Liya Huang

SIRT1 Protects Against Oxidative Stress‐Induced Endothelial Progenitor Cells Apoptosis by Inhibiting FOXO3a via FOXO3a Ubiquitination and Degradation

Cell loss due to apoptosis induced by oxidative stress is a major hurdle for endothelial progenitor cells (EPCs)‐based therapy. Sirtuin 1 (SIRT1) plays important roles in many pathophysiological processes by deacetylating various substrates, including forkhead transcription factor (FOXO). However, after deacetylation, the fate of FOXO protein remains to be explored. In the present study, we investigated whether SIRT1 exerted a protective effect on hydrogen peroxide (H2O2)‐induced EPCs apoptosis and, if so, what the underlying mechanism might be. EPCs were isolated and obtained from human umbilical cord blood by density gradient centrifugation and identified by morphology, tube formation ability, cell surface markers, and the ability to take up acetylated low‐density lipoprotein (Dil‐Ac‐LDL) and bind ulex europaeus agglutinin 1 (FITC‐UEA‐1). Immunofluorescence showed that SIRT1 is localized in the nucleus of EPCs in the presence or absence of H2O2. SIRT1 protein level in EPCs was increased by the treatment with H2O2 for 24 h. Incubation of EPCs with H2O2 dose dependently induced EPCs apoptosis. SIRT1 overexpression reduced the rate of EPCs apoptosis induced by H2O2, whereas SIRT1 downregulation and EX527, a specific SIRT1 inhibitor, exerted the opposite effect. SIRT1 overexpression decreased the total FOXO3a protein expression, whereas SIRT1 downregulation and EX527 increased the amount of FOXO3a protein. SIRT1 reduced FOXO3a transcriptional activity according to Bim expression. Co‐immunoprecipitation assay showed that SIRT1 could bind to FOXO3a, reduce its acetylation level and increase its ubiquitination level. To sum up, our work demonstrated that SIRT1 had a pivotally protective role in the regulation of EPCs apoptosis induced by H2O2 and that SIRT1 protected against apoptosis by inhibiting FOXO3a via FOXO3a ubiquitination and subsequent degradation. J. Cell. Physiol. 230: 2098–2107, 2015.

Hydrogen peroxide induced impairment of endothelial progenitor cell viability is mediated through a FoxO3a dependant mechanism.

OBJECTIVES Increased oxidative stress has been suggested to contribute to the functional impairment of endothelial progenitor cells (EPCs). The Forkhead box O transcription factors (FoxOs) are critical regulators involved in various cellular processes including cell apoptosis. Here, we investigated whether FoxOs are required in oxidative stress induced EPC apoptosis. METHODS AND RESULTS EPCs were cultured from cord blood derived mononuclear cells and treated with hydrogen peroxide (H2O2) for induction of oxidative stress. Incubation with H2O2 dose dependently reduced viability and increased apoptosis in EPCs. Western blotting showed that EPCs predominantly expressed FoxO3a and the expression was markedly increased upon H2O2 treatment. Transduction with adenoviral vectors expressing either a wide-type or a non-phosphorylatable, constitutively active mutant of FoxO3a led to further increased apoptosis of EPCs after H2O2 treatment. Conversely, FoxO3a silencing rescued EPCs from these H2O2 induced deleterious effects. Overexpression of FoxO3a also increased the level of the pro-apoptotic protein Bim, whereas FoxO3a silencing downregulated H2O2 induced Bim expression. Furthermore, Matrigel assay demonstrated that FoxO3a overexpression significantly impaired the tube forming ability of EPCs, whereas its silencing completely protected EPCs from H2O2 induced decrease of capillary formation. CONCLUSIONS These data suggest that oxidative stress induced impairment of EPC survival is mediated through a FoxO3a dependant mechanism, possibly by transcriptional regulation of Bim. Our data indicate FoxO3a as a potential therapeutic target for improvement of EPC number and function in patients with ischemic heart disease.

