Methods for depleting brain glutathione

Glutathione Deficiency during Early Postnatal Development Causes Schizophrenia-Like Symptoms and a Reduction in BDNF Levels in the Cortex and Hippocampus of Adult Sprague-Dawley Rats

Growing body of evidence points to dysregulation of redox status in the brain as an important factor in the pathogenesis of schizophrenia. The aim of our study was to evaluate the effects of l-buthionine-(S,R)-sulfoximine (BSO), a glutathione (GSH) synthesis inhibitor, and 1-[2-Bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine dihydrochloride (GBR 12909), a dopamine reuptake inhibitor, given alone or in combination, to Sprague–Dawley pups during early postnatal development (p5–p16), on the time course of the onset of schizophrenia-like behaviors, and on the expression of brain-derived neurotrophic factor (BDNF) mRNA and its protein in the prefrontal cortex (PFC) and hippocampus (HIP) during adulthood. BSO administered alone decreased the levels of BDNF mRNA and its protein both in the PFC and HIP. Treatment with the combination of BSO + GBR 12909 also decreased BDNF mRNA and its protein in the PFC, but in the HIP, only the level of BDNF protein was decreased. Schizophrenia-like behaviors in rats were assessed at three time points of adolescence (p30, p42–p44, p60–p62) and in early adulthood (p90–p92) using the social interaction test, novel object recognition test, and open field test. Social and cognitive deficits first appeared in the middle adolescence stage and continued to occur into adulthood, both in rats treated with BSO alone or with the BSO + GBR 12909 combination. Behavior corresponding to positive symptoms in humans occurred in the middle adolescence period, only in rats treated with BSO + GBR 12909. Only in the latter group, amphetamine exacerbated the existing positive symptoms in adulthood. Our data show that rats receiving the BSO + GBR 12909 combination in the early postnatal life reproduced virtually all symptoms observed in patients with schizophrenia and, therefore, can be considered a valuable neurodevelopmental model of this disease.

Alterations in the Antioxidant Enzyme Activities in the Neurodevelopmental Rat Model of Schizophrenia Induced by Glutathione Deficiency during Early Postnatal Life

The aim of the present study was to assess the effects of l-buthionine-(S,R)-sulfoximine (BSO), a glutathione (GSH) synthesis inhibitor, and GBR 12909, a dopamine reuptake inhibitor, administered alone or in combination to Sprague-Dawley rats during early postnatal development (p5-p16), on the levels of reactive oxygen species (ROS), lipid peroxidation (LP) and the activities of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione disulfide reductase (GR) in peripheral tissues (liver, kidney) and selected brain structures (prefrontal cortex, PFC; hippocampus, HIP; and striatum, STR) of 16-day-old rats. The studied parameters were analyzed with reference to the content of GSH and sulfur amino acids, methionine (Met) and cysteine (Cys) described in our previous study. This analysis showed that treatment with a BSO + GBR 12909 combination caused significant decreases in the lipid peroxidation levels in the PFC and HIP, in spite of there being no changes in ROS. The reduction of lipid peroxidation indicates a weakening of the oxidative power of the cells, and a shift in balance in favor of reducing processes. Such changes in cellular redox signaling in the PFC and HIP during early postnatal development may result in functional changes in adulthood.

Glutathione Deficiency and Alterations in the Sulfur Amino Acid Homeostasis during Early Postnatal Development as Potential Triggering Factors for Schizophrenia-Like Behavior in Adult Rats

Impaired glutathione (GSH) synthesis and dopaminergic transmission are important factors in the pathophysiology of schizophrenia. Our research aimed to assess the effects of l-buthionine-(S,R)-sulfoximine (BSO), a GSH synthesis inhibitor, and GBR 12909, a dopamine reuptake inhibitor, administered alone or in combination, to Sprague–Dawley rats during early postnatal development (p5–p16), on the levels of GSH, sulfur amino acids, global DNA methylation, and schizophrenia-like behavior. GSH, methionine (Met), homocysteine (Hcy), and cysteine (Cys) contents were determined in the liver, kidney, and in the prefrontal cortex (PFC) and hippocampus (HIP) of 16-day-old rats. DNA methylation in the PFC and HIP and schizophrenia-like behavior were assessed in adulthood (p90–p93). BSO caused the tissue-dependent decreases in GSH content and alterations in Met, Hcy, and Cys levels in the peripheral tissues and in the PFC and HIP. The changes in these parameters were accompanied by alterations in the global DNA methylation in the studied brain structures. Parallel to changes in the global DNA methylation, deficits in the social behaviors and cognitive functions were observed in adulthood. Only BSO + GBR 12909-treated rats exhibited behavioral alterations resembling positive symptoms in schizophrenia patients. Our results suggest the usefulness of this neurodevelopmental model for research on the pathomechanism of schizophrenia.

