Enzymes of glutathione synthesis in patients with myeloproliferative disorders

Differences in Blood Glutathione Levels of Patients with Advanced or Localized Carcinoma

Aims and background

The increased level of blood glutathione (GSH) is an important biochemical feature in animal epithelial tumor. The aim of this study was to investigate the blood GSH concentrations in well characterized cancer patients and healthy volunteers.

Methods

Two different groups of carcinoma cases were used. The first group consisted of 15 blood samples drawn from disseminated gastric adenocarcinoma patients, and the second group comprised 15 samples obtained from localized or locally advanced skin carcinoma cases without lymph node metastasis. GSH and hemoglobin concentrations were measured by using the method of Beutler et al.

Results

The mean blood GSH in patients who had advanced malignant disease was 129.13 ± 7.49 mg/dl and in patients who had localized cancer was 96.24 ± 3.90 mg/dl. These results indicate that the blood GSH level is 31% higher in localized carcinoma cases and 78% higher in metastatic disease than those of controls. Blood GSH concentrations were expressed on the basis of blood volume and also on hemoglobin content. Similar results were calculated with either mode of expression.

Conclusion

By comparing the two groups of patients, we found that higher blood GSH concentration was correlated with metastatic growth.

Oxidative Stress and DNA Damage in Human Gastric Carcinoma: 8-Oxo-7'8-dihydro-2'-deoxyguanosine (8-oxo-dG) as a Possible Tumor Marker

We characterized the oxidative stress (OS) status by the levels of reduced/oxidized glutathione (GSH/GSSG), malondialdehyde (MDA) and the mutagenic base 8-oxo-7′8-dihydro-2′-deoxyguanosine (8-oxo-dG) in human gastric carcinoma (HGC) samples and compared the results with normal tissue from the same patients. We also analyzed 8-oxo-dG in peripheral mononuclear cells (PMNC) and urine from healthy control subjects and in affected patients in the basal state and one, three, six, nine and twelve months after tumor resection. The levels of DNA repair enzyme mRNA expression (hOGG1, RAD51, MUYTH and MTH1) were determined in tumor specimens and compared with normal mucosa. Tumor specimens exhibited increased levels of MDA and 8-oxo-dG compared with normal gastric tissue. GSH levels were also increased, while GSSG levels remained stable. DNA repair enzyme mRNA expression was induced in the tumor tissues. Levels of 8-oxo-dG were significantly elevated in both urine and PMNC of gastric cancer patients compared with healthy controls. After gastrectomy, the levels of the damaged base in urine and PMNC decreased progressively to values close to those found in the healthy population. The high levels of 8-oxo-dG in urine may be related to the increased induction of DNA repair activity in tumor tissue, and the changes observed after tumor resection support its potential use as a tumor marker.

A possible role for oxidation stress in lymphoid leukaemias and therapeutic failure

The aim of this study was to evaluate the role of oxidative stress in the pathobiology of lymphoid leukaemias and its involvement in leukaemic relapse. For this purpose the generation of peroxides by mononuclear cells, the erythrocyte activity of superoxide-dismutase (SOD) and glutathione peroxidase (GL-PX), and the plasma levels of reduced glutathione (GSH) and vitamin E (VIT E) were determined in 52 patients with two different types of lymphoid leukaemias, chronic lymphocytic leukaemia (CLL) and acute lymphoblastic leukaemia (ALL), 36 prior to chemotherapy and 16 treated patients. A decrease in SOD and GL-PX activities was observed in ALL patients prior to therapy, while a decrease in GSH and VIT E plasma levels was observed in untreated CLL, as compared to age-matched controls. An increase in peroxides formation occurred in both types of leukaemia, as compared to age-matched controls. There are significant differences for GSH, VIT E and peroxides generation between the different types of leukaemias. In relapsed ALL patients a decrease in peroxides generation was observed which may be due to the increase of the non-enzymatic defences GSH and VIT E. These data suggest the involvement of oxidative stress in acute and chronic lymphoid leukaemias and leukaemic relapse.

