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Muscle atrophy and weakness are prevalent features of cancer. Although extensive research has characterized skeletal muscle wasting in cancer cachexia, limited studies have investigated how cardiac structure and function are affected by therapy-naive cancer. Here, the authors used orthotopic, syngeneic models of epithelial ovarian cancer and pancreatic ductal adenocarcinoma, and a patient-derived pancreatic xenograft model, to define the impacts of malignancy on cardiac structure, function, and metabolism. Tumor-bearing mice develop cardiac atrophy and intrinsic systolic and diastolic dysfunction, with arterial hypotension and exercise intolerance. In hearts of ovarian tumor-bearing mice, fatty acid-supported mitochondrial respiration decreased, and carbohydrate-supported respiration increased-showcasing a substrate shift in cardiac metabolism that is characteristic of heart failure. Epithelial ovarian cancer decreased cytoskeletal and cardioprotective gene expression, which was paralleled by down-regulation of transcription factors that regulate cardiomyocyte size and function. Patient-derived pancreatic xenograft tumor-bearing mice show altered myosin heavy chain isoform expression-also a molecular phenotype of heart failure. Markers of autophagy and ubiquitin-proteasome system were upregulated by cancer, providing evidence of catabolic signaling that promotes cardiac wasting. Together, the authors cross-validate with two cancer types, evidence of the structural, functional, and metabolic cancer-induced cardiomyopathy, thus providing translational evidence that could impact future medical management strategies for improved cancer recovery in patients.
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The role of erythropoietin (EPO) has extended beyond hematopoiesis to include cytoprotection, inotropy, and neurogenesis. Extra-renal EPO has been reported for multiple tissue/cell types, but the physiological relevance remains unknown. Although the EPO receptor is expressed by multiple cardiac cell types and human recombinant EPO increases contractility and confers cytoprotection against injury, whether the heart produces physiologically meaningful amounts of EPO in vivo is unclear. We show a distinct circadian rhythm of cardiac EPO mRNA expression in adult mice and increased mRNA expression during embryogenesis, suggesting physiological relevance to cardiac EPO production throughout life. We then generated constitutive, cardiomyocyte-specific EPO knockout mice driven by the Mlc2v promoter (EPOfl/fl:Mlc2v-cre+/-; EPOΔ/Δ-CM). During cardiogenesis, cardiac EPO mRNA expression and cellular proliferation were reduced in EPOΔ/Δ-CM hearts. However, in adult EPOΔ/Δ- CM mice, total heart weight was preserved through increased cardiomyocyte cross-sectional area, indicating the reduced cellular proliferation was compensated for by cellular hypertrophy. Echocardiography revealed no changes in cardiac dimensions, with modest reductions in ejection fraction, stroke volume, and tachycardia, whereas invasive hemodynamics showed increased cardiac contractility and lusitropy. Paradoxically, EPO mRNA expression in the heart was elevated in adult EPOΔ/Δ-CM, along with increased serum EPO protein content and hematocrit. Using RNA fluorescent in situ hybridization, we found that Epo RNA colocalized with endothelial cells in the hearts of adult EPOΔ/Δ-CM mice, identifying the endothelial cells as a cell responsible for the EPO hyper-expression. Collectively, these data identify the first physiological roles for cardiomyocyte-derived EPO. We have established cardiac EPO mRNA expression is a complex interplay of multiple cell types, where loss of embryonic cardiomyocyte EPO production results in hyper-expression from other cells within the adult heart.
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Células Endoteliais , Eritropoetina , Animais , Camundongos , Hiperplasia , Hibridização in Situ Fluorescente , Miócitos Cardíacos , RNA , RNA Mensageiro/genéticaRESUMO
Cardiovascular disease (CVD) and cancer are the leading causes of mortality worldwide. Although generally thought of as distinct diseases, the intersectional overlap between CVD and cancer is increasingly evident in both causal and mechanistic relationships. The field of cardio-oncology is largely focused on the cardiotoxic effects of cancer therapies (e.g., chemotherapy, radiation). Furthermore, the cumulative effects of cardiotoxic therapy exposure and the prevalence of CVD risk factors in patients with cancer lead to long-term morbidity and poor quality of life in this patient population, even when patients are cancer-free. Evidence from patients with cancer and animal models demonstrates that the presence of malignancy itself, independent of cardiotoxic therapy exposure or CVD risk factors, negatively impacts cardiac structure and function. As such, the primary focus of this review is the cardiac pathophysiological and molecular features of therapy-naïve cancer. We also summarize the strengths and limitations of preclinical cancer models for cardio-oncology research and discuss therapeutic strategies that have been tested experimentally for the treatment of cancer-induced cardiac atrophy and dysfunction. Finally, we explore an adjacent area of interest, called "reverse cardio-oncology," where the sequelae of heart failure augment cancer progression. Here, we emphasize the cross-disease communication between malignancy and the injured heart and discuss the importance of chronic low-grade inflammation and endocrine factors in the progression of both diseases.
