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Is Hormone Replacement Therapy a Risk Factor or a Therapeutic Option for Alzheimer's Disease? Int J Mol Sci 2023; 24:ijms24043205. [PMID: 36834617 PMCID: PMC9964432 DOI: 10.3390/ijms24043205] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/21/2023] [Accepted: 01/23/2023] [Indexed: 02/07/2023] Open
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that accounts for more than half of all dementia cases in the elderly. Interestingly, the clinical manifestations of AD disproportionately affect women, comprising two thirds of all AD cases. Although the underlying mechanisms for these sex differences are not fully elucidated, evidence suggests a link between menopause and a higher risk of developing AD, highlighting the critical role of decreased estrogen levels in AD pathogenesis. The focus of this review is to evaluate clinical and observational studies in women, which have investigated the impact of estrogens on cognition or attempted to answer the prevailing question regarding the use of hormone replacement therapy (HRT) as a preventive or therapeutic option for AD. The articles were retrieved through a systematic review of the databases: OVID, SCOPUS, and PubMed (keywords "memory", "dementia," "cognition," "Alzheimer's disease", "estrogen", "estradiol", "hormone therapy" and "hormone replacement therapy" and by searching reference sections from identified studies and review articles). This review presents the relevant literature available on the topic and discusses the mechanisms, effects, and hypotheses that contribute to the conflicting findings of HRT in the prevention and treatment of age-related cognitive deficits and AD. The literature suggests that estrogens have a clear role in modulating dementia risk, with reliable evidence showing that HRT can have both a beneficial and a deleterious effect. Importantly, recommendation for the use of HRT should consider the age of initiation and baseline characteristics, such as genotype and cardiovascular health, as well as the dosage, formulation, and duration of treatment until the risk factors that modulate the effects of HRT can be more thoroughly investigated or progress in the development of alternative treatments can be made.
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Koszegi Z, Cheong RY. Targeting the non-classical estrogen pathway in neurodegenerative diseases and brain injury disorders. Front Endocrinol (Lausanne) 2022; 13:999236. [PMID: 36187099 PMCID: PMC9521328 DOI: 10.3389/fendo.2022.999236] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 08/15/2022] [Indexed: 11/13/2022] Open
Abstract
Estrogens can alter the biology of various tissues and organs, including the brain, and thus play an essential role in modulating homeostasis. Despite its traditional role in reproduction, it is now accepted that estrogen and its analogues can exert neuroprotective effects. Several studies have shown the beneficial effects of estrogen in ameliorating and delaying the progression of neurodegenerative diseases, including Alzheimer's and Parkinson's disease and various forms of brain injury disorders. While the classical effects of estrogen through intracellular receptors are more established, the impact of the non-classical pathway through receptors located at the plasma membrane as well as the rapid stimulation of intracellular signaling cascades are still under active research. Moreover, it has been suggested that the non-classical estrogen pathway plays a crucial role in neuroprotection in various brain areas. In this mini-review, we will discuss the use of compounds targeting the non-classical estrogen pathway in their potential use as treatment in neurodegenerative diseases and brain injury disorders.
