The neuroprotective efficacy of ebselen (a glutathione peroxidase mimic) on brain damage induced by transient focal cerebral ischaemia in the rat

Effect of resveratrol on 3-nitropropionic acid-induced biochemical and behavioural changes: possible neuroprotective mechanisms

Huntington's disease is a progressive, degenerative disease characterized by abnormal body movements called chorea, and a reduction of various mental abilities. 3-Nitropropionic acid, an inhibitor of complex II of the electron transport chain, causes Huntington's disease-like symptoms in rodents. Recently, it has been reported that oxidative stress, which is one of the pathological hallmarks of various neurodegenerative disorders, also plays an important role in the pathogenesis of Huntington's disease. The present study was designed to investigate effects of resveratrol, an antioxidant with cyclooxygenase I inhibitory activity, in the 3-nitropropionic acid-induced model of Huntington's disease. Intraperitoneal administration of 3-nitropropionic acid (20 mg/kg for 4 days) caused significant loss of body weight, a decline in motor function (locomotor activity, movement pattern and vacuous chewing movements) and poor retention of memory. Repeated treatment with resveratrol (5 and 10 mg/kg, orally), once daily for a period of 8 days beginning 4 days prior to 3-nitropropionic acid administration, significantly improved the 3-nitropropionic acid-induced motor and cognitive impairment. Biochemical analysis revealed that systemic 3-nitropropionic acid administration significantly increased lipid peroxidation, nitrite levels, and depleted reduced glutathione levels, and decreased succinate dehydrogenase activity in the brains of rats. The results of the present study indicate that resveratrol (5 and 10 mg/kg, orally) significantly reversed 3-nitropropionic acid-induced motor and cognitive impairment, and that the beneficial effects of resveratrol might be attributed to its antioxidant activity.

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.

Changes in biochemical parameters in rabbits blood after oral exposure to diphenyl diselenide for long periods

The concept that selenium-containing molecules may be better antioxidants than classical antioxidants, has led to the design of synthetic organoselenium compounds. The present study was conducted to evaluate the potential toxicity of long time oral exposure to diphenyl diselenide (PhSe)2 in rabbits. Male adult New Zealand rabbits were divided into four groups, group I served as control; groups II, III and IV received 0.3, 3.0 and 30 ppm of (PhSe)2 pulverized in the chow for 8 months. A number of parameters were examined in blood as indicators of toxicity, including delta-aminolevulinate dehydratase (delta-ALA-D), catalase, glutathione peroxidase (GPx), alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine, TBARS, non-protein-SH, ascorbic acid and selenium. The results demonstrated that 6 and 8 months of 30 ppm (PhSe)2 intake caused a significant increase in blood delta-ALA-D activity. Erythrocyte non-protein thiol levels were significantly increased after 2 months of 30 ppm (PhSe)2 intake and then return to control levels after prolonged periods of intake. Ingestion of 3.0 ppm of (PhSe)2 for 8 months significantly increased catalase activity in erythrocytes. Conversely, no alterations in GPx, ALT, AST, TBARS and selenium levels were observed in rabbit serum, conversely, selenium levels in peri-renal adipose tissue were significantly increased after 8 months of 30 ppm (PhSe)2 intake, indicating its great lipophylicity. The present results suggest that diphenyl diselenide was not hepato- or renotoxic for rabbits, but caused some biochemical alterations that can be related to some pro-oxidant activity of the compound (particularly the reduction in Vitamin C).

Diphenyl ditelluride- and methylmercury-induced hyperphosphorilation of the high molecular weight neurofilament subunit is prevented by organoselenium compounds in cerebral cortex of young rats

Organotellurides are important intermediates in organic synthesis and, consequently, the occupational exposure to them is a constant risk for laboratory workers. These compounds can elicit many neurotoxic events in the central nervous system (CNS) that are associated with several neurological symptoms. In contrast, organoselenium compounds are considered to exert neuroprotective actions on such effects. Neurofilaments (NF) are important cytoskeletal proteins and phosphorylation/dephosphorylation of NF is important to stabilize the cytoskeleton. In this work we investigated the potential protective ability of the selenium compounds ebselen and diphenyl diselenide (PhSe)(2) against the effect of diphenyl ditelluride (PhTe)(2) and methylmercury (MeHg) on the total (phosphorylated plus nonphosphorylated) and phosphorylated immunocontent of the high molecular weight neurofilament subunit (NF-H) from slices of cerebral cortex of 17-day-old rats. We observed that 1muM MeHg induced hyperphosphorylation, increasing the total immunocontent of this subunit of the high-salt Triton insoluble NF-H. Otherwise, 15muM (PhTe)(2) induced hyperphosphorylation of the high-salt Triton insoluble NF-H without altering the total immunocontent of this protein into the cytoskeletal fraction. Concerning the selenium compounds, 15muM (PhSe)(2) and 5muM ebselen did not induce alteration per se on the in vitro phosphorylation of NF-H. In addition, (PhSe)(2) and ebselen at these concentrations, presented a protective effect against the action of (PhTe)(2) and MeHg, on the immunoreactivity of NF-H. Considering that hyperphosphorylation of NF-H is associated with neuronal dysfunction it is probable that the effects of (PhTe)(2) and MeHg could be related to the remarkable neurotoxicity of these organocalcogenides. Furthermore the neuroprotective action of selenium compounds against (PhTe)(2) and MeHg effects could be a promising route to be exploited for a possible treatment of calcogenides poisoning.

Effects of ethanol and diphenyl diselenide exposure on the activity of δ-aminolevulinate dehydratase from mouse liver and brain

Ethanol toxicity is affected by both environmental and inherited features. Since oxidative stress is an important molecular mechanism for ethanol-induced cellular damage, the concomitant exposure to ethanol and pro-oxidative or antioxidant compounds can alter its toxicity. Here, we investigate the effects of exposure to ethanol and/or diphenyl diselenide, an organochalcogen with antioxidant properties, on parameters related to oxidative stress (thiobarbituric acid reactive species-TBARS-and delta-aminolevulinate dehydratase-delta-ALA-D activity) in mouse liver and brain. In addition, the in vitro effects of ethanol and acetaldehyde on the activity of delta-ALA-D from human erythrocytes were also investigated. Both ethanol and diphenyl diselenide decreased hepatic delta-ALA-D activity and DL-dithiothreitol (DTT) reactivated this enzyme only after ethanol-induced inhibition. Moreover, ethanol increased liver TBARS levels, independently of the presence of diphenyl diselenide treatment. Brain delta-ALA-D activity and TBARS levels were not changed by ethanol or diphenyl diselenide exposure. Under in vitro conditions, acetaldehyde was a more potent inhibitor of delta-ALA-D from human erythrocytes when compared to ethanol, demonstrating a dose-dependent effect. This study indicates that (1) hepatic delta-ALA-D is a molecular target for the damaging effect of ethanol under in vivo conditions; (2) diphenyl diselenide and ethanol seem to inhibit delta-ALA-D by different mechanisms; (3) acetaldehyde, a metabolite of ethanol, is probably the main molecule responsible for the inhibitory effects of the parent compound on delta-ALA-D.

A small-molecule-inducible Nrf2-mediated antioxidant response provides effective prophylaxis against cerebral ischemia in vivo

The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) coordinates expression of genes required for free radical scavenging, detoxification of xenobiotics, and maintenance of redox potential. Previously, activation of this pleiotropic response was neuroprotective in cell culture models that simulate components of stroke damage. However, the role of Nrf2 in limiting stroke damage in vivo remained unclear. We report that Nrf2 activation protects the brain from cerebral ischemia in vivo. Acute (1-3 d) intracerebroventricular or intraperitoneal pretreatment with tert-butylhydroquinone (tBHQ), an Nrf2 activity inducer, reduced cortical damage and sensorimotor deficit at 24 h and even 1 month after ischemia-reperfusion in rats. Cortical glutathione levels robustly increased with tBHQ administration to rats and Nrf2-expressing mice, but not Nrf2(-/-) mice. Basal and inducible activities of antioxidant/detoxification enzymes in Nrf2(-/-) mice were reduced when compared with Nrf2(+/+) controls. Interestingly, larger infarcts were observed in Nrf2(-/-) mice at 7 d after stroke, but not at 24 h, suggesting that Nrf2 may play a role in shaping the penumbra well after the onset of ischemia. Neuronal death caused by a "penumbral" model of stroke, using intracortical endothelin-1 microinjection, was attenuated by tBHQ administration to Nrf2(+/+), but not to Nrf2(-/-) mice, confirming the Nrf2-specific action of tBHQ in vivo. We conclude that Nrf2 plays a role in modulating ischemic injury in vivo. Accordingly, Nrf2 activation by small molecule inducers may be a practical preventative treatment for stroke-prone patients.

