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Béatrice Hechler

Publications and source records attributed to Béatrice Hechler.

10 recordsLinked to original sources
PubMed2006

The platelet P2 receptors in arterial thrombosis.

ADP and ATP play a crucial role in hemostasis and thrombosis and their receptors are potential targets for antithrombotic drugs. The ATP-gated channel P2X1 and the two G protein-coupled P2Y1 and P2Y12 ADP receptors selectively contribute to platelet aggregation. Due to its central role in the formation and stabilization of a thrombus, the P2Y12 receptor is a well established target of antithrombotic drugs like clopidogrel which has proved efficacious in many clinical trials and experimental models of thrombosis. Competitive P2Y12 antagonists have also been shown to be effective in experimental thrombosis as well as in several clinical trials. Studies in P2Y1 and P2X1 knock-out mice and experimental thrombosis models using selective P2Y1 and P2X1 antagonists have shown that, depending on the conditions, these receptors could also be potential targets for new antithrombotic drugs. Since both P2X1 and P2Y1 receptor inhibition result in milder prolongation of the bleeding time as compared to P2Y12 inhibition, the idea is put forward that combination of P2 receptor antagonists could improve efficacy with diminished hemorrhagic risk. However, further studies are required to validate such a point of view.

Animals↗
PubMed2005

MRS2500 [2-iodo-N6-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphate], a potent, selective, and stable antagonist of the platelet P2Y1 receptor with strong antithrombotic activity in mice.

The platelet P2Y(1) ADP receptor is an attractive target for new antiplatelet drugs. However, because of the lack of strong and stable antagonists, only a few studies have suggested that pharmacological inhibition of the P2Y(1) receptor could efficiently inhibit experimental thrombosis in vivo. Our aim was to determine whether the newly described potent and selective P2Y(1) receptor antagonist MRS2500 [2-iodo-N(6)-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphate] could inhibit platelet function ex vivo and experimental thrombosis in mice in vivo. MRS2500 was injected intravenously into mice, and its effect on ex vivo platelet aggregation and in several models of thrombosis in vivo was determined. MRS2500 displayed high potency and stable and selective P2Y(1) receptor inhibition ex vivo. Although MRS2500 injection resulted in only moderate prolongation of the bleeding time, it provided strong protection in systemic thromboembolism induced by infusion of a mixture of collagen and adrenaline. MRS2500 also potently inhibited localized arterial thrombosis in a model of laser-induced vessel wall injury with two degrees of severity. Moreover, combination of MRS2500 with clopidogrel, the irreversible inhibitor of the platelet P2Y(12) receptor for ADP, led to increased antithrombotic efficacy compared with each alone. These results add further evidence for a role of the P2Y(1) receptor in thrombosis and validate the concept that targeting the P2Y(1) receptor could be a relevant alternative or complement to current antiplatelet strategies.

Animals↗
PubMed2005

Inhibition of platelet functions and thrombosis through selective or nonselective inhibition of the platelet P2 receptors with increasing doses of NF449 [4,4',4'',4'''-(carbonylbis(imino-5,1,3-benzenetriylbis-(carbonylimino)))tetrakis-benzene-1,3-disulfonic acid octasodium salt].

