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Leukaemia inhibitory factor and oncostatin M modulate expression of urokinase plasminogen activator and fibrinogen
H Okada1, J Woodcock-Mitchell, S Fujii
1Department of Medicine, College of Medicine, University of Vermont, Burlington 05405, USA.
Background:
Pathogenetic effects of active immune cell products on the coagulation and fibrinolytic system proteins in liver and endothelial cells--primary sites of synthesis of these proteins--have not been elucidated.
Methods:
We incubated highly differentiated human hepatoma cells (Hep G2) and human umbilical vein endothelial cells (HUVECs) for 24 h with recombinant human leukaemia inhibitory factor (LIF) and oncostatin M (OSM)--cytokines that are implicated in acute phase reactions during inflammation and which bind to the same cell surface receptor unit (glycoprotein gp 130). LIF was also given to mice in vivo. Contents of coagulation and fibrinolytic system proteins in cell culture supernatants and in mouse liver were determined.
Results:
LIF increased the accumulation of urokinase plasminogen activator (u-PA) in the Hep G2 cell culture supernatants determined by enzyme-linked immunosorbent assay (ELISA) (0.21 +/- 0.03 (SE) ng/ml at baseline; 0.40 +/- 0.05 ng/ml at 100 U/ml, P < 0.05; 0.57 +/- 0.06 ng/ml at 500 U/ml, P < 0.01; n = 9) without altering total protein content. OSM elicited a similar effect (0.25 +/- 0.04 ng/ml at baseline, 0.62 +/- 0.19 ng/ml at 1 ng/ml; P < 0.05, n = 6). A monoclonal antibody against gp 130 abrogated the response to both agents (n = 9). Plasminogen activator inhibitor type-1 (PAI-1) (assayed by ELISA, n = 9), the PAI-1 binding protein, vitronectin (immunoprecipitation, n = 3) and tissue factor (ELISA, n = 3) were not affected by LIF, but fibrinogen production increased up to twofold with LIF (500 U/ml; Western blot, n= 3). In HUVECs, synthesis of tissue type plasminogen activator or PAI-1 was not altered by LIF or OSM (ELISA, n = 9). In vivo, intraperitoneal recombinant murine LIF (2 mu g) increased liver concentrations of u-PA by 30% and fibrinogen by 220% in mice.
Conclusions:
LIF and OSM produced by immune cells may modify fibrinolysis and coagulation by altering expression of u-PA and fibrinogen, thereby contributing to coagulopathy.