Impact of 17beta-estradiol on cytokine-mediated apoptotic effects in primary hippocampal and neocortical cell cultures

Posttreatment with PaPE-1 Protects from Aβ-Induced Neurodegeneration Through Inhibiting the Expression of Alzheimer's Disease-Related Genes and Apoptosis Process That Involves Enhanced DNA Methylation of Specific Genes

Targeting the non-nuclear estrogen receptor (ER) signaling has been postulated as novel therapeutic strategy for central nervous system pathologies. Recently, we showed that newly designed PaPE-1 (Pathway Preferential Estrogen-1), which selectively activates ER non-nuclear signaling pathways, elicited neuroprotection in a cellular model of Alzheimer's disease (AD) when it was applied at the same time as amyloid-β (Aβ). Since delayed treatment reflects clinical settings better than cotreatment does, current basic study proposes a novel therapeutic approach for AD that relies on a posttreatment with PaPE-1. In this study, mouse neuronal cell cultures treated with preaggregated Aβ1-42 (10 µM) showed the presence of extracellular Aβ1-42, confirming the adequacy of the AD model used. We are the first to demonstrate that a 24-h delayed posttreatment with PaPE-1 decreased the degree of Aβ-induced neurodegeneration, restored neurite outgrowth, and inhibited the expression of AD-related genes, i.e., Rbfox, Apoe, Bace2, App, and Ngrn, except for Chat, which was stimulated. In addition, PaPE-1 elicited anti-apoptotic effects by inhibiting Aβ-induced caspase activities as well as attenuating apoptotic chromatin condensation, and in these ways, PaPE-1 prevented neuronal cell death. Posttreatment with PaPE-1 also downregulated the Aβ-affected mRNA expression of apoptosis-specific factors, such as Bax, Gsk3b, Fas, and Fasl, except for Bcl2, which was upregulated by PaPE-1. In parallel, PaPE-1 decreased the protein levels of BAX, FAS, and FASL, which were elevated in response to Aβ. PaPE-1 elicited a decrease in the BAX/BCL2 ratio that corresponds to increased methylation of the Bax gene. However, the PaPE-1-evoked Bcl2 gene hypermethylation suggests other PaPE-1-dependent mechanisms to control Aβ-induced apoptosis.

The Role of Inhaled Estradiol and Myrtenol, Alone and in Combination, in Modulating Behavioral and Functional Outcomes Following Traumatic Experimental Brain Injury: Hemodynamic, Molecular, Histological and Behavioral Study

BACKGROUND

Traumatic brain injury (TBI) is an important and growing cause of disability worldwide, and its cognitive consequences may be particularly significant. This study assessed the neuroprotective impacts of estradiol (E2), myrtenol (Myr), and the combination of the two on the neurological outcome, hemodynamic parameters, learning and memory, brain-derived neurotrophic factor (BDNF) level, phosphoinositide 3-kinases (PI3K/AKT) signaling, and inflammatory and oxidative factors in the hippocampus after TBI.

METHODS

Eighty-four adult male Wistar rats were randomly divided into 12 groups with seven rats in each (six groups to measure intracranial pressure, cerebral perfusion pressure, brain water content, and veterinary coma scale, and six groups for behavioral and molecular studies): sham, TBI, TBI/vehicle, TBI/Myr, TBI/E2, and TBI/Myr + E2 (Myr 50 mg/kg and E2 33.3 μg/kg via inhalation for 30 min after TBI induction). Brain injury was induced by using Marmarou's method. Briefly, a 300-g weight was dropped down from a 2-m height through a free-falling tube onto the head of the anesthetized animals.

RESULTS

Veterinary coma scale, learning and memory, brain water content, intracranial pressure, and cerebral perfusion pressure were impaired following TBI, and inflammation and oxidative stress were raised in the hippocampus after TBI. The BDNF level and PI3K/AKT signaling were impaired due to TBI. Inhalation of Myr and E2 had protective effects against all negative consequences of TBI by decreasing brain edema and the hippocampal content of inflammatory and oxidant factors and also by improving BDNF and PI3K/AKT in the hippocampus. Based on these data, there were no differences between alone and combination administrations.

CONCLUSIONS

Our results propose that Myr and E2 have neuroprotective effects on cognition impairments due to TBI.

