fig3

Figure 3. Mechanisms of solar-induced photoaging and carcinogenesis of the skin. Solar ultraviolet B (UVB) directly mutates cellular DNA to cause photoaging and to initiate carcinogenesis. Ultraviolet A (UVA) interacts synergistically with pollutants to form DNA-adducts, initiating carcinogenesis. Both UVA and UVB generate ROS that oxidize DNA to form 8-OHdG, leading directly to photoaging and tumor initiation. ROSs further activate signal transduction of inflammatory cytokines and matrix-destructive enzymes, which exacerbate photoaging and cellular proliferation to promote carcinogenesis. Exposure to solar (and technological) VL and IR heat also induces photoaging of the skin. (Modified from Saladi et al.^[18] with consent of authors.). ROS: reactive oxygen species; 8-OHdG: 8-hydroxy deoxyguanosine; VL: visible light; IR: infrared light