Aging-related atherosclerosis is exacerbated by arterial expression of tumor necrosis factor receptor-1: evidence from mouse models and human association studies

Stimuli-responsive polymer-based nanosystems for cardiovascular disease theranostics

Stimulus-responsive polymers have found widespread use in biomedicine due to their ability to alter their own structure in response to various stimuli, including internal factors such as pH, reactive oxygen species (ROS), and enzymes, as well as external factors like light. In the context of atherosclerotic cardiovascular diseases (CVDs), stimulus-response polymers have been extensively employed for the preparation of smart nanocarriers that can deliver therapeutic and diagnostic drugs specifically to inflammatory lesions. Compared with traditional drug delivery systems, stimulus-responsive nanosystems offer higher sensitivity, greater versatility, wider applicability, and enhanced biosafety. Recent research has made significant contributions towards designing stimulus-responsive polymer nanosystems for CVDs diagnosis and treatment. This review summarizes recent advances in this field by classifying stimulus-responsive polymer nanocarriers according to different responsiveness types and describing numerous stimuli relevant to these materials. Additionally, we discuss various applications of stimulus-responsive polymer nanomaterials in CVDs theranostics. We hope that this review will provide valuable insights into optimizing the design of stimulus-response polymers for accelerating their clinical application in diagnosing and treating CVDs.

Correlation Between GDF11 Serum Levels, Severity of Coronary Artery Lesions, and the Prognosis of Patients with ST-segment Elevation Myocardial Infarction

We aimed to explore the correlation among serum GDF11, the severity of coronary artery lesions, and the prognosis of patients with ST-segment elevation myocardial infarction (STEMI). A total of 367 patients were enrolled and divided into control (n = 172) and STEMI (n = 195) groups. Serum GDF11 (P < 0.001) was an independent predictor of STEMI and was negatively correlated with SYNTAX score (P < 0.05). ROC curve analysis showed that serum GDF11 could screen patients for major adverse cardiovascular events (MACEs). KM curve analysis showed that patients with lower concentration of GDF11 had a higher incidence of MACEs, and Cox proportional hazards regression analysis showed that the serum GDF11 (P < 0.001) was an independent predictor of MACEs. Serum GDF11 was negatively correlated with the severity of coronary lesions and was also an independent prognostic indicator of MACEs in patients with STEMI.

The age of bone marrow dictates the clonality of smooth muscle-derived cells in atherosclerotic plaques

Aging is the predominant risk factor for atherosclerosis, the leading cause of death. Rare smooth muscle cell (SMC) progenitors clonally expand giving rise to up to ~70% of atherosclerotic plaque cells; however, the effect of age on SMC clonality is not known. Our results indicate that aged bone marrow (BM)-derived cells non-cell autonomously induce SMC polyclonality and worsen atherosclerosis. Indeed, in myeloid cells from aged mice and humans, TET2 levels are reduced which epigenetically silences integrin β3 resulting in increased tumor necrosis factor [TNF]-α signaling. TNFα signals through TNF receptor 1 on SMCs to promote proliferation and induces recruitment and expansion of multiple SMC progenitors into the atherosclerotic plaque. Notably, integrin β3 overexpression in aged BM preserves dominance of the lineage of a single SMC progenitor and attenuates plaque burden. Our results demonstrate a molecular mechanism of aged macrophage-induced SMC polyclonality and atherogenesis and suggest novel therapeutic strategies.

N-acetylcysteine attenuates atherosclerosis progression in aging LDL receptor deficient mice with preserved M2 macrophages and increased CD146

BACKGROUND AND AIMS

Inflammation and reactive oxygen species (ROS) are important to the pathogenesis of atherosclerosis. The effect of antioxidants on atherosclerosis is inconsistent, and sometimes controversial. We aimed to test the hypothesis that attenuation of atherosclerosis by N-acetylcysteine (NAC) depends on NAC treatment timing and duration.

METHODS

Male LDL receptor deficient (LDLR^-/-) mice were fed a normal diet (ND) and divided into controls (on ND for 24 months), models 1-2 (at age of 9 months, starting NAC treatment for 3 or 6 months), and model 3 (at age of 18 months, starting NAC treatment for 6 months). To determine if hyperlipidemia compromises NAC treatment outcome, mice were fed a high fat diet (HFD) starting at age of 6 weeks and treated with NAC starting at 9 months of age for 6 months.

