Isoelectric focusing of brain cortex GSH S-transferase activity in mammals: evidence that polymorphism is absent in man

Lipid Peroxidation, Antioxidative Defense and Level of 8-hydroxy-2-deoxyguanosine in Cervical Cancer Patients

Background

Oxidative stress has been associated with cervical cancer. Our aim was to examine lipid peroxidation and the extent of oxidative stress in women diagnosed with different stages of cervical cancer in order to evaluate its potential role in the evolution of cancer.

Methods

We measured the concentration of thiobarbituric acid reactive substances, activities of antioxidative enzymes and 8-hydroxy-2-deoxyguanosine in 153 subjects. Enzymatic activity as well as TBARS concentration were measured spectrophotometrically, while 8-OHdG was determined by gas chromatography-mass spectrometry. PPatients were categorized: group II H-SIL; group III FIGO Ia-Ib and group IV FIGO IIa-IV.

Results

Our results showed highly significant increase in the level of lipid peroxidation in group IV when com pared to the control group, group II and group III (p<0.001). Activity of superoxide dismutase was also significantly higher in group IV when compared to control group (p<0.01), group II (p<0.01) and group III (p<0.05). Activity of catalase was also significantly higher in group IV when compared to control group (p<0.005), group II (p<0.005) and group III (p<0.05). Activity of glutathione-S-transferase was also significantly higher in group IV when compared to control group (p<0.05), group II (p<0.05) and group III (p<0.05). Activities of glutathione peroxidase and glutathione reductase showed no significant differences among the groups. Level of 8-OHdG was significantly higher in group IV than in the other groups (p<0.01).

Conclusions

It can be concluded that oxidative stress is possibly involved in the pathogenesis of cervical cancer, demonstrated by increased lipid peroxidation and an altered antioxidant defense system and higher levels of 8-OHdG.

Genomics and proteomics in solving brain complexity

The human brain is extraordinarily complex, composed of billions of neurons and trillions of synaptic connections. Neurons are organized into circuit assemblies that are modulated by specific interneurons and non-neuronal cells, such as glia and astrocytes. Data on human genome sequences predicts that each of these cells in the human brain has the potential of expressing ∼20 000 protein coding genes and tens of thousands of noncoding RNAs. A major challenge in neuroscience is to determine (1) how individual neurons and circuitry utilize this potential during development and maturation of the nervous system, and for higher brain functions such as cognition, and (2) how this potential is altered in neurological and psychiatric disorders. In this review, we will discuss how recent advances in next generation sequencing, proteomics and bioinformatics have transformed our understanding of gene expression and the functions of neural circuitry, memory storage, and disorders of cognition.

Reactivity of 6-halopurine analogs with glutathione as a radiotracer for assessing function of multidrug resistance-associated protein 1

6-Bromo-7-[(11)C]methylpurine is reported to react with glutathione via glutathione S-transferases in the brain and to be converted into a substrate for multidrug resistance-associated protein 1 (MRP1), an efflux pump. The compound with a rapid conversion rate allows quantitative assessment of MRP1 function, but this rate is probably susceptible to interspecies differences. Hence, for application to different species, including humans, it is necessary to adjust the conversion rate by modifying the chemical structure. We therefore designed 6-halo-9-(or 7)-[(14)C]methylpurine (halogen: F, Cl, Br, or I), and evaluated them in vitro with respect to enzymatic reactivity with glutathione using brain homogenates from the mouse, rat, or monkey. There was a marked difference in reactivity between these species. Changes in the position of the methyl group and halogen on N-methyl-6-halopurine provided various compounds possessing wide-ranging reactivity with glutathione. In conclusion, the adjustment of reactivity of 6-bromo-7-[(11)C]methylpurine may allow assessment of MRP1 function in the brain in various species.