Posttreatment with Ospemifene Attenuates Hypoxia- and Ischemia-Induced Apoptosis in Primary Neuronal Cells via Selective Modulation of Estrogen Receptors

Stroke and perinatal asphyxia have detrimental effects on neuronal cells, causing millions of deaths worldwide each year. Since currently available therapies are insufficient, there is an urgent need for novel neuroprotective strategies to address the effects of cerebrovascular accidents. One such recent approach is based on the neuroprotective properties of estrogen receptors (ERs). However, activation of ERs by estrogens may contribute to the development of endometriosis or hormone-dependent cancers. Therefore, in this study, we utilized ospemifene, a novel selective estrogen receptor modulator (SERM) already used in dyspareunia treatment. Here, we demonstrated that posttreatment with ospemifene in primary neocortical cell cultures subjected to 18 h of hypoxia and/or ischemia followed by 6 h of reoxygenation has robust neuroprotective potential. Ospemifene partially reverses hypoxia- and ischemia-induced changes in LDH release, the degree of neurodegeneration, and metabolic activity. The mechanism of the neuroprotective actions of ospemifene involves the inhibition of apoptosis since the compound decreases caspase-3 overactivity during hypoxia and enhances mitochondrial membrane potential during ischemia. Moreover, in both models, ospemifene decreased the levels of the proapoptotic proteins BAX, FAS, FASL, and GSK3β while increasing the level of the antiapoptotic protein BCL2. Silencing of specific ERs showed that the neuroprotective actions of ospemifene are mediated mainly via ESR1 (during hypoxia and ischemia) and GPER1 (during hypoxia), which is supported by ospemifene-evoked increases in ESR1 protein levels in hypoxic and ischemic neurons. The results identify ospemifene as a promising neuroprotectant, which in the future may be used to treat injuries due to brain hypoxia/ischemia.

Posttreatment Strategy Against Hypoxia and Ischemia Based on Selective Targeting of Nonnuclear Estrogen Receptors with PaPE-1

Newly synthesized Pathway Preferential Estrogen-1 (PaPE-1) selectively activates membrane estrogen receptors (mERs), namely, mERα and mERβ, and has been shown to evoke neuroprotection; however, its effectiveness in protecting brain tissue against hypoxia and ischemia has not been verified in a posttreatment paradigm. This is the first study showing that a 6-h delayed posttreatment with PaPE-1 inhibited hypoxia/ischemia-induced neuronal death, as indicated by neutral red uptake in mouse primary cell cultures in vitro. The effect was accompanied by substantial decreases in neurotoxicity and neurodegeneration in terms of LDH release and Fluoro-Jade C staining of damaged cells, respectively. The mechanisms of the neuroprotective action of PaPE-1 also involved apoptosis inhibition demonstrated by normalization of both mitochondrial membrane potential and expression levels of apoptosis-related genes and proteins such as Fas, Fasl, Bcl2, FAS, FASL, BCL2, BAX, and GSK3β. Furthermore, PaPE-1-evoked neuroprotection was mediated through a reduction in ROS formation and restoration of cellular metabolic activity that had become dysregulated due to hypoxia and ischemia. These data provide evidence that targeting membrane non-GPER estrogen receptors with PaPE-1 is an effective therapy that protects brain neurons from hypoxic/ischemic damage, even when applied with a 6-h delay from injury onset.

Inflammatory cytokine levels implicated in Alzheimer's disease moderate the effects of sex on verbal memory performance

Despite having an initial verbal memory advantage over men, women have greater rates of Alzheimer's disease and more rapid cognitive decline once diagnosed. Moreover, although Alzheimer's disease is influenced by inflammation, which itself has known sex differences, no study has investigated whether sex differences in memory are moderated by peripheral inflammatory activity. To address this issue, we analyzed data from 109 individuals (50 women, Mage = 71.62, range = 55-87) diagnosed as cognitively normal, or having mild cognitive impairment or Alzheimer's disease dementia. We then followed the sample for 12 months, as part of a longitudinal study of aging and Alzheimer's disease. At baseline, we assessed levels of the inflammatory cytokines interleukin (IL)-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) in plasma. At baseline and 12 months, we assessed verbal memory using the Rey Auditory Verbal Learning Test and nonverbal memory using the Brief Visuospatial Memory Test-Revised. As hypothesized, for the full sample, women exhibited stronger verbal (but not nonverbal) memory than men. In women, but not men, higher IL-1β at baseline related to poorer verbal learning across both time points and delayed recall at 12 months. The effect of sex on memory also differed by IL-1β level, with women exhibiting a memory advantage both at baseline and 12 months, but only for those with low-to-moderate IL-1β levels. Therefore, high peripheral inflammation levels may lead to a sex-specific memory vulnerability relevant for Alzheimer's disease.

