Endothelial-specific Notch blockade inhibits vascular function and tumor growth through an eNOS-dependent mechanism

eNOS plays essential roles in the developing heart and aorta linked to disruption of Notch signalling

eNOS (NOS3) is the enzyme that generates nitric oxide, a signalling molecule and regulator of vascular tone. Loss of eNOS function is associated with increased susceptibility to atherosclerosis, hypertension, thrombosis and stroke. Aortopathy and cardiac hypertrophy have also been found in eNOS null mice, but their aetiology is unclear. We evaluated eNOS nulls before and around birth for cardiac defects, revealing severe abnormalities in the ventricular myocardium and pharyngeal arch arteries. Moreover, in the aortic arch, there were fewer baroreceptors, which sense changes in blood pressure. Adult eNOS null survivors showed evidence of cardiac hypertrophy, aortopathy and cartilaginous metaplasia in the periductal region of the aortic arch. Notch1 and neuregulin were dysregulated in the forming pharyngeal arch arteries and ventricles, suggesting that these pathways may be relevant to the defects observed. Dysregulation of eNOS leads to embryonic and perinatal death, suggesting mutations in eNOS are candidates for causing congenital heart defects in humans. Surviving eNOS mutants have a deficiency of baroreceptors that likely contributes to high blood pressure and may have relevance to human patients who suffer from hypertension associated with aortic arch abnormalities.

Stromal cells in the tumor microenvironment: accomplices of tumor progression?

The tumor microenvironment (TME) is made up of cells and extracellular matrix (non-cellular component), and cellular components include cancer cells and non-malignant cells such as immune cells and stromal cells. These three types of cells establish complex signals in the body and further influence tumor genesis, development, metastasis and participate in resistance to anti-tumor therapy. It has attracted scholars to study immune cells in TME due to the significant efficacy of immune checkpoint inhibitors (ICI) and chimeric antigen receptor T (CAR-T) in solid tumors and hematologic tumors. After more than 10 years of efforts, the role of immune cells in TME and the strategy of treating tumors based on immune cells have developed rapidly. Moreover, ICI have been recommended by guidelines as first- or second-line treatment strategies in a variety of tumors. At the same time, stromal cells is another major class of cellular components in TME, which also play a very important role in tumor metabolism, growth, metastasis, immune evasion and treatment resistance. Stromal cells can be recruited from neighboring non-cancerous host stromal cells and can also be formed by transdifferentiation from stromal cells to stromal cells or from tumor cells to stromal cells. Moreover, they participate in tumor genesis, development and drug resistance by secreting various factors and exosomes, participating in tumor angiogenesis and tumor metabolism, regulating the immune response in TME and extracellular matrix. However, with the deepening understanding of stromal cells, people found that stromal cells not only have the effect of promoting tumor but also can inhibit tumor in some cases. In this review, we will introduce the origin of stromal cells in TME as well as the role and specific mechanism of stromal cells in tumorigenesis and tumor development and strategies for treatment of tumors based on stromal cells. We will focus on tumor-associated fibroblasts (CAFs), mesenchymal stem cells (MSCs), tumor-associated adipocytes (CAAs), tumor endothelial cells (TECs) and pericytes (PCs) in stromal cells.

Vascular adaptation to cancer beyond angiogenesis: The role of PTEN

Cancer is a public health problem, and it needs blood vessels to grow. Knowing more about the processes of vascular adaptation to cancer improves our chances of attacking it, since the tumor for its extension needs such adaptation to satisfy its progressive demand for nutrients. The main objective of this review is to present the reader with some fundamental molecular pathways for vascular adaptation to cancer, highlighting within them the regulatory role of homologous tensin and phosphatase protein (PTEN). Hence the review describes vascular adaptation to cancer through somewhat known processes, such as angiogenesis, but emphasizes others that are much less explored, namely the changes in vascular reactivity and remodeling of the vascular wall -intima-media thickness and adjustments in the extracellular matrix- The role of PTEN in physiological and pathological vascular mechanisms in different types of cancer is deepened, as a crucial mediator in vascular adaptation to cancer, and points pending further exploration in cancer vascularization are suggested.

Inhibition of the intracellular domain of Notch1 results in vascular endothelial cell dysfunction in sepsis

Background

Notch signaling is critical for regulating the function of vascular endothelial cells (ECs). However, the effect of the intracellular domain of Notch1 (NICD) on EC injury in sepsis remains unclear.