Ebselen protects glutamate uptake inhibition caused by methyl mercury but does not by Hg2+

Alterations of the neurotransmitter release systems in CNS have been reported in a variety of neuropathological processes associated with heavy metal toxicity. Neurotoxic effects of mercurials were investigated in vitro in cerebral cortex slices from young rats. The present study indicates that: (i) the environmental contaminants methylmercury (MeHg) and mercuric chloride (Hg2+) (50 microM) inhibited the glutamate net uptake from the cerebral cortex of 17-day-old rats; (ii) ebselen (10 microM) reverted the MeHg-induced inhibition of glutamate net uptake but did not protect the inhibition caused by Hg2+. At same time, we investigated another diorganochalcogenide, diphenyl diselenide (PhSe)2 and it was observed that this compound did not revert the action of MeHg or Hg2+; (iii) in addition, we observed that exposure of slices to 50 microM MeHg and Hg2+ for 30 min followed by Trypan blue exclusion assay resulted in 58.5 and 67.5% of staining cells, respectively, indicating a decrease in cell viability. Ebselen protected slices from the deleterious effects of MeHg, but not of Hg2+ on cell viability. Conversely, ebselen did not modify the reduction of MTT caused by MeHg and Hg2+; (iv) the protective effect of ebselen on MeHg-induced inhibition of glutamate net uptake seems to be related to its ability in maintaining cell viability.

Cooperation between antioxidants and 1,25-dihydroxyvitamin D3 in induction of leukemia HL60 cell differentiation through the JNK/AP-1/Egr-1 pathway

Vitamin D derivatives have demonstrated anti-cancer activity, but their clinical use is precluded by hypercalcemia. Previously, we found that carnosic acid potentiates differentiation of human leukemia cells induced by low concentrations of 1alpha,25-dihydroxyvitamin D(3) (1,25D(3)). In this study, we investigated if this effect is a general property of antioxidants, and whether there is a common mechanism whereby antioxidants potentiate monocytic differentiation. We found that all antioxidants tested enhanced differentiation-related cell cycle arrest induced by a low (1 nM) concentration of 1,25D(3). Addition of antioxidants to 1,25D(3) activated the JNK pathway as indicated by increased phosphorylation of c-jun and ATF-2, although each compound alone had a minimal effect. Antioxidants also enhanced the 1,25D(3)-induced AP-1 DNA binding and transactivation ability. Expression of Egr-1 and c-fos was increased by combinations of antioxidants and 1,25D(3), in parallel with the activation of the JNK pathway. The potentiation of differentiation by antioxidants was inhibited by JNK inhibitor SP600125 and a dominant negative JNK 1/2 construct, and Egr-1 and c-fos expression was proportionally decreased, suggesting that JNK pathway regulates these transcription factors. While potentiating the prodifferentiation effect of 1,25D(3), antioxidants did not promote the elevation of basal levels of intracellular calcium by 1,25D(3). The results indicate that JNK-AP1 pathway has an important role in the potentiation of 1,25D(3)-induced differentiation by antioxidants, and regulates expression of Egr-1 and c-fos. Combinations of antioxidants with 1,25D(3) should be further evaluated for use in cancer chemoprevention and therapy.

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.

Single-dose ebselen does not afford sustained neuroprotection to rats subjected to severe focal cerebral ischemia

Oxygen free radicals have been involved in the pathophysiology of cerebral ischemia, especially after spontaneous or thrombolytic reperfusion. In this study with rats, we have combined a severe focal ischemic insult (2 h) and a prolonged reperfusion time (7 days) to assess the possible sustained neuroprotective effect of ebselen (10 or 100 mg/kg), a small, lipophilic organoselenium compound which mimics glutathione peroxidase. Parietal cortical perfusion was measured by laser-Doppler flowmetry, and focal cerebral ischemia was carried out by the intraluminal thread method. We have measured plasma selenium levels, brain reduced glutathione levels, as a marker of oxidative stress, and infarct volume associated with cerebral ischemia. Focal ischemia did not alter reduced glutathione levels, while 60 min reperfusion following ischemia induced a significant (P < 0.05) decrease in reduced glutathione levels of the ipsilateral hemisphere. Pretreatment with ebselen, which induced significant (P < 0.05) increase in plasma selenium levels, did not significantly alter the decrease in reduced glutathione levels. The ischemic insult induced 30% mortality on average, with deaths always occurring within 12-48 h. Surviving rats suffered up to 25% body weight loss 1 week after the ischemic insult. Infarct volumes were 26.8 +/- 4.7% of the hemisphere in placebo-treated rats, 26.6 +/- 3.6% in 10 mg/kg ebselen-treated rats, and 25.6 +/- 6.4% in 100 mg/kg ebselen-treated rats (not significantly different). Single-dose administration of ebselen does not reduce the size of brain infarct resulting from severe focal cerebral ischemia in rats. In contrast to previous studies with relatively earlier endpoints, we have delayed the measurement of infarct volume to 1 week after the ischemic insult.

Organoselenium compounds prevent hyperphosphorylation of cytoskeletal proteins induced by the neurotoxic agent diphenyl ditelluride in cerebral cortex of young rats

In this work we investigated the protective ability of the selenium compounds ebselen and diphenyl diselenide against the effect of diphenyl ditelluride on the in vitro incorporation of 32P into intermediate filament (IF) proteins from slices of cerebral cortex of 17-day-old rats. We observed that ditelluride in the concentrations of 1, 15 and 50 microM induced hyperphosphorylation of the high-salt Triton insoluble neurofilament subunits (NF-M and NF-L), glial fibrillary acidic protein (GFAP) and vimentin, without altering the immunocontent of these proteins. Concerning the selenium compounds, diselenide (1,15 and 50 microM) did not induce alteration of the in vitro phosphorylation of the IF proteins. Otherwise, ebselen induced an altered in vitro phosphorylation of the cytoskeletal proteins in a dose-dependent manner. At intermediate concentrations (15 and 30 microM) it increased the in vitro phosphorylation even though, at low (5 microM) or high (50 and 100 microM) concentrations this compound was ineffective in altering the activity of the cytoskeletal-associated phosphorylating system. In addition, 15 microM diselenide and 5 microM ebselen, presented a protective effect against the action of ditelluride, on the phosphorylation of the proteins studied. Considering that hyperphosphorylation of cytoskeletal proteins is associated with neuronal dysfunction and neurodegeneration, it is probable that the effects of ditelluride could be related to the remarkable neurotoxicity of this organic form of tellurium. Furthermore the neuroprotective action of selenium compounds against tellurium effects could be a promising route to be exploited for a possible treatment of organic tellurium poisoning.

