Taenia solium glutathione transferase fraction activates macrophages and favors the development of Th1-type response.

Glutathione (GSH) transferase (GST) is an essential enzyme in cestodes for the detoxification of xenobiotics. In Taenia solium, two GSTs (Ts25GST and Ts26GST kDa) were isolated as a fraction (SGSTF) by GSH-Sepharose-4B. Both are located on the tegument. Immunization assays with SGSTF reduced up to 90% of the parasitic load in a murine model of cysticercosis. It prompted us to investigate how SGSTF induces this protective immune response. To test it, we exposed peritoneal macrophages to SGSTF for 24 h; such exposure favored the production of IL-12, TNF, and IL-10 as well as the expression of nitric oxide synthase 2 inducible (Nos2) and CD86, but did not induce the expression of chitinase-like 3 (Chil3). Confocal microscopy showed that the macrophages internalize the SGSTF which co-localized after 1 h with MHC-II in their plasma membranes. Macrophages exposed to SGSTF and co-cultured with anti-CD3 pre-activated T CD4+ cells, enhanced the proliferation of CD4+ cells, induced high interferon-γ (IFN-γ) secretion, and elevated the expression of CD25 and CD69, molecules associated with cell activation. Similar assay using T CD4+ cells from DO11.10 mice and ovalbumin (OVA) peptide+SGSTF as stimuli, showed enhanced cell proliferation and OVA-specific IFN-γ secretion. These data are in-line with those indicating that the P1, P5, and P6 peptides of Schistosoma japonicum 28GST highly promote T-cell proliferation and Th1 response in vitro We found that such peptides are also present on Ts25GST and Ts26GST. It suggests that SGSTF activates peritoneal macrophages to a classically activated-like phenotype, and that these macrophages induce the differentiation of T CD4+ cells toward a Th1-type response.

Tobacco plants over-expressing the sweet orange tau glutathione transferases (CsGSTUs) acquire tolerance to the diphenyl ether herbicide fluorodifen and to salt and drought stresses.

The glutathione transferases (GSTs) are members of a superfamily of enzymes with pivotal role in the detoxification of both xenobiotic and endogenous compounds. In this work, the generation and characterization of transgenic tobacco plants over-expressing tau glutathione transferases from Citrus sinensis (CsGSTU1 and CsGSTU2) and several cross-mutate forms of these genes are reported. Putative transformed plants were verified for the presence of the transgenes and the relative quantification of transgene copy number was evaluated by Taqman real time PCR. The analysis of gene expression revealed that transformed plants exhibit high levels of CsGSTU transcription suggesting that the insertion of the transgenes occurred in transcriptional active regions of the tobacco genome. In planta studies demonstrate that transformed tobacco plants gain tolerance against fluorodifen. Simultaneously, the wild type CsGSTU genes were in vitro expressed and their kinetic properties were determined using fluorodifen as substrate. The results show that CsGSTU2 follows a Michaelis-Menten hyperbolic kinetic, whereas CsGSTU1 generates a sigmoid plot typical of the regulatory enzymes, thus suggesting that when working at sub-lethal fluorodifen concentrations CsGSTU2 can counteract the herbicide injury more efficiently than the CsGSTU1. Moreover, the transgenic tobacco plant over-expressing CsGSTs exhibited both drought and salinity stress tolerance. However, as we show that CsGSTUs do not function as glutathione peroxidase in vitro, the protective effect against salt and drought stress is not due to a direct scavenging activity of the oxidative stress byproducts. The transgenic tobacco plants, which are described in the present study, can be helpful for phytoremediation of residual xenobiotics in the environment and overall the over-expression of CsGSTUs can be helpful to develop genetically modified crops with high resistance to abiotic stresses.

Biochemical and physiological characterization of a tau class glutathione transferase from rice (Oryza sativa).

