Plaque rupture in humans and mice

Z-Ligustilide: A Potential Therapeutic Agent for Atherosclerosis Complicating Cerebrovascular Disease

Atherosclerosis (AS) is one of the major catalysts of ischemic cerebrovascular disease, and the death and disease burden from AS and its cerebrovascular complications are increasing. Z-ligustilide (Z-LIG) is a key active ingredient in Angelica sinensis (Oliv.) Diels and Ligusticum chuanxiong Hort. In this paper, we first introduced LIG's physicochemical properties and pharmacokinetics. Then, we reviewed Z-LIG's intervention and therapeutic mechanisms on AS and its cerebrovascular complications. The mechanisms of Z-LIG intervention in AS include improving lipid metabolism, antioxidant and anti-inflammatory effects, protecting vascular endothelium, and inhibiting vascular endothelial fibrosis, pathological thickening, and plaque calcification. In ischemic cerebrovascular diseases complicated by AS, Z-LIG exerts practical neuroprotective effects in ischemic stroke (IS), transient ischemic attack (TIA), and vascular dementia (VaD) through anti-neuroinflammatory, anti-oxidation, anti-neuronal apoptosis, protection of the blood-brain barrier, promotion of mitochondrial division and angiogenesis, improvement of cholinergic activity, inhibition of astrocyte proliferation, and endoplasmic reticulum stress. This paper aims to provide a basis for subsequent studies of Z-LIG in the prevention and treatment of AS and its cerebrovascular complications and, thus, to promote the development of interventional drugs for AS.

Targeting Unc5b in macrophages drives atherosclerosis regression and pro-resolving immune cell function

Atherosclerosis results from lipid-driven inflammation of the arterial wall that fails to resolve. Imbalances in macrophage accumulation and function, including diminished migratory capacity and defective efferocytosis, fuel maladaptive inflammation and plaque progression. The neuroimmune guidance cue netrin-1 has dichotomous roles in inflammation partly due to its multiple receptors; in atherosclerosis, netrin-1 promotes macrophage survival and retention via its receptor Unc5b. To minimize the pleiotropic effects of targeting netrin-1, we tested the therapeutic potential of deleting Unc5b in mice with advanced atherosclerosis. We generated Unc5bfl/flCx3cr1creERT2/WT mice, which allowed conditional deletion of Un5b (∆Unc5bMØ) in monocytes and macrophages by tamoxifen injection. After inducing advanced atherosclerosis by hepatic PCSK9 overexpression and western diet feeding for 20 wk, Unc5b was deleted and hypercholesterolemia was normalized to simulate clinical lipid management. Deletion of myeloid Unc5b led to a 40% decrease in atherosclerotic plaque burden and reduced plaque complexity compared to Unc5bfl/flCx3cr1WT/WT littermate controls (CtrlMØ). Consistently, plaque macrophage content was reduced by 50% in ∆Unc5bMØ mice due to reduced plaque Ly6Chi monocyte recruitment and macrophage retention. Compared to CtrlMØ mice, plaques in ∆Unc5bMØ mice had reduced necrotic area and fewer apoptotic cells, which correlated with improved efferocytotic capacity by Unc5b-deficient macrophages in vivo and in vitro. Beneficial changes in macrophage dynamics in the plaque upon Unc5b deletion were accompanied by an increase in atheroprotective T cell populations, including T-regulatory and Th2 cells. Our data identify Unc5b in advanced atherosclerosis as a therapeutic target to induce pro-resolving restructuring of the plaque immune cells and to promote atherosclerosis regression.

Monocyte Count as a Predictor of Major Adverse Limb Events in Aortoiliac Revascularization

