Comparison of recombinant and plasma-derived antithrombin biodistribution in a rabbit model

2009 ◽  
Vol 102 (08) ◽  
pp. 302-308 ◽  
Author(s):  
Leslie Berry ◽  
Bruce Thong ◽  
Anthony Chan
Keyword(s):  
Vessel Wall ◽  
Degradation Products ◽  
Rabbit Model ◽  
Coagulation Cascade ◽  
Blood Levels ◽  
Vascular Thrombosis ◽  
Time Points ◽  
Heparin Complexes ◽  
Time Periods ◽  
Native Plasma

SummaryAntithrombin (AT) is a native plasma protein that acts as the main inhibitor of enzymes generated by the coagulation cascade. In extreme thrombotic conditions, consumption of plasma AT can make treatment with AT-associated heparin therapies less effective. Supplementation with recombinant human AT (rhAT) has shown promise but altered pharmacokinetics were observed when comparing stable heparin complexes of the plasma-derived AT (pAT) and rhAT proteins. To understand the differential clearance mechanisms,biodistribution of rhAT and pAT was determined. 125I-labelled ATryn (rhAT) or Kybernin P (pAT) was intravenously injected into rabbits. At various time points, animals were sacrificed and organs analysed for bound radioactivity. 131I-albumin, injected shortly before termination, was used as a marker for trapped blood. Levels of circulating protein + metabolites were significantly less for rhAT than pAT (p < 0.001) and removal of acid soluble fragments confirmed that differences were due to more rapid rhAT clearance. More rhAT (28% dose) than pAT (3% dose) was liver-associated by the earliest time points, corresponding to elevated rhAT degradation products in urine/feces. However, at intermediate times (4 hours), rhAT showed significantly increased arterial and venous uptake over pAT (p ≤0.001).These vessel wall interactions accounted for the primary differences between clearance of rhAT and pAT during these time periods. Overall, circulating rhAT is more rapidly lost to the liver and vessels than pAT. Increased vessel wall binding may facilitate rhAT treatment of vascular thrombosis.

Abstract 5763: Dynamic Contrast-Enhanced MRI Detects Early Plaque Progression in a Rabbit Model of Atherosclerosis

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
William S Kerwin ◽  
Jerry Ricks ◽  
Michael Rosenfeld
Keyword(s):  
Vessel Wall ◽  
High Speed ◽  
Rabbit Model ◽  
Atherosclerotic Lesion ◽  
Intraplaque Hemorrhage ◽  
Slice Thickness ◽  
Dce Mri ◽  
Dynamic Contrast Enhanced ◽  
Contrast Enhanced ◽  
Plaque Inflammation

Recent studies have used dynamic contrast-enhanced (DCE) MRI to quantify the rate of uptake of gadolinium contrast agents in atherosclerotic plaque. The transfer constant K trans , that quantifies the blood supply and permeability of the plaque, shows strong association with plaque inflammation. The purpose of this study was to explore the link between K trans and plaque inflammation in a model of early atherosclerotic lesion development. Twelve NZW rabbits were placed on a 0.2% cholesterol diet and underwent balloon injury of the descending aorta. After 12 weeks, all rabbits underwent a DCE-MRI exam, after which 6 were euthanized and perfusion fixed to harvest the atherosclerotic aortas. The remaining 6 were imaged again at 24 weeks and their aortas were harvested. The DCE-MRI procedure utilized a unique, high-speed, small field-of-view imaging technique with quadruple inversion recovery blood suppression (turbo spin echo, TR=800 ms, TE=9ms, 3mm slice thickness, 0.5mm in-plane resolution). This allowed us to observe enhancement of the vessel wall without contamination from enhancement of the adjacent lumen. The DCE-MRI results were analyzed to determine the average, relative K trans in the vessel wall and compared to histological assessments of the aortas. K trans was significantly higher at 6 months compared to 3 months within the same animals (p<0.005) and compared to those euthanized at 3 months (p<0.001). No difference was observed between the two groups at 3 months (p=0.4). Histologically, aorta cross sections at 6 months had lesions that were no thicker than those at 3 months (0.49 vs. 0.45mm, p=0.6), but complex lesion features including necrotic cores, intraplaque hemorrhage, neovessels, and deep clusters of macrophages were significantly more common at 6 months (82% vs. 18%, p<0.001). The transformation of the lesions from simple to complex morphologies from 12 weeks to 24 coincided with a significant rise in K trans . We attribute this rise to the development of neovessels in response to pro-inflammatory stimuli. We conclude that K trans can be used to probe lesion characteristics and complexity in early atherosclerosis, with applications in early diagnosis and treatment monitoring. This research has received full or partial funding support from the American Heart Association, AHA Pacific/Mountain Affiliate (Alaska, Arizona, Colorado, Hawaii, Idaho, Montana, Oregon, Washington & Wyoming).

