Immunohistochemical localization of glutathione peroxidase in infarcted human brain

Colocalization of Aluminum and Iron in Nuclei of Nerve Cells in Brains of Patients with Alzheimer's Disease

Increasing evidence indicates that metal-induced oxidative stress plays a pivotal role in the pathogenesis of Alzheimer's disease (AD). Recently, the presence of 8-hydroxydeoxyguanosine, a biomarker of oxidative DNA damage, was demonstrated in nuclear DNA (nDNA) in the AD brain. Iron (Fe) is a pro-oxidant metal capable of generating hydroxyl radicals that can oxidize DNA, and aluminum (Al) has been reported to facilitate Fe-mediated oxidation. In the present study, we examined the elements contained in the nuclei of nerve cells in AD brains using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). Our results demonstrated that Al and Fe were colocalized in the nuclei of nerve cells in the AD brain. Within the nuclei, the highest levels of both Al and Fe were measured in the nucleolus. The SEM-EDS analysis also revealed the colocalization of Al and Fe in the heterochromatin and euchromatin in neuronal nuclei in the AD brain. Notably, the levels of Al and Fe in the nucleus of nerve cells in the AD brain were markedly higher than those in age-matched control brains. We hypothesize that the colocalization of Al and Fe in the nucleus of nerve cells might induce oxidative damage to nDNA and concurrently inhibit the repair of oxidatively damaged nDNA. An imbalance caused by the increase in DNA damage and the decrease in DNA repair activities might lead to the accumulation of unrepaired damaged DNA, eventually causing neurodegeneration and the development of AD.

Activation of Nrf2/ARE signaling pathway attenuates lanthanum chloride induced injuries in primary rat astrocytes

Lanthanum (La) exposure can lead to learning and memory disorder in animals; however, the underlying mechanism of La induced neurotoxicity is still unknown.

Diphenyl diselenide modulates gene expression of antioxidant enzymes in the cerebral cortex, hippocampus and striatum of female hypothyroid rats

INTRODUCTION

Cellular antioxidant signaling can be altered either by thyroid disturbances or by selenium status.

AIMS

To investigate whether or not dietary diphenyl diselenide can modify the expression of genes of antioxidant enzymes and endpoint markers of oxidative stress under hypothyroid conditions.

METHODS

Female rats were rendered hypothyroid by continuous exposure to methimazole (MTZ; 20 mg/100 ml in the drinking water) for 3 months. Concomitantly, MTZ-treated rats were either fed or not with a diet containing diphenyl diselenide (5 ppm). mRNA levels of antioxidant enzymes and antioxidant/oxidant status were determined in the cerebral cortex, hippocampus and striatum.

RESULTS

Hypothyroidism caused a marked upregulation in mRNA expression of catalase, superoxide dismutase (SOD-1, SOD-3), glutathione peroxidase (GPx-1, GPx-4) and thioredoxin reductase (TrxR-1) in brain structures. SOD-2 was increased in the cortex and striatum, while TrxR-2 increased in the cerebral cortex. The increase in mRNA expression of antioxidant enzymes was positively correlated with the Nrf-2 transcription in the cortex and hippocampus. Hypothyroidism caused oxidative stress, namely an increase in lipid peroxidation and reactive oxygen species levels in the hippocampus and striatum, and a decrease in nonprotein thiols in the cerebral cortex. Diphenyl diselenide was effective in reducing brain oxidative stress and normalizing most of the changes observed in gene expression of antioxidant enzymes.

CONCLUSION

The present work corroborates and extends that hypothyroidism disrupts antioxidant enzyme gene expression and causes oxidative stress in the brain. Furthermore, diphenyl diselenide may be considered a promising molecule to counteract these effects in a hypothyroidism state.

The C718T polymorphism in the 3'-untranslated region of glutathione peroxidase-4 gene is a predictor of cerebral stroke in patients with essential hypertension

In the present study we have investigated the association of three single nucleotide polymorphisms in glutathione peroxidase (GPx) genes GPX1 rs1050450 (P198L), GPX3 rs2070593 (G930A) and GPX4 rs713041 (T718C) with the risk of cerebral stroke (CS) in patients with essential hypertension (EH). A total of 667 unrelated EH patients of Russian origin, including 306 hypertensives (the EH-CS group) who suffered from CS and 361 people (the EH-CS group) who did not have cerebrovascular accidents, were enrolled in the study. The variant allele 718C of the GPX4 gene was found to be significantly associated with an increased risk of CS in hypertensive patients (odds ratio (OR) 1.53, 95% confidence interval (CI) 1.23-1.90, P(adj) = 0.0003). The prevalence of the 718TC and 718CC genotypes of the GPX4 gene was higher in the EH-CS group than the EH-alone group (OR = 2.12, 95%CI 1.42-3.16, P(adj) = 0.0018). The association of the variant GPX4 genotypes with the increased risk of CS in hypertensives remained statistically significant after adjusting for confounding variables such as sex, body mass index (BMI), blood pressure and antihypertensive medication use (OR = 2.18, 95%CI 1.46-3.27, P = 0.0015). Multiple logistic regression analysis did not reveal any interaction between various combinations of GPX1, GPX3 and GPX4 genotypes regarding the risk of CS in patients with EH. The study demonstrated for the first time that the C718T polymorphism in the 3'-untranslated region of the GPX4 gene could be considered as a genetic marker of susceptibility to CS in patients with EH.