Background/Objectives: Atherosclerosis is a leading cause of death, especially in the developed world, and is marked by chronic arterial inflammation and lipid accumulation. As key players in its progression, monocytes contribute to plaque formation, inflammation, and tissue repair. Understanding monocyte involvement is crucial for developing better therapeutic approaches. The objective of this study is to assess the prognostic value of monocytes for limb-related outcomes following revascularization for complex aortoiliac lesions, thereby emphasizing the central role of monocytes in atherosclerosis. Methods: This prospective cohort study-enrolled patients who had undergone elective aortoiliac revascularization at two hospitals between January 2013 and December 2023. Patients with TASC II type D lesions were included, excluding those with aneurysmal disease. Demographic, clinical, and procedural data were gathered, and patients were monitored for limb-related outcomes. Preoperative complete blood counts were analyzed, and statistical analyses, including multivariable Cox regression, were conducted to identify predictors of major adverse limb events (MALE). Results: The study included 135 patients with a mean age of 62.4 ± 9.20 years and predominantly male (93%). Patients were followed for a median of 61 IQR [55.4-66.6] months. Smoking history (91%) was the most prevalent cardiovascular risk factor. Preoperative monocyte count >0.720 × 109/L was associated with worse 30-day limb-related outcomes (MALE: OR 7.138 95% CI: 1.509-33.764, p = 0.013) and long-term outcomes, including secondary patency (p = 0.03), major amputation (p = 0.04), and MALE (p = 0.039). Cox regression analysis confirmed an elevated monocyte count as an independent predictor of MALE (adjusted hazard ratio 2.149, 95% CI: 1.115-4.144, p = 0.022). Conclusions: This study demonstrated that patients with a higher absolute monocyte count may be more exposed to the risk of MALE in patients with aortoiliac TASC II type D lesions undergoing revascularization, with predictive accuracy in both the short and long term. Additionally, it was an independent predictor of major amputation. This new marker has the potential to serve as a cost-effective and easily available tool for risk stratification, helping identify patients at higher risk of MALE.

Moving from lipids to leukocytes: inflammation and immune cells in atherosclerosis

Atherosclerotic cardiovascular disease (ASCVD) is the most important cause of morbidity and mortality worldwide. While it is traditionally attributed to lipid accumulation in the vascular endothelium, recent research has shown that plaque inflammation is an important additional driver of atherogenesis. Though clinical outcome trials utilizing anti-inflammatory agents have proven promising in terms of reducing ASCVD risk, it is imperative to identify novel actionable targets that are more specific to atherosclerosis to mitigate adverse effects associated with systemic immune suppression. To that end, this review explores the contributions of various immune cells from the innate and adaptive immune system in promoting and mitigating atherosclerosis by integrating findings from experimental studies, high-throughput multi-omics technologies, and epidemiological research.

Atherosclerotic Plaque Epigenetic Age Acceleration Predicts a Poor Prognosis and Is Associated With Endothelial-to-Mesenchymal Transition in Humans

BACKGROUND

Epigenetic age estimators (clocks) are predictive of human mortality risk. However, it is not yet known whether the epigenetic age of atherosclerotic plaques is predictive for the risk of cardiovascular events.

METHODS

Whole-genome DNA methylation of human carotid atherosclerotic plaques (n=485) and of blood (n=93) from the Athero-Express endarterectomy cohort was used to calculate epigenetic age acceleration (EAA). EAA was linked to clinical characteristics, plaque histology, and future cardiovascular events (n=136). We studied whole-genome DNA methylation and bulk and single-cell transcriptomics to uncover molecular mechanisms of plaque EAA. We experimentally confirmed our in silico findings using in vitro experiments in primary human coronary endothelial cells.

RESULTS

Male and female patients with severe atherosclerosis had a median chronological age of 69 years. The median epigenetic age was 65 years in females (median EAA, -2.2 [interquartile range, -4.3 to 2.2] years) and 68 years in males (median EAA, -0.3 [interquartile range, -2.9 to 3.8] years). Patients with diabetes and a high body mass index had higher plaque EAA. Increased EAA of plaque predicted future events in a 3-year follow-up in a Cox regression model (univariate hazard ratio, 1.7; P=0.0034) and adjusted multivariate model (hazard ratio, 1.56; P=0.02). Plaque EAA predicted outcome independent of blood EAA (hazard ratio, 1.3; P=0.018) and of plaque hemorrhage (hazard ratio, 1.7; P=0.02). Single-cell RNA sequencing in plaque samples from 46 patients in the same cohort revealed smooth muscle and endothelial cells as important cell types in plaque EAA. Endothelial-to-mesenchymal transition was associated with EAA, which was experimentally confirmed by TGFβ-triggered endothelial-to-mesenchymal transition inducing rapid epigenetic aging in coronary endothelial cells.

CONCLUSIONS

Plaque EAA is a strong and independent marker of poor outcome in patients with severe atherosclerosis. Plaque EAA was linked to mesenchymal endothelial and smooth muscle cells. Endothelial-to-mesenchymal transition was associated with EAA, which was experimentally validated. Epigenetic aging mechanisms may provide new targets for treatments that reduce atherosclerosis complications.

