Omaveloxolone Prevents Polystyrene Microplastic-Induced Ovarian Granulosa Cell Apoptosis via the Keap1/Nrf2/HO-1 Pathway in Rats.

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 0.5 µm 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 1 week. 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 10 μM H₂O₂ for 12 h 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.