Estrogen hormones reduce lipid peroxidation in cells and tissues of the central nervous system

Estrogen and psychosis - a review and future directions

The link between sex hormones and schizophrenia has been suspected for over a century; however, scientific evidence supporting the pharmacotherapeutic effects of exogenous estrogen has only started to emerge during the past three decades. Accumulating evidence from epidemiological and basic research suggests that estrogen has a protective effect in women vulnerable to schizophrenia. Such evidence has led multiple researchers to investigate the role of estrogen in schizophrenia and its use in treatment. This narrative review provides an overview of the effects of estrogen as well as summarizes the recent work regarding estrogen as a treatment for schizophrenia, particularly the use of new-generation selective estrogen receptor modulators.

Sex and Sleep Disruption as Contributing Factors in Alzheimer's Disease

Alzheimer's disease (AD) affects more women than men, with women throughout the menopausal transition potentially being the most under researched and at-risk group. Sleep disruptions, which are an established risk factor for AD, increase in prevalence with normal aging and are exacerbated in women during menopause. Sex differences showing more disrupted sleep patterns and increased AD pathology in women and female animal models have been established in literature, with much emphasis placed on loss of circulating gonadal hormones with age. Interestingly, increases in gonadotropins such as follicle stimulating hormone are emerging to be a major contributor to AD pathogenesis and may also play a role in sleep disruption, perhaps in combination with other lesser studied hormones. Several sleep influencing regions of the brain appear to be affected early in AD progression and some may exhibit sexual dimorphisms that may contribute to increased sleep disruptions in women with age. Additionally, some of the most common sleep disorders, as well as multiple health conditions that impair sleep quality, are more prevalent and more severe in women. These conditions are often comorbid with AD and have bi-directional relationships that contribute synergistically to cognitive decline and neuropathology. The association during aging of increased sleep disruption and sleep disorders, dramatic hormonal changes during and after menopause, and increased AD pathology may be interacting and contributing factors that lead to the increased number of women living with AD.

Interplay of Metallome and Metabolome in Amyotrophic Lateral Sclerosis: A Study on Cerebrospinal Fluid of Patients Carrying Disease-Related Gene Mutations

Amyotrophic lateral sclerosis (ALS) is a lethal progressive neurodegenerative disease, characterized by a loss of function of upper and lower motor neurons. This study aimed to explore probable pathological alterations occurring in individuals with ALS compared to neurologically healthy controls through the analysis of cerebrospinal fluid (CSF), a medium, which directly interacts with brain parenchyma. A total of 7 ALS patients with disease-associated mutations (ATXN2, C9ORF72, FUS, SOD1, and TARDBP) and 13 controls were included in the study. Multiple analytical approaches were employed, including metabolomic and metallomics profiling, as well as genetic screening, using CSF samples obtained from the brain compartment. Data analysis involved the application of multivariate statistical methods. Advanced hyphenated selenium and redox metal (iron, copper, and manganese) speciation techniques and nontargeted Fourier transform ion cyclotron resonance mass spectrometry-based metabolomics were used for data acquisition. Nontargeted metabolomics showed reduced steroids, including sex hormones; additionally, copper and manganese species were found to be the most relevant features for ALS patients. This indicates a potential alteration of sex hormone pathways in the ALS-affected brain, as reflected in the CSF.

Coenzyme Q10 and Silymarin Reduce CCl4-Induced Oxidative Stress and Liver and Kidney Injury in Ovariectomized Rats—Implications for Protective Therapy in Chronic Liver and Kidney Diseases

Oxidative stress is one of the key factors in the pathophysiology of liver disease. The present study aimed to evaluate the potential impact of two antioxidants, namely coenzyme Q10 (CoQ10) and silymarin, on carbon tetrachloride (CCl₄)-induced oxidative stress and hepatic damage in ovariectomized rats. Female Long Evans rats were divided into six groups (n = 6): control, CCl₄, CCl₄ + CoQ10 (200 mg/kg), CCl₄ + silymarin (140 mg/kg), Control + CoQ10, and Control + silymarin. Plasma and tissues from liver and kidney were analyzed for oxidative stress parameters and antioxidant enzyme activities using biochemical assays. Infiltration of inflammatory cells and fibrosis were assessed by histological staining of tissue sections. Both CoQ10 and silymarin significantly lowered serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) levels that were detected to be higher in CCl₄ rats compared to controls. Significant reduction in CCl₄-induced elevated levels of oxidative stress markers malondialdehyde (MDA), nitric oxide (NO), and advanced protein oxidation product (APOP) was observed with both antioxidants. However, in control rats, CoQ10 and silymarin did not produce a significant effect. Histological analysis revealed that CCl₄ markedly increased the level of inflammatory cells infiltration and fibrosis in liver and kidney tissues, but this was significantly reduced in CCl₄ + CoQ10 and CCl₄ + silymarin groups. Taken together, our results suggest that CoQ10 and silymarin can protect the liver against oxidative damage through improved antioxidant enzyme activities and reduced lipid peroxidation. Thus, supplementation of the aforementioned antioxidants may be useful as a therapeutic intervention to protect liver health in chronic liver diseases.

Taurine prevents high-fat diet-induced-hepatic steatosis in rats by direct inhibition of hepatic sterol regulatory element-binding proteins and activation of AMPK