Roles of the lipid peroxidation product 4-hydroxynonenal in obesity, the metabolic syndrome, and associated vascular and neurodegenerative disorders

A rising tide of obesity and type 2 diabetes has resulted from the development of technologies that have made inexpensive high calorie foods readily available and exercise unnecessary for many people. Obesity and the metabolic syndrome (insulin resistance, visceral adiposity and dyslipidemia) wreak havoc on cells throughout the body thereby promoting cardiovascular and kidney disease, and degenerative diseases of the brain and body. Obesity and insulin resistance promote disease by increasing oxidative damage to proteins, lipids and DNA as the result of a combination of increased free radical production and an impaired ability of cells to detoxify the radicals and repair damaged molecules. By covalently modifying membrane-associated proteins, the membrane lipid peroxidation product 4-hydroxynonenal (HNE) may play particularly sinister roles in the metabolic syndrome and associated disease processes. HNE can damage pancreatic beta cells and can impair the ability of muscle and liver cells to respond to insulin. HNE may promote atherosclerosis by modifying lipoproteins and can cause cardiac cell damage by impairing metabolic enzymes. An adverse role for HNE in the brain in obesity and the metabolic syndrome is suggested by studies showing that HNE levels are increased in brain cells with aging and Alzheimer's disease. HNE can cause the dysfunction and degeneration of neurons by modifying membrane-associated glucose and glutamate transporters, ion-motive ATPases, enzymes involved in amyloid metabolism, and cytoskeletal proteins. Exercise and dietary energy restriction reduce HNE production and may also increase cellular systems for HNE detoxification including glutathione and oxidoreductases. The recent development of low molecular weight molecules that scavenge HNE suggests that HNE can be targeted in the design of drugs for the treatment of obesity, the metabolic syndrome, and associated disorders.

Cellular glutathione peroxidase in human brain: cellular distribution, and its potential role in the degradation of Lewy bodies in Parkinson's disease and dementia with Lewy bodies

Glutathione peroxidase (GPx-1) is regarded as one of the mammalian cell's main antioxidant enzymes inactivating hydrogen peroxide and protecting against oxidative stress. Using control, Parkinson's disease (PD), and dementia with Lewy bodies tissue (DLB) we have shown that GPx-1 is a 21-kD protein under reducing conditions in all tissues examined but is not in high abundance in human brain. Using immunohistochemistry we have mapped the cellular distribution of GPx-1 and have shown it to be in highest levels in microglia and with lower levels in neurons. Only a trace amount was detectable in astrocytes using immunofluorescence and GPx-1 was not detectable in oligodendrocytes. GPx-1 positive microglia were hypertrophied and more abundant in PD and DLB tissues and were seen to be making multiple contacts with neurons. In some cases neurons containing Lewy bodies were surrounded by microglia. Unstructured Lewy bodies were enveloped with a layer of GPx-1 that was partially colocalized with alpha-synuclein whereas concentric Lewy bodies had discrete deposits of GPx-1 around the periphery which appeared to be involved in the degradation of the Lewy bodies. These results suggest that abnormal alpha-synuclein as found in Lewy bodies produce hydrogen peroxide and these neurons are capable of directing antioxidant enzymes to regions of oxidative stress. These results also suggest that GPx-1 positive microglia are involved in neuroprotection in PD and DLB and that GPx-1 is an important antioxidant enzyme in neuronal defences.

Metabolic regulation and function of glutathione peroxidase-1

Glutathione peroxidase-1 (GPX1) represents the first identified mammalian selenoprotein, and our understanding in the metabolic regulation and function of this abundant selenoenzyme has greatly advanced during the past decade. Selenocysteine insertion sequence-associating factors, adenosine, and Abl and Arg tyrosine kinases are potent, Se-independent regulators of GPX1 gene, protein, and activity. Overwhelming evidences have been generated using the GPX1 knockout and transgenic mice for the in vivo protective role of GPX1 in coping with oxidative injury and death mediated by reactive oxygen species. However, GPX1 exerts an intriguing dual role in reactive nitrogen species (RNS)-related oxidative stress. Strikingly, knockout of GPX1 rendered mice resistant to toxicities of drugs including acetaminophen and kainic acid, known as RNS inducers. Intracellular and tissue levels of GPX1 activity affect apoptotic signaling pathway, protein kinase phosphorylation, and oxidant-mediated activation of NFkappaB. Data are accumulating to link alteration or abnormality of GPX1 expression to etiology of cancer, cardiovascular disease, neurodegeneration, autoimmune disease, and diabetes. Future research should focus on the mechanism of GPX1 in the pathogeneses and potential applications of GPX1 manipulation in the treatment of these disorders.

