Nociceptin is upregulated by FSH signaling in Sertoli cells in murine testes

FSH INCREASES LIPID DROPLET CONTENT BY REGULATING THE EXPRESSION OF GENES RELATED TO LIPID STORAGE IN RAT SERTOLI CELLS

Sertoli cells (SCs) are essential for appropriate spermatogenesis. From a metabolic standpoint, they catabolize glucose and provide germ cells with lactate, which is their main energy source. SCs also oxidize fatty acids (FAs), which are stored as triacylglycerides (TAGs) within lipid droplets (LDs), to fulfill their own energy requirements. On the other hand, it has been demonstrated that FSH regulates some of SCs functions, but little is known about its effect on lipid metabolism. In the present study, we aimed to analyze FSH-mediated regulation of (1) lipid storage in LDs and (2) the expression of genes involved in FAs activation and TAG synthesis and storage in SCs. SCs obtained from 20-day-old rats were cultured for different incubation periods with FSH (100 ng/ml). It was observed that FSH increased LD content and TAG levels in SCs. There were also increments in the expression of Plin1, Fabp5, Acsl1, Acsl4, Gpat3, and Dgat1, which suggests that these proteins may mediate the increase in TAGs and LDs elicited by FSH. Regarding the signaling involved in FSH actions, it was observed that dbcAMP increased LD, and H89, a PKA inhibitor, inhibited FSH stimulus. Also, dbcAMP increased Plin2, Fabp5, Acsl1, Acsl4, and Dgat1 mRNA levels, confirming a role of the cAMP/PKA pathway in the regulation of lipid storage in SCs. Altogether, these results suggest that FSH, via the cAMP/PKA pathway, regulates lipid storage in SCs ensuring the availability of substrates to satisfy their energy requirements.

Inhibition of miR-143-3p Restores Blood-Testis Barrier Function and Ameliorates Sertoli Cell Senescence

Due to the increasing trend of delayed childbirth, the age-related decline in male reproductive function has become a widely recognized issue. Sertoli cells (SCs) play a vital role in creating the necessary microenvironment for spermatogenesis in the testis. However, the mechanism underlying Sertoli cell aging is still unclear. In this study, senescent Sertoli cells showed a substantial upregulation of miR-143-3p expression. miR-143-3p was found to limit Sertoli cell proliferation, promote cellular senescence, and cause blood-testis barrier (BTB) dysfunction by targeting ubiquitin-conjugating enzyme E2 E3 (UBE2E3). Additionally, the TGF-β receptor inhibitor SB431542 showed potential in alleviating age-related BTB dysfunction, rescuing testicular atrophy, and reversing the reduction in germ cell numbers by negatively regulating miR-143-3p. These findings clarified the regulatory pathways underlying Sertoli cell senescence and suggested a promising therapeutic approach to restore BTB function, alleviate Sertoli cell senescence, and improve reproductive outcomes for individuals facing fertility challenges.

Oral administration of Turnera diffusa willd. ex Schult. extract ameliorates steroidogenesis and spermatogenesis impairment in the testes of rats with type-2 diabetes mellitus

ETHNOPHARMACOLOGICAL RELEVANCE

Turnera diffusa Willd. ex Schult. (T. diffusa) has traditionally been used to treat male reproductive dysfunction and have aphrodisiac properties.

AIMS OF THE STUDY

This study aims to investigate the ability of T. diffusa to ameliorate the impairment in testicular steroidogenesis and spermatogenesis in DM that might help to improve testicular function, and subsequently restore male fertility.

MATERIALS AND METHODS

DM-induced adult male rats were given 100 mg/kg/day and 200 mg/kg/day T. diffusa leaf extract orally for 28 consecutive days. Rats were then sacrificed; sperm and testes were harvested and sperm parameter analysis were performed. Histo-morphological changes in the testes were observed. Biochemical assays were performed to measure testosterone and testicular oxidative stress levels. Immunohistochemistry and double immunofluorescence were used to monitor oxidative stress and inflammation levels in testes as well as Sertoli and steroidogenic marker proteins' expression.

RESULTS

Treatment with T. diffusa restores sperm count, motility, and viability near normal and reduces sperm morphological abnormalities and sperm DNA fragmentation in diabetic rats. T. diffusa treatment also reduces testicular NOX-2 and lipid peroxidation levels, increases testicular antioxidant enzymes (SOD, CAT, and GPx) activities, ameliorates testicular inflammation via downregulating NF-ΚB, p-Ikkβ and TNF-α and upregulating IκBα expression. In diabetic rats, T. diffusa treatment increases testicular steroidogenic proteins (StAR, CYP11A1, SHBG, and ARA54, 3 and 17β-HSD) and plasma testosterone levels. Furthermore, in diabetic rats treated with T. diffusa, Sertoli cell marker proteins including Connexin 43, N-cadherin, and occludin levels in the testes were elevated.

