RESUMEN
Adipose tissue hypoxia and inflammation have been causally implicated in obesity-induced insulin resistance. Here, we report that, early in the course of high-fat diet (HFD) feeding and obesity, adipocyte respiration becomes uncoupled, leading to increased oxygen consumption and a state of relative adipocyte hypoxia. These events are sufficient to trigger HIF-1α induction, setting off the chronic adipose tissue inflammatory response characteristic of obesity. At the molecular level, these events involve saturated fatty acid stimulation of the adenine nucleotide translocase 2 (ANT2), an inner mitochondrial membrane protein, which leads to the uncoupled respiratory state. Genetic or pharmacologic inhibition of either ANT2 or HIF-1α can prevent or reverse these pathophysiologic events, restoring a state of insulin sensitivity and glucose tolerance. These results reveal the sequential series of events in obesity-induced inflammation and insulin resistance.
Asunto(s)
Adipocitos/metabolismo , Dieta Alta en Grasa , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Resistencia a la Insulina , Obesidad/metabolismo , Oxígeno/metabolismo , Translocador 2 del Nucleótido Adenina/metabolismo , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Hipoxia de la Célula , Ácidos Grasos/metabolismo , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Inflamación/metabolismo , Ácido Láctico/metabolismo , Ratones , Ratones Noqueados , Óxido Nítrico/metabolismoRESUMEN
Cytolytic activity by CD8(+) cytotoxic T lymphocytes (CTLs) is a powerful strategy for the elimination of intracellular pathogens and tumor cells. The destructive capacity of CTLs is progressively dampened during chronic infection, yet the environmental cues and molecular pathways that influence immunological 'exhaustion' remain unclear. Here we found that CTL immunity was regulated by the central transcriptional response to hypoxia, which is controlled in part by hypoxia-inducible factors (HIFs) and the von Hippel-Lindau tumor suppressor VHL. Loss of VHL, the main negative regulator of HIFs, led to lethal CTL-mediated immunopathology during chronic infection, and VHL-deficient CTLs displayed enhanced control of persistent viral infection and neoplastic growth. We found that HIFs and oxygen influenced the expression of pivotal transcription, effector and costimulatory-inhibitory molecules of CTLs, which was relevant to strategies that promote the clearance of viruses and tumors.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/inmunología , Subunidad alfa del Factor 1 Inducible por Hipoxia/inmunología , Melanoma Experimental/inmunología , Neoplasias Cutáneas/inmunología , Linfocitos T Citotóxicos/inmunología , Proteína Supresora de Tumores del Síndrome de Von Hippel-Lindau/inmunología , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/deficiencia , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Hipoxia de la Célula/inmunología , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/deficiencia , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Coriomeningitis Linfocítica/inmunología , Coriomeningitis Linfocítica/patología , Coriomeningitis Linfocítica/virología , Virus de la Coriomeningitis Linfocítica/inmunología , Melanoma Experimental/mortalidad , Melanoma Experimental/patología , Melanoma Experimental/virología , Ratones , Ratones Noqueados , Oxígeno/farmacología , Transducción de Señal/efectos de los fármacos , Neoplasias Cutáneas/mortalidad , Neoplasias Cutáneas/patología , Neoplasias Cutáneas/virología , Análisis de Supervivencia , Linfocitos T Citotóxicos/patología , Transcripción Genética/efectos de los fármacos , Proteína Supresora de Tumores del Síndrome de Von Hippel-Lindau/genéticaRESUMEN
Extensive metabolic changes accompany T cell activation, including a switch to glycolytic energy production and increased biosynthesis. Recent studies suggest that subsequent return to reliance on oxidative phosphorylation and increasing spare respiratory capacity are essential for the differentiation of memory CD8+ T cells. In contrast, we found that constitutive glycolytic metabolism and suppression of oxidative phosphorylation in CD8+ T cells, achieved by conditional deletion of hypoxia-inducible factor regulator Vhl, accelerated CD8+ memory cell differentiation during viral infection. Despite sustained glycolysis, CD8+ memory cells emerged that upregulated key memory-associated cytokine receptors and transcription factors and showed a heightened response to secondary challenge. In addition, increased glycolysis not only permitted memory formation, but it also favored the formation of long-lived effector-memory CD8+ T cells. These data redefine the role of cellular metabolism in memory cell differentiation, showing that reliance on glycolytic metabolism does not hinder formation of a protective memory population.
Asunto(s)
Infecciones por Arenaviridae/inmunología , Linfocitos T CD8-positivos/inmunología , Glucólisis/inmunología , Memoria Inmunológica/inmunología , Activación de Linfocitos/inmunología , Animales , Infecciones por Arenaviridae/metabolismo , Linfocitos T CD8-positivos/metabolismo , Diferenciación Celular/inmunología , Separación Celular , Modelos Animales de Enfermedad , Citometría de Flujo , Virus de la Coriomeningitis Linfocítica , Ratones , Ratones Transgénicos , Fosforilación OxidativaRESUMEN
The hypoxic response in cells and tissues is mediated by the family of hypoxia-inducible factor (HIF) transcription factors; these play an integral role in the metabolic changes that drive cellular adaptation to low oxygen availability. HIF expression and stabilization in immune cells can be triggered by hypoxia, but also by other factors associated with pathological stress: e.g., inflammation, infectious microorganisms, and cancer. HIF induces a number of aspects of host immune function, from boosting phagocyte microbicidal capacity to driving T cell differentiation and cytotoxic activity. Cellular metabolism is emerging as a key regulator of immunity, and it constitutes another layer of fine-tuned immune control by HIF that can dictate myeloid cell and lymphocyte development, fate, and function. Here we discuss how oxygen sensing in the immune microenvironment shapes immunological response and examine how HIF and the hypoxia pathway control innate and adaptive immunity.
Asunto(s)
Inmunidad Adaptativa , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/inmunología , Subunidad alfa del Factor 1 Inducible por Hipoxia/inmunología , Inmunidad Innata , Inflamación/inmunología , Adaptación Fisiológica , Animales , Infecciones Bacterianas/inmunología , Diferenciación Celular/inmunología , Hipoxia de la Célula/inmunología , Humanos , Inflamación/genética , Ratones , Neoplasias/inmunología , Oxígeno/metabolismo , Linfocitos T/inmunología , Virosis/inmunologíaRESUMEN
[Figure: see text].
Asunto(s)
Quimiocina CXCL12/metabolismo , Isquemia/terapia , Macrófagos/fisiología , Músculo Esquelético/irrigación sanguínea , Óxido Nítrico Sintasa de Tipo II/metabolismo , Flujo Sanguíneo Regional/fisiología , Animales , Movimiento Celular , Proliferación Celular , Quimiocina CCL2/metabolismo , Humanos , Isquemia/fisiopatología , Macrófagos/citología , Macrófagos/metabolismo , Ratones , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo II/deficiencia , Óxido Nítrico Sintasa de Tipo III/metabolismo , Plásmidos/metabolismo , Receptores CCR2/metabolismo , Receptores CXCR4/metabolismoRESUMEN
Skin plays an essential role, mediated in part by its remarkable vascular plasticity, in adaptation to environmental stimuli. Certain vertebrates, such as amphibians, respond to hypoxia in part through the skin; but it is unknown whether this tissue can influence mammalian systemic adaptation to low oxygen levels. We have found that epidermal deletion of the hypoxia-responsive transcription factor HIF-1alpha inhibits renal erythropoietin (EPO) synthesis in response to hypoxia. Conversely, mice with an epidermal deletion of the von Hippel-Lindau (VHL) factor, a negative regulator of HIF, have increased EPO synthesis and polycythemia. We show that nitric oxide release induced by the HIF pathway acts on cutaneous vascular flow to increase systemic erythropoietin expression. These results demonstrate that in mice the skin is a critical mediator of systemic responses to environmental oxygen.