Beneficial effect of antioxidants in purified neurons derived from rat cortical culture

Brain cell suspensions obtained from cerebrum of fetal rats were cultured and after 5 days neurons were separated from the residual cells. These purified neurons, which were replated on the dish, started to die within 24 h in culture. Glutathione content of these neurons decreased rapidly to less than one-tenth of the initial level after 24 h. In the presence of alpha-tocopherol, a well-known antioxidant, the neurons survived for at least 3 days, though glutathione content remained very low. Butylated hydroxyanisol had similar effect, but ascorbic acid and uric acid had no or very little effect. Serotonin, which is assumed to have an antioxidant activity, kept the neurons alive for 3 days. These results suggest that neurons separated from the other types of cells cannot survive due to the oxidative stress, which may otherwise be neutralized by a mechanism involving glutathione, and that antioxidants including serotonin has a beneficial effect on these purified neurons.

In situ immunoradiographic method for quantification of specific proteins in normal and ischemic brain regions

This study tested the application of an immunoisotopic assay for immunohistochemical localization and quantification of proteins in brain sections from rats without or with transient focal ischemia. We assessed the hypothesis that measurements of protein levels in injured brain determined by an isotopic assay using [(125)I]-protein A have greater reliability than those made by conventional immunoperoxidase labeling using diaminobenzidine. Quantification of immunoreactivities for glial fibrillary acidic protein (GFAP), glutamate transporter-1 (GLT-1) and heat shock protein-70 (HSP-70) was determined by optical density signal in the immunoisotopic and immunoperoxidase assays. In ischemic brain, the immunoisotopic assay detected protein increases (cortical penumbra HSP-70, 151+/-6%), protein decreases (cortical ischemic core GLT-1, 61+/-6%) and no changes in GFAP levels compared to controls animals. These results differed from the protein levels found by the immunoperoxidase assay, which showed elevated HSP-70, GLT-1 and GFAP in all ischemic regions. We conclude that nonspecific immunosignal confounds assessments of protein expression in injured brain and that the immunoisotopic method is a valid approach to regionally localize and quantify proteins after brain injury. The disadvantage of the falsely positive overestimation of protein immunoreactivity after stroke with the immunoperoxidase method has to be weighted with the advantage of the cellular resolution.

Selenium and brain function: a poorly recognized liaison

Molecular biology has recently contributed significantly to the recognition of selenium (Se)2 and Se-dependent enzymes as modulators of brain function. Increased oxidative stress has been proposed as a pathomechanism in neurodegenerative diseases including, among others, Parkinson's disease, stroke, and epilepsy. Glutathione peroxidases (GPx), thioredoxin reductases, and one methionine-sulfoxide-reductase are selenium-dependent enzymes involved in antioxidant defense and intracellular redox regulation and modulation. Selenium depletion in animals is associated with decreased activities of Se-dependent enzymes and leads to enhanced cell loss in models of neurodegenerative disease. Genetic inactivation of cellular GPx increases the sensitivity towards neurotoxins and brain ischemia. Conversely, increased GPx activity as a result of increased Se supply or overexpression ameliorates the outcome in the same models of disease. Genetic inactivation of selenoprotein P leads to a marked reduction of brain Se content, which has not been achieved by dietary Se depletion, and to a movement disorder and spontaneous seizures. Here we review the role of Se for the brain under physiological as well as pathophysiological conditions and highlight recent findings which open new vistas on an old essential trace element.

Selenium and selenoproteins in the brain and brain diseases

Over the past three decades, selenium has been intensively investigated as an antioxidant trace element. It is widely distributed throughout the body, but is particularly well maintained in the brain, even upon prolonged dietary selenium deficiency. Changes in selenium concentration in blood and brain have been reported in Alzheimer's disease and brain tumors. The functions of selenium are believed to be carried out by selenoproteins, in which selenium is specifically incorporated as the amino acid, selenocysteine. Several selenoproteins are expressed in brain, but many questions remain about their roles in neuronal function. Glutathione peroxidase has been localized in glial cells, and its expression is increased surrounding the damaged area in Parkinson's disease and occlusive cerebrovascular disease, consistent with its protective role against oxidative damage. Selenoprotein P has been reported to possess antioxidant activities and the ability to promote neuronal cell survival. Recent studies in cell culture and gene knockout models support a function for selenoprotein P in delivery of selenium to the brain. mRNAs for other selenoproteins, including selenoprotein W, thioredoxin reductases, 15-kDa selenoprotein and type 2 iodothyronine deiodinase, are also detected in the brain. Future research directions will surely unravel the important functions of this class of proteins in the brain.

