Inhibition of miR-200b Promotes Angiogenesis in Endothelial Cells by Activating The Notch Pathway

In this article which was published in Cell J, Vol 23, No 1, Spring 2021, on pages 51-60, the authors discovered that Figures 1B, 2D, 2F, 5B, and 5D some errors that occurred accidentally during figure organization in this article. The figures below have been corrected. The authors would like to apologies for any inconvenience caused.

Inhibition of miR-200b Promotes Angiogenesis in Endothelial Cells by Activating The Notch Pathway

Objective

Patients with diabetes mellitus frequently have chronic wounds or diabetic ulcers as a result of impaired wound healing, which may lead to limb amputation. Human umbilical vein endothelial cell (HUVEC) dysfunction also delays wound healing. Here, we investigated the mechanism of miR-200b in HUVECs under high glucose conditions and the potential of miR-200b as a therapeutic target.

Materials and Methods

In this experimental study, HUVECs were cultured with 5 or 30 mM glucose for 48 hours. Cell proliferation was evaluated by CCK-8 assays. Cell mobility was tested by wound healing and Transwell assays. Angiogenesis was analyzed in vitro Matrigel tube formation assays. Luciferase reporter assays were used to test the binding of miR-200b with Notch1.

Results

miR-200b expression was induced by high glucose treatment of HUVECs (P<0.01), and it significantly repressed cell proliferation, migration, and tube formation (P<0.05). Notch1 was directly targeted and repressed by miR-200b at both the mRNA and protein levels. Inhibition of miR-200b restored Notch1 expression (P<0.05) and reactivated the Notch pathway. The effects of miR-200b inhibition in HUVECs could be reversed by treatment with a Notch pathway inhibitor (P<0.05), indicating that the miR-200b/Notch axis modulates the proliferation, migration, and tube formation ability of HUVECs.

Conclusion

Inhibition of miR-200b activated the angiogenic ability of endothelial cells and promoted wound healing through reactivation of the Notch pathway in vitro. miR-200b could be a promising therapeutic target for treating HUVEC dysfunction.

The proangiogenic effect of iroquois homeobox transcription factor Irx3 in human microvascular endothelial cells

Angiogenesis is a dynamic process required for embryonic development. However, postnatal vascular growth is characteristic of multiple disease states. Despite insights into the multistep process in which adhesion molecules, extracellular matrix proteins, growth factors, and their receptors work in concert to form new vessels from the preexisting vasculature, there remains a lack of insight of the nuclear transcriptional mechanisms that occur within endothelial cells (ECs) in response to VEGF. Iroquois homeobox gene 3 (Irx3) is a transcription factor of the Iroquois family of homeobox genes. Irx homeodomain transcription factors are involved in the patterning and development of several tissues. Irx3 is known for its role during embryogenesis in multiple organisms. However, the expression and function of Irx3 in human postnatal vasculature remains to be investigated. Here we show that Irx3 is expressed in human microvascular endothelial cells, and expression is elevated by VEGF stimulation. Genetic Irx3 gain and loss of function studies in human microvascular endothelial cells resulted in the modulation of EC migration during wound healing, chemotaxis and invasion, and tubulogenesis. Additionally, we observed increased delta-like ligand 4 (Dll4) expression, which suggests an increase in EC tip cell population. Finally, siRNA screening studies revealed that transient knockdown of Hey1, a downstream Notch signaling mediator, resulted in increased Irx3 expression in response to VEGF treatment. Strategies to pharmacologically regulate Irx3 function in adult endothelial cells may provide new therapies for angiogenesis.

Hes3 is expressed in the adult pancreatic islet and regulates gene expression, cell growth, and insulin release

