Progression of atherosclerosis in ApoE-deficient mice that express distinct molecular forms of TNF-alpha

Novel Nongenetic Murine Model of Hyperglycemia and Hyperlipidemia-Associated Aggravated Atherosclerosis

Objective

Atherosclerosis, the main pathology underlying cardiovascular diseases is accelerated in diabetic patients. Genetic mouse models require breeding efforts which are time-consuming and costly. Our aim was to establish a new nongenetic model of inducible metabolic risk factors that mimics hyperlipidemia, hyperglycemia, or both and allows the detection of phenotypic differences dependent on the metabolic stressor(s).

Methods and Results

Wild-type mice were injected with gain-of-function PCSK9D377Y (proprotein convertase subtilisin/kexin type 9) mutant adeno-associated viral particles (AAV) and streptozotocin and fed either a high-fat diet (HFD) for 12 or 20 weeks or a high-cholesterol/high-fat diet (Paigen diet, PD) for 8 weeks. To evaluate atherosclerosis, two different vascular sites (aortic sinus and the truncus of the brachiocephalic artery) were examined in the mice. Combined hyperlipidemic and hyperglycemic (HGHCi) mice fed a HFD or PD displayed characteristic features of aggravated atherosclerosis when compared to hyperlipidemia (HCi HFD or PD) mice alone. Atherosclerotic plaques of HGHCi HFD animals were larger, showed a less stable phenotype (measured by the increased necrotic core area, reduced fibrous cap thickness, and less α-SMA-positive area) and had more inflammation (increased plasma IL-1β level, aortic pro-inflammatory gene expression, and MOMA-2-positive cells in the BCA) after 20 weeks of HFD. Differences between the HGHCi and HCi HFD models were confirmed using RNA-seq analysis of aortic tissue, revealing that significantly more genes were dysregulated in mice with combined hyperlipidemia and hyperglycemia than in the hyperlipidemia-only group. The HGHCi-associated genes were related to pathways regulating inflammation (increased Cd68, iNos, and Tnfa expression) and extracellular matrix degradation (Adamts4 and Mmp14). When comparing HFD with PD, the PD aggravated atherosclerosis to a greater extent in mice and showed plaque formation after 8 weeks. Hyperlipidemic and hyperglycemic mice fed a PD (HGHCi PD) showed less collagen (Sirius red) and increased inflammation (CD68-positive cells) within aortic plaques than hyperlipidemic mice (HCi PD). HGHCi-PD mice represent a directly inducible hyperglycemic atherosclerosis model compared with HFD-fed mice, in which atherosclerosis is severe by 8 weeks.

Conclusion

We established a nongenetically inducible mouse model allowing comparative analyses of atherosclerosis in HCi and HGHCi conditions and its modification by diet, allowing analyses of multiple metabolic hits in mice.

Calpain inhibitor prevents atherosclerosis in apolipoprotein E knockout mice by regulating mRNA expression of genes related to cholesterol uptake and efflux

PURPOSE

We previously reported that a calpain inhibitor (CAI) prevents the development of atherosclerosis in rats. This study aimed to investigate the effects of CAI (1 mg/kg) on atherosclerosis in apolipoprotein E knockout (ApoE KO) mice that were fed a high-fat diet (HFD) and explore the underlying mechanism by analyzing the expression of genes related to the uptake and efflux of cholesterol.

METHODS

Atherosclerotic plaques were evaluated. The activity of calpain in the aorta and that of superoxide dismutase (SOD) in the serum were assessed. Lipid profiles in the serum and liver were examined. Serum oxidized low-density lipoprotein (oxLDL), malondialdehyde (MDA), tumor necrosis factor (TNF-α), and interleukin-6 (IL-6) levels were measured. The mRNA expressions of CD68, TNF-α, IL-6, CD36, scavenger receptor (SR-A), peroxisome proliferator-activated receptor gamma (PPAR-γ), liver-x-receptor alpha (LXR-α), and ATP-binding cassette transporter class A1 (ABCA1) in the aorta and peritoneal macrophages were also evaluated.

RESULTS

CAI reduced calpain activity in the aorta. CAI also impeded atherosclerotic lesion formation and mRNA expression of CD68 in the aorta and peritoneal macrophages of ApoE KO mice compared with those of mice receiving HFD. However, CAI had no effect on body weight and lipid levels in both the serum and liver. CAI significantly decreased MDA, oxLDL, TNF-α, and IL-6 levels and increased SOD activity in the serum. Moreover, CAI significantly inhibited the mRNA expression of TNF-α and IL-6 genes in the aorta and peritoneal macrophages. In addition, CAI significantly downregulated the mRNA expression of scavenger receptors CD36 and SR-A and upregulated the expression of genes involved in the cholesterol efflux pathway, i.e., PPAR-γ, LXR-α, and ABCA1 in the aorta and peritoneal macrophages.

CONCLUSIONS

CAI inhibited the development of atherosclerotic lesions in ApoE KO mice, and this effect might be related to the reduction of oxidative stress and inflammation and the improvement of cholesterol intake and efflux pathways.

Deficiency of inactive rhomboid protein 2 (iRhom2) attenuates diet-induced hyperlipidaemia and early atherogenesis

AIMS

Atherosclerosis is a chronic inflammatory disease of the arterial vessel wall and anti-inflammatory treatment strategies are currently pursued to lower cardiovascular disease burden. Modulation of recently discovered inactive rhomboid protein 2 (iRhom2) attenuates shedding of tumour necrosis factor-alpha (TNF-α) selectively from immune cells. The present study aims at investigating the impact of iRhom2 deficiency on the development of atherosclerosis.

