Compounds that induce isoforms of glutathione S-transferase with properties of a critical enzyme in defense against oxidative stress

Exposure to pesticides used in rice farming (bentazone, chlorantraniliprole and tebuconazole) affects biochemical biomarkers and hepatic histopathological parameters of hammertoad tadpoles (Boana faber)

Pesticides used in rice cultivation can cause negative health effects to non-target organisms representative of natural biodiversity. In this context, the present study aimed to investigate the occurrence of pesticides in surface waters from a river that flows in the middle of a rice farming-dominated area. We were also interested in evaluate biochemical and histological effects caused by exposure (16 d) to the lower and higher concentrations of the main found herbicide (bentazone, BTZ), insecticide (chlorantraniliprole, CTP) and fungicide (tebuconazole, TBZ), isolated or mixed, in Boana faber tadpoles. No significant differences were observed in the development of the animals. Tadpoles exposed to the herbicide BTZ showed higher hepatic levels of malondialdehyde (MDA). In animals exposed to CTP, MDA levels were lower than controls. Animals exposed to the fungicide TBZ showed higher hepatic activity of glutathione S-transferase and carboxylesterase (CbE), as well as higher levels of carbonyl proteins and MDA. Animals exposed to Mix showed higher activity in CbE and glucose-6-phosphate dehydrogenase activity in the liver, as well as higher levels of MDA. In the brain and muscle of tadpoles exposed to Mix, acetylcholinesterase activity was higher. Histological changes were also observed in pesticide-exposed animals, such as increased occurrence of melanomacrophages, inflammatory infiltrates and congestion. Our data evidences the contamination of natural aquatic environments by rice pesticides, and the adverse effects of main ones in B. faber tadpoles, which suggests the contribution of pesticides derived from rice cultivation to the degradation of local biodiversity health.

Decreased malondialdehyde levels in fish (Astyanax altiparanae) exposed to diesel: Evidence of metabolism by aldehyde dehydrogenase in the liver and excretion in water

Increased malondialdehyde (MDA) levels are commonly considered an indicator of lipid peroxidation derived from oxidative stress insults promoted by exposure of fish to pollutants. However, a decrease in MDA levels after xenobiotic exposure has been also reported, an effect that is mostly attributed to enhanced antioxidant defenses. In this study, we assessed whether pollutant-mediated MDA decrease would be associated with antioxidant enhancement or with its metabolism by aldehyde dehydrogenase (ALDH) in the liver and gills of lambari (Astyanax altiparanae) exposed to diesel oil (0.001, 0.01, and 0.1 mL/L). MDA levels were decreased in the liver of lambari exposed to diesel. The activities of the antioxidant enzymes, catalase (CAT) and glutathione peroxidase (GPx), were unchanged in the liver, while that of glucose-6-phosphate dehydrogenase (G6PDH) was decreased. In contrast, levels of total glutathione (tGSH) and the activity of glutathione S-transferase (GST) were increased in the liver, which partly support antioxidant protection against lipid peroxidation. More importantly, ALDH activity increased in a concentration-dependent manner, being negatively correlated with MDA levels, indicating MDA metabolism by ALDH. In the gills, diesel exposure increased MDA and lipid hydroperoxide levels, and promoted increases in antioxidant defenses, indicating oxidative stress. Curiously, ALDH activity was undetectable in the gills, supporting the possibility of direct MDA excretion in the water by the gills. Analyses of MDA in the water revealed increased levels of MDA in the aquaria in which the fish were exposed to diesel, compared to control aquaria. A second experiment was carried out in which the fish were intraperitoneally injected with MDA (10 mg/kg) and analyzed after 1, 6, and 12 h. MDA injection caused a time-dependent decrease in hepatic MDA levels, did not alter ALDH, CAT, GPx, and GST activities, and decreased G6PDH activity and tGSH levels. In the gills, MDA injection caused a slight increase in MDA levels after 1 h, but did not alter GPx, G6PDH, and GST activities. MDA injection also enhanced CAT activity and tGSH levels in the gills. MDA concentration in water increased progressively after 1, 6, and 12 h, supporting the hypothesis of direct MDA excretion as an alternative route for MDA elimination in fish. Our results suggest that the decreased MDA levels after exposure of lambari to diesel oil pollutant probably reflects an association between enhanced antioxidant protection, MDA metabolism, and MDA excretion in water.

