Role of early growth response 1 in arteriogenesis: Impact on vascular cell proliferation and leukocyte recruitment in vivo

New insights into macrophage subsets in atherosclerosis

Macrophages in atherosclerotic patients are notably plastic and heterogeneous. Single-cell RNA sequencing (Sc RNA-seq) can provide information about all the RNAs in individual cells, and it is used to identify cell subpopulations in atherosclerosis (AS) and reveal the heterogeneity of these cells. Recently, some findings from Sc RNA-seq experiments have suggested the existence of multiple macrophage subsets in atherosclerotic plaque lesions, and these subsets exhibit significant differences in their gene expression levels and functions. These cells affect various aspects of plaque lesion development, stabilization, and regression, as well as plaque rupture. This article aims to review the content and results of current studies that used RNA-seq to explore the different types of macrophages in AS and the related molecular mechanisms as well as to identify the potential roles of these macrophage types in the pathogenesis of atherosclerotic plaques. Also, this review listed some new therapeutic targets for delaying atherosclerotic lesion progression and treatment based on the experimental results.

Functional annotation of noncoding mutations in cancer

Recurrent regulatory mutations affecting transcription factor binding sites in 2,500 cancer samples.

In a cancer genome, the noncoding sequence contains the vast majority of somatic mutations. While very few are expected to be cancer drivers, those affecting regulatory elements have the potential to have downstream effects on gene regulation that may contribute to cancer progression. To prioritize regulatory mutations, we screened somatic mutations in the Pan-Cancer Analysis of Whole Genomes cohort of 2,515 cancer genomes on individual bases to assess their potential regulatory roles in their respective cancer types. We found a highly significant enrichment of regulatory mutations associated with the deamination signature overlapping a CpG site in the CCAAT/Enhancer Binding Protein β recognition sites in many cancer types. Overall, 5,749 mutated regulatory elements were identified in 1,844 tumor samples from 39 cohorts containing 11,962 candidate regulatory mutations. Our analysis indicated 20 or more regulatory mutations in 5.5% of the samples, and an overall average of six per tumor. Several recurrent elements were identified, and major cancer-related pathways were significantly enriched for genes nearby the mutated regulatory elements. Our results provide a detailed view of the role of regulatory elements in cancer genomes.

MicroRNA-217 ameliorates inflammatory damage of endothelial cells induced by oxidized LDL by targeting EGR1

Oxidized low-density lipoprotein (ox-LDL) modulates gene transcription and expression and induces the development of endothelium inflammation and endothelial dysfunction, in which microRNAs (miRNAs) play a crucial role. However, the mechanism of ox-LDL in inflammatory damage of endothelial cells still remains elusive. Herein, we focused on the effect of hsa-miR-217-5p (miR-217) on endothelial dysfunction induced by ox-LDL by targeting early growth response protein-1 (EGR1). In the present study, 31 upregulated miRNAs and 59 downregulated miRNAs (Fold Change > 2, P value < 0.05) were identified after 6 h of 80 μg/mL ox-LDL exposure in human aortic endothelial cells (HAECs) by small RNA sequencing, including miR-217 that was significantly decreased (FC = 0.2787, P value = 5.22E-16). MiR-217 knockdown inhibited cell proliferation and increased level of IL-6, IL-1β, ICAM-1 and TNF-α, while overexpression of miR-217 relieved the growth inhibition induced by ox-LDL and demonstrated anti-inflammatory effect in HAECs. EGR1 was predicted as a potential candidate target gene of miR-217 by TargetScan. The subsequent dual-luciferase reporter assay confirmed the direct binding of miR-217 to 3'UTR of EGR1. And EGR1 expression was negatively correlated with the level of miRNA-217 in HAECs after exposure to ox-LDL. Overexpression of EGR1 recapitulated the effects of miR-217 knockdown on cell proliferation inhibition and inflammation in HAECs, while knockdown EGR1 relieved the proliferative inhibition and demonstrated anti-inflammatory effect in ox-LDL-induced HAECs. The present study confirmed miR-217 ameliorates inflammatory damage of endothelial cells induced by oxidized LDL by targeting EGR1.