Crosstalk between Nrf2 signaling pathway and inflammation in ischemic stroke: Mechanisms of action and therapeutic implications

One of the major causes of long-term disability and mortality is ischemic stroke that enjoys limited treatment approaches. On the one hand, oxidative stress, induced by excessive generation of reactive oxygen species (ROS), plays a critical role in post-stroke inflammatory response. Increased ROS generation is one of the basic factors in the progression of stroke-induced neuroinflammation. Moreover, intravenous (IV) thrombolysis using recombinant tissue plasminogen activator (rtPA) as the only medication approved for patients with acute ischemic stroke who suffer from some clinical restrictions it could not cover the complicated episodes that happen after stroke. Thus, identifying novel therapeutic targets is crucial for successful preparation of new medicines. Recent evidence indicates that the transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) contributes significantly to regulating the antioxidant production in cytosol, which causes antiinflammatory effects on neurons. New findings have shown a relationship between activation of the Nrf2 and glial cells, nuclear factor kappa B (NF-κB) pathway, the nucleotide-binding domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signaling, and expression of inflammatory markers, suggesting induction of Nrf2 activation can represent a promising therapeutic alternative as the modulators of Nrf2 dependent pathways for targeting inflammatory responses in neural tissue. Hence, this review addresses the relationship of Nrf2 signaling with inflammation and Nrf2 activators' potential as therapeutic agents. This review helps to improve required knowledge for focused therapy and the creation of modern and improved treatment choices for patients with ischemic stroke.

The accumulation of erythrocytes quantified and visualized by Glycophorin C in carotid atherosclerotic plaque reflects intraplaque hemorrhage and pre-procedural neurological symptoms

The accumulation of erythrocyte membranes within an atherosclerotic plaque may contribute to the deposition of free cholesterol and thereby the enlargement of the necrotic core. Erythrocyte membranes can be visualized and quantified in the plaque by immunostaining for the erythrocyte marker glycophorin C. Hence, we theorized that the accumulation of erythrocytes quantified by glycophorin C could function as a marker for plaque vulnerability, possibly reflecting intraplaque hemorrhage (IPH), and offering predictive value for pre-procedural neurological symptoms. We employed the CellProfiler-integrated slideToolKit workflow to visualize and quantify glycophorin C, defined as the total plaque area that is positive for glycophorin C, in single slides of culprit lesions obtained from the Athero-Express Biobank of 1819 consecutive asymptomatic and symptomatic patients who underwent carotid endarterectomy. Our assessment included the evaluation of various parameters such as lipid core, calcifications, collagen content, SMC content, and macrophage burden. These parameters were evaluated using a semi-quantitative scoring method, and the resulting data was dichotomized as predefined criteria into categories of no/minor or moderate/heavy staining. In addition, the presence or absence of IPH was also scored. The prevalence of IPH and pre-procedural neurological symptoms were 62.4% and 87.1%, respectively. The amount of glycophorin staining was significantly higher in samples from men compared to samples of women (median 7.15 (IQR:3.37, 13.41) versus median 4.06 (IQR:1.98, 8.32), p < 0.001). Glycophorin C was associated with IPH adjusted for clinical confounders (OR 1.90; 95% CI 1.63, 2.21; p =  < 0.001). Glycophorin C was significantly associated with ipsilateral pre-procedural neurological symptoms (OR:1.27, 95%CI:1.06-1.41, p = 0.005). Sex-stratified analysis, showed that this was also the case for men (OR 1.37; 95%CI 1.12, 1.69; p = 0.003), but not for women (OR 1.15; 95%CI 0.77, 1.73; p = 0.27). Glycophorin C was associated with classical features of a vulnerable plaque, such as a larger lipid core, a higher macrophage burden, less calcifications, a lower collagen and SMC content. There were marked sex differences, in men, glycophorin C was associated with calcifications and collagen while these associations were not found in women. To conclude, the accumulation of erythrocytes in atherosclerotic plaque quantified and visualized by glycophorin C was independently associated with the presence of IPH, preprocedural symptoms in men, and with a more vulnerable plaque composition in both men and women. These results strengthen the notion that the accumulation of erythrocytes quantified by glycophorin C can be used as a marker for plaque vulnerability.