Molecular characterization of kappa class glutathione S-transferase from the disk abalone (Haliotis discus discus) and changes in expression following immune and stress challenges

Glutathione S-transferase (GST; EC 2.5.1.18) isoenzymes represent a complex group of proteins that are involved in phase II detoxification in several organisms. In this study, GST kappa (GSTκ) from the disk abalone (Haliotis discus discus; AbGSTκ) was characterized at both the transcriptional and functional levels to determine its potential capacity to perform as a detoxification agent under conditions of different stress. The predicted AbGSTκ protein consists of 227 amino acids, with a predicted molecular weight of 25.6 kDa and a theoretical isoelectric point (pI) of 7.78. In silico analysis reveals that AbGSTκ is a disulfide bond formation protein A (DsbA), consisting of a thioredoxin domain, GSH binding sites (G-sites), and a catalytic residue. In contrast, no hydrophobic ligand binding site (H-site), or signal peptides, were detected. AbGSTκ showed the highest sequence identity with the orthologue from pufferfish (Takifugu obscurus) (60.0%). In a phylogenetic tree, AbGSTκ clustered closely together with other fish GSTκs, and was evolutionarily distanced from other cytosolic GSTs. The predicted three-dimensional structure clearly demonstrates that the dimer adopts a butterfly-like shape. A tissue distribution analysis revealed that GSTκ was highly expressed in the digestive tract, suggesting it has detoxification ability. Depending on the tissue and time, AbGSTκ showed different expression patterns, and levels of expression, following challenge of the abalone with immune stimulants. Enzyme kinetics of the purified recombinant proteins demonstrated its conjugating ability using 1-Chloro-2,4-dinitrobenzene (CDNB) and glutathione (GSH) as substrates, and suggested it has a low affinity for both substrates. The optimum temperature and pH for the rAbGSTκ GSH: CDNB conjugating activity were found to be 35 °C and pH 8, respectively indicating that the abalone is well adapted to a wide range of environmental conditions. Cibacron blue (100 μM) was capable of completely inhibiting rAbGSTκ (100%) with an IC₅₀ (half maximal inhibitory concentration) of 0.05 μM. A disk diffusion assay revealed that rAbGSTκ could significantly protect cells from H₂O₂, CdCl_2, and ZnCl₂. Altogether, this current study suggests that AbGSTκ is involved in detoxification and immunological host defense mechanisms and allows abalones to overcome stresses in order for them to have an increased chance of survival.

Comprehensive characterization of three glutathione S-transferase family proteins from black rockfish (Sebastes schlegelii)

Glutathione S-transferases (GSTs, EC 2.5.1.18) are categorized as phase II enzymes, which form an important multifunctional family associated with a wide variety of catalytic activities. GSTω, GSTρ, and GSTθ are cytosolic GSTs which have been extensively studied in a variety of organisms; however, few studies have focused on teleosts. Those paralogs from black rockfish (Sebastes schlegelii; RfGSTω, RfGSTρ, and RfGSTθ, respectively) were molecularly, biochemically, and functionally characterized to determine their antioxidant extent and protective aptitudes upon pathogenic stress. RfGSTω, RfGSTρ, and RfGSTθ, contained open reading frames of 717bp, 678bp, and 720bp respectively, which encoded respective proteins of 239, 226, and 240 amino acids in length. In silico analysis revealed that all RfGSTs possessed characteristic N-terminal domains bearing glutathione (GSH)-binding sites, and C-terminal domains containing substrate-binding sites. Recombinant RfGSTω (rRfGSTω) catalyzed the conjugation of GSH to dehydroascorbate (DHA), while rRfGSTθ and rRfGSTρ catalyzed to the model GST substrate 1-Chloro-2,4-dinitrobenzene (CDNB). Kinetic analysis revealed variation in Km and Vmax values for each rRfGST, indicating their different conjugation rates. The optimum conditions (pH and temperature) and inhibition assays of each protein demonstrated different optimal ranges showing their wide range of activity as an assembly. RfGSTω and RfGSTθ paralogs demonstrated their antioxidant potential towards H2O2 and heavy metals (Cd, Zn, and Cu) in vitro, while RfGSTρ had an antioxidant potential only towards heavy metals (Zn and Cu). Though all the paralogs were ubiquitously expressed in different magnitudes, RfGSTω was highly expressed in blood, whereas RfGSTρ and RfGSTθ were highly expressed in liver. The mRNA expression of RfGSTω and RfGSTθ, upon Streptococcus iniae and poly I:C stimulation, revealed a significantly up-regulated expression, whereas RfGSTρ mRNA expression was significantly down-regulated. Collectively, our findings suggest that RfGSTω, RfGSTρ, and RfGSTθ paralogs are potent in detoxifying xenobiotic toxics, capable of protecting cells from oxidative stress generated by both H2O2 and heavy metals, and finally, yet importantly, stimulated under pathogenic stress signals.

