17-beta-estradiol induces heat shock proteins in brain arteries and potentiates ischemic heat shock protein induction in glia and neurons

Molecular insights into the potential effects of selective estrogen receptor β agonists in Alzheimer's and Parkinson's diseases

Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative disorders. Pathologically, AD and PD are characterized by the accumulation of misfolded proteins. Hence, they are also called as proteinopathy diseases. Gender is considered as one of the risk factors in both diseases. Estrogens are widely accepted to be neuroprotective in several neurodegenerative disorders. Estrogens can be produced in the central nervous system, where they are called as neurosteroids. Estrogens mediate their neuroprotective action mainly through their actions on estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). However, ERα is mainly involved in the growth and development of the primary and secondary sexual organs in females. Hence, the activation of ERα is associated with undesired side effects such as gynecomastia and increase in the risk of breast cancer, thromboembolism, and feminization. Therefore, selective activation of ERβ is often considered to be safer. In this review, we explore the role of ERβ in regulating the expression and functions of AD- and PD-associated genes. Additionally, we discuss the association of these genes with the amyloid-beta peptide (Aβ) and α-synuclein mediated toxicity. Ultimately, we established a correlation between the importance of ERβ activation and the process underlying ERβ's neuroprotective mechanisms in AD and PD.

Resolution of inflammation in chronic disease via restoration of the heat shock response (HSR)

Effective resolution of inflammation via the heat shock response (HSR) is pivotal in averting the transition to chronic inflammatory states. This transition characterizes a spectrum of debilitating conditions, including insulin resistance, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular ailments. This manuscript explores a range of physiological, pharmacological, and nutraceutical interventions aimed at reinstating the HSR in the context of chronic low-grade inflammation, as well as protocols to assess the HSR. Monitoring the progression or suppression of the HSR in patients and laboratory animals offers predictive insights into the organism's capacity to combat chronic inflammation, as well as the impact of exercise and hyperthermic treatments (e.g., sauna or hot tub baths) on the HSR. Interestingly, a reciprocal correlation exists between the expression of HSR components in peripheral blood leukocytes (PBL) and the extent of local tissue proinflammatory activity in individuals afflicted by chronic inflammatory disorders. Therefore, the Heck index, contrasting extracellular 70 kDa family of heat shock proteins (HSP70) (proinflammatory) and intracellular HSP70 (anti-inflammatory) in PBL, serves as a valuable metric for HSR assessment. Our laboratory has also developed straightforward protocols for evaluating HSR by subjecting whole blood samples from both rodents and human volunteers to ex vivo heat challenges. Collectively, this discussion underscores the critical role of HSR disruption in the pathogenesis of chronic inflammatory states and emphasizes the significance of simple, cost-effective tools for clinical HSR assessment. This understanding is instrumental in the development of innovative strategies for preventing and managing chronic inflammatory diseases, which continue to exert a substantial global burden on morbidity and mortality.

Salivary cell-free HSD17B1 and HSPA1A transcripts as potential biomarkers for estrus identification in buffaloes (Bubalus bubalis)

Estrus detection is a major problem in buffaloes because of the poor expression of estrus signs leading to low reproductive efficiency. Salivary transcripts analysis is a promising tool to identify biomarkers; therefore, the present study was carried out to evaluate their potential as estrus biomarkers. The levels of HSD17B1, INHBA, HSPA1A, TES transcripts were compared in saliva during estrous cycle stages [early proestrus (day -2, EP), late proestrus (day-1, LP), estrus (E), metestrus (ME) and diestrus (DE)] of cyclic heifers (n = 8) and pluriparous (n = 8) buffaloes by employing quantitative real-time polymerase chain reaction (qRT-PCR). The levels of HSD17B1 (EP/DE 1.46-2.43 fold, LP/DE 2.49-3.06 fold; E/DE 7.21-11.9-fold p < 0.01; ME/D 1.0-1.16 fold) and HSPA1A (EP/DE 0.93-2.39 fold, LP/DE 2.68-3.23 fold; E/DE 8.52-15.18 fold p < 0.01; ME/D 0.86-1.01 fold) were significantly altered during the estrus than other estrous cycle stages in both cyclic heifers and pluriparous buffaloes. Receiver operating characteristic curve analysis revealed the ability of salivary HSD17B1 (AUC 0.96; p < 0.001) and HSPA1A (AUC 0.99; p < 0.01) to differentiate E from other stages of the estrous cycle. Significantly higher levels of HSD17B1 and HSPA1A transcripts in saliva during the estrus phase suggest their biomarkers potential for estrus detection in buffaloes.

Association of peripheral neuropathy with skeletal muscle mass and function in type two diabetes mellitus patients: A cross-sectional study

BACKGROUND & OBJECTIVE

Diabetic peripheral neuropathy (DPN) is considered to be a risk factor for development of sarcopenia. Therefore, our study aimed to detect the association between peripheral neuropathy with skeletal muscle mass and function in type two diabetes mellitus (T2DM) patients.

METHODS

A total of 176 participants, ≥45 years were included in the study. Out of 176, 60 were healthy volunteers, 60 had T2DM without neuropathy, 56 had T2DM with neuropathy. In all the participants peripheral nerve function was assessed by nerve conduction studies (Common peroneal and Sural nerve) and sarcopenia parameters were evaluated according to the Asian Working Group for Sarcopenia (AWGS) criteria.

RESULTS

The present study suggested that diabetic peripheral neuropathy (DPN) was associated with decline in muscle mass, which was found only in men. Our study showed a positive correlation between appendicular skeletal muscle index (ASMI) and common peroneal nerve amplitude and sural nerve amplitude with r=0.527, p<0.05; r=0.847, p<0.001 respectively. Furthermore, in multiple linear regression analyses, we found a positive relationship between ASMI and sural nerve amplitude after adjustment for confounders like age, duration of diabetes, and HbA1C (B=0.739; p<0.001).

CONCLUSION

As DPN patients are more prone to developing sarcopenia, and periodic assessment of skeletal muscle mass and function is warranted to initiate early lifestyle interventions in these patients, which will improve their quality of life.

Comparative Proteome Profiling of Saliva Between Estrus and Non-Estrus Stages by Employing Label-Free Quantitation (LFQ) and Tandem Mass Tag (TMT)-LC-MS/MS Analysis: An Approach for Estrus Biomarker Identification in Bubalus bubalis

Accurate determination of estrus is essentially required for efficient reproduction management of farm animals. Buffalo is a shy breeder and does not manifest overt signs of estrus that make estrus detection difficult resulting in a poor conception rate. Therefore, identifying estrus biomarkers in easily accessible biofluid such as saliva is of utmost interest. In the current study, we generated saliva proteome profiles during proestrus (PE), estrus (E), metestrus (ME), and diestrus (DE) stages of the buffalo estrous cycle using both label-free quantitation (LFQ) and labeled (TMT) quantitation and mass spectrometry analysis. A total of 520 proteins were identified as DEPs in LFQ; among these, 59 and four proteins were upregulated (FC ≥ 1.5) and downregulated (FC ≤ 0.5) during E vs. PE, ME, and DE comparisons, respectively. Similarly, TMT-LC-MS/MS analysis identified 369 DEPs; among these, 74 and 73 proteins were upregulated and downregulated during E vs. PE, ME, and DE stages, respectively. Functional annotations of GO terms showed enrichment of glycolysis, pyruvate metabolism, endopeptidase inhibitor activity, salivary secretion, innate immune response, calcium ion binding, oocyte meiosis, and estrogen signaling. Over-expression of SERPINB1, HSPA1A, VMO1, SDF4, LCN1, OBP, and ENO3 proteins during estrus was further confirmed by Western blotting. This is the first comprehensive report on differential proteome analysis of buffalo saliva between estrus and non-estrus stages. This study generated an important panel of candidate proteins that may be considered buffalo estrus biomarkers which can be applied in the development of a diagnostic kit for estrus detection in buffalo.

