Clin Res Cardiol (2025). DOI 10.1007/s00392-025-02737-x
1Medizinische Fakultät Mannheim der Universität Heidelberg I. Medizinische Klinik Mannheim, Deutschland; 2Universitätsklinikum Schleswig-Holstein Medizinische Klinik II / Kardiologie, Angiologie, Intensivmedizin Lübeck, Deutschland; 3Universitäts-Herzzentrum Freiburg - Bad Krozingen Klinik für Kardiologie und Angiologie Freiburg im Breisgau, Deutschland; 4Universitätsklinikum Mannheim GmbH I. Medizinische Klinik Mannheim, Deutschland; 5Boston Children's Hospital Boston, USA; 6Albert- Ludwigs-Universität Freiburg Innere Medizin III, Kardiologie und Angiologie Freiburg im Breisgau, Deutschland
Background:
The anaphylatoxin C5a is a potent chemoattractant and activator of neutrophils. Its receptor, C5aR1, was recently detected on platelets, where it has been implicated in controlling tissue neovascularization. However, its role in myocardial infarction (MI) remains incompletely understood.
The anaphylatoxin C5a is a potent chemoattractant and activator of neutrophils. Its receptor, C5aR1, was recently detected on platelets, where it has been implicated in controlling tissue neovascularization. However, its role in myocardial infarction (MI) remains incompletely understood.
Aim:
To investigate how platelet-expressed C5aR1 influences cardiac injury, neutrophil activation, and healing after MI, with a focus on platelet–neutrophil interactions and NET formation.
To investigate how platelet-expressed C5aR1 influences cardiac injury, neutrophil activation, and healing after MI, with a focus on platelet–neutrophil interactions and NET formation.
Methods:
MI was induced by permanent ligation of the left anterior descending (LAD) artery in four groups of 10–12-week-old male mice: Wild-type (WT) + PBS, WT + PMX205 (a C5aR1 antagonist), Platelet-specific C5aR1-deficient mice (C5aR1^flox/flox^Pf4^Cre⁺), and Cre-negative littermate controls (C5aR1^flox/flox^Pf4^Cre⁻). Echocardiography was performed on days 1 and 13 post-MI to assess cardiac function. On days 1 and 14, platelet activation (activated GPIIb/IIIa, surface P-selectin) and platelet–neutrophil complexes (PNCs; CD42b⁺/Ly6G⁺) were quantified by flow cytometry. Infarct size (TTC staining), NETs (citH3⁺ area), and neovascularization were evaluated histologically. NET induction by activated platelets was also tested ex vivo using sorted isolated platelets co-incubated with neutrophils.
MI was induced by permanent ligation of the left anterior descending (LAD) artery in four groups of 10–12-week-old male mice: Wild-type (WT) + PBS, WT + PMX205 (a C5aR1 antagonist), Platelet-specific C5aR1-deficient mice (C5aR1^flox/flox^Pf4^Cre⁺), and Cre-negative littermate controls (C5aR1^flox/flox^Pf4^Cre⁻). Echocardiography was performed on days 1 and 13 post-MI to assess cardiac function. On days 1 and 14, platelet activation (activated GPIIb/IIIa, surface P-selectin) and platelet–neutrophil complexes (PNCs; CD42b⁺/Ly6G⁺) were quantified by flow cytometry. Infarct size (TTC staining), NETs (citH3⁺ area), and neovascularization were evaluated histologically. NET induction by activated platelets was also tested ex vivo using sorted isolated platelets co-incubated with neutrophils.
Results:
Platelet-specific C5aR1-deficient mice and WT mice treated with PMX205 developed significantly smaller infarcts and showed improved ejection fractions compared to control mice. Both groups exhibited decreased platelet activation and reduced NET formation in infarcted myocardium. Interestingly, circulating PNCs were elevated in C5aR1-deficient mice, suggesting altered, potentially protective, functional crosstalk between platelets and neutrophils in the absence of platelet C5aR1. Ex vivo, immature, reticulated platelets displayed the highest expression of C5aR1 and strongly induced NET release from neutrophils. This effect was abolished by deletion of C5aR1 on platelets. PMX205 treatment and platelet-specific deletion also led to enhanced neovascularization in affected myocardium post-MI.
Platelet-specific C5aR1-deficient mice and WT mice treated with PMX205 developed significantly smaller infarcts and showed improved ejection fractions compared to control mice. Both groups exhibited decreased platelet activation and reduced NET formation in infarcted myocardium. Interestingly, circulating PNCs were elevated in C5aR1-deficient mice, suggesting altered, potentially protective, functional crosstalk between platelets and neutrophils in the absence of platelet C5aR1. Ex vivo, immature, reticulated platelets displayed the highest expression of C5aR1 and strongly induced NET release from neutrophils. This effect was abolished by deletion of C5aR1 on platelets. PMX205 treatment and platelet-specific deletion also led to enhanced neovascularization in affected myocardium post-MI.
Conclusion:
Platelet C5aR1 exacerbates myocardial injury by enhancing platelet-mediated neutrophil activation and NET formation, thereby impairing infarct healing and limiting neovascularization. These findings highlight platelet C5aR1 as a central link between thrombosis, complement, inflammation, and impaired tissue repair, thus positioning it as a promising therapeutic target following MI.
Platelet C5aR1 exacerbates myocardial injury by enhancing platelet-mediated neutrophil activation and NET formation, thereby impairing infarct healing and limiting neovascularization. These findings highlight platelet C5aR1 as a central link between thrombosis, complement, inflammation, and impaired tissue repair, thus positioning it as a promising therapeutic target following MI.