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Segura-Uribe JJ, García-de la Torre P, Castillo-Mendieta T, Bribiesca-Cruz I, Orozco-Suárez S, Soriano-Ursúa MA, Pinto-Almazán R, Fuentes-Venado CE, Guerra-Araiza C. Tibolone Improves Memory and Decreases the Content of Amyloid-β Peptides and Tau Protein in the Hippocampus of a Murine Model of Alzheimer's Disease. J Alzheimers Dis 2022; 90:1437-1447. [PMID: 36278346 DOI: 10.3233/jad-220434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Alzheimer's disease (AD) affects women more than men and consequently has been associated with menopause. Tibolone (TIB) has been used as a hormone replacement therapy to alleviate climacteric symptoms. Neuroprotective effects of TIB have also been reported in some animal models. OBJECTIVE This study aimed to assess the effect of TIB on memory and Aβ peptides and tau protein content in the hippocampus and cerebellum of transgenic 3xTgAD ovariectomized mice. METHODS Three-month-old female mice were ovariectomized. Ten days after surgery, animals were divided into four groups: wild-type (WT)+vehicle; WT+TIB (1 mg/kg); 3xTgAD+vehicle; and 3xTgAD+TIB (1 mg/kg). TIB was administered for three months, and memory was evaluated using the object-in-context recognition task. Subsequently, animals were decapitated, and the hippocampus and cerebellum were dissected. Using commercial ELISA kits, these brain structures were homogenized in a PBS buffer for quantifying Aβ40 and Aβ42 and phosphorylated and total tau.ResultsA long-term memory deficit was observed in the 3xTgAD+vehicle group. In contrast, TIB treatment improved long-term memory in the 3xTgAD+TIB group than those treated with vehicle (p < 0.05). Furthermore, TIB treatment decreased Aβ and tau content in the hippocampus of 3xTgAD mice compared to vehicle-treated groups (p < 0.05). No significant changes were observed in the cerebellum. CONCLUSION Chronic treatment with TIB showed neuroprotective effects and delayed AD neuropathology in the 3xTgAD mice. Our results support hormone replacement therapy with TIB in menopausal women for neuroprotection.
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Affiliation(s)
- Julia J Segura-Uribe
- Subdirección de Gestión de la Investigación, Hospital Infantil de Mexico Federico Gómez, Secretarya de Salud, Mexico City, Mexico
| | - Paola García-de la Torre
- Unidad de Investigación Médica en Enfermedades Neurológicas, Hospital de Especialidades, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Mexico City, Mexico
| | - Tzayaka Castillo-Mendieta
- Unidad de Investigación Médica en Farmacologya, Hospital de Especialidades, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Mexico City, Mexico
| | - Iván Bribiesca-Cruz
- Unidad de Investigación Médica en Farmacologya, Hospital de Especialidades, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Mexico City, Mexico
| | - Sandra Orozco-Suárez
- Unidad de Investigación Médica en Enfermedades Neurológicas, Hospital de Especialidades, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Mexico City, Mexico
| | - Marvin A Soriano-Ursúa
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Rodolfo Pinto-Almazán
- Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Claudia E Fuentes-Venado
- Servicio de Medicina Física y Rehabilitación, Hospital General de Zona No 197, Texcoco, State of Mexico, Mexico
| | - Christian Guerra-Araiza
- Unidad de Investigación Médica en Farmacologya, Hospital de Especialidades, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Mexico City, Mexico
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N-myc Downstream-Regulated Gene 2 (Ndrg2): A Critical Mediator of Estrogen-Induced Neuroprotection Against Cerebral Ischemic Injury. Mol Neurobiol 2022; 59:4793-4804. [PMID: 35622273 DOI: 10.1007/s12035-022-02877-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 05/04/2022] [Indexed: 10/18/2022]
Abstract
Growing evidence indicates that estrogen plays a pivotal role in neuroprotection against cerebral ischemia, but the molecular mechanism of this protection is still elusive. N-myc downstream-regulated gene 2 (Ndrg2), an estrogen-targeted gene, has been shown to exert neuroprotective effects against cerebral ischemia in male mice. However, the role of Ndrg2 in the neuroprotective effect of estrogen remains unknown. In this study, we first detected NDRG2 expression levels in the cortex and striatum in both female and male mice with western blot analyses. We then detected cerebral ischemic injury by constructing middle cerebral artery occlusion and reperfusion (MCAO-R) models in Ndrg2 knockout or conditional knockdown female mice. We further implemented estrogen, ERα, or ERβ agonist replacement in the ovariectomized (OVX) Ndrg2 knockout or conditional knockdown female mice, then tested for NDRG2 expression, glial fibrillary acidic protein (GFAP) expression, and extent of cerebral ischemic injury. We found that NDRG2 expression was significantly higher in female than in male mice in both the cortex and striatum. Ndrg2 knockouts and conditional knockdowns showed significantly aggravated cerebral ischemic injury in female mice. Estrogen and ERβ replacement treatment (DPN) led to NDRG2 upregulation in both the cortex and striatum of OVX mice. Estrogen and DPN also led to GFAP upregulation in OVX mice. However, the effect of estrogen and DPN in activating astrocytes was lost in Ndrg2 knockout OVX mice and primary cultured astrocytes, but partially retained in conditional knockdown OVX mice. Most importantly, we found that the neuroprotective effects of E2 and DPN against cerebral ischemic injury were lost in Ndrg2 knockout OVX mice but partially retained in conditional knockdown OVX mice. These findings demonstrate that estrogen alleviated cerebral ischemic injury via ERβ upregulation of Ndrg2, which could activate astrocytes, indicating that Ndrg2 is a critical mediator of E2-induced neuroprotection against cerebral ischemic injury.