Estradiol-dependent gene expression profile in the amygdala of young ovariectomized spontaneously hypertensive rats

Estrogen plays a role in cardiovascular functions, emotional health, and energy homeostasis via estrogen receptors expressed in the brain. The comorbid relationship between rising blood pressure, a decline in mood and motivation, and body weight gain after menopause, when estrogen levels drop, suggests that the same brain area(s) contributes to protection from all of these postmenopausal disorders. The amygdala, a major limbic system nucleus known to express high estrogen receptor levels, is involved in the regulation of such physiological and psychological responses. We hypothesized that elevated estrogen levels contribute to premenopausal characteristics by activating specific genes and pathways in the amygdala. We examined the effect of 1-month estradiol treatment on the gene expression profile in the amygdala of ovariectomized young adult female spontaneously hypertensive rats. Estradiol substitution significantly decreased blood pressure, prevented body weight gain, and enhanced the voluntary physical activity of ovariectomized rats. In the amygdala of ovariectomized rats, estradiol treatment downregulated the expression of genes associated with estrogen signaling, cholinergic synapse, dopaminergic synapse, and long-term depression pathways. These findings indicate that the transcriptomic characteristics of the amygdala may be involved in estrogen-dependent regulation of blood pressure, physical activity motivation, and body weight control in young adult female spontaneously hypertensive rats.

Association of sarcopenia and muscle mass with both peripheral neuropathy and nerve function in patients with type 2 diabetes

AIM

This study aimed to investigate the association of sarcopenia and muscle mass with both peripheral neuropathy and nerve function in type 2 diabetes mellitus.

METHODS

A total of 1794 patients (937 men and 857 women) with type 2 diabetes, with a mean age of 60.22 years, were enrolled for a cross-sectional study; of these, 183 patients were enrolled for a follow-up study with a median follow-up of 2.7 years. All participants underwent nerve conduction studies and muscle mass index (ASM/HT²) measurements. The composite Z scores for the sensory nerve conduction velocity (SCV) and the motor nerve conduction velocity (MCV) were calculated. The changes in ASM/HT², SCV, and MCV were calculated from the measurements nearly 2 years apart and classified into three groups: a decrease in ASM/HT² of >3%, a minor change within ±3%, and an increase in ASM/HT² of >3%.

RESULTS

The ASM/HT² of men was positively associated with the composite Z scores of MCV and SCV, and sarcopenia highly correlated with DPN after adjusting for confounding factors. The optimal cutoff point for ASM/HT² that indicated DPN was 7.09 kg/m². Furthermore, increases in ASM/HT² independently predicted a greater benefit of MCV and SCV increment outcomes, whereas a minor change in ASM/HT² only significantly associated with lower benefit in terms of SCV increment. However, this phenomenon was not observed in women.

CONCLUSIONS

Sarcopenia and DPN exhibited a close association. The increased muscle mass improved the partial MCVs and SCVs. However, a sex-related discrepancy was observed in this phenomenon.

Nitric oxide-heat shock protein axis in menopausal hot flushes: neglected metabolic issues of chronic inflammatory diseases associated with deranged heat shock response

BACKGROUND

Although some unequivocal underlying mechanisms of menopausal hot flushes have been demonstrated in animal models, the paucity of similar approaches in humans impedes further mechanistic outcomes. Human studies might show some as yet unexpected physiological mechanisms of metabolic adaptation that permeate the phase of decreased oestrogen levels in both symptomatic and asymptomatic women. This is particularly relevant because both the severity and time span of hot flushes are associated with increased risk of chronic inflammatory disease. On the other hand, oestrogen induces the expression of heat shock proteins of the 70 kDa family (HSP70), which are anti-inflammatory and cytoprotective protein chaperones, whose expression is modulated by different types of physiologically stressful situations, including heat stress and exercise. Therefore, lower HSP70 expression secondary to oestrogen deficiency increases cardiovascular risk and predisposes the patient to senescence-associated secretory phenotype (SASP) that culminates in chronic inflammatory diseases, such as obesities, type 2 diabetes, neuromuscular and neurodegenerative diseases.

OBJECTIVE AND RATIONALE

This review focuses on HSP70 and its accompanying heat shock response (HSR), which is an anti-inflammatory and antisenescent pathway whose intracellular triggering is also oestrogen-dependent via nitric oxide (NO) production. The main goal of the manuscript was to show that the vasomotor symptoms that accompany hot flushes may be a disguised clue for important neuroendocrine alterations linking oestrogen deficiency to the anti-inflammatory HSR.

SEARCH METHODS

Results from our own group and recent evidence on hypothalamic control of central temperature guided a search on PubMed and Google Scholar websites.

OUTCOMES

Oestrogen elicits rapid production of the vasodilatory gas NO, a powerful activator of HSP70 expression. Whence, part of the protective effects of oestrogen over cardiovascular and neuroendocrine systems is tied to its capacity of inducing the NO-elicited HSR. The hypothalamic areas involved in thermoregulation (infundibular nucleus in humans and arcuate nucleus in other mammals) and whose neurons are known to have their function altered after long-term oestrogen ablation, particularly kisspeptin-neurokinin B-dynorphin neurons, (KNDy) are the same that drive neuroprotective expression of HSP70 and, in many cases, this response is via NO even in the absence of oestrogen. From thence, it is not illogical that hot flushes might be related to an evolutionary adaptation to re-equip the NO-HSP70 axis during the downfall of circulating oestrogen.

WIDER IMPLICATIONS

Understanding of HSR could shed light on yet uncovered mechanisms of menopause-associated diseases as well as on possible manipulation of HSR in menopausal women through physiological, pharmacological, nutraceutical and prebiotic interventions. Moreover, decreased HSR indices (that can be clinically determined with ease) in perimenopause could be of prognostic value in predicting the moment and appropriateness of starting a HRT.

Inhibition of miR-181a protects female mice from transient focal cerebral ischemia by targeting astrocyte estrogen receptor-α

Whether the effect of miR-181a is sexually dimorphic in stroke is unknown. Prior work showed protection of male mice with miR-181a inhibition. Estrogen receptor-α (ERα) is an identified target of miR181 in endometrium. Therefore we investigated the separate and joint effects of miR-181a inhibition and 17β-estradiol (E2) replacement after ovariectomy. Adult female mice were ovariectomized and implanted with an E2- or vehicle-containing capsule for 14d prior to 1h middle cerebral artery occlusion (MCAO). Each group received either miR-181a antagomir or mismatch control by intracerebroventricular injection 24h before MCAO. After MCAO neurologic deficit and infarct volume were assessed. Primary male and female astrocyte cultures were subjected to glucose deprivation with miR-181a inhibitor or transfection control, and E2 or vehicle control, with/without ESRα knockdown with small interfering RNA. Cell death was assessed by propidium iodide staining, and lactate dehydrogenase assay. A miR-181a/ERα target site blocker (TSB), with/without miR-181a mimic, was used to confirm targeting of ERα by miR-181a in astrocytes. Individually, miR-181a inhibition or E2 decreased infarct volume and improved neurologic score in female mice, and protected male and female astrocyte cultures. Combined miR-181a inhibition plus E2 afforded greater protection of female mice and female astrocyte cultures, but not in male astrocyte cultures. MiR-181a inhibition only increased ERα levels in vivo and in female cultures, while ERα knockdown with siRNA increased cell death in both sexes. Treatment with ERα TSB was strongly protective in both sexes. In conclusion, the results of the present study suggest miR-181a inhibition enhances E2-mediated stroke protection in females in part by augmenting ERα production, a mechanism detected in female mice and female astrocytes. Sex differences were observed with combined miR-181a inhibition/E2 treatment, and miR-181a targeting of ERα.

