上皮細胞における抗菌ペプチドの発現調節機構の解明

Epithelial cells express antimicrobial peptides (AMPs) including calprotectin (S100A8/S100A9), β-defensin and lipocalin, which contribute to a host defense reaction in the innate immune system. However, the regulation of AMP expression is not well elucidated. Interleukin1-α (IL-1α), an autonomous cytokine, regulates keratinocyte differentiation and also induces the expression of keratinocyte growth factor (KGF) in fibroblasts. It is reported that KGF stimulates the growth and differentiation of keratinocytes. I confirmed the expression of calprotectin in gingiva and skin by immunohistochemical staining, and determined the effect of IL-1α and KGF on the expression of several AMPs in human keratinocytes cell line (HaCaT) and human fibroblast cell line (NB1RGB), and then clarified the regulatory mechanism of calprotectin expression induced by IL-1α and KGF with the analyses of microarray, Northern blot, RT-PCR and Western blot. Immunohistochemical staining showed that calprotectin expressed in human normal gingiva and skin, and this expression increased in periodontitis gingivae and psoriasis skins. IL-1α increased KGF mRNA expression in NB1RGB, and KGF up-regulated IL-1α mRNA expression in HaCaT. Microarray analysis revealed that IL-1α increased some AMPs, lipocalin 2 (LCN2), S100A8, S100A9 and secretory leukocyte protease inhibitor (SLPI), showing more than 2-fold expressions in HaCaT. RT-PCR and Northern blot analysis revealed that IL-1α increased mRNA expressions of S100A7, S100A8, S100A9, LCN2, SLPI, and β-defensin 2 (hBD-2) in HaCaT. On the other hand, KGF decreased the expression of S100A7, S100A8, and S100A9, and increased LCN2 and SLPI expressions. KGF did not affect hBD-2 expression. When the inhibitors of mitogen-activated protein kinase (MAPK), including p38, c-Jun N-terminal kinase, and extracellular signal-regulated kinase (ERK) were added to HaCaT, p38 inhibitor suppressed the IL-1α-up-regulated S100A8/S100A9 expression and ERK inhibitor suppressed the KGF-down-regulated S100A8/S100A9 expression. These results indicate that some AMP expressions are regulated by IL-1α and KGF in human keratinocytes and that IL-1α up-regulates and KGF down-regulates S100A8/S100A9 genes through MAPK pathway in keratinocytes.