Asunto(s)
Epidermis/fisiología , Oxígeno/metabolismo , Animales , Análisis Químico de la Sangre , Eritropoyetina/metabolismo , Humanos , Factor 1 Inducible por Hipoxia/genética , Factor 1 Inducible por Hipoxia/metabolismo , Queratinocitos/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Óxido Nítrico/sangre , Oxígeno/sangre , Proteína Supresora de Tumores del Síndrome de Von Hippel-Lindau/genética , Proteína Supresora de Tumores del Síndrome de Von Hippel-Lindau/metabolismoRESUMEN
IgG antibodies cause inflammation and organ damage in autoimmune diseases such as systemic lupus erythematosus (SLE). We investigated the metabolic profile of macrophages isolated from inflamed tissues in immune complex (IC)-associated diseases, including SLE and rheumatoid arthritis, and following IgG Fcγ receptor cross-linking. We found that human and mouse macrophages undergo a switch to glycolysis in response to IgG IC stimulation, mirroring macrophage metabolic changes in inflamed tissue in vivo. This metabolic reprogramming was required to generate a number of proinflammatory mediators, including IL-1ß, and was dependent on mTOR and hypoxia-inducible factor (HIF)1α. Inhibition of glycolysis, or genetic depletion of HIF1α, attenuated IgG IC-induced activation of macrophages in vitro, including primary human kidney macrophages. In vivo, glycolysis inhibition led to a reduction in kidney macrophage IL-1ß and reduced neutrophil recruitment in a murine model of antibody-mediated nephritis. Together, our data reveal the molecular mechanisms underpinning FcγR-mediated metabolic reprogramming in macrophages and suggest a therapeutic strategy for autoantibody-induced inflammation, including lupus nephritis.
Asunto(s)
Reprogramación Celular/fisiología , Nefritis Lúpica/metabolismo , Animales , Células Cultivadas , Dinoprostona/genética , Dinoprostona/metabolismo , Metabolismo Energético , Regulación de la Expresión Génica , Glucólisis/fisiología , Humanos , Inmunoglobulina G/metabolismo , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Riñón/citología , Macrófagos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Especies Reactivas de Oxígeno , Receptores de IgG/genética , Receptores de IgG/metabolismoRESUMEN
R-2-hydroxyglutarate accumulates to millimolar levels in cancer cells with gain-of-function isocitrate dehydrogenase 1/2 mutations. These levels of R-2-hydroxyglutarate affect 2-oxoglutarate-dependent dioxygenases. Both metabolite enantiomers, R- and S-2-hydroxyglutarate, are detectible in healthy individuals, yet their physiological function remains elusive. Here we show that 2-hydroxyglutarate accumulates in mouse CD8+ T cells in response to T-cell receptor triggering, and accumulates to millimolar levels in physiological oxygen conditions through a hypoxia-inducible factor 1-alpha (HIF-1α)-dependent mechanism. S-2-hydroxyglutarate predominates over R-2-hydroxyglutarate in activated T cells, and we demonstrate alterations in markers of CD8+ T-cell differentiation in response to this metabolite. Modulation of histone and DNA demethylation, as well as HIF-1α stability, mediate these effects. S-2-hydroxyglutarate treatment greatly enhances the in vivo proliferation, persistence and anti-tumour capacity of adoptively transferred CD8+ T cells. Thus, S-2-hydroxyglutarate acts as an immunometabolite that links environmental context, through a metabolic-epigenetic axis, to immune fate and function.
