Glutathione concentrations and glutathione S-transferase activity in human colonic neoplasms

Early-Life Exposure to Commercial Formulation Containing Deltamethrin and Cypermethrin Insecticides Impacts Redox System and Induces Unexpected Regional Effects in Rat Offspring Brain

Several studies have shown that the oxidative impact of pesticides is most prevalent in rural environments where they are intensively used. At different levels, pyrethroids are reported to promote neurodegeneration; they share the ability to promote oxidative stress, and to induce mitochondrial impairments, α-synuclein overexpression and neuronal cell loss. The present study evaluates the impact of early-life exposure to a commercial formulation containing deltamethrin (DM) and cypermethrin (CYP) at a dose of 1/100 LD50 (1.28 and 2.5 mg/kg, respectively). Rats aged 30 days old, treated from the 6th to the 21st day of life, were tested for brain antioxidant activity and α-synuclein levels. Four regions of the brain were analyzed: the striatum, cerebellum, cortex and hippocampus. Our data demonstrated a significant increase in catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) antioxidant levels in the brain regions compared to the controls. Pups exhibited no significant changes in protein carbonyl levels and lipid peroxidation. Striatal α-synuclein expression was significantly reduced in the rats exposed to DM + CYP, while the treatment resulted in a non-significant increase in the other brain areas. These findings indicate unexpected effects of postnatal treatment with the commercial formulation containing DM and CYP on brain redox state and α-synuclein expression, suggesting an adaptive response.

Resveratrol thyro-protective role in fluorosis rat model (histo-morphometric, biochemical and ultrastructural study)

BACKGROUND

Thyroid gland affection by Fluorosis is documented in a number of previous studies. Resveratrol is a natural compound of plant origin. Its protective role was demonstrated previously in mice and rats against fluoride-induced hepatotoxicity and neurotoxicity.

AIM

to detect the thyro-protective role of Resveratrol in sodium fluoride rat model.

MATERIAL AND METHODS

Forty adult male albino rats were distributed equally into: Group I (control): given 5 ml distilled water; Group II (Resveratrol): received 30 mg/kg Resveratrol; Group III (Sodium fluoride): given 10 mg/kg of Sodium Fluoride dissolved in 2.5 ml distilled water; Group IV (Sodium fluoride + Resveratrol): received 10 mg/kg of Sodium Fluoride and 30 mg/kg of Resveratrol. All doses were administered once daily by intra-gastric intubation. By the end of the experiment, rats were sedated by intra-peritoneal injection of Sodium thiopental; blood samples were collected, and thyroid lobes were dissected then processed for examination.

RESULTS

In the control and Resveratrol groups, there were multiple variable follicles filled with homogenous eosinophilic colloid and lined with flat to cuboidal thyrocytes. Large pale-staining Para follicular cells. In the Sodium fluoride - treated group there were multiple dark stained nuclei of shrunken and exfoliated cells, areas of exudate and multiple layered follicular cells with high activity of Para follicular cells immuno-histochemically. Sodium fluoride+ Resveratrol - treated group appeared with almost preserved control appearance. Findings were confirmed using morphometric and electron microscopic studies.

CONCLUSION

Resveratrol supplementation with sodium fluoride restored almost all damaged appearance and functions of the thyroid cells to normal values. Further studies are necessary to examine the extended effect of Resveratrol with increased dosage or time of treatment.

Heterojunction MnO2-nanosheet-decorated Ag nanowires with enhanced oxidase-like activity for the sensitive dual-mode detection of glutathione

The biocatalytic design of nanomaterials with enzyme-like activity is considered a reliable and promising toolkit for the generation of diagnostic agents in complex biological microenvironments. However, the preparation of nanomaterials while maintaining a high catalytic activity in tumor cells (pH 6.0-6.5) poses a prominent challenge. Herein, we constructed a biomimetic enzyme-trigged dual-mode system with colorimetry at 652 nm and photothermal biosensors to detect glutathione based on hollow MnO₂-nanosheet-decorated Ag nanowires (Ag@MnO₂) as an oxidase-like nanozyme. As expected, Ag@MnO₂ catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the absence of H₂O₂, leading to a blue-colored oxidized TMB (oxTMB) that displayed oxidase-like activity in pH 6.0. Interestingly, the portable dual-mode colorimetry and photothermal method for GSH was developed based on the redox reaction between GSH and oxTMB. This detection method exhibited a wide linear range of 0.1-55 μM for GSH with a low detection limit of 0.08 μM. This work highlights a new insight into nanotechnology by taking advantage of biomimetic design in biological analysis.

