title: Impaired fibrinolytic system in ApoE gene-deleted mice with hyperlipidemia augments deep vein thrombosis.
abstract: BACKGROUND
  Hyperlipidemia increases the level of blood plasminogen activator inhibitor-1 (PAI-1) that is responsible for regulating fibrinolysis by inhibiting both urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA). While this fibrinolytic pathway is well known, the role of PAI-1 in venous thrombosis (VT) under hyperlipidemic conditions has not been fully established. We sought to determine the effects of PAI-1 in an in vivo hyperlipidemic model of VT.
  
  
  METHODS
  C57BL/6 wild-type (WT) mice, apolipoprotein E gene-deleted mice (ApoE-/-) having hyperlipidemia, and PAI-1 gene-deleted (PAI-1-/-) mice were used in this study. Inferior vena cava (IVC) ligation below the level of the renal veins was performed to create a stasis VT. Endpoints included measuring acute thrombosis (day 2) and chronic thrombosis (days 6 and 14). At euthanasia, blood samples were collected for plasmin and PAI-1 activity. In addition, the IVC and its thrombus were evaluated for thrombus weight (TW), u-PA activity, and differential leukocyte count while the vein wall only was analyzed for monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase (MMP) 2, and MMP-9.
  
  
  RESULTS
  Compared to WT at day 2, ApoE-/-mice demonstrated a statistically significant 14% increase in TW (P < .05) and a significant 41% increase in circulating PAI-1 activity (P < .05), while showing a trend of decreased plasmin activity. In addition, TW in ApoE-/-mice was 45% higher than PAI-1-/-mice at day 2 (P < .05), 33% at day 6 (P < .01), and 41% at day 14 (P < .01). ApoE-/-mice exhibited undetectable levels of u-PA in both vein wall and thrombus, compared to WT, at all time points. Also, vein wall MMP-2 was significantly decreased by 64% at day 6 (P < .01) and 58% at day 14 (P < .05). MMP-9 was significantly decreased by 71% at day 2 (P < .01) and 48% at day 6 (P < .01), in ApoE-/-mice compared to WT mice. In addition, in ApoE-/-mice, MCP-1 was significantly decreased by 38% at day 2 (P < .01) and 67% at day 6 (P < .01) vs WT mice. As expected in ApoE mice, following a decrease in MCP-1, monocyte recruitment was significantly decreased at days 6 (P < .01) and 14 (P < .05).
  
  
  CONCLUSIONS
  A significant increase of circulating PAI-1 levels in hyperlipidemic mice correlated with an early increase in TW due to impaired fibrinolysis. The undetectable levels of u-PA in ApoE-/-mice correlated to a decrease in vein wall MMP-2, MMP-9, MCP-1, and a decrease in monocyte recruitment diminishing thrombus resolution.
authors: Department of Surgery, Section of Vascular Surgery, Conrad Jobst Vascular Research Laboratories, University of Michigan, Ann Arbor, MI 48109, USA. josediaz@med.umich.edu
authors: Jose A
authors: JA
authors: Diaz
authors: Nicole E
authors: NE
authors: Ballard-Lipka
authors: Diana M
authors: DM
authors: Farris
authors: Angela E
authors: AE
authors: Hawley
authors: Shirley K
authors: SK
authors: Wrobleski
authors: Daniel D
authors: DD
authors: Myers
authors: Peter K
authors: PK
authors: Henke
authors: Daniel A
authors: DA
authors: Lawrence
authors: Thomas W
authors: TW
authors: Wakefield
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency* / Q000235:genetics; D018932:Chemokine CCL2 / Q000378:metabolism; D004195:Disease Models, Animal; D005341:Fibrinolysin / Q000378:metabolism; D005342:Fibrinolysis / Q000235:genetics; D006949:Hyperlipidemias / Q000097:blood / Q000150:complications* / Q000235:genetics; D007958:Leukocyte Count; D008026:Ligation; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017395:Plasminogen Activator Inhibitor 1 / Q000172:deficiency / Q000235:genetics; D013997:Time Factors; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism; D014682:Vena Cava, Inferior / Q000378:metabolism* / Q000601:surgery; D020246:Venous Thrombosis / Q000097:blood / Q000209:etiology*
chemical_list: D001057:Apolipoproteins E; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D017395:Plasminogen Activator Inhibitor 1; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator; D020778:Matrix Metalloproteinase 2; C522362:Mmp2 protein, mouse; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse