Heterozygous loss of platelet glycoprotein (GP) Ib-V-IX variably affects platelet function in velocardiofacial syndrome (VCFS) patients

2007 ◽  
Vol 98 (12) ◽  
pp. 1298-1308 ◽  
Author(s):  
Hai Po Helena Liang ◽  
Marie-Christine Morel-Kopp ◽  
Julie Curtin ◽  
Meredith Wilson ◽  
John Hewson ◽  
...  
Keyword(s):  
Platelet Function ◽  
Gene Mutations ◽  
Autosomal Recessive Inheritance ◽  
Velocardiofacial Syndrome ◽  
Surface Expression ◽  
Platelet Glycoprotein ◽  
Severe Bleeding ◽  
Gene Encoding ◽  
Human Chromosome 22Q11

SummaryVelocardiofacial syndrome (VCFS) is a common, phenotypically heterogeneous developmental disorder caused by an interstitial microdeletion within human chromosome 22q11. The deleted chromosomal region in >90% of VCFS patients includes the GPIbβ gene, encoding for one subunit of the platelet GPIb-V-IX receptor, which is critical for platelet adhesion under shear, and important in aggregation and thrombin-mediated activation. Complete loss of GPIb-V-IX due to autosomal recessive inheritance of two GPIbα,Ibβ or GP9 gene mutations,results in a severe bleeding disorder,Bernard-Soulier syndrome (BSS). In this study, twenty-one confirmedVCFS patients were analyzed for platelet morphological and functional alterations, resulting from the heterozygous loss of one GPIbβ gene allele. Compared to unaffected family members,VCFS patients showed a significant decrease in platelet count; VCFS platelet size and mean platelet volume were increased, but not as markedly as in BSS. As expected from obligatory heterozygotes for GPIbβ deficiency, VCFS patients showed reduced platelet GPIb-V-IX surface expression and total GPIb content, but with considerable variation between cases. Platelet function tested using the PFA-100™ analyzer was impaired in 70% of patients. Platelet aggregation was reduced in response to a GPIb-dependent agonist, ristocetin, in 50% ofVCFS patients, with 35% showing a reduced response to thrombin receptor activating peptide. Genomic screening was performed to exclude mutations of the subunit genes, indicating that these platelet abnormalities were due to GPIbβ heterozygosity and not spontaneous BSS. In conclusion, many VCFS patients have in-vitro defects in platelet function that may increase their risk of bleeding during surgery.

scholarly journals The role of Endoplasmic Reticulum (ER) stress in pulmonary fibrosis

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Martina Korfei ◽  
Clemens Ruppert ◽  
Benjamin Loeh ◽  
Poornima Mahavadi ◽  
Andreas Guenther
Keyword(s):  
Endoplasmic Reticulum ◽  
Epithelial Cells ◽  
Er Stress ◽  
Replicative Senescence ◽  
Gene Mutations ◽  
Surfactant Protein ◽  
Alveolar Epithelial Cells ◽  
Gene Encoding ◽  
Alveolar Epithelial

AbstractThe activation of Endoplasmic Reticulum (ER) stress and Unfolded Protein Response (UPR) was first observed in patients with familial interstitial pneumonia (FIP) carrying mutations in the C-terminal BRICHOS domain of surfactant protein C (SFTPC). Here, aggresome formation and severe ER stress was demonstrated in type-II alveolar epithelial cells (AECII), which specifically express this very hydrophobic surfactant protein. In subsequent studies, FIP-patients with mutations in the gene encoding surfactant protein A2 (SFTPA2) were discovered, whose overexpression in epithelial cells in vitro also resulted in significant induction of ER stress. Moreover, prominent ER stress in AECII was also observed in FIP-patients not carrying the SFTPC/SFTPA2 mutations, as well as in patients with the more common sporadic forms of IP. Additionally, cases of adult-onset FIP with mutations in Telomerase genes and other telomereassociated components were reported. These mutations were associated with telomere shortening, which is a potential cause for triggering a persistent DNA damage response and replicative senescence in affected cells. Moreover, shortened telomeres were observed directly in the AECII of FIP-patients, and even sporadic IP cases, in the absence of any gene mutations. Here, we try to figure out the possible origins of ER stress in sporadic IP cases and non-SFTPC/SFTPA2-associated FIP.

