Glutathione S-transferase Isoenzymes Research Articles

Busulfan induces steatosis in HepaRG cells but not in primary human hepatocytes: Possible explanations and implication for the prediction of drug-induced liver injury.

The antineoplastic drug busulfan can induce different hepatic lesions including cholestasis and sinusoidal obstruction syndrome. However, hepatic steatosis has never been reported in patients. This study aimed to determine whether busulfan could induce steatosis in primary human hepatocytes (PHH) and differentiated HepaRG cells. Neutral lipids were determined in PHH and HepaRG cells. Mechanistic investigations were performed in HepaRG cells by measuring metabolic fluxes linked to lipid homeostasis, reduced glutathione (GSH) levels, and expression of genes involved in lipid metabolism and endoplasmic reticulum (ER) stress. Analysis of two previous transcriptomic datasets was carried out. Busulfan induced lipid accumulation in HepaRG cells but not in six different batches of PHH. In HepaRG cells, busulfan impaired VLDL secretion, increased fatty acid uptake, and induced ER stress. Transcriptomic data analysis and decreased GSH levels suggested that busulfan-induced steatosis might be linked to the high expression of glutathione S-transferase (GST) isoenzyme A1, which is responsible for the formation of the hepatotoxic sulfonium cation conjugate. In keeping with this, the GST inhibitor ethacrynic acid and the chemical chaperone tauroursodeoxycholic acid alleviated busulfan-induced lipid accumulation in HepaRG cells supporting the role of the sulfonium cation conjugate and ER stress in steatosis. While the HepaRG cell line is an invaluable tool for pharmacotoxicological studies, it might not be always an appropriate model to predict and mechanistically investigate drug-induced liver injury. Hence, we recommend carrying out toxicological investigations in both HepaRG cells and PHH to avoid drawing wrong conclusions on the potential hepatotoxicity of drugs and other xenobiotics.

Impact of Glutathione S-Transferase Polymorphisms on Busulfan Pharmacokinetics and Outcomes of Hematopoietic Stem Cell Transplantation.

Busulfan (Bu) is an alkylating drug used in many preparative regimens before hematopoietic stem cell transplantation (HSCT). It is conjugated in the liver mainly by glutathione S-transferase isoenzyme A1-1 ( GSTA1 ). Genetic polymorphisms in these isoenzymes may affect the pharmacokinetics of Bu and the clinical outcomes of HSCT. This study aimed to assess the impact of glutathione S-transferase ( GST ) genetic polymorphisms on the clearance of Bu and the clinical outcomes of patients undergoing HSCT. This single-center retrospective study included patients who received IV Bu before HSCT at Sultan Qaboos University Hospital (SQUH), Oman from January 2003 to October 2016. Genotyping for polymorphisms was performed for GSTM1 , GSTT1 , GSTA1 , and GSTP1 . Each GST polymorphism was analyzed for its impact on Bu clearance and HSCT outcomes. A total of 135 patients were included. The mean Bu clearance was 3.7 ± 0.98 mL/min/kg. Patients with GSTA1 A-513G heterozygosity (AG) were found to have a higher incidence of graft loss ( P = 0.006). Homozygous double null of GSTM1 and GSTT1 was associated with a higher incidence of acute graft versus host disease ( P = 0.04). Double non-null GSTM1 and GSTT1 and non-null GSTM1 increased the risk of mortality ( P = 0.034 and 0.021, respectively). GST genotyping before HSCT may predict HSCT outcomes. The results of this preliminary retrospective study need to be confirmed in a larger prospective study.

Expression and biochemical significance of Piwil2 in stem cell lines

Abstract Introduction P-element induced wimpy testis-like 2 (Piwil2) is in the Piwi gene family. Piwil2 has important roles in the self-renewal mechanism of stem cell induction and progression of numerous types of human malignancies such as lung, breast, colon, prostate, and cervical cancers. Glutathione S-transferase (GST) acts as detoxification in cancer metabolism. This study aimed to investigate the effects of the stem cell protein Piwil2 on MCF10A and MCF-7 at the GST activity levels. Materials/Methods MCF-7/Piwil2 and MCF10A/Piwil2, transfected with a plasmid carrying the Piwil2 gene, and non-transfected MCF-7 and MCF10A were cultured in a complete DMEM/F12 medium. GST A1 and P1 activity was determined in these cell lines using as substrates CDNB, EA respectively. Results According to experimental results, GST P1 activity decreased in the MCF-7/Piwil2 cells as compared with the non-transfected MCF-7 cells, however, MCF-7/Piwil2 cells demonstrated increases in GST A1 (total GST) activity. The statistically significant differences were found for the comparison of non-transfected MCF-7 and MCF-7/Piwil2 (p<0,0001), for GST enzyme activities by using CDNB and EA as substrates. These results were the same for the MCF10A cell line. Discussion It is shown for the first time that transfection studies may affect GST activity at the cellular mechanism level. The study contributes to determining the effect of transfection on GST isoenzymes and also how the Piwil2 gene may affect GST activity in the stem cell line.