Selenium Compounds Prevent the Effects of Methylmercury on the in Vitro Phosphorylation of Cytoskeletal Proteins in Cerebral Cortex of Young Rats

In this study we investigated the protective ability of the selenium compounds ebselen and diphenyldiselenide against the effect of methylmercury on the in vitro incorporation of 32P into intermediate filament (IF) proteins from the cerebral cortex of 17-day-old rats. We observed that methylmercury in the concentrations of 1 and 5 microM was able to inhibit the phosphorylating system associated with IF proteins without altering the immunocontent of these proteins. Concerning the selenium compounds, diselenide (1, 15, and 50 microM) did not induce alteration of the in vitro phosphorylation of IF proteins. Conversely, 15 microM diselenide was effective in preventing the toxic effects induced by methylmercury. Otherwise, ebselen induced an altered in vitro phosphorylation of the cytoskeletal proteins in a dose-dependent manner. Ebselen at intermediate concentrations (15 and 30 microM) increased the in vitro phosphorylation. However, at low (5 microM) or high (50 and 100 microM) concentrations it was ineffective in altering the cytoskeletal-associated phosphorylating system. Furthermore, 5 microM ebselen presented a protective effect against the action of methylmercury on the phosphorylating system. In conclusion, our results indicate that the selenium compounds ebselen and diselenide present protective actions toward the alterations of the phosphorylating system associated with the IF proteins induced by methylmercury in slices of the cerebral cortex of rats.

Ebselen and diphenyl diselenide do not change the inhibitory effect of lead acetate on delta-aminolevulinate dehidratase

It is known that lead is toxic to several species of animals, and growing data support the participation of oxidative in lead toxicity. Selenium compounds, like diphenyl diselenide and Ebselen have a thiol-peroxidase like and other antioxidant properties. In this work, we determine whether these non-thiol-containing compounds with antioxidant properties could reverse the toxicity produced by Pb(2+). Lead acetate injection followed by injection with Ebselen or diphenyl diselenide did not change the levels of non-protein thiol groups (NPSH), whereas simultaneous treatment with lead plus Ebselen reduced NPSH levels in liver. Lead and Ebselen caused a marked reduction in TBARS level in kidney, whereas lead or selenium compounds did not change TBARS levels in brain or liver. Lead acetate inhibited, δ-aminolevulinate dehydratase (ALA-D) activity in blood, liver, kidney and brain. Selenium compounds did not change enzyme activity nor the inhibitory effect of lead acetate in kidney and liver. Ebselen reversed brain ALA-D inhibition caused by Pb(2+). Reactivation index for ALA-D by DTT was higher in lead-treated groups than control groups in all tissues. Lead acetate or selenium compounds did not demonstrate alteration on [(3)H]-glutamate uptake by synaptosomes, whereas lead acetate plus Ebselen showed an increase on [(3)H]-glutamate uptake. The results of the present study indicate that ALA-D inhibition antecedes the overproduction of reactive oxygen species, which is becoming well documented in the literature.

Manipulation of antioxidant pathways in neonatal murine brain

To assess the role of brain antioxidant capacity in the pathogenesis of neonatal hypoxic-ischemic brain injury, we measured the activity of glutathione peroxidase (GPX) in both human-superoxide dismutase-1 (hSOD1) and human-GPX1 overexpressing transgenic (Tg) mice after neonatal hypoxia-ischemia (HI). We have previously shown that mice that overexpress the hSOD1 gene are more injured than their wild-type (WT) littermates after HI, and that H(2)O(2) accumulates in HI hSOD1-Tg hippocampus. We hypothesized that lower GPX activity is responsible for the accumulation of H(2)O(2). Therefore, increasing the activity of this enzyme through gene manipulation should be protective. We show that brains of hGPX1-Tg mice, in contrast to those of hSOD-Tg, have less injury after HI than WT littermates: hGPX1-Tg, median injury score = 8 (range, 0-24) versus WT, median injury score = 17 (range, 2-24), p < 0.01. GPX activity in hSOD1-Tg mice, 2 h and 24 h after HI, showed a delayed and bilateral decline in the cortex 24 h after HI (36.0 +/- 1.2 U/mg in naive hSOD1-Tg versus 29.1 +/- 1.7 U/mg in HI cortex and 29.2 +/- 2.0 for hypoxic cortex, p < 0.006). On the other hand, GPX activity in hGPX1-Tg after HI showed a significant increase by 24 h in the cortex ipsilateral to the injury (48.5 +/- 5.2 U/mg, compared with 37.2 +/- 1.5 U/mg in naive hGPX1-Tg cortex, p < 0.008). These findings support the hypothesis that the immature brain has limited GPX activity and is more susceptible to oxidative damage and may explain the paradoxical effect seen in ischemic neonatal brain when SOD1 is overexpressed.

Selenium-containing 15-Mer Peptides with High Glutathione Peroxidase-like Activity

Glutathione peroxidase (GPX) is one of the most crucial antioxidant enzymes in a variety of organisms. Here we described a new strategy for generating a novel GPX mimic by combination of a phage-displayed random 15-mer peptide library followed by computer-aided rational design and chemical mutation. The novel GPX mimic is a homodimer consisting of a 15-mer selenopeptide with an appropriate catalytic center, a specific binding site for substrates, and high catalytic efficiency. Its steady state kinetics was also studied, and the values of k(cat)/K(m)(GSH) and k(cat)/ K(mH(2)O(2)) were found to be similar to that of native GPX and the highest among the existing GPX mimics. Moreover, the novel GPX mimic was confirmed to have a strong antioxidant ability to inhibit lipid peroxidation by measuring the content of malondialdehyde, cell viability, and lactate dehydrogenase activity. Importantly, the novel GPX mimic can penetrate into the cell membrane because of its small molecular size. These characteristics endue the novel mimic with potential perspective for pharmaceutical applications.

Protective role of aryl and alkyl diselenides on lipid peroxidation

The concept that selenium-containing molecules may be better nucleophiles (and therefore antioxidants) than classical antioxidants has led to the design of synthetic organoselenium compounds. In the present study we appraised the antioxidant potential, thiol peroxidase activity, and rate of dithiotreitol and reduced glutathione oxidation of simple organodiselenide compounds in rats and mice. The present results demonstrate that alkyl and aryl diselenides are antioxidant compounds. We verified that the substitution on the aromatic moiety of diphenyl diselenide or the replacement of on aryl group by an alkyl substitute on diselenides changes their antioxidant and thiol peroxidase-like properties. The diaryl diselenides (PhSe)(2) and (p-ClPhSe)(2) presented higher thiol peroxidase activity and demonstrated better antioxidant potential than the other diselenides tested. In fact, the results revealed that alkyl diselenides, at low concentrations, were prooxidants and that aryl diselenides did not present this effect. Alkyl diselenides [(C(2)H(5)Se)(2) and (C(3)H(7)Se)(2)] demonstrated a higher potential for -SH group oxidation than aryl diselenides. In addition, this study demonstrated that diselenide protection against lipid peroxidation was different in mice and rats. The compounds tested acted more as antioxidants in the brains of mice than in the brains of rats.

Ebselen inhibits tumor necrosis factor-alpha-induced c-Jun N-terminal kinase activation and adhesion molecule expression in endothelial cells

Tumor necrosis factor-alpha (TNF-alpha) stimulates expression of endothelial cell (EC) genes that may promote atherosclerosis in part by an activation of mitogen-activated protein (MAP) kinases. Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one), a selenoorganic compound, is effective for acute ischemic stroke; however, its effect on EC has not yet been elucidated. We examined the effect of ebselen on TNF-alpha-induced MAP kinase activation and adhesion molecule expression in cultured human umbilical vein endothelial cells (HUVEC). Extracellular signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 were rapidly and significantly activated by TNF-alpha in HUVEC. TNF-alpha-induced JNK activation was inhibited by ebselen, whereas ERK1/2 and p38 were not affected. Apoptosis signal-regulated kinase 1 (ASK1) was suggested to be involved in TNF-alpha-induced JNK activation because transfection of kinase-inactive ASK1 inhibited TNF-alpha-induced JNK activation. Ebselen inhibited TNF-alpha-induced TNF receptor-associated factor 2 (TRAF2)-ASK1 complex formation and phosphorylation of stress-activated protein kinase ERK kinase 1 (SEK1), which is an upstream signaling molecule of JNK. Finally, TNF-alpha-induced activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) activation and resultant intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expressions were inhibited by ebselen. Specific inhibitors for JNK and NF-kappaB also inhibited TNF-alpha-induced ICAM-1 and VCAM-1 expressions in HUVEC. These findings suggest that ebselen prevents TNF-alpha-induced EC activation through the inhibition of TRAF2-ASK1-SEK1 signaling pathway, which leads to JNK activation. Inhibition of JNK by ebselen may imply its usefulness for the prevention of atherosclerosis relevant to EC activation.

