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CONTEXT: Heavy menstrual bleeding (HMB) is common and debilitating, but the precise endometrial mechanisms causing increased menstrual blood loss (MBL) remain undefined. We have previously identified a role for hypoxia in endometrial repair following progesterone withdrawal. OBJECTIVE: As hypoxia inducible factor 2 alpha (HIF2A) is known to alter vascular function in other tissues, we hypothesised that endometrial HIF2A is involved in pre-menstrual optimisation of endometrial function during the secretory phase to limit MBL. RESULTS: Women with objective HMB had higher endometrial HIF2A during the mid-secretory phase when compared to those with normal MBL (p=0.0269). In a mouse model of simulated menses, genetic or pharmacological manipulation of HIF2A did not significantly affect endometrial breakdown/repair, volume of MBL or endometrial hypoxia. However, 88% of Hif2a heterozygote mice reached early-full repair by 24h versus only 65% of wild-type mice. Mean MBL was 0.39 µl (±0.67) in Hif2a heterozygote mice versus 0.98 µl (±0.79) in wild-type mice. Conversely, when we increased HIF2A pre-menstrually, 11% reached early repair at by 8h versus 30% of vehicle-treated mice. Mean MBL was 2.61 µl (±1.10) in mice with HIF2A stabilisation and 2.24 µl (±1.14) in vehicle-treated mice. These non-significant but consistent trends indicate that increased endometrial HIF2A may contribute to delayed endometrial repair and HMB. CONCLUSIONS: Increased HIF2A in the secretory endometrium is unlikely to be sufficient to account for the phenotype of HMB, but limitation of HIF2 levels may optimise endometrial function at menstruation.
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Neuroinflammation and dysregulated energy metabolism are linked to motor neuron degeneration in amyotrophic lateral sclerosis (ALS). The egl-9 family hypoxia-inducible factor (EGLN) enzymes, also known as prolyl hydroxylase domain (PHD) enzymes, are metabolic sensors regulating cellular inflammation and metabolism. Using an oligonucleotide-based and a genetic approach, we showed that the downregulation of Egln2 protected motor neurons and mitigated the ALS phenotype in two zebrafish models and a mouse model of ALS. Single-nucleus RNA sequencing of the murine spinal cord revealed that the loss of EGLN2 induced an astrocyte-specific downregulation of interferon-stimulated genes, mediated via the stimulator of interferon genes (STING) protein. In addition, we found that the genetic deletion of EGLN2 restored this interferon response in patient induced pluripotent stem cell (iPSC)-derived astrocytes, confirming the link between EGLN2 and astrocytic interferon signaling. In conclusion, we identified EGLN2 as a motor neuron protective target normalizing the astrocytic interferon-dependent inflammatory axis in vivo, as well as in patient-derived cells.
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Type 2 alveolar epithelial (AT2) cells of the lung are fundamental in regulating alveolar inflammation in response to injury. Impaired mitochondrial long-chain fatty acid ß-oxidation (mtLCFAO) in AT2 cells is assumed to aggravate alveolar inflammation in acute lung injury (ALI), yet the importance of mtLCFAO to AT2 cell function needs to be defined. Here we show that expression of carnitine palmitoyltransferase 1a (CPT1a), a mtLCFAO rate limiting enzyme, in AT2 cells is significantly decreased in acute respiratory distress syndrome (ARDS). In mice, Cpt1a deletion in AT2 cells impairs mtLCFAO without reducing ATP production and alters surfactant phospholipid abundance in the alveoli. Impairing mtLCFAO in AT2 cells via deleting either Cpt1a or Acadl (acyl-CoA dehydrogenase long chain) restricts alveolar inflammation in ALI by hindering the production of the neutrophilic chemokine CXCL2 from AT2 cells. This study thus highlights mtLCFAO as immunometabolism to injury in AT2 cells and suggests impaired mtLCFAO in AT2 cells as an anti-inflammatory response in ARDS.
