Interleukin-1β suppression dampens inflammatory leucocyte production and uptake in atherosclerosis

Abstract

Aims Targeting vascular inflammation represents a novel therapeutic approach to reduce complications of atherosclerosis. Neutralizing the pro-inflammatory cytokine interleukin-1β (IL-1β) using canakinumab, a monoclonal antibody, reduces the incidence of cardiovascular events in patients after myocardial infarction (MI). The biological basis for these beneficial effects remains incompletely understood. We sought to explore the mechanisms of IL-1β-targeted therapies. Methods and Results In mice with early atherosclerosis (ApoE-/- mice on a high-cholesterol diet for six weeks), we found that three weeks of NLRP3-inflammasome inhibition or anti-IL-1β treatment (using either MCC950, an NLRP3 inflammasome inhibitor which blocks production and release of active IL-1β; or a murine analog of canakinumab) dampened accumulation of leukocytes in atherosclerotic aortas, which consequently resulted in slower progression of atherosclerosis. Causally, we found that endothelial cells from atherosclerotic aortas lowered expression of leukocyte chemoattractants and adhesion molecules upon NLRP3-inflammasome inhibition, indicating that NLRP3-inflammasome- and IL-1β-targeted therapies reduced blood leukocyte recruitment to atherosclerotic aortas. In accord, adoptive transfer experiments revealed that anti-IL-1β treatment mitigated blood myeloid cell uptake to atherosclerotic aortas. We further report that anti-IL-1β treatment and NLRP3-inflammasome inhibition reduced inflammatory leukocyte supply by decreasing proliferation of bone marrow hematopoietic stem and progenitor cells, demonstrating that suppression of IL-1β and the NLRP3-inflammasome lowered production of disease-propagating leukocytes. Using bone marrow reconstitution experiments, we observed that hematopoietic cell-specific NLRP3-inflammasome activity contributed to both enhanced recruitment and increased supply of blood inflammatory leukocytes. Further experiments that queried whether anti-IL-1β treatment reduced vascular inflammation also in post-MI accelerated atherosclerosis documented the operation of convergent mechanisms (reduced supply and uptake of inflammatory leukocytes). In line with our pre-clinical findings, post-MI patients on canakinumab treatment showed reduced blood monocyte numbers. Conclusions Our murine and human data reveal that anti-IL-1β treatment and NLRP3-inflammasome inhibition dampened vascular inflammation and progression of atherosclerosis through reduced blood inflammatory leukocyte 1) supply and 2) uptake into atherosclerotic aortas providing additional mechanistic insights into links between hematopoiesis and atherogenesis, and into the beneficial effects of NLRP3-inflammasome- and IL-1β-targeted therapies. Translational perspective Therapeutic targeting of vascular inflammation represents a promising avenue to reduce complications of atherosclerosis. Neutralizing the pro-inflammatory cytokine interleukin-1β (IL-1β) reduces the incidence of cardiovascular events in patients with prior myocardial infarction. However, the mechanisms underlying these beneficial effects remain incompletely understood. This study explored how IL-1β and NLRP3-inflammasome suppression mitigated plaque progression. Our murine and human data reveal that pharmacological anti-IL-1β treatment and NLRP3-inflammasome inhibition dampened inflammatory leukocyte accumulation in atherosclerotic aortas through 1) decreased blood inflammatory leukocyte supply and 2) reduced blood inflammatory leukocyte uptake into in atherosclerotic aortas. These data provide additional mechanistic insights into links between hematopoiesis and atherogenesis, and inform future anti-inflammatory interventions in patients with atherosclerosis.

Where the Action Is—Leukocyte Recruitment in Atherosclerosis

“…At this point, anti-inflammatory treatment strategies come to play ( Figure 2 ). The IL-1β neutralizing antibody canakinumab was one of the first solely anti-inflammatory drugs shown to reduce the recurrence of cardiovascular events in high-risk CAD patients ( 374 ), and as suggested from mouse experiments, particularly does so by reducing leukocyte production in the bone marrow and deactivating EC toward less leukocyte recruitment ( 375 ). Moreover, another such highly anti-inflammatory drug, colchicine, was proven to reduce the risk of myocardial infarction, ischemic stroke, or cardiovascular death by over 25%, of note in addition to baseline treatment with lipid-lowering agents in 97% of enrolled patients ( 376 ).…”

Modified Lipoproteins Induce Arterial Wall Inflammation During Atherogenesis

“…This novel understanding is necessary when aiming at developing new anti-atherosclerotic therapies aiming at primary prevention of ASCVD, as it dictates that the inflammatory component is not only a residual risk but a risk existing throughout the development of atherosclerosis. Recent results obtained in mice with early atherosclerosis revealed that inhibition of IL-1β and NLRP3 inflammasome reduces leukocyte accumulation in atherosclerotic aortas ( 323 ). Thus, we may predict that cardiovascular interventions utilizing lowering the levels of circulating apoB-containing lipoproteins, prevention of their modifications, and reduction of the numbers of lesional macrophages already at an initial or early stage of the long subclinical asymptomatic phase of atherosclerosis may ultimately provide us the tools required for full eradication of the clinically manifest ASCVD.…”

Macrophages in Atheromatous Plaque Developmental Stages

“…Systemic monocytosis leads to increased recruitment of macrophages to the vessel wall and the number of macrophages in the plaque correlates with plaque vulnerability: In general, the more macrophages in the plaque, the more susceptible it is to rupture ( 12 , 115 ). Systemic therapy with anti-IL1b antibodies decreases monocyte and neutrophil blood counts in experimental models and patients post myocardial infarction, and suppresses endothelial cell activation ( 54 , 116 ). Of note, in the CANTOS trial treatment with the anti-IL1b-antibody canakinumab significantly reduced rates of recurrent cardiovascular disease, independent of alterations in lipid levels ( 117 ).…”