Cardiac Aging In Mice Research Articles

Kielin/chordin-like protein deficiency causes cardiac aging in male mice.

Previous studies have demonstrated that bone morphogenetic proteins (BMPs) play important roles in cardiovascular diseases, including atherosclerosis, artery calcification, myocardial remodeling, pulmonary arterial hypertension, and diabetic cardiomyopathy. Kielin/chordin-like protein (KCP) is a secreted protein that regulates the expression and function of BMPs. However, the role of KCP in cardiac aging remains unknown. In this study, we aimed to investigate the role of KCP in cardiac aging and its possible mechanisms. Echocardiogram showed that heart function was impaired in aged mice (24 months). In addition, analysis of heart structure showed that KCP knockout (KO) aggravated cardiac remodeling in aged mice. Moreover, KCP KO increased p-smad2/3 and TGF-β expression, while decreased BMP-2 expression in aged mice. Furthermore, KCP KO increased the expression of cardiac senescence-related proteins in aged mice. KCP KO aggravated the imbalance of oxidants and antioxidants and increased the expression of proinflammatory cytokines and cardiomyocyte apoptosis in aged mice. Our study demonstrated that KCP KO aggravated cardiac aging in mice by increasing the levels of oxidative stress, inflammation, and cardiomyocyte apoptosis. KEY MESSAGE: KCP KO aggravated aging-related cardiac dysfunction and remodeling in male mice. KCP KO aggravated cardiac aging by increasing the levels of oxidative stress, inflammation, and cardiomyocyte apoptosis.

17β-Estradiol alleviates cardiac aging induced by d-galactose by downregulating the methylation of autophagy-related genes

Intrinsic cardiac aging increases cardiovascular mortality and morbidity in the elderly. Estrogen helps reduce the risk of cardiovascular disease in women, with 17β-estradiol (17β-E2) activating the autophagy pathway and inhibiting vascular aging, mainly through estrogen receptor alpha (ER α) to prevent atherosclerosis. Abnormal methylation of autophagy-related genes can impact autophagic regulation. We hypothesized that 17β-E2, specifically 17β-E2 α, downregulates the methylation of autophagy factors and delays cardiac aging. Here, we used d-galactose, 17β-E2, and ER α receptor antagonist methyl-piperidino-pyrazole (MPP) to establish different aging models in mice divided into four groups, namely negative control, D.gal, D.gal + 17β-E2, and D.gal + 17β-E2 + MPP groups. Echocardiography showed that compared with the D.gal group group, the D.gal + 17β-E2 showed substantially increased cardiac function. The level of cardiac aging markers in mice in the D.gal + 17β-E2 group was lower than that in mice in the D.gal group. Beclin1, LC3, and Atg5 mRNA and protein expression levels in mice in the D.gal + 17β-E2 group were significantly increased compared with those in the D.gal group. Additionally, Beclin1, LC3, and Atg5 methylation levels were significantly decreased in the D.gal + 17β-E2 group. All the above values of the D.gal + 17β-E2 + MPP group were between those of the D.gal and D.gal + 17β-E2 groups. The expression of Dnmt1, Dnmt2, and Dnmt3A genes was the highest in the D.gal group. In summary, our results suggest that 17β-E2, specifically 17β-E2 α, promotes autophagy by downregulating the methylation of autophagy factors, thereby inhibiting galactose-induced cardiac aging in mice. 17β-E2 may be a potential therapeutic target to mitigate the effects of cardiac aging.

The Role of Nrf2 in D-Galactose-Induced Cardiac Aging in Mice: Involvement of Oxidative Stress

Introduction: Cardiac aging is the major risk factor for advanced heart disease, which is the leading cause of death in developed countries, accounting for >30% of deaths worldwide. Objective: To discover the detailed mechanism of cardiac aging and develop an effective therapeutic candidate drug to treat or delay cardiac aging. Methods: We used D-galactose to induce cardiac aging in Nrf2^+/+ and Nrf2^–/– mice, and then treated these mice with vehicle or the Nrf2 activator, CDDO-imidazolide (CDDO-Im). Results and Conclusions: D-galactose injection significantly induced cardiac aging, cell apoptosis, and oxidative stress in Nrf2^+/+ mice, all of which were further exacerbated in Nrf2^–/– mice. CDDO-Im treatment can effectively weaken oxidative stress and enhance the activities of antioxidant enzymes, but CDDO-Im lost its antioxidative effect in the Nrf2^–/– mice. Nrf2 activator CDDO-Im could therefore effectively protect against D-galactose-induced cardiac aging by inhibiting oxidative stress, suggesting that CDDO-Im might be a potential and promising therapeutic candidate drug to treat cardiac aging.

