Expression of IL-8 by cells of the odontoblast layer in vitro

Due to their peripheral location in the dental pulp and their cellular exte nsion into dentin, odontoblasts are the first pulpal cells to encounter den tal pathogens. The association of odontoblasts with immunoglobulins and den dritic cells during microbial invasion of dentin implies that these cells m ay possess a role in the innate and adaptive pulpal immune responses, howev er this has not been examined. A pivotal step in the innate immune response is the detection of foreign antigen and the recruitment of immune effector cells to the area. IL-8 is a potent chemotactic cytokine that plays an imp ortant role in the inflammatory response. The purpose of this study was to determine if odontoblasts are capable of expressing the pro-inflammatory ch emokine IL-8. Human odontoblasts from intact, noncarious third molars were maintained in culture and exposed to Escherichia coli lipopolysaccharide (L PS) (serotype 055:B5) on day 4 for 8-10 h in a humidified 5% CO2 incubator. Control and experimental samples were assayed by reverse transcription-pol ymerase chain reaction (RT-PCR) and Western blot for the production of IL-8 mRNA and protein. Analysis of the PCR products revealed that cells of the odontoblast layer maintained in this culture model constitutively expressed low levels of IL-8, which were increased in response to E. coli LPS exposu re. Western blotting confirmed that the mRNA was translated into protein. T hese results imply that odontoblasts are capable of producing of pro-inflam matory mediators, thereby actively participating in the recruitment of neut rophils in response to bacterial by-products.