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Lesión Pulmonar Aguda , Células Epiteliales Alveolares , Carnitina O-Palmitoiltransferasa , Ácidos Grasos , Mitocondrias , Oxidación-Reducción , Síndrome de Dificultad Respiratoria , Animales , Carnitina O-Palmitoiltransferasa/metabolismo , Carnitina O-Palmitoiltransferasa/genética , Mitocondrias/metabolismo , Células Epiteliales Alveolares/metabolismo , Ácidos Grasos/metabolismo , Lesión Pulmonar Aguda/metabolismo , Lesión Pulmonar Aguda/patología , Lesión Pulmonar Aguda/inmunología , Lesión Pulmonar Aguda/genética , Ratones , Síndrome de Dificultad Respiratoria/metabolismo , Síndrome de Dificultad Respiratoria/inmunología , Síndrome de Dificultad Respiratoria/patología , Síndrome de Dificultad Respiratoria/genética , Masculino , Humanos , Quimiocina CXCL2/metabolismo , Quimiocina CXCL2/genética , Ratones Endogámicos C57BL , Neutrófilos/inmunología , Neutrófilos/metabolismo , Ratones Noqueados , Acil-CoA Deshidrogenasa de Cadena Larga/metabolismo , Acil-CoA Deshidrogenasa de Cadena Larga/genética , Inflamación/metabolismo , Inflamación/patología , Alveolos Pulmonares/metabolismo , Alveolos Pulmonares/patología , Alveolos Pulmonares/inmunología , Adenosina Trifosfato/metabolismo , Neumonía/metabolismo , Neumonía/inmunología , Neumonía/patología , Neumonía/genéticaRESUMEN
Neutrophils are sentinel immune cells with essential roles for antimicrobial defense. Most of our knowledge on neutrophil tissue navigation derived from wounding and infection models, whereas allergic conditions remained largely neglected. Here, we analyzed allergen-challenged mouse tissues and discovered that degranulating mast cells (MCs) trap living neutrophils inside them. MCs release the attractant leukotriene B4 to re-route neutrophils toward them, thus exploiting a chemotactic system that neutrophils normally use for intercellular communication. After MC intracellular trap (MIT) formation, neutrophils die, but their undigested material remains inside MC vacuoles over days. MCs benefit from MIT formation, increasing their functional and metabolic fitness. Additionally, they are more pro-inflammatory and can exocytose active neutrophilic compounds with a time delay (nexocytosis), eliciting a type 1 interferon response in surrounding macrophages. Together, our study highlights neutrophil trapping and nexocytosis as MC-mediated processes, which may relay neutrophilic features over the course of chronic allergic inflammation.
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A broad range of brain pathologies critically relies on the vasculature, and cerebrovascular disease is a leading cause of death worldwide. However, the cellular and molecular architecture of the human brain vasculature remains incompletely understood1. Here we performed single-cell RNA sequencing analysis of 606,380 freshly isolated endothelial cells, perivascular cells and other tissue-derived cells from 117 samples, from 68 human fetuses and adult patients to construct a molecular atlas of the developing fetal, adult control and diseased human brain vasculature. We identify extensive molecular heterogeneity of the vasculature of healthy fetal and adult human brains and across five vascular-dependent central nervous system (CNS) pathologies, including brain tumours and brain vascular malformations. We identify alteration of arteriovenous differentiation and reactivated fetal as well as conserved dysregulated genes and pathways in the diseased vasculature. Pathological endothelial cells display a loss of CNS-specific properties and reveal an upregulation of MHC class II molecules, indicating atypical features of CNS endothelial cells. Cell-cell interaction analyses predict substantial endothelial-to-perivascular cell ligand-receptor cross-talk, including immune-related and angiogenic pathways, thereby revealing a central role for the endothelium within brain neurovascular unit signalling networks. Our single-cell brain atlas provides insights into the molecular architecture and heterogeneity of the developing, adult/control and diseased human brain vasculature and serves as a powerful reference for future studies.
