Histopathological, Biochemical and Molecular Investigations on the Potential Endocrine Disruption of Polystyrene Nanoparticles in Adult Male Albino Rats

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.