scholarly journals Molecular Characterization of the Transcription Factors in Susceptible Poplar Infected with Virulent Melampsora larici-populina

2019 ◽  
Vol 20 (19) ◽  
pp. 4806 ◽  
Author(s):  
Qiaoli Chen ◽  
Jianan Wang ◽  
Danlei Li ◽  
Zhiying Wang ◽  
Feng Wang ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Calcium Binding ◽  
Bioinformatics Analysis ◽  
Pathological Process ◽  
Compatible Interaction ◽  
Time Points ◽  
Time Periods ◽  
Two Phases ◽  
Transcript Profiles

Transcription factors (TFs) have been shown to play important roles in determining poplar susceptibility. In this study, the transcript profiles of five resistance-related TF groups at different time points were investigated to study the roles of TFs in the compatible interaction between ‘Robusta’ (Populus nigra × P. deltoides) and the virulent E4 race of Melampsora larici-populina. The susceptibility test indicated that the parasitic process of E4 could be divided into two representative time periods: the infection phase and the production phase. Bioinformatics analysis showed that in these two phases, E4 infection induced a network of TFs in ‘Robusta’. Although some TFs responded rapidly and positively, most TFs did not respond to E4, especially during the infection phase. The ethylene, jasmonic acid, and auxin pathways were downregulated, while a calcium-binding protein was upregulated. No other significantly changed phytohormone-related genes were found, which was consistent with the pathological process in the absence of an immune response, suggesting that the lack of response of most TFs during the infection phase of E4 is related to the susceptibility of ‘Robusta’.

scholarly journals A Soluble Tissue Factor Mutant Is a Selective Anticoagulant and Antithrombotic Agent

Blood ◽  
1997 ◽  
Vol 89 (9) ◽  
pp. 3219-3227 ◽  
Author(s):  
Robert F. Kelley ◽  
Canio J. Refino ◽  
Mark P. O'Connell ◽  
Nishit Modi ◽  
Pat Sehl ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Arterial Thrombosis ◽  
Factor Viia ◽  
Rabbit Model ◽  
Coagulation Cascade ◽  
Factor X ◽  
Rabbit Plasma ◽  
Extrinsic Pathway ◽  
Antithrombotic Agent ◽  
Thrombotic Disease

Abstract One approach to developing safer and more efficacious agents for the treatment of thrombotic disease involves the design and testing of inhibitors that block specific steps in the coagulation cascade. We describe here the development of a mutant of human tissue factor (TF ) as a specific antagonist of the extrinsic pathway of blood coagulation and the testing of this mutant in a rabbit model of arterial thrombosis. Alanine substitutions of Lys residues 165 and 166 in human TF have been shown previously to diminish the cofactor function of TF in support of factor X (FX) activation catalyzed by factor VIIa (FVIIa). The K165A:K166A mutations have been incorporated into soluble TF (sTF; residues 1-219) to generate the molecule “hTFAA.” hTFAA binds FVIIa with kinetics and affinity equivalent to wild-type sTF, but the hTFAA⋅FVIIa complex shows a 34-fold reduction in catalytic efficiency for FX activation relative to the activity measured for sTF⋅FVIIa. hTFAA inhibits the activation of FX catalyzed by the complex formed between FVIIa and relipidated TF(1-243). hTFAA prolongs prothrombin time (PT) determined with human plasma and relipidated TF(1-243) or membrane bound TF, and has no effect on activated partial thromboplastin time, but is 70-fold less potent as an inhibitor of PT with rabbit plasma. The rabbit homologue of this mutant (“rTFAA”) was produced and shown to have greater potency with rabbit plasma. Both hTFAA and rTFAA display an antithrombotic effect in a rabbit model of arterial thrombosis with rTFAA giving full efficacy at a lower dose than hTFAA. Compared to heparin doses of equal antithrombotic potential, hTFAA and rTFAA cause less bleeding as judged by measurements of the cuticle bleeding time. These results indicate that TF⋅FVIIa is a good target for the development of new anticoagulant drugs for the treatment of thrombotic disease.

scholarly journals Activation of the coagulation system in polycythemia vera

Blood ◽  
1976 ◽  
Vol 47 (4) ◽  
pp. 669-678 ◽  
Author(s):  
A Carvalho ◽  
L Ellman
Keyword(s):  
Polycythemia Vera ◽  
Degradation Products ◽  
Gel Filtration ◽  
Coagulation Cascade ◽  
Coagulation System ◽  
Factor Xii ◽  
Fibrin Degradation Products ◽  
System Activation ◽  
Chronic Activation ◽  
Kallikrein Inhibitors

