GSE111535
Interleukin-1ß promotes an atheroprotective distribution of smooth muscle cells and macrophages in late stage murine atherosclerotic lesion
Despite decades of research, our understanding of processes controlling the stability of late-stage atherosclerotic plaques remains poor. However, a prevailing hypothesis is that reducing inflammation may improve plaque stability. Indeed, the potent inflammatory cytokine, interleukin-1ß (IL-1ß), has been shown to be a key driver of atherosclerosis development. Importantly, the CANTOS Trial recently demonstrated that administration of an anti-IL-1ß antibody to high-risk post-myocardial infarction (MI) patients reduced the incidence of recurrent nonfatal MI, but did not reduce the incidence of cardiovascular death or stroke. As such, although the CANTOS trial results providing exciting evidence that targeting inflammation can have clinical benefit for treating advanced atherosclerosis, extensive further investigation is needed to better understand the mechanisms by which IL-1ß inhibition impacts established lesions. Therefore, we performed intervention studies on smooth muscle cell (SMC) lineage tracing mice with advanced atherosclerosis using anti-IL- 1? or IgG control antibodies. Surprisingly, we found no effect on lesion size but a profound shift in the composition of the fibrous cap characterized by reduced collagen and SMC content but an increase in macrophage number, which was primarily driven by opposite effects on the proliferation of these respective cell types. By generating SMC-specific and macrophage-selective Il1r1 KO Apoe -/- mice, we found that SMC-specific Il1r1 KO resulted in a ~60% reduction in lesion size and lesions that were nearly devoid of YFP + SMC whereas, myeloid-selective loss of IL1R1 had no effect on lesion size, or cell composition. This suggests that SMC are a primary cell type responding to IL-1ß in atherosclerosis and that IL1 signaling in SMC is critical for their investment and retention within the fibrous cap. In addition, we found that inhibition of IL-1ß promoted an expansion of the M2 macrophage population within the fibrous cap, and that these effects may be due in part to elevated levels of IL4. Taken together, results show that IL-1ß can promote beneficial changes in late-stage murine atherosclerosis by promoting maintenance of a SMC/collagen-rich fibrous cap. Moreover, studies identify critical cell types and pathways that need to be considered when attempting to develop safer and more effective anti-inflammatory therapies for widespread treatment of atherosclerotic disease, including in moderate or low risk patients. Overall design: mRNA profiles of 18 week fed Western diet wild type (WT) SMC lineage tracing with Il1B antibody injection or IgG control were generated by deep sequencing, four animals per group, using Illumina HiSeq 2000.