•Lymphatics serve in draining interstitial fluid, in immune surveillance and fat absorption.•Lymphangiogenesis denotes formation of new lymphatics from pre-existing vessels.•Vascular endothelial ...growth factor C is an essential stimulator of lymphangiogenesis.•Lack of lymphatic function leads to painful and crippling edema.•Cancer may be accompanied by lymphangiogenesis, facilitating metastatic spread.
Lymphatic vessels are established by differentiation of lymphendothelial progenitors during embryogenesis. Lymphangiogenesis, the formation of new lymphatic vessels from pre-existing ones is rare in the healthy adult but takes place during pathological conditions such as inflammation, tissue repair and tumor growth. Conditions of dysfunctional lymphatics exist after surgical interventions or in certain genetic diseases. A key lymphangiogenic stimulator is vascular endothelial growth factor-C (VEGFC) acting on VEGF receptor-3 (VEGFR3) expressed on lymphendothelial cells. Other cytokines may act directly to regulate lymphangiogenesis positively or negatively, or indirectly by inducing expression of VEGFC. This review describes different known lymphangiogenic cytokines, their mechanism of action and role in lymphangiogenesis in health and disease.
Exaggerated signaling by vascular endothelial growth factor (VEGF)‐A and its receptor, VEGFR2, in pathologies results in poor vessel function. Still, pharmacological suppression of VEGFA/VEGFR2 may ...aggravate disease. Delineating VEGFR2 signaling in vivo provides strategies for suppression of specific VEGFR2‐induced pathways. Three VEGFR2 tyrosine residues (Y949, Y1212, and Y1173) induce downstream signaling. Here, we show that knock‐in of phenylalanine to create VEGFR2 Y1212F in C57Bl/6 and FVB mouse strains leads to loss of growth factor receptor‐bound protein 2‐ and phosphoinositide 3′‐kinase (PI3K)p85 signaling. C57Bl/6 Vegfr2Y1212F/Y1212F show reduced embryonic endothelial cell (EC) proliferation and partial lethality. FVB Vegfr2Y1212F/Y1212F show reduced postnatal EC proliferation. Reduced EC proliferation in Vegfr2Y1212F/Y1212F explants is rescued by c‐Myc overexpression. We conclude that VEGFR2 Y1212 signaling induces activation of extracellular‐signal‐regulated kinase (ERK)1/2 and Akt pathways required for c‐Myc‐dependent gene regulation, endothelial proliferation, and vessel stability.
Synopsis
Previously uncharacterized VEGFR2 phosphorylation at Y1212 promotes endothelial proliferation and vessel stability by a mechanism involving Erk1/2, Akt and c‐Myc dependent transcriptional regulation.
Phosphorylated VEGFR2 Y1212 binds GRB2 and PI3Kp85, and mediates activation of ERK1/2 and Akt signaling.
Reduced EC proliferation in Vegfr2 Y1212F explants is rescued by c‐Myc overexpression.
Vegfr2 Y1212F mutant mice are unable to activate c‐Myc, display suppressed endothelial cell proliferation and vascular deficiency.
Vegfr2 Y1212F mutation in the C57Bl/6 background leads to partial embryonic lethality.
Vegfr2 Y1212F mutation in the FVB background results in vascular deficiency in the postnatal stage only.
Previously uncharacterized VEGFR2 phosphorylation at Y1212 promotes endothelial proliferation and vessel stability by a mechanism involving Erk1/2, Akt and c‐Myc dependent transcriptional regulation.
The vasculature undergoes changes in diameter, permeability and blood flow in response to specific stimuli. The dynamics and interdependence of these responses in different vessels are largely ...unknown. Here we report a non-invasive technique to study dynamic events in different vessel categories by multi-photon microscopy and an image analysis tool, RVDM (relative velocity, direction, and morphology) allowing the identification of vessel categories by their red blood cell (RBC) parameters. Moreover, Claudin5 promoter-driven green fluorescent protein (GFP) expression is used to distinguish capillary subtypes. Intradermal injection of vascular endothelial growth factor A (VEGFA) is shown to induce leakage of circulating dextran, with vessel-type-dependent kinetics, from capillaries and venules devoid of GFP expression. VEGFA-induced leakage in capillaries coincides with vessel dilation and reduced flow velocity. Thus, intravital imaging of non-invasive stimulation combined with RVDM analysis allows for recording and quantification of very rapid events in the vasculature.
The specific role of VEGFA-induced permeability and vascular leakage in physiology and pathology has remained unclear. Here we show that VEGFA-induced vascular leakage depends on signalling initiated ...via the VEGFR2 phosphosite Y949, regulating dynamic c-Src and VE-cadherin phosphorylation. Abolished Y949 signalling in the mouse mutant Vegfr2(Y949F/Y949F) leads to VEGFA-resistant endothelial adherens junctions and a block in molecular extravasation. Vessels in Vegfr2(Y949F/Y949F) mice remain sensitive to inflammatory cytokines, and vascular morphology, blood pressure and flow parameters are normal. Tumour-bearing Vegfr2(Y949F/Y949F) mice display reduced vascular leakage and oedema, improved response to chemotherapy and, importantly, reduced metastatic spread. The inflammatory infiltration in the tumour micro-environment is unaffected. Blocking VEGFA-induced disassembly of endothelial junctions, thereby suppressing tumour oedema and metastatic spread, may be preferable to full vascular suppression in the treatment of certain cancer forms.