A model of chronic diabetic polyneuropathy: benefits from intranasal insulin are modified by sex and RAGE deletion

Human diabetic polyneuropathy (DPN) is a progressive complication of chronic diabetes mellitus. Preliminary evidence has suggested that intranasal insulin, in doses insufficient to alter hyperglycemia, suppresses the development of DPN. In this work we confirm this finding, but demonstrate that its impact is modified by sex and deletion of RAGE, the receptor for advanced glycosylation end products. We serially evaluated experimental DPN in male and female wild-type mice and male RAGE null (RN) mice, each with nondiabetic controls, during 16 wk of diabetes, the final 8 wk including groups given intranasal insulin. Age-matched nondiabetic female mice had higher motor and sensory conduction velocities than their male counterparts and had lesser conduction slowing from chronic diabetes. Intranasal insulin improved slowing in both sexes. In male RN mice, there was less conduction slowing with chronic diabetes, and intranasal insulin provided limited benefits. Rotarod testing and hindpaw grip power offered less consistent impacts. Mechanical sensitivity and thermal sensitivity were respectively but disparately changed and improved with insulin in wild-type female and male mice but not RN male mice. These studies confirm that intranasal insulin improves indexes of experimental DPN but indicates that females with DPN may differ in their underlying phenotype. RN mice had partial but incomplete protection from underlying DPN and lesser impacts from insulin. We also identify an important role for sex in the development of DPN and report evidence that insulin and AGE-RAGE pathways in its pathogenesis may overlap.

Estrogen regulates the expression of Ndrg2 in astrocytes

N-myc downstream-regulated gene 2 (Ndrg2) is a newly identified molecule that is mainly expressed in astrocytes within the central nervous system (CNS) and is involved in the proliferation and activation of astrocytes. 17β-estradiol (E2) is one of the most important circulating hormones, and in the CNS, astrocytes are a target and potential mediator of the action of E2. Our most recent study found that DPN, an estrogen receptor (ER) β-specific agonist, activated the Ndrg2 promoter and elevated endogenous NDRG2 protein expression in MCF7, HSG and T-47D cells. However, whether E2 regulates Ndrg2 expression in astrocytes remains unknown. Here, we conducted both in vivo and in vitro experiments and found that ERβ co-localized with NDRG2 in astrocytes. Furthermore, in primary cultured astrocytes, we demonstrated that E2 up-regulated Ndrg2 mRNA and protein expression in a dose- and time-dependent manner and that the ERβ agonist DPN but not the ERα agonist PPT up-regulated Ndrg2 expression. In vivo, we found that in the hippocampus of adult ovariectomized (OVX) female mice, Ndrg2 mRNA and protein expression were significantly decreased compared with those in normal adult female mice. After the OVX mice received continuous subcutaneous injections of 50μg/kg E2, 100μg/kg E2 or the ERβ agonist DPN for 10 days, the Ndrg2 expression significantly increased compared with that of the OVX mice. Our results indicate that E2 may affect astrocytes by regulating Ndrg2 expression.

Heat shock protein 70 gene polymorphisms are associated with paranoid schizophrenia in the Polish population

HSP70 genes have been considered as promising schizophrenia candidate genes based on their protective role in the central nervous system under stress conditions. In this study, we analyzed the potential implication of HSPA1A +190G/C, HSPA1B +1267A/G, and HSPA1L +2437T/C polymorphisms in the susceptibility to paranoid schizophrenia in a homogenous Caucasian Polish population. In addition, we investigated the association of the polymorphisms with the clinical variables of the disease. Two hundred and three patients with paranoid schizophrenia and 243 healthy controls were enrolled in the study. Polymorphisms of HSPA1A, -1B, and -1L genes were genotyped using the PCR-RFLP technique. Analyses were conducted in entire groups and in subgroups that were stratified according to gender. There were significant differences in the genotype and allele frequencies of HSPA1A polymorphism between the patients and controls. The +190CC genotype and +190C allele were over-represented in the patients and significantly increased the risk for developing schizophrenia (OR = 3.45 and OR = 1.61, respectively). Interestingly, such a risk was higher for females with the +190CC genotype than for males with the +190CC genotype (OR = 5.78 vs. OR = 2.76). We also identified the CGT haplotype as a risk haplotype for schizophrenia and demonstrated the effects of HSPA1A and HSPA1B genotypes on the psychopathology and age of onset. Our study provided the first evidence that the HSPA1A polymorphism may potentially increase the risk of developing paranoid schizophrenia. Further independent analyses in different populations to evaluate the role of gender are needed to replicate these results.

Differential modulatory effects of morphine on acute and chronic stress induced neurobehavioral and cellular markers in rats

The present study evaluated the effects of morphine treatments on elevated plus maze test parameters, oxidative stress markers and Hsp70 expression in normal and stressed rats. Acute and chronic stress caused neurobehavioral suppression, altered prooxidant-antioxidant balance and increased Hsp70 expression in brain homogenates in a differential manner. Morphine (1 and 5mg/kg) attenuated RS induced anxiogenesis, changes in MDA and GSH but further enhanced Hsp70 expression. Similar anxiolytic and Hsp70 enhancing effects were seen after morphine in normal rats (no RS). Exposure to chronic RS did not elicit any appreciable neurobehavioral response in EPM but enhanced MDA, lowered GSH and exaggerated the Hsp70 expression. Pretreatment with morphine did not affect the neurobehavioral response to chronic RS, but reverted the GSH and Hsp70 expression. The results suggest that morphine differentially influences acute and chronic stress induced changes in anxiety behavior and complex interactions between oxidative stress markers and Hsp70 expression which may contribute to these effects.

Reaction of small heat-shock proteins to different kinds of cellular stress in cultured rat hippocampal neurons

Upregulation of small heat-shock proteins (sHsps) in response to cellular stress is one mechanism to increase cell viability.We previously described that cultured rat hippocampal neurons express five of the 11 family members but only upregulate two of them (HspB1 and HspB5) at the protein level after heat stress. Since neurons have to cope with many other pathological conditions, we investigated in this study the expression of all five expressed sHsps on mRNA and protein level after sublethal sodium arsenite and oxidative and hyperosmotic stress. Under all three conditions, HspB1, HspB5, HspB6, and HspB8 but not HspB11 were consistently upregulated but showed differences in the time course of upregulation. The increase of sHsps always occurred earlier on mRNA level compared with protein levels. We conclude from our data that these four upregulated sHsps (HspB1, HspB5, HspB6, HspB8) act together in different proportions in the protection of neurons from various stress conditions.