Astrocytes and brain injury

Astrocytes are the most numerous cell type in the central nervous system. They provide structural, trophic, and metabolic support to neurons and modulate synaptic activity. Accordingly, impairment in these astrocyte functions during brain ischemia and other insults can critically influence neuron survival. Astrocyte functions that are known to influence neuronal survival include glutamate uptake, glutamate release, free radical scavenging, water transport, and the production of cytokines and nitric oxide. Long-term recovery after brain injury, through neurite outgrowth, synaptic plasticity, or neuron regeneration, is influenced by astrocyte surface molecule expression and trophic factor release. In addition, the death or survival of astrocytes themselves may affect the ultimate clinical outcome and rehabilitation through effects on neurogenesis and synaptic reorganization.

Trandolapril reduces infarction area after middle cerebral artery occlusion in rats

In this study, we investigated whether angiotensin-converting enzyme (ACE) is involved in the progression of cerebral infarct lesions after middle cerebral artery (MCA) occlusion in rats. After placebo or trandolapril was administered orally for 7 days, we infarcted in the territory of the right MCA by extracranial vascular occlusion and studied the effect of trandolapril on brain ACE activity and infarct size 7 days after MCA occlusion. In placebo-treated rats, brain ACE activity in the infarct side was increased by a significant 1.34-fold compared with that in the non-infarct side 7 days after MCA occlusion. Brain ACE activities in the infarct sides were suppressed to 39.8% by trandolapril treatment. The ratios of unilateral infarcts to the total coronal sectional areas in placebo- and trandolapril-treated rats were 48.1 +/- 3.3% and 37.4 +/- 2.3%, respectively, and the difference between these values was significant. These results demonstrate that inhibition of the increased brain ACE activity in infarct lesions can reduce the infarction area after MCA occlusion.

Piracetam and vinpocetine exert cytoprotective activity and prevent apoptosis of astrocytes in vitro in hypoxia and reoxygenation

The aim of the present study was to establish whether piracetam (2-pyrrolidon-N-acetamide; PIR) and vinpocetine (a vasoactive vinca alkaloid; VINP) are capable of protecting astrocytes against hypoxic injury. Using the model of astrocyte cell culture we observed the cells treated with PIR and VINP during and after in vitro simulated hypoxia. Cell viability was determined by Live/Dead Viability/Cytotoxicity Assay Kit, LDH release assay and MTT conversion test. Apoptotic cell death was distinguished by a method of Hoechst 33342 staining underfluorescence microscope and caspase-3 colorimetric assay. In addition the intracellular levels of ATP and phosphocreatine (PCr) were evaluated by bioluminescence method. Moreover, the effect of the drugs on the DNA synthesis was evaluated by measuring the incorporation of [3H]thymidine into DNA of astrocytes. PIR (0.01 and 1 mM) and VINP (0.1 and 10 microM) were added to the medium both during 24 h normoxia, 24 h hypoxia or 24 h reoxygenation. Administration of 1 mM PIR or 0.1 microM VINP to the cultures during hypoxia significantly decreases the number of dead and apoptotic cells. The antiapoptic effects of drugs in the above mentioned concentrations was also confirmed by their stimulation of mitochondrial function, the increase of intracellular ATP, and the inhibition of the caspase-3 activity. The prevention of apoptosis was accompanied by the increase in ATP and PCr levels and increase in the proliferation of astrocytes exposed to reoxygenation. The higher concentration of VINP (10 microM) was detrimental in hypoxic conditions. Our experiment proved the significant cytoprotective effect of 1 mM PIR and 0.1 microM VINP on astrocytes in vitro.

