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R W Colman

Publications and source records attributed to R W Colman.

At least 109 records · Page 6Linked to original sources
PubMed1996

Selective kallikrein-kinin system activation in inbred rats differentially susceptible to granulomatous enterocolitis.

BACKGROUND & AIMS: Crohn's disease is characterized by unrestrained inflammation with a genetic component. Genetic susceptibility and activation of the kalli-krein-kinin (contact) system were investigated in experimental enterocolitis and extraintestinal inflammation induced by bacterial polymers. METHODS: Kinetics of inflammation in inbred Lewis and Buffalo rats injected subserosally with peptidoglycan-polysaccharide polymers were correlated with in vivo and in vitro activation of the contact system. RESULTS: Lewis rats had a biphasic course of enterocolitis. Acute inflammation peaked 1 day after injection, gradually decreasing until day 14 when intestinal inflammation spontaneously reactivated and persisted for 16 weeks, accompanied by arthritis, granulomatous hepatitis, anemia, and leukocytosis. Self-limited acute enterocolitis in Buffalo rats resolved by 24 days without extraintestinal involvement. Consumption of the precursor proteins prekalli-krein and high-molecular-weight kininogen indicated activation of the plasma contact system in Lewis rats and closely correlated with chronic intestinal inflammation. Contact system activation did not occur in Buffalo rats, even during acute inflammation. In vitro studies showed a decreased rate of kininogen cleavage in Buffalo plasma. CONCLUSIONS: Selective in vivo and in vitro activation of the contact system in susceptible Lewis rats suggests that this pathway is one determinant of genetic susceptibility to granulomatous enterocolitis and systemic complications.

Acute-Phase Proteins↗
PubMed1996

Kininogen changes in human plasma following a test meal or insulin administration.

The effect of food intake and of insulin on plasma bradykinin (BK) reserves [total (TK), high-molecular-weight (HK), and low-molecular-weight kininogen (LK)] was followed by determining (by enzyme-linked immunosorbent assay) the amount of BK released by trypsin from plasma collected before and after a test meal or hyperinsulinemic clamping. LK was kininogen remaining in plasma after in vitro kaolin treatment, which removes all HK. HK was the difference between TK and LK. Thirty minutes after a test meal, TK and HK decreased by 8.0 +/- 0.6 and 39.7 +/- 6.6%, respectively, in six of seven subjects. Return to prealimentary levels occurred after 90-120 min. Hyperinsulinemia, comparable to that arising after the test meal, partly reproduced such treatment's effect on TK and HK but did not affect blood or plasma kininogen in vitro. Observed postprandial hypotension and increased leg blood flow could be caused, in part, by BK released from plasma HK after cleavage at vascular, possibly endothelial, sites activated by insulin.

Adult↗
PubMed1996

Nafamostat mesilate, a broad spectrum protease inhibitor, modulates platelet, neutrophil and contact activation in simulated extracorporeal circulation.

Activation of humoral and cellular participants in inflammation enhances the risk of postoperative bleeding and multiple organ damage in cardiopulmonary bypass (CPB). We now compare the effects of heparin alone in combination with nafamostat mesilate (NM), a protease inhibitor with specificity of trypsin-like enzymes, in an extracorporeal circuit which simulates CPB. NM significantly inhibits the release of platelet beta-thromboglobulin (beta TG) at 60 and 120 min. Platelet counts do not differ. ADP-induced aggregation decreases in circuits with NM, which is due to a direct effect of NM on platelet function. NM prevents any significant release of neutrophil elastase; at 120 min, plasma elastase-alpha 1-antitrypsin complex is 0.16 micrograms/ml in the NM group and 1.24 micrograms/ml in the control group. NM completely inhibits formation of complexes of C1 inhibitor with kallikrein and FXIIa. NM does not alter markers of complement activation (C1-C1-inhibitor complex and C5b-9), or indicators of thrombin formation (F1.2). However, at 120 min, thrombin activity as measured by release of fibrinopeptide A is significantly decreased. The data indicate that complement activation during CPB correlates poorly with neutrophil activation and that either kallikrein or FXIIa or both may be more important agonists. The ability of NM to inhibit two important contact system proteins and platelet and neutrophil release raises the possibility of suppressing the inflammatory response during clinical CPB.

