Ethanol stimulates ROS generation by mitochondria through Ca2+ mobilization and increases GFAP content in rat hippocampal astrocytes

Role of mitochondria ROS generation in ethanol-induced NLRP3 inflammasome activation and cell death in astroglial cells

Toll-like receptors (TLRs) and NOD-like receptors (NLRs) are innate immunity sensors that provide an early/effective response to pathogenic or injury conditions. We have reported that ethanol-induced TLR4 activation triggers signaling inflammatory responses in glial cells, causing neuroinflammation and brain damage. However, it is uncertain if ethanol is able to activate NLRs/inflammasome in astroglial cells, which is the mechanism of activation, and whether there is crosstalk between both immune sensors in glial cells. Here we show that chronic ethanol treatment increases the co-localization of caspase-1 with GFAP⁺ cells, and up-regulates IL-1β and IL-18 in the frontal medial cortex in WT, but not in TLR4 knockout mice. We further show that cultured cortical astrocytes expressed several inflammasomes (NLRP3, AIM2, NLRP1, and IPAF), although NLRP3 mRNA is the predominant form. Ethanol, as ATP and LPS treatments, up-regulates NLRP3 expression, and causes caspase-1 cleavage and the release of IL-1β and IL-18 in astrocytes supernatant. Ethanol-induced NLRP3/caspase-1 activation is mediated by mitochondrial (m) reactive oxygen species (ROS) generation because when using a specific mitochondria ROS scavenger, the mito-TEMPO (500 μM) or NLRP3 blocking peptide (4 μg/ml) or a specific caspase-1 inhibitor, Z-YVAD-FMK (10 μM), abrogates mROS release and reduces the up-regulation of IL-1β and IL-18 induced by ethanol or LPS or ATP. Confocal microscopy studies further confirm that ethanol, ATP or LPS promotes NLRP3/caspase-1 complex recruitment within the mitochondria to promote cell death by caspase-1-mediated pyroptosis, which accounts for ≈73% of total cell death (≈22%) and the remaining (≈25%) die by caspase-3-dependent apoptosis. Suppression of the TLR4 function abrogates most ethanol effects on NLRP3 activation and reduces cell death. These findings suggest that NLRP3 participates, in ethanol-induced neuroinflammation and highlight the NLRP3/TLR4 crosstalk in ethanol-induced brain injury.

Neuroprotection induced by N-acetylcysteine and selenium against traumatic brain injury-induced apoptosis and calcium entry in hippocampus of rat

Neurodegeneration associated with acute central nervous system injuries and diseases such as spinal cord injury and traumatic brain injury (TBI) are reported to be mediated by the regulation of apoptosis and oxidative stress through Ca(2+) influx. The thiol redox system antioxidants, such as N-acetylcysteine (NAC) and selenium (Se), display neuroprotective activities mediated at least in part by their antioxidant and anti-inflammatory properties. However, there are no reports on hippocampal apoptosis, cytosolic reactive oxygen species (ROS), or Ca(2+) values in rats with an induced TBI. Therefore, we tested the effects of Se and NAC administration on apoptosis, oxidative stress, and Ca(2+) influx through TRPV1 channel activations in the hippocampus of TBI-induced rats. The 32 rats were divided into four groups: control, TBI, TBI + NAC, and TBI + Se groups. Intraperitoneal administrations of NAC and Se were performed at 1, 24, 48, and 72 h after TBI induction. After 3 days, the hippocampal neurons were freshly isolated from the rats. In cytosolic-free Ca(2+) analyses, the neurons were stimulated with the TRPV1 channel agonist capsaicin, a pungent compound found in hot chili peppers. Cytosolic-free Ca(2+), apoptosis, cytosolic ROS levels, and caspase-3 and -9 activities were higher in the TBI group than control. The values in the hippocampus were decreased by Se and NAC administrations. In conclusion, we observed that NAC and Se have protective effects on oxidative stress, apoptosis, and Ca(2+) entry via TRPV1 channel activation in the hippocampus of this TBI model, but the effect of NAC appears to be much greater than that of Se. They are both interesting candidates for studying the amelioration of TBIs.

