warfarin and Reperfusion-Injury

Coagulation factor (F)XI was first described as a member of the contact pathway of coagulation. However, the 'classic' theory of the extrinsic and intrinsic pathway has been revised and FXI was found to be activated by thrombin and to play a role in sustained thrombin generation and fibrinolysis inhibition. Recent studies have pointed to a disproportionate role of FXI in thrombosis and hemostasis. The observations that human congenital FXI deficiency is generally accompanied by mild and injury-related bleeding, and that experimental, provoked bleeding in animals is unaffected by FXI deficiency or FXI inhibition, suggest that the FXI amplification pathway is less important for normal hemostasis in vivo. In contrast, elevated plasma levels of FXI may contribute to human thromboembolic disease and the antithrombotic efficacy of FXI inhibition has been demonstrated in numerous animal models of arterial, venous and cerebral thrombosis. Whether severe FXI deficiency in humans protects against thromboembolic events remains unclear, although some evidence exists that the occurrence of ischemic stroke or venous thrombosis is low in severely FXI-deficient patients. Because of its distinctive function in thrombosis and hemostasis, FXI is an attractive target for the treatment and prevention of thromboembolism. A novel strategy for FXI inhibition is the use of antisense technology which has been studied in various thrombosis and bleeding animal models. The results are promising and support the concept that targeting FXI might serve as a new, effective and potentially safer alternative for the treatment of thromboembolic disease in humans.

Topics: Animals; Blood Coagulation; Disease Models, Animal; Dose-Response Relationship, Drug; Factor XI; Factor XI Deficiency; Fibrinolytic Agents; Hemostasis; Humans; Mice; Models, Biological; Oligonucleotides, Antisense; Reperfusion Injury; Thromboembolism; Thrombosis; Warfarin

In acute pancreatitis (AP), pancreatic damage leads to local vascular injury, manifesting as endothelial damage and activation, increased vascular permeability, leukocyte rolling, sticking and transmigration to pancreatic tissue as well as activation of coagulation. Previous studies have shown that pretreatment with heparin or acenocoumarol inhibits the development of AP. The aim of the present study was to check the impact of pretreatment with warfarin, an oral vitamin K antagonist, on the development of ischemia/reperfusion-induced AP in rats. AP was induced by pancreatic ischemia followed by reperfusion of the gland. Warfarin (90, 180 or 270 µg/kg/dose) or vehicle were administered intragastrically once a day for 7 days before induction of AP. The effect of warfarin on the severity of AP was assessed 6 h after pancreatic reperfusion. The assessment included histological, functional, and biochemical analyses. Pretreatment with warfarin given at a dose of 90 or 180 µg/kg/dose increased the international normalized ratio and reduced morphological signs of pancreatic damage such as pancreatic edema, vacuolization of acinar cells, necrosis and the number of hemorrhages. These effects were accompanied by an improvement of pancreatic blood flow and a decrease in serum level amylase, lipase, pro-inflammatory interleukin-1β and plasma level of D-dimer. In contrast, pretreatment with warfarin given at a dose of 270 µg/kg/dose led to an increase in severity of pancreatic damage and biochemical indicators of AP. In addition, this dose of warfarin resulted in deaths in some animals. Pretreatment with low doses of warfarin inhibits the development of AP induced by pancreatic ischemia followed by reperfusion.

Topics: Acute Disease; Animals; Anticoagulants; Coumarins; Ischemia; Male; Pancreas; Pancreatitis; Rats; Rats, Wistar; Reperfusion Injury; Warfarin

Acute pancreatitis is associated with activation of coagulation and there is a close relationship between coagulation and the severity of this disease. Administration of anticoagulants such as heparin or acenocoumarol has shown to reduce the severity of acute pancreatitis and accelerate the recovery. The aim of the current study was to determine the impact of warfarin administration on the course of ischemia/reperfusion-induced acute pancreatitis. Acute pancreatitis was induced in rats by pancreatic ischemia followed by reperfusion. Vehicle (1 ml/dose) or warfarin (45, 90 or 180 μg/kg/dose in 1 ml of vehicle) were administered intragastrically once a day. The first dose of warfarin was given 24 h after the start of pancreatic reperfusion. The severity of acute pancreatitis was assessed 2, 5, 9 and 14 days after the beginning of pancreatic reperfusion. Treatment with warfarin reduces pancreatic damage and accelerates recovery in histological examination and this effect is accompanied by a faster reduction in serum activity of pancreatic digestive enzymes, lipase and amylase. In addition, warfarin led to an earlier decrease in serum concentration of pro-inflammatory interleukin-1β and plasma level of D-dimer. These effects were associated with an improvement of pancreatic blood flow. We conclude that warfarin exhibits a therapeutic effect in acute pancreatitis evoked by pancreatic ischemia followed by reperfusion.

Topics: Amylases; Animals; Anticoagulants; Biomarkers; Disease Models, Animal; Fibrin Fibrinogen Degradation Products; Interleukin-1beta; Lipase; Male; Pancreas; Pancreatitis; Rats, Wistar; Reperfusion Injury; Time Factors; Warfarin