This study investigated if the protective effect of taurine against high fat diet-induced hepatic steatosis involves modulating the hepatic activity of 5' AMP-activated protein kinase (AMPK) and levels/activity of the sterol regulatory element-binding proteins-1/2 (SREBP1/2). Rats were divided into four groups (n = 12/group) as (a) STD, fed standard diet (3.85 kcal/g); (b) STD + taurine (500 mg/kg); (c) HFD, fed HFD (4.73 kcal/g); and (d) HFD + taurine. All treatments were conducted for 12 weeks. Independent of food intake or modulating glucose or insulin levels, taurine administration to STD and HFD-fed rats significantly lowered weekly weight gain and the accumulation of the retroperitoneal, visceral and subcutaneous fats. In both groups, taurine also reduced serum and hepatic levels of triglycerides and cholesterol and reduced hepatic mRNA and protein levels of fatty acid synthase (FAS), acetyl CoA carboxylase-1 (ACC-1), HMG-CoA-reductase and HMG-CoA synthetase. In control rats only, taurine reduced hepatic levels of mature forms of sterol regulatory element-binding proteins (SREBP)-1/2. In HFD-fed rats, taurine reduced SREBP-1/2 precursor and mature forms in the livers of HFD-fed rats. Besides, taurine significantly increased levels of glutathione (GSH), the activity of superoxide dismutase (SOD), and the activity of AMPK and its downstream β-oxidation genes including peroxisome proliferator-activated receptor-α (PPAR-α) and carnitine palmitoyltransferase (CPT-1) in the livers of both the control and HFD-fed rats. In conclusion, taurine protects against HFD-induced hepatic steatosis stimulating antioxidant levels, and concomitant stimulating hepatic β-oxidation and suppressing lipid synthesis, mediated by activation of AMPK and suppression of SREBP-1.

Fenton Reaction-Induced Oxidative Damage to Membrane Lipids and Protective Effects of 17β-Estradiol in Porcine Ovary and Thyroid Homogenates

The Fenton reaction (Fe²⁺+H₂O₂→Fe³⁺+^•OH+OH^-) results in strong oxidative damage to macromolecules when iron (Fe) or hydrogen peroxide (H₂O₂) are in excess. This study aims at comparing Fe²⁺+H₂O₂-induced oxidative damage to membrane lipids (lipid peroxidation, LPO) and protective effects of 17β-estradiol (a potential antioxidant) in porcine ovary and thyroid homogenates. Iron, as one of the Fenton reaction substrates, was used in the highest achievable concentrations. Thyroid or ovary homogenates were incubated in the presence of: (1st) FeSO₄+H₂O₂ with/without 17β-estradiol (1 mM; 100, 10.0, 1.0 µM; 100, 10.0, 1.0 nM; 100, 10.0, 1.0 pM); five experiments were performed with different FeSO₄ concentrations (2400, 1200, 600, 300, 150 µM); (2nd) FeSO₄ (2400, 1200, 600, 300, 150 µM)+H₂O₂ with/without 17β-estradiol; three experiments were performed with three highest 17β-estradiol concentrations; (3rd) FeSO₄ (2400, 1200, 1100, 1000, 900, 800, 700, 600, 300, 150, 75 µM)+H₂O₂ (5 mM). LPO level [MDA+4-HDA/mg protein] was measured spectrophotometrically. The basal LPO level is lower in ovary than in thyroid homogenates. However, experimentally-induced LPO was higher in the former tissue, which was confirmed for the three highest Fe²⁺ concentrations (2400, 1200, 1100 µM). Exogenous 17β-estradiol (1 mM, 100, and 10 µM) reduced experimentally-induced LPO independently of iron concentration and that protective effect did not differ between tissues. The ovary, compared to the thyroid, reveals higher sensitivity to prooxidative effects of iron, however, it showed similar responsivity to protective 17β-estradiol activity. The therapeutic effect of 17β-estradiol against iron overload consequences should be considered with relation to both tissues.

Progesterone anti-inflammatory properties in hereditary retinal degeneration

The interactions between steroid gonadal hormones and the retina (a part of the visual system and the central nervous system (CNS)) have received limited attention and beneficial effects of these hormones in retinal diseases is controversial. Retinitis pigmentosa (RP) is the most common cause of retinal hereditary blindness and to date no treatment is available. However, results regarding the effects of progesterone on the progression of RP are promising. With the idea of demonstrating if the progesterone retinal protection in RP is related to its possible anti-inflammatory properties, we have administered orally progesterone to rd10 mice, an animal model of RP. We observed that progesterone decreased photoreceptors cell death, reactive gliosis and the increase in microglial cells caused by RP. We also examined the expression of neuronal and inducible nitric oxide synthase (nNOS and iNOS), the enzyme responsible for NO production. The results demonstrated a decrease in nNOS expression only in control mice treated with progesterone. Inflammation has been related with an increase in lipid peroxidation. Noticeably progesterone administration was able to diminish retinal malondialdehyde (MDA, a lipid peroxidation product) concentrations in rd10 mice. Altogether, we can conclude that progesterone could be a good therapeutic option not only in RP but also for other retinal diseases that have been associated with inflammation and lipid peroxidation.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

The role of inflammation and potential use of sex steroids in intracranial aneurysms and subarachnoid hemorrhage

Background

Aneurysmal subarachnoid hemorrhage (aSAH) continues to be a devastating neurological condition with a high risk of associated morbidity and mortality. Inflammation has been shown to increase the risk of complications associated with aSAH such as vasospasm and brain injury in animal models and humans. The goal of this review is to discuss the inflammatory mechanisms of aneurysm formation, rupture and vasospasm and explore the role of sex hormones in the inflammatory response to aSAH.

Methods

A literature review was performed using PubMed using the following search terms: "intracranial aneurysm," "cerebral aneurysm," "dihydroepiandrosterone sulfate" "estrogen," "hormone replacement therapy," "inflammation," "oral contraceptive," "progesterone," "sex steroids," "sex hormones" "subarachnoid hemorrhage," "testosterone." Only studies published in English language were included in the review.

Results

Studies have shown that administration of sex hormones such as progesterone and estrogen at early stages in the inflammatory cascade can lower the risk and magnitude of subsequent complications. The exact mechanism by which these hormones act on the brain, as well as their role in the inflammatory cascade is not fully understood. Moreover, conflicting results have been published on the effect of hormone replacement therapy in humans. This review will scrutinize the variations in these studies to provide a more detailed understanding of sex hormones as potential therapeutic agents for intracranial aneurysms and aSAH.

Conclusion

Inflammation may play a role in the pathogenesis of intracranial aneurysm formation and subarachnoid hemorrhage, and administration of sex hormones as anti-inflammatory agents has been associated with improved functional outcome in experimental models. Further studies are needed to determine the therapeutic role of these hormones in the intracranial aneurysms and aSAH.

