Molecular mechanism of endothelial and vascular aging: implications for cardiovascular disease

DNA damage-dependent mechanisms of ageing and disease in the macro- and microvasculature

A decline in the function of the macro- and micro-vasculature occurs with ageing. DNA damage also accumulates with ageing, and thus DNA damage and repair have important roles in physiological ageing. Considerable evidence also supports a crucial role for DNA damage in the development and progression of macrovascular disease such as atherosclerosis. These findings support the concept that prolonged exposure to risk factors is a major stimulus for DNA damage within the vasculature, in part via the generation of reactive oxygen species. Genomic instability can directly affect vascular cellular function, leading to cell cycle arrest, apoptosis and premature vascular cell senescence. In contrast, the study of age-related impaired function and DNA damage mechanisms in the microvasculature is limited, although ageing is associated with microvessel endothelial dysfunction. This review examines current knowledge on the role of DNA damage and DNA repair systems in macrovascular disease such as atherosclerosis and microvascular disease. We also discuss the cellular responses to DNA damage to identify possible strategies for prevention and treatment.

Central Role of Metabolism in Endothelial Cell Function and Vascular Disease

The importance of endothelial cell (EC) metabolism and its regulatory role in the angiogenic behavior of ECs during vessel formation and in the function of different EC subtypes determined by different vascular beds has been recognized only in the last few years. Even more importantly, apart from a role of nitric oxide and reactive oxygen species in EC dysfunction, deregulations of EC metabolism in disease only recently received increasing attention. Although comprehensive metabolic characterization of ECs still needs further investigation, the concept of targeting EC metabolism to treat vascular disease is emerging. In this overview, we summarize EC-specific metabolic pathways, describe the current knowledge on their deregulation in vascular diseases, and give an outlook on how vascular endothelial metabolism can serve as a target to normalize deregulated endothelium.

Clinical usefulness of metabolic risk factors to identify young asymptomatic women adults with subclinical atherosclerosis: A cross-sectional study

Interventions of cardiovascular disease should be implemented in early ages. But most studies were performed in middle aged or elderly adults because of the low prevalence in young, especially for women. We investigate the association between metabolic risk factors and subclinical atherosclerosis in young asymptomatic women adults, using carotid intima-media thickness (CIMT) as a marker of the atherosclerotic process.We performed a cross-sectional study of 950 Chinese young asymptomatic women adults (37.28 ± 5.16 years) who underwent a routine health screening examination. Triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), fasting blood glucose (FBG), homocysteine (HCY), gamma glutamyltransferase (GGT), uric acid, and CIMT were measured.Out of 950 subjects, 16 (1.7%) were detected with increased CIMT. Significant differences existed in the indicators including age, body mass index (BMI), TC, TG, LDL-C, LDL-C/HDL-C, non-HDL-C, and TC/HDL-C. Although TG, LDL-C, non-HDL-C, TC/HDL-C, and TG/HDL-C were the significant indicators when adjusted for age only, age, LDL-C/HDL-C, FBG, and GGT were the only independent relative indicators of increased CMIT that entered the multivariate model. The area under receiver operating characteristic curve for a linear combination of age, LDL-C/HDL-C, FBG, and GGT was 0.809 (95% confidence interval = 0.712-0.906), superior to any of the variables taken alone (age, AUC = 0.707; FBG, AUC = 0.710; LDL-C/HDL-C, AUC = 0.695; GGT, AUC = 0.648).The combined assessment of age, LDL-C/HDL-C, FBG, and GGT contributes to an early detection for subclinical atherosclerosis, providing guidance to clinicians for women's early interventions of latent cardiovascular disease. Neither of the above four individual indicators is qualified alone.

Vascular endothelial cells senescence is associated with NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation via reactive oxygen species (ROS)/thioredoxin-interacting protein (TXNIP) pathway

