(a)
(b)
Figure 2: Effect of different concentrations of H2O2 and RA on HaCaT cell viability. HaCaT cells were treated with (a) different concentrations (50–500 μM) of H2O2 for 24 hours and (b) different concentrations (0.05–0.5 mg/mL) of RA and H2O2 (100–200 μM) for 24 hours. Cell viability was assessed using the MTT method. Data are presented as means of the percentage of the untreated control cells ± SE ().