Ebselen reduces cytochrome c release from mitochondria and subsequent DNA fragmentation after transient focal cerebral ischemia in mice

The role of oxidative stress in blood-brain barrier disruption during ischemic stroke: Antioxidants in clinical trials

Ischemic stroke is one of the leading causes of death and disability. Occlusion and reperfusion of cerebral blood vessels (i.e., ischemia/reperfusion (I/R) injury) generates reactive oxygen species (ROS) that contribute to brain cell death and dysfunction of the blood-brain barrier (BBB) via oxidative stress. BBB disruption influences the pathogenesis of ischemic stroke by contributing to cerebral edema, hemorrhagic transformation, and extravasation of circulating neurotoxic proteins. An improved understanding of mechanisms for ROS-associated alterations in BBB function during ischemia/reperfusion (I/R) injury can lead to improved treatment paradigms for ischemic stroke. Unfortunately, progress in developing ROS targeted therapeutics that are effective for stroke treatment has been slow. Here, we review how ROS are produced in response to I/R injury, their effects on BBB integrity (i.e., tight junction protein complexes, transporters), and the utilization of antioxidant treatments in ischemic stroke clinical trials. Overall, knowledge in this area provides a strong translational framework for discovery of novel drugs for stroke and/or improved strategies to mitigate I/R injury in stroke patients.

Selenoprotein Gene mRNA Expression Evaluation During Renal Ischemia-Reperfusion Injury in Rats and Ebselen Intervention Effects

Effects of selenoproteins on many renal diseases have been reported. However, their role in renal ischemia-reperfusion (I/R) injury is unclear. The present study was performed to investigate the impact of ebselen and renal I/R injury on the expression of selenoproteins. Sprague-Dawley rats were pretreated with or without ebselen (10 mg/kg) through a daily single oral administration from 3 days before renal I/R surgery. RT-qPCR (real-time quantitative PCR) was performed to determine the mRNA expression of 25 selenoprotein genes in the renal tissues. The expression levels of two selenoproteins, including GPX3 (glutathione peroxidase 3) and DIO1 (iodothyronine deiodinase 1), were evaluated by Western blot or/and IHF (immunohistofluorescence) assays. Furthermore, renal function, renal damage, oxidative stress, and apoptosis were assessed. The results showed that in renal I/R injury, the mRNA levels of 15 selenoprotein genes (GPX1, GPX3, GPX4, DIO1, DIO2, TXNRD2, TXNRD3, SEPHS2, MSRB1, SELENOF, SELENOK, SELENOO, SELENOP, SELENOS, and SELENOT) were decreased, whereas those of eight selenoprotein genes (GPX2, GPX6, DIO3, TXNRD1, SELENOH, SELENOM, SELENOV, and SELENOW) were increased. I/R also induced a reduction in the expression levels of GPX3 and DIO1 proteins. In addition, our results indicated that ebselen reversed the changes in those selenoprotein genes, excluding SELENOH, SELENOM, SELENOP, and SELENOT, in renal I/R injury and alleviated I/R-induced renal dysfunction, tissue damage, oxidative stress, and apoptosis. To our knowledge, this is the first study to investigate the changes of 25 mammalian selenoprotein genes in renal I/R injury kidneys. The present study also provided more evidence for the roles of ebselen against renal I/R injury.

Exploring multifunctional antioxidants as potential agents for management of neurological disorders

Free radical or oxidative stress may be a fundamental mechanism underlying several human neurologic diseases. Therapy using free radical scavengers (antioxidants) has the potential to prevent, delay, or ameliorate many neurologic disorders. However, the biochemistry of oxidative pathobiology is complex, and optimum antioxidant therapeutic options may vary and need to be tailored to individual diseases. In vitro and animal model studies support the potential beneficial role of various antioxidant compounds in neurological disease. Antioxidants generally play an important role in reducing or preventing the cell damage and other changes which occur in the cells like mitochondrial dysfunction, DNA mutations, and lipid peroxidation in the cell membrane. Based on their mechanism of action, antioxidants can be used to treat various neurological disorders like Huntington's disease, Alzheimer's disease, and Parkinson's disease. Vitamin E has a scavenging action for reactive oxygen species (ROS) and also prevents the lipid peroxidation. Creatine generally reduces the mitochondrial dysfunction in Parkinson's disease (PD) patients. Various metal chelators are used in PD for the prevention of accumulation of the metals. Superoxidase dismutase (SOD), lipases, and proteases act as repair enzymes in patients with AD. Accordingly, the antioxidant defense system is found to be most useful for treating various neurological disorders.

Ebselen ameliorates renal ischemia-reperfusion injury via enhancing autophagy in rats

Renal ischemia-reperfusion (I/R) injury is one of the most common causes of chronic kidney disease (CKD). It brings unfavorable outcomes to the patients and leads to a considerable socioeconomic burden. The study of renal I/R injury is still one of the hot topics in the medical field. Ebselen is an organic selenide that attenuates I/R injury in various organs. However, its effect and related mechanism underlying renal I/R injury remains unclear. In this study, we established a rat model of renal I/R injury to study the preventive effect of ebselen on renal I/R injury and further explore the potential mechanism of its action. We found that ebselen pretreatment reduced renal dysfunction and tissue damage caused by renal I/R. In addition, ebselen enhanced autophagy and inhibited oxidative stress. Additionally, ebselen pretreatment activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. The protective effect of ebselen was suppressed by autophagy inhibitor wortmannin. In conclusion, ebselen could ameliorate renal I/R injury, probably by enhancing autophagy, activating the Nrf2 signaling pathway, and reducing oxidative stress.

Oxidative Stress in Ischemia/Reperfusion Injuries following Acute Ischemic Stroke

Recanalization therapy is increasingly used in the treatment of acute ischemic stroke. However, in about one third of these patients, recanalization is followed by ischemia/reperfusion injuries, and clinically to worsening of the neurological status. Much research has focused on unraveling the involved mechanisms in order to prevent or efficiently treat these injuries. What we know so far is that oxidative stress and mitochondrial dysfunction are significantly involved in the pathogenesis of ischemia/reperfusion injury. However, despite promising results obtained in experimental research, clinical studies trying to interfere with the oxidative pathways have mostly failed. The current article discusses the main mechanisms leading to ischemia/reperfusion injuries, such as mitochondrial dysfunction, excitotoxicity, and oxidative stress, and reviews the clinical trials with antioxidant molecules highlighting recent developments and future strategies.