MeCP2-mediated epigenetic regulation in senescent endothelial progenitor cells

BackgroundCellular aging may be associated with epigenetics. Methyl-CpG-binding protein 2 (MeCP2) and sirtuin 1 (SIRT1) are two important epigenetic factors. Our former work demonstrated that MeCP2 expression increased and SIRT1 expression decreased in senescent endothelial progenitor cells (EPCs). This article aims to reveal the epigenetic regulation caused by MeCP2 in EPCs and discuss its mechanism.MethodsTube formation assay and cell apoptosis detection were used to evaluate the function of senescent EPCs induced by MeCP2 overexpression. Western blot analysis was used to testify the relative protein expression changed by MeCP2. Bisulfite sequencing methylation assay and chromatin immunoprecipitation assay were used to assess the degree of methylation and the relation of MeCP2 and SIRT1.ResultsMeCP2 reduced angiogenesis of senescent EPCs, promoted apoptosis, and caused senescent EPC dysfunction through SIRT1 promoter hypermethylation and histone modification.ConclusionsMeCP2 mediated senescent EPC dysfunction through epigenetic regulation.

Identification of colorectal cancer-restricted microRNAs and their target genes based on high-throughput sequencing data

To identify potential key microRNAs (miRNAs) and their target genes for colorectal cancer (CRC). High-throughput sequencing data of miRNA expression and gene expression (ID: GSE46622) were downloaded from Gene Expression Omnibus, including matched colon tumor, normal colon epithelium, and liver metastasis tissues from eight CRC patients. Paired t-test and NOISeq separately were utilized to identify differentially expressed miRNAs (DE-miRNAs) and genes. Then, target genes with differential expression and opposite expression trends were identified for DE-miRNAs. Combined with tumor suppressor gene, tumor-associated gene, and TRANSFAC databases, CRC-restricted miRNAs were screened out based on miRNA-target pairs. Compared with normal tissues, there were 56 up- and 37 downregulated miRNAs in metastasis tissues, as well as eight up- and 30 downregulated miRNAs in tumor tissues. miRNA-1 was downregulated in tumor and metastasis tissues, while its target oncogenes TWIST1 and GATA4 were upregulated. Besides, miRNA-let-7f-1-3p was downregulated in tumor tissues, which also targeted TWIST1. In addition, miRNA-133b and miRNA-4458 were downregulated in tumor tissues, while their common target gene DUSP9 was upregulated. Conversely, miRNA-450-b-3p was upregulated in metastasis tissues, while its target tumor suppressor gene CEACAM7 showed downregulation. The identified CRC-restricted miRNAs might be implicated in cancer progression via their target genes, suggesting their potential usage in CRC treatment.

Acidic Fibroblast Growth Factor Promotes Endothelial Progenitor Cells Function via Akt/FOXO3a Pathway

Acidic fibroblast growth factor (FGF1) has been suggested to enhance the functional activities of endothelial progenitor cells (EPCs). The Forkhead homeobox type O transcription factors (FOXOs), a key substrate of the survival kinase Akt, play important roles in regulation of various cellular processes. We previously have shown that FOXO3a is the main subtype of FOXOs expressed in EPCs. Here, we aim to determine whether FGF1 promotes EPC function through Akt/FOXO3a pathway. Human peripheral blood derived EPCs were transduced with adenoviral vectors either expressing a non-phosphorylable, constitutively active triple mutant of FOXO3a (Ad-TM-FOXO3a) or a GFP control (Ad-GFP). FGF1 treatment improved functional activities of Ad-GFP transduced EPCs, including cell viability, proliferation, antiapoptosis, migration and tube formation, whereas these beneficial effects disappeared by Akt inhibitor pretreatment. Moreover, EPC function was declined by Ad-TM-FOXO3a transduction and failed to be attenuated even with FGF1 treatment. FGF1 upregulated phosphorylation levels of Akt and FOXO3a in Ad-GFP transduced EPCs, which were repressed by Akt inhibitor pretreatment. However, FGF1 failed to recover Ad-TM-FOXO3a transduced EPCs from dysfunction. These data indicate that FGF1 promoting EPC function is at least in part mediated through Akt/FOXO3a pathway. Our study may provide novel ideas for enhancing EPC angiogenic ability and optimizing EPC transplantation therapy in the future.