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Neoplasias Encefálicas , Encéfalo , Malformaciones Vasculares del Sistema Nervioso Central , Células Endoteliales , Feto , RNA-Seq , Análisis de Expresión Génica de una Sola Célula , Femenino , Humanos , Masculino , Encéfalo/irrigación sanguínea , Encéfalo/patología , Encéfalo/embriología , Encéfalo/metabolismo , Neoplasias Encefálicas/irrigación sanguínea , Neoplasias Encefálicas/patología , Comunicación Celular , Células Endoteliales/metabolismo , Células Endoteliales/patología , Células Endoteliales/citología , Feto/irrigación sanguínea , Feto/citología , Feto/embriología , Malformaciones Vasculares del Sistema Nervioso Central/patología , Antígenos HLA-D/metabolismo , Adulto , SaludRESUMEN
Growth-arrest specific 6 (GAS6) is a secreted protein that acts as a ligand for TAM receptors (TYRO3, AXL and MERTK). In humans, GAS6 circulating levels and genetic variations in GAS6 are associated with hyperglycemia and increased risk of type 2 diabetes. However, the mechanisms by which GAS6 influences glucose metabolism are not understood. Here, we show that Gas6 deficiency in mice increases insulin sensitivity and protects from diet-induced insulin resistance. Conversely, increasing GAS6 circulating levels is sufficient to reduce insulin sensitivity in vivo. GAS6 inhibits the activation of the insulin receptor (IR) and reduces insulin response in muscle cells in vitro and in vivo. Mechanistically, AXL and IR form a complex, while GAS6 reprograms signaling pathways downstream of IR. This results in increased IR endocytosis following insulin treatment. This study contributes to a better understanding of the cellular and molecular mechanisms by which GAS6 and AXL influence insulin sensitivity.
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Many individuals with cancer are resistant to immunotherapies. Here, we identify the gene encoding the pyrimidine salvage pathway enzyme cytidine deaminase (CDA) among the top upregulated metabolic genes in several immunotherapy-resistant tumors. We show that CDA in cancer cells contributes to the uridine diphosphate (UDP) pool. Extracellular UDP hijacks immunosuppressive tumor-associated macrophages (TAMs) through its receptor P2Y6. Pharmacologic or genetic inhibition of CDA in cancer cells (or P2Y6 in TAMs) disrupts TAM-mediated immunosuppression, promoting cytotoxic T cell entry and susceptibility to anti-programmed cell death protein 1 (anti-PD-1) treatment in resistant pancreatic ductal adenocarcinoma (PDAC) and melanoma models. Conversely, CDA overexpression in CDA-depleted PDACs or anti-PD-1-responsive colorectal tumors or systemic UDP administration (re)establishes resistance. In individuals with PDAC, high CDA levels in cancer cells correlate with increased TAMs, lower cytotoxic T cells and possibly anti-PD-1 resistance. In a pan-cancer single-cell atlas, CDAhigh cancer cells match with T cell cytotoxicity dysfunction and P2RY6high TAMs. Overall, we suggest CDA and P2Y6 as potential targets for cancer immunotherapy.
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Resistencia a Antineoplásicos , Inmunoterapia , Uridina Difosfato , Humanos , Uridina Difosfato/metabolismo , Inmunoterapia/métodos , Resistencia a Antineoplásicos/inmunología , Animales , Ratones , Carcinoma Ductal Pancreático/inmunología , Carcinoma Ductal Pancreático/terapia , Carcinoma Ductal Pancreático/tratamiento farmacológico , Citidina Desaminasa/metabolismo , Citidina Desaminasa/genética , Macrófagos Asociados a Tumores/inmunología , Macrófagos Asociados a Tumores/metabolismo , Línea Celular Tumoral , Receptores Purinérgicos P2/metabolismo , Macrófagos/inmunología , Macrófagos/metabolismo , Linfocitos T Citotóxicos/inmunología , Linfocitos T Citotóxicos/efectos de los fármacos , Microambiente Tumoral/inmunología , Neoplasias Pancreáticas/inmunología , Neoplasias Pancreáticas/terapia , Neoplasias Pancreáticas/tratamiento farmacológico , Nucleótidos/metabolismo , Tolerancia Inmunológica , Receptor de Muerte Celular Programada 1RESUMEN
