Mitochondria and cardiovascular aging Dai, Dao-Fu; Rabinovitch, Peter S; Ungvari, Zoltan
Circulation research,
2012-April-13, Letnik:
110, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Old age is a major risk factor for cardiovascular diseases. Several lines of evidence in experimental animal models have indicated the central role of mitochondria both in lifespan determination and ...in cardiovascular aging. In this article we review the evidence supporting the role of mitochondrial oxidative stress, mitochondrial damage and biogenesis as well as the crosstalk between mitochondria and cellular signaling in cardiac and vascular aging. Intrinsic cardiac aging in the murine model closely recapitulates age-related cardiac changes in humans (left ventricular hypertrophy, fibrosis and diastolic dysfunction), while the phenotype of vascular aging include endothelial dysfunction, reduced vascular elasticity, and chronic vascular inflammation. Both cardiac and vascular aging involve neurohormonal signaling (eg, renin-angiotensin, adrenergic, insulin-IGF1 signaling) and cell-autonomous mechanisms. The potential therapeutic strategies to improve mitochondrial function in aging and cardiovascular diseases are also discussed, with a focus on mitochondrial-targeted antioxidants, calorie restriction, calorie restriction mimetics, and exercise training.
Renal amyloidosis (RA) has a worldwide incidence of 5-13 cases per million person-years and is expected to rise in upcoming years due to growing awareness, plus improvement of diagnostic modalities. ...Diagnosing RA remains challenging, especially when encountering very small, focal, or early amyloid deposits. Since delays in diagnosis portends poor prognosis, high morbidity, and mortality, it is crucial to evaluate the performance of commonly used diagnostic modalities. This is the first study that presents a full picture of the diagnostic performance of fluorescence microscopy (FM) with a tetramethylrhodamine isothiocyanate (TRITC) filter to diagnose RA in general and stratified by compartments.
A retrospective double-blind diagnostic accuracy study of FM-TRITC filter was performed. The presence or absence of amyloid in the vascular, interstitial, and glomerular compartments was established in 316 representative Congo red-stained core biopsies with an FM-TRITC filter. This was contrasted with polarized microscopy (PM) showing apple-green birefringence as the gold standard. Sensitivity, specificity, positive and negative predictive values, likelihood ratios, and the receiver operating characteristic (ROC) curve were obtained using STATA13.
The prevalence of RA was 6.01%, comparable with that reported in the literature. Reciprocity with regard to the location and pattern of fluorescence and birefringence between the two diagnostic modalities was seen. The FM-TRITC filter has a sensitivity of 100%, specificity of 97.64%, and a positive and negative predictive value of 73.08% and 100%, respectively. The positive likelihood ratio was 42.37, and the negative was 0.00. Overall accuracy was 97.78%. The area under the ROC curve was 0.98. The Diagnostic performance of the FM-TRITC filter stratified by compartments is shown in Table 1. The area under the ROC curve was 0.99, 0.98, and 0.99 for the vascular, interstitial, and glomerular compartment, respectively. All patients with RA (n = 19) were correctly identified; this included one new case, one case with small and focal amyloid, and two early cases with less dense amyloid where birefringence was ambiguous by PM.
The FM-TRITC filter is a highly accurate, sensitive, specific, with excellent predictive values, time-efficient, easy to perform, and suitable to reproduce diagnostic modality for RA. It can accurately rule out RA in all compartments, and in most cases concomitant use of PM should not be indispensable. The diagnosis of vascular, interstitial, and glomerular amyloid deposits can be done using only the FM-TRITC filter with Congo red-stained slides. Exceptionally, a few cases of interstitial amyloidosis could be overdiagnosed due to interferences (e.g. artefacts), these cases could be further assessed with a second diagnostic modality if positive fluorescence is seen. Routine use of the FM-TRITC filter can aid in the diagnosis of early RA, even when the deposits are inconspicuous by PM.
