Ultraviolet B radiation and reactive oxygen species modulate interleukin-31 expression in T lymphocytes, monocytes and dendritic cells

BACKGROUND: Interleukin (IL)-31 is a novel Th2 T-cell cytokine that induces pruritus and dermatitis in transgenic mice. While enhanced mRNA expression of this cytokine is detected in skin samples of inflammatory skin diseases, the regulation of IL-31 expression is poorly understood. OBJECTIVES: To assess the effects of ultraviolet (UV) B radiation and H₂O₂ on IL-31 mRNA and protein expression in skin and different peripheral blood mononuclear cells (PBMCs). METHODS: The effects of UVB radiation and H₂O₂, as a prototypic reactive oxygen species, on IL-31 mRNA and protein expression were analysed in various inflammation-related cells and murine skin tissue. RESULTSTreatment of cells with UVB radiation and H₂ O₂ strongly induced IL-31 mRNA and protein expression in human PBMCs and in the skin of SKH-1 mice. Following exposure to UVB or H₂O₂, we observed increased expression of IL-31 mRNA in T cells, monocytes, macrophages, and immature and especially mature dendritic cells. H₂O₂ treatment but not UVB radiation led to a moderate upregulation of IL-31 mRNA expression in epidermal keratinocytes and dermal fibroblasts. Pretreatment of T lymphocytes with the MAPK p38 inhibitor SB203580 or the MEK1 inhibitor U0126 reduced the stimulatory effect of H₂O₂. These experiments suggest that p38 is involved in the regulation of IL-31 expression in human skin. CONCLUSIONS: Our studies reveal that UVB and reactive oxygen species stimulate the expression of IL-31 in PBMCs and skin, especially in T cells, monocytes and monocyte-derived dendritic cells.