Effects of Magnesium on Platelet Aggregation and Adhesion

1994 ◽  
Vol 72 (06) ◽  
pp. 912-918 ◽  
Author(s):  
M Gawaz ◽  
I Ott ◽  
A J Reininger ◽  
F-J Neumann
Keyword(s):  
Myocardial Infarction ◽  
Platelet Aggregation ◽  
Platelet Function ◽  
Platelet Adhesion ◽  
Bleeding Time ◽  
Magnesium Deficiency ◽  
Ex Vivo ◽  
Surface Expression ◽  
Activated Platelets

SummaryMagnesium deficiency and its association with platelet hyperreactivity has been well recognised in a variety of diseases including myocardial infarction, preeclampsia, and diabetes. In order to investigate potential effects of intravenous Mg2+ supplementation, platelet function was studied by measurements of in vitro bleeding time (BT) and of fibrinogen (Fg)-mediated aggregation of washed platelets. In addition, the effect of Mg2+ on platelet adhesion onto immobilised Fg, on Fg binding to activated platelets, and on surface expression of GMP-140 or GP53 was evaluated. Mg2+(4 mM) prolonged in vitro BT by 30% and inhibited Fg-mediated aggregation significantly, independent of the agonist used to initiate platelet aggregation (ADP, collagen, epinephrine, thrombin, phorbol ester). Adhesion of resting platelets to immobilised Fg was reduced by 50% in the presence of 2 mM Mg2+. Moreover, Mg2+ reduced Fg binding to ADP- or collagen-stimulated platelets as well as surface expression of GMP-140 with an IC50 of approximately 3 mM. Intravenous administration of Mg2+ to healthy volunteers inhibited both ADP-induced platelet aggregation (p <0.05) by 40% and binding of Fg or surface expression of GMP-140 by 30% (p <0.05). Thus, pharmacological concentrations of Mg2+ effectively inhibit platelet function in vitro and ex vivo.

Compound Heterozygosity (554-589 del, C515-T Transition) in the Platelet Glycoprotein Ibα Gene in a Patient with a Severe Bleeding Tendency

1999 ◽  
Vol 81 (04) ◽  
pp. 486-492 ◽  
Author(s):  
Maurizio Margaglione ◽  
Giovanna D’Andrea ◽  
Elvira Grandone ◽  
Vincenzo Brancaccio ◽  
Aldo Amoriello ◽  
...  
Keyword(s):  
Flow Cytometric Analysis ◽  
Normal Function ◽  
Platelet Glycoprotein ◽  
Severe Bleeding ◽  
Bleeding Tendency ◽  
Giant Platelets ◽  
Novel Variant ◽  
Leucine Rich Repeats ◽  
Von Willebrand

SummaryGiant platelets in the blood smear, absent in vitro platelet agglutination in response to ristocetin, and normal aggregation, ATP secretion and thromboxane B2 formation were found in a young patient with a life-long bleeding tendency. Ristocetin-induced von Willebrand factor binding to her platelets was less than 10% of normal. Flow cytometric analysis with monoclonal antibodies LJ-Ib-1, LJ-Ib-10, and LJ-P3 was consistent with the latter finding. SDS-PAGE analysis of solubilized platelets showed a marked reduction of the platelet glycoprotein (GP) Ibα. Genetic characterisation demonstrated that the patient and her father were heterozygous for a deletion of 36 nucleotides (positions 554-589) leading to a mutant GPIbμ (deletion of aminoacids from residue 169 to 180 and a Glu → Lys substitution at residue 181). In addition, a C → T transition at nucleotide 515 in the other allele of the GPIbα gene was found in the patient and in her mother that results in the substitution of alanine for valine in codon 156 (Bernard-Soulier type Bolzano). These variations occurred within the VI and VII leucine-rich repeats. The novel variant of Bernard-Soulier syndrome identified further suggests that the integrity of leucine-rich repeats is important for normal function of the GP Ib-IX-V receptor complex.