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Affiliation(s)
- Zsombor Koszegi
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom
| | - Rachel Y. Cheong
- Timeline Bioresearch AB, Medicon Village, Lund, Sweden
- *Correspondence: Rachel Y. Cheong,
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Partridge L, Fuentealba M, Kennedy BK. The quest to slow ageing through drug discovery. Nat Rev Drug Discov 2020; 19:513-532. [DOI: 10.1038/s41573-020-0067-7] [Citation(s) in RCA: 142] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2020] [Indexed: 02/07/2023]
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Kwakowsky A, Milne MR, Waldvogel HJ, Faull RL. Effect of Estradiol on Neurotrophin Receptors in Basal Forebrain Cholinergic Neurons: Relevance for Alzheimer's Disease. Int J Mol Sci 2016; 17:E2122. [PMID: 27999310 PMCID: PMC5187922 DOI: 10.3390/ijms17122122] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 12/05/2016] [Accepted: 12/12/2016] [Indexed: 02/06/2023] Open
Abstract
The basal forebrain is home to the largest population of cholinergic neurons in the brain. These neurons are involved in a number of cognitive functions including attention, learning and memory. Basal forebrain cholinergic neurons (BFCNs) are particularly vulnerable in a number of neurological diseases with the most notable being Alzheimer's disease, with evidence for a link between decreasing cholinergic markers and the degree of cognitive impairment. The neurotrophin growth factor system is present on these BFCNs and has been shown to promote survival and differentiation on these neurons. Clinical and animal model studies have demonstrated the neuroprotective effects of 17β-estradiol (E2) on neurodegeneration in BFCNs. It is believed that E2 interacts with neurotrophin signaling on cholinergic neurons to mediate these beneficial effects. Evidence presented in our recent study confirms that altering the levels of circulating E2 levels via ovariectomy and E2 replacement significantly affects the expression of the neurotrophin receptors on BFCN. However, we also showed that E2 differentially regulates neurotrophin receptor expression on BFCNs with effects depending on neurotrophin receptor type and neuroanatomical location. In this review, we aim to survey the current literature to understand the influence of E2 on the neurotrophin system, and the receptors and signaling pathways it mediates on BFCN. In addition, we summarize the physiological and pathophysiological significance of E2 actions on the neurotrophin system in BFCN, especially focusing on changes related to Alzheimer's disease.
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Affiliation(s)
- Andrea Kwakowsky
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
| | - Michael R Milne
- School of Biomedical Sciences, Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane 4072, QLD, Australia.
| | - Henry J Waldvogel
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
| | - Richard L Faull
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
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Kwakowsky A, Potapov K, Kim S, Peppercorn K, Tate WP, Ábrahám IM. Treatment of beta amyloid 1-42 (Aβ(1-42))-induced basal forebrain cholinergic damage by a non-classical estrogen signaling activator in vivo. Sci Rep 2016; 6:21101. [PMID: 26879842 PMCID: PMC4754683 DOI: 10.1038/srep21101] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 01/18/2016] [Indexed: 11/09/2022] Open
Abstract
In Alzheimer's disease (AD), there is a loss in cholinergic innervation targets of basal forebrain which has been implicated in substantial cognitive decline. Amyloid beta peptide (Aβ(1-42)) accumulates in AD that is highly toxic for basal forebrain cholinergic (BFC) neurons. Although the gonadal steroid estradiol is neuroprotective, the administration is associated with risk of off-target effects. Previous findings suggested that non-classical estradiol action on intracellular signaling pathways has ameliorative potential without estrogenic side effects. After Aβ(1-42) injection into mouse basal forebrain, a single dose of 4-estren-3α, 17β-diol (estren), the non-classical estradiol pathway activator, restored loss of cholinergic cortical projections and also attenuated the Aβ(1-42)-induced learning deficits. Estren rapidly and directly phosphorylates c-AMP-response-element-binding-protein and extracellular-signal-regulated-kinase-1/2 in BFC neurons and restores the cholinergic fibers via estrogen receptor-α. These findings indicated that selective activation of non-classical intracellular estrogen signaling has a potential to treat the damage of cholinergic neurons in AD.
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Affiliation(s)
- Andrea Kwakowsky
- Centre for Neuroendocrinology and Department of Physiology, Otago Medical School, University of Otago, Dunedin, New Zealand
- Centre for Brain Research and Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Kyoko Potapov
- Centre for Neuroendocrinology and Department of Physiology, Otago Medical School, University of Otago, Dunedin, New Zealand
| | - SooHyun Kim
- Centre for Neuroendocrinology and Department of Physiology, Otago Medical School, University of Otago, Dunedin, New Zealand
| | - Katie Peppercorn
- Department of Biochemistry, Otago Medical School, University of Otago, Dunedin, New Zealand
| | - Warren P. Tate
- Department of Biochemistry, Otago Medical School, University of Otago, Dunedin, New Zealand
| | - István M. Ábrahám
- Centre for Neuroendocrinology and Department of Physiology, Otago Medical School, University of Otago, Dunedin, New Zealand
- MTA-NAP-B-Molecular Neuroendocrinology Research Group, Centre for Neuroscience, Szentágothai Research Centre, Institute of Physiology, Medical School, University of Pécs, Pécs, Hungary
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Abstract
Neurosteroids, like allopregnanolone and pregnanolone, are endogenous regulators of neuronal excitability. Inside the brain, they are highly selective and potent modulators of GABAA receptor activity. Their anticonvulsant, anesthetics and anxiolytic properties are useful for the treatments of several neurological and psychiatric disorders via reducing the risks of side effects obtained with the commercial drugs. The principal disadvantages of endogenous neurosteroids administration are their rapid metabolism and their low oral bioavailability. Synthetic steroids analogues with major stability or endogenous neurosteroids stimulation synthesis might constitute promising novel strategies for the treatment of several disorders. Numerous studies indicate that the 3α-hydroxyl configuration is the key for binding and activity, but modifications in the steroid nucleus may emphasize different pharmacophores. So far, several synthetic steroids have been developed with successful neurosteroid-like effects. In this work, we summarize the properties of various synthetic steroids probed in trials throughout the analysis of several neurosteroids-like actions.