Methods

We established a cell model of vascular endothelial dysfunction and induced sepsis in a mouse model via lipopolysaccharide (LPS) injection and cecal ligation and puncture (CLP). Endothelial barrier function and expression of endothelial-related proteins were determined using CCK-8, permeability, flow cytometry, immunoblot, and immunoprecipitation assays. The effect of NICD inhibition or activation on endothelial barrier function was evaluated in vitro. Melatonin was used for NICD activation in sepsis mice. The survival rate, Evans blue dye of organs, vessel relaxation assay, immunohistochemistry, ELISA, immunoblot were used to explore the specific role of melatonin for sepsis induced vascular dysfunction in vivo.

Results

We found that LPS, interleukin 6, and serum collected from septic children could inhibit the expression of NICD and its downstream regulator Hes1, which impaired endothelial barrier function and led to EC apoptosis through the AKT pathway. Mechanistically, LPS decreased the stability of NICD by inhibiting the expression of a deubiquitylating enzyme, ubiquitin-specific proteases 8 (USP8). Melatonin, however, upregulated USP8 expression, thus maintaining the stability of NICD and Notch signaling, which ultimately reduced EC injury in our sepsis model and elevated the survival rate of septic mice.

Conclusions

We found a previously uncharacterized role of Notch1 in mediating vascular permeability during sepsis, and we showed that inhibition of NICD resulted in vascular EC dysfunction in sepsis, which was reversed by melatonin. Thus, the Notch1 signaling pathway is a potential target for the treatment of sepsis.

Therapeutic Targeting Notch2 Protects Bone Micro-Vasculatures from Methotrexate Chemotherapy-Induced Adverse Effects in Rats

Intensive cancer chemotherapy is well known to cause bone vasculature disfunction and damage, but the mechanism is poorly understood and there is a lack of treatment. Using a rat model of methotrexate (MTX) chemotherapy (five once-daily dosses at 0.75 mg/kg), this study investigated the roles of the Notch2 signalling pathway in MTX chemotherapy-induced bone micro-vasculature impairment. Gene expression, histological and micro-computed tomography (micro-CT) analyses revealed that MTX-induced micro-vasculature dilation and regression is associated with the induction of Notch2 activity in endothelial cells and increased production of inflammatory cytokine tumour necrosis factor alpha (TNFα) from osteoblasts (bone forming cells) and bone marrow cells. Blockade of Notch2 by a neutralising antibody ameliorated MTX adverse effects on bone micro-vasculature, both directly by supressing Notch2 signalling in endothelial cells and indirectly via reducing TNFα production. Furthermore, in vitro studies using rat bone marrow-derived endothelial cell revealed that MTX treatment induces Notch2/Hey1 pathway and negatively affects their ability in migration and tube formation, and Notch2 blockade can partially protect endothelial cell functions from MTX damage.

Characterization of the Notch pathway in nasal polyps of patients with chronic rhinosinusitis: A pilot study

Chronic rhinosinusitis with nasal polyps is a widespread pathology characterized by persistent inflammation of nasal and paranasal mucosa. Although it represents one of the most frequent diseases of the nasal cavities, its etiology is still not completely elucidated. There is evidence suggesting that the Notch signaling, a highly conserved intercellular pathway known to regulate many cellular processes, including inflammation, is implicated in nasal polyps formation. The purpose of this study was to investigate the expression of genes of the Notch pathway in nasal polyps from patients with chronic rhinosinusitis. Nasal polyps and adjacent mucosa tissue were obtained from 10 patients. RNA was analyzed by quantitative reverse transcriptase-polymerase chain reaction for the expression level of (1) Notch pathway components such as receptors (NOTCH1-4), ligands (DLL4, JAGGED-1), and target genes (HEY1, 2, and HES1) and (2) genes providing information on the pathogenesis of polyposis (C-MYC and SCGB1A1) and on eosinophils content (CCL26, IL5, and SAA2). We report a Notch-driven gene expression pattern in nasal polyps which correlates with the expression of genes highly expressed in eosinophils, whose presence is an important parameter to define the pathophysiologic diversity characterizing nasal polyps. Taken together, our results suggest a role for Notch signaling in the pathophysiology of polyposis. Further studies are needed to elucidate the role of Notch in nasal polyps formation and to establish whether it could represent a novel therapeutic target for this pathology.

EHD2 modulates Dll4 endocytosis during blood vessel development

OBJECTIVE

Despite the absolute requirement of Delta/Notch signaling to activate lateral inhibition during early blood vessel development, many mechanisms remain unclear about how this system is regulated. Our objective was to determine the involvement of Epsin 15 Homology Domain Containing 2 (EHD2) in delta-like ligand 4 (Dll4) endocytosis during Notch activation.

