Alveolar antioxidant status in patients with acute respiratory distress syndrome.

In the acutely inflamed lung, oxidant stress occurs within the alveolar compartment. Under these conditions, the regulation of low molecular weight antioxidants in the epithelial lining fluid is poorly understood. Therefore, antioxidant levels were measured in the bronchoalveolar lavage fluid (BALF) of patients with acute respiratory distress syndrome (ARDS; n=40) and in healthy volunteers (n=20). Reduced glutathione (GSH), oxidised glutathione (GSSG; enzymatic assay), retinol (vitamin A), alpha-tocopherol (vitamin E), ascorbic acid (vitamin C), uric acid (all by HPLC), plasmalogens (1-alkenyl-2-acyl phospholipids), polyunsaturated fatty acids (PUFA; both by gas-liquid chromatography), and F2-isoprostanes (ELISA) were quantified. All values are expressed as concentrations in cell-depleted BALF. GSSG (ARDS: 0.13+/-0.02 microM; control: 0.03+/-0.01 microM; mean+/-sem) and F2-isoprostanes (ARDS: 78+/-10 pM; control: 26+/-5 pM) were increased in ARDS, thus indicating oxidant stress. GSH levels in patients did not change significantly, whereas concentrations of vitamins A and C, vitamin E (ARDS: 77+/-15 nM; control: 26+/-3 nM) and uric acid (ARDS: 11.8+/-2.2 microM; control: 0.7+/-0.0 microM) were significantly elevated in ARDS. PUFA of total lipids, which may act as sacrificial antioxidants, increased by a factor of approximately 3 in patients, but plasmalogens showed a significant decrease. In conclusion, low molecular weight antioxidants are elevated in the alveolar compartment of patients with acute respiratory distress syndrome. Further research is warranted to elucidate the molecular mechanisms underlying this finding.