ANTIOXIDANT ADAPTIVE RESPONSE IN HUMAN BLOOD MONONUCLEAR-CELLS EXPOSED TO UVB

Human blood mononuclear cells exposed to UVB radiation develop increas ed antioxidant enzyme activities. Catalase (5.50 +/- 0.65 pmol (mg pro tein)(-1)), CuZn-superoxide dismutase (16.7 +/- 2.1 pmol (mg protein)( -1)), Mn-superoxide dismutase (11.3 +/- 1.7 pmol (mg protein) (-1)), S e-dependent glutathione peroxidase (13.2 +/- 1.5 mU (mg protein)(-1)) and Se-independent glutathione peroxidase (3.30 +/- 0.52 mU (mg protei n)(-1)) activities increase by 1.3-1.5-fold from the control activitie s after exposure to 0.3 W m(-2) of 280-315 nm light for 15 min and a 3 h dark incubation period. DT-diaphorase activity (2.86 +/- 0.21 pmol DCPIP min(-1) (mg protein)(-1)) increases threefold from the indicated control values. In contrast, cytochrome oxidase (0.36 +/- 0.04 min(-1 ) (k') (mg protein)(-1)) and succinate dehydrogenase (3.06 +/- 0.25 mu mol DCPIP min(-1) (mg protein)(-1)) activities remain unchanged durin g the same irradiation and incubation period. The treatment of cells w ith cycloheximide prevents the response triggered by WE exposure. Thes e findings suggest that an inducible antioxidant defence mechanism ope rates on photo-oxidative stress and that both superoxide dismutase and DT-diaphorase may display a concerted antioxidant role. (C) 1997 Else vier Science S.A.