Project description:While much progress has been made in identifying the mechanisms that trigger endothelial activation and inflammatory cell recruitment during atherosclerosis, less is known about the intrinsic pathways that counteract these events. Here we identified NOTCH1 as an antagonist of endothelial cell activation. NOTCH1 was constitutively expressed by adult arterial endothelium, but levels were significantly reduced by high fat diet. Furthermore, treatment of human aortic endothelial cells (HAEC) with inflammatory lipids (Ox-PAPC) and pro-inflammatory cytokines (TNFalpha and IL1beta) decreased Notch1 expression and signaling in vitro through a mechanism that requires STAT3 activation. Reduction of NOTCH1 in HAEC by siRNA, in the absence of inflammatory lipids or cytokines, increased inflammatory molecules and binding of monocytes. Conversely, some of the effects mediated by Ox-PAPC were reversed by increased NOTCH1 signaling; suggesting a link between lipid-mediated inflammation and Notch1. Interestingly, reduction of NOTCH1 by Ox-PAPC in HAEC was associated with a genetic variant previously correlated to HDL in a human GWAS. Finally endothelial Notch1 heterozygous mice showed higher diet-induced atherosclerosis. Based on these findings, we propose that reduction of endothelial NOTCH1 is a predisposing factor in the onset of vascular inflammation and initiation of atherosclerosis. Transcript profile from Human Aortic Endothelial Cells (HAEC) transfected with siRNA targeting NOTCH1 (n=3) or treated with Ox-PAPC (Oxidized 1-Palmitoyl-2-Arachidonoyl-sn-glycero-3-PhosphoCholine) for 6 hours (n=3) were compared to control HAEC (transfected with control siRNA and control media; n=3).
Project description:While much progress has been made in identifying the mechanisms that trigger endothelial activation and inflammatory cell recruitment during atherosclerosis, less is known about the intrinsic pathways that counteract these events. Here we identified NOTCH1 as an antagonist of endothelial cell activation. NOTCH1 was constitutively expressed by adult arterial endothelium, but levels were significantly reduced by high fat diet. Furthermore, treatment of human aortic endothelial cells (HAEC) with inflammatory lipids (Ox-PAPC) and pro-inflammatory cytokines (TNFalpha and IL1beta) decreased Notch1 expression and signaling in vitro through a mechanism that requires STAT3 activation. Reduction of NOTCH1 in HAEC by siRNA, in the absence of inflammatory lipids or cytokines, increased inflammatory molecules and binding of monocytes. Conversely, some of the effects mediated by Ox-PAPC were reversed by increased NOTCH1 signaling; suggesting a link between lipid-mediated inflammation and Notch1. Interestingly, reduction of NOTCH1 by Ox-PAPC in HAEC was associated with a genetic variant previously correlated to HDL in a human GWAS. Finally endothelial Notch1 heterozygous mice showed higher diet-induced atherosclerosis. Based on these findings, we propose that reduction of endothelial NOTCH1 is a predisposing factor in the onset of vascular inflammation and initiation of atherosclerosis.