Changes of auditory event-related potentials in ovariectomized rats injected with d-galactose: Protective role of rosmarinic acid

Rosmarinic acid (RA), which has multiple bioactive properties, might be a useful agent for protecting central nervous system against age related alterations. In this context, the purpose of the present study was to investigate possible protective effects of RA on mismatch negativity (MMN) component of auditory event-related potentials (AERPs) as an indicator of auditory discrimination and echoic memory in the ovariectomized (OVX) rats injected with d-galactose combined with neurochemical and histological analyses. Ninety female Wistar rats were randomly divided into six groups: sham control (S); RA-treated (R); OVX (O); OVX+RA-treated (OR); OVX+d-galactose-treated (OD); OVX+d-galactose+RA-treated (ODR). Eight weeks later, MMN responses were recorded using the oddball condition. An amplitude reduction of some components of AERPs was observed due to ovariectomy with or without d-galactose administiration and these reduction patterns were diverse for different electrode locations. MMN amplitudes were significantly lower over temporal and right frontal locations in the O and OD groups versus the S and R groups, which was accompanied by increased thiobarbituric acid reactive substances (TBARS) and hydroxy-2-nonenal (4-HNE) levels. RA treatment significantly increased AERP/MMN amplitudes and lowered the TBARS/4-HNE levels in the OR and ODR groups versus the O and OD groups, respectively. Our findings support the potential benefit of RA in the prevention of auditory distortion related to the estrogen deficiency and d-galactose administration at least partly by antioxidant actions.

Oxidative stress and altered steroidogenesis in the ovary by cholinergic stimulation of coeliac ganglion in the first proestrous in rats. Implication of nitric oxide

An ex-vivo Coeliac Ganglion-Superior Ovarian Nerve-Ovary (CG-SON-O) system from virgin rats in the first proestrous was used to test whether cholinergic stimulation of CG affects oxidative status and steroidogenesis in the ovary. The CG and the O were placed in separate buffered-compartments, connected by the SON, and the CG was stimulated by acetylcholine (Ach). To test a possible role of nitric oxide (NO) in the ovarian response to cholinergic stimulation of CG, aminoguanidine (AG) - an inhibitor of inducible-NO synthase was added to the O compartment. After 180 min incubation, the oxidative status was assessed in O whereas nitrite and steroidogenesis were assessed at 30, 120 and 180 min. Ach in CG decreased the total antioxidant capacity, but increased NO production and protein carbonization in O. Ach stimulation of CG increased estradiol, but decreased progesterone release in O by reducing the mRNAs related to their synthesis and degradation. The addition of AG to the O compartment caused an opposite effect, which was more pronounced in the presence of Ach in the CG compartment than in its absence. These results show that the stimulation of the extrinsic-cholinergic innervation of the O increases the concentration of NO, causes oxidative stress and modulates steroidogenesis in the first rat proestrous.

Astrocyte-derived growth factors and estrogen neuroprotection: role of transforming growth factor-α in estrogen-induced upregulation of glutamate transporters in astrocytes

Extensive studies from the past decade have completely revolutionized our understanding about the role of astrocytes in the brain from merely supportive cells to an active role in various physiological functions including synaptic transmission via cross-talk with neurons and neuroprotection via releasing neurotrophic factors. Particularly, numerous studies have reported that astrocytes mediate the neuroprotective effects of 17β-estradiol (E2) and selective estrogen receptor modulators (SERMs) in various clinical and experimental models of neuronal injury. Astrocytes contain two main glutamate transporters, glutamate aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1), that play a key role in preventing excitotoxic neuronal death, a process associated with most neurodegenerative diseases. E2 has been shown to increase expression of both GLAST and GLT-1 mRNA and protein and glutamate uptake in astrocytes. Growth factors such as transforming growth factor-α (TGF-α) appear to mediate E2-induced enhancement of these transporters. These findings suggest that E2 exerts neuroprotection against excitotoxic neuronal injuries, at least in part, by enhancing astrocytic glutamate transporter levels and function. Therefore, the present review will discuss proposed mechanisms involved in astrocyte-mediated E2 neuroprotection, with a focus on glutamate transporters.

Tualang honey supplement improves memory performance and hippocampal morphology in stressed ovariectomized rats

Recently, our research team has reported that Tualang honey was able to improve immediate memory in postmenopausal women comparable with that of estrogen progestin therapy. Therefore the aim of the present study was to examine the effects of Tualang honey supplement on hippocampal morphology and memory performance in ovariectomized (OVX) rats exposed to social instability stress. Female Sprague-Dawley rats were divided into six groups: (i) sham-operated controls, (ii) stressed sham-operated controls, (iii) OVX rats, (iv) stressed OVX rats, (v) stressed OVX rats treated with 17β-estradiol (E2), and (vi) stressed OVX rats treated with Tualang honey. These rats were subjected to social instability stress procedure followed by novel object recognition (NOR) test. Right brain hemispheres were subjected to Nissl staining. The number and arrangement of pyramidal neurons in regions of CA1, CA2, CA3 and the dentate gyrus (DG) were recorded. Two-way ANOVA analyses showed significant interactions between stress and OVX in both STM and LTM test as well as number of Nissl-positive cells in all hippocampal regions. Both E2 and Tualang honey treatments improved both short-term and long-term memory and enhanced the neuronal proliferation of hippocampal CA2, CA3 and DG regions compared to that of untreated stressed OVX rats.

Neuroprotective effects of progesterone in traumatic brain injury: blunted in vivo neutrophil activation at the blood-brain barrier

BACKGROUND

Progesterone (PRO) may confer a survival advantage in traumatic brain injury (TBI) by reducing cerebral edema. We hypothesized that PRO reduces edema by blocking polymorphonuclear (PMN) interactions with endothelium (EC) in the blood-brain barrier (BBB).

METHODS

CD1 mice received repeated PRO (16 mg/kg intraperitoneally) or vehicle (cyclodextrin) for 36 hours after TBI. Sham animals underwent craniotomy without TBI. The modified Neurological Severity Score graded neurologic recovery. A second craniotomy allowed in vivo observation of pial EC/PMN interactions and vascular macromolecule leakage. Wet/dry ratios assessed cerebral edema.