Asunto(s)
Linfocitos T CD8-positivos/citología , Linfocitos T CD8-positivos/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , Glutaratos/farmacología , Animales , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/metabolismo , ADN/química , ADN/metabolismo , Metilación de ADN/efectos de los fármacos , Dioxigenasas/metabolismo , Glutaratos/inmunología , Glutaratos/metabolismo , Histonas/metabolismo , Homeostasis/efectos de los fármacos , Hipoxia/metabolismo , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Ácidos Cetoglutáricos/metabolismo , Activación de Linfocitos , Lisina/metabolismo , Ratones , Oxígeno/metabolismo , Estabilidad Proteica , Receptores de Antígenos de Linfocitos T/inmunología , Proteína Supresora de Tumores del Síndrome de Von Hippel-Lindau/metabolismoRESUMEN
The Himalayan Sherpas, a human population of Tibetan descent, are highly adapted to life in the hypobaric hypoxia of high altitude. Mechanisms involving enhanced tissue oxygen delivery in comparison to Lowlander populations have been postulated to play a role in such adaptation. Whether differences in tissue oxygen utilization (i.e., metabolic adaptation) underpin this adaptation is not known, however. We sought to address this issue, applying parallel molecular, biochemical, physiological, and genetic approaches to the study of Sherpas and native Lowlanders, studied before and during exposure to hypobaric hypoxia on a gradual ascent to Mount Everest Base Camp (5,300 m). Compared with Lowlanders, Sherpas demonstrated a lower capacity for fatty acid oxidation in skeletal muscle biopsies, along with enhanced efficiency of oxygen utilization, improved muscle energetics, and protection against oxidative stress. This adaptation appeared to be related, in part, to a putatively advantageous allele for the peroxisome proliferator-activated receptor A (PPARA) gene, which was enriched in the Sherpas compared with the Lowlanders. Our findings suggest that metabolic adaptations underpin human evolution to life at high altitude, and could have an impact upon our understanding of human diseases in which hypoxia is a feature.
Asunto(s)
Adaptación Fisiológica , Altitud , Etnicidad , Hipoxia/metabolismo , Adaptación Fisiológica/genética , Adulto , Presión Atmosférica , Ciclo del Ácido Cítrico , Metabolismo Energético , Etnicidad/genética , Ácidos Grasos/metabolismo , Femenino , Frecuencia de los Genes , Glucosa/metabolismo , Glucólisis , Humanos , Hipoxia/genética , Hipoxia/fisiopatología , Masculino , Mitocondrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Nepal , Óxido Nítrico/sangre , Fosforilación Oxidativa , Estrés Oxidativo , Consumo de Oxígeno , PPAR alfa/genética , PPAR alfa/metabolismo , Polimorfismo de Nucleótido Simple , Tibet/etnologíaRESUMEN
Hypoxia-inducible factors (HIFs) play a critical role in inflammatory properties of myeloid-derived cells. The effect of HIFs on myeloid-derived cell functions in organ transplantation remains unknown, however. We transplanted hearts into transgenic mice with myeloid cell-targeted deletions of HIF-1α or its negative regulator von Hippel-Lindau (VHL) to investigate the effects of HIF-1α inactivation or HIF pathway activation, respectively, on ischemia-reperfusion injury (IRI) and acute rejection. Deletion of VHL in myeloid cells enhanced mRNA expression of anti-inflammatory genes IDO, Arg-1, and HO-1 in vitro. In vivo, VHL-/- myeloid-derived cells of allograft recipients alleviated IRI and acute rejection, evidenced by reduced cardiomyocyte damage, decreased proinflammatory cytokine mRNA levels, and absence of inflammatory infiltrate at 5 days after transplantation. Ultimately, allograft survival was significantly prolonged. In vitro, VHL-/- myeloid-derived cells dose-dependently inhibited T-cell proliferation. Myeloid cells with HIF-1α-deletion retained proinflammatory qualities in vitro and in vivo. Deletion of VHL in myeloid cells of nonimmunosuppressed cardiac allograft recipients reduced myocardial injury and acute rejection. We suggest that HIF transcription factors induce a regulatory phenotype in myeloid-derived cells, which may be harnessed as a novel therapeutic strategy to regulate immune responses after heart transplantation.
