Analyzing the toxicological effects of PET-MPs on male infertility: Insights from network toxicology, mendelian randomization, and transcriptomics

Current research indicates that polyethylene terephthalate microplastics (PET-MPs) may significantly impair male reproductive function. This study aimed to investigate the potential molecular mechanisms underlying this impairment. Potential gene targets of PET-MPs were predicted via the SwissTargetPrediction database. GWAS summary statistics for male infertility were obtained from the GWAS Catalog, and eQTL data were acquired from the eQTLGen database. SMR analysis was subsequently performed to identify genes exhibiting significant causal associations with male infertility. The potential targets of PET-MPs contributing to male infertility were ultimately identified by intersecting the two gene sets. Additionally, bulk RNA-seq and scRNA-seq analyses were employed to elucidate the potential molecular mechanisms underlying PET-MPs-induced male infertility. Our findings suggest that CLK4 may serve as a functional target through which PET-MPs contribute to male infertility, with elevated CLK4 expression representing a significant risk factor. Molecular docking and molecular dynamics simulations demonstrated that PET-MPs can form stable binding conformations with the CLK4 protein. We further identified terminally differentiated CD4⁺ T cells as a prominent risk factor for male infertility, revealing a significant positive correlation between CLK4 expression levels and Th1 cell infiltration. Additionally, CLK4 exhibited a biphasic expression pattern during spermatocyte-to-sperm differentiation, initially increasing before subsequent downregulation. These observations indicate that PET-MPs may participate in the pathogenesis of male infertility by targeting CLK4 to modulate Th1 cell infiltration and disrupt normal spermatogenic processes. In conclusion, our study demonstrates that CLK4 may serve as a potential target for PET-MP-induced male infertility, and we further elucidate the underlying molecular mechanisms.