Glutathione S-transferase π-isoform is not altered in bladder tissue from smokers

Glutathione S-transferase π (GSTπ)-isoform is a cytosolic enzyme involved in the detoxification of reactive metabolites generated from environmental pollutants and cigarette smoke. Although cigarette smoking has been implicated in the etiology of bladder cancer, no information yet exists regarding GSTπ in smokers and nonsmokers. This study was carried out to evaluate the immunohistochemical localization and to measure levels of immunoreactive GSTπ in bladder tissue from smokers and nonsmokers. Tissues from patients diagnosed with transitional cell carcinoma (TCC) were obtained from paraffin embedded blocks fixed in formalin. Bladder tissues from smokers (n = 7) and nonsmokers (n = 8), and histologically confirmed cancerous and noncancerous areas of the same patients (n = 10) were studied. The immunoreactive GSTπ was quantified by calculating its optical density with a computerized Olympus BH-2 microscope connected to a DAGE camera. Immunohistochemical staining for GSTπ appeared to be evenly distributed in the cytosol of the transitional epithelium (TE) of the noncancerous regions. In the TE from patients with advanced TCC, the staining intensity appeared to be stronger in the nuclei relative to cytoplasm, an effect that was even more pronounced in poorly differentiated cancers and in cancers with squamoid features. The immunoreactive levels of GSTπ in the superficial TE cells was approximately 1.7-fold higher compared with the rest of the TE layer (p < 0.05) in smokers and nonsmokers. No significant differences (p > 0.05) were observed between smokers and nonsmokers in either of these regions. The higher concentration of GSTπ in the TE is suggestive of the protective role of this enzyme, serving to prevent any potentially harmful xenobiotics from entering the bladder tissue. The lack of differences in the detoxifying enzymes between smokers and nonsmokers suggests that the increased susceptibility of bladder cancer in smokers is probably mediated by other mechanisms.

Biological chemistry of thiols in the vasculature and in vascular-related disease

For all their similarities in structure and common chemistry, the functions of the amino thiols in vascular biology are remarkably different. This review details the basic chemistry of sulfhydryls that dictates their functions in health and disease. In addition, the biochemistry and metabolism of each thiol are outlined, in an effort to highlight its specific contributions to the normal biology and physiology of blood vessels and to the pathogenesis of vascular-related disease.

Status of antioxidant systems in human carcinoma of uterine cervix

Lipid peroxides, glutathione content and the activities of antioxidant enzymes were estimated in patients who had carcinoma of the uterine cervix, and the values were compared with those of normal. The results showed a remarkable reduction in glutathione content and in the activities of catalase and superoxide dismutase in neoplastic tissue in stages II, III and IV (P < 0.001) whereas the activities of glutathione peroxidase and glutathione reductase were significantly lower in stage III and IV patients than that of normal controls. The tissue level of lipid peroxides and the activity of glutathione-S-transferase were found to be significantly higher than that of normals from stage II onwards. These observations suggested the impaired antioxidant status in carcinoma of the uterine cervix.

Modifications of glutathione S-transferase (GST) activity in the last period of pregnancy in rats treated with benzo(a)pyrene (BP)

Pregnant rats were treated with benzo(a)pyrene (BP) (50 mg/kg every 2 days) from day 7 of pregnancy and killed at day 16 or day 19. Km of erythrocyte glutathione S-transferase (GST) decreased during pregnancy in control rats (1.29 x 10(-3) M at day 16; 1.02 x 10(-3) M at day 19) and even more in treated rats at day 19 (0.71 x 10(-3) M). Vmax was lower in treated rats at day 19 (0.56 mumol/min/g haemoglobin) than in control rats (0.88 mumol/min/g haemoglobin) suggesting inhibition of the enzyme. Placental weight diminished in treated rats at day 19 but was not affected at day 16. Chromatofocusing of placental GST showed a single peak (pH 8.3-8.6) in control and treated rats on day 16 and an additional peak (pH 7.0-7.4) in treated rats on day 19. An increase in Km (2.84 x 10(-3) M) and Vmax (69 nmol/min/mg protein) in placental GST was observed in treated rats at day 16 (Km = 1.61 x 10(-3) M; Vmax = 43.3 nmol/min/mg protein, in control rats) followed by a decrease in these parameters in rats treated until day 19 (Km = 1.63 x 10(-3) M; Vmax = 48.7 nmol/min/mg protein). These results suggest that BP, initially, stimulates GST synthesis in placenta, followed by an inhibition of the enzyme at day 19. Fetal weight was also affected by BP treatment, especially at day 16. Km and Vmax values of fetal GST were higher in treated rats at day 16 than in control rats but these differences were not detectable at day 19. This may be explained by the more protective role of the placenta at day 19 than at day 16. Glutathione content in erythrocytes, placenta and fetus was not affected by BP.