Biochemical responses, morphometric changes, genotoxic effects and CYP1A expression in the armored catfish Pterygoplichthys anisitsi after 15 days of exposure to mineral diesel and biodiesel

Despite being considered friendlier to the environment, biodiesel fuel can be harmful to aquatic organisms, especially when combined with petroleum diesel fuel. In this work we evaluated the effects of mineral diesel fuel containing increasing concentrations of biodiesel (5% and 20%, namely B5 and B20) and pure biodiesel (B100), at concentrations of 0.001 and 0.01mLL(-1), after 15 days of exposure, in armored catfish (Pterygoplichtys anisitsi). Toxicity tests were also performed to estimate LC50 values (96h) for each compound. Biotransformation enzymes [ethoxyresorufin-O-deethylase (EROD), and glutathione S-transferase (GST)] as well as oxidative stress markers (superoxide dismutase, SOD, catalase, CAT, glutathione peroxidase, GPx, and the level of lipid peroxidation) were measured in liver and gills after treatment. Genotoxic effects were also accessed in erythrocytes using the comet assay and by evaluating the frequency of micronuclei formation. Further, the mRNA of cytochrome P450 1A (CYP1A) was also measured in liver. Mortality was not observed even exposure to concentrations as high as 6.0mLL(-1). EROD and GST activities were increased after B5 and B20 treatments; however, CYP1A mRNA induction was not observed. SOD and CAT activities were decreased, but GPx was significantly higher for all treatments in gills. There were no significant changes in lipid peroxidation, but genotoxicity markers revealed that all treatments increased comet scores. Fuels B5 and B20 increased micronuclei frequency. Our results indicate that despite being less toxic, biodiesel may cause sublethal alterations in fish that may alter long term health.

Biochemical responses in armored catfish (Pterygoplichthys anisitsi) after short-term exposure to diesel oil, pure biodiesel and biodiesel blends

Biodiesel fuel is gradually replacing petroleum-based diesel oil use. Despite the biodiesel being considered friendlier to the environment, little is known about its effects in aquatic organisms. In this work we evaluated whether biodiesel exposure can affect oxidative stress parameters and biotransformation enzymes in armored catfish (Pterygoplichthys anisitsi, Loricariidae), a South American endemic species. Thus, fish were exposed for 2 and 7d to 0.01mLL(-1) and 0.1mLL(-1) of pure diesel, pure biodiesel (B100) and blends of diesel with 5% (B5) and 20% (B20) biodiesel. Lipid peroxidation (malondialdehyde) levels and the activities of the enzymes glutathione S-transferase, superoxide dismutase, catalase and glutathione peroxidase were measured in liver and gills. Also, DNA damage (8-oxo-7, 8-dihydro-2'-deoxyguanosine) levels in gills and 7-ethoxyresorufin-O-deethylase activity in liver were assessed. Pure diesel, B5 and B20 blends changed most of the enzymes tested and in some cases, B5 and B20 induced a higher enzyme activity than pure diesel. Antioxidant system activation in P. anisitsi was effective to counteract reactive oxygen species effects, since DNA damage and lipid peroxidation levels were maintained at basal levels after all treatments. However, fish gills exposed to B20 and B100 presented increased lipid peroxidation. Despite biodiesel being more biodegradable fuel that emits less greenhouse gases, the increased lipid peroxidation showed that biofuel and its blends also represent hazards to aquatic biota.