METHODS AND RESULTS

Low-density lipoprotein receptor (LDLR)-deficient mice with additional deficiency of iRhom2 (LDLR-/-iRhom2-/-) and control (LDLR-/-) mice were fed a Western-type diet (WD) for 8 or 20 weeks to induce early or advanced atherosclerosis. Deficiency of iRhom2 resulted in a significant decrease in the size of early atherosclerotic plaques as determined in aortic root cross-sections. LDLR-/-iRhom2-/- mice exhibited significantly lower serum levels of TNF-α and lower circulating and hepatic levels of cholesterol and triglycerides compared to LDLR-/- mice at 8 weeks of WD. Analyses of hepatic bile acid concentration and gene expression at 8 weeks of WD revealed that iRhom2 deficiency prevented WD-induced repression of hepatic bile acid synthesis in LDLR-/- mice. In contrast, at 20 weeks of WD, plaque size, plaque composition, and serum levels of TNF-α or cholesterol were not different between genotypes.

CONCLUSION

Modulation of inflammation by iRhom2 deficiency attenuated diet-induced hyperlipidaemia and early atherogenesis in LDLR-/- mice. iRhom2 deficiency did not affect diet-induced plaque burden and composition in advanced atherosclerosis in LDLR-/- mice.

Decrease in the inflammatory cytokines of LPS-stimulated PBMCs of patients with atherosclerosis by a TLR-4 antagonist in the co-culture with HUVECs

Toll-like receptors (TLRs) are among the players of inflammation during atherosclerosis. We assessed the effects of Eritoran, a TLR-4 antagonist, on lipopolysaccharide (LPS)-induced cytokines production by Peripheral Blood Mononuclear Cells (PBMCs) of patients with high-stenosis (HS) (n = 6) and healthy controls (HCs) (n = 6) co-cultured with Human Umbilical Vein Endothelial Cells (HUVECs). LPS stimulation significantly increased the levels of IL-6 (P = 0.007 and P = 0.005), TNF-α (P = 0.006 and P = 0.005), IL-2 (P = 0.007 and P = 0.002), IFN-γ (P = 0.006 and P = 0.003), IL-17A (P = 0.004 and P = 0.003), IL-17F (P = 0.005 and P = 0.003), IL-5 (P = 0.007 and P = 0.005), IL-13 (P = 0.006 and P = 0.005), IL-9 (P = 0.005 and P = 0.005) and IL-21 (P = 0.007 and P = 0.005) in HUVECs co-cultured with HC and HS PBMCs as compared with un-stimulated co-culture condition, respectively. Eritoran treatment (50 μg/mL and 100 μg/mL) significantly reduced the levels of LPS-induced IL-6 (P = 0.007 and P = 0.006; P = 0.007 and P = 0.007), TNF-α (P = 0.005 and P = 0.003; P = 0.007 and P = 0.005), IL-2 (P = 0.007 and P = 0.005; P = 0.005 and P = 0.004), IFN-γ (P = 0.007 and P = 0.005; P = 0.005 and P = 0.004), IL-17A (P = 0.005 and P = 0.002; P = 0.005 and P = 0.002), IL-17F (P = 0.006 and P = 0.006; P = 0.005 and P = 0.005), IL-5 (P = 0.007 and P = 0.006; P = 0.007 and P = 0.007), IL-9 (P = 0.005 and P = 0.005; P = 0.005 and P = 0.005) and IL-21 (P = 0.007 and P = 0.007; P = 0.005 and P = 0.005) in stimulated HUVECs co-cultured with HC and HS PBMCs, compared to un-treated condition, respectively. Our results demonstrate that attenuating effect of Eritoran on the inflammatory responses to LPS is higher in PBMCs of patients with high stenosis, suggesting its potential role in ameliorating inflammatory conditions in atherosclerosis.

Cannabis Seed Oil Alleviates Experimental Atherosclerosis by Ameliorating Vascular Inflammation in Apolipoprotein-E-Deficient Mice

In recent decades, epidemiological, clinical, and experimental studies have demonstrated that a diet with antioxidant or anti-inflammatory function plays a central role in the prevention of atherosclerosis (AS). The purpose of this study was to explore the effects of Cannabis seed oil (CO) administration on in vitro antioxidant capacity as well as blood lipid profiles, lipid peroxidation, inflammatory response, and endothelial cell integrity. Female ApoE^-/- mice were fed a high-cholesterol diet and administrated with CO or phosphate-buffered saline (PBS) and seal oil by gavage for 8 weeks. The results show that CO administration reduced the levels of serum triglycerides and low-density lipoprotein cholesterol at week 6. Additionally, a decrease in serum tumor necrosis factor α and nitric oxide was also observed. Moreover, results from CD31 staining and scanning electron microscopy revealed that CO treatment alleviated the endothelial cell damage and lipid deposition induced by a high-cholesterol diet. The ratio of lesion area to the total aorta area was 19.57% for the CO group, which was lower than the PBS control group (24.67%). Collectively, CO exerted anti-atherosclerotic effects by modulating serum lipid profiles and inflammatory responses and improving endothelial cell integrity and arterial lipid deposition. The results provide a promising preventive strategy for the early progression of AS.

Cytokines as therapeutic targets for cardio- and cerebrovascular diseases

Despite major advances in prevention and treatment, cardiac and cerebral atherothrombotic complications still account for substantial morbidity and mortality worldwide. In this context, inflammation is involved in the chronic process leading atherosclerotic plaque formation and its complications, as well as in the maladaptive response to acute ischemic events. For this reason, modulation of inflammation is nowadays seen as a promising therapeutic strategy to counteract the burden of cardio- and cerebrovascular disease. Being produced and recognized by both inflammatory and vascular cells, the complex network of cytokines holds key functions in the crosstalk of these two systems and orchestrates the progression of atherothrombosis. By binding to membrane receptors, these soluble mediators trigger specific intracellular signaling pathways eventually leading to the activation of transcription factors and a deep modulation of cell function. Both stimulatory and inhibitory cytokines have been described and progressively reported as markers of disease or interesting therapeutic targets in the cardiovascular field. Nevertheless, cytokine inhibition is burdened by harmful side effects that will most likely prevent its chronic use in favor of acute administrations in well-selected subjects at high risk. Here, we summarize the current state of knowledge regarding the modulatory role of cytokines on atherosclerosis, myocardial infarction, and stroke. Then, we discuss evidence from clinical trials specifically targeting cytokines and the potential implication of these advances into daily clinical practice.

