IL-1a and KGF differentially regulate antimicrobial peptide expression in keratinocytes

Objectives: Epithelial cells express antimicrobial peptides, which contribute to host defense through the innate immune system. Interleukin1-a (IL-1a), an autonomous cytokine, regulates keratinocyte differentiation and b-defensin expression in keratinocytes, and also induces the expression of keratinocyte growth factor (KGF) in fibroblasts. KGF stimulates the growth and differentiation of keratinocytes. We found that IL-1a up-regulated the expression of calprotectin, an antimicrobial peptide (AMP). In the present study, we investigated the effect of IL-1a and KGF on the expression of several AMPs in human keratinocytes, and the regulatory mechanism of calprotectin expression by IL-1a and KGF. Methods: The immortalized human keratinocyte cell line (HaCaT) and normal human skin fibroblast (NB1RGB) were cultured at 90%-confluent conditions. Then, HaCaT were cultured with or without IL-1a or KGF for 48 h. In some experiments, HaCaT were pretreated by MAPK(p38, ERK, JNK) inhibitors and then cultured with each factor. NB1RGB were cultured with or without IL-1a for 24 h. In order to determine the expression of AMPs including S100A7, S100A8, S100A9, lipocalin (LCN2), secretory leukocyte protease inhibitor (SLPI) and b-defensin-2 (hBD-2), total RNA was extracted from the cultured cells and followed by Northern blotting and RT-PCR. Calprotectin (S100A8/S100A9) protein was determined by ELISA. Results: IL-1a increased KGF mRNA expression in fibroblasts. KGF up-regulated IL-1a mRNA expression in keratinocytes. IL-1a increased mRNA expressions of S100A7, S100A8, S100A9, LCN2, SLPI and hBD-2 in keratinocytes. On the other hand, KGF decreased the expression of S100A7, S100A8 and S100A9 mRNAs, and increased LCN2 and SLPI expression. There was no effect of KGF on hBD-2 expression. Similar effects of IL-1a and KGF on calprotectin expression were also confirmed at protein level. p38 inhibitor suppressed IL-1a-up-regulated S100A8/S100A9 expression. ERK inhibitor suppressed KGF-down-regulated S100A8/S100A9. Conclusion: These results suggest that IL-1a and KGF affect on AMP expression through a different regulation pathway in keratinocytes.