The classical phase II detoxification glutathione transferases (GSTs) are key metabolic enzymes that catalyze the conjugation of glutathione to various electrophilic compounds. A tau class GST gene (OsGSTU17) was cloned from rice, which encodes a protein of 223 amino acid residues with a calculated molecular mass of 25.18 kDa. The recombinant OsGSTU17 formed a homodimer protein and showed GSH-conjugating activity with various xenobiotics. Kinetic analysis with respect to NBD-Cl as substrate revealed a K(m) of 0.324 mM and V(max) of 0.219 micromol/min per mg of protein. The enzyme had a maximum activity at pH 7.5, and a high thermal stability with 81% of its initial activity at 55 degrees C for 15 min. Site-directed mutagenesis revealed that Ser15 in the N-terminal domain is a critical catalytic residue, responsible for stabilisation of the thiolate anion of enzyme-bound glutathione. OsGSTU17 mRNA was expressed in different tissues of rice, both above and below ground. The relative transcript levels of OsGSTU17 mRNA varied significantly among the tissues in response to CDNB, hydrogen peroxide and atrazine treatments, indicating the gene has diverse regulation mechanisms in response to abiotic stresses.

Pharmacokinetics of GST-TatdMt, a recombinant fusion protein possessing potent anti-obesity activity, in mice.

This study examined the absorption and pharmacokinetic disposition of 125I-GST-TatdMt, a recombinant Tat protein possessing potent anti-obesity activity, in mice after vascular and extravascular administration. GST-TatdMt was over-expressed in E. coli, purified, and radioiodinated using the IODO-GEN method. 125I-GST-TatdMt was administered to mice by i.v., i.p. and oral administration at doses of 652.7 nCi (102.3 microg). Upon i.v. injection, the average terminal elimination half-life (t1/2,lambdaz), AUC and AUMC were 6.4 h, 318.2 nCixh/mL and 2518 nCixh2/ mL, respectively. The highest radioactivity was observed in lung followed by liver, spleen, heart and kidney. The t1/2lambdaz values obtained from i.v., i.p., and oral administration were comparable from each other (range 5.8-6.4 h). The absolute bioavailability of 125I-GST-TatdMt was 42.8% and 60.5% after p.o. and i.p. administration, respectively. Given the cell-penetrating nature, 125I-GST-TatdMt may be absorbed into the systemic circulation to a relatively high extent after extravascular administration.

Pharmacokinetics of 125I-GST-TatdMt, a recombinant fusion protein possessing potent anti-obesity activity, after intravenous, nasal, oral, and subcutaneous administration.

This study first reports the absorption kinetics of GST-TatdMt, a recombinant Tat protein possessing potent anti-obesity activity, in rats after nasal, s.c., and p.o. administration. GST-TatdMt was over-expressed in E. coli, purified, and radioiodinated using the IODO-GEN method. The radioiodinated 125I-GST-TatdMt was administered to rats by nasal, s.c., and oral routes at doses of 7.3 microg (420.7 nCi), 146.5 microg (8413.8 nCi), and 146.5 microg (8413.8 nCi), respectively. For the determination of absolute bioavailability, 125I-GST-TatdMt was also given to rats by i.v. injection (73.2 microg, 4206.9 nCi). Following administration by extravascular routes, the systemic absorption of radioactivity was prolonged, with Cmax being attained within 4.2-8.0 h. The absolute bioavailability calculated as dose-normalized AUC(extravascular)/AUC(i.v.) was 98.0, 75.8, and 87.1% after nasal, s.c., and oral administration, respectively. The majority of administered radioactivity was excreted in urine (57.5-64.7%), with fecal excretion being less (2.5-12.7%). The distribution of 125I-GST-TatdMt to various tissues was also determined at 4 and 72 h after s.c. injection. The findings of this study suggest that this protein may be absorbed into the systemic circulation when given by extravascular administration.

A glutathione S-transferase catalyzes the dehalogenation of inhibitory metabolites of polychlorinated biphenyls.