Repeated exposure of adult rats to transient oxidative stress induces various long-lasting alterations in cognitive and behavioral functions

Exposure of neonates to oxidative stress may increase the risk of psychiatric disorders such as schizophrenia in adulthood. However, the effects of moderate oxidative stress on the adult brain are not completely understood. To address this issue, we systemically administrated 2-cyclohexen-1-one (CHX) to adult rats to transiently reduce glutathione levels. Repeated administration of CHX did not affect the acquisition or motivation of an appetitive instrumental behavior (lever pressing) rewarded by a food outcome under a progressive ratio schedule. In addition, response discrimination and reversal learning were not affected. However, acute CHX administration blunted the sensitivity of the instrumental performance to outcome devaluation, and this effect was prolonged in rats with a history of repeated CHX exposure, representing pro-depression-like phenotypes. On the other hand, repeated CHX administration reduced immobility in forced swimming tests and blunted acute cocaine-induced behaviors, implicating antidepressant-like effects. Multivariate analyses segregated a characteristic group of behavioral variables influenced by repeated CHX administration. Taken together, these findings suggest that repeated administration of CHX to adult rats did not cause a specific mental disorder, but it induced long-term alterations in behavioral and cognitive functions, possibly related to specific neural correlates.

Beta-amyloidolysis and glutathione in Alzheimer's disease

In this review, we hypothesized the importance of the interaction between the brain glutathione (GSH) system, the proteolytic tissue plasminogen activator (t-PA)/plasminogen/ plasmin system, regulated by plasminogen activator inhibitor (PAI-1), and neuroserpin in the pathogenesis of Alzheimer’s disease. The histopathological characteristic hallmark that gives personality to the diagnosis of Alzheimer’s disease is the accumulation of neurofibroid tangles located intracellularly in the brain, such as the protein tau and extracellular senile plaques made primarily of amyloidal substance. These formations of complex etiology are intimately related to GSH, brain protective antioxidants, and the proteolytic system, in which t-PA plays a key role. There is scientific evidence that suggests a relationship between aging, a number of neurodegenerative disorders, and the excessive production of reactive oxygen species and accompanying decreased brain proteolysis. The plasminogen system in the brain is an essential proteolytic mechanism that effectively degrades amyloid peptides (“beta-amyloidolysis”) through action of the plasmin, and this physiologic process may be considered to be a means of prevention of neurodegenerative disorders. In parallel to the decrease in GSH levels seen in aging, there is also a decrease in plasmin brain activity and a progressive decrease of t-PA activity, caused by a decrease in the expression of the t-PA together with an increase of the PAI-1 levels, which rise to an increment in the production of amyloid peptides and a lesser clearance of them. Better knowledge of the GSH mechanism and cerebral proteolysis will allow us to hypothesize about therapeutic practices.

Behavioral phenotyping of glutathione-deficient mice: relevance to schizophrenia and bipolar disorder

Redox-dysregulation represents a common pathogenic mechanism in schizophrenia (SZ) and bipolar disorder (BP). It may in part arise from a genetically compromised synthesis of glutathione (GSH), the major cellular antioxidant and redox-regulator. Allelic variants of the genes coding for the rate-limiting GSH synthesizing enzyme glutamate-cysteine-ligase modifier (GCLM) and/or catalytic (GCLC) subunit have been associated with SZ and BP. Using mice knockout (KO) for GCLM we have previously shown that impaired GSH synthesis is associated with morphological, functional and neurochemical anomalies similar to those in patients. Here we asked whether GSH deficit is also associated with SZ- and BP-relevant behavioral and cognitive anomalies. Accordingly, we subjected young adult GCLM-wildtype (WT), heterozygous and KO males to a battery of standard tests. Compared to WT, GCLM-KO mice displayed hyperlocomotion in the open field and forced swim test but normal activity in the home cage, suggesting that hyperlocomotion was selective to environmental novelty and mildly stressful situations. While spatial working memory and latent inhibition remained unaffected, KO mice showed a potentiated hyperlocomotor response to an acute amphetamine injection, impaired sensorymotor gating in the form of prepulse inhibition and altered social behavior compared to WT. These anomalies resemble important aspects of both SZ and the manic component of BP. As such our data support the notion that redox-dysregulation due to GSH deficit is implicated in both disorders. Moreover, our data propose the GCLM-KO mouse as a valuable model to study the behavioral and cognitive consequences of redox dysregulation in the context of psychiatric disease.

