No abstract

Summary. Background: Platelets play a central role in hemostasis, in inflammatory diseases such as atherosclerosis, and during thrombus formation following vascular injury. Thereby, platelets interact intensively with monocytes and enhance their recruitment to the vascular wall. Objectives: To investigate the role of the extracellular matrix metalloproteinase inducer (EMMPRIN) in platelet-monocyte interactions. Methods and Results: Isolated human monocytes were perfused in vitro over firmly adherent platelets to allow investigation of the role of EMMPRIN in platelet-monocyte interactions under flow conditions. Monocytes readily bound to surface-adherent platelets. Both antibody blockade and gene silencing of monocyte EMMPRIN substantially attenuated firm adhesion of monocytes to platelets at arterial and venous shear rates. In vivo, platelet interactions with the murine monocyte cell line ANA-1 were significantly decreased when ANA-1 cells were pretreated with EMMPRIN-silencing small interfering RNA prior to injection into wild-type mice. Using intravital microscopy, we showed that recruitment of EMMPRIN-silenced ANA-1 to the injured carotid artery was significantly reduced as compared with control cells. Further silencing of EMMPRIN resulted in significantly fewer ANA-1-platelet aggregates in the mouse circulation as determined by flow cytometry. Finally, we identified glycoprotein (GP)VI as a critical corresponding receptor on platelets that mediates interaction with monocyte EMMPRIN. Thus, blocking of GPVI inhibited the effect of EMMPRIN on firm monocyte adhesion to platelets under arterial flow conditions in vitro, and abrogated EMMPRINmediated platelet-monocyte aggregate formation in vivo. Conclusions: EMMPRIN supports platelet-monocyte interactions and promotes monocyte recruitment to the arterial wall. Therefore, EMMPRIN might represent a novel target to reduce vascular inflammation and atherosclerotic lesion development.

IMPORTANCEThe assessment of new antithrombotic agents with a favorable safety profile is clinically relevant. OBJECTIVE To test the efficacy and safety of revacept, a novel, lesion-directed antithrombotic drug, acting as a competitive antagonist to platelet glycoprotein VI. DESIGN, SETTING, AND PARTICIPANTSA phase 2 randomized clinical trial; patients were enrolled from 9 centers in Germany from November 20, 2017, to February 27, 2020; follow-up ended on March 27, 2020. The study included patients with stable ischemic heart disease (SIHD) undergoing elective percutaneous coronary intervention (PCI).INTERVENTIONS Single intravenous infusion of revacept, 160 mg, revacept, 80 mg, or placebo prior to the start of PCI on top of standard antithrombotic therapy. MAIN OUTCOMES AND MEASURESThe primary end point was the composite of death or myocardial injury, defined as an increase in high-sensitivity cardiac troponin to at least 5 times the upper limit of normal within 48 hours from randomization. The safety end point was bleeding type 2 to 5 according to the Bleeding Academic Research Consortium criteria at 30 days. RESULTSOf 334 participants (median age, 67.4 years; interquartile range, 60-75.1 years; 253 men [75.7%]; and 330 White participants [98.8%]), 120 were allocated to receive the 160-mg dose of revacept, 121 were allocated to receive the 80-mg dose, and 93 received placebo. The primary end point showed no significant differences between the revacept and placebo groups: 24.4%, 25.0%, and 23.3% in the revacept, 160 mg, revacept, 80 mg, and placebo groups, respectively (P = .98). The high dose of revacept was associated with a small but significant reduction of high-concentration collagen-induced platelet aggregation, with a median 26.5 AU × min (interquartile range, 0.5-62.2 AU × min) in the revacept, 160 mg, group; 43.5 AU × min (interquartile range, 22.8-99.5 AU × min) in the revacept, 80 mg, group; and 41.0 AU × min (interquartile range, 31.2-101.0 AU × min) in the placebo group (P = .02), while adenosine 5′-diphosphate-induced aggregation was not affected. Revacept did not increase Bleeding Academic Research Consortium type 2 or higher bleeding at 30 days compared with placebo: 5.0%, 5.9%, and 8.6% in the revacept, 160 mg, revacept, 80 mg, and placebo groups, respectively (P = .36). CONCLUSIONS AND RELEVANCERevacept did not reduce myocardial injury in patients with stable ischemic heart disease undergoing percutaneous coronary intervention. There were few bleeding events and no significant differences between treatment arms.