Estrogen attenuates the MPTP-induced loss of dopamine neurons from the mouse SNc despite a lack of estrogen receptors (ERalpha and ERbeta).
ABSTRACT Estrogen attenuates the loss of dopamine from striatum and dopamine neurons from the substantia nigra (SNc) in animal models of Parkinson's disease. Interestingly, estrogen receptors (ERalpha and ERbeta) are thought to be sparse or absent in mouse striatum and SNc. Since ERalpha is markedly induced in rodent cortex after ischemic injury, the present studies evaluated changes in ERs after acute treatment with the dopamine neurotoxin MPTP. Mice were injected daily with estradiol, injected with MPTP on day 6, and brains collected on day 9 or 13. Immunocytochemistry was then used to assess tyrosine hydroxylase (TH) in striatum and investigate the localization of ERalpha and ERbeta in the striatum and SNc. In addition, cryostat sections were hybridized with a riboprobe complementary to ERalpha or ERbeta mRNA. Evaluation of TH immunoreactivity revealed a dense network of fibers in the striatum of vehicle-treated animals, while a near complete loss of terminals was seen after MPTP treatment. When, however, mice were pretreated with estradiol, the MPTP-induced loss of TH was attenuated. Evaluation of ERalpha and ERbeta in the SNc and striatum demonstrated a sparse localization of both ERs in vehicle-treated mice, a pattern that did not change in animals treated with vehicle/MPTP or estradiol/MPTP. These data demonstrate that ERs are sparse in the mouse striatum and SNc and show that this pattern does not change after MPTP intoxication. This observation and the finding that estrogen affords some protection against MPTP suggest that estrogen may act via nuclear receptor independent mechanisms to protect dopamine neurons from toxins such as MPTP.
SourceAvailable from: Glenda E Gillies[Show abstract] [Hide abstract]
ABSTRACT: Parkinson’s disease (PD) displays a greater prevalence and earlier age at onset in men. This review addresses the concept that sex differences in PD are determined, largely, by biological sex differences in the NSDA system which, in turn, arise from hormonal, genetic and environmental influences. Current therapies for PD rely on dopamine replacement strategies to treat symptoms, and there is an urgent, unmet need for disease modifying agents. As a significant degree of neuroprotection against the early stages of clinical or experimental PD is seen, respectively, in human and rodent females compared with males, a better understanding of brain sex dimorphisms in the intact and injured NSDA system will shed light on mechanisms which have the potential to delay, or even halt, the progression of PD. Available evidence suggests that sex-specific, hormone-based therapeutic agents hold particular promise for developing treatments with optimal efficacy in men and women.Frontiers in Neuroendocrinology 08/2014; DOI:10.1016/j.yfrne.2014.02.002 · 7.58 Impact Factor
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ABSTRACT: Estetrol (E4) is a recently described natural estrogen with four hydroxyl-groups that is synthesized exclusively during pregnancy by the human fetal liver. It has important antioxidative activity. The aim of the present study was to define the importance of E4 in the attenuation of neonatal hypoxic-ischemic encephalopathy. Antioxidative effect of 650 μM, 3.25 mM and 6.5 mM E4 on primary hippocampal cell cultures was studied before/after H202-induced oxidative stress. To examine the oxidative stress and the cell viability, lactate dehydrogenase activity and cell proliferation colorimetric assays were performed. To study the neuroprotective and therapeutic effects of E4 in vivo neonatal hypoxic-ischemic encephalopathy model of 7-day-old newborn rat pups was used. The neuroprotective and therapeutic effectst of estetrol before/after hypoxic-ischemic insult was studied in 1 mg/kg//day, 5 mg/kg/day, 10 mg/kg/day, 50 mg/kg/day E4 pretreated/treated groups and compared with the sham and the vehicle treated groups. The body temperature of the rat pups was examined along with their body and brain weights. Brains were studied at the level of the hippocampus and cortex. Intact cell counting and expressions of microtubule-associated protein-2, doublecortin and vascular-endothelial growth factor were evaluated by histo- and immunohistochemistry. ELISAs were performed on blood samples to detect concentrations of S100B and glial fibrillary acidic protein as brain damage markers. This work reveals for the first time that E4 significantly decreases LDH activity and enhances cell proliferation in primary hippocampal neuronal cell cultures in vitro, and decreases the early gray matter loss and promotes neuro- and angiogenesis in vivo.Experimental Neurology 11/2014; 261. DOI:10.1016/j.expneurol.2014.07.015 · 4.62 Impact Factor
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ABSTRACT: Movement disorders including Parkinson's disease (PD), Huntington's disease (HD), chorea, tics, and Tourette's syndrome (TS) display sex differences in disease susceptibility, disease pathogenesis, and clinical presentation. PD is more common in males than in females. Epidemiologic studies suggest that exposure to endogenous and exogenous estrogen contributes to these sex differences. There is extensive evidence that estrogen prevents dopaminergic neuron depletion induced by neurotoxins in PD animal models and therefore is neuroprotective. Estrogen may also decrease the efficacy of other neuroprotective substances such as caffeine in females but not males. Sex chromosomes can exert effects independent of sex steroid hormones on the development and maintenance of the dopamine system. As a result of hormone, chromosome and other unknown effects, there are sexual dimorphisms in the basal ganglia, and at the molecular levels in dopaminergic neurons that may lead to distinct mechanisms of pathogenesis in males and females. In this review, we summarize the evidence that estrogen and selective estrogen receptor modulators are neuroprotective in PD and discuss potential mechanisms of action. We also briefly review how sex differences in basal ganglia function and dopaminergic pathways may impact HD, chorea, and tics/Tourette's syndrome. Further understanding of these sex differences may lead to novel therapeutic strategies for prevention and treatment of these diseases.Experimental Neurology 03/2014; DOI:10.1016/j.expneurol.2014.03.010 · 4.62 Impact Factor