Cyclophilin A is an important mediator of platelet function by regulating integrin αIIbβ3 bidirectional signalling

2014 ◽  
Vol 111 (05) ◽  
pp. 873-882 ◽  
Author(s):  
Mark Sowden ◽  
Yingqian Xu ◽  
Kristina Modjeski ◽  
Padmamalini Baskaran ◽  
Yeonghwan Kim ◽  
...  
Keyword(s):  
Platelet Function ◽  
Thrombus Formation ◽  
Cyclophilin A ◽  
Platelet Glycoprotein ◽  
Ros Production ◽  
Ppiase Activity ◽  
Isomerase Activity ◽  
Important Mediator

SummaryCyclophilin A (CyPA) is an important mediator in cardiovascular diseases. It possesses peptidyl-prolyl cis-trans isomerase activity (PPIase) and chaperone functions, which regulate protein folding, intracellular trafficking and reactive oxygen species (ROS) production. Platelet glycoprotein receptor αIIbβ3 integrin activation is the common pathway for platelet activation. It was our objective to understand the mechanism by which CyPA-regulates αIIbβ3 activation in platelets. Mice deficient for CyPA (CyPA−/−) had prolonged tail bleeding time compared to wild-type (WT) controls despite equivalent platelet numbers. In vitro studies revealed that CyPA−/− platelets exhibited dramatically decreased thrombin-induced platelet aggregation. In vivo, formation of occlusive thrombi following FeCl3 injury was also significantly impaired in CyPA−/− mice compared with WT-controls. Furthermore, CyPA deficiency inhibited flow-induced thrombus formation in vitro. Flow cytometry demonstrated that thrombin-induced ROS production and αIIbβ3 activation were reduced in CyPA−/− platelets. Coimmunoprecipitation studies showed ROS-dependent increased association of CyPA and αIIbβ3. This association was dependent upon the PPIase activity of CyPA. Significantly, fibrinogen-platelet binding, platelet spreading and cytoskeleton reorganisation were also altered in CyPA−/− platelets. Moreover, CyPA deficiency prevented thrombin-induced αIIbβ3 and cytoskeleton association. In conclusion, CyPA is an important mediator in platelet function by regulation of αIIbβ3 bidirectional signalling through increased ROS production and facilitating interaction between αIIbβ3 and the cell cytoskeleton.

scholarly journals Inhibition of dog platelet function by in vivo infusion of F(ab')2 fragments of a monoclonal antibody to the platelet glycoprotein IIb/IIIa receptor

Blood ◽  
1985 ◽  
Vol 66 (6) ◽  
pp. 1456-1459 ◽  
Author(s):  
BS Coller ◽  
LE Scudder
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Function ◽  
Adenosine Diphosphate ◽  
Platelet Glycoprotein ◽  
Antiplatelet Antibody ◽  
Spontaneous Bleeding ◽  
Aggregation Response ◽  
Total Inhibition

To assess the potential of monoclonal antibodies that inhibit platelet function in vitro as in vivo therapeutic agents, F(ab')2 fragments (0.17 to 0.81 mg/kg) of a murine monoclonal antibody (7E3) that binds to platelet glycoproteins IIb and/or IIIa and blocks platelet aggregation induced by ADP were infused into three dogs. Soon after infusion, platelets recovered from the dogs showed a decreased aggregation response to adenosine diphosphate, with the highest dose producing nearly total inhibition. These platelets also showed decreased ability to bind 125I-7E3, which was assumed to reflect occupancy of the sites by the unlabeled F(ab')2 fragments. At the highest dose, the binding decreased by 85%, reflecting the binding of approximately 44,000 molecules of 7E3 F(ab')2 per platelet. Platelet counts decreased after antibody infusion by less than 20%, and none of the dogs showed spontaneous bleeding. Both the aggregation and binding results reverted toward normal within one day. We conclude that it is possible to profoundly inhibit platelet function by in vivo infusion of F(ab')2 fragments of a monoclonal antiplatelet antibody without producing spontaneous hemorrhage or significant thrombocytopenia.

scholarly journals Suppression of erythro-megakaryocytopoiesis and the induction of reversible thrombocytopenia in mice transgenic for the thymidine kinase gene targeted by the platelet glycoprotein alpha IIb promoter.

