Project description:Blood vessels are continually exposed to circulating lipids and elevations of ApoB containing lipoproteins cause atherosclerosis. Lipoprotein metabolism is highly regulated by lipolysis, largely at the level of the capillary endothelium lining metabolically active tissues. How large blood vessels, the site of atherosclerotic vascular disease, regulate the flux of fatty acids (FA) into triglyceride (TG) rich lipid droplets (LD) is not known. Here, we show that deletion of the enzyme, adipose triglyceride lipase (ATGL) in the endothelium, leads to neutral lipid accumulation in vessels and impairs endothelial dependent vascular tone and nitric oxide synthesis to promote endothelial dysfunction. Mechanistically, the loss of ATGL leads to endoplasmic reticulum stress-induced inflammation, thereby promoting EC dysfunction. Consistent with this mechanism, deletion of endothelial ATGL markedly increases lesion size in a model of atherosclerosis. Together, these data demonstrate that the dynamics of FA flux through LD impacts EC homeostasis and consequently large vessel function during normal physiology and in a chronic disease state
Project description:Blood vessels are continually exposed to circulating lipids and elevations of ApoB containing lipoproteins cause atherosclerosis. Lipoprotein metabolism is highly regulated by lipolysis, largely at the level of the capillary endothelium lining metabolically active tissues. How large blood vessels, the site of atherosclerotic vascular disease, regulate the flux of fatty acids (FA) into triglyceride (TG) rich lipid droplets (LD) is not known. Here, we show that deletion of the enzyme, adipose triglyceride lipase (ATGL) in the endothelium, leads to neutral lipid accumulation in vessels and impairs endothelial dependent vascular tone and nitric oxide synthesis to promote endothelial dysfunction. Mechanistically, the loss of ATGL leads to endoplasmic reticulum stress-induced inflammation, thereby promoting EC dysfunction. Consistent with this mechanism, deletion of endothelial ATGL markedly increases lesion size in a model of atherosclerosis. Together, these data demonstrate that the dynamics of FA flux through LD impacts EC homeostasis and consequently large vessel function during normal physiology and in a chronic disease state
Project description:Cholesterol biosynthetic intermediates such as lanosterol and desmosterol are emergent immune regulators of macrophages in response to inflammatory stimuli or lipid overloading, respectively. However, the participation of these sterols in regulating macrophage functions in the physiological context of atherosclerosis, an inflammatory disease driven by the accumulation of cholesterol-laden macrophages in the artery wall, has remained elusive. Here we report that desmosterol, the most abundant cholesterol biosynthetic intermediate in human coronary artery lesions, plays an essential role during atherogenesis, serving as a key molecule integrating cholesterol homeostasis and immune responses in macrophages. Depletion of desmosterol in myeloid cells by overexpression of 3β-hydroxysterol Δ24-reductase (DHCR24), the enzyme that catalyzes conversion of desmosterol to cholesterol, promotes the progression of atherosclerosis. Single cell transcriptomics in isolated CD45+CD11b+ cells from atherosclerotic plaques demonstrate that depletion of desmosterol increases interferon (IFN) responses and attenuates the expression of anti-inflammatory macrophage markers. Lipidomic and transcriptomic analysis of in vivo macrophage foam cells demonstrate that desmosterol is a major endogenous liver X receptor (LXR) ligand involved in LXR/RXR activation and thus, macrophage foam cell formation. Decreased desmosterol accumulation in mitochondria promotes macrophage mito-ROS production and NLRP3-dependent inflammasome activation. Deficiency of NLRP3 or ASC rescues the increased inflammasome activity and atherogenesis observed in desmosterol-depleted macrophages. Altogether, these findings underscore the critical function of desmosterol in the atherosclerotic plaque to dampen inflammation, by integrating with macrophage cholesterol metabolism and inflammatory activation, and protecting from disease progression.
Project description:Cholesterol biosynthetic intermediates such as lanosterol and desmosterol are emergent immune regulators of macrophages in response to inflammatory stimuli or lipid overloading, respectively. However, the participation of these sterols in regulating macrophage functions in the physiological context of atherosclerosis, an inflammatory disease driven by the accumulation of cholesterol-laden macrophages in the artery wall, has remained elusive. Here we report that desmosterol, the most abundant cholesterol biosynthetic intermediate in human coronary artery lesions, plays an essential role during atherogenesis, serving as a key molecule integrating cholesterol homeostasis and immune responses in macrophages. Depletion of desmosterol in myeloid cells by overexpression of 3β-hydroxysterol Δ24-reductase (DHCR24), the enzyme that catalyzes conversion of desmosterol to cholesterol, promotes the progression of atherosclerosis. Single cell transcriptomics in isolated CD45+CD11b+ cells from atherosclerotic plaques demonstrate that depletion of desmosterol increases interferon (IFN) responses and attenuates the expression of anti-inflammatory macrophage markers. Lipidomic and transcriptomic analysis of in vivo macrophage foam cells demonstrate that desmosterol is a major endogenous liver X receptor (LXR) ligand involved in LXR/RXR activation and thus, macrophage foam cell formation. Decreased desmosterol accumulation in mitochondria promotes macrophage mito-ROS production and NLRP3-dependent inflammasome activation. Deficiency of NLRP3 or ASC rescues the increased inflammasome activity and atherogenesis observed in desmosterol-depleted macrophages. Altogether, these findings underscore the critical function of desmosterol in the atherosclerotic plaque to dampen inflammation, by integrating with macrophage cholesterol metabolism and inflammatory activation, and protecting from disease progression.