Early impairment of epigenetic pattern in neurodegeneration: Additional mechanisms behind pyrethroid toxicity

Permethrin is a synthetic pyrethroid extensively used as anti-woodworm agent and for indoor and outdoor pest control. The main route of human exposure is through fruit, vegetable and milk intake. Low dosage exposure to permethrin during neonatal brain development (from postnatal day 6 to postnatal day 21) leads to dopamine decrease in rat striatum nucleus, oxidative stress and behavioural changes linked to the development of Parkinson's like neurodegeneration later in life. The aim of this study was to evaluate the expression of genes involved in the dopaminergic pathway and epigenetic regulatory mechanisms in adolescent rats treated with permethrin during neonatal brain development. Furthermore, in order to shed light on the mechanisms associated with molecular impairments, in silico studies were performed. The outcomes show increased expression of genes related to the dopamine-synthesis pathway (Nurr1, Th, Snca), epigenetics (TET proteins and Mecp2) and exposure to toxicants (Pon1 and Pon2) in adolescent rats compared with control group. Furthermore, increased global 5mC and 5hmC levels were observed in the DNA extracted from striatum of early-life treated rats in comparison with controls. FAIRE-qPCR analysis shows that permethrin induces an enrichment of chromatin-free DNA at the level of Th and Nurr1 promoters, and ChIP-qPCR reveals a significant reduction in methylation levels at H3K9me3 position at both Th and Nurr1 promoter regions. In silico studies show that permethrin competes for the same two binding sites of known NURR1 agonists, with a lower binding free energy for permethrin, suggesting an important durable association of permethrin with the orphan receptor. Moreover, alpha-synuclein shows a strong affinity for NURR1, corroborating previous experimental outcomes on the interactions between them. This study focuses on an emerging role of early-life exposure to environmental pollutants in the regulation of late onset diseases through intriguing mechanisms that change crucial epigenetic patterns starting from adolescent age.

The possible ameliorative effect of Olea europaea L. oil against deltamethrin-induced oxidative stress and alterations of serum concentrations of thyroid and reproductive hormones in adult female rats

This study aimed to verify whether Olea europaea L. (olive) oil (OEO) exerted a protective effect against oxidative stress induced by deltamethrin (DM) and alterations of pituitary, thyroid and gonadal hormones in adult female rats. DM (0,00256 g/kg body weight),OEO (0,6 g/kg body weight) and DM with OEO were administered to rats orally for 28 days. Volatile compounds present in olive oil were analysed by GC-MS. Estradiol (E₂), Thyroxine (T4),Thyroid Stimulating Hormone (TSH), Triiodothyronine (T3), Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Progesterone (Pg) were measured in serum using Chemiluminescent Microparticle Immunoassay (CMIA). Lipid peroxidation (LPO), protein carbonyls (PCs), reduced glutathione (GSH) levels along with superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities were determined in thyroid and ovarian tissues. Sesquiterpenes, (E,E)-α-farnesene (16.45%) and α-copaene (9,86%), were analysed as the main volatile compounds of OEO. The relative weight of ovaries and thyroid and body weight significantly decreased in rats treated with DM. DM caused significant alterations in TSH, T4, FSH, Pg and E₂ levels while T3 and LH concentrations remained unchanged when compared to control. DM also increased significantly LPO and PCs levels. In addition, GSH reserves as well as CAT, GPx, SOD and GST activities were suppressed in DM-received rats. The presence of OEO with DM returned the levels of oxidative stress markers, thyroid and reproductive hormones at the control values. Our results indicate that OEO is a powerful agent able to protect against DM oxidative stress and endocrine changes.