Ebselen inhibits p38 mitogen-activated protein kinase-mediated endothelial cell death by hydrogen peroxide

Ebselen (2-phenyl-1, 2-benzisoselenazol-3[2H]-one) is a seleno-organic compound exhibiting both glutathione peroxidase and antioxidant activity. Although it has been reported that ebselen is effective against hydrogen peroxide (H(2)O(2))-induced cell death in several cell types, its effect on endothelial cell damage has not yet been elucidated. In the present study, we examined the effect of ebselen on H(2)O(2)-induced human umbilical vein endothelial cells (HUVECs) death, and its intracellular mechanism. Our findings showed that pretreatment of HUVECs with ebselen resulted in a significant recovery from H(2)O(2)-induced cell death in a concentration-dependent manner. In addition to the inhibition of lactate dehydrogenase (LDH) leakage, ebselen inhibited H(2)O(2)-induced cytochrome c release and caspase-3 activation and the resultant apoptosis in HUVECs. Moreover, it was observed that H(2)O(2) significantly stimulated activation of mitogen-activated protein (MAP) kinases, i.e., p38 MAP kinase, c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK1/2). Ebselen inhibited H(2)O(2)-induced p38 MAP kinase, but not JNK or ERK1/2 activation. Furthermore, SB203580 (4-[4-fluorophenyl]-2-[4-methylsulfinylphenyl]-5-[4-pyridyl]-1H-imidazole), a specific p38 MAP kinase inhibitor, inhibited H(2)O(2)-induced p38 MAP kinase phosphorylation, cytochrome c release, caspase-3 activation, as well as cell death in HUVECs. These findings suggest that ebselen attenuates H(2)O(2)-induced endothelial cell death through the inhibition of signaling pathways mediated by p38 MAP kinase, caspase-3, and cytochrome c release. Thus, inhibition of p38 MAP kinase by ebselen may imply its usefulness for prevention and/or treatment of endothelial cell dysfunction, which was suggested to be the first step in the development of atherosclerosis.

A new primate model of focal stroke: endothelin-1-induced middle cerebral artery occlusion and reperfusion in the common marmoset

The purpose of the present set of studies was to develop a new primate model of focal ischemia with reperfusion for long-term functional assessment in the common marmoset. Initially, the cerebral vascular anatomy of the marmoset was interrogated by Araldite-cast and ink-perfusion methods to determine the feasibility of an intravascular surgical approach. The methods showed that the internal carotid artery was highly tortuous in its passage, precluding the development of an extracranial method of inducing temporary middle cerebral artery occlusion in the marmoset. A pilot dose-response study investigated an intracranial approach of topically applying endothelin-1 (ET-1) to the M2 portion of the middle cerebral artery in a small sample of marmosets for up to 6 hours (n = 2 or 3 per group). Dose-dependent reductions in middle cerebral artery vessel caliber followed by gradual reperfusion were inversely related to increases in corrected lesion volume after ET-1 treatment, relative to vehicle control application. Finally, the functional consequences of ET-1-induced lesions to the M2 vascular territory were assessed up to 24 hours after surgery using the optimal dose established in the pilot study (2.5 nmol/25 microL). ET-1-treated marmosets (n = 4) showed marked contralateral motor deficits in grip strength and retrieval of food rewards and contralateral sensory/motor neglect towards tactile stimulation, relative to their ipsilateral side and vehicle-treated marmosets (n = 4). Strong correlations were shown between contralateral impairments and histopathologic parameters, which revealed unilateral putamen and cortical damage to the middle cerebral artery territory. No deficits were shown on general mobility, and self-care was promptly resumed in ET-1 marmosets after surgery. These results show that this novel model of ischemia with reperfusion in the marmoset has the potential to assess long-term function and to gauge the efficacy of novel therapeutic strategies targeted for clinical stroke.

Glutathione Peroxidase Overexpression Inhibits Cytochrome c Release and Proapoptotic Mediators to Protect Neurons From Experimental Stroke

Background and Purpose— Ischemic injury and reperfusion increases superoxide (O 2 − ) production and reduces the ability of neurons to scavenge free radicals, leading to the release of cytochrome c and apoptosis. Here we test whether overexpression with the use of gene therapy of the antioxidant glutathione peroxidase (Gpx), delivered before or after experimental stroke, is protective against ischemic injury.

Methods— Sixty-two rats underwent middle cerebral artery occlusion for 1 hour. Defective herpes simplex viral vectors expressing Gpx/lacZ or lacZ alone (control) were delivered into each striatum 12 hours before or 2 or 5 hours after ischemia onset.

Results— Striatal neuron survival at 2 days was improved by 36% when Gpx was delivered 12 hours before ischemia onset, 26% with a 2-hour delay, and 25% when delayed 5 hours. After ischemia, Gpx overexpression significantly reduced cytosolic translocation of cytochrome c and increased the proportion of Bcl-2–positive cells compared with cells transfected with control vector. Bax and activated caspase-3, while present in control-transfected neurons after ischemia, were rarely noted in Gpx-transfected cells.

Conclusions— Expression from these herpes simplex viral vectors begins 4 to 6 hours after injection, which suggests a 9- to 11-hour temporal therapeutic window for Gpx. This is the first study to show that overexpression of Gpx with the use of gene therapy protects against experimental stroke, even with postischemic transfection, and the neuroprotective mechanism involves attenuation of apoptosis-related events.

Ebselen, a seleno-organic antioxidant, is neuroprotective after embolic strokes in rabbits: synergism with low-dose tissue plasminogen activator

BACKGROUND AND PURPOSE

It has been proposed that antioxidants and spin-trap agents may be neuroprotective after acute ischemia stroke. Although the antioxidant ebselen is currently in clinical trials, little is known about the effectiveness of ebselen, which has glutathione peroxidase-like and anti-inflammatory properties in embolic stroke models. Therefore, we determined the effects of ebselen when administered alone or with the thrombolytic tissue plasminogen activator (tPA), the only Food and Drug Administration-approved pharmacological agent for the treatment of stroke.

METHODS

Male New Zealand White rabbits were embolized by injection of a suspension of small blood clots into the middle cerebral artery via a catheter. Five minutes after embolization, ebselen (10 to 50 mg/kg) was infused intravenously. Control rabbits received infusions of the vehicle required to solubilize ebselen. In additional rabbits, ebselen (20 mg/kg) was administered 60 minutes after embolization, either alone or in combination with tPA (0.9 or 3.3 mg/kg tPA). Behavioral analysis was conducted 24 hours after embolization, allowing determination of the effective stroke dose (P50) or clot amount (mg) that produces neurological deficits in 50% of the rabbits.

RESULTS

A drug is considered neuroprotective if it significantly increases the P50 compared with the vehicle-treated control group. The P50 of controls 24 hours after embolization was 1.35+/-0.30 mg. Rabbits treated 5 minutes after embolization with 10, 20, or 50 mg/kg ebselen had P50 values of 2.12+/-0.56, 2.82+/-0.75 (P<0.05), and 0.49+/-0.54 mg, respectively. A significant neuroprotective effect was observed with the 20-mg/kg dose, but not if there was a 60-minute delay before administration (P50=1.69+/-0.32 mg). When tPA (3.3 mg/kg) was infused 60 minutes after embolization and ebselen (20 mg/kg) was injected at either 5 (P50=2.98+/-0.18 mg) or 60 (P50=3.60+/-0.79 mg) minutes, there was no additional neuroprotective effect compared with tPA alone (P50=3.38+/-0.55 mg). However, if ebselen (20 mg/kg) was administered concomitantly with low-dose tPA (0.9 mg/kg) 60 minutes after embolization, the P50 was 3.52+/-0.73 mg (P<0.05), indicating a synergistic effect of the drug combination because neither alone was effective (P50=1.69+/-0.32 and 1.54+/-0.36 mg, respectively).

