Biology subjects

van Agthoven, J.

Publications and source records attributed to van Agthoven, J..

3 recordsLinked to original sources

bioRxiv2024

Platelet integrin αIIbβ3 plays a key role in venous thrombogenesis in a mouse model

AbstractVenous thrombosis (VT) is a common vascular disease associated with reduced survival and a high recurrence rate. Previous studies have shown that the accumulation of platelets and neutrophils at sites of endothelial cell activation is a primary event in VT, but a role for platelet IIb{beta}3 in the initiation of venous thrombosis has not been established. This task has been complicated by the increased bleeding linked to partial agonism of current IIb{beta}3 inhibitory drugs such as tirofiban (Aggrastat(R)). Here, we show that m-tirofiban, an engineered version of tirofiban, is not a partial agonist of IIb{beta}3. This is based on its cryo-EM structure in complex with human full-length IIb{beta}3 and its inability to increase expression of an activation-sensitive epitope on platelet IIb{beta}3. m-tirofiban abolished agonist-induced platelet aggregation ex vivo at concentrations that preserved clot retraction and markedly suppressed the accumulation of platelets, neutrophils, and fibrin on thrombin-activated endothelium in real-time using intravital microscopy in a mouse model of venous thrombogenesis. Unlike tirofiban, however, m-tirofiban did not increase bleeding at the thrombosis-inhibitory dose. These findings establish a key role for IIb{beta}3 in the initiation of VT, provide a guiding principle for designing potentially safer inhibitors for other integrins, and suggest that pure antagonists of IIb{beta}3 like m-tirofiban merit further consideration as potential thromboprophylaxis agents in patients at high-risk for VT and hemorrhage.

pathology↗

bioRxiv2019

Novel Pure αVβ3 Integrin Antagonists That Do Not Induce Receptor Extension, Prime the Receptor, or Enhance Angiogenesis at Low Concentrations

The integrin V{beta}3 receptor has been implicated in several important diseases, but no V{beta}3 antagonists are approved for human therapy. One possible limitation of current small-molecule antagonists is their ability to induce a major conformational change in the receptor that induces it to adopt a high-affinity ligand-binding state. In response, we used structural inferences from a pure peptide antagonist to design the small-molecule pure antagonists TDI-4161 and TDI-3761. Both compounds inhibit V{beta}3-mediated cell adhesion to V{beta}3 ligands, but do not induce the conformational change as judged by antibody binding, electron microscopy, X-ray crystallography, and receptor priming studies. Both compounds demonstrated the favorable property of inhibiting bone resorption in vitro, supporting potential value in treating osteoporosis. Neither, however, had the unfavorable property of the V{beta}3 antagonist cilengitide of paradoxically enhancing aortic sprout angiogenesis at concentrations below its IC50, which correlates with cilengitides enhancement of tumor growth in vivo.\n\nSignificance StatementV{beta}3 is a potential therapeutic target for several important human diseases, but there are currently no V{beta}3 antagonists approved for human therapy. Current candidates are primarily based on the Arg-Gly-Asp (RGD) motif and act as partial agonists in that they induce V{beta}3 to undergo a conformational change that converts it into a high-affinity ligand-binding state. We have used structure-guided design to produce pure small-molecule V{beta}3 antagonists that do not induce the conformational change as judged by protein crystallography, electron microscopy, and receptor priming. These compounds inhibit V{beta}3-mediated bone resorption in vitro, but unlike the partial agonist cilengitide, do not enhance angiogenesis at low doses, a property that correlates with low-dose cilengitides enhancement of tumor growth in vivo. These pure V{beta}3 antagonists can help define V{beta}3s role in animal models. If they demonstrate benefits over partial agonists in these model systems, they may be appropriate to consider for human therapy.

pharmacology and toxicology↗

bioRxiv2018

Structure-guided design of a pure orthosteric antagonist of integrin αIIbβ3 that inhibits thrombosis but not clot retraction

Platelet integrin lIb{beta}3 plays a critical role in both hemostasis and thrombosis. Current IIb{beta}3 antagonists are potent anti-thrombotic drugs, but also cause adverse outcomes, which limited their clinical use. Drug-induced serious bleeding, thrombocytopenia and paradoxical thrombosis have been linked to impaired clot retraction and to conformational changes in IIb{beta}3 that promote binding of preformed antibodies, natural ligands or both to IIb{beta}3. We have used structure-guided design to generate the orthosteric inhibitor Hr10 that acts as a pure IIb{beta}3 antagonist, i.e. it does not induce the conformational changes in IIb{beta}3. Hr10 is as effective as the partial agonist drug eptifibatide in blocking platelet aggregation and arteriolar thrombosis in mice. In contrast to eptifibatide, however, Hr10 preserved thrombin-induced clot retraction, suggesting that it may not perturb hemostasis. Our structure-based approach can find general utility in designing pure orthosteric inhibitors for other integrins, in providing vital tools for dissecting structure-activity relationships in IIb{beta}3, and potentially in offering safer alternatives for human therapy.

cell biology↗