Interleukin-8 Responses of Multi-Layer Gingival Epithelia to Subgingival Biofilms: Role of the Red Complex Species

Periodontitis is an infectious inflammatory disease that results in the destruction of the tooth-supporting (periodontal) tissues. The Gram-negative anaerobic species Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola, (also known as the red complex'' species) are highly associated with subgingival biofilms at periodontitis-affected sites. A major chemokine produced by the gingival epithelium in response to biofilm challenge, is interleukin (IL)-8. The aim of this in vitro study was to investigate the relative effect of the :red complex'' species as constituents of subgingival biofilms, on the regulation of IL-8 by gingival epithelia. Multi-layered organotypic human gingival epithelial cultures were challenged with a 10-species in vitro subgingival biofilm model, or its 7-species variant, excluding the red complex''. IL-8 gene expression and secretion analyses were performed by qPCR and ELISA, respectively. After 3 h, both biofilms up-regulated IL-8 gene expression, but the presence of the red complex'' resulted in 3-fold greater response. IL-8 secretion was also up-regulated by both biofilms, with no differences between them. After 24 h, the 10-species biofilm reduced IL-8 secretion to 50% of the control, but this was not affected when the red complex'' was absent. In conclusion, as part of biofilms, red complex'' species differentially regulate IL-8 in gingival epithelia, potentially affecting the chemotactic responses of the tissue.