IL-6 functions as an exocrine hormone in inflammation. Hepatocytes undergoing acute phase responses require exogenous IL-6

J Immunol. 1990 May 15;144(10):3804-8.

Abstract

We have previously shown that IL-6 is the major monocyte- and fibroblast-derived regulator of acute phase protein gene expression and synthesis in hepatocytes in inflammation. Recently, we and others have shown that rat and human hepatoma cells express IL-6 mRNA, and the question arose as to whether normal hepatocytes express IL-6 and whether any such expression occurs under normal physiologic conditions or is seen in inflammation. Poly A+ mRNA of liver from normal rats and from rats undergoing an acute phase response was not positive when probed with cDNA for rat IL-6 under conditions in which macrophage mRNA was strongly positive. We then compared poly A+ mRNA from purified hepatocytes freshly isolated from normal rats--from rats that were undergoing an acute inflammatory response and from freshly isolated normal hepatocytes that had been cultured for 24 h in the presence or absence of dexamethasone (microM). Only the mRNA from normal hepatocytes cultured for 24 h in the absence of any glucocorticoid was obviously positive for IL-6. The increased expression of gamma-fibrinogen mRNA indicated the presence of inflammation. These results confirm the identification of IL-6 as an exogenous hormone for regulating normal hepatic acute phase protein synthesis in inflammation and rules out an autocrine mechanism being active in the liver in normal homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acute-Phase Reaction / physiopathology*
  • Animals
  • Blotting, Northern
  • Gene Expression
  • Inflammation / physiopathology*
  • Interleukin-6 / physiology*
  • Liver / physiopathology*
  • Polymerase Chain Reaction
  • RNA, Messenger / genetics
  • Rats
  • Rats, Inbred Strains

Substances

  • Interleukin-6
  • RNA, Messenger