Postnatal exposure to chromium through mother's milk accelerates follicular atresia in F1 offspring through increased oxidative stress and depletion of antioxidant enzymes

Hexavalent chromium, CrVI, is a heavy metal endocrine disruptor, known as a mutagen, teratogen, and a group A carcinogen. Environmental contamination with CrVI, including drinking water, has been increasing in more than 30 cities in the United States. CrVI is rapidly converted to CrIII intracellularly, and CrIII can cause DNA strand breaks and cancer or apoptosis through different mechanisms. Our previous study demonstrated that lactational exposure to chromium results in a delay or arrest in follicle development and a decrease in steroid hormone levels in F1 female rats, both of which are mitigated (partial inhibition) by vitamin C. The current study tested the hypothesis that lactational exposure to CrIII accelerates follicle atresia in F1 offspring by increasing reactive oxygen species (ROS) and decreasing cellular antioxidants. Results showed that lactational exposure to CrIII dose-dependently increased follicular atresia and decreased steroidogenesis in postnatal day 25, 45, and 65 rats. Vitamin C mitigated or inhibited the effects of CrIII at all doses. CrIII increased hydrogen peroxide and lipid hydroperoxide in plasma and ovary; decreased the antioxidant enzymes (AOXs) GPx1, GR, SOD, and catalase; and increased glutathione S-transferase in plasma and ovary. To understand the effects of CrVI on ROS and AOXs in granulosa (GC) and theca (TC) cell compartments in the ovary, ROS levels and mRNA expression of cytosolic and mitochondrial AOXs, such as SOD1, SOD2, catalase, GLRX1, GSTM1, GSTM2, GSTA4, GR, TXN1, TXN2, TXNRD2, and PRDX3, were studied in GCs and TCs and in a spontaneously immortalized granulosa cell line (SIGC). Overall, CrVI downregulated each of the AOXs; and vitamin C mitigated the effects of CrVI on these enzymes in GCs and SIGCs, but failed to mitigate CrVI effects on GSTM1, GSTM2, TXN1, and TXN2 in TCs. Thus, these data for the first time reveal that lactational exposure to CrIII accelerated follicular atresia and decreased steroidogenesis in F1 female offspring by altering the ratio of ROS and AOXs in the ovary. Vitamin C is able to protect the ovary from CrIII-induced oxidative stress and follicle atresia through protective effects on GCs rather than TCs.

The influence of heroin abuse on glutathione-dependent enzymes in human brain

Heroin is an illicit narcotic abused by millions of people worldwide. In our earlier studies we have shown that heroin intoxication changes the antioxidant status in human brain. In the present work we continued our studies by estimating the effect of heroin abuse on reduced glutathione (GSH) and enzymes related to this cofactor, such as glutathione S-transferase detoxifying electrophilics (GST) and organic peroxides (as Se-independent glutathione peroxidase-GSHPx), and Se-dependent glutathione peroxidase (Se-GSHPx) specific mainly for hydrogen peroxide. Studies were conducted on human brains obtained from autopsy of 9 heroin abusers and 8 controls. The level of GSH and the activity of glutathione-related enzymes were determined spectrophotometrically. The expression of GST pi on mRNA and protein level was studied by RT-PCR and Western blotting, respectively. The results indicated significant increase of GST and GSHPx activities, unchanged Se-GSHPx activity, and decreased level of GSH in frontal, temporal, parietal and occipital cortex, brain stem, hippocampus, and white matter of heroin abusers. GST pi expression was increased on both mRNA and protein levels, however the increase was lower in brain stem than in other regions. Heroin affects all regions of human brain, and especially brain stem. Its intoxication leads to an increase of organic rather then inorganic peroxides in various brain regions. Glutathione S-transferase plays an important role during heroin intoxication, however its protective effect is lower in brain stem than in brain cortex or hippocampus.