Brain inflammasomes in stroke and depressive disorders: Regulation by oestrogen

Neuroinflammation is a devastating pathophysiological process that results in brain damage and neuronal death. Pathogens, cell fragments and cellular dysfunction trigger inflammatory responses. Irrespective of the cause, inflammasomes are key intracellular multiprotein signalling platforms that sense neuropathological conditions. The activation of inflammasomes leads to the auto-proteolytic cleavage of caspase-1, resulting in the proteolysis of the pro-inflammatory cytokines interleukin (IL)1β and IL18 into their bioactive forms. It also initiates pyroptosis, a type of cell death. The two cytokines contribute to the pathogenesis in acute and chronic brain diseases and also play a central role in human aging and psychiatric disorders. Sex steroids, in particular oestrogens, are well-described neuroprotective agents in the central nervous system. Oestrogens improve the functional outcome after ischaemia and traumatic brain injury, reduce neuronal death in Parkinson's and Alzheimer's disease, as well as in amyotrophic lateral sclerosis, attenuate glutamate excitotoxicity and the formation of radical oxygen species, and lessen the spread of oedema after damage. Moreover, oestrogens alleviate menopause-related depressive symptoms and have a positive influence on depressive disorders probably by influencing growth factor production and serotonergic brain circuits. Recent evidence also suggests that inflammasome signalling affects anxiety- and depressive-like behaviour and that oestrogen ameliorates depression-like behaviour through the suppression of inflammasomes. In the present review, we highlight the most recent findings demonstrating that oestrogens selectively suppress the activation of the neuroinflammatory cascade in the brain in acute and chronic brain disease models. Furthermore, we aim to describe putative regulatory signalling pathways involved in the control of inflammasomes. Finally, we consider that psychiatric disorders such as depression also contain an inflammatory component that could be modulated by oestrogen.

Nuclear deterrents: Intrinsic regulators of IL-1β-induced effects on hippocampal neurogenesis

Hippocampal neurogenesis, the process by which new neurons are born and develop into the host circuitry, begins during embryonic development and persists throughout adulthood. Over the last decade considerable insights have been made into the role of hippocampal neurogenesis in cognitive function and the cellular mechanisms behind this process. Additionally, an increasing amount of evidence exists on the impact of environmental factors, such as stress and neuroinflammation on hippocampal neurogenesis and subsequent impairments in cognition. Elevated expression of the pro-inflammatory cytokine interleukin-1β (IL-1β) in the hippocampus is established as a significant contributor to the neuronal demise evident in many neurological and psychiatric disorders and is now known to negatively regulate hippocampal neurogenesis. In order to prevent the deleterious effects of IL-1β on neurogenesis it is necessary to identify signalling pathways and regulators of neurogenesis within neural progenitor cells that can interact with IL-1β. Nuclear receptors are ligand regulated transcription factors that are involved in modulating a large number of cellular processes including neurogenesis. In this review we focus on the signalling mechanisms of specific nuclear receptors involved in regulating neurogenesis (glucocorticoid receptors, peroxisome proliferator activated receptors, estrogen receptors, and nuclear receptor subfamily 2 group E member 1 (NR2E1 or TLX)). We propose that these nuclear receptors could be targeted to inhibit neuroinflammatory signalling pathways associated with IL-1β. We discuss their potential to be therapeutic targets for neuroinflammatory disorders affecting hippocampal neurogenesis and associated cognitive function.

Enhanced delivery of daidzein into fibroblasts and neuronal cells with cationic derivatives of gamma-cyclodextrin for the control of cellular glycosaminoglycans

Two cationic derivatives of γ-cyclodextrin (GCD) were synthesized by functionalization with glycidyltrimethylammonium chloride (GTMAC) and ethylenediamine (EDA). Both these derivatives (GCD-GTMAC and GCD-EDA) have been shown to interact strongly with anionic biopolymers, unfractionated heparin (UFH) and mucin, the latter showing their mucoadhesive properties. They form inclusion complexes with daidzein (DAI), an isoflavone displaying a multitude of physiological effects, much more efficiently than the unmodified GCD. It was also shown that the complexes of these GCD derivatives with DAI and Nile Red penetrate human fibroblasts and murine hippocampal neuronal cells indicating that cationic GCD derivatives can be considered as potential delivery systems for isoflavones and other poorly water soluble compounds. Moreover, it was found that DAI delivered in cationic GCD complexes decreased the level of the cellular glycosaminoglycans (GAGs) in normal fibroblasts suggesting their possible application in the control of GAGs in mucopolysaccharidoses, lysosomal storage diseases caused by pathological accumulation of GAGs in the cells.

Melatonin and oestrogen treatments were able to improve neuroinflammation and apoptotic processes in dentate gyrus of old ovariectomized female rats