Ebselen reversed peripheral oxidative stress induced by a mouse model of sporadic Alzheimer's disease

Intracerebroventricular streptozotocin injection (icv STZ) is a well established sporadic Alzheimer's disease (AD) model in rodents. AD is characterized by neuronal degeneration accompanied by central oxidative stress. Studies also indicate peripheral oxidative damage in AD, but if the icv STZ model of sporadic AD mimics this feature is an open question. This study aimed to investigate if icv STZ administration induces peripheral oxidative stress and the antioxidant action of Ebselen, compared to the reference drug (donepezil), in this sporadic AD model. Male adult Swiss mice received icv STZ (days 1 and 3). Mice received Ebselen (10 mg/kg, i.p) or Donepezil (5 mg/kg, i.p) for 14 days. Mice were killed and the kidney and liver were excised to determine parameters of oxidative stress and toxicity markers. The mice icv STZ-injected showed peripheral oxidative stress. Ebselen reversed renal lipid peroxidation in the icv STZ administered mice by modulating NPSH levels, SOD and CAT activities, whereas Donepezil, modulated only NPSH levels. Ebselen and Donepezil counteracted hepatic lipid peroxidation in STZ-injected mice by modulating NPSH levels and CAT activity. The δ-ALA-D activity was inhibited in the kidney, but not in the liver, whereas the icv STZ-injected mice had an increase in the GST activity in both tissues. Ebselen reversed the increase in the hepatic GST activity of the STZ-injected mice. Donepezil increased renal GST activity in the control mice. In conclusion, this study demonstrates that the icv STZ administration induced peripheral oxidative stress. Ebselen, similar to Donepezil, was effective against peripheral oxidative stress in a mouse model of sporadic AD.

MiR-34a Interacts with Cytochrome c and Shapes Stroke Outcomes

Blood-brain barrier (BBB) dysfunction occurs in cerebrovascular diseases and neurodegenerative disorders such as stroke. Opening of the BBB during a stroke has a negative impact on acute outcomes. We have recently demonstrated that miR-34a regulates the BBB by targeting cytochrome c (CYC) in vitro. To investigate the role of miR-34a in a stroke, we purified primary cerebrovascular endothelial cells (pCECs) from mouse brains following 1 h transient middle cerebral artery occlusion (tMCAO) and measured real-time PCR to detect miR-34a levels. We demonstrate that the miR-34a levels are elevated in pCECs from tMCAO mice at the time point of BBB opening following 1 h tMCAO and reperfusion. Interestingly, knockout of miR-34a significantly reduces BBB permeability, alleviates disruption of tight junctions, and improves stroke outcomes compared to wild-type (WT) controls. CYC is decreased in the ischemic hemispheres and pCECs from WT but not in miR-34a^−/− mice following stroke reperfusion. We further confirmed CYC is a target of miR-34a by a dural luciferase reporter gene assay in vitro. Our study provides the first description of miR-34a affecting stroke outcomes and may lead to discovery of new mechanisms and treatments for cerebrovascular and neurodegenerative diseases such as stroke.

Pre-clinical to Clinical Translational Failures and Current Status of Clinical Trials in Stroke Therapy: A Brief Review

In stroke (cerebral ischemia), despite continuous efforts both at the experimental and clinical level, the only approved pharmacological treatment has been restricted to tissue plasminogen activator (tPA). Stroke is the leading cause of functional disability and mortality throughout worldwide. Its pathophysiology starts with energy pump failure, followed by complex signaling cascade that ultimately ends in neuronal cell death. Ischemic cascade involves excessive glutamate release followed by raised intracellular sodium and calcium influx along with free radicals' generation, activation of inflammatory cytokines, NO synthases, lipases, endonucleases and other apoptotic pathways leading to cell edema and death. At the pre-clinical stage, several agents have been tried and proven as an effective neuroprotectant in animal models of ischemia. However, these agents failed to show convincing results in terms of efficacy and safety when the trials were conducted in humans following stroke. This article highlights the various agents which have been tried in the past but failed to translate into stroke therapy along with key points that are responsible for the lagging of experimental success to translational failure in stroke treatment.

Anti-apoptotic activity of ETB receptor agonist, IRL-1620, protects neural cells in rats with cerebral ischemia

Endothelin-B receptor agonist, IRL-1620, provides significant neuroprotection following cerebral ischemia in rats. Whether this neuroprotection is due to inhibition of apoptosis is unknown. IRL-1620-treated rats following permanent middle cerebral artery occlusion (MCAO) showed significant improvement in neurological and motor functions along with a decrease in infarct volume at 24 h (-81.3%) and day 7 (-73.0%) compared to vehicle group. Cerebral blood flow (CBF) significantly improved in IRL-1620-treated animals compared to vehicle by day 7 post MCAO. IRL-1620-treated rats showed an increase in phospho-Akt and decrease in Bad level 7 h post-occlusion compared to vehicle, while Akt and Bad expression was similar in cerebral hemispheres at 24 h post-MCAO. The phospho-Bad level was lower in vehicle- but not in IRL-1620-treated rats at 24 h. Anti-apoptotic Bcl-2 expression decreased, while pro-apoptotic Bax expression increased in vehicle-treated MCAO rats, these changes were attenuated (P < 0.01) by IRL-1620. Mitochondrial membrane-bound Bax intensity significantly decreased in IRL-1620 compared to vehicle-treated MCAO rats. IRL-1620 treatment reduced (P < 0.001) the number of TUNEL-positive cells compared to vehicle at 24 h and day 7 post MCAO. The results demonstrate that IRL-1620 is neuroprotective and attenuates neural damage following cerebral ischemia in rats by increasing CBF and reducing apoptosis.

Organoselenotriazoles attenuate oxidative damage induced by mitochondrial dysfunction in mev-1 Caenorhabditis elegans mutants

Organic selenium compounds have several pharmacological activities already described, as anti-inflammatory and antitumor activities, which have been attributed to their antioxidant effects. Because they are promising in pharmacology, the synthesis of these compounds has increased significantly. As many new molecules are synthesized the use of a simple model like Caenorhabditis elegans is highly advantageous for initial evaluation of the toxicity and therapeutic potential of these molecules. The objective of this study was to evaluate the toxicity and antioxidant capacity of a series of selenotriazoles compounds in C. elegans. The animals were exposed to the compounds in liquid medium for only 30 min at the first larval stage (L1). The compounds had no toxic effects at the concentrations tested. Treatment with selenotriazoles (10 μM) partially reversed the stress induced by the pesticide paraquat (1 mM). Se-Tz Ia compound partially increased the survival of worms treated with H₂O₂ (0.5 mM). The compounds also increased the longevity of mev-1 mutants, which have a reduced life span by the production of excessive reactive oxygen species (ROS) in the mitochondria caused by a mutation in complex II of the electron transport chain. In addition, the compounds reduced the levels of ROS determined by the fluorescent probe DCF-DA as well as also reduced catalase enzyme activity in these animals. Based on the results found, it is possible to conclude that the compounds have antioxidant activity mainly in oxidative stress condition generated by a mitochondrial dysfunction in C. elegans.

