Fig. 4. Effect of NAC or sulforaphane on reactive oxygen species generation by carbon black N990. A-10 cells were pretreated with 100 μM NAC or 10 ìM sulforaphane for 1 hr and exposed to 100 μg/ml carbon black N990 for additional 3 hrs. After treatment, cells were washed with PBS and loaded with DCF-DA (2 μM). Then, images were immediately obtained by fluorescence microscope. (A) Images of DCF loaded cells. a: untreated control, b: N990-treated cells, c: cells treated with NAC and N990, d: cells treated with sulforaphane and N990. Scale bar = 30 μm. (B) Intensity of fluorescence in each pixel was measured and presented as mean ± SE. ^*P< 0.05 versus carbon black N990-alone treated cells. Sul, sulforaphane.