Polystyrene nanoparticles (PS-NPs) pollute drinking water, aquatic ecosystems, and the food chain, destroying marine life. PS-NPs represent a significant risk to the environment and humans by contaminating soil and water, leading to cytotoxic effects on human health. This investigation aimed to ascertain whether PS-NPs could be hazardous to the thyroid and adrenal glands of male albino rats. Thirty rats were divided into three groups, with 10 rats in each group and five rats per cage. Group I received distilled water. Group II: PS-NPs (3 mg/kg body weight/day). Group III received daily doses of PS-NPs (10 mg/kg body weight). Samples of the thyroid and adrenal glands were obtained, processed, and tested biochemically, histopathologically, and immunohistochemically. Results showed that both low and high doses of PS-NPs showed significantly elevated levels of thyroid-stimulating hormone and a significant reduction of free triiodothyronine (FT3) and free thyroxine(FT4). Biochemically, there was a significant reduction in total antioxidant capacity. Histopathological examination revealed nuclear pyknosis and slight hemorrhage in the cells of three zones of the adrenal gland cortex in a low dose of PS-NPs. Thyroid gland sections had a disrupted colloid secretion with altered histoarchitecture of follicular cells. There was downregulation of nuclear factor erythroid 2-related factor 2 genes and upregulation of Cytochrome c genes. Cyclo-oxygenase-2, as an inflammatory marker, significantly increased in PS-NPs in low and high doses. We concluded that PS-NPs had adverse effects on the endocrine organs' structure and function.
The increasing production and application of engineered nanoparticles have raised significant environmental and health concerns, particularly, regarding their potential release into aquatic ecosystems. Among these, multifunctional nanocomposites combining titanium dioxide (TiO2) and zinc oxide (ZnO) have garnered considerable attention due to their widespread use. This study examined the biological responses of the freshwater mussel Unio ravoisieri to TiZn nanocomposites at concentrations of 10 and 100 μg/L. In a subsequent phase, the potential protective effects of selenium (Se) against nanocomposite-induced toxicity were assessed using biochemical markers, including hydrogen peroxide (H2O2), catalase (CAT), reduced glutathione (GSH), glutathione-S-transferase (GST), malondialdehyde (MDA) levels, and acetylcholinesterase (AChE) activity. The results demonstrated that exposure to TiZn nanocomposites alone induced oxidative stress in the digestive gland, with elevated levels of CAT, GST, AChE, GSH, and MDA in a concentration-dependent manner. However, selenium co-administration at 100 μg/L significantly mitigated these oxidative responses, highlighting its potential as a protective agent against nanocomposite-induced toxicity. These findings suggest promising avenues for the use of selenium in reducing nanoparticle-related environmental stress in aquatic organisms.

