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PubMedDate not supplied

Activation of the plasma kinin forming cascade along cell surfaces.

Proteins of the plasma kinin-forming cascade bind to endothelial cells and activation of the cascade can be initiated along the surface. The light chain of high molecular weight kininogen (HK) (domain 5) and factor XII bind to gC1qR, the heavy chain of HK (domain 3) binds to cytokeratin 1 and the interactions are zinc dependent. Prekallikrein binds to domain 6 of HK. Antisera to gC1qR and cytokeratin 1 inhibit binding and activation. Incubation of normal plasma with endothelial cells leads to gradual conversion of prekallikrein to kallikrein, while plasma deficient in factor XII or HK are inactive within a 2-hour time frame. Thus factor XII is critical for activation to proceed. Augmentation of these reactions may occur when C1 inhibitor is functionally deficient or with ACE inhibitors which also inhibit kininases.

Carrier Proteins↗
PubMed1994

Stearic acid, clotting, and thrombosis.

Stearic acid causes hypercoagulability of the blood by activation of factor XII and by aggregation of blood platelets. Injection of unbound stearic acid (sodium salt) into the systemic circulation of dogs was followed by massive generalized thrombosis and sudden death. Similar infusions into birds, which are deficient in factor XII, did not cause hypercoagulability or thrombosis. The effects of the long-chain saturated fatty acids could be prevented by using albumin to bind the stearic acid at a molar ratio of free fatty acid (FFA) to albumin of < 2. The major issue is whether eating foods rich in stearic acid can cause a thrombogenic effect. We have no experimental evidence to support this concept. If a thrombogenic effect of long-chain saturated fatty acids exists in humans, it is most likely to occur as an aberration of fatty acid transport in which the FFA-albumin molar ratio exceeds 2 either as a result of very high plasma FFA concentrations from lipid mobilization or a low concentration of albumin in the blood as found in disease states such as the nephrotic syndrome.

Animals↗
PubMed1977

Oxygen-induced consumptive coagulopathy and its enhancement by lead acetate.

The exposure of rats to 100% oxygen at 1 atmosphere leads to a prolongation of prothrombin times and activated partial thromboplastin times. This development is associated with a consumption of factor XII, VIII, and VII activities and with the appearance of fibrin monomers and fibrinogen degradation products. Lead acetate enhances all oxygen-induced changes of the coagulation systems drastically. The O2 survival time of chicks which are naturally deficient in factor XII is greatly increased over that of rats and is not affected by lead acetate. Oxygen survival times of rats suffering from chronic respiratory disease (CRD) are also significantly increased when compared with normal rats. It appears that consumptive coagulopathy and disseminated intravascular coagulation are early events in oxygen exposure, and that their development is accelerated by lead ions.

Animals↗
PubMed1977

Activation of factor XII by tobacco glycoprotein.

A glycoprotein of mol wt ca. 18,000 daltons isolated from cured tobacco leaves (TGP-L) and from cigarette smoke condensate (TGP-CSC) activated factor XII in normal human plasma in vitro as measured by (a) shortening of the partial thromboplastin time, (b) shortening of the lysis time of euglobulin clots, and (c) generation of kinin activity. These effects were not demonstrable in plasma deficient in factor XII. The capacity of TGP-L and TGP-CSC to activate factor XII was shown to depend on the presence of rutin, a substance chemically similar to quercetin and ellagic acid, which are known activators of factor XII. Rutin and rutin coupled to bovine serum albumin, but not bovine serum albumin alone, were also demonstrated to activate factor XII. The presence in cigarette smoke of material that is both allergenic and capable of activating factor XII of the intrinsic pathway of coagulatin may be important to the pathogenesis of cardiovascular and pulmonary disease associated with cigarette smoking.

Animals↗
PubMed1984

Enhanced prothrombin-converting activity and factor Xa binding of platelets activated by the alternative complement pathway.

Platelet prothrombin-converting activity and factor Xa binding were studied after exposure of human platelet rich plasma (PRP) to various conditions leading to platelet activation. Zymosan resulted in increased platelet-bound C3, enhanced prothrombin-converting activity and increased factor Xa binding. Similar findings were observed with normal platelets resuspended in factor XII-deficient plasma. The combined use of zymosan and thrombin to activate platelets resulted in synergistic prothrombin-converting activity and factor Xa binding. In contrast, no synergism was obtained with the concomitant use of zymosan and collagen, suggesting that collagen and zymosan share the same pathway for platelet activation. Heterologous antibody to factor V completely inhibited the platelet prothrombin-converting activity for all modes of platelet activation, indicating that this activity is mediated by factor V.

Blood Platelets↗
PubMed1997

[Regulation of biological functions by the Kallikrein-Kinin system].

Research on the kallikrein-kinin system started from the discovery of urinary hypotensive substance in Germany around 1940-1950. Since then, numbers of researchers have explored this field including related inhibitors, enzymes and autacoids, from all over the world. Components of the kallikrein-kinin system have been analysed extensively, especially since the epoch of the discovery of the deficient patients in these components. Recent progress of gene techniques also enhanced the progress of the study in the kallikrein-kinin field. In this review I discuss about 1) Components and the difference of plasma kallikrein system and glandular kallikrein system; 2) Impact of the discovery of the deficient plasma in Factor XII, prekallikrein, kininogens as well as in C1INH, and consequent knowledge from the studies of these deficients; 3) Biological roles of the kallikrein-kinin system; and recent topics in this field.