The transcription factor Hes3 is a component of a signaling pathway that supports the growth of neural stem cells with profound consequences in neurodegenerative disease models. Here we explored whether Hes3 also regulates pancreatic islet cells. We showed that Hes3 is expressed in human and rodent pancreatic islets. In mouse islets it co-localizes with alpha and beta cell markers. We employed the mouse insulinoma cell line MIN6 to perform in vitro characterization and functional studies in conditions known to modulate Hes3 based upon our previous work using neural stem cell cultures. In these conditions, cells showed elevated Hes3 expression and nuclear localization, grew efficiently, and showed higher evoked insulin release responses, compared with serum-containing conditions. They also exhibited higher expression of the transcription factor Pdx1 and insulin. Furthermore, they were responsive to pharmacological treatments with the GLP-1 analog Exendin-4, which increased nuclear Hes3 localization. We employed a transfection approach to address specific functions of Hes3. Hes3 RNA interference opposed cell growth and affected gene expression as revealed by DNA microarrays. Western blotting and PCR approaches specifically showed that Hes3 RNA interference opposes the expression of Pdx1 and insulin. Hes3 overexpression (using a Hes3-GFP fusion construct) confirmed a role of Hes3 in regulating Pdx1 expression. Hes3 RNA interference reduced evoked insulin release. Mice lacking Hes3 exhibited increased islet damage by streptozotocin. These data suggest roles of Hes3 in pancreatic islet function.

Fatty acid-binding protein 4, a point of convergence for angiogenic and metabolic signaling pathways in endothelial cells

Fatty acid-binding protein 4 (FABP4) is an adipogenic protein and is implicated in atherosclerosis, insulin resistance, and cancer. In endothelial cells, FABP4 is induced by VEGFA, and inhibition of FABP4 blocks most of the VEGFA effects. We investigated the DLL4-NOTCH-dependent regulation of FABP4 in human umbilical vein endothelial cells by gene/protein expression and interaction analyses following inhibitor treatment and RNA interference. We found that FABP4 is directly induced by NOTCH. Stimulation of NOTCH signaling with human recombinant DLL4 led to FABP4 induction, independently of VEGFA. FABP4 induction by VEGFA was reduced by blockade of DLL4 binding to NOTCH or inhibition of NOTCH signal transduction. Chromatin immunoprecipitation of the NOTCH intracellular domain showed increased binding to two specific regions in the FABP4 promoter. The induction of FABP4 gene expression was dependent on the transcription factor FOXO1, which was essential for basal expression of FABP4, and FABP4 up-regulation following stimulation of the VEGFA and/or the NOTCH pathway. Thus, we show that the DLL4-NOTCH pathway mediates endothelial FABP4 expression. This indicates that induction of the angiogenesis-restricting DLL4-NOTCH can have pro-angiogenic effects via this pathway. It also provides a link between DLL4-NOTCH and FOXO1-mediated regulation of endothelial gene transcription, and it shows that DLL4-NOTCH is a nodal point in the integration of pro-angiogenic and metabolic signaling in endothelial cells. This may be crucial for angiogenesis in the tumor environment.

Adropin is a brain membrane-bound protein regulating physical activity via the NB-3/Notch signaling pathway in mice

Adropin is a highly conserved polypeptide that has been suggested to act as an endocrine factor that plays important roles in metabolic regulation, insulin sensitivity, and endothelial functions. However, in this study, we provide evidence demonstrating that adropin is a plasma membrane protein expressed abundantly in the brain. Using a yeast two-hybrid screening approach, we identified NB-3/Contactin 6, a brain-specific, non-canonical, membrane-tethered Notch1 ligand, as an interaction partner of adropin. Furthermore, this interaction promotes NB3-induced activation of Notch signaling and the expression of Notch target genes. We also generated and characterized adropin knockout mice to explore the role of adropin in vivo. Adropin knockout mice exhibited decreased locomotor activity and impaired motor coordination coupled with defective synapse formation, a phenotype similar to NB-3 knockout mice. Taken together, our data suggest that adropin is a membrane-bound protein that interacts with the brain-specific Notch1 ligand NB3. It regulates physical activity and motor coordination via the NB-3/Notch signaling pathway and plays an important role in cerebellum development in mice.

Alteration of mitochondrial proteome due to activation of Notch1 signaling pathway

The Notch signaling pathway, a known regulator of cell fate decisions, proliferation, and apoptosis, has recently been implicated in the regulation of glycolysis, which affects tumor progression. However, the impact of Notch on other metabolic pathways remains to be elucidated. To gain more insights into the Notch signaling and its role in regulation of metabolism, we studied the mitochondrial proteome in Notch1-activated K562 cells using a comparative proteomics approach. The proteomic study led to the identification of 10 unique proteins that were altered due to Notch1 activation. Eight of these proteins belonged to mitochondria-localized metabolic pathways like oxidative phosphorylation, glutamine metabolism, Krebs cycle, and fatty acid oxidation. Validation of some of these findings showed that constitutive activation of Notch1 deregulated glutamine metabolism and Complex 1 of the respiratory chain. Furthermore, the deregulation of glutamine metabolism involved the canonical Notch signaling and its downstream effectors. The study also reports the effect of Notch signaling on mitochondrial function and status of high energy intermediates ATP, NADH, and NADPH. Thus our study shows the effect of Notch signaling on mitochondrial proteome, which in turn affects the functioning of key metabolic pathways, thereby connecting an important signaling pathway to the regulation of cellular metabolism.