BphK is a glutathione S-transferase of unclear physiological function that occurs in some bacterial biphenyl catabolic (bph) pathways. We demonstrated that BphK of Burkholderia xenovorans strain LB400 catalyzes the dehalogenation of 3-chloro 2-hydroxy-6-oxo-6-phenyl-2,4-dienoates (HOPDAs), compounds that are produced by the cometabolism of polychlorinated biphenyls (PCBs) by the bph pathway and that inhibit the pathway's hydrolase. A one-column protocol was developed to purify heterologously produced BphK. The purified enzyme had the greatest specificity for 3-Cl HOPDA (kcat/Km, approximately 10(4) M(-1) s(-1)), which it dechlorinated approximately 3 orders of magnitude more efficiently than 4-chlorobenzoate, a previously proposed substrate of BphK. The enzyme also catalyzed the dechlorination of 5-Cl HOPDA and 3,9,11-triCl HOPDA. By contrast, BphK did not detectably transform HOPDA, 4-Cl HOPDA, or chlorinated 2,3-dihydroxybiphenyls. The BphK-catalyzed dehalogenation proceeded via a ternary-complex mechanism and consumed 2 equivalents of glutathione (GSH) (Km for GSH in the presence of 3-Cl HOPDA, approximately 0.1 mM). A reaction mechanism consistent with the enzyme's specificity is proposed. The ability of BphK to dehalogenate inhibitory PCB metabolites supports the hypothesis that this enzyme was recruited to facilitate PCB degradation by the bph pathway.

Dose-linear pharmacokinetics, tissue distribution, and excretion of a recombinant fusion protein 125I-GST-TatdMt possessing potent anti-obesity activity.

This study first examined the pharmacokinetic disposition of GST-TatdMt, a recombinant Tat protein possessing potent anti-obesity activity, in rats after i.v. injection. GST-TatdMt was over-expressed in E. coli, purified, and radioiodinated using the IODO-GEN method. The radioiodinated 125I-GST-TatdMt was administered to rats at doses of 9 microg (1640 nCi), 18 mug (3388 nCi), and 35 microg (6420 nCi). Upon administration, the total radioactivity in serum declined bi-exponentially, with the average terminal elimination half-life ranging from 13.7 to 15.7 h. There was a linear relationship between dose and AUC(INF) (r2=1.000) and between dose and Co (r2=0.999). The fraction of administered radioactivity excreted in feces was low (mean range 1.5-2.8%), while the majority of the radioactivity was excreted in urine (mean range 54.9-61.4%). The radioactivity found in the liver, lungs, spleen, and kidneys were higher than in serum, but the tissue-to-serum ratios were relatively low (<1.64). The radioactivity in testes, adipose tissue, heart, and brain was lower than in serum (tissue-to-serum ratios 0.046-0.27). The findings of this study indicate dose-linear pharmacokinetics of 125I-GST-TatdMt in rats over the i.v. dose range studied.

Organ distribution and kinetics of Glutathione transferase from African river prawn, Macrobrachium vollenhovenii (Herklots).

The distribution of glutathione transferase (GST) in the major organs of African river prawn (Macrobrachium vollenhovenii) was studied. All the organs studied had GST activity. The specific activity of the extract from the hepatopancreas was highest while that from the muscle lowest. Purified GST from the hepatopancreas which could conjugate glutathione (GSH) with only 1-chloro-2,4-dinitrobenzene (CDNB) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBDCl) among some electrophilic substrates tested, had a K(m)(NBDCl) of 2.2+/-0.12 mmol l(-1) while the K(m)CDNB was 2.03+/-0.29 mmol l(-1). Chloride ion, a product of the enzymatic reaction readily inhibited the conjugation of CDNB with GSH with an I50 of 0.12 mmol l(-1), whereas chloride ion up to 0.6 mol l(-1) had no inhibitory effect on the conjugation of GSH with NBDCl. However, nitrite inhibited the two reactions but the K(i) for the conjugation of NBDCl was lower than the K(i) for the conjugation of CDNB. The enzyme had an optimum temperature of 40 degrees C and an activation energy of 35.1 kJ/mol. The overall results show that M. vollenhovenii GST (mvGST) uses different mechanisms for different electrophilic substrates. The high K(m) of mvGST for the electrophilic substrates may be a special physiological adaptation for effective xenobiotic detoxication.