Stroke neuroprotection: oestrogen and insulin-like growth factor-1 interactions and the role of microglia

Oestrogen has been shown to be neuroprotective for stroke and other neural injury models. Oestrogen promotes a neuroprotective phenotype through myriad actions, including stimulating neurogenesis, promoting neuronal differentiation and survival, suppressing neuroinflammation and maintaining the integrity of the blood-brain barrier. At the molecular level, oestrogen directly modulates genes that are beneficial for repair and regeneration via the canonical oestrogen receptor. Increasingly, evidence indicates that oestrogen acts in concert with growth factors to initiate neuroprotection. Oestrogen and insulin-like growth factor (IGF)-1 act cooperatively to influence cell survival, and combined steroid hormone/growth factor interaction has been well documented in the context of neurones and astrocytes. Here, we summarise the evidence that oestrogen-mediated neuroprotection is critically dependent on IGF-1 signalling, and specifically focus on microglia as the source of IGF-1 and the locus of oestrogen-IGF-1 interactions in stroke neuroprotection.

Involvement of heat shock protein 70 in the DNA protective effect from estrogen

As an endogenous cytoprotective factor, the protection of estrogen and heat shock protein-70 (Hsp70) on DNA has been documented, respectively, but the functional interaction between estrogen and Hsp70 on DNA damage repair is largely unknown. We therefore investigated the relation between estrogen and Hsp70 in terms of DNA protection in in vitro. The findings showed a significant reduction in cell survival and elevation in oxidative stress while cells were exposed to amyloid β (Aβ25-35) peptide, but preincubation of the cells with 17β-estradiol (17β-E2) ameliorated this situation. In addition, 17β-E2 alleviated oxidized DNA damage induced by Aβ and elevated the expression of Hsp70. However, the beneficial properties of 17β-E2 on reducing DNA damage were attenuated when Hsp70 gene was silenced accordingly. These results indicate that Hsp70 plays a role in DNA protection mediated by estrogen, and the DNA protection may be involved in Alzheimer's disease preventive effect from estrogen.

Rapid activation of nuclear factor κB by 17β-estradiol and selective estrogen receptor modulators: pathways mediating cellular protection

17β-Estradiol (E2) treatment activates a set of protective response that has been found to protect cells from injury and more importantly to significantly abate the injuries associated with trauma-hemorrhage in vivo. Rapid NF-κB activation has been found to be an important signaling step in E2-mediated protection in cell culture, in vivo ischemia, and trauma-hemorrhage. In the current study, we investigated the signaling cascades linking E2 signaling with NF-κB activation and the protective response and compared them with the effects of two selective estrogen receptor modulators (SERMs), raloxifene and tamoxifen. Two candidate pathways, mitogen-activated protein kinases and phosphatidylinositol-3-kinase (PI3K) were studied. Selective inhibitors were used to identify each pathway's contribution to NF-κB activation. Treatment of human coronary artery endothelial cells with E2 activated PI3K/Akt, p38, and JNK, all of which activated ERK1/2 followed by NF-κB activation. The combined activation of Akt, p38, and JNK was essential to activate NF-κB. The two SERMs activated PI3K and p38, which then phosphorylated ERK1/2 and activated NF-κB independent of the JNK pathway. Nuclear factor κB activation by these compounds protected cells from hypoxia/reoxygenation injury. However, E2, unlike either SERM, led to modest increases in apoptosis through the JNK pathway. Selective estrogen receptor modulator treatment led to increased expression of the protective proteins, Mn superoxide dismutase, and endothelial nitric oxide synthase, which was not seen with E2. These results provide new insight into the pathways activating NF-κB by E2 and SERMs and demonstrate that SERMs may have greater protective benefits than E2 in adult endothelial cells and potentially in vivo, as well.

Overexpression of human HSP27 protects sensory neurons from diabetes

OBJECTIVES

To evaluate whether augmenting neuronal protective mechanisms might slow or arrest experimental diabetic peripheral neuropathy (DPN). DPN is one of the most common neurodegenerative disorders and is rising in prevalence. How it targets sensory neurons is uncertain; the disorder is irreversible and untreatable. We explored the intrinsic protective properties of overexpressed human HSP27 on experimental DPN. HSP27 is a small pro-survival heat shock protein that also increases axonal regeneration.

METHODS

Experimental diabetes was superimposed on mice overexpressing a human HSP27 transgene and its impact was evaluated on epidermal innervation, behavioral tests of sensation and electrophysiological indices of DPN.

RESULTS

Mice that overexpress human HSP27 in their sensory and motor neurons and that were made diabetic for 6 months by streptozotocin treatment were protected from a range of neuropathic abnormalities, including loss of footpad thermal sensation, mechanical allodynia, loss of epidermal innervation, and slowing of sensory conduction velocity. The protection was selective for sensory neurons in comparison to motor neurons and at 6 months provided better protection in female than male mice. Markers of RAGE-NFκB activation were attenuated by the transgene.

CONCLUSIONS

The findings support the idea that diabetic polyneuropathy involves a unique, sensory-centric neurodegenerative process which can be reduced by overexpressing a single gene, an important starting point for new disease-modifying therapeutic approaches.

17β-Estradiol inhibits apoptotic cell death of oligodendrocytes by inhibiting RhoA-JNK3 activation after spinal cord injury

A delayed oligodendrocyte cell death after spinal cord injury (SCI) contributes to chronic demyelination of spared axons, leading to a permanent neurological deficit. Therefore, therapeutic approaches to prevent oligodendrocyte cell death after SCI should be considered. Estrogens are well known to have a broad neuroprotective effect, but the protective effect of estrogens on oligodendrocytes after injury is largely unknown. Here, we demonstrated that 17β-estradiol attenuates apoptosis of oligodendrocytes by inhibiting RhoA and c-Jun-N-terminal kinase activation after SCI. Estrogen receptor (ER)-α and -β were expressed in oligodendrocytes of the spinal cord, and 17β-estradiol treatment significantly inhibited oligodendrocyte cell death at 7 d after injury as compared with vehicle (cyclodextrin) control. 17β-Estradiol also attenuated caspase-3 and -9 activation at 7 d and reduced the loss of axons from progressive degeneration. In addition, 17β-estradiol inhibited RhoA and JNK3 activation, which were activated and peaked at 3 and/or 5 d after injury. Furthermore, administration of Rho inhibitor, PEP-1-C3 exoenzyme, inhibited RhoA and JNK3 activation, and decreased phosphorylated c-Jun level at 5 d after injury. Additionally, the attenuation of RhoA and JNK3 activation as well as oligodendrocyte cell death by 17β-estradiol was reversed by ER antagonist, ICI182780. Our results thus indicate that 17β-estradiol treatment improves functional recovery after SCI in part by reducing oligodendrocyte cell death via inhibition of RhoA and JNK3 activation, which were ER dependent. Furthermore, improvement of hindlimb motor function by posttreatment of 17β-estradiol suggests its potential as a therapeutic agent for SCI patients.

GPR30 regulates glutamate transporter GLT-1 expression in rat primary astrocytes

The G protein-coupled estrogen receptor GPR30 contributes to the neuroprotective effects of 17β-estradiol (E2); however, the mechanisms associated with this protection have yet to be elucidated. Given that E2 increases astrocytic expression of glutamate transporter-1 (GLT-1), which would prevent excitotoxic-induced neuronal death, we proposed that GPR30 mediates E2 action on GLT-1 expression. To investigate this hypothesis, we examined the effects of G1, a selective agonist of GPR30, and GPR30 siRNA on astrocytic GLT-1 expression, as well as glutamate uptake in rat primary astrocytes, and explored potential signaling pathways linking GPR30 to GLT-1. G1 increased GLT-1 protein and mRNA levels, subject to regulation by both MAPK and PI3K signaling. Inhibition of TGF-α receptor suppressed the G1-induced increase in GLT-1 expression. Silencing GPR30 reduced the expression of both GLT-1 and TGF-α and abrogated the G1-induced increase in GLT-1 expression. Moreover, the G1-induced increase in GLT-1 protein expression was abolished by a protein kinase A inhibitor and an NF-κB inhibitor. G1 also enhanced cAMP response element-binding protein (CREB), as well as both NF-κB p50 and NF-κB p65 binding to the GLT-1 promoter. Finally, to model dysfunction of glutamate transporters, manganese was used, and G1 was found to attenuate manganese-induced impairment in GLT-1 protein expression and glutamate uptake. Taken together, the present data demonstrate that activation of GPR30 increases GLT-1 expression via multiple pathways, suggesting that GPR30 is worthwhile as a potential target to be explored for developing therapeutics of excitotoxic neuronal injury.