Psoriasis: Comorbidities

Psoriasis has long been known as a disease with many complications, but was attributed to diet and obesity. However, in recent years, psoriasis itself has been recognized as a series of systemic inflammatory diseases, and that the cytokines involved can induce a variety of other diseases. Individuals with psoriasis were also found to have higher incidences of cerebral and cardiovascular diseases and a younger age at death compared to healthy individuals. However, no clear guidelines have been defined regarding how much vascular lesion testing should be performed in patients with psoriasis. In this report, I attempt to unravel the objective data on psoriasis and its complications from various reviews and reports, and introduce the impact of biologics, which are currently the main treatment for psoriasis, on cardiac vascular disease.

Cardiometabolic risks and atherosclerotic disease in ApoE knockout mice: Effect of spinal cord injury and Salsalate anti-inflammatory pharmacotherapy

OBJECTIVE

To test in mice with a double mutation of the ApoE gene (ApoE-/-) whether spinal cord injury (SCI) hastens the native trajectory of, and established component risks for, atherosclerotic disease (AD), and whether Salsalate anti-inflammatory pharmacotherapy attenuates the impact of SCI.

METHODS

ApoE-/- mice were anesthetized and underwent a T9 laminectomy. Exposed spinal cords were given a contusion injury (70 k-dynes). Sham animals underwent all surgical procedures, excluding injury. Injured animals were randomized to 2 groups: SCI or SCI+Salsalate [120 mg/Kg/day i.p.]. Mice were serially sacrificed at 20-, 24-, and 28-weeks post-SCI, and body mass was recorded. At sacrifice, heart and aorta were harvested intact, fixed in 10% buffered formalin, cleaned and cut longitudinally for en face preparation. The aortic tree was stained with oil-red-O (ORO). AD lesion histomorphometry was calculated from the proportional area of ORO. Plasma total cholesterol, triglycerides and proatherogenic inflammatory cytokines (PAIC's) were analyzed.

RESULTS

AD lesion in the aortic arch progressively increased in ApoE-/-, significant at 24- and 28-weeks. AD in SCI is significantly greater at 24- and 28-weeks compared to time-controlled ApoE-/-. Salsalate treatment attenuates the SCI-induced increase at these time points. Body mass in all SCI groups are significantly reduced compared to time-controlled ApoE-/-. Cholesterol and triglycerides are significantly higher with SCI by 24- and 28-weeks, compared to ApoE-/-, and Salsalate reduces the SCI-induced effect on cholesterol. PAIC's interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNFα), monocyte chemoattractant protein-1 (MCP-1), and chemokine (C-C motif) ligand 5 (CCL-5) are significantly greater with SCI compared to ApoE-/- at varying timepoints. Salsalate confers a marginal reducing effect on PAIC's by 28-weeks compared to SCI. Regression models determine that each PAIC is a significant and positive predictor of lesion. (p's <0.05).

CONCLUSIONS

SCI accelerates aortic AD and associated risk factors, and anti-inflammatory treatment may attenuate the impact of SCI on AD outcomes. PAIC's IL-1β, IL-6, TNFα, MCP-1, and CCL-5 may be effective predictors of AD.

Complexity of TNF-α Signaling in Heart Disease

Heart disease is a leading cause of death with unmet clinical needs for targeted treatment options. Tumor necrosis factor alpha (TNF-α) represents a master pro-inflammatory cytokine that plays an important role in many immunopathogenic processes. Anti-TNF-α therapy is widely used in treating autoimmune inflammatory disorders, but in case of patients with heart disease, this treatment was unsuccessful or even harmful. The underlying reasons remain elusive until today. This review summarizes the effects of anti-TNF-α treatment in patients with and without heart disease and describes the involvement of TNF-α signaling in a number of animal models of cardiovascular diseases. We specifically focused on the role of TNF-α in specific cardiovascular conditions and in defined cardiac cell types. Although some mechanisms, mainly in disease development, are quite well known, a comprehensive understanding of TNF-α signaling in the failing heart is still incomplete. Published data identify pathogenic and cardioprotective mechanisms of TNF-α in the affected heart and highlight the differential role of two TNF-α receptors pointing to the complexity of the TNF-α signaling. In the light of these findings, it seems that targeting the TNF-α pathway in heart disease may show therapeutic benefits, but this approach must be more specific and selectively block pathogenic mechanisms. To this aim, more research is needed to better understand the molecular mechanisms of TNF-α signaling in the failing heart.

Targeted anti-inflammatory therapy is a new insight for reducing cardiovascular events: A review from physiology to the clinic

Despite considerable progressions, cardiovascular disease (CVD) is still one of the major causes of mortality around the world, indicates an important and unmet clinical need. Recently, extensive studies have been performed on the role of inflammatory factors as either a major or surrogate factor in the pathophysiology of CVD. Epidemiological observations suggest the theory of the role of inflammatory mediators in the development of cardiovascular events. This may support the idea that targeted anti-inflammatory therapies, on the background of traditional validated medical therapies, can play a significant role in prevention and even reduction of cardiovascular disorders. Many randomized controlled trials have shown that drugs commonly useful for primary and secondary prevention of CVD have an anti-inflammatory mechanism. Further, many anti-inflammatory drugs are being examined because of their potential to reduce the risk of cardiovascular problems. In this study, we review the process of inflammation in the development of cardiovascular events, both in vivo and clinical evidence in immunotherapy for CVD.