Animals↗
PubMed1988

Structural changes of plasma high molecular weight kininogen after in vitro activation and in sepsis.

High molecular weight kininogen (HMWK) is a multifunctional protein that is a parent molecule for bradykinin, a cofactor for coagulation, and an inhibitor of cysteine proteases. On immunoblot, nonreduced plasma HMWK is usually two bands at 140 kd and 120 kd; reduced plasma HMWK is a single band at 120 kd. In both concentration-dependent and time-dependent experiments kaolin-activated normal plasma HMWK becomes cleaved in an ordered sequence. When nonreduced, HMWK on immunoblot in kaolin-activated plasma changes in size from a 140 kd band through a 120 kd intermediate to result in a stable 100 kd protein. When reduced, HMWK on immunoblot in kaolin-activated plasma changes from a single 120 kd band through a 56 kd intermediate to result in a stable 46 kd protein. A similar sequence of cleavage of plasma HMWK occurs when the soluble activator dextran sulfate is used to stimulate the system. Cleavage of plasma HMWK after kaolin activation occurs similarly in factor XI-deficient plasma as in normal plasma but is decreased in prekallikrein-deficient plasma. Prolonged kaolin activation of prekallikrein-deficient plasma results in HMWK cleavage to bands below 120 kd. No band of plasma HMWK below 120 kd appears in prolonged kaolin-activated factor XII-deficient plasma. In some patients with sepsis, detectable cleavage of plasma HMWK to bands below 120 kd may not be seen, even though the patient has other evidence for contact system activation. In conclusion, these studies indicate that certain cleaved patterns of plasma HMWK on immunoblot indicate prior activation of the contact system. However, the absence of these cleaved forms of plasma HMWK in a single plasma does not exclude the occurrence of contact activation.

Bacterial Infections↗
PubMed1982

Acquired antibody to factor XI in a patient with congenital factor XI deficiency.

The results of studies in a patient with congenital deficiency of Factor XI who developed an inhibitor are presented. The patient presented with a severe, apparently spontaneous bleed into the thigh, which progressed despite infusion of fresh frozen plasma, but which responded promptly to activated prothrombin complex. During therapy with plasma his clotting time and Factor XI level were unresponsive and a Factor XI inhibitor titer of 6,000 U/ml was attained. The inhibitor was isolated and found to be polyclonal immunoglobulin G (IgG), predominantly of subclass 4. The specificity of the antibodies for Factor XI was shown by the ability of isolated inhibitor bound to polyacrylamide beads to remove Factor XI selectively from normal plasma. The binding of (125)I-labeled factor XI to the inhibitor was studied and an affinity constant of 1.65 x 10(10) liter/mol was found. Complexing of the antibodies with Factor XI was shown to block multiple activities of the clotting factor. Factor XI complexed with antibody did not bind to high molecular weight kininogen or undergo activation and cleavage by two-chain Factor XII. The complex of activated Factor XI with inhibitor prevented the cleavage and activation of Factor IX. Hence the inhibitor appears to act by binding to multiple sites on the Factor XI molecule and preventing its interaction with other molecules. Clinically these interactions of the inhibitor with Factor XI result in a state of severe Factor XI deficiency. The clinical circumstances of the case, with severe hemorrhage refractory to plasma infusion but readily responsive to an alternate clot-promoting agent, suggest that a defect of intrinsic system activation was critical, supporting the inference that Factor XI does participate in normal hemostasis. The clinical course of this patient, who has only had two documented hemorrhages in the presence of the inhibitor, is not as severe as that of patients with severe Factor VIII or IX deficiency. This suggests that physiologic activation of Factors XI and IX does not occur exclusively in series because deficiency of factors XII, XI, VIII, and IX should then have similar hemostatic consequences. We propose that independent mechanisms for bypass of Factors XII and XI are important in physiologic activation of coagulation.

Animals↗
PubMed1993

The relationship between factor VII coagulant activity and factor XII activation induced in plasma by endogenous or exogenously added contact surface.

The contribution of various enzymes in the activation of factor VII, determined from the increase in factor VII coagulant activity (VIIc), was investigated following the exposure of citrated plasma to low temperature. The contact system of coagulation was initiated either by the contact surface present in certain plasmas (i.e. plasma from women in late pregnancy) or by micellar stearate added to plasma diluted with an equal volume of buffer (plasma from normal healthy subjects or from women in late pregnancy). With either of the contact surfaces, increase of VIIc and the concentration of enzymes derived from factor XII (XIIa) depended on the potency of the contact surface. The stearate-induced VIIc in diluted plasmas from women in late pregnancy or from normal subjects was inhibited by 60-70% in the presence of anti-factor IX monoclonal antibody. VIIc was not increased in XII-deficient plasma following the addition of stearate. The addition of purified human factor XII to this plasma restored the increase in VIIc and the activation of factor XII. In factor IX-deficient plasma, the stearate-induced increase in VIIc was only 38% of that seen in normal plasma and was restored by the addition of purified factor IX. Similarly in factor XI-deficient plasma, the stearate-induced increase in VIIc and the factor XII activation were 48% and 69% of that found in normal plasma. The addition of EDTA (2 mM) did not alter the extent of factor XII activation induced by contact surface, but it did inhibit the rise in VIIc. It is concluded that in the presence of contact surface the activation of factor XII and the sequential activation of factor XI and of factor IX results in the activation of factor VII. Activated factor IX is responsible for the major part of the factor VII activation whereas the rest may be through the direct activation by XIIa.

Antibodies, Monoclonal↗