Nitric oxide synthase-I containing cortical interneurons co-express antioxidative enzymes and anti-apoptotic Bcl-2 following focal ischemia: evidence for direct and indirect mechanisms towards their resistance to neuropathology

Neuronal nitric oxide-I is constitutively expressed in approximately 2% of cortical interneurons and is co-localized with gamma-amino butric acid, somatostatin or neuropeptide Y. These interneurons additionally express high amounts of glutamate receptors which mediate the glutamate-induced hyperexcitation following cerebral injury, under these conditions nitric oxide production increases contributing to a potentiation of oxidative stress. However, perilesional nitric oxide synthase-I containing neurons are known to be resistant to ischemic and excitotoxic injury. In vitro studies show that nitrosonium and nitroxyl ions inactivate N-methyl-D-aspartate receptors, resulting in neuroprotection. The question remains of how these cells are protected against their own high intracellular nitric oxide production after activation. In this study, we investigated immunocytochemically nitric oxide synthase-I containing cortical neurons in rats after unilateral, cortical photothrombosis. In this model of focal ischemia, perilesional, constitutively nitric oxide synthase-I containing neurons survived and co-expressed antioxidative enzymes, such as manganese- and copper-zinc-dependent superoxide dismutases, heme oxygenase-2 and cytosolic glutathione peroxidase. This enhanced antioxidant expression was accompanied by a strong perinuclear presence of the antiapoptotic Bcl-2 protein. No colocalization was detectable with upregulated heme oxygenase-1 in glia and the superoxide and prostaglandin G(2)-producing cyclooxygenase-2 in neurons. These results suggest that nitric oxide synthase-I containing interneurons are protected against intracellular oxidative damage and apoptosis by Bcl-2 and several potent antioxidative enzymes. Since nitric oxide synthase-I positive neurons do not express superoxide-producing enzymes such as cyclooxygenase-1, xanthine oxidase and cyclooxygenase-2 in response to injury, this may additionally contribute to their resistance by reducing their internal peroxynitrite, H(2)O(2)-formation and caspase activation.

Does trimetazidine exert cytoprotective activity on astrocytes subjected to hypoxia in vitro?

The aim of the present study was to establish whether trimetazidine (TMZ) is capable of protecting astrocytes against hypoxic injury. Using the model of astrocyte cell culture we tried to observe the cells treated with TMZ before, during and after hypoxia simulated in vitro. Cell viability was determined by Live/Dead (viability/cytotoxicity) Assay Kit and MTT conversion test. Apoptotic cell death was distinguished by a method using fluorescence microscopy with Hoechst 33342. The effect of the drug on the DNA synthesis was evaluated by measuring the incorporation of [3H]thymidine into DNA of astrocytes. TMZ stimulates the proliferation of astrocytes most significant one when the astrocytes are exposed to the drug in normoxia, hypoxia and/or re-oxygenation. Adding TMZ into cultures during re-oxygenation and hypoxial re-oxygenation significantly decreases the number of dead and apoptotic cells. Our experiment has proved that TMZ exerts the most significantly cytoprotective effect on astrocytes in vitro when added during hypoxia and/or re-oxygenation. We may conclude that the protective effect of TMZ depends on the sequence of drug adding and hypoxia/ re-oxygenation onset.

Role of astrocytes in pathogenesis of ischemic brain injury

Astrocytes play an important role in the homeostasis of the CNS both in normal conditions and after ischemic injury. The swelling of astrocytes is observed during and several seconds after brain ischemia. Then ischemia stimulates sequential morphological and biochemical changes in glia and induces its proliferation. Reactive astrocytes demonstrate stellate morphology, increased glial fibrillary acidic protein (GFAP) immunoreactivity, increased number of mitochondria as well as elevated enzymatic and non-enzymatic antioxidant activities. Astrocytes can re-uptake and metabolize glutamate and in this way they control its extracellular concentration. The ability of astrocytes to protect neurons against the toxic action of free radicals depends on their specific energy metabolism, high glutathione level, increased antioxidant enzyme activity (catalase, superoxide dismutase, glutathione peroxidase) and overexpression of antiapoptotic bcl-2 gene. Astrocytes produce cytokines (TNF-alpha, IL-1, IL-6) involved in the initiation and maintaining of immunological response in the CNS. In astrocytes, like in neurones, ischemia induces the expression of immediate early genes: c-fos, c-jun, fos B, jun B, jun D, Krox-24, NGFI-B and others. The protein products of these genes modulate the expression of different proteins, both destructive ones and those involved in the neuroprotective processes.

Metabolism and functions of glutathione in brain

The tripeptide glutathione is the thiol compound present in the highest concentration in cells of all organs. Glutathione has many physiological functions including its involvement in the defense against reactive oxygen species. The cells of the human brain consume about 20% of the oxygen utilized by the body but constitute only 2% of the body weight. Consequently, reactive oxygen species which are continuously generated during oxidative metabolism will be generated in high rates within the brain. Therefore, the detoxification of reactive oxygen species is an essential task within the brain and the involvement of the antioxidant glutathione in such processes is very important. The main focus of this review article will be recent results on glutathione metabolism of different brain cell types in culture. The glutathione content of brain cells depends strongly on the availability of precursors for glutathione. Different types of brain cells prefer different extracellular glutathione precursors. Glutathione is involved in the disposal of peroxides by brain cells and in the protection against reactive oxygen species. In coculture astroglial cells protect other neural cell types against the toxicity of various compounds. One mechanism for this interaction is the supply by astroglial cells of glutathione precursors to neighboring cells. Recent results confirm the prominent role of astrocytes in glutathione metabolism and the defense against reactive oxygen species in brain. These results also suggest an involvement of a compromised astroglial glutathione system in the oxidative stress reported for neurological disorders.