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Mancino DNJ, Lima A, Roig P, García Segura LM, De Nicola AF, Garay LI. Tibolone restrains neuroinflammation in mouse experimental autoimmune encephalomyelitis. J Neuroendocrinol 2022; 34:e13078. [PMID: 34961984 DOI: 10.1111/jne.13078] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 11/03/2021] [Accepted: 12/03/2021] [Indexed: 11/26/2022]
Abstract
Multiple sclerosis (MS) is an immune-mediated and degenerating disease in which myelin sheaths are damaged as a result of chronic progressive inflammation of the central nervous system. Tibolone [(7α,17α)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-in-3-one], a synthetic estrogenic compound with tissue-specific actions and used for menopausal hormone therapy, shows neuroprotective and antioxidant properties both in vivo and in vitro. In the present study, we analyzed whether tibolone plays a therapeutic role in experimental autoimmune encephalomyelitis (EAE) mice, a commonly used model of MS. Female C57BL/6 mice were induced with the myelin oligodendrocyte glycoprotein MOG35-55 and received s.c. tibolone (0.08 mg kg-1 ) injection every other day from the day of induction until death on the acute phase of the disease. Reactive gliosis, Toll like receptor 4 (TLR4), high mobility group box protein 1 (HMGB1), inflammasome parameters, activated Akt levels and myelin were assessed by a real-time polymerase chain reaction, immunohistochemistry, and western blot analysis. Our findings indicated that, in the EAE spinal cord, tibolone reversed the astrocytic and microglial reaction, and reduced the hyperexpression of TLR4 and HMGB1, as well as NLR family pyrin domain containing 3-caspase 1-interleukin-1β inflammasome activation. At the same time, tibolone attenuated the Akt/nuclear factor kappa B pathway and limited the white matter demyelination area. Estrogen receptor expression was unaltered with tibolone treatment. Clinically, tibolone improved neurological symptoms without uterine compromise. Overall, our data suggest that tibolone may serve as a promising agent for the attenuation of MS-related inflammation.
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Affiliation(s)
- Dalila N J Mancino
- Laboratory of Neuroendocrine Biochemistry, Instituto de Biologia y Medicina Experimental - CONICET, Buenos Aires, Argentina
| | - Analia Lima
- Laboratory of Neuroendocrine Biochemistry, Instituto de Biologia y Medicina Experimental - CONICET, Buenos Aires, Argentina
| | - Paulina Roig
- Laboratory of Neuroendocrine Biochemistry, Instituto de Biologia y Medicina Experimental - CONICET, Buenos Aires, Argentina
| | | | - Alejandro F De Nicola
- Laboratory of Neuroendocrine Biochemistry, Instituto de Biologia y Medicina Experimental - CONICET, Buenos Aires, Argentina
- Department of Human Biochemistry, University of Buenos Aires, Buenos Aires, Argentina
| | - Laura I Garay
- Laboratory of Neuroendocrine Biochemistry, Instituto de Biologia y Medicina Experimental - CONICET, Buenos Aires, Argentina
- Department of Human Biochemistry, University of Buenos Aires, Buenos Aires, Argentina
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Del Río JP, Molina S, Hidalgo-Lanussa O, Garcia-Segura LM, Barreto GE. Tibolone as Hormonal Therapy and Neuroprotective Agent. Trends Endocrinol Metab 2020; 31:742-759. [PMID: 32507541 DOI: 10.1016/j.tem.2020.04.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 04/24/2020] [Indexed: 12/11/2022]
Abstract
Tibolone (TIB), a selective tissue estrogenic activity regulator (STEAR) in clinical use by postmenopausal women, activates hormonal receptors in a tissue-specific manner. Estrogenic activity is present mostly in the brain, vagina, and bone, while the inactive forms predominate in the endometrium and breast. Conflicting literature on TIB's actions has been observed. While it has benefits for vasomotor symptoms, bone demineralization, and sexual health, a higher relative risk of hormone-sensitive cancer has been reported. In the brain, TIB can improve mood and cognition, neuroinflammation, and reactive gliosis. This review aims to discuss the systemic effects of TIB on peri- and post-menopausal women and its role in the brain. We suggest that TIB is a hormonal therapy with promising neuroprotective properties.
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Affiliation(s)
- Juan Pablo Del Río
- Reproductive Health Research Institute, Santiago, Chile; Translational Psychiatry Laboratory, Clínica Psiquiátrica Universitaria, Hospital Clínico, Universidad de Chile, Santiago, Chile; Millennium Nucleus to Improve the Mental Health of Adolescents and Youths (Imhay), Santiago, Chile
| | | | - Oscar Hidalgo-Lanussa
- Departamento de Nutrición y Bioquímica, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Luis Miguel Garcia-Segura
- Instituto Cajal, CSIC, Madrid, Spain; Centro de Investigación Biomédica en Red Fragilidad y Envejecimiento Saludable (CIBERFES), Instituto de Salud Carlos III, Madrid, Spain
| | - George E Barreto
- Department of Biological Sciences, School of Natural Sciences, University of Limerick, Limerick, Ireland; Health Research Institute, University of Limerick, Limerick, Ireland.
