YTHDF3-Dependent m6A Modification of cGAS Drives Nanoparticle-Induced Senescence in Spermatocytes.

BACKGROUND: Nanoplastics (NPs), owing to their small size and ability to cross the blood-testis barrier, pose a potential risk to the male reproductive system. However, the molecular mechanisms underlying NP-induced reproductive toxicity, particularly cell senescence, remain poorly understood. OBJECTIVES: This study aims to investigate the mechanisms by which polystyrene nanoplastics (PS-NPs) induce spermatocyte senescence, with a particular focus on the role of YTHDF3-mediated m6A RNA methylation in regulating the cGAS-NF-κB signaling pathway. MATERIALS AND METHODS: Exposure was established in male C57BL/6 mice via tracheal instillation of PS-NPs, supplemented with spermatogonial cells (GC-2). Testicular dysfunction and spermatocyte senescence were assessed. Further investigations focused on m6A modification and the cGAS-NF-κB signaling axis. Functional studies and knockout experiments were conducted to investigate the role of YTHDF3 and its phase separation. RESULTS: PS-NPs exposure led to disrupted testicular architecture, decreased sperm quality, and induced spermatocyte senescence in a concentration-dependent manner. Mechanistically, PS-NPs activated the cGAS-NF-κB signaling axis, resulting in reduced mitochondrial membrane potential and impaired mitochondrial function. This activation not only promoted senescence but also suppressed antioxidant defenses, accelerating the aging process. Epigenetically, PS-NPs upregulated the m6A methyltransferase METTL3 and the reader protein YTHDF3. YTHDF3 underwent liquid-liquid phase separation (LLPS) to form intracellular condensates, directly binding to m6A-modified sites on cGAS mRNA and regulating its stability. Knockdown of YTHDF3 significantly attenuated cGAS activation and alleviated the senescence phenotype. DISCUSSION AND CONCLUSION: This study identifies a novel mechanism where YTHDF3-mediated m6A modification, driven by phase separation, activates the cGAS-NF-κB pathway in response to PS-NPs, leading to mitochondrial damage and spermatocyte senescence. These findings provide new insights into the epigenetic and phase separation-based mechanisms of nanoplastic reproductive toxicity and suggest potential intervention strategies targeting m6A modification, phase separation, or the cGAS pathway.