Anticoagulants↗
PubMed1995

Inhibition of the conversion of pre-interleukins-1 alpha and 1 beta to mature cytokines by p-benzoquinone, a metabolite of benzene.

Chronic exposure of humans to benzene causes severe bone marrow cell depression leading to aplastic anemia. Marrow stromal macrophage dysfunction and deficient interleukin-1 production has been reported for patients with severe aplastic anemia. The stromal macrophage, a target of benzene toxicity, is involved in hematopoietic regulation through the synthesis of several cytokines including interleukin-1, which is required for production by stromal fibroblasts of a number of cytokines required for the survival of hematopoietic progenitor cells. We have previously demonstrated that hydroquinone, a major toxic metabolite of benzene in marrow, prevents the proteolytic conversion of 31 kDa pre-interleukin-1 alpha to the 17 kDa cytokine by calpain in purified murine stromal macrophages. Furthermore, stromal macrophages from benzene-treated mice produce the 31 kDa pre-interleukin-1 alpha when stimulated in culture with endotoxin, but cannot convert the precursor to interleukin-1 alpha. In this report, we show that 1,4-benzoquinone, the oxidation product of hydroquinone in the cell, causes a concentration-dependent inhibition of highly purified human platelet calpain with an IC50 of 3 microM. Hydroquinone also inhibits the processing of pre-interleukin-1 beta by interleukin-1 beta convertase. The addition of 2 microM hydroquinone to B1 cells that undergo autocrine stimulation by interleukin-1 beta resulted in the cessation of autocrine cell growth and interleukin-1 beta secretion into the culture medium, as determined by Western immunoblots of the culture supernatants. Purified converting enzyme treated with 3 microM benzoquinone was incapable of converting 31 kDa recombinant pre-interleukin-1 beta to the 17 kDa mature cytokine as analyzed by polyacrylamide gel electrophoresis and Western immunoblotting. These findings support our observations in a mouse model that benzene-induced bone marrow cell depression results from a lack of interleukin-1 alpha subsequent to an inhibition by benzoquinone of calpain, the protease required for converting pre-interleukin-1 alpha to active cytokine. The results may provide a basis for studying benzene-induced aplastic anemia in a mouse model.

Benzene↗
PubMed1995

Cofactors V and VIII after endotoxin administration to human volunteers.

Coagulation factor V (FV) and factor VIII (FVIII) are usually decreased in septicemic DIC. Low doses of endotoxin administered to healthy volunteers stimulate activation of the fibrinolytic, contact and coagulation systems, but not clinical DIC. Following the administration of endotoxin (4 ng/kg) to normal volunteers (n = 15), we applied new assays for FV antigens using monoclonal antibodies to the activation peptide (C1) and to the light chain of FV. At 5 hours, FV coagulant activity was significantly decreased (64 +/- 9%), as was the FV light chain antigen (74 +/- 6%), without a change in factor V C1 antigen or total protein C. In contrast, FVIII coagulant activity was greater than preinfusion levels at 2-5 hours. The decrease in FV activity may be due to APC cleavage of FV heavy chain, but the loss of light chain antigen suggests that plasmin and/or calpain also contribute. APC may not be the only enzyme responsible for cofactor inactivation. FV is one of the most sensitive markers, even reflecting subclinical activation of coagulation.

