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.