Histidine-rich glycoprotein binds factor XIIa with high affinity and inhibits contact-initiated coagulation

Blood ◽  
2011 ◽  
Vol 117 (15) ◽  
pp. 4134-4141 ◽  
Author(s):  
Jessica L. MacQuarrie ◽  
Alan R. Stafford ◽  
Jonathan W. Yau ◽  
Beverly A. Leslie ◽  
Trang T. Vu ◽  
...  
Keyword(s):  
Partial Thromboplastin Time ◽  
Activated Partial Thromboplastin Time ◽  
Factor Xii ◽  
Intrinsic Pathway ◽  
High Affinity ◽  
Factor Xiia ◽  
Platelet Release ◽  
Contact Pathway ◽  
Physiologic Role

Abstract Histidine-rich glycoprotein (HRG) circulates in plasma at a concentration of 2μM and binds plasminogen, fibrinogen, and thrombospondin. Despite these interactions, the physiologic role of HRG is unknown. Previous studies have shown that mice and humans deficient in HRG have shortened plasma clotting times. To better understand this phenomenon, we examined the effect of HRG on clotting tests. HRG prolongs the activated partial thromboplastin time in a concentration-dependent fashion but has no effect on tissue factor–induced clotting, localizing its effect to the contact pathway. Plasma immunodepleted of HRG exhibits a shortened activated partial thromboplastin time that is restored to baseline with HRG replenishment. To explore how HRG affects the contact pathway, we examined its binding to factors XII, XIIa, XI, and XIa. HRG binds factor XIIa with high affinity, an interaction that is enhanced in the presence of Zn2+, but does not bind factors XII, XI, or XIa. In addition, HRG inhibits autoactivation of factor XII and factor XIIa–mediated activation of factor XI. These results suggest that, by binding to factor XIIa, HRG modulates the intrinsic pathway of coagulation, particularly in the vicinity of a thrombus where platelet release of HRG and Zn2+ will promote this interaction.

scholarly journals Identification of the factor XII contact activation site enables sensitive coagulation diagnostics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Marco Heestermans ◽  
Clément Naudin ◽  
Reiner K. Mailer ◽  
Sandra Konrath ◽  
Kristin Klaetschke ◽  
...  
Keyword(s):  
Partial Thromboplastin Time ◽  
Thrombin Generation ◽  
Thrombus Formation ◽  
Coagulation Factors ◽  
Activated Partial Thromboplastin Time ◽  
Plasma Kallikrein ◽  
Factor Xii ◽  
Contact Activation ◽  
Intrinsic Pathway ◽  
Surface Binding

AbstractContact activation refers to the process of surface-induced activation of factor XII (FXII), which initiates blood coagulation and is captured by the activated partial thromboplastin time (aPTT) assay. Here, we show the mechanism and diagnostic implications of FXII contact activation. Screening of recombinant FXII mutants identified a continuous stretch of residues Gln317–Ser339 that was essential for FXII surface binding and activation, thrombin generation and coagulation. Peptides spanning these 23 residues competed with surface-induced FXII activation. Although FXII mutants lacking residues Gln317–Ser339 were susceptible to activation by plasmin and plasma kallikrein, they were ineffective in supporting arterial and venous thrombus formation in mice. Antibodies raised against the Gln317–Ser339 region induced FXII activation and triggered controllable contact activation in solution leading to thrombin generation by the intrinsic pathway of coagulation. The antibody-activated aPTT allows for standardization of particulate aPTT reagents and for sensitive monitoring of coagulation factors VIII, IX, XI.