Diphenyl diselenide in its selenol form has dehydroascorbate reductase and glutathione S-transferase-like activity dependent on the glutathione content

Objectives

The antioxidant action of diphenyl diselenide ((PhSe)2) is attributed to the mechanism by which (PhSe)2 has pharmacological activity. Although (PhSe)2 has glutathione peroxidase mimetic activity, the exact mechanism involved in its antioxidant effect has not yet been completely elucidated. In the present study, mechanisms involved in the antioxidant property of (PhSe)2 (1–50 µm) were investigated.

Methods

Dehydroascorbate (DHA) reductase- and glutathione S-transferase (GST)-like activity, 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity and the protection against the oxidation of Fe2+ were evaluated.

Key findings

(PhSe)2 at concentrations equal to, or greater than, 5 µm showed DHA reductase- and GST-like activity. (PhSe)2 was not a scavenger of DPPH or ABTS radicals and did not protect against the oxidation of Fe2+.

Conclusions

These results clearly indicated that DHA reductase- and GST-like activity are the mechanisms involved in the antioxidant effect of (PhSe)2.

Small-molecule NOX inhibitors: ROS-generating NADPH oxidases as therapeutic targets

NOX NADPH oxidases are electron-transporting membrane enzymes whose primary function is the generation of reactive oxygen species (ROS). ROS produced by NOX enzymes show a variety of biologic functions, such as microbial killing, blood pressure regulation, and otoconia formation. Strong evidence suggests that NOX enzymes are major contributors to oxidative damage in pathologic conditions. Blocking the undesirable actions of NOX enzymes, therefore, is a therapeutic strategy for treating oxidative stress-related pathologies, such as ischemia/reperfusion tissue injury, and neurodegenerative and metabolic diseases. Most currently available NOX inhibitors have low selectivity, potency, and bioavailability, precluding a pharmacologic demonstration of NOX as therapeutic targets in vivo. This review has two main purposes. First, we describe a systematic approach that we believe should be followed in the search for truly selective NOX inhibitors. Second, we present a critical review of small-molecule NOX inhibitors described over the last two decades, including recently published patents from the pharmaceutical industry. Structures, activities, and in vitro/in vivo specificity of these NOX inhibitors are discussed. We conclude that NOX inhibition is a pertinent and promising novel pharmacologic concept, but that major efforts will be necessary to develop specific NOX inhibitors suited for clinical application.

Antioxidant effect of a novel class of telluroacetilene compounds: studies in vitro and in vivo

AIMS

The effect of telluroacetylenes a-d on pharmacological assays was investigated in vitro. A second objective of this study was to investigate the antioxidant action of compound b against the oxidative damage induced by sodium nitroprusside (SNP) in mouse brain.

MAIN METHODS

In in vitro experiments, lipid peroxidation (LP) and protein carbonyl (PC) levels and delta-aminolevulinate dehydratase (delta-ALA-D) activity were carried out in rat brain homogenate. The thiol peroxidase-like activity and DPPH radical scavenging of telluroacetylenes a-d were investigated. In in vivo experiments, mice received SNP (0.335 micromol per site) intra cerebroventricular (i.c.v.) thirty minutes after oral administration of telluroacetylene b (10 mg/kg). After 1 h, animals were euthanized. The levels of LP and delta-ALA-D, catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST) activities were carried out in mouse brain homogenate.

KEY FINDINGS

Telluroacetylenes a-d, at low muM range, reduced LP and PC levels in rat brain homogenate. Telluroacetylenes a-d showed effect of scavenging DPPH radicals. delta-ALA-D activity was inhibited by telloruacetylenes a-d, at high muM range, in rat brain homogenate. Brains of mice treated with SNP showed an increase in LP and the reduction in delta-ALA-D, GR and GST activities. Telluroacetylene b protected against the oxidative stress caused by SNP in brain of rats.

