Role of dentilisin in Treponema denticola epithelial cell layer penetration

Treponema denticola is an oral anaerobic spirochete implicated in periodontal diseases. The chymotrypsin-like protease, dentilisin (PrtP), has been suggested to be an important virulence factor of T. denticola. In this study, we examined the role of dentilisin in T. denticola epithelial monolayer penetration by comparing the wild type and prtP mutant. Wild-type T. denticola can disrupt transepithelial resistance (TER) and substantially penetrate the HEp-2 cell layer. The prtP mutant altered the monolayer only slightly and penetrated the Hep-2 layer in very low numbers. The membrane fraction of wild-type T. denticola is able to complement the prtP mutant in monolayer penetration, while the comparable fraction from the mutant has no such effect. Immunofluorescence studies suggested that wild-type T. denticola altered the TER by likely degrading the tight junctional proteins such as ZO-1. Cytotoxicity was not a major factor in the disruption of TER. The outer membrane vesicles (OMVs) of wild-type T. denticola also disrupted epithelial barrier function and penetrated the epithelial layers. Taken together, these results suggest that T. denticola penetrates the epithelial cell monolayers by altering cellular tight junctions.