Discovery of gonadotropin-inhibitory hormone (GnIH), progress in GnIH research on reproductive physiology and behavior and perspective of GnIH research on neuroendocrine regulation of reproduction

Effect of active immunization with OPN5 on follicular development and egg production in quail under different photoperiods

OPN5 is one of the main deep brain photoreceptors (DBPs), converting photoperiodic information into neuroendocrine signals to regulate reproduction in birds. This study investigated the mechanism of OPN5-mediated photoperiodic regulation of reproduction by active immunization against OPN5. 96 female quail were divided into OPN5-immunized and control group under the same photoperiod: 16 L:8 D (d 1 to d 35), 8 L:16 D (d 36 to d 70) and 12 L:12 D (d 71 to d 126). OPN5-immunized group was conducted with OPN5 protein vaccination and control group was given a blank vaccine. Samples were collected on d 1, d 30, d 60, and d 126. Results showed switching photoperiod to 8 L:16 D decreased the laying rate, GSI%, numbers of YFs and WFs, serum levels of PRL, P4 and E2, and pituitary PRL and TSHβ protein expressions in both groups (P < 0.05). Whereas the OPN5-immunized group exhibited higher laying rates than the control group (P < 0.05). The control group showed reduced GnRHR and TSHβ gene expressions in the pituitary and increased GnIH and DIO3 transcript and/or protein abundance in the hypothalamus. (P < 0.05). The OPN5-immunized group had lower DIO3 expression at both mRNA and protein levels. (P < 0.05). Switching photoperiod from 8 L:16 D to 12 L:12 D increased the laying rates, GSI%, numbers of YFs and WFs, serum levels of PRL, and PRL protein expression in both groups (P < 0.05), and the responses were more pronounced in OPN5-immunized group (P < 0.05). In contrast to the control group, quail with OPN5-immunization had higher OPN5 and DIO2 transcript and/or protein levels but lower DIO3 expressions in the hypothalamus along the transition photoperiods (P < 0.05). The results revealed that OPN5 responds to photoperiod transition, and its activation mediates related signaling to up-regulate TSH-DIO2/DIO3 pathway and VIP-PRL secretion to prime quail reproductive functions.

Chronic unpredictable stress (CUS) reduced phoenixin expression, induced abnormal sperm and testis morphology in male rats

Chronic stress caused by prolonged emotional pressure can lead to various physiological issues, including reproductive dysfunction. Although reproductive problems can also induce chronic stress, the impact of chronic stress-induced reproductive dysfunction remains contentious. This study investigates the effects of chronic unpredictable stress (CUS) on reproductive neuropeptides, sperm quality, and testicular morphology. Sixteen twelve-week-old Sprague Dawley rats were divided into two groups: a non-stress control group and a CUS-induced group. The CUS regimen involved various stressors over 28 days, with both groups undergoing behavioural assessments through sucrose-preference and forced-swim tests. Hypothalamic gene expression levels of CRH, PNX, GPR173, kisspeptin, GnRH, GnIH, and spexin neuropeptides were measured via qPCR, while plasma cortisol, luteinizing hormone (LH), and testosterone concentrations were quantified using ELISA. Seminal fluid and testis samples were collected for sperm analysis and histopathological evaluation, respectively. Results showed altered behaviours in CUS-induced rats, reflecting stress impacts. Hypothalamic corticotropin-releasing hormone (CRH) expression and plasma cortisol levels were significantly higher in CUS-induced rats compared to controls (p < 0.05). Conversely, phoenixin (PNX) expression decreased in the CUS group (p < 0.05), while kisspeptin, spexin, and gonadotropin-inhibitory hormone (GnIH) levels showed no significant differences between groups. Despite a significant increase in GnRH expression (p < 0.05), plasma LH and testosterone concentrations were significantly lower (p < 0.05) in CUS-induced rats. Histopathological analysis revealed abnormal testis morphology in CUS-induced rats, including disrupted architecture, visible interstitial spaces between seminiferous tubules, and absence of spermatogenesis. In conclusion, CUS affects reproductive function by modulating PNX and GnRH expression, influencing cortisol levels, and subsequently reducing plasma LH and testosterone concentrations. This study highlights the complex interplay between chronic stress and reproductive health, emphasizing the significant impact of stress on reproductive functions.