Protective Effect of Alpha-Lipoic Acid on Cypermethrin-Induced Oxidative Stress in Wistar Rats

Cypermethrin (CY), a class II pyrethroid pesticide, is globally used to control insects in the household and in agriculture. Despite beneficial roles, its uncontrolled and repetitive application leads to unintended effects in non-target organisms. In light of the relevant anti-oxidant properties of alpha-lipoic acid (ALA), in the work described herein we tested the effect of a commercially available ALA formulation on cypermethrin (CY)-induced oxidative stress in Wistar rats. The rats were orally administered with 53.14 mg/kg of ALA and 35.71 mg/kg of CY for 60 days. The treatment with CY did not induce changes in either locomotor activities or in body weight. Differences were observed on superoxide dismutase (SOD), catalase (CAT) and lipid peroxidation that were re-established by ALA treatment at similar levels of the placebo group. Furthermore, ALA formulation increased glutathione (GSH) level and glutathione peroxidase (GPx) activity. Because of the widespread use of CY, higher amounts of pesticide residues are present in food, and a diet supplementation with ALA could be an active free radical scavenger protecting against diseases associated with oxidative stress.

Imbalance in redox system of rat liver following permethrin treatment in adolescence and neonatal age

The effect of different permethrin treatments on the redox system of rat liver, is presented. Two types of oral administration were chosen: (i) sub-chronic treatment (1/10 of LD50 for 60 days) during adolescence (5 weeks old) and (ii) sub-acute treatment (1/44 of LD50 for 15 days) during early life (from postnatal days 6-21). The results show that adolescent permethrin treatment induces damage to the liver redox system, increasing lipid and protein peroxidation and reducing membrane fluidity in the hydrophilic--hydrophobic region of the bilayer. In addition, glutathione peroxidase (GPx) and GSH levels resulted decreased, while glutathione transferase (GST) and catalase (CAT) levels increased. The rats treated in early life with permethrin and sacrificed in adult age, showed less signs of damage compared to those exposed during adolescence in which lipid peroxidation was increased by 32%, whereas for the first group the raise was only 11%. Moreover, fluidity improved in the deeper hydrophobic membrane region of the treated group, while the level of CAT was significantly lower compared to the control one. Although sub-chronic treatment increased CAT and GST and decreased GPx and GSH levels, the present data suggest that a shorter exposure to permethrin during neonatal age decreased CAT level and it could represent an important risk factor for the onset of long-term liver damage.

Glutathione levels in human tumors

This review summarizes clinical studies in which glutathione was measured in tumor tissue from patients with brain, breast, gastrointestinal, gynecological, head and neck and lung cancer. Glutathione tends to be elevated in breast, ovarian, head and neck, and lung cancer and lower in brain and liver tumors compared to disease-free tissue. Cervical, colorectal, gastric, and esophageal cancers show both higher and lower levels of tumor glutathione. Some studies show an inverse relationship between patient survival and tumor glutathione. Based on this survey, we recommend approaches that may improve the clinical value of glutathione as a biomarker.

Early life permethrin insecticide treatment leads to heart damage in adult rats

Early life environmental exposure to xenobiotics could represent a critical period for the onset of permanent alterations in the structure and function of different organs. Cardiovascular diseases can be related to various factors including environmental toxicants. The aim of the present study was to evaluate the effect of early life permethrin treatment (1/50 LD(50), from 6th to 21st day of life) on heart of adult rats. Increased DNA damage, decreased heart cell membrane fluidity, increased cholesterol content, protein and lipid oxidation were measured in heart cells from adult rats treated with permethrin during the neonatal period with respect to control rats. Moreover, the same group showed higher levels of cholesterol, IL-1β, IL-2, IFN-γ, rat-Rantes and IL-10 cytokines and decreased albumin content in plasma. Lower cholesterol levels and perturbation in the phospholipid lateral diffusion together with decreased GSH levels and increased GPx activity were measured in heart mitochondria of the treated group. Our findings support the evidence that the neonatal period has a critical role in the development of heart disease in adulthood. We hypothesize that the alterations observed in adult rats could depend on epigenetic changes that occurred during this period which influence gene expression throughout the rat's life, leading to alterations of certain parameters related to cardiac function.

The Role of Glutathione in Intestinal Dysfunction

Glutathione plays an important cytoprotective role in the gut. Animal studies have demonstrated that the provisions of glutathione precursors are protective for different types of free-radical-mediated cellular injury. There is a need to clarify the potential role of glutathione supplementation in ischemia-reperfusion injury and inflammatory bowel disease. More speculative is whether treatment with glutathione precursors can modify the progress of colorectal cancer.

