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LDL delivery of microbial small RNAs drives atherosclerosis through macrophage TLR8.

Ryan M AllenDanielle L MichellAshley B CavnarWanying ZhuNeil MakhijaniDanielle M ContrerasChase A RabyElizabeth M SemlerCarlisle DeJuliusMark CastleberryYoumin ZhangMarisol Ramirez-SolanoShilin ZhaoCraig L DuvallAmanda C DoranQuanhu ShengMacRae F LintonKasey C Vickers
Published in: Nature cell biology (2022)
Macrophages present a spectrum of phenotypes that mediate both the pathogenesis and resolution of atherosclerotic lesions. Inflammatory macrophage phenotypes are pro-atherogenic, but the stimulatory factors that promote these phenotypes remain incompletely defined. Here we demonstrate that microbial small RNAs (msRNA) are enriched on low-density lipoprotein (LDL) and drive pro-inflammatory macrophage polarization and cytokine secretion via activation of the RNA sensor toll-like receptor 8 (TLR8). Removal of msRNA cargo during LDL re-constitution yields particles that readily promote sterol loading but fail to stimulate inflammatory activation. Competitive antagonism of TLR8 with non-targeting locked nucleic acids was found to prevent native LDL-induced macrophage polarization in vitro, and re-organize lesion macrophage phenotypes in vivo, as determined by single-cell RNA sequencing. Critically, this was associated with reduced disease burden in distinct mouse models of atherosclerosis. These results identify LDL-msRNA as instigators of atherosclerosis-associated inflammation and support alternative functions of LDL beyond cholesterol transport.
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