ABSTRACT
BACKGROUND: Haem levels are associated with thrombosis in a variety of diseases, as well as being a contributing cause of thrombotic events in animal models. MATERIALS AND METHODS: We retrospectively analyzed samples from 39 children who underwent cardiac surgery with cardiopulmonary bypass, including 15 children who developed a postoperative thrombosis and 24 controls. RESULTS: Patients who developed thrombosis postoperatively had statistically significant higher average haem levels over time (presurgery to 12 h postsurgery) compared to patients who did not develop thrombosis. CONCLUSION: Higher cell-free total haem levels are associated with a higher risk of thrombosis in a paediatric cardiac surgical cohort.
Subject(s)
Heart Defects, Congenital/blood , Heme/metabolism , Thrombosis/blood , Biomarkers/blood , Cardiopulmonary Bypass , Case-Control Studies , Female , Heart Defects, Congenital/surgery , Humans , Infant , Male , Retrospective Studies , Risk FactorsABSTRACT
Following initial platelet activation, arachidonic acid is metabolised by cyclooxygenase-1 and 12-lipoxygenase (12-LOX). While the role of 12-LOX in the platelet is not well defined, recent evidence suggests that it may be important for regulation of platelet activity and is agonist-specific in the manner in which it regulates platelet function. Using small molecule inhibitors selective for 12-LOX and 12-LOX-deficient mice, the role of 12-LOX in regulation of human platelet activation and thrombosis was investigated. Pharmacologically inhibiting 12-LOX resulted in attenuation of platelet aggregation, selective inhibition of dense versus alpha granule secretion, and inhibition of platelet adhesion under flow for PAR4 and collagen. Additionally, 12-LOX-deficient mice showed attenuated integrin activity to PAR4-AP and convulxin compared to wild-type mice. Finally, platelet activation by PARs was shown to be differentially dependent on COX-1 and 12-LOX with PAR1 relying on COX-1 oxidation of arachidonic acid while PAR4 being more dependent on 12-LOX for normal platelet function. These studies demonstrate an important role for 12-LOX in regulating platelet activation and thrombosis. Furthermore, the data presented here provide a basis for potentially targeting 12-LOX as a means to attenuate unwanted platelet activation and clot formation.
Subject(s)
Arachidonate 12-Lipoxygenase/metabolism , Blood Platelets/metabolism , Platelet Membrane Glycoproteins/metabolism , Receptors, Thrombin/metabolism , 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid/chemistry , Animals , Cyclooxygenase 1/metabolism , Eicosanoids/metabolism , Flow Cytometry , Humans , Mice , Mice, Transgenic , Platelet Activation , Platelet Adhesiveness , Platelet Aggregation , Thrombosis/metabolism , Time FactorsABSTRACT
OBJECTIVES: To determine whether dysregulation of platelet signaling mechanisms contributes to the increased risk of thrombosis associated with diabetes, using a type I diabetes mouse model. METHODS AND RESULTS: Type I diabetes was induced in C57Bl6 mice following streptozotocin injection. Arterial thrombosis, platelet signaling and function were assessed 4 weeks later in comparison with non-diabetic control mice. Fifty-seven per cent of diabetic mice (glucose level of > 250 mg dL(-1) ) developed stable occlusive thrombi after FeCl3 injury, as compared with 5% of their non-diabetic counterparts, suggesting that diabetic mice are more sensitive to arterial injury (P ≤ 0.02). Platelets from diabetic mice were more sensitive to protease-activated receptor 4 (PAR4) agonist-induced fibrinogen binding than platelets from non-diabetic mice, and the average Akt phosphorylation induced by PAR4 agonist peptide was greater (P ≤ 0.01) in platelets from diabetic mice. Recent studies suggest that insulin-like growth factor 1 (IGF-1) potentiates Akt phosphorylation in platelets. To determine whether IGF-1 signaling contributes to the increase in PAR4 sensitivity in platelets from diabetic mice, platelet signaling and function were evaluated in the presence of inhibitors of the IGF-1 receptor. IGF-1 receptor inhibition reduced Akt phosphorylation and fibrinogen binding in platelets from diabetic mice to levels consistent with those seen in normoglycemic platelets, but had no significant effect on platelets from non-diabetic mice. CONCLUSIONS: The results suggest that platelets from mice with streptozotocin-induced diabetes show enhanced platelet Akt phosphorylation and activity resulting from IGF-1-dependent mechanisms. Increases in platelet Akt activation may explain the enhanced sensitivity to thrombotic insult seen in diabetic mice.