RESULTS

NAC treatment for 6 months, not for 3 months, significantly attenuated atherosclerosis progression, but did not reverse atherosclerotic lesions, in aging LDLR^-/- mice on ND. NAC had no effect on atherosclerotic lesions in mice on HFD. NAC treatment significantly decreased aortic ROS production, and the levels of inflammatory cytokines in serum and aorta of aging LDLR^-/- mice with increased CD146 level. Bone marrow transplantation study with GFP-positive bone marrow cells showed that NAC treatment preserved M2 population and M2 polarization in the aorta of LDLR^-/- mice.

CONCLUSIONS

Early and adequate NAC treatment could effectively attenuate inflammation and atherosclerosis progression with preserved M2 population and increased CD146 level in aging LDLR^-/- mice without extreme hyperlipidemia.

Proteins linked to atherosclerosis and cell proliferation are associated with the shrunken pore syndrome in heart failure patients: Shrunken pore syndrome and proteomic associations

PURPOSE

The "Shrunken pore syndrome" (SPS) is characterized by a difference in renal filtration between cystatin C and creatinine, resulting in a low eGFR_cystatinC /eGFR_creatinine -ratio. Studies have demonstrated a high risk for cardiovascular morbidity and mortality for patients with SPS. In this discovery study, we explored associations between SPS and proteins implicated in cardiovascular disease and inflammation in patients with heart failure.

EXPERIMENTAL DESIGN

Plasma samples from 300 individuals in HARVEST-Malmö trial hospitalized for the diagnosis of heart failure (mean age 74.9 ± 11.5 years; 30.0% female), were analyzed with a proximity extension assay consisting of 92 proteins. A Bonferroni-corrected p-value of 0.05/92 = 5.4 × 10^-4 was considered significant in the initial age and sex-adjusted analyses. Presence of SPS was defined as eGFR_cystatinC ≤ 60% of eGFR_creatinine .

RESULTS

SPS presented with significant associations (p < 5.4 × 10^-4 ) in age and sex-adjusted logistic regressions with elevated levels of six proteins; scavenger receptor cysteine rich type 1 protein M130, tumor necrosis factor receptor 1, tumor necrosis factor receptor 2, osteoprotegerin, interleukin-2 receptor subunit alpha, and tyrosine-protein kinase receptor UFO. All proteins remained associated (p < 0.05) with SPS after multivariate adjustments.

CONCLUSIONS AND CLINICAL RELEVANCE

In heart failure patients, SPS was associated with proteins linked to atherosclerosis and cell proliferation.

Targeting and clearance of senescent foamy macrophages and senescent endothelial cells by antibody-functionalized mesoporous silica nanoparticles for alleviating aorta atherosclerosis

Senescent cells drive atherosclerosis at all stages and contribute to cardiovascular disease. However, the markers in these senescent aortic plaques have not been well studied, creating a huge obstacle in the exploration of a precise and efficient system for atherosclerosis treatment. Recently, CD9 has been found to induce cellular senescence and aggravated atherosclerotic plaque formation in apolipoprotein E knockout (ApoE^-/-) mice. In the present study, this result has been leveraged to develop CD9 antibody-modified, hyaluronic acid-coated mesoporous silica nanoparticles with a hyaluronidase-responsive drug release profile. In invitro models of senescent foamy macrophages and senescent endothelial cells stimulated with oxidized high-density-lipoprotein, the CD9 antibody-modified mesoporous silica nanoparticles exhibit high cellular uptake; reduce the reactive oxygen species level, high-density lipoprotein oxidation, and production of TNF-α and IL-6; and attenuate the senescence process, contributing to improved cell viability. In vivo experiment demonstrated that these nanoparticles can successfully target the senescent lesion areas, deliver the anti-senescence drug rosuvastatin to the senescent atherosclerotic plaques (mainly endothelial cells and macrophages), and alleviate the progression of atherosclerosis in ApoE^-/- mice. By providing deep insight regarding the markers in senescent atherosclerotic plaque and developing a nano-system targeting this lesion area, the study proposes a novel and an accurate therapeutic approach for mitigating atherosclerosis through senescent cell clearance.

Mechanisms of NLRP3 priming in inflammaging and age related diseases

The NLRP3 inflammasome is a vital part of the innate immune response, whilst its aberrant activation drives the progression of a number of non-communicable diseases. Thus, NLRP3 inflammasome assembly must be tightly controlled at several checkpoints. The priming step of NLRP3 inflammasome activation is associated with increased NLRP3 gene expression, as well as post-translational modifications that control NLRP3 levels and licence the NLRP3 protein for inflammasome assembly. Increasing life expectancy in modern society is accompanied by a growing percentage of elderly individuals. The process of aging is associated with chronic inflammation that drives and/or worsens a range of age related non-communicable conditions. The NLRP3 inflammasome is known to contribute to pathological inflammation in many settings, but the mechanisms that prime NLRP3 for activation throughout aging and related co-morbidities have not been extensively reviewed. Here we dissect the biochemical changes that occur during aging and the pathogenesis of age related diseases and analyse the mechanisms by which they prime the NLRP3 inflammasome, thus exacerbating inflammation.

