RESUMEN
BACKGROUND: Much of what we know about insulin resistance is based on studies from metabolically active tissues such as the liver, adipose tissue, and skeletal muscle. Emerging evidence suggests that the vascular endothelium plays a crucial role in systemic insulin resistance; however, the underlying mechanisms remain incompletely understood. Arf6 (ADP ribosylation factor 6) is a small GTPase that plays a critical role in endothelial cell function. Here, we tested the hypothesis that the deletion of endothelial Arf6 will result in systemic insulin resistance. METHODS: We used mouse models of constitutive endothelial cell-specific Arf6 deletion (Arf6f/- Tie2Cre+) and tamoxifen-inducible Arf6 knockout (Arf6f/f Cdh5CreER+). Endothelium-dependent vasodilation was assessed using pressure myography. Metabolic function was assessed using a battery of metabolic assessments including glucose and insulin tolerance tests and hyperinsulinemic-euglycemic clamps. We used a fluorescence microsphere-based technique to measure tissue blood flow. Skeletal muscle capillary density was assessed using intravital microscopy. RESULTS: Endothelial Arf6 deletion impaired insulin-stimulated vasodilation in white adipose tissue and skeletal muscle feed arteries. The impairment in vasodilation was primarily due to attenuated insulin-stimulated nitric oxide bioavailability but independent of altered acetylcholine-mediated or sodium nitroprusside-mediated vasodilation. Endothelial cell-specific deletion of Arf6 also resulted in systematic insulin resistance in normal chow-fed mice and glucose intolerance in high-fat diet-fed obese mice. The underlying mechanisms of glucose intolerance were reductions in insulin-stimulated blood flow and glucose uptake in the skeletal muscle and were independent of changes in capillary density or vascular permeability. CONCLUSIONS: Results from this study support the conclusion that endothelial Arf6 signaling is essential for maintaining insulin sensitivity. Reduced expression of endothelial Arf6 impairs insulin-mediated vasodilation and results in systemic insulin resistance. These results have therapeutic implications for diseases that are associated with endothelial cell dysfunction and insulin resistance such as diabetes.
Asunto(s)
Factor 6 de Ribosilación del ADP , Endotelio , Resistencia a la Insulina , Músculo Esquelético , Ratones , Factor 6 de Ribosilación del ADP/genética , Factor 6 de Ribosilación del ADP/metabolismo , Endotelio/metabolismo , Ratones Endogámicos C57BL , Intolerancia a la Glucosa , Tamoxifeno , Ratones Noqueados , Tejido Adiposo Blanco/metabolismo , Tejido Adiposo Blanco/patología , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Obesidad/metabolismo , Obesidad/patología , Glucosa/metabolismo , Dieta Alta en Grasa , Ratones Obesos , VasodilataciónRESUMEN
KEY POINTS: Increased large artery stiffness and impaired endothelium-dependent dilatation occur with advanced age. We sought to determine whether T cells mechanistically contribute to age-related arterial dysfunction. We found that old mice exhibited greater proinflammatory T cell accumulation around both the aorta and mesenteric arteries. Pharmacologic depletion or genetic deletion of T cells in old mice resulted in ameliorated large artery stiffness and greater endothelium-dependent dilatation compared with mice with T cells intact. ABSTRACT: Ageing of the arteries is characterized by increased large artery stiffness and impaired endothelium-dependent dilatation. T cells contribute to hypertension in acute rodent models but whether they contribute to chronic age-related arterial dysfunction is unknown. To determine whether T cells directly mediate age-related arterial dysfunction, we examined large elastic artery and resistance artery function in young (4-6 months) and old (22-24 months) wild-type mice treated with anti-CD3 F(ab'2) fragments to deplete T cells (150 µg, i.p. every 7 days for 28 days) or isotype control fragments. Old mice exhibited greater numbers of T cells in both aorta and mesenteric vasculature when compared with young mice. Old mice treated with anti-CD3 fragments exhibited depletion of T cells in blood, spleen, aorta and mesenteric vasculature. Old mice also exhibited greater numbers of aortic and mesenteric IFN-γ and TNF-α-producing T cells when compared with young mice. Old control mice exhibited greater large artery stiffness and impaired resistance artery endothelium-dependent dilatation in comparison with young mice. In old mice, large artery stiffness was ameliorated with anti-CD3 treatment. Anti-CD3-treated old mice also exhibited greater endothelium-dependent dilatation than age-matched controls. We also examined arterial function in young and old Rag-1-/- mice, which lack lymphocytes. Rag-1-/- mice exhibited blunted increases in large artery stiffness with age compared with wild-type mice. Old Rag-1-/- mice also exhibited greater endothelium-dependent dilatation compared with old wild-type mice. Collectively, these results demonstrate that T cells play an important role in age-related arterial dysfunction.