Astrocyte phenotype and prevention against oxidative damage in neurotoxicity

Astrocytes possess a potent array of protective systems. These are chiefly targeted against oxidised products and radicals, which are frequently present in increased amounts following exposure of nervous tissue to a range of toxic insults. Following exposure to the toxic chemicals astrocytes commonly respond by alteration in phenotype with upregulation of a large number of molecules, including those controlling the protective systems. This article summarizes evidence, largely obtained from in vitro studies, which supports the concept that some of the changes in astrocyte phenotype are associated with increased protection against the cytotoxicity caused by the oxidative damage that results from exposure to range of neurotoxicants.

Unilateral upregulation of cyclooxygenase-2 following cerebral, cortical photothrombosis in the rat: suppression by MK-801 and co-distribution with enzymes involved in the oxidative stress cascade

Cyclooxygenase-2 (COX-2) is an essential enzyme for prostaglandin synthesis from arachidonic acid, during which considerable amounts of superoxide are produced. During pathological conditions, superoxide and nitric oxide (NO) rapidly form peroxynitrite, a potent cytotoxin, causing symptoms referred to as oxidative stress response. Superoxide is controlled by enzymes such as manganese- or copper-zinc-dependent superoxide dismutase (Mn-SOD, CuZn-SOD), glutathione peroxidase (GPx) and antioxidants derived from heme oxygenase (HO) activity such as biliverdin and bilirubin. NO derives from 3 NO-synthases (NOS I-III) from which the calcium-dependent NOS-I and III are activated rapidly due to hyperexcitation. We studied the induction of COX-2 by immunohistochemistry at days 1, 2 and 5 following cortical photothrombosis in normal and MK-801 treated rats. The results showed a weak constitutive, neuronal expression of COX-2 in cortex and amygdala. Layers II+III contained considerably more COX-2 than infragranular layers. One and 2 days following injury COX-2 was highly upregulated in the supragranular layers of the whole injured hemisphere compared with sham-operated animals and compared to the contralateral unlesioned hemisphere, whereas at day 5 COX-2 levels had returned to baseline. MK-801 treatment caused a reduction in COX-2 upregulation at day one and by day 2 no significant differences between injured and contralateral hemisphere were measurable. COX-2 positive neurons were found in close association with NOS-I containing neurons and their fibers but were not colocalized. In addition, codistribution of COX-2 was found with HO-1, CuZn-SOD and GPx containing cells, whereas COX-2 was colocalized with HO-2 and/or MnSOD in cortical neurons.

Management of oxidative stress in the CNS: the many roles of glutathione

An outline is given of mechanisms that generate oxidative stress and inflammation. Considered are the metabolic mechanisms that give rise to peroxides, the source of strong oxidants; the production of dicarbonyls that interact with macromolecules to form advanced glycation endproducts; and the role that activation of the transcription factor NF(Kappa)B has in the expression of pro-inflammatory genes. Management of oxidative stress is considered by outlining the central role of reduced glutathione (GSH) in peroxide scavenging, dicarbonyl scavenging and activation of NF(Kappa)B. Cellular GSH levels are dictated by the balance between consumption, oxidation of GSH, reduction of oxidized-glutathione, and synthesis. The rate-limiting enzyme in GSH synthesis is L-gamma-glutamyl-L-cysteine synthase, a phase II enzyme. Phase II enzyme inducers are found in many fruits and vegetables. It is suggested that dietary phase II enzyme inducers be investigated for their potential for preventing or retarding the development of degenerative diseases that have an underlying oxidative stress and inflammatory component.

