Ex vivo effects of bisphenol A or zearalenone on the prepubertal rat testis.

Bisphenol A (BPA) and zearalenone (ZEA) are two widespread xenoestrogens involved in male reproductive disorders. Few studies investigated the effects of these compounds on the prepubertal testis, which is highly sensitive to endocrine disruptors such as xenoestrogens. An ex vivo approach was performed to evaluate the effects of BPA or ZEA (10-11, 10-9, 10-6 M) on the testes of 20 and 25 dpp rats. To investigate the involvement of classical nuclear ER-mediated estrogen signaling in these effects, pre-incubation with an antagonist (ICI 182.780 10-6 M) was performed. BPA and ZEA have similar effects on spermatogenesis- and steroidogenesis-related endpoints in the immature testis, but our study highlights different age-dependent patterns of sensitivity to each compound during the prepubertal period. Moreover, our results indicate that the effects of BPA are likely to be induced by nuclear ER, whereas those of ZEA appear to involve other mechanisms.

Deoxynivalenol enhances estrogen receptor alpha-induced signaling by ligand-independent transactivation.

Deoxynivalenol (DON), which is one of the prevalent mycotoxins in food and feeds, exerts adverse effects on animal and human health. These effects are mainly associated with its ribotoxic properties, although few studies suggest the involvement of other mechanisms of action. To assess the ability of DON to disrupt estrogen signaling, we conducted an in vitro study using MCF-7 and MDA-MB-231 cells. After 72h, DON reduced cell viability in both cell lines, thus highlighting its well-known cytotoxic effect. However, after 6h, DON increased the expression of estrogen-responsive genes, hence demonstrating the stimulation of estrogen signaling by this mycotoxin after a short-term exposure. This effect was partially reversed by siRNA-mediated silencing of ERα expression and by 4-hydroxytamoxifen (ERα antagonist), but neither by G36 (GPER antagonist) nor by the siRNA-mediated silencing of PPARγ2 expression. Moreover, DON exposure induced an increase in the level of ERα phosphorylation at serine 167. Furthermore, when combined with zearalenone (a naturally co-occurring mycotoxin recognized as an endocrine disruptor), DON increased the expression of estrogen-responsive genes to a greater extent than each individual compound taken separately. Taken together, our results suggest, for the first time, that DON can disrupt estrogen signaling through the ligand-independent activation of ERα.

Maternal obesity increases insulin resistance, low-grade inflammation and osteochondrosis lesions in foals and yearlings until 18 months of age.

INTRODUCTION: Obesity is a growing concern in horses. The effects of maternal obesity on maternal metabolism and low-grade inflammation during pregnancy, as well as offspring growth, metabolism, low-grade inflammation, testicular maturation and osteochondrotic lesions until 18 months of age were investigated. MATERIAL AND METHODS: Twenty-four mares were used and separated into two groups at insemination according to body condition score (BCS): Normal (N, n = 10, BCS ≤4) and Obese (O, n = 14, BCS ≥4.25). BCS and plasma glucose, insulin, triglyceride, urea, non-esterified fatty acid, serum amyloid A (SAA), leptin and adiponectin concentrations were monitored throughout gestation. At 300 days of gestation, a Frequently Sampled Intravenous Glucose Tolerance Test (FSIGT) was performed. After parturition, foals' weight and size were monitored until 18 months of age with plasma SAA, leptin, adiponectin, triiodothyronine (T3), thyroxine (T4) and cortisol concentrations measured at regular intervals. At 6, 12 and 18 months of age, FSIGT and osteoarticular examinations were performed. Males were gelded at one year and expression of genes involved in testicular maturation analysed by RT-qPCR. RESULTS: Throughout the experiment, maternal BCS was higher in O versus N mares. During gestation, plasma urea and adiponectin were decreased and SAA and leptin increased in O versus N mares. O mares were also more insulin resistant than N mares with a higher glucose effectiveness. Postnatally, there was no difference in offspring growth between groups. Nevertheless, plasma SAA concentrations were increased in O versus N foals until 6 months, with O foals being consistently more insulin resistant with a higher glucose effectiveness. At 12 months of age, O foals were significantly more affected by osteochondrosis than N foals. All other parameters were not different between groups. CONCLUSION: In conclusion, maternal obesity altered metabolism and increased low-grade inflammation in both dams and foals. The risk of developing osteochondrosis at 12 months of age was also higher in foals born to obese dams.

Maternal parity affects placental development, growth and metabolism of foals until 1 year and a half.