Human pluripotent stem cells (PSCs) represent an attractive source of cardiomyocytes with potential applications including disease modeling, drug discovery and safety screening, and novel cell-based ...cardiac therapies. Insights from embryology have contributed to the development of efficient, reliable methods capable of generating large quantities of human PSC-cardiomyocytes with cardiac purities ranging up to 90%. However, for human PSCs to meet their full potential, the field must identify methods to generate cardiomyocyte populations that are uniform in subtype (e.g. homogeneous ventricular cardiomyocytes) and have more mature structural and functional properties. For in vivo applications, cardiomyocyte production must be highly scalable and clinical grade, and we will need to overcome challenges including graft cell death, immune rejection, arrhythmogenesis, and tumorigenic potential. Here we discuss the types of human PSCs, commonly used methods to guide their differentiation into cardiomyocytes, the phenotype of the resultant cardiomyocytes, and the remaining obstacles to their successful translation.
Human pluripotent stem cells (PSCs) can be isolated from the inner cell mass (ICM) or reprogrammed from somatic cell sources (e.g. fibroblasts), yielding embryonic stem cells and induced pluripotent stem cells, respectively. Multiple protocols exist to guide the differentiation of both human PSC types into cardiomyocytes, including embryoid body (EB)- and monolayer-based methods. Human PSC-derived cardiomyocytes show tremendous promise, but a number of major obstacles must be overcome before they can be successful translated into a practical source of heart cells for disease modeling, drug screening and cell-based cardiac therapies. Display omitted
Summary
Chronic caloric restriction (CR) and rapamycin inhibit the mechanistic target of rapamycin (mTOR) signaling, thereby regulating metabolism and suppressing protein synthesis. Caloric ...restriction or rapamycin extends murine lifespan and ameliorates many aging‐associated disorders; however, the beneficial effects of shorter treatment on cardiac aging are not as well understood. Using a recently developed deuterated‐leucine labeling method, we investigated the effect of short‐term (10 weeks) CR or rapamycin on the proteomics turnover and remodeling of the aging mouse heart. Functionally, we observed that short‐term CR and rapamycin both reversed the pre‐existing age‐dependent cardiac hypertrophy and diastolic dysfunction. There was no significant change in the cardiac global proteome (823 proteins) turnover with age, with a median half‐life 9.1 days in the 5‐month‐old hearts and 8.8 days in the 27‐month‐old hearts. However, proteome half‐lives of old hearts significantly increased after short‐term CR (30%) or rapamycin (12%). This was accompanied by attenuation of age‐dependent protein oxidative damage and ubiquitination. Quantitative proteomics and pathway analysis revealed an age‐dependent decreased abundance of proteins involved in mitochondrial function, electron transport chain, citric acid cycle, and fatty acid metabolism as well as increased abundance of proteins involved in glycolysis and oxidative stress response. This age‐dependent cardiac proteome remodeling was significantly reversed by short‐term CR or rapamycin, demonstrating a concordance with the beneficial effect on cardiac physiology. The metabolic shift induced by rapamycin was confirmed by metabolomic analysis.
