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Navin AK, Aruldhas MM, Mani KK, Navaneethabalakrishnan S, Venkatachalam S, Banu SK. Unraveling Hypothalamus-Pituitary dysregulation: Hypergonadotropism in F 1 progeny due to prenatal exposure to hexavalent chromium. J Biochem Mol Toxicol 2024; 38:e23699. [PMID: 38532648 DOI: 10.1002/jbt.23699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 02/18/2024] [Accepted: 03/12/2024] [Indexed: 03/28/2024]
Abstract
The endocrine disruptor hexavalent chromium [Cr(VI)] is a proven reproductive toxicant. We recently demonstrated that prenatal Cr(VI) exposure causes testicular resistance to gonadotropins, resulting in hypergonadotropic hypoandrogenism in F1 rats. However, the mechanism driving hypergonadotropism in F1 rats exposed to Cr(VI) prenatally remains an enigma. Therefore, we hypothesized that 'Prenatal Cr(VI) exposure may disrupt steroid hormones-mediated negative feedback regulation of the hypothalamic GnRH, and its receptor in the pituitary of F1 rats, leading to hypergonadotropism.' We administered potassium dichromate (50, 100, or 200 mg/L) to pregnant rats through drinking water between days 9 and 14, and their male F1 offspring were euthanized at 60 days of age. Prenatal Cr(VI) exposure in F1 rats resulted in the accumulation of Cr in the hypothalamus and pituitary. Western blot detected decreased hypothalamic GnRH, Kisspeptin1, and its receptor GPR54, along with diminished ERα, AR, aromatase, and 5α reductase, and GnRH regulatory transcription factors Pit-1 and GATA-4 proteins. Immunohistochemical studies revealed increased immunopositivity of GnRH receptor, AR, 5α reductase, ERα, ERβ, and aromatase proteins in the pituitary, whereas decreased Kisspeptin1, GPR54, and inhibin β. Our findings imply that Cr(VI) exposure during the prenatal period disrupts the hypothalamic Kisspeptin-GPR54-Pit-1/GATA4-GnRH network, boosting the pituitary GnRH receptor. We conclude that prenatal exposure to Cr(VI) alters GnRH expression in the hypothalamus and its receptor in the pituitary of F1 progeny through interfering with the negative feedback effect of androgens and estrogens.
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Affiliation(s)
- Ajit Kumar Navin
- Department of Endocrinology, Dr. A.L.M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Taramani-Velachery Link Road, Chennai, Tamil Nadu, India
| | - Mariajoseph Michael Aruldhas
- Department of Endocrinology, Dr. A.L.M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Taramani-Velachery Link Road, Chennai, Tamil Nadu, India
| | - Kathiresh Kumar Mani
- Department of Endocrinology, Dr. A.L.M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Taramani-Velachery Link Road, Chennai, Tamil Nadu, India
| | - Shobana Navaneethabalakrishnan
- Department of Endocrinology, Dr. A.L.M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Taramani-Velachery Link Road, Chennai, Tamil Nadu, India
| | - Sankar Venkatachalam
- Department of Anatomy, Dr. A.L.M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani Campus, Taramani-Velachery Link Road, Chennai, Tamil Nadu, India
| | - Sakhila K Banu
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine & Biomedical Sciences, TAMU-4458, Texas A&M University, College Station, TX, USA
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Ryan GE, Bohaczuk SC, Cassin J, Witham EA, Shojaei S, Ho EV, Thackray VG, Mellon PL. Androgen receptor positively regulates gonadotropin-releasing hormone receptor in pituitary gonadotropes. Mol Cell Endocrinol 2021; 530:111286. [PMID: 33872733 PMCID: PMC8177864 DOI: 10.1016/j.mce.2021.111286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 03/29/2021] [Accepted: 04/13/2021] [Indexed: 11/30/2022]
Abstract
Within pituitary gonadotropes, the gonadotropin-releasing hormone receptor (GnRHR) receives hypothalamic input from GnRH neurons that is critical for reproduction. Previous studies have suggested that androgens may regulate GnRHR, although the mechanisms remain unknown. In this study, we demonstrated that androgens positively regulate Gnrhr mRNA in mice. We then investigated the effects of androgens and androgen receptor (AR) on Gnrhr promoter activity in immortalized mouse LβT2 cells, which represent mature gonadotropes. We found that AR positively regulates the Gnrhr proximal promoter, and that this effect requires a hormone response element (HRE) half site at -159/-153 relative to the transcription start site. We also identified nonconsensus, full-length HREs at -499/-484 and -159/-144, which are both positively regulated by androgens on a heterologous promoter. Furthermore, AR associates with the Gnrhr promoter in ChIP. Altogether, we report that GnRHR is positively regulated by androgens through recruitment of AR to the Gnrhr proximal promoter.
