Unknown,Transcriptomics,Genomics,Proteomics

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Endothelial NOTCH1 is suppressed by circulating lipids and antagonizes inflammation during atherosclerosis

ABSTRACT: 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).

ORGANISM(S): Homo sapiens

SUBMITTER: Anais Briot

PROVIDER: E-GEOD-72633 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Oxidized phospholipids are thought to promote atherogenesis by stimulating endothelial cells (ECs) to produce inflammatory cytokines, such as IL-8. In studies with mouse models, we previously demonstrated that genetic variation in inflammatory responses of endothelial cells to oxidized lipids contributes importantly to atherosclerosis susceptibility. We now show that similar variations occur in cultured aortic ECs derived from multiple heart transplant donors. These variations were stably maintained between passages and, thus, reflect either genetic or epigenetic regulatory differences. Expression array analysis of aortic EC cultures derived from 12 individuals revealed that >1,000 genes were regulated by oxidized phospholipids. We have used the observed variations in the sampled population to construct a gene coexpression network comprised of 15 modules of highly connected genes. We show that several identified modules are significantly enriched in genes for known pathways and confirm a module enriched for unfolded protein response (UPR) genes using siRNA and the UPR inducer tunicamycin. On the basis of the constructed network, we predicted that a gene of unknown function (MGC4504) present in the UPR module is a target for UPR transcriptional activator ATF4. Our data also indicate that IL-8 is present in the UPR module and is regulated, in part, by the UPR. We validate these by using siRNA. In conclusion, we show that interindividual variability can be used to group genes into pathways and predict gene-gene regulatory relationships, thus identifying targets potentially involved in susceptibility to common diseases such as atherosclerosis. Twelve individual HAEC lines were treated in duplicate (in 35-mm dishes) for 4 h in media containing PAPC (40 μg/ml) or oxidized PAPC (OxPAPC) at 20 ug/ml or 40 μg/ml. Cytoplasmic RNA was isolated by using an RNAeasy kit (Qiagen) and analyzed on an Agilent 2100 Bioanalyzer (Agilent, Palo Alto, CA) to assess RNA integrity. Double-stranded cDNAs were synthesized from total RNA by using the cDNA Synthesis System (Invitrogen, Carlsbad, CA). Biotin-labeled cRNA was generated and used to probe Affymetrix (Santa Clara, CA) Human Genome U133 Plus 2.0 arrays according to the manufacturer’s recommendations (Affymetrix). The Microarray Suite 5.0 software (Affymetrix) was used to analyze image data and make the absolute call for each measurement. The array data were normalized with the median invariant method (31).

Project description:The transition of the endothelium to a pro-inflammatory state is key to progression of chronic inflammatory diseases including rheumatoid arthritis, chronic bowel disease and atherosclerosis. In atherosclerosis it is hypothesized that low density lipoproteins (LDL) that become trapped in the intima of the blood vessels are oxidized to minimally modified LDL (mmLDL) and that these serve as an important contributing factors to endothelial dysfunction. Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphatidylcholine (OX-PAPC), a model of the active phospholipid components of mmLDL affects the expression of hundreds of genes involved in inflammatory and other biological processes in human aortic endothelial cells (HAECs). We hypothesized that microRNAs (miRNAs) partially regulate this response. Using next generation sequencing, we identified miR-21-3p and miR-27a-5p to be induced 4-fold and 3-fold, respectively in response to OX-PAPC treatment compared to control treatment in HAECs. To identify the targets, we performed whole genome transcript profiling following transient over-expression of these two miRNAs followed by. In total, 1254 genes were down-regulated with 925 of them overlapping between the two miRNAs. Functional enrichment analysis using Gene Ontology predicted that the two miRNAs were involved in the regulation of NF-κB signaling. We characterized the Toll/interleukin-1 receptor (TIR) domain-containing adaptor protein TICAM2 as a direct target of miR-21-3p and miR-27a-5p. Furthermore, we showed that over-expression of miR-21-3p and miR-27a-5p lead to decreased p65 translocation to the nucleus and decreased the expression of known NF-κB downstream target genes confirming both miRNAs’ role in negatively regulating NF-κB signaling in endothelial cells. mRNA expression profiling of human aortic endothelial cells from two separate donors that were transfected with 1 nM microRNA mimics and negative control. The miRIDIAN mimics used were miR-21-3p (Catalog Number:C-301023-01-0005), miR-27a-5p (Catalog No: C-301028-01-0005), negative control (Catalog No: CN-001000-01-05)

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Endothelial NOTCH1 is suppressed by circulating lipids and antagonizes inflammation during atherosclerosis

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