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:Aim: To determine the role of NOTCH during the response-to-injury and subsequent chronic inflammatory process of the arterial wall underlying atherosclerosis. Methods and results: We have generated an endothelial-specific RBPJK depleted mice using the Cdh5 cadherin promoter (ApoE-/-;RBPJflox/flox;Cdh5- CreERT). Endothelial-specific deletion of the Notch effector RBPJK or systemic deletion of the Notch1 receptor in athero-susceptible ApoE-/- mice fed a HC diet for 6 weeks resulted in reduced atherosclerosis in the aortic arch and sinus. Intravital microscopy revealed decreased leukocyte rolling on the endothelium of ApoE-/-;RBPJflox/flox;Cdh5- CreERT, that correlated with the lesser presence of leukocyts and macrophages in the vascular wall. Consistent with this, transcriptome analysis revealed that proinflammatory and endothelial activation pathways were downregulated in atherosclerotic tissue of RBPJk-mutant mice.. Jagged1 signaling upregulation in endothelial cells promotes the physical interaction and nuclear translocation of the intracellular domain of the Notch1 receptor (N1ICD) with NF-kB,. This N1ICD and NF-kB interaction is required for reciprocal transactivation of target genes including vascular cell adhesion molecule-1 (Vcam1). Conclusions: Notch signaling pathway inactivation decreases leukocyte rolling, thereby preventing endothelial dysfunction and vascular inflammation. Thus attenuating Notch signaling may constitute a useful therapeutic strategy for atherosclerosis. Key words: atherosclerosis, endothelium, signaling pathways, Notch, NF-kB, transcriptional regulation
Project description:Increased monocyte adhesion to dysfunctional endothelial cells (ECs) orchestrated by chemokines plays an important role in arterial inflammation during atherosclerosis. Endothelial microRNAs (miRNAs) processed by the RNase Dicer1 determine the phenotype of ECs by posttranscriptional regulation of gene expression. However, the impact of endothelial miRNAs on endothelial inflammation and atherosclerosis is currently unclear. To study the effect of Dicer-dependent miRNAs in ECs during the development of atherosclerosis, Apoe-/- mice with an inducible, EC-specific knock-out of Dicer (EC-Dicerflox) and control mice (EC-DicerWT) mice were treated with tamoxifen to induce Cre-recombinase activity and fed with a high fat-diet (HFD) for 4 weeks. The comparison of the miRNA expression profile in the aortas of EC-Dicerflox and EC-DicerWT mice after 4 weeks of a HFD was performed to identify EC-specific miRNAs that may play a role in the EC function during atherogenesis.
Project description:We investigated the role of SNO-GNIA2 in HG+oxLDL-induced endothelial inflammation during the development of diabetes-accelerated atherosclerosis and found that SNO-GNAI2 could promote endothelial inflammation through dysregulating Hippo-YAP . We hypothesized that SNO-GNAI2 induced Hippo-YAP dysfunction through enhancing coupling and activating G-protein coupling receptors (GPCRs).
Project description:Increased monocyte adhesion to dysfunctional endothelial cells (ECs) orchestrated by chemokines plays an important role in arterial inflammation during atherosclerosis. Endothelial microRNAs (miRNAs) processed by the RNase Dicer1 determine the phenotype of ECs by posttranscriptional regulation of gene expression. However, the impact of endothelial miRNAs on endothelial inflammation and atherosclerosis is currently unclear. To study the effect of Dicer-dependent miRNAs in ECs on atherosclerosis, Apoe-/- mice with an inducible, EC-specific knock-out of Dicer (EC-Dicerflox) and control mice (EC-DicerWT) mice were treated with tamoxifen to induce Cre-recombinase activity and fed with a high fat-diet (HFD) for 12 weeks. The comparison of the miRNA expression profile in the aortas of EC-Dicerflox and EC-DicerWT mice after 12 weeks of a HFD was performed to identify EC-specific miRNAs that may play a role in the EC function during atherogenesis.
Project description:It is well recognized that men and women differ in circulating lipid profiles and consequently coronary artery disease (CAD). While sex hormones like estrogens are thought to protect women from CAD risk by promoting protective lipid profiles, hormone replacement therapy in women paradoxically increases CAD risk. Biological sex is determined by both sex chromosomes and sex hormones. We used mouse models to separate effects of sex chromosomes and hormones on atherosclerosis, circulating lipids and intestinal fat metabolism. We found that an XX sex chromosome complement increases food intake, body weight, fat absorption, serum lipid concentrations and atherosclerosis in gonadal male and female mice, indicating a primary effect of sex chromosome complement. Small intestine expression of enzymes involved in lipid absorption and chylomicron assembly were increased in XX male and female mice with elevated intestinal lipids. These results reveal that an XX sex chromosome complement promotes the absorption and bioavailability of dietary fat to accelerate the development of atherosclerosis.