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Cardiotoxicidade , Doenças Cardiovasculares , Neoplasias , Humanos , Doenças Cardiovasculares/etiologia , Neoplasias/complicações , Neoplasias/tratamento farmacológico , Animais , Antineoplásicos/efeitos adversos , Fatores de Risco , Cardio-OncologiaRESUMO
Cardiac fibroblasts play a pivotal role in maintaining heart homeostasis by depositing extracellular matrix (ECM) to provide structural support for the myocardium, vasculature, and neuronal network and by contributing to essential physiological processes. In response to injury such as myocardial infarction or pressure overload, fibroblasts become activated, leading to increased ECM production that can ultimately drive left ventricular remodeling and progress to heart failure. Recently, the AJP-Heart and Circulatory Physiology issued a call for papers on cardiac fibroblasts that yielded articles with topics spanning fibroblast physiology, technical considerations, signaling pathways, and interactions with other cell types. This mini-review summarizes those articles and places the new findings in the context of what is currently known for cardiac fibroblasts and what future directions remain.
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BACKGROUND: Maintenance of the kidney filtration barrier requires coordinated interactions between podocytes and the underlying glomerular basement membrane (GBM). GBM ligands bind podocyte integrins, which triggers actin-based signaling events critical for adhesion. Nck1/2 adaptors have emerged as essential regulators of podocyte cytoskeletal dynamics. However, the precise signaling mechanisms mediated by Nck1/2 adaptors in podocytes remain to be fully elucidated. METHODS: We generated podocytes deficient in Nck1 and Nck2 and used transcriptomic approaches to profile expression differences. Proteomic techniques identified specific binding partners for Nck1 and Nck2 in podocytes. We used cultured podocytes and mice deficient in Nck1 and/or Nck2, along with podocyte injury models, to comprehensively verify our findings. RESULTS: Compound loss of Nck1/2 altered expression of genes involved in actin binding, cell adhesion, and extracellular matrix composition. Accordingly, Nck1/2-deficient podocytes showed defects in actin organization and cell adhesion in vitro, with podocyte detachment and altered GBM morphology present in vivo. We identified distinct interactomes for Nck1 and Nck2 and uncovered a mechanism by which Nck1 and Nck2 cooperate to regulate actin bundling at focal adhesions via α actinin-4. Furthermore, loss of Nck1 or Nck2 resulted in increased matrix deposition in vivo, with more prominent defects in Nck2-deficient mice, consistent with enhanced susceptibility to podocyte injury. CONCLUSION: These findings reveal distinct, yet complementary, roles for Nck proteins in regulating podocyte adhesion, controlling GBM composition, and sustaining filtration barrier integrity.
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Podócitos , Actinina/metabolismo , Actinas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Membrana Basal Glomerular/metabolismo , Camundongos , Proteínas Oncogênicas/metabolismo , Podócitos/metabolismo , ProteômicaRESUMO
BACKGROUND: Cigarette smokers are at increased risk of acquiring influenza, developing severe disease and requiring hospitalisation/intensive care unit admission following infection. However, immune mechanisms underlying this predisposition are incompletely understood, and therapeutic strategies for influenza are limited. METHODS: We used a mouse model of concurrent cigarette smoke exposure and H1N1 influenza infection, colony-stimulating factor (CSF)3 supplementation/receptor (CSF3R) blockade and single-cell RNA sequencing (scRNAseq) to investigate this relationship. RESULTS: Cigarette smoke exposure exacerbated features of viral pneumonia such as oedema, hypoxaemia and pulmonary neutrophilia. Smoke-exposed infected mice demonstrated an increase in viral (v)RNA, but not replication-competent viral particles, relative to infection-only controls. Interstitial rather than airspace neutrophilia positively predicted morbidity in smoke-exposed infected mice. Screening of pulmonary cytokines using a novel dysregulation score identified an exacerbated expression of CSF3 and interleukin-6 in the context of smoke exposure and influenza. Recombinant (r)CSF3 supplementation during influenza aggravated morbidity, hypothermia and oedema, while anti-CSF3R treatment of smoke-exposed infected mice improved alveolar-capillary barrier function. scRNAseq delineated a shift in the distribution of Csf3 + cells towards neutrophils in the context of cigarette smoke and influenza. However, although smoke-exposed lungs were enriched for infected, highly activated neutrophils, gene signatures of these cells largely reflected an exacerbated form of typical influenza with select unique regulatory features. CONCLUSION: This work provides novel insight into the mechanisms by which cigarette smoke exacerbates influenza infection, unveiling potential therapeutic targets (e.g. excess vRNA accumulation, oedematous CSF3R signalling) for use in this context, and potential limitations for clinical rCSF3 therapy during viral infectious disease.
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Fumar Cigarros , Vírus da Influenza A Subtipo H1N1 , Influenza Humana , Animais , Fumar Cigarros/efeitos adversos , Humanos , Pulmão/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Neutrófilos , NicotianaRESUMO
KEY POINTS: Although the role of TBC1D1 within the heart remains unknown, expression of TBC1D1 increases in the left ventricle following an acute infarction, suggesting a biological importance within this tissue. We investigated the mechanistic role of TBC1D1 within the heart, aiming to establish the consequences of attenuating TBC1D1 signalling in the development of diabetic cardiomyopathy, as well as to determine potential sex differences. TBC1D1 ablation increased plasma membrane fatty acid binding protein content and myocardial palmitate oxidation. Following high-fat feeding, TBC1D1 ablation dramatically increased fibrosis and induced end-diastolic dysfunction in both male and female rats in the absence of changes in mitochondrial bioenergetics. Altogether, independent of sex, ablating TBC1D1 predisposes the left ventricle to pathological remodelling following high-fat feeding, and suggests TBC1D1 protects against diabetic cardiomyopathy. ABSTRACT: TBC1D1, a Rab-GTPase activating protein, is involved in the regulation of glucose handling and substrate metabolism within skeletal muscle, and is essential for maintaining pancreatic ß-cell mass and insulin secretion. However, the function of TBC1D1 within the heart is largely unknown. Therefore, we examined the role of TBC1D1 in the left ventricle and the functional consequence of ablating TBC1D1 on the susceptibility to high-fat diet-induced abnormalities. Since mutations within TBC1D1 (R125W) display stronger associations with clinical parameters in women, we further examined possible sex differences in the predisposition to diabetic cardiomyopathy. In control-fed animals, TBC1D1 ablation did not alter insulin-stimulated glucose uptake, or echocardiogram parameters, but increased accumulation of a plasma membrane fatty acid transporter and the capacity for palmitate oxidation. When challenged with an 8 week high-fat diet, TBC1D1 knockout rats displayed a four-fold increase in fibrosis compared to wild-type animals, and this was associated with diastolic dysfunction, suggesting a predisposition to diet-induced cardiomyopathy. Interestingly, high-fat feeding only induced cardiac hypertrophy in male TBC1D1 knockout animals, implicating a possible sex difference. Mitochondrial respiratory capacity and substrate sensitivity to pyruvate and ADP were not altered by diet or TBC1D1 ablation, nor were markers of oxidative stress, or indices of overt heart failure. Altogether, independent of sex, ablation of TBC1D1 not only increased the susceptibility to high-fat diet-induced diastolic dysfunction and left ventricular fibrosis, independent of sex, but also predisposed male animals to the development of cardiac hypertrophy. These data suggest that TBC1D1 may exert cardioprotective effects in the development of diabetic cardiomyopathy.
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Cardiomiopatias/fisiopatologia , Proteínas Ativadoras de GTPase/fisiologia , Proteínas/fisiologia , Animais , Cardiomiopatias/genética , Dieta Hiperlipídica , Feminino , Proteínas Ativadoras de GTPase/genética , Técnicas de Inativação de Genes , Glucose/metabolismo , Ventrículos do Coração/fisiopatologia , Insulina , Masculino , Músculo Esquelético , Proteínas/genética , Ratos , Fatores SexuaisRESUMO
KEY POINTS: Ninety-eight per cent of patients with Duchenne muscular dystrophy (DMD) develop cardiomyopathy, with 40% developing heart failure. While increased propensity for mitochondrial induction of cell death has been observed in left ventricle, it remains unknown whether this is linked to impaired mitochondrial respiratory control and elevated H2 O2 emission prior to the onset of cardiomyopathy. Classic mouse models of DMD demonstrate hyper-regeneration in skeletal muscle which may mask mitochondrial abnormalities. Using a model with less regenerative capacity that is more akin to DMD patients, we observed elevated left ventricular mitochondrial H2 O2 and impaired oxidative phosphorylation in the absence of cardiac remodelling or overt cardiac dysfunction at 4 weeks. These impairments were associated with dysfunctions at complex I, governance by ADP and creatine-dependent phosphate shuttling, which results in a less efficient response to energy demands. Mitochondria may be a therapeutic target for the treatment of cardiomyopathy in DMD. ABSTRACT: In Duchenne muscular dystrophy (DMD), mitochondrial dysfunction is predicted as a response to numerous cellular stressors, yet the contribution of mitochondria to the onset of cardiomyopathy remains unknown. To resolve this uncertainty, we designed in vitro assessments of mitochondrial bioenergetics to model mitochondrial control parameters that influence cardiac function. Both left ventricular mitochondrial responsiveness to the central bioenergetic controller ADP and the ability of creatine to facilitate mitochondrial-cytoplasmic phosphate shuttling were assessed. These measurements were performed in D2.B10-DMDmdx /2J mice - a model that demonstrates skeletal muscle atrophy and weakness due to limited regenerative capacities and cardiomyopathy more akin to people with DMD than classic models. At 4 weeks of age, there was no evidence of cardiac remodelling or cardiac dysfunction despite impairments in ADP-stimulated respiration and ADP attenuation of H2 O2 emission. These impairments were seen at both submaximal and maximal ADP concentrations despite no reductions in mitochondrial content markers. The ability of creatine to enhance ADP's control of mitochondrial bioenergetics was also impaired, suggesting an impairment in mitochondrial creatine kinase-dependent phosphate shuttling. Susceptibly to permeability transition pore opening and the subsequent activation of cell death pathways remained unchanged. Mitochondrial H2 O2 emission was elevated despite no change in markers of irreversible oxidative damage, suggesting alternative redox signalling mechanisms should be explored. These findings demonstrate that selective mitochondrial dysfunction precedes the onset of overt cardiomyopathy in D2.mdx mice, suggesting that improving mitochondrial bioenergetics by restoring ADP, creatine-dependent phosphate shuttling and complex I should be considered for treating DMD patients.
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Cardiopatias , Distrofia Muscular de Duchenne , Animais , Metabolismo Energético , Cardiopatias/metabolismo , Ventrículos do Coração , Humanos , Camundongos , Camundongos Endogâmicos mdx , Mitocôndrias/metabolismo , Distrofia Muscular de Duchenne/metabolismoRESUMO
Traditionally, the evaluation of cardiac function has focused on systolic function; however, there is a growing appreciation for the contribution of diastolic function to overall cardiac health. Given the emerging interest in evaluating diastolic function in all models of heart failure, there is a need for sensitivity, accuracy, and precision in the hemodynamic assessment of diastolic function. Hemodynamics measure cardiac pressures in vivo, offering a direct assessment of diastolic function. In this review, we summarize the underlying principles of diastolic function, dividing diastole into two phases: 1) relaxation and 2) filling. We identify parameters used to comprehensively evaluate diastolic function by hemodynamics, clarify how each parameter is obtained, and consider the advantages and limitations associated with each measure. We provide a summary of the sensitivity of each diastolic parameter to loading conditions. Furthermore, we discuss differences that can occur in the accuracy of diastolic and systolic indices when generated by automated software compared with custom software analysis and the magnitude each parameter is influenced during inspiration with healthy breathing and a mild breathing load, commonly expected in heart failure. Finally, we identify key variables to control (e.g., body temperature, anesthetic, sampling rate) when collecting hemodynamic data. This review provides fundamental knowledge for users to succeed in troubleshooting and guidelines for evaluating diastolic function by hemodynamics in experimental models of heart failure.
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Pressão Sanguínea , Modelos Animais de Doenças , Insuficiência Cardíaca/fisiopatologia , Guias de Prática Clínica como Assunto , Função Ventricular , Animais , Testes de Função Cardíaca/métodos , Testes de Função Cardíaca/normasRESUMO
KEY POINTS: In the present study, we provide evidence for divergent physiological responses to moderate compared to severe hypoxia, addressing an important knowledge gap related to severity, duration and after-effects of hypoxia encountered in cardiopulmonary situations. The physiological responses to moderate and severe hypoxia were not proportional, linear or concurrent with the time-of-day. Hypoxia elicited severity-dependent physiological responses that either persisted or fluctuated throughout normoxic recovery. The physiological basis for these distinct cardiovascular responses implicates a shift in the sympathovagal set point and probably not molecular changes at the artery resulting from hypoxic stress. ABSTRACT: Hypoxia is both a consequence and cause of many acute and chronic diseases. Severe hypoxia causes hypertension with cardiovascular sequelae; however, the rare studies using moderate severities of hypoxia indicate that it can be beneficial, suggesting that hypoxia may not always be detrimental. Comparisons between studies are difficult because of the varied classifications of hypoxic severities, methods of delivery and use of anaesthetics. Thus, to investigate the long-term effects of moderate hypoxia on cardiovascular health, radiotelemetry was used to obtain in vivo physiological measurements in unanaesthetized mice during 24 h of either moderate (FIO2=0.15) or severe (FIO2=0.09) hypoxia, followed by 72 h of normoxic recovery. Systolic blood pressure was decreased during recovery following moderate hypoxia but increased following severe hypoxia. Moderate and severe hypoxia increased haeme oxygenase-1 expression during recovery, suggesting parity in hypoxic stress at the level of the artery. Severe but not moderate hypoxia increased the low/high frequency ratio of heart rate variability 72 h post-hypoxia, indicating a shift in sympathovagal balance. Moderate hypoxia dampened the amplitude of circadian rhythm, whereas severe disrupted rhythm during the entire insult, with perturbations persisting throughout normoxic recovery. Thus, hypoxic severity differentially regulates circadian blood pressure.