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Affiliation(s)
- Mariana Rey
- Laboratorio de Neurobiología, Instituto de Biología y Medicina Experimental (IBYME-CONICET), Vuelta de Obligado 2490, (C1428ADN) Ciudad Autónoma de Buenos Aires, Argentina
| | - Héctor Coirini
- Laboratorio de Neurobiología, Instituto de Biología y Medicina Experimental (IBYME-CONICET), Vuelta de Obligado 2490, (C1428ADN) Ciudad Autónoma de Buenos Aires, Argentina ; Departamento de Bioquímica Humana, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, Ciudad Autónoma de Buenos Aires, Argentina
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Liao W, Jin G, Zhao M, Yang H. The effect of genistein on the content and activity of α- and β-secretase and protein kinase C in Aβ-injured hippocampal neurons. Basic Clin Pharmacol Toxicol 2012; 112:182-5. [PMID: 22994425 DOI: 10.1111/bcpt.12009] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 09/10/2012] [Indexed: 11/29/2022]
Abstract
Genistein (Gen), a derivative of soy isoflavone aglycone, has been shown to exert significant protective effect on Aβ-induced neurotoxicity and neuroinjury. However, its underlying mechanism remains elusive. The objective was to investigate the inhibitory effect of Gen on Aβ-induced neurotoxicity and to elucidate the underlying mechanism. Primary rat hippocampal neurons were pre-treated with Gen for 2 hr followed by incubation with Aβ 25-35 for an additional 24 hr. The cell viability was assessed by MTT assay. The content and activity of α-, β-secretase and protein kinase C (PKC) were measured, and the antagonistic effect of PKC inhibitor Myr was also analysed to clarify the molecular mechanism of Gen inhibition of Aβ-induced toxicity to hippocampal neurons. The results showed that pre-treatment with Gen significantly increased the cell viability and presented the best effect at the final concentration of 0.375 µg/mL. Gen increases the activity of α-secretase but down-regulates the β-secretase activity. It also enhances the expression and activity of PKC. Myr, a PKC inhibitor, partially blocks the activation effect of Gen. Gen exerts protective effect on Aβ-induced neurotoxicity via activating the PKC signalling pathway, which further regulates the activities of α- and β-secretase and thereby inhibits the formation and toxicity of Aβ.
