Bacteria-derived hydrogen sulfide promotes IL-8 production from epithelial cells

Hydrogen sulfide (H₂S), a volatile sulfur compound, is implicated as a cause of inflammation, especially when it is produced by bacteria colonizing gastrointestinal organs. However, it is unclear if H₂S produced by periodontal pathogens affects the inflammatory responses mediated by oral/gingival epithelial cells. Therefore, the aims of this study were (1) to compare the in vitro production of H₂S among 14 strains of oral bacteria and (2) to evaluate the effects of H₂S on inflammatory response induced in host oral/gingival epithelial cells. Porphyromonas gingivalis (Pg) produced the most H₂S in culture, which, in turn, resulted in the promotion of proinflammatory cytokine IL-8 from both gingival and oral epithelial cells. The up-regulation of IL-8 expression was reproduced by the exogenously applied H₂S. Furthermore, the mutant strains of Pg that do not produce major soluble virulent factors, i.e. gingipains, still showed the production of H₂S, as well as the promotion of epithelial IL-8 production, which was abrogated by H₂S scavenging reagents. These results demonstrated that Pg produces a concentration of H₂S capable of up-regulating IL-8 expression induced in gingival and oral epithelial cells, revealing a possible mechanism that may promote the inflammation in periodontal disease.