Chronic ethanol exposure during adolescence in rats induces motor impairments and cerebral cortex damage associated with oxidative stress

Binge drinking is common among adolescents, and this type of ethanol exposure may lead to long-term nervous system damage. In the current study, we evaluated motor performance and tissue alterations in the cerebral cortex of rats subjected to intermittent intoxication with ethanol from adolescence to adulthood. Adolescent male Wistar rats (35 days old) were treated with distilled water or ethanol (6.5 g/kg/day, 22.5% w/v) during 55 days by gavage to complete 90 days of age. The open field, inclined plane and the rotarod tests were used to assess the spontaneous locomotor activity and motor coordination performance in adult animals. Following completion of behavioral tests, half of animals were submitted to immunohistochemical evaluation of NeuN (marker of neuronal bodies), GFAP (a marker of astrocytes) and Iba1 (microglia marker) in the cerebral cortex while the other half of the animals were subjected to analysis of oxidative stress markers by biochemical assays. Chronic ethanol intoxication in rats from adolescence to adulthood induced significant motor deficits including impaired spontaneous locomotion, coordination and muscle strength. These behavioral impairments were accompanied by marked changes in all cellular populations evaluated as well as increased levels of nitrite and lipid peroxidation in the cerebral cortex. These findings indicate that continuous ethanol intoxication from adolescence to adulthood is able to provide neurobehavioral and neurodegenerative damage to cerebral cortex.

In vivo study of ethanol-activated brain protein kinase A: manipulations of Ca2+ distribution and flux

BACKGROUND

The cAMP-dependent protein kinase (PKA) signaling transduction pathway has been shown to play an important role in the modulation of several ethanol (EtOH)-induced behavioral actions. In vivo, short-term exposure to EtOH up-regulates the cAMP-signaling cascade. Interestingly, different Ca(2+) -dependent cAMP-PKA cascade mediators play a critical role in the neurobehavioral response to EtOH, being of special relevance to the Ca(2+) -dependent adenylyl cyclases 1 and 8. We hypothesize an intracellular PKA activation elicited by EtOH administration, which may be regulated by a Ca(2+) -dependent mechanism as an early cellular response. Thus, the present work aims to explore the role of Ca(2+) (internal and external) on the EtOH-activated PKA cascade.

METHODS

Swiss male mice received an intraperitoneal injection of EtOH (0 or 4 g/kg), and brains were dissected following a temporal pattern (7, 15, 30, 45, 90, or 120 minutes). Either the enzymatic PKA activity or its fingerprint was analyzed on different brain areas (cortex, hypothalamus, hippocampus, and striatum). To explore the role of Ca(2+) on the EtOH-activated PKA cascade, mice were pretreated with diltiazem (0 or 20 mg/kg), dantrolene (0 or 5 mg/kg), or 3,7-Dimethyl-1-(2-propynyl)xanthine (0 or 1 mg/kg) 30 minutes before EtOH (4 g/kg) administration. After 45 minutes of EtOH administration, brains were removed and dissected to measure the PKA activity or its fingerprint.

RESULTS

Results from these experiments showed an EtOH-dependent activation of PKA in different brain areas. Manipulations involving a disruption of intracellular Ca(2+) release from the endoplasmic reticulum resulted in a decreased EtOH-induced activation of PKA. On the contrary, extracellular-to-cytoplasm Ca(2+) manipulations did not prevent the PKA activation by EtOH.

CONCLUSIONS

Altogether, these results show the critical role of stored Ca(2+) as an intracellular mediator of different neurobiological actions of EtOH and provide further evidence of a possible new target for EtOH within the central nervous system.