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Hipóxia/fisiopatologia , Animais , Pressão Sanguínea , Frequência Cardíaca , Masculino , Camundongos Endogâmicos C57BLRESUMO
Supplementation with dietary inorganic nitrate ([Formula: see text]) is increasingly recognized to confer cardioprotective effects in both healthy and clinical populations. While the mechanism(s) remains ambiguous, in skeletal muscle oral consumption of NaNO3 has been shown to improve mitochondrial efficiency. Whether NaNO3 has similar effects on mitochondria within the heart is unknown. Therefore, we comprehensively investigated the effect of NaNO3 supplementation on in vivo left ventricular (LV) function and mitochondrial bioenergetics. Healthy male Sprague-Dawley rats were supplemented with NaNO3 (1 g/l) in their drinking water for 7 days. Echocardiography and invasive hemodynamics were used to assess LV morphology and function. Blood pressure (BP) was measured by tail-cuff and invasive hemodynamics. Mitochondrial bioenergetics were measured in LV isolated mitochondria and permeabilized muscle fibers by high-resolution respirometry and fluorometry. Nitrate decreased ( P < 0.05) BP, LV end-diastolic pressure, and maximal LV pressure. Rates of LV relaxation (when normalized to mean arterial pressure) tended ( P = 0.13) to be higher with nitrate supplementation. However, nitrate did not alter LV mitochondrial respiration, coupling efficiency, or oxygen affinity in isolated mitochondria or permeabilized muscle fibers. In contrast, nitrate increased ( P < 0.05) the propensity for mitochondrial H2O2 emission in the absence of changes in cellular redox state and decreased the sensitivity of mitochondria to ADP (apparent Km). These results add to the therapeutic potential of nitrate supplementation in cardiovascular diseases and suggest that nitrate may confer these beneficial effects via mitochondrial redox signaling.
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Suplementos Nutricionais , Metabolismo Energético/efeitos dos fármacos , Peróxido de Hidrogênio/metabolismo , Mitocôndrias Cardíacas/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Nitratos/farmacologia , Difosfato de Adenosina/metabolismo , Animais , Pressão Sanguínea/efeitos dos fármacos , Masculino , Mitocôndrias Cardíacas/metabolismo , Contração Miocárdica/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Oxirredução , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos , Função Ventricular Esquerda/efeitos dos fármacos , Pressão Ventricular/efeitos dos fármacosRESUMO
Moderate anemia is associated with increased mortality and morbidity, including acute kidney injury (AKI), in surgical patients. A red blood cell (RBC)-specific antibody model was utilized to determine whether moderate subacute anemia could result in tissue hypoxia as a potential mechanism of injury. Cardiovascular and hypoxic cellular responses were measured in transgenic mice capable of expressing hypoxia-inducible factor-1α (HIF-1α)/luciferase activity in vivo. Antibody-mediated anemia was associated with mild intravascular hemolysis (6 h) and splenic RBC sequestration ( day 4), resulting in a nadir hemoglobin concentration of 89 ± 13 g/l on day 4. At this time point, renal tissue oxygen tension (PtO2) was decreased in anemic mice relative to controls (13.1 ± 4.3 vs. 20.8 ± 3.7 mmHg, P < 0.001). Renal tissue hypoxia was associated with an increase in HIF/luciferase expression in vivo ( P = 0.04) and a 20-fold relative increase in renal erythropoietin mRNA transcription ( P < 0.001) but no increase in renal blood flow ( P = 0.67). By contrast, brain PtO2 was maintained in anemic mice relative to controls (22.7 ± 5.2 vs. 23.4 ± 9.8 mmHg, P = 0.59) in part because of an increase in internal carotid artery blood flow (80%, P < 0.001) and preserved cerebrovascular reactivity. Despite these adaptive changes, an increase in brain HIF-dependent mRNA levels was observed (erythropoietin: P < 0.001; heme oxygenase-1: P = 0.01), providing evidence for subtle cerebral tissue hypoxia in anemic mice. These data demonstrate that moderate subacute anemia causes significant renal tissue hypoxia, whereas adaptive cerebrovascular responses limit the degree of cerebral tissue hypoxia. Further studies are required to assess whether hypoxia is a mechanism for acute kidney injury associated with anemia.
