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Prokai-Tatrai K, Prokai L. The impact of 17β-estradiol on the estrogen-deficient female brain: from mechanisms to therapy with hot flushes as target symptoms. Front Endocrinol (Lausanne) 2024; 14:1310432. [PMID: 38260155 PMCID: PMC10800853 DOI: 10.3389/fendo.2023.1310432] [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: 10/09/2023] [Accepted: 12/18/2023] [Indexed: 01/24/2024] Open
Abstract
Sex steroids are essential for whole body development and functions. Among these steroids, 17β-estradiol (E2) has been known as the principal "female" hormone. However, E2's actions are not restricted to reproduction, as it plays a myriad of important roles throughout the body including the brain. In fact, this hormone also has profound effects on the female brain throughout the life span. The brain receives this gonadal hormone from the circulation, and local formation of E2 from testosterone via aromatase has been shown. Therefore, the brain appears to be not only a target but also a producer of this steroid. The beneficial broad actions of the hormone in the brain are the end result of well-orchestrated delayed genomic and rapid non-genomic responses. A drastic and steady decline in circulating E2 in a female occurs naturally over an extended period of time starting with the perimenopausal transition, as ovarian functions are gradually declining until the complete cessation of the menstrual cycle. The waning of endogenous E2 in the blood leads to an estrogen-deficient brain. This adversely impacts neural and behavioral functions and may lead to a constellation of maladies such as vasomotor symptoms with varying severity among women and, also, over time within an individual. Vasomotor symptoms triggered apparently by estrogen deficiency are related to abnormal changes in the hypothalamus particularly involving its preoptic and anterior areas. However, conventional hormone therapies to "re-estrogenize" the brain carry risks due to multiple confounding factors including unwanted hormonal exposure of the periphery. In this review, we focus on hot flushes as the archetypic manifestation of estrogen deprivation in the brain. Beyond our current mechanistic understanding of the symptoms, we highlight the arduous process and various obstacles of developing effective and safe therapies for hot flushes using E2. We discuss our preclinical efforts to constrain E2's beneficial actions to the brain by the DHED prodrug our laboratory developed to treat maladies associated with the hypoestrogenic brain.
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Affiliation(s)
- Katalin Prokai-Tatrai
- Department of Pharmacology & Neuroscience, University of North Texas Health Science Center, Fort Worth, TX, United States
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Abstract
The thermoregulatory functions may vary with age. Thermosensitivity is active in neonates and children; both heat production and heat loss effector mechanisms are functional but easily exhaustable. Proportional and lasting defense against thermal challenges is difficult, and both hypothermia and hyperthermia may easily develop. Febrile or hypothermic responses to infections or endotoxin can also develop, together with confusion. In small children febrile convulsions may be dangerous. In old age the resting body temperature may be lower than in young adults. Further, thermosensitivity decreases, the thresholds for activating skin vasomotor and evaporative responses or metabolism are shifted, and responses to thermal challenges are delayed or insufficient: both hypothermia and hyperthermia may develop easily. Infection-induced fevers are often limited or absent, or replaced by hypothermia. Various types of brain damage may induce special forms of hypothermia, hyperthermia, or severe fever. Impaired mental state often accompanies hypothermia and hyperthermia, and may occasionally be a dominant feature of infection (instead of the most commonly observed fever). Aging brings about a turning point in women's life: the menopause. The well-known influence of regular hormonal cycles on the thermoregulation of a woman of fertile age gives way to menopausal hot flushes caused by estrogen withdrawal. Not all details of this thermoregulatory anomaly are fully understood yet.
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Shults CL, Dingwall CB, Kim CK, Pinceti E, Rao YS, Pak TR. 17β-estradiol regulates the RNA-binding protein Nova1, which then regulates the alternative splicing of estrogen receptor β in the aging female rat brain. Neurobiol Aging 2017; 61:13-22. [PMID: 29031089 DOI: 10.1016/j.neurobiolaging.2017.09.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 11/18/2022]
Abstract
Alternative RNA splicing results in the translation of diverse protein products arising from a common nucleotide sequence. These alternative protein products are often functional and can have widely divergent actions from the canonical protein. Studies in humans and other vertebrate animals have demonstrated that alternative splicing events increase with advanced age, sometimes resulting in pathological consequences. Menopause represents a critical transition for women, where the beneficial effects of estrogens are no longer evident; therefore, factors underlying increased pathological conditions in women are confounded by the dual factors of aging and declining estrogens. Estrogen receptors (ERs) are subject to alternative splicing, the spliced variants increase following menopause, and they fail to efficiently activate estrogen-dependent signaling pathways. However, the factors that regulate the alternative splicing of ERs remain unknown. We demonstrate novel evidence supporting a potential biological feedback loop where 17β-estradiol regulates the RNA-binding protein Nova1, which, in turn, regulates the alternative splicing of ERβ. These data increase our understanding of ER alternative splicing and could have potential implications for women taking hormone replacement therapy after menopause.
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Affiliation(s)
- Cody L Shults
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Caitlin B Dingwall
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Chun K Kim
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Elena Pinceti
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Yathindar S Rao
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Toni R Pak
- Department of Cell and Molecular Physiology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA.