MeCP2 mediated dysfunction in senescent EPCs

Aging endothelial progenitor cells (EPCs) exhibit functional impairment in terms of proliferation, migration and survival. SIRT1 plays an important role in improving EPCs function. MeCP2, another important epigenetic regulator, is involved in regulating many life-related activities such as cell growth, death and senescence. Here we aim to explore the effect of MeCP2 on the functional activities of senescent EPCs and the underlying mechanisms. By using western blot and real-time PCR, we found that the expression levels of MeCP2 were up-regulated and SIRT1 were down-regulated with replicative senescence and H2O2-induced senescence. Through transduction with adenoviral vectors, EPCs overexpressing MeCP2 had significantly reduced EPCs function, and silencing MeCP2 improved EPCs function. In addition, the protein and mRNA levels of SIRT1 were decreased with MeCP2 overexpression and increased with MeCP2 knockdown. Through co-transfection of EPCs with MeCP2 and SIRT1, we observed that SIRT1 could reverse the effects of MeCP2 on EPCs. In summary, our work demonstrated that MeCP2 inhibited SIRT1 in senescent EPCs.

The Effect of Mecp2 on Heart Failure

Background/Aims: Heart failure is the end result of various kinds of cardiovascular diseases. It has a high rate of morbidity and mortality. This article aims to determine the effect of MeCP2, a key epigenetic regulator, on heart failure. Methods: The genes associated with heart failure were selected and analyzed using Gene Ontology (GO) term analysis and protein-protein interaction (PPI) network analysis. Significantly up- or downregulated genes in a heart failure animal model were identified, and the genes that had the same or opposite alteration trends as MeCP2 were also recognized. Eighteen hub genes were picked based on topological parameters, and then aberrantly expressed genes with MeCP2 overexpression or knockout were analyzed by GO term, KEGG pathway and PPI analyses. Results: MeCP2 was downregulated in the heart failure animal model. Through comparison and alignment, 10 dysregulated genes were selected from the 18 hub genes (JAK1, SETD1B, HRC, TTN, LYZ2, TPM3, MYH11, MYH6, ALOX5AP, DECR1). These genes were mainly enriched in cytoskeletal regulation mediated by Rho GTPase and inflammation mediated by chemokine and cytokine signaling pathways. Conclusions: These dysregulated genes provide a better understanding of the underlying mechanisms of the effect of MeCP2 on heart failure and might be used as targets and prognostic markers of heart failure.

Effect and safety of combination lipid-lowering therapies based on statin treatment versus statin monotherapies on patients with high risk of cardiovascular events

This study aimed to compare the effect and safety of statin monotherapies and combination therapies on lipid‐lowing therapies. We searched for published randomized controlled trial (RCT) reports of statin monotherapies and combination therapies in patients with high risk of cardiovascular events, and extracted lipid levels to perform meta‐analysis. A total of 12 RCT reports were included in this study. According to the new guidelines (low‐density lipoprotein cholesterol [LDL‐C] < 100 mg/dL, high‐density lipoprotein cholesterol [HDL‐C] > 130 mg/dL), the percent of LDL‐C attaining goals in combination therapy is more than that of monotherapy (risk ratio [RR] = 1.43, 95% confidence interval [CI]: 1.13 to 1.82, P = 0.003), and the percent of LDL‐C and HDL‐C attaining goals in combination therapy is greater than that of monotherapy (RR = 1.43, 95% CI: 1.24 to 1.65, P = 0.000). The changing level of blood lipid had significant statistical difference between the two groups. The degree of blood lipid lowered by combination therapy was larger than in monotherapy (standard mean difference [SMD] = −0.45, 95% CI: −0.75 to −0.14, P = 0.004; SMD = −0.72, 95% CI: 0.04 to 1.39, P = 0.039; and SMD = −0.71, 95% CI: −1.12 to −0.3, P = 0.001 in LDL‐C, HDL‐C, and triglyceride, respectively). The incidence of adverse events was not significantly different between the two groups (RR = 1.15, 95% CI: 0.91 to 1.37, P = 0.096; RR = 1.5, 95% CI: 0.55 to 4.1, P = 0.427; RR = 0.63, 95% CI: 0.33 to 1.24, P = 0.181 in incidence of total adverse events, drug‐related treatment, and myalgia, respectively). Combination therapy can bring better effect in reducing lipid. It does not increase the incidence of adverse events, so it can be used widely and safely.