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The Synthetic Steroid Tibolone Decreases Reactive Gliosis and Neuronal Death in the Cerebral Cortex of Female Mice After a Stab Wound Injury. Mol Neurobiol 2018; 55:8651-8667. [PMID: 29582398 DOI: 10.1007/s12035-018-1008-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 03/15/2018] [Indexed: 02/07/2023]
Abstract
Previous studies have shown that estradiol reduces reactive gliosis after a stab wound injury in the cerebral cortex. Since the therapeutic use of estradiol is limited by its peripheral hormonal effects, it is of interest to determine whether synthetic estrogenic compounds with tissue-specific actions regulate reactive gliosis. Tibolone is a synthetic steroid that is widely used for the treatment of climacteric symptoms and/or the prevention of osteoporosis. In this study, we have assessed the effect of tibolone on reactive gliosis in the cerebral cortex after a stab wound brain injury in ovariectomized adult female mice. By 7 days after brain injury, tibolone reduced the number of glial fibrillary acidic protein (GFAP) immunoreactive astrocytes, the number of ionized calcium binding adaptor molecule 1 (Iba1) immunoreactive microglia, and the number of microglial cells with a reactive phenotype in comparison to vehicle-injected animals. These effects on gliosis were associated with a reduction in neuronal loss in the proximity to the wound, suggesting that tibolone exerts beneficial homeostatic actions in the cerebral cortex after an acute brain injury.
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Khaksari M, Hajmohammadi M, Sepehri G. The effect of angiotensin receptor type 2 inhibition and estrogen on experimental traumatic brain injury. ARCHIVES OF TRAUMA RESEARCH 2018. [DOI: 10.4103/atr.atr_51_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Effects of Tibolone on the Central Nervous System: Clinical and Experimental Approaches. BIOMED RESEARCH INTERNATIONAL 2017; 2017:8630764. [PMID: 28191467 PMCID: PMC5278195 DOI: 10.1155/2017/8630764] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/10/2016] [Accepted: 12/22/2016] [Indexed: 11/25/2022]
Abstract
Hormone replacement therapy (HRT) increases the risk of endometrial and breast cancer. A strategy to reduce this incidence is the use of tibolone (TIB). The aim of this paper was to address the effects of TIB on the central nervous system (CNS). For the present review, MEDLINE (via PubMed), LILACS (via BIREME), Ovid Global Health, SCOPUS, Scielo, and PsycINFO (ProQuest Research Library) electronic databases were searched for the results of controlled clinical trials on peri- and postmenopausal women published from 1990 to September 2016. Also, this paper reviews experimental studies performed to analyze neuroprotective effects, cognitive deficits, neuroplasticity, oxidative stress, and stroke using TIB. Although there are few studies on the effect of this hormone in the CNS, it has been reported that TIB decreases lipid peroxidation levels and improves memory and learning. TIB has important neuroprotective effects that could prevent the risk of neurodegenerative diseases in postmenopausal women as well as the benefits of HRT in counteracting hot flashes, improving mood, and libido. Some reports have found that TIB delays cognitive impairment in various models of neuronal damage. It also modifies brain plasticity since it acts as an endocrine modulator regulating neurotransmitters, Tau phosphorylation, and decreasing neuronal death. Finally, its antioxidant effects have also been reported in different animal models.
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Galea LAM, Frick KM, Hampson E, Sohrabji F, Choleris E. Why estrogens matter for behavior and brain health. Neurosci Biobehav Rev 2016; 76:363-379. [PMID: 27039345 PMCID: PMC5045786 DOI: 10.1016/j.neubiorev.2016.03.024] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/21/2016] [Accepted: 03/29/2016] [Indexed: 12/22/2022]
Abstract
The National Institutes of Health (NIH) has required the inclusion of women in clinical studies since 1993, which has enhanced our understanding of how biological sex affects certain medical conditions and allowed the development of sex-specific treatment protocols. However, NIH's policy did not previously apply to basic research, and the NIH recently introduced a new policy requiring all new grant applications to explicitly address sex as a biological variable. The policy itself is grounded in the results of numerous investigations in animals and humans illustrating the existence of sex differences in the brain and behavior, and the importance of sex hormones, particularly estrogens, in regulating physiology and behavior. Here, we review findings from our laboratories, and others, demonstrating how estrogens influence brain and behavior in adult females. Research from subjects throughout the adult lifespan on topics ranging from social behavior, learning and memory, to disease risk will be discussed to frame an understanding of why estrogens matter to behavioral neuroscience.
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Affiliation(s)
- Liisa A M Galea
- Department of Psychology, Centre for Brain Health, University of British Columbia, Vancouver, BC V6T1Z4, Canada.
| | - Karyn M Frick
- Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, United States
| | - Elizabeth Hampson
- Department of Psychology, University of Western Ontario, London, ON N6A 5C2, Canada
| | - Farida Sohrabji
- Department of Neuroscience and Experimental Therapeutics, Texas A&M HSC College of Medicine, Bryan, TX 77807, United States
| | - Elena Choleris
- Department of Psychology and Neuroscience Program, University of Guelph, Guelph, ON N1G 2W1, Canada
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Braun CMJ, Roberge C. Gender-related protection from or vulnerability to severe CNS diseases: gonado-structural and/or gonado-activational? A meta-analysis of relevant epidemiological studies. Int J Dev Neurosci 2014; 38:36-51. [PMID: 25109841 DOI: 10.1016/j.ijdevneu.2014.07.009] [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: 06/23/2014] [Revised: 07/29/2014] [Accepted: 07/30/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND A vast scientific literature has dealt with gender-specific risk for brain disorder. That field is evolving toward a consensus to the effect that the estrogen hormone family is outstandingly and uniquely neuroprotective. However, the epidemiology relevant to this general outlook remains piecemeal. METHOD The present investigation strategically formats the relevant epidemiological findings around the world in order to quantitatively meta-analyze gender ratio of risk for a variety of relevant severe central nervous system (CNS) diseases at all three gonadal stages of the life cycle, pre pubertal, post adolescent/pre menopausal, and post menopausal. RESULTS The data quantitatively establish that (1) no single epidemiological study should be cited as evidence of gender-specific neuroprotection against the most common severe CNS diseases because the gender-specific risk ratios are contradictory from one study to the other; (2) risk for severe CNS disease is indeed significantly gender-specific, but either gender can be protected: it depends on the disease, not at all on the age bracket. CONCLUSION Our assay of gender-specific risk for severe brain disease around the world has not been able to support the idea according to which any one gender-prevalent gonadal steroid hormone dominates as a neuroprotective agent at natural concentrations.
