Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The glycoprotein complex GPIIb-IIIa of the platelet membrane and CD18 of the monocyte membrane have been established as being the central figure for the adhesion processes of the corresponding cells. The molecular structure of these 2 GPs bears some similarities. It was proposed recently that LFA-1 and Mo-1 (CD18 family) and GPIIb-IIIa might be encoded by the same gene. For this purpose, we studied the expression of Mo-1, Mo-2 (as control) receptors on monocytes and GPIIIa and GPIIb-IIIa on platelets of two GT patients as compared to normal healthy subjects. Monoclonal antibodies anti Mo-1, MO-2, AP-3 and AP-2 were used to measure the expression of the respective antigens by indirect immunofluorescence procedure. The fluorescence of the labelled cells was analysed with an Ortho Cytofluorograph 50-H. The resulting Mean Fluorescence Intensity (MFI) values of AP-2 and AP-3 showed that the patients had a total absence of GPIIb-IIIa antigens. However, Mo-1, as well as those of control Mo-2, in patients (MO-1: 672 and 716; Mo-2: 453 and 637) were similar to that of normal subjects (Mo-1: 735 +/- 74; Mo-2: 585 +/- 35; mean +/- SEM). Therefore, the normal expression of Mo-1 receptors on the monocytes of Glanzmann's thrombasthenia patients suggests different genomic regulations for Mo-1 antigens on the monocyte and GPIIb-IIIa complex on the platelet.
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PMID:Normal expression of the adhesive structure Mo-1 on monocytes from patients with Glanzmann's thrombasthenia. 201 Jul 2

Platelet autoantigen-autoantibody-monocyte interaction was studied by utilization of a specific monoclonal antibody (MoAb) 10E5 to trap and immobilize the GPIIb-GPIIIa complex on microtiter plates. Peripheral blood mononuclear cells (PBMC) or purified monocytes formed distinct morphologic clusters after incubation with immobilized antigen for 18 hours at 37 degrees C. PBMC of 18 and 19 patients with autoimmune thrombocytopenic purpura (ATP) formed 48 +/- 6.8 (SEM) clusters/well compared with 7.4 +/- 1.0 for control subjects, P less than .001. The number of clusters per well correlated inversely and exponentially with platelet count, r = -.8, n = 21, indicating that the GPIIb-GPIIIa autoantigen is pathophysiologically relevant. Binding of ATP PBMC to immobilized GPIIb-GPIIIa could be inhibited by F(ab')2 fragments of immunoglobulin (Ig) G of ATP patients, indicating that monocyte IgG bound to autoantigen by its F(ab')2 domain. Optimal cluster formation could be obtained with normal monocytes if preincubated with ATP IgG but not with F(ab')2 fragments of ATP IgG, indicating that ATP IgG binds to monocytes by its Fc domain. Armed monocytes (ie, normal monocytes preincubated with ATP IgG) bound to immobilized autoantigen 5.8-fold greater than normal monocytes incubated with immobilized autoantigen opsonized with ATP IgG. Armed monocyte adhesion could be inhibited 81% from 18.9 +/- 1.6 to 3.6 +/- 0.5 clusters/well by prior fixation with 0.1% formalin, whereas fixation of IgG before arming of monocytes was not inhibitory. MoAb MM41, directed against the alpha m-chain of the Mac-1 adhesive protein receptor of monocytes, inhibited cluster formation by 79%. Thus, (1) armed monocyte interaction with autoantigen is considerably more effective than monocyte interaction with opsonized autoantigen; (2) armed monocyte interaction requires specific F(ab')2-antigen recognition; and (3) monocyte-autoantigen interaction requires a secondary nonimmunologic adhesive event.
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PMID:Regulation of autoimmune anti-platelet antibody-mediated adhesion of monocytes to platelet GPIIb/GPIIIa: effect of armed monocytes and the Mac-1 receptor. 218 3

