Patho-Physiology of Kallikrein System

ANNALS OF CLINICAL AND LABORATORY SCIENCE, Vol. 10, No. 3 Copyright (£) 1980, Institute for Clinical Science, Inc. Patho-Physiology of Kallikrein System ROBERT W. COLMAN, M.D. Thrombosis Center and Hematology ¡Oncology, Section of the Department of Medicine, Temple University School of Medicine, Philadelphia, PA 19140 ABSTRACT The properties of the contact factors, factor XII, high molecular weight kininogen and prekallikrein are described as well as the abnormalities in the hereditary deficiencies of these proteins. The interactions of each of these proteins with the other as well as their regulation by plasma proteolytic inhibitors such as Cl inhibitor and antithrombin III are delineated. Biochemical techniques for measuring this system are discussed. Condi tions associated with abnormal synthesis of these proteins are described. Diseases in which increased kinin formation has been documented as well as disorders where there is strong evidence for the activation of kallikrein are presented. Further knowledge of this system should increase our under standing of its pathophysiological alterations. Introduction illustrates the various control mechanism possible in proteolysis, including activa The plasma proteolytic enzyme systems tion of inactive precursors, positive feed of coagulation, fibrinolysis and kinin for back, stochiometric inhibition, multistep mation have been categorized as a “tan amplification and enzymatic degradation gled web.” The three interlocking net of active products. works are linked together in two ways. Factor XII (a beta globulin), molecular First, the initiating pathways are common weight 90,000, is first converted to an ac and factor XII (Hageman) factor is a pro tive derivative of the same size, factor tein intimately involved in all. Second, at Xlla, upon exposure to negatively least four inhibitors with defined specific charged foreign surfaces which in vivo is ity each have the capacity to regulate more the subendothelial basement membrane. than one system. The current understand The importance of factor XII for initiation ing of the three interlocking networks that of the various plasma proteolytic systems mediate the vascular responses necessary is emphasized by the fact that Hageman for hemostasis, fibrinolysis and vasodila factor deficient plasm a not only has a very tion (kinin forming system) are displayed prolonged partial thromboplastin time in figure 1. The working of these enzymes (PTT), which measures the steps to the 220 0091-7370/80/0500-0220 $01.20 © Institute for Clinical Science, Inc. PATHO-PHYSIOLOGY OF KALLIKREIN SYSTEM 2 2 1 formation of thrombin, but it also fails to support surface initiated fibrinolysis as Bradykinn well as the generation of bradykinin. These pathways have been shown to be Plasmin mediated by the various Hageman factor substrates. I Plasminogli Activation of Proteins Activation of other proteins is required for the coagulation pathway to proceed. Hageman factor activation of prekalli- 1I------ Prothrombinl—^ iSlPL.Ca ........s- krein generates the enzyme kallikrein which digests kininogen to liberate the FIG U R E 1. Participation of components of the vasoactive peptide bradykinin. However, kallikrein-kinin system in coagulation and fibrinoly sis. Boxed components represent precursors. factor Xlla, though a potent coagulant, has Dashed arrows represent transformation of precur relatively less activity in initiating kalli sor to product. Solid arrows are actions of a proteoly krein or plasmin formation. To perform tic enzyme. Dotted arrows are nonproteolytic activa these latter functions effectively, factor tion. Kgn = kininogen. Xlla must be proteolysedto Hageman fac tor fragments (XII/). The formation of these activators are a site for control since tal abnormalities have disclosed new the eventual products of the reaction exert functions for old proteins. a positive feedback in their own formation. Thromboplastin Factor Kallikrein can in the fluid phase cleave factor XII to Hageman factor fragments In 1965, Fletcher trait deficiency11 was (molecular weight 30,000) which are described as an autosomal recessive dis much more potent in prekallikrein activa order characterized by a diminished rate tion than the intact molecule .1 H ig h of surface mediated coagulation. This molecular weight (HMW) kininogen has a plasma possessed an unusual abnormality central place in the scheme. It is the pre in that the partial thromboplastin time, a ferred substrate from which kallikrein re measure of overall intrinsic coagulation, leases bradykinin. It also potentiates the returned to normal as the time of incuba conversion of Hageman factor to activated tion with surface (kaolin) was increased. Hageman factor on a surface22 an d to The factor in normal plasma which cor Hageman factor fragments in the fluid rected the deficiency was partially puri phase.10 In addition, it potentiates the ac fied. In 1972, the corrective protein was tion of activated Hageman factor on clot identified as prekallikrein.24 The Fletcher ting factor XI and