Olfactory neuroblastoma/esthesioneuroblastoma (ONB) is an uncommon neuroectodermal neoplasm thought to arise from the olfactory epithelium. Little is known about its molecular pathogenesis. For this ...study, a retrospective cohort of
n
= 66 tumor samples with the institutional diagnosis of ONB was analyzed by immunohistochemistry, genome-wide DNA methylation profiling, copy number analysis, and in a subset, next-generation panel sequencing of 560 tumor-associated genes. DNA methylation profiles were compared to those of relevant differential diagnoses of ONB. Unsupervised hierarchical clustering analysis of DNA methylation data revealed four subgroups among institutionally diagnosed ONB. The largest group (
n
= 42, 64%, Core ONB) presented with classical ONB histology and no overlap with other classes upon methylation profiling-based t-distributed stochastic neighbor embedding (t-SNE) analysis. A second DNA methylation group (
n
= 7, 11%) with CpG island methylator phenotype (CIMP) consisted of cases with strong expression of cytokeratin, no or scarce chromogranin A expression and
IDH2
hotspot mutation in all cases. T-SNE analysis clustered these cases together with sinonasal carcinoma with
IDH2
mutation. Four cases (6%) formed a small group characterized by an overall high level of DNA methylation, but without CIMP. The fourth group consisted of 13 cases that had heterogeneous DNA methylation profiles and strong cytokeratin expression in most cases. In t-SNE analysis, these cases mostly grouped among sinonasal adenocarcinoma, squamous cell carcinoma, and undifferentiated carcinoma. Copy number analysis indicated highly recurrent chromosomal changes among Core ONB with a high frequency of combined loss of chromosome 1–4, 8–10, and 12. NGS sequencing did not reveal highly recurrent mutations in ONB, with the only recurrently mutated genes being
TP53
and
DNMT3A
. In conclusion, we demonstrate that institutionally diagnosed ONB are a heterogeneous group of tumors. Expression of cytokeratin, chromogranin A, the mutational status of
IDH2
as well as DNA methylation patterns may greatly aid in the precise classification of ONB.
PALMD (palmdelphin) belongs to the family of paralemmin proteins implicated in cytoskeletal regulation. Single nucleotide polymorphisms in the
locus that result in reduced expression are strong risk ...factors for development of calcific aortic valve stenosis and predict severity of the disease.
Immunodetection and public database screening showed dominant expression of PALMD in endothelial cells (ECs) in brain and cardiovascular tissues including aortic valves. Mass spectrometry, coimmunoprecipitation, and immunofluorescent staining allowed identification of PALMD partners. The consequence of loss of PALMD expression was assessed in small interferring RNA-treated EC cultures, knockout mice, and human valve samples. RNA sequencing of ECs and transcript arrays on valve samples from an aortic valve study cohort including patients with the single nucleotide polymorphism rs7543130 informed about gene regulatory changes.
ECs express the cytosolic
splice variant, which associated with RANGAP1 (RAN GTP hydrolyase activating protein 1). RANGAP1 regulates the activity of the GTPase RAN and thereby nucleocytoplasmic shuttling via XPO1 (Exportin1). Reduced PALMD expression resulted in subcellular relocalization of RANGAP1 and XPO1, and nuclear arrest of the XPO1 cargoes p53 and p21. This indicates an important role for PALMD in nucleocytoplasmic transport and consequently in gene regulation because of the effect on localization of transcriptional regulators. Changes in EC responsiveness on loss of
expression included failure to form a perinuclear actin cap when exposed to flow, indicating lack of protection against mechanical stress. Loss of the actin cap correlated with misalignment of the nuclear long axis relative to the cell body, observed in
-deficient ECs,
mouse aorta, and human aortic valve samples derived from patients with calcific aortic valve stenosis. In agreement with these changes in EC behavior, gene ontology analysis showed enrichment of nuclear- and cytoskeleton-related terms in
-silenced ECs.
We identify RANGAP1 as a PALMD partner in ECs. Disrupting the PALMD/RANGAP1 complex alters the subcellular localization of RANGAP1 and XPO1, and leads to nuclear arrest of the XPO1 cargoes p53 and p21, accompanied by gene regulatory changes and loss of actin-dependent nuclear resilience. Combined, these consequences of reduced
expression provide a mechanistic underpinning for PALMD's contribution to calcific aortic valve stenosis pathology.
