Fumaric acid dialkyl esters deprive cultured rat oligodendroglial cells of glutathione and upregulate the expression of heme oxygenase 1.

Fumaric acid esters (FAE) are currently tested in clinical studies for their potential to treat multiple sclerosis. Since cellular glutathione is involved in the detoxification of xenobiotics and has been reported to form conjugates with FAE, we have analysed the consequences of an application of various FAE to oligodendroglial cells, using the oligodendroglial cell line OLN-93 and oligodendroglia-rich secondary cultures as model systems. In a concentration of 100 microM, dimethylfumarate (DMF) and diethylfumarate (DEF), but not fumarate nor the monoalkyl esters monomethylfumarate or monoethylfumarate, almost completely deprived both OLN-93 cells and secondary oligodendroglial cultures within 60 min of their cellular glutathione. None of the FAE applied compromised cell viability, nor did a treatment with DMF or DEF cause any extracellular accumulation of glutathione. Half-maximal effects on the cellular glutathione content of OLN-93 cells after 60 min of incubation were observed in the presence of 10 microM DMF or DEF. In contrast, fumaric acid monoalkyl esters had to be applied in millimolar concentrations to decrease the cellular glutathione content significantly within 60 min. After removal of DMF, OLN-93 cells completely restored their cellular glutathione content and strongly upregulated heme oxygenase 1. Thus, alterations in glutathione and heme oxygenase metabolism have to be considered when oligodendrocytes are exposed to fumaric acid dialkyl esters.

Sustained hydrogen peroxide stress decreases lactate production by cultured astrocytes.

Oxidative stress and disrupted energy metabolism are common to many pathological conditions of the brain. Because astrocytes play an important role in the glucose metabolism of the brain, we have investigated whether sustained oxidative stress affects astroglial glucose metabolism with cultured primary rat astrocytes as a model system. Cultured astrocytes were exposed to a sustained concentration of approximately 50 muM H(2)O(2) in the presence of [U-(13)C]glucose, and cellular and extracellular contents of lactate and glucose were analysed by enzymatic assays and NMR spectroscopy. Exposure of the cells to sustained H(2)O(2) stress for up to 120 min significantly lowered the rate of lactate accumulation in the media to 61% +/- 14% of that in cultures incubated without peroxide. In addition, the ratio of lactate release to glucose consumption was lowered in peroxide-treated astrocytes to 77% +/- 13% of that in control cells, and the specific activity of glyceraldehyde-3-phosphate dehydrogenase had declined to about 10% of control cells within 90 min. In addition, the (13)C enrichment of intracellular and extracellular [(13)C]lactate was about 30% and 95%, respectively, and was not affected by the presence of peroxide, demonstrating that two metabolic pools of lactate are present in cultured astrocytes. The decreased rate of lactate production by astrocytes that have been exposed to peroxide stress is a new example of an alteration by oxidative stress of an important metabolic pathway in astrocytes. Such alterations could contribute to the pathological conditions that have been connected with oxidative stress and disrupted energy metabolism in the brain.

Structure-activity relationships for the impact of selected isothiazol-3-one biocides on glutathione metabolism and glutathione reductase of the human liver cell line Hep G2.

To investigate the toxic mode of action of isothiazol-3-one biocides the four compounds N-methylisothiazol-3-one (MIT), 5-chloro-N-methylisothiazol-3-one (CIT), N-octylisothiazol-3-one (OIT) and 4,5-dichloro-N-octylisothiazol-3-one (DCOIT) were purified and tested as single chemical entities for their effects on the human hepatoblastoma cell line Hep G2 and on isolated and cellular glutathione reductase GR). The two chlorinated substances CIT and DCOIT significantly decreased the amount of total cellular glutathione (GSx) in a dose and time dependent manner. Concomitantly, an increase in the level of oxidised glutathione (GSSG) was observed. The resulting shift in the GSH/GSSG ratio entailing the breakdown of the cellular thiol reduction potential was accompanied by necrotic morphological changes like swelling of the plasma membrane and subsequent lysis of the cells. Additionally, CIT and DCOIT were found to inhibit cellular GR in the cells in a concentration dependent manner. The T-SAR-based (thinking in terms of structure-activity relationships) comparison of the chlorine-substituted structures CIT and DCOIT with their non-chlorinated and less active analogues MIT and OIT identified the chlorine substituents and the resulting reaction mechanisms to be the key structural mediators of the observed toxic effects. Furthermore, differences in the activity of both chlorinated substances could be explained using the T-SAR approach to link the lipophilicity and the intrinsic glutathione-reactivity of the compounds to the expected target site concentrations inside the cells.