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Rigidez Vascular , Envejecimiento , Animales , Endotelio Vascular , Arterias Mesentéricas , Ratones , Linfocitos T , VasodilataciónRESUMEN
Advancing age promotes cardiovascular disease (CVD), the leading cause of death in the United States and many developed nations. Two major age-related arterial phenotypes, large elastic artery stiffening and endothelial dysfunction, are independent predictors of future CVD diagnosis and likely are responsible for the development of CVD in older adults. Not limited to traditional CVD, these age-related changes in the vasculature also contribute to other age-related diseases that influence mammalian health span and potential life span. This review explores mechanisms that influence age-related large elastic artery stiffening and endothelial dysfunction at the tissue level via inflammation and oxidative stress and at the cellular level via Klotho and energy-sensing pathways (AMPK [AMP-activated protein kinase], SIRT [sirtuins], and mTOR [mammalian target of rapamycin]). We also discuss how long-term calorie restriction-a health span- and life span-extending intervention-can prevent many of these age-related vascular phenotypes through the prevention of deleterious alterations in these mechanisms. Lastly, we discuss emerging novel mechanisms of vascular aging, including senescence and genomic instability within cells of the vasculature. As the population of older adults steadily expands, elucidating the cellular and molecular mechanisms of vascular dysfunction with age is critical to better direct appropriate and measured strategies that use pharmacological and lifestyle interventions to reduce risk of CVD within this population.
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Envejecimiento/metabolismo , Arterias/metabolismo , Enfermedades Cardiovasculares/metabolismo , Senescencia Celular , Mediadores de Inflamación/metabolismo , Estrés Oxidativo , Rigidez Vascular , Factores de Edad , Envejecimiento/genética , Envejecimiento/patología , Animales , Arterias/patología , Arterias/fisiopatología , Autofagia , Enfermedades Cardiovasculares/genética , Enfermedades Cardiovasculares/patología , Enfermedades Cardiovasculares/fisiopatología , Inestabilidad Genómica , Humanos , Transducción de SeñalRESUMEN
Age-related vascular dysfunction in large elastic and resistance arteries is associated with reductions in microvascular perfusion and elevations in blood pressure. Recent evidence indicates that telomere uncapping-induced senescence in vascular cells may be an important source of oxidative stress and vascular dysfunction in aging, but the causal relationship between these processes has yet to be elucidated. To test this important unexplored hypothesis, we measured arterial senescence signaling and oxidative stress, carotid and mesenteric artery endothelium-dependent vasodilatory capacity, markers of mesenteric microvascular perfusion and endothelial glycocalyx deterioration, and blood pressure in a novel mouse model of Cre-inducible whole body Trf2 deletion and telomere uncapping. Trf2 deletion led to a 320% increase in arterial senescence signaling (Pâ¯<â¯.05). There was a concurrent 29% and 22% reduction in peak endothelium-dependent vasodilation in carotid and mesenteric arteries, respectively, as well as a 63% reduction in mesenteric microvascular endothelial glycocalyx thickness (all Pâ¯≤â¯.01). Mesenteric microvascular perfusion was reduced by 8% and systolic blood pressure was increased by 9% following Trf2 deletion (both Pâ¯<â¯.05). Trf2 deletion also led to a pro-oxidative arterial phenotype characterized by increased in NADPH oxidase gene expression; a 210% increase in superoxide levels that was partly dependent on NADPH oxidase activity; and an oxidative stress mediated reduction in carotid artery vasodilation (all Pâ¯≤â¯.05). Collectively, our findings demonstrate that induced Trf2 deletion leads to telomere uncapping, increased senescence signaling, and oxidative stress mediated functional impairments in the vasculature similar to those seen in human aging.
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Envejecimiento/metabolismo , Arterias/metabolismo , Senescencia Celular , Eliminación de Gen , Estrés Oxidativo , Transducción de Señal , Telómero/metabolismo , Proteína 2 de Unión a Repeticiones Teloméricas/deficiencia , Tejido Adiposo/metabolismo , Animales , Presión Sanguínea , Peso Corporal , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Glicocálix/metabolismo , Ratones , Microvasos/metabolismo , Perfusión , Fenotipo , Homeostasis del Telómero , Proteína 2 de Unión a Repeticiones Teloméricas/metabolismo , VasodilataciónRESUMEN
Blood flow regulation is a critical factor for tissue oxygenation and substrate supply. Increased reactivity of arteries to vasoconstrictors may increase vascular resistance, resulting in reduced blood flow. We aimed to investigate the effect of a high-fat (HF) diet on stiffness and vasoconstrictor reactivity of white adipose tissue (WAT) and brown adipose tissue (BAT) resistance arteries and also investigated the interconversion of both adipose depots in the setting of a HF diet. Vasoconstrictor reactivity and passive morphology and mechanical properties of arteries from B6D2F1 mice (5 mo old) fed normal chow (NC) or a HF diet (8 wk) were measured using pressure myography. Receptor gene expression in WAT and BAT arteries and markers of WAT and BAT were assessed in whole tissue lysates by real-time RT-PCR. Despite greater receptor-independent vasoconstriction (in response to KCl, P < 0.01), vasoconstriction in response to angiotensin II ( P < 0.01) was lower in NC-BAT than NC-WAT arteries and similar in response to endothelin-1 ( P = 0.07) and norepinephrine ( P = 0.11) in NC-BAT and NC-WAT arteries. With the exception of BAT artery reactivity to endothelin-1 and angiotensin II, the HF diet tended to attenuate reactivity in arteries from both adipose depots and increased expression of adipose markers in BAT. No significant differences in morphology or passive mechanical properties were found between adipose types or diet conditions. Alterations in gene expression of adipose markers after the HF diet suggest beiging of BAT. An increase in brown adipocytes in the absence of increased BAT mass may be a compensatory mechanism to dissipate excess energy from a HF diet. NEW & NOTEWORTHY Despite no differences in passive mechanical properties and greater receptor-independent vasoconstriction, receptor-mediated vasoconstriction was either lower in brown than white adipose tissue arteries or similar in brown and white adipose tissue arteries. A high-fat diet has a greater impact on vasoconstrictor responses in white adipose tissue but leads to altered adipose tissue gene expression consistent with beiging of the brown adipose tissue.