Tissue expression of glutathione S transferase isoenzymes in vitiligo

ABSTRACT The association of glutathione S-transferase (GST) enzymes with vitiligo is inconclusive. To evaluate tissue expressions of GST isoenzymes in vitiligo patients and to compare these expressions with healthy controls, we used 26 active depigmented patches on the trunk of vitiligo patients and 20 healthy sex and age matched controls. Punch biopsies were taken from the lesioned or normal skin. Tissue expression of GST isoenzymes were analyzed immunohistochemically. Tissue expression of GSTT1, GSTA1 and GSTP1 was significantly higher in the patient group than controls. Tissue expression of GSTM1 was not significantly different between the two groups. The increased tissue expression of GSTT1, GSTA1 and GSTP1 may represent a response to excess free radical formation in vitiligo and may support the role of oxidative stress in the pathogenesis of vitiligo.

Comparison of the tissue expressions of glutathione S transferase isoenzymes among patients with morphea and healthy controls: A preliminary study.

Morphea is an inflammatory connective tissue disorder, which is characterized by sclerosis in skin and subcutaneous tissues with a chronic progress. The oxidative stress in pathogenesis of sclerosing diseases was proposed in several studies with conflicting results. To explore the tissue expressions of Glutathione S transferase (GST) isoenzymes in patients with morphea and compare these expressions with healthy controls. Twenty-two morphea patients and 20 sex and age matched healthy controls were enrolled in this study. Four millimeter punch biopsies were performed from the active sclerotic plaques of morphea patients. Tissue samples of control group were obtained from nonlesional normal skin biopsy specimens. The protein expressions of GST isoenzymes were analyzed immunohistochemically. Tissue expressions of GSTP1, GSTT1, and GSTA1 isoenzymes in morphea patients were found to be significantly higher than in control tissues. There was no significant difference in GSTM1 isoenzyme expression between the two groups. The increased tissue expressions of GSTA1, GSTP1, and GSTT1 isoenzymes in morphea may represent the activated GST enzymes in response to excessive free radical formation and may also support the hypothesis of increased oxidative stress in morphea etiopathogenesis.

[Resonance light scattering spectroscopy can directly characterize protein solubility].

To develop a fast, sensitive and cost-effective method based on resonance light scattering (RLS) for characterization of protein solubility to facilitate detection of changes in solubility of mutant proteins. We examined the response curve of RLS intensities to the protein concentrations in synchronous scanning mode. The curve intersection points were searched to predict the maximal concentrations of the protein in dispersion state, which defined the solubility of the protein in this given state. Bovine serum albumin (BSA, 0-50 g/L) was used as the model to investigate the influences of pH values (6.5, 7.0, and 7.4) and salt concentrations (0.05, 0.10, 0.15, and 0.20 mol/L) on the determined solubility. The solubility of glutathione S-transferase isoenzymes alpha (GSTA, 0-27.0 g/L) and Mμ (GSTM, 0-20.0 g/L) were estimated for comparison. The RLS-based method was used to determine the solubility of uricase (MGU, 0-0.4 g/L) to provide assistance in improving the solubility of its mutants. We identified two intersection points in the RLS response curves of the tested proteins, among which the lower one represented an approximation of the maximal concentration (or the solubility of the protein) in single molecular dispersion, and the higher one the saturated concentration of the protein in multiple molecular aggregation. In HEPES buffer, the two intersection points of BSA (isoelectric point 4.6) both increased with the increase of pH (6.5-7.4), and their values were ~1.2 g/L and ~33 g/L at pH 7.4, respectively; the latter concentration approached the solubility of commercial BSA in the same buffer at the same pH. The addition of NaCl reduced the values of the two intersection points, and increasing salt ion concentration decreased the values of the lower intersection points. Further characterizations of GSTA and GSTM showed that the low concentration intersection points of the two proteins were ~0.7 g/L and ~0.8 g/L, and their high concentration intersection points were ~10 g/L and ~11 g/L, respectively, both lower than those of BSA, indicating the feasibility of the direct characterization of protein solubility by RLS. The two concentration intersection points of MGU were 0.24 g/L and 0.30 g/L, respectively, and the low concentration intersection point of its selected mutant was increased by 2 times. RLS allows direct characterization of the solubility of macromolecular proteins. This method, which is simple and sensitive and needs only a small amount of proteins, has a unique advantage for rapid comparison of solubility of low-abundance protein mutants.