Contribution of the Potassium Channels KV1.3 and KCa3.1 to Smooth Muscle Cell Proliferation in Growing Collateral Arteries

Collateral artery growth (arteriogenesis) involves the proliferation of vascular endothelial cells (ECs) and smooth muscle cells (SMCs). Whereas the proliferation of ECs is directly related to shear stress, the driving force for arteriogenesis, little is known about the mechanisms of SMC proliferation. Here we investigated the functional relevance of the potassium channels K_V1.3 and K_Ca3.1 for SMC proliferation in arteriogenesis. Employing a murine hindlimb model of arteriogenesis, we found that blocking K_V1.3 with PAP-1 or K_Ca3.1. with TRAM-34, both interfered with reperfusion recovery after femoral artery ligation as shown by Laser-Doppler Imaging. However, only treatment with PAP-1 resulted in a reduced SMC proliferation. qRT-PCR results revealed an impaired downregulation of α smooth muscle-actin (αSM-actin) and a repressed expression of fibroblast growth factor receptor 1 (Fgfr1) and platelet derived growth factor receptor b (Pdgfrb) in growing collaterals in vivo and in primary murine arterial SMCs in vitro under K_V1.3. blockade, but not when K_Ca3.1 was blocked. Moreover, treatment with PAP-1 impaired the mRNA expression of the cell cycle regulator early growth response-1 (Egr1) in vivo and in vitro. Together, these data indicate that K_V1.3 but not K_Ca3.1 contributes to SMC proliferation in arteriogenesis.

Insulin Treatment Forces Arteriogenesis in Diabetes Mellitus by Upregulation of the Early Growth Response-1 (Egr-1) Pathway in Mice

The process of arteriogenesis is severely compromised in patients with diabetes mellitus (DM). Earlier studies have reported the importance of Egr-1 in promoting collateral outward remodeling. However, the role of Egr-1 in the presence of DM in outward vessel remodeling was not studied. We hypothesized that Egr-1 expression may be compromised in DM which may lead to impaired collateral vessel growth. Here, we investigated the relevance of the transcription factor Egr-1 for the process of collateral artery growth in diabetic mice. Induction of arteriogenesis by femoral artery ligation resulted in an increased expression of Egr-1 on mRNA and protein level but was severely compromised in streptozotocin-induced diabetic mice. Diabetes mellitus mice showed a significantly reduced expression of Egr-1 endothelial downstream genes Intercellular Adhesion Molecule-1 (ICAM-1) and urokinase Plasminogen Activator (uPA), relevant for extravasation of leukocytes which promote arteriogenesis. Fluorescent-activated cell sorting analyses confirmed reduced leukocyte recruitment. Diabetes mellitus mice showed a reduced expression of the proliferation marker Ki-67 in growing collaterals whose luminal diameters were also reduced. The Splicing Factor-1 (SF-1), which is critical for smooth muscle cell proliferation and phenotype switch, was found to be elevated in collaterals of DM mice. Treatment of DM mice with insulin normalized the expression of Egr-1 and its downstream targets and restored leukocyte recruitment. SF-1 expression and the diameter of growing collaterals were normalized by insulin treatment as well. In summary, our results showed that Egr-1 signaling was impaired in DM mice; however, it can be rescued by insulin treatment.

Oxidative burst and Dectin-1-triggered phagocytosis affected by norepinephrine and endocannabinoids: implications for fungal clearance under stress