The aim of this study was to determine the outcomes of oestrogen and melatonin treatments following long-term ovarian hormone depletion on neuroinflammation and apoptotic processes in dentate gyrus of hippocampi. Forty-six female Wistar rats of 22 months of age were used. Twelve of them remained intact, and the other 34 were ovariectomized at 12 months of age. Ovariectomized animals were divided into three groups and treated for 10 weeks with oestrogens, melatonin or saline. All rats were killed by decapitation at 24 months of age, and dentate gyri were collected. A group of 2 month-old intact female rats was used as young control. The levels of pro-inflammatory cytokines and heat shock protein 70 (HSP 70) were analysed by ELISA. The expressions of TNFα, IL1β, GFAP, nNOS, iNOS, HO-1, NFκB, Bax, Bad, AIF, Bcl2 and SIRT1 genes were detected by real-time (RT)-PCR. Western blots were used to measure the protein expression of NFκB p65, NFκB p50/105, IκBα, IκBβ, p38 MAPK, MAP-2 and synapsin I. We have assessed the ability of 17β-oestradiol and melatonin administration to downregulate markers of neuroinflammation in the dentate gyrus of ovariectomized female rats. Results indicated that 17β-oestradiol and melatonin treatments were able to significantly decrease expression of pro-inflammatory cytokines, iNOS and HO-1 in the hippocampus when compared to non-treated animals. A similar age- and long-term ovarian hormone depletion- related increase in GFAP was also attenuated after both melatonin and oestradiol treatments. In a similar way to oestradiol, melatonin decreased the activation of p38 MAPK and NFκB pathways. The treatments enhanced the levels of synaptic molecules synapsin I and MAP-2 and have been shown to modulate the pro-antiapoptotic ratio favouring the second and to increase SIRT1 expression. These findings support the potential therapeutic role of melatonin and oestradiol as protective anti-inflammatory agents for the central nervous system during menopause.

Spongionella secondary metabolites protect mitochondrial function in cortical neurons against oxidative stress

The marine habitat provides a large number of structurally-diverse bioactive compounds for drug development. Marine sponges have been studied over many years and are found to be a rich source of these bioactive chemicals. This study is focused on the evaluation of the activity of six diterpene derivatives isolated from Spongionella sp. on mitochondrial function using an oxidative in vitro stress model. The test compounds include the Gracilins (A, H, K, J and L) and tetrahydroaplysulphurin-1. Compounds were co-incubated with hydrogen peroxide for 12 hours to determine their protective capacities and their effect on markers of apoptosis and Nrf2/ARE pathways was evaluated. Results conclude that Gracilins preserve neurons against oxidative damage, and that in particular, tetrahydroaplysulphurin-1 shows a complete neuroprotective activity. Oxidative stress is linked to mitochondrial dysfunction and consequently to neurodegenerative disorders like Parkinson and Alzheimer diseases, Friedreich ataxia or Amyotrophic lateral sclerosis. This neuroprotection against oxidation conditions suggest that these metabolites could be interesting lead candidates in drug development for neurodegenerative diseases.

Mitigation of ROS insults by Streptomyces secondary metabolites in primary cortical neurons

Oxidative stress is a common point in neurodegenerative diseases, widely connected with mitochondrial dysfunction. In this study, we screened seven natural products from Streptomyces sources against hydrogen peroxide insult in primary cortical neurons, an oxidative stress in vitro model. We showed the ability of these compounds to inhibit neuronal cytotoxicity and to reduce ROS release after 12 h treatment. Among the tested compounds, the quinone anhydroexfoliamycin and the red pyrrole-type pigment undecylprodigiosin stand out. These two compounds displayed the most complete protection against oxidative stress with mitochondrial function improvement, ROS production inhibition, and increase of antioxidant enzyme levels, glutathione and catalase. Further investigations confirmed that anhydroexfoliamycin acts over the Nrf2-ARE pathway, as a Nrf2 nuclear translocation inductor, and is able to strongly inhibit the effect of the mitochondrial uncoupler FCCP over cytosolic Ca(2+), pointing to mitochondria as a cellular target for this molecule. In addition, both compounds were able to reduce caspase-3 activity induced by the apoptotic enhancer staurosporine, but undecylprodigiosin failed to inhibit FCCP effects and it did not act over the Nrf2 pathway as was the case for anhydroexfoliamycin. These results show that Streptomyces metabolites could be useful for the development of new drugs for prevention of neurodegenerative disorders such as Parkinson's and Alzheimer's diseases and cerebral ischemia.

Sex steroid hormone-mediated functional regulation of microglia-like BV-2 cells during hypoxia

17β-estradiol (E2) and progesterone (P) are neuroprotective hormones in different neurological disorders and in particular under hypoxic conditions in the brain. Both hormones dampen brain-intrinsic immune responses and regulate local glial cell function. Besides astrocytes which are functionally regulated in a manifold and complex manner, especially microglial cells are in the focus of steroid-mediated neuroprotection. In previous studies using a transient brain artery occlusion model, we demonstrated that microglial characteristics are critically modified after the administration of either E2 or P. We here studied the influence of sex steroids on the murine BV-2 microglia cell line under hypoxic conditions. Hypoxia changed the cell morphology from an amoeboid-like phenotype with processes to a rounded shape of secreting cell type. BV-2 cells expressed both estrogen receptor-β and progesterone receptors under each condition. Oxygen deprivation increased the expression of inducible nitric oxide synthetase (iNOS) and up-regulated selected cytokines and chemokines. Both hormones selectively prevented the induction of pro-inflammatory iNOS, interleukin IL-1ß, and chemokine ligand CCL5, whereas anti-inflammatory IL-10 and protective TREM 2 were up-regulated by sex steroids. Sex hormones abrogated hypoxia-dependent reduction of BV-2 phagocytic activity. We demonstrate that BV-2 microglia cells respond to hypoxia by enhanced pro-inflammatory cytokine secretion and reduced phagocytic activity. This effect is prevented by sex steroids resulting in a switch of BV-2 cells from a pro-inflammatory to a more anti-inflammatory phenotype. Anti-inflammatory effects of gonadal steroids might directly be mediated through hormone-microglia interactions in addition to known effects via astroglial regulation.

