Expression of IL-1 beta and IL-8 by human gingival epithelial cells in response to Actinobacillus actinomycetemcomitans

The interaction between epithelial cells and microorganisms is the most imp ortant step in bacterial infections. Epithelial cells in response to exposu re to pathogenic bacteria produce cytokines that initiate inflammation. How ever, little is known about the cytokine response of gingival epithelial ce lls to periodontopathogenic bacteria. Actinobacillus actinomycetemcomitans is thought to play a significant role in the initiation of periodontitis be cause of its bacteriological characteristics. In the present study, we inve stigated the cytokine induction by human gingival epithelial cells (HGEC) f ollowing exposure to A. actinomycetemcomitans in comparison with human ging ival fibroblasts (HGF) in culture. Northern blot analysis showed that mRNAs of interleukin 1 beta (IL-1 beta) and IL-8, but not IL-6, in HGEC were ind uced in response to A. actinomycetemcomitans. Secretion of IL-8 by HGEC was also increased following A. actinomycetemcomitans challenge, whereas produ ction of IL-1 beta could not be detected. The levels of IL-8 and its mRNA w ere increased depending on the concentration of A. actinomycetemcomitans. T he co-culture with HGF and A. actinomycetemcomitans resulted in an increase in the levels of IL-6 and IL-8 mRNA in HGF. However, HGF exposed to A. act inomycetemcomitans, showed no expression of IL-1 beta mRNA, These findings demonstrated that HGEC and HGF stimulated with A. actinomycetemcomitans hav e different profiles in cytokine mRNA expression. Furthermore, A. actinomyc etemcomitans may play an important role in amplifying the local immune resp onse and in initiating inflammatory reaction through release of IL-8 from g ingival epithelial cells. (C) 2001 Academic Press.