Our aim was to determine whether the newly described P2X1 antagonist NF449 [4,4',4'',4'''-(carbonylbis(imino-5,1,3-benzenetriylbis(carbonylimino)))tetrakis-benzene-1,3-disulfonic acid octasodium salt] could selectively antagonize the platelet P2X1 receptor and how it affected platelet function. NF449 inhibited alpha,beta-methyleneadenosine 5'-triphosphate-induced shape change (IC50 = 83 +/- 13 nM; n = 3) and calcium influx (pA2 = 7.2 +/- 0.1; n = 3) (pIC50 = 6.95) in washed human platelets treated with apyrase to prevent desensitization of the P2X1 receptor. NF449 also antagonized the calcium rise mediated by the P2Y1 receptor, but with lower potency (IC50 = 5.8 +/- 2.2 microM; n = 3). In contrast, it was a very weak antagonist of the P2Y12-mediated inhibition of adenylyl cyclase activity. Selective blockade of the P2X1 receptor with NF449 led to reduced collagen-induced aggregation, confirming a role of this receptor in platelet activation induced by collagen. Intravenous injection of 10 mg/kg NF449 into mice resulted in selective inhibition of the P2X1 receptor and decreased intravascular platelet aggregation in a model of systemic thromboembolism (35 +/- 4 versus 51 +/- 3%) (P = 0.0061; n = 10) but without prolongation of the bleeding time (106 +/- 16 versus 78 +/- 7 s; n = 10) (N.S.; P = 0.1209). At a higher dose (50 mg/kg), NF449 inhibited the three platelet P2 receptors. This led to a further reduction in platelet consumption compared with mice injected with saline (13 +/- 4 versus 42 +/- 3%) (P = 0.0002; n = 5). NF449 also reduced dose-dependently the size of thrombi formed after laser-induced injury of mesenteric arterioles. Overall, our results indicate that NF449 constitutes a new tool to investigate the functions of the P2X1 receptor and could be a starting compound in the search for new antithrombotic drugs targeting the platelet P2 receptors.

Adenosine Diphosphate↗
PubMed2005

Importance of platelet phospholipase Cgamma2 signaling in arterial thrombosis as a function of lesion severity.

OBJECTIVE: Platelet activation occurs in response to adhesion receptors for von Willebrand factor (GPIb-V-IX) and collagen (GPVI and alpha2beta1 integrin) acting upstream of phospholipase C (PLC) gamma2. However, PLCbeta transduces signals from Galphaq protein-coupled receptors for soluble agonists (P2y1, TxA2/TP, and thrombin/PAR). A Gi-dependent pathway amplifies most of these responses. METHODS AND RESULTS: To evaluate the role of adhesion receptors signaling in arterial thrombosis, PLCgamma2 knockout mice were studied in blood perfusion assays over fibrillar collagen and in a laser-induced mesenteric artery model of thrombosis. In vitro, PLCgamma2-deficient platelets formed a single layer incapable of generating a thrombus on collagen, whereas Galphaq-deficient platelets formed reduced size aggregates compared with wild-type cells. In the in vivo model, PLCgamma2-/- mice displayed defective thrombus formation in superficial lesions but productive thrombosis after a more severe laser injury. In contrast, resistance to thrombosis was observed in Galphaq-/- mice in both levels of injury. CONCLUSIONS: These results demonstrate that signaling through PLCgamma2 plays an important role in arterial thrombosis, but that its contribution depends on the severity of the vascular lesion.

Animals↗
PubMed2005

The P2 receptors in platelet function.

After vessel wall injury, platelets adhere to the exposed subendothelium, are activated, and release mediators such as thromboxane A (2) (TXA (2)) and nucleotides stored at very high concentration in the so-called dense granules. Among other soluble agents, released nucleotides act in a positive feedback mechanism to cause further platelet activation and amplify platelet responses induced by agents such as thrombin or collagen. Adenine nucleotides act on platelets through three distinct P2 receptors: two are G protein-coupled adenosine diphosphate (ADP) receptors, namely the P2Y (1) and P2Y (12) receptor subtypes; the P2X (1) receptor ligand-gated cation channel is activated by adenosine triphosphate (ATP). The P2Y (1) receptor initiates platelet aggregation but is not sufficient for a full platelet aggregation in response to ADP, whereas the P2Y (12) receptor is responsible for completion of the aggregation to ADP. This receptor, the molecular target of the antithrombotic drug clopidogrel, is responsible for most of the potentiating effects of ADP when platelets are stimulated by agents such as thrombin, collagen, or immune complexes. The P2X (1) receptor is involved in platelet shape change and in activation by collagen under shear conditions. Each of these receptors is coupled to specific signal transduction pathways in response to ADP or ATP and is differentially involved in all of the sequential events involved in platelet function and hemostasis. As such, they represent potential targets for antithrombotic drugs.

