Figure 3.

Ultraviolet radiation (UVR), pollutants, and chemicals can activate surface receptors either directly or indirectly by activating reactive oxygen species (ROS). Thus, signaling pathways are activated, resulting in protein damage, cell apoptosis, DNA modification, lipid peroxidation, and production of proinflammatory mediators. UVR: ultraviolet radiation; NF-κβ: nuclear factor kappa-B; AP-1: activator protein-1; IL-1R: interleukin-1 receptor; TNFR: tumor necrosis factor receptor; JAK-STAT: Janus kinase-signal transducer and activator of transcription; IL-6R: interleukin-6 receptor; MAPK: mitogen-activated protein kinase; EGFR: epidermal growth factor receptor; PGE2: Prostaglandin E2. Yellow, blue and black arrows indicate direction.