Protective effects of orally administered thymol against titanium dioxide nanoparticle-induced testicular damage

In this study, we investigated the potential of thymol and its mode of action to protect against the titanium dioxide (TiO₂) nanoparticle-induced testicular damage. Twenty-four rats were randomly divided into four groups: control group, TiO₂ (100 mg/kg BW/day) group, TiO₂ + thymol (10 mg/kg BW/day) group, and TiO₂ + thymol (30 mg/kg BW/day) group. With the exception of the control group, all animals received orally TiO₂ nanoparticles for 60 days. In treatment groups, animals were given orally thymol 1 h before TiO₂ nanoparticles. Epididymal sperm parameters, testicular histopathology, and spermatogenesis assessments were performed for evaluation of the TiO₂ and thymol effects on the testis. Furthermore, antioxidative enzyme activities such as catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD), and malondialdehyde (MDA), glutathione (GSH) levels and ferric-reducing antioxidant power (FRAP) value were measured. Intragastric administration of TiO₂ for 60 consecutive days caused a significant decrease in sperm quality, widespread histopathological alteration, and significantly induced oxidative stress as manifested by elevated MDA levels and a remarkable decline in antioxidant enzyme activities such as CAT, SOD, and GPx, and also FRAP and GSH levels in testis tissue. Nearly all of these alterations were significantly ameliorated in the groups that orally received thymol before TiO₂ nanoparticles administration. The results of this study demonstrated that thymol improved the spermatogenesis defects induced by TiO₂ nanoparticles in rats in a dose-dependent manner by protecting the testes against the testicular toxicity. Reduction in TiO₂ nanoparticle-induced oxidative stress may have a major role in this protective effect.