Lower Glutathione S-transferase Activity Research Articles

Assessment of glutathione-S-transferase and glutathione reductase in patients with squamous-cell carcinoma of buccal mucosa.

Serum and tumor cytosolic levels of glutathione-S-transferase (GST) and glutathione-reductase (GR) activity were determined spectrophotometrically. The levels were correlated with clinicopathological criteria and a tobacco-associated protein band (T band) found in serum. The results showed significantly decreased mean serum GST levels (p < 0.02) in cancer patients as compared with controls. However, mean serum GR levels were significantly higher in patients than in controls (p < 0.01). T-band-positive patients showed low GST and low GR activity as compared with T-band-negative patients. Tumor cytosolic-enzyme levels of GST and GR activity were significantly higher (p < 0.0003 and p < 0.0001, respectively) than in corresponding adjacent noncancerous mucosa. Tumour cytosolic GST and GR activity showed significant association with clinicopathologic criteria, e.g., stage, histologic grade and nodal involvement. T-band-negative patients showed significantly higher levels of GST (p < 0.0001) than did T-band-positive patients. Low levels of cytosolic GST may be associated with increased susceptibility towards carcinogen-induced damage. The results suggest that the presence of T band in the sera may be associated with a high-risk phenotype due to decreased detoxification ability.

Detoxification Strategies of Two Types of Spiders Revealed by Cypermethrin Application

In order to compare the detoxification capacities of two species of spiders, Linyphia triangularis and Pardosa prativaga were exposed to a commonly used pesticide, cypermethrin (a chlorinated pyrethroid). Two detoxification enzyme systems — glutathione S-transferase (GST) and glutathione peroxidase (GSH-Px) — were assayed as biomarkers. The two species of spiders have different life-styles and eat different food, and in our experiment were at different stages of their life-cycle. Therefore, differences in detoxification strategies could be expected. From our results, we suggest two different strategies. L. triangularis had a generally high basal level of GST, which could be further induced by exposure to cypermethrin. The basal activity of GSH-Px was relatively low, and no response to toxic exposure could be traced. Thus, this enzyme plays only a minor role in the detoxification process of cypermethrin in L. triangularis. In P. prativaga, a low basal GST activity was found. However, the basal level of GSH-Px was comparable to that of L. triangularis. A significant rise in GSH-Px activity (with t-butyl-hydroxyperoxide as substrate) was apparent 12 hours after exposure. This may indicate that P450 enzyme systems are involved in the cypermethrin metabolising process in P. prativaga. In addition, GSH-Px activity (with H2O2as substrate) could be traced in P. prativaga but not in L. triangularis, indicating that a true peroxidase system is active in P. prativaga.

Glutathione S-transferase activity in epithelial ovarian cancer: Association with response to chemotherapy and disease outcome

Conflicting data have been reported about the association between glutathione S-transferase (GST), a family of proteins implicated in detoxification of cytotoxic drugs in human ovarian in vitro models, and response to chemotherapy and prognosis in ovarian cancer patients. The aim of this study was to analyze the possible clinical role of GST activity in a large series of primary ovarian cancer patients. The study included a large series of primary untreated ovarian cancer patients who underwent cytoreductive surgery and chemotherapy and who were followed up in a single institution. GST activity levels were assessed in tumor extracts by using a biochemical assay. A cut-off of 250 units of enzymatic activity was chosen according to the receiver operating characteristics (ROC) curve. GST activity levels were distributed in an asymmetrical manner (median: 266 units; range: 4-918 units) and did not seem to be associated with stage, histopathological grading, ascites, or residual tumor after surgery. Higher GST activity levels were found in patients who responded to chemotherapy (median: 298 units, range: 50-691) than in those who responded only partially (median: 227 units, range: 19-747) or not at all to chemotherapy (median: 246 units, range: 4-811) (H = 7.02, P = 0.029). Moreover, the percentage of cases with > 250 units was significantly higher among complete responders (66%) than partial responders (37%) or non-responders (48%) (chi 2 = 7.32; P = 0.025). When multivariate analysis, including clinico-pathological parameters and GST activity status as predictors of response to chemotherapy, was carried out, residual tumor, stage and GST status retained independent predictive value. Patients with high GST activity had more favourable prognosis than those with low GST activity. The median PFS was 42 months for patients with high GST activity compared to 17 months for those with low GST activity (P = 0.037). The median overall survival was 72 months for high-GST-activity and 42 months for low-GST-activity patients (P = 0.043). Substantially similar results were obtained in the subgroup of stage II-III-IV ovarian cancer patients. Multivariate analysis including the clinico-pathological parameters and GST activity status was performed in stage III-IV ovarian cancer patients: Stage IV disease, residual tumor > 2 cm, the presence of ascites and low GST activity status retained independent negative prognostic roles. A direct association between high GST activity and a better clinical outcome in terms of response to chemotherapy and survival has been observed in a large series of primary untreated ovarian cancer patients. These results, which are contrary to the expectations raised by in vitro studies, emphasize the need for caution when translating in vitro-generated hypotheses to the clinical setting.