Alpha-glutathione S-transferase in the assessment of hepatotoxicity--its diagnostic utility in comparison with other recognized markers in the Wistar Han rat.

The diagnostic utility of alpha-glutathione S-transferase (alphaGST) in the assessment of acute hepatotoxicity was compared with a range of markers including alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Rats were given a single oral dose of either alpha-naphthylisothiocynate (AN IT), bromobenzene (BrB). or thioacetamide (TAM) at concentrations previously shown to induce marked hepatotoxicity. The progression of each hepatic lesion was monitored by the measurement of a battery of markers, including alphaGST, in plasma collected at time points ranging from 3 h to 7 days after dosing. alphaGST was seen to increase significantly at 24 h (ANIT/BrB) and 3 h (TAM) postdosing, corresponding with histopathological findings. For each compound, when the degree of insult was most severe, fold increases in alphaGST were greater than those seen with ALT and AST, yet lower than those seen with glutamate dehydrogenase (BrB and ANIT). sorbitol dehydrogenase (TAM), or total bilirubin and bile acids (ANIT). Elevations in alphaGST were also detected no earlier than any other marker. AlphaGST in the rat was shown to be a valid marker of hepatotoxicity; however, its measurement offered no additional information in detecting either the time of onset/recovery or the severity of each type of hepatic injury induced.

Direct recovery of glutathione S-transferase by expanded bed adsorption: anion exchange as an alternative to metal affinity fusions.

The use of expanded beds of ion-exchange adsorbents for the direct recovery of a recombinant intracellular protein, glutathione S-transferase (GST), from unclarified Escherichia coli homogenates is described. The results form the basis for a comparison between this approach for purifying GST and a chelating fusion strategy and highlight the need to consider the additional costs entailed by these more-complicated approaches. The separation performance was investigated with respect to choice of anion or cation exchanger, adsorption pH, load volume, sample preparation, and stepwise elution protocol. Anion exchange was found to be more appropriate than cation exchange, as the low pHs involved in the latter caused a loss of activity. The optimal pH for adsorption was found to be 9 with a dynamic capacity from clarified homogenate in packed mode of 112 U mL(-1) (11.2 mg GST mL(-1)). As increasing volumes of unclarified homogenate were applied to the expanded bed, the yield of GST in the eluate decreased, and the purification factor was found to increase and then decrease. This was due to the displacement of weakly bound proteins by GST and then its displacement by even more strongly binding proteins. The dynamic capacity of the anion exchanger, STREAMLINE DEAE, from unclarified homogenate in expanded mode decreased slightly to 85 U mL(-1) (8.5 mg GST mL(-1)). The elution protocol for GST from the anion exchanger was then adjusted to try to maximize the degree of purification. Anion exchange expanded bed adsorption of GST from unclarified E. coli homogenate gave an eluted yield of 95.7% and 1.64-fold purification. Interestingly, a decrease in the expression level of GST in the feedstream from 23 down to 13% caused a decrease in the dynamic capacity from 85 to 14.5 U mL(-1) whereas the degree of purification remained similar.

GST-pi expression in BCR-ABL+ and BCR-ABL- cells from CML patients

En nuestro laboratorio durante varios años se ha estudiado a la enzima glutatión-sulfhidrilo-transferasa-pi (GST-pi). Experimentos recientes mostraron que la GST-pi es expresada en diferentes etapas de maduración celular durante la hematopoyesis en cultivo líquido de CPMO de pacientes con LMC candidatos a alotrasplante. Sugiriendo que la expresión de la GST-pi fue en células malignas. En el presente trabajo, confirmamos lo anterior mediante la detección por inmunofluorescencia de la GST-pi en células BCR-ABL+ y BCR-ABL- evaluadas por FISH en SP de 30 pacientes con LMC, durante diferentes etapas clínicas: tratamiento (T), recaída hematológica (R), crisis blástica (CB) y post-alotrasplante (PT). Así como en SP de 30 donadores del Banco de Sangre del Instituto. Los resultados, expresados como porcentaje de células, fueron: BCR-ABL+ GST-pi+: T= 1-67 por ciento, R= 33-69 por ciento, BC= 90-100 por ciento y PT= 1-2 por ciento; BCR-ABL- GST-pi+: T= 2-31 por ciento, R= 5-18 por ciento, BC= 0-10 por ciento y PT= 2-5 por ciento; BCR-ABL- GST-pi-: T= 2-97 por ciento, R= 13-62 por ciento, BC= 0 por ciento y PT= 93-96 por ciento; BCR-ABL+ GST-pi-: T= 0 por ciento, R= 0 por ciento, BC= 0 por ciento y PT= 0 por ciento. La GST-pi no se expresó en las células de los donadores. Los resultados obtenidos confirman nuestras observaciones previas y sugieren que la expresión de la GST-pi podría usarse para evaluar la enfermedad mínima residual en los pacientes con LMC.