BACKGROUND & AIMS: Cystic fibrosis (CF) is considered a multisystemic disorder in which CF-associated liver disease (CFLD) is the third most common cause of mortality. Currently, no effective treatment is available for CFLD because its pathophysiology is still unclear. Interestingly, CFLD exhibits identical vascular characteristics as non-cirrhotic portal hypertension, recently classified as porto-sinusoidal vascular disorders (PSVD). METHODS: Since endothelial cells (ECs) are an important component in PSVD, we performed single-cell RNA sequencing (scRNA-seq) on four explant livers from CFLD patients to identify differential endothelial characteristics which could contribute to the disease. We comprehensively characterized the endothelial compartment and compared it with publicly available scRNA-seq datasets from cirrhotic and healthy livers. Key gene signatures were validated ex vivo on patient tissues. RESULTS: We found that ECs from CF liver explants are more closely related to healthy than cirrhotic patients. In CF patients we also discovered a distinct population of liver sinusoidal ECs-coined CF LSECs-upregulating genes involved in the complement cascade and coagulation. Finally, our immunostainings further validated the predominant periportal location of CF LSECs. CONCLUSIONS: Our work showed novel aspects of human liver ECs at the single-cell level thereby supporting endothelial involvement in CFLD, and reinforcing the hypothesis that ECs could be a driver of PSVD. Therefore, considering the vascular compartment in CF and CFLD may help developing new therapeutic approaches for these diseases.
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Activación de Complemento , Fibrosis Quística , Células Endoteliales , Análisis de Secuencia de ARN , Análisis de la Célula Individual , Humanos , Fibrosis Quística/genética , Células Endoteliales/metabolismo , Hígado/patología , Hígado/metabolismo , Masculino , Femenino , Adulto , Cirrosis Hepática/genética , Cirrosis Hepática/patología , Hepatopatías/genéticaRESUMEN
The energy cost of neuronal activity is mainly sustained by glucose1,2. However, in an apparent paradox, neurons modestly metabolize glucose through glycolysis3-6, a circumstance that can be accounted for by the constant degradation of 6-phosphofructo-2-kinase-fructose-2,6-bisphosphatase-3 (PFKFB3)3,7,8, a key glycolysis-promoting enzyme. To evaluate the in vivo physiological importance of this hypoglycolytic metabolism, here we genetically engineered mice with their neurons transformed into active glycolytic cells through Pfkfb3 expression. In vivo molecular, biochemical and metabolic flux analyses of these neurons revealed an accumulation of anomalous mitochondria, complex I disassembly, bioenergetic deficiency and mitochondrial redox stress. Notably, glycolysis-mediated nicotinamide adenine dinucleotide (NAD+) reduction impaired sirtuin-dependent autophagy. Furthermore, these mice displayed cognitive decline and a metabolic syndrome that was mimicked by confining Pfkfb3 expression to hypothalamic neurons. Neuron-specific genetic ablation of mitochondrial redox stress or brain NAD+ restoration corrected these behavioural alterations. Thus, the weak glycolytic nature of neurons is required to sustain higher-order organismal functions.
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Cognición , Glucólisis , Neuronas , Fosfofructoquinasa-2 , Animales , Neuronas/metabolismo , Ratones , Fosfofructoquinasa-2/metabolismo , Fosfofructoquinasa-2/genética , Cognición/fisiología , Mitocondrias/metabolismo , Metabolismo Energético , NAD/metabolismo , Glucosa/metabolismoRESUMEN
Endothelial cells (ECs) are highly glycolytic, but whether they generate glycolytic intermediates via gluconeogenesis (GNG) in glucose-deprived conditions remains unknown. Here, we report that glucose-deprived ECs upregulate the GNG enzyme PCK2 and rely on a PCK2-dependent truncated GNG, whereby lactate and glutamine are used for the synthesis of lower glycolytic intermediates that enter the serine and glycerophospholipid biosynthesis pathways, which can play key roles in redox homeostasis and phospholipid synthesis, respectively. Unexpectedly, however, even in normal glucose conditions, and independent of its enzymatic activity, PCK2 silencing perturbs proteostasis, beyond its traditional GNG role. Indeed, PCK2-silenced ECs have an impaired unfolded protein response, leading to accumulation of misfolded proteins, which due to defective proteasomes and impaired autophagy, results in the accumulation of protein aggregates in lysosomes and EC demise. Ultimately, loss of PCK2 in ECs impaired vessel sprouting. This study identifies a role for PCK2 in proteostasis beyond GNG.
