Possible Role of Gingival Epithelial Cells in Host Defense Mechanism of Periodontal Disease Progression

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The purpose of the present research project was to detect the expression of secretory leukocyte protease inhibitor (SLPI) and IL-1 receptor antagonist (IL-1ra) in gingival epithelial cells and to clarify the possible relationship between SLPI in gingival crevicular fluid (GCF) and the periodontal clinical parameters.SLPI was immunocytochemically detected on frozen-sectioned gingival epithelium and expressed on the surface and inside of cultured gingival keratinocytes from healthy gingiva. The levels of SLPI and α1-protease inhibitor (α1-PI) and neutrophil elastase (NE) activity in GCF were measured and periodontal clinical parameters were examined in fifteen adult periodontitis patients. In thirty examined sites, significantly higher amounts of SLPI, α1-PI, NE and GCF were consistently obtained in samples from periodontitis sites than in samples from healthy sites. SLPI, α1-PI and NE were found to correlate with probing depth. NE andα1-PI were significantly correlated with increasing c … More linical attachment loss. These results suggested that SLPI andα1-PI may be related to the inflammation in periodontitis sites.To clarify the expression of IL-1 and IL-1ra in human gingival keratinocytes, we studied the protein production and mRNA expression of IL-1α and IL-1ra in human cultured gingival keratinocytes using enzyme-linked immunosorbent assay and reverse transcription polymerase chain reaction (RT-PCR). Furthermore, we studied immunohistochemically the presence of IL-1αand IL-1ra in the epithelium of healthy and inflamed gingiva. The level of cell-associated IL-1α was significantly increased under stimulation of TNF-α, while the level of IL- 1α in conditioned medium and the levels of IL-1ra protein were not influenced by TNF-α. IL-1α and intracellular IL-1ra mRNA transcripts were enhanced under stimulation with TNF-αby RT-PCR. Furthermore, the presence of IL-1ra, but not IL-1α, found by immunohistochemistry in the epithelium of gingiva. These results indicated that human gingival keratinocytes expressed IL-1αand IL-1ra, and may be involved in the regulation of inflammation of periodontal disease by IL-1αand IL-1ra. Less