Effects of antiepileptic drugs on antioxidant and oxidant molecular pathways: focus on trace elements

Current reports on trace elements, oxidative stress, and the effect of antiepileptic drugs are poor and controversial. We aimed to review effects of most common used antiepileptics on antioxidant, trace element, calcium ion (Ca(2+)) influx, and oxidant systems in human and experimental animal models. Observations of lower blood or tissue antioxidant levels in epileptic patients and animals compared to controls in recent publications may commonly support the proposed crucial role of antioxidants in the pathogenesis of epilepsy. Effects of old and new antiepileptics on reactive oxygen species (ROS) production in epilepsy are controversial. The old antiepileptic drugs like valproic acid, phenytoin, and carbamazepine induced ROS overproduction, while new epileptic drugs (e.g., topiramate and zonisamide) induced scavenger effects on over production of ROS in human and animals. Antioxidant trace element levels such as selenium, copper, and zinc were generally low in the blood of epileptic patients, indicating trace element deficiencies in the pathogenesis of epilepsy. Recent papers indicate that selenium with/without topiramate administration in human and animals decreased seizure levels, although antioxidant values were increased. Recent studies also reported that sustained depolarization of mitochondrial membranes, enhanced ROS production and Ca(2+) influx may be modulated by topiramate. In conclusion, there is a large number of recent studies about the role of antioxidants or neuroprotectants in clinical and experimental models of epilepsy. New antiepileptic drugs are more prone to restore antioxidant redox systems in brain and neurons.

Selenium and topiramate attenuates blood oxidative toxicity in patients with epilepsy: a clinical pilot study

It is well known that oxidative stress plays an important role in the etiology of epilepsy. We investigated effects of selenium (Se) and topiramate (TPM) combination supplementation on antioxidant and oxidant values in control and patients with epilepsy and refractory epilepsy. For the aim, we used control (n = 19), epilepsy + TPM (n = 19), epilepsy + TPM + Se (n = 15) groups. We also used control (n = 15), refractory epilepsy (n = 15), and refractory epilepsy + Se (n = 8) groups. TPM (0.2 mg/daily) and Se, as sodium selenite (twice daily with 0.1 mg doses), were orally supplemented to the patients for 45 days. Erythrocyte lipid peroxidation levels were higher in refractory epilepsy groups than in control although its level and seizure numbers were decreased in TPM and TPM + Se supplemented groups of the patients. The erythrocyte reduced glutathione (GSH), glutathione peroxidase (GSH-Px), plasma total antioxidant status (TAS), and vitamin E concentration in refractory epilepsy group were lower than in control. However, the erythrocyte and plasma TAS, erythrocyte GSH and GSH-Px, and plasma vitamins A and C values were increased either by Se or Se + TPM in epilepsy and refractory epilepsy groups. There were no effects of TPM and Se on plasma β-carotene values in the groups. In conclusion, TPM and selenium caused protective effects on the epilepsy and refractory epilepsy-induced oxidative injury by inhibiting free radical production and supporting antioxidant redox system.

Epidemiology and inflammatory bowel diseases

The role of alcohol in causing or aggravating the pathogenesis of inflammatory bowel disease is unclear. For finding a conclusive answer for this valuable question we conducted this review. Only two studies were identified that successfully fulfilled our inclusive criteria. Usual consumption of alcohol reduced the risk compared with less frequent use (odds ratio = 0.57, 95%CI: 0.37-0.86). Light alcoholic drinking has protective effects against development of ulcerative colitis. But this inverse association disappeared when smoking was included.

Brief alcohol exposure alters transcription in astrocytes via the heat shock pathway

