The kinetics and magnitude of the synergistic activation of the serum amyloid A promoter by IL-1 beta and IL-6 is determined by the order of cytokine addition.
Human serum amyloid A protein (A-SAA) is a major hepatic acute-phase protein, the concentration of which increases by up to 1000-fold during inflammation. This induction is primarily due to synergistic transcriptional up-regulation by pro-inflammatory cytokines, principally interleukin (IL)-1 and IL-6. Using HepG2 hepatoma cells transfected with pGL2-SAA2pt, a cytokine-responsive human SAA2 promoter/luciferase reporter gene construct, we show that stimulation with IL-1 beta prior to IL-6 is essential for maximal synergistic transcriptional induction of the SAA2 gene. The reciprocal treatment, i.e. stimulation of the promoter with IL-6 before IL-1 beta results in significantly less synergistic activation of the SAA2 promoter. These findings strongly suggest that in vitro studies of acute-phase-protein induction using combinations of cytokines should be designed to reflect the chronology of their participation in the cytokine cascade.
Uhlar
C M
CM
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104-6084, USA.
Whitehead
A S
AS
D004338:Drug Combinations; D004357:Drug Synergism; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D007700:Kinetics; D011401:Promoter Regions, Genetic / Q000276:immunology*; D000685:Serum Amyloid A Protein / Q000096:biosynthesis / Q000235:genetics*; D013997:Time Factors; D015533:Transcriptional Activation / Q000276:immunology*; D014407:Tumor Cells, Cultured
D004338:Drug Combinations; D007375:Interleukin-1; D015850:Interleukin-6; D000685:Serum Amyloid A Protein