17beta-estradiol and enriched environment accelerate cognitive recovery after focal brain ischemia

Strategies for Treatment of Disease-Associated Dementia Beyond Alzheimer's Disease: An Update

Memory, cognition, dementia, and neurodegeneration are complexly interlinked processes with various mechanistic pathways, leading to a range of clinical outcomes. They are strongly associated with pathological conditions like Alzheimer's disease, Parkinson's disease, schizophrenia, and stroke and are a growing concern for their timely diagnosis and management. Several cognitionenhancing interventions for management include non-pharmacological interventions like diet, exercise, and physical activity, while pharmacological interventions include medicinal agents, herbal agents, and nutritional supplements. This review critically analyzed and discussed the currently available agents under different drug development phases designed to target the molecular targets, including cholinergic receptor, glutamatergic system, GABAergic targets, glycine site, serotonergic targets, histamine receptors, etc. Understanding memory formation and pathways involved therein aids in opening the new gateways to treating cognitive disorders. However, clinical studies suggest that there is still a dearth of knowledge about the pathological mechanism involved in neurological conditions, making the dropouts of agents from the initial phases of the clinical trial. Hence, a better understanding of the disease biology, mode of drug action, and interlinked mechanistic pathways at a molecular level is required.

Environmental enrichment combined with fasudil treatment inhibits neuronal death in the hippocampal CA1 region and ameliorates memory deficits

Currently, no specific treatment exists to promote recovery from cognitive impairment after a stroke. Dysfunction of the actin cytoskeleton correlates well with poststroke cognitive declines, and its reorganization requires proper regulation of Rho-associated kinase (ROCK) proteins. Fasudil downregulates ROCK activation and protects neurons against cytoskeleton collapse in the acute phase after stroke. An enriched environment can reduce poststroke cognitive impairment. However, the efficacy of environmental enrichment combined with fasudil treatment remains poorly understood. A photothrombotic stroke model was established in 6-week-old male C57BL/6 mice. Twenty-four hours after modeling, these animals were intraperitoneally administered fasudil (10 mg/kg) once daily for 14 successive days and/or provided with environmental enrichment for 21 successive days. After exposure to environmental enrichment combined with fasudil treatment, the number of neurons in the hippocampal CA1 region increased significantly, the expression and proportion of p-cofilin in the hippocampus decreased, and the distribution of F-actin in the hippocampal CA1 region increased significantly. Furthermore, the performance of mouse stroke models in the tail suspension test and step-through passive avoidance test improved significantly. These findings suggest that environmental enrichment combined with fasudil treatment can ameliorate memory dysfunction through inhibition of the hippocampal ROCK/cofilin pathway, alteration of the dynamic distribution of F-actin, and inhibition of neuronal death in the hippocampal CA1 region. The efficacy of environmental enrichment combined with fasudil treatment was superior to that of fasudil treatment alone. This study was approved by the Animal Ethics Committee of Fudan University of China (approval No. 2019-Huashan Hospital JS-139) on February 20, 2019.

MRI Evaluation of Axonal Remodeling After Combination Treatment With Xiaoshuan Enteric-Coated Capsule and Enriched Environment in Rats After Ischemic Stroke