Astrocytes are critical for maintaining homeostasis in the central nervous system (CNS), and also participate in the genomic response of the brain to drugs of abuse, including alcohol. In this study, we investigated ethanol regulation of gene expression in astrocytes. A microarray screen revealed that a brief exposure of cortical astrocytes to ethanol increased the expression of a large number of genes. Among the alcohol-responsive genes (ARGs) are glial-specific immune response genes, as well as genes involved in the regulation of transcription, cell proliferation, and differentiation, and genes of the cytoskeleton and extracellular matrix. Genes involved in metabolism were also upregulated by alcohol exposure, including genes associated with oxidoreductase activity, insulin-like growth factor signaling, acetyl-CoA, and lipid metabolism. Previous microarray studies performed on ethanol-treated hepatocyte cultures and mouse liver tissue revealed the induction of almost identical classes of genes to those identified in our microarray experiments, suggesting that alcohol induces similar signaling mechanisms in the brain and liver. We found that acute ethanol exposure activated heat shock factor 1 (HSF1) in astrocytes, as demonstrated by the translocation of this transcription factor to the nucleus and the induction of a family of known HSF1-dependent genes, the heat shock proteins (Hsps). Transfection of a constitutively transcriptionally active Hsf1 construct into astrocytes induced many of the ARGs identified in our microarray study supporting the hypothesis that HSF1 transcriptional activity, as part of the heat shock cascade, may mediate the ethanol induction of these genes. These data indicate that acute ethanol exposure alters gene expression in astrocytes, in part via the activation of HSF1 and the heat shock cascade.

Cdc42-dependent activation of NADPH oxidase is involved in ethanol-induced neuronal oxidative stress

It has been suggested that excessive reactive oxygen species (ROS) and oxidative stress play an important role in ethanol-induced damage to both the developing and mature central nervous system (CNS). The mechanisms underlying ethanol-induced neuronal ROS, however, remain unclear. In this study, we investigated the role of NADPH oxidase (NOX) in ethanol-induced ROS generation. We demonstrated that ethanol activated NOX and inhibition of NOX reduced ethanol-promoted ROS generation. Ethanol significantly increased the expression of p47^phox and p67^phox, the essential subunits for NOX activation in cultured neuronal cells and the cerebral cortex of infant mice. Ethanol caused serine phosphorylation and membrane translocation of p47^phox and p67^phox, which were prerequisites for NOX assembly and activation. Knocking down p47^phox with the small interfering RNA was sufficient to attenuate ethanol-induced ROS production and ameliorate ethanol-mediated oxidative damage, which is indicated by a decrease in protein oxidation and lipid peroxidation. Ethanol activated cell division cycle 42 (Cdc42) and overexpression of a dominant negative (DN) Cdc42 abrogate ethanol-induced NOX activation and ROS generation. These results suggest that Cdc42-dependent NOX activation mediates ethanol-induced oxidative damages to neurons.

Implications of central immune signaling caused by drugs of abuse: mechanisms, mediators and new therapeutic approaches for prediction and treatment of drug dependence

In the past two decades a trickle of manuscripts examining the non-neuronal central nervous system immune consequences of the drugs of abuse has now swollen to a significant body of work. Initially, these studies reported associative evidence of central nervous system proinflammation resulting from exposure to the drugs of abuse demonstrating key implications for neurotoxicity and disease progression associated with, for example, HIV infection. However, more recently this drug-induced activation of central immune signaling is now understood to contribute substantially to the pharmacodynamic actions of the drugs of abuse, by enhancing the engagement of classical mesolimbic dopamine reward pathways and withdrawal centers. This review will highlight the key in vivo animal, human, biological and molecular evidence of these central immune signaling actions of opioids, alcohol, cocaine, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA). Excitingly, this new appreciation of central immune signaling activity of drugs of abuse provides novel therapeutic interventions and opportunities to identify 'at risk' individuals through the use of immunogenetics. Discussion will also cover the evidence of modulation of this signaling by existing clinical and pre-clinical drug candidates, and novel pharmacological targets. Finally, following examination of the breadth of central immune signaling actions of the drugs of abuse highlighted here, the current known common immune signaling components will be outlined and their impact on established addiction neurocircuitry discussed, thereby synthesizing a common neuroimmune hypothesis of addiction.