Systematic review and analysis of human proteomics aging studies unveils a novel proteomic aging clock and identifies key processes that change with age

The development of clinical interventions that significantly improve human healthspan requires robust markers of biological age as well as thoughtful therapeutic targets. To promote these goals, we performed a systematic review and analysis of human aging and proteomics studies. The systematic review includes 36 different proteomics analyses, each of which identified proteins that significantly changed with age. We discovered 1,128 proteins that had been reported by at least two or more analyses and 32 proteins that had been reported by five or more analyses. Each of these 32 proteins has known connections relevant to aging and age-related disease. GDF15, for example, extends both lifespan and healthspan when overexpressed in mice and is additionally required for the anti-diabetic drug metformin to exert beneficial effects on body weight and energy balance. Bioinformatic enrichment analyses of our 1,128 commonly identified proteins heavily implicated processes relevant to inflammation, the extracellular matrix, and gene regulation. We additionally propose a novel proteomic aging clock comprised of proteins that were reported to change with age in plasma in three or more different studies. Using a large patient cohort comprised of 3,301 subjects (aged 18-76 years), we demonstrate that this clock is able to accurately predict human age.

Weak association of a TNFRSF1A polymorphism with Behcet's disease in Chinese Han

The purpose of this study was to investigate whether single nucleotide polymorphisms (SNPs) of the tumor necrosis factor receptor superfamily (TNFRSF) and their ligand (TNFSF) gene are associated with susceptibility to Behcet's Disease (BD) in Chinese Han. A two-phase case-control study was performed in 1055 BD patients and 1829 healthy controls. A total of 27 SNPs was tested using MassARRAY iPLEX® technology. Data were analyzed using a Chi-square (χ2) test and Fisher's exact calibration test. The Bonferroni correction was applied for multiple testing. A statistically significant higher frequency of the A allele and a lower frequency of the G allele of rs1800692 was found in BD (Pc = 0.013, OR = 1.233, 95% CI = 1.103-1.379: Pc = 0.013, OR = 0.811, 95% CI = 0.725-0.907, respectively). Our findings indicate that TNFRSF1A might confer genetic susceptibility to BD in a Chinese Han population.

Arsenic, cadmium, and mercury-induced hypertension: mechanisms and epidemiological findings

Arsenic (As), cadmium (Cd), and mercury (Hg) are toxic elements widely distributed in the environment. Exposure to these elements was attributed to produce several acute and chronic illnesses including hypertension. The aim of this review is to provide a summary of the most frequently proposed mechanisms underlying hypertension associated with As, Cd, and Hg exposure including: oxidative stress, impaired nitric oxide (NO) signaling, modified vascular response to neurotransmitters and disturbed vascular muscle Ca²⁺ signaling, renal damage, and interference with the renin-angiotensin system. Due to the complexity of the vascular system, a combination rather than a singular mechanism needs to be considered. In addition, epidemiological findings showing the relationship between various biomarkers of metal exposure and hypertension are described. Given the complex etiology of hypertension, further epidemiological studies evaluating the roles of confounding factors such as age, gender, and life style are still necessary.

Translating the biology of adipokines in atherosclerosis and cardiovascular diseases: Gaps and open questions

AIM

Critically discuss the available data, to identify the current gaps and to provide key concepts that will help clinicians in translating the biology of adipokines in the context of atherosclerosis and cardio-metabolic diseases.

DATA SYNTHESIS

Adipose tissue is nowadays recognized as an active endocrine organ, a function related to the ability to secrete adipokines (such as leptin and adiponectin) and pro-inflammatory cytokines (tumor necrosis factor alpha and resistin). Studies in vitro and in animal models have observed that obesity status presents a chronic low-grade inflammation as the consequence of the immune cells infiltrating the adipose tissue as well as adipocytes. This inflammatory signature is often related to the presence of cardiovascular diseases, including atherosclerosis and thrombosis. These links are less clear in humans, where the role of adipokines as prognostic marker and/or player in cardiovascular diseases is not as clear as that observed in experimental models. Moreover, plasma adipokine levels might reflect a condition of adipokine-resistance in which adipokine redundancy occurs. The investigation of the cardio-metabolic phenotype of carriers of single nucleotide polymorphisms affecting the levels or function of a specific adipokine might help determine their relevance in humans. Thus, the aim of the present review is to critically discuss the available data, identify the current gaps and provide key concepts that will help clinicians translate the biology of adipokines in the context of atherosclerosis and cardio-metabolic diseases.