CONCLUSION

T. diffusa treatment could help to ameliorate the detrimental effects of DM on the testes, thus this plant has potential to be used to restore male fertility.

Follicle-stimulating hormone signaling in Sertoli cells: a licence to the early stages of spermatogenesis

Follicle-stimulating hormone signaling is essential for the initiation and early stages of spermatogenesis. Follicle-stimulating hormone receptor is exclusively expressed in Sertoli cells. As the only type of somatic cell in the seminiferous tubule, Sertoli cells regulate spermatogenesis not only by controlling their own number and function but also through paracrine actions to nourish germ cells surrounded by Sertoli cells. After follicle-stimulating hormone binds to its receptor and activates the follicle-stimulating hormone signaling pathway, follicle-stimulating hormone signaling will establish a normal Sertoli cell number and promote their differentiation. Spermatogonia pool maintenance, spermatogonia differentiation and their entry into meiosis are also positively regulated by follicle-stimulating hormone signaling. In addition, follicle-stimulating hormone signaling regulates germ cell survival and limits their apoptosis. Our review summarizes the aforementioned functions of follicle-stimulating hormone signaling in Sertoli cells. We also describe the clinical potential of follicle-stimulating hormone treatment in male patients with infertility. Furthermore, our review may be helpful for developing better therapies for treating patients with dysfunctional follicle-stimulating hormone signaling in Sertoli cells.

Testicular Hypoplasia with Normal Fertility in Neudesin-Knockout Mice

Neudesin is a secretory protein involved in the brain development during embryonic period and diet-induced development of adipose tissue. Although neudesin is also expressed in the testis, its physiological functions in the testis have not been documented. Therefore, we examined neudesin-encoding neuron-derived neurotrophic factor (Nenf) gene-knockout (Neudesin-KO) mice to clarify the functions of neudesin in the testis. The testicular size of the Neudesin-KO mice was significantly smaller than that of wild-type (WT) mice. However, histological analyses did not reveal any abnormalities in the testis, caput epididymis, and cauda epididymis. Sperm number in the cauda epididymis was comparable between WT and KO mice. Neudesin-KO male mice produced vaginal plugs on paired WT female mice, with a frequency similar to that in WT male mice. A similar number of embryos were developed in the females copulated with WT and Neudesin-KO males. Molecular analysis indicated that the ion transporters Slc19a1 and Kcnk3 were more expressed in the testis of Neudesin-KO mice than in the testis of WT mice, suggesting that the transport of ions and some nutrients in the testis has some abnormalities. Testicular size decreased on postnatal day 6, but not on the day of birth, indicating that neudesin is involved in the postnatal, but not embryonic, development of testis. These results indicate a novel role of neudesin in the development of testis.

Actions and Roles of FSH in Germinative Cells

Follicle stimulating hormone (FSH) is produced by the pituitary gland in a coordinated hypothalamic-pituitary-gonadal (HPG) axis event, plays important roles in reproduction and germ cell development during different phases of reproductive development (fetal, neonatal, puberty, and adult life), and is consequently essential for fertility. FSH is a heterodimeric glycoprotein hormone of two dissociable subunits, α and β. The FSH β-subunit (FSHβ) function starts upon coupling to its specific receptor: follicle-stimulating hormone receptor (FSHR). FSHRs are localized mainly on the surface of target cells on the testis and ovary (granulosa and Sertoli cells) and have recently been found in testicular stem cells and extra-gonadal tissue. Several reproduction disorders are associated with absent or low FSH secretion, with mutation of the FSH β-subunit or the FSH receptor, and/or its signaling pathways. However, the influence of FSH on germ cells is still poorly understood; some studies have suggested that this hormone also plays a determinant role in the self-renewal of germinative cells and acts to increase undifferentiated spermatogonia proliferation. In addition, in vitro, together with other factors, it assists the process of differentiation of primordial germ cells (PGCLCs) into gametes (oocyte-like and SSCLCs). In this review, we describe relevant research on the influence of FSH on spermatogenesis and folliculogenesis, mainly in the germ cell of humans and other species. The possible roles of FSH in germ cell generation in vitro are also presented.