Immune-Inflammation in Atherosclerosis: A New Twist in an Old Tale

Background and Objective:

Atherosclerosis, a chronic and progressive inflammatory disease, is triggered by the activation of endothelial cells followed by infiltration of innate and adaptive immune cells including monocytes and T cells in arterial walls. Major populations of T cells found in human atherosclerotic lesions are antigen-specific activated CD4+ effectors and/or memory T cells from Th1, Th17, Th2 and Treg subsets. In this review, we will discuss the significance of T cell orchestrated immune inflammation in the development and progression of atherosclerosis.

Discussion:

Pathogen/oxidative stress/lipid induced primary endothelial wound cannot develop to a full-blown atherosclerotic lesion in the absence of chronically induced inflammation. While the primary inflammatory response might be viewed as a lone innate response, the persistence of such a profound response over time must be (and is) associated with diverse local and systemic T cell responses. The interplay between T cells and innate cells contributes to a phenomenon called immuneinflammation and has an impact on the progression and outcome of the lesion. In recent years immuneinflammation, an old term, has had a comeback in connecting the puzzle pieces of chronic inflammatory diseases.

Conclusion:

Taking one-step back and looking from afar at the players of immune-inflammation may help us provide a broader perspective of these complicated interactions. This may lead to the identification of new drug targets and the development of new therapies as well as preventative measures.

The Dual Role of Surfactant Protein-D in Vascular Inflammation and Development of Cardiovascular Disease

Cardiovascular disease (CVD) is responsible for 31% of all global deaths. Atherosclerosis is the major cause of cardiovascular disease and is a chronic inflammatory disorder in the arteries. Atherosclerosis is characterized by the accumulation of cholesterol, extracellular matrix, and immune cells in the vascular wall. Recently, the collectin surfactant protein-D (SP-D), an important regulator of the pulmonary immune response, was found to be expressed in the vasculature. Several in vitro studies have examined the role of SP-D in the vascular inflammation leading to atherosclerosis. These studies show that SP-D plays a dual role in the development of atherosclerosis. In general, SP-D shows anti-inflammatory properties, and dampens local inflammation in the vessel, as well as systemic inflammation. However, SP-D can also exert a pro-inflammatory role, as it stimulates C-C chemokine receptor 2 inflammatory blood monocytes to secrete tumor necrosis-factor α and increases secretion of interferon-γ from natural killer cells. In vivo studies examining the role of SP-D in the development of atherosclerosis agree that SP-D plays a proatherogenic role, with SP-D knockout mice having smaller atherosclerotic plaque areas, which might be caused by a decreased systemic inflammation. Clinical studies examining the association between SP-D and cardiovascular disease have reported a positive association between circulatory SP-D level, carotid intima-media thickness, and coronary artery calcification. Other studies have found that circulatory SP-D is correlated with increased risk of both total and cardiovascular disease mortality. Both in vitro, in vivo, and clinical studies examining the relationship between SP-D and CVDs will be discussed in this review.

Ticagrelor induces paraoxonase-1 (PON1) and better protects hypercholesterolemic mice against atherosclerosis compared to clopidogrel

Ticagrelor (TIC), a P2Y purinoceptor 12 (P2Y₁₂)-receptor antagonist, has been widely used to treat patients with acute coronary syndrome. Although animal studies suggest that TIC protects against atherosclerosis, it remains unknown whether it does so through its potent platelet inhibition or through other pathways. Here, we placed hypercholesterolemic Ldlr^-/-Apobec1^-/- mice on a high-fat diet and treated them with either 25 mg/kg/day of clopidogrel (CLO) or 180 mg/kg/day of TIC for 16 weeks and evaluated the extent of atherosclerosis. Both treatments equally inhibited platelets as determined by ex vivo platelet aggregation assays. The extent of atherosclerosis, however, was significantly less in the TIC group than in the CLO group. Immunohistochemical staining and ELISA showed that TIC treatment was associated with less macrophage infiltration to the atherosclerotic intima and lower serum levels of CCL4, CXCL10, and TNFα, respectively, than CLO treatment. Treatment with TIC, but not CLO, was associated with higher serum activity and tissue level of paraoxonase-1 (PON1), an anti-atherosclerotic molecule, suggesting that TIC might exert greater anti-atherosclerotic activity, compared with CLO, through its unique ability to induce PON1. Although further studies are needed, TIC may prove to be a viable strategy in the prevention and treatment of chronic stable human atherosclerosis.

Is Interleukin-38 a key player cytokine in atherosclerosis immune gene therapy?

Atherosclerosis, a chronic inflammatory disease of the arteries associated with lipids and other metabolic alterations is a leading cause of death all around the world and its rate is raising as a result of unhealthy lifestyles. Reports by World Health Organization indicate that 31% of all death occurrences are due to heart attacks and strokes. Today, the most common medicines for treating atherosclerosis are statins which are HMG-coA reductase inhibitors. Beside their benefits in treating atherosclerosis, some side effects have been reported as well. Thus, therapeutic methods based on statins should be evaluated to result in more beneficial effects. Since atherosclerosis is an inflammatory disorder, an anti-inflammatory component can decrease the impact of this disease. Interleukin-38, a newly discovered anti-inflammatory cytokine, which acts as an Interleukin-36 receptor antagonist can block Nuclear Factor KB and Activator protein-1 signaling pathways, and block atherogenic core formation accordingly. This novel proposed immune gene therapy can be applied to atherosclerosis treatment in a trial study. In this hypothesis, Interleukin-38 gene is transferred into bone marrow Mesenchymal Stem Cells of atherosclerotic mouse model Apo E-/- via an adenoviral vector. It is expected that Interleukin-38 gene expression by Mesenchymal Stem Cells can efficiently remedy atherosclerosis without the side effects of statins.

