Hepatitis B virus X protein transactivates human interleukin-8 gene through acting on nuclear factor kB and CCAAT/enhancer-binding protein-like cis-elements.

Interleukin-8 (IL-8) is a newly described leukocyte chemotactic and activating cytokine that belongs to the novel family of inflammatory cytokines whose genes locate on human chromosome 4, q12-21 region. The production of IL-8 is usually not constitutive and can be induced rapidly and abundantly in different cell types by a variety of stimuli such as lipopolysaccharide, interleukin-1, tumor necrosis factor-alpha as well as a tumor promotor phorbol myristate acetate. We report here that in addition to these stimuli the IL-8 gene can also be induced by the protein X of the hepatitis B virus (HBV-X) as evidenced by the enhanced IL-8 mRNA expression and IL-8 production observed in HBV-X-transfected cells. Furthermore, using several deletion mutants of the 5'-flanking regulatory region of the human IL-8 gene linked to the chloramphenicol acetyl transferase gene as a reporter, we have established here that both nuclear factor kB and CCAAT/enhancer-binding protein-like cis-elements located at -94 to -71 base pairs of IL-8 gene are essential and sufficient for the induction of the IL-8 gene by HBV-X. The same elements have been identified recently by us to be interleukin-1-, tumor necrosis factor-alpha-, and phorbol myristate acetate-responsive elements on the IL-8 gene. This suggests the existence of a common pathway for these inflammatory cytokines and HBV-X to activate the IL-8 gene. These observations might be relevant to the pathogenesis of inflammation in viral hepatitis.