Method: Human oral keratinocytes (TERT-OKF6 cell lines) were grown to near-confluence in smoke-conditioned (0.2%, 0.5%, 1%, 2% or 5% concentration) or normal media and challenged with commensal or pathogenic biofilms grown under tobacco smoke-conditioned or normal media in a 1:100 multiplicity of infection. Supernatant was collected at 2,4,6 and 8 hours and the levels of 27 cytokines, chemokines and growth factors analyzed by multiplexed bead-based flow cytometry. Cytokines levels were compared between groups and across time-points using parametric tests.
Result: Both pathogenic and commensal biofilms elicited a time-dependent and concentration immune response from the epithelial cells (p<0.05, repeated measures ANOVA) and the magnitudes of the responses were similar to those of previous investigations. Smoke-conditioned commensal biofilms elicited similar levels of IL1-ra, TNF-a, IL-6, IL-8, IL-9, IL-12, G-CSF, and VEGF responses when compared to non-conditioned controls (p>0.05, repeated measures ANOVA), however, smoke-conditioned pathogenic biofilms elicited significantly lower concentrations of IL-6, IL-8, IL-12, IL-13, TNF-a, G-CSF and VEGF and higher levels of PDGF and IL-9 after 4 hours when compared to controls (p<0.05).
Conclusion: Our results demonstrate that smoking selectively decreases the pro-inflammatory potential of pathogenic biofilms in a time and concentration dependent manner, while not modulating of the immune response to a commensal biofilm. These findings suggest a mechanism by which smoking affects host-bacterial interactions