Inflammasomes, Neutrophil Extracellular Traps, and Cholesterol

Activation of macrophage inflammasomes leads to interleukin (IL)-1b and IL-18 secretion and promotes atherosclerosis and its complications in mice and humans. However, the specific role and underlying mechanisms of the inflammasome in atherogenesis are topics of active research. Several studies in hyperlipidemic mouse models found that the NLRP3 inflammasome contributes to atherosclerosis, but recent work suggests that a second hit, such as defective cholesterol efflux or accumulation of oxidized mitochondrial DNA, may be required for significant inflammasome activation. Cholesterol crystal uptake or formation in lysosomes may damage membranes and activate NLRP3 inflammasomes. Alternatively, plasma or endoplasmic reticulum membrane cholesterol accumulation may condition macrophages for inflammasome activation in the presence of danger-associated molecular patterns, such as oxidized LDL. Inflammasome activation in macrophages or neutrophils leads to Gasdermin-D cleavage that induces membrane pore formation, releasing IL-1b and IL-18, and eventuating in pyroptosis or neutrophil extracellular trap formation (NETosis). In humans, inflammasome activation and NETosis may contribute to atherosclerotic plaque erosion and thrombosis, especially in patients with type 2 diabetes, chronic kidney disease, or clonal hematopoiesis. Suppression of the inflammasome by activation of cholesterol efflux or by direct inhibition of inflammasome components may benefit patients with cardiovascular disease and underlying susceptibility to inflammasome activation.