RESULTS

Compared with the vehicle, PRO reduced subjective cerebral swelling (2.9 ± .1 vs 1.2 ± .1, P < .001), PMN rolling (95 ± 1.8 vs 57 ± 2.0 cells/100 μm/min, P < .001), total EC/PMN adhesion (2.0 ± .4 vs .8 ± .1 PMN/100 μm, P < .01), and vascular permeability (51.8% ± 4.9% vs 27.1% ± 4.6%, P < .01). TBI groups had similar a Neurological Severity Score and cerebral wet/dry ratios (P > .05).

CONCLUSIONS

PRO reduces live pericontusional EC/PMN and BBB macromolecular leakage after TBI. Direct PRO effects on the microcirculation warrant further investigation.

Brain tissue oxidative damage as a possible mechanism for the deleterious effect of a chronic high dose of estradiol on learning and memory in ovariectomized rats

In addition to antioxidative effects, estrogens also exert pro-oxidative actions. The effect of chronic administration of a high dose of estradiol valerate on Morris water maze tasks and brain tissues oxidative damage was investigated. The Sham-Est and OVX-Est groups were treated with estradiol valerate (4 mg/kg) for 12 weeks. Escape latency and traveled path in the Sham-Est and OVX-Est groups were significantly higher than in the Sham and OVX groups (p≪0.01 and p≪0.001). In the probe trial, the animals of the Sham-Est and OVX-Est groups spent lower time in Q1 compared to Sham and OVX groups (p≪0.05 and p≪0.001). In Sham-Est and OVX-Est groups, the brain tissue total thiol concentration was significantly lower, and malondialdehyde (MDA) concentrations were higher than in the Sham and OVX groups (p≪0.05 and p≪0.001). It is concluded that administration of high exogenous levels of estradiol impairs performance and enhances oxidative stress.

Estrogen and neuroprotection: from clinical observations to molecular mechanisms

We now appreciate that estrogen is a pleiotropic gonadal steroid that exerts profound effects on the plasticity and cell survival of the adult brain. Over the past century, the life span of women has increased, but the age of the menopause remains constant. This means that women may now live over one third of their lives in a hypoestrogenic, postmenopausal state. The impact of prolonged hypoestrogenicity on the brain is now a critical health concern as we realize that these women may suffer an increased risk of cognitive dysfunction and neurodegeneration due to a variety of diseases. Accumulating evidence from both clinical and basic science studies indicates that estrogen exerts critical protective actions against neurodegenerative conditions such as Alzheimer's disease and stroke. Here, we review the discoveries that comprise our current understanding of estrogen action against neurodegeneration. These findings carry far-reaching possibilities for improving the quality of life in our aging population.

Neuroprotective effects of 17β-estradiol after hypovolemic cardiac arrest in immature piglets: the role of nitric oxide and peroxidation

We recently reported that cerebral and cardiac injuries are mitigated in immature female piglets after severe hemorrhage with subsequent cardiac arrest. Female sex was also associated with a smaller increase in the cerebral expression of inducible nitric oxide synthase (iNOS) and neuronal nitric oxide synthase (nNOS). In the current study, we tested the hypothesis that exogenously administered 17β-estradiol (E₂) can improve neurological outcome by NOS modulation. Thirty-nine sexually immature piglets were bled to a mean arterial pressure of 35 mmHg over 15 min. Fifty micrograms per kilogram of E₂ was then administered to 10 male and 10 female animals (estradiol group), whereas control animals (n = 10 males and 9 females) received equal volume of normal saline. The animals were then subjected to ventricular fibrillation (4 min) followed by up to 15 min of open-chest cardiopulmonary resuscitation. Vasopressin 0.4 U · kg⁻¹ and amiodarone 0.5 mg · kg⁻¹ were given, and 3 mL · kg⁻¹ of 7.5% saline with 6% dextran was administered over 20 min. All surviving animals were killed after 3 h, and their brains examined for histological injury and NOS expression. No significant differences were observed in survival or hemodynamics between the groups. Compared with the control group, animals in the E₂ group exhibited a significantly smaller increase in nNOS and iNOS expression, a smaller blood-brain-barrier disruption, and a mitigated neuronal injury. There was a significant correlation between nNOS and iNOS levels and neuronal injury. Interestingly, estradiol attenuated cerebral damage (including lower activation of nNOS and iNOS) both in male and female piglets. In conclusion, in our immature piglet model of hypovolemic cardiac arrest, E₂ downregulates iNOS and nNOS expression and results in decreased blood-brain-barrier permeability disruption and smaller neuronal injury.

The potential for estrogens in preventing Alzheimer's disease and vascular dementia

Estrogens are the best-studied class of drugs for potential use in the prevention of Alzheimer's disease (AD). These steroids have been shown to be potent neuroprotectants both in vitro and in vivo, and to exert effects that are consistent with their potential use in prevention of AD. These include the prevention of the processing of amyloid precursor protein (APP) into beta-amyloid (Aß), the reduction in tau hyperphosphorylation, and the elimination of catastrophic attempts at neuronal mitosis. Further, epidemiological data support the efficacy of early postmenopausal use of estrogens for the delay or prevention of AD. Collectively, this evidence supports the further development of estrogen-like compounds for prevention of AD. Several approaches to enhance brain specificity of estrogen action are now underway in an attempt to reduce the side effects of chronic estrogen therapy in AD.