Dopaminergic system modulation, behavioral changes, and oxidative stress after neonatal administration of pyrethroids

Pyrethroids are a class of insecticides involved in different neurological disorders. They cross the blood-brain barrier and exert their effect on dopaminergic system, contributing to the burden of oxidative stress in Parkinson's disease through several pathways. The aim of the present study was to evaluate the effect of neonatal exposition to permethrin and cypermethrin (1/10 of DL(50)) in rats from the eighth to the fifteenth day of life. Open-field studies showed increased spontaneous locomotor activity in the groups treated with permethrin and the one treated with cypermethrin, while a higher number of center entries and time spent in the center was observed for the cypermethrin-treated group. Lower dopamine and higher homovanillic acid levels were measured in the striatum from both treated groups. A reduction of blood glutathione peroxidase content was measured, while no change in blood superoxide dismutase was observed. Carbonyl group formation increased in striatum, but not in erythrocytes. Lipid peroxidation occurred in erythrocytes, but not in striatum. No changes in fluidity at different depths of plasma membrane were measured in striatum or erythrocytes. The activation of monocyte NADPH oxidase by phorbol esters (PMA) shows that superoxide anion production was reduced in the pyrethroid-treated groups compared to the control group. Our studies suggest that neonatal exposition to permethrin or cypermethrin induces long-lasting effects after developmental exposure giving changes in open-field behaviors, striatal monoamine level, and increased oxidative stress. Although the action of pyrethroids on various target cells is different, a preferential interaction with the extracellular side of plasma membrane proteins can be observed.

Expression of the glutathione enzyme system of human colon mucosa by localisation, gender and age

BACKGROUND

The glutathione S-transferases (GST) can metabolise endogenous and exogenous toxins and carcinogens by catalysing the conjugation of diverse electrophiles with reduced glutathione (GSH). Variations of GST enzyme activity could influence the susceptibility of developing cancers in certain areas of the gastrointestinal tract.

AIMS

The expression of the components of the glutathione system in the colon was investigated with respect to age, gender and localisation.

METHODS

Biopsies of macroscopically normal mucosa from both proximal and distal colon were collected from 208 patients (106 females, 102 males; mean age 61 years), who underwent colonoscopy for various clinical reasons. GSH content, total GST enzyme activity and the levels of the GST isoenzymes glutathione S-transferase P1 (GSTP1) and glutathione S-transferase M1 (GSTM1) were determined.

RESULTS

GST enzyme activity, GSH and GSTP1 levels decreased significantly from proximal to distal colon (GST activity: 264 vs. 244 nmol/min/mg protein, p < 0.001, GSH content: 32 vs. 30 nmol/mg protein, p = 0.022 and GSTP1 levels: 2.25 vs. 2.10 mug/mg protein, p < 0.001). In female patients there was a significant stepwise increase of GST-activities and GSTP1 levels from the age of under 50 years to over 70 years. Oral sex hormone substitution among female patients between 50 and 70 years suppressed GST-activities and GSTP1 content.

CONCLUSIONS

The GSH-system in the colonic mucosa is expressed at a lower level in the distal colon (sigma) than in the colon transversum; whether this small difference translates into variations of incidence of colorectal cancer remains to be seen. Females express higher enzyme levels as they grow older, while in males no significant age effects were found. Elderly females might be better equipped with protective GSH-enzymes in the colon than males and this could contribute to the lower incidence of colorectal carcinomas in females.

Effects of oxygen on the antioxidant responses of normal and transformed cells

Basal antioxidant defense levels are often aberrant in tumor cells; however, less attention has been given to differences in the way that normal and transformed cells respond to changes in oxidative stress. This study evaluated differences in the responses of various normal and transformed cell lines to different oxygen tensions. Exposure to hyperoxia generally failed to induce either the activity of GSH peroxidase (GPx) or the manganese-containing form of superoxide dismutase (MnSOD) after 48 h, although at 605 mm Hg oxygen, small inductions of MnSOD activity were observed in adult lung fibroblasts and amelanotic melanoma. Exposure to 605 mm Hg O2 for 48 h was inhibitory to GPx activity. MnSOD activity was strongly induced in virally transformed WI-38 cells by treatment with the herbicide paraquat or inhibition of GSH synthesis with BSO. In normal cells GSH concentration was proportional to ambient oxygen tension. Tumor cells exhibited greater GSH concentrations at low oxygen tensions than normal cells but were unable to increase GSH in response to elevation of oxygen tension. These results reveal differences in tumor and normal cell responses to changes in ambient oxygen tension and show that MnSOD activity is inducible when an appropriate stimulus is applied.