Loss of Repressor Activator Protein 1 Precipitates Cardiac Aging in Mice via p53/PPARα Signaling

BackgroundTelomere dysfunction has been linked to many aspects of the aging process. Increasing evidence indicates that telomere dysfunction leads to cardiac mitochondrial defects. Mammalian repressor activator protein 1 (Rap1) is one of the components of shelterin complex and essential for the maintenance of telomere length and structural integrity. Our preliminary work showed that aged Rap1 knockout (Rap1−/−) mice exhibited more pronounced aging‐associated phenotypes (including earlier hair graying, hair loss, reduced body weight). However, the effects of Rap1 on mitochondrial function and its contribution to cardiac aging are largely unknown. Thus, the present study investigated whether or not loss of Rap1 in mice precipitates cardiac aging and explored the underlying mechanisms.Methods and ResultsMice cardiac function was assessed with transthoracic echocardiography performed noninvasively using a Vevo 2100 high‐resolution imaging system. Deletion of Rap1 in mice aggravated aging‐related cardiac structural changes and dysfunction, as evidenced by increased left ventricular (LV) posterior wall end‐diastole and LV mass, reductions in ejection fraction and fractional shortening, as well as significantly reduced myocardial performance index (all p < 0.05, Rap1−/− vs. age‐matched counterparts). These changes were associated with greater cardiac senescence (enhanced SA‐β‐gal staining), cardiac hypertrophy (enhanced wheat germ agglutinin staining and increased the ratio of heart weight with body weight), abnormalities in the mitochondrial ultrastructure (cristae fragmentation, vacuolization). Mechanistically, Rap1 deficiency led to shorter telomere (T/S ratio), enhanced DNA damage (γH2AX) and increased nuclear p53 level in vivo in the myocardium and in primary cardiomyocytes when compared to age‐matched counterparts (one year old). Chromatin immunoprecipitation revealed that p53 directly binded to the promote site of PPARα [a central regulator of cardiac fatty acid metabolism (FAM)] and repressed its expression. Rap1 deficiency impaired FAM (reduced CD36, CPT1α, ACADL level and palmitate‐induced oxygen consumption), while PFTα (a p53 inhibitor, i.p. 1.1 mg/kg/day) treatment in Rap1−/− mice significantly alleviated cardiac aging and enhanced FAM by restoration of PPARα.ConclusionsWith aging, Rap1 deficiency may lead to shorter telomere length, increase DNA damage and thereby activate p53, which in turn suppresses PPARα, leading to impaired FAM and mitochondrial defects with abnormal cardiac structure and dysfunction. These findings may identify a new cardiac dimension in the physiological role played by telomere‐Rap1.Support or Funding InformationThe authors’ work was supported by the General Research Fund (17123718M, Research Grants Council of Hong Kong).

Abstract 16948: TXLNB is Necessary for Physiological Hypertrophy During Cardiac Aging