Adult↗
PubMed1995

Divalent metal cation requirement and possible classification of cGMP-inhibited phosphodiesterase as a metallohydrolase.

cGMP-inhibited phosphodiesterase (cGI-PDE) has been found to require a divalent metal cation for cAMP hydrolysis. The cGI-PDE isolated from human platelets exhibited significantly higher enzymatic activity when incubated with Mn2+, Mg2+, and Co2+. The addition of Zn2+, Cd2+, Ca2+, K+, or Na+ to the enzyme did not enhance the activity and, when present in high concentration (> 1.0 microM), Zn2+ and Cd2+ inhibited the enzymatic activity of cGI-PDE. The inhibition by Zn2+ (and Cd2+) was partially prevented by preincubation of the enzyme with Mn2+. The enzyme was also inhibited by metal chelators EDTA and 1,10-phenanthroline and not by their non-metal-chelating analogs. The partial protection against chelation (and inhibition) was afforded by AMP (the product of cAMP hydrolysis).

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1995

Inhibition of ADP-induced platelet responses by covalent modification of aggregin, a putative ADP receptor, by 8-(4-bromo-2,3-dioxobutylthio)ADP.

ADP is an important platelet agonist which initiates platelet shape change, aggregation, exposure of fibrinogen receptors, and calcium mobilization. Because of the limitations of previously used affinity analogs and photo-labeling studies as well as controversies surrounding the identity of an ADP receptor on platelets, we have used an affinity label capable of alkylating a putative exofacial receptor on platelets. We now report that 8-(4-bromo-2,3-dioxobutylthio)adenosine-5'-diphosphate (8-BDB-TADP), which is an analog of the natural ligand ADP, blocked ADP-induced platelet shape change, aggregation, exposure of fibrinogen-binding sites, secretion, and calcium mobilization. Following modification by 8-BDB-TADP, the rates of aggregation of platelets induced by thrombin, a calcium ionophore (A23187) or a stimulator of protein kinase C (phorbol myristate acetate) were minimally affected. However, the 8-BDB-TADP-modified platelets exhibited decreased rates of aggregation in response to ADP, as well as collagen and a thromboxane mimetic (U46619), both of which partially require ADP. Autoradiograms of the gels obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of solubilized platelets modified by either [beta-32P]8-BDB-TADP, or 8-BDB-TADP and NaB[3H]4 showed the presence of a single radiolabeled protein band at 100 kDa. The intensity of this band was reduced when platelets were preincubated with ADP, ATP, and 8-bromo-ADP prior to labeling by the radioactive 8-BDB-TADP. The results show that 8-BDB-TADP selectively and covalently labeled aggregin (100 kDa), a putative ADP receptor, resulting in a loss of ADP-induced platelet responses.

Adenosine Diphosphate↗
PubMed1995

Determination of gene structure by intron trapping using polymerase chain reaction: application to the human plasma prekallikrein gene.

We have devised a method to determine gene structure that utilizes the known gene structure of homologous proteins and the polymerase chain reaction (PCR). Because homologous proteins have evolved from a common ancestral gene, it is possible to design primers corresponding to the adjacent exon sequences in the protein of interest. These primers could then be used in a PCR using normal genomic DNA as template. The resultant PCR product is then subcloned and the nuceotide sequence of the insert is determined. This information provides the exon-intron junction sequences and the partial sequences of the intron. We have applied this method to trap introns A, H, and J of human plasma prekallikrein gene and determined their exon-intron junction sequences. The primers were designed based on the known cDNA sequence of human plasma prekallikrein and gene structures of rat plasma prekallikrein and human coagulation factor XI (which is 50% identical in the primary sequence). The intron-exon junctions are at identical sites to those of the rat plasma prekallikrein gene. The intron sequences thus obtained will be useful in designing primers for exon trapping and sequence analysis of plasma prekallikrein gene from patients with defective plasma prekallikrein. This technique will also allow the determination of the entire gene structure.

Amino Acid Sequence↗
PubMed1995

Inhibition of plasma kallikrein prevents peptidoglycan-induced arthritis in the Lewis rat.

