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Cai D, Zhou Z, Cai B, Wang Z, Ju X, Kong S, Yang X, Lin D, Nie Q. Metabolomics reveals the reasons for the occurrence of Pendulous-comb related to egg production performance. Poult Sci 2024; 103:103867. [PMID: 38820880 PMCID: PMC11167520 DOI: 10.1016/j.psj.2024.103867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 04/30/2024] [Accepted: 05/13/2024] [Indexed: 06/02/2024] Open
Abstract
The chicken comb is an essential secondary sexual characteristic to measure sexual maturity and is closely related to reproductive performance. Pendulous comb (PC) and upright comb (UC) are 2 common comb phenotypes in hens, which have been highly associated with egg production performance. However, the reasons for the formation of PC remain undetermined. In this study, we first characterized the PC and UC chicken at start (at 175 d age), peak (at 217 d age), and postlaying (at 300 d age) and found that PC and UC could transform for each other. Furthermore, we suggested that PC chicken demonstrated better egg production performance than UC chicken, especially characterizing comb type in the start-laying period. Moreover, we performed histological evaluation of PC and UC tissue, which suggested that the low density of collagen fibers and acid mucopolysaccharides might lead to the formation of PC. To further explore the possible reasons for PC formation, we performed an untargeted metabolomic analysis of serum between PC and UC chicken in the start, peak, and postlaying periods. The enrichment analysis of period-unique differentially expressed metabolites (DEMs) between PC and UC showed that the different metabolic pathways and nutritional levels might contribute to the formation of PC in the different laying periods. Our research provided critical insights into the phenotypic diversity of chicken comb, establishing a foundation for early selection of chicken egg production performance.
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Affiliation(s)
- Danfeng Cai
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China
| | - Zhen Zhou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China
| | - Bolin Cai
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China
| | - Zhijun Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China; College of Animal Science and Technology, Zhejiang Agriculture and Forestry University, Lin'an 311300, China
| | - Xing Ju
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China
| | - Shaofen Kong
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China
| | - Xin Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China
| | - Duo Lin
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China
| | - Qinghua Nie
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Lingnan Guangdong Laboratory of Agriculture, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China; Guangdong Provincial Key Lab of Agro-Animal Genomics and Molecular Breeding, and Key Laboratory of Chicken Genetics, Breeding and Reproduction, Ministry of Agriculture, Guangzhou, Guangdong 510642, China.
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Dai R, Huang J, Cui L, Sun R, Qiu X, Wang Y, Sun Y. Gut microbiota and metabolites in estrus cycle and their changes in a menopausal transition rat model with typical neuroendocrine aging. Front Endocrinol (Lausanne) 2023; 14:1282694. [PMID: 38161977 PMCID: PMC10755682 DOI: 10.3389/fendo.2023.1282694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 11/13/2023] [Indexed: 01/03/2024] Open
Abstract
Background Neuroendocrine alterations in the mid-life hypothalamus coupled with reproductive decline herald the initiation of menopausal transition. The certain feature and contribution of gut microflora and metabolites to neuroendocrine changes in the menopausal transition remain largely unknown. Methods Fecal samples of rats experiencing different reproductive stages were collected and processed for 16S rRNA and liquid chromatography-mass spectrometry sequencing. The differences of gut microbiota and metabolites between young and middle-aged rats during proestrus and diestrus were analyzed, and their relationships to neuroendocrine aging were then examined. Results At the genus level, Anaeroyorax, Rikenella, Tyzzerella_3, and Atopostipes were abundant at proestrus, while Romboutsia, Turicibacter, Clostridium_sensu_stricto_1, Ruminococcaceae_NK4A214_group, CHKCI002, Ruminococcaceae_UCG-010, Staphylococcus, Family_XII_AD3011_group, Ruminococcaceae UCG-011, and Christensenellaceae_R_7_group were enriched in the diestrus of middle-aged rats. DNF00809, Phocea, and Lachnospiraceae_UCG-006 were found abundant during proestrus instead, while Bacteroides, Lactobacillus, Erysipelatoclostridium, Anaeroplasma, Anaerofustis, Parasutterella, and Enterococcus were enriched at the diestrus of young female individuals. Discriminatory metabolites were identified involving 90 metabolic pathways among the animal sets, which were enriched for steroid hormone biosynthesis, arachidonic metabolism, primary bile acid synthesis, and ovarian steroidogenesis. A total of 21 metabolites lacking in hormone-associated changes in middle-aged female individuals presented positive or negative correlations with the circulating luteinizing hormone, bile acid, fibroblast growth factor 19, and gut hormones. Moreover, close correlations were detected between the intestinal bacteria and their metabolites. Conclusion This study documents specific gut microbial composition changes and concomitant shifting trends of metabolites during menopausal transition, which may initiate the gut-brain dysfunction in neuroendocrine aging.
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Affiliation(s)
- Ruoxi Dai
- Hospital and Institute of Obstetrics and Gynecology, Fudan University, Shanghai, China
| | - Jianqin Huang
- Hospital and Institute of Obstetrics and Gynecology, Fudan University, Shanghai, China
- The Academy of Integrative Medicine, Fudan University, Shanghai, China
- Shanghai Key Laboratory of Female Reproductive Endocrine-Related Disease, Hospital of Obstetrics and Gynecology, Fudan University, Shanghai, China
| | - Liyuan Cui
- Hospital and Institute of Obstetrics and Gynecology, Fudan University, Shanghai, China
| | - Ruiqi Sun
- Department of Clinical Medicine, Clinical College of Anhui Medical University, Hefei, China
| | - Xuemin Qiu
- Hospital and Institute of Obstetrics and Gynecology, Fudan University, Shanghai, China
| | - Yan Wang
- Hospital and Institute of Obstetrics and Gynecology, Fudan University, Shanghai, China
| | - Yan Sun
- Hospital and Institute of Obstetrics and Gynecology, Fudan University, Shanghai, China
- The Academy of Integrative Medicine, Fudan University, Shanghai, China
- Shanghai Key Laboratory of Female Reproductive Endocrine-Related Disease, Hospital of Obstetrics and Gynecology, Fudan University, Shanghai, China
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Wang X, Wang L, Xiang W. Mechanisms of ovarian aging in women: a review. J Ovarian Res 2023; 16:67. [PMID: 37024976 PMCID: PMC10080932 DOI: 10.1186/s13048-023-01151-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Accepted: 03/29/2023] [Indexed: 04/08/2023] Open
Abstract
Ovarian aging is a natural and physiological aging process characterized by loss of quantity and quality of oocyte or follicular pool. As it is generally accepted that women are born with a finite follicle pool that will go through constant decline without renewing, which, together with decreased oocyte quality, makes a severe situation for women who is of advanced age but desperate for a healthy baby. The aim of our review was to investigate mechanisms leading to ovarian aging by discussing both extra- and intra- ovarian factors and to identify genetic characteristics of ovarian aging. The mechanisms were identified as both extra-ovarian alternation of hypothalamic-pituitary-ovarian axis and intra-ovarian alternation of ovary itself, including telomere, mitochondria, oxidative stress, DNA damage, protein homeostasis, aneuploidy, apoptosis and autophagy. Moreover, here we reviewed related Genome-wide association studies (GWAS studies) from 2009 to 2021 and next generation sequencing (NGS) studies of primary ovarian insufficiency (POI) in order to describe genetic characteristics of ovarian aging. It is reasonable to wish more reliable anti-aging interventions for ovarian aging as the exploration of mechanisms and genetics being progressing.
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Affiliation(s)
- Xiangfei Wang
- Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Lingjuan Wang
- Department of Obstetrics and Gynecology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Wenpei Xiang
- Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
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Bahena-Alvarez D, Millan-Aldaco D, Rincón-Heredia R, Escamilla-Avila N, Hernandez-Cruz A. Expression of voltage-gated Ca2+ channels, Insp3Rs, and RyRs in the immature mouse ovary. J Ovarian Res 2022; 15:85. [PMID: 35869556 PMCID: PMC9306205 DOI: 10.1186/s13048-022-01015-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 06/27/2022] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
The postnatal mammalian ovary undergoes a series of changes to ensure the maturation of sufficient follicles to support ovulation and fecundation over the reproductive life. It is well known that intracellular [Ca2+]i signals are necessary for ovulation, fertilization, and egg activation. However, we lack detailed knowledge of the molecular identity, cellular distribution, and functional role of Ca2+ channels expressed during folliculogenesis. In the neonatal period, ovarian maturation is controlled by protein growth factors released from the oocyte and granulosa cells. Conversely, during the early infantile period, maturation becomes gonadotropin-dependent and is controlled by granulosa and theca cells. The significance of intracellular Ca2+ signaling in folliculogenesis is supported by the observation that mice lacking the expression of Ca2+/calmodulin-dependent kinase IV in granulosa cells suffer abnormal follicular development and impaired fertility.
Results
Using immunofluorescence in frozen ovarian sections and confocal microscopy, we assessed the expression of high-voltage activated Ca2+ channel alpha subunits and InsP3 and ryanodine receptors in the postnatal period from 3 to 16 days. During the neonatal stage, oocytes from primordial and primary follicles show high expression of various Ca2+-selective channels, with granulosa and stroma cells expressing significantly less. These channels are likely involved in supporting Ca2+-dependent secretion of peptide growth factors. In contrast, during the early and late infantile periods, Ca2+ channel expression in the oocyte diminishes, increasing significantly in the granulosa and particularly in immature theca cells surrounding secondary follicles.
Conclusions
The developmental switch of Ca2+ channel expression from the oocytes to the perifollicular cells likely reflects the vanishing role of the oocytes once granulosa and theca cells take control of folliculogenesis in response to gonadotropins acting on their receptors.
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Gilfarb RA, Leuner B. GABA System Modifications During Periods of Hormonal Flux Across the Female Lifespan. Front Behav Neurosci 2022; 16:802530. [PMID: 35783228 PMCID: PMC9245048 DOI: 10.3389/fnbeh.2022.802530] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 02/21/2022] [Indexed: 01/10/2023] Open
Abstract
The female lifespan is marked by periods of dramatic hormonal fluctuation. Changes in the ovarian hormones estradiol and progesterone, in addition to the progesterone metabolite allopregnanolone, are among the most significant and have been shown to have widespread effects on the brain. This review summarizes current understanding of alterations that occur within the GABA system during the major hormonal transition periods of puberty, the ovarian cycle, pregnancy and the postpartum period, as well as reproductive aging. The functional impacts of altered inhibitory activity during these times are also discussed. Lastly, avenues for future research are identified, which, if pursued, can broaden understanding of the GABA system in the female brain and potentially lead to better treatments for women experiencing changes in brain function at each of these hormonal transition periods.
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Affiliation(s)
- Rachel A. Gilfarb
- Neuroscience Graduate Program, The Ohio State University, Columbus, OH, United States
| | - Benedetta Leuner
- Department of Psychology, The Ohio State University, Columbus, OH, United States
- Department of Neuroscience, The Ohio State University, Columbus, OH, United States
- *Correspondence: Benedetta Leuner,
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Mansano NDS, Paradela RS, Bohlen TM, Zanardi IM, Chaves FM, Silveira MA, Tavares MR, Donato J, Frazao R. Vasoactive intestinal peptide exerts an excitatory effect on hypothalamic kisspeptin neurons during estrogen negative feedback. Mol Cell Endocrinol 2022; 542:111532. [PMID: 34915098 DOI: 10.1016/j.mce.2021.111532] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 12/10/2021] [Accepted: 12/11/2021] [Indexed: 12/30/2022]
Abstract
Hypothalamic kisspeptin neurons are the primary modulators of gonadotropin-releasing hormone (GnRH) neurons. It has been shown that circadian rhythms driven by the suprachiasmatic nucleus (SCN) contribute to GnRH secretion. Kisspeptin neurons are potential targets of SCN neurons due to reciprocal connections with the anteroventral periventricular and rostral periventricular nuclei (AVPV/PeN) and the arcuate nucleus of the hypothalamus (ARH). Vasoactive intestinal peptide (VIP), a notable SCN neurotransmitter, modulates GnRH secretion depending on serum estradiol levels, aging or time of the day. Considering that kisspeptin neurons may act as interneurons and mediate VIP's effects on the reproductive axis, we investigated the effects of VIP on hypothalamic kisspeptin neurons in female mice during estrogen negative feedback. Our findings indicate that VIP induces a TTX-independent depolarization of approximately 30% of AVPV/PeN kisspeptin neurons in gonad-intact (diestrus) and ovariectomized (OVX) mice. In the ARH, the percentage of kisspeptin neurons that were depolarized by VIP was even higher (approximately 90%). An intracerebroventricular infusion of VIP leds to an increased percentage of kisspeptin neurons expressing the phosphoSer133 cAMP-response-element-binding protein (pCREB) in the AVPV/PeN. On the other hand, pCREB expression in ARH kisspeptin neurons was similar between saline- and VIP-injected mice. Thus, VIP can recruit different signaling pathways to modulate AVPV/PeN or ARH kisspeptin neurons, resulting in distinct cellular responses. The expression of VIP receptors (VPACR) was upregulated in the AVPV/PeN, but not in the ARH, of OVX mice compared to mice on diestrus and estradiol-primed OVX mice. Our findings indicate that VIP directly influences distinct cellular aspects of the AVPV/PeN and ARH kisspeptin neurons during estrogen negative feedback, possibly to influence pulsatile LH secretion.
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Affiliation(s)
- Naira da Silva Mansano
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Regina Silva Paradela
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Tabata M Bohlen
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Izabela M Zanardi
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Fernanda Machado Chaves
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Marina Augusto Silveira
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Mariana Rosolen Tavares
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Jose Donato
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil
| | - Renata Frazao
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil.
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Bizzozzero-Hiriart M, Di Giorgio NP, Libertun C, Lux-Lantos VAR. GABAB Receptor Antagonism from Birth to Weaning Permanently Modifies Kiss1 Expression in the Hypothalamus and Gonads in Mice. Neuroendocrinology 2022; 112:998-1026. [PMID: 34963114 DOI: 10.1159/000521649] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Accepted: 12/22/2021] [Indexed: 11/19/2022]
Abstract
INTRODUCTION The kisspeptin gene Kiss1 is expressed in two hypothalamic areas: anteroventral periventricular nucleus/periventricular nucleus (AVPV/PeN) and arcuate nucleus (ARC), and also in gonads. Several pieces of evidence suggests that gamma-amino butyric acid B receptors (GABAB) signaling can regulate Kiss1 expression. Here, we inhibited GABAB signaling from PND2 to PND21 and evaluated the hypothalamic-pituitary-gonadal (HPG) axis. METHODS BALB/c mice were treated on postnatal days 2-21 (PND2-PND21) with CGP55845 (GABAB antagonist) and evaluated in PND21 and adulthood: gene expression (qPCR) in the hypothalamus and gonads, hormones by radioimmunoassay, gonad histochemistry (H&E), puberty onset, and estrous cycles. RESULTS At PND21, CGP inhibited Kiss1 and Tac2 and increased Pdyn and Gabbr1 in the ARC of both sexes and decreased Th only in female AVPV/PeN. Serum follicle-stimulating hormone (FSH) and testis weight were decreased in CGP-males, and puberty onset was delayed. In adults, Kiss1, Tac2, Pdyn, Pgr, Cyp19a1, and Gad1 were downregulated, while Gabbr1 was upregulated in the ARC of both sexes. In the AVPV/PeN, Kiss1, Th, Cyp19a1, and Pgr were decreased while Gad1 was increased in CGP-females, whereas Cyp19a1 was increased in CGP-males. Serum FSH was increased in CGP-males while prolactin was increased in CGP-females. Testosterone and progesterone were increased in ovaries from CGP-females, in which Kiss1, Cyp19a1, and Esr1 were downregulated while Hsd3b2 was upregulated, together with increased atretic and decreased ovulatory follicles. Testes from CGP-males showed decreased progesterone, increased Gabbr1, Kiss1, Kiss1r, and Esr2 and decreased Cyp19a1, and clear signs of seminiferous tubules atrophy. CONCLUSION These results demonstrate that appropriate GABAB signaling during this critical prepubertal period is necessary for the normal development of the HPG axis.
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Affiliation(s)
- Marianne Bizzozzero-Hiriart
- Laboratorio de Neuroendocrinología, Instituto de Biología y Medicina Experimental (IBYME-CONICET), Buenos Aires, Argentina
| | - Noelia P Di Giorgio
- Laboratorio de Neuroendocrinología, Instituto de Biología y Medicina Experimental (IBYME-CONICET), Buenos Aires, Argentina
| | - Carlos Libertun
- Laboratorio de Neuroendocrinología, Instituto de Biología y Medicina Experimental (IBYME-CONICET), Buenos Aires, Argentina
- Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Victoria A R Lux-Lantos
- Laboratorio de Neuroendocrinología, Instituto de Biología y Medicina Experimental (IBYME-CONICET), Buenos Aires, Argentina
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Santollo J, Collett JA, Edwards AA. The anti-dipsogenic and anti-natriorexigenic effects of estradiol, but not the anti-pressor effect, are lost in aged female rats. Physiol Rep 2021; 9:e14948. [PMID: 34288542 PMCID: PMC8290476 DOI: 10.14814/phy2.14948] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 06/08/2021] [Indexed: 11/24/2022] Open
Abstract
Estradiol (E2) inhibits fluid intake in several species, which may help to defend fluid homeostasis by preventing excessive extracellular fluid volume. Although this phenomenon is well established using the rat model, it has only been studied directly in young adults. Because aging influences the neuronal sensitivity to E2 and the fluid intake effects of E2 are mediated in the brain, we tested the hypothesis that aging influences the fluid intake effects of E2 in female rats. To do so, we examined water and NaCl intake in addition to the pressor effect after central angiotensin II treatment in young (3-4 months), middle-aged (10-12 months), and old (16-18 months) ovariectomized rats treated with estradiol benzoate (EB). As expected, EB treatment reduced water and NaCl intake in young rats. EB treatment, however, did not reduce water intake in old rats, nor did it reduce NaCl intake in middle-aged or old rats. The ability of EB to reduce blood pressure was, in contrast, observed in all three age groups. Next, we also measured the gene expression of estrogen receptors (ERs) and the angiotensin type 1 receptor (AT1R) in the areas of the brain that control fluid balance. ERβ, G protein estrogen receptor (GPER), and AT1R were reduced in the paraventricular nucleus of the hypothalamus in middle-aged and old rats, compared to young rats. These results suggest the estrogenic control of fluid intake is modified by age. Older animals lost the fluid intake effects of E2, which correlated with decreased ER and AT1R expression in the hypothalamus.
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Affiliation(s)
| | - Jason A. Collett
- Department of BiologyUniversity of KentuckyLexingtonKYUSA
- Department of Anatomy, Cell Biology and PhysiologyIndiana University School of MedicineIndianapolisINUSA
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Zhang L, Chen L, Meng Z, Jia M, Li R, Yan S, Tian S, Zhou Z, Diao J. Effects of L-Glufosinate-ammonium and temperature on reproduction controlled by neuroendocrine system in lizard (Eremias argus). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 257:113564. [PMID: 31753638 DOI: 10.1016/j.envpol.2019.113564] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 10/15/2019] [Accepted: 11/01/2019] [Indexed: 06/10/2023]
Abstract
In the context of global warming, an important issue is that many pesticides become more toxic, putting non-target organisms at higher risk of pesticide exposure. Eremias argus (a native Chinese lizard) was selected as animal model in this study. As a kind of poikilothermic vertebrate, E.argus is sensitive to temperature change. The experimental design [(with or without L-Glufosinate-ammonium (L-GLA) pollution × two temperatures (25 and 30 °C)] was used in this study for 90 days to identify the chronic effects of the pesticide-temperature interaction on the lizards' neuroendocrine-regulated reproduction. Survival rate, body weight, clutch characteristics, testicular histopathology, the content of neurotransmitters and related enzyme activity, the level of sex steroid, the expression of Heat shock protein 70 (HSP70), antioxidant system, the accumulation and degradation of L-GLA were examined. Results showed that L-GLA disrupt reproduction of lizards through hypothalamus-pituitary-gonad (HPG) axis. In addition, temperature can not only change the environmental behavior of pesticides, but also alter the physiological characteristics of lizards. Thus, our results emphasized that temperature is an essential abiotic factor that should not be overlooked in ecotoxicological studies.