A prolonged stress burden is known to hamper the efficiency of both the innate and the adaptive immune systems and to attenuate the stress responses by the catecholaminergic and endocannabinoid (EC) systems. Key mechanisms of innate immunity are the eradication of pathogens through phagocytosis and the respiratory burst. We tested the concentration-dependent, spontaneous and stimulated (via TNFα and N-formylmethionine-leucyl-phenylalanine) release of reactive oxygen species (ROS) by human polymorphonuclear leukocytes (PMNs) in vitro in response to norepinephrine (NE) and AM1241, a pharmacological ligand for the EC receptor CB2. We evaluated phagocytosis of Dectin-1 ligating zymosan particles and tested the cytokine response against Candida antigen in an in vitro cytokine release assay. Increasing concentrations of NE did not affect phagocytosis, yet stimulated ROS release was attenuated gradually reaching maximum suppression at 500 nM. Adrenergic receptor (AR) mechanisms using non-AR-selective (labetalol) as well as specific α-(prazosin) and β-(propranolol) receptor antagonists were tested. Results show that only labetalol and propranolol were able to recuperate cytotoxicity in the presence of NE, evidencing a β-receptor-mediated effect. The CB2 agonist, AM1241, inhibited phagocytosis at 10 µM and spontaneous peroxide release by PMNs. Use of the inverse CB2 receptor agonist SR144528 led to partial recuperation of ROS production, confirming the functional role of CB2. Additionally, AM1241 delayed early activation of monocytes and induced suppression of IL-2 and IL-6 levels in response to Candida via lower activity of mammalian target of rapamycin (mTOR). These findings provide new insights into key mechanisms of innate immunity under stressful conditions where ligands to the sympatho-adrenergic and EC system are released.

Inflammatory monocyte response due to altered wall shear stress in an isolated femoral artery model

Arteriogenesis (collateral formation) is accompanied by a pro-inflammatory state that may be related to the wall shear stress (WSS) within the neo-collateral vessels. Examining the pro-inflammatory component in situ or in vivo is complex. In an ex vivo mouse femoral artery perfusion model, we examined the effect of wall shear stress on pro-arteriogenic inflammatory markers and monocyte adhesion. In a femoral artery model with defined pulsatile flow, WSS was controlled (at physiological stress, 1.4×, and 2× physiological stress) during a 24 h perfusion before gene expression levels and monocyte adhesion were assessed. Significant upregulation of expression was found for the cytokine TNFα, adhesion molecule ICAM-1, growth factor TGFβ, and the transcription factor Egr-1 at varying levels of increased WSS compared to physiological control. Further, trends toward upregulation were found for FGF-2, the cytokine MCP-1 and adhesion molecules VCAM-1 and P-selectin with increased WSS. Finally, monocytes adhesion increased in response to increased WSS. We have developed a murine femoral artery model for studying changes in WSS ex vivo and show that the artery responds by upregulating inflammatory cytokines, adhesion molecules and growth factors consistent with previous in vivo findings.

Estimating hemodynamic shear stress in murine peripheral collateral arteries by two-photon line scanning

Changes in wall shear stress of blood vessels are assumed to be an important component of many physiological and pathophysiological processes. However, due to technical limitations experimental in vivo data are rarely available. Here, we investigated two-photon excitation fluorescence microscopy as an option to measure vessel diameter as well as blood flow velocities in a murine hindlimb model of arteriogenesis (collateral artery growth). Using line scanning at high frequencies, we measured the movement of blood cells along the vessel axis. We found that peak systolic blood flow velocity averaged 9 mm/s and vessel diameter 42 µm in resting collaterals. Induction of arteriogenesis by femoral artery ligation resulted in a significant increase in centerline peak systolic velocity after 1 day with an average of 51 mm/s, whereas the averaged luminal diameter of collaterals (52 µm) changed much less. Thereof calculations revealed a significant fourfold increase in hemodynamic wall shear rate. Our results indicate that two-photon line scanning is a suitable tool to estimate wall shear stress e.g., in experimental animal models, such as of arteriogenesis, which may not only help to understand the relevance of mechanical forces in vivo, but also to adjust wall shear stress in ex vivo investigations on isolated vessels as well as cell culture experiments.

Early growth response factor-1 DNA enzyme 1 inhibits the formation of abdominal aortic aneurysm in rats

The aim of the present study was to characterize the effects of early growth response factor-1 DNA enzyme (EDRz) in a rat abdominal aortic aneurysm (AAA) model to determine the mechanism by which EDRz inhibits AAA and affects the formation of AAA by regulating the activity of matrix metalloproteinase (MMP)-2 and MMP-9. EDRz was transfected into the abdominal aorta of rats using the jetPRIME transfection reagent following infusion with elastase. Fluorescent microscopy, hematoxylin and eosin staining, ultrastructural analysis, reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemical analysis were performed to characterize the response to EDRz. The EDRz group showed minimal aneurysm formation when compared with the control group, with significantly lower aortic diameter expansion (2.5±0.1 vs. 3.5±0.1 mm; P<0.05). Early growth response factor 1 (Egr-1) mRNA and protein levels were significantly decreased in the EDRz group, as expected. The decrease in Egr-1 was accompanied by decreases in the mRNA and protein levels of MMP-2 and MMP-9 (P<0.05). Transfection of the Egr-1 specific synthetic DNA enzyme EDRz significantly reduced AAA following elastase infusion in rats, at least in part due to the decreased expression of downstream MMP-2 and MMP-9.