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Tejido Adiposo Pardo/efectos de los fármacos , Tejido Adiposo Blanco/efectos de los fármacos , Arterias/efectos de los fármacos , Dieta Alta en Grasa , Grasas de la Dieta/farmacología , Vasoconstricción , Tejido Adiposo Pardo/irrigación sanguínea , Tejido Adiposo Blanco/irrigación sanguínea , Angiotensina II/farmacología , Animales , Arterias/fisiología , Endotelina-1/farmacología , Masculino , Ratones , Norepinefrina/farmacología , Vasoconstrictores/farmacologíaRESUMEN
OBJECTIVE: Accumulating evidence suggests the vascular endothelium plays a fundamental role in the pathophysiology of obesity by regulating the functional status of white adipose and systemic metabolism. Robo4 is expressed specifically in endothelial cells and increases vascular stability and inhibits angiogenesis. We sought to determine the role of Robo4 in modulating cardiometabolic function in response to high-fat feeding. METHODS: We examined exercise capacity, glucose tolerance, and white adipose tissue artery gene expression, endothelium-dependent dilation (EDD), and angiogenesis in wild type and Robo4 knockout (KO) mice fed normal chow (NC) or a high-fat diet (HFD). RESULTS: We found Robo4 deletion enhances exercise capacity in NC-fed mice and HFD markedly increased the expression of the Robo4 ligand, Slit2, in white adipose tissue. Deletion of Robo4 increased angiogenesis in white adipose tissue and protected against HFD-induced impairments in white adipose artery vasodilation and glucose intolerance. CONCLUSIONS: We demonstrate a novel functional role for Robo4 in endothelial cell function and metabolic homeostasis in white adipose tissue, with Robo4 deletion protecting against endothelial and metabolic dysfunction associated with a HFD. Our findings suggest that Robo4-dependent signaling pathways may be a novel target in anti-obesity therapy.
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Tejido Adiposo Blanco , Arterias , Grasas de la Dieta/efectos adversos , Endotelio Vascular , Eliminación de Gen , Regulación de la Expresión Génica/efectos de los fármacos , Receptores de Superficie Celular , Tejido Adiposo Blanco/irrigación sanguínea , Tejido Adiposo Blanco/metabolismo , Tejido Adiposo Blanco/patología , Animales , Arterias/metabolismo , Arterias/patología , Grasas de la Dieta/farmacología , Endotelio Vascular/metabolismo , Endotelio Vascular/patología , Péptidos y Proteínas de Señalización Intercelular/biosíntesis , Péptidos y Proteínas de Señalización Intercelular/genética , Ratones , Ratones Noqueados , Neovascularización Fisiológica/efectos de los fármacos , Neovascularización Fisiológica/genética , Proteínas del Tejido Nervioso/biosíntesis , Proteínas del Tejido Nervioso/genética , Receptores de Superficie Celular/biosíntesis , Receptores de Superficie Celular/deficiencia , Vasodilatación/efectos de los fármacos , Vasodilatación/genéticaRESUMEN
NEW FINDINGS: What is the central question of this study? Greater large artery stiffness is associated with dysfunctional resistance artery vasodilatory responses, impaired memory and greater risk of Alzheimer's disease. However, it is unknown whether stiffer large arteries affect cerebral and skeletal muscle feed artery responses to vasoconstrictors. What is the main finding and its importance? In a mouse model with greater large artery stiffness (Eln+/- ), we find an exacerbated vasoconstrictor response to angiotensin II in cerebral arteries, but not skeletal muscle feed arteries, thus implicating altered cerebral artery angiotensin II responsiveness in the poor brain outcomes associated with greater large artery stiffness. ABSTRACT: Greater stiffness of the large elastic arteries is associated with end-organ damage and dysfunction. At the same time, resistance artery vasoconstrictor responsiveness influences vascular tone and organ blood flow. However, it is unknown whether large elastic artery stiffness modulates the responsiveness to vasoconstrictors in resistance arteries of the cerebral or skeletal muscle circulations. We previously described the elastin haploinsufficient (Eln+/- ) mouse as a model with greater aortic stiffness, but with similar cerebral and skeletal muscle feed artery stiffness to wild-type (Eln+/+ ) mice. Here, we used this model to examine the relationship between large elastic artery stiffness and resistance artery vasoconstrictor responses. In middle cerebral arteries (MCAs), vasoconstriction in response to angiotensin II (Ang II) was â¼40% greater in Eln+/- compared with Eln+/+ mice (P = 0.02), and this group difference was ameliorated by losartan, indicating a role for Ang II type 1 receptors (AT1Rs). In gastrocnemius feed arteries, Eln+/- and Eln+/+ mice did not differ in the response to Ang II. In addition, the vasoconstrictor responses to noradrenaline, endothelin-1 and potassium chloride were not different between Eln+/- and Eln+/+ mice for either MCAs or gastrocnemius feed arteries. The MCA AT1R gene expression did not differ between groups, whereas Ang II type 2 receptor gene expression was â¼50% lower in MCAs from Eln+/- versus Eln+/+ mice (P = 0.01). In conclusion, greater large elastic artery stiffness is associated with an exacerbated vasoconstriction response to Ang II in cerebral arteries, but is not associated with the responses to other vasoconstrictors in either cerebral or skeletal muscle feed arteries.