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Injúria Renal Aguda/sangue , Anemia/sangue , Anticorpos Monoclonais , Encéfalo/irrigação sanguínea , Eritrócitos/metabolismo , Hipóxia Encefálica/sangue , Rim/irrigação sanguínea , Oxigênio/sangue , Injúria Renal Aguda/imunologia , Injúria Renal Aguda/patologia , Injúria Renal Aguda/fisiopatologia , Anemia/imunologia , Anemia/patologia , Anemia/fisiopatologia , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Circulação Cerebrovascular , Modelos Animais de Doenças , Eritrócitos/imunologia , Eritrócitos/patologia , Eritropoetina/genética , Eritropoetina/metabolismo , Glicoforinas/sangue , Glicoforinas/imunologia , Hemólise , Hipóxia Encefálica/imunologia , Hipóxia Encefálica/patologia , Hipóxia Encefálica/fisiopatologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Rim/metabolismo , Rim/patologia , Masculino , Camundongos Transgênicos , Circulação Renal , Índice de Gravidade de Doença , Baço/metabolismo , Baço/patologia , Regulação para CimaRESUMO
During physiological stress (e.g., exercise, hypoxia), blood flow is shunted to specific anatomical regions to protect critical organs; yet, splenic blood flow in these circumstances remains to be investigated. Despite being classically viewed as a non-critical organ, recent experimental and epidemiological evidence suggests the spleen plays a significant role in cardiovascular pathophysiology. We hypothesized that splenic blood flow is prioritized in the development of heart failure (i.e., chronic state of reduced cardiac output). Five-week-old male Wistar rats were randomized for either myocardial infarction (MI; n = 58) or sham (n = 56) surgery. At 2, 5, and 9 weeks post-surgery, Doppler ultrasound measurements of the splenic, left renal, left common carotid, and left femoral arteries were performed. Cardiac function was assessed at all time points using echocardiography and at 9 weeks post-surgery using invasive hemodynamic analysis. Splenic and cerebral blood flow was preferentially maintained at 9 weeks post-MI, whereas blood flow to the lower limb and kidney were reduced. Spleen size increased by 5 weeks post-MI and remained elevated. Splenic blood flow was maintained in conditions of decreased cardiac output, when other tissues showed decreased blood flow. The maintenance of blood flow in the face of decreased cardiac output indicates that splenic function is being prioritized during heart failure.
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Débito Cardíaco , Insuficiência Cardíaca/fisiopatologia , Infarto do Miocárdio/fisiopatologia , Fluxo Sanguíneo Regional , Baço/irrigação sanguínea , Animais , Modelos Animais de Doenças , Progressão da Doença , Ecocardiografia , Coração/diagnóstico por imagem , Coração/fisiopatologia , Humanos , Masculino , Infarto do Miocárdio/etiologia , Tamanho do Órgão , Ratos , Ratos Wistar , Baço/diagnóstico por imagem , Baço/fisiopatologia , Ultrassonografia DopplerRESUMO
BACKGROUND: Clinical guidelines recommend monitoring of blood pressure at home using an automatic blood pressure device for the management of hypertension. Devices are not often calibrated against direct blood pressure measures, leaving health care providers and patients with less reliable information than is possible with current technology. Rigorous assessments of medical devices are necessary for establishing clinical utility. OBJECTIVE: The purpose of our study was 2-fold: (1) to assess the validity and perform iterative calibration of indirect blood pressure measurements by a noninvasive wrist cuff blood pressure device in direct comparison with simultaneously recorded peripheral and central intra-arterial blood pressure measurements and (2) to assess the validity of the measurements thereafter of the noninvasive wrist cuff blood pressure device in comparison with measurements by a noninvasive upper arm blood pressure device to the Canadian hypertension guidelines. METHODS: The cloud-based blood pressure algorithms for an oscillometric wrist cuff device were iteratively calibrated to direct pressure measures in 20 consented patient participants. We then assessed measurement validity of the device, using Bland-Altman analysis during routine cardiovascular catheterization. RESULTS: The precalibrated absolute mean difference between direct intra-arterial to wrist cuff pressure measurements were 10.8 (SD 9.7) for systolic and 16.1 (SD 6.3) for diastolic. The postcalibrated absolute mean difference was 7.2 (SD 5.1) for systolic and 4.3 (SD 3.3) for diastolic pressures. This is an improvement in accuracy of 33% systolic and 73% diastolic with a 48% reduction in the variability for both measures. Furthermore, the wrist cuff device demonstrated similar sensitivity in measuring high blood pressure compared with the direct intra-arterial method. The device, when calibrated to direct aortic pressures, demonstrated the potential to reduce a treatment gap in high blood pressure measurements. CONCLUSIONS: The systolic pressure measurements of the wrist cuff have been iteratively calibrated using gold standard central (ascending aortic) pressure. This improves the accuracy of the indirect measures and potentially reduces the treatment gap. Devices that undergo auscultatory (indirect) calibration for licensing can be greatly improved by additional iterative calibration via intra-arterial (direct) measures of blood pressure. Further clinical trials with repeated use of the device over time are needed to assess the reliability of the device in accordance with current and evolving guidelines for informed decision making in the management of hypertension. TRIAL REGISTRATION: ClinicalTrials.gov NCT03015363; https://clinicaltrials.gov/ct2/show/NCT03015363 (Archived by WebCite at http://www.webcitation.org/6xPZgseYS).