Expressions of glutathione S-transferase alpha, mu, pi, and theta in the skin samples of patients with acne rosacea.

Data point to the importance of oxidative stress in rosacea. Glutathione S-transferases (GSTs) have substantial roles in a wide variety of oxidative stress-related conditions. To evaluate the immunohistochemical staining characteristics of GST alpha (GSTA), mu (GSTM), pi (GSTP), and theta (GSTT) in patients with rosacea. The study included 23 women and 7 men with rosacea (mean±SD age 49±11year) and 15 healthy control subjects (10 women, 5 men; mean±SD age 47.86±10.88year). For each patient, the average disease duration, disease subtype, ocular involvement, and severity score were recorded. A 3-mm punch biopsy was taken from the facial skin of each patient and control. Expression of GST isoenzymes was analyzed immunohistochemically. Expressions of GSTM1, GSTP1, and GSTT1 were significantly elevated in patients with rosacea compared to those in the control group (P=.0001, P=.0002, P<.0001, respectively). In the rosacea group, GSTT1 expression was significantly stronger than GSTP1 and GSTA1 expressions (P=.019, P<.0001, respectively). There were no significant associations between expressions of GST isoenzymes and gender, age, average duration of illness, disease subtype, ocular involvement, or severity score in the patient group (all P>.05). In rosacea, the significant increase of GSTT1, GSTP1, and GSTM1 expressions might result from activation of GST as an outcome of extreme free radical generation from triggered neutrophils or ultraviolet vulnerability. These findings support the relevance of oxidant stress in the pathogenesis of rosacea.

In Utero Exposure of Atrazine and its effects on Chronobiology and Gene Expression of Glutathione S‐Transferase

Atrazine is a common herbicide that has been implicated in multiple health issues. The enzyme that degrades atrazine is Glutathione S‐Transferase (GST). GST is a detoxifying enzyme present in high concentrations in the liver; the GST isoenzyme pi is specifically responsible for the breakdown of atrazine. Previous research showed decreased expression of GST when mice are exposed to atrazine. Studies have also shown that there is circadian regulation of GST. This study investigated the effect atrazine had on circadian rhythm of GST by utilizing CD‐1 mice exposed in utero to atrazine. The results showed that atrazine inhibited the circadian rhythm of not just GST, but also Period 1, a circadian regulating protein.

Glutathione S-transferase Isoenzymes in Lung Carcinoma Patients receiving Platinum-based Chemotherapy and Effects of Ethyl Alcohol and Smoking on Treatment Response

Glutathione S-transferase Isoenzymes in Lung Carcinoma Patients receiving Platinum-based Chemotherapy and Effects of Ethyl Alcohol and Smoking on Treatment Response

Glutathione S-Transferase Enzymes in Plant-Pathogen Interactions.

Plant glutathione S-transferases (GSTs) are ubiquitous and multifunctional enzymes encoded by large gene families. A characteristic feature of GST genes is their high inducibility by a wide range of stress conditions including biotic stress. Early studies on the role of GSTs in plant biotic stress showed that certain GST genes are specifically up-regulated by microbial infections. Later numerous transcriptome-wide investigations proved that distinct groups of GSTs are markedly induced in the early phase of bacterial, fungal and viral infections. Proteomic investigations also confirmed the accumulation of multiple GST proteins in infected plants. Furthermore, functional studies revealed that overexpression or silencing of specific GSTs can markedly modify disease symptoms and also pathogen multiplication rates. However, very limited information is available about the exact metabolic functions of disease-induced GST isoenzymes and about their endogenous substrates. The already recognized roles of GSTs are the detoxification of toxic substances by their conjugation with glutathione, the attenuation of oxidative stress and the participation in hormone transport. Some GSTs display glutathione peroxidase activity and these GSTs can detoxify toxic lipid hydroperoxides that accumulate during infections. GSTs can also possess ligandin functions and participate in the intracellular transport of auxins. Notably, the expression of multiple GSTs is massively activated by salicylic acid and some GST enzymes were demonstrated to be receptor proteins of salicylic acid. Furthermore, induction of GST genes or elevated GST activities have often been observed in plants treated with beneficial microbes (bacteria and fungi) that induce a systemic resistance response (ISR) to subsequent pathogen infections. Further research is needed to reveal the exact metabolic functions of GST isoenzymes in infected plants and to understand their contribution to disease resistance.