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Affiliation(s)
- Luyao Zhang
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China; Beijing Advanced Innovation Center for Food Nutrition and Human Health, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Li Chen
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China; Beijing Advanced Innovation Center for Food Nutrition and Human Health, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Zhiyuan Meng
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China; Beijing Advanced Innovation Center for Food Nutrition and Human Health, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Ming Jia
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China; Beijing Advanced Innovation Center for Food Nutrition and Human Health, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Ruisheng Li
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Sen Yan
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China; Beijing Advanced Innovation Center for Food Nutrition and Human Health, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Sinuo Tian
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Zhiqiang Zhou
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China; Beijing Advanced Innovation Center for Food Nutrition and Human Health, Yuanmingyuan West Road 2, Beijing 100193, China
| | - Jinling Diao
- Department of Applied Chemistry, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100193, China; Beijing Advanced Innovation Center for Food Nutrition and Human Health, Yuanmingyuan West Road 2, Beijing 100193, China.
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Xu W, Huang J, Li L, Zhang X, Wang Y, Tong G, Sun Y. Alterations of estradiol-induced histone H3 acetylation in the preoptic area and anteroventral periventricular nucleus of middle-aged female rats. Biochem Biophys Res Commun 2019; 516:894-899. [PMID: 31272713 DOI: 10.1016/j.bbrc.2019.06.145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 06/26/2019] [Indexed: 02/06/2023]
Abstract
In this study we investigated the characteristics of histone H3 acetylation in the anterior hypothalamus under E2 positive feedback to gain a better understanding of the mechanism underlying reduced GnRH neuron activation and altered gene expression in female reproductive aging. Young and middle-aged female rats were ovariectomized (OVX) and treated with estradiol (E2) or oil. C-Fos expression, the number of GnRH neurons co-localized with c-Fos in the preoptic area (POA), and the number of acetylated histone H3 cells in the POA and anteroventral periventricular nucleus (AVPV) were quantified at the time of the expected GnRH neuron activation. We used real-time PCR to evaluate the expression of Esr1 target genes including Kiss1 and VGluT2 and genes known as Esr1 coregulators in the anterior hypothalamus. Our results show that in the young females, E2 markedly increased histone H3 acetylation in the POA and AVPV, coincident with increased c-Fos and GnRH neuron activation in the POA. In middle-aged females, E2-induced histone H3 acetylation was reduced in the POA but was not significantly altered in the AVPV. This occurred in association with a reduction of c-Fos expression and the number of GnRH cells expressing c-Fos in the POA as well as a down-regulation of Kiss1 and VGluT2 mRNA expression in the anterior hypothalamus of the animals. E2 caused significant decreases in Ncoa2 and Crebbp mRNA expression in the anterior hypothalamus of young, but not middle-aged females. Taken together, these data suggest that alterations of histone H3 acetylation in the POA and AVPV and the inability of Ncoa2 and Crebbp to respond to E2 in the middle-aged anterior hypothalamus partially contribute to the decline of GnRH neuron activation and E2 target gene expression changes that occur in female along with reproductive aging.
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Affiliation(s)
- Wen Xu
- Hospital & Institute of Obstetrics and Gynecology, Fudan University, Shanghai, 200011, China
| | - Jianqin Huang
- Hospital & Institute of Obstetrics and Gynecology, Fudan University, Shanghai, 200011, China; The Academy of Integrative Medicine of Fudan University, Shanghai, 200011, China
| | - Lisha Li
- Hospital & Institute of Obstetrics and Gynecology, Fudan University, Shanghai, 200011, China
| | - Xinyan Zhang
- Hospital & Institute of Obstetrics and Gynecology, Fudan University, Shanghai, 200011, China
| | - Yan Wang
- Hospital & Institute of Obstetrics and Gynecology, Fudan University, Shanghai, 200011, China
| | - Guoqing Tong
- Reproduction Center, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China.
| | - Yan Sun
- Hospital & Institute of Obstetrics and Gynecology, Fudan University, Shanghai, 200011, China; The Academy of Integrative Medicine of Fudan University, Shanghai, 200011, China; Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease, Shanghai, 200011, China.
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11
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Xu W, An X, Zhang N, Li L, Zhang X, Wang Y, Wang L, Sun Y. Middle-aged female rats lack changes in histone H3 acetylation in the anterior hypothalamus observed in young females on the day of a luteinizing hormone surge. Biosci Trends 2019; 13:334-341. [PMID: 31434815 DOI: 10.5582/bst.2019.01162] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Histone acetylation has recently been implicated in gene transcription and estradiol (E2) actions in the hypothalamus. This study aims to determine the involvement of histone acetylation in mediating E2-induced luteinizing hormone (LH) surge to understand the mechanism underlying LH surge dysfunction in female reproductive aging. Young and middle-aged female rats were ovariectomized (OVX) and treated with hormone or oil once per day for two days. At the time of the expected LH surge, blood samples were taken for LH assay. The anterior and posterior hypothalami were dissected, histone H3/H4 acetylation and histone deacetylases (HDACs) 4, -5, -10 and -11 protein expressions were measured using Western blotting. Our results show that in the young females, E2 markedly increased histone H3 acetylation while significantly reducing HDAC10 protein expression in the anterior hypothalamus. Notably, E2-induced alterations of histone H3 acetylation and HDAC10 in the anterior hypothalamus were absent in middle-aged females, associated with a reduced LH release. However, age alters histone H4 acetylation in both the anterior and posterior hypothalamus and significantly increased HDAC 4 and -5 protein expression in the anterior hypothalamus. Taken together, these data suggest that histone H3 acetylation in the anterior hypothalamus may mediate E2 regulation of LH surge and the process possibly through decreasing HDAC10. The missed responsiveness of histone H3 acetylation and HDAC10 expression to E2 in the anterior hypothalamus may contribute to LH surge failure that occurs in female reproductive aging.
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Affiliation(s)
- Wen Xu
- Hospital of Obstetrics and Gynecology, Fudan University
| | - Xiaofei An
- Jiangsu Province Hospital of Chinese Medicine, Affiliated Hospital of Nanjing University of Chinese Medicine
| | - Na Zhang
- Hospital of Obstetrics and Gynecology, Fudan University.,Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease
| | - Lisha Li
- Hospital of Obstetrics and Gynecology, Fudan University.,Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease
| | - Xinyan Zhang
- Hospital of Obstetrics and Gynecology, Fudan University.,Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease
| | - Yan Wang
- Hospital of Obstetrics and Gynecology, Fudan University.,Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease
| | - Ling Wang
- Hospital of Obstetrics and Gynecology, Fudan University.,Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease.,The Academy of Integrative Medicine of Fudan University
| | - Yan Sun
- Hospital of Obstetrics and Gynecology, Fudan University.,Shanghai Key Laboratory of Female Reproductive Endocrine-related Disease.,The Academy of Integrative Medicine of Fudan University
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Ma S, Li D, Jiang J, Shen B. Role of the Medial Preoptic Area in Electroacupuncture Treatment of Reproductive Dysfunction in Ovariectomised Rats. Acupunct Med 2018; 35:52-58. [DOI: 10.1136/acupmed-2015-010839] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2016] [Indexed: 11/04/2022]
Abstract
Objective To investigate the role of the medial preoptic area (MPOA) of the hypothalamus in electroacupuncture (EA) treatment of reproductive dysfunction in ovariectomised (OVX) rats and to examine the underlying mechanisms of action. Methods 62 female Sprague-Dawley rats (200–220 g) underwent bilateral ovariectomy (OVX). Three weeks later, 32 rats assigned to experiment 1 were randomly divided into four groups: two groups underwent MPOA lesioning (n=16) followed by EA at CV4, CV3, SP6 and bilateral Zigong (30 min per day) for 3 days (OVX+MPOA+EA group, n=8) or no treatment (OVX+MPOA group, n=8); and two groups underwent sham (S) surgery (n=16) followed by EA (OVX+SMPOA+EA group, n=8) or no treatment (OVX+SMPOA group, n=8). Plasma oestradiol and luteinising hormone (LH) were measured by radioimmunoassay and mature vaginal epithelial cells stained and quantified post-treatment. 30 rats assigned to experiment 2 were randomised to receive EA (OVX+EA group, n=15) or remain untreated (OVX group, n=15), following which push-pull perfusion in combination with high pressure liquid chromatography/electrochemical (HPLC-EC) detection was used to measure neurotransmitter release in the MPOA. Results EA significantly increased the percentage of mature vaginal epithelial cells and plasma oestradiol levels in sham MPOA-lesioned rats compared with MPOA-lesioned OVX rats (p<0.05). In sham MPOA-lesioned OVX rats, EA significantly decreased plasma LH levels compared with no treatment (p<0.01). HPLC-EC results showed that γ-aminobutyric acid (GABA) and β-endorphin levels in the MPAO were significantly increased in OVX rats following EA (p<0.01). Conclusions The present study suggests that the MPOA plays a crucial role in EA treatment of abnormal reproductive function in OVX rats.
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Affiliation(s)
- Shulan Ma
- Training Center of Medical Experiments, Basic Medical School, Fudan University, Shanghai, China
- Department of Integrative Medicine and Neurobiology, State Key Lab of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Dongju Li
- Training Center of Medical Experiments, Basic Medical School, Fudan University, Shanghai, China
| | - Jianwei Jiang
- Department of Integrative Medicine and Neurobiology, State Key Lab of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Bo Shen
- Institute of Radiation Medicine, Fudan University, Shanghai, China
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Estrogen-induced neuroimmunomodulation as facilitator of and barrier to reproductive aging in brain and lymphoid organs. J Chem Neuroanat 2018; 95:6-12. [PMID: 29477446 DOI: 10.1016/j.jchemneu.2018.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 01/22/2018] [Accepted: 02/20/2018] [Indexed: 12/27/2022]
Abstract
Reproductive aging in females is marked by alterations in gonadal hormones, estrogen and progesterone, that facilitate cessation of reproductive cycles and onset of female-specific diseases such as autoimmune and neurodegenerative diseases, hormone-dependent cancers, and osteoporosis. Bidirectional communication between the three homeostatic systems, nervous system, endocrine system, and immune system, is essential for the maintenance of health and any dysfunction in the cross-talk promotes the development of diseases and cancer. The pleiotropic effects of estrogen on neural-immune interactions may promote either neuroprotection or inflammatory conditions depending on the site of action, dose and duration of treatment, type of estrogen receptors and its influence on intracellular signaling pathways, etc. Our studies involving treatment of early middle-aged female rats with low and high doses of estrogen and examining the brain areas, thymus, spleen, and lymph nodes revealed that estrogen-induced changes in neural-immune interactions are markedly affected in thymus followed by spleen and lymph nodes while it confers neuroprotection in the brain areas. These alterations are determined by antioxidant enzyme status, growth factors, intracellular signaling pathways involved in cell survival and inflammation, and metabolic enzymes and thus, may regulate the various stages in female reproductive aging. It is imperative that detailed longitudinal studies are carried out to understand the mechanisms of neuroendocrine-immune interactions in reproductive aging to facilitate healthy aging and for the development of better treatment strategies for female-specific diseases.
