Project description:Hypercholesterolemia, the driving force of atherosclerosis, accelerates the expansion and mobilization of hematopoietic stem and progenitor cells (HSPCs). The molecular determinants connecting hypercholesterolemia with hematopoiesis are underexplored. Here we report that a novel somite-derived pro-hematopoietic cue, AIBP, orchestrates HSPC emergence from the hemogenic endothelium, a type of specialized endothelium manifesting hematopoietic potential. Mechanistically, AIBP-mediated cholesterol efflux activates endothelial Srebp2, the master transcription factor for cholesterol biosynthesis, which transactivates Notch and promotes HSPC emergence. Srebp2 inhibition impairs hypercholesterolemia-induced HSPC expansion. Srebp2 activation and Notch upregulation are associated with HSPC expansion in hypercholesterolemic human subjects. Genome-wide ChIP-seq, RNA-seq, and ATAC-seq indicate that Srebp2 trans-regulates Notch pathway genes required for hematopoiesis. Our studies outline a novel AIBP-regulated Srebp2-dependent paradigm for HSPC emergence in development and HPSC expansion in atherosclerotic cardiovascular disease.
Project description:Hypercholesterolemia, the driving force of atherosclerosis, accelerates the expansion and mobilization of hematopoietic stem and progenitor cells (HSPCs). The molecular determinants connecting hypercholesterolemia with hematopoiesis are unclear. Here, we report that a somite-derived prohematopoietic cue, AIBP, orchestrates HSPC emergence from the hemogenic endothelium, a type of specialized endothelium manifesting hematopoietic potential. Mechanistically, AIBP-mediated cholesterol efflux activates endothelial Srebp2, the master transcription factor for cholesterol biosynthesis, which in turn transactivates Notch and promotes HSPC emergence. Srebp2 inhibition impairs hypercholesterolemia-induced HSPC expansion. Srebp2 activation and Notch up-regulation are associated with HSPC expansion in hypercholesterolemic human subjects. Genome-wide chromatin immunoprecipitation followed by sequencing (ChIP-seq), RNA sequencing (RNA-seq), and assay for transposase-accessible chromatin using sequencing (ATAC-seq) indicate that Srebp2 transregulates Notch pathway genes required for hematopoiesis. Our studies outline an AIBP-regulated Srebp2-dependent paradigm for HSPC emergence in development and HPSC expansion in atherosclerotic cardiovascular disease.
Project description:Impaired cholesterol efflux pathways is a hallmark of lung adenocarcinoma. We used single cell RNA sequencing (scRNA-seq) to analyze the impact of defective cholesterol efflux on cell diversity in lung tumor
Project description:The activation of Liver X Receptor (LXR) promotes cholesterol efflux and repression of inflammatory genes with anti-atherogenic consequences. The mechanisms underlying repressive activity of LXR are controversial and have been attributed to cholesterol efflux or to transrepression of Activator Protein-1 (AP-1) activity. Here, we find that cholesterol efflux contributes to LXR repression, while direct repressive functions of LXR also play a key role but are independent of AP-1. We use ATAC-seq to show that LXR reduces chromatin accessibility in cis at inflammatory gene enhancers containing LXR binding sites. Targets of this repressive activity are associated with leukocyte adhesion and neutrophil migration, and LXR agonist treatment suppresses neutrophil recruitment in a mouse model of sterile peritonitis. These studies suggest a model of repression in which liganded LXR binds in cis to canonical nuclear receptor binding sites and represses pro-atherogenic leukocyte functions in tandem with induction of LXR targets mediating cholesterol efflux.
Project description:The activation of Liver X Receptor (LXR) promotes cholesterol efflux and repression of inflammatory genes with anti-atherogenic consequences. The mechanisms underlying repressive activity of LXR are controversial and have been attributed to cholesterol efflux or to transrepression of Activator Protein-1 (AP-1) activity. Here, we find that cholesterol efflux contributes to LXR repression, while direct repressive functions of LXR also play a key role but are independent of AP-1. We use ATAC-seq to show that LXR reduces chromatin accessibility in cis at inflammatory gene enhancers containing LXR binding sites. Targets of this repressive activity are associated with leukocyte adhesion and neutrophil migration, and LXR agonist treatment suppresses neutrophil recruitment in a mouse model of sterile peritonitis. These studies suggest a model of repression in which liganded LXR binds in cis to canonical nuclear receptor binding sites and represses pro-atherogenic leukocyte functions in tandem with induction of LXR targets mediating cholesterol efflux.
Project description:Tumor-associated macrophages (TAM) have been shown to have important roles in the malignant progression of various cancers. However, macrophages also posses intrinsic tumoricidal activity and can promote the activity of cytotoxic lymphocytes, but they rapidly adopt an alternative phenotype within tumors, associated with immune-suppression and trophic functions that support tumor growth. The mechanisms that promote TAM polarization in the tumor-microenvironment remain poorly understood, these mechanisms may represent important therapeutic targets to block the tumor-promoting functions of TAM and restore their anti-tumor potential. Here we have characterized TAM in a mouse model of metastatic ovarian cancer. We show that ovarian cancer cells promote membrane-cholesterol efflux and the depletion of lipid rafts from macrophages. Increased cholesterol efflux promoted IL-4 mediated reprogramming while inhibiting IFNg-induced gene expression. These studies reveal an unexpected role for tumor-induced membrane-cholesterol efflux in driving the IL-4 signaling and the tumor-promoting functions of TAM, while rendering them refractory to pro-inflammatory stimuli. Thus, preventing cholesterol efflux in TAM could represent a novel therapeutic strategy to block pro-tumor functions and restore anti-tumor immunity.
Project description:ATP binding cassette subfamily member 1 (ABCA1) and G1 (ABCG1) are cholesterol efflux transporter to prevent excess intracellular cholesterol accumulation. We here report the deletion of Abca1 and Abcg1 results in the significant increased expression of Cd38, a multi-faceted ectoenzyme with NADase activity.
Project description:The relation of serial changes in plaque morphology of obstructive nonculprit lesions to HDL efflux, inflammation and transcriptome perturbations in response to high-dose statin therapy (YELLOW II study). YELLOW II is a prospective single center study. Stable patients who were scheduled for elective coronary angiography and/or coronary artery stenting were screened for this study. The final target population were patients with multivessel disease requiring staged intervention, culprit vessel initially and non-culprit vessel later, with maxLCBI4mm greater than 150 by NIRS. Patients underwent PCI for a culprit lesion followed by OCT and NIRS/IVUS of an obstructive non-culprit lesion (NCL). All subjects received rosuvastatin, 40 mg every day for 8-12 weeks. The NCL was reimaged and underwent intervention as a part of staged intervention. Blood samples were obtained for cholesterol efflux capacity (CEC) quantification and peripheral PBMC isolation. Despite the extensive evidence for the beneficial effects of statins on clinical outcomes, the mechanisms underlying these effects in remain elusive. In a prospective study, 85 patients with stable multivessel coronary artery disease underwent percutaneous coronary intervention for a culprit lesion followed by intracoronary multi-modality imaging including optical coherence tomography (OCT) of an obstructive NCL. All subjects received 40 mg of rosuvastatin every day for 8-12 weeks, when the NCL was reimaged and intervention was performed. Blood samples were drawn at both times to assess cholesterol efflux capacity (CEC) and transcriptomic profile in peripheral blood mononuclear cells (PBMC).
Project description:Cholesterol is an essential cell membrane component and precursor in metabolic pathways. Control of cholesterol levels is essential to human health. The endocrine hormone FGF19 potently inhibits CYP7A1, which controls a key step in cholesterol catabolism. However, the molecular mechanisms that integrate FGF19 with other cholesterol metabolic pathways are incompletely understood. Here we show that FGF19 and analogue promote HDL biogenesis and cholesterol efflux from the liver by selectively modulating liver X receptor signaling without inducing hepatic steatosis. We further identify ATP-binding cassette transporter A1 and FGFR4 as mediators of this effect. In dyslipidemic Apoe-/- mice fed a Western diet, treatment with FGF19 analogue dramatically reduced atherosclerotic lesion area in aortas. In healthy human volunteers, FGF19 analogue caused a placebo-adjusted increase in HDL cholesterol levels of 26% in seven days. These findings outline a regulatory role for FGF19 in cholesterol metabolism and advance our understanding of the mechanisms that coordinate sterol homeostasis. We used microarrays to detail the global programme of gene expression affected by FGF19 treatment in mice.
Project description:Specific mutations in Apolipoprotein A-I (ApoA-I) of high-density lipoprotein (HDL) are responsible for a late-onset systemic amyloidosis. Carriers do not exhibit increased cardiovascular disease risk despite reduced levels of ApoA-I/ HDL-cholesterol. To explain this paradox, we show that the HDL particle profile of L75P and L174S patients presents a higher relative abundance of the 8.4 nm vs 9.6 nm particles, and that serum from patients, as well as reconstituted 8.4 and 9.6 nm HDL particles (rHDL), possess increased capacity to catalyze cholesterol efflux from macrophages. Synchrotron radiation circular dichroism and hydrogen-deuterium exchange revealed that the variants in 8.4 nm rHDL have altered secondary structure composition and display a more flexible binding to lipids compared to their native counterpart. The reduced HDL-cholesterol levels of patients carrying ApoA-I amyloidogenic variants are thus balanced by higher proportion of small, dense HDL particles and better cholesterol efflux due to altered, region-specific protein structure dynamics.