An early treatment with 17-β-estradiol is neuroprotective against the long-term effects of neonatal ionizing radiation exposure

Ionizing radiations can induce oxidative stress on target tissues, acting mainly through reactive oxygen species (ROS). The aim of this work was to investigate if 17-β-estradiol (βE) was able to prevent hippocampal-related behavioral and biochemical changes induced by neonatal ionizing radiation exposure and to elucidate a potential neuroprotective mechanism. Male Wistar rats were irradiated with 5 Gy of X-rays between 24 and 48 h after birth. A subset of rats was subcutaneously administered with successive injections of βE or 17-α-estradiol (αE), prior and after irradiation. Rats were subjected to different behavioral tasks to evaluate habituation and associative memory as well as anxiety levels. Hippocampal ROS levels and protein kinase C (PKC) activity were also assessed. Results show that although βE was unable to prevent radiation-induced hippocampal PKC activity changes, most behavioral abnormalities were reversed. Moreover, hippocampal ROS levels in βE-treated irradiated rats approached control values. In addition, αE administered to irradiated animals was effective in preventing radiation-induced alterations. In conclusion, βE was able to counteract behavioral and biochemical changes induced in irradiated animals, probably acting through an antioxidant mechanism.

Aromatase expression in cultured fetal sheep astrocytes after nitrosative/oxidative damage

Aromatase, the enzyme converting androgens into estrogens, is involved in many brain processes such as neural differentiation and plasticity or the prevention of cell death. We have previously observed an increase in aromatase immunoreactivity in sheep neurons exposed in vitro to the oxidant 3-nitro-L: -tyrosine. However, little is known regarding the way that sheep astrocytes cope with nitrosative stress, a condition occurring in sheep in the pathogenesis of neurodegenerative disorders such as scrapie and Maedi-Visna. Our aim has been to evaluate the effects of 3-nitro-L-tyrosine on astrocyte primary cultures from 90-day-old fetal sheep brain. Living cells were observed and characterized by immunofluorescence with a GFAP antibody, which indicated that the majority of the cells were astrocytes. A viability assay was performed on both untreated and treated cells. Reverse transcription with the polymerase chain reaction was undertaken to monitor time- and dose-dependent variations in aromatase gene expression. Stressed astrocytes showed signs of deterioration, were reduced in number, and appeared round with few short processes; the cell death rate was ∼30%. Aromatase expression was detected starting from a 24-h exposure to 1 mM 3-nitro-L-tyrosine and reached the highest levels at 72 h. Thus, oxidative damage probably results in the local production of neuroprotective estradiol by reactive astrocytes via the aromatization of testosterone.

Mechanisms of estrogens' dose-dependent neuroprotective and neurodamaging effects in experimental models of cerebral ischemia

Ever since the hypothesis was put forward that estrogens could protect against cerebral ischemia, numerous studies have investigated the mechanisms of their effects. Despite initial studies showing ameliorating effects, later trials in both humans and animals have yielded contrasting results regarding the fundamental issue of whether estrogens are neuroprotective or neurodamaging. Therefore, investigations of the possible mechanisms of estrogen actions in brain ischemia have been difficult to assess. A recently published systematic review from our laboratory indicates that the dichotomy in experimental rat studies may be caused by the use of insufficiently validated estrogen administration methods resulting in serum hormone concentrations far from those intended, and that physiological estrogen concentrations are neuroprotective while supraphysiological concentrations augment the damage from cerebral ischemia. This evidence offers a new perspective on the mechanisms of estrogens’ actions in cerebral ischemia, and also has a direct bearing on the hormone replacement therapy debate. Estrogens affect their target organs by several different pathways and receptors, and the mechanisms proposed for their effects on stroke probably prevail in different concentration ranges. In the current article, previously suggested neuroprotective and neurodamaging mechanisms are reviewed in a hormone concentration perspective in an effort to provide a mechanistic framework for the dose-dependent paradoxical effects of estrogens in stroke. It is concluded that five protective mechanisms, namely decreased apoptosis, growth factor regulation, vascular modulation, indirect antioxidant properties and decreased inflammation, and the proposed damaging mechanism of increased inflammation, are currently supported by experiments performed in optimal biological settings.

Effects on DHEA levels by estrogen in rat astrocytes and CNS co-cultures via the regulation of CYP7B1-mediated metabolism

The neurosteroid dehydroepiandrosterone (DHEA) is formed locally in the CNS and has been implicated in several processes essential for CNS function, including control of neuronal survival. An important metabolic pathway for DHEA in the CNS involves the steroid hydroxylase CYP7B1. In previous studies, CYP7B1 was identified as a target for estrogen regulation in cells of kidney and liver. In the current study, we examined effects of estrogens on CYP7B1-mediated metabolism of DHEA in primary cultures of rat astrocytes and co-cultures of rat CNS cells. Astrocytes, which interact with neurons in several ways, are important for brain neurosteroidogenesis. We found that estradiol significantly suppressed CYP7B1-mediated DHEA hydroxylation in primary mixed CNS cultures from fetal and newborn rats. Also, CYP7B1-mediated DHEA hydroxylation and CYP7B1 mRNA were markedly suppressed by estrogen in primary cultures of rat astrocytes. Interestingly, diarylpropionitrile, a well-known agonist of estrogen receptor β, also suppressed CYP7B1-mediated hydroxylation of DHEA. Several previous studies have reported neuroprotective effects of estrogens. The current data indicate that one of the mechanisms whereby estrogen can exert protective effects in the CNS may involve increase of the levels of DHEA by suppression of its metabolism.

Lipid peroxidation in rats treated with vincristine sulphate and nandrolone decanoate

Brain and serum lipid peroxidation was studied in rats treated with vincristine sulphate and different doses of nandrolone decanoate. Thirty rats were distributed into six groups (n=5). The treatments were applied once a week for two weeks. Sample collection was performed in the third week. Treatments during the first week were: G1 (control) - physiologic solution, G2 - vincristine sulphate (4mg/m²), G3 - physiologic solution, G4 - physiologic solution, G5- vincristine sulphate (4mg/m²), and G6 - vincristine sulphate (4mg/m²). In the second week, they were: G1 (control) - physiologic solution, G2- physiologic solution, G3 - nandrolone decanoate (1.8mg/kg-1), G4 - nandrolone decanoate (10mg/kg-1), G5 - nandrolone decanoate (1.8mg/kg-1), and G6 - nandrolone decanoate (10mg/kg-1). Lipid peroxidation increased with the isolated use of vincristine and nandrolone decanoate, and with vincristine associated to the highest dose of the ester as well. These results suggest that vincristine sulphate and nandrolone decanoate increase free radical production. Therapeutic dose of nandrolone decanoate when associated with vincristine sulphate proved to be beneficial, as it was able to protect the organism from damaging processes involved in free radical production

