Roles of Coagulation and fibrinolysis in angiotensin II-enhanced microvascular thrombosis

Abstract

Objective: AngII-induced HTN is associated with accelerated thrombus development in arterioles. This study assessed the contributions of different components of the coagulation cascade and fibrinolysis to AngII-mediated microvascular thrombosis.

Methods: Light/dye-induced thrombus formation (the time of onset and flow cessation) was quantified in cremaster muscle arterioles of AngII infused (two weeks) WT/AngII mice, EPCR-TgN, and mice deficient in PAI-1. WT/AngII mice were also treated with either tissue factor antibody, antithrombin III, heparin, hirudin, or murine APC.

Results: TF immunoblockade or hirudin treatment did not prevent the AngII-induced acceleration of thrombosis. While antithrombin III treatment prevented the acceleration in both thrombus onset and flow cessation, heparin only improved the time for blood flow cessation. Neither WT mice treated with murine APC nor EPCR-TgN were protected against AngII-induced thrombus development. A similar lack of protection was noted in PAI-1deficient mice.

Conclusion: These findings implicate a role for thrombin generation pathway in the accelerated thrombosis induced by AngII and suggest that an impaired protein C pathway and increased PAI-1 do not make a significant contribution to this model of microvascular thrombosis.

Keywords: angiotensin II; anticoagulants; coagulation; fibrinolysis; thrombosis.

© 2014 John Wiley & Sons Ltd.

Figures

Figure 1

Effects of tissue factor (TF) immunoblockade on light-dye-induced thrombus formation in cremaster muscle arterioles of wild type mice infused with angiotensin II (AngII) for 2 wks. WT = control wild type (WT) mice (n=12); WT-AngII = WT mice implanted with AngII-loaded pump for 2 weeks (n=12); WT-AngII-TF Ab = WT mice with AngII-loaded pump treated with a TF neutralizing antibody 20 min before photoactivation (n=7). ** Indicates p

Figure 2

Effects of thrombin inhibition on AngII-enhanced thrombosis. Panel A: A comparison of untreated and heparin treated (WT-AngII-heparin) WT mice implanted with AngII loaded pumps. WT mice (n=12); WT-AngII mice (n=12); WT-AngII-heparin (n =5) receiving heparin 10 min prior to photoexposure. Panel B: A comparison of untreated WT mice (n=12) and WT-AngII (n=5) receiving hirudin 5 min prior epi-illumination hypertensive mice. Panel C: A comparison of untreated and antithrombin III (ATIII, administered 5 min prior to photoactivation) treated WT mice. WT controls (n=12); WT-AngII (n=12); WT-AngII-ATIII (n = 5). ** Indicates p<0.01 vs WT; *** indicates p<0.001 vs WT; # indicates p<0.05 vs WT-AngII; ## indicates p<0.01 vs WT-AngII.

Figure 3

Effects of treatment with murine activated protein C (APC) (Panel A) or genetic overexpression of the endothelial protein C receptor (EPCR-TgN) (Panel B) on AngII-accelerated light/dye-induced thrombus formation in cremaster muscle arterioles. WT mice (n=12); WT-AngII mice (n=12); WT-AngII-APC (n=6); EPCR-TgN-AngII (n=6). ** Indicates p<0.01 vs WT; *** indicates p<0.001 vs WT.

Figure 4

Light/dye-induced thrombosis in plasminogen activator inhibitor-1 (PAI-1) deficient mice implanted with AngII-loaded pump for 2 weeks. WT mice (n=12); WT-AngII mice (n=12); PAI-1−/−-AngII (n=4). ** Indicates p<0.01 vs WT; *** indicates p<0.001 vs WT.