Primiparous mares are known to produce smaller foals than multiparous mares. This difference seems to be partly explained by the reduced exchange surface and volume of the placental villi in primiparous compared to multiparous placentas. The effect of maternal parity on foals' post-natal growth, metabolism and sexual maturation, however, has been given little consideration. The objectives of this work were to analyse placental biometry and structure at term, growth of foals and yearlings, their metabolism and testicular maturation at one year of age. Twenty multiparous mares (M), aged over 6 years and 12 primiparous mares (P), aged up to 5 years were artificially inseminated with the same stallion and monitored the same way until foaling. At birth, foals and placentas were measured and placentas were sampled above at the umbilical cord insertion, as well as in the pregnant and the non-pregnant horn to perform stereological analyses. Foals were weighed and measured until 540 days of age. At 120 and 360 days of age, an Intravenous Glucose Tolerance Test was performed on foals and yearlings. At 360 days of age, the males were castrated and testicular maturation analysed by RT-qPCR. At birth, P dams produced lighter and smaller foals and placentas. The foal birth weight to placental surface ratio was lower in the P compared to the M group. P Foals remained lighter than M foals until 360 days of age and smaller until at least 540 days of age. At 120 days of age, P foals had a higher glucose tolerance than M foals, and then may be less mature than M foals in terms of the control of their glucose homeostasis. At 360 days of age, the testicles of prepubertal P stallions were less mature in the P vs the M group. In conclusion, primiparous dams produce intrauterine growth restricted, less mature and smaller foals compared to multiparous dams with altered metabolism and growth until at least 540 days of age. These differences could affect the sport career of these foals, especially if it begins at an early age.

Estrogen, a female hormone involved in spermatogenesis.

In mammalian testes, aromatase irreversibly converts androgens (C19 steroid) into estrogens (C18) and is present in the endoplasmic reticulum of numerous tissues. In purified adult rat germ cells (pachytene spermatocytes and round spermatids) we have shown the presence of a functional aromatase (transcript, protein and biological activity) and the estrogen production is roughly identical to that of Leydig cells. In addition, transcripts of aromatase varied according to the germ cell type and the stages of seminiferous epithelium in an adult rat. In contrast with the androgen receptors mainly localized in somatic cells, estrogen receptors (ERs) are described in all testicular cells. Moreover, besides the presence of high affinity ERα and ERß a rapid membrane effects have been recently reported and we demonstrated that GPR30 (a transmembrane intracellular estrogen receptor) was expressed in adult rat pachytene spermatocytes and in round spermatids. Thus estrogens through both GPR30 and genomic effects are able to activate the rapid signaling cascade, which in turn triggers an apoptotic mitochondrial pathway (via an increase in Bax expression) and a concomitant decrease of cyclin A1 and B1 gene levels as well as in controlling apoptosis and maturation/differentiation of round spermatids. Hence, the role of estrogen (either intracrine, paracrine or autocrine) in spermatogenesis (proliferation, apoptosis, survival and maturation) is now obvious taking into account the simultaneous presence of a biologically active aromatase and the widespread distribution of estrogen receptors especially during the spermiogenesis steps.

Estrogen signaling in testicular cells.

Aromatase transforms irreversibly androgens into estrogens and is present in the endoplasmic reticulum of various tissues including the mammalian testis. In rat all testicular cells except peritubular cells express aromatase. Indeed in adult rat germ cells (pachytene spermatocytes and round spermatids) we have demonstrated the presence of a functional aromatase (transcript, protein and biological activity) and the estrogen output is equivalent to that of Leydig cells. In addition in the adult rat, transcripts of aromatase vary according to the germ cell type and to the stages of seminiferous epithelium. By contrast with the androgen receptors mainly localized in somatic cells, estrogen receptors (ERs) are described in most of the testicular cells including germ cells. Moreover, besides the presence of high affinity ERα and/or ERß, a rapid membrane effect has been recently reported and we demonstrated that GPR30 (a transmembrane intracellular estrogen receptor) is expressed in adult rat pachytene spermatocytes. Therefore estrogens through both GPR30 and ERα are able to activate the rapid EGFR/ERK/c-jun signaling cascade, which in turn triggers an apoptotic mitochondrial pathway involving an increase in Bax expression and a concomitant reduction of cyclin A1 and B1 gene levels. In another study in round spermatids of adult rat we have shown that the rapid membrane effect of estradiol is also efficient in controlling apoptosis and maturation / differentiation of these haploid germ cells. In man the presence of a biologically active aromatase and of estrogen receptors has been reported in Leydig cells, but also in immature germ cells and ejaculated spermatozoa. Thus the role of estrogen (intracrine, autocrine and / or paracrine) in spermatogenesis (proliferation, apoptosis, survival and maturation) and more generally, in male reproduction is now evidenced taking into account the simultaneous presence of a biologically active aromatase and the widespread distribution of estrogen receptors especially in haploid germ cells.