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Merkley CM, Coolen LM, Goodman RL, Lehman MN. Evidence for Changes in Numbers of Synaptic Inputs onto KNDy and GnRH Neurones during the Preovulatory LH Surge in the Ewe. J Neuroendocrinol 2015; 27:624-35. [PMID: 25976424 PMCID: PMC4809364 DOI: 10.1111/jne.12293] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 04/19/2015] [Accepted: 05/10/2015] [Indexed: 11/28/2022]
Abstract
Kisspeptin neurones located in the arcuate nucleus (ARC) and preoptic area (POA) are critical mediators of gonadal steroid feedback onto gonadotrophin-releasing hormone (GnRH) neurones. ARC kisspeptin cells that co-localise neurokinin B (NKB) and dynorphin (Dyn), are collectively referred to as KNDy (Kisspeptin/NKB/Dyn) neurones, and have been shown in mice to also co-express the vesicular glutamate transporter, vGlut2, an established glutamatergic marker. The ARC in rodents has long been known as a site of hormone-induced neuroplasticity, and changes in synaptic inputs to ARC neurones in rodents occur over the oestrous cycle. Based on this evidence, the the present study aimed to examine possible changes across the ovine oestrous cycle in synaptic inputs onto kisspeptin cells in the ARC (KNDy) and POA, and inputs onto GnRH neurones. Gonadal-intact breeding season ewes were perfused using 4% paraformaldehyde during either the luteal or follicular phase of the oestrous cycle, with the latter group killed at the time of the luteinising hormone (LH) surge. Hypothalamic sections were processed for triple-label immunodetection of kisspeptin/vGlut2/synaptophysin or kisspeptin/vGlut2/GnRH. The total numbers of synaptophysin- and vGlut2-positive inputs to ARC KNDy neurones were significantly increased at the time of the LH surge compared to the luteal phase; because these did not contain kisspeptin, they do not arise from KNDy neurones. By contrast to the ARC, the total number of synaptophysin-positive inputs onto POA kisspeptin neurones did not differ between luteal phase and surge animals. The total number of kisspeptin and vGlut2 inputs onto GnRH neurones in the mediobasal hypothalamus (MBH) was also increased during the LH surge, and could be attributed to an increase in the number of KNDy (double-labelled kisspeptin + vGlut2) inputs. Taken together, these results provide novel evidence of synaptic plasticity at the level of inputs onto KNDy and GnRH neurones during the ovine oestrous cycle. Such changes may contribute to the generation of the preovulatory GnRH/LH surge.
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Affiliation(s)
- Christina M. Merkley
- Neuroscience Graduate Program, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Lique M. Coolen
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
| | - Robert L. Goodman
- Department of Physiology and Pharmacology, West Virginia University, Morgantown, West Virginia, 26506, USA
| | - Michael N. Lehman
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
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Yin W, Sun Z, Mendenhall JM, Walker DM, Riha PD, Bezner KS, Gore AC. Expression of Vesicular Glutamate Transporter 2 (vGluT2) on Large Dense-Core Vesicles within GnRH Neuroterminals of Aging Female Rats. PLoS One 2015; 10:e0129633. [PMID: 26053743 PMCID: PMC4459826 DOI: 10.1371/journal.pone.0129633] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 05/10/2015] [Indexed: 11/20/2022] Open
Abstract
The pulsatile release of GnRH is crucial for normal reproductive physiology across the life cycle, a process that is regulated by hypothalamic neurotransmitters. GnRH terminals co-express the vesicular glutamate transporter 2 (vGluT2) as a marker of a glutamatergic phenotype. The current study sought to elucidate the relationship between glutamate and GnRH nerve terminals in the median eminence—the site of GnRH release into the portal capillary vasculature. We also determined whether this co-expression may change during reproductive senescence, and if steroid hormones, which affect responsiveness of GnRH neurons to glutamate, may alter the co-expression pattern. Female Sprague-Dawley rats were ovariectomized at young adult, middle-aged and old ages (~4, 11, and 22 months, respectively) and treated four weeks later with sequential vehicle + vehicle (VEH + VEH), estradiol + vehicle (E2 + VEH), or estradiol + progesterone (E2+P4). Rats were perfused 24 hours after the second hormone treatment. Confocal microscopy was used to determine colocalization of GnRH and vGluT2 immunofluorescence in the median eminence. Post-embedding immunogold labeling of GnRH and vGluT2, and a serial electron microscopy (EM) technique were used to determine the cellular interaction between GnRH terminals and glutamate signaling. Confocal analysis showed that GnRH and vGluT2 immunofluorescent puncta were extensively colocalized in the median eminence and that their density declined with age but was unaffected by short-term hormone treatment. EM results showed that vGluT2 immunoreactivity was extensively associated with large dense-core vesicles, suggesting a unique glutamatergic signaling pathway in GnRH terminals. Our results provide novel subcellular information about the intimate relationship between GnRH terminals and glutamate in the median eminence.
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Affiliation(s)
- Weiling Yin
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
| | - Zengrong Sun
- School of Public Health, Tianjin Medical University, Tianjin, China
| | - John M. Mendenhall
- Institute for Neuroscience, University of Texas at Austin, Austin, Texas, United States of America
| | - Deena M. Walker
- Institute for Neuroscience, University of Texas at Austin, Austin, Texas, United States of America
| | - Penny D. Riha
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
| | - Kelsey S. Bezner
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
| | - Andrea C. Gore
- Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas, United States of America
- Institute for Neuroscience, University of Texas at Austin, Austin, Texas, United States of America
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
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Kermath BA, Riha PD, Woller MJ, Wolfe A, Gore AC. Hypothalamic molecular changes underlying natural reproductive senescence in the female rat. Endocrinology 2014; 155:3597-609. [PMID: 24914937 PMCID: PMC4138577 DOI: 10.1210/en.2014-1017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The role of the hypothalamus in female reproductive senescence is unclear. Here we identified novel molecular neuroendocrine changes during the natural progression from regular reproductive cycles to acyclicity in middle-aged female rats, comparable with the perimenopausal progression in women. Expression of 48 neuroendocrine genes was quantified within three hypothalamic regions: the anteroventral periventricular nucleus, the site of steroid positive feedback onto GnRH neurons; the arcuate nucleus (ARC), the site of negative feedback and pulsatile GnRH release; and the median eminence (ME), the site of GnRH secretion. Surprisingly, the majority of changes occurred in the ARC and ME, with few effects in anteroventral periventricular nucleus. The overall pattern was increased mRNA levels with chronological age and decreases with reproductive cycle status in middle-aged rats. Affected genes included transcription factors (Stat5b, Arnt, Ahr), sex steroid hormone receptors (Esr1, Esr2, Pgr, Ar), steroidogenic enzymes (Sts, Hsd17b8), growth factors (Igf1, Tgfa), and neuropeptides (Kiss1, Tac2, Gnrh1). Bionetwork analysis revealed region-specific correlations between genes and hormones. Immunohistochemical analyses of kisspeptin and estrogen receptor-α in the ARC demonstrated age-related decreases in kisspeptin cell numbers as well as kisspeptin-estrogen receptor-α dual-labeled cells. Taken together, these results identify unexpectedly strong roles for the ME and ARC during reproductive decline and highlight fundamental differences between middle-aged rats with regular cycles and all other groups. Our data provide evidence of decreased excitatory stimulation and altered hormone feedback with aging and suggest novel neuroendocrine pathways that warrant future study. Furthermore, these changes may impact other neuroendocrine systems that undergo functional declines with age.
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Affiliation(s)
- Bailey A Kermath
- Institute for Neuroscience (B.A.K., A.C.G.), Division of Pharmacology and Toxicology (P.D.R., A.C.G.), and Institute for Cell and Molecular Biology (A.C.G.), The University of Texas at Austin, Austin, Texas 78712; Department of Biology (M.J.W.), University of Wisconsin-Whitewater, Whitewater, Wisconsin 53190; and Department of Pediatrics (A.W.), Johns Hopkins University School of Medicine, Baltimore Maryland 21287
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17
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Kauffman AS, Sun Y, Kim J, Khan AR, Shu J, Neal-Perry G. Vasoactive intestinal peptide modulation of the steroid-induced LH surge involves kisspeptin signaling in young but not in middle-aged female rats. Endocrinology 2014; 155:2222-32. [PMID: 24654782 PMCID: PMC4020928 DOI: 10.1210/en.2013-1793] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Age-related LH surge dysfunction in middle-aged rats is characterized, in part, by reduced responsiveness to estradiol (E2)-positive feedback and reduced hypothalamic kisspeptin neurotransmission. Vasoactive intestinal peptide (VIP) neurons in the suprachiasmatic nucleus project to hypothalamic regions that house kisspeptin neurons. Additionally, middle-age females express less VIP mRNA in the suprachiasmatic nucleus on the day of the LH surge and intracerebroventricular (icv) VIP infusion restores LH surges. We tested the hypothesis that icv infusion of VIP modulates the LH surge through effects on the kisspeptin and RFamide-related peptide-3 (RFRP-3; an estradiol-regulated inhibitor of GnRH neurons) neurotransmitter systems. Brains were collected for in situ hybridization analyses from ovariectomized and ovarian hormone-primed young and middle-aged females infused with VIP or saline. The percentage of GnRH and Kiss1 cells coexpressing cfos and total Kiss1 mRNA were reduced in saline-infused middle-aged compared with young females. In young females, VIP reduced the percentage of GnRH and Kiss1 cells coexpressing cfos, suggesting that increased VIP signaling in young females adversely affected the function of Kiss1 and GnRH neurons. In middle-aged females, VIP increased the percentage of GnRH but not Kiss1 neurons coexpressing cfos, suggesting VIP affects LH release in middle-aged females through kisspeptin-independent effects on GnRH neurons. Neither reproductive age nor VIP affected Rfrp cell number, Rfrp mRNA levels per cell, or coexpression of cfos in Rfrp cells. These data suggest that VIP differentially affects activation of GnRH and kisspeptin neurons of female rats in an age-dependent manner.