SIGNIFICANCE

The results support an antioxidant effect of telluroacetylenes a-d in vitro. Telluroacetylene b protected against oxidative damage caused by SNP in mouse brain, suggesting an antioxidant effect of this compound.

Antioxidant effect of diphenyl diselenide on oxidative damage induced by smoke in rats: involvement of glutathione

In the present study, the involvement of glutathione system in the restorative effect of diphenyl diselenide (PhSe)(2) on damage induced by cigarette smoke was investigated. Rat pups were progressively exposed to four, five, and six cigarettes for exposure periods of 15 min during their first, second, and third weeks of life. Thiobarbituric acid reactive species (TBARS) levels, components of the enzymatic antioxidant defenses (superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) activities), and non-enzymatic antioxidant defenses (vitamin C and non-protein thiol (NPSH) levels) were examined in lungs of pups. The results demonstrated an increase in lipid peroxidation and the alteration in non-enzymatic and enzymatic antioxidant defenses induced by cigarette smoke exposure in lung of pups. Administration of (PhSe)(2) (0.5mg/kg) restored TBARS levels and antioxidant defenses in lungs of rat pups exposed to cigarette smoke. (PhSe)(2) treatment increased NPSH levels and GST activity per se in lungs of rat pups. Together these results indicate that (PhSe)(2) restored oxidative damage induced by cigarette smoke exposure in lungs of rat pups. The glutathione system is involved in antioxidant effect of this compound.

Sequence, biochemical characteristics and expression of a novel Sigma-class of glutathione S-transferase from the intertidal copepod, Tigriopus japonicus with a possible role in antioxidant defense

Glutathione S-transferases (GSTs) play a major role in detoxification of xenobiotics and antioxidant defense. Here we report full-length cDNA sequence of a novel Sigma-class of GST (GST-S) from the intertidal copepod Tigriopus japonicus. The full sequence was of 1,136 bp in length containing an open reading frame (ORF) of 651 bp that encoded 217 amino acid residues. The recombinant Tigriopus GST-S was highly expressed in transformed Escherichia coli. Kinetic properties and effects of pH, temperature and chemical inhibitors on Tigriopus GST-S were also studied. The expression of GST-S was studied using real-time RT-PCR in response to exposure to two oxidative stresses-inducing agents, viz., hydrogen peroxide (H(2)O(2)) and heavy metals (copper, manganese). It was observed that H(2)O(2) (2mM) exposure down-regulated its expression at the initial stage but there was recovery and up-regulation shortly afterwards. In case of heavy metal exposure there was concentration-dependent increase in Tigriopus GST-S gene expression up to 24h. These results suggest that Tigriopus GST-S expression is modulated by prooxidant chemicals and it may play a role against oxidative stress. A majority of other GST isoforms is known to play an important role in antioxidant defense. This study provides a preliminary insight into the possible antioxidant role for Sigma-class of GST in T. japonicus.

Inhibition of cytosolic glutathione S-transferase activity from rat liver by copper

H(2)O(2) inactivation of particular GST isoforms has been reported, with no information regarding the overall effect of other ROS on cytosolic GST activity. The present work describes the inactivation of total cytosolic GST activity from liver rats by the oxygen radical-generating system Cu(2+)/ascorbate. We have previously shown that this system may change some enzymatic activities of thiol proteins through two mechanisms: ROS-induced oxidation and non-specific Cu(2+) binding to protein thiol groups. In the present study, we show that nanomolar Cu(2+) in the absence of ascorbate did not modify total cytosolic GST activity; the same concentrations of Cu(2+) in the presence of ascorbate, however, inhibited this activity. Micromolar Cu(2+) in either the absence or presence of ascorbate inhibited cytosolic GST activity. Kinetic studies show that GSH but no 1-chloro-2,4-dinitrobenzene prevent the inhibition on cytosolic GST induced by micromolar Cu(2+) either in the absence or presence of ascorbate. On the other hand, NEM and mersalyl acid, both thiol-alkylating agents, inhibited GST activity with differential reactivity in a dose-dependent manner. Taken together, these results suggest that an inhibitory Cu(2+)-binding effect is likely to be negligible on the overall inhibition of cytosolic GST activity observed by the Cu(2+)/ascorbate system. We discuss how modification of GST-thiol groups is related to the inhibition of cytosolic GST activity.

