Inhibitory roles of the mammalian GnIH ortholog RFRP3 in testicular activities in adult mice

Abstract

The aim of this study was to evaluate the effects of in vivo and in vitro treatments with RFamide-related peptide 3 (RFRP3), a mammalian gonadotropin-inhibitory hormone ortholog, on testicular activities, i.e. spermatogenesis and steroidogenesis, in mice. Mice were treated in vivo with different doses of RFRP3 (control: 0.02 mg, 0.2 mg, and 2.0 mg/day) for 8 days. For in vitro study, the testes of mice were evaluated with different doses of RFRP3 (control: 1 and 10 ng/ml) with or without LH (control: 10 and 100 ng/ml) for 24 h at 37 8C. RFRP3 treatment produced significant changes in the body mass, circulating steroid level, and testicular activity in mice. RFRP3 treatment also caused dose-dependent histological changes in spermatogenesis, such as decline in germ cell proliferation and survival markers and increase in apoptotic markers in testis. Both in vivo and in vitro studies showed the inhibitory effect of RFRP3 on testosterone synthesis in the testis. RFRP3 inhibited the expression of the receptor for LH (LHCGR), STAR protein, cytochrome P450 side-chain cleavage (CYP11A1) and 3b-hydroxysteroid dehydrogenase in the testis, and testosterone secretion dose dependently. This study also suggested that the inhibitory effect of RFRP3 in the testis may be mediated through local production of GnRH. Thus, RFRP3 inhibits testicular steroidogenesis and spermatogenesis either indirectly through GnRH or by directly influencing germ cell proliferation, survival, and apoptosis.

Apoptosis-mediated testicular alteration in Japanese quail (Coturnix coturnix japonica) in response to temporal phase relation of serotonergic and dopaminergic oscillations

“…Thus, testicular stimulation/inhibition of sex steroid production and testicular cell survival/apoptosis appears to be the outcome of local (through testicular GnIH and its receptor) effects, which may be also altered by the temporal phase relation of neural oscillations. It is well documented from both in vitro and in vivo analyses that the mammalian GnIH ortholog RFRP3 has a direct effect on testicular steroidogenesis in mice (Anjum et al, 2014). The GnRH-GnIH system, through their receptors, may play a role in the autocrine/paracrine regulation of testosterone production and regulate optimal testicular activity in birds and mammals.…”

“…Singh et al (2011) has demonstrated the direct inhibitory effect of GnIH on ovarian steroidogenesis in mice. Anjum et al (2014) showed the direct effect of RFRP3 in vitro and in vivo on testicular steroidogenesis in mice, and different doses of RFRP3 resulted in a significant decrease in testosterone synthesis in mice testes. GnIH modulates testosterone production and spermatogenesis directly as well as indirectly through its paracrine and endocrine function, mediated via its receptors present in the Sertoli, Leydig and germ cells .…”

“…Alternatively, it is also possible that the testicular GnRH-GnIH system modulates testicular growth locally (Tsutsui et al, 2010;Anjum et al, 2014). However, a direct effect of photoperiod or other treatments (except intra-testicular injections) on the testicular activity bypassing the central/HPG axis seems unlikely.…”

Molecular, cellular, morphological, physiological and behavioral aspects of gonadotropin-inhibitory hormone

“…Treatment of prehierarchial follicular granulosa cells with GnIH significantly decreased basal but not FSH-stimulated cellular viability in vitro (Maddineni et al, 2008b). Anjum et al (2014) evaluated the effects of RFRP-3 on testicular activities, spermatogenesis and steroidogenesis, in vivo and in vitro in mice. RFRP-3 treatment caused dose-dependent histological changes in spermatogenesis, such as decline in germ cell proliferation and survival markers and increase in apoptotic markers.…”

How to contribute to the progress of neuroendocrinology: New insights from discovering novel neuropeptides and neurosteroids regulating pituitary and brain functions

“…In addition to central action of GnIH, direct regulation of gonadal activity by GnIH is becoming clear. GnIH and GnIH receptor are expressed in steroidogenic cells and germ cells in gonads in birds and mammals (Anjum et al, 2014;Bentley et al, 2008;Oishi et al, 2012;Singh et al, 2008Singh et al, , 2011aSingh et al, , 2011bZhao et al, 2010), and GnIH possibly acts by an autocrine/paracrine manner to suppress gonadal steroid production and germ cell differentiation and maturation (Anjum et al, 2014;Bentley et al, 2008;Oishi et al, 2012;Singh et al, 2008Singh et al, , 2011aSingh et al, , 2011bZhao et al, 2010).…”