Asunto(s)
Trasplante de Corazón , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Células Mieloides/citología , Miocitos Cardíacos/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/metabolismo , Aloinjertos , Animales , Proliferación Celular , Femenino , Supervivencia de Injerto , Inflamación , Linfocitos/citología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Fenotipo , ARN Mensajero/metabolismo , Daño por Reperfusión , Linfocitos T/citología , Trasplante HomólogoRESUMEN
Hypoxic pulmonary vasoconstriction is correlated with pulmonary vascular remodeling. The hypoxia-inducible transcription factors (HIFs) HIF-1α and HIF-2α are known to contribute to the process of hypoxic pulmonary vascular remodeling; however, the specific role of pulmonary endothelial HIF expression in this process, and in the physiological process of vasoconstriction in response to hypoxia, remains unclear. Here we show that pulmonary endothelial HIF-2α is a critical regulator of hypoxia-induced pulmonary arterial hypertension. The rise in right ventricular systolic pressure (RVSP) normally observed following chronic hypoxic exposure was absent in mice with pulmonary endothelial HIF-2α deletion. The RVSP of mice lacking HIF-2α in pulmonary endothelium after exposure to hypoxia was not significantly different from normoxic WT mice and much lower than the RVSP values seen in WT littermate controls and mice with pulmonary endothelial deletion of HIF-1α exposed to hypoxia. Endothelial HIF-2α deletion also protected mice from hypoxia remodeling. Pulmonary endothelial deletion of arginase-1, a downstream target of HIF-2α, likewise attenuated many of the pathophysiological symptoms associated with hypoxic pulmonary hypertension. We propose a mechanism whereby chronic hypoxia enhances HIF-2α stability, which causes increased arginase expression and dysregulates normal vascular NO homeostasis. These data offer new insight into the role of pulmonary endothelial HIF-2α in regulating the pulmonary vascular response to hypoxia.
Asunto(s)
Arginasa/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Endotelio Vascular/metabolismo , Hipertensión Pulmonar/metabolismo , Animales , Arginasa/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Hipoxia de la Célula , Células Cultivadas , Endotelio Vascular/citología , Humanos , Hipertensión Pulmonar/genética , Hipoxia , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Óxido Nítrico/metabolismo , Función Ventricular Derecha/genética , Función Ventricular Derecha/fisiología , Presión Ventricular/genética , Presión Ventricular/fisiologíaRESUMEN
Despite the increased risk of thrombosis in cancer patients compared with healthy individuals, mechanisms that regulate cancer-induced hypercoagulation are incompletely understood. The aim of this study was to investigate whether cell-specific hypoxia-inducible factor (HIF) 1α regulates cancer-associated hypercoagulation, using in vitro clotting assays and in vivo cancer models. In mouse lung and mammary tumor cells, hypoxia led to increases in cell adhesion, clotting, and fibrin deposition; these increases were eliminated in HIF1α null cells. Increased levels of HIF1α were also associated with increased tissue factor expression in human breast tumor samples. Conversely, deletion of endothelial (but not myeloid) cell-specific HIF1α doubled pulmonary fibrin deposition, and trebled thrombus formation compared with wildtype littermates in tumor-bearing mice. Our data suggest that tumor and endothelial cell-specific HIF1α may have opposing roles in cancer-associated coagulation and thrombosis. Off-target effects of manipulating the HIF1 axis in cancer patients should be carefully considered when managing thrombotic complications.