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Affiliation(s)
- Claude M J Braun
- Department of Psychology, Université du Québec à Montréal, Canada.
| | - Carl Roberge
- Department of Psychology, Université du Québec à Montréal, Canada
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Ström JO, Ingberg E. Impact of methodology on estrogens' effects on cerebral ischemia in rats: an updated meta-analysis. BMC Neurosci 2014; 15:22. [PMID: 24495535 PMCID: PMC3975994 DOI: 10.1186/1471-2202-15-22] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 01/29/2014] [Indexed: 12/15/2022] Open
Abstract
Background Although most animal stroke studies have demonstrated potent neuroprotective effects of estrogens, there are a number of articles reporting the opposite. In 2009, we made the case that this dichotomy was related to administered estrogen dose. Several other suggestions for the discordant results have also been propagated, including the age of the experimental animals and the length of hypoestrogenicity prior to estrogen administration. These two suggestions have gained much popularity, probably because of their kinship with the window of opportunity hypothesis, which is commonly used to explain the analogous dichotomy among human studies. We were therefore encouraged to perform an updated meta-analysis, and to improve it by including all relevant variables in a large multiple regression model, where the impact of confounders could be controlled for. Results The multiple regression model revealed an indisputable impact of estrogen administration mode on the effects of estrogens in ischemic stroke. Subcutaneous slow-release pellets differed from the injection and silastic capsule treatments in terms of impact of estrogens on ischemic stroke, showing that the first mentioned were more prone to render estrogens damaging. Neither the use of elderly animals nor the adoption of longer wash-out periods influenced estrogens’ effects on experimental ischemic stroke in rats. Conclusions We conclude that the discordant results regarding estrogens’ effects in rat models of ischemic stroke are a consequence of differences in estrogen administration modes. These results are not only of importance for the ongoing debate regarding menopausal hormone therapy, but also have an important bearing on experimental stroke methodology and the apparent translational roadblock for suggested stroke interventions.
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Affiliation(s)
- Jakob O Ström
- Vårdvetenskapligt Forskningscentrum/Centre for Health Sciences, Örebro University Hospital, County Council of Örebro, Örebro SE-703 62, Sweden.
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Sohrabji F, Selvamani A, Balden R. Revisiting the timing hypothesis: biomarkers that define the therapeutic window of estrogen for stroke. Horm Behav 2013; 63:222-30. [PMID: 22728278 PMCID: PMC3483414 DOI: 10.1016/j.yhbeh.2012.06.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 06/11/2012] [Accepted: 06/12/2012] [Indexed: 02/06/2023]
Abstract
Significantly extended life expectancy coupled with contemporary sedentary lifestyles and poor nutrition has created a global epidemic of cardiovascular disease and stroke. For women, this issue is complicated by the discrepant outcomes of hormone therapy (HT) for stroke incidence and severity as well as the therapeutic complications for stroke associated with advancing age. Here we propose that the impact of estrogen therapy cannot be considered in isolation, but should include age-related changes in endocrine, immune, and nucleic acid mediators that collaborate with estrogen to produce neuroprotective effects commonly seen in younger, healthier demographics. Due to their role as modulators of ischemic cell death, the post-stroke inflammatory response, and neuronal survival and regeneration, this review proposes that Insulin-like Growth Factor (IGF)-1, Vitamin D, and discrete members of the family of non-coding RNA peptides called microRNAs (miRNAs) may be crucial biochemical markers that help determine the neuroprotective "window" of HT. Specifically, IGF-1 confers neuroprotection in concert with, and independently of, estrogen and failure of the insulin/IGF-1 axis is associated with metabolic disturbances that increase the risk for stroke. Vitamin D and miRNAs regulate and complement IGF-1 mediated function and neuroprotective efficacy via modulation of IGF-1 availability and neural stem cell and immune cell proliferation, differentiation and secretions. Together, age-related decline of these factors differentially affects stroke risk, severity, and outcome, and may provide a novel therapeutic adjunct to traditional HT practices.
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Affiliation(s)
- Farida Sohrabji
- Department of Neuroscience and Experimental Therapeutics, Women's Health in Neuroscience Program, Texas A&M Health Science Center, College Station, TX 77843-1114, USA.