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Arterias Cerebrales/efectos de los fármacos , Músculo Esquelético/efectos de los fármacos , Rigidez Vascular/efectos de los fármacos , Vasoconstricción/efectos de los fármacos , Vasoconstrictores/farmacología , Angiotensina II/farmacología , Animales , Arterias Cerebrales/metabolismo , Arterias Cerebrales/fisiopatología , Modelos Animales de Enfermedad , Endotelina-1/metabolismo , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/metabolismo , Endotelio Vascular/fisiopatología , Losartán/farmacología , Masculino , Ratones , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiopatología , Norepinefrina/metabolismo , Receptor de Angiotensina Tipo 1/metabolismo , Rigidez Vascular/fisiología , Vasoconstricción/fisiologíaRESUMEN
Age-related microvascular dysfunction is well characterized in rodents and humans, but little is known about the properties of the microvascular endothelial glycocalyx in advanced age. We examined the glycocalyx in microvessels of young and old male C57BL6 mice (young: 6.1 ± 0.1 mo vs. old: 24.6 ± 0.2 mo) using intravital microscopy and transmission electron microscopy and in human participants (young: 29 ± 1 yr vs. old: 60 ± 2 yr) using intravital microscopy. Glycocalyx thickness in mesenteric and skeletal muscle microvessels was 51-54% lower in old compared with young mice. We also observed 33% lower glycocalyx thickness in the sublingual microcirculation of humans in advanced age. The perfused boundary region, a marker of glycocalyx barrier function, was also obtained using an automated capture and analysis system. In advanced age, we observed a 10-22% greater perfused boundary region in mice and humans, indicating a more penetrable glycocalyx. Finally, using this automated analysis system, we examined perfused microvascular density and red blood cell (RBC) fraction. Perfused microvascular density is a marker of microvascular function that reflects the length of perfused microvessel segments in a given area; RBC fraction represents the heterogeneity in RBC presence between microvessel segments. Compared with young, the perfused microvascular density was 16-21% lower and RBC fraction was 5-14% lower in older mice and in older humans. These data provide novel evidence that, across mammalian species, a diminished glycocalyx is present in advanced age and is accompanied by markers of impaired microvascular perfusion. Age-related glycocalyx deterioration may be an important contributor to microvascular dysfunction in older adults and subsequent pathophysiology. NEW & NOTEWORTHY Advanced age is characterized by microvascular dysfunction that contributes to age-related cardiovascular diseases, but little is known about endothelial glycocalyx properties in advanced age. This study reveals, for the first time, lower glycocalyx thickness and barrier function that is accompanied by impaired microvascular perfusion in both mice and humans in advanced age.
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Envejecimiento/metabolismo , Endotelio Vascular/citología , Glicocálix/ultraestructura , Adulto , Animales , Endotelio Vascular/crecimiento & desarrollo , Endotelio Vascular/metabolismo , Femenino , Glicocálix/metabolismo , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Persona de Mediana EdadRESUMEN
Cardiovascular disease (CVD) is the leading cause of death in the industrialized world. Aging is the most predictive risk factor for CVD and is associated with arterial inflammation which contributes to increased CVD risk. Although age-related arterial inflammation has been described in both humans and animals, only a limited number of inflammatory mediators, cytokines and chemokines have been identified. In this investigation we sought to determine whether lifespan extending interventions, including crowded litter early life nutrient deprivation (CL), traditional lifelong caloric restriction (CR) and lifelong Rapamycin treatment (Rap) would attenuate age-related arterial inflammation using multi analyte profiling. Aortas from Young (4-6months), Old (22months), Old CL, Old CR and Old Rap mice were homogenized and cytokine concentrations were assessed using Luminex Multi Analyte Profiling. Chemokines involved in immune cell recruitment, such as CCL2, CXCL9, CXCL10, GMCSF and MCSF, were increased in Old vs. Young (p<0.05). The age-related increase of CXCL10 was prevented by CR (p<0.05 vs. Old). MSCF concentrations were lower in aortas of Rap treated mice (p<0.05 vs. Old). Interleukins (IL), IL-1α, IL-1ß and IL-10, were also greater in Old vs. Young mice (p<0.05). These data demonstrate selected lifespan extending interventions can prevent or limit age-related increases in selected aortic chemokines.
