The Role of Glutathione and Glutathione S-Transferases in the Metabolism of Chemical Carcinogens and Other Electrophilic Agents

Summary The sulfhydryl status of normal and tumour cells is critically important in determining their susceptibility to various cytostatic agents. As a sulfhydryl compound, mesna (sodium 2-mercaptoethanesulfonate) which is used in large doses to prevent haemorrhagic cystitis associated with certain chemotherapeutic regimens might derange cellular thiol homeostasis. In order to investigate the effects of mesna on the concentrations of thiols in plasma, cysteine, glutathione and their disulfides were measured by HPLC following the oral and intravenous administration of mesna to healthy volunteers. After 7.3 mmol mesna i.v. free cysteine rose from 8.2 (95% CI 7.0-9.4) nmol ml' to 53.6 (47.4-59.8) nmol ml-' at 5 min, most likely due to reduction of circulating cystine by the sulfhydryl drug. This initial rise was followed by a marked decrease of total cyst(e)ine in plasma from 276 (215-337) nmol ml-' to a nadir of 102 (McGown & Fox, 1986). Similarly, the sulfhydryl status of normal cells is an important determinant of their defense against the toxic effects of the same cytostatic drugs (Chasseaud, 1979). Mesna (sodium 2-mercaptoethanesulfonate) is increasingly used to prevent haemorrhagic cystitis associated with chemotherapeutic regimens containing high doses of ifosfamide and cyclophosphamide (Dechant et al., 1991). Although mesna is very polar and does not passively enter cells to a significant extent (Ormstad et al., 1983), the sulfhydryl drug could still markedly affect cellular thiol homeostasis. High concentrations of the sulfhydryl could reduce circulating cystine, thereby making more cysteine available to cells since cysteine is more readily taken up by many cell types than cystine (Issels et al., 1988). In addition, cysteine-mesna mixed disulfides have been identified in urine (Jones et al., 1985;Duran et al., 1981). Mesna might thus result in a substantial loss of cyst(e)ine. Since the effects of intravenous and oral mesna on circulating physiological thiols are not known and the mesna-induced loss of cyst(e)ine has not been quantitated, the concentrations of cysteine, glutathione and their disulfides in plasma and urine were measured following the oral and intravenous administration of mesna to healthy volunteers. Subjects and methodsThe effects of mesna (sodium-2-mercaptoethane-sulfonate) on plasma cyst(e)ine and glutathione after intravenous and oral administration were studied in eight healthy volunteers, two females and six men, 24 to 39 years of age, all within 10% of ideal body weight. Informed consent was obtained from each of the participants. The study was approved by the ethics committee of the local medical school. After an overnight fast an indwelling catheter was placed into an antecubital vein of both arms in order to obtain blood repeatedly without tourniquet. Two blood samples were obtained 10 min apart before the administration of mesna in order to determine the basal concentrations of glutathione and cyst(e)ine.Intravenous mesna was infused over 2 min at a dose of 1.2 g (7.3 mmol; AS...

mentioning

confidence: 99%

Depletion of circulating cyst(e)ine by oral and intravenous mesna

Stofer-Vogel

Cerny²,

Küpfer³

et al. 1993

“…There are therefore several similarities but also some significant differences in GST expression in solid tumours and cell lines. Whether the differences are because expression is lost during the generation of the cell lines or whether it reflects the individuality of human tumours remains to be clearly established.The glutathione S-transferases (GST) are a multigene family of dimeric proteins which play a central role in the detoxification of electrophilic xenobiotics (Chasseaud, 1979). In man, cytosolic GSTs have been divided into three major classes termed alpha (basic), mu (neutral) and pi (acidic) (Mannervik, 1985;Stockman et al, 1987).…”

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confidence: 99%

“…The glutathione S-transferases (GST) are a multigene family of dimeric proteins which play a central role in the detoxification of electrophilic xenobiotics (Chasseaud, 1979). In man, cytosolic GSTs have been divided into three major classes termed alpha (basic), mu (neutral) and pi (acidic) (Mannervik, 1985;Stockman et al, 1987).…”

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confidence: 99%

Glutathione S-transferase isoenzymes in human tumours and tumour derived cell lines

