Candida albicans Sap6 Initiates Oral Mucosal Inflammation via the Protease Activated Receptor PAR2.

Candida albicans Sap6, a secreted aspartyl protease (Sap), contributes to fungal virulence in oral candidiasis. Beside its protease activity, Sap6 contains RGD (RGDRGD) motif required for its binding to host integrins. Sap6 activates immune cells to induce proinflammatory cytokines, although its ability to interact and activate human oral epithelial cells (OECs) remain unknown. Addition of purified recombinant Sap6 (rSap6) to OECs resulted in production of IL-1ß and IL-8 cytokines similar to live hyphal C. albicans. OECs exposed to rSap6 showed phosphorylation of p38 and MKP1 and expression of c-Fos not found with C. albicans Δsap6, heat-inactivated Sap6, or rSap6ΔRGD . Heat inactivated rSap6 was able to induce IL-1ß but not IL-8 in OECs, while rSap6ΔRGD induced IL-8 but not IL-1ß suggesting parallel signaling pathways. C. albicans hyphae increased surface expression of Protease Activated Receptors PAR1, PAR2 and PAR3, while rSap6 increased PAR2 expression exclusively. Pretreatment of OECs with a PAR2 antagonist blocked rSap6-induced p38 MAPK signaling and IL-8 release, while rSap6ΔRGD had reduced MKP1 signaling and IL-1ß release independent from PAR2. OECs exposed to rSap6 exhibited loss of barrier function as measured by TEER and reduction in levels of E-cadherin and occludin junctional proteins that was prevented by pretreating OECs with a PAR2 antagonist. OECs treated with PAR2 antagonist also showed reduced rSap6-mediated invasion by C. albicans cells. Thus, Sap6 may initiate OEC responses mediated both through protease activation of PAR2 and by its RGD domain. This novel role of PAR2 suggests new drug targets to block C. albicans oral infection.

Dental caries and head and neck cancers.

IMPORTANCE: Dental caries is the demineralization of tooth structures by lactic acid from fermentation of carbohydrates by commensal gram-positive bacteria. Cariogenic bacteria have been shown to elicit a potent Th1 cytokine polarization and a cell-mediated immune response. OBJECTIVE: To test the association between dental caries and head and neck squamous cell carcinoma (HNSCC). DESIGN, SETTING, AND PARTICIPANTS: Case-control study in a comprehensive cancer center including all patients with newly diagnosed primary HNSCC between 1999 and 2007 as cases and all patients without a cancer diagnosis as controls. Those with a history of cancer, dysplasia, or immunodeficiency or who were younger than 21 years were excluded. EXPOSURES: Dental caries, fillings, crowns, and endodontic treatments, measured by the number of affected teeth; missing teeth. We also computed an index variable: decayed, missing, and filled teeth (DMFT). MAIN OUTCOMES AND MEASURES: Incident HNSCC. RESULTS: We included 620 participants (399 cases and 221 controls). Cases had a significantly lower mean (SD) number of teeth with caries (1.58 [2.52] vs 2.04 [2.15]; P = .03), crowns (1.27 [2.65] vs 2.10 [3.57]; P = .01), endodontic treatments (0.56 [1.24] vs 1.01 [2.04]; P = .01), and fillings (5.39 [4.31] vs 6.17 [4.51]; P = .04) but more missing teeth (13.71 [10.27] vs 8.50 [8.32]; P < .001) than controls. There was no significant difference in mean DMFT. After adjustment for age at diagnosis, sex, marital status, smoking status, and alcohol use, those in the upper tertiles of caries (odds ratio [OR], 0.32 [95% CI, 0.19-0.55]; P for trend = .001), crowns (OR, 0.46 [95% CI, 0.26-0.84]; P for trend = .03), and endodontic treatments (OR, 0.55 [95% CI, 0.30-1.01]; P for trend = .15) were less likely to have HNSCC than those in the lower tertiles. Missing teeth was no longer associated with HNSCC after adjustment for confounding. CONCLUSIONS AND RELEVANCE: There is an inverse association between HNSCC and dental caries. This study provides insights for future studies to assess potential beneficial effects of lactic acid bacteria and the associated immune response on HNSCC.

Stress-induced susceptibility to bacterial infection during cutaneous wound healing.

Psychological stress delays wound healing and decreases immune/inflammatory responses required for bacterial clearance. To determine if stress increases the susceptibility to wound infection, female SKH-1 mice were subjected to restraint stress (RST) beginning 3 days prior to the placement of cutaneous wounds. Viable bacteria were quantified from harvested wounds. RST delayed healing by 30% and caused a 2- to 5-log increase in opportunistic bacteria (e.g., Staphylococcus aureus) when compared to wounds from control animals (p <.05). By day 7, 85.4% of the wounds from RST mice had bacterial counts predictive of infection compared to 27.4% from control mice (p <.001). To assess the role of RST-induced glucocorticoids in bacterial clearance, mice were treated with the glucocorticoid receptor antagonist RU486. RU486 reduced opportunistic bacteria by nearly 1 log in wounds from RST mice (p <.05). Thus, stress impairs bacterial clearance during wound healing, resulting in a significant increase in the incidence of opportunistic infection.