Blood glutathione levels in head and neck malignancies

Blood glutathione was estimated in fifty patients of head and neck cancer in the age group of 18-76 years and the results were compared with a group of normal healthy controls. Mean blood glutathione level was found to be significantly lowered in patients than the controls. Irrespective of the site, TNM classification, histopathology, and character of lesion, fall in blood glutathione was nearly same in all the patients. The mean level was significantly increased after radiotherapy when compared with the levels before radiotherapy. The decreased levels of GSH in-patients with head and neck cancer, observed in the present study, may be due to its increased utilization by the cells. The results suggest that patients with head and neck cancer have increased oxidative stress.

Antioxidant enzyme activities and the production of MDA and 8-oxo-dG in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a neoplastic disease susceptible to antioxidant enzyme alterations and oxidative stress. We have examined the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), and the oxidized/reduced glutathione (GSSG/GSH) ratio together with the levels of malondialdehyde (MDA) and 8-oxo-2'-deoxyguanosine (8-oxo-dG) in lymphocytes of CLL patients and compared them with those of normal subjects of the same age. SOD and CAT activity decreased in CLL lymphocytes while GPx activity increased. GSH content of CLL lymphocytes also increased, and GSSG concentration remained constant. Thus, a reduced GSSG/GSH ratio was obtained. The oxidation product MDA, and the damaged DNA base 8-oxo-dG were also increased in CLL. The observed changes in enzyme activities, GSSG/GSH ratio, and MDA were significantly enhanced as the duration of the disease increased in years. The results support a predominant oxidative stress status in CLL lymphocytes and emphasize the role of the examined parameters as markers of the disease evolution.

Increased glutathione in chronic lymphocytic leukemia lymphocytes

Following reports on a variety of interactions between glutathione (GSH) concentration and clinical parameters in solid tumors, a study was undertaken in order to determine the GSH intracellular content of chronic lymphocytic leukemia (CLL) lymphocytes. The results from a group of 16 patients consecutively studied indicate tht B-CLL cells have twice as much GSH as lymphocytes from normal subjects, suggesting that this measurement may be helpful in the understanding of the metabolic mechanism of the disease and the rationale of therapy.

Improved assay of the enzymes of glutathione synthesis: gamma-glutamylcysteine synthetase and glutathione synthetase

New methods for the estimation of red cell gamma-glutamylcysteine synthetase and glutathione synthetase have been developed. gamma-32P ATP is allowed to equilibrate until the gamma and beta phosphate groups are equally labelled. The amount of 32Pi released in the presence of glutamic acid and cysteine, the substrates for GC-S or in the presence of gamma-glutamylcysteine and glycine, the substrates of GSH-S, is measured. This is accomplished by extraction of the phosphomolybdate complex into isobutanol-benzene. The methods are linear with time and hemolysate concentration. Normal values are presented.

Normal glutathione content and some related enzyme activities in the fetal erythrocytes

Pure fetal blood was obtained by direct-vision fetoscopy from 66 fetuses at 17-24 weeks gestation. The concentration of GSH and the activities of the enzymes gamma-glutamylcysteine synthetase (GCS), glutathione synthetase (GS), glutathione reductase (GR) and glutathione peroxidase (GPx) were analysed by established techniques to find the normal ranges for this gestational age. The ranges were relatively narrow and could serve as reference values for the prenatal diagnosis of defects in the GSH metabolism of erythrocytes. The results were compared with those obtained from 38 normal adults and with published values on neonatal blood. In the case of GR a comparison was also made with maternal blood. In comparison with adults, fetal erythrocytes showed higher GSH concentration and GCS activity and lower GS and GPx activities. This pattern resembled that found in neonatal erythrocytes except for the GCS activity, which was higher in the fetal cells. Furthermore the differences between fetal and adult erythrocytes were more pronounced than those between neonatal and adult cells. The GR activity of fetal erythrocytes was also higher than that of either normal adult or maternal blood. This difference, however, was reduced to an insignificant level when the enzyme was activated in vitro by flavin adenine dinucleotide (FAD) because of a relatively low per cent activation of the GR in the fetal erythrocytes.