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Affiliation(s)
- Weiliang Liao
- Guangdong Pharmaceutical University, Guangzhou, China
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Koszegi Z, Szego ÉM, Cheong RY, Tolod-Kemp E, Ábrahám IM. Postlesion estradiol treatment increases cortical cholinergic innervations via estrogen receptor-α dependent nonclassical estrogen signaling in vivo. Endocrinology 2011; 152:3471-82. [PMID: 21791565 DOI: 10.1210/en.2011-1017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
17β-Estradiol (E2) treatment exerts rapid, nonclassical actions via intracellular signal transduction system in basal forebrain cholinergic (BFC) neurons in vivo. Here we examined the effect of E2 treatment on lesioned BFC neurons in ovariectomized mice and the role of E2-induced nonclassical action in this treatment. Mice given an N-methyl-d-aspartic acid (NMDA) injection into the substantia innominata-nucleus basalis magnocellularis complex (SI-NBM) exhibited cholinergic cell loss in the SI-NBM and ipsilateral cholinergic fiber loss in the cortex. A single injection of E2 after NMDA lesion did not have an effect on cholinergic cell loss in the SI-NBM, but it restored the ipsilateral cholinergic fiber density in the cortex in a time- and dose-dependent manner. The most effective cholinergic fiber restoration was observed with 33 ng/g E2 treatment at 1 h after NMDA lesion. The E2-induced cholinergic fiber restoration was absent in neuron-specific estrogen receptor-α knockout mice in vivo. Selective activation of nonclassical estrogen signaling in vivo by estren induced E2-like restorative actions. Selective blockade of the MAPK or protein kinase A pathway in vivo prevented E2's ability to restore cholinergic fiber loss. Finally, studies in intact female mice revealed an E2-induced restorative effect that was similar to that of E2-treated ovariectomized mice. These observations demonstrate that a single E2 treatment restores the BFC fiber loss in the cortex, regardless of endogenous E2 levels. They also reveal the critical role of nonclassical estrogen signaling via estrogen receptor-α and protein kinase A-MAPK pathways in E2-induced restorative action in the cholinergic system in vivo.
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Affiliation(s)
- Zsombor Koszegi
- Centre for Neuroendocrinology and Department of Physiology, Otago School of Medical Sciences, University of Otago, 9054 Dunedin, New Zealand
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Action of estrogen on survival of basal forebrain cholinergic neurons: promoting amelioration. Psychoneuroendocrinology 2009; 34 Suppl 1:S104-12. [PMID: 19560872 DOI: 10.1016/j.psyneuen.2009.05.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 05/30/2009] [Accepted: 05/30/2009] [Indexed: 11/23/2022]
Abstract
Extensive studies during the past two decades provide compelling evidence that the gonadal steroid, estrogen, has the potential to affect the viability of basal forebrain cholinergic neurons. These observations reflect a unique ameliorative feature of estrogen as it restores and protects the cholinergic neurons against noxious stimuli or neurodegenerative processes. Hence, we first address the ameliorative function of estrogen on basal forebrain cholinergic neurons such as the actions of estrogen on neuronal plasticity of cholinergic neurons, estrogen-induced memory enhancement and the ameliorative role of estrogen on cholinergic neuron related neurodegenerative processes such as Alzheimer's disease. Second, we survey recent data as to possible mechanisms underlying the ameliorative actions of estrogen; influencing the amyloid precursor protein processing, enhancement in neurotrophin receptor signaling and estrogen-induced non-classical actions on second messenger systems. In addition, clinical relevance, pitfalls and future aspects of estrogen therapy on basal forebrain cholinergic neurons will be discussed.
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Moos WH, Dykens JA, Nohynek D, Rubinchik E, Howell N. Review of the effects of 17α-estradiol in humans: a less feminizing estrogen with neuroprotective potential. Drug Dev Res 2009. [DOI: 10.1002/ddr.20284] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Wang Z, Zhang X, Wang H, Qi L, Lou Y. Neuroprotective effects of icaritin against beta amyloid-induced neurotoxicity in primary cultured rat neuronal cells via estrogen-dependent pathway. Neuroscience 2007; 145:911-22. [PMID: 17321691 DOI: 10.1016/j.neuroscience.2006.12.059] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2006] [Revised: 12/13/2006] [Accepted: 12/27/2006] [Indexed: 10/23/2022]
Abstract
Beta-amyloid protein (Abeta) is the hallmark of pathogenic neurotoxins which contribute greatly to Alzheimer's disease (AD)-associated cascade including severe neuronal loss. In present study, icaritin, an active natural ingredient from a Chinese plant, Epimedium sagittatum maxim, was investigated to assess its neuroprotective effect against the toxicity induced with Abeta(25-35) in primary cultured rat cortical neuronal cells as well as the underlying mechanisms. Abeta(25-35) induced neuronal toxicity, characterized by decreased cell viability, lactate dehydrogenase (LDH) release, and neuronal DNA condensation, which is associated with both the loss of membrane potential and the alteration of the expression of Bcl-2 family proteins. The phenotype alternation induced by Abeta(25-35) could be reversed by icaritin. Furthermore, the neuroprotective effects of icaritin mentioned above were estrogen receptor dependent due to the blocking action induced by estrogen receptor antagonist ICI 182,780 and well matched binding affinity with estrogen receptor by a receptor-ligand docking experiment. mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor PD98059 weakened the protective effects, which implied mitogen-activated protein kinase/extracellular signal-regulated kinase pathway may also be involved in and partly contributed to the neuroprotective effects of icaritin.