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Determinação da Pressão Arterial/instrumentação , Monitores de Pressão Arterial/normas , Pressão Sanguínea/fisiologia , Hipertensão/diagnóstico , Punho/irrigação sanguínea , Adulto , Idoso , Calibragem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos TestesRESUMO
Podocytes are specialized epithelial cells of the kidney blood filtration barrier that contribute to permselectivity via a series of interdigitating actin-rich foot processes. Positioned between adjacent projections is a unique cell junction known as the slit diaphragm, which is physically connected to the actin cytoskeleton via the transmembrane protein nephrin. Evidence indicates that tyrosine phosphorylation of the intracellular tail of nephrin initiates signaling events, including recruitment of cytoplasmic adaptor proteins Nck1 and Nck2 that regulate actin cytoskeletal dynamics. Nephrin tyrosine phosphorylation is altered in human and experimental renal diseases characterized by pathologic foot process remodeling, prompting the hypothesis that phosphonephrin signaling directly influences podocyte morphology. To explore this possibility, we generated and analyzed knockin mice with mutations that disrupt nephrin tyrosine phosphorylation and Nck1/2 binding (nephrin(Y3F/Y3F) mice). Homozygous nephrin(Y3F/Y3F) mice developed progressive proteinuria accompanied by structural changes in the filtration barrier, including podocyte foot process effacement, irregular thickening of the glomerular basement membrane, and dilated capillary loops, with a similar but later onset phenotype in heterozygous animals. Furthermore, compared with wild-type mice, nephrin(Y3F/Y3F) mice displayed delayed recovery in podocyte injury models. Profiling of nephrin tyrosine phosphorylation dynamics in wild-type mice subjected to podocyte injury indicated site-specific differences in phosphorylation at baseline, injury, and recovery, which correlated with loss of nephrin-Nck1/2 association during foot process effacement. Our results define an essential requirement for nephrin tyrosine phosphorylation in stabilizing podocyte morphology and suggest a model in which dynamic changes in phosphotyrosine-based signaling confer plasticity to the podocyte actin cytoskeleton.
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Podócitos/fisiologia , Podócitos/ultraestrutura , Tirosina/metabolismo , Animais , Feminino , Masculino , Proteínas de Membrana , Camundongos , Camundongos Endogâmicos C57BL , Fosforilação , Transdução de SinaisRESUMO
Dyspnea and reduced exercise capacity, caused, in part, by respiratory muscle dysfunction, are common symptoms in patients with heart failure (HF). However, the etiology of diaphragmatic dysfunction has not been identified. To investigate the effects of HF on diaphragmatic function, models of HF were surgically induced in CD-1 mice by transverse aortic constriction (TAC) and acute myocardial infarction (AMI), respectively. Assessment of myocardial function, isolated diaphragmatic strip function, myofilament force-pCa relationship, and phosphorylation status of myofilament proteins was performed at either 2 or 18 wk postsurgery. Echocardiography and invasive hemodynamics revealed development of HF by 18 wk postsurgery in both models. In vitro diaphragmatic force production was preserved in all groups while morphometric analysis revealed diaphragmatic atrophy and fibrosis in 18 wk TAC and AMI groups. Isometric force-pCa measurements of myofilament preparations revealed reduced Ca(2+) sensitivity of force generation and force generation at half-maximum and maximum Ca(2+) activation in 18 wk TAC. The rate of force redevelopment (ktr) was reduced in all HF groups at high levels of Ca(2+) activation. Finally, there were significant changes in the myofilament phosphorylation status of the 18 wk TAC group. This includes a decrease in the phosphorylation of troponin T, desmin, myosin light chain (MLC) 1, and MLC 2 as well as a shift in myosin isoforms. These results indicate that there are multiple changes in diaphragmatic myofilament function, which are specific to the type and stage of HF and occur before overt impairment of in vitro force production.