We investigate whether the previously shown contact system activation plays a pathogenetic role in a rat model of acute inflammation induced by peptidoglycan-polysaccharide (PG-APS) using a new specific plasma kallikrein inhibitor, Bz-Pro-Phe-boroArg-OH (P8720). Group I (control) received neither PG-APS nor inhibitor. Group II (disease-treated) received PG-APS intraperitoneally (IP) and P8720 orally. Group III (disease-untreated) received PG-APS IP. Anemia was evident at 49 h in group III but was not present (P < 0.01) in groups I and II. Spleen weight was significantly decreased in group II compared to group III. Acute arthritis progressively developed in group III from 27 to 49 h, but P8720 decreased the joint swelling in group II by 61% (P < 0.0005). We observed a significant fall in prekallikrein and factor XI (P < 0.01) in groups II and III but not in group I. The decrease in the functional levels of high molecular weight kininogen (P < 0.05) observed in group III were prevented by P8720 in group II. The changes in T-kininogen and alpha 1-inhibitor 3 acute-phase proteins were partially prevented by P8720. We conclude that the inflammatory reactions leading to arthritis and anemia, as well as the acute-phase reaction, are due in part to contact activation, and that specific kallikrein inhibitors may have therapeutic potential.

Acute-Phase Proteins↗
PubMed1995

Prognostic value of assessing contact system activation and factor V in systemic inflammatory response syndrome.

OBJECTIVE: To test if serially sampled determinations of the contact system proteins and factor V have prognostic value for death in patients who develop the systemic inflammatory response syndrome. DESIGN: Prospective, observational study with sequential measurements in an inception cohort. SETTING: Medical intensive care unit (ICU) in a community hospital. PATIENTS: Over a 1-yr period, a population base sample of 23 patients was selected from all ICU admissions who met established criteria for the systemic inflammatory response syndrome. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Components of the contact system, factor XII, prekallikrein, high-molecular-weight kininogen, factor XI, alpha 2-macroglobulin-kallikrein complexes and factor V values were measured in plasma samples collected serially (day of admission, and at 2, 12, 24, 48 and/or 72 hrs or at discharge). Data were analyzed to determine if admission values or serially obtained values within 48 hrs were useful in predicting outcome. Fourteen patients survived and nine died. At admission, in all patients, assay values indicated that prekallikrein, high-molecular-weight kininogen, and factor V were significantly lower than normal (as observed in a range of 20 to 23 healthy adults), alpha 2-macroglobulin-kallikrein complexes were higher than normal, while concentrations of factor XII and factor XI were in the normal range. No differences were detected in the admission values between survivors and nonsurvivors, nor between patients with positive or negative blood cultures. However, subsequent values demonstrated a difference in values between survivors and nonsurvivors. Survivors showed improvement in high molecular weight kininogen values and higher than normal factor V values, as compared with nonsurvivors. CONCLUSIONS: Low or persistently low serial factor XII, high-molecular-weight kininogen and factor V values are associated with a poor prognosis, whereas high or increasing values of factor XII, high-molecular-weight kininogen, prekallikrein, and factor V all correlate with a favorable outcome.

Aged↗
PubMed1994

High molecular weight kininogen binds to Mac-1 on neutrophils by its heavy chain (domain 3) and its light chain (domain 5).

