Thymoquinone (TQ), the main constituent of the volatile oil derived from Nigella sativa has shown pharmacological benefits against various diseases while nicotine is an active component in cigarette that is known to be detrimental. This study was conducted to assess the ameliorating effects of TQ on sperm count, membrane, mitochondria and testosterone of nicotine-treated rats. Rats were randomized into four groups: control, nicotine, TQ, and nicotine with TQ. Nicotine (5 mg/kg bwt/day) was subcutaneously injected for 30 days to induce damaging effects on sperm and testosterone level. Rats were HIGHLIGHTS• Nicotine negatively affected sperm count, membrane, mitochondria and testosterone level.Rosli, F.D.; et al.

Purpose: To assess the effects of thymoquinone (TQ) on the integrity of sperm DNA in nicotineinduced sperm impairment in rats. Methods: Adult male Sprague Dawley rats were randomized into four equal groups: control group received normal saline orally for 60 days; nicotine group was subcutaneously injected with 5 mg/kg/day nicotine for 30 days and then given normal saline for the next 30 days; TQ group was given normal saline for 30 days followed by TQ at 5 mg/kg/day for 30 days; and nicotine-TQ group received 5 mg/kg of nicotine for 30 days and 5mg/kg of TQ for another 30 days. Sperm DNA breakages were evaluated using Comet assay. The expression levels of protamine 1 (PT1) and transition nuclear protein 2 (Tnp2) genes which are essential for the proper compaction of the sperm DNA were analyzed by quantitative polymerase chain reaction (qPCR). Results: Thymoquinone significantly decreased DNA fragmentation in the sperm of nicotine-treated rats. However, there was no change in PT1 gene expression. Tnp2 was downregulated in the nicotine group and slightly upregulated in nicotine-TQ group (p < 0.05). Conclusion: The results demonstrate the potential benefits of TQ in improving sperm DNA quality of nicotine-induced male infertility.

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