Neuroprotective strategies and the underlying molecular basis of cerebrovascular stroke

Stroke is a leading cause of disability in the US. Although there has been significant progress in the area of medical and surgical thrombolytic technologies, neuroprotective agents to prevent secondary cerebral injury and to minimize disability remain limited. Only limited success has been reported in preclinical and clinical trials evaluating a variety of compounds. In this review, the authors discuss the most up-to-date information regarding the underlying molecular biology of stroke as well as strategies that aim to mitigate this complex signaling cascade. Results of historical research trials involving N-methyl-d-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor antagonists, clomethiazole, antioxidants, citicoline, nitric oxide, and immune regulators have laid the groundwork for current progress. In addition, more recent studies involving therapeutic hypothermia, magnesium, albumin, glyburide, uric acid, and a variety of other treatments have provided more options. The use of neuroprotective agents in combination or with existing thrombolytic treatments may be one of many exciting areas of further development. Although past trials of neuroprotective agents in ischemic stroke have been limited, significant insights into mechanisms of stroke, animal models, and trial design have incrementally improved approaches for future therapies.

Ebselen Decreases Oxygen Free Radical Production and Iron Concentrations in the Hearts of Chronically Iron-Overloaded Mice

Chronic iron overload is a major cause of cardiac failure throughout the world, but its pathogenesis remains to be clarified. It is conjectured that the toxicity of iron is due to its ability to catalyze the formation of oxygen free radicals (OFR), which can damage cellular membranes, proteins, and DNA. The authors report on the cardioprotective effects of the glutathione peroxidase (GPx) mimic ebselen on iron concentrations in the heart and GPx activity, and on the production of the cytotoxic aldehydes hexanal, 4-hydroxyl-2-nonenal (HNE), and malondialdehyde (MDA). Fifteen B6D2F1 mice were randomized to 1 of 3 treatment groups for a total of 20 treatments: 1) control (0.1 mL normal saline i.p. per mouse, per day); 2) iron-only (10 mg iron dextran i.p. per mouse, per day); 3) iron plus ebselen (25 mg/kg p.o. per mouse, per day). In comparison to iron-only treated mice, the authors’ findings show that supplementation with ebselen can decrease both cytotoxic aldehyde and iron concentrations in heart tissue. Additionally, mice supplemented with ebselen had an increase in GPx activity level in comparison to iron-only treated mice. To the authors’knowledge, this is the first study to examine the cardioprotective effects of ebselen against OFR damage in a model of chronic iron overload. These findings suggest that ebselen may have significance in the management of disorders of iron overload.

Neuronal hypoxia disrupts mitochondrial fusion

Brain ischemia/reperfusion injury results in death of vulnerable neurons and extensive brain damage. It is well known that mitochondrial release of cytochrome c (cyto c) is a hallmark of neuronal death, however the molecular events underlying this release are largely unknown. We tested the hypothesis that cyto c release is regulated by breakdown of the cristae architecture maintenance protein, optic atrophy 1 (OPA1), located in the inner mitochondrial membrane. We simulated ischemia/reperfusion in isolated primary rat neurons and interrogated OPA1 release from the mitochondria, OPA1 oligomeric breakdown, and concomitant dysfunction of mitochondrial dynamic state. We found that ischemia/reperfusion induces cyto c release and cell death that corresponds to multiple changes in OPA1, including: (i) translocation of the mitochondrial fusion protein OPA1 from the mitochondria to the cytosol, (ii) increase in the short isoform of OPA1, suggestive of proteolytic processing, (iii) breakdown of OPA1 oligomers in the mitochondria, and (iv) increased mitochondrial fission. Thus, we present novel evidence of a connection between release of cyto c from mitochondria and disruption of the mitochondrial fusion.

Momordica charantia polysaccharides could protect against cerebral ischemia/reperfusion injury through inhibiting oxidative stress mediated c-Jun N-terminal kinase 3 signaling pathway

Momordica charantia (MC) is a medicinal plant for stroke treatment in Traditional Chinese Medicine, but its active compounds and molecular targets are unknown yet. M. charantia polysaccharide (MCP) is one of the important bioactive components in MC. In the present study, we tested the hypothesis that MCP has neuroprotective effects against cerebral ischemia/reperfusion injury through scavenging superoxide (O2(-)), nitric oxide (NO) and peroxynitrite (ONOO(-)) and inhibiting c-Jun N-terminal protein kinase (JNK3) signaling cascades. We conducted experiments with in vivo global and focal cerebral ischemia/reperfusion rat models and in vitro oxygen glucose deprivation (OGD) neural cells. The effects of MCP on apoptotic cell death and infarction volume, the bioactivities of scavenging O2(-), NO and ONOO(-), inhibiting lipid peroxidation and modulating JNK3 signaling pathway were investigated. Major results are summarized as below: (1) MCP dose-dependently attenuated apoptotic cell death in neural cells under OGD condition in vitro and reduced infarction volume in ischemic brains in vivo; (2) MCP had directing scavenging effects on NO, O2(-) and ONOO(-) and inhibited lipid peroxidation; (3) MCP inhibited the activations of JNK3/c-Jun/Fas-L and JNK3/cytochrome C/caspases-3 signaling cascades in ischemic brains in vivo. Taken together, we conclude that MCP could be a promising neuroprotective ingredient of M. charantia and its mechanisms could be at least in part attributed to its antioxidant activities and inhibiting JNK3 signaling cascades during cerebral ischemia/reperfusion injury.

Oxidative Stress and the Use of Antioxidants in Stroke

Transient or permanent interruption of cerebral blood flow by occlusion of a cerebral artery gives rise to an ischaemic stroke leading to irreversible damage or dysfunction to the cells within the affected tissue along with permanent or reversible neurological deficit. Extensive research has identified excitotoxicity, oxidative stress, inflammation and cell death as key contributory pathways underlying lesion progression. The cornerstone of treatment for acute ischaemic stroke remains reperfusion therapy with recombinant tissue plasminogen activator (rt-PA). The downstream sequelae of events resulting from spontaneous or pharmacological reperfusion lead to an imbalance in the production of harmful reactive oxygen species (ROS) over endogenous anti-oxidant protection strategies. As such, anti-oxidant therapy has long been investigated as a means to reduce the extent of injury resulting from ischaemic stroke with varying degrees of success. Here we discuss the production and source of these ROS and the various strategies employed to modulate levels. These strategies broadly attempt to inhibit ROS production or increase scavenging or degradation of ROS. While early clinical studies have failed to translate success from bench to bedside, the combination of anti-oxidants with existing thrombolytics or novel neuroprotectants may represent an avenue worthy of clinical investigation. Clearly, there is a pressing need to identify new therapeutic alternatives for the vast majority of patients who are not eligible to receive rt-PA for this debilitating and devastating disease.