The Effect of Tocotrienol-Rich Fraction on the Expression of Glutathione S-Transferase Isoenzymes in Mice Liver

Glutathione S-transferase isoenzymes (GSTs) catalyze the conjugation reaction between glutathione and electrophilic compounds. GSTs are involved in the detoxification of toxic and carcinogenic compounds, thus protecting the body from toxic injuries. Tocotrienols are part of the vitamin E family and is believed to possess potent antioxidant activity. The objective of this study was to determine the effect of increasing doses of tocotrienol rich fraction (TRF) supplementation on liver GSTs gene and protein expression. A total of 30 male ICR white mice were divided into five groups (n=6 for each group) and given treatment for 14 days through oral supplementation. Groups were divided as follows: - three groups administered with TRF at doses of 200, 500 and 1000 mg/kg, respectively, a positive control group administered with 100 mg/kg butylated hydroxyanisole (BHA) and a control group administered with only the vehicle (corn oil). At day 15, the mice were sacrificed and their livers isolated. Total RNA was extracted from the liver and quantitative real-time polymerase chain reaction (qPCR) assays were performed to analyze GSTs gene expression. Total liver protein was also extracted and the protein expression of GSTs was determined by Western blotting. The results showed that TRF oral supplementation caused a significant dose-dependent increase in liver GST isoenzymes gene and protein expression, compared to controls. In conclusion, TRF oral supplementation for 14 days resulted in increased gene and protein expression of GST isoenzymes in mice liver dose-dependently, with the highest expression seen in mice treated with 1000 mg/kg TRF.

Glutathione peroxidase and glutathione S-transferase in blood and liver from a hypoxia-tolerant fish under oxygen deprivation

Liver enzyme activities can be employed as biomarkers, but liver can only be obtained with death of the specimen. On the other hand, blood withdrawal is a non-lethal procedure. Accordingly, the hypothesis of this study is to verify if glutathione peroxidase (GPX) and glutathione S-transferase (GST) activities in blood parallel those in the liver of the hypoxia-tolerant fish, Piaractus mesopotamicus (pacu), submitted to hypoxia conditions. GPX was assayed with H2O2 in cytosols from both liver and erythrocytes and exhibited no significant variation, either in erythrocytes or in liver, when comparing pacus under normoxia with those under hypoxia (42 h). GST activity with chloro-dinitrobenzene (CDNB), an artificial substrate suitable for almost all GST isoenzymes, was compared to activity with 4-hydroxy-nonenal (4-HNE), a physiological endogenous substrate. GST activity with CDNB did not change in liver or in erythrocyte cytosols in pacus under hypoxia compared to those under normoxia. On the other hand, a significant decrease in erythrocyte activity with 4-HNE was observed after 42 h of hypoxia in both erythrocytes and liver, which may be a response to increased lipid oxidation in erythrocytes. Erythrocyte GST activity was 3-fold higher with 4-HNE than with CDNB, indicating that 4-HNE is a more appropriate substrate to determine GST activity in pacu erythrocytes.

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, CdCl2, 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.

Glutathione S-Transferase Protein Expression in Different Life Stages of Zebrafish (Danio rerio).

Zebrafish is a widely used animal model in biomedical sciences and toxicology. Although evidence for the presence of phases I and II xenobiotic defense mechanisms in zebrafish exists on the transcriptional and enzyme activity level, little is known about the protein expression of xenobiotic metabolizing enzymes. Given the important role of glutathione S-transferases (GSTs) in phase II biotransformation, we analyzed cytosolic GST proteins in zebrafish early life stages and different organs of adult male and female fish, using a targeted proteomics approach. The established multiple reaction monitoring-based assays enable the measurement of the relative abundance of specific GST isoenzymes and GST classes in zebrafish through a combination of proteotypic peptides and peptides shared within the same class. GSTs of the classes alpha, mu, pi and rho are expressed in zebrafish embryo as early as 4 h postfertilization (hpf). The majority of GST enzymes are present at 72 hpf followed by a continuous increase in expression thereafter. In adult zebrafish, GST expression is organ dependent, with most of the GST classes showing the highest expression in the liver. The expression of a wide range of cytosolic GST isoenzymes and classes in zebrafish early life stages and adulthood supports the use of zebrafish as a model organism in chemical-related investigations.

