Tramadol has been used by millions of patients as an analgesic drug to relief the severe pain caused by cancers and other diseases. The current study aimed to investigate the protective effects of antioxidants (garlic and selenium) against the toxic effects of tramadol on semen characteristics, steroid hormones, the protein expressions of different cytochrome P450 isozymes [CYP 21A2, CYP 19, and 11A1], and on antioxidant enzyme activities in testes of rabbits. Western immunoblotting, spectrophotometric, and histological methods were used in this study. Tramadol (1.5 mg/kg body weight) was administered orally to male rabbits for up to three months (three times/week), and after pretreatment of rabbits with garlic (800 mg/kg) and/or selenium (1 mg/kg body weight) by 2 h. The present study showed that motilities, semen volumes, morphologies, sperm counts, testosterone, and estrogen levels were significantly decreased after 4, 8, and 12 weeks of tramadol treatment. In addition, the protein expressions of CYP 21A2, CYP 19, and 11A1 were down-regulated in the testes of the tramadol-treated rabbits. On the other hand, pretreatment of rabbits with garlic, selenium, and/or garlic-selenium for 2 h before administration of tramadol restored the downregulated CYP 21A2 and 11A1 to their normal levels after 12 weeks of tramadol treatment. Activities of antioxidant enzymes including glutathione reductase, glutathione peroxidase, glutathione S-transferase, catalase, superoxide dismutase, and levels of glutathione were inhibited in the testes of tramadol-treated rabbits. On the other hand, free radical levels were significantly increased in the testes of tramadol-treated rabbits for 12 weeks. Interestingly, such changes in the activities of antioxidant enzymes as well as free radical levels caused by tramadol were restored to their normal levels in the rabbits pretreated with either selenium, garlic, and/or their combination. Histopathological investigations showed that tramadol caused substantial vacuolization with the presence of damaged immature spermatozoid in the testes. However, selenium and garlic treatments showed an increase in healthy sperm production with normal mitotic and meiotic divisions. The present study illustrated for the first time the mechanisms of low steroid hormone levels in the testes of tramadol-treated rabbits which could be due to the downregulation of CYPs proteins, induction of oxidative stress, and inhibition of antioxidant enzyme activities. In addition, the present data showed that such toxic effects of tramadol were attenuated and restored to their normal levels after pretreatment of rabbits with garlic, selenium, and/or their combination. This finding may pave the way for a new approach to reducing the toxicity of tramadol.
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