APPROACH AND RESULTS

Using both in vivo and in vitro models, we demonstrate that EHD2 is a novel modulator of Notch activation in endothelial cells through controlling endocytosis of Dll4. In vitro, EHD2 localized to plasma membrane-bound Dll4 and caveolae. Chemical disruption of caveolae complexes resulted in EHD2 failing to organize around Dll4 as well as loss of Dll4 internalization. Reduced Dll4 internalization blunted Notch activation in endothelial cells. In vivo, EHD2 is primarily expressed in the vasculature, colocalizing with junctional marker VE-cadherin and Dll4. Knockout of EHD2 in zebrafish produced a significant increase in dysmorphic sprouts in zebrafish intersomitic vessels during development and a reduction in downstream Notch signaling.

CONCLUSIONS

Overall, we demonstrate that EHD2 is necessary for Dll4 transcytosis and downstream Notch activation.

Co-Culture of Primary Human Coronary Artery and Internal Thoracic Artery Endothelial Cells Results in Mutually Beneficial Paracrine Interactions

Although saphenous veins (SVs) are commonly used as conduits for coronary artery bypass grafting (CABG), internal thoracic artery (ITA) grafts have significantly higher long-term patency. As SVs and ITA endothelial cells (ECs) have a considerable level of heterogeneity, we suggested that synergistic paracrine interactions between CA and ITA ECs (HCAECs and HITAECs, respectively) may explain the increased resistance of ITA grafts and adjacent CAs to atherosclerosis and restenosis. In this study, we measured the gene and protein expression of the molecules responsible for endothelial homeostasis, pro-inflammatory response, and endothelial-to-mesenchymal transition in HCAECs co-cultured with either HITAECs or SV ECs (HSaVECs) for an ascending duration. Upon the co-culture, HCAECs and HITAECs showed augmented expression of endothelial nitric oxide synthase (eNOS) and reduced expression of endothelial-to-mesenchymal transition transcription factors Snail and Slug when compared to the HCAEC–HSaVEC model. HCAECs co-cultured with HITAECs demonstrated an upregulation of HES1, a master regulator of arterial specification, of which the expression was also exclusively induced in HSaVECs co-cultured with HCAECs, suggestive of their arterialisation. In addition, co-culture of HCAECs and HITAECs promoted the release of pro-angiogenic molecules. To conclude, co-culture of HCAECs and HITAECs results in reciprocal and beneficial paracrine interactions that might contribute to the better performance of ITA grafts upon CABG.

MicroRNA-155 induces protection against cerebral ischemia/reperfusion injury through regulation of the Notch pathway in vivo

microRNA (miR)-155 has been demonstrated to participate in the regulation of endothelium during cerebral ischemia. In the present study, it was aimed to investigate the molecular mechanism of miR-155 in the regulation of cerebral ischemia/reperfusion (I/R) injury with middle cerebral artery occlusion (MCAO) in mice. The MCAO model was established in C57BL/6 mice. Transfection of miR-155 mimics and miR-155 inhibitors was performed to alter the expression of miR-155. The level of miR-155 was measured by RT-qPCR analysis. The western blotting results demonstrated that deletion of miR-155 increased the expression of Notch1, intracellular Notch receptor domain (NICD) and hairy and enhancer of split-1 (Hes1) levels. In addition, the percentage of terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling-positive cells and caspase-3 levels were decreased following treatment with a miR-155 inhibitor compared with the Pre-IR group. Notably, disrupting miR-155 also increased nitric oxide (NO) production and the expression of endothelial NO synthase (eNOS), leading to downregulation of brain water content and Evans blue levels. However, overexpression of miR-155 restored all these changes to similar levels observed in the cerebral I/R injury group. The expressions of Notch1, NICD and Hes1 were also decreased to the cerebral I/R injury condition. In conclusion, a novel mechanism was identified for abrogating normal NO production and eNOS expression via the aberrant expression of the Notch signaling pathway, a mechanism that may be modulated by miR-155. Together, these results reveal important functions of miR-155 in regulating the Notch signaling pathway of the nervous system, and a potential role for miR-155 as a crucial therapy target for cerebral stroke.

