Albumin-induced increase in matrix metalloproteinase (MMP)-9 involves reactive oxygen species. (a) Representative images of 5-(and-6)-carboxy-2′,7′-dichlorodihydrofluorescein diacetate (carboxy-H2DCF-DA) fluorescence alone (green) or merged with DAPI nuclear stain (blue) in astrocytes treated with BSA, PBS (inset) or BSA with polyethylene glycol–superoxide dismutase (PEG-SOD, 200U) or polyethylene glycol–catalase (PEG-CAT) or the positive control tert-butyl hydroperoxide (TBHP). Treatment with albumin induced an increase in the DCF-DA fluorescence in astrocytes that was suppressed by the presence of PEG-SOD and PEG-CAT. Bars represent 50 μm. The data represent two independent experiments, each performed in duplicate. Representative zymogram and corresponding quantification of the level of MMP-9 release by astrocytes treated with albumin in the presence (+) or absence (−) of (b) PEG-SOD and PEG-CAT, and (c) the NADPH oxidase inhibitor, diphenyleneiodonium chloride (DPI). Inhibition of albumin-induced increase in MMP-9 by antioxidant enzymes SOD and CAT and the NADPH oxidase inhibitor, DPI suggest that the increase in MMP-9 involves reactive oxygen species. Data are representative of mean ± SEM of three independent experiments. ***P < 0.001 compared with the BSA-treated group.