GDF11 Protects against Endothelial Injury and Reduces Atherosclerotic Lesion Formation in Apolipoprotein E-Null Mice

Growth differentiation factor 11 (GDF11) reduces cardiac hypertrophy, improves cerebral vasculature and enhances neurogenesis in ageing mice. Higher growth differentiation factor 11/8 (GDF11/8) is associated with lower risk of cardiovascular events in humans. Here, we showed that adeno-associated viruses-GDF11 and recombinant GDF11 protein improve endothelial dysfunction, decrease endothelial apoptosis, and reduce inflammation, consequently decrease atherosclerotic plaques area in apolipoprotein E-/- mice. Moreover, adeno-associated viruses-GDF11 and recombinant GDF11 stabilize atherosclerotic plaques by selectively decreasing in macrophages and T lymphocytes, while increasing in collagen and vascular smooth muscle cells within plaques. In addition, GDF11 inhibit palmitic acid-induced endothelial apoptosis and ameliorate palmitic acid-induced inflammatory response in RAW264.7 macrophages in vitro. Mechanistically, GDF11 activates the TGF-β/Smad2/3, AMPK/endothelial nitricoxide synthase (eNOS) while suppresses JNK and NF-κB pathways. In humans, circulating GDF11/8 is positively associated with flow-mediated endothelium-dependent dilation in overweight subjects. We concluded that adeno-associated viruses-GDF11 and recombinant GDF11 protect against endothelial injury and reduce atherosclerosis in apolipoprotein E-/- mice, thus may be providing a novel approach to the treatment of atherosclerosis.

Experimental reduction of miR-92a mimics arterial aging

MicroRNAs (miRs) are small non-coding RNAs that are important regulators of aging and cardiovascular diseases. MiR-92a is important in developmental vascular growth and tumorigenesis and two of its putative targets, tumor necrosis factor alpha receptor 1 (TNFR1) and collagen type 1, play a role in age-related arterial dysfunction. We hypothesized that reduced miR-92a expression contributes to age-related arterial dysfunction characterized by endothelial dysfunction and increased large artery stiffness. MiR-92a is reduced 39% (RT-PCR, p<0.05) in arteries of older adults compared to young adults. Similarly, there was a 40% reduction in miR-92a in aortas of old (29months, n=13) compared to young (6months, n=11) B6D2F1 mice, an established model of vascular aging. To determine if reduced miR-92a contributes to arterial dysfunction; miR-92a was inhibited in vivo in young mice using antagomirs (I.P., 4wks). Antagomir treatment was associated with a concomitant 48% increase in TNFR1 (Western blot, p<0.05), 19% increase in type 1 collagen (immunohistochemistry, p<0.01), and a reduction in endothelial dependent dilation (max dilation: 93±1 vs. 73±5%, p<0.01) in response to acetylcholine (ACh, 10(-9) to 10(-4)M). Treatment with the nitric oxide (NO) synthase inhibitor, L-NAME (10(-4)M), revealed that impaired ACh dilation after antagomir treatment resulted from reduced NO bioavailability. Inhibition of miR-92a also increased arterial stiffness (pulse wave velocity, 309±13 vs. 484±52cm/s, p<0.05). Together, these results suggest that experimental reductions in arterial miR-92a partially mimic the arterial aging phenotype and we speculate that modulating miR-92a may provide a therapeutic strategy to improve age-related arterial dysfunction.

Case-Only Survival Analysis Reveals Unique Effects of Genotype, Sex, and Coronary Disease Severity on Survivorship

