Effects of IL-1β and IL-6 on tissue-type plasminogen activator expression in vascular endothelial cells

Pia Larsson, Erik Ulfhammer, Lena Karlsson, Maria Bokarewa, Karin Wåhlander, Sverker Jern

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Introduction: 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)-1β and IL-6 on t-PA gene and protein expression, and elucidated by which signaling mechanisms the effects are mediated. Materials and Methods: Cultured human umbilical vein endothelial cells (HUVEC) were exposed to recombinant IL-1β 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-1β caused a distinct suppression of t-PA transcript and protein levels, mediated primarily by NF-κB signaling. This cytokine also increased binding of NF-κB subunits to a t-PA specific κB 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-1β impairs fibrinolytic capacity in vascular endothelial cells by an NF-κB 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.

Original languageEnglish
Pages (from-to)342-351
Number of pages10
JournalThrombosis Research
Issue number2
Publication statusPublished - 1 Dec 2008
Externally publishedYes


  • Fibrinolysis
  • Inflammation
  • Interleukin-1β
  • Interleukin-6
  • NF-κB
  • t-PA

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