Stage-Related Increase in the Proportion of Apoptotic Germ Cells and Altered Frequencies of Stages in the Spermatogenic Cycle Following Gestational, Lactational, and Direct Exposure of Male Rats to p-Nonylphenol

Abstract

The cumulative effects of environmental toxicants, for example, the alkylphenol, para-nonylphenol (p-NP) are of concern. Our previous study showed that p-NP reduced several testicular morphometric parameters, including sperm counts. The present study reexamined material collected in that study to determine the mechanistic basis of p-NP action on spermatogenic development in the offspring. Seven-day pregnant Sprague-Dawley rats were treated with vehicle or 100 or 250 mg/kg p-NP through gestation, lactation and afterward directly to all male offspring until 10 weeks of age. Both doses of p-NP significantly (P < 0.02) increased the number of germ cells with in situ end-labeled fragmented DNA (TUNEL positive) by 1.9-fold and 1.7-fold, respectively, and specifically in stages XII-XIV and I-III. TUNEL-labeling was, however, selective, and excluded labeling of basal cells with apoptotic morphology. Cleaved caspase-3 immunohistochemistry strongly labeled basal cells (spermatogonia and early spermatocytes) with condensed marginated chromatin but not degenerate germ cells lacking definitive nuclear material found throughout the epithelium. Only the caspase index (ratio of number of caspase positive to number of degenerate cells) of the 100-mg/kg p-NP group was significantly (p < 0.05) threefold greater than controls. Whereas both doses and either 250 or 100 mg/kg treatment alone significantly (p < 0.002) reduced the frequencies (duration) of stages I-III, VII-VIII, and late VIII-IX (spermiating and recently spermiated tubules), respectively, both doses significantly (p < 0.002) increased the frequencies of stages IV-VI and all stages containing late-stage spermatocytes (XII-XIII) and meiotic cell divisions (XIV). Thus, p-NP, an environmentally persistent xenoestrogen, insidiously alters the spermatogenic cycle and spermatogenic process in male offspring.

Testicular apoptosis in feral Clarias gariepinus using TUNEL and cleaved caspase-3 immunohistochemistry

“…Negative controls were generated by omitting the primary antibody and by serial dilution of the primary antibody, as well as by using a rabbit monoclonal antibody to cleaved caspase-3. The rat testicular sections used as positive controls were those from a previous study (McClusky et al, 2007).…”

4-Nonylphenol induces autophagy and attenuates mTOR-p70S6K/4EBP1 signaling by modulating AMPK activation in Sertoli cells

“…Importantly, our previous study outlined that NP treatment triggers Sertoli cell (SC) autophagy, probably through the ROS-mediated AMPK-mTOR pathway (Duan et al 2016c). Additionally, NP exposure is shown to increase oxidative stress and germ cell apoptosis in testis, to cause seminiferous tubule degeneration and to reduce hormone secretion, consequently impairing sperm parameters, capacitation and morphology (Duan et al 2016a;Duan et al 2016b;Lu et al 2014;McClusky et al 2007). Although increasing evidence suggests that autophagy activity may play an important function in the pathogenesis of male reproductive toxicity (Han et al 2015), no information regarding NP effects on autophagy induction in vivo is currently available.…”

Aneuploid sperm formation in rainbow trout exposed to the environmental estrogen 17α-ethynylestradiol

“…Through these actions environmental estrogens affect vertebrate reproduction across a wide range of doses causing reduced fertility and fecundity, altered reproductive behavior, gonad morphological changes, and decreased embryonic survival (25)(26)(27)(28)(29)(30)(31)(32)(33)(34). Although both sexes are affected, males exhibit the highest degree and number of detrimental effects.…”

“…Although both sexes are affected, males exhibit the highest degree and number of detrimental effects. Specific male defects caused by environmental estrogen exposures in vertebrates include: intersex (25,29), diminished sperm count (27,(35)(36)(37), genital tract alterations (38), increased germ cell apoptosis (30,33), and male induced embryonic mortality (31,39).…”

“…Although most rodent model studies show decreased sperm production and/or increased apoptosis of germ cells after exposure (27,30,33,35), others have failed to confirm these findings (40). Additionally, recent in vitro exposures of human spermatozoa to catechol estrogens (e.g., quercetin, diethylstilbestrol and pyrocatechol) indicate an impact on sperm DNA integrity through altered redox cycling, but estrogen (17␤-estradiol) and other estrogen analogues (nonylphenol and BPA) do not show this effect (41).…”