Role of NFKB/REL and iKa in the regulation of KC mRNA levels in rat hepatoma (HTC) cells

KC, a member of the IL-8 a-chemokine family, is rapidly induced in the rat hepatoma cell line (HTC) when treated with an LPS-induced conditioned medium (LPS-CM) from a mouse monocyte cell line. The induction occurred very rapidly and peaked at 2 hr. after treatment. However, the level of KC mRNA induction is reduced when dexamethasone (Dex) is added to the LPS-CM. Since the KC promoter has a functional NFxB binding site we analyzed the effects of LPS-CM ±Dex on levels of RelA/p65, p50 and IkBo, a member of the NFxS inhibitor family to determine whether the levels of these regulatory proteins are altered during the induction and suppression of the KC gene expression. The NFicB binding activities and protein levels of RelA/p65 and p50 in nuclear extracts increased after 15 min. of LPS-CM treatment. At the same time, the cytoplasmic level of these proteins as well as DcBa were reduced after 15 min. of treatment. The mRNA for IkBa was induced after 30 min. and the level of mRNA induction was reduced by the addition of Dex. Studies are in progress to identify the components of LPS-CM that mediate KC induction. Our studies suggest that regulation of the induction of KC gene mRNA by LPS-CM and its suppression in the presence of Dex might be mediated through interactions with NFKB/IkBo.