Objectives We investigated the effect of reducing mitochondrial oxidative stress by the mitochondrial-targeted antioxidant peptide SS-31 in hypertensive cardiomyopathy. Background Oxidative stress ...has been implicated in hypertensive cardiovascular diseases. Mitochondria and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase have been proposed as primary sites of reactive oxygen species (ROS) generation. Methods The mitochondrial targeted antioxidant peptide SS-31 was used to determine the role of mitochondrial oxidative stress in angiotensin II (Ang)-induced cardiomyopathy as well as in Gαq overexpressing mice with heart failure. Results Ang induces mitochondrial ROS in neonatal cardiomyocytes, which is prevented by SS-31, but not the nontargeted antioxidant N-acetyl cysteine (NAC). Continuous administration of Ang for 4 weeks in mice significantly increased both systolic and diastolic blood pressure, and this was not affected by SS-31 treatment. Ang was associated with up-regulation of NADPH oxidase 4 (NOX4) expression and increased cardiac mitochondrial protein oxidative damage, and induced the signaling for mitochondrial biogenesis. Reducing mitochondrial ROS by SS-31 substantially attenuated Ang-induced NOX4 up-regulation, mitochondrial oxidative damage, up-regulation of mitochondrial biogenesis, and phosphorylation of p38 mitogen-activated protein kinase and prevented apoptosis, concomitant with amelioration of Ang-induced cardiac hypertrophy, diastolic dysfunction, and fibrosis, despite the absence of blood pressure-lowering effect. The NAC did not show any beneficial effect. The SS-31 administration for 4 weeks also partially rescued the heart failure phenotype of Gαq overexpressing mice. Conclusions Mitochondrial targeted peptide SS-31 ameliorates cardiomyopathy resulting from prolonged Ang stimulation as well as Gαq overexpression, suggesting its potential clinical application for target organ protection in hypertensive cardiovascular diseases.
Cardiovascular diseases (CVDs) are the major causes of death in the western world. The incidence of cardiovascular disease as well as the rate of cardiovascular mortality and morbidity increase ...exponentially in the elderly population, suggesting that age per se is a major risk factor of CVDs. The physiologic changes of human cardiac aging mainly include left ventricular hypertrophy, diastolic dysfunction, valvular degeneration, increased cardiac fibrosis, increased prevalence of atrial fibrillation, and decreased maximal exercise capacity. Many of these changes are closely recapitulated in animal models commonly used in an aging study, including rodents, flies, and monkeys. The application of genetically modified aged mice has provided direct evidence of several critical molecular mechanisms involved in cardiac aging, such as mitochondrial oxidative stress, insulin/insulin-like growth factor/PI3K pathway, adrenergic and renin angiotensin II signaling, and nutrient signaling pathways. This article also reviews the central role of mitochondrial oxidative stress in CVDs and the plausible mechanisms underlying the progression toward heart failure in the susceptible aging hearts. Finally, the understanding of the molecular mechanisms of cardiac aging may support the potential clinical application of several "anti-aging" strategies that treat CVDs and improve healthy cardiac aging.
This study investigated the direct roles of hydrogen peroxide (H2O2) in kidney aging using transgenic mice overexpressing glutathione peroxidase‐1 (GPX1 TG). We demonstrated that kidneys in old mice ...recapitulated kidneys in elderly humans and were characterized by glomerulosclerosis, tubular atrophy, interstitial fibrosis, and loss of cortical mass. Scavenging H2O2 by GPX1 TG significantly reduced mitochondrial and total cellular reactive oxygen species (ROS) and mitigated oxidative damage, thus improving these pathologies. The potential mechanisms by which ROS are increased in the aged kidney include a decreased abundance of an anti‐aging hormone, Klotho, in kidney tissue, and decreased expression of nuclear respiratory factor 2 (Nrf2), a master regulator of the stress response. Decreased Klotho or Nrf2 was not improved in the kidneys of old GPX1 TG mice, even though mitochondrial morphology was better preserved. Using laser capture microdissection followed by label‐free shotgun proteomics analysis, we show that the glomerular proteome in old mice was characterized by decreased abundance of cytoskeletal proteins (critical for maintaining normal glomerular function) and heat shock proteins, leading to increased accumulation of apolipoprotein E and inflammatory molecules. Targeted proteomic analysis of kidney tubules from old mice showed decreased abundance of fatty acid oxidation enzymes and antioxidant proteins, as well as increased abundance of glycolytic enzymes and molecular chaperones. GPX1 TG partially attenuated the remodeling of glomerular and tubule proteomes in aged kidneys. In summary, mitochondria from GPX1 TG mice are protected and kidney aging is ameliorated via its antioxidant activities, independent and downstream of Nrf2 or Klotho signaling.