Evaluation of tissue levels of glutathione S-transferases (GST) isoenzymes in patients with discoid lupus erythematosus

Aim: Cutaneous lupus erythematosus (CLE) has a multifactorial pathogenesis involving genetic and environmental triggers and congenital and acquired immune response. The aim of this study was to investigate the effects of Glutathione S-Transferases (GST) isoenzymes including GSTT1, GSTM1, and GSTP1 in the CLE patients with an etiology of solar radiation exposure. Material and Methods: Paraffin-embedded skin biopsy sections from the patients were stained by immunohistochemical methods. The results were evaluated under a light microscope by a pathologist. The pattern, localization, and distribution of the immunohistochemical staining were recorded for each patient. Staining of the nucleus or cytoplasm was considered as positive staining. The accuracy of staining was determined based on the intensity and percentage of staining. Results: No significant difference was found between the patient and control groups regarding staining intensity. In terms of staining percentage, the prevalence of GSTP1-3 genotype was significantly lower in the patient group compared to the control group (25% vs. 63.33%) (p=0.002). Conclusion: No significant difference was observed in the staining intensity of GSTP1, GSTT1, and GSTM1 between the patient and control groups and the staining percentage in some genotypes was even higher in the control group compared to the patient group.

Enzymatic activity induction of GST-family isoenzymes from pesticide mixture used in floriculture.

Glutathione S-transferases (GSTs) comprise a number of genes that codify for a group of isoenzymes that participate in phase II xenobiotic detoxification by means of conjugation with glutathione, producing hydrosoluble compounds. It has been demonstrated that some pesticides are substrates for GST isoenzymes. Floriculture is one of the main economic activities in the municipalities of Villa Guerrero and Atlacomulco; pesticides, applied as mixtures, are intensively used in this activity. In this study, total GST enzymatic activity and glutathione S-transferases theta 1 (GSTT1) enzymatic activity were calculated for a group of floriculture workers exposed to pesticides and for an unexposed group. The former comprised 169 floriculture workers, while the latter, 96 students. The value of the median GST enzymatic activity in the exposed group was 0.560 and 0.169μmol/min/mL in the unexposed individuals. GSTT1 activity was 1.234μmol/min/mL in the exposed group and 0.221μmol/min/mL in the unexposed group. Mann-Whitney U test showed a significant difference between these groups, for both total GST and GSTT1, p<0.001. Our results show that exposure to pesticides increases the activities of total GST and GSTT1 enzymes.

Evaluation of oxidative stress via protein expression of glutathione S-transferase and cytochrome p450 (CYP450) ısoenzymes in psoriasis vulgaris patients treated with methotrexate

Introduction: Oxidative stress is the imbalance between oxidant-antioxidant systems and may play a major role in the psoriasis pathogenesis. Cytochrome (CYP) is a family of enzymes that are responsible for the metabolism of various endogenous and exogenous substances such as drug metabolism. Most importantly, the antioxidant system is the glutathione S-transferases (GST), which decrease oxidative stress by reducing oxidative products.Aim: We aimed to evaluate the expressions of isoenzymes of GST and CYP families and the beneficial role of metotrexate (MTX) in this process.Material and methods: This study included 21 patients with psoriasis and 22 healthy subjects. We treated all the patients with 10–15 mg/week of MTX for minimum 12 weeks. Expressions of GST and CYP enzymes were assessed by immunohistochemical staining.Results: GSTK1, GSTM1 and GSTT1 expressions were significantly higher in the psoriasis tissues than in the control tissues (p < 0.05; p < 0.05; p < 0.05, respectively). In the psoriasis patients, GSTO1 expression was similar the control group. CYP1B1 and CYP2E1 expressions were significantly higher in the pre-treatment and post-treatment psoriasis tissues than in the control tissues (p < 0.05; p < 0.05; p < 0.05; p < 0.05, respectively).Conclusion: We found a significant increase in the tissue levels of, either expression of GST, or CYP, which has important role in drug metabolism and oxidative stress. MTX treatment resulted in marked clinical improvement, yet we found that MTX did not have any significant effect on these parameters. CYP2E1 is especially the most important enzyme for MTX metabolism since it is the primarily responsible of the toxic metabolism of various drugs. The other experimental studies involving greater number of patients and other different drug are needed to enlighten the role of oxidant and antioxidant systems and the other possible mechanisms for the pathogenesis of psoriasis.