Endothelial dysfunction caused by endothelial cells senescence and chronic inflammation is tightly linked to the development of cardiovascular diseases. NLRP3 (NOD-like receptor family pyrin domain-containing3) inflammasome plays a central role in inflammatory response that is associated with diverse inflammatory diseases. This study explores the effects and possible mechanisms of NLRP3 inflammasome in endothelial cells senescence. Results show an increment of pro-inflammatory cytokine interleukin (IL) -1β secretion and caspase-1 activation during the senescence of endothelial cells induced by bleomycin. Moreover, secreted IL-1β promoted endothelial cells senescence through up-regulation of p53/p21 protein expression. NLRP3 inflammasome was found to mediate IL-1β secretion through the production of ROS (reactive oxygen species) during the senescence of endothelial cells. Furthermore, the association of TXNIP (thioredoxin-interacting protein) with NLRP3 induced by ROS promoted NLRP3 inflammasome activation in senescent endothelial cells. In addition, the expressions of NLRP3 inflammasome related genes, ASC (apoptosis associated speck-like protein containing a CARD), TXNIP, cleaved caspase-1 and IL-1β, were also increased in vitro and in vivo studies. These findings indicate that endothelial senescence could be mediated through ROS and NLRP3 inflammasome signaling pathways, suggesting a potential target for the prevention of endothelial senescence-related cardiovascular diseases.

Association of Preoperative Platelet-to-Lymphocyte Ratio with Atrial Fibrillation after Coronary Artery Bypass Graft Surgery

OBJECTIVE

The aim of this study was to investigate the association between platelet-to-lymphocyte ratio (PLR) and atrial fibrillation (AF) after coronary artery bypass graft (CABG) surgery.

SUBJECTS AND METHODS

A total of 125 patients were retrospectively analyzed. AF was diagnosed using standard clinical criteria, and PLR was calculated as the ratio of the platelets to lymphocytes, obtained from the blood samples that were taken in the fasting state before CABG surgery. The association of different variables with postoperative AF and PLR was calculated using univariate and multivariate analysis. The receiver operating characteristics curve was used to determine the sensitivity and specificity of PLR and the optimal cutoff value for predicting post-CABG AF.

RESULTS

Of the 125 patients, 50 with AF (mean age: 67.0 ± 9.5 years, 38 males and 12 females) and 75 patients without AF (mean age: 61.1 ± 9.1 years, 58 males and 17 females) were identified, and the difference in the mean age was statistically significant (p = 0.01). PLR was also significantly higher in those with AF (152.8 ± 82.2) than those without AF (118.2 ± 32.9) (p = 0.012). Univariate analysis showed that age and PLR were associated with AF after CABG surgery (p < 0.001 and p = 0.005, respectively). Using a multivariate logistic regression model with the backward elimination method, age and PLR remained as independent predictors of AF after CABG surgery (p < 0.001 and p = 0.005, respectively). PLR levels >119.3 predicted postoperative AF with 64% sensitivity and 56% specificity (AUC: 0.634, p = 0.012).

CONCLUSION

In this study, age and PLR level were independent predictors of AF after CABG surgery. Patients with an elevated preoperative PLR were at higher risk of AF after CABG surgery.

FGF21 represses cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 signaling pathway in an AMPK-dependent manner

Cerebrovascular aging has a high relationship with stroke and neurodegenerative disease. In the present study, we evaluated the influence of fibroblast growth factor 21 (FGF21) on angiotensin (Ang II)-mediated cerebrovascular aging in human brain vascular smooth muscle cells (hBVSMCs). Ang II induced remarkable aging-phenotypes in hBVSMCs, including enhanced SA-β-gal staining and NBS1 protein expression. First, we used immunoblotting assay to confirm protein expression of FGF21 receptor (FGFR1) and the co-receptor β-Klotho in cultured hBVSMCs. Second, we found that FGF21 treatment partly prevented the aging-related changes induced by Ang II. FGF21 inhibited Ang II-enhanced ROS production/superoxide anion levels, rescued the Ang II-reduced Complex IV and citrate synthase activities, and suppressed the Ang II-induced meprin protein expression. Third, we showed that FGF21 not only inhibited the Ang II-induced p53 activation, but also blocked the action of Ang II on Siah-1-TRF signaling pathway which is upstream factors for p53 activation. At last, either chemical inhibition of AMPK signaling pathway by a specific antagonist Compound C or knockdown of AMPKα1/2 isoform using siRNA, successfully abolished the anti-aging action of FGF21 in hBVSMCs. These results indicate that FGF21 protects against Ang II-induced cerebrovascular aging via improving mitochondrial biogenesis and inhibiting p53 activation in an AMPK-dependent manner, and highlight the therapeutic value of FGF21 in cerebrovascular aging-related diseases such as stroke and neurodegenerative disease.