Glutathione Peroxidase‐1 overexpression reduces oxidative stress, preserves mitochondrial cristae structures, and improves kidney pathology and proteome gemodeling in the glomeruli and tubules of old mouse kidneys. These beneficial effects are downstream and independent of Klotho and Nrf2 signaling.
Summary
Mitochondrial defects have been found in aging and several age‐related diseases. Mice with a homozygous mutation in the exonuclease encoding domain of mitochondrial DNA polymerase gamma ...(Polgm/m) are prone to age‐dependent accumulation of mitochondrial DNA mutations and have shown a broad spectrum of aging‐like phenotypes. However, the mechanism of cardiac phenotypes in relation to the role of mitochondrial DNA mutations and oxidative stress in this mouse model has not been fully addressed. We demonstrate age‐dependent cardiomyopathy in Polgm/m mice, which by 13–14 months of age displays marked cardiac hypertrophy and dilatation, impairment of systolic and diastolic function, and increased cardiac fibrosis. This age‐dependent cardiomyopathy is associated with increases in mitochondrial DNA (mtDNA) deletions and protein oxidative damage, increased expression of apoptotic and senescence markers, as well as a decline in signaling for mitochondrial biogenesis. The relationship of these changes to mitochondrial reactive oxygen species (ROS) was tested by crossing Polgm/m mice with mice that overexpress mitochondrial targeted catalase (mCAT). All of the above phenotypes were partially rescued in Polgm/m/mCAT mice. These data indicate that accumulation of mitochondrial DNA damage with age can lead to cardiomyopathy and that this phenotype is partly mediated by mitochondrial oxidative stress.
Age is a major risk factor for cardiovascular diseases, not only because it prolongs exposure to several other cardiovascular risks, but also owing to intrinsic cardiac aging, which reduces cardiac ...functional reserve, predisposes the heart to stress, and contributes to increased cardiovascular mortality in the elderly. Intrinsic cardiac aging in the murine model closely recapitulates age-related cardiac changes in humans, including left ventricular hypertrophy, fibrosis, and diastolic dysfunction. Cardiac aging in mice is accompanied by accumulation of mitochondrial protein oxidation, increased mitochondrial DNA mutations, increased mitochondrial biogenesis, as well as decreased cardiac SERCA2 protein. All of these age-related changes are significantly attenuated in mice overexpressing catalase targeted to mitochondria. These findings demonstrate the critical role of mitochondrial reactive oxygen species in cardiac aging and support the potential application of mitochondrial antioxidants to cardiac aging and age-related cardiovascular diseases.
Mitotic catastrophe (MC) is a major cause of podocyte loss in vitro and in vivo. We evaluated urine samples (n = 184 urine samples from diabetic patients; n = 41 patients) from diabetic patients and ...determined the presence of podocytes in the urine and studied their characteristics, specifically asking whether apoptosis versus MC is present. We also evaluated diabetic glomeruli in renal biopsy specimens by electron microscopy (n = 54). A battery of stains including the antibody to podocalyxin (PCX) were used. PCX and podocytes (PCX+podo) showed nuclear morphologies such as a i) mononucleated normal shape (8.7%), ii) large and abnormal shape (3.8%), iii) multinucleated with or without micronucleoli (31.2%), iv) mitotic spindles (8.2%), v) single nucleus and denucleation combined (10.3%), and vi) denucleation only (37.0%). Large size/abnormal shape, multinucleation, mitotic spindles, and a combination of single nucleus and denucleation were considered features of MC (53.5%). Dual staining of PCX+podo was positive for Glepp 1 (50%), whereas none of PCX+podo were positive for nephrin, podocin, leukocyte, or parietal epithelial cell markers (cytokeratin 8), annexin V, cleaved caspase-3, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. Ten percent of PCX+podo were positive for phosphorylated vimentin. Electron microscopy identified cellular and nuclear podocyte changes characteristic of MC. The majority of urine podocytes in diabetic patients showed MC, not apoptosis. This noninvasive approach may be clinically useful in determining progressive diabetic nephropathy or response to therapeutic intervention.
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