Effects of organoselenium compounds on early and late brain biochemical alterations in sepsis-survivor rats

Studies have consistently reported the participation of oxidative stress, energetic metabolism impairment, and creatine kinase (CK) activity alterations in rat brain in early times in an animal model of sepsis and persist for up to 10 days. We have assessed the antioxidant effects of administration of Ebselen (Eb) e diphenyl diselenide (PhSe)2 two organoselenium compounds on brain oxidative stress, energetic metabolism, and CK activity 12, 24 h, and 10 days after sepsis by cecal ligation and perforation (CLP) in rats. Male Wistar rats underwent either sham operation or CLP and were treated with oral injection of Eb (50 mg/kg) or (PhSe)2 (50 mg/kg) or vehicle. 12, 24 h, and 10 days after CLP, the rats were sacrificed, and samples from brain (hippocampus, striatum, cerebellum, prefrontal cortex, and cortex) were obtained and assayed for thiobarbituric acid reactive species and protein carbonyls formation, mitochondrial respiratory chain, and CK activity. We observed in the results a reduction of oxidative damage to lipids and proteins in the different cerebral structures studied and times with the administration of (PhSe)2; however, Eb seems to exert the same effect. Such changes are reflected in the assessment of mitochondrial respiratory chain complexes by reversing the decreased activity of the complex caused by the model of CLP and CK activity. Our data provide the first experimental demonstration that (PhSe)2 was able to reduce the brain dysfunction associated with CLP-induced sepsis in rats, by decreasing oxidative stress parameters mitochondrial dysfunction and CK activity in early times and in late time.

Oligodendrocyte pathophysiology and treatment strategies in cerebral ischemia

Oligodendrocytes (OLs), the myelin-forming cells of the central nervous system, form a functional unit with axons and play a crucial role in axonal integrity. An episode of hypoxia-ischemia causes rapid and severe damage to these particularly vulnerable cells via multiple pathways such as overactivation of glutamate and ATP receptors, oxidative stress, and disruption of mitochondrial function. The cardinal effect of OL pathology is demyelination and dysmyelination, and this has profound effects on axonal function, transport, structure, metabolism, and survival. The OL is a primary target of ischemia in adult-onset stroke and especially in periventricular leukomalacia and should be considered as a primary therapeutic target in these conditions. More emphasis is needed on therapeutic strategies that target OLs, myelin, and their receptors, as these have the potential to significantly attenuate white matter injury and to establish functional recovery of white matter after stroke. In this review, we will summarize recent progress on the role of OLs in white matter ischemic injury and the current and emerging principles that form the basis for protective strategies against OL death.

In vitroevaluation of glutathione peroxidase (GPx)-like activity and antioxidant properties of some Ebselen analogues

Four analogues of Ebselen were synthesized and their glutathione peroxidase activity and antioxidant property evaluated and compared to Ebselen. Among the studied compounds, only diselenide [3] exhibited both glutathione peroxidase activity and radical-scavenging capability. Compounds [3] and [4] showed a strong inhibitory effect (53% and 43%, respectively) on the lipid peroxidation of linoleic acid compared to Ebselen and selenide derivatives ([1] and [2]) which were less active (28%, 26% and 18% inhibition, respectively). A concentration-dependent inhibitory effect was also found in the model of the formation of ABTS*+ radical cation: 65% and 89% inhibition for compound [3] at 10(-4) M and 5 x 10(-5) M, respectively, and 68% and 90% for compound [4], compared to 14% and 52% inhibition for Ebselen and the diselenides [1] and [2] (29%, 46% and 45%, 68%, respectively). By EPR spin trapping technique, the following inhibitory profile of the Ebselen analogues was observed towards the formation of thiyl radicals: Ebselen = [3]>[1]>[2]>[4]. Studies with compound [3] are in progress on oxidative stress cell models.

Melatonin: the smart killer: the human trophoblast as a model

Melatonin has both the ability to induce intrinsic apoptosis in tumor cells while it inhibits it in non-tumor cells. Melatonin kills tumor cells through induction of reactive oxygen species generation and activation of pro-apoptotic pathways. In contrast, melatonin promotes the survival of non-tumor cells due to its antioxidant properties and the inhibition of pro-apoptotic pathways. In primary human villous trophoblast, a known pseudo-tumorigenic tissue, melatonin promotes the survival through inhibition of the Bax/Bcl-2 pathway while in BeWo choriocarcinoma cell line melatonin induces permeabilization of the mitochondrial membrane leading to cellular death. These findings suggest that the trophoblast is a good model to study the differential effects of melatonin on the intrinsic apoptosis pathway. This review describes the differential effects of melatonin on the intrinsic apoptosis pathway in tumor and non-tumor cells and presents the trophoblast as a novel model system in which to study these effects of melatonin.

Multiple aberrations in shared inflammatory and oxidative & nitrosative stress (IO&NS) pathways explain the co-association of depression and cardiovascular disorder (CVD), and the increased risk for CVD and due mortality in depressed patients

There is evidence that there is a bidirectional relationship between major depression and cardiovascular disorder (CVD): depressed patients are a population at risk for increased cardiac morbidity and mortality, and depression is more frequent in patients who suffer from CVD. There is also evidence that inflammatory and oxidative and nitrosative stress (IO&NS) pathways underpin the common pathophysiology of both CVD and major depression. Activation of these pathways may increase risk for both disorders and contribute to shared risk. The shared IO&NS pathways that may contribute to CVD and depression comprise the following: increased levels of pro-inflammatory cytokines, like interleukin-1β (IL-1β), IL-2, IL-6, IL-8, IL-12, tumor necrosis factor-α, and interferon-γ; T cell activation; increased acute phase proteins, like C-reactive protein, haptoglobin, fibrinogen and α1-antitrypsin; complement factors; increased LPS load through bacterial translocation and subsequent gut-derived inflammation; induction of indoleamine 2,3-dioxygenase with increased levels of tryptophan catabolites; decreased levels of antioxidants, like coenzyme Q10, zinc, vitamin E, glutathione and glutathione peroxidase; increased O&NS characterized by oxidative damage to low density lipoprotein (LDL) and phospholipid inositol, increased malondialdehyde, and damage to DNA and mitochondria; increased nitrosative stress; and decreased ω3 polyunsaturated fatty acids (PUFAs). The complex interplay between the abovementioned IO&NS pathways in depression results in pro-atherogenic effects and should be regarded as a risk factor to future clinical CVD and due mortality. We suggest that major depression should be added as a risk factor to the Charlson "comorbidity" index. It is advised that patients with (sub)chronic or recurrent major depression should routinely be assessed by serology tests to predict if they have an increased risk to cardiovascular disorders.