Transcriptional Analysis of Endothelial Cell Alternation Induced by Atrial Natriuretic Polypeptide in Human Umbilical Vein Endothelial Cells

The aim of this study was to explore how atrial natriuretic polypeptide (ANP) affects the properties and function of endothelial cells. Gene expression data GSE56976 generated at 0, 1, and 6 hours after ANP incubation in human umbilical vein endothelial cells (HUVEC) was used. Microarray data were preprocessed for differentially expressed genes (DEGs) in each time-dependent group. Next, gene ontology (GO), pathway analysis, and transcriptional regulation were performed. Co-expression clustering analysis of DEGs and functional enrichment analysis of co-expression modules were processed. RT-PCR analysis was performed to validate gene expression. DEGs were obtained and their counts were increased from 0 hours to 6 hours. No overlapping DEGs were obtained among the 3 groups. The DEGs of ANP_6hours, including TGFB2 (transforming growth factor, beta 2), LTF (lactotransferrin/lactoferrin), and ETV7 (Ets variant 7) were mainly related with cell apoptosis and immune responses. The DEGs in the network of ANP_0hour were mainly associated with epithelial ion transport processes. In addition, 3 co-expressed modules were detected. CSF2 (colony stimulating factor 2) and PF4 (platelet factor 4) of the blue module were related with cytolysis, while FXYD1 (FXYD domain containing ion transport regulator 1) and TGFB2 of the yellow module were mainly enriched in ion transport and the ovulation cycle. The expression of TGFB2 obtained by microarray analysis was consistent with that of RT-PCR. Ion transport could be affected promptly after ANP treatment, and subsequently, the cytolysis of vein endothelial cells may be promoted and endothelial permeability would be enhanced, followed by activated immune responses.

Gene expression profiles and signaling mechanisms in α2B-adrenoceptor-evoked proliferation of vascular smooth muscle cells

BACKGROUND

α2-adrenoceptors are important regulators of vascular tone and blood pressure. Regulation of cell proliferation is a less well investigated consequence of α2-adrenoceptor activation. We have previously shown that α2B-adrenoceptor activation stimulates proliferation of vascular smooth muscle cells (VSMCs). This may be important for blood vessel development and plasticity and for the pathology and therapeutics of cardiovascular disorders. The underlying cellular mechanisms have remained mostly unknown. This study explored pathways of regulation of gene expression and intracellular signaling related to α2B-adrenoceptor-evoked VSMC proliferation.

RESULTS

The cellular mechanisms and signaling pathways of α2B-adrenoceptor-evoked proliferation of VSMCs are complex and include redundancy. Functional enrichment analysis and pathway analysis identified differentially expressed genes associated with α2B-adrenoceptor-regulated VSMC proliferation. They included the upregulated genes Egr1, F3, Ptgs2 and Serpine1 and the downregulated genes Cx3cl1, Cav1, Rhoa, Nppb and Prrx1. The most highly upregulated gene, Lypd8, represents a novel finding in the VSMC context. Inhibitor library screening and kinase activity profiling were applied to identify kinases in the involved signaling pathways. Putative upstream kinases identified by two different screens included PKC, Raf-1, Src, the MAP kinases p38 and JNK and the receptor tyrosine kinases EGFR and HGF/HGFR. As a novel finding, the Src family kinase Lyn was also identified as a putative upstream kinase.