Oxidative stress in schizophrenia: an integrated approach

Oxidative stress has been suggested to contribute to the pathophysiology of schizophrenia. In particular, oxidative damage to lipids, proteins, and DNA as observed in schizophrenia is known to impair cell viability and function, which may subsequently account for the deteriorating course of the illness. Currently available evidence points towards an alteration in the activities of enzymatic and nonenzymatic antioxidant systems in schizophrenia. In fact, experimental models have demonstrated that oxidative stress induces behavioral and molecular anomalies strikingly similar to those observed in schizophrenia. These findings suggest that oxidative stress is intimately linked to a variety of pathophysiological processes, such as inflammation, oligodendrocyte abnormalities, mitochondrial dysfunction, hypoactive N-methyl-d-aspartate receptors and the impairment of fast-spiking gamma-aminobutyric acid interneurons. Such self-sustaining mechanisms may progressively worsen producing the functional and structural consequences associated with schizophrenia. Recent clinical studies have shown antioxidant treatment to be effective in ameliorating schizophrenic symptoms. Hence, identifying viable therapeutic strategies to tackle oxidative stress and the resulting physiological disturbances provide an exciting opportunity for the treatment and ultimately prevention of schizophrenia.

Effects of N-acetyl-cysteine treatment on glutathione depletion and a short-term spatial memory deficit in 2-cyclohexene-1-one-treated rats

Glutathione (GSH) is the primary antioxidant in the body and is present in high levels in the brain. Levels of GSH and other antioxidants are significantly altered in major psychiatric illnesses, such as schizophrenia. Recent clinical trials have demonstrated that chronic treatment with N-acetyl-l-cysteine (NAC), a GSH precursor, improved symptoms in individuals with this illness. We previously showed in rats and mice that depletion of GSH by treatment with 2-cyclohexene-1-one (CHX) induced short-term spatial memory deficits in the Y-maze test. The aim of present study was to characterise the effect of NAC in this CHX-induced glutathione depletion model. Consistent with our previous studies, CHX treatment induced approximately 50% reduction of GSH levels in striatum, hippocampus and frontal cortex tissue. GSH depletion was significantly rescued by either 1.2 g/kg or 1.6 g/kg of NAC administration, with a full recovery observed in the frontal cortex after the high dose of NAC. CHX treatment also induced a disruption in short-term spatial recognition memory in Y-maze test, as measured by the duration of time spent in the novel arm. This disruption was reversed by treatment with 1.6 g/kg of NAC. In conclusion, this study suggests that rescue of depleted levels of GSH in the brain restores cognitive deficits, as measured by the Y-maze. These effects appear to be dose-dependent and region-specific. These results may be relevant to the understanding and management of the cognitive symptoms of schizophrenia and bipolar disorder.

Dopamine D2 receptor knockout mice develop features of Parkinson disease

OBJECTIVE

This study questions whether increased dopamine (DA) turnover in nigral neurons leads to formation of Lewy bodies (LBs), the characteristic alpha-synuclein-containing cytoplasmic inclusion of Parkinson disease (PD).

METHODS

Mice with targeted deletion of the dopamine D(2) receptor gene (D(2)R[-/-]) have higher striatal and nigral dopamine turnover and elevated oxidative stress. These mice were examined for evidence of histological, biochemical, and gene expression changes consistent with a synucleinopathy.

RESULTS

LB-like cytoplasmic inclusions containing alpha-synuclein and ubiquitin were present in substantia nigra pars compacta (SNpc) neurons of older D(2)R(-/-) mice, and were also occasionally seen in aged wild-type mice. These inclusions displaced the nucleus of affected cells and were eosinophilic. Diffuse cytosolic alpha-synuclein immunoreactivity in SNpc neurons increased with age in both wild-type and D(2)R(-/-) mice, most likely because of redistribution of alpha-synuclein from striatal terminals to SNpc cell bodies. Gene and protein expression studies indicated endoplasmic reticulum (ER) stress and changes in trafficking and autophagic pathways in D(2)R(-/-) SNpc. These changes were accompanied by a loss of DA terminals in the dorsal striatum, although there was no evidence of progressive cell death in the SNpc.

INTERPRETATION

Increased sprouting and DA turnover, as observed in PD and D(2)R(-/-) mice, augments LB-like inclusions and axonal degeneration of dopaminergic neurons. These changes are associated with ER stress and autophagy.