1995 ◽  
Vol 181 (6) ◽  
pp. 2141-2151 ◽  
Author(s):  
D Tronik-Le Roux ◽  
V Roullot ◽  
A Schweitzer ◽  
R Berthier ◽  
G Marguerie
Keyword(s):  
Transgenic Mice ◽  
Thymidine Kinase ◽  
Progenitor Cells ◽  
Regulatory Region ◽  
Platelet Glycoprotein ◽  
Gene Encoding ◽  
Kinase Gene ◽  
Myeloid Progenitor Cells ◽  
Simplex Virus

The mechanisms that regulate the commitment of a totipotent stem cell to the megakaryocytic lineage are largely unknown. Using a molecular approach to the study of megakaryocytopoiesis and platelet production, mice in which thrombocytopoiesis could be controlled were produced by targeting the expression of the herpes simplex virus thymidine kinase toxigene to megakaryocytes using the regulatory region of the gene encoding the alpha subunit of the platelet integrin alpha IIb beta 3. The programmed eradication of the megakaryocytic lineage was induced by treating transgenic mice bearing the hybrid construct (alpha IIbtk) with the antiherpetic drug ganciclovir (GCV). After 10 d of treatment, the platelet number was reduced by &gt; 94.6%. After discontinuing GCV, the bone marrow was repopulated with megakaryocytes and the platelet count was restored within 7 d. Prolonged GCV treatment induced erythropenia in the transgenic mice. Assays of myeloid progenitor cells in vitro demonstrated that the transgene was expressed in early erythro-megakaryocytic progenitor cells. The reversibility and facility of this system provides a powerful model to determine both the critical events in megakaryocytic and erythroid lineage development and for evaluating the precise role that platelets play in the pathogenesis of a number of vascular occlusive disorders.

Selective inhibition of the platelet phosphoinositide 3-kinase p110β as promising new strategy for platelet protection during extracorporeal circulation

2008 ◽  
Vol 99 (03) ◽  
pp. 609-615 ◽  
Author(s):  
Hans Wendel ◽  
Klaus Dietz ◽  
Daniela Schiebold ◽  
Karlheinz Peter ◽  
Simone Schoenwaelder ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Activation ◽  
Platelet Function ◽  
Extracorporeal Circulation ◽  
Ventricular Assist Devices ◽  
Platelet Glycoprotein ◽  
Promising Alternative ◽  
Phosphoinositide 3 Kinase

SummaryExtracorporeal circulation (ECC) is used in cardiac surgery for cardiopulmonary bypass as well as in ventricular assist devices and for extracorporeal membrane oxygenation. Blood contact with the artificial surface and shear stress of ECC activates platelets and leukocytes resulting in a coagulopathy and proinflammatory events. Blockers of the platelet glycoprotein (GP) IIb/IIIa (CD41/CD61) can protect platelet function during ECC, a phenomenon called “platelet anaesthesia”, but may be involved in post-ECC bleeding. We hypothesized that the new selective phosphoinositide 3-kinase p110β inhibitor TGX-221 that inhibits shear-induced platelet activation without prolonging the bleeding time in vivo may also protect platelet function during ECC. Heparinized blood of healthy volunteers (n=6) was treated in vitro with either the GP IIb/IIIa blocker tirofiban, TGX-221 or as control and circulated in an ECC moand after 30 minutes circulation CD41 expression on the ECCtubing as measure for platelet-ECC binding and generation of the platelet activation marker β-thromboglobulin were determined using ELISA. Platelet aggregation and platelet-granulocyte binding were analysed in flow cytometry. After log-transforming the data statistical evaluation was performed using multifactor ANOVA in combination with Tukey’s HSD test (global alpha = 5%).Tirofiban and TGX-221 inhibited platelet-ECC interaction, platelet aggregation and platelet-granulocyte binding. Tirofiban also inhibited ECC-induced β-thromboglobulin release.The observed inhibition of platelet-ECC interaction and platelet activation by tirofiban contributes to explain the mechanism of“platelet anaesthesia”.TGX-221 represents a promising alternative to GP IIb/IIIa blockade and should be further investigated for use during ECC in vivo.

