Subchronic reproductive effects of 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFAES), an alternative to PFOS, on adult male mice

With a similar structure to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFAES) has been widely used as a mist suppressant in the chromium plating industry in China since the 1970s. After being disregarded for the past 30 years, 6:2 Cl-PFAES has now been detected in environmental matrices and human sera, suggesting potential health concerns. We carried out a subchronic exposure study to investigate the reproductive toxicity of 6:2 Cl-PFAES exposure (0, 0.04, 0.2, and 1.0 mg/kg/d body weight, 56 d) in adult male BALB/c mice. Results showed that relative epididymis and testis weights decreased in the 1.0 mg/kg/d group compared with the control. However, no changes were observed in the serum levels of testosterone, estradiol, follicle-stimulating hormone (FSH), or luteinizing hormone (LH), nor in the histopathological structure of the epididymis and testis and sperm count. In addition, 56 d of consecutive gavage of 1.0 mg/kg/d of 6:2 Cl-PFAES did not affect male mouse fertility. RNA sequencing showed that no genes were significantly altered in the testes after 6:2 Cl-PFAES exposure. Several testicular genes, which are sensitive to PFOS exposure, were also detected using Western blotting, and included steroidogenic proteins, STAR, CYP11A1, CYP17A1, and 3β-HSD and cell junction proteins, occludin, β-catenin, and connexin 43; however, none were changed after 6:2 Cl-PFAES exposure. Except for a decrease in the relative epididymis and testis weights in the 1.0 mg/kg/d group, 6:2 Cl-PFAES exposure for 56 d exerted no significant effect on the serum levels of reproductive hormones or the testicular mRNA profilesin adult male mice, implying a relative weak reproductive injury potential compared with that of PFOS.