Pivotal role of PAI-1 in a murine model of hepatic vein thrombosis

Abstract

Hepatic veno-occlusive disease (VOD) is a common complication of high-dose chemotherapy associated with bone marrow transplantation. While the pathogenesis of VOD is uncertain, plasminogen activator inhibitor-1 (PAI-1) has emerged as a diagnostic marker and predictor of VOD in humans. In this study, we investigated the role of PAI-1 in a murine model of VOD produced by long-term nitric oxide synthase inhibition using L-NAME. After 6 weeks, wild-type (WT) mice developed extensive fibrinoid hepatic venous thrombi and biochemical evidence of hepatic injury and dysfunction. In contrast, PAI-1-deficient mice were largely protected from the development of hepatic vein thrombosis. Furthermore, WT mice that received tiplaxtinin, an antagonist of PAI-1, were effectively protected from L-NAME-induced thrombosis. Taken together, these data indicate that NO and PAI-1 play pivotal and antagonistic roles in hepatic vein thrombosis and that PAI-1 is a potential target in the prevention and treatment of VOD in humans.

Figure 1.

NOS inhibition and hepatic venous thrombosis. Masson trichrome stains of representative livers from WT+L-NAME (A-C), WT+L-NAME+tiplaxtinin (PAI-039) (D-F), and PAI-1^-/-+L-NAME (G-I) mice after 6 weeks of L-NAME treatment at the indicated magnifications. Arrows illustrate the extent of venous thrombi in WT mice. Images were visualized using an Olympus BX40 microscope equipped with 10×/0.30, 20×/0.50, and 40×/0.90 Plan Apo objective lenses and an Optronics digital camera (Optronics, Goleta, CA). Images were acquired with Magnafire 1.0 software (Optronics) and were processed for publication with Image Pro Plus 4.5 software (Media Cybernetics, Silver Spring, MD). (J) Calculated percent occluded luminal area in all 3 treatment groups (P < .001 for WT vs PAI-1 knockout [KO]; and P < .001 for WT vs WT+tiplaxtinin by ANOVA). Values shown are mean ± SEM.

Figure 2.

AST and bilirubin levels. (A) Total serum bilirubin and AST levels are elevated in WT mice receiving L-NAME but not in PAI-1^-/- mice or in WT mice receiving tiplaxtinin (PAI-039). (B) Tiplaxtinin (PAI-039) reduced plasma PAI-1 activity in WT mice receiving L-NAME.