Cardiac aging in mice and humans is associated with cardiac hypertrophy, fibrosis, diastolic dysfunction, and a reduced ability to adapt to stress. Recent evidence suggests that cardiac proteostasis - the coordinated regulation of protein synthesis, repair, and degradation mechanisms - is dysregulated during cardiac aging and contributes to cardiac structural and functional deficits, but the underlying molecular mechanisms are unknown. In recent work, we identified beta-taxilin ( TXLNB ) as a cardiac-enriched protein that regulates cardiomyocyte proteostasis. Overexpression of TXLNB in neonatal rat cardiomyocytes increased protein synthesis, decreased ubiquitination, increased proteasome activity, and increased autophagy. In addition, TXLNB -knockout ( TXLNB -KO) mice generated by CRISPR/Cas9 exhibited altered cardiac proteasome activities (Fig. 1A: decreased 26Sβ5 activity (p=0.025, n=8), increased 26Sβ1 activity (p=0.13, n=8), and accumulate ubiquitinated proteins (Fig. 1B). Despite this profound proteasomal insufficiency, TXLNB -KO mice develop normal cardiac structure and function (at 12 weeks of age) and show appropriate hypertrophic responses to pressure overload via transverse aortic constriction. This suggests that TXLNB is not required for cardiac development or cardiac hypertrophy in young mice. We therefore initiated follow-up studies in 3, 6, 10, and 24 week-old mice to evaluate the role of TXLNB in aging-related cardiac hypertrophy. In these mice, there was no significant difference in body weight or tibia length based on genotype; however, between 10-24 months of age, TXLNB -KO mice did not show the typical increase in heart size observed in WT mice (Fig.1C, 10 months, p=0.023, n=7; 24 months, p=0.026, n=3-4). This suggests that TXLNB is necessary for adaptive cardiac remodeling that occurs during aging. Ongoing work will establish if aged TXLNB -KO mice have decreased cardiac function or an impaired adaptation to cardiac stress.

HSP27 Alleviates Cardiac Aging in Mice via a Mechanism Involving Antioxidation and Mitophagy Activation.

Aging-induced cardiac dysfunction is a prominent feature of cardiac aging. Heat shock protein 27 (HSP27) protects cardiac function against ischemia or chemical challenge. We hypothesized that HSP27 attenuates cardiac aging. Transgenic (Tg) mice with cardiac-specific expression of the HSP27 gene and wild-type (WT) littermates were employed in the experiments. Echocardiography revealed a significant decline in the cardiac function of old WT mice compared with young WT mice. In striking contrast, the aging-induced impairment of cardiac function was attenuated in old Tg mice compared with old WT mice. Levels of cardiac aging markers were lower in old Tg mouse hearts than in old WT mouse hearts. Less interstitial fibrosis and lower contents of reactive oxygen species and ubiquitin-conjugated proteins were detected in old Tg hearts than in old WT hearts. Furthermore, old Tg hearts demonstrated lower accumulation of LC3-II and p62 than old WT hearts. Levels of Atg13, Vps34, and Rab7 were also higher in old Tg hearts than in old WT hearts. Additionally, old Tg hearts had higher levels of PINK1 and Parkin than old WT hearts, suggesting that mitophagy was activated in old Tg hearts. Taken together, HSP27 alleviated cardiac aging and this action involved antioxidation and mitophagy activation.

Overexpression of Catalase Diminishes Oxidative Cysteine Modifications of Cardiac Proteins.

Reactive protein cysteine thiolates are instrumental in redox regulation. Oxidants, such as hydrogen peroxide (H2O2), react with thiolates to form oxidative post-translational modifications, enabling physiological redox signaling. Cardiac disease and aging are associated with oxidative stress which can impair redox signaling by altering essential cysteine thiolates. We previously found that cardiac-specific overexpression of catalase (Cat), an enzyme that detoxifies excess H2O2, protected from oxidative stress and delayed cardiac aging in mice. Using redox proteomics and systems biology, we sought to identify the cysteines that could play a key role in cardiac disease and aging. With a ‘Tandem Mass Tag’ (TMT) labeling strategy and mass spectrometry, we investigated differential reversible cysteine oxidation in the cardiac proteome of wild type and Cat transgenic (Tg) mice. Reversible cysteine oxidation was measured as thiol occupancy, the ratio of total available versus reversibly oxidized cysteine thiols. Catalase overexpression globally decreased thiol occupancy by ≥1.3 fold in 82 proteins, including numerous mitochondrial and contractile proteins. Systems biology analysis assigned the majority of proteins with differentially modified thiols in Cat Tg mice to pathways of aging and cardiac disease, including cellular stress response, proteostasis, and apoptosis. In addition, Cat Tg mice exhibited diminished protein glutathione adducts and decreased H2O2 production from mitochondrial complex I and II, suggesting improved function of cardiac mitochondria. In conclusion, our data suggest that catalase may alleviate cardiac disease and aging by moderating global protein cysteine thiol oxidation.