Female gender remains an independent risk factor for poor outcome after acute nontraumatic intracerebral hemorrhage

Objective. To study whether gender influences outcome after intracerebral hemorrhage (ICH). Methods. Cohort study of 245 consecutive adults presenting to the emergency department with spontaneous ICH from January 2006 to December 2008. Patients with subarachnoid hemorrhage, extradural hemorrhage, and recurrence of hemorrhage were excluded. Results. There were no differences noted between genders in stroke severity (NIHSS) at presentation, ICH volume, or intraventricular extension (IVE) of hemorrhage. Despite this, females had 1.94 times higher odds of having a bad outcome (modified Rankin score (mRs) ≥3) as compared to males (95% CI 1.12 to 3.3) and 1.84 times higher odds of early mortality (95% CI 1.02–3.33). analyzing known variables influencing mortality in ICH, the authors found that females did have higher serum glucose levels on arrival (P = 0.0096) and 4.2 times higher odds for a cerebellar involvement than males (95% CI 1.63–10.75). After adjusting for age, NIHSS, glucose levels, hemorrhage volume, and IVE, female gender remained an independent predictor of early mortality (P = 0.0127). Conclusions. Female gender may be an independent predictor of early mortality in ICH patients, even after adjustment for stroke severity, hemorrhage volume, IVE, serum glucose levels, and age.

Inhibition of PIKfyve by YM-201636 dysregulates autophagy and leads to apoptosis-independent neuronal cell death

The lipid phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P₂), synthesised by PIKfyve, regulates a number of intracellular membrane trafficking pathways. Genetic alteration of the PIKfyve complex, leading to even a mild reduction in PtdIns(3,5)P₂, results in marked neurodegeneration via an uncharacterised mechanism. In the present study we have shown that selectively inhibiting PIKfyve activity, using YM-201636, significantly reduces the survival of primary mouse hippocampal neurons in culture. YM-201636 treatment promoted vacuolation of endolysosomal membranes followed by apoptosis-independent cell death. Many vacuoles contained intravacuolar membranes and inclusions reminiscent of autolysosomes. Accordingly, YM-201636 treatment increased the level of the autophagosomal marker protein LC3-II, an effect that was potentiated by inhibition of lysosomal proteases, suggesting that alterations in autophagy could be a contributing factor to neuronal cell death.

Sexual dimorphism on cytokines expression in the temporomandibular joint: the role of gonadal steroid hormones

Temporomandibular joint pain-related conditions are generally characterized by local inflammation; however, little studies have focused on the role of gonadal hormones in the expression of inflammatory mediators, such as cytokines. Therefore, we asked whether gonadal steroid hormones affect formalin-induced cytokines expression in the rat temporomcandibular joint. The expression of tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and cytokine-induced neutrophil chemoattractant (CINC)-1 was significantly higher in males than in diestrus and proestrus females and was decreased by orchiectomy and restored by testosterone replacement. The expression of IL-6 was significantly higher in diestrus and proestrus females than in males, and was decreased by ovariectomy and restored by estradiol or progesterone administration. We conclude that testosterone increases the expression of TNF-α, IL-1β and CINC-1, and estradiol and progesterone increase the expression of IL-6. New clinical approaches based on inhibition of pro-inflammatory mediators are starting to supplant traditional immunosuppressive therapies and gonadal hormones may influence their effectiveness or clinical dosage.

Sex steroids control neuroinflammatory processes in the brain: relevance for acute ischaemia and degenerative demyelination

Sex steroids have been demonstrated as powerful compounds to protect neurones and neural tissue from neurotoxic challenges and during neurodegeneration. A multitude of cellular actions have been attributed to female gonadal steroid hormones, including the regulation of pro-survival and anti-apoptotic factors, bioenergetic demands and radical elimination, growth factor allocation and counteracting against excitotoxicity. In recent years, immune-modulatory and anti-inflammatory characteristics of oestrogen and progesterone have also come under scrutiny. To date, each of these physiological responses has been considered to be partially and selectively integrated in the mediation of steroid-mediated cell protection and tested in suitable animal models and in vitro systems. To what extent these individual effects contribute to the overall neural protection remains sketchy. One idea is that a battery of cellular mechanisms operates at the same time. On the other hand, interactions and the control of the brain-intrinsic and peripheral immune system may play an additional and perhaps pioneering function in this scenario, notwithstanding the importance of secondary adjuvant mechanisms. In the present review, we highlight neuroprotective effects of oestrogen and progesterone in two different disease models of the brain, namely acute ischaemic and demyelination damage, which represent the most common acute and degenerative neurological disorders in humans. Besides other inflammatory parameters, we discuss the idea that chemokine expression and signalling appear to be early hallmarks in both diseases and are positively affected by sex steroids. In addition, the complex interplay with local brain-resident immune-competent cells appears to be controlled by the steroid environment.