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Células Endoteliales , Gluconeogénesis , Fosfoenolpiruvato Carboxiquinasa (GTP) , Proteostasis , Gluconeogénesis/genética , Humanos , Células Endoteliales/metabolismo , Fosfoenolpiruvato Carboxiquinasa (GTP)/metabolismo , Fosfoenolpiruvato Carboxiquinasa (GTP)/genética , Células Endoteliales de la Vena Umbilical Humana/metabolismo , Glucosa/metabolismo , Autofagia , Respuesta de Proteína Desplegada , Fosfoenolpiruvato Carboxiquinasa (ATP)RESUMEN
Cancer cells re-program normal lung endothelial cells (EC) into tumor-associated endothelial cells (TEC) that form leaky vessels supporting carcinogenesis. Transcriptional regulators that control the reprogramming of EC into TEC are poorly understood. We identified Forkhead box F1 (FOXF1) as a critical regulator of EC-to-TEC transition. FOXF1 was highly expressed in normal lung vasculature but was decreased in TEC within non-small cell lung cancers (NSCLC). Low FOXF1 correlated with poor overall survival of NSCLC patients. In mice, endothelial-specific deletion of FOXF1 decreased pericyte coverage, increased vessel permeability and hypoxia, and promoted lung tumor growth and metastasis. Endothelial-specific overexpression of FOXF1 normalized tumor vessels and inhibited the progression of lung cancer. FOXF1 deficiency decreased Wnt/ß-catenin signaling in TECs through direct transcriptional activation of Fzd4. Restoring FZD4 expression in FOXF1-deficient TECs through endothelial-specific nanoparticle delivery of Fzd4 cDNA rescued Wnt/ß-catenin signaling in TECs, normalized tumor vessels and inhibited the progression of lung cancer. Altogether, FOXF1 increases tumor vessel stability, and inhibits lung cancer progression by stimulating FZD4/Wnt/ß-catenin signaling in TECs. Nanoparticle delivery of FZD4 cDNA has promise for future therapies in NSCLC.
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Células Endoteliales , Factores de Transcripción Forkhead , Receptores Frizzled , Neoplasias Pulmonares , Animales , Humanos , Ratones , Carcinoma de Pulmón de Células no Pequeñas/patología , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/irrigación sanguínea , Progresión de la Enfermedad , Células Endoteliales/metabolismo , Células Endoteliales/patología , Factores de Transcripción Forkhead/metabolismo , Factores de Transcripción Forkhead/genética , Receptores Frizzled/metabolismo , Receptores Frizzled/genética , Neoplasias Pulmonares/patología , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/irrigación sanguínea , Neoplasias Pulmonares/metabolismo , Neovascularización Patológica/genética , Vía de Señalización WntRESUMEN
Metabolism has recently emerged as a major target of genes implicated in the evolutionary expansion of human neocortex. One such gene is the human-specific gene ARHGAP11B. During human neocortex development, ARHGAP11B increases the abundance of basal radial glia, key progenitors for neocortex expansion, by stimulating glutaminolysis (glutamine-to-glutamate-to-alpha-ketoglutarate) in mitochondria. Here we show that the ape-specific protein GLUD2 (glutamate dehydrogenase 2), which also operates in mitochondria and converts glutamate-to-αKG, enhances ARHGAP11B's ability to increase basal radial glia abundance. ARHGAP11B + GLUD2 double-transgenic bRG show increased production of aspartate, a metabolite essential for cell proliferation, from glutamate via alpha-ketoglutarate and the TCA cycle. Hence, during human evolution, a human-specific gene exploited the existence of another gene that emerged during ape evolution, to increase, via concerted changes in metabolism, progenitor abundance and neocortex size.