Dynamics of nitrotyrosine formation and decay in rat brain during focal ischemia-reperfusion

The purpose of this study was to establish the dynamics of nitrotyrosine (NO2-Tyr) formation and decay during the rise of NO2-Tyr in rat brain subjected to 2-hour focal ischemia-reperfusion, and to evaluate the role of inducible nitric oxide synthase in the rise. The authors first determined the half life of NO2-Tyr in rat brain at 24 hours after the start of reperfusion by blocking NO2-Tyr formation with N(G)-monomethyl-L-arginine and after the decay of NO2-Tyr by means of a hydrolysis/HPLC procedure. The values obtained were approximately 2 hours in both peri-infarct and core-of-infarct regions. Using the same hydrolysis/HPLC procedure, the ratio of nitrotyrosine to tyrosine from the 2-hour occlusion to as much as 72 hours after the start of reperfusion was measured in the presence and absence of aminoguanidine (100 mg/kg intraperitoneally twice a day). In the absence of aminoguanidine, the ratio of NO2-Tyr in the peri-infarct and core-of-infarct regions reached 0.95% +/- 0.34% and 0.52% +/- 0.34%, respectively, at 1 hour after the start of reperfusion. The elevated levels persisted until 48 hours, then declined. The peri-infarct region showed the highest percent NO2-Tyr level, followed by the core of infarct, then the caudoputamen. Aminoguanidine significantly reduced NO2-Tyr formation (up to 90% inhibition) during 24 to 48 hours. The authors conclude that inducible nitric oxide synthase is predominantly responsible for NO2-Tyr formation, at least in the late phase of reperfusion. These results have important implications for the therapeutic time window and choice of nitric oxide synthase inhibitors in patients with cerebral infarction.

Induction of heme oxygenase protein protects neurons in cortex and striatum, but not in hippocampus, against transient forebrain ischemia

To clarify whether heme oxygenase-1 (HO-1) protein plays a protective role against cerebral ischemia, we investigated the effects of an HO inhibitor (tin mesoporphyrin IX [SnMP] three doses of 30 micromol/kg, intraperitoneally) and an HO inducer (hemin, three doses of 30 micromol/kg, intraperitoneally) on the pathologic outcome and on the immunohistochemical reaction for HO-1 after 20-minute transient forebrain ischemia followed by 3-day reperfusion in rats. Hemin significantly increased viable neurons in the cortex (compared to the SnMP-treated group, P < .05) and striatum (compared to the saline-treated group at P < .01 and SnMP-treated group at P < .05), and intense HO-1 immunoreactivity was observed in cortex and striatum, whereas the administration of SnMP tended to decrease viable neurons in the parietal cortex. In contrast, neither hemin nor SnMP affected the pathologic outcome in the CA1 and CA3 hippocampi, in which HO-1 immunoreactivity was weak. These results suggest that induction of HO-1 protein may contribute to cellular defense against ischemic damage in brain regions where potential ability to synthesize HO-1 is retained in ischemia.

Immunocytochemical localization of seleno-glutathione peroxidase in the adult mouse brain

Cytoplasmic seleno-glutathione peroxidase, by reducing hydrogen peroxide and fatty acid hydroperoxides, may be a major protective enzyme against oxidative damage in the brain. Oxidative damage is strongly suspected to contribute to normal aging and neurodegenerative process of Alzheimer's and Parkinson's diseases. We report here an immunocytochemical analysis of the localization of glutathione peroxidase in the adult mouse brain, carried out with an affinity-purified polyclonal antibody. Most of the brain areas analysed showed weak to strong glutathione peroxidase immunoreactivity, expressed in both neurons and glial cells. The strongest immunoreactivity was found in the reticular thalamic and red nuclei. Highly immunoreactive neurons were observed in the cerebral cortex (layer II), the CA1, dentate gyrus and pontine nucleus. Other regions, such as the caudate-putamen, septum nuclei, diagonal band of Broca, hippocampus, thalamus and hypothalamus, showed moderate staining. This study provides original information about the wide distribution of glutathione peroxidase in the mouse brain. Double-staining experiments indicated that specific subsets of cholinergic neurons in septal and diagonal band nuclei were negative for this antigen. Similarly, many dopaminergic neurons of the substantia nigra pars compacta expressed low levels of glutathione peroxidase antigen, in contrast to the ventral tegmental area, wherein most catecholaminergic cells were strongly positive. A lack of glutathione peroxidase in subsets of dopaminergic or cholinergic neurons may thus confer a relative sensitivity of these cells to oxidative injury of various origins, including catecholamine oxidation, neurotoxins and excitotoxicity.