ADAM12 is expressed by astrocytes during experimental demyelination

A disintegrin and metalloproteinase (ADAM) 12 represents a member of a large family of similarly structured multi-domain proteins. In the central nervous system (CNS), ADAM12 has been suggested to play a role in brain development, glioblastoma cell proliferation, and in experimental autoimmune encephalomyelitis. Furthermore, ADAM12 was reported to be almost exclusively expressed by oligodendrocytes and could, therefore, be considered as suitable marker for this cell type. In the present study, we investigated ADAM12 expression in the healthy and pathologically altered murine CNS. As pathological paradigm, we used the cuprizone demyelination model in which myelin loss during multiple sclerosis is imitated. Besides APC(+) oligodendrocytes, SMI311(+) neurons and GFAP(+) astrocytes express ADAM12 in the adult mouse brain. ADAM12 expression was further analyzed in vitro. After the induction of demyelination, we observed that activated astrocytes are the main source of ADAM12 in brain regions affected by oligodendrocyte loss. Exposure of astrocytes in vitro to either lipopolysaccharides (LPS), tumor necrosis factor alpha (TNFalpha), glutamate, or hydrogen peroxide revealed a highly stimulus-specific regulation of ADAM12 expression which was not seen in microglial BV2 cells. It appears that LPS- and TNFalpha-induced ADAM12 expression is mediated via the classic NFkappaB pathway. In summary, we demonstrated that ADAM12 is not a suitable marker for oligodendrocytes. Our results further suggest that ADAM12 might be implicated in the course of distinct CNS diseases such as demyelinating disorders.

Combined 17beta-oestradiol and progesterone treatment prevents neuronal cell injury in cortical but not midbrain neurones or neuroblastoma cells

Oestrogens are powerful endogenous and exogenous neuroprotective hormones in animal models of brain injury, including focal cerebral ischaemia. This protective effect has been demonstrated under a variety of different treatments and injury paradigms, such as in vivo and in vitro stroke conditions. Neuroprotection in the central nervous system by progesterone is less defined. In the present study, cultured cortical and midbrain mouse neurones and human neuroblastoma cells (SH-SY5Y) were exposed to combined glucose-serum deprivation (CGSD), which is regarded as a reliable model mimicking the effects of ischaemia in vitro. Cell viability was assayed using lactate dehydrogenase release and metabolic activity. Conditions for CGSD treatment were chosen to yield half-maximal cell death rates. The validity of CGSD in vitro was compared with permanent middle cerebral artery occlusion (MCAO) in vivo. CGSD for 4 h induced half-maximal neuronal cell death. MCAO in vivo for the same period resulted in significant neuronal loss, also suggesting the validity of CGSD as a suitable stroke-like in vitro model. Combined steroid treatment (17beta-oestradiol and progesterone) but not the application of single steroids abolished CGSD-induced cell death of cortical neurones in vitro. By contrast, no cell protection was found in midbrain neurones or neuroblastoma cells. The co-application of oestrogen (ICI 182,780) or progesterone (RU-486) receptor antagonists did not obviously counteract the protective steroid effects. This suggests the operation of nonclassical steroid mechanisms and their implication in mediation of hormonal effects. The surplus of combined protective hormonal effects might be a result of the observed influence of progesterone application on neuronal oestradiol synthesis. The data obtained in the present study clearly highlight the potential of a combined steroid treatment under toxic degenerative brain pathologies.

17beta-estradiol and progesterone prevent cuprizone provoked demyelination of corpus callosum in male mice

Sex hormones, for example, estrogen and progesterone, are thought to affect and delay progression of multiple sclerosis (MS) in pregnant women. Although both steroid hormones are neuroprotective in the brain and elevated during pregnancy, only estrogen was tested in clinical trials. To evaluate the role of 17beta-estradiol (E) and progesterone (P) in prevention demyelination, young adult male mice were fed with cuprizone for a defined time interval and simultaneously treated with steroids by repeated injections into the neck region. The status of myelination was analyzed by magnetic resonance imaging and conventional histological staining. The individual application of E and P resulted only in a moderate prevention of demyelination in the corpus callosum (CC). The combined treatment with both steroid hormones counteracted the process of demyelination. Expression of the mature (PLP and MBP) and premature (PDGF-alpha-R) oligodendrocyte markers were significantly increased after hormone application in the affected CC. In addition, both hormones stimulated astrogliosis and the expression of IGF-1. Microglial invasion in demyelinated CC was pronounced and additionally localized in the midline of CC after hormone treatment. These data show that sex steroids can protect the brain from demyelination and stimulate remyelination. It appears that only the administration of both hormones is fully effective. The beneficial steroid effect requires interactions with oligodendrocytes possibly by preventing their degeneration or recruitment from precursor cells which are stimulated to remyelinated fibers. The positive hormonal influence on myelination in the CNS may be a future therapeutically strategy for the treatment of MS.