Xiaoshuan enteric-coated capsule (XSEC) is a compound Chinese medicine widely used for the treatment of ischemic stroke. Enriched environment (EE) is a rehabilitative intervention designed to facilitate physical, cognitive, and social activity after brain injury. This study aimed to assess whether the XSEC and EE combination could provide synergistic efficacy in axonal remodeling compared to that with a single treatment after ischemic stroke using magnetic resonance imaging (MRI) followed by histological analysis. Rats were subjected to permanent middle cerebral artery occlusion and treated with XSEC and EE alone or in combination for 30 days. T2-weighted imaging and diffusion tensor imaging (DTI) were performed to examine the infarct volume and axonal remodeling, respectively. The co-localization of Ki67 with NG2 or CNPase was examined by immunofluorescence staining to assess oligodendrogenesis. The expressions of growth associated protein-43 (GAP-43) and growth inhibitors NogoA/Nogo receptor (NgR)/RhoA/Rho-associated kinase2 (ROCK2) were measured using western blot and qRT-PCR. The Morris water maze (MWM) was performed to evaluate the cognitive function. MRI and histological measurements indicated XSEC and EE individually benefited axonal reorganization after stroke. Notably, XSEC + EE decreased infarct volume compared with XSEC or EE monotherapy and increased ipsilateral residual volume compared with vehicle group. DTI showed XSEC + EE robustly increased fractional anisotropy while decreased axial diffusivity and radial diffusivity in the injured cortex, striatum, and external capsule. Meanwhile, diffusion tensor tractography revealed XSEC + EE elevated fiber density in the cortex and external capsule and increased fiber length in the striatum and external capsule compared with the monotherapies. These MRI measurements, confirmed by histology, showed that XSEC + EE promoted axonal restoration. Additionally, XSEC + EE amplified oligodendrogenesis, decreased the expressions of NogoA/NgR/RhoA/ROCK2, and increased the expression of GAP-43 in the peri-infarct tissues. In parallel to these findings, rats treated with XSEC + EE exhibited higher cognitive recovery than those treated with XSEC or EE monotherapy, as evidenced by MWM test. Taken together, our data implicated that XSEC + EE exerted synergistic effects on alleviating atrophy and encouraging axonal reorganization partially by promoting oligodendrogenesis and overcoming intrinsic growth-inhibitory signaling, thereby facilitating higher cognitive recovery.

Tissue Injury and Astrocytic Reaction, But Not Cognitive Deficits, Are Dependent on Hypoxia Duration in Very Immature Rats Undergoing Neonatal Hypoxia-Ischemia

Preterm birth and hypoxia-ischemia (HI) are major causes of neonatal death and neurological disabilities in newborns. The widely used preclinical HI model combines carotid occlusion with hypoxia exposure; however, the relationship between different hypoxia exposure periods with brain tissue loss, astrocyte reactivity and behavioral impairments following HI is lacking. Present study evaluated HI-induced behavioral and morphological consequences in rats exposed to different periods of hypoxia at postnatal day 3. Wistar rats of both sexes were assigned into four groups: control group, HI-120 min, HI-180 min and HI-210 min. Neurodevelopmental reflexes, exploratory abilities and cognitive function were assessed. At adulthood, tissue damage and reactive astrogliosis were measured. Animals exposed to HI-180 and HI-210 min had delayed neurodevelopmental reflexes compared to control group. Histological assessment showed tissue loss that was restricted to the ipsilateral hemisphere in lower periods of hypoxia exposure (120 and 180 min) but affected both hemispheres when 210 min was used. Reactive astrogliosis was increased only after 210 min of hypoxia. Interestingly, cognitive deficits were induced regardless the duration of hypoxia and there were correlations between behavioral parameters and cortex, hippocampus and corpus callosum volumes. These results show the duration of hypoxia has a close relationship with astrocytic response and tissue damage progression. Furthermore, the long-lasting cognitive memory deficit and its association with brain structures beyond the hippocampus suggests that complex anatomical changes should be involved in functional alterations taking place as hypoxia duration is increased, even when the cognitive impairment limit is achieved.

Neuroprotective effects of therapeutic hypercapnia on spatial memory and sensorimotor impairment via anti-apoptotic mechanisms after focal cerebral ischemia/reperfusion

A number of studies have demonstrated that therapeutic hypercapnia ameliorates neurological deficits and attenuates the histological damage of cerebral ischemia-reperfusion injury. However, the effects of therapeutic hypercapnia on impaired spatial memory have not been reported. Here we aimed to investigate the effects and mechanisms of therapeutic hypercapnia on spatial memory in a rat model of focal cerebral ischemia induced by middle cerebral artery occlusion/reperfusion (MCAO/R). Adult male rats were randomly assigned into three experimental groups: sham (sham operation), IR (MCAO/R), and hypercapnia [arterial blood CO2 tension (PaCO2) 80-100 mmHg+IR] groups. Sensorimotor deficits and spatial memory testing were evaluated by an 18-point scoring system and an 8-arm radial maze task, respectively. The hippocampal histological damage and the percentage of apoptotic neurons were evaluated by hematoxylin and eosin (HE) staining as well as flow cytometry. Western blotting was used to investigate the changes of the apoptosis-related Bcl-2 and Bax proteins. The results indicated that hypercapnia treatment significantly improved the abilities of impaired sensorimotor and spatial memory after MCAO/R. Moreover, hypercapnia treatment significantly increased the percentage of surviving neurons and decreased the percentage of apoptotic neurons in the hippocampus after MCAO/R damage. The expressions of anti-apoptotic protein Bcl-2 and pro-apoptotic protein Bax were significantly increased and decreased in the hypercapnia treated rats, respectively. These findings suggest that therapeutic hypercapnia can attenuate neuronal apoptosis and improve impaired spatial memory and sensorimotor after MCAO/R, which may be attributable to its anti-apoptotic effects through modulation of apoptosis-related protein.