Stage-dependent regulation of oligodendrocyte development and enhancement of myelin repair by dominant negative Master-mind 1 protein

Notch signaling has been implicated in the inhibition of oligodendrocyte differentiation and myelin gene expression during early development. However, inactivation of a particular Notch or Hes gene only produces a mild phenotype in oligodendrocyte development possibly due to the functional redundancies among closely related family members. To uncover the full role of Notch signaling in myelin development and regeneration, we generated the Sox10^rtTA/+ ; TetO-dnMAML1 double transgenic mice in which expression of dominant negative Master-mind 1 (dnMAML1) gene can be selectively induced in oligodendrocyte precursor cells (OPCs) for complete blockade of Notch signaling. It is found that dnMAML1 expression leads to robust precocious OL differentiation and premature axonal myelination in the spinal cord, possibly by upregulating Nkx2.2 and downregulating Pdgfra expression. Unexpectedly, at late embryonic stages, dnMAML1 expression dramatically increased the number of OPCs, indicating a stage-dependent effect of Notch signaling on OPC proliferation. In addition, dnMAML1 also significantly enhances axonal remyelination following chemical-induced demyelination, providing a promising therapeutic target for lesion repair in demyelinating disease.

MicroRNA-34a promotes CMECs apoptosis and upregulate inflammatory cytokines, thus worsening CMECs damage and inhibiting angiogenesis by negatively targeting the Notch signaling pathway

OBJECTIVE

Recently, microRNA-34a (miR-34a) has been reported to lead to secretion of proinflammatory cytokine in endothelial cells, whereas whether miR-34a plays a protective role in damaged cardiac microvascular endothelial cells (CMECs) remains to be determined. Herein, the purpose of this study is to explore the effect of miR-34a in mediating Notch signaling pathway in apoptosis and angiogenesis of damaged CMECs.

METHODS

The primary mice CMECs were isolated, cultivated, and identified before establishment of damaged CMEC model by incubation with homocysteine (HCY) for 24 hours. Quantitative reverse-transcription polymerase chain reaction and Western blot analysis were applied to determine the expressions of miR-34a and Notch1. Cell viability and cell apoptosis were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Hochest 33258 staining. Capillary-like structures formation assay was used to detect the capillary-like structures in CMECs. The expressions of inflammatory cytokines and angiogenesis factors were determined by enzyme-linked immunosorbent assay.

RESULTS

In contrast to the blank group, the HCY and negative control groups demonstrated with elevated expressions of miR-34a, interleukin (IL)-1β, IL-6, and increased cell apoptosis rate, but decreased expressions of Notch1, IL-10, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and human growth factor (HGF), as well as attenuated cell viability and capillary-like structures of cells formation ability. In comparison with HCY group, the expressions of miR-34a, IL-1β, IL-6, and apoptosis rate were increased, whereas the expressions of Notch1, VEGF, bFGF, HGF, cell viability, and capillary-like structures of cells formation were inhibited in miR-34a mimic group.

CONCLUSION

This study demonstrates that miR-34a can promote CMEC apoptosis and upregulate inflammatory cytokines, thus worsening CMEC damage and inhibiting angiogenesis by negatively targeting the Notch signaling pathway.

Protective effect of HSP27 in atherosclerosis and coronary heart disease by inhibiting reactive oxygen species

OBJECTIVE

To clarify the mechanism of heat shock protein 27 (HSP27) as a diagnostic biomarker in coronary heart disease (CHD) and atherosclerosis (AS).

METHOD

Expressions of HSP27 in patients with CHD and healthy controls were determined by enzyme-linked immunosorbent assay and the expressions of HSP27 in aortas of patients with CHD and healthy controls were measured by immunohistochemistry. Receiver operating characteristic curve was applied to assess the diagnostic performance of HSP27 in CHD. ApoE^-/- mice were included and accordingly grouped. The expressions of HSP27 in AS plaque were measured by quantitative real-time polymerase chain reaction, immunohistochemistry, and Western blot analysis. AS plaque was observed using hematoxylin and eosin staining. DHE was used to detect reactive oxygen species (ROS) levels in aortas. The expressions of mitochondrial apoptosis-related proteins were measured by Western blot analysis. Cell apoptosis was determined by TUNEL staining.

RESULTS

HSP27 was highly expressed in patients with CHD than in healthy controls ( P < 0.01). In comparison to the normal group, the model group had increased the relative positive area of HSP27 and higher expressions of HSP27, Bax, caspase-3, and apoptosis index (AI) but decreased Bcl-2 expression in AS plaque, as well as larger plaque areas and elevated ROS levels in the aorta (all P < 0.05). The HSP27-small interfering RNA group had increased expressions of Bax, caspase-3, and AI but decreased Bcl-2 and HSP27 expressions in AS plaque, as well as larger plaque areas, the relative positive area of HSP27 and higher ROS levels in aorta when compared with those in the model group (all P < 0.05).