Glutathione depletion in the brain disrupts short-term spatial memory in the Y-maze in rats and mice

Oxidative stress and reduced brain glutathione (GSH) levels have been reported in psychiatric illnesses including schizophrenia and bipolar disorder. However the role of GSH in cognitive impairment in the illness remains unclear. Treatment of Sprague-Dawley rats and C57Bl/6 mice with 2-cyclohexene-1-one (CHX) dose-dependently reduced striatal and frontal cortical GSH levels similar to those in schizophrenia. In both species, GSH depletion resulted in disruption of short-term spatial recognition memory in a Y-maze test. In conclusion, GSH depletion induces cognitive impairment, which may be relevant to the role of GSH in psychiatric illnesses.

In vivo depletion of endogenous glutathione facilitates trimethyltin-induced neuronal damage in the dentate gyrus of mice by enhancing oxidative stress

Acute treatment with trimethyltin chloride (TMT) produces neuronal damage in the hippocampal dentate gyrus of mice. We investigated the in vivo role of glutathione in mechanisms associated with TMT-induced neural cell damage in the hippocampus by examining mice depleted of endogenous glutathione by prior treatment with 2-cyclohexen-1-one (CHO). In the hippocampus of animals treated with CHO 1h beforehand, a significant increase was seen in the number of single-stranded DNA-positive cells in the dentate gyrus when determined on day 2 after the injection of TMT at a dose of 2.0 mg/kg. Immunoblot analysis revealed that CHO treatment induced a significant increase in the phosphorylation of c-Jun N-terminal kinase in the cytosolic and nuclear fractions obtained from the dentate gyrus at 16 h after the TMT injection. There was also a concomitant increase in the level of phospho-c-Jun in the cytosol at 16 h after the injection. Expectedly, lipid peroxidation was increased by TMT in the hippocampus, and was enhanced by the CHO treatment. Moreover, CHO treatment facilitated behavioral changes induced by TMT. Taken together, our data indicate that TMT-induced neuronal damage is caused by activation of cell death signals induced at least in part by oxidative stress. We conclude that endogenous glutathione protectively regulates neuronal damage induced by TMT by attenuating oxidative stress.

Trapping 4-fluorobenzyl chloride in human plasma with chemical derivatization followed by quantitative bioanalysis using high-performance liquid chromatography/tandem mass spectrometry

A quantitative bioanalytical method involving chemical derivatization, solid phase extraction (SPE) and high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) was developed for the determination of 4-fluorobenzyl chloride (4FBCl) in human plasma. 4FBCl is a volatile and reactive molecule that is very unstable in human plasma. In order to stabilize 4FBCl in plasma samples prior to storage, 4-dimethylaminopyridine (DMAP) was added, forming a stable quaternary amine salt derivative. A three-step weak cation-exchange SPE procedure was then employed to remove excess DMAP. The plasma extracts were analyzed by HPLC/MS/MS using a TurboIonspray interface and multiple reaction monitoring. Unlike 4FBCl, the quaternary amine derivative shows excellent sensitivity in electrospray mass spectrometry. The method was validated over a concentration range of 0.5-500 ng/mL using 45 microL of plasma. The maximum within-run and between-run precision observed in a three-run validation for quality control (QC) samples was 12.5 and 7.6%, respectively. The maximum percentage bias observed at all QC sample concentrations was 11.9%. The method has proven to be robust and compatible with high-throughput bioanalysis.

Decreased Tissue Accumulation of 6-Deoxy-6-[18F]fluoro-L-ascorbic Acid in Glutathione-Deficient Rats Induced by Administration of Diethyl Maleate

The relationship between in vivo biodistribution of 6-deoxy-6-[18F]fluoro-L-ascorbic acid (18F-DFA) and the content of tissue glutathione (GSH) was investigated in Wistar male rats. Following intravenous administration of 18F-DFA, the accumulation of radioactivity in most tissues, including the adrenal glands, liver and brain, was significantly reduced together with a decrease in the content of GSH by preloading of diethyl maleate (DEM) which depletes cellular GSH. Similar decreased uptake was also observed in the distribution of L-[1-14C]ascorbic acid (14C-AA) after DEM treatment. The possible biological mechanisms, including competition with endogenous AA and ascorbate recycling, that modulate the uptake and accumulation into tissues of 18F-DFA and 14C-AA in GSH-deficient rats are discussed.

