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Abot A, Robert V, Fleurot R, Dardente H, Hellier V, Froment P, Duittoz A, Knauf C, Dufourny L. How does apelin affect LH levels? An investigation at the level of GnRH and KNDy neurons. Mol Cell Endocrinol 2022; 557:111752. [PMID: 35973528 DOI: 10.1016/j.mce.2022.111752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 07/27/2022] [Accepted: 08/04/2022] [Indexed: 11/19/2022]
Abstract
Hypothalamic control of reproduction relies on GnRH and kisspeptin (KP) secretions. KP neurons are sensitive to sex steroids and metabolic status and their distribution overlaps with neurons producing apelin, a metabolic hormone known to decrease LH secretion in rats. Here, we observed neuroanatomical contacts between apelin fibers and both KP and GnRH neurons in the hypothalamus of male rodents. Intracerebroventricular apelin infusion for 2 weeks in male mice did not decrease LH levels nor did it affect gene expression for KP, neurokinin B and dynorphin. Finally, increasing apelin concentrations did not modulate Ca2+ levels of cultured GnRH neurons, while 10 μM apelin infusion on forskolin pretreated GnRH neurons revoked a rhythmic activity in 18% of GnRH neurons. These results suggest that acute apelin effect on LH secretion does not involve modulation of gene expression in KP neurons but may affect the secretory activity of GnRH neurons.
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Affiliation(s)
- Anne Abot
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1220, Université Paul Sabatier, UPS, Institut de Recherche en Santé Digestive et Nutrition (IRSD), CHU Purpan, Place du Docteur Baylac, International Laboratory NeuroMicrobiota, CS 60039, 31024, Toulouse Cedex 3, France
| | - Vincent Robert
- CNRS, IFCE, INRAE, Université de Tours, PRC, F-37380, Nouzilly, France
| | - Renaud Fleurot
- CNRS, IFCE, INRAE, Université de Tours, PRC, F-37380, Nouzilly, France
| | - Hugues Dardente
- CNRS, IFCE, INRAE, Université de Tours, PRC, F-37380, Nouzilly, France
| | - Vincent Hellier
- CNRS, IFCE, INRAE, Université de Tours, PRC, F-37380, Nouzilly, France
| | - Pascal Froment
- CNRS, IFCE, INRAE, Université de Tours, PRC, F-37380, Nouzilly, France
| | - Anne Duittoz
- CNRS, IFCE, INRAE, Université de Tours, PRC, F-37380, Nouzilly, France
| | - Claude Knauf
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1220, Université Paul Sabatier, UPS, Institut de Recherche en Santé Digestive et Nutrition (IRSD), CHU Purpan, Place du Docteur Baylac, International Laboratory NeuroMicrobiota, CS 60039, 31024, Toulouse Cedex 3, France
| | - Laurence Dufourny
- CNRS, IFCE, INRAE, Université de Tours, PRC, F-37380, Nouzilly, France.
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Delli V, Silva MSB, Prévot V, Chachlaki K. The KiNG of reproduction: Kisspeptin/ nNOS interactions shaping hypothalamic GnRH release. Mol Cell Endocrinol 2021; 532:111302. [PMID: 33964320 DOI: 10.1016/j.mce.2021.111302] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 04/20/2021] [Accepted: 04/23/2021] [Indexed: 12/21/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) is the master regulator of the hypothalamic-pituitary-gonadal (HPG) axis, and therefore of fertility and reproduction. The release pattern of GnRH by the hypothalamus includes both pulses and surges. However, despite a considerable body of evidence in support of a determinant role for kisspeptin, the mechanisms regulating a GnRH pulse and surge remain a topic of debate. In this review we challenge the view of kisspeptin as an absolute "monarch", and instead present the idea of a Kisspeptin-nNOS-GnRH or "KiNG" network that is responsible for generating the "GnRH pulse" and "GnRH surge". In particular, the neuromodulator nitric oxide (NO) has opposite effects to kisspeptin on GnRH secretion in many respects, acting as the Yin to kisspeptin's Yang and creating a dynamic system in which kisspeptin provides the "ON" signal, promoting GnRH release, while NO mediates the "OFF" signal, acting as a tonic brake on GnRH secretion. This interplay between an activator and an inhibitor, which is in turn fine-tuned by the gonadal steroid environment, thus leads to the generation of GnRH pulses and surges and is crucial for the proper development and function of the reproductive axis.
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Affiliation(s)
- Virginia Delli
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France
| | - Mauro S B Silva
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France
| | - Vincent Prévot
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France
| | - Konstantina Chachlaki
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S 1172, F-59000, Lille, France; FHU, 1000 Days for Health, F-59000, Lille, France; University Research Institute of Child Health and Precision Medicine, National and Kapodistrian University of Athens, "Aghia Sophia" Children's Hospital, Athens, Greece.
