Abstract
During the acute phase response to tissue injury or inflammation, the concentration of several plasma proteins change. Previous work (29-34) suggested a role for interleukin 1 (IL-1) in the acute phase response. The availability of recombinant-generated mouse IL-1 prompted a study designed to directly test the function of IL-1 and its mechanism of action on hepatic synthesis of two positive acute phase proteins (serum amyloid A [SAA] and complement factor B), and a negative acute phase reactant (albumin). Intravenous injection of purified recombinant-generated murine-IL-1 into C3H/HeJ endotoxin-resistant mice induced a dose-dependent increase in SAA-specific hepatic messenger RNA (mRNA), and an increase in SAA plasma protein concentration. In primary murine hepatocyte cultures, both the recombinant IL-1 and highly purified human IL-1 induced a dose- and time-dependent, reversible increase in expression of the SAA and factor B genes, and a decrease in albumin gene expression. This regulation is pretranslational, since the kinetics and direction of change in specific mRNA for SAA, factor B, and albumin correspond to the changes in synthesis of the respective proteins. Moreover, the effect of IL-1 was specific, since actin gene expression was unaffected, and the IL-1 response was inhibited by antibody specific for IL-1. These data provide direct evidence that a single mediator, IL-1, can effect the positive and negative changes in specific hepatic gene expression characteristic of the acute phase response.