COX-1(+/-)COX-2(-/-) genotype in mice is associated with shortened time to carotid artery occlusion through increased
1Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St Louis, MO 63110, USA.
Background:
We found a high incidence of thrombotic deaths in COX-1(+/-)COX-2(-/-) mice and sought to define the mechanism of these events. The cyclooxygenase products thromboxane A(2) and prostacyclin are important in the regulation of coagulation but their role in fibrinolysis is largely unexplored. PAI-1 blocks fibrinolysis by inhibiting plasminogen activator.
Aim:
Our objective was to explain the mechanism of increased thrombosis associated with the COX-1(+/-)COX-2(-/-) genotype.
Methods:
Carotid artery occlusion times were measured after photochemical injury. PAI-1 levels were measured in the plasma by ELISA. PAI-1 levels in the aorta were measured by RT-PCR and Western blotting. Urinary metabolites of Thromboxane A(2) and prostacyclin were measured by ELISA.
Results:
The COX-1(+/-)COX-2(-/-) genotype is associated with a decreased time to occlusion in the carotid artery thrombosis model (30 ± 5 minutes vs 60 ± minutes in wild type, p<.001). The COX-1(-/-)COX-2(+/+), COX-1(+/-)COX-2(+/-) and COX-1(+/-)COX-2(+/+) all had occlusion times similar to wild type. COX-1(+/+)COX-2(-/-) had a prolonged occlusion time. COX-1(+/-)COX-2(-/-) had increased PAI-1 levels in the plasma and aorta and with a prolonged euglobulin lysis time (37.4 ± 10.2 hours vs 15.6 ± 9.8 hours in wild type, p<.004). The decreased time to occlusion in the COX-1(+/-)COX2(-/-) mice was normalized by an inhibitory antibody to PAI-1 whereas the antibody had no effect on the time to occlusion in wild type mice.
Conclusion:
The COX-1(+/-)COX-2(-/-) genotype is associated with a shortened time to occlusion in the carotid thrombosis model and the shortened time to occlusion is mediated through increased PAI-1 levels resulting in decreased fibrinolysis.
Insights
Mice with a specific COX-2 genetic variation (COX-1(+/-)COX-2(-/-)) experienced faster carotid artery thrombosis due to elevated PAI-1 levels, which inhibit fibrinolysis.
Area of Science:
- Biochemistry
- Genetics
- Cardiovascular Biology
Background:
- Thrombotic deaths are prevalent in COX-1(+/-)COX-2(-/-) mice.
- Cyclooxygenase products thromboxane A(2) and prostacyclin regulate coagulation, but their role in fibrinolysis is understudied.
- Plasminogen activator inhibitor-1 (PAI-1) inhibits fibrinolysis by blocking plasminogen activator.
Purpose of the Study:
- To elucidate the mechanism behind the heightened thrombosis observed in the COX-1(+/-)COX-2(-/-) genotype.
- To investigate the role of PAI-1 in COX-1(+/-)COX-2(-/-) mediated thrombosis.
Main Methods:
- Carotid artery occlusion times were assessed post-photochemical injury.
- Plasma and aortic PAI-1 levels were quantified using ELISA, RT-PCR, and Western blotting.
- Urinary metabolites of thromboxane A(2) and prostacyclin were measured via ELISA.
Main Results:
- COX-1(+/-)COX-2(-/-) mice exhibited significantly reduced carotid artery occlusion times (30 ± 5 min) compared to wild-type mice (60 ± min).
- These mice also showed elevated plasma and aortic PAI-1 levels and prolonged euglobulin lysis times (37.4 ± 10.2 hours vs. 15.6 ± 9.8 hours).
- Inhibition of PAI-1 normalized the shortened occlusion time in COX-1(+/-)COX-2(-/-) mice.
Conclusions:
- The COX-1(+/-)COX-2(-/-) genotype accelerates carotid thrombosis.
- This accelerated thrombosis is mediated by increased PAI-1 levels, leading to impaired fibrinolysis.