Asunto(s)
Coagulación Sanguínea , Neoplasias de la Mama/metabolismo , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Neoplasias Mamarias Experimentales/metabolismo , Trombofilia/metabolismo , Animales , Neoplasias de la Mama/genética , Neoplasias de la Mama/patología , Adhesión Celular , Células Endoteliales/metabolismo , Células Endoteliales/patología , Femenino , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Neoplasias Mamarias Experimentales/genética , Neoplasias Mamarias Experimentales/patología , Ratones , Ratones Noqueados , Trombofilia/genética , Trombofilia/patologíaRESUMEN
Hypoxic response and inflammation both involve the action of the hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha. Previous studies have revealed that both HIF-alpha proteins are in a number of aspects similarly regulated post-translationally. However, the functional interrelationship of these two isoforms remains largely unclear. The polarization of macrophages controls functionally divergent processes; one of these is nitric oxide (NO) production, which in turn is controlled in part by HIF factors. We show here that the HIF-alpha isoforms can be differentially activated: HIF-1alpha is induced by Th1 cytokines in M1 macrophage polarization, whereas HIF-2alpha is induced by Th2 cytokines during an M2 response. This differential response was most evident in polarized macrophages through HIF-alpha isoform-specific regulation of the inducible NO synthase gene by HIF-1alpha, and the arginase1 gene by HIF-2alpha. In silico modeling predicted that regulation of overall NO availability is due to differential regulation of HIF-1alpha versus HIF-2alpha, acting to, respectively, either increase or suppress NO synthesis. An in vivo model of endotoxin challenge confirmed this; thus, these studies reveal that the two homologous transcription factors, HIF-1alpha and HIF-2alpha, can have physiologically antagonistic functions, but that their antiphase regulation allows them to coordinately regulate NO production in a cytokine-induced and transcription-dependent fashion.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Regulación de la Expresión Génica , Homeostasis/fisiología , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Macrófagos/metabolismo , Óxido Nítrico/metabolismo , Animales , Arginasa/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Simulación por Computador , Citocinas/metabolismo , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Modelos Biológicos , Óxido Nítrico Sintasa de Tipo II/metabolismo , Isoformas de Proteínas , Células TH1 , Células Th2RESUMEN
PURPOSE OF REVIEW: Textbook theory holds that blood pressure (BP) is regulated by the brain, by blood vessels, or by the kidney. Recent evidence suggests that BP could be regulated in the skin. RECENT FINDINGS: The skin holds a complex capillary counter current system, which controls body temperature, skin perfusion, and apparently systemic BP. Epidemiological data suggest that sunlight exposure plays a role in controlling BP. Ultraviolet A radiation produces vasodilation and a fall in BP. Keratinocytes and immune cells control blood flow in the extensive countercurrent loop system of the skin by producing nitric oxide, a key regulator of vascular tone. The balance between hypoxia-inducible factor-1α and hypoxia-inducible factor-2α activity in keratinocytes controls skin perfusion, systemic thermoregulation, and systemic BP by nitric oxide-dependent mechanisms. Furthermore, the skin accumulates Na which generates a barrier to promote immunological host defense. Immune cells control skin Na metabolism and the clearance of Na via the lymphatic system. Reduced lymphatic clearance increases BP. SUMMARY: Apart from the well-known role of the brain, blood vessels, and the kidney, the skin is important for systemic BP control in humans and in experimental animals.
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Presión Sanguínea/fisiología , Piel/irrigación sanguínea , Animales , Enfermedades Cardiovasculares/prevención & control , Humanos , Queratinocitos/fisiología , Macrófagos/fisiología , Flujo Sanguíneo Regional , Sodio/metabolismo , Luz SolarRESUMEN
Neutrophil lifespan and function are regulated by hypoxia via components of the hypoxia inducible factor (HIF)/von Hippel Lindau/hydroxylase pathway, including specific roles for HIF-1α and prolyl hydroxylase-3. HIF-2α has both distinct and overlapping biological roles with HIF-1α and has not previously been studied in the context of neutrophil biology. We investigated the role of HIF-2α in regulating key neutrophil functions. Human and murine peripheral blood neutrophils expressed HIF-2α, with expression up-regulated by acute and chronic inflammatory stimuli and in disease-associated inflammatory neutrophil. HIF2A gain-of-function mutations resulted in a reduction in neutrophil apoptosis both ex vivo, through the study of patient cells, and in vivo in a zebrafish tail injury model. In contrast, HIF-2α-deficient murine inflammatory neutrophils displayed increased sensitivity to nitrosative stress induced apoptosis ex vivo and increased neutrophil apoptosis in vivo, resulting in a reduction in neutrophilic inflammation and reduced tissue injury. Expression of HIF-2α was temporally dissociated from HIF-1α in vivo and predominated in the resolution phase of inflammation. These data support a critical and selective role for HIF-2α in persistence of neutrophilic inflammation and provide a platform to dissect the therapeutic utility of targeting HIF-2α in chronic inflammatory diseases.