Platelet-Bound Prekallikrein Promotes Pro-Urokinase-Induced Clot Lysis: A Mechanism for Targeting the Factor XII Dependent Intrinsic Pathway of Fibrinolysis

1994 ◽  
Vol 71 (03) ◽  
pp. 347-352 ◽  
Author(s):  
Jean-Pierre Loza ◽  
Victor Gurewich ◽  
Michael Johnstone ◽  
Ralph Pannell
Keyword(s):  
Platelet Rich Plasma ◽  
Specific Inhibitor ◽  
Specific Effect ◽  
Clot Lysis ◽  
Factor Xii ◽  
Intrinsic Pathway ◽  
Clot Retraction ◽  
Enzymatic Mechanism ◽  
Low Concentrations ◽  
Factor Xiia

SummaryClots formed from platelet rich plasma were found to be lysed more readily by low concentrations of pro-urokinase (pro-UK) than clots formed from platelet poor plasma. This was not a non-specific effect since the reverse occurred with tissue plasminogen activator. A mechanical explanation due to platelet-mediated clot retraction was excluded by experiments in which retraction was inhibited with cyto-chalasin B. Therefore, a platelet-mediated enzymatic mechanism was postulated to explain the promotion of fibrinolysis. Casein autography of isolated platelets revealed a ≈ 90 kDa band of activity which comigrated with plasma prekallikrein (PK)/kallikrein, a known activator of pro-UK. Furthermore, treatment of platelets with plasma PK activator (PPA), consisting essentially of factor XIIa, induced activation of pro-UK and of chromomgenic substrate for kallikrein (S-2302). This activity corresponded to approximately 40-200 pM kallikrein per 10 8 washed and gel filtered platelets per ml. The activation of pro-UK by PPA-pretreated platelets was dose-dependent and inhibited by soybean trypsin inhibitor but not by bdellin, a specific inhibitor of plasmin, nor by the corn inhibitor of factor XIIa. Kinetic analysis of pro-UK activation by kallikrein showed promotion of the reaction by platelets. The KM of the reaction was reduced by platelets by ≈ 7-fold, while the kcat was essentially unchanged. In conclusion, PK was shown to be tightly associated with platelets where it can be activated by factor XIIa during clotting. The activation of pro-UK by platelet-bound kallikrein provides an explanation for the observed platelet mediated promotion of pro-UK-induced clot lysis. Since pro-UK and plasminogen have also been shown to be associated with platelets, the present findings suggest a mechanism by which the factor Xlla-dependent intrinsic pathway of fibrinolysis can be localized and targeted to a thrombus.

How to Optimize Activated Partial Thromboplastin Time (APTT) Testing: Solutions to Establishing and Verifying Normal Reference Intervals and Assessing APTT Reagents for Sensitivity to Heparin, Lupus Anticoagulant, and Clotting Factors

2019 ◽  
Vol 45 (01) ◽  
pp. 022-035 ◽  
Author(s):  
Geoffrey Kershaw ◽  
Soma Mohammed ◽  
Giuseppe Lippi ◽  
Emmanuel Favaloro
Keyword(s):  
Molecular Weight ◽  
Partial Thromboplastin Time ◽  
Lupus Anticoagulant ◽  
High Sensitivity ◽  
Activated Partial Thromboplastin Time ◽  
Factor Xii ◽  
Reference Ranges ◽  
Clotting Factors ◽  
Hospital System ◽  
Normal Reference

AbstractThe activated partial thromboplastin time (APTT) assay is a very common coagulation test, used for several reasons. The test is conventionally used for assessing the contact factor (intrinsic) pathway of blood coagulation, and thus for screening deficiencies in this pathway, most typically factors VIII, IX, and XI. The APTT is also sensitive to contact factor deficiencies, including factor XII, prekallikrein, and high-molecular-weight kininogen. The APTT may also be elevated in a variety of conditions, including liver disease, vitamin K deficiency, and disseminated intravascular coagulation. The APTT can also be used for monitoring unfractionated heparin (UFH) therapy, as well as for screening lupus anticoagulant (LA) or for assessing thrombosis risk. Which of these separate uses is important to a given laboratory or clinician depends on the laboratory and the clinical context. For example, UFH sensitivity is important in hospital-based laboratories, where UFH therapy is used, but not in hospital-based laboratories where low-molecular-weight heparin (LMWH) is largely employed or where UFH may be assessed by anti-factor Xa testing, or in private/community laboratories not associated with a hospital system. High sensitivity to (low levels of) factors VIII, IX, and XI is generally preferred, as their deficiencies are clinically significant. Also preferred, but not usually achieved, is low sensitivity to factor XII and other contact factors, as these deficiencies are usually asymptomatic. Nevertheless, a good knowledge of factor sensitivity is usually needed, if only to help explain the reasons for a prolonged APTT in a given patient, or whether factor testing or other investigation is required. A good working knowledge of reagents sensitivity to LA is also advisable, especially when the reagent is used as part of a LA test panel, or else as a “general-purpose screening reagent.” The current report is aimed at providing some guidance around these questions, and is intended as a kind of “how to” guide, that will enable laboratories to assess APTT reagents in regard to their sensitivity to heparin, LA, and clotting factors. The report also provides some advice on generation of normal reference ranges, as well as solutions for troubleshooting prolonged APTTs, when performing factor testing or searching for inhibitors.

scholarly journals Inherited Factor XII Deficiency—What Is the Real Concern for Neuroanesthesiologist: Bleeding or Clotting

2020 ◽  
Author(s):  
Mouleeswaran Sundaram ◽  
Sonia Bansal ◽  
Rohini M. Surve
Keyword(s):  
Perioperative Management ◽  
Activated Partial Thromboplastin Time ◽  
Factor Xii ◽  
Intrinsic Pathway ◽  
Vertebral Fusion ◽  
Factor Xii Deficiency ◽  
Risk Of Bleeding ◽  
Increased Risk ◽  
Patient Factor

AbstractFactor XII deficiency is a rare disorder that can complicate the perioperative management of a patient. Factor XII plays an important role in the activation of intrinsic pathway of coagulation; the deficiency, therefore, results in prolongation of activated partial thromboplastin time (aPTT). This aPTT prolongation is expected to cause increased bleeding during surgery. However, on the contrary, in vivo isolated factor XII deficiency is associated with increased risk of thromboembolism (this risk being higher than the risk of bleeding). We report the perioperative management of a patient with factor XII deficiency who underwent cervical vertebral fusion (C1–C2) for atlantoaxial dislocation.

scholarly journals Rapid Loss of Factor XII- and XI-Activity in Ellagic Acid Activated Normal Plasma: Role of Plasma Inhibitors and Implications for Automated Aptt-Recording

1977 ◽  
Author(s):  
J. H. Joist ◽  
J. F. Cowan ◽  
M. Khan
Keyword(s):  
Ellagic Acid ◽  
Clinical Laboratory ◽  
Coagulation Factors ◽  
Activation Process ◽  
Factor Xii ◽  
Naturally Occurring ◽  
Normal Plasma ◽  
Factor Xiia ◽  
Loss Of Contact

Rapid prolongation of the activated partial thromboplastin time (aPTT) of normal plasma upon incubation with ellagic acid containing aPTT reagents was observed. The aPTT prolongation was not due to time dependent changes in pH in the incubation mixtures or loss of activity of the labile coagulation factors VIII and V, but occurred as a result of rapid progressive inactivation of ellagic acid activated factors XII and XI. Prolongation of the aPTT and loss of contact factor activities was not observed in plasma incubated with particulate activator reagents. This finding seemed to indicate that adsorption of factors XII and XI to larger particles during the activation process may protect these factors from inactivation by naturally occurring plasma inhibitors. Evidence is presented which supports previous observations that Ci-inhibitor, α1-antitrypsin and antithrombin III (in the presence of heparin contribute to factor XIIa- and XIa-inactivation in ellagic acid activated plasma and that plasma albumin may compete with factor XII for ellagic acid binding. The findings indicate that ellagic acid containing aPTT reagents have unfavorable properties which seriously limit their usefulness in the clinical laboratory, particularly in respect to recording of the aPTT with certain fully automated clot timers.

scholarly journals Factor XII in PMM2-CDG patients: role of N-glycosylation in the secretion and function of the first element of the contact pathway

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Raquel López-Gálvez ◽  
María Eugenia de la Morena-Barrio ◽  
Alberto López-Lera ◽  
Monika Pathak ◽  
Antonia Miñano ◽  
...  
Keyword(s):  
Factor Xii ◽  
Clinical Effects ◽  
Wild Type ◽  
Vascular Events ◽  
Contact Phase ◽  
Glycosylation Sites ◽  
Expression Model ◽  
Contact Pathway ◽  
And Function

Abstract Background Congenital disorders of glycosylation (CDG) are rare diseases with impaired glycosylation and multiorgan disfunction, including hemostatic and inflammatory disorders. Factor XII (FXII), the first element of the contact phase, has an emerging role in hemostasia and inflammation. FXII deficiency protects against thrombosis and the p.Thr309Lys variant is involved in hereditary angioedema through the hyperreactivity caused by the associated defective O-glycosylation. We studied FXII in CDG aiming to supply further information of the glycosylation of this molecule, and its functional and clinical effects. Plasma FXII from 46 PMM2-CDG patients was evaluated by coagulometric and by Western Blot in basal conditions, treated with N-glycosydase F or activated by silica or dextran sulfate. A recombinant FXII expression model was used to validate the secretion and glycosylation of wild-type and variants targeting the two described FXII N-glycosylation sites (p.Asn230Lys; p.Asn414Lys) as well as the p.Thr309Lys variant. Results PMM2-CDG patients had normal FXII levels (117%) but high proportions of a form lacking N-glycosylation at Asn414. Recombinant FXII p.Asn230Lys, and p.Asn230Lys&p.Asn414Lys had impaired secretion and increased intracellular retention compared to wild-type, p.Thr309Lys and p.Asn414Lys variants. The hypoglycosylated form of PMM2-CDG activated similarly than FXII fully glycosylated. Accordingly, no PMM2-CDG had angioedema. FXII levels did not associate to vascular events, but hypoglycosylated FXII, like hypoglycosylated transferrin, antithrombin and FXI levels did it. Conclusions N-glycosylation at Asn230 is essential for FXII secretion. PMM2-CDG have high levels of FXII lacking N-glycosylation at Asn414, but this glycoform displays similar activation than fully glycosylated, explaining the absence of angioedema in CDG.

One-stage Assay for Hageman Factor (Factor XII). Further Studies on the Role of Hageman Factor in Blood Coagulation

1963 ◽  
Vol 09 (03) ◽  
pp. 557-569 ◽  
Author(s):  
C Haanen ◽  
John G. G Schoenmakers
Keyword(s):  
Factor Ix ◽  
Factor Xii ◽  
Charged Surface ◽  
Dilution Curve ◽  
Adsorbed State ◽  
Hageman Factor ◽  
High Affinity ◽  
One Stage ◽  
Glass Surfaces

SummaryA one stage assay for Hageman Factor (HF) activity is described. Maximal standardization was achieved by lyophilizing substrate plasma, cephalin suspension and standard reference plasma in small aliquots. A dilution curve was constructed, using a highly purified HF preparation. The assay is not completely specific and is invalidated by the presence of activated Factor IX and XI. So all materials to be tested were first adsorbed on Al(OH)3-gel to exclude Factor IX and possibly most of Factor XI.Purified activated HF still possesses a high affinity for glass surfaces, thus activation may not alter the molecule at the side of affinity for the glass surface. Moreover purified activated HF is still more active in the presence of glass thus in the adsorbed state. These observations support the idea that the so called activation of Hageman Factor is a reversible phenomenon, whereby the molecule unfolds and uncovers active groups as soon as it is adsorbed on a negatively charged surface.

A Monoclonal Antibody Raised against Human β-factor XIIa which also Recognizes α-factor XIIa but not Factor XII or Complexes of Factor XIIa with C1 Esterase Inhibitor

2000 ◽  
Vol 83 (06) ◽  
pp. 874-881 ◽  
Author(s):  
M. Esnouf ◽  
Annette Burgess ◽  
Alister Dodds ◽  
Anna Sarphie ◽  
George Miller
Keyword(s):  
Monoclonal Antibody ◽  
Gel Filtration ◽  
Complex Surface ◽  
Factor Xii ◽  
Binding Studies ◽  
Western Blots ◽  
High Affinity ◽  
Factor Xiia ◽  
Health And Disease ◽  
Esterase Inhibitor

SummaryA monoclonal antibody (mAb 2/215) against human β-factor XIIa (β-FXIIa), was shown by equilibrium binding studies to have a high affinity for α-factor XIIa (α-FXIIa) (Kd 1.8 nM) and β-FXIIa (Kd 0.65 nM) but no detectable reaction with FXII zymogen or α - esterase inhibitor (C1-INH) complex. Surface plasmon resonance studies showed that the mAb 2/215 bound to immobilized α-FXIIa with high affinity (KD 3.93 ± 1.46 × 10−11 M). Western blots employing mAb 2/215 indicated that human plasma contained small amounts of α-FXIIa but no β-FXIIa. mAb 2/215 did not inhibit the amidolytic activity of β-FXIIa and protected β-FXIIa from inhibition by C1-INH. The recovery by ELISA ,employing mAb 2/215 as the capture antibody, of α-FXIIa added to plasma was 11.3%, 42% after inhibition of α-FXIIa with 3:4dichloroisocoumarin, and 82% when 0.5% TritonX100 was added to the assay. Gel filtration showed that the majority of plasma α-FXIIa existed as a complex (Mr ∼170000). This distinctive mAb increases the capacity to study the contact system in health and disease.

DEMONSTRATION OF Cl-INHIBITOR COMPLEXES IN PLASMA BY HIGHLY SENSITIVE RADIOIMMUNOASSAYS USING A MONOCLONAL ANTIBODY AGAINST A NEODETERMINANT ON COMPLEXED Cl-INHIBITOR

1987 ◽  
Author(s):  
J H Nuijens ◽  
C C M Huijbregets ◽  
L G Thijs ◽  
C E Hack
Keyword(s):  
Monoclonal Antibody ◽  
Contact System ◽  
Factor Xii ◽  
Optimal Conditions ◽  
Spleen Cells ◽  
Highly Sensitive ◽  
Factor Xiia

Levels of factor XIIa- and kallikrein-Cl inhibitor (Cl-Inh) complexes in plasma reflect activation of the contact system in vivo. Here, we report the development of radioimmunoassays (RIAs) for these complexes using a monoclonal antibody (mAb K0K12) that reacts with a neodeterminant exposed on Cl-Inh after interaction with proteases. mAb K0K12 was obtained by a fusion experiment with spleen cells of a mouse hyperimmunized with Cl-Inh complexes.Experiments with purified Cl-Inh incubated with either Cls or elastase revealed that the determinant for mAb KOK12 is exposed on complexed as well as proteolytically inactivated (modified) Cl-Inh.Radioimmunoassays (RIAs) for the detection of factor Xlla-Cl-Inh and kallikrein-Cl-Inh complexes were performed as follows: mAb K0K12 was coupled to Sepharose and incubated with the sample to be tested. Binding of Cl-Inh complexes was detected by a subsequent incubation with 125I-antibodies against factor XII or (pre)kallikrein.With these RIAs, activation of 0.1% of factor XII or prekal-likrein in plasma is easily detected.Optimal conditions for blood sampling and processing were established, i.e. conditions that prevented any in vitro activation of factor XII and prekallikrein. Levels of factor XIIa-Cl-Inh and kallikrein-Cl-Inh complexes in plasma samples from normal donors were less than 0.1 U/ml (100 U/ml is the maximal amount of Cl-Inh complexes generated in pooled plasma by DXS). Considerably higher, and fluctuating levels were observed in patients with diseases such as septicaemia. These highly sensitive RIAs will facilitate studies concerning the role of the contact system in human pathophysiology.

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