3,5,6-trichloro-2-pyridinol intensifies the effect of chlorpyrifos on the paracrine function of Sertoli cells by preventing binding of testosterone and the androgen receptor

3,5,6-Trichloro-2-pyridinol (TCP) is an important biomarker and one of the final metabolites of chlorpyrifos (CPF). TCP inhibits secretion of sex hormones. Similar to CPF, TCP can bind to sex steroid hormone receptors and decrease the secretion of sex hormones. However, little attention has been paid to the ability of TCP and CPF to interfere with androgen receptor (AR) in Sertoli cells. This study aimed to explain how TCP promotes the inhibitory effect of CPF on the paracrine function of Sertoli cells. Western blotting indicated that after 20 weeks of exposure, expression of AR in testes was significantly reduced by CPF. An in vitro assay measured the cytotoxicity of CPF, TCP and diethylphosphate (DEP) on viability of Sertoli cells by Cell Counting Kit-8. CPF cytotoxicity was greater than that of TCP, and TCP cytotoxicity was greater than that of DEP at concentrations of 1000 μmol/L. Western blotting indicated that TCP and CPF both decreased expression of AR and cAMP-response element binding protein phosphorylation, while DEP had no effect in Sertoli cells, which are important in regulating paracrine function of Sertoli cells. The fluorescence measurements and docking studies revealed that testosterone, CPF and TCP showed four types of intermolecular interactions with AR, highlighting alkyl bonds with some of the same amino acids. Compared with testosterone, CPF and TCP also showed significant synergistic interaction with AR. CPF interacted with more amino acids and interaction energy than TCP did. This research elucidates TCP in the antiandrogenic effect of CPF on the paracrine function and suggests that TCP or chemicals with a trichloropyridine structure must be considered during reproductive toxicity assessment of potential environmental pollutants.

Chlorpyrifos-induced reproductive toxicity in rats could be partly relieved under high-fat diet

The widely used pesticide, chlorpyrifos, was found to inhibit the secretion of sex hormones and decrease the count and quality of sperm. A high-fat diet damaged the reproductive system by inducing oxidative damage and interfering with hormone synthesis, indicating the possibility of diet-specific effects of chlorpyrifos on reproductive toxicity. Several studies have demonstrated diet-specific toxicity of pesticides in the central nervous system, metabolism and gut microbiome, but the effect of a high-fat diet on the reproductive toxicity of chlorpyrifos has not been studied. In this study, rats were fed a normal-fat or high-fat diet and exposed to 3.0 mg chlorpyrifos/kg body weight by gavage for 20 weeks. Chlorpyrifos changed the sperm, serum hormones, oxidative stress in the testis, and enzyme activity related to spermatogenesis in rat testes when comparing the different diets. Chlorpyrifos significantly decreased total sperm count, serum testosterone and gonadotropin levels and the activity of enzymes involved in spermatogenesis, as well as lead to oxidative damage in the testis. It was interesting that a high-fat diet relieved all these effects, and chlorpyrifos only exhibited obvious reproductive toxicity in the normal-fat condition. It was necessary to consider the effect of dietary fats when evaluating pesticide toxicity.

Multiple signaling pathways in Sertoli cells: recent findings in spermatogenesis

The functions of Sertoli cells in spermatogenesis have attracted much more attention recently. Normal spermatogenesis depends on Sertoli cells, mainly due to their influence on nutrient supply, maintenance of cell junctions, and support for germ cells' mitosis and meiosis. Accumulating evidence in the past decade has highlighted the dominant functions of the MAPK, AMPK, and TGF-β/Smad signaling pathways during spermatogenesis. Among these pathways, the MAPK signaling pathway regulates dynamics of tight junctions and adherens junctions, proliferation and meiosis of germ cells, proliferation and lactate production of Sertoli cells; the AMPK and the TGF-β/Smad signaling pathways both affect dynamics of tight junctions and adherens junctions, as well as the proliferation of Sertoli cells. The AMPK signaling pathway also regulates lactate supply. These signaling pathways combine to form a complex regulatory network for spermatogenesis. In testicular tumors or infertile patients, the activities of these signaling pathways in Sertoli cells are abnormal. Clarifying the mechanisms of signaling pathways in Sertoli cells on spermatogenesis provides new insights into the physiological functions of Sertoli cells in male reproduction, and also serves as a pre-requisite to identify potential therapeutic targets in abnormal spermatogenesis including testicular tumor and male infertility.