scholarly journals Inhibition of dog platelet function by in vivo infusion of F(ab')2 fragments of a monoclonal antibody to the platelet glycoprotein IIb/IIIa receptor

Blood ◽  
1985 ◽  
Vol 66 (6) ◽  
pp. 1456-1459 ◽  
Author(s):  
BS Coller ◽  
LE Scudder
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Function ◽  
Adenosine Diphosphate ◽  
Platelet Glycoprotein ◽  
Antiplatelet Antibody ◽  
Spontaneous Bleeding ◽  
Aggregation Response ◽  
Total Inhibition

Abstract To assess the potential of monoclonal antibodies that inhibit platelet function in vitro as in vivo therapeutic agents, F(ab')2 fragments (0.17 to 0.81 mg/kg) of a murine monoclonal antibody (7E3) that binds to platelet glycoproteins IIb and/or IIIa and blocks platelet aggregation induced by ADP were infused into three dogs. Soon after infusion, platelets recovered from the dogs showed a decreased aggregation response to adenosine diphosphate, with the highest dose producing nearly total inhibition. These platelets also showed decreased ability to bind 125I-7E3, which was assumed to reflect occupancy of the sites by the unlabeled F(ab')2 fragments. At the highest dose, the binding decreased by 85%, reflecting the binding of approximately 44,000 molecules of 7E3 F(ab')2 per platelet. Platelet counts decreased after antibody infusion by less than 20%, and none of the dogs showed spontaneous bleeding. Both the aggregation and binding results reverted toward normal within one day. We conclude that it is possible to profoundly inhibit platelet function by in vivo infusion of F(ab')2 fragments of a monoclonal antiplatelet antibody without producing spontaneous hemorrhage or significant thrombocytopenia.

Genetic deletion of mouse platelet glycoprotein Ibβ produces a Bernard-Soulier phenotype with increased α-granule size

Blood ◽  
2004 ◽  
Vol 104 (8) ◽  
pp. 2339-2344 ◽  
Author(s):  
Kazunobu Kato ◽  
Constantino Martinez ◽  
Susan Russell ◽  
Paquita Nurden ◽  
Alan Nurden ◽  
...  
Keyword(s):  
Fold Increase ◽  
Granule Size ◽  
Platelet Glycoprotein ◽  
Severe Bleeding ◽  
Gene Encoding ◽  
Protein Levels ◽  
Transmission Electron ◽  
Presynaptic Protein ◽  
Bernard Soulier Syndrome

Abstract Here we report the characterization of a mouse model of the Bernard-Soulier syndrome generated by a targeted disruption of the gene encoding the glycoprotein (GP) Ibβ subunit of the GP Ib-IX complex. Similar to a Bernard-Soulier model generated by disruption of the mouse GP Ibα subunit, GP IbβNull mice display macrothrombocytopenia and a severe bleeding phenotype. When examined by transmission electron microscopy, the large platelets produced by a GP IbβNull genotype revealed α-granules with increased size as compared with the α-granules from control mouse platelets. Data are presented linking the overexpression of a septin protein, SEPT5, to the presence of larger α-granules in the GP IbβNull platelet. The SEPT5 gene resides approximately 250 nucleotides 5′ to the GP Ibβ gene and has been associated with modulating exocytosis from neurons and platelets as part of a presynaptic protein complex. Fusion mRNA transcripts present in megakaryocytes can contain both the SEPT5 and GP Ibβ coding sequences as a result in an imperfect polyadenylation signal within the 3′ end of both the human and mouse SEPT5 genes. We observed a 2- to 3-fold increase in SEPT5 protein levels in platelets from GP IbβNull mice. These results implicate SEPT5 levels in the maintenance of normal α-granule size and may explain the variant granules associated with human GP Ibβ mutations and the Bernard-Soulier syndrome.

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