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Affiliation(s)
- Alexander S Kauffman
- Department of Reproductive Medicine (A.S.K., J.K., A.R.K.), University of California, San Diego, La Jolla, California; Department of Obstetrics/Gynecology and Women's Health (Y.S., J.S., G.N.-P., Albert Einstein College of Medicine, Bronx, New York; and Dominick P. Purpura Department of Neuroscience (G.N.-P.), Albert Einstein College of Medicine, Bronx, New York
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18
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Neal-Perry G, Yao D, Shu J, Sun Y, Etgen AM. Insulin-like growth factor-I regulates LH release by modulation of kisspeptin and NMDA-mediated neurotransmission in young and middle-aged female rats. Endocrinology 2014; 155:1827-37. [PMID: 24617524 PMCID: PMC3990844 DOI: 10.1210/en.2013-1682] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
This study investigated potential mechanisms by which age and IGF-I receptor (IGF-Ir) signaling in the neuroendocrine hypothalamus affect estradiol-positive feedback effects on GnRH neuronal activation and on kisspeptin and N-methyl-D-aspartate (NMDA)-induced LH release and on the abundance of NMDA receptor subunits Nr1 and Nr2b and Kiss1r transcript and protein in the hypothalamus of young and middle-aged female rats. We infused vehicle, IGF-I, or JB-1, a selective antagonist of IGF-Ir, into the third ventricle of ovariectomized female rats primed with estradiol or vehicle and injected with vehicle, kisspeptin (3 or 30 nmol/kg), or NMDA (15 or 30 mg/kg). Regardless of dose, NMDA and kisspeptin resulted in significantly more LH release, GnRH/c-Fos colabeling, and c-Fos immunoreative cells in young than in middle-aged females. Estradiol priming significantly increased Kiss1r, Nr1, and Nr2b receptor transcript and protein abundance in young but not middle-aged female hypothalamus. JB-1 attenuated kisspeptin and NMDA-induced LH release, numbers of GnRH/c-Fos and c-Fos cells, and Kiss1r, Nr1, and Nr2b transcript and protein abundance in young females to levels observed in middle-aged females. IGF-I significantly enhanced NMDA and kisspeptin-induced LH release in middle-aged females without increasing numbers of GnRH/c-Fos or c-Fos immunoreactive cells. IGF-I infusion in middle-aged females also increased Kiss1r, Nr1, and Nr2b protein and transcript to levels that were equivalent to young estradiol-primed females. These findings indicate that age-related changes in estradiol-regulated responsiveness to excitatory input from glutamate and kisspeptin reflect reduced IGF-Ir signaling.
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MESH Headings
- Aging
- Animals
- Female
- Gene Expression Regulation, Developmental/drug effects
- Hypothalamo-Hypophyseal System/growth & development
- Hypothalamo-Hypophyseal System/metabolism
- Hypothalamus/cytology
- Hypothalamus/drug effects
- Hypothalamus/growth & development
- Hypothalamus/metabolism
- Infusions, Intraventricular
- Insulin-Like Growth Factor I/administration & dosage
- Insulin-Like Growth Factor I/analogs & derivatives
- Insulin-Like Growth Factor I/antagonists & inhibitors
- Insulin-Like Growth Factor I/metabolism
- Kisspeptins/metabolism
- Luteinizing Hormone/metabolism
- N-Methylaspartate/metabolism
- Nerve Tissue Proteins/agonists
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neuroendocrine Cells/cytology
- Neuroendocrine Cells/drug effects
- Neuroendocrine Cells/metabolism
- Oligopeptides/administration & dosage
- Oligopeptides/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor, IGF Type 1/agonists
- Receptor, IGF Type 1/antagonists & inhibitors
- Receptor, IGF Type 1/metabolism
- Receptors, G-Protein-Coupled/biosynthesis
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Kisspeptin-1
- Receptors, N-Methyl-D-Aspartate/agonists
- Receptors, N-Methyl-D-Aspartate/genetics
- Receptors, N-Methyl-D-Aspartate/metabolism
- Signal Transduction/drug effects
- Synaptic Transmission/drug effects
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Affiliation(s)
- Genevieve Neal-Perry
- Department of Obstetrics and Gynecology (G.N.-P., J.S., Y.S., A.M.E.) and the Dominick P. Purpura Department of Neuroscience (G.N.-P., A.M.E.), Albert Einstein College of Medicine, Bronx, New York 10461; and Internal Medicine of Tongji Hospital (D.Y.), Huazhong University of Science and Technology, Wuhan 430030, R.P. China
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Soga T, Kitahashi T, Clarke IJ, Parhar IS. Gonadotropin-inhibitory hormone promoter-driven enhanced green fluorescent protein expression decreases during aging in female rats. Endocrinology 2014; 155:1944-55. [PMID: 24605826 DOI: 10.1210/en.2013-1786] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Gonadotropin-inhibitory hormone (GnIH) neurons project to GnRH neurons to negatively regulate reproductive function. To fully explore the projections of the GnIH neurons, we created transgenic rats carrying an enhanced green fluorescent protein (EGFP) tagged to the GnIH promoter. With these animals, we show that EGFP-GnIH neurons are localized mainly in the dorsomedial hypothalamic nucleus (DMN) and project to the hypothalamus, telencephalon, and diencephalic thalamus, which parallels and confirms immunocytochemical and gene expression studies. We observed an age-related reduction in c-Fos-positive GnIH cell numbers in female rats. Furthermore, GnIH fiber appositions to GnRH neurons in the preoptic area were lessened in middle-aged females (70 weeks old) compared with their younger counterparts (9-12 weeks old). The fiber density in other brain areas was also reduced in middle-aged female rats. The expression of estrogen and progesterone receptors mRNA in subsets of EGFP-GnIH neurons was shown in laser-dissected single EGFP-GnIH neurons. We then examined estradiol-17β and progesterone regulation of GnIH neurons, using c-Fos presence as a marker. Estradiol-17β treatment reduced c-Fos labeling in EGFP-GnIH neurons in the DMN of young ovariectomized adult females but had no effect in middle-aged females. Progesterone had no effect on the number of GnIH cells positive for c-Fos. We conclude that there is an age-related decline in GnIH neuron number and GnIH inputs to GnRH neurons. We also conclude that the response of GnIH neurons to estrogen diminishes with reproductive aging.
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Affiliation(s)
- Tomoko Soga
- Brain Research Institute (T.S., T.K., I.S.P.), School of Medicine and Health Sciences, Monash University, Sunway, PJ 46150, Malaysia; and Department of Physiology (I.J.C.), Monash University, Victoria 3880, Australia
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Kermath BA, Riha PD, Sajjad A, Gore AC. Effects of chronic NMDA-NR2b inhibition in the median eminence of the reproductive senescent female rat. J Neuroendocrinol 2013; 25:887-97. [PMID: 23957788 PMCID: PMC3800684 DOI: 10.1111/jne.12087] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 08/05/2013] [Accepted: 08/10/2013] [Indexed: 01/07/2023]
Abstract
Gonadotrophin-releasing hormone (GnRH) neurones of the hypothalamic-pituitary-gonadal (HPG) axis drive reproductive function and undergo age-related decreases in activation during the transition to reproductive senescence. Decreased GnRH secretion from the median eminence (ME) partially arises from attenuated glutamatergic signalling via the NMDA receptor (NMDAR) and may be a result of changing NMDAR stoichiometry to favour NR2b over NR2a subunit expression with ageing. We have previously shown that the systemic inhibition of NR2b-containing receptors with ifenprodil, an NR2b-specific antagonist, stimulates parameters of luteinising hormone (used as a proxy for GnRH) release in both young and middle-aged females. In the present study, we chronically administered ifenprodil, an NR2b-specific antagonist, at the site of GnRH terminals in the ME or at GnRH perikarya in the preoptic area, in reproductively senescent middle-aged female rats, aiming to determine whether NR2b antagonism could restore aspects of reproductive functionality. Effects on oestrous cyclicity, serum hormones, and protein expression of GnRH, NR2b and phosphorylated NR2b (Tyr-1472) in the ME were measured. Chronic ifenprodil treatment in the ME (but not the preoptic area) altered oestrous cyclicity by increasing the percentage of days spent in pro-oestrus. This was accompanied by increased GnRH fluorescence intensity in the external ME zone and a greater proportion of GnRH terminals that co-labelled with pNR2b with treatment. We also observed changes in the relationships between protein immunofluorescence, serum hormone levels and other aspects of reproductive physiology in acyclic females, as revealed by bionetwork analysis. Together, these data support the hypothesis that NMDAR-NR2b expression and phosphorylation state play a role in reproductive senescence and highlight the ME as a major player in reproductive ageing.