Nicotinamide adenine dinucleotide phosphate-regenerating system coupled to a glutathione-reductase microtiter method for determination of total glutathione concentrations in adherent growing cancer cell lines

Improvements in the traditional glutathione (GSH)-reductase recycling method for determining total glutathione levels in adherent growing cells have been achieved by eliminating the direct use of expensive nicotinamide adenine dinucleotide phosphate (NADPH) and normalizing the levels of GSH to moles/liter instead of the more usual but more error-prone method of normalizing with cellular protein. A glucose-6-phosphate-dehydrogenase auxiliary reaction has been added to the microtiter-adapted enzyme method of Tietze; thus NADP(+) and glucose-6-phosphate replace NADPH in the method. This modification lowers the possibility for substrate inhibition of the reductase by high levels of NADPH during the initial phase of the reaction while at the same time reducing the assay costs by 75-85%. To calculate the cellular concentration of GSH, the number of cells used for the GSH determination, estimated by counting cell nuclei of benzalkonium chloride-lysed cells with a Coulter Counter Z2, and the average cell volume, also determined with the Coulter Counter, are multiplied to give the total sample volume. The quotient of the amount of GSH found in the cells and the total sample volume yields the GSH concentration in moles/liter. The assay has been validated with respect to precision (+/-2.6%), relative accuracy (-4.2 %), linearity (r(2)=0.98), linear range (0.5-10 microM), and limit of detection (80 pmol). Recovery was cell line dependent and ranged between 70 and 103% in the six cell lines. As an application of this method, the GSH concentrations in six human cancer cell lines were determined, without and with a 24-h preincubation with 200 microM D,L-buthionine-S,R-sulfoximine (BSO), an inhibitor of GSH biosynthesis. As expected, BSO lowered GSH levels on the average 85%.

Glutathione and glutathione-related enzymes in colorectal cancer patients

In recent years much attention has been focused on the role of glutathione (GSH) and GSH-related enzymes such as glutathione peroxidase (GSH Px), glutathione reductase (GSH Red), and glutathione S-transferase (GST) in the inhibition of free radical-induced carcinogenesis. In this study, erythrocyte GSH levels and activities of GSH Px, GSH Red, and GST were determined in patients with colorectal tumors (n = 20, mean age 54.5 +/- 8.3 yr). Erythrocyte GSH Red and GST activities were significantly higher in patients with colorectal tumors. Erythrocyte GSH levels and GSH Px activities were found to be significantly decreased in the patients. When the patients were classified based on their clinical grading (Dukes classifications), there was no significant difference in studied parameters between Dukes B and Dukes C. Our results suggest that oxidative stress may play an important role in colorectal tumorigenesis and that these events have no effect on the clinical grading of the colorectal tumor.

Intracellular glutathione is a cofactor in methylseleninic acid-induced apoptotic cell death of human hepatoma HEPG(2) cells

Selenium is a widely studied dietary anticancer agent. Among various selenium compounds, the methylated forms appear to be particularly effective in cancer prevention. Intracellular glutathione (GSH) is known to be involved in the metabolism of many methylated forms of selenium. In this study, we investigated the role of intracellular GSH in methylseleninic acid (MSeA)-induced apoptosis in human hepatoma (HepG(2)) cells. MSeA was shown to deplete intracellular GSH rapidly, preceding the typical apoptotic changes such as DNA fragmentation as measured by the TUNEL assay. When the intracellular GSH concentration was enhanced using N-acetylcysteiene (NAC) (a GSH synthesis precursor) and decreased using buthionine sufoxamine (BSO) (a GSH synthesis inhibitor), NAC markedly augmented MSeA-induced apoptosis, while BSO significantly inhibited MSeA-induced apoptosis. Different from the effect of sodium selenite, there was no measurable superoxide radical level in MSeA-treated cells. These observations suggest that intracellular GSH mainly acts as a cofactor to facilitate MSeA-induced apoptosis, while its antioxidant function becomes largely irrelevant. It is thus postulated that some cancer cells, such as liver cancer cells with higher level of intracellular GSH, would be more susceptible to MSeA cytotoxicity.