Effects of glutathione depletion by 2-cyclohexen-1-one on excitatory amino acids-induced enhancement of activator protein-1 DNA binding in murine hippocampus

We have investigated the role of glutathione in mechanisms associated with excitatory amino acid signaling to the nuclear transcription factor activator protein-1 (AP1) in the brain using mice depleted of endogenous glutathione by prior treatment with 2-cyclohexen-1-one (CHX). In the hippocampus of animals treated with CHX 2 h before, a significant increase was seen in enhancement of AP1 DNA binding when determined 2 h after the injection of kainic acid (KA) at low doses. The sensitization to KA was not seen in animals injected with CHX 24 h before, in coincidence with the recovery of glutathione contents to the normal levels. By contrast, CHX did not significantly affect the potentiation by NMDA of AP1 binding under any experimental conditions. Prior treatment with CHX resulted in facilitation of behavioral changes induced by KA without affecting those induced by NMDA. These results suggest that endogenous glutathione may be at least in part involved in molecular mechanisms underlying transcriptional control by KA, but not by NMDA, signals of cellular functions.

Cerebral antioxidant status and free radical generation following glutathione depletion and subsequent recovery

This study was aimed to evaluate the oxidative damage, production of reactive oxygen species and the status of antioxidative defenses following cerebral GSH depletion induced by two classical depletors, diethylmaleate (DEM, 3 mmol/kg, i.p.) and phorone (PHO, 4 mmol/kg, i.p.). The treatment decreased (40-43%) brain glutathione levels at 2 h, followed by a partial recovery at 24 h. Cerebral glutathione depletion by these agents increased the levels of superoxide anion and hydroxyl radical at both the time intervals; however, hydrogen peroxide was high at 24 h only. It also produced a dramatic increase in the protein carbonyls at 2 h but not at 24h, without any significant effect on lipid peroxidation and conjugated diene levels. These rats showed a significantly lowered superoxide dismutase activity both at 2 h and 24 h of exposure, as compared to controls. Glutathione depletion enhanced catalase activity markedly at 2 h, followed by some recovery at 24 h. While Se-independent glutathione peroxidase (GPx) and glutathione S-transferase activities were increased at both 2 and 24 h time intervals, Se-dependent GPx and glucose-6-phosphate dehydrogenase were induced at 2 h only. Glutathione depletion decreased ceruloplasmin and vitamin E levels significantly at 2 h. However, ascorbic acid remained unaffected. It may be concluded that an acute cerebral glutathione depletion generates higher levels of reactive oxygen species, which may be responsible for oxidative modification of proteins. Some of these changes appear to recover soon after an activation of a variety of cellular antioxidant defense mechanisms and glutathione restoration. It appears that central nervous system is highly vulnerable to oxidative damage following a moderate glutathione depletion that may result from certain diseases or xenobiotic exposures.

In vivo modulation of rodent glutathione and its role in peroxynitrite-induced neocortical synaptosomal membrane protein damage

Peroxynitrite, formed by the reaction between nitric oxide and superoxide, leads to the oxidation of proteins, lipids, and DNA, and nitrates thiols such as cysteine and glutathione, and amino acids like tyrosine. Previous in vitro studies have shown glutathione to be an efficient scavenger of peroxynitrite, protecting synaptosomal membranes from protein oxidation, the enzyme glutamine synthetase from inactivation, and preventing the death of hippocampal neurons in culture. The current study was undertaken to see if in vivo modulation of glutathione levels would affect brain cortical synaptosomal membrane proteins and their subsequent reaction with peroxynitrite. Glutathione levels were depleted, in vivo, by injecting animals with 2-cyclohexen-1-one (CHX, 100 mg/kg body weight), and levels of glutathione were enhanced by injecting animals with N-acetylcysteine (NAC, 200 mg/kg body weight), which gets metabolized to cysteine, a precursor of glutathione. Changes in membrane protein conformation and structure in synaptosomes subsequently isolated from these animals were examined using electron paramagnetic resonance, before and after in vitro addition of peroxynitrite. The animals injected with the glutathione depletant CHX showed greater damage to the membrane proteins both before and after peroxynitrite treatment, compared to the non-injected controls. The membrane proteins from animals injected with NAC were comparable to controls before peroxynitrite treatment and were partially protected against peroxynitrite-induced damage. This study showed that modulation of endogenous glutathione levels can affect the degree of peroxynitrite-induced brain membrane damage and may have potential therapeutic significance for oxidative stress-associated neurodegenerative disorders.