Hageman factor frag trait plasma also possessed an abnormality ments on the reciprocal activation of kal in the rate of surface mediated firinolysis likrein.14 Kallikrein also directly activates and generated no bradykinin upon incu plasminbgen to plasmin, the enzyme re bation with kaolin. This last abnormality sponsible for fibrinolysis.4 R ecently, it has is expected if the plasma contained no been demonstrated by us that Hageman prekallikrein, but one would not have factor fragments can activate factor VII.21 readily predicted an effect upon the Thus, a link is created between the intrin coagulation and fibrinolytic pathways. sic and extrinsic pathways. In the dissec The presence of both of these abnor tion of the system, patients with congeni- malities suggested an effect upon Hage- 222 COLMAN man factor, one protein common to each pathway. Correction of both the coagula tion and fibrinolytic defects of Fletcher trait plasma by activated Hageman factor in the absence of a surface demonstrated that the abnormality was a diminished rate of formation of activated Hageman factor. This positive feedback of kallikrein may account for the decrease of surface initiated fibrinolysis and coagulation in Fletcher factor trait. An additional protein was found to be required for surface activation of Hage man factor as a result of investigation of F ig u r e 2. Comparison of the kaolin-activated three patients in different laboratories. In euglobulin lysis time of Williams trait plasma, nor 1974, a 64-year-old woman Mrs. Williams, mal plasma, and Fletcher trait plasma. Precisely 0.5 was referred, owing to an abnormal intrin ml of each plasma or an equal mixture of Williams and Fletcher trait plasmas were added to 4.25 ml of sic coagulation system in which all known sodium acetate buffer, pH 4.8. Exactly 0.25 ml of factors were normal. The results of further kaolin (8 mg per m l) was then added, the mixture was incubated at 37° C, and aliquots of 0.2 ml were re investigation of her coagulation defect re moved at intervals. The plasmin generated was de vealed that the abnormal partial throm termined as the euglobulin lysis time. boplastin time test was corrected by one- quarter volume of Hageman trait or tion, the addition of Hageman factor frag Fletcher trait plasma, indicating that these ments or even purified plasma kallikrein plasmas contained adequate concen did not initiate kinin formation indicating trations of the missing factor in William’s complete lack of kininogen. This result trait plasma. Unlike Fletcher trait plasma, was confirmed by demonstrating that Wil prolonged incubation with kaolin failed to liam’s plasma did not react with an an correct the coagulation abnormality of tiserum against kininogen. However, low William’s trait.3 molecular weight kininogen did not cor- A profound defect was also found in the fibrinolytic system of William’s plasma. The addition of kaolin markedly in creased the fibrinolytic potential of nor mal plasma shown as an increase of the reciprocal of the euglobulin lysis time (figure 2). As previously reported, Fletcher plasma showed a decreased rate of activation by kaolin. In contrast, Wil liam’s plasma showed virtually no in crease of fibrinolytic activity after expo sure to kaolin. A mixture of equal volumes of William’s and Fletcher plasma com pletely corrected the defect. Similar de Slice No. fects were found in the conversion of pre- F ig u r e 3. Alkaline disc gel electrophoresis at kallikrein to kallikrein. pH 9.3 of 30 ixg of high molecular weight kininogen When kaolin was added to William’s (B4-) obtained from Bio-Gel 0.5 m. A replicate disc plasma, no bradykinin was detected by gel was sliced and eluted; this eluate was assayed for kininogen antigen by counterimmunoelectro- bioassay. Although this might have been phoresis and for its ability to correct the coagulation due to the failure of prekallikrein activa- defect of Williams trait plasma. PATHO-PHYSIOLOGY OF KALLIKREIN SYSTEM 2 2 3 rect the fibrinolytic, coagulation and prekallikrein activation defects in William’s plasma. About 15 percent of kininogen is in a high molecular weight form. To determine whether or not the HMW kininogen is identical to William’s factor, HMW kininogen was purified with the use of an immunoabsorbent column of monospecific kininogen antiserum. HMW kininogen ran as a single peak on disc electrophoresis. Elution of an un stained gel showed that the kininogen antigen and William’s factor, as measured by a coagulant assay, were in the same position (figure 3). Thus, the major coagulant factor missing in William’s plasma appears to be similar or identical to HMW kininogen which by itself cor rects all the defects. Evaluation of Abnormalities (units/ml) FIGURE 4. Prekallikrein (1.0 kallikrein esterase In evaluating the abnormalities in defi unit) was incubated with HF/ (0.6 ¡x g per ml) for 3 cient plasma, it became clear that prekal- min at 37°C in the presence of various concen likrein and HMW kininogen are coagula trations of high molecular weight kininogen.

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