Characterization of the promoters of Epsilon glutathione transferases in the mosquito Anopheles gambiae and their response to oxidative stress

Epsilon class GSTs (glutathione transferases) are expressed at higher levels in Anopheles gambiae mosquitoes that are resistant to DDT [1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane] than in insecticide-susceptible individuals. At least one of the eight Epsilon GSTs in this species, GSTe2, efficiently metabolizes DDT to DDE [1,1-dichloro-2,2-bis-(p-chlorophenyl)ethane]. In the present study, we investigated the factors regulating expression of this class of GSTs. The activity of the promoter regions of GSTe2 and GSTe3 were compared between resistant and susceptible strains by transfecting recombinant reporter constructs into an A. gambiae cell line. The GSTe2 promoter from the resistant strain exhibited 2.8-fold higher activity than that of the susceptible strain. Six polymorphic sites were identified in the 352 bp sequence immediately upstream of GSTe2. Among these, a 2 bp adenosine indel (insertion/deletion) was found to have the greatest effect on determining promoter activity. The activity of the GSTe3 promoter was elevated to a lesser degree in the DDT-resistant strain (1.3-fold). The role of putative transcription-factor-binding sites in controlling promoter activity was investigated by sequentially deleting the promoter constructs. Several putative transcription-factor-binding sites that are responsive to oxidative stress were present within the core promoters of these GSTs, hence the effect of H2O2 exposure on the transcription of the Epsilon GSTs was investigated. In the DDT-resistant strain, expression of GSTe1, GSTe2 and GSTe3 was significantly increased by a 1-h exposure to H2O2, whereas, in the susceptible strain, only GSTe3 expression responded to this treatment.

A study of glutathione S-transferase pi expression in central nervous system of subjects with amyotrophic lateral sclerosis using RNA extraction from formalin-fixed, paraffin-embedded material

The expression of glutathione S-transferase pi (GST pi), an enzyme responsible for inactivation of a large variety of toxic compounds was studied in spinal cord, motor and sensory brain cortex obtained from patients who died in the course of amyotrophic lateral sclerosis (ALS). The studies were performed on formalin-fixed, paraffin-embedded (FFPE) and freshly frozen tissues. The method of RNA isolation from FFPE was modified. A significant decrease of GST pi-mRNA expression was found in cervical spinal cord and motor brain cortex of ALS subjects comparing to analogue control tissues (P<0.01), as well as in motor cortex of ALS subjects comparing to their sensory cortex (P<0.05). In spinal cords the decrease in GST pi-mRNA expression was accompanied by a decrease of GST pi protein level. Results indicated lowered GST pi expression on both mRNA and protein levels in the regions of nervous system affected by ALS. The non-properly inactivated by GST toxic electrophiles and organic peroxides may thus contribute to motor neurons damage.

Effects of salinity on biomarker responses in Crassostrea rhizophorae (Mollusca, Bivalvia) exposed to diesel oil

Crassostrea rhizophorae is a euryhaline oyster that inhabits mangrove areas, which are widely distributed along the Brazilian coast. The aim of this study was to investigate the effects of salinity (9, 15, 25, and 35ppt) on the activities of glutathione S-transferase (GST), glucose 6-phosphate dehydrogenase (G6PDH), catalase (CAT), and acetylcholinesterase (AChE) in the digestive gland of this species after exposure to diesel oil for 7 days at nominal concentrations of 0.01, 0.1, and 1mlL(-1) and after depuration for 24h and 7 days. GST activity increased in a diesel oil concentration-dependent manner at salinities 25 and 15ppt and remained slightly elevated even after depuration periods of 24h and 7 days. No changes were observed in the activities of G6PDH, CAT, and AChE in the oysters exposed to diesel and depurated. Based on these results, GST activity in the digestive gland of C. rhizophorae might be used as a biomarker of exposure to diesel oil in sites where the salinity is between 15 and 25ppt, values usually observed in mangrove ecosystems.