Adenosine Diphosphate↗
PubMed2005

The platelet P2 receptors in thrombosis.

Adenosine diphosphate (ADP) and adenosine triphosphate (ATP) play a crucial role in hemostasis and thrombosis, and their receptors are potential targets for antithrombotic drugs. The ATP-gated channel P2X (1) and the two G protein-coupled P2Y (1) and P2Y (12) ADP receptors selectively contribute to platelet aggregation. Because of its central role in the formation and stabilization of a thrombus, the P2Y (12) receptor is a well-established target of antithrombotic drugs such as clopidogrel, which has proven efficacy in many clinical trials and experimental models of thrombosis. Competitive P2Y (12) antagonists have also been shown to be effective in experimental thrombosis as well as in several clinical trials. Studies in P2Y (1) and P2X (1) knockout mice and experimental thrombosis models using selective P2Y (1) and P2X (1) antagonists have shown that, depending on the conditions, these receptors could also be potential targets for new antithrombotic drugs. Because both P2X (1) and P2Y (1) receptor inhibition result in milder prolongation of the bleeding time as compared with P2Y (12) inhibition, the idea is put forward that combinations of P2 receptor antagonists could improve efficacy with diminished hemorrhagic risk. However, further studies with stronger and more selective P2 receptor antagonists are required to validate such a point of view.

Adenosine Diphosphate↗
PubMed2004

Differential regulation and relocalization of the platelet P2Y receptors after activation: a way to avoid loss of hemostatic properties?

In the present study, we investigated the desensitization and trafficking of the P2Y1 and P2Y12 receptors after agonist-induced stimulation of platelets or astrocytoma cells transfected with the P2Y1 or P2Y12 receptors fused to green fluorescent protein. In platelets and in transfected cells, exposure to 10 microM ADP caused desensitization of the P2Y1 receptor-driven calcium signal, whereas the P2Y12 receptor-mediated inhibition of cAMP formation was not affected. Plasma membranes from ADP-stimulated platelets also retained P2Y12 activity. Agonist-induced P2Y1 receptor desensitization was accompanied by its internalization in platelets and transfected cells. In contrast, although a substantial fraction of P2Y12 receptors was rapidly and transiently internalized, most of the P2Y12 receptors remained at the plasma membrane. Activated P2Y1 receptors were internalized through a clathrin-dependent pathway in cells and platelets, whereas the P2Y12 receptors seemed to use a distinct, clathrin-independent pathway. Together, these data indicate that the P2Y1 and P2Y12 receptors are differentially regulated upon activation. The absence of desensitization of the Gi protein-coupled P2Y12 receptor-dependent responses could represent a mechanism to preserve the hemostatic properties of otherwise unresponsive platelets.

Adenosine Diphosphate↗
PubMed2003

A role of the fast ATP-gated P2X1 cation channel in thrombosis of small arteries in vivo.

The P2X1 receptor is a fast ATP-gated cation channel expressed in blood platelets, where its role has been difficult to assess due to its rapid desensitization and the lack of pharmacological tools. In this paper, we have used P2X1-/- and wild-type mouse platelets, treated with apyrase to prevent desensitization, to demonstrate the function of P2X1 in the response to thrombogenic stimuli. In vitro, the collagen-induced aggregation and secretion of P2X1-deficient platelets was decreased, as was adhesion and thrombus growth on a collagen-coated surface, particularly when the wall shear rate was elevated. In vivo, the functional role of P2X1 could be demonstrated using two models of platelet-dependent thrombotic occlusion of small arteries, in which blood flow is characterized by a high shear rate. The mortality of P2X1-/- mice in a model of systemic thromboembolism was reduced and the size of mural thrombi formed after a laser-induced vessel wall injury was decreased as compared with normal mice, whereas the time for complete thrombus removal was shortened. Overall, the P2X1 receptor appears to contribute to the formation of platelet thrombi, particularly in arteries in which shear forces are high.

Adenosine Triphosphate↗