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Affiliation(s)
- Genevieve E Ryan
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Stephanie C Bohaczuk
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Jessica Cassin
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Emily A Witham
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Shadi Shojaei
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Emily V Ho
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Varykina G Thackray
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Pamela L Mellon
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
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Cui P, Ma T, Tamadon A, Han S, Li B, Chen Z, An X, Shao LR, Wang Y, Feng Y. Hypothalamic DNA methylation in rats with dihydrotestosterone-induced polycystic ovary syndrome: effects of low-frequency electro-acupuncture. Exp Physiol 2018; 103:1618-1632. [DOI: 10.1113/ep087163] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 09/10/2018] [Indexed: 12/19/2022]
Affiliation(s)
- Peng Cui
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
| | - Tong Ma
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
| | - Amin Tamadon
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
| | - Sha Han
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
| | - Bing Li
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
| | - Zheyi Chen
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
| | - Xiaofei An
- Department of Endocrinology, Jiangsu Province Hospital of Chinese Medicine; Affiliated Hospital of Nanjing University of Chinese Medicine; Nanjing 210029 China
| | - Linus R. Shao
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy; University of Gothenburg; 40530 Gothenburg Sweden
| | - Yanqing Wang
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function
| | - Yi Feng
- Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology; Fudan Institutes of Integrative Medicine; Fudan University; Shanghai 200032 China
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function
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Linscott ML, Chung WCJ. Fibroblast Growth Factor 8 Expression in GT1-7 GnRH-Secreting Neurons Is Androgen-Independent, but Can Be Upregulated by the Inhibition of DNA Methyltransferases. Front Cell Dev Biol 2016; 4:34. [PMID: 27200347 PMCID: PMC4853385 DOI: 10.3389/fcell.2016.00034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 04/13/2016] [Indexed: 11/13/2022] Open
Abstract
Fibroblast growth factor 8 (FGF8) is a potent morphogen that regulates the embryonic development of hypothalamic neuroendocrine cells. Indeed, using Fgf8 hypomorphic mice, we showed that reduced Fgf8 mRNA expression completely eliminated the presence of gonadotropin-releasing hormone (GnRH) neurons. These findings suggest that FGF8 signaling is required during the embryonic development of mouse GnRH neurons. Additionally, in situ hybridization studies showed that the embryonic primordial birth place of GnRH neurons, the olfactory placode, is highly enriched for Fgf8 mRNA expression. Taken together these data underscore the importance of FGF8 signaling for GnRH emergence. However, an important question remains unanswered: How is Fgf8 gene expression regulated in the developing embryonic mouse brain? One major candidate is the androgen receptor (AR), which has been shown to upregulate Fgf8 mRNA in 60-70% of newly diagnosed prostate cancers. Therefore, we hypothesized that ARs may be involved in the regulation of Fgf8 transcription in the developing mouse brain. To test this hypothesis, we used chromatin-immunoprecipitation (ChIP) assays to elucidate whether ARs interact with the 5'UTR region upstream of the translational start site of the Fgf8 gene in immortalized mouse GnRH neurons (GT1-7) and nasal explants. Our data showed that while AR interacts with the Fgf8 promoter region, this interaction was androgen-independent, and that androgen treatment did not affect Fgf8 mRNA levels, indicating that androgen signaling does not induce Fgf8 transcription. In contrast, inhibition of DNA methyltransferases (DNMT) significantly upregulated Fgf8 mRNA levels indicating that Fgf8 transcriptional activity may be dependent on DNA methylation status.
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Affiliation(s)
- Megan L Linscott
- Department of Biological Sciences, Kent State University Kent, OH, USA
| | - Wilson C J Chung
- Department of Biological Sciences, Kent State UniversityKent, OH, USA; School of Biomedical Sciences, Kent State UniversityKent, OH, USA
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Jin JM, Yang WX. Molecular regulation of hypothalamus-pituitary-gonads axis in males. Gene 2014; 551:15-25. [PMID: 25168889 DOI: 10.1016/j.gene.2014.08.048] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 07/24/2014] [Accepted: 08/24/2014] [Indexed: 10/24/2022]
Abstract
The hypothalamic-pituitary-gonadal axis (HPG) plays vital roles in reproduction and steroid hormone production in both sexes. The focus of this review is upon gene structures, receptor structures and the signaling pathways of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The hormones' functions in reproduction as well as consequences resulting from mutations are also summarized. Specific characteristics of hormones such as the pulsatile secretions of GnRH are also covered. The different regulators of the HPG axis are introduced including kisspeptin, activin, inhibin, follistatin, androgens and estrogen. This review includes not only their basic information, but also their unique function in the HPG axis. Here we view the HPG axis as a whole, so relations between ligands and receptors are well described crossing different levels of the HPG axis. Hormone interactions and transformations are also considered. The major information of this article is depicted in three figures summarizing the current discoveries on the HPG axis. This article systematically introduces the basic knowledge of the HPG axis and provides information of the current advances relating to reproductive hormones.
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Affiliation(s)
- Jia-Min Jin
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Wan-Xi Yang
- The Sperm Laboratory, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
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