High molecular weight kininogen (HK) binds specifically, saturably, and reversibly to neutrophils and also reciprocally inhibits the binding of fibrinogen to neutrophils. Since fibrinogen binds to the leukocyte integrin CD11b/18 (Mac-1, alpha M beta 2), we investigated whether HK bound to Mac-1 and whether the binding site was similar to that for factor X. We also examined whether one or both chains of cleaved HK (HKa) were involved. Two monoclonal antibodies, 2B5 (0.29 microM) to HK heavy chain domains 2 (D2) and 3 (D3), and C11C1 (0.26 microM) to HK light chain domain 5 (D5), inhibited by 99 and 93% the binding, respectively, of 125I-HK (8.3 nM) to neutrophils. To minimize steric hindrance, we further demonstrated that the Fab' fragments of 2B5 and C11C1 were able to inhibit the binding of this ligand to virtually the same extent as the intact antibody, indicating that, as in binding of HK to platelets and endothelial cells, both chains are involved. To directly demonstrate the involvement of each chain, we showed that the reduced alkylated light chain derived from HK and low molecular weight kininogen, which contains the same heavy chain as HK, each markedly inhibited the binding of HK to neutrophils. We localized the domain responsible for the binding in each chain by showing that recombinant D3 and D5 decreased the binding of HK to neutrophils. To define the receptor for HK, we employed three monoclonal antibodies to Mac-1: OKM1 and OKM10 to epitopes on the alpha M subunit and IB4 to an epitope on the beta 2 chain. OKM1, which can inhibit fibrinogen binding to neutrophils, inhibited HK binding by 79%, whereas the other antibodies inhibited HK binding less than 25%. Coagulation factor X also binds to Mac-1 on monocytes at a similar site to C3bi. Synthetic peptides which define noncontiguous surface loops in factor X that interact with Mac-1, failed to inhibit 125I-HK binding to neutrophils. We conclude that HK binds, via domains on its heavy chain, D3, and light chain, D5, to Mac-1 on the neutrophil surface, and HK occupies a site overlapping with fibrinogen and different from factor X.

Amino Acid Sequence↗
PubMed1994

The shape of high molecular weight kininogen. Organization into structural domains, changes with activation, and interactions with prekallikrein, as determined by electron microscopy.

Knowledge of the organization of the kininogen gene and protein structure and function correlations has allowed the development of a model of high molecular weight kininogen. Domains 1-3 on the heavy chain are evolutionarily related to cystatin and the latter two are inhibitors of cysteine proteases. Proteolytic cleavage in domain 4 to release bradykinin causes a conformational change, exposing a surface-binding region (domain 5) on the disulfide-linked light chain. The carboxyl-terminal domain 6 contains a zymogen binding sequence for factor XI and prekallikrein which, with domain 5, accounts for its cofactor activity. To explore further the domain structure, we have determined the shapes of high molecular weight kininogen and prekallikrein by electron microscopy of rotary shadowed preparations and computer image processing. High molecular weight kininogen appears to be a linear array of three linked globular regions about 16 nm long, with the two ends also connected by another thin strand. Both prekallikrein and kallikrein have a compact globular shape, with a subdivision that is sometimes visible. Different functional domains of high molecular weight kininogen were identified by monoclonal antibodies against these regions, as well as ligand binding of prekallikrein. These studies indicate that one end globular region is the prekallikrein-binding domain, the other comprises the cysteine protease inhibitor domains and the smaller central nodule is the surface-binding domain. Cleavage of high molecular weight kininogen with plasma kallikrein to yield two-chain high molecular weight kininogen results in a striking change in conformation: the central surface-binding domain swings out so that it is still adjacent to the prekallikrein-binding domain but no longer in the middle. These structural studies provide insight into the interactions of these proteins and aspects of the mechanisms of their actions.

Amino Acid Sequence↗
PubMed1994

Localization of the binding site on plasma kallikrein for high-molecular-weight kininogen to both apple 1 and apple 4 domains of the heavy chain.

The C-terminal end of the heavy chain of human plasma prekallikrein or kallikrein contains a binding site for high-molecular-weight kininogen, the nonenzymatic procofactor of contact activation. To further map this binding site, a series of overlapping peptides were synthesized. The amount of kallikrein that bound to kininogen-coated microtiter plate wells in the presence of increasing concentrations of each peptide was determined by kallikrein amidolytic activity. A peptide encompassing Lys266-Gly295 of kallikrein, conformationally constrained by a disulfide bond, displayed the lowest Kd value (approximately 67 microM). The linear peptide, Leu262-Gly295, displayed lower affinity (129 microM). N-terminal or C-terminal truncation/extension peptides of this sequence diminished binding activity. Since the closely related protein, factor XI, has been shown to bind kininogen, a kallikrein-based peptide (Phe56-Gly86) homologous to the binding domain of FXI, was examined and found to possess less, but significant, binding affinity for kininogen (Kd 530 microM). Isothermal titration calorimetry was used to assess binding between the kallikrein-based peptides and a peptide encompassing the kallikrein binding domain in kininogen (Ser565-Lys595). Leu262-Gly295 possesses potent binding activity (Kd 52 microM), while Phe56-Gly86 displays poorer binding activity (Kd 400 microM). These interactions are endothermic and entropically favored, suggesting that a conformational rearrangement takes place upon binding. We conclude that the binding site for kininogen within prekallikrein is composed of discontinuous linear segments that form a contiguous surface in the folded protein.

