Interactions between periodontal bacteria and human oral epithelial cells:Fusobacterium nucleatum adheres to and invades epithelial cells

Bacteria are causative agents of periodontal diseases. Interactions between oral bacteria and gingival epithelial cells are essential aspects of perio dontal infections. Using an in vitro tissue culture model, a selected group of gram-negative anaerobic bacteria frequently associated Rith periodontal diseases, including Bacteroides forsythus, Campylobacter curvus, Eikenella corrodens, Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotel la intermedia, were examined for their ability to adhere to and invade prim ary cultures of human gingival epithelial cells (HGEC). The effects of thes e bacteria on the production of interleukin-8 (IL-8), a proinflammatory che mokine, were also measured. These studies provided an initial demonstration that F. nucleatum adhered to and invaded HGEC and that this was accompanie d by high levels of IL-8 secretion from the epithelial cells, The attachmen t and invasion characteristics of F. nucleatum were also tested using KB ce lls, an oral epithelial cell line, The invasion was verified by transmissio n electron microscopy and with metabolic inhibitors, Invasion appeared to o ccur via a "zipping" mechanism and required the involvement of actins, micr otubules, signal transduction, protein synthesis, and energy metabolism of the epithelial cell, as well as protein synthesis by F. nucleatum. A sponta neous mutant, lam, of F. nucleatum, isolated as defective in autoagglutinat ion, was unable to attach to or invade HGEC or KB cells, further indicating the requirement of bacterial components in these processes. Sugar inhibiti on assays indicated that lectin-like interactions were involved in the atta chment of F. nucleatum to KB cells, Investigation of these new virulence ph enotypes should improve our understanding of the role of F. nucleatum in pe riodontal infections.