Ameliorative Effect of Melatonin Against Reproductive Toxicity of Tramadol in Rats via the Regulation of Oxidative Stress, Mitochondrial Dysfunction, and Apoptosis-related Gene Expression Signaling Pathway

BACKGROUND: The aim of the present study was to investigate the protective properties of melatonin (MT) against oxidative stress, mitochondrial dysfunction, and apoptosis induced by tramadol-reproductive toxicity in male rats. METHODS: The rats were divided into the 7 groups of control, melatonin (1.5 mg/kg), tramadol (50 mg/kg), and melatonin (1, 1.5 and 2.5 mg/kg) administered 30 minutes before tramadol and vitamin C group (100 mg/kg). All injections were performed intraperitoneally. After administration for 3 consecutive weeks, the animals were killed and testis tissues were used for assessment of oxidative stress markers including lipid peroxidation (LPO), glutathione (GSH) content and protein carbonyl (PrC), and sperm analysis. Mitochondria were isolated from rat’s testis using differential centrifugation technique and were studied in terms of mitochondrial viability, mitochondrial membrane potential (MMP), and mitochondrial swelling. The other part of the tissue sample was placed in RNA protector solution for assessment of Bax and Bcl-2 gene expression through real-time polymerase chain reaction (real-time PCR) assay. FINDINGS: Tramadol caused a significant decline in epidermal sperm count, motility, and morphology, as well as a significant decrease in GSH level and mitochondrial function, and a significant evaluation of LPO, PrC, MMP, and mitochondrial swelling. In addition, tramadol induced a significant decrease in Bcl-2 gene expression, and increase in Bax gene expression. However, pretreatment of rats with MT improved sperm analysis, and testicular antioxidative status, and mitochondrial function. Furthermore, MT pretreatment regulated testicular Bcl-2 and Bax expressions. CONCLUSION: Considering the protective effects of MT against reproductive toxicity induced by tramadol, this compound can be used as a possible agent for the prevention and treatment of tramadol-induced reproductive toxicity.