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Nitric oxide resets kisspeptin-excited GnRH neurons via PIP2 replenishment. Proc Natl Acad Sci U S A 2021; 118:2012339118. [PMID: 33443156 DOI: 10.1073/pnas.2012339118] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Fertility relies upon pulsatile release of gonadotropin-releasing hormone (GnRH) that drives pulsatile luteinizing hormone secretion. Kisspeptin (KP) neurons in the arcuate nucleus are at the center of the GnRH pulse generation and the steroid feedback control of GnRH secretion. However, KP evokes a long-lasting response in GnRH neurons that is hard to reconcile with periodic GnRH activity required to drive GnRH pulses. Using calcium imaging, we show that 1) the tetrodotoxin-insensitive calcium response evoked by KP relies upon the ongoing activity of canonical transient receptor potential channels maintaining voltage-gated calcium channels in an activated state, 2) the duration of the calcium response is determined by the rate of resynthesis of phosphatidylinositol 4,5-bisphosphate (PIP2), and 3) nitric oxide terminates the calcium response by facilitating the resynthesis of PIP2 via the canonical pathway guanylyl cyclase/3',5'-cyclic guanosine monophosphate/protein kinase G. In addition, our data indicate that exposure to nitric oxide after KP facilitates the calcium response to a subsequent KP application. This effect was replicated using electrophysiology on GnRH neurons in acute brain slices. The interplay between KP and nitric oxide signaling provides a mechanism for modulation of the refractory period of GnRH neurons after KP exposure and places nitric oxide as an important component for tonic GnRH neuronal pulses.
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Bálint F, Csillag V, Vastagh C, Liposits Z, Farkas I. Insulin-Like Growth Factor 1 Increases GABAergic Neurotransmission to GnRH Neurons via Suppressing the Retrograde Tonic Endocannabinoid Signaling Pathway in Mice. Neuroendocrinology 2021; 111:1219-1230. [PMID: 33361699 DOI: 10.1159/000514043] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 12/23/2020] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Hypophysiotropic gonadotropin-releasing hormone (GnRH) neurons orchestrate various physiological events that control the onset of puberty. Previous studies showed that insulin-like growth factor 1 (IGF-1) induces the secretion of GnRH and accelerates the onset of puberty, suggesting a regulatory role of this hormone upon GnRH neurons. METHODS To reveal responsiveness of GnRH neurons to IGF-1 and elucidate molecular pathways acting downstream to the IGF-1 receptor (IGF-1R), in vitro electrophysiological experiments were carried out on GnRH-GFP neurons in acute brain slices from prepubertal (23-29 days) and pubertal (50 days) male mice. RESULTS Administration of IGF-1 (13 nM) significantly increased the firing rate and frequency of spontaneous postsynaptic currents and that of excitatory GABAergic miniature postsynaptic currents (mPSCs). No GABAergic mPSCs were induced by IGF-1 in the presence of the GABAA-R blocker picrotoxin. The increase in the mPSC frequency was prevented by the use of the IGF-1R antagonist, JB1 (1 µM), or the intracellularly applied PI3K blocker (LY294002, 50 µM), showing involvement of IGF-1R and PI3K in the mechanism. Blockade of the transient receptor potential vanilloid 1, an element of the tonic retrograde endocannabinoid machinery, by AMG9810 (10 µM) or antagonizing the cannabinoid receptor type-1 by AM251 (1 µM) abolished the effect. DISCUSSION/CONCLUSION These findings indicate that IGF-1 arrests the tonic retrograde endocannabinoid pathway in GnRH neurons, and this disinhibition increases the release of GABA from presynaptic terminals that, in turn, activates GnRH neurons leading to the fine-tuning of the hypothalamo-pituitary-gonadal axis.