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Zhang J, Bai W, Wang W, Jiang H, Jin B, Liu Y, Liu S, Wang K, Jia J, Qin L. Mechanisms underlying alterations in norepinephrine levels in the locus coeruleus of ovariectomized rats: Modulation by estradiol valerate and black cohosh. Neuroscience 2017; 354:110-121. [PMID: 28457819 DOI: 10.1016/j.neuroscience.2017.04.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 04/02/2017] [Accepted: 04/20/2017] [Indexed: 11/30/2022]
Abstract
Hot flushes are common in menopause. Norepinephrine (NE), primarily synthesized in the locus coeruleus (LC), plays a major role in central thermoregulation. Furthermore, we previously observed decreased dopamine beta hydroxylase (DβH), a key enzyme in NE synthesis, in LC neurons following ovariectomy. In this study, we explore the mechanisms underlying decreased NE levels in the LC (LC-NE) in ovariectomized (OVX) rats, and the modulating effects of estradiol valerate (E2) and black cohosh (ICR). We used high-performance liquid chromatography to detect LC-NE in SHAM, OVX, OVX-E2, and OVX-ICR groups. Western blotting and immunohistochemistry were performed to investigate the expression of NE metabolic enzymes, the NE reuptake transporter (NET), and estrogen receptors (ERs) in the LC. We observed significant LC-NE decreases in the OVX group. E2 and ICR enhanced LC-NE but did not restore them to SHAM levels. Ovariectomy affected NE synthesis, degradation, and reuptake. Levels of NE catabolic enzymes monoamine oxidase A (MAOA) and catechol-O-methyltransferase (COMT) decreased, while NET expression increased. E2 restored MAOA and COMT to SHAM levels but had no effect on NET. ICR restored COMT and NET to SHAM levels but had no effect on MAOA. Moreover, the OVX group also exhibited decreased expression of ERα and ERβ. E2 enhanced the expression of ERα and ERβ, while ICR only enhanced ERβexpression. Taken together, reduced NE in OVX rats resulted from reduced synthesis and increased degradation and reuptake. E2 and ICR may regulate these processes in different ways through various ERs.
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Affiliation(s)
- Jing Zhang
- Anatomy and Embryology Department, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Wenpei Bai
- Obstetrics and Gynecology Department, Beijing Shijitan Hospital, Beijing 100083, China
| | - Wenjuan Wang
- Anatomy and Embryology Department, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Hai Jiang
- Anatomy and Embryology Department, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Biao Jin
- Anatomy and Embryology Department, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Yao Liu
- Department of Cardiology, Peking University People's Hospital, Beijing 100044, China
| | - Shuya Liu
- Department of Stomatology, General Hospital of Armed Police, Beijing 100039, China
| | - Ke Wang
- Anatomy and Embryology Department, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Jing Jia
- Department of Stomatology, General Hospital of Armed Police, Beijing 100039, China
| | - Lihua Qin
- Anatomy and Embryology Department, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China.
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Pinceti E, Shults CL, Rao YS, Pak TR. Differential Effects of E2 on MAPK Activity in the Brain and Heart of Aged Female Rats. PLoS One 2016; 11:e0160276. [PMID: 27487271 PMCID: PMC4972350 DOI: 10.1371/journal.pone.0160276] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 07/15/2016] [Indexed: 12/21/2022] Open
Abstract
Aging and the coincident loss of circulating estrogens at menopause lead to increased risks for neurological and cardiovascular pathologies. Clinical studies show that estrogen therapy (ET) can be beneficial in mitigating these negative effects, in both the brain and heart, when it is initiated shortly after the perimenopausal transition. However, this same therapy is detrimental when initiated >10 years postmenopause. Importantly, the molecular mechanisms underlying this age-related switch in ET efficacy are unknown. Estrogen receptors (ERs) mediate the neuroprotective and cardioprotective functions of estrogens by modulating gene transcription or, non-genomically, by activating second messenger signaling pathways, such as mitogen activated protein kinases (MAPK). These kinases are critical regulators of cell signaling pathways and have widespread downstream effects. Our hypothesis is that age and estrogen deprivation following menopause alters the expression and activation of the MAPK family members p38 and ERK in the brain and heart. To test this hypothesis, we used a surgically induced model of menopause in 18 month old rats through bilateral ovariectomy (OVX) followed by an acute dose of 17β-estradiol (E2) administered at varying time points post-OVX (1 week, 4 weeks, 8 weeks, or 12 weeks). Age and E2 treatment differentially regulated kinase activity in both the brain and heart, and the effects were also brain region specific. MAPK signaling plays an integral role in aging, and the aberrant regulation of those signaling pathways might be involved in age-related disorders. Clinical studies show benefits of ET during early menopause but detrimental effects later, which might be reflective of changes in kinase expression and activation status.
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Affiliation(s)
- Elena Pinceti
- Department of Cell and Molecular Physiology, Health Science Division, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Cody L. Shults
- Department of Cell and Molecular Physiology, Health Science Division, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Yathindar S. Rao
- Department of Cell and Molecular Physiology, Health Science Division, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Toni R. Pak
- Department of Cell and Molecular Physiology, Health Science Division, Loyola University Chicago, Maywood, Illinois, United States of America
- * E-mail:
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