Structural changes induced by daily music listening in the recovering brain after middle cerebral artery stroke: a voxel-based morphometry study

Music is a highly complex and versatile stimulus for the brain that engages many temporal, frontal, parietal, cerebellar, and subcortical areas involved in auditory, cognitive, emotional, and motor processing. Regular musical activities have been shown to effectively enhance the structure and function of many brain areas, making music a potential tool also in neurological rehabilitation. In our previous randomized controlled study, we found that listening to music on a daily basis can improve cognitive recovery and improve mood after an acute middle cerebral artery stroke. Extending this study, a voxel-based morphometry (VBM) analysis utilizing cost function masking was performed on the acute and 6-month post-stroke stage structural magnetic resonance imaging data of the patients (n = 49) who either listened to their favorite music [music group (MG), n = 16] or verbal material [audio book group (ABG), n = 18] or did not receive any listening material [control group (CG), n = 15] during the 6-month recovery period. Although all groups showed significant gray matter volume (GMV) increases from the acute to the 6-month stage, there was a specific network of frontal areas [left and right superior frontal gyrus (SFG), right medial SFG] and limbic areas [left ventral/subgenual anterior cingulate cortex (SACC) and right ventral striatum (VS)] in patients with left hemisphere damage in which the GMV increases were larger in the MG than in the ABG and in the CG. Moreover, the GM reorganization in the frontal areas correlated with enhanced recovery of verbal memory, focused attention, and language skills, whereas the GM reorganization in the SACC correlated with reduced negative mood. This study adds on previous results, showing that music listening after stroke not only enhances behavioral recovery, but also induces fine-grained neuroanatomical changes in the recovering brain.

Long-term and spatial memory effects of selective β1-antagonists after transient focal ischaemia in rats

BACKGROUND

Although various reports have shown that β-antagonists provide neuroprotective effects after cerebral ischaemia, their effect on spatial memory after transient focal ischaemia is not known. We investigated the treatment of β1-antagonists on neurological outcome spatial memory for 1 month after focal cerebral ischaemia in rats.

METHODS

Male rats randomly received an i.v. infusion of saline 0.5 ml h(-1), esmolol 200 μg kg(-1) min(-1), or landiolol 50 μg kg(-1) min(-1). Infusion was initiated 30 min before middle cerebral artery occlusion and continued for 24 h. The infarct areas in the hippocampus and striatum were measured after the final retention trial and neurological examinations.

RESULTS

Neurological deficit scores in the landiolol- and esmolol-treated rats were significantly lower than in the control rats at 1, 4, 7, and 11 days after ischaemia (P<0.05). Using the Morris water maze to assess spatial memory, we found that escape latency and swimming path length to the platform were significantly shorter in the landiolol-treated rats, compared with the saline-treated rats at 4 and 11 days after ischaemia (P<0.05). The mean (SD) infarct area was 19.1 (8.0)% in the striatum and 18.6 (10.0)% in the hippocampus of the landiolol-treated rats, and 16.8 (14.0)% and 16.8 (15.0)% in the striatum and hippocampus, respectively, of esmolol-treated rats. This was significantly less than in control rats [striatum 31.7 (14.0)% and hippocampus 29.8 (13.0)%, P<0.05].

CONCLUSIONS

The current study indicates that although esmolol and landiolol provided long-term neuroprotection in terms of histological outcome, they had no effect on neurological outcome and spatial memory retention.