CONCLUSIONS

α2B-adrenoceptors may mediate their pro-proliferative effects in VSMCs by promoting the activity of bFGF and PDGF and the growth factor receptors EGFR, HGFR and VEGFR-1/2. The Src family kinase Lyn was also identified as a putative upstream kinase. Lyn is known to be expressed in VSMCs and has been identified as an important regulator of GPCR trafficking and GPCR effects on cell proliferation. Identified Ser/Thr kinases included several PKC isoforms and the β-adrenoceptor kinases 1 and 2. Cross-talk between the signaling mechanisms involved in α2B-adrenoceptor-evoked VSMC proliferation thus appears to involve PKC activation, subsequent changes in gene expression, transactivation of EGFR, and modulation of kinase activities and growth factor-mediated signaling. While many of the identified individual signals were relatively small in terms of effect size, many of them were validated by combining pathway analysis and our integrated screening approach.

Role for Egr1 in the Transcriptional Program Associated with Neuronal Differentiation of PC12 Cells

PC12 cells are a well-established model to study how differences in signal transduction duration can elicit distinct cell behaviors. Epidermal growth factor (EGF) activates transient ERK signaling in PC12 cells that lasts 30–60 min, which in turn promotes proliferation; nerve growth factor (NGF) activates more sustained ERK signaling that lasts 4–6 h, which in turns induces neuronal differentiation. Data presented here extend a previous study by Mullenbrock et al. (2011) that demonstrated that sustained ERK signaling in response to NGF induces preferential expression of a 69-member gene set compared to transient ERK signaling in response to EGF and that the transcription factors AP-1 and CREB play a major role in the preferential expression of several genes within the set. Here, we examined whether the Egr family of transcription factors also contributes to the preferential expression of the gene set in response to NGF. Our data demonstrate that NGF causes transient induction of all Egr family member transcripts, but a corresponding induction of protein was detected for only Egr1 and 2. Chromatin immunoprecipitation experiments provided clearest evidence that, after induction, Egr1 binds 12 of the 69 genes that are preferentially expressed during sustained ERK signaling. In addition, Egr1 expression and binding upstream of its target genes were both sustained in response to NGF versus EGF within the same timeframe that its targets are preferentially expressed. These data thus provide evidence that Egr1 contributes to the transcriptional program activated by sustained ERK signaling in response to NGF, specifically by contributing to the preferential expression of its target genes identified here.

Arginase inhibition attenuates arteriogenesis and interferes with M2 macrophage accumulation

l-Arginine is the common substrate for nitric oxide synthases (NOS) and arginase. Whereas the contribution of NOS to collateral artery growth (arteriogenesis) has been demonstrated, the functional role of arginase remains to be elucidated and was topic of the present study. Arteriogenesis was induced in mice by ligation of the femoral artery. Laser Doppler perfusion measurements demonstrated a significant reduction in arteriogenesis in mice treated with the arginase inhibitor nor-NOHA (N(ω)-hydroxy-nor-arginine). Accompanying in vitro results on murine primary arterial endothelial cells and smooth muscle cells revealed that nor-NOHA treatment interfered with cell proliferation and resulted in increased nitrate/nitrite levels, indicative for increased NO production. Immuno-histological analyses on tissue samples demonstrated that nor-NOHA administration caused a significant reduction in M2 macrophage accumulation around growing collateral arteries. Gene expression studies on isolated growing collaterals evidenced that nor-NOHA treatment abolished the differential expression of Icam1 (intercellular adhesion molecule 1). From our data we conclude that arginase activity is essential for arteriogenesis by promoting perivascular M2 macrophage accumulation as well as arterial cell proliferation.

PDGF induces SphK1 expression via Egr-1 to promote pulmonary artery smooth muscle cell proliferation