Comparative ultrastructural analysis of mitochondria in the CA1 and CA3 hippocampal pyramidal cells following global ischemia in Mongolian gerbils

Post-ischemic injury of the hippocampus unrolls at different levels and has both functional and structural implications. The deficiency in neuron energy metabolism is an initiating factor. We performed transmission electron microscopic (TEM) comparative analysis of mitochondria in excitatory spine synapses in CA1 stratum radiatum and CA3 hippocampal areas after 5 min of global cerebral ischemia in Mongolian gerbils, 4 and 7 days after reperfusion. Electron microscopy and unbiased morphometric methods were used to evaluate synaptic plasticity, and the number and size of mitochondria in synaptic terminals. We compared the morphological organization of mitochondria in presynaptic terminals between CA1 and CA3 areas in control and post-ischemic condition according to the following morphometric parameters: mitochondrial volume fraction, mitochondrial frequency in CA1 and CA3 terminals, mean number of mitochondria per presynaptic terminal, frequency of damaged mitochondria in terminals, and density of presynaptic terminals. Our ultrastructural study revealed statistically significant differences in morphometric parameters between CA1 and CA3 areas in control conditions, as well as in post-ischemic conditions. Also, we found temporal differences in measured parameters obtained 4 and 7 days after reperfusion. This study showed significant morphological differences in the organization of mitochondria in excitatory spine synapses between CA1 and CA3 areas, which corresponded with already known differences in functionality and sensitivity to the ischemic insult. Our conclusion is that revealed post-ischemic changes in mitochondrial distribution in presynaptic CA1 and CA3 terminals could be an indicator of hippocampal metabolic dysfunction and synaptic plasticity.

An insight into the protection of rat liver against ischemia/reperfusion injury by 2-selenium-bridged beta-cyclodextrin

AIM

The reperfusion following liver ischemia results in the damage and apoptosis of hepatocytes. The aim of this study was to investigate the possible effects and mechanism of a new synthesized glutathione peroxidase (GPX) mimic, 2-selenium-bridged beta-cyclodextrin (2-SeCD), on rat liver ischemia-reperfusion (I/R) injury.

METHODS

Male Wistar rats (n = 32) were randomly divided into four groups: I. sham-operated group, II. I/R group, III. I/R +2-SeCD group, IV. I/R + Ebselen group. Hepatic I/R was administered by 90 min of ischemia and 12 h of reperfusion. Liver tissues were collected at the end of reperfusion period for measurement of various biochemical parameters.

RESULTS

The serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) activity and tissue malondialdehyde, myeloperoxidase levels were increased in I/R group, while the increase was significantly reduced by 2-SeCD treatment. The glutathione level, depressed by I/R, was elevated back to normal levels by treatment with 2-SeCD. Severe hepatic damage were observed by light and transmission electron microscopy whilst pretreatment with 2-SeCD resulted in tissue and cellular preservation. Furthermore, 2-SeCD reduced cytochrome c release from mitochondria and subsequent DNA fragmentation by regulating Bcl-2/Bax expression ratio. RESULTS suggested that 2-SeCD was more effective than ebselen in the reversal of the alteration in tissue structural and biochemical parameters caused by I/R injury.

CONCLUSION

2-selenium-bridged beta-cyclodextrin playes an important role in the protection of liver against I/R injury and this treatment may be a novel pharmacological agent for liver surgery.

The antiapoptotic activity of melatonin in neurodegenerative diseases

Melatonin plays a neuroprotective role in models of neurodegenerative diseases. However, the molecular mechanisms underlying neuroprotection by melatonin are not well understood. Apoptotic cell death in the central nervous system is a feature of neurodegenerative diseases. The intrinsic and extrinsic apoptotic pathways and the antiapoptotic survival signal pathways play critical roles in neurodegeneration. This review summarizes the reports to date showing inhibition by melatonin of the intrinsic apoptotic pathways in neurodegenerative diseases including stroke, Alzheimer disease, Parkinson disease, Huntington disease, and amyotrophic lateral sclerosis. Furthermore, the activation of survival signal pathways by melatonin in neurodegenerative diseases is discussed.

Marine compound Xyloketal B protects PC12 cells against OGD-induced cell damage

Xyloketal B is a novel marine compound with unique chemical structure isolated from mangrove fungus Xylaria sp. (no. 2508). Recently, we have demonstrated that Xyloketal B is an antioxidant and can protect against oxidized low density lipoprotein (LDL)-induced cell injury. In the present study, we investigated whether Xyloketal B can protect against ischemia-induced cell injury in an in vitro oxygen glucose deprivation (OGD) model of ischemic stroke in PC12 cells. We found that Xyloketal B could directly scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical and protect PC12 cells against OGD insult. Furthermore, Xyloketal B alleviated OGD-induced mitochondria superoxide, mitochondria fragmentation and GTPase dynamin-related protein 1 (Drp1) overexpression as well as reduction of mitochondrial membrane potential. All together, the present study demonstrates that Xyloketal B protects PC12 cells against OGD-induced cell injury and that the anti-oxidative property and protective action on mitochondria may account for its neuroprotective actions.

Heterogeneity of microglia and TNF signaling as determinants for neuronal death or survival

Microglia do not constitute a single, uniform cell population, but rather comprise cells with varied phenotypes, some which are beneficial and others that may require active regulatory control. Thus, gaining a better understanding of the heterogeneity of resident microglia responses will contribute to any interpretation regarding the impact of any such response in the brain. Microglia are the primary source of the pro-inflammatory cytokine, tumor necrosis factor (TNF) that can initiate various effects through the activation of membrane receptors. The TNF p55 receptor contains a death domain and activation normally leads to cellular apoptosis; however, under specific conditions, receptor activation can also lead to the activation of NF-kappaB and contribute to cell survival. These divergent outcomes have been linked to receptor localization with receptor internalization leading to cell death and membrane localization supporting cell survival. A second TNF receptor, TNF p75 receptor, is normally linked to cell growth and survival, however, it can cooperate with the p55 receptor and contribute to cell death. Thus, while an elevation in TNFalpha in the brain is often considered an indicator of microglia activation and neuroinflammation, a number of factors come into play to determine the final outcome. Data are reviewed demonstrating that heterogeneity in morphological response of microglia and the expression of TNFalpha and TNF receptors are critical in identifying and characterizing neurotoxic events as they relate to neuroinflammation, neuronal damage and in stimulating neuroprotection.

Effect of glutathione peroxidase mimic ebselen (PZ51) on endothelium and vascular structure of stroke‐prone spontaneously hypertensive rats

BACKGROUND

To investigate whether extrinsic antioxidant seleno-glutathione peroxidase mimic ebselen (PZ51) can protect endothelium and vascular structure of stroke-prone spontaneously hypertensive rats (SHRsp) during the chronic process of hypertension.

METHODS

Twenty-two 8-week-old SHRsp were randomized into a PZ51 group and a control group, and administered by gavage for 6 weeks. We examined the level of nitric oxide (NO) and malonaldehyde (MDA) in plasma. The intima-media thickness (IMT) of the common carotid artery (CCA) was measured by an image-analysis system. The endothelium of the CCA was observed by scanning electron microscopy. The eNOS protein of the major artery was assayed by immunohistochemistry and western blotting.

RESULTS

Compared with the control group, PZ51 decreased plasma MDA (7.88+/-1.06 vs 10.88+/-1.73 nmol/l, p<0.001) and increased plasma NO (40.02+/-9.74 vs 22.22+/-10.05 micromol/l, p<0.001), increased eNOS protein expression (8.25+/-2.36 vs 4.46+/-3.14, p=0.026), decreased IMT (69.85+/-5.47 vs 76.60+/-6.53 microm, p<0.05) significantly and alleviated the damage to the endothelium of the CCA.