Two monoclonal anti-platelet antibodies, 3B2 and 8G11, have been raised that are specific for normal human platelets. 3B2 is unique in that it has decreased reactivity for platelets from 16 patients with autoimmune thrombocytopenic purpura [mean platelet count, 65,000 +/- 6,000 (SEM)]. With 8G11 in an enzyme-linked immunosorbent assay, the mean of the ratios of patient platelet OD to control platelet OD was 0.95 +/- 0.07, whereas with 3B2, the mean of the ratios of patient platelet OD to control OD was 0.24 +/- 0.04, P less than 0.001. With 3B2 the mean of the OD ratios of five patients with autoimmune thrombocytopenic purpura in remission (greater than 150,000 platelets per mm3) compared to controls was 0.80 +/- 0.14. 3B2 did not react with platelets from a patient with Glanzmann's thrombasthenia, in which membranes lack glycoproteins IIb and IIIa (GPIIb and GPIIIa). Platelet membranes were run on crossed immunoelectrophoresis against a rabbit polyclonal anti-human platelet membrane antibody with 125I-labeled purified 3B2 in an intermediate spacer gel. 3B2 reacted with the GPIIb-GPIIIa-Ca2+ complex in the presence of excess Ca2+ and with GPIIb alone in the presence of excess EGTA. When Triton X-100-solubilized platelet membranes were immunoprecipitated with 3B2 plus rabbit anti-mouse IgG, reduced, and run on NaDodSO4/polyacrylamide gel electrophoresis, a single protein band was obtained with a molecular weight of 120,000 (the molecular weight of GPIIb). Thus, the reactivity of monoclonal antibody 3B2 with GPIIb or the GPIIb-GPIIIa-Ca2+ complex appears to be inhibited by the presence of autoantibody on platelets.
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PMID:A monoclonal anti-platelet antibody with decreased reactivity for autoimmune thrombocytopenic platelets. 641 61

Soluble fibrinogen binding to agonist-stimulated blood platelets is the essential physiologic function of the glycoprotein IIb-IIIa (GPIIb-IIIa) receptor. We describe a method of quantifying this receptor-ligand interaction by using flow cytometry to detect the binding of fluorescein-labeled fibrinogen to activated platelets. Fibrinogen conjugated with fluorescein isothiocyanate (FITC-FGN) was structurally and functionally indistinguishable from native fibrinogen when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, thrombin clottability, and receptor affinity studies. Platelet samples, at a concentration of 2 x 10(7) ml, were incubated with FITC-FGN and activated with adenosine diphosphate (ADP) before cytometric acquisition of fluorescence and scatter data. ADP-induced binding of soluble FITC-FGN to platelet GPIIb-IIIa was specific, time dependent, and saturable. Cytometric analysis of FITC calibration beads allowed generation of standard curves relating bead fluorescence intensity to the number of fluorescein equivalents per bead. With this information, platelet fluorescence intensity was converted into the number of FITC-FGN molecules bound per platelet. Such quantitative analysis of fibrinogen binding yielded a dissociation constant of 2.48 +/- 0.5 x 10(-7) mol/L and a maximum fibrinogen binding capacity of 42, 124 +/- 5, 628 molecules per platelet (mean +/- SEM), which are comparable to published results with radioligand assays. The simplicity, sensitivity, and quantifiability of this method may make it a useful technique for basic and clinical research involving GPIIb-IIIa function.
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PMID:Quantitation of soluble fibrinogen binding to platelets by fluorescence-activated flow cytometry. 751 93

Bleeding is a prominent feature of uremia and remains a significant cause of morbidity in hemodialysis (HD)-dependent patients. To measure the impact of the HD procedure, we performed a prospective cross-over study in eight patients placed consecutively for 2-week periods each on low-flux biocompatible polymethylmethacrylate, low-flux complement-activating cuprophane, and high-flux biocompatible polysulfone membranes. The primary measure of platelet function studied was shear-induced platelet aggregation (SIPA), which has been shown to be a physiologically relevant marker of platelet function and involves the interaction of von Willebrand factor (vWf) with platelet membrane glycoproteins (GP) Ib and IIb-IIIa. Flow-cytometric analysis of the surface expression of platelet membrane GP Ib and GP IIb-IIIa was performed using fluorescein isothiocyanate (FITC)-conjugated monoclonal antibodies CD42b and CD41a, respectively. Multivariate analysis did not demonstrate a statistically significant effect of the type of dialysis membrane on platelet aggregation, calcium flux, or thromboxane B2 production. There was a marked decrease of SIPA in HD patients (pre-HD, mean +/- SEM, 19% +/- 3%) compared with normal controls (43% +/- 3%, P < 0.001), with a further decrease after the HD procedure (post-HD, 12% +/- 2%, P = 0.015 compared with pre-HD). This intradialytic decrease in SIPA correlated with a decrease in GP Ib (pre-HD, 385 +/- 21 mean fluorescence intensity [MFI]; post-HD, 285 +/- 21 MFI, P = 0.0001). GP IIb-IIIa was also significantly decreased post-HD (pre-HD, 1,022 +/- 70 MFI; post-HD, 881 +/- 64 MFI, P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Defective platelet aggregation in uremia is transiently worsened by hemodialysis. 770 50