Vascular Electrical Stimulation with Wireless, Battery-Free, and Fully Implantable Features Reduces Atherosclerotic Plaque Formation Through Sirt1-Mediated Autophagy

Electrical stimulation (ES) is a safe and effective procedure in clinical rehabilitation with few adverse effects. However, studies on ES for atherosclerosis (AS) are scarce because ES does not provide a long-term intervention for chronic disease processes. Battery-free implants and surgically mounted them in the abdominal aorta of high-fat-fed Apolipoprotein E (ApoE-/- ) mice are used, which are electrically stimulated for four weeks using a wireless ES device to observe changes in atherosclerotic plaques. Results showed that there is almost no growth of atherosclerotic plaque at the stimulated site in AopE-/- mice after ES. RNA-sequencing (RNA-seq) analysis of Thp-1 macrophages reveal that the transcriptional activity of autophagy-related genes increase substantially after ES. Additionally, ES reduces lipid accumulation in macrophages by restoring ABCA1- and ABCG1-mediated cholesterol efflux. Mechanistically, it is demonstrated that ES reduced lipid accumulation through Sirtuin 1 (Sirt1)/Autophagy related 5 (Atg5) pathway-mediated autophagy. Furthermore, ES reverse autophagic dysfunction in macrophages of AopE-/- mouse plaques by restoring Sirt1, blunting P62 accumulation, and inhibiting the secretion of interleukin (IL)-6, resulting in the alleviation of atherosclerotic lesion formation. Here, a novel approach is shown in which ES can be used as a promising therapeutic strategy for AS treatment through Sirt1/Atg5 pathway-mediated autophagy.

Splenic Infarction with Myocardial Injury in a Diabetic Patient: A Case Report

Splenic infarction (SI) is an uncommon complication of type 2 diabetes (T2D). Diabetes predisposes individuals to blood vessel abnormalities, such as atherosclerosis or thrombosis, increasing the risk of vessel occlusion and subsequent tissue infarction. If the diabetic patient has other serious diseases, such as a severe pneumonia infection and acute cardiac infarction, SI incidence may go unrecognized, making it challenging for physicians to identify. This case report discussed an 80-year-old hospitalized diabetic woman with a history of chronic bronchitis and 20 years of T2D who suffered an SI. The patient was at elevated risk for thrombosis of atrial fibrillation, manifested as an embolism of the spleen characterized by a high concentration of white blood cells. This patient also demonstrated a rapid increase in cardiac biomarkers troponin I, suggesting acute myocardial infarction (AMI) and increased amylase, which could not preclude the concern about the existence of acute pancreatitis. Abdominal CT displayed the calcification of only the splenic and other arteries, and low-density shadows were observed at the center portion of the spleen. This case demonstrated the significant occurrence of thrombotic complications in various blood vessels of multiple organs in T2D patients. Thus, clinicians should be aware of the possibility of simultaneous acute vascular infarction of several organs in diabetic patients with prior vascular constriction.

Overview of multifunctional cysteinyl cathepsins in atherosclerosis-based cardiovascular disease: from insights into molecular functions to clinical implications

Cysteinyl cathepsins (CTSs) are widely known to have a proteolysis function that mediates recycling of unwanted proteins in endosomes and lysosomes, and investigation of CTSs has greatly improved with advances in live-imaging techniques both in vivo and in vitro, leading to three key findings. (1) CTSs are relocated from the lysosomes to other cellular spaces (i.e., cytosol, nucleus, nuclear membrane, plasma membrane, and extracellular milieu). (2) In addition to acidic cellular compartments, CTSs also exert biological activity in neutral environments. (3) CTSs also exert multiple nontraditional functions in, for example, extracellular matrix metabolism, cell signaling transduction, protein processing/trafficking, and cellular events. Various stimuli regulate the expression and activities of CTSs in vivo and vitro-e.g., inflammatory cytokines, oxidative stress, neurohormones, and growth factors. Accumulating evidence has confirmed the participation of CTSs in vascular diseases characterized by atherosclerosis, plaque rupture, thrombosis, calcification, aneurysm, restenosis/in-stent-restenosis, and neovasel formation. Circulating and tissue CTSs are promising as biomarkers and as a diagnostic imaging tool in patients with atherosclerosis-based cardiovascular disease (ACVD), and pharmacological interventions with their specific and non-specific inhibitors, and cardiovascular drugs might have potential for the therapeutic targeting of CTSs in animals. This review focuses on the update findings on CTS biology and the involvement of CTSs in the initiation and progression of ACVD and discusses the potential use of CTSs as biomarkers and small-molecule targets to prevent deleterious nontraditional functions in ACVD.