Reelin regulates male mouse reproductive capacity via the sertoli cells

Reelin plays important roles in brain development. Reeler mutant mice that lack the protein reelin (RELN) suffer from cell type- and region-dependent changes in their neocortical layers, and adult reeler mutant mice have dilated seminiferous tubules. Meanwhile, the mechanism by which Reelin regulates the spermatogenic cell development in mice and their reproductive abilities remains unclear. In the present study, we used reeler mutant mice to investigate the effects of Reelin on reproduction in mice. The results indicated variations in sex hormone expression among the reeler mice, indicating that they produce few offspring and their spermatogenic cells are irregularly developed. Moreover, glial cell line-derived neurotrophic factor (GDNF)/GDNF family receptor alpha 1, Ras/extracellular regulated protein kinases (ERK), and promyelocytic leukemia zinc finger (PLZF)/chemokine (C-X-C motif) receptor 4 (CXCR4) serve as potential regulatory pathways that respond to the changes in sertoli cells and the niche of male germ cells. Our findings provided valuable insights into the role of reeler in the reproductive abilities of male mice and development of their spermatogonia stem cells.

Effects of nociceptin and nocistatin on uterine contraction

The presence and effects of nociceptin (N/OFQ) and nocistatin (NST) in the central nervous system have been reasonably well described, but less data are available on their peripheral functions. Besides their presence in several peripheral organs (white blood cells, airway, liver, skin, vascular and intestinal smooth muscles, ovary, and testis), they have been found in the pregnant myometrium in both rat and human. The level of their precursor prepronociceptin is elevated in the preterm human myometrium as compared with full-term samples, whereas it gradually increases toward term in the pregnant rat uterus. Both N/OFQ and NST inhibit myometrial contractions, an effect which can be enhanced by naloxone and blocked by Ca²⁺-dependent K⁺ channel (BK(Ca)) inhibitors. Both compounds increase the myometrial cAMP level which may be responsible for the activation of this channel and subsequent intracellular hyperpolarization. NST releases calcitonin gene-related peptide from the sensory nerve ends, which explains its cAMP-elevating effect. In contrast with the nervous system, where they behave as antagonists, N/OFQ and NST are able to potentiate the uterine-relaxing effect of each other in both rat and human tissues. Further studies are required to clarify the roles of N/OFQ and NST in the regulation of the myometrial contractions and the perception of pain during delivery.

Nociceptin and meiosis during spermatogenesis in postnatal testes

Phosphorylated Rec8, a key component of cohesin, mediates the association and disassociation, "dynamics," of chromosomes occurring in synaptonemal complex formation, crossover recombination, and sister chromatid cohesion during meiosis in germ cells. Yet, the extrinsic factors triggering meiotic chromosome dynamics remained unclear. In postnatal testes, follicle-stimulating hormone (FSH) acts directly on somatic Sertoli cells to activate gene expression via an intracellular signaling pathway composed of cAMP, cAMP-dependent protein kinase (PKA), and cAMP-response element-binding protein (CREB), and promotes germ cell development and spermatogenesis indirectly. Yet, the paracrine factors mediating the FSH effects to germ cells remained elusive. We have shown that nociceptin, known as a neuropeptide, is upregulated by FSH signaling through cAMP/PKA/CREB pathway in Sertoli cells of postnatal murine testes. Chromatin immunoprecipitation from Sertoli cells demonstrated that CREB phosphorylated at Ser133 associates with prepronociceptin gene encoding nociceptin. Analyses with Sertoli cells and testes revealed that both prepronociceptin mRNA and the nociceptin peptide are induced after FSH signaling is activated. In addition, the nociceptin peptide is induced in testes after 9 days post partum following FSH surge. Thus, our findings may identify nociceptin as a novel paracrine mediator of the FSH effects in the regulation of spermatogenesis; however, very little has known about the functional role of nociceptin in spermatogenesis. We have shown that nociceptin induces Rec8 phosphorylation, triggering chromosome dynamics, during meiosis in spermatocytes of postnatal murine testes. The nociceptin receptor Oprl-1 is exclusively expressed in the plasma membrane of testicular germ cells, mostly spermatocytes. Treatment of testes with nociceptin resulted in a rapid phosphorylation of Rec8. Injection of nociceptin into mice stimulated Rec8 phosphorylation and meiotic chromosome dynamics in testes, whereas injection of nocistatin, a specific inhibitor for nociceptin, abolished them. Therefore, our findings suggest that nociceptin is a novel extrinsic factor that plays a crucial role in the progress of meiosis during spermatogenesis.

