Thymoquinone dose-dependently attenuates myocardial injury induced by isoproterenol in rats via integrated modulation of oxidative stress, inflammation, apoptosis, autophagy and fibrosis

Abstract As rats develop myocardial infarction (MI) like lesions when injected with large doses of isoproterenol (ISO), this investigation was designed to evaluate the effects of low and high doses of thymoquinone (TQ) on ISO-induced myocardial injury in rats. Adult male rats were divided into control, TQ20 (20 mg/kg/day), TQ50 (50 mg/kg/day), and ISO, TQ20 + ISO and TQ50 + ISO groups. In these rats, biochemical, immunobiochemical and histopathological studies were carried out to evaluate myocardial oxidative stress, inflammation, apoptosis, fibrosis and autophagy and serum cardiac biomarkers. The results showed that TQ pretreatment in ISO-administered rats produced a dose-dependent significant reduction of the myocardial infarct size, markedly reduced the ISO-induced elevation in serum cardiac markers and demonstrated several other important findings related to the cardioprotective efficacy of TQ. First, this study is the first reported research work showing that TQ treatment could increase the myocardial reduced glutathione baseline level, adding an indirect antioxidant effect to its known direct free radical scavenging effect. Second, pretreatment with TQ significantly reduced the markers of myocardial oxidative stress, inflammation, fibrosis and apoptosis. Third, TQ acted as an autophagy enhancer ameliorating myocardial cell damage and dysfunction. Thus, the changes associated with ISO-induced myocardial injury were ameliorated with TQ pretreatment. Additionally, the extent of observed improvement was significantly greater with the high TQ dose than with the low dose use. These findings raise the possibility that TQ may serve as a promising prophylactic cardioprotective therapy for patients who are at risk of developing myocardial injury as in cases of MI.