Enriched environment prevents hypobaric hypoxia induced neurodegeneration and is independent of antioxidant signaling

Hypobaric hypoxia (HH) induced neurodegeneration has been attributed to several factors including increased oxidative stress, glutamate excitotoxicity, decreased growth factors, apoptosis, etc. Though enriched environment (EE) has been known to have beneficial effects in various neurological disorders, its effect on HH mediated neurodegeneration remains to be studied. Therefore, the present study was conducted to explore the effect of EE on HH induced neurodegeneration. Male Sprague-Dawley rats were placed in enriched and standard conditions during exposure to HH (7 days) equivalent to an altitude of 25,000 ft. The effect of EE on oxidative stress markers, apoptosis, and corticosterone level in hippocampus was investigated. EE during exposure to HH was found to decrease neurodegeneration as evident from decreased caspase 3 expression and LDH leakage. However, no significant changes were observed in ROS, MDA, and antioxidant status of hippocampus. HH elevates corticosterone level and affected the diurnal corticoid rhythm which may contribute to neurodegeneration, whereas EE ameliorate this effect. Because of the association of neurotrophins and stress and/or corticosterone the BDNF and NGF levels were also examined and it was found that HH decreases their level but concurrent exposure to EE maintains their level. Moreover, inhibition of Tyrosine kinase receptor (Trk) with K252a nullifies the protective effect of EE, whereas Trk activation with agonist, amitriptyline showed protective effect similar to EE. Taken together, we conclude that EE has a potential to ameliorate HH mediated neuronal degeneration which may act through antioxidant independent pathway by modulation of neurotrophins.

Nano-zinc oxide damages spatial cognition capability via over-enhanced long-term potentiation in hippocampus of Wistar rats

This study focused on the effects of zinc oxide nanoparticles (nano-ZnO) on spatial learning and memory and synaptic plasticity in the hippocampus of young rats, and tried to interpret the underlying mechanism. Rats were randomly divided into four groups. Nano-ZnO and phosphate-buffered saline were administered in 4-week-old rats for 8 weeks. Subsequently, performance in Morris water maze (MWM) was determined, and then long-term potentiation (LTP) and depotentiation were measured in the perforant pathway to dentate gyrus (DG) in anesthetized rats. The data showed that, (1) in MWM, the escape latency was prolonged in the nano-ZnO group and, (2) LTP was significantly enhanced in the nano-ZnO group, while depotentiation was barely influenced in the DG region of the nano-ZnO group. This bidirectional effect on long-term synaptic plasticity broke the balance between stability and flexibility of cognition. The spatial learning and memory ability was attenuated by the alteration of synaptic plasticity in nano-ZnO-treated rats.

Gonadal steroids prevent cell damage and stimulate behavioral recovery after transient middle cerebral artery occlusion in male and female rats

17β-estradiol (E) and progesterone (P) are neuroprotective factors in the brain preventing neuronal death under different injury paradigms. Our previous work demonstrates that both steroids compensate neuronal damage and activate distinct neuroprotective strategies such as improving local energy metabolism and abating pro-inflammatory responses. The current study explored steroid hormone-mediated protection from brain damage and restoration of behavioral function after 1h transient middle cerebral artery occlusion (tMCAO). Male and ovariectomized female rats were studied 24h after stroke. Both steroid hormones reduced the cortical infarct area in males and females to a similar extent. A maximum effect of ~60-70% reduction of the infarct size was evident after P and a combined treatment with both hormones. No infarct protection was seen in the basal ganglia. Testing of motor and sensory behavioral revealed an equal high degree of functional recovery in all three hormone groups. Gene expression studies in the delineated penumbra revealed that estrogen receptor (ER) alpha and beta are locally up-regulated. tMCAO-mediated induction of the pro-inflammatory chemokines CCL2, CCL5 and interleukin 6 was attenuated by E and P, whereas the expression of vascular endothelial growth factor (VEGF) was fortified. Local expression of microglia/macrophage/lymphocyte markers, i.e. Iba1, CD68 and CD3, were significantly reduced in the penumbra after hormone treatment suggesting attenuation of microglia and lymphocyte attraction. These results demonstrate the neuroprotective potency of a combined treatment with E and P under ischemic conditions in both sexes and point at the regulation of chemokine-microglia/lymphocyte interactions as a supposable mechanism implicated in cell protection.