Integrated Transcriptomic-Metabolomic Analysis Reveals the Effect of Different Light Intensities on Ovarian Development in Chickens

Light is a key environmental factor regulating reproduction in avians. However, the mechanism of light intensity regulating ovarian development is still unclear. In this study, 5-week-old (5 wk) partridge broiler breeders were randomly divided into a low-light-intensity group (LL group) and a natural-light-intensity group (NL group) (n = 100). In the rearing period (5 wk to 22 wk), the light intensity of the LL group and NL group were 0.41 ± 0.05 lux and 45.39 ± 1.09 lux, and in the laying period (23 wk to 32 wk) they were 23.92 ± 0.06 lux and 66.93 ± 0.76 lux, respectively. Samples were collected on 22 wk and 32 wk. The results showed that the LL group had a later age at first egg and a longer laying period than the NL group. Serum P4 and LH levels in the LL group were higher than in the NL group on 22 wk (p < 0.05). On 32 wk, P4, E2, LH and FSH levels in the LL group were lower than in the NL group (p < 0.05). Ovarian transcriptomics and metabolomics identified 128 differentially expressed genes (DEGs) and 467 differential metabolites (DMs) on 22 wk; 155 DEGs and 531 DMs on 32 wk between two groups. An enrichment analysis of these DEGs and DMs identified key signaling pathways, including steroid hormone biosynthesis, neuroactive ligand-receptor interaction. In these pathways, genes such as CYP21A1, SSTR2, and NPY may regulate the synthesis of metabolites, including tryptamine, triglycerides, and phenylalanine. These genes and metabolites may play a dominant role in the light-intensity regulation of ovarian development and laying performance in broiler breeders.

Zinc modulates hypothalamo-pituitary-gonadal-liver axis to impair reproduction in female Mystus vittatus (Bloch, 1794)

The present study investigated the effects of zinc on the hypothalamo-pituitary-gonadal-liver (HPGL) axis of the bagrid catfish Mystus vittatus. Female fish (pre-ovulatory and ovulatory phases) were exposed to zinc sulphate at 1/10th of LC50 (5.62 mg/L) for 60 days and sacrificed at every 15-day interval to collect tissues. Zinc concentration in all tissues was significantly higher in the metal-exposed group at all exposure durations compared to control for both phases. Metallothionein (MT) levels increased in the brain, liver and ovary of fish from both phases with exposure duration. Reactive oxygen species (ROS) generation in the brain, liver and ovary tissues increased with exposure duration at both reproductive phases while serum cortisol levels in ovulatory fish increased significantly compared to pre-ovulatory. Condition factor, gonadosomatic index and hepatosomatic index decreased in Zn-exposed fish. Brain GnRH and kisspeptin levels decreased significantly in the Zn-exposed group for both phases. GnIH was significantly higher in Zn-exposed fish. Serum FSH levels in pre-ovulatory and LH levels in ovulatory fish decreased gradually with an increase in the duration of exposure. Zn exposure reduced vitellogenin (Vtg) and estradiol (E2) in the liver and ovary with an increase in duration from both phases. Ovary maturation-inducing hormone (MIH) levels showed a decrease with exposure duration in ovulatory fish. Moreover, Zn-exposed ovulatory fish showed a degenerated oocyte nucleus due to the disintegration of the nuclear membrane. It might be inferred that Zn altered the HPGL regulatory system of M. vittatus reproduction at both the pre-ovulatory and ovulatory phases.