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Selvamani A, Sohrabji F. Reproductive age modulates the impact of focal ischemia on the forebrain as well as the effects of estrogen treatment in female rats. Neurobiol Aging 2010; 31:1618-28. [PMID: 18829137 PMCID: PMC2909345 DOI: 10.1016/j.neurobiolaging.2008.08.014] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 08/02/2008] [Accepted: 08/21/2008] [Indexed: 01/23/2023]
Abstract
While human observational studies and animal studies report a neuroprotective role for estrogen therapy in stroke, the multicenter placebo-controlled Women's Health Initiative (WHI) study concluded that hormone therapy increased the risk for stroke in postmenopausal women. The present study therefore tested the hypothesis that estrogen replacement would increase the severity of a stroke-like injury in females when this replacement occurs after a prolonged hypoestrogenic period, such as the menopause or reproductive senescence, but not when given to females that were normally cycling immediately prior to the hormone replacement. Two groups of female rats were used: multiparous females with normal but lengthened estrus cycles (mature adults), and older multiparous females currently in a persistent acyclic state (reproductive senescent). Animals were either used intact, or were bilaterally ovariectomized and immediately replaced with a 17beta-estradiol pellet or control pellet. Animals were subject to a forelimb placing test (a test for sensorimotor deficit) and thereafter to middle cerebral artery occlusion (MCAo) by stereotaxic injection of the vasoconstrictive peptide endothelin-1, adjacent to the MCA. One week after stroke, behavioral tests were performed again. Cortical and striatal infarct volume, measured from brain slices, was significantly greater in intact reproductive senescent females as compared to intact mature adults. Furthermore, estrogen treatment to ovariectomized mature adult females significantly reduced the cortical infarct volume. Paradoxically, estrogen treatment to ovariectomized reproductive senescent females significantly increased cortical and striatal infarct volumes as compared to control pellet replaced senescent females. Significant post-stroke behavioral deficit was observed in all groups on the side contralateral to the lesion, while senescent females also exhibited deficits on the ipsilateral side, in the cross-midline forelimb placement test. Using an animal model that approximates the natural ovarian aging process, these findings strongly support the hypothesis that the effectiveness of estrogen therapy in protecting brain health may depend critically on the time of initiation with respect to a female's reproductive status.
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Affiliation(s)
- Amutha Selvamani
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, College Station, TX 77843−1114, United States
| | - Farida Sohrabji
- Department of Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center, College Station, TX 77843−1114, United States
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Abstract
Evidence exists for the potential protective effects of circulating ovarian hormones in stroke, and oestrogen reduces brain damage in animal ischaemia models. However, a recent clinical trial indicated that HRT (hormone-replacement therapy) increased the incidence of stroke in post-menopausal women, and detrimental effects of oestrogen on stroke outcome have been identified in a meta-analysis of HRT trials and in pre-clinical research studies. Therefore oestrogen is not an agent that can be promoted as a potential stroke therapy. Many published reviews have reported the neuroprotective effects of oestrogen in stroke, but have failed to include information on the detrimental effects. This issue is addressed in the present review, along with potential mechanisms of action, and the translational capacity of pre-clinical research.
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Strom JO, Theodorsson A, Theodorsson E. Dose-related neuroprotective versus neurodamaging effects of estrogens in rat cerebral ischemia: a systematic analysis. J Cereb Blood Flow Metab 2009; 29:1359-72. [PMID: 19458604 DOI: 10.1038/jcbfm.2009.66] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Numerous studies of the effects of estrogens for stroke prevention have yielded conflicting results in human and animal studies alike. We present a systematical analysis of study design and methodological differences between 66 studies where estrogens' impact on ischemic brain damage in rat models has been investigated, providing evidence that the differences in results may be explained by high estrogen doses produced by slow-release pellets. These pellets have been used in all studies showing increased neurologic damage because of estrogens. Our data indicate that the increased neurologic damage is related to the pellets' plasma concentration profile with an early, prolonged, supraphysiological peak. Neither the method of inducing the ischemic brain lesions, the choice of variables for measuring outcome, the measured plasma concentrations of estrogens at the time of ischemia nor rat population attributes (sex, strain, age, and diseases) are factors contributing to the discrepancies in results. This suggests that the effects of estrogens for stroke prevention are concentration related with a complex dose-response curve, and underscores the importance of carefully validating the experimental methods used. Future studies of hormone-replacement therapy in women may have to take dosage and administration regimens into account.
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Affiliation(s)
- Jakob O Strom
- Department of Clinical Chemistry, Institution of Clinical and Experimental Medicine, Linköping University Hospital, Linköping, Sweden
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Abstract
Biologic sex and sex steroids are important factors in clinical and experimental stroke and traumatic brain injury (TBI). Laboratory data strongly show that progesterone treatment after TBI reduces edema, improves outcomes, and restores blood-brain barrier function. Clinical studies to date agree with these data, and there are ongoing human trials for progesterone treatment after TBI. Estrogen has accumulated an impressive reputation as a neuroprotectant when evaluated at physiologically relevant doses in laboratory studies of stroke, but translation to patients remains to be shown. The role of androgens in male stroke or TBI is understudied and important to pursue given the epidemiology of stroke and trauma in men. To date, male sex steroids remain largely evaluated at the bench rather than the bedside. This review evaluates key evidence and highlights the importance of the platform on which brain injury occurs (i.e., genetic sex and hormonal modulators).