Inflammation, heat shock proteins, and type 2 diabetes

We propose that type 2 diabetes results from a vicious cycle of metabolically induced inflammation, impaired insulin responsiveness, and subsequent loss of homeostatic signaling. A crucial and previously under-recognized event contributing to this loss of homeostasis is a reduction in heat shock proteins (HSPs, or stress proteins). The central causal pathways of this cycle are the following: (a) obesity-driven inflammation promotes insulin resistance; (b) impaired insulin signaling in turn reduces the expression of HSPs, leaving tissues vulnerable to damage and allowing the accumulation of harmful proteins aggregates; and (c) resulting damage to the pancreatic beta-cell leads to further losses in insulin signaling, while a decline in anti-inflammatory HSPs allows inflammation to expand unhindered. Obesity and sedentary lifestyle perpetuate this cycle, while dieting and exercise forestall it by raising HSPs, reducing inflammation, and improving insulin signaling. Because HSP expression carries substantial metabolic costs, it is likely that an evolutionary history of high activity levels and resource scarcity selected for more conservative HSP expression than is appropriate for our current environment of caloric abundance.

Sex-dependent effect of BAG1 in ameliorating motor deficits of Huntington disease transgenic mice

The pathogenesis of Huntington disease (HD) is attributed to the misfolding of huntingtin (htt) caused by an expanded polyglutamine (polyQ) domain. Considerable effort has been devoted to identifying molecules that can prevent or reduce htt misfolding and the associated neuropathology. Although overexpression of chaperones is known to reduce htt cytotoxicity in cellular models, only modest protection is seen with Hsp70 overexpression in HD mouse models. Because the activity of Hsp70 is modulated by co-chaperones, an interesting issue is whether the in vivo effects of chaperones on polyQ protein toxicity are dependent on other modulators. In the present study, we focused on BAG1, a co-chaperone that interacts with Hsp70 and regulates its activity. Of htt mice expressing the N171-82Q mutant, we found that male N171-82Q mice show a greater deficit in rotarod performance than female N171-82Q mice. This sex-dependent motor deficit was improved by crossing N171-82Q mice with transgenic mice overexpressing BAG1 in neurons. Transgenic BAG1 also reduces the levels of mutant htt in synaptosomal fraction of male HD mice. Overexpression of BAG1 augmented the effects of Hsp70 by reducing aggregation of mutant htt in cultured cells and improving neurite outgrowth in htt-transfected PC12 cells. These findings suggest that the effects of chaperones on HD pathology are influenced by both their modulators and sex-dependent factors.

Heme oxygenase-1 stabilizes the blood-spinal cord barrier and limits oxidative stress and white matter damage in the acutely injured murine spinal cord

We hypothesized that heme oxygenase (HO)-1, the inducible form of HO, represents an important defense against early oxidative injury in the traumatized spinal cord by stabilizing the blood-spinal cord barrier and limiting the infiltration of leukocytes. To test this hypothesis, we first examined the immunoexpression of HO-1 and compared barrier permeability and leukocyte infiltration in spinal cord-injured HO-1-deficient (+/-) and wild-type (WT, +/+) mice. Heme oxygenase was expressed in both endothelial cells and glia of the injured cord. Barrier disruption to luciferase and infiltration of neutrophils were significantly greater in the HO-1+/- than WT mice at 24 h postinjury (P<or=0.019 and =0.049, respectively). We next examined by Western immunoblots the generation of 4-hydroxynoneal (HNE) and malondialdehyde (MDA), major products of lipid peroxidation, in the injured epicenter. There was a significant increase in 10 kDa HNE- and MDA-modified proteins in the HO-1+/- as compared with WT mice (P=0.037 and 0.043, respectively). Finally, we compared the degradation of myelin basic protein (MBP), an indicator of white matter damage, in the HO-1+/- and WT mice by Western immunoblots. There was significantly greater degradation of MBP in the HO-1+/- compared with WT mice (P=0.049). Together, these findings show that HO-1 modulates oxidative stress and white matter injury in the acutely injured spinal cord. This modulation may be partially attributed to the ability of HO-1 to stabilize the blood-spinal cord barrier and limit neutrophil infiltration.

Impairments of heat shock protein expression and MAPK translocation in the central nervous system of follitropin receptor knockout mice

The central nervous system is exposed to the chronic oxidative stress during aging when the endogenous defence weakens and the load of reactive oxygen species enhances. Sex hormones and heat shock proteins (Hsps) participate in these responses to stress. Their regulation is disturbed in aging. We assessed the expression of Hsps in hippocampus and cortex of follitropin receptor knockout (FORKO) mice, known to exhibit gender and age-dependent imbalance in sex steroids and gonadotropins. These imbalances could contribute to an impaired regulation of Hsps thereby increasing the risk of developing neurodegenerative disorders. Our study shows that, in the hippocampus the expression of Hsp70 and Hsp25 was reduced in 20-month-old FORKO mice. However, in the cortex both Hsps were significantly down regulated only in elderly females. There is a well-established co-regulation between Hsps and mitogen-activated protein kinases (MAPKs). Significant, gender-specific impairments in the translocation of phosphorylated ERK and JNK were found in the CNS structures in aged FORKO mice. Our results suggest that hormonal imbalances lead to a disturbed subcellular distribution of activated MAPKs which contribute to the impairments of signal transduction networks maintaining normal physiological functions in the cortex and hippocampus that are associated with neurodegenerative changes in aging.

The protective effects of 17beta-estradiol on hepatic ischemia-reperfusion injury in rat model, associated with regulation of heat-shock protein expression

BACKGROUND

Ischemia-reperfusion (I/R) injury, which was commonly seen in the field of hepatic surgical intervention, impaired liver regeneration and predisposed to liver failure. Previous studies have shown gender dimorphic response of the liver for various hepatic stresses including I/R injury, hemorrhagic shock-resuscitation, liver cirrhosis, endotoxemia, and chronic alcoholic consumption, and demonstrated gender dimorphism in hepatocellular dysfunction after experimental trauma and hemorrhage. The objective of this study was to examine the hypothesis that the protective effects of 17beta-estradiol (E2) in hepatic I/R injury were associated with increasing heat-shock protein 70 expression.

MATERIALS AND METHODS

Sprague-Dawley male and female rats were randomly divided into male and female sham, I/R, and E2 + I/R groups. The model of reduced-size liver ischemia and reperfusion was used. Except for the sham-operated groups, all rats were subjected to 70% liver ischemia for 45 min followed by resection of the remaining 30% nonischemic lobes and reperfusion of ischemic tissue. For each group, five rats were used to investigate the survival during a week after operation; blood samples and liver tissues were obtained in the remaining animals after 3, 12, and 24 h of reperfusion to assess serum alanine aminotransferase, aspartate aminotransferase, liver tissue NO(2)(-) + NO(3)(-), malondialdehyde content, superoxide dismutase, nitric oxide synthase, and myeloperoxidase activity, Hsp70 expression, and apoptosis ratio.