The effect of gonadotropin-inhibitory hormone on steroidogenesis and spermatogenesis by acting through the hypothalamic-pituitary-testis axis in mice

Gonadotropin inhibitory hormone (GnIH) is essential for regulating the reproduction of mammals and inhibiting testicular activities in mice. This study aimed to explore the mechanism of GnIH on spermatogenesis and steroidogenesis by acting through the hypothalamus-pituitary-testis axis of mice. Mice were subcutaneously injected with different doses of GnIH (1 μg/150 μL, 3 μg/150 μL, 6 μg/150 μL, 150 μL saline, twice daily) for 11 days. Subsequently, luteinizing hormone (LH), testosterone (T), and inhibin B (INH B) levels of peripheral blood were determined, and the expression of GnRH synthesis-related genes (GnRH-1, Kiss-1, NPY) and gonadotropin synthesis-related genes (FSH β, LH β, GnRH receptor) in the hypothalamus and pituitary gland were respectively detected. Additionally, the expression of steroidogenesis-related genes/proteins (P450scc, StAR and 3β-HSD) and spermatogenesis-related proteins/genes including LH receptor (LHR), androgen receptor (AR), heat shock factor-2 (HSF-2) and INH B were analyzed using western blot and q-PCR. Results showed that GnIH treatment significantly reduced the concentration of LH in the peripheral blood. Further analysis revealed that GnIH treatment markedly reduced the expression of GnRHImRNA and Kiss-1 mRNA in the hypothalamus, and mRNA levels of FSH β, LH β, and GnRHR genes in the pituitary. We also observed that GnIH treatment significantly decreased T levels and expression of the P450scc, StAR, and 3β-HSD proteins in the testis. Furthermore, GnIH treatment down-regulated LHR, AR proteins, and HSF-2 gene in the testis. Importantly, the INH B concentration of and INH βb mRNA levels significantly declined following GnIH treatment. Additionally, GnIH treatment may induce germ cell apoptosis in the testis of mice. In conclusion, GnIH may suppress spermatogenesis and steroidogenesis by acting through the hypothalamus-pituitary-testis axis in mice.

Gonadotropin-inhibitory hormone and its receptors in teleosts: Physiological roles and mechanisms of actions

Gonadotropin-inhibitory hormone (GnIH) was the first reported hypothalamic neuropeptide inhibiting reproduction in vertebrates. Since its discovery in the quail brain, its orthologs have been identified in a variety of vertebrate species and even protochordates. Depending on the species, the GnIH precursor polypeptides comprise two, three or four mature peptides of the RFamide family. It has been well documented that GnIH inhibits reproduction at the brain-pituitary-gonadal levels and participates in metabolism, stress response, and social behaviors in birds and mammals. However, most studies in fish have mainly been focused on the physiological roles of GnIH in the control of reproduction and results obtained are in some cases conflicting, leaving aside its potential roles in the regulation of other functions. In this manuscript we summarize the information available in fish with respect to the structural diversity of GnIH peptides and functional roles of GnIH in reproduction and other physiological processes. We also highlight the molecular mechanisms of GnIH actions on target cells and possible interactions with other neuroendocrine factors.

Impact of stress on male fertility: role of gonadotropin inhibitory hormone

Studies have implicated oxidative stress-sensitive signaling in the pathogenesis of stress-induced male infertility. However, apart from oxidative stress, gonadotropin inhibitory hormone (GnIH) plays a major role. The present study provides a detailed review of the role of GnIH in stress-induced male infertility. Available evidence-based data revealed that GnIH enhances the release of corticosteroids by activating the hypothalamic-pituitary-adrenal axis. GnIH also mediates the inhibition of the conversion of thyroxine (T4) to triiodothyronine (T3) by suppressing the hypothalamic-pituitary-thyroidal axis. In addition, GnIH inhibits gonadotropin-releasing hormone (GnRH), thus suppressing the hypothalamic-pituitary-testicular axis, and by extension testosterone biosynthesis. More so, GnIH inhibits kisspeptin release. These events distort testicular histoarchitecture, impair testicular and adrenal steroidogenesis, lower spermatogenesis, and deteriorate sperm quality and function. In conclusion, GnIH, via multiple mechanisms, plays a key role in stress-induced male infertility. Suppression of GnIH under stressful conditions may thus be a beneficial prophylactic and/or therapeutic strategy.

