increased use of junk food containing high level of fat. The present study was aimed at investigating the effect of high fat diet on heart and liver tissues of rats when they were co-treated with arsenic. This study was established by elucidating heart weight to body weight ratio as well as analysis of the various functional markers, oxidative stress biomarkers and also the activity of the antioxidant enzymes. Histological analysis confirmed the biochemical investigations. From this study it can be concluded that high fat diet increased arsenic induced oxidative stress.

Melatonin protects against isoproterenol-induced alterations in cardiac mitochondrial energy-metabolizing enzymes, apoptotic proteins, and assists in complete recovery from myocardial injury in rats.

Abstract:  The present study was undertaken to explore the protective effect of melatonin against isoproterenol bitartrate (ISO)‐induced rat myocardial injury and to test whether melatonin has a role in preventing myocardial injury and recovery when the ISO‐induced stress is withdrawn. Treatment for rats with ISO altered the activities of some of the key mitochondrial enzymes related to energy metabolism, the levels of some stress proteins, and the proteins related to apoptosis. These changes were found to be ameliorated when the animals were pretreated with melatonin at a dose of 10 mg/kg BW, i.p. In addition to its ability to reduce ISO‐induced mitochondrial dysfunction, we also studied the role of melatonin in the recovery of the cardiac tissue after ISO‐induced damage. Continuation of melatonin treatment in rats after the withdrawal of ISO treatment was found to reduce the activities of cardiac injury biomarkers including serum glutamate oxaloacetate transaminase (SGOT), lactate dehydrogenase (LDH), and cardio‐specific LDH1 to control levels. The levels of tissue lipid peroxidation and reduced glutathione were also brought back to that seen in control animals by continued melatonin treatment. Continuation of melatonin treatment in post‐ISO treatment period was also found to improve cardiac tissue morphology and heart function. Thus, the findings indicate melatonin’s ability to provide cardio protection at a low pharmacological dose and its role in the recovery process. Melatonin, a molecule with very low or no toxicity may be considered as a therapeutic for the treatment for ischemic heart disease.

Mechanisms of isoproterenol-induced cardiac mitochondrial damage: protective actions of melatonin.

Mitochondrial dysfunction due to oxidative damage is the key feature of several diseases. We have earlier reported mitochondrial damage resulting from the generation of oxidative stress as a major pathophysiological effect of isoproterenol (ISO)‐induced myocardial ischemia in rats. That melatonin is an antioxidant that ameliorates oxidative stress in experimental animals as well as in humans is well established. We previously demonstrated that melatonin provides cardioprotection against ISO‐induced myocardial injury as a result of its antioxidant properties. The mechanism of ISO‐induced cardiac mitochondrial damage and protection by melatonin, however, remains to be elucidated in vitro. In this study, we provide evidence that ISO causes dysfunction of isolated goat heart mitochondria. Incubation of cardiac mitochondria with increasing concentrations of ISO decreased mitochondrial succinate dehydrogenase (SDH) activity, which plays a pivotal role in mitochondrial bioenergetics, as well as altered the activities of other key enzymes of the Krebs cycle and the respiratory chain. Co‐incubation of ISO‐challenged mitochondria with melatonin prevented the alterations in enzyme activity. That these changes in mitochondrial energy metabolism were due to the perpetration of oxidative stress by ISO was evident from the increased levels of lipid peroxidation and decreased reduced glutathione/oxidized glutathione ratio. ISO‐induced oxidative stress also altered mitochondrial redox potential and brought about changes in the activity of the antioxidant enzymes manganese superoxide dismutase and glutathione peroxidase, eventually leading to alterations in total ATPase activity and membrane potential. Melatonin ameliorated these changes likely through its antioxidant abilities suggesting a possible mechanism of cardioprotection by this indole against ISO‐induced myocardial injury.