Recommended Approaches for the Evaluation of Testicular and Epididymal Toxicity

Abstract

Background Bisphenol S (BPS) is increasingly used as a replacement for bisphenol A in the manufacture of products containing polycarbonates and epoxy resins. However, further studies of BPS exposure are needed for the assessment of health risks to humans. In this study we assessed the potential harmfulness of low-dose BPS on reproduction in male mice. Methods To simulate human exposure under experimental conditions, 8-week-old outbred ICR male mice received 8 weeks of drinking water containing a broad range of BPS doses 0.001, 1.0, or 100 µg/kg body weight (bw)/day, BPS1-3 or vehicle control. Mice were sacrificed and testicular tissue taken for histological analysis and protein identification by nano-liquid chromatography/mass spectrometry (MS) and sperm collected for immunodetection of acetylated lysine and phosphorylated tyrosine followed by protein characterisation using matrix-assisted laser desorption ionisation time-of-flight MS (MALDI-TOF MS). Results The results indicate that compared to vehicle, 100 µg/kg/day exposure (BPS3) leads to 1) significant histopathology in testicular tissue; and, 2) higher levels of the histone protein γH2AX, a reliable marker of DNA damage. There were fewer mature spermatozoa in the germ layer in the experimental group treated with 1 µg/kg bw (BPS2). Finally, Western blot and MALDI-TOF MS studies showed significant alterations in the sperm acetylome and phosphorylome in mice treated with the lowest (BPS1) exposure (0.001 µg/kg/day). Conclusions In summary, this range of qualitative and quantitative findings in young male mice raise the possibility that relatively low doses of BPS may impair mammalian reproduction through epigenetic modifications of sperm proteins.

Proliferative and Nonproliferative Lesions of the Rat and Mouse Male Reproductive System

“…In many cases, testicular toxicity is cell-specific and stagespecific during the early stages of its development, but with continued dosing, cell degeneration becomes more generalized and nonspecific. In this respect, examination of spermatogenesis with stage awareness is generally most valuable for compound exposures of 1 month or less (Lanning et al 2002). Due to the variable appearance of seminiferous tubular changes in short-term versus chronic studies, terminology that deals with cell-and stage-specific changes and terminology that can be used for nonspecific changes have both been presented.…”

“…Exfoliation, Germ Cell ( Figure 22 Lanning et al 2002) or it can be a secondary event associated with nonspecific germ cell degeneration. In the case of colchicine and carbendazim, extensive sloughing of the adluminal germ cells and Sertoli cell processes is due to effects on the microtubules that form the Sertoli cell cytoskeleton.…”

“…Proper microscopic assessment of testicular tissue in toxicity studies requires use of sexually mature animals, appropriate fixation, sampling and processing (Foley 2001;Lanning et al 2002;Latendresse et al 2002;Kittel et al 2004), and an understanding of spermatogenesis and its histologic presentation in the species under consideration ).…”

Spermatogenesis in the Cynomolgus Monkey (Macaca fascicularis): A Practical Guide for Routine Morphological Staging

“…For this purpose it is essential to distinguish drug-induced histological changes from the normal variation. Therefore, an adequate understanding of the organization and dynamics of the process of spermatogenesis of the test animal used is a prerequisite (Foley, 2001;Lanning et al, 2002). Unfortunately, detailed and up-to-date information on the general organization of the testes in monkeys is limited.…”

“…Microscopic evaluation should be carried out as a qualitative examination with the awareness of the spermatogenic cycle. Quantitative measurements of tubular stages and their frequency distribution are not recommended for screening studies (Lanning et al, 2002).…”