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Proteínas Activadoras de GTPasa , Glutamato Deshidrogenasa , Neocórtex , Neocórtex/metabolismo , Neocórtex/embriología , Neocórtex/crecimiento & desarrollo , Neocórtex/citología , Humanos , Animales , Glutamato Deshidrogenasa/metabolismo , Glutamato Deshidrogenasa/genética , Proteínas Activadoras de GTPasa/metabolismo , Proteínas Activadoras de GTPasa/genética , Ácidos Cetoglutáricos/metabolismo , Neuroglía/metabolismo , Ácido Glutámico/metabolismo , Mitocondrias/metabolismo , Mitocondrias/genética , Ratones , Ciclo del Ácido Cítrico/genética , FemeninoRESUMEN
Natural killer (NK) cells are a vital part of the innate immune system capable of rapidly clearing mutated or infected cells from the body and promoting an immune response. Here, we find that NK cells activated by viral infection or tumor challenge increase uptake of fatty acids and their expression of carnitine palmitoyltransferase I (CPT1A), a critical enzyme for long-chain fatty acid oxidation. Using a mouse model with an NK cell-specific deletion of CPT1A, combined with stable 13C isotope tracing, we observe reduced mitochondrial function and fatty acid-derived aspartate production in CPT1A-deficient NK cells. Furthermore, CPT1A-deficient NK cells show reduced proliferation after viral infection and diminished protection against cancer due to impaired actin cytoskeleton rearrangement. Together, our findings highlight that fatty acid oxidation promotes NK cell metabolic resilience, processes that can be optimized in NK cell-based immunotherapies.
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Neoplasias , Virosis , Humanos , Metabolismo de los Lípidos , Células Asesinas Naturales , Ácidos GrasosRESUMEN
Hypoxia-inducible factors (HIFs) are highly conserved transcription factors that are crucial for adaptation of metazoans to limited oxygen availability. Recently, HIF activation and inhibition have emerged as therapeutic targets in various human diseases. Pharmacologically desirable effects of HIF activation include erythropoiesis stimulation, cellular metabolism optimization during hypoxia and adaptive responses during ischaemia and inflammation. By contrast, HIF inhibition has been explored as a therapy for various cancers, retinal neovascularization and pulmonary hypertension. This Review discusses the biochemical mechanisms that control HIF stabilization and the molecular strategies that can be exploited pharmacologically to activate or inhibit HIFs. In addition, we examine medical conditions that benefit from targeting HIFs, the potential side effects of HIF activation or inhibition and future challenges in this field.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Neoplasias , Humanos , Hipoxia/tratamiento farmacológico , Hipoxia/metabolismo , Factores de Transcripción , Neoplasias/tratamiento farmacológico , OxígenoRESUMEN
Angiogenesis and lymphangiogenesis, the formation of new blood or lymphatic vessels, respectively, from preexisting vasculature is essential during embryonic development, but also occurs during tissue repair and in pathological conditions (cancer; ocular disease; ischemic, infectious and inflammatory disorders), which are all characterized to a certain extent by inflammatory conditions. Hence, a rapid, inexpensive, feasible / technically easy, reliable assay of inflammation-induced (lymph-)angiogenesis is highly valuable. In this context, the corneal thermal cauterization assay in mice is a simple, low-cost, reproducible, insightful and labor-saving assay to gauge the role of inflammation in angiogenesis and lymphangiogenesis. However, to the best of our knowledge, there is no standardized protocol to perform this assay. Here, we provide a step-by-step description of the model's procedures, which include:â¢The thermal cauterization of the corneas,â¢Enucleation and dissection of the corneas,â¢Subsequent immunofluorescence staining of the neovasculature, and morphometric analysis. We also discuss ethical considerations and aspects related to animal welfare guidelines. Altogether, this paper will help to increase the reproducibility of the corneal thermal cauterization model and facilitate its use for angiogenesis and lymphangiogenesis research.