Activity and expression of glutathione S-transferase pi in patients with amyotrophic lateral sclerosis

Glutathione S-transferase (GST, EC 2.5.1.18) is an enzyme responsible for inactivation of a large variety of toxic, electrophilic compounds and organic peroxides. GST activity and GST pi expression were studied in patients with amyotrophic lateral sclerosis (ALS). Studies were conducted on cerebrospinal fluid (CSF), blood serum and peripheral blood mononuclear cells (PBMC) obtained from 40 ALS patients. CSF from 30 subjects without neurological diseases and blood from 40 healthy blood donors were used as controls. GST activity assayed with 1-chloro-2,4-dinitrobenzene (substrate for transferase activity) and cumene peroxide (substrate for peroxidase activity) was significantly decreased in PBMC of ALS patients, as well as the GST pi expression on both mRNA and protein level. The mean peroxidase activity was however significantly increased in CSF and serum of ALS patients with the specificity of 80% and 73%, and the sensitivity of 78% and 85%, respectively. It can thus be concluded that the protective barrier formed by GST is originally affected in peripheral blood of ALS patients, and may increase their vulnerability to toxic effects of electrophilic compounds and organic peroxides. Studies on a larger group are needed to answer the question whether GSH-Px determination may be implicated in the diagnosis of ALS.

Antioxidants as treatment for neurodegenerative disorders

Oxidative stress is a ubiquitously observed hallmark of neurodegenerative disorders. Neuronal cell dysfunction and cell death due to oxidative stress may causally contribute to the pathogenesis of progressive neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, as well as acute syndromes of neurodegeneration, such as ischaemic and haemorrhagic stroke. Neuroprotective antioxidants are considered a promising approach to slowing the progression and limiting the extent of neuronal cell loss in these disorders. The clinical evidence demonstrating that antioxidant compounds can act as protective drugs in neurodegenerative disease, however, is still relatively scarce. In the following review, the available data from clinical, animal and cell biological studies regarding the role of antioxidant neuroprotection in progressive neurodegenerative disease will be summarised, focussing particularly on Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. The general complications in developing potent neuroprotective antioxidant drugs directed against these long-term degenerative conditions will also be discussed. The major challenges for drug development are the slow kinetics of disease progression, the unsolved mechanistic questions concerning the final causalities of cell death, the necessity to attain an effective permeation of the blood-brain barrier and the need to reduce the high concentrations currently required to evoke protective effects in cellular and animal model systems. Finally, an outlook as to which direction antioxidant drug development and clinical practice may be leading to in the near future will be provided.

Dietary ortho phenols that induce glutathione S-transferase and increase the resistance of cells to hydrogen peroxide are potential cancer chemopreventives that act by two mechanisms: the alleviation of oxidative stress and the detoxification of mutagenic xenobiotics

Oxidative stress is implicated in the etiology of cancer, hence compounds that alleviate oxidative stress by inducing enzymes that defend against free radical damage might be useful as cancer chemopreventives. Glutathione S-transferase (GST) has been suggested to be a candidate for a critical enzyme in protecting cells against free radical damage, in part, because its level of induction correlates with protection of the cell line IMR-32 against hydrogen peroxide-induced oxidative stress. The present study identified dietary ortho phenols that both induce GST and protect the cell line IMR-32 against hydrogen peroxide-caused oxidative stress. The ortho phenol (o-phenol) inducers were better protectors against oxidative stress than a number of GST inducers that did not bear phenolic groups, possibly because the phenol residues of the ortho phenols allowed their action as antioxidants as well as inducers of GST. GST has previously been thought to protect cells against cancer by detoxifying mutagenic xenobiotics. The present results suggest that ortho phenol inducers of GST might be useful as cancer chemopreventives that act by two independent mechanisms, the alleviation of oxidative stress and the detoxification of mutagenic xenobiotics.