Effect of iodoacetic acid on the reproductive system of male mice

Abstract

Iodoacetic acid (IAA) is one of the most common water disinfection byproducts (DBPs). Humans and animals are widely and continuously exposed to it. Many species of water DBPs are harmful to the reproductive system of organisms. Nevertheless, the potential effects of IAA exposure on testosterone and spermatogenesis in vivo remain ambiguous. Spermatogenous cells are the site of spermatogenesis, Leydig cells are the site of testosterone synthesis, and Sertoli cells build the blood-testis barrier (BTB), providing a stable environment for the aforementioned important physiological functions in testicular tissue. Therefore, we observed the effects of IAA on spermatogenic cells, Leydig cells, and Sertoli cells in the testis. In this study, we found that oral administration of IAA (35 mg/kg body weight per day for 28 days) in male mice increased serum LH levels and reduced sperm motility, affecting average path velocity and straight line velocity of sperm. In addition, IAA promoted the expression of γH2AX, a marker for DNA double-strand breaks. Moreover, IAA downregulated the protein expression of the scavenger receptor class B type 1 (SRB1), and decreased lipid droplet transport into Leydig cells, which reduced the storage of testosterone synthesis raw materials and might cause a drop in testosterone production. Furthermore, IAA did not affect the function of BTB. Thus, our results indicated that IAA exposure affected spermatogenesis and testosterone synthesis by inducing DNA damage and reducing lipid droplet transport.

Keywords: SRB1; iodoacetic acid; sperm; testis; testosterone; γH2AX.

FIGURE 1

Effects of IAA exposure on general condition and serum hormone levels in mice. During the IAA exposure, the body weights of the mice were recorded twice a week. Only weekly values are shown in the graph (A). Pictures of mice and testis (B), testicular weight (C), and the relative weight of testis (D) between the two groups were recorded after sacrifice. Hematoxylin-eosin (H&E) sections of testicular tissue of mice were also recorded and the pathological morphology was observed (E). After IAA exposure, serum FSH, LH, and testosterone levels of mice were detected by ELISA (F–H). Data are presented as the mean ± SEM. * Significant differences compared to control (p < 0.05).

FIGURE 2

Changes of spermatogenesis-related indexes were observed from gene expression and protein level, respectively. The expression of the following genes, such as Dazl, Vasa, Plzf, c-Kit, H2ax, Stra8, Sycp1, Sycp3, Tnp2, and Piwil1, in the testis tissue of the two groups were detected by real-time PCR (qRT-PCR) technology (A). Also, the changes of protein levels such as VASA, DAZL, and γH2AX between the two groups of mice were observed by Western Blot (B,C) and immunofluorescence staining experiments (D–G). * Significant differences compared to the control (p < 0.05).

FIGURE 3

Lipid droplet storage in Leydig cells and changes in testosterone synthase from gene expression and protein levels were examined. Cholesterol storage in Leydig cells between the two groups was visualized by BODIPY staining (A,B). The relative mRNA levels of the following indicators, Lhcgr, Srb1, Star, Cyp17a1, Cyp11a1, 3β-hsd, and Cyp19a1, were detected by qRT-PCR (C). Also, the protein levels of cholesterol transporter SRB1 and testosterone synthase STAR, CYP11A1, and CYP17A1 were observed by Western Blot (D,E) and immunofluorescence staining experiments (F–I). * Significant differences compared to the control (p < 0.05).

FIGURE 4

Changes of BTB-related indexes were detected from gene expression and protein level. Relative mRNA levels between the two groups, Wt-1, Claudin-11, Nectin-2, Zo-2, β-catenin, Jam-A, N-cadherin and Connexin-43, were observed (A). The protein levels of WT-1, N-cadherin, and β-catenin were also observed by Western Blot (B,C) and immunofluorescence staining experiments (D,E). * Significant differences compared to the control (p < 0.05).