Residual effects of focal brain ischaemia upon cannabinoid CB(1) receptor density and functionality in female rats

Ischaemic insult results in short-term changes in cannabinoid-1 (CB(1)) receptor expression in the brain, but it is not known whether long-term changes occur, which could potentially mean a change in the intrinsic ability of the brain to withstand new ischaemic episodes. In this study, we have investigated the expression and functionality of CB(1) receptors in coronal brain slices obtained from ovariectomised female rats 46days after middle cerebral artery occlusion (MCAO). The animals were treated with either 17ß-oestradiol or placebo pellets 6h after MCAO and thereafter housed either in isolated or enriched environments. [(3)H]CP55,940 autoradiography indicated no significant effect of 17ß-oestradiol treatment or housing environment upon CB(1) receptor densities. There was, however, a modest but significant decrease in the CB(1) receptor density on the ipsilateral side relative to the contralateral side in the frontal cortex, parietal cortex, CA1-CA3 regions of the hippocampus, thalamus and hypothalamus. CB(1) receptor functionality was assessed by measurement of basal and CP55,940-stimulated [(35)S]GTPγS autoradiography. In the frontal cortex, parietal cortex, CA1-CA3 regions of the hippocampus and dentate gyrus, a robust stimulation, blocked by the CB(1) receptor inverse agonist AM251, was seen. There were no significant changes in the response to CP55,940 with respect either to the 17ß-oestradiol treatment, housing environment or MCAO. Our results reveal that although there are modest long-term decreases in ipsilateral CB(1) receptor densities following MCAO in female rats, these decreases do not result in a functional CB(1) receptor deficit.

Sex-dependent antipsychotic capacity of 17β-estradiol in the latent inhibition model: a typical antipsychotic drug in both sexes, atypical antipsychotic drug in males

The estrogen hypothesis of schizophrenia suggests that estrogen is a natural neuroprotector in women and that exogenous estrogen may have antipsychotic potential, but results of clinical studies have been inconsistent. We have recently shown using the latent inhibition (LI) model of schizophrenia that 17β-estradiol exerts antipsychotic activity in ovariectomized (OVX) rats. The present study sought to extend the characterization of the antipsychotic action of 17β-estradiol (10, 50 and 150 μg/kg) by testing its capacity to reverse amphetamine- and MK-801-induced LI aberrations in gonadally intact female and male rats. No-drug controls of both sexes showed LI, ie, reduced efficacy of a previously non-reinforced stimulus to gain behavioral control when paired with reinforcement, if conditioned with two but not five tone-shock pairings. In both sexes, amphetamine (1 mg/kg) and MK-801 (50 μg/kg) produced disruption (under weak conditioning) and persistence (under strong conditioning) of LI, modeling positive and negative/cognitive symptoms, respectively. 17β-estradiol at 50 and 150 μg/kg potentiated LI under strong conditioning and reversed amphetamine-induced LI disruption in both males and females, mimicking the action of typical and atypical antipsychotic drugs (APDs) in the LI model. 17β-estradiol also reversed MK-induced persistent LI, an effect mimicking atypical APDs and NMDA receptor enhancers, but this effect was observed in males and OVX females but not in intact females. These findings indicate that in the LI model, 17β-estradiol exerts a clear-cut antipsychotic activity in both sexes and, remarkably, is more efficacious in males and OVX females where it also exerts activity considered predictive of anti-negative/cognitive symptoms.

Extranuclear estrogen receptors mediate the neuroprotective effects of estrogen in the rat hippocampus

Background

17β-estradiol (E2) has been implicated to exert neuroprotective effects in the brain following cerebral ischemia. Classically, E2 is thought to exert its effects via genomic signaling mediated by interaction with nuclear estrogen receptors. However, the role and contribution of extranuclear estrogen receptors (ER) is unclear and was the subject of the current study.

Methodology/Principal Findings

To accomplish this goal, we employed two E2 conjugates (E2 dendrimer, EDC, and E2-BSA) that can interact with extranuclear ER and exert rapid nongenomic signaling, but lack the ability to interact with nuclear ER due to their inability to enter the nucleus. EDC or E2-BSA (10 µM) was injected icv 60 min prior to global cerebral ischemia (GCI). FITC-tagged EDC or E2-BSA revealed high uptake in the hippocampal CA1 region after icv injection, with a membrane (extranuclear) localization pattern in cells. Both EDC and E2-BSA exerted robust neuroprotection in the CA1 against GCI, and the effect was blocked by the ER antagonist, ICI182,780. EDC and E2-BSA both rapidly enhanced activation of the prosurvival kinases, ERK and Akt, while attenuating activation of the proapoptotic kinase, JNK following GCI, effects that were blocked by ICI182,780. Administration of an MEK or PI3K inhibitor blocked the neuroprotective effects of EDC and E2-BSA. Further studies showed that EDC increased p-CREB and BDNF in the CA1 region in an ERK- and Akt-dependent manner, and that cognitive outcome after GCI was preserved by EDC in an ER-dependent manner.

