Poncz, M. | bioRxiv Science

bioRxiv2019

Neutrophil extracellular trap stabilization leads to improved outcomes in murine models of sepsis

Sepsis is characterized by multi-organ system dysfunction that occurs due to infection. It is associated with unacceptably high morbidity and mortality and in need of improved therapeutic intervention. Neutrophils play a crucial role in sepsis, releasing neutrophil extracellular traps (NETs) composed of DNA complexed with histones and toxic antimicrobial proteins that ensnare pathogens but also damage host tissues. At presentation, patients likely have a significant NET burden contributing to the multi-organ damage. Therefore, interventions that prevent NET release would likely be ineffective at preventing NET-based injury. Treatments that enhance NET degradation may liberate captured bacteria and toxic NET degradation products (NDPs) and therefore be of limited therapeutic benefit. We propose that interventions that stabilize NETs and sequester NDPs may be protective in sepsis. Platelet factor 4 (PF4, CXCL4) a platelet-associated chemokine, binds and compacts NETs, increasing their resistance to deoxyribonuclease I. A monoclonal antibody, KKO, which binds to PF4-NET complexes, further enhances this resistance. We now show that PF4 increases NET-mediated bacterial capture in vitro, reduces the release of NDPs, and improves outcome in murine models of sepsis. An Fc-modified KKO further enhances deoxyribonuclease resistance, decreases NDP release, and increases survival in these models, supporting a novel NET-targeting approach to improve outcomes in sepsis.

immunology↗

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↗