Self-renewal and differentiation of muscle satellite cells are regulated by the Fas-associated death domain

Making the decision between self-renewal and differentiation of adult stem cells is critical for tissue repair and homeostasis. Here we show that the apoptotic adaptor Fas-associated death domain (FADD) regulates the fate decisions of muscle satellite cells (SCs). FADD phosphorylation was specifically induced in cycling SCs, which was high in metaphase and declined in later anaphase. Furthermore, phosphorylated FADD at Ser-191 accumulated in the uncommitted cycling SCs and was asymmetrically localized in the self-renewing daughter SCs. SCs containing a phosphoryl-mimicking mutation at Ser-191 of FADD (FADD-D) expressed higher levels of stem-like markers and reduced commitment-associated markers. Moreover, a phosphoryl-mimicking mutation at Ser-191 of FADD suppressed SC activation and differentiation, which promoted the cycling SCs into a reversible quiescent state. Therefore, these data indicate that FADD regulates the fate determination of cycling SCs.

Proinflammatory cytokine tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) suppresses satellite cell self-renewal through inversely modulating Notch and NF-κB signaling pathways

Satellite cell self-renewal is an essential process to maintaining the robustness of skeletal muscle regenerative capacity. However, extrinsic factors that regulate self-renewal of satellite cells are not well understood. Here, we demonstrate that TWEAK cytokine reduces the proportion of Pax7(+)/MyoD(-) cells (an index of self-renewal) on myofiber explants and represses multiple components of Notch signaling in satellite cell cultures. The number of Pax7(+) cells is significantly increased in skeletal muscle of TWEAK knock-out (KO) mice compared with wild-type in response to injury. Furthermore, Notch signaling is significantly elevated in cultured satellite cells and in regenerating myofibers of TWEAK-KO mice. Forced activation of Notch signaling through overexpression of the Notch1 intracellular domain (N1ICD) rescued the TWEAK-mediated inhibition of satellite cell self-renewal. TWEAK also activates the NF-κB transcription factor in satellite cells and inhibition of NF-κB significantly improved the number of Pax7(+) cells in TWEAK-treated cultures. Furthermore, our results demonstrate that a reciprocal interaction between NF-κB and Notch signaling governs the inhibitory effect of TWEAK on satellite cell self-renewal. Collectively, our study demonstrates that TWEAK suppresses satellite cell self-renewal through activating NF-κB and repressing Notch signaling.

Analysis of gene expression on ngn3 gene signaling pathway in endocrine pancreatic cancer

In order to define the undifferentiated transcriptional factors present in neurogenesis of pancreatic β-islet cells, we studied the effect of Pdx1 in embryonic stem cell derived endocrine lineage. There are undifferentiated transcriptional progenitors Pdx1+/Ptf1a+/Cpa1+ tracking the growth of acini, ducts, α and β-islet cells. The upregulated transcriptional factors Pdx1 and ngn3 specify consequences of cell cycle regulation in early gut endocrine cells. The undifferentiated transcriptional factors basic helix loop helix (bHLH) protein regulate Ptf1a+/Cpa1+ in acini, ducts and it also regulate ngn3 to decrease expression of insulin and other pancreas secretions. The Pdx1+ and other unknown gene mutations show abnormal growth of neurogenesis in endocrine lineages. Using microarray based gene expression analysis to determine undifferential gene ontology in tissue specific gene regulation and disease progression that common in both metabolic and biological signaling pathways. The data expression profiles of ngn3 of wild- type pancreatic islet and islet derived tumor stem cells provide information on endocrine specific ngn3 genes. Therefore, 3755 genes were significantly regulated by Ngn3 induced pancreatic islet cell development. Moreover 317 upregulated and 175 downregulated, 757 genes deemed as undifferential expressions in endocrine cell. Furthermore to predict signaling pathways that associates with diabetes is highlighted.

