Abstract
Microplastics (MPs) are persistent environmental pollutants that enter the circulatory system and subsequently reduce sperm quantity and quality. However, the influence of polystyrene MPs (PS-MPs) on the ovary and relevant mechanisms remain elusive. Herein, we aimed to examine the impact of PS-MPs on oxidative disorders in ovarian tissues and elucidate the underlying mechanisms. Healthy female rats were treated with different concentrations of 0.5µm PS-MPs (diluted in deionized H2O) for 90 days. Upon examination of hematoxylin-eosin-stained ovarian tissue sections, the number of growing follicles was reduced in PS-MP-treated rats when compared with that in control rats. Enzyme-linked immunosorbent assays revealed that PS-MP exposure markedly reduced anti-Müllerian hormone (AMH) levels. Treatment with PS-MPs downregulated superoxide dismutase, glutathione, and catalase activities in ovarian tissues while upregulating malondialdehyde levels. Furthermore, exposure to PS-MP blocked the Keap1/Nrf2/HO-1 signal transduction pathway. PS-MPs also triggered apoptosis in the ovarian tissue, as evidenced by increased TUNEL staining and expression levels of cleaved caspase-9, Bax, and Bcl-2. To reactivate the Keap1/Nrf2/HO-1 pathway, rats were co-administered PS-MPs and omaveloxolone (Oma), an Nrf2 activator, for 1week. We found that Oma could counteract the PS-MP-mediated effects on oxidative disorder, apoptosis, AMH production, and follicle number in rat ovarian tissues. To develop an in vitro model, granulosa cells (GCs) were treated with 10μM H2O2 for 12h to induce oxidative stress. H2O2-stimulated GCs exhibited attenuated cell growth and upregulated apoptosis and oxidative stress. Oma administration could ameliorate the H2O2-induced effects in terms of regulating cell viability, apoptosis, and oxidative stress in GCs. In summary, PS-MPs could induce apoptosis and oxidative stress via the Keap1/Nrf2/HO-1 signaling pathway in both rats and GCs.
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