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

Summary 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. Results Treatment of cells with UVB radiation and H2O2 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.