CONCLUSIONS

This study indicates that ebselen may be neuroprotective when administered shortly after an embolic stroke, but the time- and dose-response analyses suggest that it has a narrow therapeutic window. Nevertheless, ebselen may be beneficial if administered concomitantly with a thrombolytic because it significantly enhanced the neuroprotective activity of low-dose tPA.

Ebselen attenuates cochlear damage caused by acoustic trauma

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a seleno-organic compound, mimics glutathione peroxidase and reacts with peroxynitrite. It is reported to protect against gentamicin- and cisplatin-induced ototoxicity. We investigated whether it protects the cochlea from acoustic trauma. Male pigmented guinea pigs (250-300 g) with normal auditory brainstem response (ABR) thresholds were exposed for 5 h to 125 dB sound pressure level octave band noise centered at 4 kHz. One hour before and 18 h after exposure, they received orally 0.25 ml chloroform solution containing 0, 10, or 30 mg/kg ebselen (n=6, 5 and 5, respectively). The protective effect of ebselen was evaluated by ABR measurement and quantitative hair cell assessment. Treatment significantly (P<0.01) reduced the extent of permanent threshold shifts and outer hair cell loss. Interestingly, the protective effect of a 30 mg/kg dose was less than that of a 10 mg/kg dose. There were no adverse systemic or auditory function effects in three unexposed control subjects given 30 mg/kg ebselen. These findings indicate that ebselen attenuates noise-induced cochlear damage. The concentration that provides optimal protection against such damage has now to be determined.

Dual effect of ebselen on mitochondrial permeability transition

This study reports an investigation on the effect of the seleno-organic compound ebselen on rat liver mitochondria. We show that low concentrations of ebselen induced an increase in rat liver mitochondrial membrane permeability, resulting in swelling and loss of membrane potential. These effects were mediated by the opening of the permeability transition pore. They required Ca(2+), were independent of pyridine nucleotide oxidation, and involved the oxidation of thiol groups. Ebselen pore induction is apparently promoted by the glutathione peroxidase mimicking activity of the drug. Opposite effects, that is, inhibition of both pore opening and thiol oxidation, were observed when concentrations higher than 20 micro M were used. These data demonstrate that ebselen is able to modulate the opening of the permeability transition pore and that it might be a critical event for both the proapoptotic and cytoprotective activities of the drug.

Ebselen attenuates reserpine-induced orofacial dyskinesia and oxidative stress in rat striatum

Reserpine-induced orofacial dyskinesia is an alleged animal model of tardive dyskinesia whose pathophysiology has been related to striatal oxidative stress. In the present investigation, the authors examined whether ebselen, an antioxidant organochalcogen with glutathione peroxidase-like activity, changes the behavioral and neurochemical effect of acute reserpine administration. Reserpine injection for 3 days every other day caused a significant increase on the tongue protrusion frequency and ebselen (30 mg/kg ip for 4 days, starting 1 day before reserpine) reversed partially the effect of reserpine (P<.05). Reserpine- and reserpine+ebselen-treated groups displayed an increase in vacuous chewing frequency when compared to control and ebselen-treated groups (P<.05) Reserpine increased the duration of facial twitching and ebselen reversed partially the effect of reserpine (P<.01). Reserpine increased significantly the thiobarbituric acid-reactive species (TBARS) levels, and ebselen reversed the effect of reserpine on TBARS production in rat striatum. The results of the present study clearly indicated that ebselen has a protective role against reserpine-induced orofacial dyskinesia and reversed the increase in TBARS production caused by reserpine administration. Consequently, the use of ebselen as a therapeutic agent for the treatment of tardive dyskinesia should be considered.

Antioxidant ebselen reduces oxidative damage in focal cerebral ischemia

The antioxidant and neuroprotective potential of the glutathione peroxidase mimic ebselen has been investigated in experimental stroke. Intravenous ebselen (1 mg/kg/h) or vehicle infusion was started 45 min before permanent middle cerebral artery occlusion in the rat, and continued until the end of the experiment. The topography and extent of oxidative damage to the brain was assessed immunohistochemically using an antibody for DNA damage that identified hydroxylated products of 2'-deoxyguanosine (8-OHdG/8-oxodGuo) and an antibody for lipid peroxidation that identified the 4-hydroxynonenal histidine adduct (4-HNE). Ischemic damage was mapped and evaluated with standard histopathology. In the vehicle-treated rats immunopositive staining for both 8-oxodGuo and 4-HNE extended beyond the boundary of ischemic damage. In ebselen-treated rats, the extent of tissue immunopositive for 8-oxodGuo, and 4-HNE was less than that demonstrating ischemic damage confirming the antioxidant mechanism of action in vivo. In addition, ebselen treatment induced a 28% reduction in cortical ischemic damage (p <.02).

A novel antioxidant mechanism of ebselen involving ebselen diselenide, a substrate of mammalian thioredoxin and thioredoxin reductase

The antioxidant mechanism of ebselen involves recently discovered reductions by mammalian thioredoxin reductase (TrxR) and thioredoxin (Trx) forming ebselen selenol. Here we describe a previously unknown reaction; ebselen reacts with its selenol forming an ebselen diselenide with a rate constant of 372 m(-1)s(-1). The diselenide also was a substrate of TrxR forming the selenol with K(m) of 40 microm and k(cat) of 79 min(-1) (k(cat)/K(m) of 3.3 x 10(4) m(-1)s(-1)). Trx increased the reduction because of its fast reaction with diselenide (rate constant 1.7 x 10(3) m(-1)s(-1)). Diselenide stimulated the H2O2 reductase activity of TrxR, even more efficiently with Trx present. Because the mechanism of ebselen as an antioxidant has been assumed to involve glutathione peroxidase-like activity, we compared the H2O2 reductase activity of ebselen with the GSH and Trx systems. TrxR at 50 nm, far below the estimated physiological level, gave 8-fold higher activity compared with 1 mm GSH; addition of 5 microm Trx increased this difference to 13-fold. The rate constant of ebselen selenol reacting with H2O2 was estimated to be faster than 350 m(-1)s(-1). We propose novel mechanisms for ebselen antioxidant action involving ebselen selenol and diselenide formation, with the thioredoxin system rather than glutathione as the predominant effector and target.

Ebselen attenuates oxidative stress-induced apoptosis via the inhibition of the c-Jun N-terminal kinase and activator protein-1 signalling pathway in PC12 cells

1: Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one) is a selenoorganic compound exhibiting both glutathione peroxidase activity and antioxidant activity. Although it has been reported that ebselen is effective for oxidative stress-induced neuronal damage both in vivo and clinically, the precise mechanisms of the efficacy have not yet been elucidated. Thus, we hypothesized that ebselen may affect reactive oxygen species-induced mitogen-activated protein (MAP) kinase activation in cultured PC12 cells. 2: Our findings showed that hydrogen peroxide (H(2)O(2)) stimulated rapid and significant activation of extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and p38 in PC12 cells, which is a model of catecholamine-containing neurons. 3: H(2)O(2)-induced JNK activation was inhibited by ebselen, whereas ERK1/2 and p38 activation by H(2)O(2) were not affected by ebselen. 4: Inhibition by ebselen of H(2)O(2)-induced hydroxyl radical generation in PC12 cells was observed using electron paramagnetic resonance measurements. Ebselen also inhibited H(2)O(2)-induced increases in DNA binding activity of activator protein-1 (AP-1), a downstream transcription factor of JNK, composed of the c-Jun homo/heterodimer. 5: Finally, pretreatment of cells with ebselen resulted in a significant recovery from cell death including apoptosis by H(2)O(2) in PC12 cells. 6 These findings suggest that ebselen attenuates oxidative stress-induced neuronal cell death through the inhibition of the JNK and AP-1 signalling pathway. Thus, inhibition of JNK by ebselen may imply its usefulness for treatment of ischaemic cerebral diseases relevant to neuronal cell death.