Impact of sex steroids on neuroinflammatory processes and experimental multiple sclerosis

Synthetic and natural estrogens as well as progestins modulate neuronal development and activity. Neurons and glia are endowed with high-affinity steroid receptors. Besides regulating brain physiology, both steroids conciliate neuroprotection against toxicity and neurodegeneration. The majority of data derive from in vitro studies, although more recently, animal models have proven the efficaciousness of steroids as neuroprotective factors. Indications for a safeguarding role also emerge from first clinical trials. Gender-specific prevalence of degenerative disorders might be associated with the loss of hormonal activity or steroid malfunctions. Our studies and evidence from the literature support the view that steroids attenuate neuroinflammation by reducing the pro-inflammatory property of astrocytes. This effect appears variable depending on the brain region and toxic condition. Both hormones can individually mediate protection, but they are more effective in cooperation. A second research line, using an animal model for multiple sclerosis, provides evidence that steroids achieve remyelination after demyelination. The underlying cellular mechanisms involve interactions with astroglia, insulin-like growth factor-1 responses, and the recruitment of oligodendrocytes.

Selective regulation of growth factor expression in cultured cortical astrocytes by neuro-pathological toxins

Astrocytes are integrated in the complex regulation of neurodegeneration and neuronal damage in the CNS. It is well-known that astroglia produces a plethora of growth factors which might be protective for neurons. Growth factors prevent neurons from cell death and promote proliferation and differentiation of precursor cells. Previous data suggest that astrocytes may respond to toxic stimuli by a selective mobilization of guarding molecules. In the present study, we have investigated the potency of different pathological stimuli such as lipopolysaccharides, tumor necrosis factor alpha, glutamate, and hydrogen peroxide to activate cultured cortical astroglia and stimulate growth factor expression. Astroglial cultures were exposed to the above factors for 24h at non-toxic concentrations for astrocytes. Growth factor expression was analyzed by real-time PCR, oligo-microarray technique, and ELISA. Insulin-like growth factor-1 was selectively down-regulated by lipopolysaccharides and tumor necrosis factor alpha, bone morphogenetic protein 6 by all stimuli. In contrast, lipopolysaccharides, tumor necrosis factor alpha, and glutamate increased leukemia inhibitory factor. Fibroblast growth factor 2 was up-regulated by lipopolysaccharides and tumor necrosis factor alpha and down-regulated by hydrogen peroxide. Besides hydrogen peroxide, all other stimuli promoted vascular epithelial growth factor A mRNA and protein expression. It appears that lipopolysaccharides but not tumor necrosis factor alpha effects on vascular epithelial growth factor A depend on the classic NFkappaB pathway. Our data clearly demonstrate that astroglia actively responses to diverse pathological compounds by a selective expression pattern of growth factors. These findings make astrocytes likely candidates to participate in disease-specific characteristics of neuronal support or damage.

Functional alterations of the nigrostriatal dopamine system in estrogen receptor-alpha knockout (ERKO) mice

Estrogen represents an important factor for the development and function of the nigrostriatal dopamine system. Estrogen also controls sex-specific differentiation and activity of the nigrostriatal dopaminergic system. We used an estrogen receptor-alpha knockout (-/-) model (ERKO) to study the influence of this particular receptor subtype on the regulation of functional characteristics of the male and female nigrostriatal dopamine system. On the striatal level, we found a sex-specific regulation of dopamine D1 receptors (D1) and dopamine receptor-interacting protein 78 (Drip78). In female (-/-) mice D1 receptor expression levels were increased compared to wild type (wt) animals, whereas in male (-/-) mice Drip78 mRNA levels were decreased compared to wt. In the midbrain, expression of tyrosine hydroxylase (TH) and brain-derived neurotrophic factor (BDNF) was reduced in (-/-) mice of both sexes. Glial cell line-derived neurotrophic factor (GDNF) expression was not affected. These data demonstrate that the integrity of estrogen receptor-alpha (ERalpha) signalling is necessary for the regulation of gene expression of proteins known to be important for the function of the nigrostriatal system at the postsynaptic striatal and presynaptic midbrain level.