Survival bias may unduly impact genetic association with complex diseases; gene-specific survival effects may further complicate such investigations. Coronary artery disease (CAD) is a complex phenotype for which little is understood about gene-specific survival effects; yet, such information can offer insight into refining genetic associations, improving replications, and can provide candidate genes for both mortality risk and improved survivorship in CAD. Building on our previous work, the purpose of this current study was to: evaluate LSAMP SNP-specific hazards for all-cause mortality post-catheterization in a larger cohort of our CAD cases; and, perform additional replication in an independent dataset. We examined two LSAMP SNPs—rs1462845 and rs6788787—using CAD case-only Cox proportional hazards regression for additive genetic effects, censored on time-to-all-cause mortality or last follow-up among Caucasian subjects from the Catheterization Genetics Study (CATHGEN; n = 2,224) and the Intermountain Heart Collaborative Study (IMHC; n = 3,008). Only after controlling for age, sex, body mass index, histories of smoking, type 2 diabetes, hyperlipidemia and hypertension (HR = 1.11, 95%CI = 1.01–1.22, p = 0.032), rs1462845 conferred significantly increased hazards of all-cause mortality among CAD cases. Even after controlling for multiple covariates, but in only the primary cohort, rs6788787 conferred significantly improved survival (HR = 0.80, 95% CI = 0.69–0.92, p = 0.002). Post-hoc analyses further stratifying by sex and disease severity revealed replicated effects for rs1462845: even after adjusting for aforementioned covariates and coronary interventional procedures, males with severe burden of CAD had significantly amplified hazards of death with the minor variant of rs1462845 in both cohorts (HR = 1.29, 95% CI = 1.08–1.55, p = 0.00456; replication HR = 1.25, 95% CI = 1.05–1.49, p = 0.013). Kaplan-Meier curves revealed unique cohort-specific genotype effects on survival. Additional analyses demonstrated that the homozygous risk genotype (‘A/A’) fully explained the increased hazard in both cohorts. None of the post-hoc analyses in control subjects were significant for any model. This suggests that genetic effects of rs1462845 on survival are unique to CAD presence. This represents formal, replicated evidence of genetic contribution of rs1462845 to increased risk for all-cause mortality; the contribution is unique to CAD case status and specific to males with severe burden of CAD.

Hydroxy-Safflower Yellow A inhibits the TNFR1-Mediated Classical NF-κB Pathway by Inducing Shedding of TNFR1

Hydroxy-safflower yellow A (HSYA) is the major active component of safflower, a traditional Asia herbal medicine well known for its cardiovascular protective activities. The purpose of this study was to investigate the effect of HSYA on TNF-α-induced inflammatory responses in arterial endothelial cells (AECs) and to explore the mechanisms involved. The results showed that HSYA suppressed the up-regulation of ICAM-1 expression in TNF-α-stimulated AECs in a dose-dependent manner. High concentration (120 μM) HSYA significantly inhibited the TNF-α-induced adhesion of RAW264.7 cells to AECs. HSYA blocked the TNFR1-mediated phosphorylation and degradation of IκBα and also prevented the nuclear translocation of NF-κB p65. Moreover, HSYA reduced the cell surface level of TNFR1 and increased the content of sTNFR1 in the culture media. TNF-α processing inhibitor-0 (TAPI-0) prevented the HSYA inhibition of TNFR1-induced IκBα degradation, implying the occurrence of TNFR1 shedding. Furthermore, HSYA induced phosphorylation of TNF-α converting enzyme (TACE) at threonine 735, which is thought to be required for its activation. Conclusively, HSYA suppressed TNF-α-induced inflammatory responses in AECs, at least in part by inhibiting the TNFR1-mediated classical NF-κB pathway. TACE-mediated TNFR1 shedding can be involved in this effect. Our study provides new evidence for the antiinflammatory and anti-atherosclerotic effects of HSYA. Copyright © 2016 John Wiley & Sons, Ltd.

Characterization of lipid parameters in diabetic and non-diabetic atherosclerotic patients

Background & Objective

The relationship between lipid profile perturbation and diabetes associated complications has long been an area of interest. Dyslipidemia is a potent predictor of cardiovascular morbidity and mortality in diabetic patients. The aim of present study was to investigate relationship between aging and lipid profiles in diabetic and non-diabetic atherosclerotic patients.

Methods

Five hundred and seventy six individuals (45–75 year age) participated in this study. Among these, 192 were having history of diabetes mellitus and atherosclerosis. Individuals are categorized on the base of health (normal, non-diabetic atherosclerosis, diabetic atherosclerosis) and age (45–55 years, 56–65 years, and 66–75 years). All the participants were subjected to the procedures like a detailed history, biochemical analysis for fasting blood sugar, hemoglobin A1c, total cholesterol (TC), triglycerides (TG), low-density lipoprotein-(LDL), very low-density lipoprotein (VLDL) and high-density lipoprotein (HDL). All these parameters were compared between diabetic and non-diabetic atherosclerotic patients of all three age groups. TC/HDL and LDL/HDL were also calculated.

Results

Diabetic atherosclerotic individuals (both males and females) had high level of TC, TG, LDL, VLDL and low level of HDL in comparison to non-diabetic atherosclerotic and normal control individuals. Among all three age groups, lipoprotein abnormality was observed to be more frequent in females than males. There was a significant increase in TC/HDL and LDL/HDL ratio in diabetic atherosclerotic subjects compared to age and sex matched non-diabetic atherosclerotic and normal control.

