Crucial Involvement of IL-6 in Thrombus Resolution in Mice via Macrophage Recruitment and the Induction of Proteolytic Enzymes.

After the ligation of the inferior vena cava (IVC) of wild-type (WT) mice, venous thrombi formed and grew progressively until 5 days and resolved thereafter. Concomitantly, intrathrombotic gene expression of was enhanced later than 5 days after IVC ligation. IL-6 protein expression was detected mainly in F4/80-positive macrophages in thrombus. When -deficient () mice were treated in the same manner, thrombus mass was significantly larger than in WT mice. Moreover, the recovery of thrombosed IVC blood flow was markedly delayed in compared with WT mice. F4/80-positive macrophages in thrombus expressed proteolytic enzymes such as matrix metalloproteinase () , and urokinase-type plasminogen activator (); and their mRNA expression was significantly reduced in mice. Consistently, the administration of anti-IL-6 antibody delayed the thrombus resolution in WT mice, whereas IL-6 administration accelerated thrombus resolution in WT and mice. Moreover, IL-6 enhanced , and mRNA expression in WT-derived peritoneal macrophages in a dose-dependent manner; and the enhancement was abrogated by a specific Stat3 inhibitor, Stattic. Thus, IL-6/Stat3 signaling pathway can promote thrombus resolution by enhancing , and expression in macrophages.