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Envejecimiento , Arterias/inmunología , Quimiocina CXCL10/sangre , Factor Estimulante de Colonias de Macrófagos/sangre , Animales , Restricción Calórica , Enfermedades Cardiovasculares/tratamiento farmacológico , Enfermedades Cardiovasculares/prevención & control , Quimiocina CCL2/biosíntesis , Quimiocina CCL4/biosíntesis , Quimiocina CXCL10/inmunología , Quimiocinas/biosíntesis , Quimiocinas/inmunología , Citocinas/biosíntesis , Citocinas/inmunología , Intervención Médica Temprana , Interleucina-10/biosíntesis , Interleucina-1beta/sangre , Interleucinas/biosíntesis , Interleucinas/inmunología , Factor Estimulante de Colonias de Macrófagos/inmunología , Masculino , Ratones , Sirolimus/uso terapéuticoAsunto(s)
Dieta Occidental , Rigidez Vascular , Animales , Inflamación , Ratones , Estrés Oxidativo , Análisis de la Onda del PulsoRESUMEN
BACKGROUND: Cerebral cavernous malformation (CCM) is a hemorrhagic stroke disease affecting up to 0.5% of North Americans that has no approved nonsurgical treatment. A subset of patients have a hereditary form of the disease due primarily to loss-of-function mutations in KRIT1, CCM2, or PDCD10. We sought to identify known drugs that could be repurposed to treat CCM. METHODS AND RESULTS: We developed an unbiased screening platform based on both cellular and animal models of loss of function of CCM2. Our discovery strategy consisted of 4 steps: an automated immunofluorescence and machine-learning-based primary screen of structural phenotypes in human endothelial cells deficient in CCM2, a secondary screen of functional changes in endothelial stability in these same cells, a rapid in vivo tertiary screen of dermal microvascular leak in mice lacking endothelial Ccm2, and finally a quaternary screen of CCM lesion burden in these same mice. We screened 2100 known drugs and bioactive compounds and identified 2 candidates, cholecalciferol (vitamin D3) and tempol (a scavenger of superoxide), for further study. Each drug decreased lesion burden in a mouse model of CCM vascular disease by ≈50%. CONCLUSIONS: By identifying known drugs as potential therapeutics for CCM, we have decreased the time, cost, and risk of bringing treatments to patients. Each drug also prompts additional exploration of biomarkers of CCM disease. We further suggest that the structure-function screening platform presented here may be adapted and scaled to facilitate drug discovery for diverse loss-of-function genetic vascular disease.
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Neoplasias del Sistema Nervioso Central/tratamiento farmacológico , Modelos Animales de Enfermedad , Reposicionamiento de Medicamentos/métodos , Hemangioma Cavernoso del Sistema Nervioso Central/tratamiento farmacológico , Animales , Células Cultivadas , Neoplasias del Sistema Nervioso Central/patología , Colecalciferol/farmacología , Colecalciferol/uso terapéutico , Ensayos de Selección de Medicamentos Antitumorales/métodos , Células Endoteliales/efectos de los fármacos , Células Endoteliales/patología , Depuradores de Radicales Libres/farmacología , Depuradores de Radicales Libres/uso terapéutico , Hemangioma Cavernoso del Sistema Nervioso Central/patología , Humanos , Ratones , Ratones Noqueados , Ratones Transgénicos , Resultado del TratamientoRESUMEN
Cardiovascular disease (CVD) is the leading cause of death in the United States and aging is a major risk factor for CVD development. One of the major age-related arterial phenotypes thought to be responsible for the development of CVD in older adults is endothelial dysfunction. Endothelial function is modulated by traditional CVD risk factors in young adults, but advancing age is independently associated with the development of vascular endothelial dysfunction. This endothelial dysfunction results from a reduction in nitric oxide bioavailability downstream of endothelial oxidative stress and inflammation that can be further modulated by traditional CVD risk factors in older adults. Greater endothelial oxidative stress with aging is a result of augmented production from the intracellular enzymes NADPH oxidase and uncoupled eNOS, as well as from mitochondrial respiration in the absence of appropriate increases in antioxidant defenses as regulated by relevant transcription factors, such as FOXO. Interestingly, it appears that NFkB, a critical inflammatory transcription factor, is sensitive to this age-related endothelial redox change and its activation induces transcription of pro-inflammatory cytokines that can further suppress endothelial function, thus creating a vicious feed-forward cycle. This review will discuss the two macro-mechanistic processes, oxidative stress and inflammation, that contribute to endothelial dysfunction with advancing age as well as the cellular and molecular events that lead to the vicious cycle of inflammation and oxidative stress in the aged endothelium. Other potential mediators of this pro-inflammatory endothelial phenotype are increases in immune or senescent cells in the vasculature. Of note, genomic instability, telomere dysfunction or DNA damage has been shown to trigger cell senescence via the p53/p21 pathway and result in increased inflammatory signaling in arteries from older adults. This review will discuss the current state of knowledge regarding the emerging concepts of senescence and genomic instability as mechanisms underlying oxidative stress and inflammation in the aged endothelium. Lastly, energy sensitive/stress resistance pathways (SIRT-1, AMPK, mTOR) are altered in endothelial cells and/or arteries with aging and these pathways may modulate endothelial function via key oxidative stress and inflammation-related transcription factors. This review will also discuss what is known about the role of "energy sensing" longevity pathways in modulating endothelial function with advancing age. With the growing population of older adults, elucidating the cellular and molecular mechanisms of endothelial dysfunction with age is critical to establishing appropriate and measured strategies to utilize pharmacological and lifestyle interventions aimed at alleviating CVD risk. This article is part of a Special Issue entitled "SI: CV Aging".