Oxidative stress has been reported to be a main cause of neuronal cell death in ischemia reperfusion injury (IRI). Nuclear factor-erythroid 2-related factor 2 (Nrf2) is an important factor involved in anti-oxidative responses. We previously reported that bardoxolone methyl (BARD), an Nrf2 activator, prevented damage induced by IRI. In this study, we investigated the effect of BARD on hemorrhagic transformation in the context of blood brain barrier (BBB) protection.. Mice received pre-treatment with warfarin (4.0 mg/kg, p.o.). IRI was subsequently induced 18 h after the warfarin administration by transient middle cerebral artery occlusion (MCAO) for 6 h. BARD (0.06, 0.2, 0.6 or 2.0 mg/kg) or saline was injected intravenously immediately after reperfusion. The infarct volume, neurological score, intracranial hemorrhage volume, and BBB permeability were evaluated 24 h after MCAO. The survival rate and behavioral functional recovery were evaluated for 7 days following IRI. Furthermore, the effects of BARD on BBB components were investigated by western blotting and immunostaining analysis.. BARD suppressed warfarin-mediated increases in the intracranial hemorrhage volume without affecting the infarct volume. BBB permeability was also suppressed by administration of BARD. Western blotting showed that BARD increased expression of BBB components such as endothelial cells, pericytes, and tight junction proteins. Furthermore, immunostaining showed that BARD induced localization of Nrf2 to endothelial cells and pericytes.. BARD suppressed the exacerbation hemorrhage caused by warfarin pretreatment and ameliorated BBB disruption by protecting endothelial cells, pericytes, and tight junction protein expressions. These results indicate that Nrf2 activators may be an effective therapy against hemorrhagic transformation caused by anticoagulant drugs.

Topics: Animals; Anticoagulants; Antigens, CD; Behavior, Animal; Blood-Brain Barrier; Brain Ischemia; Cadherins; Endothelial Cells; Intracranial Hemorrhages; Male; Mice; Neurons; NF-E2-Related Factor 2; Oleanolic Acid; Pericytes; Reperfusion Injury; Survival Analysis; Tight Junction Proteins; Warfarin

Warfarin-related nephropathy (WRN) occurs under conditions of overanticoagulation with warfarin. WRN is characterized by glomerular hemorrhage with occlusive tubular red blood cell (RBC) casts and acute kidney injury (AKI). Herein we test the hypothesis that oxidative stress plays a role in the AKI of WRN. 5/6 Nephrectomy rats were treated with either warfarin (0.04 mg·kg⁻¹·day⁻¹) alone or with four different doses of the antioxidant N-acetylcysteine (NAC). Also tested was the ability of our NAC regimen to mitigate AKI in a standard ischemia-reperfusion model in the rat. Warfarin resulted in a threefold or greater increase in prothrombin time in each experimental group. Serum creatinine (Scr) increased progressively in animals receiving only warfarin + vehicle. However, in animals receiving warfarin + NAC, the increase in Scr was lessened, starting at 40 mg·kg⁻¹·day⁻¹ NAC, and completely prevented at 80 mg·kg⁻¹·day⁻¹ NAC. NAC did not decrease hematuria or obstructive RBC casts, but mitigated acute tubular injury. Oxidative stress in the kidney was increased in animals with WRN and it was decreased by NAC. The NAC regimen used in the WRN model preserved kidney function in the ischemia-reperfusion model. Treatment with deferoxamine (iron chelator) did not affect WRN. No iron was detected in tubular epithelial cells. In conclusion, this work taken together with our previous works in WRN shows that glomerular hematuria is a necessary but not sufficient explanation for the AKI in WRN. The dominant mechanism of the AKI of WRN is tubular obstruction by RBC casts with increased oxidative stress in the kidney.

Topics: Acetylcysteine; Acute Kidney Injury; Animals; Creatinine; Deferoxamine; Erythrocytes; Male; Nephrectomy; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Urine; Warfarin

The prevalence of long-term oral anticoagulant therapy is rising. Treatment options for patients who have an ischemic stroke under oral anticoagulant therapy are limited, and clinical data on the risk of hemorrhagic transformation (HT) in this condition are scarce. We therefore aimed to establish a mouse model of ischemic stroke occurring during oral anticoagulant therapy to assess the frequency and characteristics of HT.. C57BL/6 mice (n=59) were pretreated with warfarin. Untreated mice (n=32) served as controls. We performed a 3-hour transient filament occlusion of the right middle cerebral artery. In a first set of animals, ischemic lesion size and HT were evaluated macroscopically at 24 hours after middle cerebral artery occlusion. In a second set of mice, quantitative analysis of HT was performed at different time points after middle cerebral artery occlusion and in animals with different international normalized ratio levels using a photometric hemoglobin assay.. Oral anticoagulant therapy at the onset of ischemia led to HT in all anticoagulated mice, whereas only 14% of the control mice showed HT. Mean HT blood volume 24 hours after middle cerebral artery occlusion was 0.3±0.4 μL in controls, 4.2±1.7 μL in mice anticoagulated to a mean international normalized ratio of 1.9±0.5 (P<0.05 versus controls), and 5.2±2.7 μL in mice with an international normalized ratio of 2.9±0.9 (P<0.001 versus controls). Anticoagulated mice euthanized at the time point of reperfusion had less HT than mice euthanized after 21 hours of reperfusion (1.6±0.5 μL versus 5.9±3.6 μL, P<0.05).. We present a mouse model of ischemic stroke occurring during oral anticoagulant therapy. Warfarin pretreatment dramatically increases the risk of HT 24 hours after middle cerebral artery occlusion. Reperfusion injury seems to be a critical component in this condition.

Topics: Animals; Anticoagulants; Brain Ischemia; Cerebral Hemorrhage; Cerebrovascular Circulation; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Infarction, Middle Cerebral Artery; Male; Mice; Mice, Inbred C57BL; Reperfusion Injury; Risk Factors; Stroke; Warfarin

Topics: Animals; Aspirin; Brain Damage, Chronic; Brain Ischemia; Calcium Channel Blockers; Cerebral Hemorrhage; Cerebrovascular Circulation; Clinical Trials as Topic; Fibrinolytic Agents; Heparin; Heparin, Low-Molecular-Weight; Humans; N-Methylaspartate; Neuroprotective Agents; Platelet Aggregation Inhibitors; Reperfusion Injury; Rodentia; Thrombolytic Therapy; Warfarin