Phenotype transition from wild mouflon to domestic sheep

The domestication of animals started around 12,000 years ago in the Near East region. This "endless process" is characterized by the gradual accumulation of changes that progressively marked the genetic, phenotypic and physiological differences between wild and domesticated species. The main distinctive phenotypic characteristics are not all directly attributable to the human-mediated selection of more productive traits. In the last decades, two main hypotheses have been proposed to clarify the emergence of such a set of phenotypic traits across a variety of domestic species. The first hypothesis relates the phenotype of the domesticated species to an altered thyroid hormone-based signaling, whereas the second one relates it to changes in the neural crest cells induced by selection of animals for tameness. These two hypotheses are not necessarily mutually exclusive since they may have contributed differently to the process over time and space. The adaptation model induced by domestication can be adopted to clarify some aspects (that are still controversial and debated) of the long-term evolutionary process leading from the wild Neolithic mouflon to the current domestic sheep. Indeed, sheep are among the earliest animals to have been domesticated by humans, around 12,000 years ago, and since then, they have represented a crucial resource in human history. The aim of this review is to shed light on the molecular mechanisms and the specific genomic variants that underlie the phenotypic variability between sheep and mouflon. In this regard, we carried out a critical review of the most recent studies on the molecular mechanisms that are most accredited to be responsible for coat color and phenotype, tail size and presence of horns. We also highlight that, in such a complicate context, sheep/mouflon hybrids represent a powerful and innovative model for studying the mechanism by which the phenotypic traits related to the phenotypic responses to domestication are inherited. Knowledge of these mechanisms could have a significant impact on the selection of more productive breeds. In fact, as in a journey back in time of animal domestication, the genetic traits of today's domestic species are being progressively and deliberately shaped according to human needs, in a direction opposite to that followed during domestication.

Molecular characterization and ontogenetic expression profiles of LPXRFa and its receptor in Japanese flounder (Paralichthys olivaceus)

Investigations concerning the LPXRFa system are rarely conducted in flatfish species. Here, we first identified and characterized lpxrfa and its cognate receptor lpxrfa-r genes in the Japanese flounder (Paralichthys olivaceus). The coding DNA sequence of lpxrfa was 579 bp in length, wich encoded a 192-aa preprohormone that can produce three mature LPXRFa peptides. The open reading frame (ORF) of lpxrfa-r was 1446 bp in size, and encoded a 481-aa LPXRFa-R protein that encompassed seven hydrophobic transmembrane domains. Subsequently, tissue distribution expression profiles of lpxrfa and lpxrfa-r transcripts were assayed by quantitative real-time PCR. The results indicated that expressions of lpxrfa transcripts were detected at the highest levels in the brain of both females and males, however, lpxrfa-r transcripts were remarkablely expressed in the brain tissue of female fish and in the testis tissue of male fish. Furthermore, transcript levels of lpxrfa and lpxrfa-r genes were investigated during early ontogenetic development, with the maximum expression levels at 30 days post-hatching. Overall, these data contribute to providing preliminary proof for the existence and structure of the LPXRFa system in Japanese flounder, and the study is just the foundation for researching physiological function of LPXRFa system in this species.

Endocrine and molecular regulation mechanisms of follicular development and egg-laying in quails under different photoperiods

Photoperiod is a key environmental factor in regulating bird reproduction and induces neuroendocrine changes through the hypothalamic-pituitary-gonadal (HPG) axis. OPN5, as a deep-brain photoreceptor, transmits light signals to regulate follicular development through TSH-DIO2/DIO3. However, the mechanism among OPN5, TSH-DIO2/DIO3, and VIP/PRL in the HPG axis underlying the photoperiodic regulation of bird reproduction is unclear. In this study, 72 laying quails with 8-week-old were randomly divided into the long-day (LD) group [16 light (L): 8 dark (D)] and the short-day (SD) group (8 L:16 D), and then samples were collected on d 1, d 11, d 22, and d 36 of the experiment. The results showed that compared with the LD group, the SD group significantly inhibited follicular development (P < 0.05), decreased the P4, E2, LH, and PRL in serum (P < 0.05), downregulated the expression of GnRHR, VIP, PRL, OPN5, DIO2, and LHβ (P < 0.05), reduced the expression of GnRH and TSHβ (P > 0.05), and promoted DIO3, GnIH gene expression (P < 0.01). The short photoperiod downregulates OPN5, TSHβ, and DIO2 and upregulates DIO3 expression to regulate the GnRH/GnIH system. The downregulation of GnRHR and upregulation of GnIH resulted in a decrease in LH secretion, which withdrew the gonadotropic effects on ovarian follicles development. Slow down of follicular development and egg laying may also arise from lack of PRL potentiation to small follicle development under short days.