Oestrogen and progesterone reduce lipopolysaccharide-induced expression of tumour necrosis factor-alpha and interleukin-18 in midbrain astrocytes

Besides microglia, astrocytes exert an important regulatory function in the initiation and control of neuro-inflammatory processes in the central nervous system. Clinical and experimental data suggest that sex steroids are neuroprotective and that neurological/neurodegenerative disorders display sex-specific characteristics. Astroglia is known to respond to toxic stimuli by secretion of distinct pro-inflammatory/apoptotic cytokines. In the present study, we investigated the influence of oestrogen and progesterone on the expression of the cytokines tumour necrosis factor (TNF)-alpha and interleukin (IL)-18 in primary astrocytes obtained from neonatal mouse midbrain and cerebral cortex after the stimulation with lipopolysaccharides (LPS). LPS strongly induced the expression of TNF-alpha in astrocytes from both brain regions and IL-18 in those from midbrain. Oestrogen significantly attenuated LPS-induced TNF-alpha expression in the midbrain glia but not in the cortex glia. Combined treatment with oestrogen and progesterone together diminished LPS-induced IL-18 expression in the midbrain completely. Both steroid effects could be specifically antagonised by the steroid hormone receptor antagonists ICI 182 780 and mifepristone. We conclude that neuroprotective oestrogen and progesterone effects in the midbrain might be in part the consequence of a reduced pro-inflammatory response of astroglia.

Estradiol attenuates hyperoxia-induced cell death in the developing white matter

OBJECTIVE

Periventricular leukomalacia is the predominant type of brain injury in preterm infants underlying the development of cerebral palsy. Periventricular leukomalacia has its peak incidence at 23 to 32 weeks postconceptional age characterized by extensive oligodendrocyte migration and maturation. Oxygen toxicity has been identified as a possible contributing factor to the pathogenesis of cerebral palsy in survivors of preterm birth. 17beta-estradiol (E2) is important for the development and function of the central nervous system. Furthermore, neuroprotective properties have been attributed to estrogens. We examined the effect of E2 on hyperoxia-induced cell death in the developing white matter in the rat brain.

METHODS

Six-day-old (P6) rat pups, the immature oligodendroglial cell line (OLN-93), and primary oligodendrocyte cultures were subjected to 80% O(2) in the presence or absence of E2 (600 microg/kg intraperitoneally in vivo, 10(-6)-10(-10)M in vitro). Cell counts and lactate dehydrogenase assay were used to assess cell survival. Immunoblot analysis was used for detection of estrogen receptor expression and investigation of apoptotic signaling pathways. White matter injury was assessed by myelin basic protein immunocytochemistry at P11.

RESULTS

E2 produced significant dose-dependent protection against oxygen-induced apoptotic cell death in primary oligodendrocytes. Treatment with E2 prevented hyperoxia-induced proapoptotic Fas-upregulation and caspase-3 activation. Finally, E2 antagonized hyperoxia-induced inactivation of extracellular signal-regulated kinase 1 and 2 and Akt, key kinases of the mitogen-activated protein kinase and phosphatidylinositol 3-kinase cell survival promoting pathways, respectively. Loss of myelin basic protein labeling was seen in P11 pups after oxygen exposure, and E2 attenuated this injury.

INTERPRETATION

These results suggest a possible role for estrogens in the prevention of neonatal oxygen-induced white matter injury.

Evidence to Implicate Early Modulation of Interleukin‐1β Expression in the Neuroprotection Afforded by 17β‐Estradiol in Male Rats Undergone Transient Middle Cerebral Artery Occlusion

Neuroprotection exerted by 17beta-estradiol (17beta-E(2)) has been widely investigated in animal models of acute cerebral ischemia. Estrogens interact with intracellular receptors (ERalpha and ERbeta) to modulate the transcription of target genes, including those implicated in neuronal survival. Neuroprotection may also occur via interaction with ER-like membrane receptors mediating rapid, non-genomic, actions or via receptor-independent mechanisms. There is also evidence that blockade of inflammatory factors may represent an important mechanism involved in estrogenic neuroprotection. Here we investigate whether reduced brain damage by acute pharmacological treatment with 17beta-E(2) in male rats subjected to transient (2h) middle cerebral artery occlusion (tMCAo) involves modulation of interleukin-1beta (IL-1beta), a proinflammatory cytokine strongly implicated in the pathophysiology of ischemic stroke. Administration of 17beta-E(2) (0.2mg/kg, i.p., 1h before tMCAo) results in significant reduction of brain infarct volume, and this is reverted by the ER antagonist ICI 182,780 (0.25mg/kg, i.p.) administered 1h before 17beta-E(2). Two hours MCAo followed by 2-h reperfusion results in a significant, threefold increase of IL-1beta levels in the cortical tissue ipsilateral to the ischemic damage. Interestingly, a pretreatment with a neuroprotective dose of 17beta-E(2) attenuates the cytokine elevation and this appears to occur through ER activation. In addition, neuroprotection by 17beta-E(2) is accompanied by reduced cytochrome c translocation both in the striatum and in the cortex as revealed by Western blotting 3h after reperfusion. In conclusion, we report the original observation that neuroprotection exerted by 17beta-E(2) in a rat model of transient focal brain ischemia is accompanied by reduced cytochrome c translocation to the cytosol and involves early modulation of IL-1beta production.