歯肉上皮細胞におけるカルプロテクチンの発現調節

Calprotecin, a heterodimer of S100A8 and A9, is an antimicrobial protein produced by leukocytes, macrophages and epithelial cells. Although calprotectin plays an important role in innate immunity, the regulatory mechanism is unclear. Calprotectin is localized in a spinous cell layer of the gingival epithelium, hence, it is hypothesized that the calprotectin expression in keratinocytes may be related to the epithelial cell differentiation. It is reported that interleukin-1α (IL-1α) and calcium stimulate keratinocyte differentiation and that transforming growth factor-β (TGF-β) and retinoic acid (RA) suppress the differentiation. To study the regulatory mechanism of calprotectin in differentiation, the effects of IL-1α, calcium, TGF-β and RA on the expression of S100A8/A9 was investigated in cultured human gingival keratinocytes. Immunostaining of cultured cells was performed to detect the differentiation markers of epithelial cells such as cytokeratin 14 (CK14), involucrin and filaggrin. Northern blotting and ELISA were performed to detect calprotectin mRNA and proteins, respectively. Human S100A8 and S100A9 promoter was characterized by luciferase assay and electrophoretic mobility shift assay (EMSA). Immunohistochemical findings showed that involucrin and filaggrin markedly expressed in cells treated with IL-1α and calcium but rarely expressed in cells treated with TGF-β and that CK14 evenly expressed in all experimental group. From Northern blotting and ELISA analysis, mRNA expression of S100A8/A9 mRNAs and the protein levels were increased by IL-1α and calcium, whereas they were decreased by TGF-β. Addition of RA inhibited the IL-1α-induced stimulation of S100A8/A9 expression. Luciferase assay of 5'-upstream region of S100A8 in HaCaT clonal epithelial cells revealed that the -765/-722 and -256/-111 were essential to A8 promoter activity and each domain contained C/EBP (CCAAT enhancer binding protein) binding sites. In the case of S100A9, the result showed that the -188/-53 region is essential to A9 promoter activity and this domain also contained C/EBP binding sites. EMSA showed that DNA binding activity of C/EBPα were enhanced in keratinocytes by IL-1α or calcium, but suppressed by TGF-β. These results demonstrate that calprotectin expressions are related to the differentiation of keratinocytes and C/EBPα is one of the regulators of calprotectin expression in keratinocytes.

公開日:2010年1月24日で登録したコンテンツは、国立情報学研究所において電子化したものです。