Caspase-1–mediated pathway promotes generation of thromboinflammatory microparticles
Andrea S. Rothmeier, Patrizia Marchese, Brian G. Petrich, Christian Furlan-Freguia, Mark H. Ginsberg, Zaverio M. Ruggeri, Wolfram Ruf
Andrea S. Rothmeier, Patrizia Marchese, Brian G. Petrich, Christian Furlan-Freguia, Mark H. Ginsberg, Zaverio M. Ruggeri, Wolfram Ruf
View: Text | PDF
Research Article Hematology

Caspase-1–mediated pathway promotes generation of thromboinflammatory microparticles

Abstract

Extracellular ATP is a signal of tissue damage and induces macrophage responses that amplify inflammation and coagulation. Here we demonstrate that ATP signaling through macrophage P2X7 receptors uncouples the thioredoxin (TRX)/TRX reductase (TRXR) system and activates the inflammasome through endosome-generated ROS. TRXR and inflammasome activity promoted filopodia formation, cellular release of reduced TRX, and generation of extracellular thiol pathway–dependent, procoagulant microparticles (MPs). Additionally, inflammasome-induced activation of an intracellular caspase-1/calpain cysteine protease cascade degraded filamin, thereby severing bonds between the cytoskeleton and tissue factor (TF), the cell surface receptor responsible for coagulation activation. This cascade enabled TF trafficking from rafts to filopodia and ultimately onto phosphatidylserine-positive, highly procoagulant MPs. Furthermore, caspase-1 specifically facilitated cell surface actin exposure, which was required for the final release of highly procoagulant MPs from filopodia. Together, the results of this study delineate a thromboinflammatory pathway and suggest that components of this pathway have potential as pharmacological targets to simultaneously attenuate inflammation and innate immune cell–induced thrombosis.

Authors

Andrea S. Rothmeier, Patrizia Marchese, Brian G. Petrich, Christian Furlan-Freguia, Mark H. Ginsberg, Zaverio M. Ruggeri, Wolfram Ruf

×

Figure 10

Schematic illustration of the proposed thromboinflammatory MP release pathway in macrophages.

Options: View larger image (or click on image) Download as PowerPoint
Schematic illustration of the proposed thromboinflammatory MP release pa...
Macrophage priming by IFN-γ and TLR ligands induces transcriptional upregulation of TF and proinflammatory interleukins. Activation of the macrophage P2RX7 by ATP triggers TRXR-dependent release of TRX, leading to reductive changes of the extracellular proteome, as indicated by the extracellular free thiol (SH) groups. The intracellular depletion of TRX abolishes regulatory functions of TRX and causes actin remodeling and filopodia formation as well as TXNIP-mediated inflammasome assembly and caspase-1 activation. Active caspase-1 mediates maturation and release of the proinflammatory cytokine IL-1β and facilitates activation of calpain, which in turn reverses TF retention by filamin (indicated as a red rod on the cytoplasmic side of TF) and thereby allows raft-dependent trafficking of TF onto filopodia. Membrane receptors TF, integrin β1, and PSGL1 assemble with marker proteins of highly procoagulant MPs, γ-actin, and PDI when released from PS-rich filopodia, facilitated by caspase-1 and resulting in highly procoagulant thromboinflammatory MPs. Key pharmacological inhibitors used here are placed next to their targets to indicate where the thromboinflammatory pathway is inhibited.