CONCLUSION

HSP27 exerts its protective role by suppressing ROS and AS progression by inhibiting mitochondria apoptosis pathway in CHD.

Endothelial Notch activation reshapes the angiocrine of sinusoidal endothelia to aggravate liver fibrosis and blunt regeneration in mice

Liver sinusoidal endothelial cells (LSECs) critically regulate liver homeostasis and diseases through angiocrine factors. Notch is critical in endothelial cells (ECs). In the current study, Notch signaling was activated by inducible EC-specific expression of the Notch intracellular domain (NIC). We found that endothelial Notch activation damaged liver homeostasis. Notch activation resulted in decreased fenestration and increased basement membrane, and a gene expression profile with decreased LSEC-associated genes and increased continuous EC-associated genes, suggesting LSEC dedifferentiation. Consistently, endothelial Notch activation enhanced hepatic fibrosis (HF) induced by CCl₄ . Notch activation attenuated endothelial nitric oxide synthase (eNOS)/soluble guanylate cyclase (sGC) signaling, and activation of sGC by 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) reversed the dedifferentiation phenotype. In addition, Notch activation subverted the hepatocyte-supporting angiocrine profile of LSECs by down-regulating critical hepatocyte mitogens, including Wnt2a, Wnt9b, and hepatocyte growth factor (HGF). This led to compromised hepatocyte proliferation under both quiescent and regenerating conditions. Whereas expression of Wnt2a and Wnt9b was dependent on eNOS-sGC signaling, HGF expression was not rescued by the sGC activator, suggesting heterogeneous mechanisms of LSECs to maintain hepatocyte homeostasis.

CONCLUSION

Endothelial Notch activation results in LSEC dedifferentiation and accelerated liver fibrogenesis through eNOS-sGC signaling, and alters the angiocrine profile of LSECs to compromise hepatocyte proliferation and liver regeneration (LR). (Hepatology 2018).

Mechanism of melanoma cells selective apoptosis induced by a photoactive NADPH analogue

Melanoma is one of the most lethal cancers when it reaches a metastatic stage. Despite the spectacular achievements of targeted therapies (BRAF inhibitors) or immuno-therapies (anti-CTLA4 or anti-PD1), most patients with melanoma will need additional treatments. Here we used a photoactive NADPH analogue called NS1 to induce cell death by inhibition of NADPH oxidases NOX in melanoma cells, including melanoma cells isolated from patients. In contrast, healthy melanocytes growth was unaffected by NS1 treatment.

NS1 established an early Endoplasmic Reticulum stress by the early release of calcium mediated by (a) calcium-dependent redox-sensitive ion channel(s). These events initiated autophagy and apoptosis in all tested melanoma cells independently of their mutational status. The autophagy promoted by NS1 was incomplete. The autophagic flux was blocked at late stage events, consistent with the accumulation of p62, and a close localization of LC3 with NS1 associated with NS1 inhibition of NOX1 in autophagosomes. This hypothesis of a specific incomplete autophagy and apoptosis driven by NS1 was comforted by the use of siRNAs and pharmacological inhibitors blocking different processes. This study highlights the potential therapeutic interest of NS1 inducing cell death by triggering a selective ER stress and incomplete autophagy in melanoma cells harbouring wt and BRAF mutation.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

The role of nitric oxide in melanoma

Nitric oxide (NO) is a small gaseous signaling molecule that mediates its effects in melanoma through free radical formation and enzymatic processes. Investigations have demonstrated multiple roles for NO in melanoma pathology via immune surveillance, apoptosis, angiogenesis, melanogenesis, and on the melanoma cell itself. In general, elevated levels of NO prognosticate a poor outcome for melanoma patients. However, there are processes where the relative concentration of NO in different environments may also serve to limit melanoma proliferation. This review serves to outline the roles of NO in melanoma development and proliferation. As demonstrated by multiple in vivo murine models and observations from human tissue, NO may promote melanoma formation and proliferation through its interaction via inhibitory immune cells, inhibition of apoptosis, stimulation of pro-tumorigenic cytokines, activation of tumor associated macrophages, alteration of angiogenic processes, and stimulation of melanoma formation itself.