Pulmonary arterial hypertension (PAH) is a progressive, life-threatening disease for which there is currently no curative treatment available. Pathologic changes in this disease involve remodeling of the pulmonary vasculature, including marked proliferation of pulmonary artery smooth muscle cells (PASMCs). Recently, the bioactive lipid sphingosine-1-phosphate (S1P) and its activating kinase, sphingosine kinase 1 (SphK1), have been shown to be upregulated in PAH and promote PASMC proliferation. The mechanisms regulating the transcriptional upregulation of SphK1 in PASMCs are unknown. In this study, we investigated the role of platelet-derived growth factor (PDGF), a PAH-relevant stimuli associated with enhanced PASMC proliferation, on SphK1 expression regulation. In human PASMCs (hPASMCs), PDGF significantly increased SphK1 mRNA and protein expression and induced cell proliferation. Selective inhibition of SphK1 attenuated PDGF-induced hPASMC proliferation. In silico promoter analysis for SphK1 identified several binding sites for early growth response protein 1 (Egr-1), a PDGF-associated transcription factor. Luciferase assays demonstrated that PDGF activates the SphK1 promoter in hPASMCs, and truncation of the 5'-promoter reduced PDGF-induced SphK1 expression. Stimulation of hPASMCs with PDGF induced Egr-1 protein expression, and direct binding of Egr-1 to the SphK1 promoter was confirmed by chromatin immunoprecipitation analysis. Inhibition of ERK signaling prevented induction of Egr-1 by PDGF. Silencing of Egr-1 attenuated PDGF-induced SphK1 expression and hPASMC proliferation. These studies demonstrate that SphK1 is regulated by PDGF in hPASMCs via the transcription factor Egr-1, promoting cell proliferation. This novel mechanism of SphK1 regulation may be a therapeutic target in pulmonary vascular remodeling in PAH.

In vitro effects of low-level aldehyde exposures on human umbilical vein endothelial cells

Aldehydes cause gene expression changes for genes associated with cardiovascular disease. Exposure to aldehydes from tobacco smoke needs to be controlled.

A critical role for Egr-1 during vascular remodelling in pulmonary arterial hypertension

AIMS

Pulmonary arterial hypertension (PAH) is characterized by the development of unique neointimal lesions in the small pulmonary arteries, leading to increased right ventricular (RV) afterload and failure. Novel therapeutic strategies are needed that target these neointimal lesions. Recently, the transcription factor Egr-1 (early growth response protein 1) was demonstrated to be up-regulated early in experimental neointimal PAH. Its effect on disease development, however, is unknown. We aimed to uncover a novel role for Egr-1 as a molecular inductor for disease development in PAH.

METHODS AND RESULTS

In experimental flow-associated PAH in rats, we investigated the effects of Egr-1 down-regulation on pulmonary vascular remodelling, including neointimal development, and disease progression. Intravenous administration of catalytic oligodeoxynucleotides (DNA enzymes, DNAzymes) resulted in down-regulation of pulmonary vascular Egr-1 expression. Compared with vehicle or scrambled DNAzymes, DNAzymes attenuated pulmonary vascular remodelling, including the development of occlusive neointimal lesions. Selective down-regulation of Egr-1 in vivo led to reduced expression of vascular PDGF-B, TGF-β, IL-6, and p53, resulting in a reduction of vascular proliferation and increased apoptosis. DNAzyme treatment further attenuated pulmonary vascular resistance, RV systolic pressure, and RV hypertrophy. In contrast, in non-neointimal PH rodents, DNAzyme treatment had no effect on pulmonary vascular and RV remodelling. Finally, pharmacological inhibition of Egr-1 with pioglitazone, a peroxisome proliferator activated receptor-γ ligand, attenuated vascular remodelling including the development of neointimal lesions.

CONCLUSIONS

These results indicate that Egr-1 governs pulmonary vascular remodelling and the development of characteristic vascular neointimal lesions in flow-associated PAH. Egr-1 is therefore a potential target for future PAH treatment.

Inhibition of Egr1 expression underlies the anti-mitogenic effects of cAMP in vascular smooth muscle cells

AIMS

Cyclic AMP inhibits vascular smooth muscle cell (VSMC) proliferation which is important in the aetiology of numerous vascular diseases. The anti-mitogenic properties of cAMP in VSMC are dependent on activation of protein kinase A (PKA) and exchange protein activated by cAMP (EPAC), but the mechanisms are unclear.