Lewis

Forrester²,

Hayes³

et al. 1989

Edinburgh, Edinburgh Royal Infirmary, Edinburgh EH3 9 YW; and 3Department of Clinical Oncology, Newcastle General Hospital, Newcastle-upon-Tyne, UK.Summary An increasing body of evidence indicates that glutathione S-transferases play a role in the intrinsic and acquired resistance of tumours to anticancer drugs. In view of the wide use of tumour cell lines to understand the factors which confer either sensitivity or resistance to chemotherapeutic agents we have determined glutathione S-transferase (GST) activity and isozyme composition in nine human cell lines. These data have been compared with the values obtained in solid tumours. In most cases overall GST activity was higher in the tumours than in the cell lines. This was most pronounced for the breast tumour samples relative to MCF7 cell line. The pi class GST subunit was present at similar concentration in the cell lines and the tumours, and in most cases was the most abundant subunit present. The alpha and mu class GST were expressed in most of the cell lines but at much lower concentration than the pi class subunit. Also considerable variability particularly in the expression of the mu subunits was observed. This was also the case for the expression of these subunits in the solid tumour samples. The levels of these GSTs (when expressed) in the solid tumours was invariably higher than that observed in the cell lines. There are therefore several similarities but also some significant differences in GST expression in solid tumours and cell lines. Whether the differences are because expression is lost during the generation of the cell lines or whether it reflects the individuality of human tumours remains to be clearly established.The glutathione S-transferases (GST) are a multigene family of dimeric proteins which play a central role in the detoxification of electrophilic xenobiotics (Chasseaud, 1979). In man, cytosolic GSTs have been divided into three major classes termed alpha (basic), mu (neutral) and pi (acidic) (Mannervik, 1985;Stockman et al., 1987). Proteins within these groups have marked differences in their substrate specificity. There is a growing body of evidence which indicates that GST play an important role in both carcinogenesis and drug resistance. For example, certain compounds which inhibit chemical carcinogenesis are often inducers of the GST in the target tissue (Benson et al., 1978;Benson & Barretto, 1985). These proteins are also overexpressed in preneoplastic lesions (Kitahara et al., 1984;Pickett et al., 1984; Buchmann et al., 1985) and, in addition, have been demonstrated to be increased in both normal and tumour cells exposed to cytotoxic drugs (Adams et al., 1985;Wang & Tew, 1985;Carmichael et al., 1986;Batist et al., 1986;Evans et al., 1987;Robson et al., 1987;Wolf et al., 1987a;.It is likely that glutathione S-transferase levels and isoenzyme composition will play a role in both the intrinsic and acquired resistance to cancer chemotherapy (McGowan & Fox, 1986;Wolf et al., 1987b;Buller et al., 1987;Lewis et al., 1988a). Surpris...

“…GSH has a role in the detoxification of drugs and carcinogens, protection of cells from free radical damage and reactive oxygen compounds, participates in protein and DNA synthesis and in the regulation of enzyme activity (Meister & Anderson, 1983;Orrenius & Moldeus, 1984;Chasseaud, 1979). Altered levels of GSH are frequently observed in experimental animal neoplasia (Roomi et al, 1985, Fiala et al., 1976 but GSH levels in human neoplasia have been reported only for carcinomas of the stomach and colon (Siegers et al, 1983;Siegers et al, 1984).…”

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confidence: 99%

Glutathione localisation in benign and malignant human breast lesions

Murray¹,

Burke²,

Ewen³

1987

Summary Reduced glutathione (GSH) has been demonstrated in benign and malignant human breast lesions using a newly.developed histofluorescence technique. GSH was present in every lesion and in each case was localised to the epithelium. A semi-quantitative assessment revealed a moderate amount of GSH in normal epithelium and fibroadenoma and a high level in apocrine metaplasia, epitheliosis and intraduct carcinoma. Invasive ductal carcinoma contained a variable amount of GSH. Correlation between fluorescence intensity and histological grade of ductal carcinomas was almost statistically significant but a relationship to oestrogen receptor status was not detected. The rapid assessment of GSH in breast cancer may aid in the selection of optimum chemotherapeutic regimens.Reduced glutathione (GSH) is a thiol containing tripeptide which is involved in a variety of cellular functions. GSH has a role in the detoxification of drugs and carcinogens, protection of cells from free radical damage and reactive oxygen compounds, participates in protein and DNA synthesis and in the regulation of enzyme activity (Meister & Anderson, 1983;Orrenius & Moldeus, 1984;Chasseaud, 1979). Altered levels of GSH are frequently observed in experimental animal neoplasia (Roomi et al., 1985, Fiala et al., 1976 but GSH levels in human neoplasia have been reported only for carcinomas of the stomach and colon (Siegers et al., 1983;Siegers et al., 1984). GSH in human breast tissue has not been investigated previously, although GSH-associated enzymes have been studied both biochemically (Di Ilio et al., 1985) and histochemically (Levine et al., 1983;Bard et al., 1986).Tumour GSH appears to be an important factor in determining the effectiveness of a variety of anti-cancer chemotherapeutic drugs, in general a low level of GSH being associated with increased chemotherapeutic efficiency (Arrick & Nathan, 1984;Romine and Kessel, 1986;Crook et al., 1986).We have studied the localisation and amount of GSH in normal and pathological human breast tissue using our recently developed specific histofluorescence method for GSH (Murray et al., 1986 (dichroic mirror) for epi-illumination (set at position 1, 50% transmission at 400 nm), a UGI excitation filter (band pass filter, peak transmission 365nm) and a K430 high pass emission filter (50% transmission at 430 nm).The distribution of fluorescence in each section was recorded and the intensity of GSH fluorescence assessed in semi-quantitatively on a 4-point scale (0=no fluorescence, + = slight fluorescence, + + =moderate fluorescence, + + + = bright fluorescence).Relationship between GSH concentration and histofluorescence Five known concentrations of authentic GSH (2, 4, 6, 8, 10mM) in 0.1 M formic acid were each mixed with 1% polyvinylpyrrolidone (PVP: 2 ml GSH solution plus 1 ml PVP), droplets applied to glass slides and then dried in air. The slides were then reacted with o-phthalaldehyde as described above, examined with fluorescence microscopy and the fluorescence intensity assessed semi-quantitati...