CONCLUSION

Administration of PZ51 for 6 weeks can protect the endothelium and inhibit vascular remodeling, maybe due to its suppression of lipid peroxide formation and increase in eNOS protein expression.

Mitochondrial impacts of insecticidal formate esters in insecticide-resistant and insecticide-susceptible Drosophila melanogaster

BACKGROUND

Previous research on insecticidal formate esters in flies and mosquitoes has documented toxicity profiles, metabolism characteristics and neurological impacts. The research presented here investigated mitochondrial impacts of insecticidal formate esters and their hydrolyzed metabolite formic acid in the model dipteran insect Drosophila melanogaster Meig. These studies compared two Drosophila strains: an insecticide-susceptible strain (Canton-S) and a strain resistant by cytochrome P450 overexpression (Hikone-R).

RESULTS

In initial studies investigating inhibition of mitochondrial cytochrome c oxidase, two proven insecticidal materials (hydramethylnon and sodium cyanide) caused significant inhibition. However, for insecticidal formate esters and formic acid, no significant inhibition was identified in either fly strain. Mitochondrial impacts of formate esters were then investigated further by tracking toxicant-induced cytochrome c release from mitochondria into the cytoplasm, a biomarker of apoptosis and neurological dysfunction. Formic acid and three positive control treatments (rotenone, antimycin A and sodium cyanide) induced cytochrome c release, verifying that formic acid is capable of causing mitochondrial disruption. However, when comparing formate ester hydrolysis and cytochrome c release between Drosophila strains, formic acid liberation was only weakly correlated with cytochrome c release in the susceptible Canton-S strain (r(2) = 0.70). The resistant Hikone-R strain showed no correlation (r(2) < 0.0001) between formate ester hydrolysis and cytochrome c release.

CONCLUSION

The findings of this study provide confirmation of mitochondrial impacts by insecticidal formate esters and suggest links between mitochondrial disruption, respiratory inhibition, apoptosis and formate-ester-induced neurotoxicity.

Methazolamide and melatonin inhibit mitochondrial cytochrome C release and are neuroprotective in experimental models of ischemic injury

BACKGROUND AND PURPOSE

The identification of a neuroprotective drug for stroke remains elusive. Given that mitochondria play a key role both in maintaining cellular energetic homeostasis and in triggering the activation of cell death pathways, we evaluated the efficacy of newly identified inhibitors of cytochrome c release in hypoxia/ischemia induced cell death. We demonstrate that methazolamide and melatonin are protective in cellular and in vivo models of neuronal hypoxia.

METHODS

The effects of methazolamide and melatonin were tested in oxygen/glucose deprivation-induced death of primary cerebrocortical neurons. Mitochondrial membrane potential, release of apoptogenic mitochondrial factors, pro-IL-1beta processing, and activation of caspase -1 and -3 were evaluated. Methazolamide and melatonin were also studied in a middle cerebral artery occlusion mouse model. Infarct volume, neurological function, and biochemical events were examined in the absence or presence of the 2 drugs.

RESULTS

Methazolamide and melatonin inhibit oxygen/glucose deprivation-induced cell death, loss of mitochondrial membrane potential, release of mitochondrial factors, pro-IL-1beta processing, and activation of caspase-1 and -3 in primary cerebrocortical neurons. Furthermore, they decrease infarct size and improve neurological scores after middle cerebral artery occlusion in mice.

CONCLUSIONS

We demonstrate that methazolamide and melatonin are neuroprotective against cerebral ischemia and provide evidence of the effectiveness of a mitochondrial-based drug screen in identifying neuroprotective drugs. Given the proven human safety of melatonin and methazolamide, and their ability to cross the blood-brain-barrier, these drugs are attractive as potential novel therapies for ischemic injury.

Astaxanthin reduces ischemic brain injury in adult rats

Astaxanthin (ATX) is a dietary carotenoid of crustaceans and fish that contributes to their coloration. Dietary ATX is important for development and survival of salmonids and crustaceans and has been shown to reduce cardiac ischemic injury in rodents. The purpose of this study was to examine whether ATX can protect against ischemic injury in the mammalian brain. Adult rats were injected intracerebroventricularly with ATX or vehicle prior to a 60-min middle cerebral artery occlusion (MCAo). ATX was present in the infarction area at 70-75 min after onset of MCAo. Treatment with ATX, compared to vehicle, increased locomotor activity in stroke rats and reduced cerebral infarction at 2 d after MCAo. To evaluate the protective mechanisms of ATX against stroke, brain tissues were assayed for free radical damage, apoptosis, and excitoxicity. ATX antagonized ischemia-mediated loss of aconitase activity and reduced glutamate release, lipid peroxidation, translocation of cytochrome c, and TUNEL labeling in the ischemic cortex. ATX did not alter physiological parameters, such as body temperature, brain temperature, cerebral blood flow, blood gases, blood pressure, and pH. Collectively, our data suggest that ATX can reduce ischemia-related injury in brain tissue through the inhibition of oxidative stress, reduction of glutamate release, and antiapoptosis. ATX may be clinically useful for patients vulnerable or prone to ischemic events.

Selenium compounds counteract the stimulation of ecto-nucleotidase activities in rat cultured cerebellar granule cells: putative correlation with neuroprotective effects

Glutamate is the main excitatory neurotransmitter in brain involved in pathophysiology of several brain injuries. In this context, glutamate showed to stimulate ecto-nucleotidase activities in cerebellar granule cells increasing extracellular adenosine levels, an important neuromodulator in the CNS able to prevent cell damage. The organoselenium compounds, such as ebselen and diphenyl diselenide [(PhSe)(2)], display neuroprotective activities mediated at least in part by their antioxidant and anti-inflammatory properties. Ebselen was described to prevent glutamate-induced lipid peroxidation and cell death in cerebellar granule cells and (PhSe)(2) modify glutamatergic synapse parameters in vitro and in vivo. In the present study, we investigated the effects of ebselen or (PhSe)(2) on glutamate-induced stimulation of ecto-nucleotidase activities in rat cultured cerebellar granule cells. Glutamate increased nucleotide hydrolysis at lower concentrations (10 and 100 microM) than described in the literature and this effect was counteracted by both organoselenium compounds tested. Based on these results, we investigated the association of organoselenium effects with their antioxidant properties searching for redox site modulation by using the alkylant agent N-ethylmaleimide (NEM). Our results suggest that selenium compounds, as well as the well-known antioxidant trolox, can avoid the increase on glutamate-induced stimulation of ecto-nucleotidase activities probably due to their antioxidant properties.

