CD40-TRAF2/3/5 Signaling Promotes Cardiac Repair by Mediating Macrophage Efferocytosis After Myocardial Infarction

Area of Science:

• Immunology
• Cardiovascular Biology
• Cellular Biology

Background:

• Macrophage-mediated efferocytosis is critical for tissue remodeling after myocardial infarction (MI).
• Efficient efferocytosis aids in cardiomyocyte survival, reparative macrophage transition, and inflammation resolution.
• The role of CD40 and its downstream signaling adaptors (TRAF2/3/5, TRAF6) in cardiac efferocytosis post-MI requires elucidation.

Purpose of the Study:

• To investigate the function of CD40 and its downstream signaling pathways (TRAF2/3/5 and TRAF6) in cardiac macrophage efferocytosis following MI.
• To determine the impact of CD40 deficiency on cardiac repair and macrophage function post-MI.

Main Methods:

• Utilized myeloid- and macrophage-specific CD40-deficient mice to assess CD40's significance in post-MI repair.
• Employed single-cell RNA sequencing to evaluate CD40's effects on macrophage functional states.
• Assessed efferocytosis and inflammation using flow cytometry, immunofluorescence, Western blot, and ELISA.
• Investigated specific TRAF signaling pathways using CD40-TRAF2/3/5^-/- and CD40-TRAF6^-/- mice.

Main Results:

• CD40 expression increased post-MI, predominantly in myeloid-derived macrophages, and its deficiency worsened cardiac function and infarct size.
• CD40 deficiency impaired macrophage efferocytosis and reduced reparative macrophage precursors.
• The CD40-TRAF2/3/5 signaling pathway, involving STAT6, was identified as crucial for CD40-mediated efferocytosis, distinct from TRAF6 signaling.

Conclusions:

• Macrophage CD40 plays a pivotal role in promoting post-MI repair by enhancing efferocytosis.
• The CD40-TRAF2/3/5 signaling axis is the primary mediator of CD40-associated efferocytosis, rather than TRAF6.
• Targeting the CD40-TRAF2/3/5 pathway offers a potential therapeutic strategy for improving cardiac repair post-MI.