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Although VEGF-B was discovered as a VEGF-A homolog a long time ago, the angiogenic effect of VEGF-B remains poorly understood with limited and diverse findings from different groups. Notwithstanding, drugs that inhibit VEGF-B together with other VEGF family members are being used to treat patients with various neovascular diseases. It is therefore critical to have a better understanding of the angiogenic effect of VEGF-B and the underlying mechanisms. Using comprehensive in vitro and in vivo methods and models, we reveal here for the first time an unexpected and surprising function of VEGF-B as an endogenous inhibitor of angiogenesis by inhibiting the FGF2/FGFR1 pathway when the latter is abundantly expressed. Mechanistically, we unveil that VEGF-B binds to FGFR1, induces FGFR1/VEGFR1 complex formation, and suppresses FGF2-induced Erk activation, and inhibits FGF2-driven angiogenesis and tumor growth. Our work uncovers a previously unrecognized novel function of VEGF-B in tethering the FGF2/FGFR1 pathway. Given the anti-angiogenic nature of VEGF-B under conditions of high FGF2/FGFR1 levels, caution is warranted when modulating VEGF-B activity to treat neovascular diseases.
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Factor 2 de Crecimiento de Fibroblastos , Factor B de Crecimiento Endotelial Vascular , Humanos , Factor 2 de Crecimiento de Fibroblastos/genética , Inmunoterapia , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/genéticaRESUMEN
Whole-body glucose homeostasis is coordinated through secretion of glucagon and insulin from pancreatic islets. When glucose is low, glucagon is released from α-cells to stimulate hepatic glucose production. However, the mechanisms that regulate glucagon secretion from pancreatic α-cells remain unclear. Here we show that in α-cells, the interaction between fatty acid oxidation and glucose metabolism controls glucagon secretion. The glucose-dependent inhibition of glucagon secretion relies on pyruvate dehydrogenase and carnitine palmitoyl transferase 1a activity and lowering of mitochondrial fatty acid oxidation by increases in glucose. This results in reduced intracellular ATP and leads to membrane repolarization and inhibition of glucagon secretion. These findings provide a new framework for the metabolic regulation of the α-cell, where regulation of fatty acid oxidation by glucose accounts for the stimulation and inhibition of glucagon secretion. ARTICLE HIGHLIGHTS: It has become clear that dysregulation of glucagon secretion and α-cell function plays an important role in the development of diabetes, but we do not know how glucagon secretion is regulated. Here we asked whether glucose inhibits fatty acid oxidation in α-cells to regulate glucagon secretion. We found that fatty acid oxidation is required for the inhibitory effects of glucose on glucagon secretion through reductions in ATP. These findings provide a new framework for the regulation of glucagon secretion by glucose.
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Células Secretoras de Glucagón , Islotes Pancreáticos , Adenosina Trifosfato/metabolismo , Glucemia/metabolismo , Ácidos Grasos/metabolismo , Glucagón/metabolismo , Células Secretoras de Glucagón/metabolismo , Glucosa/farmacología , Glucosa/metabolismo , Insulina/metabolismo , Islotes Pancreáticos/metabolismo , Humanos , Animales , RatonesRESUMEN
Having direct access to brain vasculature, astrocytes can take up available blood nutrients and metabolize them to fulfil their own energy needs and deliver metabolic intermediates to local synapses1,2. These glial cells should be, therefore, metabolically adaptable to swap different substrates. However, in vitro and in vivo studies consistently show that astrocytes are primarily glycolytic3-7, suggesting glucose is their main metabolic precursor. Notably, transcriptomic data8,9 and in vitro10 studies reveal that mouse astrocytes are capable of mitochondrially oxidizing fatty acids and that they can detoxify excess neuronal-derived fatty acids in disease models11,12. Still, the factual metabolic advantage of fatty acid use by astrocytes and its physiological impact on higher-order cerebral functions remain unknown. Here, we show that knockout of carnitine-palmitoyl transferase-1A (CPT1A)-a key enzyme of mitochondrial fatty acid oxidation-in adult mouse astrocytes causes cognitive impairment. Mechanistically, decreased fatty acid oxidation rewired astrocytic pyruvate metabolism to facilitate electron flux through a super-assembled mitochondrial respiratory chain, resulting in attenuation of reactive oxygen species formation. Thus, astrocytes naturally metabolize fatty acids to preserve the mitochondrial respiratory chain in an energetically inefficient disassembled conformation that secures signalling reactive oxygen species and sustains cognitive performance.