Neuroprotection for ischemic stroke: past, present and future

Neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection. Rigorously conducted experimental studies in animal models of brain ischemia provide incontrovertible proof-of-principle that high-grade protection of the ischemic brain is an achievable goal. Nonetheless, many agents have been brought to clinical trial without a sufficiently compelling evidence-based pre-clinical foundation. At this writing, around 160 clinical trials of neuroprotection for ischemic stroke have been initiated. Of the approximately 120 completed trials, two-thirds were smaller early-phase safety-feasibility studies. The remaining one-third were typically larger (>200 subjects) phase II or III trials, but, disappointingly, only fewer than one-half of these administered neuroprotective therapy within the 4-6h therapeutic window within which efficacious neuroprotection is considered to be achievable. This fact alone helps to account for the abundance of "failed" trials. This review presents a close survey of the most extensively evaluated neuroprotective agents and classes and considers both the strengths and weakness of the pre-clinical evidence as well as the results and shortcomings of the clinical trials themselves. Among the agent-classes considered are calcium channel blockers; glutamate antagonists; GABA agonists; antioxidants/radical scavengers; phospholipid precursor; nitric oxide signal-transduction down-regulator; leukocyte inhibitors; hemodilution; and a miscellany of other agents. Among promising ongoing efforts, therapeutic hypothermia, high-dose human albumin therapy, and hyperacute magnesium therapy are considered in detail. The potential of combination therapies is highlighted. Issues of clinical-trial funding, the need for improved translational strategies and clinical-trial design, and "thinking outside the box" are emphasized.

THE SPECIFIC FREE RADICAL SCAVENGER EDARAVONE SUPPRESSES BLEOMYCIN-INDUCED ACUTE PULMONARY INJURY IN RABBITS

1. Intratracheal instillation of bleomycin induces a condition in rabbits that serves as a useful model of human pulmonary fibrosis. Bleomycin-induced production of reactive oxygen species leads to acute lung inflammation and induction of apoptosis, which is followed by pulmonary fibrosis at a later chronic stage. In the present study, we tested whether edaravone, a free radical scavenger, would suppress bleomycin-induced acute pulmonary inflammation. 2. Rabbits were divided into three groups (n = 10 in each): (i) a bleomycin-treated group, which received intratracheal instillation of 2 mg/kg bleomycin; (ii) a bleomycin + edaravone group, which received a 10 day regimen of daily intravenous injections of edaravone (3 mg/kg per day) beginning 3 days before bleomycin instillation; and (iii) a saline control group. Rabbits were killed for analysis 7 days after bleomycin administration. 3. In lung tissues from the bleomycin-treated group, marked infiltration of inflammatory cells, consisting mainly of lymphocytes, neutrophils and eosinophils, was observed. In addition, significantly increased numbers of TUNEL-positive (apoptotic) and transforming growth factor-beta-positive cells were seen. All these effects were significantly attenuated by treatment with edaravone. 4. The findings of the present study suggest that edaravone may be useful in the prevention of acute lung injury resulting from the production of reactive oxygen species.

Ebselen treatment reduces noise induced hearing loss via the mimicry and induction of glutathione peroxidase

Previous studies indicate that noise induced hearing loss (NIHL) involves a decrease in glutathione peroxidase (GPx) activity and a subsequent loss of outer hair cells (OHC). However, the cellular localization of this GPx decrease and the link to OHC loss are still poorly understood. In this report, we examined the cellular localization of GPx (GPx1, GPx 3 and GPx 4) in F-344 rat before and after noise exposure and after oral treatment with ebselen, a small molecule mimic of GPx activity. Results indicate that GPx1 is the major isoform within the cochlea and is highly expressed in cells of the organ of Corti, spiral ganglia, stria vascularis, and spiral ligament. Within 5h of noise exposure (4h at 113 dB, 4-16 kHz), significant OHC loss was already apparent in regions coincident with the 8-16 kHz region of the cochlea. In addition, the stria vascularis exhibited significant edema or swelling and a decrease in GPx1 immunoreactivity or fluorescent intensity. Treatment with ebselen (4 mg/kg p.o.) before and immediately after noise exposure reduced both OHC loss and the swelling of the stria vascularis typically observed within 5h post-noise exposure. Interestingly, GPx1 levels increased in the stria vascularis after noise and ebselen treatment vs noise and vehicle-only treatment, and exceeded baseline no noise control levels. These data indicate that ebselen acts to prevent the acute loss of OHCs and reduces the acute swelling of the stria vascularis by two potential mechanisms: one, as a ROS/RNS scavenger through its intrinsic GPx activity, and two, as a stimulator of GPx1 expression or activity. This latter mechanism may be due to the preservation of endogenous GPx1 from ROS/RNS induced degradation and/or the stimulation of GPx1 expression or activity.

Tacrolimus (FK506) attenuates biphasic cytochrome c release and Bad phosphorylation following transient cerebral ischemia in mice

Tacrolimus (FK506) has a neuroprotective action on cerebral infarction produced by cerebral ischemia, however, detailed mechanisms underlying this action have not been fully elucidated. We examined temporal profiles of survival-and death-related signals, Bad phosphorylation, release of cytochrome c (cyt.c), activation of caspase 3 and DNA fragmentation in the brain during and after middle cerebral artery occlusion (MCAo) in mice, and then examined the effect of tacrolimus on these signals. C57BL/6J mice were subjected to transient MCAo by intraluminal suture insertion for 60 min. Tacrolimus (1 mg/kg, i.p.) was administered immediately after MCAo. There were biphasic increases in the release of cyt.c in the ischemic core and penumbra; with the first increase toward the end of the occlusion period and the second increase 3-12 h after reperfusion. Tacrolimus significantly inhibited the increase of cytosolic cyt.c during ischemia and reperfusion. Phosphorylated Bad, Ser-136 (P-Bad(136)) and Ser-155 (P-Bad(155)) were detected 30 min after MCAo and after reperfusion in the ischemic cortex, respectively. Tacrolimus increased P-Bad(136) during ischemia and prolonged P-Bad(155) expression after reperfusion. Tacrolimus also decreased caspase-3 and terminal deoxynucleotidyl transferase-mediated DNA nick-end labeling-positive cells, and reduced the size of infarct 24 h after reperfusion. Our study provided the first evidence that the neuroprotective action of tacrolimus involved inhibition of biphasic cyt.c release from mitochondria, possibly via up-regulation of Bad phosphorylation at different sites after focal cerebral ischemia and reperfusion.

Ebselen induced C6 glioma cell death in oxygen and glucose deprivation

Studies have shown that ebselen is an antiinflammatory and antioxidative agent. Its protective effect has been investigated in oxidative stress related diseases such as cerebral ischemia in recent years. However, experimental evidence also shows that ebselen causes cell death in several different cell types. Whether ebselen will have a beneficial or detrimental effect on cells under ischemic condition is not known. Herein, we studied the effect of ebselen on C6 glioma cells under oxygen and glucose deprivation (OGD), an in vitro ischemic model. We found that ebselen significantly enhanced cell death after 3 h of OGD as observed by lactase dehydrogenase (LDH) release and cellular morphological changes. Further studies revealed that depletion of cellular glutathione level by the combined action of ebselen and OGD played a role in enhanced cell death as demonstrated by the following evidence: (1) cellular GSH was significantly depleted by the combined effort of ebselen and OGD, compared to that of ebselen or OGD insult alone; (2) exogenous addition of N-acetyl cysteine completely diminished the cell damage induced by ebselen and OGD; (3) supplement of glucose, which provides cellular reducing agents and thus maintains cellular GSH level, to the OGD medium diminished C6 cell damage induced by ebselen. We conclude that depleting cellular glutathione plays an important role in ebselen-induced cell death with OGD. Our results suggest that ebselen can have a beneficial or toxic effect, depending on the availability of GSH.