Amino Acid Sequence↗
PubMed1994

An autoantibody to human plasma prekallikrein blocks activation of the contact system.

A patient without a history of bleeding or thromboembolism presented with an activated partial thromboplastin time (aPTT) of 55.1 s (normal 24-38 s). Incubation of the patient plasma with an equal volume of normal plasma failed to correct the aPTT, suggesting the presence of an inhibitor. The MRVVT (modified Russell Viper venom time) was normal, and the anti-cardiolipin antibody titres were not elevated, indicating that the presence of a lupus anticoagulant was unlikely. Plasma prekallikrein (PK) measured by a coagulant assay (2 U/dl) was very low, but PK was in the low normal range (approximately 65%) when measured by an enzymatic assay (amidolytic) or by an antigenic assay (ELISA). The purified patient IgG reacted with purified PK, the heavy chain, and the 28 kD fragment of the heavy chain, indicating that it contained an autoantibody to PK. The purified IgG did not directly inhibit the amidolytic activity of kallikrein, but it did inhibit the activation of PK to kallikrein by activated factor XII. Activation of the contact system by dextran sulphate, as reflected by the cleavage of HK on a Western blot, was inhibited when the patient IgG was added to pooled normal plasma. The antibody appears to be oligoclonal with IgG1 being most abundant, followed by IgG4. This report appears to be the first of a spontaneously occurring antibody to prekallikrein.

Autoantibodies↗
PubMed1994

Alpha 1-antitrypsin Pittsburgh (Met358-->Arg) inhibits the contact pathway of intrinsic coagulation and alters the release of human neutrophil elastase during simulated extracorporeal circulation.

Cardiopulmonary bypass prolongs bleeding time, increases postoperative blood loss, and triggers activation of plasma proteolytic enzyme systems and blood cells referred to as the "whole body inflammatory response". Contact of blood with synthetic surfaces leads to qualitative and quantitative alterations in platelets, neutrophils, contact and complement systems. Contact and complement pathway proteins both induce neutrophil activation. alpha 1-antitrypsin Pittsburgh (Met358-->Arg), a mutant of alpha 1-antitrypsin, is a potent inhibitor of plasma kallikrein and thrombin. We investigated whether this recombinant mutant protein inhibited platelet activation, as well as contact and/or complement-induced neutrophil activation during simulated extracorporeal circulation. Arg358 alpha 1-antitrypsin did not prevent the 34% drop in platelet count at 5 min of recirculation, did not block the 50% decrease in ADP-induced platelet aggregation at 120 min of recirculation, nor inhibit the release of 6.06 +/- 1.07 micrograms/ml beta-thromboglobulin at 120 min of recirculation suggesting that the inhibitor had little effect on platelet activation. However, Arg358 alpha 1-antitrypsin totally blocked kallikrein-C1-inhibitor complex formation but not C1-C1-inhibitor complex formation. Most importantly, Arg358 alpha 1-antitrypsin decreased the release of 1.11 +/- 0.16 micrograms/ml human neutrophil elastase by 43%. The attenuation of neutrophil activation in the absence of an effect on complement activation via the classical pathway, supports the concept that kallikrein is a major mediator of neutrophil degranulation during cardiopulmonary bypass.

Arginine↗