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Affiliation(s)
- Bailey A. Kermath
- Institute for Neuroscience, The University of Texas at Austin, Austin TX 78712 USA
| | - Penny D. Riha
- Division of Pharmacology and Toxicology, The University of Texas at Austin, Austin, TX 78712 USA.F
| | - Ahmar Sajjad
- Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, TX 78712 USA
| | - Andrea C. Gore
- Institute for Neuroscience, The University of Texas at Austin, Austin TX 78712 USA
- Division of Pharmacology and Toxicology, The University of Texas at Austin, Austin, TX 78712 USA.F
- Institute for Cell and Molecular Biology, The University of Texas at Austin, Austin, TX 78712 USA
- Corresponding author: Andrea C. Gore, The University of Texas at Austin, 107 W. Dean Keeton, C0875, Austin, TX 78712, Phone (512) 471-3669, Fax (512) 471-5002,
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Zhang J, Yang LM, Pan XD, Lin N, Chen XC. Increased vesicular γ-GABA transporter and decreased phosphorylation of synapsin I in the rostral preoptic area is associated with decreased gonadotrophin-releasing hormone and c-Fos coexpression in middle-aged female mice. J Neuroendocrinol 2013; 25:753-61. [PMID: 23679216 DOI: 10.1111/jne.12050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 03/23/2013] [Accepted: 05/12/2013] [Indexed: 12/01/2022]
Abstract
Hypothalamic glutamate (Glu) and γ-GABA neurotransmission are involved in the ovarian hormone-induced gonadotrophin-releasing hormone (GnRH)/luteinising hormone (LH) surge in rodents. Studies have shown that reduced Glu and increased γ-GABA in the rostral preoptic area (rPOA) of the hypothalamus, where most activated GnRH neurones are located, play a key role in decreasing the reproductive function of female rats. However, the mechanism underlying the altered balance of these neurotransmitters is poorly understood. In the present study, we observed a decline in the function of GnRH neurones in the rPOA at the time of the GnRH/LH surge in middle-aged intact female mice with regular oestrous cycles. In young mice, there is an increase of vesicular Glu transporter 2 on the pro-oestrus afternoon, which is not observed in middle-aged mice. By contrast, vesicular γ-GABA transporter levels in young mice decrease at the time of the LH surge, whereas they increase in middle-aged mice. Of note, we found that, in middle-aged mice at the time of the GnRH/LH surge, the phosphorylation of synapsin I at Ser603 and Ca(2+) /calmodulin-dependent kinase IIα was significantly lower than in young mice. These data suggest that, in middle-aged mice, higher levels of presynaptic stores of GABA, a lack of increase of Glu and a decreased ability of synaptic vesicle mobilisation could account for the imbalance of Glu and GABA in the rPOA, which decreases the activation of GnRH neurones.
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Affiliation(s)
- Jing Zhang
- Key Laboratory of Brain Aging and Neurodegenerative Disease, Fujian Institute of Geriatrics, The Affiliated Union Hospital of Fujian Medical University, Fuzhou, China
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Rodríguez SS, Schwerdt JI, Barbeito CG, Flamini MA, Han Y, Bohn MC, Goya RG. Hypothalamic IGF-I gene therapy prolongs estrous cyclicity and protects ovarian structure in middle-aged female rats. Endocrinology 2013; 154:2166-73. [PMID: 23584855 PMCID: PMC3740492 DOI: 10.1210/en.2013-1069] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
There is substantial evidence that age-related ovarian failure in rats is preceded by abnormal responsiveness of the neuroendocrine axis to estrogen positive feedback. Because IGF-I seems to act as a permissive factor for proper GnRH neuronal response to estrogen positive feedback and considering that the hypothalamic content of IGF-I declines in middle-aged (M-A) rats, we assessed the effectiveness of long-term IGF-I gene therapy in the mediobasal hypothalamus (MBH) of M-A female rats to extend regular cyclicity and preserve ovarian structure. We used 3 groups of M-A rats: 1 group of intact animals and 2 groups injected, at 36.2 weeks of age, in the MBH with either a bicistronic recombinant adeno-associated virus (rAAV) harboring the genes for IGF-I and the red fluorescent protein DsRed2, or a control rAAV expressing only DsRed2. Daily vaginal smears were taken throughout the study, which ended at 49.5 weeks of age. We measured serum levels of reproductive hormones and assessed ovarian histology at the end of the study. Although most of the rats injected with the IGF-I rAAV had, on the average, well-preserved estrous cyclicity as well as a generally normal ovarian histology, the intact and control rAAV groups showed a high percentage of acyclic rats at the end of the study and ovaries with numerous enlarged cysts and scarce corpora lutea. Serum LH was higher and hyperprolactinemia lower in the treated animals. These results suggest that overexpression of IGF-I in the MBH prolongs normal ovarian function in M-A female rats.
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Affiliation(s)
- Silvia S Rodríguez
- Instituto de Investigaciones Bioquímicas de La Plata, University of La Plata, 1900 La Plata, Argentina
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23
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Kermath BA, Gore AC. Neuroendocrine control of the transition to reproductive senescence: lessons learned from the female rodent model. Neuroendocrinology 2012; 96:1-12. [PMID: 22354218 PMCID: PMC3574559 DOI: 10.1159/000335994] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 12/06/2011] [Indexed: 01/19/2023]
Abstract
The natural transition to reproductive senescence is an important physiological process that occurs with aging, resulting in menopause in women and diminished or lost fertility in most mammalian species. This review focuses on how rodent models have informed our knowledge of age-related changes in gonadotropin-releasing hormone (GnRH) neurosecretory function and the subsequent loss of reproductive capacity. Studies in rats and mice have shown molecular, morphological and functional changes in GnRH cells. Furthermore, during reproductive aging altered sex steroid feedback to the hypothalamus contributes to a decrease of stimulatory signaling and increase in inhibitory tone onto GnRH neurons. At the site of the GnRH terminals where the peptide is released into the portal vasculature, the cytoarchitecture of the median eminence becomes disorganized with aging, and mechanisms of glial-GnRH neuronal communication may be disrupted. These changes can result in the dysregulation of GnRH secretion with reproductive decline. Interestingly, reproductive aging effects on the GnRH circuitry are observed in middle age even prior to any obvious physiological changes in cyclicity. We speculate that the hypothalamus may play a critical role in this mid-life transition. Because there are substantial species differences in these aging processes, we also compare and contrast rodent aging to that in primates. Work discussed herein shows that in order to understand neuroendocrine mechanisms of reproductive senescence, further research needs to be conducted in ovarian-intact models.
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Affiliation(s)
- Bailey A. Kermath
- Institute for Neurosciences; The University of Texas at Austin, Austin, TX, 78712, USA
| | - Andrea C. Gore
- Institute for Neurosciences; The University of Texas at Austin, Austin, TX, 78712, USA
- Division of Pharmacology & Toxicology; The University of Texas at Austin, Austin, TX, 78712, USA
- Institute for Cellular & Molecular Biology; The University of Texas at Austin, Austin, TX, 78712, USA
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Sun Y, Shu J, Kyei K, Neal-Perry GS. Intracerebroventricular infusion of vasoactive intestinal Peptide rescues the luteinizing hormone surge in middle-aged female rats. Front Endocrinol (Lausanne) 2012; 3:24. [PMID: 22654857 PMCID: PMC3356100 DOI: 10.3389/fendo.2012.00024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 01/31/2012] [Indexed: 12/02/2022] Open
Abstract
Reproductive aging is characterized by delayed and attenuated luteinizing hormone (LH) surges apparent in middle-aged rats. The suprachiasmatic nucleus (SCN) contains the circadian clock that is responsible for the timing of diverse neuroendocrine rhythms. Electrophysiological studies suggest vasoactive intestinal peptide (VIP) originating from the SCN excites gonadotropin-releasing hormone (GnRH) neurons and affects daily patterns of GnRH-LH release. Age-related LH surge dysfunction correlates with reduced VIP mRNA expression in the SCN and fewer GnRH neurons with VIP contacts expressing c-fos, a marker of neuronal activation, on the day of the LH surge. To determine if age-related LH surge dysfunction reflects reduced VIP availability or altered VIP responsiveness under estradiol positive feedback conditions, we assessed the effect of intracerebroventricular (icv) VIP infusion on c-fos expression in GnRH neurons and on LH release in ovariohysterectomized, hormone-primed young and middle-aged rats. Icv infusion of VIP between 1300 and 1600 h significantly advanced the time of peak LH release, increased total and peak LH release, and increased the number of GnRH neurons expressing c-fos on the day of the LH surge in middle-aged rats. Surprisingly, icv infusion of VIP in young females significantly reduced the number of GnRH neurons expressing c-fos and delayed and reduced the LH surge. These observations suggest that a critical balance of VIP signaling is required to activate GnRH neurons for an appropriately timed and robust LH surge in young and middle-aged females. Age-related LH surge changes may, in part, result from decreased availability and reduced VIP-mediated neurotransmission under estradiol positive feedback conditions.
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Affiliation(s)
- Yan Sun
- Department of Obstetrics/Gynecology and Women’s Health, Albert Einstein College of MedicineBronx, NY, USA
| | - Jun Shu
- Department of Obstetrics/Gynecology and Women’s Health, Albert Einstein College of MedicineBronx, NY, USA
| | - Kwame Kyei
- Department of Obstetrics/Gynecology and Women’s Health, Albert Einstein College of MedicineBronx, NY, USA
| | - Genevieve S. Neal-Perry
- Department of Obstetrics/Gynecology and Women’s Health, Albert Einstein College of MedicineBronx, NY, USA
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronx, NY, USA
- *Correspondence: Genevieve S. Neal-Perry, Department of Obstetrics/Gynecology and Women’s Health, Albert Einstein College of Medicine, 1300 Morris Park Avenue, U1211, Bronx, NY 10461, USA. e-mail:
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Petersen SL, Krishnan S, Aggison LK, Intlekofer KA, Moura PJ. Sexual differentiation of the gonadotropin surge release mechanism: a new role for the canonical NfκB signaling pathway. Front Neuroendocrinol 2012; 33:36-44. [PMID: 21741397 DOI: 10.1016/j.yfrne.2011.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 06/09/2011] [Accepted: 06/11/2011] [Indexed: 12/30/2022]
Abstract
Sex differences in luteinizing hormone (LH) release patterns are controlled by the hypothalamus, established during the perinatal period and required for fertility. Female mammals exhibit a cyclic surge pattern of LH release, while males show a tonic release pattern. In rodents, the LH surge pattern is dictated by the anteroventral periventricular nucleus (AVPV), an estrogen receptor-rich structure that is larger and more cell-dense in females. Sex differences result from mitochondrial cell death triggered in perinatal males by estradiol derived from aromatization of testosterone. Herein we provide an historical perspective and an update describing evidence that molecules important for cell survival and cell death in the immune system also control these processes in the developing AVPV. We conclude with a new model proposing that development of the female AVPV requires constitutive activation of the Tnfα, Tnf receptor 2, NfκB and Bcl2 pathway that is blocked by induction of Tnf receptor-associated factor 2-inhibiting protein (Traip) in the male.
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Affiliation(s)
- Sandra L Petersen
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, MA 01003, United States.