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Affiliation(s)
- Paco S Herson
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, Oregon, USA
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Noppens RR, Kofler J, Grafe MR, Hurn PD, Traystman RJ. Estradiol after cardiac arrest and cardiopulmonary resuscitation is neuroprotective and mediated through estrogen receptor-beta. J Cereb Blood Flow Metab 2009; 29:277-86. [PMID: 18957991 PMCID: PMC2682442 DOI: 10.1038/jcbfm.2008.116] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We evaluated long-term administration of estrogen after cardiac arrest and cardiopulmonary resuscitation (CA/CPR) on neurohistopathological and behavioral outcome. We also examined the effect of estrogen receptor (ER) stimulation using ER-alpha agonist propyl pyrazole triol (PPT) and ER-beta agonist diarylpropionitrile (DPN) on neuronal survival after CA/CPR to determine whether possible neuroprotective effects of estrogen are ER-mediated. Male C57Bl/6 mice underwent 10 mins of CA/CPR and 3-day survival. In protocol 1, intravenous injection of vehicle (NaCl 0.9%) and 0.5 or 2.5 microg 17beta-estradiol (E2 loading dose) was performed followed by subcutaneous implants containing vehicle (oil) or E2 (12.6 microg), according to a treatment group. In experimental protocol 2, mice were injected (intravenously) with the ER-alpha agonist PPT or ER-beta agonist DPN followed by Alzet pump implants (subcutaneously) containing PPT (200 microg) or DPN (800 microg). Long-term E2 administration reduced neuronal injury in the striatum after administration of either loading dose (41%+/-19%, 35%+/-26% of injured neurons), as compared with vehicle (68%+/-7%, P<0.01), with no effect in the hippocampal CA1 field. In protocol 2, treatment with ER-beta agonist DPN reduced neuronal injury in the striatum (51%+/-13% injured neurons) as compared with ER-alpha agonist PPT (68%+/-10%) and vehicle (69%+/-11%; P<0.01). Estrogen receptor-beta agonist DPN reduced neuronal injury in the hippocampal CA1 field (29%+/-22% injured neurons) as compared with ER-alpha agonist PPT treatment (62%+/-33%; P<0.05). Injury was not different in hippocampal CA1 between vehicle and ER-alpha agonist-treated animals. We conclude that long-term E2 administration after CA/CPR is neuroprotective and that this effect is most likely mediated via ER-beta.
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Affiliation(s)
- Ruediger R Noppens
- Department of Anesthesiology and Peri-Operative Medicine, Oregon Health and Science University, Portland, Oregon, USA
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17
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Abstract
Anesthesiologists are frequently confronted with patients who are at risk for neurological complications due to perioperative stroke or prior traumatic brain injury. In this review, we address the growing and fascinating body of data that suggests gender and sex steroids influence the pathophysiology of injury and outcome for these patients. Cerebral ischemia, traumatic brain injury, and epilepsy are reviewed in the context of potential sex differences in mechanisms and outcomes of brain injury and the role of estrogen, progesterone, and androgens in shaping these processes. Lastly, implications for current and future perioperative and intensive care are identified.
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Affiliation(s)
- Kamila Vagnerova
- Department of Anesthesiology and Peri-Operative Medicine, Oregon Health and Science University, Portland, Oregon 97239, USA
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18
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Farr TD, Carswell HVO, McCann DJ, Sato M, Bryant HU, Dodge JA, Macrae IM. The selective oestrogen receptor modulator, LY362321, is not neuroprotective in a rat model of transient focal ischaemia. J Neuroendocrinol 2008; 20:366-74. [PMID: 18208545 DOI: 10.1111/j.1365-2826.2008.01648.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Selective oestrogen receptor modulators (SERMs) may offer improved alternatives to oestrogen as neuroprotectants in experimental stroke. The present study investigated the role of a novel SERM, LY362321, in a rat model of transient middle cerebral artery occlusion (MCAO). Female Sprague-Dawley rats were ovariectomised and began receiving daily s.c. injections of either 1 mg/kg (n = 13), 10 mg/kg (n = 14) of LY362321, or vehicle (n = 13). The left MCA was temporarily occluded (90 min), with cortical blood flow monitoring, at 12 days post ovariectomy. Sensorimotor function was assessed using a neurological score prior to the MCAO and daily for 3 days following the MCAO. Tissue was processed for infarct volume assessment using 2,3,5-triphenyltetra-zolium chloride staining. The results indicated that there were no significant differences amongst groups in cortical blood flow during the MCAO. Furthermore, there was no significant difference in infarct size amongst vehicle, 1, and 10 mg/kg treated animals: 22.9 +/- 5.0, 16.7 +/- 4.2, and 21.1 +/- 4.1, respectively, one-way anova [F(2,32) = 0.542, P = 0.587]. The MCAO induced a significant decline in neurological score in the vehicle group (from 14 to 7 at 24 h post-MCAO) but this was not significantly affected by LY362321 at either dose. In conclusion, pretreatment with a low or high dose of the novel SERM LY362321 did not significantly influence cerebral blood flow, infarct volume, or sensorimotor function in rats exposed to transient MCAO.
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Affiliation(s)
- T D Farr
- Wellcome Surgical Institute and 7T MRI Facility, Division of Clinical Neuroscience, University of Glasgow, Glasgow, UK.
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19
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McCullough LD, Koerner IP, Hurn PD. Effects of gender and sex steroids on ischemic injury. HANDBOOK OF CLINICAL NEUROLOGY 2008; 92:149-69. [PMID: 18790274 DOI: 10.1016/s0072-9752(08)01908-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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20
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Macrae IM, Carswell HV. Oestrogen and stroke: the potential for harm as well as benefit. Biochem Soc Trans 2007; 34:1362-5. [PMID: 17073819 DOI: 10.1042/bst0341362] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Epidemiological studies point to a beneficial influence of the female reproductive hormones on stroke risk in that women have a lower incidence of stroke prior to the menopause compared with men, but this difference weakens with age and stroke risk in women rises after the menopause. However, recent Women's Health Initiative trials in post-menopausal women report an increased stroke risk on hormone replacement therapy. An influence of gender is also apparent on stroke outcome in animal models: female rats exposed to transient MCA (middle cerebral artery) occlusion sustain less brain damage than age-matched males, with loss of protection following ovariectomy. The major hormone thought to be responsible for beneficial influences on stroke incidence and outcome is oestrogen, and a large preclinical literature now exists where exogenously administered oestrogen has been studied in male and ovariectomized female rats using a range of stroke models and outcome measures. Most of these studies administer oestrogen prior to the stroke, use a model of transient ischaemia followed by reperfusion and report a significant oestrogen-induced neuroprotection. However, in some studies where the MCA is permanently occluded, oestrogen pre-treatment in ovariectomized female rats has been shown to significantly exacerbate ischaemic damage. Therefore preclinical results demonstrate harmful as well as beneficial influences of oestrogen on the ischaemic brain, highlighting the need for further study to elucidate the mechanisms responsible for both detrimental and beneficial influences. Ultimately, this could lead to the development of new classes of oestrogenic compounds with improved risk/benefit profiles, designed to selectively activate pathways inducing only the beneficial effects of oestrogen in vivo.