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Senescencia Celular , Células Endoteliales/patología , Animales , Enfermedades Cardiovasculares/patología , Endotelio Vascular/patología , Metabolismo Energético , Inestabilidad Genómica , HumanosRESUMEN
KEY POINTS: Increased large artery stiffness is a hallmark of arterial dysfunction with advancing age and is also present in other disease conditions such as diabetes. Increased large artery stiffness is correlated with resistance artery dysfunction in humans. Using a mouse model of altered arterial elastin content, this is the first study to examine the cause-and-effect relationship between large artery stiffness and peripheral resistance artery function. Our results indicate that mice with genetically greater large artery stiffness have impaired cerebral artery endothelial function, but generally preserved skeletal muscle feed artery endothelial function. The mechanisms for impaired cerebral artery endothelial function are reduced nitric oxide bioavailability and increased oxidative stress. These findings suggest that interventions that target large artery stiffness may be important to reduce disease risk associated with cerebral artery dysfunction in conditions such as advancing age. ABSTRACT: Advancing age as well as diseases such as diabetes are characterized by both increased large artery stiffness and impaired peripheral artery function. It has been hypothesized that greater large artery stiffness causes peripheral artery dysfunction; however, a cause-and-effect relationship has not previously been established. We used elastin heterozygote mice (Eln(+/-) ) as a model of increased large artery stiffness without co-morbidities unrelated to the large artery properties. Aortic stiffness, measured by pulse wave velocity, was â¼35% greater in Eln(+/-) mice than in wild-type (Eln(+/+) ) mice (P = 0.04). Endothelium-dependent dilatation (EDD), assessed by the maximal dilatation to acetylcholine, was â¼40% lower in Eln(+/-) than Eln(+/+) mice in the middle cerebral artery (MCA, P < 0.001), but was similar between groups in the gastrocnemius feed arteries (GFA, P = 0.79). In the MCA, EDD did not differ between groups after incubation with the nitric oxide (NO) synthase inhibitor N(ω) -nitro-l-arginine methyl ester (P > 0.05), indicating that lower NO bioavailability contributed to the impaired EDD in Eln(+/-) mice. Superoxide production and content of the oxidative stress marker nitrotyrosine was higher in MCAs from Eln(+/-) compared with Eln(+/+) mice (P < 0.05). In the MCA, after incubation with the superoxide scavenger TEMPOL, maximal EDD improved by â¼65% in Eln(+/-) (P = 0.002), but was unchanged in Eln(+/+) mice (P = 0.17). These results indicate that greater large artery stiffness has a more profound effect on endothelial function in cerebral arteries compared with skeletal muscle feed arteries. Greater large artery stiffness can cause cerebral artery endothelial dysfunction by reducing NO bioavailability and increasing oxidative stress.
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Arterias Cerebrales/fisiopatología , Endotelio Vascular/fisiopatología , Músculo Esquelético/irrigación sanguínea , Rigidez Vascular/fisiología , Animales , Arterias Cerebrales/efectos de los fármacos , Modelos Animales de Enfermedad , Elastina/genética , Elastina/metabolismo , Endotelio Vascular/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Indometacina/farmacología , Ratones , Ratones Noqueados , NG-Nitroarginina Metil Éster/farmacología , Resistencia Vascular/efectos de los fármacos , Resistencia Vascular/fisiología , Rigidez Vascular/efectos de los fármacos , Vasodilatación/efectos de los fármacos , Vasodilatación/fisiologíaRESUMEN
The critical influence of the white adipose tissue (WAT) on metabolism is well-appreciated in obesity, but adipose tissue dysfunction as a mechanism underlying age-associated metabolic dysfunction requires elucidation. To explore this possibility, we assessed metabolism and measures of epididymal (e)WAT mitochondria and artery function in young (6.1 ± 0.4 months) and old (29.6 ± 0.2 months) B6D2F1 mice. There were no group differences in average daily oxygen consumption, fasted blood glucose or plasma free fatty acids, but fasted plasma insulin and the homeostatic model assessment of insulin resistance (HOMA-IR%) were higher in the old (â¼50-85%, P < 0.05). Tissue mass (P < 0.05) and adipocyte area were lower (â¼60%) (P < 0.01) and fibrosis was greater (sevenfold, P < 0.01) in eWAT with older age. The old also exhibited greater liver triglycerides (â¼60%, P < 0.05). The mitochondrial respiratory oxygen flux after the addition of glutamate and malate (GM), adenosine diphosphate (d), succinate (S) and octanoyl carnitine (O) were one- to twofold higher in eWAT of old mice (P < 0.05). Despite no change in the respiratory control ratio, substrate control ratios of GMOd/GMd and GMOSd/GMd were â¼30-40% lower in old mice (P < 0.05) and were concomitant with increased nitrotyrosine (P < 0.05) and reduced expression of brown adipose markers (P < 0.05). Ageing reduced vascularity (â¼50%, P < 0.01), angiogenic capacity (twofold, P < 0.05) and expression of vascular endothelial growth factor (â¼50%, P < 0.05) in eWAT. Finally, endothelium-dependent dilation was lower (P < 0.01) in isolated arteries from eWAT arteries of the old mice. Thus, metabolic dysfunction with advancing age occurs in concert with dysfunction in the adipose tissue characterized by both mitochondrial and arterial dysfunction.