Intracellular calcium chelation with BAPTA-AM modulates ethanol-induced behavioral effects in mice

Calcium (Ca(2+)) has been characterized as one of the most ubiquitous, universal and versatile intracellular signaling molecules responsible for controlling numerous cellular processes. Ethanol-induced effects on Ca(2+) distribution and flux have been widely studied in vitro, showing that acute ethanol administration can modulate intracellular Ca(2+) concentrations in a dose dependent manner. In vivo, the relationship between Ca(2+) manipulation and the corresponding ethanol-induced behavioral effects have focused on Ca(2+) flux through voltage-gated Ca(2+) channels. The present study investigated the role of inward Ca(2+) currents in ethanol-induced psychomotor effects (stimulation and sedation) and ethanol intake. We studied the effects of the fast Ca(2+) chelator, BAPTA-AM, on ethanol-induced locomotor activity and the sedative effects of ethanol. Swiss (RjOrl) mice were pretreated with BAPTA-AM (0-10 mg/kg) 30 min before an ethanol (0-4 g/kg) challenge. Our results revealed that pretreatment with BAPTA-AM prevented locomotor stimulation produced by ethanol without altering basal locomotion. In contrast, BAPTA-AM reversed ethanol-induced hypnotic effects. In a second set of experiments, we investigated the effects of intracellular Ca(2+) chelation on ethanol intake. Following a drinking-in-the-dark methodology, male C57BL/6J mice were offered 20% v/v ethanol, tap water, or 0.1% sweetened water. The results of these experiments revealed that BAPTA-AM pretreatment (0-5 mg/kg) reduced ethanol consumption in a dose-dependent manner while leaving water and sweetened water intake unaffected. Our findings support the role of inward Ca(2+) currents in mediating different behavioral responses induced by ethanol. Our results are discussed together with data indicating that ethanol appears to be more sensitive to intracellular Ca(2+) manipulations than other psychoactive drugs.

Inflammation, mitochondria, and the inhibition of adult neurogenesis

The process of neurogenesis continues throughout life, with thousands of new neurons generated every day in the mammalian brain. Impairment of hippocampal neurogenesis has been suggested to be involved in neurodegenerative conditions, including the cognitive decline associated with aging, Alzheimer's disease, Parkinson's disease, and ionizing radiation. These neurodegenerative conditions are all characterized by proinflammatory changes and increased numbers of activated microglia. Activated microglia produce a variety of proinflammatory factors, including interleukin-6, tumor necrosis factor-α, reactive oxygen species, and nitric oxide, all of which are antineurogenic. These same factors have also been shown to suppress mitochondrial function, but the role of mitochondria in neurogenesis remains barely investigated. This brief review summarizes the findings of several studies that support a role for mitochondrial impairment as part of the mechanism of the reduction of neurogenesis associated with inflammation.

Ethanol reduces kainate-evoked glutamate secretion in rat hippocampal astrocytes

In this study we have used rat hippocampal astrocytes in culture to investigate the effect of ethanol on kainate-induced glutamate secretion. Our results show that kainate (10 μM to 500 μM) stimulated glutamate release from astrocytes. Preincubation of astrocytes in the presence of ethanol induced a concentration-dependent (1mM-50mM) inhibition of glutamate release caused by stimulation of cells with 100 μM kainate. Inhibition of alcohol-dehydrogenase, by preincubation of astrocytes in the presence of 4-methylpyrazole (1mM), abolished ethanol-induced inhibition of glutamate release in response to kainate. On the other hand, preincubation of astrocytes in the presence of the antioxidant cinnamtannin B-1 (10 μM) also blocked ethanol inhibitory action on glutamate release in response to kainate. Ethanol (50mM) reduced Ca(2+) mobilization in response to kainate, whereas cinnamtannin B-1 reversed the inhibitory action of ethanol on Ca(2+) mobilization by kainate. Our results are consistent with an inhibitory action of ethanol on glutamate secretion from hippocampal astrocytes. The inhibitory effects of ethanol are probably due to its oxidative metabolization, involves reactive oxygen species production, and a lower Ca(2+) mobilization by kainate. Taking into account the pivotal role that astrocytes play within the central nervous system, especially in relation to neurons, the negative effects of ethanol on the release of glutamate might affect neuron-glia communication in the hippocampus, which might lead to functional defects in the brain.