Notch1 receptor regulates AKT protein activation loop (Thr308) dephosphorylation through modulation of the PP2A phosphatase in phosphatase and tensin homolog (PTEN)-null T-cell acute lymphoblastic leukemia cells

Notch1 activating mutations occur in more than 50% of T-cell acute lymphoblastic leukemia (T-ALL) cases and increase expression of Notch1 target genes, some of which activate AKT. HES1 transcriptionally silences phosphatase and tensin homolog (PTEN), resulting in AKT activation, which is reversed by Notch1 inhibition with γ-secretase inhibitors (GSIs). Mutational loss of PTEN is frequent in T-ALL and promotes resistance to GSIs due to AKT activation. GSI treatments increased AKT-Thr(308) phosphorylation and signaling in PTEN-deficient, GSI-resistant T-ALL cell lines (Jurkat, CCRF-CEM, and MOLT3), suggesting that Notch1 represses AKT independent of its PTEN transcriptional effects. AKT-Thr(308) phosphorylation and downstream signaling were also increased by knocking down Notch1 in Jurkat (N1KD) cells. This was blocked by treatment with the AKT inhibitor perifosine. The PI3K inhibitor wortmannin and the protein phosphatase type 2A (PP2A) inhibitor okadaic acid both impacted AKT-Thr(308) phosphorylation to a greater extent in nontargeted control than N1KD cells, suggesting decreased dephosphorylation of AKT-Thr(308) by PP2A in the latter. Phosphorylations of AMP-activated protein kinaseα (AMPKα)-Thr(172) and p70S6K-Thr(389), both PP2A substrates, were also increased in both N1KD and GSI-treated cells and responded to okadaic acid treatment. A transcriptional regulatory mechanism was implied because ectopic expression of dominant-negative mastermind-like protein 1 increased and wild-type HES1 decreased phosphorylation of these PP2A targets. This was independent of changes in PP2A subunit levels or in vitro PP2A activity, but was accompanied by decreased association of PP2A with AKT in N1KD cells. These results suggest that Notch1 can regulate PP2A dephosphorylation of critical cellular regulators including AKT, AMPKα, and p70S6K.

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) and nuclear factor κB signaling in glioblastoma cancer stem cells regulates the Notch pathway

Malignant gliomas are locally aggressive, highly vascular tumors that have a dismal prognosis, and present therapies provide little improvement in the disease course and outcome. Many types of malignancies, including glioblastoma, originate from a population of cancer stem cells (CSCs) that are able to initiate and maintain tumors. Although CSCs only represent a small fraction of cells within a tumor, their high tumor-initiating capacity and therapeutic resistance drives tumorigenesis. Therefore, it is imperative to identify pathways associated with CSCs to devise strategies to selectively target them. In this study, we describe a novel relationship between glioblastoma CSCs and the Notch pathway, which involves the constitutive activation of STAT3 and NF-κB signaling. Glioma CSCs were isolated and maintained in vitro using an adherent culture system, and the biological properties were compared with the traditional cultures of CSCs grown as multicellular spheres under nonadherent culture conditions. Interestingly, both adherent and spheroid glioma CSCs show constitutive activation of the STAT3/NF-κB signaling pathway and up-regulation of STAT3- and NF-κB-dependent genes. Gene expression profiling also identified components of the Notch pathway as being deregulated in glioma CSCs, and the deregulated expression of these genes was sensitive to treatment with STAT3 and NF-κB inhibitors. This finding is particularly important because Notch signaling appears to play a key role in CSCs in a variety of cancers and controls cell fate determination, survival, proliferation, and the maintenance of stem cells. The constitutive activation of STAT3 and NF-κB signaling pathways that leads to the regulation of Notch pathway genes in glioma CSCs identifies novel therapeutic targets for the treatment of glioma.