Glutathione S - transferases class Pi and Mi and their significance in oncology.

In this article the current data, which shows that glutathione S-transferases (GST) class Pi and Mi are interesting and promising biomarkers in acute and chronic inflammatory processes as well as in the oncology, were presented based on the review of the latest experimental and clinical studies. The article shows their characteristics, functions and participation (direct - GST Pi, indirect - GST Mi) in the regulation of signaling pathways of JNK kinases, which are involved in cell differentiation. Overexpression of glutathione S-transferases class Pi and Mi in many cancer cells plays a key role in cancer treatment, making them resistant to chemotherapy. GST isoenzymes are involved in the metabolism of various types of xenobiotics and endogenous substrates, so their altered expression in cancer tissues as well as in serum and urine could be an important potential marker of the cancer and an indicator of oxidative stress. The study shows the role of glutathione S-transferases in redox homeostasis of tumor cells and in the mechanism of resistance to anticancer drugs.

Biochemical Characterization of the Detoxifying Enzyme Glutathione Transferase P1-1 from the Camel Camelus Dromedarius.

Glutathione transferase (GST, EC 2.5.1.18) is a primary line of defense against toxicities of electrophile compounds and oxidative stress and therefore is involved in stress-response and cell detoxification. In the present study, we investigated the catalytic and structural properties of the glutathione transferase (GST) isoenzyme P1-1 from Camelus dromedarius (CdGSTP1-1). Recombinant CdGSTP1-1 was produced in Escherichia coli BL21(DE3) and purified to electrophoretic homogeneity. Kinetic analysis revealed that CdGSTP1-1 displays broad substrate specificity and shows high activity towards halogenated aryl-compounds, isothiocyanates and hydroperoxides. Computation analysis and structural comparison of the catalytic and ligand binding sites of CdGSTP1-1 with other pi class GSTs allowed the identification of major structural variations that affect the active site pocket and the catalytic mechanism., Affinity labeling and kinetic inhibition studies identified key regions that form the ligandin-binding site (L-site) and gave further insights into the mechanism of non-substrate ligand recognition. The results of the present study provide new information into camelid detoxifying mechanism and new knowledge into the diversity and complex enzymatic functions of GST superfamily.

Investigation of Glutathione S-Transferase Isoenzyme Protein Expression in Patients With Pterygium.

We investigated glutathione S-transferase (GST) enzymes in terms of their potential effects on the pathogenesis of pterygium. Twenty-six pterygium specimens and 15 normal conjunctival specimens of 15 control subjects were investigated. Expressions of GST (alpha, mu, pi, and theta) enzymes were assessed by immunohistochemical staining. A brown color in the cytoplasm and/or nuclei of epithelial cells was evaluated as positive staining for GST enzymes. For each antibody, the intensity of the reaction [negative (-), weak (1+), moderate (2+), or strong (3+)] was determined to describe the immunoreactions. The median age was 52 years in the both groups. There was no significant difference between the groups in terms of age, sex, and intraocular pressure measurements (P > 0.05 for all). Of the 26 pterygium specimens, 15 (57.7%) (8 weak, 4 moderate, and 3 strong staining) were identified with GST pi-1 (GSTP1) expression and 20 (76.9%) (12 weak, 7 moderate, and 1 strong staining) with GST theta-1 (GSTT1) expression. Of the 15 control specimens, 4 (26.7%) (4 weak staining) were identified with the GSTP1 expression, and 1 (6.7%) with GSTT1 expression. GSTP1 and GSTT1 expressions were significantly higher in the pterygium specimens than in the controls (P = 0.043, P < 0.001; respectively). None of tissue specimens had positive staining for GST mu-1 or GST alpha-1 in both groups (both; P = 1.00). The significant increase of GSTP1 and GSTT1 expressions in pterygium may be because of the increased activation of GST in response to excessive free radical formation from ultraviolet exposure to maintain antioxidant capacity in pterygium.