Immunolocalization of glutathione reductase in the murine brain

Free radical species arise from the univalent reduction of oxygen. The cytosolic agent H2O2, produced during enzymatic scavenging of the superoxide radical (O2-) is in turn removed predominantly via the oxidation of reduced glutathione (GSH) to the oxidized form (GSSG) by glutathione peroxidase. Subsequently GSSG is recycled back to GSH by glutathione reductase (GSH-red). Little is known about the distribution of this enzyme in the brain. The aim of this study was to determine the distribution of this enzyme in the brain of different murine species by means of immunocytochemical techniques, although most attention was given to the distribution of GSH-red in the forebrain. In most brain areas GSH-red positive neurons were detected, but the regional intracellular staining intensity differed markedly. The pre-piriform and piriform cortices, the pyramidal cell layers of the hippocampus, and the dentate gyrus were heavily stained. The caudate nucleus displayed a progressive increase in the intracellular staining intensity from the rostral to the caudolateral parts. Furthermore, in the thalamus, there was a gradual decrease in GSH-red staining from the medial to the lateral parts. The mesencephalon was poor in immunopositive cells, and in the substantia nigra pars reticulata, almost no labeling was detected. However, the substantia nigra pars compacta showed an intense GSH-red immunoreactivity. The results show a specific localization of glutathione reductase in distinct brain regions, suggesting a variable potency of different brain areas in dealing with the damaging oxidative actions of free radicals. Also, differential GSH-red expression patterns were found in the various murine species. Some species showed a pronounced GSH-red immunoreactivity in glial cells, specifically in regions that lacked neuronal GSH-red immunoreactivity.

Melatonin reduces H2O2-induced lipid peroxidation in homogenates of different rat brain regions

The ability of melatonin to modify H2O2-induced lipid peroxidation in brain homogenates was determined. The concentrations of brain malonaldehyde (MDA) and 4-hydroxyalkenals (4-HDA) were assayed as an index of induced membrane oxidative damage. Homogenates from five different regions of the brain (cerebral cortex, cerebellum, hippocampus, hypothalamus, and corpus striatum) derived from two different strains of rats, Sprague-Dawley and Wistar, were incubated with either H2O2 (5 mM) alone or H2O2 together with melatonin at increasing concentrations ranging from 0.1 to 4 mM. The basal level of lipid peroxidation was strain-dependent and about 100% higher in homogenates from the brain of Wistar rats than those measured in Sprague-Dawley rats. MDA + 4-HDA levels increased after H2O2 treatment in homogenates obtained from each region of the brain in both rat strains but the sensitivity of the homogenates from Sprague-Dawley rats was greater than that for the homogenates from Wistar rats (increases after H2O2 from 45 to 165% compared 20 to 40% for Sprague-Dawley and Wistar rats, respectively). Melatonin co-treatment reduced H2O2-induced lipid peroxidation in brain homogenates in a concentration-dependent manner; the degree of protection against lipid peroxidation was similar in all brain regions.

Melatonin administration prevents lipopolysaccharide-induced oxidative damage in phenobarbital-treated animals

The protective effect of melatonin on lipopolysaccharide (LPS)-induced oxidative damage in phenobarbital-treated rats was measured using the following parameters: changes in total glutathione (tGSH) concentration, levels of oxidized glutathione (GSSG), the activity of the antioxidant enzyme glutathione peroxidase (GSH-PX) in both brain and liver, and the content of cytochrome P450 reductase in liver. Melatonin was injected intraperitoneally (ip, 4mg/kg BW) every hour for 4 h after LPS administration; control animals received 4 injections of diluent. LPS was given (ip, 4 mg/kg) 6 h before the animals were killed. Prior to the LPS injection, animals were pretreated with phenobarbital (PB), a stimulator of cytochrome P450 reductase, at a dose 80 mg/kg BW ip for 3 consecutive days. One group of animals received LPS together with Nw-nitro-L-arginine methyl ester (L-NAME), a blocker of nitric oxide synthase (NOS) (for 4 days given in drinking water at a concentration of 50 mM). In liver, PB, in all groups, increased significantly both the concentration of tGSH and the activity of GSH-PX. When the animals were injected with LPS the levels of tGSH and GSSG were significantly higher compared with other groups while melatonin and L-NAME significantly enhanced tGSH when compared with that in the LPS-treated rats. Melatonin alone reduced GSSG levels and enhanced the activity of GSH-PX in LPS-treated animals. Additionally, LPS diminished the content of cytochrome P450 reductase with this effect being largely prevented by L-NAME administration. Melatonin did not change the content of P450 either in PB- or LPS-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of mitochondria in the etiology and pathogenesis of Parkinson's disease

We discuss the etiology and pathogenesis of Parkinson's disease (PD). Our group and others have found a decrease in complex I of the mitochondrial electron transfer complex in the substantia nigra of patients with PD; in addition, we reported loss of the alpha-ketoglutarate dehydrogenase complex (KGDHC) in the substantia nigra. Dual loss of complex I and the KGDHC will deleteriously affect the electron transport and ATP synthesis; we believe that energy crisis is the most important mechanism of nigral cell death in PD. Oxidative stress has also been implicated as an important contributor to nigral cell death in PD, but we believe that oxidative stress is a secondary phenomenon to respiratory failure, because respiratory failure will increase oxygen free-radical formation and consume glutathione. The primary cause of mitochondrial respiratory failure has not been elucidated yet, but additive effect of environmental neurotoxins in genetically predisposed persons appears to be the most likely possibility.