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Affiliation(s)
- Z Wang
- Institute of Pharmacology & Toxicology and Biochemical Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Yu-hang-tang Road 388, Hangzhou 310058, China
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Chakraborti A, Gulati K, Ray A. Estrogen Actions on Brain and Behavior: Recent Insights and Future Challenges. Rev Neurosci 2007; 18:395-416. [DOI: 10.1515/revneuro.2007.18.5.395] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Howell N, Dykens J, Moos WH. Alzheimer's disease, estrogens, and clinical trials: a case study in drug development for complex disorders. Drug Dev Res 2006. [DOI: 10.1002/ddr.20046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Cordey M, Pike CJ. Conventional protein kinase C isoforms mediate neuroprotection induced by phorbol ester and estrogen. J Neurochem 2005; 96:204-17. [PMID: 16336227 DOI: 10.1111/j.1471-4159.2005.03545.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Rapid signal transduction pathways play a prominent role in mediating neuroprotective actions of estrogen in the CNS. We have previously shown that estrogen-induced neuroprotection of primary cerebrocortical neurons from beta-amyloid peptide (Abeta) toxicity depends on activation of protein kinase C (PKC). PKC activation with phorbol-12-myristate-13-acetate (PMA) also provides neuroprotection in this paradigm. Because the PKC family includes several isoforms that have opposing roles in regulating cell survival, we sought to identify which PKC isoforms contribute to neuroprotection induced by PMA and estrogen. We detected protein expression of multiple PKC isoforms in primary neuron cultures, including conventional (alpha, betaI, betaII), novel (delta, epsilon, theta) and atypical (zeta, iota/lambda) PKC. Using a panel of isoform-specific peptide inhibitors and activators, we find that novel and atypical PKC isoforms do not participate in the mechanism of either PMA or estrogen neuroprotection. In contrast, a selective peptide activator of conventional PKC isoforms provides dose-dependent neuroprotection against Abeta toxicity. In addition, peptide inhibitors of conventional, betaI, or betaII PKC isoforms significantly reduce protection afforded by PMA or 17beta-estradiol. Taken together, these data provide evidence that conventional PKC isoforms mediate phorbol ester and estrogen neuroprotection of cultured neurons challenged by Abeta toxicity.
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Affiliation(s)
- Myriam Cordey
- Neuroscience Graduate Program and Andrus Gerontology Center, University of Southern California, Los Angeles, California 90089-0191, USA
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Cordey M, Pike CJ. Neuroprotective properties of selective estrogen receptor agonists in cultured neurons. Brain Res 2005; 1045:217-23. [PMID: 15910780 DOI: 10.1016/j.brainres.2005.03.032] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Revised: 03/12/2005] [Accepted: 03/15/2005] [Indexed: 11/21/2022]
Abstract
To investigate the role of the estrogen receptor (ER) in mediating neuroprotection, the neuroprotective profiles of selective ER agonists for ERalpha and ERbeta, propylpyrazole triol (PPT) and 2,3-bis(4-hydroxyphenyl) proprionitrile (DPN), respectively, were compared to that of 17beta-estradiol and 17alpha-estradiol in primary neuron cultures challenged by beta-amyloid toxicity. All compounds were found to be neuroprotective in an ER-dependent manner. However, protein kinase C (PKC) inhibition completely blocked the protective effects of 17beta-estradiol and 17alpha-estradiol and significantly attenuated PPT but not DPN neuroprotection. These data indicate that estrogen-mediated neuroprotection likely involves a variety of mechanisms and that protection due to PKC activation is more likely due to ERalpha compared to ERbeta.
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Affiliation(s)
- Myriam Cordey
- Neuroscience Graduate Program and Andrus Gerontology Center, University of Southern California, 3715 McClintock Avenue, Los Angeles, CA 90089-0191, USA
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