Notch Signaling in Endothelial Cells: Is It the Therapeutic Target for Vascular Neointimal Hyperplasia?

Blood vessels respond to injury through a healing process that includes neointimal hyperplasia. The vascular endothelium is a monolayer of cells that separates the outer vascular wall from the inner circulating blood. The disruption and exposure of endothelial cells (ECs) to subintimal components initiate the neointimal formation. ECs not only act as a highly selective barrier to prevent early pathological changes of neointimal hyperplasia, but also synthesize and release molecules to maintain vascular homeostasis. After vascular injury, ECs exhibit varied responses, including proliferation, regeneration, apoptosis, phenotypic switching, interacting with other cells by direct contact or secreted molecules and the change of barrier function. This brief review presents the functional role of the evolutionarily-conserved Notch pathway in neointimal hyperplasia, notably by regulating endothelial cell functions (proliferation, regeneration, apoptosis, differentiation, cell-cell interaction). Understanding endothelial cell biology should help us define methods to prompt cell proliferation, prevent cell apoptosis and dysfunction, block neointimal hyperplasia and vessel narrowing.

Transdifferentiated Human Vascular Smooth Muscle Cells are a New Potential Cell Source for Endothelial Regeneration

Endothelial dysfunction is widely implicated in cardiovascular pathological changes and development of vascular disease. In view of the fact that the spontaneous endothelial cell (EC) regeneration is a slow and insufficient process, it is of great interest to explore alternative cell sources capable of generating functional ECs. Vascular smooth muscle cell (SMC) composes the majority of the vascular wall and retains phenotypic plasticity in response to various stimuli. The aim of this study is to test the feasibility of the conversion of SMC into functional EC through the use of reprogramming factors. Human SMCs are first dedifferentiated for 4 days to achieve a vascular progenitor state expressing CD34, by introducing transcription factors OCT4, SOX2, KLF4 and c-MYC. These SMC-derived progenitors are then differentiated along the endothelial lineage. The SMC-converted ECs exhibit typical endothelial markers expression and endothelial functions in vitro, in vivo and in disease model. Further comprehensive analysis indicates that mesenchymal-to-epithelial transition is requisite to initiate SMCs reprogramming into vascular progenitors and that members of the Notch signalling pathway regulate further differentiation of the progenitors into endothelial lineage. Together, we provide the first evidence of the feasibility of the conversion of human SMCs towards endothelial lineage through an intermediate vascular progenitor state induced by reprogramming.

Vorinostat suppresses hypoxia signaling by modulating nuclear translocation of hypoxia inducible factor 1 alpha

Histone deacetylase inhibitors (HDACis) are a potent class of tumor-suppressive agents traditionally believed to exert their effects through loosening tightly-wound chromatin resulting in de-inhibition of various tumor suppressive genes. Recent literature however has shown altered intratumoral hypoxia signaling with HDACi administration not attributable to changes in chromatin structure. We sought to determine the precise mechanism of HDACi-mediated hypoxia signaling attenuation using vorinostat (SAHA), an FDA-approved class I/IIb/IV HDACi. Through an in-vitro and in-vivo approach utilizing cell lines for hepatocellular carcinoma (HCC), osteosarcoma (OS), and glioblastoma (GBM), we demonstrate that SAHA potently inhibits HIF-a nuclear translocation via direct acetylation of its associated chaperone, heat shock protein 90 (Hsp90). In the presence of SAHA we found elevated levels of acetyl-Hsp90, decreased interaction between acetyl-Hsp90 and HIF-a, decreased nuclear/cytoplasmic HIF-α expression, absent HIF-α association with its nuclear karyopharyin Importin, and markedly decreased HIF-a transcriptional activity. These changes were associated with downregulation of downstream hypoxia molecules such as endothelin 1, erythropoietin, glucose transporter 1, and vascular endothelial growth factor. Findings were replicated in an in-vivo Hep3B HRE-Luc expressing xenograft, and were associated with significant decreases in xenograft tumor size. Altogether, this study highlights a novel mechanism of action of an important class of chemotherapeutic.

Overexpression of Jagged1 Ameliorates Aged Rat-Derived Endothelial Progenitor Cell Functions and Improves Its Transfusion Efficiency for Rat Balloon-Induced Arterial Injury

BACKGROUND

Endothelial progenitor cell (EPC) has significant age-dependent alterations in properties, but the role of Jagged1 in aging-induced decline of EPC functions remains unclear.