Assuntos
Diafragma/metabolismo , Dispneia/metabolismo , Insuficiência Cardíaca/metabolismo , Contração Isométrica , Proteínas Musculares/metabolismo , Força Muscular , Miofibrilas/metabolismo , Animais , Sinalização do Cálcio , Diafragma/fisiopatologia , Modelos Animais de Doenças , Progressão da Doença , Dispneia/fisiopatologia , Insuficiência Cardíaca/fisiopatologia , Técnicas In Vitro , Masculino , Camundongos , Infarto do Miocárdio/metabolismo , Infarto do Miocárdio/fisiopatologia , Fosforilação , Fatores de Tempo , Remodelação VentricularRESUMO
The obesity epidemic is considered one of the most serious public health problems of the modern world. Physical therapy is the most accessible form of treatment; however, compliance is a major obstacle due to exercise intolerance and dyspnea. Respiratory muscle atrophy is a cause of dyspnea, yet little is known of obesity-induced respiratory muscle dysfunction. Our objective was to investigate whether obesity-induced skeletal muscle wasting occurs in the diaphragm, the main skeletal muscle involved in inspiration, using the Zucker diabetic fatty (ZDF) rat. After 14 wk, ZDF rats developed obesity, hyperglycemia, and insulin resistance, compared with lean controls. Hemodynamic analysis revealed ZDF rats have impaired cardiac relaxation (P = 0.001) with elevated end-diastolic pressure (P = 0.006), indicative of diastolic dysfunction. Assessment of diaphragm function revealed weakness (P = 0.0296) in the absence of intrinsic muscle impairment in ZDF rats. Diaphragm morphology revealed increased fibrosis (P < 0.0001), atrophy (P < 0.0001), and reduced myosin heavy-chain content (P < 0.001), compared with lean controls. These changes are accompanied by activation of the myostatin signaling pathway with increased serum myostatin (P = 0.017), increased gene expression (P = 0.030) in the diaphragm and retroperitoneal adipose (P = 0.033), and increased SMAD2 phosphorylation in the diaphragm (P = 0.048). Here, we have confirmed the presence of respiratory muscle atrophy and weakness in an obese, diabetic model. We have also identified a pathological role for myostatin signaling in obesity, with systemic contributions from the adipose tissue, a nonskeletal muscle source. These findings have significant implications for future treatment strategies of exercise intolerance in an obese, diabetic population.
Assuntos
Diabetes Mellitus Experimental/fisiopatologia , Debilidade Muscular/fisiopatologia , Músculos Respiratórios/fisiopatologia , Animais , Diabetes Mellitus Experimental/complicações , Hemodinâmica , Resistência à Insulina , Masculino , Debilidade Muscular/patologia , Miostatina/metabolismo , Obesidade/fisiopatologia , Ratos , Ratos Zucker , Músculos Respiratórios/patologia , Transdução de Sinais , Proteína Smad2/genética , Proteína Smad2/metabolismo , Regulação para CimaRESUMO
Blood flow data from contracting muscle in humans indicates that adenosine (ADO) stimulates the production of nitric oxide (NO) and vasodilating prostaglandins (PG) to produce arteriolar vasodilatation in a redundant fashion such that when one is inhibited the other can compensate. We sought to determine whether these redundant mechanisms are employed at the microvascular level. First, we determined whether PGs were involved in active hyperaemia at the microvascular level. We stimulated four to five skeletal muscle fibres in the anaesthetized hamster cremaster preparation in situ and measured the change in diameter of 2A arterioles (maximum diameter 40 µm, third arteriolar level up from the capillaries) at a site of overlap with the stimulated muscle fibres before and after 2 min of contraction [stimulus frequencies: 4, 20 and 60 Hz at 15 contractions per minute (CPM) or contraction frequencies of 6, 15 or 60 CPM at 20 Hz; 250 ms train duration]. Muscle fibres were stimulated in the absence and presence of the phospholipase A2 inhibitor quinacrine. Further, we applied a range of concentrations of ADO (10(-7)-10(-5) M) extraluminally, (to mimic muscle contraction) in the absence and presence of L-NAME (NO synthase inhibitor), indomethacin (INDO, cyclooxygenase inhibitor) and L-NAME + INDO and observed the response of 2A arterioles. We repeated the latter experiment on a different level of the cremaster microvasculature (1A arterioles) and on the microvasculature of a different skeletal muscle (gluteus maximus, 2A arterioles). We observed that quinacrine inhibited vasodilatation during muscle contraction at intermediate and high contraction frequencies (15 and 60 CPM). L-NAME, INDO and L-NAME + INDO were not effective at inhibiting vasodilatation induced by any concentration of ADO tested in 2A and 1A arterioles in the cremaster muscle or 2A arterioles in the gluteus maximus muscle. Our data show that PGs are involved in the vasodilatation of the microvasculature in response to muscle contraction but did not obtain evidence that extraluminal ADO causes vasodilatation through NO or PG or both. Thus, we propose that PG-induced microvascular vasodilation during exercise is independent of ADO.