Octopus S-crystallins with endogenous glutathione S-transferase (GST) activity: sequence comparison and evolutionary relationships with authentic GST enzymes

S-Crystallin is a major protein present in the lenses of cephalopods (octopus and squid). To facilitate the cloning of this crystallin gene, cDNA was constructed from the poly(A)+ mRNA of octopus lenses, and amplified by PCR for nucleotide sequencing. Sequencing of 10 of 15 positive clones coding for this crystallin revealed three distinct S-crystallin isoforms with 61-64% identity in nucleotide sequences and 42-58% similarity in amino acid sequences when compared with homologous crystallins in squid lenses. These charge-isomeric crystallins also show between 26 and 33% amino acid sequence identity to four major classes of glutathione S-transferase (GST), a major detoxification enzyme present in most mammalian tissues. For further analysis, expression of one of the S-crystallin cDNAs was carried out in the bacterial expression system pQE-30, and the S-crystallin protein produced in Escherichia coli was purified to homogeneity to determine the enzymic properties. We found that the expressed octopus S-crystallin possessed much lower GST activity than the authentic GSTs from other tissues. Sequence comparison and construction of phylogenetic trees for S-crystallins from squid and octopus lenses and various classes of GSTs revealed that S-crystallins represent a multigene family which is structurally related to Alpha-class GSTs and probably derived from the ancestral GST by gene duplication and subsequent multiple mutational substitutions.

Erythrocyte metabolism in the Koala, the common brushtail possum and the whiptail wallaby

Erythrocyte metabolism was studied in the koala (Phascolarctos cinereus), the common brushtail possum (Trichosurus vulpecula) and the whiptail wallaby (Macropus parryi). Aspects of metabolism studied were the levels of ATP, 2,3-diphosphoglycerate (2,3-DPG) and reduced glutathione (GSH), activities of erythrocyte enzymes, glycolytic rate, the rate of glutathione S-conjugate transport (GCT), susceptibility of erythrocytes to an oxidising agent and the effect of eucalyptus oil on the red cells. Some of the major findings were that compared to common brushtail possum and the whiptail wallaby, the koala red cells (a) produced significantly greater amounts of lactate; (b) had significantly lower activity of glutathione S-transferase, (c) had significantly lower rate of GCT, (d) were more susceptible to oxidant stress induced by acetylphenylhydrazine (APH) and (e) exhibited a greater degree of haemolysis when incubated with eucalyptus oil.

Levels of glycolytic enzymes and metabolites in the red blood cells of the red-legged pademelon, Thylogale stigmatica (macropodidae: marsupialia)

1. 1. Haematology, red cell enzymes and metabolites and the rates of lacate production by the red blood cells incubated with different substrates were measured in the blood from a small marsupial, the red-legged pademelon ( Thylogale stigmatica). 2. 2. In comparison with other marsupials of similar body weight, pademelon red cells have lower levels of adenosine triphosphate (ATP) and a lower activity of glutathione S-transferase. 3. 3. Red cells incubated with inosine did not produce lactate, a finding which is not uncommon in marsupials.

Glutathiones-transferase activity of leukemic cells as a prognostic factor for response to chemotherapy in acute leukemias

This paper presents an analysis of glutathione S-transferase (GST) activity of leukemic cells in 30 patients with acute leukemias and its predictive value for therapy. Blast cells were isolated from peripheral blood or bone marrow before induction therapy using Ficoll density gradient. GST activity was measured according to the spectrophotometric assay based on the use of 1-chloro-2,4-dinitrobenzene as a substrate. The results did not show any significant differences between activities of the enzyme within the different leukemia types according to the French-American-British (FAB) classification. The patients who achieved complete remission demonstrated the lowest value of enzyme activity. The highest enzyme activity was observed in those patients who achieved partial remission and the non-responsive patients presented a GST value within the median of these two groups. Two categories of patients were represented within the non-responsive treatment group. One was resistant to the conventional therapy and in the other death was caused by infectious or hemorrhagic complications. The mean GST activity in these two groups of patients differ greatly. These results suggest that low GST activity of leukemic cells could be a favourable prognostic factor whereas high GST values could help to find out the group of patients who should be further analysed prior to induction therapy.

Glutathione conjugation. An enzymatic basis for atrazine resistance in corn.

The primary factor for atrazine selectivity in corn (Zea mays) is the activity of a soluble enzyme, glutathione S-transferase, which detoxifies atrazine by catalyzing the formation of an atrazine-glutathione conjugate (GS-atrazine). The nonenzymatic, benzoxazinone-catalyzed hydrolysis of atrazine to hydroxyatrazine contributed to the total resistance of corn to atrazine, but the nonenzymatic detoxication pathway does not seem to be essential for resistance. All corn lines investigated, except for susceptible GT112, rapidly detoxified atrazine by glutathione conjugation. Only GT112 had low glutathione S-transferase activity. Hydroxyatrazine was found in significant quantities only when atrazine was introduced initially into the roots. The amount of hydroxyatrazine formed was nearly equal for susceptible GT112 and most of the resistant corn lines investigated. This investigation indicates that some plants protect themselves against toxic organic halide compounds with a mechanism similar to that known to exist in animals.