Macrophage C3aR1 Mediates Sepsis-Induced Myocardial Injury by Triggering Neutrophil Necroptosis

Area of Science:

• Immunology
• Cardiology
• Molecular Biology

Background:

• Sepsis-induced myocardial injury (SIMI) is a major cause of death in critical care.
• Immune responses, particularly involving macrophages and neutrophils, are central to SIMI.
• The precise mechanisms of macrophage-neutrophil crosstalk in SIMI are not fully understood.

Purpose of the Study:

• To investigate the role of complement C3a receptor 1 (C3aR1) in mediating macrophage-neutrophil crosstalk during SIMI.
• To elucidate the signaling pathways involved in C3aR1-mediated inflammation in the context of SIMI.
• To assess the therapeutic potential of targeting C3aR1 in SIMI.

Main Methods:

• Utilized a cecal ligation and puncture (CLP) rat model for SIMI.
• Employed an in vitro co-culture system with THP-1 macrophages, HL-60 cells, and AC16 cardiomyocytes.
• Investigated C3aR1's effect on macrophage polarization and neutrophil necroptosis via the TLR4/NF-κB pathway.
• Performed cardiac-specific C3aR1 knockdown in vivo.

Main Results:

• C3aR1 activation promotes M1 macrophage polarization through the TLR4/NF-κB pathway.
• M1 macrophages induce neutrophil necroptosis, releasing chemokines and creating an inflammatory loop.
• This loop exacerbates cardiomyocyte injury, leading to cardiac dysfunction.
• Cardiac-specific C3aR1 knockdown reduced myocardial damage, inflammation, and improved cardiac function.

Conclusions:

• C3aR1 is a critical mediator of macrophage-neutrophil crosstalk in sepsis-induced myocardial injury.
• Targeting C3aR1 may offer a novel therapeutic strategy for sepsis-induced cardiac complications.
• Understanding this crosstalk pathway is key to developing effective treatments for SIMI.