Abstract Thrombosis is one of the major complications of polycythemia vera. Seventeen patients with polycythemia vera in good hematologic control were evaluated for abnormalities of the coagulation system. Activation of the intrinsic coagulation cascade was suggested by low levels of factor XII, prekallikrein, and kallikrein inhibitors in 12 of 17 patients. The group also demonstrated a significant increase in soluble fibrin complexes using plasma gel filtration on 4% agarose. Fibrin degradation products were normal and antithrombin III levels were slightly elevated. It appears that patients with polycythemia vera have chronic activation of the coagulation system, probably initiated by activation of factor XII. No correlation between the degree of coagulation abnormalities and thromboembolic complications was evident in this group of patients.

scholarly journals Postangioplasty Restenosis Followed with Magnetic Resonance Imaging in an Atherosclerotic Rabbit Model

2012 ◽  
Vol 2012 ◽  
pp. 1-8
Author(s):  
Mari Hänni ◽  
Olli Leppänen ◽  
Örjan Smedby
Keyword(s):  
Vessel Wall ◽  
Distal Part ◽  
Rabbit Model ◽  
Transluminal Angioplasty ◽  
Proton Density ◽  
Histopathological Analysis ◽  
Resonance Imaging ◽  
Significant Difference ◽  
New Zealand White Rabbits ◽  
Percutaneous Transluminal

Rationale and Objectives. Testing a quantitative, noninvasive method to assess postangioplasty vessel wall changes in an animal model.Material and Methods. Six New Zealand white rabbits were subjected to atherosclerotic injury, including cholesterol-enriched diet, deendothelialization, and percutaneous transluminal angioplasty (PTA) in the distal part of abdominal aorta (four weeks after deendothelialization). The animals were examined with a 1.5T MRI scanner at three times as follows: baseline (six weeks after diet start and two days after PTA) and four weeks and 10 weeks after-PTA. Inflow angiosequence (M2DI) and proton-density-weighted sequence (PDW) were performed to examine the aorta with axial slices. To identify the inner and outer vessel wall boundaries, a dynamic contour algorithm (Gradient Vector Flow Snakes) was applied to the images, followed by calculation of the vessel wall dimensions. The results were compared with histopathological analysis.Results. The wall thickness in the lesion was significantly higher than in the control region at 4 and 10 weeks, reflecting induction of experimentally created after-angioplasty lesion. At baseline, no significant difference between the two regions was present.Conclusions. It is possible to follow the development of vessel wall changes after-PTA with MRI in this rabbit model.

scholarly journals Susceptibility to Thrombin-Induced Platelet Microbicidal Protein Is Associated with Increased Fluconazole Efficacy against Experimental Endocarditis Due to Candida albicans

2004 ◽  
Vol 48 (8) ◽  
pp. 3051-3056 ◽  
Author(s):  
Michael R. Yeaman ◽  
Darwin Cheng ◽  
Bhavesh Desai ◽  
Leon I. Kupferwasser ◽  
Yan-Qiong Xiong ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Host Defense ◽  
Rabbit Model ◽  
Fungal Burden ◽  
Treatment Groups ◽  
Time Points ◽  
Platelet Microbicidal Protein ◽  
The Relationship

ABSTRACT Platelet microbicidal proteins (PMPs) are believed to be integral to host defense against endovascular infection. We previously demonstrated that susceptibility to thrombin-induced PMP 1 (tPMP-1) in vitro negatively influences Candida albicans virulence in the rabbit model of infective endocarditis (IE). This study evaluated the relationship between in vitro tPMP-1 susceptibility (tPMP-1s) or resistance (tPMP-1r) and efficacy of fluconazole (FLU) therapy of IE due to C. albicans. Candida IE was established in rabbits with either tPMP-1s or tPMP-1r strains. Treatment groups received FLU (100 mg/kg/day) intraperitoneally for 7 or 14 days; control animals received no therapy. At these time points, cardiac vegetations, kidneys, and spleens were quantitatively cultured to assess fungal burden. At both 7 and 14 days and in all target tissues, the extent of candidal clearance by FLU was greater in animals infected with the tPMP-1s strain than in those infected with the tPMP-1r strain. These differences were statistically significant in the spleen and kidney. Corroborating these in vivo data, FLU (a candidastatic agent), in combination with tPMP-1, exerted an enhanced fungicidal effect in vitro against tPMP-1s and tPMP-1r C. albicans, with the extent of this effect greatest against the tPMP-1s strain. Collectively, these results support the concept that tPMP-1 susceptibility contributes to the net efficacy of FLU against C. albicans IE in vivo, particularly in tissues in which platelets and tPMP-1 likely play significant roles in host defense.