Conclusions

Degree of dyslipidemia increases with increase in age in both genders. Female are more prone to diabetic dyslipidemia and hence have more risk of developing atherosclerosis with increasing age.

Endothelial cell senescence and age-related vascular diseases

Advanced age is an independent risk factor for ageing-related complex diseases, such as coronary artery disease, stroke, and hypertension, which are common but life threatening and related to the ageing-associated vascular dysfunction. On the other hand, patients with progeria syndromes suffer from serious atherosclerosis, suggesting that the impaired vascular functions may be critical to organismal ageing, or vice versa. However, it remains largely unknown how vascular cells, particularly endothelial cell, become senescent and how the senescence impairs the vascular functions and contributes to the age-related vascular diseases over time. Here, we review the recent progress on the characteristics of vascular ageing and endothelial cell senescence in vitro and in vivo, evaluate how genetic and environmental factors as well as autophagy and stem cell influence endothelial cell senescence and how the senescence contributes to the age-related vascular phenotypes, such as atherosclerosis and increased vascular stiffness, and explore the possibility whether we can delay the age-related vascular diseases through the control of vascular ageing.

Nonalcoholic steatohepatitis as a novel player in metabolic syndrome-induced erectile dysfunction: an experimental study in the rabbit

A pathogenic link between erectile dysfunction (ED) and metabolic syndrome (MetS) is now well established. Nonalcoholic steatohepatitis (NASH), the hepatic hallmark of MetS, is regarded as an active player in the pathogenesis of MetS-associated cardiovascular disease (CVD). This study was aimed at evaluating the relationship between MetS-induced NASH and penile dysfunction. We used a non-genomic, high fat diet (HFD)-induced, rabbit model of MetS, and treated HFD rabbits with testosterone (T), with the selective farnesoid X receptor (FXR) agonist obeticholic acid (OCA), or with the anti-TNFα mAb infliximab. Rabbits fed a regular diet were used as controls. Liver histomorphological and gene expression analysis demonstrated NASH in HFD rabbits. Several genes related to inflammation (including TNFα), activation of stellate cells, fibrosis, and lipid metabolism parameters were negatively associated to maximal acetylcholine (Ach)-induced relaxation in penis. When all these putative liver determinants of penile Ach responsiveness were tested as covariates in a multivariate model, only the association between hepatic TNFα expression and Ach response was confirmed. Accordingly, circulating levels of TNFα were increased 15-fold in HFD rabbits. T and OCA dosing in HFD rabbits both reduced TNFα liver expression and plasma levels, with a parallel increase of penile eNOS expression and responsiveness to Ach. Also neutralization of TNFα with infliximab treatment fully normalized HFD-induced hypo-responsiveness to Ach, as well as responsiveness to vardenafil, a phosphodiesterase type 5 inhibitor. Thus, MetS-induced NASH in HFD rabbits plays an active role in the pathogenesis of ED, likely through TNFα, as indicated by treatments reducing liver and circulating TNFα levels (T or OCA), or neutralizing TNFα action (infliximab), which significantly improve penile responsiveness to Ach in HFD rabbits.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

The genetic basis for survivorship in coronary artery disease

Survivorship is a trait characterized by endurance and virility in the face of hardship. It is largely considered a psychosocial attribute developed during fatal conditions, rather than a biological trait for robustness in the context of complex, age-dependent diseases like coronary artery disease (CAD). The purpose of this paper is to present the novel phenotype, survivorship in CAD as an observed survival advantage concurrent with clinically significant CAD. We present a model for characterizing survivorship in CAD and its relationships with overlapping time- and clinically-related phenotypes. We offer an optimal measurement interval for investigating survivorship in CAD. We hypothesize genetic contributions to this construct and review the literature for evidence of genetic contribution to overlapping phenotypes in support of our hypothesis. We also present preliminary evidence of genetic effects on survival in people with clinically significant CAD from a primary case-control study of symptomatic coronary disease. Identifying gene variants that confer improved survival in the context of clinically appreciable CAD may improve our understanding of cardioprotective mechanisms acting at the gene level and potentially impact patients clinically in the future. Further, characterizing other survival-variant genetic effects may improve signal-to-noise ratio in detecting gene associations for CAD.

