Protection pathways in the skin against ultraviolet radiation (UVR). UVR induces DNA damage, which leads to activation of p53 and the formation of POMC and MC1R activation factors. MC1R action can be blocked by ASIP. Upon receptor activation of cAMP, dopachrome tautomerase (DCT) activity is upregulated and this leads to the generation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA). MC1R also activates melanosome maturation and transfer to the keratinocyte. DHICA removes reactive oxygen species (ROS), and activates catalase (CAT) and peroxisome proliferator activated receptor (PPAR) in keratinocytes. Finally, DCT provides antagonistic feedback to p53 in melanocytes .