Effect of 2-cyclohexene-1-one-induced glutathione diminution on ischemia/reperfusion-induced alterations in the physical state of brain synaptosomal membrane proteins and lipids

Glutathione is able to protect membrane proteins from oxidative stress. In ischemia/reperfusion injury, free radicals cause synaptosomal membrane protein and lipid oxidation that is prevented by the free radical scavenger N-tert-butyl-alpha-phenylnitrone (Hall N. C. et al. (1995) Neuroscience 64, 81-89; 69, 591-600). We wondered if diminution of glutathione would lead to further membrane alterations. Accordingly, the effects of glutathione depletion, by intraperitoneal administration of 2-cyclohexene-1-one, on the physical state of cortical synaptosomal membrane proteins and lipids, with and without global ischemia/reperfusion, were studied in vivo and in vitro in adult and aged gerbils utilizing electron paramagnetic resonance spectrometry. 2-Cyclohexene-1-one (100 mg/kg, i.p.) was administered 30 min prior to 10-min ischemia followed by 1 or 14 h reperfusion. This glutathione reduction agent was also administered to gerbils under the same temporal schedule in the absence of ischemia and compared to untreated controls. Synaptosomal membranes were labeled with a protein-specific spin label, 2,2,6,6-tetramethyl-4-maleimidopiperidine-1-oxyl, or a lipid-specific spin probe, 5-doxylstearic acid. There were no significant changes in the physical state of the lipid portion of synaptosomal membranes when comparing ischemia reperfusion and 2-cyclohexene-1-one-treated ischemia reperfusion in either the adult or aged gerbils. However, glutathione depletion without ischemia/reperfusion caused significant changes in the physical state of the protein portion of cortical synaptosomal membranes in both the adult and aged models. Glutathione depletion, without ischemia/reperfusion, in the adult model showed a maximum change at 3 h that returned to control values by 14 h. In contrast, the aged model showed significant changes at 1 h reperfusion, which did not return to control values by 14 h reperfusion. Glutathione depletion combined with ischemia/reperfusion caused initial protein change in both adult and aged models at 1 h reperfusion, which did not return toward control values by 14 h reperfusion. The results of this study suggest that glutathione depletion increases the severity of membrane protein damage associated with ischemia/reperfusion injury.

Age- and peroxidative stress-related modifications of the cerebral enzymatic activities linked to mitochondria and the glutathione system

The aging brain undergoes a process of enhanced peroxidative stress, as shown by reports of altered membrane lipids, oxidized proteins, and damaged DNA. The aims of this review are to examine: (1) the possible contribution of mitochondrial processes to the formation and release of reactive oxygen species (ROS) in the aging brain; and (2) the age-related changes of antioxidant defenses, both enzymatic and nonenzymatic. It will focus on studies investigating the role of the electron transfer chain as the site of ROS formation in brain aging and the alterations of the glutathione system, also in relation to the effects of exogenous pro-oxidant agents. The possible role of peroxidative stress in age-related neurodegenerative diseases will also be discussed.

Depletion of brain glutathione is accompanied by impaired mitochondrial function and decreased N-acetyl aspartate concentration

The effect of depletion of reduced glutathione (GSH) on brain mitochondrial function and N-acetyl aspartate concentration has been investigated. Using pre-weanling rats, GSH was depleted by L-buthionine sulfoximine administration for up to 10 days. In both whole brain homogenates and purified mitochondrial preparations complex IV (cytochrome c oxidase) activity was decreased, by up to 27%, as a result of this treatment. In addition, after 10 days of GSH depletion, citrate synthase activity was significantly reduced, by 18%, in the purified mitochondrial preparations, but not in whole brain homogenates, suggesting increased leakiness of the mitochondrial membrane. The whole brain N-acetyl aspartate concentration was also significantly depleted at this time point, by 11%. It is concluded that brain GSH is important for the maintenance of optimum mitochondrial function and that prolonged depletion leads also to loss of neuronal integrity. The relevance of these findings to Parkinson's disease and the inborn errors of glutathione metabolism are also discussed.

Free radical scavenger depletion in post-ischemic reperfusion brain damage

In the present study the influence of pretreatment with various GSH depletors such as buthionine sulfoximine (BSO) and diethylmaleate (DEM) was investigated in rats following cerebral post-ischemic reperfusion. Moreover, the effect of diethyldithiocarbamic acid (DDC), inhibitor of endogenous Cu,Zn-SOD, was evaluated. A significant depletion (40% of control value) of GSH levels was observed 24 h after DEM administration; after 48 h the value reached control levels. BSO showed maximal GSH depletion (59%) 24 h after administration and it was constant for almost 48 h. DDC administration caused a marked decrease (60%) of Cu,Zn-SOD activity 4 h after the injection and induced a marked decrease in percentage of survival with respect to control (untreated, ischemic) rats, when administered 4 h before ischemia. BSO and DEM prolonged the survival time of animals when administered 24 h before ischemia. This last paradoxical effect is unclear at present, but it might be due to an influence on glutamate cascade.

