Study On The Mechanism Of Blood-testis Barrier Disruption Induced By Hexafluoropropylene Oxide

As alternatives to perfluorooctanoic acid(PFOA),hexafluoropropylene oxide(HFPO)homologues,including hexafluoropropylene oxide dimer acid(HFPO-DA),hexafluoropropylene oxide trimer acid(HFPO-TA),and hexafluoropropylene oxide tetramer acid(HFPO-Te A),have been used in the fluoropolymer industry for a long time.These compounds have attracted widespread attention in recent years due to their environmental ubiquity and high potential for bioaccumulation and toxicity.Here,in vivo mouse experiments and mouse testicular Sertoli cell line TM4 were employed to explore the effects and underlying molecular mechanisms of HFPO homologues on blood-testis barrier.The following research results were obtained:(1)Male BALB/C mice were exposed to HFPO and PFOA by gavage for 28 days,and the pathological structure,permeability,immunofluorescence and western blotting of testis were anaylzed.The results showed that the structure of testicular spermatogenic tubule was disregulated after HFPO and PFOA exposure,and biotin diffused into the tubule lumen,which indicated that the blood-testis barrier was significantly damaged,and the permeability of the blood-testis barrier was increased.Immunofluorescence and western blot experiments showed that HFPO homologs and PFOA up-regulated the expression of matrix metalloproteinase-9(MMP-9)in the testis,promoted the degradation of occludin,and induced the damage of the blood.(2)TM4 cells were exposed to HFPO-DA/HFPO-TA/HFPO-Te A/PFOA,respectively.The damage of TM4 cells barrier in vitro model,expression of tight junction proteins(occludin)and activation of p38 MAPK signaling pathway were analyzed by transepithelial electrical resistance(TER)measurements,q RT-PCR and western blot.The results showed that these compounds induced the damage of the blood-testis barrier by promoting the phosphorylation of p38 protein,activating the p38 MAPK signaling pathway,up-regulating the expression of MMP-9,and promoting the degradation of tight junction protein occludin,which was consistent with the results of in vivo experiments.In conclusion,the results of this study demonstrated that HFPO homologues and PFOA promote the degradation of tight junction protein occludin in the blood-testis barrier by activating the p38 MAPK/MMP-9 pathway,thus damaging the blood-testis barrier.Combined with several experimental results,the order of toxicity induced blood-testis barrier damage was HFPO-Te A > HFPO-TA > PFOA > HFPO-DA.This study explored the effects and mechanisms of PFOA and HFPO homologues on blood-testis barrier injury,supplemented the understanding of reproductive toxicity of HFPO homologs,and provided theoretical reference for health risk assessment and future design of novel substitutes.