Ebselen protects against the reduction in levels of drug-metabolizing enzymes in livers of rats with deoxycholic acid-induced liver injury

Ebselen is a seleno-organic compound that inhibits oxidative stress by lipid peroxidation through a glutathione peroxidase-like activity. We studied the effect of ebselen on the expression of hepatic drug-metabolizing enzymes in rats with deoxycholic acid-induced liver injury. Hydrophobic bile acids, such as deoxycholic acid, are known to cause cholestatic liver injury, and it was reported that expression of hepatic cytochrome P-450 (CYP) was reduced by deoxycholic acid administration in rats. Hydrophobic bile acids induce lipid peroxidation in the liver, and this may be one mechanism of the development of liver injury. In the present study, we investigated the effect of ebselen (30 mg/kg/day for 10 days) on rats ingesting deoxycholic acid (1% of diet for 10 days). Deoxycholic acid decreased levels of CYP1A1, 2B1, 2E1 and 3A2 to 34, 58, 62 and 37% of control values, respectively, and increased serum alkaline phosphatase (ALP) and alanine aminotransferase (ALT) activities to 1.8 and 8.6 times the levels of controls, respectively. Administration of ebselen with deoxycholic acid prevented the decreases in levels of CYP1A1 and 3A2 (86 and 65% of control, respectively) and the increases in serum ALP and ALT activities (1.4 and 1.9 times of control, respectively) caused by deoxycholic acid. These results indicate that ebselen may have a protective effect against hydrophobic bile acid-induced liver injury.

Ebselen: a substrate for human thioredoxin reductase strongly stimulating its hydroperoxide reductase activity and a superfast thioredoxin oxidant

Ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one], a seleno-organic compound with glutathione peroxidase-like activity is used in clinical trials against stroke. Human and bovine TrxR catalyzed the reduction of ebselen to ebselen selenol by NADPH with an apparent K(M)-value of 2.5 microM and a kcat of 588 min(-1). The addition of thioredoxin (Trx) stimulated the TrxR-catalyzed reduction of ebselen several-fold. This result was caused by a very fast oxidation of reduced Trx by ebselen with a rate constant in excess of 2 x 10(7) M(-1) s(-1). This rate is orders of magnitude faster than the reaction of dithiol Trx with insulin disulfides. Ebselen competed with disulfide substrates for reduction by Trx and, therefore, acted as an inhibitor of protein disulfide reduction by the Trx system. The inherent H2O2 reductase activity of mammalian TrxR dependent on its active-site selenocysteine residue was stimulated 10-fold by 2 microM ebselen and 25-fold in the additional presence of 5 microM Trx. Furthermore, the apparent K(M)-value of TrxR for H2O2 was lowered 25-fold to about 100 microM. Our results demonstrate that ebselen is a TrxR peroxidase which, in the presence of Trx, acted as a mimic of a peroxiredoxin. The activity with TrxR and oxidation of reduced Trx offer mechanistic explanations for the in vivo effects of ebselen as an antioxidant and anti-inflammatory agent. Our results demonstrate that the mechanism of action of ebselen may be predominantly via the Trx system rather than via glutathione.

Ebselen suppresses late airway responses and airway inflammation in guinea pigs

Although ebselen, a seleno-organic compound, inhibits inflammation in various animal models, its efficacy as an anti-asthma drug remains to be clarified. In this study, we investigated the inhibitory effect of ebselen on a guinea pig asthma model. Ebselen was orally administered at dosages of 1-20 mg/kg 2 h before an ovalbumin (OA) challenge, and then airway responses, airway inflammation, the generation of superoxide, H(2)O(2), and nitrotyrosine, and the induction of inducible nitric oxide synthase (iNOS) were evaluated. Sensitized animals challenged with OA aerosol showed dual airflow limitations, i.e., immediate and late airway responses (IAR and LAR). Ebselen significantly inhibited LAR at dosages greater than 10 mg/kg, but did not inhibit IAR at any dosage. Bronchoalveolar lavage (BAL) examination showed that airway inflammation was significantly suppressed by ebselen at 10 mg/kg. The generation of superoxide and H(2)O(2) occurred on endothelial cells of LAR bronchi, and was inhibited by 10 mg/kg of ebselen. Superoxide generation was inhibited by diphenyleneiodonium chloride (DPI), a NAD(P)H oxidase inhibitor, but not by allopurinol, a xanthine oxidase inhibitor. Immunoreactivities for iNOS and nitrotyrosine were also observed on endothelial cells of LAR bronchi and were abolished in ebselen-treated animals. The present findings suggest that ebselen can be applied as a new therapeutic agent for asthma. The possible mechanisms by which ebselen inhibits LAR likely involve suppression of oxidant formation and iNOS induction in endothelial cells.

Ebselen blocks the quinolinic acid-induced production of thiobarbituric acid reactive species but does not prevent the behavioral alterations produced by intra-striatal quinolinic acid administration in the rat

Ebselen (EBS) is a seleno-organic compound with glutathione peroxidase-like activity which is neuroprotective in acute stroke ischemia. In this study, we investigated the effect of EBS on quinolinic acid (QA)-induced neurotoxicity. EBS inhibited QA-induced production of thiobarbituric acid reactive species (TBARS) by striatal homogenates in vitro with an IC(50) of 1.85 microM. Intra-striatal injection of QA (360 nmol) increased striatal content of TBARS and induced convulsions and contralateral rotational behavior. Intra-striatal pre-injection of EBS (10 nmol) 15 min before QA abolished QA-induced TBARS production but did not alter QA-induced behavioral effects. The present findings suggest that EBS acts on post-receptor events, neutralizing free radicals produced by overstimulation of N-methyl-D-aspartate receptors.

Oxidative and nitrosative stress in acute renal ischemia

First Published July 12, 2001; 10.1152/ajprenal.0071.2001.—Generation of reactive oxygen species and nitric oxide in hypoxia-reperfusion injury may form a cytotoxic metabolite, peroxynitrite, which is capable of causing lipid peroxidation and DNA damage. This study was designed to examine the contribution of oxidative and nitrosative stress to the renal damage in ischemic acute renal failure (iARF). iARF was initiated in rats by 45-min renal artery clamping. This resulted in lipid peroxidation, DNA damage, and nitrotyrosine modification confirmed both by Western and immunohistochemical analyses. Three groups of animals were randomly treated with an inhibitor of inducible nitric oxide synthase (NOS),l- N 6-(1-iminoethyl)lysine (l-Nil), cell-permeable lecithinized superoxide dismutase (SOD), or both. Each treatment resulted in amelioration of renal dysfunction, as well as reduced nitrotyrosine formation, lipid peroxidation, and DNA damage, thus suggesting that peroxynitrite rather than superoxide anion is responsible for lipid peroxidation and DNA damage. Therefore, in a separate series of experiments, a scavenger of peroxynitrite, ebselen, was administered before the reperfusion period. This treatment resulted in a comparable degree of amelioration of iARF. In conclusion, the present study provides the first attempt to elucidate the role of peroxynitrite in initiation of the cascade of lipid peroxidation and DNA damage to ischemic kidneys. The results demonstrate that l-Nil , lecithinized SOD, and ebselen treatments improve renal function due to their suppression of peroxynitrite production or its scavenging, consequently preventing lipid peroxidation and oxidative DNA damage.

