Gper and ESRs are expressed in rat round spermatids and mediate oestrogen‐dependent rapid pathways modulating expression of cyclin B1 and Bax

Abstract

Spermatogenesis is a precisely controlled and timed process, comprising mitotic divisions of spermatogonia, meiotic divisions of spermatocytes, maturation and differentiation of haploid spermatids giving rise to spermatozoa. It is well known that the maintenance of spermatogenesis is controlled by gonadotrophins and testosterone, the effects of which are modulated by a complex network of locally produced factors, including oestrogens. However, it remains uncertain whether oestrogens are able to activate rapid signalling pathways directly in male germ cells. Classically, oestrogens act by binding to oestrogen receptors (ESRs) 1 and 2. Recently, it has been demonstrated that rapid oestrogen action can also be mediated by the G-protein-coupled oestrogen receptor 1 (Gper). The aim of the present study was to investigate ESRs and Gper expression in primary cultures of adult rat round spermatids (RS) and define if oestradiol (E2) is able to activate, through these receptors, pathways involved in the regulation of genes controlling rat RS apoptosis and/or maturation. In this study, we demonstrated that rat RS express ESR1, ESR2 and Gper. Short-time treatment of RS with E2, the selective Gper agonist G1 and the selective ESR1 and ERβ agonists, 4,4',4"-(4-propyl-[1H]pyrazole-1,3,5-triyl) trisphenol (PPT) and 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN), respectively, determined activation of Extra-cellular signal-regulated kinase (ERK1/2) through the involvement of epidermal growth factor receptor transactivation. In addition, we investigated the effects of ESRs and Gper pathway activation on factors involved in RS maturation. Expression of cyclin B1 mRNA was downregulated by E2, G1 and PPT, but not by DPN. A concomitant and inverse regulation of the pro-apoptotic factor Bax mRNA expression was observed in the same conditions, with DPN being the only one determining an increase in this factor expression. Collectively, these data demonstrate that E2 activates, through ESRs and Gper, pathways involved in the regulation of genes controlling rat RS apoptosis and differentiation such as cyclin B1 and Bax.

17β-estradiol signaling and regulation of Sertoli cell function

“…It is important to emphasize, that low doses of bisphenol A stimulate human seminoma (JKT-1) cell proliferation by allowing a rapid membrane-initiated activation of cAMP-dependent protein kinase (PKA) and cGMPdependent protein kinase (PKG) signaling pathways associated rats. 49 Gper transcript is also observed in the mouse spermatogonial GC-1 cell line, 50 in rat pachytene spermatocytes and round spermatids 45,51 and in primary culture of Sertoli cells.…”

The Blood-Testis Barrier and Its Implications for Male Contraception

“…The combined nongenomic and genomic actions of estrogens thus confers cell-specific function in the testis. Recent studies have also identified a third estrogen receptor: GPR30 (G-protein-coupled receptor, a transmembrane intracellular estrogen receptor) in rat pachytene spermatocytes and round spermatids that regulates germ cell apoptosis and differentiation (Chimento et al, 2010(Chimento et al, , 2011. GPR30 and ER␣ were also shown to be strongly expressed by Sertoli cells cultured in vitro and activated by estrogen treatment in immature rats (Lucas et al, 2008).…”

“…Thus, TNF␣ plays a significant role in determining the size of the germ cell population in the seminiferous epithelium via its effects on germ cell apoptosis, because more than 75% of germ cells that arise during spermatogenesis undergo spontaneous degeneration (Clermont, 1963;Huckins and Oakberg, 1978;Bartke, 1995;Billig et al, 1995;Shaha, 2008). In this context, it noteworthy that estrogen (e.g., estradiol-17␤) also regulates germ cell (e.g., pachytene spermatocytes) apoptosis via its effects on cyclins A1 and B1 (Chimento et al, 2010(Chimento et al, , 2011, reactive oxygen species, as well as the Fas-FasL system (Lee et al, 1999;Shaha, 2008;Shaha et al, 2010;Aitken et al, 2011). It remains to be determined whether TNF␣ works independently or in concert with estrogen to maintain the optimal number of germ cells in the epithelium during spermatogenesis.…”

International Union of Basic and Clinical Pharmacology. XCVII. G Protein–Coupled Estrogen Receptor and Its Pharmacologic Modulators

“…GPER expression and function have been reported in spermatogonia and spermatids (Sirianni et al, 2008;Chimento et al, 2011;Sheng and Zhu, 2011), Sertoli cells (Lucas et al, 2010), Leydig cells (Chimento et al, 2014a;Vaucher et al, 2014), and gubernaculum testis cells (Zhang et al, 2014c). Furthermore, seminoma-associated GPER genetic variants (Chevalier et al, 2014), GPER overexpression in human seminoma (Franco et al, 2011;Chevalier et al, 2012b), and other testicular germ cell tumors (Franco et al, 2011), as well as GPER-mediated tumor cell proliferation in response to estrogenic compounds, such as bisphenol A (Chevalier et al, 2012a), have been reported.…”