Nrf2-targeted antioxidant biomarkers in Nrf2 WT versus KO mice after UVB exposure. Nrf2 WT and KO mice were irradiated with a single dose of UVB (300 mJ/cm2). Expression of the Nrf2-regulated antioxidant protein HO-1 was measured in the skin. β-Actin served as the endogenous housekeeping protein. Protein samples (50 μg) were subjected to western blotting, and the relative intensity was calculated by dividing the intensity of the protein band by that of the control sample on the same blot and then normalizing against the intensity of β-actin on the same membrane. After UVB irradiation, HO-1 expression was increased in WT mice but increased in much lesser extent in KO mice.