Conclusions/Significance

In conclusion, the current study demonstrates that activation of extranuclear ER results in induction of ERK-Akt-CREB-BDNF signaling in the hippocampal CA1 region, which significantly reduces ischemic neuronal injury and preserves cognitive function following GCI. The study adds to a growing literature that suggests that extranuclear ER can have important actions in the brain.

Asymmetric regulation by estrogen at the cholinergic gene locus in differentiated NG108-15 neuronal cells

AIMS

Estrogen acts as a neurogenerative and neuroprotective factor in the cholinergic system. Choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) are regarded as markers of cholinergic neurons. The genes coding these proteins are located at a common locus, the cholinergic gene locus. However, few details concerning activation of the locus have been obtained. We examined the effect of estrogen on the activation pattern of the locus using a cholinergic cell line.

MAIN METHODS

NG108-15 neuronal cells, as a model of cholinergic neurons, were used. Dose-dependent effects of estradiol (E2) on the gene expression of ChAT and VAChT were quantitatively determined by a real-time RT-PCR. The expression of ChAT mRNA variants was qualitatively evaluated by RT-PCR using specific primers.

KEY FINDINGS

The expression of ChAT and VAChT mRNA was strongly enhanced with the induction of differentiation. The enhanced expression of ChAT mRNA was further increased dose-dependently by E2 (10(-10) to 10(-7)M), while that of VAChT mRNA did not respond to E2. The up-regulation of ChAT mRNA expression by E2 was abolished by co-treatment with a pure-antagonist of estrogen receptors. A qualitative analysis of ChAT mRNA variants revealed the R types, which share a common sequence with the VAChT gene, and type M ChAT mRNA to mainly be expressed, and that the appearance of these variants was not altered by E2.

SIGNIFICANCE

The cholinergic gene locus in differentiated NG108-15 neuronal cells is further activated by E2, but the effect is restricted to the transcription of ChAT gene.

Different methods for administering 17beta-estradiol to ovariectomized rats result in opposite effects on ischemic brain damage

Background

Numerous stroke studies have controversially shown estrogens to be either neuroprotective or neurodamaging. The discordant results observed in rat brain ischemia models may be a consequence of discrepancies in estrogen administration modes resulting in plasma concentration profiles far from those intended. To test this hypothesis we reproduced in detail and extended an earlier study from our lab using a different mode of 17β-estradiol administration; home-made silastic capsules instead of commercial slow-release 17β-estradiol pellets. Four groups of female rats (n = 12) were ovariectomized and administered 17β-estradiol or placebo via silastic capsules. All animals underwent MCAo fourteen days after ovariectomy and were sacrificed three days later.

Results

In contrast to our earlier results using the commercial pellets, the group receiving 17β-estradiol during the entire experiment had significantly smaller lesions than the group receiving placebo (mean ± SEM: 3.85 ± 0.70% versus 7.15 ± 0.27% of total slice area, respectively; p = 0.015). No significant neuroprotection was found when the 17β-estradiol was administered only during the two weeks before or the three days immediately after MCAo.

Conclusions

The results indicate that different estrogen treatment regimens result in diametrically different effects on cerebral ischemia. Thus the effects of estrogens on ischemic damage seem to be concentration-related, with a biphasic, or even more complex, dose-response relation. These findings have implications for the design of animal experiments and also have a bearing on the estrogen doses used for peri-menopausal hormone replacement therapy.

