Effect of ascorbic acid on hydroxyl radical generation by chemical, enzymatic and cellular systems. Importance for antioxidant prevention of pulmonary emphysema.

The ability of ascorbic acid (AA) (25 to 500 microM) to increase OH production by a chemical (Fe(2+)-EDTA-H2O2), an enzymatic (xanthine-xanthine oxidase-Fe(2+)-EDTA) and a cellular system (3.10(6) human polymorphonuclear leukocytes (PMNL) or murine peritoneal macrophages (PM) activated with 7.2 ng PMA/ml) was studied. At all concentrations used AA strongly enhanced OH generation by the chemical and the enzymatic systems. However, the maximal increase of about 14-fold was found for incomplete chemical system (10 microM Fe(2+)-20 microM EDTA) and 500 microM AA. In the case of phorbol-myristate-acetate-activated-PMNL and macrophages, the moderate increase in OH formation was only caused by low AA concentrations. At 50 microM AA, the OH formation was 112 +/- 3 and 117 +/- 4% of control, respectively. Higher AA concentrations had no influence or even decreased OH formation by phagocytes. It is suggested that administration of AA will not significantly enhance OH generation from pulmonary phagocytes and could be useful for prevention of the oxidant-mediated lung injury related to inflammation.