Myeloid CD40 deficiency reduces atherosclerosis by impairing macrophages’ transition into a pro-inflammatory state

AIMS: CD40 and its ligand, CD40L, play a critical role in driving atherosclerotic plaque development. Disrupted CD40-signalling reduces experimental atherosclerosis and induces a favourable stable plaque phenotype. We recently showed that small molecule-based inhibition of CD40-tumour necrosis factor receptor associated factor-6 interactions attenuates atherosclerosis in hyperlipidaemic mice via macrophage-driven mechanisms. The present study aims to detail the function of myeloid CD40 in atherosclerosis using myeloid-specific CD40-deficient mice. METHOD AND RESULTS: Cd40(flox/flox) and LysM-cre Cd40(flox/flox) mice on an Apoe(−/−) background were generated (CD40(wt) and CD40(mac−/−), respectively). Atherosclerotic lesion size, as well as plaque macrophage content, was reduced in CD40(mac−/−) compared to CD40(wt) mice, and their plaques displayed a reduction in necrotic core size. Transcriptomics analysis of the CD40(mac−/−) atherosclerotic aorta revealed downregulated pathways of immune pathways and inflammatory responses. Loss of CD40 in macrophages changed the representation of aortic macrophage subsets. Mass cytometry analysis revealed a higher content of a subset of alternative or resident-like CD206(+)CD209b(−) macrophages in the atherosclerotic aorta of CD40(mac−/−) compared to CD40(wt) mice. RNA-sequencing of bone marrow-derived macrophages of CD40(mac−/−) mice demonstrated upregulation of genes associated with alternatively activated macrophages (including Folr2, Thbs1, Sdc1, and Tns1). CONCLUSIONS: We here show that absence of CD40 signalling in myeloid cells reduces atherosclerosis and limits systemic inflammation by preventing a shift in macrophage polarization towards pro-inflammatory states. Our study confirms the merit of macrophage-targeted inhibition of CD40 as a valuable therapeutic strategy to combat atherosclerosis.