The role of oxidative stress in fetal alcohol spectrum disorders

The ingestion of alcohol/ethanol during pregnancy can result in abnormal fetal development in both humans and a variety of experimental animal models. Depending on the pattern of consumption, the dose, and the period of exposure to ethanol, a myriad of structural and functional deficits can be observed. These teratogenic effects are thought to result from the ethanol-induced dysregulation of a variety of intracellular pathways ultimately culminating in toxicity and cell death. For instance, ethanol exposure can lead to the generation of reactive oxygen species (ROS) and produce an imbalance in the intracellular redox state, leading to an overall increase in oxidative stress. In the present review we will provide an up-to-date summary on the effects of prenatal/neonatal ethanol exposure on the levels of oxidative stress in the central nervous system (CNS) of experimental models of fetal alcohol spectrum disorders (FASD). We will also review the evidence for the use of antioxidants as potential therapeutic strategies for the treatment of some of the neuropathological deficits characteristic of both rodent models of FASD and children afflicted with these disorders. We conclude that an imbalance in the intracellular redox state contributes to the deficits seen in FASD and suggest that antioxidants are potential candidates for the development of novel therapeutic strategies for the treatment of these developmental disorders.

Acute ethanol exposure disrupts actin cytoskeleton and generates reactive oxygen species in c6 cells

Central nervous system dysfunctions are among the most significant effects of exposure to ethanol and the glial cells that play an important role in maintaining neuronal function, are extremely involved with these effects. The actin cytoskeleton plays a crucial role in a wide variety of cellular functions, especially when there is some injury. Therefore the aim of the present study was to analyze the short-term effects of ethanol (50, 100 and 200 mM) on the cytoskeleton of C6 glioma cells. Here we report that acute ethanol exposure profoundly disrupts the actin cytoskeleton in C6 cells decreasing stress fiber formation and downregulating RhoA and vinculin immunocontent. In contrast, microtubule and GFAP networks were not altered. We further demonstrate that anti-oxidants prevent ethanol-induced actin alterations, suggesting that the actions of ethanol on the actin cytoskeleton are related with generation of reactive oxygen species (ROS) in these cells. Our results show that ethanol at concentrations described to be toxic to the central nervous system was able to target the cytoskeleton of C6 cells and this effect could be related with increased ROS generation. Therefore, we propose that the dynamic restructuring of the cytoskeleton of glial cells might contribute to the response to the injury provoked by binge-like ethanol exposure in brain.

p66SHC-mediated mitochondrial dysfunction in renal proximal tubule cells during oxidative injury

Mitochondrial dysfunction is involved in pathopysiology of ischemia-reperfusion-induced acute kidney injury (AKI). The p66shc adaptor protein is a newly recognized mediator of mitochondrial dysfunction, which might play a role in AKI-induced renal tubular injury. Oxidative stress-mediated Serine36 phosphorylation of p66shc facilitates its transportation to the mitochondria where it oxidizes cytochrome c and generates excessive amount of reactive oxygen species (ROS). The consequence is mitochondrial depolarization and injury. Earlier we determined that p66shc plays an essential role in injury of cultured mouse renal proximal tubule cells during oxidative stress. Here, we studied the role of p66shc in ROS generation and consequent mitochondrial dysfunction during oxidative injury in renal proximal tubule cells. We employed p66shc knockdown renal proximal tubule cells and cells that overexpress wild-type, Serine phosphorylation (S36A), or cytochrome c-binding (W134F) mutants of p66shc. Inhibition of the mitochondrial electron transport chain or the mitochondrial permeability transition revealed that hydrogen peroxide-induced injury is mitochondrial ROS and consequent mitochondrial depolarization dependent. We also found that through Ser36 phosphorylation and mitochondria/cytochrome c binding, p66shc mediates those effects. We propose a similar mechanism in vivo as we demonstrated mitochondrial binding of p66shc as well as its association with cytochrome c in the postischemic kidneys of mice. Thus, manipulating p66shc might offer a new therapeutic modality to ameliorate renal ischemic injury.

