Ferroptosis is involved in the damage of ocular lens under long-term PM2.5 exposure in rat models and humans

Abstract

Epidemiological studies show a positive association between air pollution and age-related cataracts, but the pathogenic mechanism remains unclear. This study first demonstrates that fine particulate matter (PM2.5) induces ferroptosis in the lens, leading to morphological and functional disorders, through human, animal, and cellular samples. In 3-week PM2.5-exposed rat models (10 µl 1 mg/ml PM2.5 suspension per eye, 4 times a day), we find that many vacuoles form in the lens equatorial region by analysis of haematoxylin and eosin staining after PM2.5 exposure. Using iron and glutathione (GSH) assay kits, we found increased Fe2+ contents and decreased GSH levels in PM2.5-exposed rats’ lenses. Additionally, the lipid peroxide 4-hydroxynonenal (4-HNE) was also found to be elevated with immunoblot, suggesting ferroptosis is involved. Ferroptosis was also observed in human lens epithelial cells treated with 25, 50, and 100 µg/ml PM2.5 suspension for 24 h, accompanied by decreased cell viability and migration. Furthermore, we collect about 60 human lens anterior capsule (HLAC) samples for RNA-seq. The results show that compared to HLACs from areas with PM2.5 concentration ≤30 μg/m³, ferroptosis-related genes expression of those from areas with PM2.5 concentration ≥35 μg/m³ are significantly altered, such as glutathione peroxidase 4 and STEAP family member 3. Also, human lens in areas with high PM2.5 concentrations showed elevated levels of transferrin receptor and 4-HNE with immunoblot, and down-regulated expression of connexin 43 (Cx43) through immunofluorescent. These results demonstrate that ferroptosis plays a key role in PM2.5-induced cataractogenesis.

Keywords

• Particulate matter
• Ocular lens
• Ferroptosis
• Connexin43
• Human lens epithelial cells