Colloid cysts of the third ventricle: immunohistochemical evidence for nonneuroepithelial differentiation

The histogenesis of colloid cysts (CCs) of the third ventricle has been a subject of controversy. We examined, using immunohistochemical techniques, four CCs for the presence of cytokeratins (CKs), glutathione S-transferase isoenzymes (GST-pi, GST-mu), and glial fibrillary acidic protein. Antibodies to both low molecular weight CKs (anti-CK8) and to a mixture of CKs (AE1/AE3) were used. For comparison, normal fetal and adult choroid plexus, ependyma, and nasal mucosa were also examined. The epithelium lining all four CCs showed positive immunostaining for the CKs and GST-pi but not for GST-mu or glial fibrillary acidic protein. Fetal and adult nasal mucosa showed a pattern of immunohistochemical staining almost identical to that of CCs. In contrast, fetal and adult choroid plexus tissue showed positive immunostaining for GST-pi and low molecular weight CKs but not for the CK mixture (AE1/AE3). Fetal and adult ependyma were negative for both CKs and GST-pi. These results suggest that CCs differentiate along nonneural lines distinct from the neuroepithelial differentiation of the choroid plexus and ependyma.

Enhanced glutathione S-transferase (GST) activity in pregnant rats treated with benzo(a)pyrene

Administration of Benzo(a)pyrene (BP, 50 mg/kg/d) to pregnant rats significantly increased Glutathione S-transferase (GST) activity in placental tissue-extract (Vmax = 40 nmol/min/mg protein and 69 nmol/min/mg protein in controls versus treated animals respectively; P less than 0.01) and total fetal tissue-extract (Vmax = 51 nmol/min/mg protein and 82 nmol/min/mg protein in controls versus treated animals respectively; P less than 0.01) indicating an induction effect of BP on the GST system. An increase in the Km values was also observed: 1.61 x 10(-3) M and 2.84 x 10(-3) M in control versus treated placentae; 1.38 x 10(-3) M and 2.05 x 10(-3) M in control versus treated fetuses. A competitive effect on the enzyme by the BP present in the sample may also be involved. The glutathione content in both tissues did not show any changes after the treatment with BP. This increase in the GST system was not sufficient to protect the fetus. BP affected the reproductive performance of pregnant rats by significantly increasing the number of resorptions and fetal wastage, and, also, by decreasing the fetal weight.

Glutathione-S-transferase activity in human superficial transitional cell carcinoma of the bladder. Comparison with healthy controls

Glutathione-S-transferase (GST) activity and glutathione (GSH) content have been studied in human urinary bladder (UB) specimens obtained from healthy controls (HC) (n = 8) and from patients with superficial transitional cell carcinoma (TCC) (n = 9), either in TCC and in adjacent normal (ANE) tissues of the same patient. The GST activity was significantly higher in TCC in comparison with ANE (ten fold) and with HC (five fold). This activity was also significantly higher in HC than in ANE (two fold). The Km values obtained in the whole population (1.26 +/- 0.3 X 10(-3) mol/l) suggest that a unique form of isoenzyme is present in the UB epithelium and that it is the same acidic form "rho" described in erythrocytes. The GSH content was significantly higher in TCC than in ANE (2.5 fold) and also that in HC (three fold). A good correlation between GST activity and GSH content was observed in HC but not in TCC or ANE. These results demonstrate the relation between the activity of the GST system and the development of the TCC as well as its role in the cellular resistance to chemotherapy. A possible decrease of the GST activity before the development of the tumor is also discussed.

