Methods: Human oral keratinocytes (TERT-OKF6 cell lines) were grown to near-confluence in cigarette smoke-conditioned or normal media and challenged with commensal or pathogenic biofilms grown under normal conditions or in media conditioned with 1% smoke in a 1:100 multiplicity of infection. Supernatant was collected at 2,4,6 and 8 hours and the levels of 27 immune mediators were analyzed by multiplexed bead-based flow cytometry. Cytokines levels were compared between groups using parametric tests.
Results: Pathogenic and commensal biofilms elicited a time-dependent immune response from the epithelial cells (p<0.05, repeated measures ANOVA). Smoke-conditioned commensal biofilms elicited similar levels of IL1-RA, TNF-α, IL-6, IL-8, IL-9, IL-12, G-CSF, and VEGF responses when compared to non-smoked controls. Smoke-conditioned pathogenic biofilms elicited significantly greater concentrations of IL-6, IL-8, IL-12, IL-13, TNF-α, G-CSF and VEGF and lower levels of PDGF and IL-9 after 4 hours when compared to controls (p<0.05). Smoke-conditioned host cells responded with lower levels of IL-6, IL-8, IL-9, IL-12 and VEGF to the commensal biofilm at all time points when compared to the controls (p<0.05, 2-sample t-test), however, there was no difference in the immune response to a pathogenic biofilm between smoke-conditioned host cells and controls.
Conclusions: Smoking increases the pro-inflammatory potential of pathogenic biofilms while promoting a suppression of the immune response to a commensal biofilm. These findings suggest a mechanism by which smoking affects subgingival host-bacterial interactions and increases susceptibility to disease.
Keywords: Biofilm, Cell culture, Epithelium/epithelial, Host-microbial interactions and Tobacco
See more of: Periodontal Research - Pathogenesis