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Affiliation(s)
- I M Macrae
- Division of Clinical Neuroscience, Wellcome Surgical Institute, University of Glasgow, Garscube Estate, Glasgow G61 1QH, UK.
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21
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Gibson CL, Gray LJ, Murphy SP, Bath PMW. Estrogens and experimental ischemic stroke: a systematic review. J Cereb Blood Flow Metab 2006; 26:1103-13. [PMID: 16437060 DOI: 10.1038/sj.jcbfm.9600270] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Estrogens are believed to provide females with endogenous protection against cerebrovascular events although clinical trials studying long-term hormone replacement have yielded disappointing results. In contrast, estrogens might be neuroprotective after experimental ischemia. We performed a systematic review of controlled experimental studies that administered estrogens before, or after, cerebral ischemia and measured lesion volume. Relevant studies were found from searching PubMed, Embase and Web of Science. From 161 identified publications, 27 studies using 1,304 experimental subjects were analyzed using the Cochrane Review Manager software. Estrogens reduced lesion volume in a dose-dependent manner, after either transient (P<0.001) or permanent (P<0.001) ischemia and whether administered before or up to 4 h after ischemia onset; no studies assessed efficacy for later time periods. The effect size for estrogens decreased with increasing quality scores for studies of transient ischemia. Estrogens reduced lesion volume when administered to ovariectomized females and young adult males, but had no effect in intact females. Limited data were present for aged animals and the full dose-response relationship was not available in all experimental groups. On the basis of these data, estrogens are a candidate treatment for ischemic stroke, although further preclinical studies are also warranted.
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Affiliation(s)
- Claire L Gibson
- Institute of Cell Signalling, Queen's Medical Centre, University of Nottingham, Nottingham, UK.
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22
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Sohrabji F, Bake S. Age-related changes in neuroprotection: is estrogen pro-inflammatory for the reproductive senescent brain? Endocrine 2006; 29:191-7. [PMID: 16785595 DOI: 10.1385/endo:29:2:191] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Revised: 11/30/1999] [Accepted: 10/25/2005] [Indexed: 11/11/2022]
Abstract
Estrogen replacement therapy (ERT) is widely prescribed to postmenopausal women for relief from the adverse vasomotor effects of menopause, to reduce bone loss, to improve cardiovascular health, and to protect against metabolic disorders. However, there is now greater awareness of the increased risk to benefit ratio from the recently concluded Women's Health Initiative Memory Study (WHIMS), which reported that ERT increased the risk of cognitive impairment and dementia in elderly women. Studies from the experimental literature indicate that while estrogen is neuroprotective in many instances, estrogen replacement can be deleterious in some cases. These differences may be partly due to the age and species of the experimental model. The majority of the experimental data comes from studies where the age or endocrine status of the animal model is not comparable to that of menopausal or postmenopausal women, such as those in the WHIMS study. In this review, we will focus on age-related changes in estrogen's neuroprotective effects and evidence that reproductive senescence-related changes in the blood-brain barrier and the immune system may result in deleterious consequences for ERT.
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Affiliation(s)
- Farida Sohrabji
- Neuroscience and Experimental Therapeutics, Department of Human Anatomy & Medical Neurobiology, TAMHSC College of Medicine, College Station, TX 77843-1114, USA.
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23
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Theodorsson A, Theodorsson E. Estradiol increases brain lesions in the cortex and lateral striatum after transient occlusion of the middle cerebral artery in rats: no effect of ischemia on galanin in the stroke area but decreased levels in the hippocampus. Peptides 2005; 26:2257-64. [PMID: 15919133 DOI: 10.1016/j.peptides.2005.04.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Revised: 04/21/2005] [Accepted: 04/22/2005] [Indexed: 10/25/2022]
Abstract
A distinctive feature of galanin expression is that it is extensively increased by neuronal injury, estrogens, Alzheimer's disease and during development. Since stroke is amongst the clinically most important causes of neuronal injury we studied the tissue concentrations of galanin in a rat stroke model and the possibility of modulating this effect with estrogen. Transient focal middle cerebral artery ischemia was induced in rats that 2 weeks earlier underwent ovariectomy and received 1.5mg 17beta-estradiol slow-release or placebo pellets. The concentrations of galanin and neuropeptide Y were measured after observation periods of 3, 7 and 14 days in extracts of punch biopsies from both the lesioned and the contra lateral control hemisphere. The galanin levels were not changed in any of the brain regions studied except in the hippocampus where they were lower in the ischemic hemisphere in both the estrogen- and placebo-treated animals compared to the corresponding contra lateral intact hemisphere (p=0.015). Estrogen treatment up-regulated galanin concentrations in both the ventral and dorsal hippocampus (p=0.003). The effects on the galanin concentrations were similar after all observation periods: 3, 7 and 14 days (p=0.144). No significant changes were observed in the concentration of neuropeptide Y in response to the lesions. The ischemic lesions were markedly larger in the estrogen-treated animals observed after 3 days compared to the corresponding control group. In the estrogen group the lesion was largest at bregma and the slice 2mm anterior to the bregma, 82% and 435% larger than in the control group (p<0.001). A similar, but much less pronounced (not statistically significant) difference was seen in the groups observed after 7 and 14 days. Earlier studies of lesions in the peripheral and central nervous systems have generally shown an up-regulation of galanin markers in response to but at a distance from the injury. Our results indicate that galanin is not involved in the response of the ischemic penumbra itself to stroke, whereas it may participate in the reactions of the neural stem-cell rich hippocampus to stroke.