Oxidative and nitrosative stress in acute renal ischemia

Generation of reactive oxygen species and nitric oxide in hypoxia-reperfusion injury may form a cytotoxic metabolite, peroxynitrite, which is capable of causing lipid peroxidation and DNA damage. This study was designed to examine the contribution of oxidative and nitrosative stress to the renal damage in ischemic acute renal failure (iARF). iARF was initiated in rats by 45-min renal artery clamping. This resulted in lipid peroxidation, DNA damage, and nitrotyrosine modification confirmed both by Western and immunohistochemical analyses. Three groups of animals were randomly treated with an inhibitor of inducible nitric oxide synthase (NOS), L-N(6)-(1-iminoethyl)lysine (L-Nil), cell-permeable lecithinized superoxide dismutase (SOD), or both. Each treatment resulted in amelioration of renal dysfunction, as well as reduced nitrotyrosine formation, lipid peroxidation, and DNA damage, thus suggesting that peroxynitrite rather than superoxide anion is responsible for lipid peroxidation and DNA damage. Therefore, in a separate series of experiments, a scavenger of peroxynitrite, ebselen, was administered before the reperfusion period. This treatment resulted in a comparable degree of amelioration of iARF. In conclusion, the present study provides the first attempt to elucidate the role of peroxynitrite in initiation of the cascade of lipid peroxidation and DNA damage to ischemic kidneys. The results demonstrate that L-Nil, lecithinized SOD, and ebselen treatments improve renal function due to their suppression of peroxynitrite production or its scavenging, consequently preventing lipid peroxidation and oxidative DNA damage.

Ebselen protects both gray and white matter in a rodent model of focal cerebral ischemia

BACKGROUND AND PURPOSE

The neuroprotective efficacy of an intravenous formulation of the antioxidant ebselen has been comprehensively assessed with specific regard to conventional quantitative histopathology, subcortical axonal damage, neurological deficit, and principal mechanism of action.

METHODS

Transient focal ischemia (2 hours of intraluminal thread-induced ischemia with 22 hours of reperfusion) was induced in the rat. Ebselen (1 mg/kg bolus plus 1 mg/kg per hour IV) or vehicle was administered at the start of reperfusion and continued to 24 hours. Neurological deficit was assessed 24 hours after ischemia. Gray matter damage was evaluated by quantitative histopathology. Axonal damage was determined with amyloid precursor protein immunohistochemistry used as a marker of disrupted axonal flow and Tau-1 immunohistochemistry to identify oligodendrocyte pathology. Oxidative damage was determined by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4-hydroxynonenal (4-HNE) immunohistochemistry.

RESULTS

Ebselen significantly reduced the volume of gray matter damage in the cerebral hemisphere (by 53.6% compared with vehicle, P<0.02). Axonal damage was reduced by 46.8% (P<0.002) and the volume of oligodendrocyte pathology was reduced by 60.9% (P<0.005). The neurological deficit score was reduced by 40.7% (P<0.05) and the volume of tissue immunopositive for 8-OHdG and 4-HNE was reduced by 65% (P<0.002) and 66% (P<0.001), respectively, in ebselen-treated animals.

CONCLUSIONS

Delayed (2-hour) treatment with intravenous ebselen significantly reduced gray and white matter damage and neurological deficit associated with transient ischemia. The reduction in tissue displaying evidence of oxidative stress suggests that the major mechanism of action is attenuation of free radical damage.

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

BACKGROUND AND PURPOSE

The seleno-organic compound ebselen has both antioxidant and anti-inflammatory properties. Although ebselen has been shown to protect the brain against stroke, it is unclear how ebselen provides neuroprotection. In the present study the authors examined whether ebselen inhibits neuronal apoptosis resulting from transient focal cerebral ischemia in mice. The cytochrome c release and DNA fragmentation, both of which are biochemical markers of apoptosis, were compared between vehicle- and ebselen-treated mice.

METHODS

Cerebral ischemia was induced by transient middle cerebral artery occlusion for 30 minutes in ICR mice under halothane anesthesia. Ebselen (10 mg/kg) was given orally twice, 30 minutes before ischemia and 12 hours after reperfusion. By Western blot analysis, we examined release of mitochondrial cytochrome c. To evaluate brain damage, the brain sections were treated for terminal deoxynucleotidyl transferase-mediated DNA nick-end labeling (TUNEL) and Nissl staining. Prolonged neuroprotective efficacy of ebselen was determined by counting neuronal nuclei (NeuN) immunopositive cells at 21 days after ischemia.

RESULTS

- Cytochrome c release was detected in the ischemic hemisphere at 3 to 24 hours after ischemia. Ebselen treatment diminished the cytochrome c release at 12 and 24 hours. In addition, ebselen decreased both DNA fragmentation determined by TUNEL and brain damage volume at 3 days after ischemia. Furthermore, ebselen increased the number of NeuN immunopositive cells at 21 days after ischemia.

CONCLUSIONS

These results indicate that ebselen attenuates ischemic neuronal apoptosis by inhibiting cytochrome c release. Ebselen may be a potential compound in stroke therapy.

Mitochondria as target for antiischemic drugs

The cessation of blood flow followed by a reperfusion period results in severe damages to cell structures. This induces a complex cascade of events involving, more particularly, a loss of energy, an alteration of ionic homeostasis promoting H(+) and Ca(2+) build up and the generation of free radicals. In this context, mitochondria are highly vulnerable and play a predominant role in the cell signaling leading from life to death. This is why, recently, efforts to find an effective therapy for ischemia-reperfusion injury have focused on mitochondria. This review summarizes the pharmacological strategies which are currently developed and the potential mitochondrial targets which could be involved in the protection of cells.

Malondialdehyde, glutathione peroxidase and superoxide dismutase in peripheral blood erythrocytes of patients with acute cerebral ischemia

The levels of malondialdehyde (MDA), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD-1) were measured in the red blood cells (RBC) of 34 patients with acute ischemic hemispheric stroke on the first and seventh day after their stroke onset, and compared with 30 control individuals matched for sex, age and stroke risk factors. Within the first 24 h after stroke, SOD and GSH-Px activities were significantly decreased and MDA levels were significantly elevated in the patients compared with control subjects. Decrease in SOD and GSH-Px activities and increase in MDA levels showed significant correlation with infarct size, initial stroke severity assessed by NIH stroke scale and poor short-term prognosis. Observed changes in the RBC oxygen scavenging process returned to values not different from those of control subjects within seven days after stroke. Our results indicated that antioxidant enzyme concentrations decreased below normal levels in the acute period following ischemic stroke. Until the recovery of antioxidant defence mechanisms, which occurred up to seven days after stroke onset according to our results, the use of neuroprotective therapy against oxyradical injury seems reliable.

Reactive oxygen radicals in signaling and damage in the ischemic brain

Reactive oxygen species have been implicated in brain injury after ischemic stroke. These oxidants can react and damage the cellular macromolecules by virtue of the reactivity that leads to cell injury and necrosis. Oxidants are also mediators in signaling involving mitochondria, DNA repair enzymes, and transcription factors that may lead to apoptosis after cerebral ischemia. Transgenic or knockout mice with cell- or site-specific prooxidant and antioxidant enzymes provide useful tools in dissecting the events involving oxidative stress in signaling and damage in ischemic brain injury.

Ebselen lowers plasma interleukin-6 levels and glial heme oxygenase-1 expression after focal photothrombotic brain ischemia

Heme oxygenase-1, an inducible heat shock protein, is upregulated by oxidative stress, and its expression is modulated by proinflammatory cytokines such as IL-1 and IL-6. In the present study, we investigated the effects of postlesional, orally applied ebselen, a neuroprotective antioxidant, on serum levels of IL-6 and cerebral heme oxygenase-1 expression following focal ischemia induced by photothrombosis. Ebselen (50 mg/kg body weight) was given 30 min postlesion to male Wistar rats. Animals were divided into four groups: sham-operated vehicle control (n = 9), sham-operated ebselen control (n = 8), lesioned vehicle control (n = 14), and lesioned ebselen-treated (n = 17). Ebselen treatment resulted in a significant lowering of IL-6 plasma levels (26 +/- 5 pg/ml) as compared with that seen in lesioned vehicle controls (48 +/- 9 pg/ml) at 24 h postlesion. In sham-operated rats IL-6 was not detectable. Heme oxygenase-1-positive glial cells were quantitated within topographically determined perilesional brain regions. Within the 0.5-mm-wide rim region directly associated with the lesion core, no differences in the amount of heme oxygenase-1-positive glial cells were found. However, in the more remote ipsilateral perilesional cortex, significantly fewer heme oxygenase-1-positive glial cells were present within the supragranular cortical layers of lesioned ebselen-treated rats compared to lesioned vehicle controls (P < 0.001). In sham-operated rats, no glial heme oxygenase-1 induction occurred. The results indicate that postlesional ebselen treatment lowered plasma IL-6 levels subsequent to a photothrombotic lesion concomitant with a lowering of the heme oxygenase-1 response in glial cells.

