Am. Healy et Td. Gelehrter, INDUCTION OF PLASMINOGEN-ACTIVATOR INHIBITOR-1 IN HEPG2 HUMAN HEPATOMA-CELLS BY MEDIATORS OF THE ACUTE-PHASE RESPONSE, The Journal of biological chemistry, 269(29), 1994, pp. 19095-19100
The liver plays a central role in the systemic acute phase response of
an organism to injury. Plasminogen activator inhibitor-1 (PAI-1), a m
ajor regulator of fibrinolysis, is an important component of the acute
phase response in humans. The source of plasma PAI-1 has been a matte
r of controversy, but recent in situ hybridization experiments have de
monstrated that human hepatocytes express the PAI-1 gene in vivo. Howe
ver, little is known about regulation of human hepatic PAI-1 gene expr
ession by mediators of the acute phase response. We have analyzed the
regulation of PAI-1 mRNA accumulation by interleukin (IL)-1, IL-6, and
dexamethasone, known mediators of the acute phase response, in HepG2
cells, a highly differentiated human hepatoma cell line that produces
a broad spectrum of acute phase proteins including PAI-1. Incubation o
f HepG2 cells with IL-1 resulted in a rapid and transient 40-fold indu
ction of the 3.2-kilobase PAI-1 mRNA and a 30-fold induction of the 2.
2-kilobase PAI-1 mRNA Although IL-6 alone had only a modest effect on
PAI-1 expression, in combination with IL-1, it caused a synergistic in
duction of PAI-1 mRNA accumulation. Dexamethasone alone did not increa
se PAI-1 mRNA accumulation but enhanced it in combination with IL-1. U
sing nuclear run-on experiments, we determined that the mechanism by w
hich IL-1 alone, or in combination with IL-6, induced PAI-1 mRMA accum
ulation was to cause a 10-15-fold, transient stimulation of PAI-1 gene
transcription. We found no evidence of an effect of these cytokines o
n PAI-1 mRNA stability. These data demonstrate that mediators of the a
cute phase response induce the accumulation of PAI-1 mRNA in human hep
atoma cells by rapidly and transiently increasing the transcription of
the PAI-1 gene.