Role of NOX2 in mediating doxorubicin-induced senescence in human endothelial progenitor cells

Senescence exerts a great impact on both biological and functional properties of circulating endothelial progenitor cells (EPCs), especially in cardiovascular diseases where the physiological process of aging is accelerated upon clinical administration of certain drugs such as doxorubicin. EPC impairment contributes to doxorubicin-induced cardiotoxicity. Doxorubicin accelerates EPC aging, although mechanisms underlying this phenomenon remain to be fully clarified. Here we investigated if Nox2 activity is able to modulate the premature senescence induced in vitro by doxorubicin in human EPCs. Results showed that in conditioned media obtained from late EPC cultures, the levels of interleukin-6, isoprostanes and nitric oxide bioavailability were increased and reduced respectively after 3h of doxorubicin treatment. These derangements returned to physiological levels when cells were co-treated with apocynin or gp91ds-tat (antioxidant and specific Nox2 inhibitors, respectively). Accordingly, Nox2 activity resulted to be activated by doxorubicin. Importantly, we found that Nox2 inhibition reduced doxorubicin-induced EPC senescence, as indicated by a lower percentage of β-gal positive EPCs. In conclusion, Nox2 activity efficiently contributes to the mechanism of oxidative stress-induced increase in premature aging conferred by doxorubicin. The importance of modulation of Nox2 in human EPCs could reveal a useful tool to restore EPC physiological function and properties.

Homocysteine is associated with the progression of non-culprit coronary lesions in elderly acute coronary syndrome patients after percutaneous coronary intervention

BACKGROUND

The influence of homocysteine (Hcy) on the migration and proliferation of vascular smooth muscle cells has been well established. However, the impact of Hcy levels on the progression of non-culprit coronary lesions (NCCLs) is controversial. This study aims to evaluate whether the plasma level of Hcy is related to the progression of NCCLs after percutaneous coronary stent implantation in elderly patients with acute coronary syndrome (ACS).

METHODS

A total of 223 elderly patients (≥ 65 years old) with ACS undergoing stent implantation and follow-up coronary angiography were enrolled. Laboratory determination comprised of blood sample evaluation for Hcy was carried out before baseline coronary intervention. The patients were classified into two groups according to the blood Hcy tertiles (≥ 15 mmol/L or < 15 mmol/L). Patients were followed up for 12.2 months. NCCL progression was assessed by three-dimensional quantitative coronary angiography.

RESULTS

A significantly higher ratio of NCCL progression was observed in the group with baseline Hcy concentrations above 15 mmol/L compared to the group with concentrations below 15 mmol/L (41/127, 32.3% vs. 14/96, 14.6%, P = 0.002). Multivariate Cox regression analysis showed that Hcy and diabetes mellitus were independent risk factors for NCCL progression. The crude hazard ratio (HR) of NCCL progression for Hcy level was 1.056 (95% CI: 1.01-1.104, P = 0.015). The adjusted HR of NCCL progression for Hcy level was 1.024 (95% CI: 1.007-1.042, P = 0.007). The adjusted HR of NCCL progression for diabetes mellitus was 1.992 (95% CI: 1.15-3.44, P = 0.013).

CONCLUSIONS

Hcy is an independent risk factor for NCCL progression after 12 months of follow-up in elderly patients with ACS who has undergone percutaneous coronary stenting.

Macrophage Migration Inhibitory Factor (MIF) Deficiency Exacerbates Aging-Induced Cardiac Remodeling and Dysfunction Despite Improved Inflammation: Role of Autophagy Regulation

Aging leads to unfavorable geometric and functional sequelae in the heart. The proinflammatory cytokine macrophage migration inhibitory factor (MIF) plays a role in the maintenance of cardiac homeostasis under stress conditions although its impact in cardiac aging remains elusive. This study was designed to evaluate the role of MIF in aging-induced cardiac anomalies and the underlying mechanism involved. Cardiac geometry, contractile and intracellular Ca²⁺ properties were examined in young (3–4 mo) or old (24 mo) wild type and MIF knockout (MIF^−/−) mice. Our data revealed that MIF knockout exacerbated aging-induced unfavorable structural and functional changes in the heart. The detrimental effect of MIF knockout was associated with accentuated loss in cardiac autophagy with aging. Aging promoted cardiac inflammation, the effect was attenuated by MIF knockout. Intriguingly, aging-induced unfavorable responses were reversed by treatment with the autophagy inducer rapamycin, with improved myocardial ATP availability in aged WT and MIF^−/− mice. Using an in vitro model of senescence, MIF knockdown exacerbated doxorubicin-induced premature senescence in H9C2 myoblasts, the effect was ablated by MIF replenishment. Our data indicated that MIF knockout exacerbates aging-induced cardiac remodeling and functional anomalies despite improved inflammation, probably through attenuating loss of autophagy and ATP availability in the heart.