CYSTEINE DEFICIENCY POTENTIATES FATTY ACID-MEDIATED OXIDATIVE STRESS IN CULTURED ENDOTHELIAL-CELLS

Cysteine deficiency may compromise the availability of cellular glutat hione (GSH) to protect vascular endothelial cells against oxidative st ress. To test this hypothesis, the impact of different concentrations of cysteine, a limiting precursor in glutathione synthesis, on cellula r GSH levels was determined. Experiments were conducted using a porcin e endothelial cell model system modified to allow intervention in amin o acid levels. A 24-h exposure to cysteine-deficient medium (13 mg/L) resulted in decreased cellular GSH levels. Furthermore, metabolic rela tionships of cysteine deficiency and oxidative stress were studied by exposing endothelial cells to 90 mu M 18-carbon fatty acids differing in degree of unsaturation for 6 or 24 hours. Cellular GSH content was decreased as a result of fatty acid exposure in both cysteine adequate and cysteine deficient cultures. The most marked decrease in GSH leve ls was observed in cells treated with linoleic acid (18:2) for 24 hour s under cysteine-deficient conditions. Additional treatment with vitam in E did not prevent the decrease in GSH in 18:2-treated, cysteine def icient, cell cultures. Exposing endothelial cells to fatty acids for 6 h in cysteine deficient conditions contributed to an increase in conj ugated diene formation, an indication of enhanced oxidative stress. Th ese data suggest that GSH plays an essential role in the protection of endothelial cells against oxidative stress. The present results also indicate the importance of cysteine as a critical amino acid to mainta in adequate levels of GSH in cultured endothelial cells.