Effects of IL-1beta and IL-6 on tissue-type plasminogen activator expression in vascular endothelial cells.
BACKGROUND
The increased risk of thrombus formation in inflammatory conditions is generally considered to be due to the pro-coagulant effect of inflammatory cytokines. However, cytokines may also decrease the expression of the key fibrinolytic enzyme tissue-type plasminogen activator (t-PA) causing a reduced clearance of emerging intravascular thrombi. This study investigated the effects of the inflammatory cytokines interleukin (IL)-1beta and IL-6 on t-PA gene and protein expression, and elucidated by which signaling mechanisms the effects are mediated.


METHODS
Cultured human umbilical vein endothelial cells (HUVEC) were exposed to recombinant IL-1beta or IL-6. t-PA mRNA was quantified by real-time RT-PCR and t-PA antigen by ELISA. To clarify signaling mechanisms, selective inhibitors of major cytokine-activated signaling pathways were used. Interactions of nuclear proteins with potential t-PA gene regulatory elements were studied by gel shift assays.


RESULTS
Already at low concentrations, IL-1beta caused a distinct suppression of t-PA transcript and protein levels, mediated primarily by NF-kappaB signaling. This cytokine also increased binding of NF-kappaB subunits to a t-PA specific kappaB element. IL-6 stimulation per se did not affect t-PA mRNA or protein levels whereas soluble IL-6 receptor, in the presence of endogenous IL-6, suppressed t-PA expression.


CONCLUSIONS
We conclude that the proinflammatory cytokine IL-1beta impairs fibrinolytic capacity in vascular endothelial cells by an NF-kappaB dependent suppression of t-PA expression. In contrast, an effect of IL-6 on t-PA expression could not be detected, probably due to lack of IL-6 receptor expression on HUVEC.
Larsson
Pia
P
Department of Emergency and Cardiovascular Medicine, Sahlgrenska University Hospital/Ostra, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden.
Ulfhammer
Erik
E
Karlsson
Lena
L
Bokarewa
Maria
M
Wåhlander
Karin
K
Jern
Sverker
S
D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology
D017077:Culture Media, Conditioned; D053583:Interleukin-1beta; D015850:Interleukin-6; D012333:RNA, Messenger; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator