Combined intratracheal instillation of trace emerging pollutants induced testicular damage

The current number of emerging contaminants worldwide may reach tens of thousands. However, research on the extra-pulmonary toxicity induced by combined exposure of extremely low-dose emerging pollutants remains extremely limited. This study examined testicular injury induced by intratracheal instillation of two prevalent and frequently co-occurring emerging contaminants at ambient levels: polystyrene nanoparticles (PS) and perfluorooctane sulfonate (PFOS). With a 3 × 3 factorial design, male mice were intratracheally instilled with PS (0, 1.5 and 7.5 mg/kg) and/or PFOS (0, 5 and 25 μg/kg) once a week for 4 weeks. The instillation of PS in combination with PFOS induced more severe testicular histopathological injury, impairment of sperm counts and quality, reduced serum testosterone (T) levels and disruption of the blood-testis barrier (BTB). Furthermore, the testicular transcriptomic analysis identified the differentially expressed genes (DEGs) in the PS and PFOS co-exposure group, especially with Ldlr and Vegfd downregulation, and the DEGs were significantly enriched in vascular morphogenesis and development pathways and cholesterol metabolism pathways. In parallel, the protein expression of LDLR was decreased, the expression of testicular vascular endothelial markers (CD31 and VEGF) and tight junction proteins (ZO-1 and OCLN) was significantly reduced in the PS and PFOS co-exposure group compared with the control group (p < 0.05). Moreover, the testicular steroidogenic enzymes (StAR, CYP11A1, CYP17A1) were significantly reduced in the PS and PFOS co-exposure group compared with the control group (p < 0.05). Surprisingly, PS was detected in the testicular tissue in both PS and PS+PFOS groups. Our findings highlight an underappreciated risk of inhaling trace emerging pollutants mixtures on male fertility.