The Role of Cytokines in the Development of Atherosclerosis

Atherosclerosis contributes to the development of many cardiovascular diseases, which remain the leading cause of death in developed countries. Atherosclerosis is a chronic inflammatory disease of large and medium-sized arteries. It is caused by dyslipidemia and mediated by both innate and adaptive immune responses. Inflammation is a key factor at all stages of atherosclerosis progression. Cells involved in pathogenesis of atherosclerosis were shown to be activated by soluble factors, cytokines, that strongly influence the disease development. Pro-inflammatory cytokines accelerate atherosclerosis progression, while anti-inflammatory cytokines ameliorate the disease. In this review, we discuss the latest findings on the role of cytokines in the development and progression of atherosclerosis.

The Antiatherogenic Effect of Fish Oil in Male Mice Is Associated with a Diminished Release of Endothelial ADAM17 and ADAM10 Substrates

BACKGROUND

Growing evidence suggests that disintegrin and metalloprotease (ADAM) 17 (ADAM17) and ADAM10 contribute to the pathogenesis of vascular diseases. ADAM17 promotes inflammatory processes by liberating tumor necrosis factor α, interleukin 6 receptor (IL-6R), and tumor necrosis factor receptor 1 (TNFR1). ADAM17 and ADAM10 modulate vascular permeability by cleaving endothelial adhesion molecules such as junctional adhesion molecule A (JAM-A) and vascular endothelial cadherin (VE-cadherin), respectively.

OBJECTIVE

This study was designed to investigate whether a link might exist between the protective effects of fish oil (FO) supplementation against atherosclerosis and ADAM function.

METHODS

Male LDL receptor knockout (LDLR(-/-)) mice and male wild-type (WT) mice were fed a Western diet (200 g/kg fat, 1.5 g/kg cholesterol) containing either 20% lard (LDLR(-/-)-lard and WT-lard groups) or 10% lard combined with 10% FO (LDLR(-/-)-FO and WT-FO groups) for 12 wk. Atherosclerotic lesion development and fatty acid composition of liver microsomes were evaluated. ADAM10 and ADAM17 expression was determined by quantitative real-time polymerase chain reaction and immunoblot analyses. Concentrations of soluble ADAM substrates in plasma and liver extracts were measured by ELISA.

RESULTS

Diets supplemented with FO markedly reduced development of early atherosclerotic lesions in LDLR(-/-) mice (LDLR(-/-)-lard group vs. LDLR(-/-)-FO group mean ± SD: 29.6 ± 6.1% vs. 22.5 ± 4.2%, P < 0.05). This was not accompanied by changes in expression of ADAM17 or ADAM10 in the aorta or liver. No dietary effects on circulating TNFR1 (LDLR(-/-)-lard group vs. LDLR(-/-)-FO group mean ± SD: 1.22 ± 0.23 vs. 1.39 ± 0.28, P > 0.2) or IL-6R (1.06 ± 0.12 vs. 0.98 ± 0.09 fold of WT-lard group, P > 0.1), classical substrates of ADAM17 on macrophages, and neutrophil granulocytes were observed. However, a reduction in atherosclerotic lesions in the LDLR(-/-)-FO group was accompanied by a significant reduction in the circulating endothelial cell adhesion molecules JAM-A (LDLR(-/-)-lard group vs. LDLR(-/-)-FO group mean ± SD: 1.42 ± 0.20 vs. 0.95 ± 0.56 fold of WT-lard group, P < 0.05), intercellular adhesion molecule 1 (1.15 ± 0.14 vs. 0.88 ± 0.17 fold of WT-lard group, P < 0.05), and VE-cadherin (0.88 ± 0.12 vs. 0.72 ± 0.15 fold of WT-lard group, P < 0.05), reflecting reduced ADAM activity in endothelial cells.

CONCLUSION

FO exerted an antiatherogenic effect on male LDLR(-/-) mice that was accompanied by a reduced release of ADAM17 and ADAM10 substrates from endothelial cells. It is suggested that FO-decreased ADAM activity contributes to improved endothelial barrier function and thus counteracts intimal lipoprotein insudation and macrophage accumulation.

Cytokines in atherosclerosis: Key players in all stages of disease and promising therapeutic targets

Atherosclerosis, a chronic inflammatory disorder of the arteries, is responsible for most deaths in westernized societies with numbers increasing at a marked rate in developing countries. The disease is initiated by the activation of the endothelium by various risk factors leading to chemokine-mediated recruitment of immune cells. The uptake of modified lipoproteins by macrophages along with defective cholesterol efflux gives rise to foam cells associated with the fatty streak in the early phase of the disease. As the disease progresses, complex fibrotic plaques are produced as a result of lysis of foam cells, migration and proliferation of vascular smooth muscle cells and continued inflammatory response. Such plaques are stabilized by the extracellular matrix produced by smooth muscle cells and destabilized by matrix metalloproteinase from macrophages. Rupture of unstable plaques and subsequent thrombosis leads to clinical complications such as myocardial infarction. Cytokines are involved in all stages of atherosclerosis and have a profound influence on the pathogenesis of this disease. This review will describe our current understanding of the roles of different cytokines in atherosclerosis together with therapeutic approaches aimed at manipulating their actions.