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26
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Abstract
The median eminence at the base of the hypothalamus serves as an interface between the neural and peripheral endocrine systems. It releases hypothalamic-releasing hormones into the portal capillary bed for transport to the anterior pituitary, which provides further signals to target endocrine systems. Of specific relevance to reproduction, a group of about 1000 neurons in mammals release the gonadotropin-releasing hormone (GnRH) peptide from neuroterminals in the median eminence. During the life cycle, there are dramatic changes in reproductive demands, and we focus this review on how GnRH terminals in the median eminence change during reproductive senescence. We discuss morphological and functional properties of the median eminence, and how relationships among GnRH terminals and their microenvironment of nerve terminals, glial cells, and the portal capillary vasculature determine the ability of GnRH peptide to be secreted and to reach its target in the anterior pituitary gland.
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Affiliation(s)
- Weiling Yin
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, USA
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Christian CA, Moenter SM. The neurobiology of preovulatory and estradiol-induced gonadotropin-releasing hormone surges. Endocr Rev 2010; 31:544-77. [PMID: 20237240 PMCID: PMC3365847 DOI: 10.1210/er.2009-0023] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Accepted: 02/18/2010] [Indexed: 12/14/2022]
Abstract
Ovarian steroids normally exert homeostatic negative feedback on GnRH release. During sustained exposure to elevated estradiol in the late follicular phase of the reproductive cycle, however, the feedback action of estradiol switches to positive, inducing a surge of GnRH release from the brain, which signals the pituitary LH surge that triggers ovulation. In rodents, this switch appears dependent on a circadian signal that times the surge to a specific time of day (e.g., late afternoon in nocturnal species). Although the precise nature of this daily signal and the mechanism of the switch from negative to positive feedback have remained elusive, work in the past decade has provided much insight into the role of circadian/diurnal and estradiol-dependent signals in GnRH/LH surge regulation and timing. Here we review the current knowledge of the neurobiology of the GnRH surge, in particular the actions of estradiol on GnRH neurons and their synaptic afferents, the regulation of GnRH neurons by fast synaptic transmission mediated by the neurotransmitters gamma-aminobutyric acid and glutamate, and the host of excitatory and inhibitory neuromodulators including kisspeptin, vasoactive intestinal polypeptide, catecholamines, neurokinin B, and RFamide-related peptides, that appear essential for GnRH surge regulation, and ultimately ovulation and fertility.
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Affiliation(s)
- Catherine A Christian
- Departments of Medicine and Cell Biology, University of Virginia, Charlottesville, 22908, USA.
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Neal-Perry G, Nejat E, Dicken C. The neuroendocrine physiology of female reproductive aging: An update. Maturitas 2010; 67:34-8. [PMID: 20570066 DOI: 10.1016/j.maturitas.2010.04.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2010] [Revised: 04/24/2010] [Accepted: 04/26/2010] [Indexed: 11/16/2022]
Abstract
The transition into menopause is a complex process that affects fertility and increases the risk for a number of health problems in aging women that include, but are not limited to osteoporosis, heart disease, diabetes mellitus and cognitive dysfunction. Improved nutrition and enhanced access to medical care have increased the average lifespan for women in developed countries, and many will spend more than one-third of their life in a post-menopausal state. Epidemiological studies indicate that a delayed natural menopause confers longevity and decelerates the appearance of much age-related morbidity, suggesting that developing treatments to delay menopause would significantly improve quality of life for women. Although menopause is ultimately defined by ovarian follicular exhaustion, several lines of scientific evidence in humans and animals now suggest that dysregulation of estradiol feedback mechanisms and hypothalamic-pituitary dysfunction contributes to the onset and progression of reproductive senescence, independent of ovarian failure. This article provides a brief update on our current understanding of the role of the hypothalamic-pituitary axis in the onset of and transition into female reproductive senescence.
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Affiliation(s)
- Genevieve Neal-Perry
- Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynecology, Montefiore Medical Center and Albert Einstein College of Medicine and Yeshiva University, Bronx, NY, USA.
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Khan M, De Sevilla L, Mahesh VB, Brann DW. Enhanced glutamatergic and decreased GABAergic synaptic appositions to GnRH neurons on proestrus in the rat: modulatory effect of aging. PLoS One 2010; 5:e10172. [PMID: 20418960 PMCID: PMC2854717 DOI: 10.1371/journal.pone.0010172] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 03/22/2010] [Indexed: 01/02/2023] Open
Abstract
Background Previous work by our lab and others has implicated glutamate as a major excitatory signal to gonadotropin hormone releasing hormone (GnRH) neurons, with gamma amino butyric acid (GABA) serving as a potential major inhibitory signal. However, it is unknown whether GABAergic and/or glutamatergic synaptic appositions to GnRH neurons changes on the day of the proestrous LH surge or is affected by aging. Methodology/Principal Findings To examine this question, synaptic terminal appositions on GnRH neurons for VGAT (vesicular GABA transporter) and VGLUT2 (vesicular glutamate transporter-2), markers of GABAergic and glutamatergic synaptic terminals, respectively, was examined by immunohistochemistry and confocal microscopic analysis in young and middle-aged diestrous and proestrous rats. The results show that in young proestrous rats at the time of LH surge, we observed reciprocal changes in the VGAT and VGLUT2 positive terminals apposing GnRH neurons, where VGAT terminal appositions were decreased and VGLUT2 terminal appositions were significantly increased, as compared to young diestrus control animals. Interestingly, in middle-aged cycling animals this divergent modulation of VGAT and VGLUT2 terminal apposition was greatly impaired, as no significant differences were observed between VGAT and VGLUT2 terminals apposing GnRH neurons at proestrous. However, the density of VGAT and VGLUT2 terminals apposing GnRH neurons were both significantly increased in the middle-aged animals. Conclusions/Significance In conclusion, there is an increase in glutamatergic and decrease in GABAergic synaptic terminal appositions on GnRH neurons on proestrus in young animals, which may serve to facilitate activation of GnRH neurons. In contrast, middle-aged diestrous and proestrous animals show a significant increase in both VGAT and VGLUT synaptic terminal appositions on GnRH neurons as compared to young animals, and the cycle-related change in these appositions between diestrus and proestrus that is observed in young animals is lost.
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Affiliation(s)
- Mohammad Khan
- Institute of Molecular Medicine and Genetics, Developmental Neurobiology Program, Medical College of Georgia, Augusta, Georgia, United States of America
| | - Liesl De Sevilla
- Institute of Molecular Medicine and Genetics, Developmental Neurobiology Program, Medical College of Georgia, Augusta, Georgia, United States of America
| | - Virendra B. Mahesh
- Institute of Molecular Medicine and Genetics, Developmental Neurobiology Program, Medical College of Georgia, Augusta, Georgia, United States of America
| | - Darrell W. Brann
- Institute of Molecular Medicine and Genetics, Developmental Neurobiology Program, Medical College of Georgia, Augusta, Georgia, United States of America
- * E-mail:
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Biancardi VC, Campos RR, Stern JE. Altered balance of gamma-aminobutyric acidergic and glutamatergic afferent inputs in rostral ventrolateral medulla-projecting neurons in the paraventricular nucleus of the hypothalamus of renovascular hypertensive rats. J Comp Neurol 2010; 518:567-85. [PMID: 20034060 DOI: 10.1002/cne.22256] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An imbalance of excitatory and inhibitory functions has been shown to contribute to numerous pathological disorders. Accumulating evidence supports the idea that a change in hypothalamic gamma-aminobutyric acid (GABA)-ergic inhibitory and glutamatergic excitatory synaptic functions contributes to exacerbated neurohumoral drive in prevalent cardiovascular disorders, including hypertension. However, the precise underlying mechanisms and neuronal substrates are still not fully elucidated. In the present study, we combined quantitative immunohistochemistry with neuronal tract tracing to determine whether plastic remodeling of afferent GABAergic and glutamatergic inputs into identified RVLM-projecting neurons of the hypothalamic paraventricular nucleus (PVN-RVLM) contributes to an imbalanced excitatory/inhibitory function in renovascular hypertensive rats (RVH). Our results indicate that both GABAergic and glutamatergic innervation densities increased in oxytocin-positive, PVN-RVLM (OT-PVN-RVLM) neurons in RVH rats. Despite this concomitant increase, time-dependent and compartment-specific differences in the reorganization of these inputs resulted in an altered balance of excitatory/inhibitory inputs in somatic and dendritic compartments. A net predominance of excitatory over inhibitory inputs was found in OT-PVN-RVLM proximal dendrites. Our results indicate that, along with previously described changes in neurotransmitter release probability and postsynaptic receptor function, remodeling of GABAergic and glutamatergic afferent inputs contributes as an underlying mechanism to the altered excitatory/inhibitory balance in the PVN of hypertensive rats.
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31
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Todd BJ, Merhi ZO, Shu J, Etgen AM, Neal-Perry GS. Hypothalamic insulin-like growth factor-I receptors are necessary for hormone-dependent luteinizing hormone surges: implications for female reproductive aging. Endocrinology 2010; 151:1356-66. [PMID: 20097715 PMCID: PMC2840696 DOI: 10.1210/en.2009-1009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Brain IGF-I receptors are required for maintenance of estrous cycles in young adult female rats. Circulating and hypothalamic IGF-I levels decrease with aging, suggesting a role for IGF-I in the onset of reproductive senescence. Therefore, the present study investigated potential mechanisms of action of brain IGF-I receptors in the regulation of LH surges in young adult and middle-aged rats. We continuously infused IGF-I, the selective IGF-I receptor antagonist JB-1, or vehicle into the third ventricle of ovariectomized young adult and middle-aged female rats primed with estradiol and progesterone. Pharmacological blockade of IGF-I receptors attenuated and delayed the LH surge in young adult rats, reminiscent of the LH surge pattern that heralds the onset of reproductive senescence in middle-aged female rats. Infusion of IGF-I alone had no effect on the LH surge but reversed JB-1 attenuation of the surge in young females. In middle-aged rats, infusion of low doses of IGF-I partially restored LH surge amplitude, and infusion of JB-1 completely obliterated the surge. Intraventricular infusion of IGF-I or JB-1 did not modify pituitary sensitivity to exogenous GnRH or GnRH peptide content in the anterior or mediobasal hypothalamus in either young or middle-aged rats. These findings support the hypothesis that brain IGF-I receptor signaling is necessary for GnRH neuron activation under estrogen-positive feedback conditions and that decreased brain IGF-I signaling in middle-aged females contributes, in part, to LH surge dysfunction by disrupting estradiol-sensitive processes that affect GnRH neuron activation and/or GnRH release.