Asunto(s)
Tejido Adiposo/metabolismo , Envejecimiento/metabolismo , Neovascularización Fisiológica , Tejido Adiposo/irrigación sanguínea , Tejido Adiposo/crecimiento & desarrollo , Tejido Adiposo/fisiología , Envejecimiento/fisiología , Animales , Arterias/metabolismo , Arterias/fisiología , Peso Corporal , Carnitina/análogos & derivados , Carnitina/metabolismo , Ácido Glutámico/metabolismo , Malatos/metabolismo , Masculino , Ratones , Mitocondrias/metabolismo , Estrés Oxidativo , Consumo de Oxígeno , Ácido Succínico/metabolismo , Triglicéridos/metabolismo , Tirosina/análogos & derivados , Tirosina/metabolismo , VasodilataciónRESUMEN
Cbl-associated protein (Cap) is a member of a phosphatidylinositol 3-kinase-independent pathway for insulin-stimulated translocation of the glucose transporter GLUT4. Despite this positive role of Cap in glucose uptake, here we show that deletion of the gene encoding Cap (official gene name: Sorbs1) protects against high-fat diet (HFD)-induced insulin resistance in mice while also having an opposite, insulin-sensitizing effect, accompanied by reduced tissue markers of inflammation. Given the emerging role of chronic inflammation in insulin resistance and the macrophage in initiating this inflammatory process, we considered that Sorbs1 deletion from macrophages may have resulted in the observed protection from HFD-induced insulin resistance. Using bone marrow transplantation to generate functional Sorbs1-null macrophages, we show that the insulin-sensitive phenotype can be transferred to wild-type mice by transplantation of Sorbs1-null bone marrow. These studies show that macrophages are an important cell type in the induction of insulin resistance and that Cap has a modulatory role in this function.
Asunto(s)
Eliminación de Gen , Resistencia a la Insulina/genética , Proteínas de Microfilamentos/genética , Adipocitos/metabolismo , Animales , Trasplante de Médula Ósea , Grasas de la Dieta , Histocitoquímica , Immunoblotting , Resistencia a la Insulina/fisiología , Macrófagos/metabolismo , Imagen por Resonancia Magnética , Masculino , Ratones , Ratones Noqueados , Proteínas de Microfilamentos/metabolismoRESUMEN
Aging is a major risk factor for atherosclerosis and cardiovascular disease (CVD). Two major age-associated arterial phenotypes, endothelial dysfunction and large elastic arterial stiffness, are autonomous predictors of future CVD diagnosis and contribute to the progression of CVD in older adults. Senescent cells lose the capacity to proliferate but remain metabolically active and secrete inflammatory factors termed senescence-associated secretory phenotype (SASP), leading to an increase in inflammation and oxidative stress. Accumulation of senescent cells is linked with the progression of age-related diseases and has been known to play a role in cardiovascular disease. In this brief review, we describe the characteristics and mechanisms of senescent cell accumulation and how senescent cells promote endothelial dysfunction and arterial stiffness. We focus on a range of novel therapeutic strategies aimed at reducing the burden of endothelial dysfunction leading to atherosclerosis through targeting senescent cells. Studies have begun to investigate a specific class of drugs that are able to selectively eliminate senescent cells, termed senolytics, which have shown great promise in reversing the aging phenotype and ameliorating pathologies in age-related disorders, creating a new opportunity for aging research. Generating therapies targeting the elimination of senescent cells would improve health span and increase longevity, making senolytics a promising therapy for cardiovascular diseases.
RESUMEN
Systemic inhibition of the mammalian target of rapamycin (mTOR) delays aging and many age-related conditions including arterial and metabolic dysfunction. However, the mechanisms and tissues involved in these beneficial effects remain largely unknown. Here, we demonstrate that activation of S6K, a downstream target of mTOR, is increased in arteries with advancing age, and that this occurs preferentially in the endothelium compared with the vascular smooth muscle. Induced endothelial cell-specific deletion of mTOR reduced protein expression by 60-70%. Although this did not significantly alter arterial and metabolic function in young mice, endothelial mTOR reduction reversed arterial stiffening and improved endothelium-dependent dilation (EDD) in old mice, indicating an improvement in age-related arterial dysfunction. Improvement in arterial function in old mice was concomitant with reductions in arterial cellular senescence, inflammation, and oxidative stress. The reduction in endothelial mTOR also improved glucose tolerance in old mice, and this was associated with attenuated hepatic gluconeogenesis and improved lipid tolerance, but was independent of alterations in peripheral insulin sensitivity, pancreatic beta cell function, or fasted plasma lipids in old mice. Lastly, we found that endothelial mTOR reduction suppressed gene expression of senescence and inflammatory markers in endothelial-rich (i.e., lung) and metabolically active organs (i.e., liver and adipose tissue), which may have contributed to the improvement in metabolic function in old mice. This is the first evidence demonstrating that reducing endothelial mTOR in old age improves arterial and metabolic function. These findings have implications for future drug development.