METHODS AND RESULTS

Selective agonists of PKA and EPAC synergistically inhibited Egr1 expression, which was essential for VSMC proliferation. Forskolin, adenosine, A2B receptor agonist BAY60-6583 and Cicaprost also inhibited Egr1 expression in VSMC but not in endothelial cells. Inhibition of Egr1 by cAMP was independent of cAMP response element binding protein (CREB) activity but dependent on inhibition of serum response element (SRE) activity. SRF binding to the Egr1 promoter was not modulated by cAMP stimulation. However, Egr1 expression was dependent on the SRF co-factors Elk1 and 4 but independent of MAL. Inhibition of SRE-dependent Egr1 expression was due to synergistic inhibition of Rac1 activity by PKA and EPAC, resulting in rapid cytoskeleton remodelling and nuclear export of ERK1/2. This was associated with de-phosphorylation of the SRF co-factor Elk1.

CONCLUSION

cAMP inhibits VSMC proliferation by rapidly inhibiting Egr1 expression. This occurs, at least in part, via inhibition of Rac1 activity leading to rapid actin-cytoskeleton remodelling, nuclear export of ERK1/2, impaired Elk1-phosphorylation and inhibition of SRE activity. This identifies one of the earliest mechanisms underlying the anti-mitogenic effects of cAMP in VSMC but not in endothelial cells, making it an attractive target for selective inhibition of VSMC proliferation.

Functional and pathway enrichment analysis for integrated regulatory network of high- and low-metastatic lung cancer

Metastasis is a common feature of lung cancer, involving relationships between genes, proteins and miRNAs. However, lack of early detection and limited options for targeted therapies are weaknesses that cantribute to the dismal statistics observed in lung cancer metastasis. In this paper, gene expression profiling analysis for genes differentially expressed between high- (95D) and low-metastatic lung cancer cell lines (95C) was performed using gene annotation, pathway analysis, literature mining, and the integrated regulatory network as well as motif analysis of miRNA-DEG and TF-DEG. In addition, the expression of EGR-1 (early growth reponse-1) in surgically resected lung squamous carcinomas, adenocarcinomas and normal lung tissue was detected by immunohistochemistry to reveal the relationships between EGR-1 and lung cancer metastasis. A total of 570 different expressed genes (DEGs) were screened, the vast majority of up-regulated DEGs were connected to cell adhesion and focal adhesion. EGR-1 was observed in the center node of the regulatory network, which seems to play a role in the process of cancer metastasis, and further immunohistochemistry detection confirmed this reasoning. Besides EGR-1, several significant module-related DEGs were enriched in the pathway within cancer and focal adhesion according to KEGG pathway enrichment analysis of network modules. The construction of an integrated regulatory network and the functional prediction of EGR-1 provided us with the cytological basis of lung cancer metastasis research and an understanding of the mechanism of metastasis in lung cancer. EGR-1 should be considered as a potential target gene in therapeutic agent for lung cancer metastasis.

Early vessel destabilization mediated by Angiopoietin-2 and subsequent vessel maturation via Angiopoietin-1 induce functional neovasculature after ischemia

Background

We assessed whether Angiopoietin-2 (Ang2), a Tie2 ligand and partial antagonist of Angiopoietin-1 (Ang1), is required for early vessel destabilization during postischemic angiogenesis, when combined with vascular growth factors.

Methods

In vitro, matrigel co-cultures assessed endothelial-cell tube formation and pericyte recruitment after stimulation of VEGF-A, Apelin (APLN), Ang1 with or without Ang2. In a murine hindlimb ischemia model, adeno-associated virus (rAAV, 3×10¹² virusparticles) transduction of VEGF-A, APLN and Ang1 with or without Ang2 (continuous or early expression d0-3) was performed intramuscularly (d-14). Femoral artery ligation was performed at d0, followed by laser doppler perfusion meassurements (LDI) 7 and 14. At d7 (early timepoint) and d14 (late timepoint), histological analysis of capillary/muscle fiber ratio (CMF-R, PECAM-1) and pericyte/capillary ratio (PC-R, NG2) was performed.

Results

In vitro, VEGF-A, APLN and Ang1 induced ring formation, but only APLN and Ang1 recruited pericytes. Ang2 did not affect tube formation by APLN, but reduced pericyte recruitment after APLN or Ang1 overexpression. In vivo, rAAV.VEGF-A did not alter LDI-perfusion at d14, consistent with an impaired PC-R despite a rise in CMF-R. rAAV.APLN improved perfusion at d14, with or without continuous Ang2, increasing CMF-R and PC-R. rAAV.Ang1 improved perfusion at d14, when combined with rAAV.Ang2 (d0-3), accompanied by an increased CMF-R and PC-R.