Cytokines and Immune Responses in Murine Atherosclerosis

Atherosclerosis is an inflammatory disease of the vessel wall characterized by activation of the innate immune system, with macrophages as the main players, as well as the adaptive immune system, characterized by a Th1-dominant immune response. Cytokines play a major role in the initiation and regulation of inflammation. In recent years, many studies have investigated the role of these molecules in experimental models of atherosclerosis. While some cytokines such as TNF or IFNγ clearly had atherogenic effects, others such as IL-10 were found to be atheroprotective. However, studies investigating the different cytokines in experimental atherosclerosis revealed that the cytokine system is complex with both disease stage-dependent and site-specific effects. In this review, we strive to provide an overview of the main cytokines involved in atherosclerosis and to shed light on their individual role during atherogenesis.

Metoprolol reduces proinflammatory cytokines and atherosclerosis in ApoE-/- mice

A few studies in animals and humans suggest that metoprolol (β1-selective adrenoceptor antagonist) may have a direct antiatherosclerotic effect. However, the mechanism behind this protective effect has not been established. The aim of the present study was to evaluate the effect of metoprolol on development of atherosclerosis in ApoE^−/− mice and investigate its effect on the release of proinflammatory cytokines. Male ApoE^−/− mice were treated with metoprolol (2.5 mg/kg/h) or saline for 11 weeks via osmotic minipumps. Atherosclerosis was assessed in thoracic aorta and aortic root. Total cholesterol levels and Th1/Th2 cytokines were analyzed in serum and macrophage content in lesions by immunohistochemistry. Metoprolol significantly reduced atherosclerotic plaque area in thoracic aorta (P < 0.05 versus Control). Further, metoprolol reduced serum TNFα and the chemokine CXCL1 (P < 0.01 versus Control for both) as well as decreasing the macrophage content in the plaques (P < 0.01 versus Control). Total cholesterol levels were not affected. In this study we found that a moderate dose of metoprolol significantly reduced atherosclerotic plaque area in thoracic aorta of ApoE^−/− mice. Metoprolol also decreased serum levels of proinflammatory cytokines TNFα and CXCL1 and macrophage content in the plaques, showing that metoprolol has an anti-inflammatory effect.

Behavioural, metabolic, and endothelial effects of the TNF-α suppressor thalidomide on rats subjected to chronic mild stress and fed an atherogenic diet

There is accumulating evidence suggesting that depression is a risk factor for cardiovascular diseases. This study aimed to examine the hypothesis that the proinflammatory cytokine TNF-α would partially explain the link between depression and atherosclerotic endothelial changes. Rats were distributed among 6 groups: (i) control group; (ii) group subjected to chronic mild stress (CMS); (iii) group fed a cholesterol–cholic acid–thiouracil (CCT diet); and (iv) CMS group fed the CCT diet and treated with the vehicle for 8 weeks. The last 2 groups were subjected to CMS–CCT and received thalidomide (THAL) or imipramine (IMIP). Rats were assessed behaviorally (sucrose preference, open field, and forced-swimming tests). TNF-α protein was assessed from the serum, aorta, and liver. Aortic TNF-α gene expression (assessed using RT–PCR), serum lipid profile, and insulin levels were measured. Endothelial function was assessed in isolated aortic rings. The THAL and IMIP groups showed ameliorated CMS–CCT-related behavioral changes. CMS–CCT-induced metabolic and endothelial dysfunctions were improved in the THAL group but were worsened in the IMIP group. RT–PCR showed a significant reduction of aortic TNF-α mRNA expression in the THAL and IMIP treatment groups. These data paralleled the findings for aortic immunohistochemistry. The THAL group, but not the IMIP group, showed improved CMS–CCT-induced changes in the vascular reactivity of the aortic rings. Thus, TNF-α provides a target link between depression, metabolic syndrome, and endothelial dysfunction. This could open a new therapeutic approach to address the comorbidities of depression.

HIV, inflammation, and calcium in atherosclerosis

Atherosclerosis is consistently higher among the HIV-positive patients, with or without treatment, than among the HIV-negative population. Risk factors linked to atherosclerotic cardiovascular disease in HIV infection are both traditional and HIV specific although the underlying mechanisms are not fully delineated. Three key sequential biological processes are postulated to accelerate progression of atherosclerosis in the context of HIV: (1) inflammation, (2) transformation of monocytes to macrophages and then foam cells, and (3) apoptosis of foam cells leading to plaque development through Ca(2+)-dependent endoplasmic reticulum stress. These proatherogenic mechanisms are further affected when HIV interacts with the genes involved in various phases within this network.

Diverse roles of macrophages in atherosclerosis: from inflammatory biology to biomarker discovery

Cardiovascular disease, a leading cause of mortality in developed countries, is mainly caused by atherosclerosis, a chronic inflammatory disease. Macrophages, which differentiate from monocytes that are recruited from the blood, account for the majority of leukocytes in atherosclerotic plaques. Apoptosis and the suppressed clearance of apoptotic macrophages (efferocytosis) are associated with vulnerable plaques that are prone to rupture, leading to thrombosis. Based on the central functions of macrophages in atherogenesis, cytokines, chemokines, enzymes, or microRNAs related to or produced by macrophages have become important clinical prognostic or diagnostic biomarkers. This paper discusses the impact of monocyte-derived macrophages in early atherogenesis and advanced disease. The role and possible future development of macrophage inflammatory biomarkers are also described.

Animal models of organic heart valve disease

Heart valve disease is a frequently encountered pathology, related to high morbidity and mortality rates in industrialized and developing countries. Animal models are interesting to investigate the causality, but also underlying mechanisms and potential treatments of human valvular diseases. Recently, animal models of heart valve disease have been developed, which allow to investigate the pathophysiology, and to follow the progression and the potential regression of disease with therapeutics over time. The present review provides an overview of animal models of primary, organic heart valve disease: myxoid age-related, infectious, drug-induced, degenerative calcified, and mechanically induced valvular heart disease.