Genetic Deletion of Fkbp12.6 Accelerates Cardiac Aging in Mice

Aims: Cardiac aging is one of the main causes of heart dysfunction and other cardiac diseases. FK506 binding protein 12.6 (FKBP12.6) modulates Ca2+ release from the sarcoplasmic reticulum in cardiomyocytes. Previous studies implied that genetic deletion of FKBP12.6 leads to cardiac aging related phenotypes. However, the role and mechanism of FKBP12.6 in the process of cardiac aging remain unclear.Methods and Results: To assess whether FKBP12.6 is involved in cardiac aging and age-related heart dysfunction, FKBP12.6 knockout (KO) and control littermate mice were used throughout the study. We found a significant association between deletion of FKBP12.6 and cardiac aging. Indeed, aged FKBP12.6 KO mice exhibited markedly impaired cardiac function compared to wild-type. Strikingly, FKBP12.6 deletion resulted also in increased levels of cell cycle inhibitors p16 and p19, augmented cardiac fibrosis, cell death, and shorter telomeres. Finally, we demonstrated that FKBP12.6 deletion enhanced insulin signaling in the hearts, resulting in AKT phosphorylation, augmented mTOR activity, and impaired autophagy.Conclusions: Taken together, these results identify that genetic deletion of FKBP12.6 promotes cardiac aging and indicate that the activation of the AKT/mTOR pathway plays a mechanistic role in the process.

45 - Short Term Treatment with Mitochondrial Protective Peptide Reverses Cardiac Aging in Mice

45 - Short Term Treatment with Mitochondrial Protective Peptide Reverses Cardiac Aging in Mice

Overexpression of Catalase Targeted to Mitochondria Attenuates Murine Cardiac Aging

Age is a major risk for cardiovascular diseases. Although mitochondrial reactive oxygen species have been proposed as one of the causes of aging, their role in cardiac aging remains unclear. We have previously shown that overexpression of catalase targeted to mitochondria (mCAT) prolongs murine median lifespan by 17% to 21%. We used echocardiography to study cardiac function in aging cohorts of wild-type and mCAT mice. Changes found in wild-type mice recapitulate human aging: age-dependent increases in left ventricular mass index and left atrial dimension, worsening of the myocardial performance index, and a decline in diastolic function. Cardiac aging in mice is accompanied by accumulation of mitochondrial protein oxidation, increased mitochondrial DNA mutations and deletions and mitochondrial biogenesis, increased ventricular fibrosis, enlarged myocardial fiber size, decreased cardiac SERCA2 protein, and activation of the calcineurin-nuclear factor of activated T-cell pathway. All of these age-related changes were significantly attenuated in mCAT mice. Analysis of survival of 130 mice demonstrated that echocardiographic cardiac aging risk scores were significant predictors of mortality. The estimated attributable risk to mortality for these 2 parameters was 55%. This study shows that cardiac aging in the mouse closely recapitulates human aging and demonstrates the critical role of mitochondrial reactive oxygen species in cardiac aging and the impact of cardiac aging on survival. These findings also support the potential application of mitochondrial antioxidants in reactive oxygen species-related cardiovascular diseases.

P-11 Suppression of Insulin Signaling Improves Protein Homeostasis and Prevents Cardiac Aging in Mice

P-9 Delayed Enhancement on Cardiac Magnetic Resonance and Clinical, Morphological and ECG Features in Hypertrophic Cardiomyopathy Hiroshi Satoh1, Fumitaka Matoh2, Katsunori Shiraki1, Takeji Saitoh1, Masao Saotome1, Tsuyoshi Urushida1, Hideki Katoh1, Hideharu Hayashi1. 1Internal Medicine III, Hamamatsu University School of Medicine, Japan, 2Department of Cardiology, Omaezaki General Hospital, Japan