Participation of L-type calcium channels in ethanol-induced behavioral stimulation and motor incoordination: effects of diltiazem and verapamil

Calcium flux through voltage gate calcium channels (VGCC) is involved in many neuronal processes such as membrane depolarization, gene expression, hormone secretion, and neurotransmitter release. Several studies have shown that either acute or chronic exposure to ethanol modifies calcium influx through high voltage activated channels. Of special relevance is the L-type VGCC. Pharmacological manipulation of L-type calcium channels affects ethanol intake, ethanol discrimination and manifestations of withdrawal syndrome. The present study investigates the role of L-type channels on the psychomotor effects (stimulation and sedation/ataxia) of ethanol by testing the effects of different L-type calcium channel blockers (CCB) on such behaviors. Mice were pretreated intraperitoneally with the CCB, diltiazem (0-40 mg/kg) or verapamil (0-30 mg/kg) 30 min before ethanol (0-3.5 g/kg). Locomotion was measured in an open field chamber for 20 min immediately after ethanol. The two CCB tested prevented locomotor stimulation, but not locomotor suppression produced by ethanol. Doses of the two CCB which reduced ethanol stimulation, did not alter spontaneous locomotion. The ataxic effects of ethanol (1.25 g/kg), measured with an accelerating rotarod task, were not affected by diltiazem (20mg/kg) or verapamil (15 mg/kg). In addition, our results indicated that ethanol is more sensitive to the antagonism of L-type calcium channels than other drugs with stimulant properties; doses of the two CCB that reduced ethanol stimulation did not reduce the psychomotor effects of amphetamine, caffeine or cocaine. In conclusion, these data provide further evidence of the important involvement of L-type calcium channels in the behavioral effects produced by ethanol.

Intermediate filaments take the heat as stress proteins

Intermediate filament (IF) proteins and heat shock proteins (HSPs) are large multimember families that share several features, including protein abundance, significant upregulation in response to a variety of stresses, cytoprotective functions, and the phenocopying of several human diseases after IF protein or HSP mutation. We are now coming to understand that these common elements point to IFs as important cellular stress proteins with some roles akin to those already well-characterized for HSPs. Unique functional roles for IFs include protection from mechanical stress, whereas HSPs are characteristically involved in protein folding and as chaperones. Shared IF and HSP cytoprotective roles include inhibition of apoptosis, organelle homeostasis, and scaffolding. In this report, we review data that corroborate the view that IFs function as highly specialized cytoskeletal stress proteins that promote cellular organization and homeostasis.

Thymosin-beta4 attenuates ethanol-induced neurotoxicity in cultured cerebral cortical astrocytes by inhibiting apoptosis

Thymosin-beta4 (Tbeta4) is a major actin monomer-binding peptide in mammalian tissues and plays a crucial role in the nervous system in synaptogenesis, neuronal survival and migration, axonal growth, and plastic changes of dendritic spines. However, it is unknown whether Tbeta4 is also involved in challenges with external stress such as ethanol-induced neurotoxicity. In the present study, we investigated the effects of Tbeta4 on ethanol-induced neurotoxicity in cultured cerebral cortical astrocytes and the underlying mechanisms. Primarily cultured astrocytes were treated with 1 microg/ml Tbeta4 2 h prior to administration of 100 mM ethanol for 0.5, 1, 3 and 6 days, respectively. The results showed that ethanol caused neurotoxicity in cultured astrocytes, as shown by declined cell viability, distinct astroglial apoptosis and increased intracellular peroxidation. Tbeta4 markedly promoted cell viability, ameliorated the injury of intracellular glial fibrillary acidic protein-immunopositive cytoskeletal structures, reduced the percentage of apoptotic astrocyte and cellular DNA fragmentation, suppressed caspase-3 activity and upregulated Bcl-2 expression, inhibited the accumulation of reactive oxygen species and production of malondialdehyde in ethanol-treated astrocytes in a time-dependent manner. These data indicated that Tbeta4 attenuates ethanol-induced neurotoxicity in cultured cortical astrocytes through inhibition of apoptosis signaling, and one of the mechanisms underlying the capacity of Tbeta4 to suppress apoptosis may in part be due to its effect of anti-peroxidation.

