Factor V Leiden: a genetic risk factor for thrombotic microangiopathy in patients with normal von Willebrand factor–cleaving protease activity

Raife, Thomas J.; Lentz, Steven R.; Atkinson, Bonnie S.; Vesely, Sara K.; Hessner, Martin J.

doi:10.1182/blood.v99.2.437

Cited by 50 publications

(48 citation statements)

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“…The cleavage of multimeric VWF by leukocyte proteases was analyzed in a modified version of the assay described by Furlan et al 21 and Raife et al 22 Purified VWF (Humate P; ZLB Behring GmbH) at a final concentration of 3 U/mL was incubated with enzymes for various times at 37°C in 5 mM Tris buffer, pH 8.0, with or without 1.5 mM urea. Final enzyme concentrations in the reaction were as follows: elastase 138 nM, PR3 172 nM, and cathepsin G 8.6 nM.…”

Section: Cleavage Of Multimeric Vwf Under Denaturing Conditionsmentioning

confidence: 99%

Leukocyte proteases cleave von Willebrand factor at or near the ADAMTS13 cleavage site

Raife

Cao

Atkinson

et al. 2009

Blood

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103

110

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The function of von Willebrand factor (VWF) is regulated by proteolysis, which limits its multimeric size and ability to tether platelets. The importance of ADAMTS13 metalloprotease in VWF regulation is demonstrated by the association between severe deficiency of ADAMTS13 and thrombotic thrombocytopenic purpura (TTP). However, ADAMTS13 activity levels do not always correlate with the clinical course of TTP, suggesting that other proteases could be important in regulating VWF. We identified 4 leukocyte IntroductionThe hemostatic activity of von Willebrand factor (VWF) is regulated in blood by the metalloprotease ADAMTS13, which cleaves VWF in the A2 domain. 1 The importance of VWF regulation by ADAMTS13 is demonstrated by the close association between severe deficiency of ADAMTS13 activity and thrombotic thrombocytopenic purpura (TTP). 2,3 However, the association between ADAMTS13 activity and TTP is imperfect. Patients with inhibitor-mediated ADAMTS13 deficiency can achieve clinical remission despite persistent severe deficiency of ADAMTS13 activity, 2,4 and not all patients with congenital deficiency of ADAMTS13 develop TTP. 5 Moreover, VWF proteolysis can be paradoxically increased in TTP patients during acute episodes. 6 These observations suggest the existence of other important disease-modifying factors in TTP, in addition to ADAMTS13.Disease-modifying factors in TTP may include other VWFcleaving proteases. Before the discovery of ADAMTS13, the proteases calpain, neutrophil elastase, and cathepsin G were known to cleave VWF. [7][8][9][10][11][12] However, the exact cleavage sites were not determined, and the physiologic relevance of these proteases was unknown. It was known that normal plasma contained proteolytic fragments of VWF having masses of approximately 176 kDa and 140 kDa. The primary cleavage site that gave rise to these fragments was identified as the Y1605-M1606 peptide bond. 13 In studies seeking to identify the responsible protease, Tsai et al 8,9,14 observed that neutrophil proteases cleaved high-molecular-weight VWF into a series of multimers indistinguishable from those found in normal plasma. By contrast, Berkowitz et al 10 concluded that VWF cleavage fragments generated by neutrophil elastase were different from the 176-kDa and 140-kDa fragments found in plasma. The role of leukocyte proteases in VWF regulation remained unresolved, and was later overshadowed by the discovery of ADAMTS13.In this study, we demonstrate that under denaturing and fluid shear stress conditions multiple leukocyte proteases cleave VWF predominantly in the central A2 domain. We also show that activated neutrophils, but not normal neutrophils, retain VWF cleaving activity in the presence of plasma inhibitors, suggesting that leukocyte proteases may regulate VWF function under physiologic conditions. Methods Patients and plasmaBlood samples were obtained from volunteer subjects after informed consent, in accordance with the Declaration of Helsinki, sanctioned by the institutional human research subject committees o...

