SOLUBLE INTERLEUKIN-6 (IL-6) RECEPTOR INFLUENCES THE EXPRESSION OF THE PROTOONCOGENE JUNB AND THE PRODUCTION OF FIBRINOGEN IN THE HEPG2 HUMAN HEPATOMA-CELL LINE AND PRIMARY RAT HEPATOCYTES

Interleukin 6 (IL-6) belongs to a family of cytokines using receptors sharing a common signal-transducing chain, gp130 and containing a spec ific ligand-binding chain (IL-6R alpha), It,vas shown that both the me mbrane-bound and the soluble form (sIL-6R) of this ligand specific rec eptor chain occurs naturally. The soluble form of IL-6 receptor was fo und to be able to associate with the membrane-bound gp130 and to gener ate active IL-6 receptor complex capable of inducing signal transducti on, This study on a human hepatoma cell line and primary rat hepatocyt es examined how the effectiveness of IL-6 is modified by the presence of soluble IL-6 receptor and whether the sIL-6R in the absence of IL-6 acts on hepatocytes, The authors studied the gene expression of junB, a member of the Jun family of transcription factors, and the producti on of fibrinogen in response to IL-6 and sIL-6R. The data show that in hepatic cells, endogeneously expressing IL-6R, the IL-6 induced junB and fibrinogen expression is inhibited by the presence of sIL-6R, In a ddition we found that sIL-6R alone (in the absence of IL-6) induced ju nB mRNA expression, but had no effect on fibrinogen production. (C) 19 98 Academic Press.