Figure 4: Effect of phototherapy on NO level. One hour after the addition of LPS (1 μg.mL-1) in the culture medium, the U937 cells were irradiated with a fluency of 4.5 J/cm2 during 60 seconds. U937 cells were pretreated one hour before the LPS with 20 mM Nacetylcysteine (NAC). Twelvw hours after LPS, the concentrations of nitrite (4A) or nitrate (4B) were measured using the Griess reagent system. Each bar represents mean ± S.D. of three independent experiments. Statistical differences were considered when p<0.05.