Ethanol alters the physiology of neuron-glia communication

In the central nervous system (CNS), both neurones and astrocytes play crucial roles. On a cellular level, brain activity involves continuous interactions within complex cellular circuits established between neural cells and glia. Although it was initially considered that neurones were the major cell type in cerebral function, nowadays astrocytes are considered to contribute to cerebral function too. Astrocytes support normal neuronal activity, including synaptic function, by regulating the extracellular environment with respect to ions and neurotransmitters. There is a plethora of noxious agents which can lead to the development of alterations in organs and functional systems, and that will end in a chronic prognosis. Among the potentially harmful external agents we can find ethanol consumption, whose consequences have been recognized as a major public health concern. Deregulation of cell cycle has devastating effects on the integrity of cells, and has been closely associated with the development of pathologies which can lead to dysfunction and cell death. An alteration of normal neuronal-glial physiology could represent the basis of neurodegenerative processes. In this review we will pay attention on to the recent findings in astrocyte function and their role toward neurons under ethanol consumption.

Ameliorative effects of Ocimum sanctum in sciatic nerve transection-induced neuropathy in rats

OBJECTIVES

The present study was aimed at investigating the ameliorative effect of Ocimum sanctum in sciatic nerve transection (axotomy)-induced peripheral neuropathy in rats.

MATERIALS AND METHODS

Sciatic nerve transection-induced axonal degeneration was assessed histopathologically. Paw pressure, Von Frey Hair, tail cold-hyperalgesia, motor in-coordination tests were performed to assess the extent of neuropathy. Biochemical estimations of thiobarbituric acid reactive species (TBARS), reduced glutathione (GSH), and total calcium levels were also performed. Methanolic extract of Ocimum sanctum at different doses (50, 100 and 200mg/kg p.o.) was administered for 10 consecutive days starting from the day of surgery.

RESULTS

Administration of Ocimum sanctum attenuated sciatic nerve transection-induced axonal degeneration, reduction of nociceptive threshold and motor in-coordination. Moreover, it also attenuated axotomy-induced rise in TBARS, total calcium and decrease in GSH levels in a dose-dependent manner.

CONCLUSION

Anti-oxidant and calcium attenuating actions may be responsible for observed ameliorative effects of Ocimum sanctum in axotomy-induced neuropathy.

Ethanol induces glutamate secretion by Ca2+ mobilization and ROS generation in rat hippocampal astrocytes

In this study we have investigated the effect of ethanol on [Ca2+]c by microfluorimetry and glutamate secretion using an enzyme-linked system, in rat hippocampal astrocytes in culture. Our results show that ethanol (1-200 mM) evoked a dose-dependent increase in glutamate secretion. 50 mM ethanol, a concentration within the range of blood alcohol levels in intoxicated humans, induced a release of Ca2+ from intracellular stores in the form of oscillations. Ca2+-mobilizing effect of ethanol was not prevented by preincubation of cells in the presence of 2 mM of the antioxidant dithiothreitol. Ethanol-evoked glutamate secretion was reduced when extracellular Ca2+ was omitted (medium containing 0.5 mM EGTA) and following preincubation of astrocytes in the presence of the intracellular Ca2+ chelator 1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetraacetoxy-methyl ester (10 microM). Preincubation of astrocytes in the presence of 2 mM of the antioxidant dithiothreitol significantly reduced ethanol-evoked glutamate secretion. Finally, preincubation of astrocytes in the presence of bafilomycin (50 nM) significantly reduced ethanol-induced neurotransmitter release, indicating that exocytosis is involved in glutamate secretion. In conclusion, our results suggest that ethanol mobilizes Ca2+ from intracellular stores, and stimulates a Ca2+-dependent glutamate secretion, probably involving reactive oxygen species production, and therefore creating a situation potentially leading to neurotoxicity in the hippocampus.