The mitochondrial electron transfer alteration as a factor involved in the brain aging

The tissutal concentrations of reduced glutathione (GSH) and the contents of some key components in the electron transfer chain (namely ubiquinone, cytochromes b, c1, c, and aa3) of the intraterminal mitochondria are measured in the forebrains from 20-, 60-, or 100-week-old Wistar rats. Moreover, in 60-week-old rats, the biochemical analyses are performed also 18 h after the induction of a peroxidative stress by cyclohexene-1-one. The rats have been i.p. pretreated for 8 weeks (7 days/week) with agents acting on macrocirculation (papaverine), carbohydrate metabolism (hopanthenate), lipid metabolism (phosphatidylcholine), energy transduction (theniloxazine), and dopaminergic system (dihydroergocriptine). Brain aging is characterized by the decrease in both GSH and mitochondrial cytochrome aa3, without changes in ubiquinone and cytochrome b populations. In the same way, the peroxidative stress induced by cyclohexene-1-one causes both a GSH depletion and an imbalance among the concentrations of the mitochondrial electron transfer carriers. Only cytochrome aa3 retains all the partially-reduced oxygen intermediates tightly bound to its active sites. Therefore, it is possible to hypothesize that an electron leakage at the level of the auto-oxidizing chain components (i.e., cytochrome b and ubiquinone populations) increases the release of activated oxygen species (superoxide radical, hydroxyl radical). The treatment with the quoted pharmacological tools suggests that GSH and mitochondrial electron transfer carriers are functionally linked, but not interdependent one another.

Effects of exogenous factors on the cerebral glutathione in rodents

Since glutathione is thought to be involved in cerebral functions, changes in the glutathione level imply modulations of the neurotransmission in addition to all the known effects of GSH. It was investigated whether alterations of the cerebral glutathione can be induced by consumption of GSH, by inhibition or stimulation of the synthesis of GSH, or by an inhibition of the re-reduction of the oxidized glutathione. Aminophenazone, propyphenazone, acetaminophen, phenytoin, morphine and nitrofurantoin, known to deplete hepatic GSH, had no effects on cerebral GSH. Diethyl maleate (0.6 ml/kg) decreased the cerebral content of GSH and GSSG in adult rats as well as in fetuses. The depletion of the cerebral GSH caused by diethyl maleate treatment for 4 days was followed by an increase up to 125% and a subsequent return to the normal level after 1 week. In rats starved up to 71 h deficiency of exogenous amino acids caused only a minimal or no decrease in cerebral GSH. The specific inhibitor of the gamma-glutamylcysteine synthetase BSO only depleted GSH in the brain of young mice following the repeated s.c. administration of a high dose (890 mg/kg). After cobaltous chloride (20 mg/kg; twice a day for 2 or 4 days) the GSH level in the brain was unchanged. In vivo inhibition of the cerebral glutathione reductase was caused by ammonium metavanadate (12.5 mg/kg; three times a week for 6 weeks). Nitrofurantoin (150 mg/kg) had no effect. After lomustine (10 mg/kg) a minimal increase in glutathione reductase was found, but simultaneously also an increase in GSSG and of the ratio GSSG/total glutathione.

Sequential damage in mitochondrial complexes by peroxidative stress

The biochemical characteristics of the electron transfer chain are evaluated in purified non-synaptic ("free") mitochondria from the forebrain of 60-week-old rats weekly subjected to peroxidative stress (once, twice, or three times) by the electrophilic prooxidant 2-cyclohexene-1-one. The following parameters are evaluated: (a) content of respiratory components, namely ubiquinone, cytochrome b, cytochrome c1, cytochrome c; (b) specific activity of enzymes, namely citrate synthase, succinate dehydrogenase, rotenone-sensitive NADH: cytochrome c reductase, cytochrome oxidase; (c) concentration of reduced glutathione (GSH). Before the first peroxidative stress induction, the rats are administered for 8 weeks by intraperitoneal injection of vehicle, papaverine, delta-yohimbine, almitrine or hopanthenate. The rats are treated also during the week(s) before the second or third peroxidative stress. The cerebral peroxidative stress induces: (a) initially, a decrease in brain GSH concentration concomitant with a decrease in the mitochondrial activity of cytochrome oxidase of aa3-type (complex IV), without changes in ubiquinone and cytochrome b populations; (b) subsequently, an alteration in the transfer molecule cytochrome c and, finally, in rotenone-sensitive NADH-cytochrome c reductase (complex I) and succinate dehydrogenase (complex II). The selective sensitivity of the chain components to peroxidative stress is supported by the effects of the concomitant subchronic treatment with agents acting at different biochemical steps. In fact, almitrine sets limits to its effects at cytochrome c content and aa3-type cytochrome oxidase activity, while delta-yohimbine sets limits to its effects at the level of tricarboxylic acid cycle (citrate synthase) and/or of intermediary between tricarboxylic acid cycle and complex II (succinate dehydrogenase).(ABSTRACT TRUNCATED AT 250 WORDS)