RESULTS

Compared with I/R groups, male and female E2 + I/R groups showed less I/R-induced injury, and SOD and eNOS activity and Hsp70 expression were increased significantly (P < 0.01). A higher rate of apoptosis was observed in the I/R group versus the E2 + I/R group, a significant increase of MDA, NO(2)(-) + NO(3)(-), and MPO of liver tissues and serum transaminase were also observed in the I/R group versus the E2 + I/R group. The survival rate was significantly higher in the male E2 + I/R group than in the male I/R group.

CONCLUSION

E2 pretreatment had protective effects on liver in hepatic I/R injury. The mechanism of this protection might be related to overexpression of Hsp70.

Cerebral neurons and glial cell types inducing heat shock protein Hsp70 following heat stress in the rat

In this chapter, the distribution of Hsp70 in brain cell types following whole body hyperthermia is reviewed. The prevalence of Hsp70 expression in oligodendrocytes, microglia, and vascular cells in this type of stress contrasts with scarcity of Hsp70 induction in astrocytes and most neurons of the hyperthermic brain. However, a similarity between hyperthermic- and arsenite-induced brain patterns of Hsp70 expression supports the view that denaturation of specific proteins plays a major role in the selectivity of glial/vascular expression also during hyperthermia in vivo. The mechanism of neuronal Hsp70 non-responsiveness in heat stress despite their ability to use Hsc70 in a partial heat stress response remains to be elucidated.

HSPBAP1 is found extensively in the anterior temporal neocortex of patients with intractable epilepsy

Heat Shock Protein BAP1 (heat shock 27-kDa-associated protein 1, HSPBAP1) inhibits the function of heat shock protein 27, which has a neuroprotective effect during experimentally induced epileptic neuropathology. In our study, fluorescence quantitative polymerase chain reaction, immunohistochemistry, immunofluorescence, western blot were used to test the levels of HSPBAP1 mRNA and protein in surgical samples of the anterior temporal neocortex of patients with intractable epilepsy (IE) and normal controls samples. HSPBAP1 mRNA was abnormally expressed in the anterior temporal neocortex of patients with IE. Moreover, HSPBAP1 was found extensively in the cytoplasm of neurons and glial cells in all epilepsy specimens. Western blot showed a clear immunoreactive band of HSPBAP1 in IE specimens whereas it was absent in control specimens. The expression of HSPBAP1 mRNA and protein in the anterior temporal neocortex from patients with IE may play a role in the development of epileptic seizures in patients with cell loss in this brain region. Additional studies will be required to elucidate the mechanism by which HSPBAP1 affects brain function in IE.

Steroids and glial cell function

Hormonal and locally produced steroids act in the nervous system as neuroendocrine regulators, as trophic factors and as neuromodulators and have a major impact on neural development and function. Glial cells play a prominent role in the local production of steroids and in the mediation of steroid effects on neurons and other glial cells. In this review, we examine the role of glia in the synthesis and metabolism of steroids and the functional implications of glial steroidogenesis. We analyze the mechanisms of steroid signaling on glia, including the role of nuclear receptors and the mechanisms of membrane and cytoplasmic signaling mediated by changes in intracellular calcium levels and activation of signaling kinases. Effects of steroids on functional parameters of glia, such as proliferation, myelin formation, metabolism, cytoskeletal reorganization, and gliosis are also reviewed, as well as the implications of steroid actions on glia for the regulation of synaptic function and connectivity, the regulation of neuroendocrine events, and the response of neural tissue to injury.

Influence of sex steroid hormones on cerebrovascular function

The cerebral vasculature is a target tissue for sex steroid hormones. Estrogens, androgens, and progestins all influence the function and pathophysiology of the cerebral circulation. Estrogen decreases cerebral vascular tone and increases cerebral blood flow by enhancing endothelial-derived nitric oxide and prostacyclin pathways. Testosterone has opposite effects, increasing cerebral artery tone. Cerebrovascular inflammation is suppressed by estrogen but increased by testosterone and progesterone. Evidence suggests that sex steroids also modulate blood-brain barrier permeability. Estrogen has important protective effects on cerebral endothelial cells by increasing mitochondrial efficiency, decreasing free radical production, promoting cell survival, and stimulating angiogenesis. Although much has been learned regarding hormonal effects on brain blood vessels, most studies involve young, healthy animals. It is becoming apparent that hormonal effects may be modified by aging or disease states such as diabetes. Furthermore, effects of testosterone are complicated because this steroid is also converted to estrogen, systemically and possibly within the vessels themselves. Elucidating the impact of sex steroids on the cerebral vasculature is important for understanding male-female differences in stroke and conditions such as menstrual migraine and preeclampsia-related cerebral edema in pregnancy. Cerebrovascular effects of sex steroids also need to be considered in untangling current controversies regarding consequences of hormone replacement therapies and steroid abuse.

CO as a cellular signaling molecule

Many biological functions of heme oxygenase (HO), such as cytoprotection against oxidative stress, vasodilation, neurotransmission in the central or peripheral nervous systems, and anti-inflammatory, anti-apoptotic, or anti-proliferative potential, have been attributed to its enzymatic byproduct carbon monoxide (CO), although roles for biliverdin/bilirubin and iron have also been proposed. In addition to these well-characterized effects, recent findings reveal that HO-derived CO may act as an oxygen sensor and circadian modulator of heme biosynthesis. In lymphocytes, CO may participate in regulatory T cell function. A number of the known signaling effects of CO depend on stimulation of soluble guanylate cyclase and/or activation of mitogen-activated protein kinases (MAPK). Furthermore, modulation of caveolin-1 status may serve as an essential component of certain aspects of CO action, such as growth control. In this review, we summarize recent findings of the beneficial or detrimental effects of endogenous CO with an emphasis on the signaling pathways and downstream targets that trigger the action of this gas.

Estradiol improves cardiac and hepatic function after trauma-hemorrhage: role of enhanced heat shock protein expression

Although studies indicate that 17β-estradiol administration after trauma-hemorrhage (T-H) improves cardiac and hepatic functions, the underlying mechanisms remain unclear. Because the induction of heat shock proteins (HSPs) can protect cardiac and hepatic functions, we hypothesized that these proteins contribute to the salutary effects of estradiol after T-H. To test this hypothesis, male Sprague-Dawley rats (∼300 g) underwent laparotomy and hemorrhagic shock (35–40 mmHg for ∼90 min) followed by resuscitation with four times the shed blood volume in the form of Ringer lactate. 17β-estradiol (1 mg/kg body wt) was administered at the end of the resuscitation. Five hours after T-H and resuscitation there was a significant decrease in cardiac output, positive and negative maximal rate of left ventricular pressure. Liver function as determined by bile production and indocyanine green clearance was also compromised after T-H and resuscitation. This was accompanied by an increase in plasma alanine aminotransferase (ALT) levels and liver perfusate lactic dehydrogenase levels. Furthermore, circulating levels of TNF-α, IL-6, and IL-10 were also increased. In addition to decreased cardiac and hepatic function, there was an increase in cardiac HSP32 expression and a reduction in HSP60 expression after T-H. In the liver, HSP32 and HSP70 were increased after T-H. There was no change in heart HSP70 and liver HSP60 after T-H and resuscitation. Estradiol administration at the end of T-H and resuscitation increased heart/liver HSPs expression, ameliorated the impairment of heart/liver functions, and significantly prevented the increase in plasma levels of ALT, TNF-α, and IL-6. The ability of estradiol to induce HSPs expression in the heart and the liver suggests that HSPs, in part, mediate the salutary effects of 17β-estradiol on organ functions after T-H.