Vein graft neointimal hyperplasia is exacerbated by CXCR4 signaling in vein graft-extrinsic cells

OBJECTIVE

Because vein graft neointimal hyperplasia engenders vein graft failure, and because most vein graft neointimal cells derive from outside the vein graft, we sought to determine whether vein graft neointimal hyperplasia is affected by activity of the CXC chemokine receptor-4 (CXCR4), which is important for bone marrow-derived cell migration.

METHODS

In congenic Cxcr4(-/+) and wild-type (WT) recipient mice, we performed interposition grafting of the common carotid artery with the inferior vena cava (IVC) of either Cxcr4(-/+) or WT mice to create four surgically chimeric groups of mice (n ≥ 5 each), characterized by vein graft donor/recipient: WT/WT; Cxcr4(-/+)/WT; WT/Cxcr4(-/+); and Cxcr4(-/+)/Cxcr4(-/+); vein grafts were harvested 6 weeks postoperatively.

RESULTS

The agonist for CXCR4 is expressed by cells in the arterializing vein graft. Vein graft neointimal hyperplasia was reduced by reducing CXCR4 activity in vein graft-extrinsic cells, but not in vein graft-intrinsic cells: the rank order of neointimal hyperplasia was WT/WT ≈ Cxcr4(-/+)/WT > WT/Cxcr4(-/+) ≈ Cxcr4(-/+)/Cxcr4(-/+); CXCR4 deficiency in graft-extrinsic cells reduced neointimal hyperplasia by 39% to 47% (P < .05). Vein graft medial area was equivalent in all grafts except Cxcr4(-/+)/Cxcr4(-/+), in which the medial area was 60% ± 20% greater (P < .05). Vein graft re-endothelialization was indistinguishable among all three vein graft groups. However, the prevalence of medial leukocytes was 40% ± 10% lower in Cxcr4(-/+)/Cxcr4(-/+) than in WT/WT vein grafts (P < .05), and the prevalence of smooth muscle actin-positive cells was 45% ± 20% higher (P < .05).

CONCLUSIONS

We conclude that CXCR4 contributes to vein graft neointimal hyperplasia through mechanisms that alter homing to the vein graft of graft-extrinsic cells, particularly leukocytes.

CLINICAL RELEVANCE

The utility of autologous vein grafts is severely reduced by neointimal hyperplasia, which accelerates subsequent graft atherosclerosis. Our study demonstrates that vein graft neointimal hyperplasia is aggravated by activity of the cell-surface “CXC” chemokine receptor-4 (CXCR4), which is critical for recruitment of bone marrow-derived cells to sites of inflammation. Our model for CXCR4 deficiency used mice with heterozygous deficiency of Cxcr4. Consequently, our results suggest the possibility that a CXCR4 antagonist--like plerixafor, currently in clinical use--could be applied to vein grafts periadventitially, and perhaps achieve beneficial effects on vein graft neointimal hyperplasia.

NF-κB regulates MICA gene transcription in endothelial cell through a genetically inhibitable control site

Endothelial cells form a barrier between blood and the underlying vessel wall, which characteristically demonstrates inflammatory damage in atherosclerotic disease. MICA is a highly polymorphic ligand for the activating immune receptor NKG2D and can be expressed on endothelial cells. We hypothesized that damaged vessel walls, such as those involved in atherosclerosis, might express MICA, which could contribute to the vascular immunopathology. Immune activation resulting from MICA expression could play a significant role in the development of vascular damage. We have demonstrated that TNFα up-regulates MICA on human endothelial cells. The up-regulation is mediated by NF-κB, and we have defined the regulatory control site responsible for this at -130 bp upstream of the MICA transcription start site. This site overlaps with a heat shock response element and integrates input from the two pathways. We have shown that in atherosclerotic lesions there is expression of MICA on endothelial cells. Using lentivirus-mediated gene delivery in primary human endothelial cells, we were able to inhibit the MICA response to TNFα with a truncated HSF1 that lacked a transactivation domain. This highlights the potential for transcription-based therapeutic approaches in atherosclerotic vascular disease to reduce immune-mediated endothelial and vessel wall damage.

G protein-coupled receptor kinase-5 attenuates atherosclerosis by regulating receptor tyrosine kinases and 7-transmembrane receptors

OBJECTIVE

G protein-coupled receptor kinase-5 (GRK5) is a widely expressed Ser/Thr kinase that regulates several atherogenic receptors and may activate or inhibit nuclear factor-κB (NF-κB). This study sought to determine whether and by what mechanisms GRK5 affects atherosclerosis.