Oxidative stress and gene regulation

Reactive oxygen species are produced by all aerobic cells and are widely believed to play a pivotal role in aging as well as a number of degenerative diseases. The consequences of the generation of oxidants in cells does not appear to be limited to promotion of deleterious effects. Alterations in oxidative metabolism have long been known to occur during differentiation and development. Experimental perturbations in cellular redox state have been shown to exert a strong impact on these processes. The discovery of specific genes and pathways affected by oxidants led to the hypothesis that reactive oxygen species serve as subcellular messengers in gene regulatory and signal transduction pathways. Additionally, antioxidants can activate numerous genes and pathways. The burgeoning growth in the number of pathways shown to be dependent on oxidation or antioxidation has accelerated during the last decade. In the discussion presented here, we provide a tabular summary of many of the redox effects on gene expression and signaling pathways that are currently known to exist.

Resistance factors in colon cancer tissue and the adjacent normal colon tissue: glutathione S-transferases alpha and pi, glutathione and aldehyde dehydrogenase

Glutathione S-transferases (GST) alpha and pi, glutathione (GSH) and aldehyde dehydrogenase (ADH) were determined in colorectal cancer tissue specimens and in the adjacent normal colon tissue. The median contents in normal and cancer tissue were 8.1 (2.3-30.3) (5-95% quantiles) and 15.1 (5.3-50.3) microg/mg protein for GST pi (P = 0.035), 0.0 (0.0-1.4) and 0.4 (0.0-3.5) microg/mg protein for GST alpha (P = 0.019), 7.3 (1.3-22.7) and 5.6 (2.3-26.0) microg/mg protein for GSH (P = 0.171) and 30.8 (13.0-42.0) and 23.2 (9.0-32.9) microg/mg protein for ADH (P = 0.0017), respectively. Thus, the mean GST alpha and pi both significantly increased in colon cancer compared to the adjacent normal tissue, which underlines their importance as possible resistance factors. A highly significant correlation was obtained between the GSH content in colon cancer and normal tissue (P = 0.0017). Thus, the constitutive GSH expression seems to be maintained during tumor development. A similar correlation was obtained for ADH (P = 0.0075), but the median ADH was lower in cancer tissue compared to the adjacent normal tissue (P = 0.0017). Contrary to GSH and ADH, GST pi did not correlate between normal and colon cancer tissue. Whereas GSH and ADH correlated in normal colon tissue (P = 0.014), no significant correlation for GSH and ADH was observed in colon cancer tissue (P = 0.109). In conclusion, significant correlations between colon cancer and normal tissue were obtained, suggesting that the expression levels of these resistance factors are maintained during carcinogenesis in most patients.

Glutathione S-transferases as biomarkers of organ damage: applications of rodent and canine GST enzyme immunoassays

The cytosolic glutathione S-transferase (GST) enzymes serve as ideal biomarkers of organ damage as they exhibit many of the required characteristics, i.e. specific localisation, high cytosolic concentration and relatively short half-life. The role of GSTs as early indicators of organ damage is applicable to both human and animal models. Because of the regio-specific localisation of the different isoforms of GST in liver and kidney, simultaneous monitoring of classes of GSTs in biological matrices permits the identification of specific areas of damage within a particular organ. Immunoassays have been developed which quantify canine alpha GST and roden microGST (Yb1). The immunoassays are solid phase EIAs, where GST in the sample or standard is captured by a specific anti-GST antibody coated onto the solid phase. After washing, a specific enzyme-labelled IgG conjugate is added which binds to the captured GST. After a further washing step, substrate is added and a colour developed. The absorbance is measured on an ELISA plate reader and is directly proportional to the amount of GST present in the sample. The assays are performed at room temperature and can be completed within 3 h. The immunoassays are specific for each GST and have a range of 0-100 micrograms/l. A range of assay parameters were investigated to validate the EIAs for GST detection. The assays are sensitive and reproducible. CV for inter- and intra-assay variation were below 9% for Yb1 assay and below 20% for the canine alpha GST EIA. Recovery of spiked GST over the standard curve range was 102 and 99%, respectively. No prozone effect was observed and samples exhibited linearity of dilution in both assays. Validation has shown that using these enzyme immunoassay, Yb1 and canine alpha GST can be measured accurately and precisely in biological matrices, tissue homogenates and cell lines and that changes in GST levels can be detected. The use of these assays have important applications in both in vitro and in vivo toxicity studies, where GST's serve as sensitive marker of hepatocellular and renal cell integrity.