METHODS

2- and 20-month old healthy male Sprague-Dawley rats were used in present study. Jagged1 gene transfection was performed in EPC isolated from aged (AEPC) and young rats (YEPC), respectively. Experiments were divided into 4 groups: (1) pIRES2-EGFP (PE) group, (2) PE-combined N-[N-(3, 5-difluoro-phenacetyl)-1- alany1]-S-phenyglycine t-butyl ester (DAPT) (PE + D) group, (3) pIRES2 EGFP-Jagged1 (PEJ) group, and (4) PEJ combined DAPT (PEJ + D) group. Notch molecules were detected by real-time quantitative polymerase chain reaction or Western blotting. CD34, CD133, CD45, and KDR markers were detected by flow cytometry. EPC migration and proliferation were detected with a modified Boyden chamber and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay, respectively; the tube formation ability was assayed by in vitro angiogenesis kit; EPC transfusion after Jagged1 gene transfection was performed in rat carotid artery injury models.

RESULTS

Jagged1 gene transfection effectively activates notch-signaling pathway. Compared with PE groups, overexpression of Jagged1 significantly promoted AEPC functions including proliferation, migration, the tube formation ability, and cell differentiation, these effects could be reasonably diminished by DAPT. In vivo study demonstrated that Jagged1 overexpressing also significantly promoted AEPC homing to the vascular injury sites and decreases the neointima formation after vascular injury.

CONCLUSIONS

Overexpression of Jagged1 ameliorates aged rat-derived EPC functions and increases its transfusion efficiency for balloon-induced rat arterial injury.

"Decoding" Angiogenesis: New Facets Controlling Endothelial Cell Behavior

Angiogenesis, the formation of new blood vessels, is a unique and crucial biological process occurring during both development and adulthood. A better understanding of the mechanisms that regulates such process is mandatory to intervene in pathophysiological conditions. Here we highlight some recent argument on new players that are critical in endothelial cells, by summarizing novel discoveries that regulate notorious vascular pathways such as Vascular Endothelial Growth Factor (VEGF), Notch and Planar Cell Polarity (PCP), and by discussing more recent findings that put metabolism, redox signaling and hemodynamic forces as novel unforeseen facets in angiogenesis. These new aspects, that critically regulate angiogenesis and vascular homeostasis in health and diseased, represent unforeseen new ground to develop anti-angiogenic therapies.

Regulation of NADPH-dependent Nitric Oxide and reactive oxygen species signalling in endothelial and melanoma cells by a photoactive NADPH analogue

Nitric Oxide (NO) and Reactive oxygen species (ROS) are endogenous regulators of angiogenesis-related events as endothelial cell proliferation and survival, but NO/ROS defect or unbalance contribute to cancers. We recently designed a novel photoactive inhibitor of NO-Synthases (NOS) called NS1, which binds their NADPH site in vitro. Here, we show that NS1 inhibited NO formed in aortic rings. NS1-induced NO decrease led to an inhibition of angiogenesis in a model of VEGF-induced endothelial tubes formation. Beside this effect, NS1 reduced ROS levels in endothelial and melanoma A375 cells and in aorta. In metastatic melanoma cells, NS1 first induced a strong decrease of VEGF and blocked melanoma cell cycle at G2/M. NS1 decreased NOX₄ and ROS levels that could lead to a specific proliferation arrest and cell death. In contrast, NS1 did not perturb melanocytes growth.

Altogether, NS1 revealed a possible cross-talk between eNOS- and NOX₄ –associated pathways in melanoma cells via VEGF, Erk and Akt modulation by NS1 that could be targeted to stop proliferation. NS1 thus constitutes a promising tool that modulates NO and redox stresses by targeting and directly inhibiting eNOS and, at least indirectly, NADPH oxidase(s), with great potential to control angiogenesis.

23814, an Inhibitory Antibody of Ligand-Mediated Notch1 Activation, Modulates Angiogenesis and Inhibits Tumor Growth without Gastrointestinal Toxicity

Dysregulation of Notch signaling has been implicated in the development of many different types of cancer. Notch inhibitors are being tested in the clinic, but in most cases gastrointestinal and other toxicities have limited the dosage and, therefore, the effectiveness of these therapies. Herein, we describe the generation of a monoclonal antibody against the ligand-binding domain of the Notch1 receptor that specifically blocks ligand-induced activation. This antibody, 23814, recognizes both human and murine Notch1 with similar affinity, enabling examination of the effects on both tumor and host tissue in preclinical models. 23814 blocked Notch1 function in vivo, inhibited functional angiogenesis, and inhibited tumor growth without causing gastrointestinal toxicity. The lack of toxicity allowed for combination of 23814 and the VEGFR inhibitor tivozanib, resulting in significant growth inhibition of several VEGFR inhibitor-resistant tumor models. Analysis of the gene expression profiles of an extensive collection of murine breast tumors enabled the successful prediction of which tumors were most likely to respond to the combination of 23814 and tivozanib. Therefore, the use of a specific Notch1 antibody that does not induce significant toxicity may allow combination treatment with angiogenesis inhibitors or other targeted agents to achieve enhanced therapeutic benefit.

