Antioxidants block the effect of TCDD to increase keratinocyte differentiation. (A) CEs were isolated after treatment, control or TCDD for 72h in the presence or absence of one of the following antioxidants: DPPD (2.5µM), quercetin (10µM), or catalase (500U/ml). a indicates a significant difference between the control and TCDD-treated samples (mean [n = 4] ± SD); b indicates a significant difference between TCDD alone- and the TCDD plus antioxidant–treated samples, p < 0.05. (B) CEs were isolated after treatment, control, or TCDD for 72h in the presence or absence of one of the antioxidants, NAC (1.25mM), catalase (500U/ml), PEG-catalase (1000U/ml), or the AHR antagonist, CH223191 (1μM). a indicates a significant difference between the control and TCDD-treated samples (mean [n = 4] ± SD); b indicates a significant difference between TCDD alone- and the TCDD plus antioxidant- or antagonist-treated samples, p < 0.05.