YTHDF3‐Dependent m 6 A Modification of cGAS Drives Nanoparticle‐Induced Senescence in Spermatocytes

ABSTRACT 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 m 6 A 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 m 6 A 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 m 6 A methyltransferase METTL3 and the reader protein YTHDF3. YTHDF3 underwent liquid–liquid phase separation (LLPS) to form intracellular condensates, directly binding to m 6 A‐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 m 6 A 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 m 6 A modification, phase separation, or the cGAS pathway.