Effects of diphenyl–diselenide on orofacial dyskinesia model in rats

Recently, we have described the beneficial effects of Diphenyl diselenide, an organochalcogen with glutathione peroxidase-like activity, on reserpine-induced orofacial dyskinesia in old rats. In this study, our aim was to examine the effects of diselenide on haloperidol-induced orofacial dyskinesia in rats. Male wistar rats received one single dose of Haloperidol decanoate (57 mg/kg/im) or control. After this dose, the animals received daily administration of diphenyl diselenide (1, 5 or 10 mg/kg/sc) or control, during 28 days. Twenty-four hours after the last diselenide or control solution injection, all the rats were observed for quantification of oral dyskinesia through the frequency of vacuous chewing movements (VCM) and tongue protrusion (TP) and the duration of facial twitching (FT). Haloperidol caused a significant increase in VCM, TP and FT observed in the 4 weekly evaluations (p<0.05). The co-administration of diselenide (5 mg/kg) reversed this effect for all the parameters in four behavioral sessions. The results of the present study demonstrate the possible protective activity of diphenyl diselenide on haloperidol-induced orofacial diskinesia. This effect is in accordance to the involvement of neurotoxicity in orofacial dyskinesia and suggest that studies be continued with new antioxidant compounds.

Inhibition of caspase-dependent mitochondrial permeability transition protects airway epithelial cells against mustard-induced apoptosis

In the present study, the toxicity of yperite, SM, and its structural analogue mechlorethamine, HN2, was investigated in a human bronchial epithelial cell line 16HBE. Cell detachment was initiated by caspase-2 activation, down-regulation of Bcl-2 and loss of mitochondrial membrane potential. Only in detached cells, mustards induced apoptosis associated with increase in p53 expression, Bax activation, decrease in Bcl-2 expression, opening of the mitochondrial permeability transition pore, release of cytochrome c, caspase-2, -3, -8, -9 and -13 activation and DNA fragmentation. Apoptosis, occurring only in detached cells, could be recognized as anoikis and the mitochondrion, involved both in cell detachment and subsequent cell death, appears to be a crucial checkpoint. Based on our understanding of the apoptotic pathway triggered by mustards, we demonstrated that inhibition of the mitochondrial pathway by ebselen, melatonin and cyclosporine A markedly prevented mustard-induced anoikis, pointing to these drugs as interesting candidates for the treatment of mustard-induced airway epithelial lesions.

Compounds for the prevention and treatment of noise-induced hearing loss

Noise-induced hearing loss (NIHL) is the leading occupational disease and a major contributor to the development of age-related hearing loss. The pharmacological prevention and treatment of NIHL has been under preclinical investigation for the past 20 years. Promising treatments have now been identified and entered into clinical development. Within the next five years, safe and effective drugs could be approved as the first generation of otoprotectants. This review covers strategies that are under investigation for NIHL. Drugs that effectively prevent and treat NIHL will have a significant impact on medical costs, disability compensation and several issues affecting the quality of life.

Oxidative stress is involved in the permeabilization of the inner membrane of brain mitochondria exposed to hypoxia/reoxygenation and low micromolar Ca2+

From in vivo models of stroke it is known that ischemia/reperfusion induces oxidative stress that is accompanied by deterioration of brain mitochondria. Previously, we reported that the increase in Ca2+ induces functional breakdown and morphological disintegration in brain mitochondria subjected to hypoxia/reoxygenation (H/R). Protection by ADP indicated the involvement of the mitochondrial permeability transition pore in the mechanism of membrane permeabilization. Until now it has been unclear how reactive oxygen species (ROS) contribute to this process. We now report that brain mitochondria which had been subjected to H/R in the presence of low micromolar Ca2+ display low state 3 respiration (20% of control), loss of cytochrome c, and reduced glutathione levels (75% of control). During reoxygenation, significant mitochondrial generation of hydrogen peroxide (H2O2) was detected. The addition of the membrane permeant superoxide anion scavenger TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) suppressed the production of H2O2 by brain mitochondria metabolizing glutamate plus malate by 80% under normoxic conditions. TEMPOL partially protected brain mitochondria exposed to H/R and low micromolar Ca2+ from decrease in state 3 respiration (from 25% of control to 60% of control with TEMPOL) and permeabilization of the inner membrane. Membrane permeabilization was obvious, because state 3 respiration could be stimulated by extramitochondrial NADH. Our data suggest that ROS and Ca2+ synergistically induce permeabilization of the inner membrane of brain mitochondria exposed to H/R. However, permeabilization can only partially be prevented by suppressing mitochondrial generation of ROS. We conclude that transient deprivation of oxygen and glucose during temporary ischemia coupled with elevation in cytosolic Ca2+ concentration triggers ROS generation and mitochondrial permeabilization, resulting in neural cell death.

Protective effect of antioxidant ebselen (PZ51) on the cerebral cortex of stroke-prone spontaneously hypertensive rats

An increase in reactive oxygen species has been shown to play a role in perpetuating hypertension and cerebral injury in stroke-prone spontaneously hypertensive rats (SHRsp). Lipid peroxidation in the cerebral cortex is much more intense in SHRsp after establishment of severe hypertension as compared to that in normotensive Wistar-Kyoto rats (WKY). Cortical neurons from SHRsp are more vulnerable to hypoxia and hyponutritional conditions. We sought to investigate whether long-term administration of seleno-glutathione peroxidase mimic ebselen (PZ51) would have a protective effect on cortical neurons in SHRsp, and, if so, the possible mechanisms of this effect. Twenty-two 8-week-old SHRsp were randomized into a PZ51 group and control group. Age-matched WKY were used as normal controls. We examined the levels of malonaldehyde (MDA) and nitric oxide (NO) in the cerebral cortex (CC) homogenate, detected the three isoforms of nitric oxide synthase (NOS) by Western blotting, and examined cortical neurons by transmission electron microscopy. The results showed that PZ51 treatment significantly decreased both MDA and NO in the CC, inhibited inducible nitric oxide synthase (iNOS) protein expression, and alleviated the damage to cortical neurons compared to the findings for the control group. In conclusion, the present study showed that PZ51 administration suppressed lipid peroxidation and inhibited iNOS protein expression in CC homogenate, and it was suggested that these mechanisms may play a role in the protective effects of PZ51 on cortical neurons of SHRsp.