Intrinsic selectivity of Notch 1 for Delta-like 4 over Delta-like 1

Notch signaling makes critical contributions to cell fate determination in all metazoan organisms, yet remarkably little is known about the binding affinity of the four mammalian Notch receptors for their three Delta-like and two Jagged family ligands. Here, we utilized signaling assays and biochemical studies of purified recombinant ligand and receptor molecules to investigate the differences in signaling behavior and intrinsic affinity between Notch1-Dll1 and Notch1-Dll4 complexes. Systematic deletion mutagenesis of the human Notch1 ectodomain revealed that epidermal growth factor (EGF) repeats 6-15 are sufficient to maintain signaling in a reporter assay at levels comparable with the full-length receptor, and identified important contributions from EGF repeats 8-10 in conveying an activating signal in response to either Dll1 or Dll4. Truncation studies of the Dll1 and Dll4 ectodomains showed that the MNNL-EGF3 region was both necessary and sufficient for full activation. Plate-based and cell binding assays revealed a specific, calcium-dependent interaction between cell-surface and recombinant Notch receptors and ligand molecules. Finally, direct measurement of the binding affinity of Notch1 EGF repeats 6-15 for Dll1 and Dll4 revealed that Dll4 binds with at least an order of magnitude higher affinity than Dll1. Together, these studies give new insights into the features of ligand recognition by Notch1, and highlight how intrinsic differences in the biochemical behavior of receptor-ligand complexes can influence receptor-mediated responses of developmental signaling pathways.

Increased cAMP in monocytes augments Notch signaling mechanisms by elevating RBP-J and transducin-like enhancer of Split (TLE)

In cells of the innate immune system, pathological increases in intracellular cAMP attenuate immune responses and contribute to infections by bacteria such as Bacillus anthracis. In this work, cAMP from B. anthracis edema toxin (ET) is found to activate the Notch signaling pathway in both mouse macrophages and human monocytes. ET as well as a cell-permeable activator of PKA induce Notch target genes (HES1, HEY1, IL2RA, and IL7R) and are able to significantly enhance the induction of these Notch target genes by a Toll-like receptor ligand. Elevated cAMP also resulted in increased levels of Groucho/transducin-like enhancer of Split (TLE) and led to increased amounts of a transcriptional repressor complex consisting of TLE and the Notch target Hes1. To address the mechanism used by ET to activate Notch signaling, components of Notch signaling were examined, and results revealed that ET increased levels of recombinant recognition sequence binding protein at the Jκ site (RBP-J), a DNA binding protein and principal transcriptional regulator of Notch signaling. Overexpression studies indicated that RBP-J was sufficient to activate Notch signaling and potentiate LPS-induced Notch signaling. Further examination of the mechanism used by ET to activate Notch signaling revealed that C/EBP β, a transcription factor activated by cAMP, helped activate Notch signaling and up-regulated RBP-J. These studies demonstrate that cAMP activates Notch signaling and increases the expression of TLE, which could be an important mechanism utilized by cAMP to suppress immune responses.

Inflammatory cytokines induce NOTCH signaling in nucleus pulposus cells: implications in intervertebral disc degeneration

The objective of the study was to investigate how inflammatory cytokines, IL-1β, and TNF-α control NOTCH signaling activity in nucleus pulposus (NP) cells. An increase in expression of selective NOTCH receptors (NOTCH1 and -2), ligand (JAGGED2), and target genes (HES1, HEY1, and HEY2) was observed in NP cells following cytokine treatment. A concomitant increase in NOTCH signaling as evidenced by induction in activity of target gene HES1 and HEY1 promoters and reporter 12xCSL was seen. Moreover, treatment increased activity of a 2-kb NOTCH2 promoter. Treatment of cells with NF-κB and MAPK inhibitors abolished the inductive effect of cytokines on NOTCH2 promoter and its expression. Gain and loss-of-function studies confirmed the inductive effect of p65 on NOTCH2 promoter activity. In contrast, p50 blocked the cytokine induction of promoter activity. Supporting promoter studies, lentiviral delivery of sh-p65, and sh-IKKβ significantly decreased cytokine dependent change in NOTCH2 expression. Interestingly, MAPK signaling showed an isoform-specific control of NOTCH2 promoter; p38α/β2/δ, ERK1, and ERK2 contributed to cytokine dependent induction, whereas p38γ played no role. Analysis of human NP tissues showed that NOTCH1 and -2 and HEY2 expression correlated with each other. Moreover, expression of NOTCH2 and IL-1β as well as the number of cells immunopositive for NOTCH2 significantly increased in histologically degenerate discs compared with non-degenerate discs. Taken together, these results explain the observed dysregulated expression of NOTCH genes in degenerative disc disease. Thus, controlling IL-1β and TNF-α activities during disc disease may restore NOTCH signaling and nucleus pulposus cell function.