Establishment of Wild-Derived Strains of Japanese Quail (Coturnix japonica) in Field and Laboratory Experiments

Domestic quail are used as both farm and laboratory animals. As the wild ancestor of quails is "endangered," field studies are needed to conserve them. If wild-derived strains of quail are established, they will be unique genetic resources for both farm and laboratory animals. The purpose of the present study was to conduct a field study and create wild-derived quail strains using the breeding stocks in Tokachi, Hokkaido, Japan. Field observations from 2019 to 2022 indicate that wild quails migrate and stay at reproductive sites from late April to late October. Our estimations of the approximate ages of the observed and captured quails imply that adult males have intermittent reproductive opportunities from May to August. Morphological traits collected from adult and juvenile quails in the 2019-2022 population were similar to those previously reported for Japan's 1914 and 1970 populations. Using natural mating of captured wild males and domestic (Dom) females, we established the W50 and W75 strains, which possessed 50% and 75% genetic contributions from the wild stocks. These unique genetic resources can be applied for future conservation and experimental use to understand the domestication history and genetic basis of quantitative traits.

Molecular cloning and bioinformatic characterization of Gonadotropin Inhibitory Hormone (GnIH) and its receptors in the freshwater murrel, Channa punctatus (Bloch, 1793)

Gonadotropin inhibitory hormone belonging to the RFamide peptide family, a hypothalamic neuropeptide, regulates Hypothalamus-pituitary-gonadal (HPG) axis and inhibits gonadal development. GnIH polypeptide precursor has an Arg-Phe-NH2 (RFamide) motif at the C-terminal, which has LPXRF (X = Q or L) domain. The actions of GnIH are mediated through G-protein coupled receptors and upto three receptors have been characterized in many teleosts. GnIH exerts its inhibitory effect on the HPG axis through direct interaction with GnRH and Kisspeptin neurons in the brain and acts directly on the pituitary gonadotrophs. To decipher the role of GnIH in Indian freshwater murrel, Channa punctatus, we sequenced the cDNA encoding GnIH and its two receptors. The identified GnIH mRNA encodes three RFamide peptides having -MPMRF, -MPQRF, and -LPQRFamide motifs. In silico analysis of the amino acid sequence of GnIH exhibits its molecular and functional properties and the protein-protein interaction with significant factors regulating the HPG axis. The 3-D structure of GnIH and its receptors, provides more relevant information about the active residues of these proteins which might be involved in their functioning and interaction with other proteins. Molecular dynamic simulation of GnIH protein has provided more insight into its dynamic behavior. The expression of GnIH and its receptors, shows an inverse correlation with gonadal development during the annual reproductive cycle.

Crosstalk between kisspeptin and gonadotropin-inhibitory hormone in the silence of puberty: preclinical evidence from a calcium signaling study

Kisspeptin and gonadotropin-inhibitory hormone (GnIH) are among suggested neuroendocrine modulators of reproductive function. Intracellular calcium signaling is a critical component in the regulation of a variety of physiological and pathological processes including neurotransmitter release, and, therefore, can be used as signaling indicator for investigating the involvement of kisspeptin, GnIH, and gonadotropin-releasing hormone (GnRH) release. Hence, this study investigated the effects of kisspeptin and GnIH on calcium signaling using immortalized hypothalamic cells (rHypoE-8) as a model. Kisspeptin neurons were loaded with the ratiometric calcium dye (Fura-2 AM, 1 μmol) and intracellular free calcium ([Ca²⁺]_i) responses were quantified using digital fluorescence imaging system. Kisspeptin-10 (100, 300, and 1000 nM) caused a significant increase in [Ca²⁺]_i in rHypoE-8 cells (n = 58, n = 64, and n = 49, respectively, p < 0.001). The kisspeptin receptor antagonist, P234, inhibited the calcium responses to kisspeptin (p < 0.001, n = 32). GnIH (100 and 1000 nM), alone, did not cause any significant change in the mean basal [Ca²⁺]_i levels in kisspeptin cells, but GnIH attenuated the kisspeptin-evoked [Ca²⁺]_i transients (n = 47, p < 0.001). This novel findings of [Ca²⁺]_i signaling in in vitro setting implicate that kisspeptin and GnIH may exert their effects on hypothalamus-pituitary-gonadal (HPG) axis by modulating kisspeptin neurons. These results also implicate that kisspeptin neurons may have an autocrine regulation.