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Affiliation(s)
- Brigitte J Todd
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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32
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Chan YM, Broder-Fingert S, Wong KM, Seminara SB. Kisspeptin/Gpr54-independent gonadotrophin-releasing hormone activity in Kiss1 and Gpr54 mutant mice. J Neuroendocrinol 2009; 21:1015-23. [PMID: 19840236 PMCID: PMC2789182 DOI: 10.1111/j.1365-2826.2009.01926.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The kisspeptin/Gpr54 signalling pathway plays a critical role in reproduction by stimulating the secretion of gonadotrophin-releasing hormone (GnRH), yet mice carrying mutations in Kiss1 (which encodes kisspeptin) or Gpr54 exhibit partial sexual maturation. For example, a proportion of female Kiss1(-/-) and Gpr54(-/-) mice exhibit vaginal oestrus, and some male Kiss1(-/-) and Gpr54(-/-) mice exhibit spermatogenesis. To characterise this partial sexual maturation, we examined the vaginal cytology of female Kiss1(-/-) and Gpr54(-/-) mice over time. Almost all mutant mice eventually enter oestrus, and then spontaneously transition from oestrus to dioestrus and back to oestrus again. These transitions are not associated with ovulation, and the frequency of these transitions increases with age. The oestrus exhibited by female Kiss1(-/-) and Gpr54(-/-) mice was disrupted by the administration of the competitive GnRH antagonist acyline, which also resulted in lower uterine weights and, in Kiss1(-/-) mice, lower serum follicle-stimulating hormone (FSH) and luteinising hormone (LH) concentrations. Similarly, male Kiss1(-/-) and Gpr54(-/-) mice treated with acyline had smaller testicular sizes and an absence of mature sperm. In addition to examining intact Kiss1(-/-) and Gpr54(-/-) mice, we also assessed the effects of acyline on gonadotrophin concentrations in gonadectomised mice. Gonadectomy resulted in a significant increase in serum FSH concentrations in male Gpr54(-/-) and Kiss1(-/-) mice. Acyline administration to gonadectomised Kiss1(-/-) and Gpr54(-/-) male mice lowered serum FSH and LH concentrations significantly. By contrast to males, gonadectomy did not result in significant gonadotrophin changes in female Kiss1(-/-) and Gpr54(-/-) mice, but acyline administration was followed by a decrease in LH concentrations. These results demonstrate that, although kisspeptin signalling is critical for the high levels of GnRH activity required for normal sexual maturation and for ovulation, Kiss1(-/-) and Gpr54(-/-) mice retain some degree of GnRH activity. This GnRH activity is sufficient to produce significant effects on vaginal cytology and uterine weights in female mice and on spermatogenesis and testicular weights in male mice.
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Affiliation(s)
- Y M Chan
- Reproductive Endocrine Unit and Harvard Reproductive Sciences Center, Massachusetts General Hospital, Boston, MA 02114, USA.
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33
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Neal-Perry G, Lebesgue D, Lederman M, Shu J, Zeevalk GD, Etgen AM. The excitatory peptide kisspeptin restores the luteinizing hormone surge and modulates amino acid neurotransmission in the medial preoptic area of middle-aged rats. Endocrinology 2009; 150:3699-708. [PMID: 19423763 PMCID: PMC2717872 DOI: 10.1210/en.2008-1667] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Reproductive success depends on a robust and appropriately timed preovulatory LH surge. The LH surge, in turn, requires ovarian steroid modulation of GnRH neuron activation by the neuropeptide kisspeptin and glutamate and gamma-aminobutyric acid (GABA) neurotransmission in the medial preoptic area (mPOA). Middle-aged females exhibit reduced excitation of GnRH neurons and attenuated LH surges under estrogen-positive feedback conditions, in part, due to increased GABA and decreased glutamate neurotransmission in the mPOA. This study tested the hypothesis that altered kisspeptin regulation by ovarian steroids plays a role in age-related LH surge dysfunction. We demonstrate that middle-aged rats exhibiting delayed and attenuated LH surges have reduced levels of Kiss1 mRNA in the anterior hypothalamus under estrogen-positive feedback conditions. Kisspeptin application directly into the mPOA rescues total LH release and the LH surge amplitude in middle-aged rats and increases glutamate and decreases GABA release to levels seen in the mPOA of young females. Moreover, the N-methyl-D-aspartate receptor antagonist MK801 blocks kisspeptin reinstatement of the LH surge. These observations suggest that age-related LH surge dysfunction results, in part, from reduced kisspeptin drive under estrogen-positive feedback conditions and that kisspeptin regulates GnRH/LH release, in part, through modulation of mPOA glutamate and GABA release.
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Affiliation(s)
- Genevieve Neal-Perry
- Department of Obstetrics and Gynecology and Women's Health, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Age-related LH surge dysfunction correlates with reduced responsiveness of hypothalamic anteroventral periventricular nucleus kisspeptin neurons to estradiol positive feedback in middle-aged rats. Neuropharmacology 2009; 58:314-20. [PMID: 19559035 DOI: 10.1016/j.neuropharm.2009.06.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 06/16/2009] [Accepted: 06/16/2009] [Indexed: 11/24/2022]
Abstract
Female reproductive aging in rats is characterized by reduced gonadotropin releasing hormone (GnRH) neuronal activation under estradiol positive feedback conditions and a delayed and attenuated luteinizing hormone (LH) surge. The newly identified excitatory neuropeptide kisspeptin is proposed to be a critical mediator of the pubertal transition and the ovarian steroid-induced LH surge. We previously showed that estradiol induces less kisspeptin mRNA expression in the anterior hypothalamus [anatomical location of anteroventral periventricular nucleus (AVPV)] in middle-aged than in young rats and intrahypothalamic infusion of kisspeptin restores LH surge amplitude in middle-aged females. Thus, reduced kisspeptin neurotransmission may contribute to age-related LH surge abnormalities. This study tested the hypothesis that middle-aged females will also exhibit reduced numbers of kisspeptin immunopositive neurons in the AVPV under estradiol positive feedback conditions. Using immunohistochemistry, we demonstrate that middle-aged females primed with ovarian steroids have fewer AVPV kisspeptin immunopositive neurons than young females. Age did not affect kisspeptin mRNA expression in the pituitary, numbers of kisspeptin immunopositive neurons in the arcuate nucleus, or estradiol-dependent reductions in kisspeptin mRNA expression in the posterior hypothalamus (containing the arcuate nucleus). These data strongly suggest that age-related LH surge dysfunction results, in part, from a reduced sensitivity of AVPV kisspeptin neurons to estradiol and hence decreased availability of AVPV kisspeptin neurons to activate GnRH neurons under positive feedback conditions.
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Maffucci JA, Noel ML, Gillette R, Wu D, Gore AC. Age- and hormone-regulation of N-methyl-D-aspartate receptor subunit NR2b in the anteroventral periventricular nucleus of the female rat: implications for reproductive senescence. J Neuroendocrinol 2009; 21:506-17. [PMID: 19302193 PMCID: PMC2930127 DOI: 10.1111/j.1365-2826.2009.01860.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glutamate, acting through its N-methyl-D-aspartate (NMDA) and non-NMDA receptors in the hypothalamus, regulates reproductive neuroendocrine functions via direct and indirect actions upon gonadotrophin-releasing hormone (GnRH) neurones. Previous studies indicate that the NMDA receptor subunit NR2b undergoes changes in protein and gene expression in the hypothalamus in general, and on GnRH neurones in particular, during reproductive ageing. In the present study, we examined whether the NR2b-expressing cell population, both alone and in association with the NR1 subunit (i.e. the latter subunit is necessary for a functional NMDA receptor), is altered as a function of age and ⁄ or steroid hormone treatment. Studies focused on the anteroventral periventricular (AVPV) nucleus of the hypothalamus, a region critically involved in the control of reproduction. Young (3-5 months), middle-aged (9-12 months), and aged (approximately 22 months) female rats were ovariectomised and, 1 month later, they were treated sequentially with oestradiol plus progesterone, oestradiol plus vehicle, or vehicle plus vehicle, then perfused. Quantitative stereologic analysis of NR2b-immunoreactive cell numbers in the AVPV showed an age-associated decrease in the density of NR2b-immunoreactive cells, but no effect of hormone treatment. In a second study, immunofluorescent double labelling of NR2b and NR1 was analysed by confocal microscopy of fraction volume, a semi-quantitative measure of fluorescence intensity. No effect of ageing was detected for immunofluorescent NR1 or NR2b alone, whereas the NR2b fraction volume increased in the oestradiol plus vehicle group. With ageing, the fraction volume of the NR2b/NR1-colocalised subunits increased. Together with the stereology results, this suggests that, although fewer cells express the NR2b subunit in the ageing AVPV, a greater percentage of these subunits are co-expressed with NR1. Our results suggest that the subunit composition of NMDA receptors in the AVPV undergo both age- and hormonal-regulation, which may be related to previous observations of changes in functional responses of reproductive neuroendocrine systems to NMDA receptor modulators with ageing.
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Affiliation(s)
- J A Maffucci
- Institute for Neuroscience, University of Texas at Austin, USA
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Maffucci JA, Gore AC. Chapter 2: hypothalamic neural systems controlling the female reproductive life cycle gonadotropin-releasing hormone, glutamate, and GABA. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 274:69-127. [PMID: 19349036 DOI: 10.1016/s1937-6448(08)02002-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The hypothalamic-pituitary-gonadal (HPG) axis undergoes a number of changes throughout the reproductive life cycle that are responsible for the development, puberty, adulthood, and senescence of reproductive systems. This natural progression is dictated by the neural network controlling the hypothalamus including the cells that synthesize and release gonadotropin-releasing hormone (GnRH) and their regulatory neurotransmitters. Glutamate and GABA are the primary excitatory and inhibitory neurotransmitters in the central nervous system, and as such contribute a great deal to modulating this axis throughout the lifetime via their actions on receptors in the hypothalamus, both directly on GnRH neurons as well as indirectly through other hypothalamic neural networks. Interactions among GnRH neurons, glutamate, and GABA, including the regulation of GnRH gene and protein expression, hormone release, and modulation by estrogen, are critical to age-appropriate changes in reproductive function. Here, we present evidence for the modulation of GnRH neurosecretory cells by the balance of glutamate and GABA in the hypothalamus, and the functional consequences of these interactions on reproductive physiology across the life cycle.
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