Conclusion

The combination of early vessel destabilization (Ang2 d0-3) and continuous Ang1 overexpression improves hindlimb perfusion, pointing to the importance of early vessel destabilization and subsequent vessel maturation for enhanced therapeutic neovascularization.

Transfected early growth response gene-1 DNA enzyme prevents stenosis and occlusion of autogenous vein graft in vivo

The aim of this study was to detect the inhibitory action of the early growth response gene-1 DNA enzyme (EDRz) as a carrying agent by liposomes on vascular smooth muscle cell proliferation and intimal hyperplasia. An autogenous vein graft model was established. EDRz was transfected to the graft vein. The vein graft samples were obtained on each time point after surgery. The expression of the EDRz transfected in the vein graft was detected using a fluorescent microscope. Early growth response gene-1 (Egr-1) mRNA was measured using reverse transcription-PCR and in situ hybridization. And the protein expression of Egr-1 was detected by using western blot and immunohistochemistry analyses. EDRz was located at the media of the vein graft from 2 to 24 h, 7 h after grafting. The Egr-1 protein was mainly located in the medial VSMCs, monocytes, and endothelium cells during the early phase of the vein graft. The degree of VSMC proliferation and thickness of intima were obviously relieved compared with the no-gene therapy group. EDRz can reduce Egr-1 expression in autogenous vein grafts, effectively restrain VSMC proliferation and intimal hyperplasia, and prevent vascular stenosis and occlusion after vein graft.

Insulin-like growth-factor-1-induced PKB signaling and Egr-1 expression is inhibited by curcumin in A-10 vascular smooth muscle cells

Insulin-like growth factor 1 (IGF-1) is a mitogenic factor that stimulates the signaling pathways responsible for inducing hypertrophic and proliferative responses in vascular smooth muscle cells (VSMC). We have previously demonstrated that IGF-1 receptor (IGF-1R) plays a key role in transducing the hypertrophic and proliferative responses of angiotensin II (Ang-II) and endothelin-1 (ET-1). Curcumin, a polyphenolic compound derived from the spice turmeric is known to possess antiproliferative properties and exerts vasculoprotective effects. However, the ability of curcumin to modulate IGF-1-induced signaling responses in VSMC remains to be investigated. In this study, we determined the effect of curcumin on IGF-1-induced phosphorylation of protein kinase B (PKB), glycogen synthase kinase-3β (GSK-3β), and IGF-1R in VSMC. Curcumin inhibited IGF-1-induced phosphorylation of PKB and GSK-3β as well as the IGF-1R β subunit in a dose-dependent fashion. In addition, IGF-1-induced expression of early growth response protein 1 (Egr-1) which plays a pathogenic role in vascular dysfunctions, was also attenuated by curcumin. In conclusion, these results indicate that curcumin is a potent inhibitor of key components of the IGF-1-induced mitogenic and proliferative signaling system in VSMC, and suggest that curcumin-induced attenuation of these signaling components may constitute a potential mechanism for its vasculoprotective effects.

Disease progression mediated by egr-1 associated signaling in response to oxidative stress

When cellular reducing enzymes fail to shield the cell from increased amounts of reactive oxygen species (ROS), oxidative stress arises. The redox state is misbalanced, DNA and proteins are damaged and cellular transcription networks are activated. This condition can lead to the initiation and/or to the progression of atherosclerosis, tumors or pulmonary hypertension; diseases that are decisively furthered by the presence of oxidizing agents. Redox sensitive genes, like the zinc finger transcription factor early growth response 1 (Egr-1), play a pivotal role in the pathophysiology of these diseases. Apart from inducing apoptosis, signaling partners like the MEK/ERK pathway or the protein kinase C (PKC) can activate salvage programs such as cell proliferation that do not ameliorate, but rather worsen their outcome. Here, we review the currently available data on Egr-1 related signal transduction cascades in response to oxidative stress in the progression of epidemiologically significant diseases. Knowing the molecular pathways behind the pathology will greatly enhance our ability to identify possible targets for the development of new therapeutic strategies.