A reappraisal of the gamma-glutamylcysteine synthetase activity in haemolysates from normal erythrocytes by two different methods

gamma-Glutamylcysteine synthetase catalyses the combination of L-glutamate and L-cysteine to form gamma-glutamylcysteine with a stoichiometric conversion of ATP to ADP and inorganic phosphate (Pi). During the estimation of this enzyme in haemolysates from normal erythrocytes it was found that the Pi released was more than the amount of gamma-glutamylcysteine synthesised. Furthermore, the activity estimated by analysing either product was higher than the corresponding values reported in the literature. An investigation into these discrepancies resulted in improvements of the assay methods which produced two substantially different normal ranges for the gamma-glutamylcysteine synthetase activity in haemolysates: one derived from the Pi released and the other from the gamma-glutamylcysteine synthesised during the enzymatic reaction.

Clinical significance of the glutathione-conjugating system

Glutathione displays important functions in living cells of many species, human included. Apart from its direct antioxidative activity, which supports the maintenance of the reduced state of proteinthiols, and its possible role in amino acid transport across membranes, it appears to exert several detoxification functions. These include the conjugation of electrophilic compounds and the reduction of H2O2 and lipid hydroperoxides. Disorders in GSH synthesis and metabolism are known and produce hemolysis in the first place. Little data exist concerning GSH and the GSH-dependent enzymes involved in its various functions in normal and diseased human tissues. The aim of this review is to stimulate research in this area.

Red cell pyrimidine 5'-nucleotidase and glutathione in myeloproliferative and lymphoproliferative disorders

Red cell reduced glutatione (GSH) and pyrimidine 5'-nucleotidase (Pry 5'-NT) were measured in a variety of myeloproliferative and lymphoproliferative disorders. Raised levels of GSH were found in chronic lymphocytic leukaemia, Hodgkin's disease, non-Hodgkin's lymphoma, Waldenstrom's macroglobulinaemia and myeloma. Decreased activity of Pyr 5'-NT was found in acute myeloblastic leukaemia, acute lymphoblastic leukaemia, chronic granulocytic leukaemia, chronic lymphocytic leukaemia, Hodgkin's disease and non-Hodgkin's lymphoma. There was no correlation between the raised GSH levels and decrease Pry 5'-NT levels.

Haemolytic anaemia with hereditary pyruvate kinase instability developing acute leukaemia

The case of a 27-year-old woman with pancytopenia, revealing acute monocytic leukaemia and haemolytic anaemia, is described in detail. The underlying cause for the red cell destruction was found to be a pyruvate kinase (PK) instability. Further investigation into three generations of her family (n = 12) disclosed a hereditary PK instability. This was proven by performing biochemical studies to elucidate mutants representing a structurally defective enzyme. Since conversions of pancytopenia with acquired red cell enzyme deficiency into leukaemia have been described, our observation emphasizes that hereditary red cell enzymopathy might also be associated with adult acute leukaemia.

Red cell enzymes

As compared to other cells of the body, the mammalian red cell has one of the simplest structural organizations. As a result, this cell has been extensively used in studies involving the structure, function, and integrity of cell membranes as well as cytoplasmic events. Additionally, the metabolic activities of the red blood cell are also relatively simple. During the past quarter century or so, an ocean of knowledge has been gathered on various aspects of red cell metabolism and function. The fields of enzymes, hemoglobin, membrane, and metabolic products comprise the major portion of this knowledge. These advances have made valuable contributions to biochemistry and medicine. Despite these favorable aspects of this simple, anucleated cell, it must be conceded that our knowledge about the red cell is far from complete. We are still in the dark concerning the mechanism involved in several aspects of its membrane, hemoglobin, enzymes, and a large number of other constituents. For example, a large number of enzymes with known catalytic activity but with unknown function have eluded investigators despite active pursuit. This review will be a consolidation of our present knowledge of human red cell enzymes, with particular reference to their usefulness in the diagnosis and therapy of disease. Owing to the multitude of publications by prominent investigators on each of the approximately 50 enzymes discussed in this review, it was impossible to cite a majority of them.