The anti-oxidant ebselen antagonizes the release of the apoptogenic factor cytochrome c induced by Fe2+/citrate in rat liver mitochondria

We studied the effects of ebselen (a seleno-organic anti-oxidant), on the release of the apoptogenic factor, cytochrome c, in two different experimental situations damaging mitochondria: (1) Fe(2+)/citrate, known to induce lipid peroxidation consecutively to an oxidative stress; and (2) atractyloside, a ligand of the adenine nucleotide translocator. The effects of ebselen were compared to those of butylated hydroxytoluene (BHT, an inhibitor of lipid peroxidation), and cyclosporine A (CsA, a classical pore antagonist). Ebselen, like BHT, inhibited Fe(2+)/citrate-induced release of cytochrome c, whereas CsA was inactive. On the contrary, neither ebselen nor BHT inhibited atractyloside-induced release of cytochrome c, whereas CsA was potently active. The antioxidant properties of ebselen may protect mitochondria from the consequences of the release of cytochrome c. Thus, it is suggested that the neuroprotective effect of ebselen previously demonstrated in humans and in animals may be due, at least in part, to a mitochondrial protection.

Cerebral ischemia: gene activation, neuronal injury, and the protective role of antioxidants

A large number of gene products appear after an ischemic insult making it difficult to decipher which genes are involved in tissue injury. Reactive oxygen species (ROS) can influence gene expression and have a role in the events that lead to neuronal death. In global cerebral ischemia the oxidative responsive transcription factor, NF-kappa B, is persistently activated in neurons that are destined to die. There are several potential routes through which NF-kappa B can act to induce neuronal death, including production of death proteins and an aborted attempt to reenter the cell cycle. NF-kappa B is only transiently activated in neurons that survive. Persistent NF-kappa B activation can be blocked by antioxidants, which suggests that the neuroprotective effect of antioxidants may be due to inhibiting activation of NF-kappa B.

Impairment of synaptic transmission by transient hypoxia in hippocampal slices: improved recovery in glutathione peroxidase transgenic mice

There is increasing evidence that oxygen free radicals contribute to ischemic brain injury. It is unclear, however, to what extent specific antioxidant enzymes can prevent or reverse the impairment of synaptic function caused by transient hypoxia. In this study, we investigated in transgenic (Tg) mice whether a moderate increase in glutathione peroxidase-1 (GPx1) may improve the capacity of CA1 pyramidal cells to recover synaptic transmission after a short period of hypoxia in vitro. In control hippocampal slices, transient hypoxia (7-9 min) produced irreversible loss of excitatory postsynaptic potentials. Complete recovery of synaptic transmission was observed with homozygous Tg-MT-GPx-6 mice after reoxygenation, and, after repeated episodes of hypoxia, synaptic transmission was still viable in most Tg slices, in contrast to non-Tg slices. Moreover, hypoxic episodes abolished the capacity of hippocampal slices to generate long-term potentiation in area CA1 of control mice, whereas a significant extent of long-term potentiation expression was still preserved in Tg tissues. We also demonstrated that susceptibility to N-methyl-d-aspartate-mediated oxidative injury was reduced in Tg hippocampal slices. In conclusion, our results suggest that a moderate GPx increase can be sufficient to prevent irreversible functional damage produced by transient hypoxia in the hippocampus and to help maintain basic electrophysiological mechanisms involved in memory formation.

Effect of an antioxidant, ebselen, on development of chronic cerebral vasospasm after subarachnoid hemorrhage in primates

BACKGROUND

Oxidation and/or free radical reactions after subarachnoid hemorrhage (SAH) may be involved in the development of chronic cerebral vasospasm. The inhibition of these reactions is thought to be one of the therapeutic strategies for prevention of cerebral vasospasm. We investigated the effect of Ebselen, a synthetic seleno-organic compound, which exhibits anti-oxidation by glutathione peroxidaselike activity to inhibit free radical reactions by lipid peroxidation on the development of chronic cerebral vasospasm in a primate model.

METHODS

Seventeen monkeys were used. SAH was produced by introduction of a blood clot around the right middle cerebral artery and the right side of the circle of Willis in all animals. The monkeys were randomly divided into three groups according to Ebselen dosage: 1) no dosage or non-treated group; 2) high-dose Ebselen group; and 3) low-dose Ebselen group. The drug was administered at 10 mg/Kg in the high-dose group and 5 mg/Kg in the low-dose group twice a day in each group for 7 days after SAH. The vessel diameter was evaluated on angiograms before the induction of SAH and at Day 7 following SAH.

RESULTS

In the untreated group, the angiograms showed significant (p < 0.05) reductions of the mean vessel caliber of the right internal carotid (ICA) (38 +/- 10% reduction) and the middle cerebral artery (MCA) (56 +/- 9.7%) compared with the baseline value before SAH. In the high-dose Ebselen-treated group, the mean percent reduction in vessel caliber of the right ICA (16 +/- 11%) and MCA (28 +/- 9.5%) on Day 7 angiograms were significantly (p < 0.05) lower than those in the nontreated group, whereas the mean percent reduction of these vessels in the low-dose Ebselen-treated group showed no significant difference compared with the untreated group.

CONCLUSIONS

Chronic cerebral vasospasm was inhibited in the animals in which a relatively large amount of Ebselen was administered for 7 days after SAH. The results suggest that the oxidation or free radical reaction by lipid peroxidation after SAH might be involved in the pathogenesis of vasospasm, and that inhibition of these reactions by drugs, such as Ebselen, may have a promising effect for prevention of vasospasm.

Ebselen: prospective therapy for cerebral ischaemia

Stroke occurs due to haemorrhage or occlusive injury and results in ischaemia and reperfusion injury. A variety of destructive mechanisms are involved including oxygen radical generation, calcium overload, cytotoxicity and apoptosis as well as the generation of inflammatory mediators. Ebselen, 2-phenyl-1, 2-benzisoselenazol-3(2H)-one (PZ 51, DR3305), is a mimic of GSH peroxidase which also reacts with peroxynitrite and can inhibit enzymes such as lipoxygenases, NO synthases, NADPH oxidase, protein kinase C and H(+)/K(+)-ATPase. Ebselen is in a late stage of development for the treatment of stroke. The molecular actions of ebselen contribute to its anti-inflammatory and anti-oxidant properties, which have been demonstrated in a variety of in vivo models. Numerous in vitro experiments using isolated LDL, liposomes, microsomes, isolated cells and organs have established that ebselen protects against oxidative challenge. Unlike many inorganic and aliphatic selenium compounds, ebselen has low toxicity as metabolism of the compound does not liberate the selenium moiety, which remains within the ring structure. Subsequent metabolism involves methylation, glucuronidation and hydroxylation. Experimental studies in rats and dogs have revealed that ebselen is able to inhibit both vasospasm and tissue damage in stroke models, which correlates with its inhibitory effects on oxidative processes. Results from randomised, placebo-controlled, double-blind clinical studies on the neurological consequences of acute ischaemic stroke, subarachnoid haemorrhage and acute middle cerebral artery occlusion, have revealed that ebselen significantly enhances outcome in patients who have experienced occlusive cerebral ischaemia of limited duration. The benefit achieved with ebselen is closely related to the rapidity with which the treatment is initiated, following the onset of the stroke attack. Safety and tolerability are good and no adverse effects have become apparent. Ebselen is currently at the pre-registration stage for subarachnoid haemorrhage and stroke in Japan.