Augmentation of Actinobacillus actinomycetemcomitans invasion of human oral epithelial cells and up-regulation of interleukin-8 production by saliva CD14.
It has recently been shown that human salivary glands constitutively express CD14, an important molecule in innate immunity, and that a soluble form of CD14 is secreted in saliva. The concentration of CD14 in parotid (a serous gland) saliva was comparable to that in normal serum and 10-fold the amount in whole saliva, although the physiological function of saliva CD14 remained unclear. Actinobacillus actinomycetemcomitans is a periodontopathic bacterium and is able to invade oral epithelial cells. The present study showed that upon exposure to live A. actinomycetemcomitans Y4 for 2 h, human oral epithelial HSC-2 cells produced interleukin-8 (IL-8) for a further 24 h and whole saliva augmented the production induced by A. actinomycetemcomitans Y4. Parotid saliva showed a more pronounced effect on the production of IL-8 than whole saliva. Neither saliva preparation itself had IL-8-inducing activity. Parotid saliva exhibited antibacterial activity against a low concentration of A. actinomycetemcomitans Y4, but recombinant CD14 did not show the activity. The internalization of A. actinomycetemcomitans Y4 into HSC-2 cells was inhibited by cytochalasin B, indicating that the process was actin dependent, and depletion of CD14 from parotid saliva inhibited the invasion and, as a consequence, inhibited production of IL-8. Furthermore, human recombinant CD14 augmented invasion and IL-8 production. These results suggest that saliva CD14 promoted the invasion of oral epithelial cells by A. actinomycetemcomitans and consequently augmented the production of IL-8, playing an important role in innate immunity in the oral cavity.
D000328:Adult; D016976:Aggregatibacter actinomycetemcomitans / Q000276:immunology* / Q000472:pathogenicity*; D002460:Cell Line; D004847:Epithelial Cells / Q000276:immunology / Q000382:microbiology; D006801:Humans; D007113:Immunity, Innate; D066298:In Vitro Techniques; D016209:Interleukin-8 / Q000096:biosynthesis*; D018950:Lipopolysaccharide Receptors / Q000378:metabolism*; D009055:Mouth / Q000276:immunology* / Q000382:microbiology*; D012463:Saliva / Q000276:immunology* / Q000382:microbiology*; D015854:Up-Regulation; D014774:Virulence / Q000276:immunology
D016209:Interleukin-8; D018950:Lipopolysaccharide Receptors