Regulation of spermatogonial stem cell self-renewal and spermatocyte meiosis by Sertoli cell signaling

Spermatogenesis is a continuous and productive process supported by the self-renewal and differentiation of spermatogonial stem cells (SSCs), which arise from undifferentiated precursors known as gonocytes and are strictly controlled in a special 'niche' microenvironment in the seminiferous tubules. Sertoli cells, the only somatic cell type in the tubules, directly interact with SSCs to control their proliferation and differentiation through the secretion of specific factors. Spermatocyte meiosis is another key step of spermatogenesis, which is regulated by Sertoli cells on the luminal side of the blood-testis barrier through paracrine signaling. In this review, we mainly focus on the role of Sertoli cells in the regulation of SSC self-renewal and spermatocyte meiosis, with particular emphasis on paracrine and endocrine-mediated signaling pathways. Sertoli cell growth factors, such as glial cell line-derived neurotrophic factor (GDNF) and fibroblast growth factor 2 (FGF2), as well as Sertoli cell transcription factors, such as ETS variant 5 (ERM; also known as ETV5), nociceptin, neuregulin 1 (NRG1), and androgen receptor (AR), have been identified as the most important upstream factors that regulate SSC self-renewal and spermatocyte meiosis. Other transcription factors and signaling pathways (GDNF-RET-GFRA1 signaling, FGF2-MAP2K1 signaling, CXCL12-CXCR4 signaling, CCL9-CCR1 signaling, FSH-nociceptin/OPRL1, retinoic acid/FSH-NRG/ERBB4, and AR/RB-ARID4A/ARID4B) are also addressed.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Nocistatin inhibits pregnant rat uterine contractions in vitro: roles of calcitonin gene-related peptide and calcium-dependent potassium channel

The endogenous neuropeptide nociceptin/orphanin FQ, translated from the prepronociceptin gene, exerts a contraction-inhibitory effect on the rat uterus. As nocistatin has been reported to cause functional antagonism of the pro-nociceptive effects of nociceptin, we set out to investigate its effects on the pregnant rat uterus and to elucidate its signalling pathway. The expression of prepronociceptin mRNA in the uterus and nocistatin levels in the uterus and the plasma were confirmed by RT-PCR and radioimmunoassay. The uterine levels of prepronociceptin mRNA and nocistatin were significantly increased by the last day of pregnancy, while the plasma nocistatin levels remained unchanged. In the isolated organ bath studies nocistatin inhibited the prostaglandin- and the KCl-evoked contractions in the uterus dose-dependently. This latter effect was decreased by preincubation with capsaicin. Incubation with calcitonin gene-related peptide after capsaicin treatment caused an elevation in the contraction-inhibitory effect of nocistatin. The effect of nocistatin was also decreased by the Ca(2+)-dependent K(+) channel inhibitor paxilline, against spontaneous uterine contractions. Nociceptin potentiated the action of nocistatin. Naloxone decreased the effect of nocistatin administered either alone or in combination with nociceptin. In Ca(2+)-poor environment, this effect of naloxone was suspended. Enzyme immunoassay for the uterine intracellular cAMP levels partially confirmed the results of in vitro contractility studies. We conclude that nocistatin, generated locally in the uterus, exerts an inhibitory effect, the mechanism being mediated in part by Ca(2+)-dependent K(+) channels, the elevation of cAMP levels and sensory neuropeptides.

Nociceptin induces Rec8 phosphorylation and meiosis in postnatal murine testes

Phosphorylated Rec8, a key component of cohesin, mediates the association and disassociation, "dynamics," of chromosomes occurring in synaptonemal complex formation, crossover recombination, and sister chromatid cohesion during meiosis. Yet, the extrinsic factors triggering meiotic chromosome dynamics remain elusive. We have recently found that nociceptin, known as a neuropeptide, is up-regulated by follicle-stimulating hormone in Sertoli cells in postnatal murine testes; however, very little is known about the functional role of nociceptin in spermatogenesis. Here, we show that nociceptin induces Rec8 phosphorylation, triggering chromosome dynamics, in spermatocytes during meiosis in postnatal murine testes. The nociceptin receptor Oprl-1 is exclusively expressed in the plasma membrane of testicular germ cells, mostly spermatocytes. Treatment of testes with nociceptin resulted in a rapid phosphorylation of Rec8. Injection of nociceptin into mice stimulated Rec8 phosphorylation and meiotic chromosome dynamics in testes, whereas injection of nocistatin, a specific inhibitor of nociceptin, abolished them. These findings suggest that nociceptin is a novel extrinsic factor that plays a crucial role in the progress of meiosis.