The adsorption of substrate-binding domain of PHB depolymerases to the surface of poly(3-hydroxybutyric acid).

The binding characteristic of PHB depolymerase has been studied by using glutathione S-transferase (GST) fusion proteins with substrate-binding domain of three bacterial PHB depolymerases, Alcaligenes faecalis, Comamonas acidovorans and Comamonas testosteroni. Analysis using immuno-gold labeling technique and transmission electron microscopy indicated that a novel GST fusion protein derived from A. Faecalis enzyme adsorbed to the surface of poly(3-hydroxybutyric acid) (P(3HB)) single crystals like other fusion proteins. Comparison of inhibiting degree of P(3HB) powder hydrolysis activity of PHB depolymerase by fusion proteins indicated that three fusion proteins bind to P(3HB) powder in the same degree. The measurement of the surface hydrophobicity of proteins suggests that the interaction of the substrate-binding domain with insoluble P(3HB) may include not only a hydrophobic effect but also molecule-specific contacts.

Influence of non-nutrient plant components on biotransformation enzymes.

Plant foods contain numerous non-nutritive substances which exert biological activity. Most attention has been focused on the anticarcinogenic effects of these compounds. Many of the mechanisms involved include induction or inhibition of biotransformation enzymes. Each individual has its own isoenzyme pattern for the various drug-metabolizing enzymes. The multiplicity of these enzymes results in differential responses to dietary constituents. A substance may increase the level of a certain P450, and decrease the level of another. Although this complicates matters considerably, it also offers the possibility of specifically influencing biotransformation directed at a particular compound, e.g., a cytostatic agent. Using the important class of the glutathione S-transferase (GST) as an example, the various phenotypic and genetic origins of interindividual variation are described. Genetic variation is especially important for the mu and thetra class enzymes. The induction of individual isoenzymes of the GST has been studied in man rat. It was shown that the changes in the GST isoenzyme pattern induced by Brussels sprouts in rat liver and intestine were very similar to that caused by administration of ally isothiocyanate, and not to that resulting from goitrin. In man Brussels sprouts led to induction of GST alpha only. A number of naturally occurring catechols, or more likely the quinones derived from them, are effective irreversible inhibitors of GST. Eugenol, for instance, lowers GST activity in man. A second class of compounds which shows promise are alpha, beta-unsaturated aldehydes and ketones. A number of naturally occurring representatives of this class inhibit GST pi irreversibly, and ethacrynic acid, a drug with a similar reactive moiety in its structure, has already been shown to be quite useful to inhibit GST activity in cellular systems. Several approaches for future studies on the effects of dietary constituents are indicated: 1) further studies on the mechanisms of induction and inhibition of biotransformation enzymes: 2) careful studies using human volunteers, where the effects can be studied in isolation as much as possible; 3) studies of the disposition and kinetics of the dietary constituents themselves, to assess the relevance of inducing agents in food for the day-to-day human situation.

A glutathione S-transferases isozyme (bGST 5.8) involved in the metabolism of 4-hydroxy-2-trans-nonenal is localized in bovine lens epithelium.

