Project description:Atherosclerosis is a focal disease that preferentially develop in the regions of atheroprone disturbed flow, but less in regions of atheroprotective laminar flow. The mechanisms by which atheroprotective laminar flow prevents atherosclerosis at the epigenetic level remain largely unknown. In this study, we observed that laminar flow decreased histone methyltransferase EZH2, which imposes a repressive epigenetic mark of histone 3 lysine 27 trimethylation (H3K27me3) onto target gene promoters, leading to transcriptional silencing. To evaluate the effect of atheroprotective flow on EZH2 and H3K27me3 dependent genome-wide transcriptional profile, we performed RNA-sequencing study on laminar flow and EZH2 siRNA treated human endothelial cells. Venn diagram was used to compare the common regulated genes by both laminar flow and EZH2 depletion. We found atheroprotective flow and EZH2 depletion altere endothelial gene landscape, which include upregulating atheroprotective genes while downregulating pro-atherosclerotic genes.
Project description:Doxorubicin suppresses flow-dependent vasoprotective programs triggering a dysfunctional endothelial cell phenotype. Microarrays were used to profile the transcriptome of Doxorubicin treated endothelial cells exposed to atheroprotective flow
Project description:Statins protect against the development of atherosclerosis via cholesterol-dependent and –independent mechanisms. Understanding the molecular mechanisms mediating simvastatin induced atheroprotective effects is critical for designing anti-atherosclerotic agents. Here, we showed that simvastatin decreases the expression of the Polycomb methyltransferase EZH2 in endothelial cells. To better understand the influence of the simvastatin-induced EZH2 downregulation on endothelial transcriptome, we performed RNA-sequencing study to evaluate differential gene expression after overexpression of EZH2 in the presence of simvastatin treatment. We found simvastatin treatment altered a subset of genes that can be rescued with EZH2 overexpression. Therefore, simvastatin treated endothelial cells display an atheroprotective phenotype by downregulating EZH2.
Project description:Overexpression of EZH2 in estrogen receptor negative (ER-) breast cancer promotes metastasis. EZH2 has been mainly studied as the catalytic component of the Polycomb Repressive Complex 2 (PRC2) that mediates gene repression by trimethylating histone H3 at lysine 27 (H3K27me3). However, how EZH2 drives metastasis despite the low H3K27me3 levels observed in ER- breast cancer is unknown. We have shown that in human invasive carcinomas and distant metastases, cytoplasmic EZH2 phosphorylated at T367 is significantly associated with ER- disease and low H3K27me3 levels. Here, we explore the interactome of EZH2 and of a phosphodeficient mutant EZH2_T367A. We identified novel interactors of EZH2, and identified interactions that are dependent on the phosphorylation and cellular localization of EZH2 that may play a role in EZH2 dependent metastatic progression.
Project description:High uniform fluid shear stress (FSS) is atheroprotective and preserves the endothelial phenotype and function through activation of downstream mediators such as MAPK7 (Erk5). Endothelial cells respond to FSS thanks to mechanotransduction. However, how the resulting signaling is integrated and resolved at the epigenetic level, remains elusive. We hypothesized that Polycomb methyltransferase EZH2 is involved in the effects of FSS in human endothelial cells. We showed that FSS decreases the expression of the Polycomb methyltransferase EZH2. Despite simultaneous activation of MAPK7, MAPK7 pathway does not directly influence the transcription of EZH2. Interestingly though, the knock down of EZH2 activates the protective MAPK7 signaling in endothelial cells, even in the absence of FSS. To understand the influence of the FSS-decreased expression of EZH2 on endothelial transcriptome, we performed RNA-seq and differential gene expression analysis. We identified candidate groups of genes dependent on both EZH2 and FSS. Among those, Gene Ontology overrepresentation analysis revealed highly significant enrichment of the cell cycle-related genes, suggesting changes in proliferation. Indeed, the depletion of EZH2 strongly inhibited endothelial proliferation, indicating cell cycle arrest. The concomitant decrease in CCNA expression suggests the transition of endothelial cells into a quiescent phenotype. Further bioinformatical analysis suggested TXNIP as a possible mediator between EZH2 and cell cycle-related gene network. Our data show that EZH2 is a FSS-responsive gene. Decreased EZH2 levels enhance the activation of the atheroprotective MAPK7 signaling. Decrease in EZH2 under FSS mediates the decrease in the expression of the network of cell cycle-related genes, which allows the cells to enter quiescence. EZH2 is therefore important for the protective effects of FSS in endothelium.
Project description:<div><b>OBJECTIVE:</b> Atherosclerotic plaque development is closely associated with the hemodynamic forces applied to endothelial cells (EC). Among these, shear stress (SS) plays a key role in disease development since changes in flow intensity and direction could stimulate an atheroprone or atheroprotective phenotype. EC under low or oscillatory SS (LSS) shows upregulation of inflammatory, adhesion and cellular permeability molecules. On the contrary, cells under high or laminar SS (HSS) increase their expression of protective and anti-inflammatory factors. The mechanism behind SS regulation of an atheroprotective phenotype is not completely elucidated.</div><div><b>APPROACH and RESULTS:</b> Here we used proteomics and metabolomics to better understand the changes in endothelial cells (HUVECs) under in vitro LSS and HSS that promote an atheroprone or atheroprotective profile and how these modifications can be connected to atherosclerosis development. Our data showed that lipid metabolism, in special cholesterol metabolism, was downregulated in cells under LSS. The LDLR showed significant alterations both at the quantitative expression level, as well as regarding post-translational modifications. Under LSS, LDLR was seen at lower concentrations and with a different glycosylation profile. Finally, modulating LDLR with atorvastatin led to the recapitulation of a HSS metabolic phenotype in EC under LSS.</div><div><b>CONCLUSIONS:</b> Altogether, our data suggest that there is significant modulation of lipid metabolism in endothelial cells under different SS intensities and that this could contribute to the atheroprone phenotype of LSS. Statin treatment was able to partially recover the protective profile of these cells.</div>
Project description:To profile shear stress-regulated endothelial transcriptomes, we performed RNA-seq with HUVECs subjected to different shear flow conditions, including atheroprotective pulsatile shear (PS, 12±4 dyn/cm2) and atheroprone oscillatory shear (OS, 0.5±4 dyn/cm2), or kept as static control (ST) for four time periods (1, 4, 12 and 24 hours)
Project description:Laminar flow on endothelial cells in vitro activates MEF2 transcription factors to induce expression of atheroprotective genes. Here we sought to establish in vivo MEF2 functions in the endothelium through endothelial-specific deletion of Mef2c. Our results show that endothelial Mef2c regulates migration of vascular smooth muscle from the tunica media into the intima through fenestrations in the internal elastic lamina. Moreover, Mef2c regulates actin stress fiber formation in the endothelium. To investigate Mef2c-dependent targets in the endothelium, we perform transcriptome profiling on RNA isolated from the aortic endothelium with or without Mef2c deletion.