Effects of Bacterial Extracts on Il-8 Production by Human Dental Pulp Cells

The objective of this study was to determine the effects of Prevotella intermedia, Fusobacterium nucleatum and Lactobacillus casei on the production of IL-8 by human dental pulp cells. Human dental pulp cells from teeth of young patients (aged 18-25 years) were cultured and tested with sonicated P. intermedia ATCC 25611, F. nucleatum ATCC 25586 and L. casei ATCC 4646 extracts. IL-8 secreted into the culture supernatants were measured at 6, 12 and 24 hours using a quantitative sandwich enzyme immunoassay technique. Cell viability was evaluated using trypan blue exclusion technique. IL-8 production by human dental pulp cells increased significantly at 12 and 24 hours after exposure to P. intermedia and F. nucleatum, whereas L. casei extract exhibited low IL-8 production. The sonicated bacterial extracts did not significantly affect viability or total number of dental pulp cells. Polymorphonuclear cells and mononuclear phagocytes are key components of the host defense against invading microbes. Polymorphonuclear cells tend to predominate in acute infections, whereas a mononuclear infiltrate is more often seen in chronic infections. The nature of the leukocyte infiltrate affects the progress of the disease. Therefore, factors that regulate the recruitment of specific leukocytes represent an important component of the host response. Chemokines are a recently described family of chemotactic cytokines (Graves and Jiang, 1995). Unlike the classic leukocyte chemoattractants, they exhibit a relatively high degree of specificity. The best-studied member of this group is interleukin-8 (IL-8), which is secreted by several cell types, including monocytes and macrophages, fibroblasts, endothelial cells, and keratinocytes (Graves and Jiang, 1995). In addition, dental pulp fibroblasts, which are considered as cells primarily concerned with providing physical barriers and structural components in pulpal tissue, are thought to be one of the cellular sources of IL-8. The most important function of IL-8 is the attraction of polymorphonuclear leukocytes. It is also important in the SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 524 Vol 37 No. 3 May 2006 activation of leukocyte adhesion molecules and as chemoattractant in directed leukocyte migration. High levels of IL-8 have been demonstrated in various inflammatory diseases, including pulpal inflammation (Huang et al, 1999) and periapical lesions (Shimauchi et al, 2001). To investigate the mechanism that may contribute to the pathologic reaction of pulpal tissue due to bacterial infection, we have examined the different expression of IL-8 by human dental pulp cells stimulated in vitro by sonicated extracts of P. intermedia, F. nucleatum and L. casei. MATERIALS AND METHODS