Glutathione transferases in human nasal mucosa

Glutathione transferase (GST) was investigated with 1-chloro-2,4-dinitrobenzene as substrate in tissues specimens of human nasal mucosa. The average +/- (SD) of GST activity in the cytosol was 76.8 +/- 21 nmol/min/mg with a range of 47-113. Using affinity chromatography and isoelectric focusing, the isozymes of GST from human nasal mucosa have been purified and characterized. On the criteria of isoelectric point, substrate specificities, apparent subunit molecular weight, sensitivity to characteristic inhibitors and immunological properties the major GST purified (about 85% of total activity) can be identified as class pi GST. Although a limited amount of class alpha GST was expressed by human nasal mucosa, no class mu isoenzymes was noted. In addition, we have also identified a GST subunit that cannot be related to any of three major classes of human GST.

Glutathione metabolizing enzyme activities in human thyroid

Glutathione peroxidases, glutathione transferase, glutathione reductase and gamma-glutamyl transpeptidase activities were analyzed in human thyroid tissues obtained from 17 patients undergoing resectional surgery because of a malignancy. It was deduced, from measurements of glutathione peroxidase activity with both H202 and cumene hydroperoxide, that thyroid contains only the selenium enzyme. The absence of selenium independent glutathione peroxidase activity in thyroid was confirmed with gel filtration experiments. An interindividual variation of about 28-fold was found measuring glutathione transferase activity with 1-chloro-2,4-dinitrobenzene. Subjecting a fraction of human thyroid cytosols partially purified by G-100 Sephadex column to isoelectricfocusing run, a single peak of glutathione transferase activity centered at pH 4.6 was obtained. An adequate level of glutathione reductase and gamma-glutamyl transpeptidase activities was also found in all specimens investigated.

Glutathione transferase activity during Bufo bufo development

High levels of glutathione transferase activity were measured during the development of the embryos of Bufo bufo including unfertilized eggs. After stage 4 glutathione transferase activity gradually decreased until stage 25 when the minimum was reached. No change in the number of isozymes was noted during development according to isoelectric focusing analysis performed on the cytosolic fractions of selected stages.

Isoenzyme patterns of glutathione transferases from mammalian erythrocytes

The occurrence of glutathione transferase isoenzymes in mammalian erythrocytes was investigated. The enzymes present in the hemolysates of human, horse, beef, pig, and sheep erythrocytes were purified by a column of GSH-linked epoxy-activated Sepharose 6B and subjected to an isoelectric focusing run in the pH range 3.5-10. Human and horse preparations were resolved in a single peak of activity centered at pH 4.6 and 5.9, respectively. Two forms with a maximum of activity at pH 4.9 and 7.0 and four with a maximum at pH 5.9, 6.5, 7.1, and 8.1 were separated from bovine and porcine erythrocytes. At least six forms ranging from pH 4.3 to pH 7.1 were present in the ovine preparation, the neutral contributing more than 90% of total activity. The subunit composition of affinity-bound fractions was studied by sodium dodecyl sulfate-gel electrophoresis. The analysis revealed that erythrocyte glutathione transferases are composed of subunits of identical molecular weights. This result suggests that the polymorphism existing in beef, pig, and sheep may be due to charge isomers. The erythrocyte glutathione transferases did not express selenium-independent GSH peroxidase activity.

The isolation, characterisation and kinetics of glutathione-S-transferase from human platelets

Glutathione S-transferase activity from human platelets was purified to homogeneity by affinity chromatography. The purified enzyme was found to be the acidic form and its molecular and catalytic properties were identical to acidic glutathione S-transferases purified from other human tissues. The purified platelet enzyme had no peroxidase activity and did not protect microsomes against peroxidation.