The UV response of the skin: A review of the MAPK, NFkB and TNFa signal transduction pathways

The sun emits different types of ultraviolet (UV) light. Our skin is a natural target of UV radiation which is involved in vitamin D3 production in our body. UV radiation at high doses is an environmental carcinogen which can elicit skin damage as well as inducing skin cancer. It can mediate inflammatory and immunological reactions through activation of receptors, DNA/RNA damage and production of reactive oxygen species. It is also involved in the release of pro-inflammatory cytokines, of which TNFa has been implicated in tumorigenic activities. In order to mediate its effects, UV radiation is known to activate multiple signalling cascades such as the p38 MAPK, Jun N-terminal kinase, extracellular signal-regulated kinase 1/2 and NFjB pathways in skin cells. The role each of these pathways plays in mediating the release of cytokines such as TNFa remains to be fully characterized. Once the function of these pathways is known, this information may provide for the formulation of therapy which will prevent the release of immunosuppressive cytokines resulting in a reduction in skin cancer formation.