METHODS AND RESULTS

Grk5(-/-)/Apoe(-/-) mice developed 50% greater aortic atherosclerosis than Apoe(-/-) mice and demonstrated greater proliferation of macrophages and smooth muscle cells (SMCs) in atherosclerotic lesions. In Apoe(-/-) mice, carotid interposition grafts from Grk5(-/-) mice demonstrated greater upregulation of cell adhesion molecules than grafts from wild-type mice and, subsequently, more atherosclerosis. By comparing Grk5(-/-) with wild-type cells, we found that GRK5 desensitized 2 key atherogenic receptor tyrosine kinases: the platelet-derived growth factor receptor-β in SMCs, by augmenting ubiquitination/degradation; and the colony-stimulating factor-1 receptor (CSF-1R) in macrophages, by reducing CSF-1-induced tyrosyl phosphorylation. GRK5 activity in monocytes also reduced migration promoted by the 7-transmembrane receptor for monocyte chemoattractant protein-1 CC chemokine receptor-2. Whereas GRK5 diminished NF-κB-dependent gene expression in SMCs and endothelial cells, it had no effect on NF-κB activity in macrophages.

CONCLUSIONS

GRK5 attenuates atherosclerosis through multiple cell type-specific mechanisms, including reduction of SMC and endothelial cell NF-κB activity and desensitization of receptor-specific signaling through the monocyte CC chemokine receptor-2, macrophage CSF-1R, and the SMC platelet-derived growth factor receptor-β.

ST6Gal-I regulates macrophage apoptosis via α2-6 sialylation of the TNFR1 death receptor

Macrophages play a central role in innate immunity, however mechanisms regulating macrophage survival are not fully understood. Herein we describe a novel apoptotic pathway involving α2-6 sialylation of the TNFR1 death receptor by the ST6Gal-I sialyltransferase. Variant glycosylation of TNFR1 has not previously been implicated in TNFR1 function, and little is known regarding the TNFR1 glycan composition. To study sialylation in macrophages, we treated U937 monocytic cells with PMA, which stimulates both macrophage differentiation and apoptosis. Interestingly, macrophage differentiation induces ST6Gal-I down-regulation, leading to reduced α2-6 sialylation of selected receptors. To prevent loss of α2-6 sialylation, we forced constitutive expression of ST6Gal-I, and found that this strongly inhibited PMA-induced apoptosis. Given that PMA-mediated apoptosis is thought to result from up-regulation of TNFα, which then activates TNFR1, we next evaluated the α2-6 sialylation of TNFR1. U937 cells with forced ST6Gal-I displayed TNFR1 with elevated α2-6 sialylation, and this was associated with diminished TNFα-stimulated apoptosis. Correspondingly, removal of α2-6 sialylation from TNFR1 through either neuraminidase treatment or expression of ST6Gal-I shRNA markedly enhanced TNFα-mediated apoptosis. To confirm the physiologic importance of TNFR1 sialylation, we generated overexpressing ST6Gal-I transgenic mice. Peritoneal macrophages from transgenic lines displayed TNFR1 with elevated α2-6 sialylation, and these cells were significantly protected against TNFα-stimulated apoptosis. Moreover, greater numbers of thioglycollate-induced peritoneal cells were observed in transgenic mice. These collective results highlight a new mechanism of TNFR1 regulation, and further intimate that loss of α2-6 sialylation during macrophage differentiation may limit macrophage lifespan by sensitizing cells to TNFα-stimulated apoptosis.

Tumor necrosis factor superfamily molecules in acute coronary syndromes

Accumulating evidence suggests that inflammatory pathways play an essential role in all stages of atherogenesis. Inflammatory processes are not only involved in plaque progression, but seem also to play a critical role in plaque rupture. Members of the tumor necrosis factor (TNF) superfamiliy are potent regulators of inflammation and cell survival and consist of 20 ligands that signal through 29 different receptors. Several lines of evidence suggest that TNF-related molecules are involved in the development of acute coronary syndromes (ACS). Most, convincing evidence exists for CD40 ligand-CD40 interaction, but several other members of the TNF superfamily seem also to be involved in this immune-mediated promotion of plaque instability, including LIGHT, receptor activator of nuclear factor κB ligand, and TNF-α. These plaque destabilization pathways involve the bidirectional interaction between platelets and endothelial cells/monocytes, activation of vascular smooth muscle cells, and co-stimulatory effects on T cells, promoting inflammation, thrombus formation, matrix degradation, and apoptosis. TNF-related pathways could contribute to the non-resolving inflammation that characterizes atherosclerosis, representing pathogenic loops that are operating during plaque rupture and the development of ACS. These TNF-related molecules could also represent attractive new targets for therapy in this disorder.