Porphyromonas gingivalis gingipain-R enhances interleukin-8 but decreases gamma interferon-inducible protein 10 production by human gingival fibroblasts in response to T-cell contact

Proteases produced by Porphyromonas gingivalis, an oral pathogen, are consi dered important virulence factors and may affect the responses of cells equ ipped with proteinase-activated receptors, The aim of this study was to inv estigate the effect of the arginine-specific cysteine protease gingipain-R produced by P, gingivalis on chemokine production by human gingival fibrobl asts (HGF) and the effect of gingipain-R treatment on the subsequent contac t-dependent activation of HGF by T cells. HGF incubated in the presence of purified 47-kDa gingipain-R showed increased levels of interleukin-8 (IL-8) mRNA, Cyclooxygenase-2 (COX-2) mRNA was also induced, Further exposure of HGF to activated T cells resulted in the dose- and time-dependent enhanceme nt of IL-8 transcription and release. T-cell membrane-bound tumor necrosis factor (TNF) was the ligand inducing IL-8 production by HGF, since TNF neut ralization abrogated HGF responses to T-cell contact. The enhanced IL-8 rel ease was due, at least in part, to prostaglandin-E, production, which was m ostly blocked by indomethacin. Gingipain-R proteolytic activity was require d since heat inactivation, specific synthetic protease inhibitors, and the natural substrate competitor histatin 5 abrogated its effects. The enhanced production of IL-8 in response to T-cell contact was specific since monocy te chemotactic protein-1 (MCP-1) production was unaffected while interferon -gamma-inducible protein-10 (IP-10) was inhibited. The sum of these activit ies may result in the recruitment of differential cell types to sites of in flammation since IL-8 preferentially recruits neutrophils and IP-10 attract s activated T cells and may be relevant to the pathogenesis of periodontiti s.