Objective: Having identified TLR3 as one of the important receptors in primary gingival epithelial cells inflammation, we hypothesized that its downstream signalling may control other TLRs expression and require Myd88 for proinflammatory cytokines expression.
Method: To test this hypothesis, we utilized primary human gingival epithelial cells (HGECs) isolated from healthy young donors. These cells were stimulated with 5 µg/ml Polyinosinic:polycytidylic acid (Poly I:C). After stimulation, the mRNA was subjected to qPCR array analysis. The supernatants were used to measure ELISA for IL-6 and TNFα production. We used RNA interference of TLR2, TLR3 and Myd88 to study the effect of Poly I:C on gingival epithelial cells in Pro-inflammatory cytokine production.
Results: In this study, stimulation of human gingival epithelial cells with Poly I:C led to robust increase in pro-inflammatory cytokines and other TLRs in particular TLR2 expression. siRNA knock-down of TLR3 significantly down-regulated TLR2 and Myd88 mRNA and pro-inflammatory cytokine expression. siRNA against Myd88 down-regulated TLR2 and pro-inflammatory cytokine expression upon Poly I:C treatment.
Conclusion: We have identified a previously unknown interactive TLR3 signalling pathway underlying the importance of TLRs interplay in human gingival epithelial cells inflammation.