ells were incubated with 150 mM H2O2. Apoptosis was detected using DeadEndTM Fluorometric TUNEL System and cells were counterstained with DAPI. The percent positive cells were detected with a fluorescent microscope and NIS-Elements software. 4, keratin-1, -10 and -14, involucrin, FOXO1, FOXO3, BID, TRADD, integrin-b1, -b3 and b6 by real-time PCR using Roche primers and probe sets. Results were normalized to a housekeeping gene, ribosomal protein L32. Statistical analysis Statistical significance was determined by one-way analysis of variance for most assays. For RNAi assays significance was determined by ANOVA with Tukey’s post-hoc test. Significant differences were established at P,0.05. The experiments were performed 3 times with similar results. Cytokine and Keratin mRNA Levels Results The barrier function of primary keratinocytes was measured 9405293 by use of fluorescent labeled dextran. The amount of dextran that crossed the gingival epithelial barrier was inversely related to the concentration of P. gingivalis in a dose-dependent manner. P. gingivalis caused a 2 to 4 fold increase in barrier breakdown. F. nucleatum caused a trend toward increased breakdown but was not statistically significant. S. gordonii did not disrupt the epithelial barrier . To P. gingivalis Modulates FOXO1 and FOXO3 determine whether this was due to proteolytic enzymes PHGEC were incubated simultaneously with P. gingivalis and leupeptin. P. gingivalis induced a 4 fold increase in loss of barrier function as measured by fluorescence intensity and half of this increase was Oleandrin site blocked by leupeptin. As noted above, F. nucleatum and S. gordonii had no effect on epithelial barrier function nor was it affected by leupeptin in the absence of P. gingivalis . The effect of bacteria on three-dimensional cultures of gingival epithelial cells was examined by assessing the degree of apoptosis that each induced. P. gingivalis and F. nucleatum both stimulated a 3 to 4 fold increase in apoptosis which was statistically significant at 56108 bacteria. S. 
gordonii had no effect on apoptosis. To determine whether gingipains played a prominent role in apoptosis, cells were co-incubated with bacteria and leupeptin. Leupeptin reduced P. gingivalis stimulated apoptosis by 20%, which was significant but had no effect on F. nucleatum stimulated apoptosis. Thus gingipains contributed but did not play a predominant role in P. gingivalis induced apoptosis of multi-layer cultures and had no effect on F. nucleatum induced apoptosis. The expression of keratin-1 and -10 reflects the level of differentiation with both increasing as differentiation occurs. mRNA levels of keratin-1 and 24637873 -10 increased 50 to 100 fold when differentiation was stimulated in PHGEC when exposed to an airliquid interface. This increase occurred within one week of culture. When undifferentiated PHGEC were challenged with P. gingivalis in the absence of an air-liquid interface a,100 fold increase in keratin-1 was stimulated. P gingivalis induced a 6 fold increase in keratin-1 and -10 mRNA levels in multi-layered, well-differentiated PGHEC. Similar results were obtained with keratin-10. In contrast, F. nucleatum and S. gordonii had little effect on expression of these keratinocyte differentiation markers . Since TLR-4 and TLR-2 are important host response genes we examined their mRNA levels as a function of differentiation status 6 P. gingivalis Modulates FOXO1 and FOXO3 . The formation of a multi-layer culture with induced keratin