Figure 3: Effect of phototherapy on ROS level. U937 cells were stimulated with LPS (1 μg.mL-1) and treated with phototherapy (4.5 J/cm2) during 60 seconds. One hour before the stimulation with LPS, U937 cells were pretreated with 20 mM N-acetylcysteine (NAC). Twelve hours after LPS addition, the ROS level in U937 cells was measured. Results are expressed as fluorescence units. Each bar represents mean ± S.D. of three independent experiments. Statistical differences were considered when p<0.05.