Angiogenesis is the result of the combined activity of the tumor microenvironment and signaling molecules. The angiogenic switch is represented as an imbalance between pro- and anti-angiogenic ...factors and is a rate-limiting step in the development of tumors. Eph receptor tyrosine kinases and their membrane-anchored ligands, known as ephrins, constitute the largest receptor tyrosine kinase (RTK) subfamily and are considered a major family of pro-angiogenic RTKs. Ewing sarcoma (EWS) is a highly aggressive bone and soft tissue tumor affecting children and young adults. As other solid tumors, EWS are reliant on a functional vascular network for the delivery of nutrients and oxygen and for the removal of waste. Based on the biological roles of EphA2 in promoting angiogenesis, we explored the functional role of this receptor and its relationship with caveolin-1 (CAV1) in EWS angiogenesis. We demonstrated that lack of CAV1 results in a significant reduction in micro vascular density (MVD) on 3 different in vivo models. In vitro, this phenomenon correlated with inactivation of EphA2 receptor, lack of AKT response and downregulation of bFGF. We also demonstrated that secreted bFGF from EWS cells acted as chemoattractant for endothelial cells. Furthermore, interaction between EphA2 and CAV1 was necessary for the right localization and signaling of the receptor to produce bFGF through AKT and promote migration of endothelial cells. Finally, introduction of a dominant-negative form of EphA2 into EWS cells mostly reproduced the effects occurred by CAV1 silencing, strongly suggesting that the axis EphA2-CAV1 participates in the promotion of endothelial cell migration toward the tumors favoring EWS angiogenesis.
The acute phase of myocardial infarction (MI) is accompanied by edema contributing to tissue damage and disease outcome. Here, we aimed to identify the mechanism whereby vascular endothelial growth ...factor (VEGF)-A induces myocardial edema in the acute phase of MI to eventually promote development of therapeutics to specifically suppress VEGFA-regulated vascular permeability while preserving collateral vessel formation.
VEGFA regulates vascular permeability and edema by activation of VEGF receptor-2 (VEGFR2), leading to induction of several signaling pathways including the cytoplasmic tyrosine kinase c-Src. The activated c-Src in turn phosphorylates vascular endothelial (VE)-cadherin, leading to dissociation of endothelial adherens junctions. A particular tyrosine at position 949 in mouse VEGFR2 has been shown to be required for activation of c-Src. Wild-type mice and mice with phenylalanine replacing tyrosine (Y) 949 in VEGFR2 (
) were challenged with MI through permanent ligation of the left anterior descending coronary artery. The infarct size was similar in wild-type and mutant mice, but left ventricular wall edema and fibrinogen deposition, indicative of vascular leakage, were reduced in the
strain. When challenged with large infarcts, the
mice survived significantly better than the wild-type strain. Moreover, neutrophil infiltration and levels of myeloperoxidase were low in the infarcted
hearts, correlating with improved survival.
tyrosine phosphorylation of VE-cadherin at Y685, implicated in regulation of vascular permeability, was induced by circulating VEGFA in the wild-type but remained at baseline levels in the
hearts.
Suppression of VEGFA/VEGFR2-regulated vascular permeability leads to diminished edema without affecting vascular density correlating with improved myocardial parameters and survival after MI.
Low-density lipoprotein (LDL) plasma concentration decline is a biomarker for acute inflammatory diseases, including coronavirus disease-2019 (COVID-19). Phenotypic changes in LDL during COVID-19 may ...be equally related to adverse clinical outcomes.
Individuals hospitalized due to COVID-19 (n = 40) were enrolled. Blood samples were collected on days 0, 2, 4, 6, and 30 (D0, D2, D4, D6, and D30). Oxidized LDL (ox-LDL), and lipoprotein-associated phospholipase A2 (Lp-PLA2) activity were measured. In a consecutive series of cases (n = 13), LDL was isolated by gradient ultracentrifugation from D0 and D6 and was quantified by lipidomic analysis. Association between clinical outcomes and LDL phenotypic changes was investigated.
In the first 30 days, 42.5% of participants died due to Covid-19. The serum ox-LDL increased from D0 to D6 (p < 0.005) and decreased at D30. Moreover, individuals who had an ox-LDL increase from D0 to D6 to over the 90th percentile died. The plasma Lp-PLA2 activity also increased progressively from D0 to D30 (p < 0.005), and the change from D0 to D6 in Lp-PLA2 and ox-LDL were positively correlated (r = 0.65, p < 0.0001). An exploratory untargeted lipidomic analysis uncovered 308 individual lipids in isolated LDL particles. Paired-test analysis from D0 and D6 revealed higher concentrations of 32 lipid species during disease progression, mainly represented by lysophosphatidyl choline and phosphatidylinositol. In addition, 69 lipid species were exclusively modulated in the LDL particles from non-survivors as compared to survivors.
Phenotypic changes in LDL particles are associated with disease progression and adverse clinical outcomes in COVID-19 patients and could serve as a potential prognostic biomarker.
•Oxidation in the apo-B moiety of ox-LDL increases during the acute phase of COVID-19 and is related to mortality.•Plasma Lp-PLA2 activity also increases and is related to the increase in ox-LDL.•Among non-survivors, 69 species of lipids in LDL were altered during disease progression.•Altered phospholipids (e.g., phosphatidylcholine) were found exclusively in LDL from non-survivors.
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