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Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Regulación de la Expresión Génica , Inflamación , Neutrófilos/metabolismo , Animales , Apoptosis , Hipoxia de la Célula , Proteínas Fluorescentes Verdes/metabolismo , Humanos , Inmunohistoquímica , Ratones , Ratones Endogámicos C57BL , Muramidasa , Neutrófilos/citología , Fagocitosis , Fenotipo , ARN/metabolismo , Estallido Respiratorio , Pez CebraRESUMEN
In mammals, hypoxia-triggered erythropoietin release increases red blood cell mass to meet tissue oxygen demands. Using male Wistar rats, we unmask a previously unrecognized regulatory pathway of erythropoiesis involving suppressor control by the NO metabolite and ubiquitous dietary component nitrate. We find that circulating hemoglobin levels are modulated by nitrate at concentrations achievable by dietary intervention under normoxic and hypoxic conditions; a moderate dose of nitrate administered via the drinking water (7 mg NaNO3/kg body weight/d) lowered hemoglobin concentration and hematocrit after 6 d compared with nonsupplemented/NaCl-supplemented controls. The underlying mechanism is suppression of hepatic erythropoietin expression associated with the downregulation of tissue hypoxia markers, suggesting increased pO2. At higher nitrate doses, however, a partial reversal of this effect occurred; this was accompanied by increased renal erythropoietin expression and stabilization of hypoxia-inducible factors, likely brought about by the relative anemia. Thus, hepatic and renal hypoxia-sensing pathways act in concert to modulate hemoglobin in response to nitrate, converging at an optimal minimal hemoglobin concentration appropriate to the environmental/physiologic situation. Suppression of hepatic erythropoietin expression by nitrate may thus act to decrease blood viscosity while matching oxygen supply to demand, whereas renal oxygen sensing could act as a brake, averting a potentially detrimental fall in hematocrit.
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Suplementos Dietéticos , Eritropoyesis/efectos de los fármacos , Eritropoyetina/metabolismo , Hemoglobinas/metabolismo , Hipoxia/metabolismo , Nitratos/administración & dosificación , Oxígeno/metabolismo , Animales , Epoetina alfa , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Técnicas para Inmunoenzimas , Riñón/efectos de los fármacos , Riñón/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Nitratos/farmacología , Ratas , Ratas Wistar , Proteínas Recombinantes/metabolismoRESUMEN
In women, estrogen deficiency after menopause frequently accelerates osteoclastic bone resorption, leading to osteoporosis, the most common skeletal disorder. However, mechanisms underlying osteoporosis resulting from estrogen deficiency remain largely unknown. Here we show that in bone-resorbing osteoclasts, estrogen-dependent destabilization of hypoxia-inducible factor 1 alpha (HIF1α), which is unstable in the presence of oxygen, plays a pivotal role in promoting bone loss in estrogen-deficient conditions. In vitro, HIF1α was destabilized by estrogen treatment even in hypoxic conditions, and estrogen loss in ovariectomized (Ovx) mice stabilized HIF1α in osteoclasts and promoted their activation and subsequent bone loss in vivo. Osteoclast-specific HIF1α inactivation antagonized bone loss in Ovx mice and osteoclast-specific estrogen receptor alpha deficient mice, both models of estrogen-deficient osteoporosis. Oral administration of a HIF1α inhibitor protected Ovx mice from osteoclast activation and bone loss. Thus, HIF1α represents a promising therapeutic target in osteoporosis.