Estrogen reduces 11beta-hydroxysteroid dehydrogenase type 1 in liver and visceral, but not subcutaneous, adipose tissue in rats

Following menopause, body fat is redistributed from peripheral to central depots. This may be linked to the age related decrease in estrogen levels. We hypothesized that estrogen supplementation could counteract this fat redistribution through tissue-specific modulation of glucocorticoid exposure. We measured fat depot masses and the expression and activity of the glucocorticoid-activating enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) in fat and liver of ovariectomized female rats treated with or without 17beta-estradiol. 11betaHSD1 converts inert cortisone, or 11-dehydrocorticosterone in rats into active cortisol and corticosterone. Estradiol-treated rats gained less weight and had significantly lower visceral adipose tissue weight than nontreated rats (P < 0.01); subcutaneous adipose weight was unaltered. In addition, 11betaHSD1 activity/expression was downregulated in liver and visceral, but not subcutaneous, fat of estradiol-treated rats (P < 0.001 for both). This downregulation altered the balance of 11betaHSD1 expression and activity between adipose tissue depots, with higher levels in subcutaneous than visceral adipose tissue of estradiol-treated animals (P < 0.05 for both), opposite the pattern in ovariectomized rats not treated with estradiol (P < 0.001 for mRNA expression). Thus, estrogen modulates fat distribution, at least in part, through effects on tissue-specific glucocorticoid metabolism, suggesting that estrogen replacement therapy could influence obesity related morbidity in postmenopausal women.

Epigenetic regulation of estrogen receptor alpha gene expression in the mouse cortex during early postnatal development

Estrogens play a critical role in brain development by acting on areas that express estrogen receptors. In the rodent cortex, estrogen receptor alpha (ER alpha) mRNA expression is high early in postnatal development but declines starting at postnatal day (PND) 10 and is virtually absent in the adult cortex. The mechanisms controlling this regulation are largely unknown. Methylation is important for gene silencing during development in many tissues, including the brain. In the present study, we examined the methylation status of ER alpha 5' untranslated exons during early postnatal development in male and female mice using methylation-specific PCR and pyrosequencing. Several regions of ER alpha promoter displayed a significant increase in methylation at PND 18 and 25 compared with PND 4. DNA methyltransferases (DNMT) are important for the initiation and maintenance of methylation. Real-time PCR showed that DNMT3A, the de novo DNMT peaked at PND 10 and was decreased by PND 25. DNMT1, which is important for maintenance of methylation, increased across development and stayed high in adult cortex. The methyl-CpG-binding protein 2 (MeCP2) is also important for stabilization of methylation. A chromatin immunoprecipitation assay showed a correlation between association of MeCP2 with ER alpha promoter and the increase in methylation and decrease in ER alpha expression after PND 10. In mice containing a mutant MeCP2 protein, ER alpha mRNA expression and promoter methylation patterns across development were different compared with wild-type mice. These data suggest that methylation of ER alpha promoters regulates ER alpha mRNA expression in the cortex during postnatal development in a MeCP2-dependent fashion.

Acute estradiol protects CA1 neurons from ischemia-induced apoptotic cell death via the PI3K/Akt pathway

Global ischemia arising during cardiac arrest or cardiac surgery causes highly selective, delayed death of hippocampal CA1 neurons. Exogenous estradiol ameliorates global ischemia-induced neuronal death and cognitive impairment in male and female rodents. However, the molecular mechanisms by which a single acute injection of estradiol administered after the ischemic event intervenes in global ischemia-induced apoptotic cell death are unclear. Here we show that acute estradiol acts via the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling cascade to protect CA1 neurons in ovariectomized female rats. We demonstrate that global ischemia promotes early activation of glycogen synthase kinase-3beta (GSK3beta) and forkhead transcription factor of the O class (FOXO)3A, known Akt targets that are related to cell survival, and activation of caspase-3. Estradiol prevents ischemia-induced dephosphorylation and activation of GSK3beta and FOXO3A, and the caspase death cascade. These findings support a model whereby estradiol acts by activation of PI3K/Akt signaling to promote neuronal survival in the face of global ischemia.

Long-term survival and serial assessment of stroke damage and recovery - practical and methodological considerations

Impairments caused by stroke remain the main cause for adult disability. Despite a vigorous research effort, only 1 thrombolytic treatment has been approved in acute stroke (<3h). The limitations of preclinical studies and how these can be overcome have been the subject of various guidelines. However, often these guidelines focus on the acute stroke setting and omit long-term outcome measures, such as behaviour and neuroimaging. The considerations and practicalities of including the serial assessment of these approaches and their significance to establish therapeutic efficacy are discussed here.