Asunto(s)
Endotelio Vascular , Vasodilatación , Animales , Ratones , Vasodilatación/fisiología , Envejecimiento/metabolismo , Arterias/metabolismo , Estrés Oxidativo , Serina-Treonina Quinasas TOR/metabolismo , Células Endoteliales/metabolismo , Sirolimus/farmacología , Mamíferos/metabolismoRESUMEN
Arterial telomere dysfunction may contribute to chronic arterial inflammation by inducing cellular senescence and subsequent senescence-associated inflammation. Although telomere shortening has been associated with arterial aging in humans, age-related telomere uncapping has not been described in non-cultured human tissues and may have substantial prognostic value. In skeletal muscle feed arteries from 104 younger, middle-aged, and older adults, we assessed the potential role of age-related telomere uncapping in arterial inflammation. Telomere uncapping, measured by p-histone γ-H2A.X (ser139) localized to telomeres (chromatin immunoprecipitation; ChIP), and telomeric repeat binding factor 2 bound to telomeres (ChIP) was greater in arteries from older adults compared with those from younger adults. There was greater tumor suppressor protein p53 (P53)/cyclin-dependent kinase inhibitor 1A (P21)-induced senescence, measured by P53 bound to P21 gene promoter (ChIP), and greater expression of P21, interleukin 8, and monocyte chemotactic protein 1 mRNA (RT-PCR) in arteries from older adults compared with younger adults. Telomere uncapping was a highly influential covariate for the age-group difference in P53/P21-induced senescence. Despite progressive age-related telomere shortening in human arteries, mean telomere length was not associated with telomere uncapping or P53/P21-induced senescence. Collectively, these findings demonstrate that advancing age is associated with greater telomere uncapping in arteries, which is linked to P53/P21-induced senescence independent of telomere shortening.
Asunto(s)
Envejecimiento/genética , Arteritis/genética , Senescencia Celular , Músculo Esquelético/irrigación sanguínea , Acortamiento del Telómero , Telómero/metabolismo , Adulto , Factores de Edad , Anciano , Envejecimiento/inmunología , Envejecimiento/metabolismo , Envejecimiento/patología , Análisis de Varianza , Arterias/inmunología , Arterias/metabolismo , Arterias/patología , Arteritis/inmunología , Arteritis/metabolismo , Arteritis/patología , Sitios de Unión , Quimiocina CCL2/genética , Distribución de Chi-Cuadrado , Inmunoprecipitación de Cromatina , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Femenino , Histonas/metabolismo , Humanos , Interleucina-8/genética , Masculino , Persona de Mediana Edad , Fosforilación , Reacción en Cadena de la Polimerasa , Medicamentos bajo Prescripción/uso terapéutico , Regiones Promotoras Genéticas , ARN Mensajero/metabolismo , Factores de Riesgo , Proteína 2 de Unión a Repeticiones Teloméricas/metabolismo , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
Endothelial cells are located at the crucial interface between circulating blood and semi-solid tissues and have many important roles in maintaining systemic physiological function. The vascular endothelium is particularly susceptible to pathogenic stimuli that activate tumour suppressor pathways leading to cellular senescence. We now understand that senescent endothelial cells are highly active, secretory and pro-inflammatory, and have an aberrant morphological phenotype. Moreover, endothelial senescence has been identified as an important contributor to various cardiovascular and metabolic diseases. In this Review, we discuss the consequences of endothelial cell exposure to damaging stimuli (haemodynamic forces and circulating and endothelial-derived factors) and the cellular and molecular mechanisms that induce endothelial cell senescence. We also discuss how endothelial cell senescence causes arterial dysfunction and contributes to clinical cardiovascular diseases and metabolic disorders. Finally, we summarize the latest evidence on the effect of eliminating senescent endothelial cells (senolysis) and identify important remaining questions to be addressed in future studies.
Asunto(s)
Enfermedades Cardiovasculares , Células Endoteliales , Humanos , Células Endoteliales/fisiología , Senescencia Celular/fisiología , Endotelio Vascular/metabolismo , Enfermedades Cardiovasculares/metabolismoRESUMEN
Advanced age is accompanied by arterial dysfunction, as well as a diminished glycocalyx, which may be linked to reduced high molecular weight-hyaluronan (HMW-HA) synthesis. However, the impact of glycocalyx deterioration in age-related arterial dysfunction is unknown. We sought to determine if manipulations in glycocalyx properties would alter arterial function. Tamoxifen-induced hyaluronan synthase 2 (Has2) reduction was used to decrease glycocalyx properties. Three weeks post-tamoxifen treatment, glycocalyx thickness was lower in Has2 knockout compared to wild-type mice (P<0.05). Has2 reduction induced arterial dysfunction, demonstrated by impaired endothelium-dependent dilation (EDD) and elevated aortic stiffness (P<0.05). To augment glycocalyx properties, old mice received 10 weeks of a glycocalyx-targeted therapy via Endocalyx™ (old+ECX), which contains HMW-HA and other glycocalyx components. Compared to old control mice, glycocalyx properties and EDD were augmented, and aortic stiffness decreased in old+ECX mice (P<0.05). Old+ECX mice had a more youthful aortic phenotype, demonstrated by lower collagen content and higher elastin content than old control mice (P<0.05). Functional outcomes were repeated in old mice that underwent a diet supplemented solely with HMW-HA (old+HA). Compared to old controls, glycocalyx properties and EDD were augmented, and aortic stiffness was lower in old+HA mice (P<0.05). We did not observe any differences between old+HA and old+ECX mice (P>0.05). Has2 reduction phenocopies age-related arterial dysfunction, while 10 weeks of glycocalyx-targeted therapy that restores the glycocalyx also ameliorates age-related arterial dysfunction. These findings suggest that the glycocalyx may be a viable therapeutic target to ameliorate age-related arterial dysfunction.