17β-Estradiol attenuates blood–brain barrier disruption induced by cerebral ischemia–reperfusion injury in female rats

Disruption of blood-brain barrier (BBB), mediated through matrix metalloproteinases (MMPs), is a critical event during cerebral ischemia. While neuroprotective effects of estrogens have been well established in ischemic stroke models, the effects of estrogens on BBB integrity remain to be elucidated. In the present study, we determined effects of 17beta-estradiol (E2) on BBB disruption induced by transient focal cerebral ischemia and its effects on MMP2 and MMP9 activation. Transient cerebral ischemia was induced by middle cerebral artery (MCA) occlusion for 1 h followed by reperfusion in ovariectomized rats. E2 (100 microg/kg) or vehicle was administered 2 h before MCA occlusion. BBB integrity was determined by fluorescent detection of extravasated Evans blue. In separate experiments, effect of E2 on MMP2 and MMP9 expression and activation was determined by immunoblot and MMPs activity assay. E2 treatment prevented more than 50% and 30% of BBB disruption in the ischemic cortex and subcortex at 4 h after reperfusion, respectively. MMP2 and MMP9 expression was elevated at 2 h and peaked at 4 h after reperfusion in the ischemic cortex, which was markedly reduced by E2 treatment. E2 treatment also attenuated the increase of MMPs activity induced by ischemia-reperfusion injury. In conclusion, estrogens could attenuate BBB disruption induced by transient cerebral ischemia, by inhibition of MMP2 and MMP9 activation. Our results suggest an important role of estrogens as multiple targeting protectants against ischemic stroke on cellular as well as vascular components of central nervous system.

A systematic review of currently available pharmacological neuroprotective agents as a sole intervention before anticipated or induced cardiac arrest

We conducted a Medline search for controlled studies evaluating currently available drugs for pharmacological neuroprotection. They had to be administered prior to transient global cerebral ischaemia without further non-pharmacological measures. We deliberately excluded focal ischaemia since its pathophysiology is substantially different from global ischaemia. A total of 45 articles conducted exclusively in laboratory animals met these criteria. The following classes of agents were evaluated: anaesthetics, GABAergic drugs, calcium-antagonists, anticonvulsives, sodium-channel blockers, potassium-channel activators, NMDA-receptor antagonists, hormones, vasodilators, dopamine- and alpha2-agonists, magnesium, xanthine oxidase- and cyclooxygenase inhibitors, a nootropic, a protease inhibitor, and immunosuppressants. Some of them were applied chronically and others administered via clinically impracticable routes. The available literature favours isoflurane, phenytoin, lamotrigine, magnesium, and potentially, nimodipine, and flunarizine. If factors like costs, toxicity, side effects, route and mode of application are considered, isoflurane and MgSO4 that have also been safely applied to patients with compromised left ventricular pump function are advantageous but their true role in human neuroprotection remains unclear.

Sex differences and the effect of hormonal therapy on ischemic brain injury

Epidemiological data emphasize the importance of sex differences in the mortality and morbidity of stroke and cardiovascular disease. The importance of hormonal influences on stroke outcome has pointed out the importance of gender, age, and presence of neural hormones. This clinical data has been substantiated by various experimental studies using clinically relevant models of cerebral ischemia and stroke. Published findings emphasize that male and female animals respond differently to periods of cerebral ischemia and that various combinations of hormonal treatments can provide protection, both histopathological and behavioral. Mechanisms underlying the hormonal effects on ischemic outcome are multifactorial. These include effects on vascular integrity and cerebral blood flow, excitotoxicity, oxidation pathways, inflammation, and apoptosis. Although many studies have shown positive results with hormonal treatments, negative findings have also been presented. Explanations for the limitations of hormonal treatment include uncertainties regarding therapeutic window, specific therapeutic dose range, as well as the specific pathophysiological processes being targeted. Additional studies are therefore required to clarify under what conditions hormonal therapy is most protective or not warranted. Experimental studies utilizing a variety of cerebral ischemia and stroke models are reviewed to indicate under what conditions sex differences and hormonal therapy are most important in terms of functional outcome.

Bilateral, vascular and perivascular glial upregulation of heat shock protein-27 after repeated epileptic seizures

Heat shock protein-27 (HSP-27) is an inducible stress response protein. It inhibits apoptotic cell death and is a reliable marker for oxidative stress. We studied the induction of HSP-27 in rat brains on days 1, 4 and 14 after repeated, pentylenetetrazole (PTZ)-induced seizures using immunohistochemisty. Saline treated control rats showed no induction of HSP-27. HSP-27 reactive astrocytes were rarely seen 1 or 4 days after PTZ injection. When present, single astrocytes were located in the cortex and/or the hippocampus. After 14 days PTZ treatment, a bilateral distribution of HSP-27 immunoreactive glia was present in piriform and entorhinal cortices and in the dentate gyrus of most brains. Rats with most intense HSP-27 upregulation showed HSP-27 in amygdala and thalamic nuclei. Astrocytes associated with blood vessels presented strongest HSP-27 staining, but did not show upregulation of gial fibrillary acidic protein and none responded with HSP-47 expression. Additionally, HSP-27 immunoreactivity increased in the endothelial cells of blood vessels in the affected brain regions, although no neuronal induction occurred. Contrastingly, a subconvulsive dose of the glutamine synthetase inhibitor L-methionine sulfoxime, which acts directly on astrocytes, resulted in a rapid, homogeneous astrocyte-specific HSP-27 upregulation within 24 h. Thus, repeated PTZ-induced seizure activity elicits a focal "heat shock" response in endothelial cells and astrocytes of selected cerebral regions indicating that expression of HSP-27 occurred in a seizure-dependent manner within the affected cerebral circuitries. Therefore, this PTZ-model of repeated seizure activity exhibited a cortical pattern of HSP-27 expression which is most comparable to that known from patients with epilepsy.

Mechanism of salutary effects of estradiol on organ function after trauma-hemorrhage: upregulation of heme oxygenase

A growing body of evidence indicates that heme degradation products may counteract the deleterious consequences of hypoxia and/or ischemia-reperfusion injury. Because heme oxygenase (HO)-1 induction after adverse circulatory conditions is known to be protective, and because females in the proestrus cycle (with high estrogen) have better hepatic function and less hepatic damage than males after trauma-hemorrhage, we hypothesized that estrogen administration in males after trauma-hemorrhage will upregulate HO activity and protect the organs against dysfunction and injury. To test this hypothesis, male Sprague-Dawley rats underwent 5-cm laparotomy and hemorrhagic shock (35–40 mmHg for 93 ± 2 min), followed by resuscitation with four times the shed blood volume in the form of Ringer lactate. 17β-Estradiol and/or the specific HO enzyme inhibitor chromium mesoporphyrin (CrMP) were administered at the end of resuscitation, and the animals were killed 24 h thereafter. Trauma-hemorrhage reduced cardiac output, myocardial contractility, and serum albumin levels. Portal pressure and serum alanine aminotransferase levels were markedly increased under those conditions. These parameters were significantly improved in the 17β-estradiol-treated rats. Estradiol treatment also induced increased HO-1 mRNA expression, HO-1 protein levels, and HO enzymatic activity in cardiac and hepatic tissue compared with vehicle-treated trauma-hemorrhage rats. Administration of the HO inhibitor CrMP prevented the estradiol-induced attenuation of shock-induced organ dysfunction and damage. Thus the salutary effects of estradiol administration on organ function after trauma-hemorrhage are mediated in part via upregulation of HO-1 expression and activity.

