USF1 deficiency alleviates inflammation, enhances cholesterol efflux and prevents cholesterol accumulation in macrophages

Abstract

BackgroundThe focus of studies on high-density lipoproteins (HDL) has shifted from HDL-cholesterol (HDL-C) to HDL function. We recently demonstrated that low USF1 expression in mice and humans associates with high plasma HDL-C and low triglyceride levels, as well as protection against obesity, insulin resistance, and atherosclerosis. Here, we studied the impact of USF1 deficiency on HDL functional capacity and macrophage atherogenic functions, including inflammation, cholesterol efflux, and cholesterol accumulation.MethodsWe used a congenic Usf1 deficient mice in C57Bl/6JRccHsd background and blood samples were collected to isolate HDL for structural and functional studies. Lentiviral preparations containing the USF1 silencing shRNA expression vector were used to silence USF1 in human THP-1 and Huh-7 cells. Cholesterol efflux from acetyl-LDL loaded THP-1 macrophages was measured using HDL and plasma as acceptors. Gene expression analysis from USF1 silenced peritoneal macrophages was carried out using Affymetrix protocols.ResultsWe show that Usf1 deficiency not only increases HDL-C levels in vivo, consistent with elevated ABCA1 protein expression in hepatic cell lines, but also improves the functional capacity of HDL particles. HDL particles derived from Usf1 deficient mice remove cholesterol more efficiently from macrophages, attributed to their higher contents of phospholipids. Furthermore, silencing of USF1 in macrophages enhanced the cholesterol efflux capacity of these cells. These findings are consistent with reduced inflammatory burden of USF1 deficient macrophages, manifested by reduced secretion of pro-inflammatory cytokines MCP-1 and IL-1β and protection against inflammation-induced macrophage cholesterol accumulation in a cell-autonomous manner.ConclusionsOur findings identify USF1 as a novel factor regulating HDL functionality, showing that USF1 inactivation boosts cholesterol efflux, reduces macrophage inflammation and attenuates macrophage cholesterol accumulation, linking improved macrophage cholesterol metabolism and inflammatory pathways to the antiatherogenic function of USF1 deficiency.

Association of CXCR6 with COVID-19 severity: delineating the host genetic factors in transcriptomic regulation

“…Among the top TFs (relevance score > 0.2) that drove this trajectory, the DNA-binding RELA-NFKB1 complex is involved in several biological processes, such as inflammation, immunity, and cell growth initiated by external stimuli. MYC gene is related to the cell cycle and apoptosis pathway and upstream transcription factor 1 ( USF1 ) is related to metabolic alteration associated inflammation process (Ruuth et al 2018 ). In summary, the TF results are well consistent with our previous hallmark pathway findings (Supplementary Table S5 and S6).…”

Phenome-wide and expression quantitative trait locus associations of coronavirus disease 2019 genetic risk loci

“…USF1 is a transcription factor that modulates several genes involved in lipid and glucose metabolism such as apolipoproteins and lipases including PNPLA2, a triglyceride lipase that catalyzes the initial step in triglyceride hydrolysis (Aguilar-Salinas et al, 2014;Taghizadeh et al, 2019). Knockout studies of USF1 in mice have been shown to enhance cholesterol efflux in macrophages and downregulate secretion of pro-inflammatory cytokines such as MCP-1 and IL-1b (Ruuth et al, 2018) and USF1 variants in humans have been associated with familial combined hyperlipidemia and coronary artery disease (Fan et al, 2014;Laurila et al, 2016;Ruuth et al, 2018). Interestingly, a recent study by Dias et al showed that monocytes from COVID-19 have increased lipid droplet accumulation and that pharmacological inhibition of lipid droplet formation led to a significant inhibition of replication of SARS-CoV-2 (Dias et al, 2020).…”

Hematopoietic upstream stimulating factor 1 deficiency is associated with increased atherosclerosis susceptibility in LDL receptor knockout mice

“…Since macrophages as scavenging cells cannot limit the intake of cholesterol-rich lipoprotein particles, they rely fully on active transport of cholesterol out of the cell via ATP-binding cassette transporters such as ABCA1 and ABCG1 to overcome their transformation into foam cells 21 . In vitro studies have recently shown that elimination of USF1 from human THP-1 macrophages induces cellular ABCA1 protein levels and a parallel rise in the rate of cholesterol efflux to wild-type mouse serum 18 . Furthermore USF1 deficient macrophages displayed reduced inflammatory burden with reduced secretion of the pro-inflammatory cytokines monocyte chemoattractant protein-1 and interleukin-1β, thereby supporting the cholesterol efflux process 18 .…”