Cholesterol-induced Thrombogenicity of the Vessel Wall: Inhibitory Effect of Fluvastatin

2002 ◽  
Vol 87 (04) ◽  
pp. 748-755 ◽  
Author(s):  
Marina Camera ◽  
Vincenzo Toschi ◽  
Carmen Comparato ◽  
Roberta Baetta ◽  
Francesca Rossi ◽  
...  
Keyword(s):  
Serum Cholesterol ◽  
Transcriptional Activation ◽  
Vessel Wall ◽  
Arterial Wall ◽  
Thrombus Formation ◽  
Plasma Cholesterol ◽  
Elevated Serum ◽  
Rabbit Model ◽  
Cholesterol Levels ◽  
Platelet Deposition

SummaryHigh cholesterol levels are a known risk factor for coronary events. The molecular links between high serum cholesterol and the increased thrombogenicity of the arterial wall are still matter of investigation. In the present study we investigate the relationship between plasma cholesterol, thrombus formation and TF expression in a atherosclerotic rabbit model.Hypercholesterolemic rabbits showed a pronounced TF staining as well as NF-κB activation in the aortic arch. A consistent vessel wall platelet deposition was also observed. Treatment with fluvastatin reduced lipid accumulation, TF overexpression (-60%), NF-κB activation, and platelet deposition (-56%). In vitro studies showed that the drug upregulated IκBa in unstimulated as well as in TNFa-stimulated cells and also impaired the TNF-α-induced Cdc42 prenylation, indicating that fluvastatin interferes with the transcriptional activation of TF gene.These results indicate that the prothrombotic phenotype of arterial wall, associated with elevated serum cholesterol levels, is mediated by TF overexpression. Fluvastatin treatment reduces the prothrombotic tendency by inhibiting TF synthesis.

The contributions of the α2β1 integrin to vascular thrombosis in vivo

Blood ◽  
2003 ◽  
Vol 102 (10) ◽  
pp. 3652-3657 ◽  
Author(s):  
Li He ◽  
Loretta K. Pappan ◽  
David G. Grenache ◽  
Zhengzhi Li ◽  
Douglas M. Tollefsen ◽  
...  
Keyword(s):  
Vascular Injury ◽  
Vessel Wall ◽  
Platelet Adhesion ◽  
Thrombus Formation ◽  
Critical Role ◽  
Flow Conditions ◽  
In Vivo Models ◽  
Vascular Thrombosis ◽  
Α2β1 Integrin

AbstractThe α2β1 integrin serves as a receptor for collagens, laminin, and several other nonmatrix ligands. Many studies have suggested that the α2β1 integrin is a critical mediator of platelet adhesion to collagen within the vessel wall after vascular injury and that the interactions of the platelet α2β1 integrin with subendothelial collagen after vascular injury are required for proper hemostasis. We have used the α2β1 integrin-deficient mouse to evaluate the contributions of the α2β1 integrin in 2 in vivo models of thrombosis. Studies using a model of endothelial injury to the carotid artery reveal that the α2β1 integrin plays a critical role in vascular thrombosis at the blood-vessel wall interface under flow conditions. In contrast, the α2β1 integrin is not required for the formation of thrombi and pulmonary emboli following intravascular injection of collagen. Our results are the first to document a critical in vivo role for the α2β1 integrin in thrombus formation at the vessel wall under conditions of shear following vascular injury. (Blood. 2003;102:3652-3657)

scholarly journals Estimation of causal effects of a time-varying exposure at multiple time points through Multivariable Mendelian randomization

2022 ◽  
Author(s):  
Eleanor Sanderson ◽  
Tom G Richardson ◽  
Tim T Morris ◽  
Kate Tilling ◽  
George Davey Smith
Keyword(s):  
Direct Effect ◽  
Genetic Variants ◽  
Causal Effect ◽  
Smoking Behaviour ◽  
Causal Effects ◽  
Mendelian Randomisation ◽  
Multiple Time ◽  
Time Points ◽  
Time Periods ◽  
Multiple Time Points

Mendelian Randomisation (MR) is a powerful tool in epidemiology to estimate the causal effect of an exposure on an outcome in the presence of unobserved confounding, by utilising genetic variants as instrumental variables (IVs) for the exposure. The effects obtained from MR studies are often interpreted as the lifetime effect of the exposure in question. However, the causal effects of many exposures are thought to vary throughout an individual's lifetime and there may be periods during which an exposure has more of an effect on a particular outcome. Multivariable MR (MVMR) is an extension of MR that allows for multiple, potentially highly related, exposures to be included in an MR estimation. MVMR estimates the direct effect of each exposure on the outcome conditional on all of the other exposures included in the estimation. We explore the use of MVMR to estimate the direct effect of a single exposure at different time points in an individual's lifetime on an outcome. We use simulations to illustrate the interpretation of the results from such analyses and the key assumptions required. We show that causal effects at different time periods can be estimated through MVMR when the association between the genetic variants used as instruments and the exposure measured at those time periods varies, however this estimation will not necessarily identify exact time periods over which an exposure has the most effect on the outcome. We illustrate the method through estimation of the causal effects of childhood and adult BMI on smoking behaviour.

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