Depletion of glutathione interferes with induction of glycerolphosphate dehydrogenase in the brains of young rats

In the rat brain hydrocortisone induces the enzyme, glycerolphosphate dehydrogenase (GPDH), during the first postnatal week. The present studies focused on a hypothetical role for glutathione-S-transferase (GST) in that phenomenon. Two forms of GST, Yb and Yp, had been detected in glial cells in mature rat brains, and it was suggested that they might function in hormone transport. Now GSTs have also been observed in the brains of 1-day-old rats. Two glutathione-depleting agents, buthionine sulfoximine and cyclohexene-1-one, were administered to rats, along with hydrocortisone, during the first postnatal week. Hydrocortisone or a depleting agent alone was administered to control animals. During the early days of the experiment there were lower GPDH specific activities in brains from the animals given hydrocortisone plus a depleting agent than in those from animals given hydrocortisone alone. Depleting agents alone did not affect the specific activities of GPDH. It is suggested that one function of the GST in rat brain is transport of hydrocortisone between or within glial cells.

Age-related acute depletion of cerebral glutathione by peroxidative stress

Cyclohexene-1-one and cycloheptene-1-one cause a severe age-related depletion of reduced glutathione (GSH) in the forebrain of 5- or 15- or 25-month-old rats. Chronic pretreatment with phosphatidylcholine partially inhibits the GSH depletion in old forebrains by the prooxidants tested, suggesting that in aged animals alterations in mitochondrial inner membrane phospholipid composition and/or cytochrome oxidase activity might play a role in oxygen free-radical production.

Influence of aging on the acute depletion of reduced glutathione induced by electrophilic agents

A severe age-dependent depletion of reduced glutathione (GSH) occurs in rat forebrain at 1-3 h from intraperitoneal injection of the electrophilic agents cyclohexene-1-one and cycloheptene-1-one. Chronic pretreatment with central dopamine agonists (i.e., ergot alkaloids; particularly, dihydroergocriptine) partially counteracts the GSH depletion induced in 15-month-old forebrains by the prooxidants tested. In contrast, chronic pretreatment with a vasodilator agent (i.e., papaverine) magnifies the GSH depletion.

Effective depletion of glutathione in rat striatum and substantia nigra by L-buthionine sulfoximine in combination with 2-cyclohexene-1-one

The effects of L-buthionine sulfoximine (L-BSO), 2-cyclohexene-1-one and diethylmaleate (DEM) on the concentration of rat brain glutathione (GSH) were investigated. Both DEM and 2-cyclohexene-1-one, administered subcutaneously, produced marked and rapid reduction of brain GSH, but 2-cyclohexene-1-one appeared less toxic than DEM. Six hours after 2-cyclohexene-1-one (100 microliters/kg) the striatal GSH concentration was 35% of control values, whereas the level was 55% of controls at 24 h and 80% of controls at 48 h. Similar results were obtained with DEM (800 microliters/kg). L-BSO (3.2 mg), administered intracerebroventricularly, produced a slower depletion of brain GSH. A 55% reduction of striatal GSH was obtained 24 h after the administration, and the level was approximately 50% of control at 48 h. Thus, the effect of 2-cyclohexene-1-one and DEM is rapid in onset but relatively short lasting, whereas the disappearance of brain GSH after L-BSO is slower but the effect is more long-lasting. By combining L-BSO with either 2-cyclohexene-1-one or DEM both a rapid and long-lasting GSH depletion was obtained that was more profound than after any of the drugs alone. The combination of L-BSO and 2-cyclohexene-1-one was well tolerated, but the combination of L-BSO and DEM led to death in half of the rats the second day after injection. The disappearance rate of GSH after L-BSO alone gives an estimate of the turn-over of GSH. We found the turn-over of GSH to be higher in the substantia nigra pars compacta than in the striatum. The present work suggest that L-BSO and 2-cyclohexene-1-one would be very useful for evaluation of the biological role of GSH in the central nervous system.