Expression of GnIH and its effects on follicle development and steroidogenesis in quail ovaries under different photoperiods

Photoperiod is an important environmental factor that influence seasonal reproduction behavior in bird and GnIH can play a function in this process through the reproductive axis, and some studies suggest that GnIH may have a direct role at the gonadal level. To investigate the expression of GnIH and its effects on follicle development and steroidogenesis in quail ovaries under different photoperiods, 72 healthy laying quails of 8-wk-old were randomly divided into long day (LD) group [16 light (L): 8 dark (D)] (n = 36) and short day (SD) group (8L:16D) (n = 36). Samples were collected from each group on d1, d11, d22, and d36 of the experiment. The result showed that short day treatment upregulated the level of GnIH in the gonads (P < 0.05), decreased the expression level of CYP19A1,3β-HSD, StAR, LHR, and FSHR and increased the expression level of AMH, AMHR2, GDF9, and BMP15 to inhibit follicle development and ovulation, thus affecting the egg production performance of quails. In vitro culture of quail granulosa cells and treatment with different concentrations of GnIH (0, 1, 10, and 100 ng/mL) for 24 h. Result showed that GnIH inhibited the levels of FSHR, LHR, and steroid synthesis pathways in granulosa cells, upregulated the levels of AMHR2, GDF9, and BMP15. The results suggest that the inhibition of follicle development and reduced egg production in quail by short day treatment is due to GnIH acting at the gonadal level, and GnIH affected the steroid synthesis by inhibiting gonadotropin receptors.

Expression of polyamines and its association with GnRH-I in the hypothalamus during aging in rodent model

GnRH-I and GnIH are the key neuropeptides that regulate the hypothalamic-pituitary-gonadal axis in mammals during aging. Polyamines are important aliphatic amines that are expressed in the brain and show variation with aging. The present study demonstrates evidence of variation in the level of expression of polyamines, GnRH-I and GnIH in the hypothalamus of female mice during aging. The study also suggests regulatory effects of polyamines over expression of the hypothalamic GnRH-I. The study shows a significant positive correlation between polyamines, its associated factors and GnRH-I along with significant negative correlation between polyamines, its associated factors and GnIH. This is the first study to report the effect of polyamines along with lactate or TNF-α or both on GnRH-I expression in GT1-7 cell line. TNF-α and lactate significantly decreased hypothalamic GnRH-I mRNA expression in GT1-7 cells when treated for 24 h. Polyamines (putrescine and agmatine) in contrast, significantly increased GnRH-I mRNA expression in GT1-7 cells when treated for 24 h. Also, polyamines increased GnRH-I mRNA expression when treated in presence of TNF-α or lactate thereby suggesting its neuro-protective role. This study also found 3809 differentially expressed genes through RNA-seq done between the hypothalamic GT1-7 cells treated with putrescine only versus TNF-α and putrescine. The present study suggests for the first time that putrescine treatment to TNFα-primed GT1-7 cells upregulates GnRH-I expression via regulation of several pathways such as calcium ion pathway, estrogen signaling, clock genes as well as regulating other metabolic process like neuronal differentiation and neurulation.