The influence of age of lead exposure on adult gray matter volume

Childhood lead exposure is associated with decreased cognitive abilities and executive functioning localized within the prefrontal cortex. Several studies have observed stronger associations between blood lead measurements obtained later in life than earlier measures, but there are no imaging studies investigating the developmental trajectory of blood lead levels taken during childhood on adult gray matter volume. In this study, we recruited 157 adults (20.8+/-1.5 years of age) from the Cincinnati Lead Study to undergo high resolution volumetric magnetic resonance imaging. Adjusted voxel-wise regression analyses were performed for associations between adult gray matter volume loss and yearly mean blood lead levels from 1 to 6 years of age in the entire cohort and by sex. We observed significant inverse associations between gray matter volume loss and annual mean blood lead levels from 3 to 6 years of age. The extent of prefrontal gray matter associated with yearly mean blood lead levels increased with advancing age of the subjects. The inverse associations between gray matter volume loss and yearly mean blood lead measurements were more pronounced in the frontal lobes of men than women. Analysis of women yielded significantly weaker associations between yearly mean blood lead levels and gray matter volume at all ages than either men or the combined cohort of men and women together. These results suggest that blood lead concentrations obtained during later childhood demonstrate greater loss in gray matter volume than childhood mean or maximum values. The relationship between childhood blood lead levels and gray matter volume loss was predominantly observed in the frontal lobes of males. This study demonstrates that maximum blood lead levels do not fully account for gray matter changes associated with childhood lead exposure, particularly in the frontal lobes of young men.

Complexities of oestrogen in stroke

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.

Mitochondrial mechanisms of estrogen neuroprotection

Mitochondria have become a primary focus in our search not only for the mechanism(s) of neuronal death but also for neuroprotective drugs and therapies that can delay or prevent Alzheimer's disease and other chronic neurodegenerative conditions. This is because mitochrondria play a central role in regulating viability and death of neurons, and mitochondrial dysfunction has been shown to contribute to neuronal death seen in neurodegenerative diseases. In this article, we review the evidence for the role of mitochondria in cell death and neurodegeneration and provide evidence that estrogens have multiple effects on mitochondria that enhance or preserve mitochondrial function during pathologic circumstances such as excitotoxicity, oxidative stress, and others. As such, estrogens and novel non-hormonal analogs have come to figure prominently in our efforts to protect neurons against both acute brain injury and chronic neurodegeneration.

Mechanisms of gender-linked ischemic brain injury

Biological sex is an important determinant of stroke risk and outcome. Women are protected from cerebrovascular disease relative to men, an observation commonly attributed to the protective effect of female sex hormones, estrogen and progesterone. However, sex differences in brain injury persist well beyond the menopause and can be found in the pediatric population, suggesting that the effects of reproductive steroids may not completely explain sexual dimorphism in stroke. We review recent advances in our understanding of sex steroids (estradiol, progesterone and testosterone) in the context of ischemic cell death and neuroprotection. Understanding the molecular and cell-based mechanisms underlying sex differences in ischemic brain injury will lead to a better understanding of basic mechanisms of brain cell death and is an important step toward designing more effective therapeutic interventions in stroke.

Role of protein phosphatases and mitochondria in the neuroprotective effects of estrogens

In the present treatise, we provide evidence that the neuroprotective and mito-protective effects of estrogens are inexorably linked and involve the ability of estrogens to maintain mitochondrial function during neurotoxic stress. This is achieved by the induction of nuclear and mitochondrial gene expression, the maintenance of protein phosphatases levels in a manner that likely involves modulation of the phosphorylation state of signaling kinases and mitochondrial pro- and anti-apoptotic proteins, and the potent redox/antioxidant activity of estrogens. These estrogen actions are mediated through a combination of estrogens receptor (ER)-mediated effects on nuclear and mitochondrial transcription of protein vital to mitochondrial function, ER-mediated, non-genomic signaling and non-ER-mediated effects of estrogens on signaling and oxidative stress. Collectively, these multifaceted, coordinated action of estrogens leads to their potency in protecting neurons from a wide variety of acute insults as well as chronic neurodegenerative processes.

Protective actions of sex steroid hormones in Alzheimer's disease

Risk for Alzheimer's disease (AD) is associated with age-related loss of sex steroid hormones in both women and men. In post-menopausal women, the precipitous depletion of estrogens and progestogens is hypothesized to increase susceptibility to AD pathogenesis, a concept largely supported by epidemiological evidence but refuted by some clinical findings. Experimental evidence suggests that estrogens have numerous neuroprotective actions relevant to prevention of AD, in particular promotion of neuron viability and reduction of beta-amyloid accumulation, a critical factor in the initiation and progression of AD. Recent findings suggest neural responsiveness to estrogen can diminish with age, reducing neuroprotective actions of estrogen and, consequently, potentially limiting the utility of hormone therapies in aged women. In addition, estrogen neuroprotective actions are also modulated by progestogens. Specifically, continuous progestogen exposure is associated with inhibition of estrogen actions whereas cyclic delivery of progestogens may enhance neural benefits of estrogen. In recent years, emerging literature has begun to elucidate a parallel relationship of sex steroid hormones and AD risk in men. Normal age-related testosterone loss in men is associated with increased risk to several diseases including AD. Like estrogen, testosterone has been established as an endogenous neuroprotective factor that not only increases neuronal resilience against AD-related insults, but also reduces beta-amyloid accumulation. Androgen neuroprotective effects are mediated both directly by activation of androgen pathways and indirectly by aromatization to estradiol and initiation of protective estrogen signaling mechanisms. The successful use of hormone therapies in aging men and women to delay, prevent, and or treat AD will require additional research to optimize key parameters of hormone therapy and may benefit from the continuing development of selective estrogen and androgen receptor modulators.

Sex, sex steroids, and brain injury

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).

Gender and the injured brain

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.