Protein kinases and associated pathways in pluripotent state and lineage differentiation

Protein kinases (PKs) mediate the reversible conversion of substrate proteins to phosphorylated forms, a key process in controlling intracellular signaling transduction cascades. Pluripotency is, among others, characterized by specifically expressed PKs forming a highly interconnected regulatory network that culminates in a finely-balanced molecular switch. Current high-throughput phosphoproteomic approaches have shed light on the specific regulatory PKs and their function in controlling pluripotent states. Pluripotent cell-derived endothelial and hematopoietic developments represent an example of the importance of pluripotency in cancer therapeutics and organ regeneration. This review attempts to provide the hitherto known kinome profile and the individual characterization of PK-related pathways that regulate pluripotency. Elucidating the underlying intrinsic and extrinsic signals may improve our understanding of the different pluripotent states, the maintenance or induction of pluripotency, and the ability to tailor lineage differentiation, with a particular focus on endothelial cell differentiation for anti-cancer treatment, cell-based tissue engineering, and regenerative medicine strategies.

Effect of Notch expression in glioma stem cells on therapeutic response to chemo-radiotherapy in recurrent glioblastoma

Glioma stem cells (GSCs) have the capacity to repopulate tumors and mediate resistance to radiotherapy and chemotherapy. The Notch signaling pathway is important in proliferation, stem cell maintenance, cell differentiation, and tumorigenesis in GSCs. In this study, we compared CD133, Notch, and VEGF expressions in histological sections of primary and recurrent glioblastomas after radiotherapy and chemotherapy. In vitro study, the γ-secretase inhibitor inhibited NICD, Hes1 and pVEGFR2 expressions in GSCs. GSCs cultured under endothelial conditions undergo endothelial differentiation. Tumor samples were collected from 27 patients at the time of tumor recurrence. We used immunohistochemical techniques to compare expression of CD133, Notch-1 and VEGF. Expressions of CD133-, Notch-1-, and VEGF-positive glioma cells were higher in recurrent glioblastoma after radiotherapy and chemotherapy. To determine the clinical importance of Notch-1 expression in glioblastoma, we analyzed 15 patients who had received bevacizumab therapy followed by a second surgery at recurrence. OS was significantly longer in cases with Notch-1 negativity (8.8 months) than in those with I Notch-1 positivity (6.8 months). We noted that GSCs have the potential for endothelial differentiation with Notch activity. We believe that Notch-1 is a potential target and/or biomarker for antiangiogenic treatments.

The role of notch in the cardiovascular system: potential adverse effects of investigational notch inhibitors

Targeting the Notch pathway is a new promising therapeutic approach for cancer patients. Inhibition of Notch is effective in the oncology setting because it causes a reduction of highly proliferative tumor cells and it inhibits survival of cancer stem cells, which are considered responsible for tumor recurrence and metastasis. Additionally, since Delta-like ligand 4 (Dll4)-activated Notch signaling is a major modulator of angiogenesis, anti-Dll4 agents are being investigated to reduce vascularization of the tumor. Notch plays a major role in the heart during the development and, after birth, in response to cardiac damage. Therefore, agents used to inhibit Notch in the tumors (gamma secretase inhibitors and anti-Dll4 agents) could potentially affect myocardial repair. The past experience with trastuzumab and other tyrosine kinase inhibitors used for cancer therapy demonstrates that the possible cardiotoxicity of agents targeting shared pathways between cancer and heart and the vasculature should be considered. To date, Notch inhibition in cancer patients has resulted only in mild gastrointestinal toxicity. Little is known about the potential long-term cardiotoxicity associated to Notch inhibition in cancer patients. In this review, we will focus on mechanisms through which inhibition of Notch signaling could lead to cardiomyocytes and endothelial dysfunctions. These adverse effects could contrast with the benefits of therapeutic responses in cancer cells during times of increased cardiac stress and/or in the presence of cardiovascular risk factor.