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Affiliation(s)
- Flóra Bálint
- Institute of Experimental Medicine, Laboratory of Endocrine Neurobiology, Budapest, Hungary
| | - Veronika Csillag
- Institute of Experimental Medicine, Laboratory of Endocrine Neurobiology, Budapest, Hungary
- Roska Tamás Doctoral School of Sciences and Technology, Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest, Hungary
| | - Csaba Vastagh
- Institute of Experimental Medicine, Laboratory of Endocrine Neurobiology, Budapest, Hungary
| | - Zsolt Liposits
- Institute of Experimental Medicine, Laboratory of Endocrine Neurobiology, Budapest, Hungary
- Department of Neuroscience, Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest, Hungary
| | - Imre Farkas
- Institute of Experimental Medicine, Laboratory of Endocrine Neurobiology, Budapest, Hungary,
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McCosh RB, Lopez JA, Szeligo BM, Bedenbaugh MN, Hileman SM, Coolen LM, Lehman MN, Goodman RL. Evidence that Nitric Oxide Is Critical for LH Surge Generation in Female Sheep. Endocrinology 2020; 161:bqaa010. [PMID: 32067028 PMCID: PMC7060766 DOI: 10.1210/endocr/bqaa010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 01/31/2020] [Indexed: 12/14/2022]
Abstract
Elevated and sustained estradiol concentrations cause a gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) surge that is necessary for ovulation. In sheep, several different neural systems have been implicated in this stimulatory action of estradiol and this study focused on somatostatin (SST) neurons in the ventral lateral region of the ventral medial nucleus (vlVMN) which express c-Fos during the surge. First, we determined if increased activity of SST neurons could be related to elevated GnRH secretion by assessing SST synapses onto GnRH neurons and neurons coexpressing kisspeptin, neurokinin B, dynorphin (KNDy). We found that the percentage of preoptic area GnRH neurons that receive SST input increased during the surge compared with other phases of the cycle. However, since SST is generally inhibitory, and pharmacological manipulation of SST signaling did not alter the LH surge in sheep, we hypothesized that nitric oxide (NO) was also produced by these neurons to account for their activation during the surge. In support of this hypothesis we found that (1) the majority of SST cells in the vlVMN (>80%) contained neuronal nitric oxide synthase (nNOS); (2) the expression of c-Fos in dual-labeled SST-nNOS cells, but not in single-labeled cells, increased during the surge compared with other phases of the cycle; and (3) intracerebroventricular (ICV) infusion of the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester, completely blocked the estrogen-induced LH surge. These data support the hypothesis that the population of SST-nNOS cells in the vlVMN are a source of NO that is critical for the LH surge, and we propose that they are an important site of estradiol positive feedback in sheep.
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Affiliation(s)
- Richard B McCosh
- Department of Physiology and Pharmacology, West Virginia University Health Science Center, Morgantown, West Virginia
| | - Justin A Lopez
- Department of Physiology and Pharmacology, West Virginia University Health Science Center, Morgantown, West Virginia
| | - Brett M Szeligo
- Department of Physiology and Pharmacology, West Virginia University Health Science Center, Morgantown, West Virginia
| | - Michelle N Bedenbaugh
- Department of Physiology and Pharmacology, West Virginia University Health Science Center, Morgantown, West Virginia
| | - Stanley M Hileman
- Department of Physiology and Pharmacology, West Virginia University Health Science Center, Morgantown, West Virginia
| | - Lique M Coolen
- Brain Health Research Institute, Kent State University, Kent, Ohio
- Department of Biological Sciences, Kent State University, Kent, Ohio
| | - Michael N Lehman
- Brain Health Research Institute, Kent State University, Kent, Ohio
| | - Robert L Goodman
- Department of Physiology and Pharmacology, West Virginia University Health Science Center, Morgantown, West Virginia
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Estradiol Increases Glutamate and GABA Neurotransmission into GnRH Neurons via Retrograde NO-Signaling in Proestrous Mice during the Positive Estradiol Feedback Period. eNeuro 2018; 5:eN-NWR-0057-18. [PMID: 30079374 PMCID: PMC6073979 DOI: 10.1523/eneuro.0057-18.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 06/26/2018] [Accepted: 07/09/2018] [Indexed: 12/20/2022] Open
Abstract
Surge release of gonadotropin-releasing hormone (GnRH) is essential in the activation of pituitary gonadal unit at proestrus afternoon preceded by the rise of serum 17β-estradiol (E2) level during positive feedback period. Here, we describe a mechanism of positive estradiol feedback regulation acting directly on GnRH-green fluorescent protein (GFP) neurons of mice. Whole-cell clamp and loose patch recordings revealed that a high physiological dose of estradiol (200 pM), significantly increased firing rate at proestrus afternoon. The mPSC frequency at proestrus afternoon also increased, whereas it decreased at metestrus afternoon and had no effect at proestrus morning. Inhibition of the estrogen receptor β (ERβ), intracellular blockade of the Src kinase and phosphatidylinositol 3 kinase (PI3K) and scavenge of nitric oxide (NO) inside GnRH neurons prevented the facilitatory estradiol effect indicating involvement of the ERβ/Src/PI3K/Akt/nNOS pathway in this fast, direct stimulatory effect. Immunohistochemistry localized soluble guanylate cyclase, the main NO receptor, in both glutamatergic and GABAergic terminals innervating GnRH neurons. Accordingly, estradiol facilitated neurotransmissions to GnRH neurons via both GABAA-R and glutamate/AMPA/kainate-R. These results indicate that estradiol acts directly on GnRH neurons via the ERβ/Akt/nNOS pathway at proestrus afternoon generating NO that retrogradely accelerates GABA and glutamate release from the presynaptic terminals contacting GnRH neurons. The newly explored mechanism might contribute to the regulation of the GnRH surge, a fundamental prerequisite of the ovulation.
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