Previous studies have suggested that a group of GST isozymes (bGST 5.8) with substrate preference for 4-hydroxy-2-trans-nonenal (4-HNE) were present in bovine retina, cornea, iris-ciliary body and sclera, but not in lens. The present studies demonstrate that bGST 5.8 is present in bovine lens epithelium and absent in the cortex and nucleus. Immunochemical studies demonstrated that the enzyme is selectively expressed in epithelium where it can be induced by about 2.5-fold when the lenses are cultured in Medium-199 for 24 hr in the presence of 10 microM BHT. bGST 5.8 was purified to homogeneity from the epithelium using immunoaffinity chromatography. Upon SDS-PAGE, the enzyme showed a single band corresponding to an M(r) value of 25 kDa and its CNBr-peptide maps in SDS-gels were identical to those of the isozymes of this group of GSTs reported previously. The enzyme exhibited high activity towards 4-HNE, and showed glutathione peroxidase activity towards phospholipid hydroperoxides. The Km values of the enzyme for 4-HNE (57 microM from control and 52 microM from BHT-treated) were in the same range as those reported for GSTs 5.8 of human ocular tissues. However, the Kcat value of the lens epithelium enzyme for 4-HNE (15.4 mol mol-1 sec-1 from control, and 20.2 mol mol-1 sec-1 from BHT treated) were considerably less than those reported for the human ocular GST 5.8. Results of these studies suggested that a GST isozyme involved in the detoxification of the electrophilic products of lipid peroxidation was localized in the epithelium of bovine lens.

Purification, characterization and tissue distribution of human class theta glutathione S-transferase T1-1.

A high activity glutathione S-transferase T1-1 (GSTT1-1) towards dichloromethane was isolated from human liver cytosol and purified to homogenity in 18.5% yield with a purification factor of 4400-fold. The GSTT1-1 was also isolated from erythrocytes, but the enzyme activity decreased rapidly in the final stages of purification. The purified GSTT1-1-s were homo-dimeric enzymes with a subunit M1 value 25,300 and pI 6 64, as confirmed by SDS-PAGE, IEF and Western blot analysis. The N-terminal amino acid sequences of GSTT1-1 from liver and red blood cells, analyzed up to the 12th amino acid, were identical. Immunoblot analysis revealed that GSTT1-1 was also present in lung, kidney, brain, skeletal muscle, heart, small intestine and spleen, but not in lymphocytes.

Detoxification of vinyl carbamate epoxide by glutathione: evidence for participation of glutathione S-transferases in metabolism of ethyl carbamate.

Vinyl carbamate epoxide (VCO) is believed to be the metabolite of ethyl carbamate (EC) ultimately responsible for its carcinogenic effects. This study investigates the role of glutathione (GSH) in protection against VCO-mediated adduct formation, and the involvement of glutathione S-transferases (GSTs) in detoxification of VCO. Formation of 1,N6-ethenoadenosine from VCO and adenosine in vitro was employed as a measure of VCO toxicity. GSH inhibited formation of ethenoadenosine in a concentration-dependent manner at concentrations ranging from 1 to 8 mM. This effect was significantly enhanced by addition of rat liver GST. Mouse liver cytosol was also found to inhibit formation of ethenoadenosine in a concentration-dependent manner, and the inhibition was relieved by addition of S-octylglutathione, a competitive inhibitor of GST. Pretreatment of mice with 1% dietary (2(3)-tert-butyl-4-hydroxyanisole (BHA) caused parallel increases in cytosolic GST activity and cytosolic enhancement of detoxification of VCO by GSH. Furthermore, BHA increased hepatic steady-state concentrations of GSH greater than twofold. The effect of BHA on detoxification of EC in vivo was examined using formation of 2-oxoethylvaline (OEV) adducts of hemoglobin as a biomarker. Pretreatment with BHA decreased overall formation of OEV adducts 23%. The major conclusions of this study are (1) VCO can be detoxified by spontaneous conjugation with GSH, (2) conjugation of VCO with GST can be catalyzed by GST(s), (3) pretreatment with BHA protects against binding of active EC metabolites in vitro and in vivo, and (4) the protective effect of BHA against EC is mediated by increases in GST activity and GSH concentration.