Resveratrol and quercetin, two natural polyphenols, reduce apoptotic neuronal cell death induced by neuroinflammation

Parkinson's disease (PD) is a movement disorder characterized by a progressive loss of nigrostriatal dopaminergic neurons. Microglia activation and neuroinflammation have been associated with the pathogenesis of PD. Indeed, cytokines have been proposed as candidates that mediate the apoptotic cell death of dopaminergic neurons seen in PD. In this study, we investigated the effect of two natural polyphenols, resveratrol and quercetin, on neuroinflammation. For glial cells, we observed that lipopolysaccharide (LPS)-induced mRNA levels of two proinflammatory genes, interleukin 1-alpha and tumor necrosis factor-alpha, are strongly decreased by treatments with resveratrol or quercetin. We also undertook microglial-neuronal coculture to examine the influence of resveratrol and quercetin on dopaminergic neuronal cell death evoked by LPS-activated microglia. Cytotoxicity assays were performed to evaluate the percentage of cell death, with apoptotic cells identified by both the TdT-mediated dUTP nick end labeling technique and the detection of cleaved caspase-3. We report that treatment of N9 microglial cells with resveratrol or quercetin successfully reduced the inflammation-mediated apoptotic death of neuronal cells in our coculture system. Altogether our results demonstrate that resveratrol and quercetin diminished apoptotic neuronal cell death induced by microglial activation and suggest that these two phytoestrogens may be potent antiinflammatory compounds.

Progesterone exerts neuroprotective effects after brain injury

Progesterone, although still widely considered primarily a sex hormone, is an important agent affecting many central nervous system functions. This review assesses recent, primarily in vivo, evidence that progesterone can play an important role in promoting and enhancing repair after traumatic brain injury and stroke. Although many of its specific actions on neuroplasticity remain to be discovered, there is growing evidence that this hormone may be a safe and effective treatment for traumatic brain injury and other neural disorders in humans.

Investigation of the role of SMN1 and SMN2 haploinsufficiency as a risk factor for Hirayama's disease: Clinical, neurophysiological and genetic characteristics in a Spanish series of 13 patients

OBJECTIVE

The effect of the number of copies in the SMN1 and SMN2 genes - the most extensively studied susceptibility and modifying genetic factors in adult onset motor neuron diseases - as a genetic risk factor for Hirayama's disease (HirD) has never been studied. The purpose of this study was to investigate the influence of the number of copies of the SMN1/SMN2 genes on the resulting phenotype in 13 HirD Spanish patients.

PATIENTS AND METHODS

We performed a qualitative and quantitative SMN1/SMN2 gene analysis in 13 unrelated HirD patients. The phenotype-genotype correlation was investigated, paying particular attention to the effect of the SMN1/SMN2 copy number on the disease's phenotype.

RESULTS

No patient had a homozygous deletion of the SMN1 or SMN2. No differences were found when comparing the SMN1 and SMN2 copy number distributions of the healthy population and HirD patients, and they do not therefore appear to be a susceptibility factor. There was also no correlation found between the number of copies of the SMN1 and SMN2 and the severity of the resulting phenotype.

CONCLUSION

Our results suggest that SMN1 and SMN2 are not predisposing factors for HirD and therefore support a lack of association between these genes and the resulting phenotype.

Retinal ganglion cell protection by 17-beta-estradiol in a mouse model of inherited glaucoma

Glaucoma is the second leading cause of blindness in the world. The ultimate cause of vision loss due to glaucoma is thought to be retinal ganglion cell (RGC) apoptosis. Neuroprotection of RGC is becoming an important approach of glaucoma therapy. Several lines of evidence suggest that estrogen has neurotrophic and neuroprotective properties. In this study, we examine the role of estrogen in preventing RGC loss in DBA/2J mouse, an in vivo model of an inherited (pigmentary) glaucoma. Two-month-old female DBA/2J mice were anesthetized and ovariectomized with or without subcutaneous 17beta-estradiol (betaE2) pellet implantation. RGC survival was evaluated from flat-mounted whole retinas by counting retrograde-labeled cells. The loss of nerve fibers and RGC were also evaluated in paraffin-fixed retinal cross sections. Biochemical alterations in the retinas of DBA/2J mice in response to systemic injection of betaE2 were also examined. We have made several important observations showing that: (1) betaE2 treatment reduced the loss of RGC and neurofibers through inhibition of ganglion cell apoptosis, (2) betaE2 activated Akt and cAMP-responsive-element-binding-protein (CREB), (3) betaE2 up-regulated thioredoxin-1 (Trx-1) expression, (4) betaE2 reduced the increased activations of mitogen-activated protein kinases (MAPK) and NF-kappaB, (5) betaE2 inhibited the increased interleukin-18 (IL-18) expression, and (6) treatment with tamoxifen, an estrogen receptor antagonist, blocked betaE2-mediated activation of Akt and inhibition of MAPK phosphorylation in the retinas of DBA/2J mice. These findings suggest the possible involvement of multiple biochemical events, including estrogen receptor/Akt/CREB/thioredoxin-1, and estrogen receptor/MAPK/NF-kappaB, in estrogen-mediated retinal ganglion cell protection.

Oxidative stress: A bridge between Down's syndrome and Alzheimer's disease

Besides the genetic, biochemical and neuropathological analogies between Down's syndrome (DS) and Alzheimer's disease (AD), there is ample evidence of the involvement of oxidative stress (OS) in the pathogenesis of both disorders. The present paper reviews the publications on DS and AD in the past 10 years in light of the "gene dosage" and "two-hit" hypotheses, with regard to the alterations caused by OS in both the central nervous system and the periphery, and the main pipeline of antioxidant therapeutic strategies. OS occurs decades prior to the signature pathology and manifests as lipid, protein and DNA oxidation, and mitochondrial abnormalities. In clinical settings, the assessment of OS has traditionally been hampered by the use of assays that suffer from inherent problems related to specificity and/or sensitivity, which explains some of the conflicting results presented in this work. For DS, no scientifically proven diet or drug is yet available, and AD trials have not provided a satisfactory approach for the prevention of and therapy against OS, although most of them still need evidence-based confirmation. In the future, a balanced up-regulation of endogenous antioxidants, together with multiple exogenous antioxidant supplementation, may be expected to be one of the most promising treatment methods.

