IL-1 and IL-6 induce hepatocyte plasminogen activator inhibitor-1 expression through independent signaling pathways converging on C/EBPdelta.
To elucidate signaling pathways activated by IL-1 and IL-6 that contribute to increased expression of plasminogen activator inhibitor-1 (PAI-1), we studied human hepatoma (HepG2) cells and primary mouse hepatocytes. HepG2 cell PAI-1 mRNA increased in response to IL-1beta, IL-6, and IL-1beta plus IL-6 as shown by real-time PCR. Activity of the transiently transfected PAI-1 promoter (-829 to +36 bp) increased as well. Systematic promoter deletion assays showed that the region from -239 to -210 bp containing a putative CCAAT-enhancer binding protein (C/EBP) binding site was critical. Point mutations in this region abolished the IL-1beta and IL-6 responses. Antibody interference electrophoretic mobility shift assays showed that C/EBPdelta (but not C/EBPalpha or C/EBPbeta) binding and protein were increased by IL-1beta, IL-6, and IL-1beta plus IL-6 in HepG2 cells. IL-1beta and IL-6 increased expression of both PAI-1 mRNA and C/EBPdelta mRNA in mouse primary hepatocytes as well. Downregulation of C/EBPdelta induced with small interfering RNA (siRNA) decreased secretion of PAI-1. As judged from results obtained with inhibitors, signal transduction in all three of the mitogen-activated protein kinase pathways was involved in IL-1-inducible PAI-1 expression. By contrast, JAK signaling was responsible for the IL-6-induced inducible expression. Thus IL-1 and IL-6 exert directionally similar effects on PAI-1 expression, but the induction involves distinct signaling pathways with a final common mediator, C/EBPdelta.
Dong
Jie
J
Cardiovascular Research Institute, Colchester Research Facility, University of Vermont, 208 South Park Drive, Colchester, VT 05446, USA.
Fujii
Satoshi
S
Imagawa
Shogo
S
Matsumoto
Shuichiro
S
Matsushita
Michiaki
M
Todo
Satoru
S
Tsutsui
Hiroyuki
H
Sobel
Burton E
BE
D000818:Animals; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics / Q000378:metabolism*; D002457:Cell Extracts / Q000737:chemistry; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D002874:Chromosome Mapping; D015536:Down-Regulation; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology*; D051379:Mice; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020218:Response Elements / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology*
D002457:Cell Extracts; D053583:Interleukin-1beta; D015850:Interleukin-6; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051743:CCAAT-Enhancer-Binding Protein-delta