Developmental aspects of the hypothalamic-pituitary network related to reproduction in teleost fish

The hypothalamic-pituitary-gonadal axis is the main system that regulates reproduction in vertebrates through a complex network that involves different neuropeptides, neurotransmitters, and pituitary hormones. Considering that this axis is established early on life, the main goal of the present work is to gather information on its development and the actions of its components during early life stages. This review focuses on fish because their neuroanatomical characteristics make them excellent models to study neuroendocrine systems. The following points are discussed: i) developmental functions of the neuroendocrine components of this network, and ii) developmental disruptions that may impact adult reproduction. The importance of the components of this network and their susceptibility to external/internal signals that can alter their specific early functions and/or even the establishment of the reproductive axis, indicate that more studies are necessary to understand this complex and dynamic network.

Immunodistribution of RFamide-related peptide-3 (RFRP-3) during the seminiferous epithelium cycle in a desert rodent Psammomys obesus

The Sand rat, Psammomys obesus, living northwest of the Algerian Sahara, presents a seasonal reproductive cycle. The purposes of this study were firstly to determine the stages of seminiferous epithelium cycle (SEC) by histological and morphometric analysis and secondly to investigate, for the first time, the testicular expression of RFamide-related peptide-3 (RFRP-3) during the SEC by immunohistochemistry. The results showed that the SEC consists of 14 stages according to the tubular morphology method. RFRP-3 was observed in both testicular compartments: the tubular and the interstitial. Leydig cells exhibited the highest RFRP-3 signal (30.73 % ± 4.80) compared to Sertoli cells (13-15 %). In the germline, RFRP-3 was detected during the late prophase I of meiosis in late pachytene, diplotene and metaphasic spermatocytes I. In addition, only round and triangular spermatids were positive during spermiogenesis. Referring to the SEC, it was found that the increased staining of RFRP-3 in spermatocytes I coincided with late pachytene of XI and XII stages (16.90 % ± 0.69 and 16.61 % ± 0.28, respectively). In spermatids, the labeling decreased in the triangular ones at stage IX (8.04 % ± 0.42). These results suggest the involvement of RFRP-3 in the control of SEC in P. obesus.

Gonadotropin-inhibiting hormone promotes apoptosis of bovine ovary granulosa cells

Gonadotropin-inhibiting hormone (GnIH) inhibits the synthesis and release of gonadotropin by binding to its receptor. GnIH is involved in animal reproductive regulation, especially ovary function. It can regulate the proliferation, apoptosis and hormone secretion of follicular cells. However, the role and molecular mechanism of GnIH in bovine granulosa cell (bGC) apoptosis is unclear. Here, the effects of GnIH on proliferation, apoptosis, and mitochondrial function of bGCs were detected. A 10^-6 mol/mL concentration of GnIH inhibited bGC proliferation, promoted GC apoptosis, and damaged mitochondrial function. Additionally, GnIH significantly decreased the phosphorylation level of p38 (P < 0.01). To explore the role of the p38 signaling pathway in the process of GnIH-induced apoptosis in bGCs, an activator of p38 (U46619) was used to pretreat bGCs. U46619 pretreatment significantly alleviated GnIH damage to bGCs, including proliferation, apoptosis, and mitochondrial function. In conclusion, these results demonstrated that GnIH inhibited proliferation and promoted apoptosis of bGCs via the p38 signaling pathway.

Is Melatonin the Cornucopia of the 21st Century?

Melatonin, an indoleamine hormone produced and secreted at night by pinealocytes and extra-pineal cells, plays an important role in timing circadian rhythms (24-h internal clock) and regulating the sleep/wake cycle in humans. However, in recent years melatonin has gained much attention mainly because of its demonstrated powerful lipophilic antioxidant and free radical scavenging action. Melatonin has been proven to be twice as active as vitamin E, believed to be the most effective lipophilic antioxidant. Melatonin-induced signal transduction through melatonin receptors promotes the expression of antioxidant enzymes as well as inflammation-related genes. Melatonin also exerts an immunomodulatory action through the stimulation of high-affinity receptors expressed in immunocompetent cells. Here, we reviewed the efficacy, safety and side effects of melatonin supplementation in treating oxidative stress- and/or inflammation-related disorders, such as obesity, cardiovascular diseases, immune disorders, infectious diseases, cancer, neurodegenerative diseases, as well as osteoporosis and infertility.