Structure-nongenomic neuroprotection relationship of estrogens and estrogen-derived compounds

Nongenomic estrogen signaling pathways involve extranuclear estrogen receptors or function independently from estrogen receptors. These pathways participate in neuroprotection elicited by the hormone. Additional nongenomic neuroprotective effects are attributable to antioxidant and antiinflammatory actions of estrogens. Numerous chemical modifications to afford neuroprotective compounds from estrogens while eliminating estrogenicity and maintaining or enhancing nongenomic neuroprotection have been described. This review highlights recent structure-activity studies that revealed the importance of antioxidant effects for neuroprotective estrogen analogues and derivatives.

Reproductive hormones modulate oxidative stress in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by gradual cognitive decline, impairments in speech and language, and dysfunction in the sensorimotor systems, culminating in complete reliance on nursing care. Oxidative stress, caused by an imbalance in the pro-oxidant/antioxidant mechanisms in the body, has been implicated in AD pathogenesis, as in many other age-associated diseases such as atherosclerosis, Parkinson disease, and amyotrophic lateral sclerosis. Although the hormones estrogen, progesterone, testosterone, and luteinizing hormone are best known for their roles in reproduction, many studies show these hormones have other roles, including neuroprotection. Changes in the levels of these hormones that occur in reproductive senescence are hypothesized to increase risk of AD, as a result of reduced protection against oxidative insults. The Abeta peptide, overproduction of which is thought to be a key pathogenic event in the development of AD, is neurotoxic, most likely due to its ability to promote oxidative stress. The reproductive hormones are known to influence Abeta metabolism, and this review discusses the beneficial and detrimental effects these hormones have on Abeta production and oxidative stress, and their relevance in potential AD therapies.

Complex actions of sex steroids in adipose tissue, the cardiovascular system, and brain: Insights from basic science and clinical studies

Recent publications describing the results of the Women's Health Initiative (WHI) and other studies reporting the impact of hormone therapy on aging women have spurred reexamination of the broad use of estrogens and progestins during the postmenopausal years. Here, we review the complex pharmacology of these hormones, the diverse and sometimes opposite effects that result from the use of different estrogenic and progestinic compounds, given via different delivery routes in different concentrations and treatment sequence, and to women of different ages and health status. We examine our new and growing appreciation of the role of estrogens in the immune system and the inflammatory response, and we pose the concept that estrogen's interface with this system may be at the core of some of the effects on multiple physiological systems, such as the adipose/metabolic system, the cardiovascular system, and the central nervous system. We compare and contrast clinical and basic science studies as we focus on the actions of estrogens in these systems because the untoward effects of hormone therapy reported in the WHI were not expected. The broad interpretation and publicity of the results of the WHI have resulted in a general condemnation of all hormone replacement in postmenopausal women. In fact, careful review of the extensive literature suggests that data resulting from the WHI and other recent studies should be interpreted within the narrow context of the study design. We argue that these results should encourage us to perform new studies that take advantage of a dialogue between basic scientists and clinician scientists to ensure appropriate design, incorporation of current knowledge, and proper interpretation of results. Only then will we have a better understanding of what hormonal compounds should be used in which populations of women and at what stages of menopausal/postmenopausal life.

The case for progesterone

Recent clinical trials in hormone therapy (HT) for women approaching or past menopause have been disappointing. Most women who have been taking conjugated equine estrogens combined with synthetic progestins have been encouraged to stop these supplements because of increased health risks. The results of the clinical trials may be accurate about the risks associated with the synthetic compounds and combinations, but the data do not reflect what might have been the case if 17beta-estradiol had been tested with natural progesterone instead of synthetic medroxyprogesterone acetate. For the most part, in almost all work on HT, estrogens have been given the primary focus despite the fact that progesterone has important properties that can enhance the repair of neurodegenerative and traumatic injuries to the central nervous system. This article reviews some of those properties and discusses the evidence suggesting that, if HT is to be reconsidered, progesterone should be given more attention as a potent neurotrophic agent that may play an important role in reducing or preventing motor, cognitive, and sensory impairments that can accompany senescence in both males and females.

Traumatic brain injury outcomes in pre- and post- menopausal females versus age-matched males

Gender differences in outcomes from major trauma have been described previously, and exogenous female hormone administration appears to be neuroprotective following traumatic brain injury (TBI). This analysis explored outcomes in pre- and post-menopausal females versus age-matched males. A total of 13,437 patients (n = 3,178 females, n = 10,259 males) with moderate-to-severe TBI (head AIS > or = 3) were identified from our county trauma registry. Overall mortality was similar between males and females (22% for both). Logistic regression was used to compare gender outcome differences, with a separate analysis performed for premenopausal (< 50 years) versus postmenopausal (> or = 50 years) patients, and after stratification by decade of life. No statistically significant difference in outcomes was observed for pre-menopausal females versus males (odds ratio [OR] 1.06; 95% confidence interval [CI] 0.83, 1.35; p = 0.633), but outcomes were significantly better in postmenopausal females versus males (OR 0.63, 95% CI 0.48-0.81, p < 0.001) after adjusting for age, mechanism of injury, Glasgow Coma Scale (GCS), hypotension (SBP < or = 90 mm Hg), head Abbreviated Injury Score (AIS), and Injury Severity Score (ISS). Stratification by decade of life revealed the gender survival differential inflection point to occur between ages 40-49 (OR 1.06, 95% CI 0.66-1.71, p = 0.798) and ages 50-59 (OR 0.38, 95% CI 0.20-0.74, p = 0.005). In addition, Revised Trauma Score and Injury Severity Score (TRISS) was used to calculate probability of survival (PS); all patients were then stratified by decade of life, and males and females were compared with regard to mean survival differential (outcome - PS). The identical pattern of improved outcomes in post-menopausal but not pre-menopausal females versus age-matched males was observed. These data suggest that endogenous female sex hormone production is not neuroprotective.