Aortic valve disease and treatment: the need for naturally engineered solutions

The aortic valve regulates unidirectional flow of oxygenated blood to the myocardium and arterial system. The natural anatomical geometry and microstructural complexity ensures biomechanically and hemodynamically efficient function. The compliant cusps are populated with unique cell phenotypes that continually remodel tissue for long-term durability within an extremely demanding mechanical environment. Alteration from normal valve homeostasis arises from genetic and microenvironmental (mechanical) sources, which lead to congenital and/or premature structural degeneration. Aortic valve stenosis pathobiology shares some features of atherosclerosis, but its final calcification endpoint is distinct. Despite its broad and significant clinical significance, very little is known about the mechanisms of normal valve mechanobiology and mechanisms of disease. This is reflected in the paucity of predictive diagnostic tools, early stage interventional strategies, and stagnation in regenerative medicine innovation. Tissue engineering has unique potential for aortic valve disease therapy, but overcoming current design pitfalls will require even more multidisciplinary effort. This review summarizes the latest advancements in aortic valve research and highlights important future directions.

Tumor necrosis factor inhibitors as novel therapeutic tools for vascular remodeling diseases

Vascular remodeling diseases (VRDs) are characterized by enhanced inflammation and proliferative and apoptosis-resistant vascular smooth muscle cells (VSMCs). The sustainability of this phenotype has been attributed in part to the activation of the transcription factor hypoxia-inducible factor-1 (HIF-1). There is evidence that circulating cytokines can act as HIF-1 activators in a variety of tissues, including VSMCs. Increased circulating tumor necrosis factor (TNF) levels have been associated with vascular diseases, but the mechanisms involved remain unknown. We hypothesized that increased circulating levels of TNF promotes VRDs by the activation of HIF-1, resulting in VSMC proliferation and resistance to apoptosis. Circulating TNF levels were significantly increased in patients with vascular diseases (n = 19) compared with healthy donors (n = 15). Using human carotid artery smooth muscle cells (CASMCs), we demonstrated that TNF (100 ng/ml) activates HIF-1 (HIF-1α expression), leading to increased CASMC proliferation (Ki-67 and PCNA staining) and resistance to mitochondrial-dependent apoptosis [tetramethylrhodamine methyl ester perchlorate (TMRM), terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL), annexin-V staining]. In vivo, TNF inhibition using polyethylene glycol coupled with TNF membrane receptor 1 (PEGsTNFR1), a soluble TNF receptor inhibiting circulating TNF, prevented carotid artery postinjury media remodeling and neointima development in rats. This effect was associated with lowered HIF-1 activation and decreased CASMC proliferation. In conclusion, we demonstrate for the first time that the inhibition of the TNF/Akt/HIF-1 axis prevents vascular remodeling. TNF inhibitors may therefore represent new and interesting therapeutic tools against VRDs.

Role of the nuclear receptors HNF4 alpha, PPAR alpha, and LXRs in the TNF alpha-mediated inhibition of human apolipoprotein A-I gene expression in HepG2 cells

The expression of the apolipoprotein A-I gene (apoA-I) in hepatocytes is repressed by pro-inflammatory cytokines such as IL-1beta and TNFalpha. In this work, we have demonstrated that treatment of HepG2 human hepatoma cells with chemical inhibitors for JNK, p38 protein kinases, and NFkappaB transcription factor abolishes the TNFalpha-mediated inhibition of human apoA-I gene expression in HepG2 cells. In addition, we have shown that TNFalpha decreases also the rate of secretion of apoA-I protein by HepG2 cells, and this effect depends on JNK and p38, but not on NFkappaB and MEK1/2 signaling pathways. The inhibitory effect of TNFalpha has been found to be mediated by the hepatic enhancer of the apoA-I gene. The decrease in the level of human apoA-I gene expression under the impact of TNFalpha appears to be partly mediated by the inhibition of HNF4alpha and PPARalpha gene expression. Treatment of HepG2 cells with PPARalpha antagonist (MK886) or LXR agonist (TO901317) abolishes the TNFalpha-mediated decrease in the level of apoA-I gene expression. PPARalpha agonist (WY-14643) abolishes the negative effect of TNFalpha on apoA-I gene expression in the case of simultaneous inhibition of MEK1/2, although neither inhibition of MEK1/2 nor addition of WY-14643 leads to the blocking of the TNFalpha-mediated decrease in the level of apoA-I gene expression individually. The ligand-dependent regulation of apoA-I gene expression by PPARalpha appears to be affected by the TNFalpha-mediated activation of MEK1/2 kinases, probably through PPARalpha phosphorylation. Treatment of HepG2 cells with PPARalpha and LXR synthetic agonists also blocks the inhibition of apoA-I protein secretion in HepG2 cells under the impact of TNFalpha. A chromatin immunoprecipitation assay demonstrates that TNFalpha leads to a 2-fold decrease in the level of PPARalpha binding with the apoA-I gene hepatic enhancer. At the same time, the level of LXRbeta binding with the apoA-I gene hepatic enhancer is increased 3-fold under the impact of TNFalpha. These results suggest that nuclear receptors HNF4alpha, PPARalpha, and LXRs are involved in the TNFalpha-mediated downregulation of human apoA-I gene expression and apoA-I protein secretion in HepG2 cells.

Fn14-Fc Fusion Protein Regulates Atherosclerosis in ApoE −/− Mice and Inhibits Macrophage Lipid Uptake In Vitro

Objective— TWEAK is a multifunctional cytokine belonging to the tumor necrosis factor superfamily and binds to the receptor Fn14. TWEAK and Fn14 are expressed in atherosclerotic plaques in areas rich in macrophages and foam cells. We investigated the role of TWEAK/Fn14 interactions in ApoE −/− mice and bone marrow–derived macrophages in vitro.