1α,25-Dihydroxy-vitamin D3 in combination with 17β-estradiol lowers the cortical expression of heat shock protein-27 following experimentally induced focal cortical ischemia in rats

1alpha,25-(OH)(2)-vitamin-D(3) (1,25-D(3)) and 17beta-estradiol are both known to act neuroprotective in certain experimental in vitro and in vivo settings. We studied the effects of 1,25-D(3) or 17beta-estradiol or their combined application on heat shock protein-27 (HSP-27) distribution after focal cortical ischemia using the photothrombosis model. HSP-27 is a well-established marker of the cerebral oxidative stress response and a potent inhibitor of apoptosis. Lesioned rats were injected i.p. one hour after injury with either 1 microg 1,25-D(3)/kg or 7 microg 17beta-estradiol/kg or a combination of both steroids. Groups of non-lesioned steroid-treated rats and lesioned, solvent-treated rats served as controls. Treatment with both steroids did not affect the size of the lesion. In addition, 17beta-estradiol resulted in significant reduction of HSP-27 induction, whereas the combination of 1,25-D(3)+17beta-estradiol resulted in a highly significant reduction of HSP-27 within the infracted cerebral cortex, indicating that both steroids act synergistically in a protective manner.

Glia-neuron crosstalk in the neuroprotective mechanisms of sex steroid hormones

Proteins involved in the intramitochondrial trafficking of cholesterol, the first step in steroidogenesis, such as the steroidogenic acute regulatory protein (StAR) and the peripheral-type benzodiazepine receptor (PBR), are upregulated in the nervous system after injury. Accordingly, a local increase in the levels of steroids, such as pregnenolone and progesterone, is observed following traumatic injury in the brain and spinal cord. The expression and activity of aromatase, the enzyme that synthesizes estradiol, is also increased in injured brain areas and its inhibition results in an increased neurodegeneration. These findings suggest that an increase in steroidogenesis is part of an overall mechanism used by the nervous tissue to cope with neurodegenerative conditions. Neural steroidogenesis is the result of a coordinated interaction of neurons and glia. For example, after neural injury, there is an upregulation of StAR in neurons and of PBR in microglia and astroglia. Aromatase is expressed in neurons under basal conditions and is upregulated in reactive astrocytes after injury. Some of the steroids produced by glia are neuroprotective. Progesterone and progesterone derivatives produced by Schwann cells, promote myelin formation and the remyelination and regeneration of injured nerves. In the central nervous system, the steroids produced by glia regulate synaptic function, affect anxiety, cognition, sleep and behavior, and exert neuroprotective and reparative roles. In addition, glial cells are targets for steroids and mediate some of the effects of these molecules on neurons, including the regulation of survival and regeneration.

Bilirubin as a cerebrospinal fluid marker of sentinel subarachnoid hemorrhage: a preliminary report in pigs

OBJECT

A model of subarachnoid hemorrhage (SAH) in pigs was developed to investigate bilirubin concentration in cerebrospinal fluid (CSF) as a potential marker of sentinel SAH.

METHODS

Seven male Yorkshire pigs received a 250-microl injection of either whole autologous arterial blood (four animals) or isotonic saline (three animals) into the cisternae magna in an effort to produce volumetrically a model of sentinel SAH and a control injection model, respectively. Cerebrospinal fluid volumes of 100 microl were then collected from both the lumbar cistern and cisternae magna at 1 to 2-hour intervals for a total of 24 hours postinjection. The CSF was then tested for bilirubin. Mean concentrations of bilirubin (+/- standard deviation [SD]) obtained from the lumbar cistern 24 hours following the injection of blood or saline were 4.38 +/- 1.04 microM in the SAH animals and 1.02 +/- 0.05 microM in the controls. At 24 hours postinjection, mean concentrations (+/- SD) of cisternae magna bilirubin were 7.29 +/- 1.33 microM and 1.33 +/- 0.14 microM in the SAH animals and controls, respectively. In the SAH group, both the lumbar cistern and cisternae magna bilirubin concentrations differed significantly from baseline values 12 hours following SAH.

CONCLUSIONS

Elevated concentrations of CSF bilirubin can be detected following a low-volume SAH, and the production of bilirubin occurred over a predictable time course. Twelve hours after hemorrhage, an elevated CSF bilirubin concentration was an indicator of hemolysis occurring in the subarachnoid spaces. The presence of bilirubin in CSF is a potential marker for differentiating SAHs from traumatic lumbar punctures in humans.

Hemin induces heme oxygenase-1 in spinal cord vasculature and attenuates barrier disruption and neutrophil infiltration in the injured murine spinal cord

Heme oxygenase-1 (HO-1) has been shown to alter vascular function in part by attenuating inflammation. We induced HO-1 in blood vessels in the spinal cord by systemic administration of hemin. Twenty-four hours later, immediately prior to euthanasia, fluorescence conjugated Lycopersicon esculentum (tomato) lectin was given intravenously to label the vasculature. HO-1 was induced in blood vessels, particularly in the white matter, as evidenced by the immunolocalization of HO-1 in lectin positive vessels. Western blots confirmed the hemin-mediated induction of HO-1 in the uninjured spinal cord. We next examined the extent to which treatment with hemin or vehicle, 24 h prior to a moderate contusion injury, influenced early vascular dysfunction in the injured cord. All animals were euthanized 24 h after injury. Luciferase, a marker of barrier integrity, was given intravenously 30 min prior to euthanasia. The spinal cord was either prepared for quantification of luciferase activity or fixed by vascular perfusion and prepared for the immunolocalization of neutrophils. There was a significant attenuation of barrier permeability to luciferase and a significant reduction in the number of neutrophils in hemin treated animals as compared to the vehicle treated group. Together, these findings demonstrate that vascular induction of HO-1 modulates barrier function and neutrophil infiltration and suggest that this protein may be useful for limiting the early vascular dysfunction and inflammation that occurs in the acutely injured spinal cord.

Heat Shock Protein-27 Is Upregulated in the Temporal Cortex of Patients with Epilepsy

PURPOSE

Heat shock protein-27 (HSP-27) belongs to the group of small heat shock proteins that become induced in response to various pathologic conditions. HSP-27 has been shown to protect cells and subcellular structures, particularly mitochondria, and serves as a carrier for estradiol. It is a reliable marker for tissues affected by oxidative stress. Oxidative stress and related cellular defence mechanisms are currently thought to play a major role during experimentally induced epileptic neuropathology. We addressed the question whether HSP-27 becomes induced in the neocortex resected from patients with pharmacoresistant epilepsy.

METHODS

Human epileptic temporal neocortex was obtained during neurosurgery, and control tissue was obtained at autopsy from subjects without known neurologic diseases. The tissues were either frozen for Western blot analysis or fixed in Zamboni's fixative for the topographic detection of HSP-27 at the cellular level by means of immunohistochemistry.

RESULTS

HSP-27 was highly expressed in all epilepsy specimens and in the cortex of a patient who died in the final stage of multiple sclerosis (positive control), whereas only low amounts of HSP-27 were detectable in control brains. In epilepsy patients, HSP-27 was present in astrocytes and in the walls of blood vessels. The intracortical distribution patterns varied strongly among the epilepsy specimens.

CONCLUSIONS

These results demonstrate that HSP-27 becomes induced in response to epileptic pathology. Although the functional aspects of HSP-27 induction during human epilepsy have yet to be elucidated, it can be concluded that HSP-27 is a marker for cortical regions in which a stress response has been caused by seizures.