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Affiliation(s)
- Annette Theodorsson
- Department of Biomedicine and Surgery/Division of Clinical Chemistry, University Hospital, SE-581 85 Linkoping, Sweden
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24
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Abstract
Women are protected from stroke relative to men until the years of menopause. Because stroke is the leading cause of serious, long-term disability in the United States, modeling sex-specific mechanisms and outcomes in animals is vital to research. Important research questions are focused on the effects of hormone replacement therapy, age, reproductive status, and identification of sex-specific risk factors. Available research relevant to stroke in the female has almost exclusively utilized rodent models. Gender-linked stroke outcomes are more detectable in experimental studies than in clinical trials and observational studies. Various estrogens have been extensively studied as neuroprotective agents in women, animals, and a variety of in vitro models of neural injury and degeneration. Most data in animal and cell models are based on 17 beta estradiol and suggest that this steroid is neuroprotective in injury from ischemia/reperfusion. However, current evidence for the clinical benefits of hormone replacement therapy is unclear. Future research in this area will need to expand into stroke models utilizing higher order, gyrencephalic animals such as nonhuman primates if we are to improve extrapolation to the human scenario and to direct and enhance the design of ongoing and future clinical studies and trials.
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Affiliation(s)
- Stephanie J Murphy
- Department of Anesthesiology and Peri-Operative Medicine, Oregon Health and Science University, Portland, OR, USA
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25
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Murphy S, McCullough L, Littleton-Kearney M, Hurn P. Estrogen and selective estrogen receptor modulators: neuroprotection in the Women's Health Initiative era. Endocrine 2003; 21:17-26. [PMID: 12777699 DOI: 10.1385/endo:21:1:17] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2003] [Revised: 02/04/2003] [Accepted: 02/11/2003] [Indexed: 11/11/2022]
Abstract
Estrogen has been comprehensively studied as a neuroprotective agent in women, animals, and a variety of in vitro models of neural injury and degeneration. Most data suggest that estrogen can benefit the ischemic brain and reduce cell death. However, recent data from the Women's Health Initiative have raised concerns about the utility and safety of chronic estrogen use in women. While estrogen is a potent and reproducible neuroprotectant in animals and in vitro, its current administration in women has had unanticipated and paradoxical effects. Nonetheless, estrogen's diverse actions make it an ideal prototype for developing new neuroprotectants such as selective estrogen receptor modulators (SERMs). SERMs represent a class of drugs with mixed estrogen agonistic and antagonistic activity. Experimental and clinical data suggest a neuroprotective role for SERMs in normal and injured brain. The discrepancy among observational studies, preclinical data, and clinical trials emphasizes the need for further study of the mechanisms leading to the increased incidence of stroke observed in postmenopausal women. Research is still needed to optimize combined or estrogen alone hormone replacement therapy options as well as the prevention/management of cerebrovascular/ central nervous system disorders. This review critiques estrogen and SERMs' neuroprotective potential in experimental and clinical studies of stroke and cerebrovascular disease.
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Affiliation(s)
- Stephanie Murphy
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, MD, USA.
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26
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Liu Z, Gastard M, Verina T, Bora S, Mouton PR, Koliatsos VE. Estrogens modulate experimentally induced apoptosis of granule cells in the adult hippocampus. J Comp Neurol 2001; 441:1-8. [PMID: 11745631 DOI: 10.1002/cne.1393] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Estrogens are known to have broad effects on neuronal plasticity, but their specific role in neuronal cell death has not been determined. In the present study, we investigated the effects of beta-estradiol on an experimental model of apoptosis of granule cells of the dentate gyrus, i.e., apoptosis induced by intraventricular injection of the microtubule polymerization inhibitor colchicine. Cell death was characterized with multiple methods, including TUNEL and DNA electrophoresis. Nonrandom digestion of DNA was observed within 8-10 hours after colchicine injection, followed by condensation and fragmentation of granule cell nuclei and extensive anterograde degeneration of mossy fibers/terminals in 2 days. We compared the outcomes of the above-described manipulation in ovariectomized or sham-operated rats and animals treated daily with beta-estradiol or vehicle. Animals were lesioned with colchicine or vehicle 2 weeks after ovariectomy or sham operation. Beta-estradiol or vehicle was administered for 1 week prior to lesion and was continued for a further 2 weeks. Total numbers and densities of granule cells in different animal groups were counted by stereology in various anteroposterior levels of the hippocampus. Our results show that ovariectomy intensifies colchicine-induced granule cell apoptosis, which is ameliorated by exogenous beta-estradiol. In doses that ameliorate the adverse effect of ovariectomy, exogenous beta-estradiol appears to have no effect of preventing granule cell death in animals with intact ovaries; i.e., an estrogen excess is not more neuroprotective than physiological levels of these hormones. Taken together, our results indicate that estrogen deprivation increases the vulnerability of hippocampal neurons to injury and may predispose to neurological diseases occurring after menopause.
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Affiliation(s)
- Z Liu
- Department of Pathology (Division of Neuropathology), The Johns Hopkins Medical Institutions, 720 Rutland Avenue, Baltimore, MD 21205, USA
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