Bleeding and platelet dysfunction are prominent features of uremia. Sh ear-induced platelet aggregation (SIPA) involves the interaction of von Willebrand factor (vWF) with platelet membrane glycoproteins (GP) Ib and IIb-IIIa, the same receptor-ligand pair involved in in vivo adhesion and aggregation of platelets in the arterial circulation. We have used a modified rotational cone-plate viscometer to measure SIPA and calcium flux in platelets. Flow cytometric analysis of the surface expression of GP Ib and IIb-IIIa was performed using flourescein isothiocyanate-conjugated monoclonal antibodies CD42b and CD41a, respectively. Uremic patients showed decreased SIPA (controls, 43% +/- 2% [mean +/- SEM]; chronic renal failure patients, 36% +/- 3%; chronic hemodialysis patients, 26% +/- 2%; P < 0.001) along with a decrease in GP IIb-IIIa (controls, chronic renal failure patients, and chronic hemodialysis patients, 840 +/- 25, 649 +/- 42, 661 +/- 38 mean flourescence intensity, respectively; P < 0.0001). Glycoprotein Ib in uremic patients was not significantly different from normal. Chronic hemodialysis patients also demonstrated increased platelet-bound fibrinogen (P < 0.001) and platelet-bound vWF (p < 0.01). Calcium flux and thromboxane B(2) generation during SIPA of uremic platelets was normal. However, uremic plasma showed twice the normal concentration of vWF (P < 0.001) and sodium dodecyl sulfate agarose gel electrophoresis revealed the presence of fibrinogen fragments. Mixing experiments demonstrated an inhibitory effect of uremic plasma on SIPA of normal platelets (decreased from 39% +/- 3% at baseline to 31% +/- 3% after incubation in uremic plasma) along with an activation-independent increase in platelet-bound fibrinogen and platelet-bound vWF. When uremic platelets were incubated in normal plasma, their SIPA increased from 12% +/- 5% at baseline to 18% +/- 4% after incubation in normal plasma; (P = 0.002), although it did not return to normal. These results suggest that the uremic platelet dysfunction results from decreased GP IIb-IIa availability due to receptor occupancy by fibrinogen fragments (and possibly vWF fragments).
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PMID:Uremic patients have decreased shear-induced platelet aggregation mediated by decreased availability of glycoprotein IIb-IIIa receptors. 860 4