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Section: Cleavage Of Multimeric Vwf Under Denaturing Conditionsmentioning

confidence: 99%

Leukocyte proteases cleave von Willebrand factor at or near the ADAMTS13 cleavage site

Raife

Cao

Atkinson

et al. 2009

Blood

Self Cite

103

110

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“…7,42 Similar to our observations, an additional study reported that 12 (29%) of 42 patients with TTP-HUS were African American; 11 (37%) of 30 patients who had ADAMTS13 deficiency were African Americans, and only 1 (8%) of 12 patients who did not have ADAMTS13 deficiency was African American. 24 The explanation for the increased relative frequency of African Americans among patients with clinically diagnosed TTP-HUS is unknown.…”

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confidence: 99%

ADAMTS13 activity in thrombotic thrombocytopenic purpura–hemolytic uremic syndrome: relation to presenting features and clinical outcomes in a prospective cohort of 142 patients

Vesely

George

Lämmle

et al. 2003

Blood

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637

757

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Initial management of patients with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) is difficult because of lack of specific diagnostic criteria, high mortality without plasma exchange treatment, and risks of plasma exchange. Although severe ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type 1 repeats) deficiency may be specific for TTP, the role of ADAMTS13 activity measurements for initial management decisions is unknown. ADAMTS13 was measured before beginning plasma exchange treatment in 142 (88%) of 161 consecutive patients with clinically diagnosed TTP-HUS with assignment to 1 of 4 categories: less than 5% (severe deficiency), 5% to 9%, 10% to 25%, and more than 25%. Eighteen (

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“…5,11 Briefly, 98 lL of undiluted sample plasma mixed with 50 lL of purified VWF (final concentration 3U/mL), 10 mmol/L Pefabloc SC (Boehringer, Mannheim, Germany), and 8 lL of 10 mmol/L BaCl 2 , was dialyzed (1.5 mol/L urea, 0.005 mol/L Tris, pH 8.0) in a hydrophilic filter membrane (VSWP, 47-mm diameter; Milipore, Bedford, MA) for 15 hours at 378C. The reaction was quenched with 10 lL of 0.2 mol/L EDTA, pH 7.4.…”

Section: Adamts13 Assaymentioning

confidence: 98%

“…5,11,12 In this study, TMA refers to disorders usually referred to by referring physicians as TTP, HUS, or TTP/HUS, which, by the standards of care in southeastern Wisconsin, warranted treatment by plasma exchange. The diagnostic criteria for TMA in this study included thrombocytopenia, microangiopathic hemolytic anemia, elevated lactate dehydrogenase, and absence of a diagnosis of disseminated intravascular coagulation or other plausible alternative diagnosis.…”

Section: Patients and Samplesmentioning

confidence: 99%

Hematocrit and C‐reactive protein predict treatment response times in ADAMTS13‐deficient thrombotic microangiopathy

Samia

Friedman

Gottschall

et al. 2011

J of Clinical Apheresis

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Thrombotic microangiopathy (TMA) syndromes are a heterogeneous group of microvascular syndromes that are typically treated with plasma exchange and other adjunctive therapies. Important pathogenic factors, such as ADAMTS13 deficiency, define distinct subsets of TMA. New treatments for TMA are being explored that are hypothesized to bring about remission more quickly. However, the existing factors that influence response to treatment time are poorly understood. We hypothesized that common laboratory parameters available at the time of treatment initiation might correlate with the number of days of plasma exchange required to induce remission. We therefore retrospectively compared pretreatment platelet counts, hematocrit levels, and C-reactive protein (CRP) levels to the number of days of plasma exchange treatment in 27 ADAMTS13-deficient TMA patients and 25 non-ADAMTS13-deficient patients that achieved remission. Using quantile regression analysis, we observed that in ADAMTS13-deficient patients, higher initial hematocrit levels significantly correlated with shorter treatment response times. In addition, for ADAMTS13-deficient patients, elevated levels of CRP correlated directly with longer response times. Higher platelet counts were associated with a nonsignificant trend toward shorter response times. In non-ADAMTS13-deficient TMA patients no significant correlations were observed. Our results suggest that when conducting clinical trials of adjunctive treatments for TMA, clinical data, including ADAMTS13 levels, pretreatment hematocrit levels, and CRP levels may be informative in interpreting response to treatment times.

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Factor V Leiden: a genetic risk factor for thrombotic microangiopathy in patients with normal von Willebrand factor–cleaving protease activity

Cited by 50 publications

References 50 publications

Leukocyte proteases cleave von Willebrand factor at or near the ADAMTS13 cleavage site

Leukocyte proteases cleave von Willebrand factor at or near the ADAMTS13 cleavage site

ADAMTS13 activity in thrombotic thrombocytopenic purpura–hemolytic uremic syndrome: relation to presenting features and clinical outcomes in a prospective cohort of 142 patients

Hematocrit and C‐reactive protein predict treatment response times in ADAMTS13‐deficient thrombotic microangiopathy

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