Ultraviolet-induced damage in the skin and cornea: Implication for inflammatory cytokine, macrophage migration inhibitory factor

Ultraviolet (UV) irradiation represents a significant environmental and occupational hazard that can cause acute and chronic inflammatory changes in the exposed skin and cornea. The inflammatory changes of acute exposure include erythema (sunburn) of the skin and photokeratitis of the cornea. Chronic exposure to solar UV irradiation leads to photoaging, immunosuppression and ultimately carcinogenesis in the skin. After skin and cornea damage by UV radiation, these tissues are known to secrete a number of cytokines, including interleukin (IL)-1, IL-6 and tumor necrosis factor (TNF)-. Macrophage migration inhibitory factor (MIF) was originally identified as a lymphokine that concentrates macrophages at inflammatory loci, and it is a potent activator of macrophages in vivo which is considered to play an important role in cell-mediated immunity. Since the molecular cloning of MIF cDNA, MIF has been re-evaluated as a proinflammatory cytokine and pituitary derived hormone that potentiates endotoxemia. MIF is ubiquitously expressed in various tissues, including the skin and cornea. This article reviews the latest findings on the roles of MIF with regard to UV-induced damage in the skin and cornea.