To examine the hypothesis that surface P-selectin-positive (degranulated) platelets are rapidly cleared from the circulation, we developed novel methods for tracking of platelets and measurement of platelet function in vivo. Washed platelets prepared from nonhuman primates (baboons) were labeled with PKH2 (a lipophilic fluorescent dye), thrombin-activated, washed, and reinfused into the same baboons. Three-color whole blood flow cytometry was used to simultaneously (i) identify platelets with a mAb directed against glycoprotein (GP)IIb-IIIa (integrin alpha 11b beta 3), (ii) distinguish infused platelets by their PKH2 fluorescence, and (iii) analyze platelet function with mAbs. Two hours after infusion of autologous thrombin-activated platelets (P-selectin-positive, PKH2-labeled), 95 +/- 1% (mean +/- SEM, n = 5) of the circulating PKH2-labeled platelets had become P-selectin-negative. Compared with platelets not activated with thrombin preinfusion, the recovery of these circulating PKH2-labeled, P-selectin-negative platelets was similar 24 h after infusion and only slightly less 48 h after infusion. The loss of platelet surface P-selectin was fully accounted for by a 67.1 +/- 16.7 ng/ml increase in the plasma concentration of soluble P-selectin. The circulating PKH2-labeled, P-selectin-negative platelets were still able to function in vivo, as determined by their (i) participation in platelet aggregates emerging from a bleeding time wound, (ii) binding to Dacron in an arteriovenous shunt, (iii) binding of mAb PAC1 (directed against the fibrinogen binding site on GPIIb-IIIa), and (iv) generation of procoagulant platelet-derived microparticles. In summary, (i) circulating degranulated platelets rapidly lose surface P-selectin to the plasma pool, but continue to circulate and function; and (ii) we have developed novel three-color whole blood flow cytometric methods for tracking of platelets and measurement of platelet function in vivo.
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PMID:In vivo tracking of platelets: circulating degranulated platelets rapidly lose surface P-selectin but continue to circulate and function. 887 31

Reperfusion injury after coronary occlusion is in part mediated by leukocyte activation and adhesion. Platelets may interact with polymorphonuclear granulocytes (PMNs), causing aggravated reperfusion injury. We studied whether c7E3Fab, a chimeric Fab fragment blocking platelet glycoprotein (GP) IIb/IIIa, decreases PMN-platelet-dependent myocardial dysfunction after ischemia. Isolated guinea pig hearts (n=5 per group) perfused at a constant flow of 5 mL/min were subjected to ischemia (15 minutes, 37 degrees C) and reperfusion. Human PMNs (10x10(6) cells, 3 mL), platelets (400x10(6), 3 mL), and fibrinogen (1 mg/mL) were infused for 3 minutes after 2 minutes of reperfusion, with or without c7E3Fab. Flow cytometry detected GPIIb/IIIa (platelets) and MAC-1 (aMbeta2, PMNs) as well as coaggregates of both in the effluent, whereas double-fluorescence microscopy visualized intracoronary PMN-platelet coaggregates. Postischemic recovery of pressure-volume work (12-cm H(2)O preload and 60-mm Hg afterload) was defined as the ratio of postischemic to preischemic external heart work (mean+/-SEM). c7E3Fab reduced platelet GPIIb/IIIa detection to 10% of controls, blocked a transcoronary MAC-1 increase (+25% without versus -23% with c7E3Fab), and inhibited PMN-platelet coaggregation in the effluent (49+/-12% without versus 17+/-2% with c7E3Fab) as well as in the hearts themselves (5.0+/-0.7/cm(2) without versus 1.2+/-0.3/cm(2) surface area with c7E3Fab). Postischemic recovery of external heart work (83+/-5% in cell-free hearts) declined to 46+/-4% after postischemic PMN-platelet infusion, but not in the presence of c7E3Fab (74+/-11%) or LPM19c (71+/-6%). We conclude that c7E3Fab inhibits formation of PMN-platelet aggregates during myocardial reperfusion, an effect that protects against PMN-platelet-dependent stunning.
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PMID:c7E3Fab reduces postischemic leukocyte-thrombocyte interaction mediated by fibrinogen. Implications for myocardial reperfusion injury. 1103 Dec 8