Methods and Results— ApoE −/− mice were treated with TWEAK-inhibiting fusion protein, Fn14-Fc, in an early (5 to 17 weeks of age) or delayed (17 to 29 weeks of age) setting. In the aortic arch, Fn14-Fc as compared to control treatment resulted in advanced plaques which were smaller (early treatment), fewer (delayed treatment), lower in fibrotic content (early and delayed treatment), and exhibited an increased macrophage content and smaller macrophage size (delayed treatment). There were no differences in apoptosis in atherosclerotic plaques after Fn14-Fc versus control Ab treatment. However, blocking TWEAK resulted in less macrophage uptake of modified lipids in vitro.

Conclusions— Fn14-Fc fusion protein treatment did not prevent lesion initiation but inhibited some features of plaque progression and induced a unique advanced plaque phenotype with increased macrophage content and smaller macrophage size, which may be attributable to reduced lipid uptake. These findings indicate that TWEAK/Fn14 interactions regulate atherosclerosis and mediate lipid uptake in macrophages.

Immune and inflammatory mechanisms of atherosclerosis (*)

Atherosclerosis is an inflammatory disease of the wall of large- and medium-sized arteries that is precipitated by elevated levels of low-density lipoprotein (LDL) cholesterol in the blood. Although dendritic cells (DCs) and lymphocytes are found in the adventitia of normal arteries, their number is greatly expanded and their distribution changed in human and mouse atherosclerotic arteries. Macrophages, DCs, foam cells, lymphocytes, and other inflammatory cells are found in the intimal atherosclerotic lesions. Beneath these lesions, adventitial leukocytes organize in clusters that resemble tertiary lymphoid tissues. Experimental interventions can reduce the number of available blood monocytes, from which macrophages and most DCs and foam cells are derived, and reduce atherosclerotic lesion burden without altering blood lipids. Under proatherogenic conditions, nitric oxide production from endothelial cells is reduced and the burden of reactive oxygen species (ROS) and advanced glycation end products (AGE) is increased. Incapacitating ROS-generating NADPH oxidase or the receptor for AGE (RAGE) has beneficial effects. Targeting inflammatory adhesion molecules also reduces atherosclerosis. Conversely, removing or blocking IL-10 or TGF-beta accelerates atherosclerosis. Regulatory T cells and B1 cells secreting natural antibodies are atheroprotective. This review summarizes our current understanding of inflammatory and immune mechanisms in atherosclerosis.

Tumor necrosis factor-alpha deficiency retards early fatty-streak lesion by influencing the expression of inflammatory factors in apoE-null mice

Tumor necrosis factor-alpha (TNF-alpha), a key inflammatory cytokine, plays an important role in atherosclerosis. However, its precise characters in primary stage of the disease remain unclear. To assess the influence of TNF-alpha on inflammatory factors in aorta and liver in apoE and TNF-alpha double mutant (AT) mice, a comparative study on early fatty-streak lesion, the mRNA level of target gene in aorta and liver of adolescent AT and apoE-null (apoE(-/-)) mice were achieved. The characteristics of expression of inflammatory factors, and early fatty-streak lesion relevance were analyzed. The plasma cytokines in 6-week-old AT and apoE(-/-) mice were also measured. Lipid accumulation in the intima of the aorta existed as early as 3 weeks of age in apoE(-/-) mice. Fatty-streak lesion was mild in AT mice but prominent in apoE(-/-) mice, at age of 6 weeks. Furthermore, most interesting findings indicate that mRNA levels of pro-atherosclerotic factors, i.e. IL-1beta, IFN-gamma, ICAM-1, VCAM-1, MCP-1, GM-CSF and NF-kappaB (p65) were significantly downregulated in AT mice. Whereas IL-2 and IkappaB-alpha were upregulated in aorta of AT mice versus those in apoE(-/-) mice (p<0.01) and the transcript levels of pro-inflammatory cytokines, such as IL-1beta, IFN-gamma, ICAM-1, VCAM-1, MCP-1 and GM-CSF, increased with atherogenesis progression. On the other hand, the expression of these inflammatory factors in the liver displayed somewhat similar fashion to those in the aorta. Moreover, the plasma lipids profile in AT mice showed less pro-atherogenic than that of apoE(-/-) mice. Our data indicated that TNF-alpha deficiency surely, although not completely, retards fatty-streak lesion formation due to downregulated expression of the pro-atherosclerotic inflammatory factors in the present circumstance.

[The two sides of ADAM17 in inflammation: implications in atherosclerosis and obesity]

ADAM17 was initially characterized as the TNF Alpha Converting Enzyme (TACE) and, until now, has been the most studied member of the ADAM family. It is a type I transmembrane metalloproteinase involved in the shedding of the extracellular domain of several transmembrane proteins (at least 40) such as cytokines, growth factors, receptors or adhesion molecules. As a consequence, depending on the transmembrane molecule cleaved, one may expect possible opposite effects of ADAM17 activity on inflammation (e.g. TNF and its receptors). The role of ADAM17 in regulating inflammatory cellular processes is clearly demonstrated in cells deficient in active ADAM17 or expressing substrates mutated for the ADAM17 cleavage site. As ADAM17-deficient mice died at birth, mice overexpressing the mutated uncleavable form of some substrates and recently conditional knock-out of ADAM17 are used to approach in vivo the role of this metalloprotease in regulating inflammation. Arguments are provided that ADAM17 plays a role in atherosclerosis, in adipose tissue metabolism, insulin resistance and diabetes. The multitude of substrates cleaved by ADAM17 makes this enzyme an attractive candidate to study its role in inflammation-driven pathologies.