Asunto(s)
Estradiol/análogos & derivados , Estrógenos/deficiencia , Subunidad alfa del Factor 1 Inducible por Hipoxia/antagonistas & inhibidores , Osteoclastos/fisiología , Osteoporosis Posmenopáusica/tratamiento farmacológico , Osteoporosis Posmenopáusica/fisiopatología , 2-Metoxiestradiol , Administración Oral , Animales , Células Cultivadas , Cruzamientos Genéticos , Ensayo de Inmunoadsorción Enzimática , Estradiol/administración & dosificación , Estradiol/farmacología , Femenino , Genotipo , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Immunoblotting , Inmunohistoquímica , Inmunoprecipitación , Etiquetado Corte-Fin in Situ , Ratones , Ratones Noqueados , Osteoclastos/efectos de los fármacos , Osteoporosis Posmenopáusica/metabolismo , Reacción en Cadena de la PolimerasaRESUMEN
Vascular flow through tissues is regulated via a number of homeostatic mechanisms. Localized control of tissue blood flow, or autoregulation, is a key factor in regulating tissue perfusion and oxygenation. We show here that the net balance between two hypoxia-inducible factor (HIF) transcription factor isoforms, HIF-1α and HIF-2α, is an essential mechanism regulating both local and systemic blood flow in the skin of mice. We also show that balance of HIF isoforms in keratinocyte-specific mutant mice affects thermal adaptation, exercise capacity, and systemic arterial pressure. The two primary HIF isoforms achieve these effects in opposing ways that are associated with HIF isoform regulation of nitric oxide production. We also show that a correlation exists between altered levels of HIF isoforms in the skin and the degree of idiopathic hypertension in human subjects. Thus, the balance between HIF-1α and HIF-2α expression in keratinocytes is a control element of both tissue perfusion and systemic arterial pressure, with potential implications in human hypertension.
Asunto(s)
Presión Arterial/fisiología , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Piel/irrigación sanguínea , Piel/metabolismo , Adulto , Anciano , Animales , Arginasa/genética , Arginasa/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Western Blotting , Femenino , Humanos , Hipertensión/tratamiento farmacológico , Hipertensión/fisiopatología , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Inmunohistoquímica , Queratinocitos/citología , Queratinocitos/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Persona de Mediana Edad , Óxido Nítrico Sintasa de Tipo II/genética , Óxido Nítrico Sintasa de Tipo II/metabolismo , Óxido Nítrico Sintasa de Tipo III/genética , Óxido Nítrico Sintasa de Tipo III/metabolismo , Flujo Sanguíneo Regional/fisiología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Adulto JovenRESUMEN
BACKGROUND: Insulin sensitivity in skeletal muscle is associated with metabolic flexibility, including a high capacity to increase fatty acid (FA) oxidation in response to increased lipid supply. Lipid overload, however, can result in incomplete FA oxidation and accumulation of potentially harmful intermediates where mitochondrial tricarboxylic acid cycle capacity cannot keep pace with rates of ß-oxidation. Enhancement of muscle FA oxidation in combination with mitochondrial biogenesis is therefore emerging as a strategy to treat metabolic disease. Dietary inorganic nitrate was recently shown to reverse aspects of the metabolic syndrome in rodents by as yet incompletely defined mechanisms. RESULTS: Herein, we report that nitrate enhances skeletal muscle FA oxidation in rodents in a dose-dependent manner. We show that nitrate induces FA oxidation through a soluble guanylate cyclase (sGC)/cGMP-mediated PPARß/δ- and PPARα-dependent mechanism. Enhanced PPARß/δ and PPARα expression and DNA binding induces expression of FA oxidation enzymes, increasing muscle carnitine and lowering tissue malonyl-CoA concentrations, thereby supporting intra-mitochondrial pathways of FA oxidation and enhancing mitochondrial respiration. At higher doses, nitrate induces mitochondrial biogenesis, further increasing FA oxidation and lowering long-chain FA concentrations. Meanwhile, nitrate did not affect mitochondrial FA oxidation in PPARα(-/-) mice. In C2C12 myotubes, nitrate increased expression of the PPARα targets Cpt1b, Acadl, Hadh and Ucp3, and enhanced oxidative phosphorylation rates with palmitoyl-carnitine; however, these changes in gene expression and respiration were prevented by inhibition of either sGC or protein kinase G. Elevation of cGMP, via the inhibition of phosphodiesterase 5 by sildenafil, also increased expression of Cpt1b, Acadl and Ucp3, as well as CPT1B protein levels, and further enhanced the effect of nitrate supplementation. CONCLUSIONS: Nitrate may therefore be effective in the treatment of metabolic disease by inducing FA oxidation in muscle.