Growth state dependent increase of glutathione by homocysteine and other thiols, and homocysteine formation in glutathione depleted mouse cell lines

Djurhuus, Rljne; Svardal, A.; Ueland, Per Magne

doi:10.1016/0006-2952(90)90046-n

Cited by 19 publications

(17 citation statements)

References 20 publications

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“…in our study would be sufficient to lower intracellular homocysteine, its translocation out of cells, and lower the concentration of homocysteine in plasma by 51% or 63% by regular metabolism. In addition, a low intracellular level of glutathione does not influence the intracellular level of homocysteine in vitro (Djurhuus et al 1990;Hultberg et al 1995). Increased intracellular level of homocysteine and increased translocation of homocysteine out of cells could therefore not account for the observed effects of BSO on the plasma homocysteine concentration in our study.…”

Section: Discussioncontrasting

confidence: 32%

Untitled

2000

Pharmacology & Toxicology

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Elevated plasma homocysteine concentration in humans is associated with increased risk of arteriosclerosis and ischaemic heart disease. We studied whether the plasma homocysteine concentration could be changed by administration of drugs that modulate the concentration of glutathione in both plasma and tissue. Male wistar rats received reduced glutathione (0.5 mmol/kg), N-acetylcysteine (0.5 mmol/kg), L-buthionine-[S,R]-sulfoximine (2 mmol/kg) or Ringer acetate intravenously. Twenty min. later an arterial blood sample was drawn for the measurement of homocysteine and other thiols in the plasma. The thiols were quantified by reversed-phase ion-pair liquid chromatography and fluorescence detection. The total homocysteine concentration in plasma of fasted rats was 6.1∫0.5 mM. Intravenous administration of reduced glutathione or N-acetylcysteine reduced the homocysteine concentration in plasma significantly by 51% to 3.0∫0.3 mM and 63% to 2.2∫0.2 mM, respectively (PϽ0.05). In contrast, L-buthionine-[S,R]-sulfoximine increased the concentration of homocysteine by 41% to 8.6∫0.6 mM (PϽ0.05). The glutathione concentration in plasma was 19.5∫1.9 mM in controls and was unchanged by N-acetylcysteine administration. Reduced glutathione increased plasma glutathione to 379.7∫22.9 mM (PϽ0.05), whereas L-buthionine-[S R]-sulfoximine lowered the plasma glutathione concentration to 5.3∫0.4 mM. Homocysteine was negatively correlated to the glutathione (rΩª0.399, PϽ0.01) and the cysteine (rΩª0.52, PϽ0.01) concentrations in plasma. Our conclusion is that modulation of the glutathione levels influences the concentration of homocysteine in plasma of rats.An elevated concentration of homocysteine in plasma constitutes an independent risk of vascular disease (Graham et al. 1997;Robinson et al. 1998). It seems clear that homocysteine damages venous and arterial endothelial cells, which is probably related to the production of hydrogen peroxide during oxidation of homocysteine to homocystine. The cellular damage can be prevented by catalase (Wilcken & Dudman 1989). Homocysteine also has mitogenic properties on vascular smooth muscle cells and reduces the cell proliferation of the endothelium (Tsai et al. 1994). However, the mechanisms by which homocysteine induces atherosclerotic disease, are not fully clarified.Factors that influence the plasma homocysteine level are therefore of interest for chemoprevention of atherosclerotic heart disease. Folic acid, vitamin B 6 and B 12 , alone or in combination, lower the plasma level of homocysteine both among patients with a pathologically high plasma homocysteine level (Lobo et al. 1999) and in persons with plasma homocysteine levels within normal range (Dierkes et al. 1998).N-acetylcysteine lowers the plasma level of homocysteine also in patients with a high level of lipoprotein (a) (Wiklund et al. 1996) and in healthy volunteers (Hultberg et al. 1994). N-Acetylcysteine is often used clinically as a safe substrate Author for correspondence: Kjell K. Øvrebø, Surgical Research Laborator...

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Section: Discussioncontrasting

confidence: 32%

Untitled

2000

Pharmacology & Toxicology

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“…These adaptations were approach (Djurhuus et al, 1990) by plotting the export rates versus cell density. This presentation was chosen in the light of the experiments depicted in Fig.…”

Section: Experimental Designmentioning

confidence: 99%

Homocysteine export from cells cultured in the presence of physiological or superfluous levels of methionine: Methionine loading of non‐transformed, transformed, proliferating, and quiescent cells in culture

Christensen

Refsum

Vintermyr

et al. 1991

Journal Cellular Physiology

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Determination of the transient increase in plasma homocysteine following administration of excess methionine is an established procedure for the diagnosis of defects in homocysteine metabolism in patients. This so-called methionine loading test has been used for 25 years, but the knowledge of the response of various cell types to excess methionine is limited. In the present paper we investigated homocysteine export from various cell types cultured in the presence of increasing concentrations (15-1,000 microM) of methionine. For comparison of homocysteine export, the export rates per million cells were plotted versus cell density for proliferating cells, and versus time for quiescent cells. The homocysteine export from growing cells was greatest during early to mid-exponential growth phase, and then decreased as a function of cell density. The export rate was higher from phytohemagglutinin-stimulated than non-stimulated lymphocytes, and higher from proliferating than from quiescent fibroblasts. The hepatocytes showed highest export rate among the cell types investigated. The enhancement of homocysteine export by excess methionine ranged from no stimulation to marked enhancement, depending on cell type investigated, and three different response patterns could be distinguished: 1) quiescent fibroblasts and growing murine lymphoma cell showed no significant increase in homocysteine export following methionine loading; export from human lymphocytes was only slightly enhanced in the presence of excess methionine; 2) the homocysteine export from proliferating hepatoma cells and benign and transformed fibroblasts was stimulated three to eightfold by increasing the methionine concentration in the medium from 15 to 1,000 microM; and 3) the response to methionine loading was particularly increased (about 15-fold) in non-transformed primary hepatocytes in stationary culture. The results outline a potentially useful procedure for the comparison of homocysteine export during cell growth in the presence of various concentrations of methionine. The results are discussed in relation to the special feature of homocysteine metabolism in various cell types and tissues including liver, and to the possible source of plasma homocysteine following methionine loading in vivo.

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“…Manganaro et al (1995) (Issels et al, 1988), OvCa cells (Isse1s and Nagele, 1990) and mouse fibroblasts (Djurhuus et al, 1990) following CSH exposure. CSH induces the synthesis of GSH by 1) forming mixed (lisulfides with extraceUu1ar cystine thereby generating the GSH precursor, cysteine and 2) promoting the transport of cysteine into ceUs where it can be utilized for de IIOVO GSH biosynthesis (Isse1s et al, 1988).…”

Section: Csh-mediated Oxidative Stressmentioning

confidence: 99%