Glutathione S-transferase PI (GST-pi) class expression by immunohistochemistry in benign and malignant prostate tissue

PURPOSE

Glutathione S-transferase (GST) enzymes may prevent carcinogenesis through inactivation of reactive electrophiles by conjugation to reduced glutathione. Recently, it was reported that most prostate cancers fail to express GST-pi despite an abundant presence in benign prostate tissue, suggesting a common genetic alteration. To define its presence in prostate tissue, we evaluated GST-pi expression in a variety of prostate tissues.

MATERIALS AND METHODS

Immunostaining with anti-GST-pi antibody was performed on 69 benign prostates, 44 malignant prostates, 12 incidental prostate carcinomas and 17 prostatic intraepithelial neoplasia (PIN) specimens. Specimens were evaluated for the presence and percent of GST-pi. Within benign tissue, GST-pi immunostaining was distinguished between basal cells and secretory acinar epithelium.

RESULTS

In benign epithelium, the basal cells demonstrated intense staining in all cases. The mean percent staining among the basal cells was 67% (R 40-90%). The acinar epithelium stained weakly positive in 94% (65/69) of specimens, however the mean percent staining was only 5% (R 0-25%). GST-pi was detected in only 3.5% (2/56) of the prostate cancers. No incidental prostate cancers and only one (6%) high grade PIN stained positive.

CONCLUSIONS

Our study confirms the absence of GST-pi expression in prostate cancer and high grade PIN. Furthermore, GST-pi expression correlates well with the basal cell phenotype, but not with benign epithelial cells. The lack of staining among prostate cancer cells may reflect the absence of a basal cell layer, suggesting that GST-pi is involved more in epithelial differentiation and questioning its role in the malignant transformation of prostatic acinar cells.

Active transport of glutathione S-conjugate in human colon adenocarcinoma cells

The formation of the glutathione S-conjugate of monochlorobimane (GSH-bimane) in human colon adenocarcinoma cells was identified by HPLC-fluorimetry and its transport from the cells was found to be temperature-sensitive, saturable and ATP-dependent. The apparent K(m) and Vmax values were 2.4 +/- 0.5 nmol GSH-bimane/10(6) cells and 0.5 +/- 0.1 nmol GSH-bimane/min per 10(6) cells, respectively. This active transport of GSH-bimane was inhibited by low micromolar concentrations of classical uncouplers of oxidative phosphorylation, namely carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), carbonylcyanide m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP). The efflux of GSH-bimane was competitively inhibited by chlorambucil (CMB) and 1-chloro-2,4-dinitrobenzene (CDNB), two other substrates of GST. This study demonstrates the presence and kinetic measurements of the glutathione S-conjugate export (GS-X) pump in human colon cancer cells, an export pump whose function has been implicated in the phenomenon of multidrug resistance.

Effects of antioxidants on the anti-proliferation induced by protein synthesis inhibitors in human brain tumor cells

The effects of protein synthesis inhibitors (cycloheximide, anisomycin, puromycin and emetine) on the growth of human brain tumor cells were investigated using U-373 MG human astrocytoma and SK-N-MC human neuroblastoma cell lines. These agents inhibited the growth of the tumor cells in a dose-dependent manner. However, these agents did not affect cell viability evaluated by the trypan blue exclusion method, indicating that growth inhibition was due to the inhibition of cell proliferation rather than the induction of cytotoxicity. Anti-proliferation induced by these agents was significantly blocked by the treatments with either free radical scavengers or antioxidants. These results suggest that enhanced oxidative stress may be involved in the anti-proliferation induced by the protein synthesis inhibitors in human brain tumor cells.

Messenger RNA expression of resistance factors and their correlation to the proliferative activity in childhood acute lymphoblastic leukemia

In this report we analyzed the mRNA expression of the resistance-related enzymes DNA topoisomerase II (Topo II), thymidylate synthase (TS), glutathione S-transferase-pi (GST-pi) and glutathione peroxidase (GP) in childhood acute lymphoblastic leukemia (ALL) and their correlation to the proliferative activity, determined by Ki-67. RNA of blast cells from 54 children with untreated ALL were examined by dot blot hybridization. We found a significant positive correlation between Topo II and TS and cell proliferation. No significant correlation was detected between the mRNA expression of the glutathione-dependent enzymes GST-pi or GP and Ki-67. The results were substantiated by a semiquantitative RT-PCR-assay and by immunocytochemistry.