P.gingivalis HtpG induces IL-8 in Monocytic and Microvascular Endothelial Cells

IL-8 is a member of the C-X-C family of chemokines that has a diverse spectrum of biological activities including T cell, neutrophil and basophil chemotactic properties. In the course of inflammation, IL-8 attracts and activates leukocytes at the site of infection leading to leukocyte infiltration, which may subsequently culminate into tissue damage. Some bacterial chaperones can elicit a strong pro-inflammatory response in cells of the innate immune system. Objectives: To determine if Porphyromonas gingivalis chaperones induce production of IL-8 from monocytic and endothelial cells. Methods: Whole cells or recombinant P.ginigvalis HtpG (an HSP90 homologue) protein and was produced and used to stimulate monocytes (THP-1) and Human Microvascular Vein Endothelial Cells (HMVEC)in vitro. IL-8 gene activation was monitored by mRNA analysis and cytokine production by ELISA. Results: IL-8 mRNA production was found to be induced in cultured monocytic/ HMVEC cells treated with P. gingivalis cells or rHtpG protein, as was the IL-8 protein as measured by ELISA. The production was dose-dependent. Pre-incubation of P. gingivaliscells or rHtpG preparations with anti-HtpG antibody significantly inhibited IL-8 production from HtpG challenged monocytic/HMVEC cells. A HtpG knockout mutant also induced less IL-8 mRNA and protein when used to challenge the same cells. Conclusions: These results suggest that P. gingivalis HtpG is closely associated with IL-8 production in both monocytic and HMVEC cells and might be involved in IL-8 mediated immunopathogenesis in a number of infections. Supported by NIH-DE11117.