Nitric oxide (NO) is known to modulate platelet adhesion and aggregation, which are both mediated by fibrinogen receptor glycoprotein (GP)IIb/IIIa. To investigate effects of NO on GPIIb/IIIa activation and inactivation, platelets were exposed to NO donor 3-morpholino-sydnonimine (SIN-1) before and after stimulation with different agonists: thromboxane analog U-46619, epinephrine, adenosine diphosphate, human a-thrombin, and phorbol-12-myristate-13-acetate (0.02 micromol/l). (1) Flow cytometry analysis of SIN-1-pre-incubated samples using PAC-1 monoclonal antibody revealed an inhibition of receptor activation by 80.9 +/- 1.2, 71.3 +/- 1.8, 56 +/- 4.9, 87 +/- 3.4, and 56 +/- 5% (mean +/- SEM, relative to baseline). (2) Administration of SIN-1 after stimulation reversed receptor activation by 55 +/- 5.2, 56 +/- 2.0, 53 +/- 5.4, 42 +/- 4.3, and 44 +/- 5%, respectively. With 0.1 micromol/l phorbol-12-myristate-13-acetate, GPIIb/IIIa activation was irreversible. (3) SIN-1 effects could completely be blocked by equimolar addition of guanylyl cyclase inhibitor 1H(1,2,4)oxadiazolo(4,3-alpha)quinoxalin-1-on. (4) Spontaneous receptor closure after activation with human alpha-thrombin and adenosine diphosphate was not due to platelet-derived NO; SIN-1, however accelerated spontaneous receptor inactivation. (5) SIN-1-inactivated receptors still responded to stimulation. In conclusion, SIN-1 or NO modulates GPIIb/IIIa conformational change in vitro via guanosine 3',5'-monophosphate-dependent pathways. Whereas spontaneous receptor inactivation may be enhanced by exogenous NO, platelet-derived NO is not involved in receptor inactivation.
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PMID:Inactivation of platelet glycoprotein IIb/IIIa receptor by nitric oxide donor 3-morpholino-sydnonimine. 1294 73

An unknown epitope of apolipoprotein (a) antagonizes fibrinogen binding to agonist-stimulated platelet's fibrinogen (GPIIb/IIIa) receptor yielding lipoprotein (a) mediated decreased platelet aggregation. The purpose of this study was to test the hypothesis that human apolipoprotein (a)'s single arginyl-glycyl-aspartyl (RGD) epitope, unique to apolipoprotein (a) in lipoprotein (a) binds to the RGD binding motif on the IIb subunit of the GPIIb/IIIa receptor thus reducing platelet-bound fibrinogen and consequently decreasing agonist-stimulated platelet aggregation. Platelets (N=30 subjects) were prepared from fresh plasma, washed three times in Tyrode's buffer and stimulated using 10 microM ADP or 2 microg/ml collagen. Lipoprotein (a) was isolated from plasma using lectin affinity chromatography followed by ultracentrifugation. The peptide RGDS inhibited (125)I-labelled lipoprotein (a) binding to autologous platelets with IC-50's of 25.1+/-2.2 (mean+/-SEM) and 15.4+/-1.3 microM for collagen- and ADP-stimulation respectively. Further, RGDS reduced platelet binding of (125)I-labelled fibrinogen IC-50's of 35.5+/-3.2 (mean+/-SEM) and 20.7+/-2.2 microM for collagen- and ADP-stimulation respectively. The monoclonal antibody PAC-1, uniquely directed at the RGD binding motif on the IIb subunit on collagen- and ADP-stimulated platelets, inhibited binding of (125)I-labelled lipoprotein (a) with IC-50's of 6.4+/-0.7 and 2.5+/-2.2 microg/10(8) platelets for collagen- and ADP-stimulation respectively. Additionally, PAC-1 reduced platelet bound of (125)I-labelled fibrinogen with IC-50's of 9.0+/-1.4 and 4.1+/-2.2 microg/10(8) platelets for collagen- and ADP-stimulation respectively. In a dose-related fashion, a polyclonal antibody, specific for the RGD epitope on apolipoprotein (a), restored platelet aggregation to control levels, inhibited (125)I-labelled lipoprotein (a) binding, and increased (125)I-labelled fibrinogen by displacing lipoprotein (a) from the GPIIb/IIIa receptor. Thus a never before demonstrated aspect of the mechanism of lipoprotein (a)'s suggested novel role as an endogenous regulator of fibrinogen binding to collagen- and ADP-stimulated platelets has been shown. In conclusion, lipoprotein (a), via apolipoprotein (a)'s RGD epitope, binds to the RGD binding motif on the IIb protein of the GPIIb/IIIa receptor consequently reducing platelet-bound fibrinogen which results in decreased platelet aggregation.
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PMID:Arginyl-glycyl-aspartyl (RGD) epitope of human apolipoprotein (a) inhibits platelet aggregation by antagonizing the IIb subunit of the fibrinogen (GPIIb/IIIa) receptor. 1686 Mar 75


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