PPARγ (Peroxisome Proliferator-Activated Receptor γ) Deacetylation Suppresses Aging-Associated Atherosclerosis and Hypercholesterolemia

BACKGROUND

Atherosclerosis is a medical urgency manifesting at the onset of hypercholesterolemia and is associated with aging. Activation of PPARγ (peroxisome proliferator-activated receptor γ) counteracts metabolic dysfunction influenced by aging, and its deacetylation displays an atheroprotective property. Despite the marked increase of PPARγ acetylation during aging, it is unknown whether PPARγ acetylation is a pathogenic contributor to aging-associated atherosclerosis.

METHODS

Mice with constitutive deacetylation-mimetic PPARγ mutations on lysine residues K268 and K293 (2KR) in an LDL (low-density lipoprotein)-receptor knockout (Ldlr-/-) background (2KR:Ldlr-/-) were aged for 18 months on a standard laboratory diet to examine the cardiometabolic phenotype, which was confirmed in Western-type diet-fed 2KR:Ldlr+/- mice. Whole-liver RNA-sequencing and in vitro studies in bone marrow-derived macrophages were conducted to decipher the mechanism.

RESULTS

In contrast to severe atherosclerosis in WT:Ldlr-/- mice, aged 2KR:Ldlr-/- mice developed little to no plaque, which was underlain by a significantly improved plasma lipid profile, with particular reductions in circulating LDL. The protection from hypercholesterolemia was recapitulated in Western-type diet-fed 2KR:Ldlr+/- mice. Liver RNA-sequencing analysis revealed suppression of liver inflammation rather than changes in cholesterol metabolism. This anti-inflammatory effect of 2KR was attributed to polarized M2 activation of macrophages. Additionally, the upregulation of core circadian component Bmal1 (brain and muscle ARNT-like 1), perceived to be involved in anti-inflammatory immunity, was observed in the liver and bone marrow-derived macrophages.

CONCLUSIONS

PPARγ deacetylation in mice prevents the development of aging-associated atherosclerosis and hypercholesterolemia, in association with the anti-inflammatory phenotype of 2KR macrophages.

Therapeutic strategies targeting inflammation and immunity in atherosclerosis: how to proceed?

Atherosclerosis is a chronic inflammatory disease of the arterial wall, characterized by the formation of plaques containing lipid, connective tissue and immune cells in the intima of large and medium-sized arteries. Over the past three decades, a substantial reduction in cardiovascular mortality has been achieved largely through LDL-cholesterol-lowering regimes and therapies targeting other traditional risk factors for cardiovascular disease, such as hypertension, smoking, diabetes mellitus and obesity. However, the overall benefits of targeting these risk factors have stagnated, and a huge global burden of cardiovascular disease remains. The indispensable role of immunological components in the establishment and chronicity of atherosclerosis has come to the forefront as a clinical target, with proof-of-principle studies demonstrating the benefit and challenges of targeting inflammation and the immune system in cardiovascular disease. In this Review, we provide an overview of the role of the immune system in atherosclerosis by discussing findings from preclinical research and clinical trials. We also identify important challenges that need to be addressed to advance the field and for successful clinical translation, including patient selection, identification of responders and non-responders to immunotherapies, implementation of patient immunophenotyping and potential surrogate end points for vascular inflammation. Finally, we provide strategic guidance for the translation of novel targets of immunotherapy into improvements in patient outcomes.

In this Review, the authors provide an overview of the immune cells involved in atherosclerosis, discuss preclinical research and published and ongoing clinical trials assessing the therapeutic potential of targeting the immune system in atherosclerosis, highlight emerging therapeutic targets from preclinical studies and identify challenges for successful clinical translation.

Inflammation is an important component of the pathophysiology of cardiovascular disease; an imbalance between pro-inflammatory and anti-inflammatory processes drives chronic inflammation and the formation of atherosclerotic plaques in the vessel wall.

Clinical trials assessing canakinumab and colchicine therapies in atherosclerotic cardiovascular disease have provided proof-of-principle of the benefits associated with therapeutic targeting of the immune system in atherosclerosis.

The immunosuppressive adverse effects associated with the systemic use of anti-inflammatory drugs can be minimized through targeted delivery of anti-inflammatory drugs to the atherosclerotic plaque, defining the window of opportunity for treatment and identifying more specific targets for cardiovascular inflammation.

Implementing immunophenotyping in clinical trials in patients with atherosclerotic cardiovascular disease will allow the identification of immune signatures and the selection of patients with the highest probability of deriving benefit from a specific therapy.

Clinical stratification via novel risk factors and discovery of new surrogate markers of vascular inflammation are crucial for identifying new immunotherapeutic targets and their successful translation into the clinic.

Modulation of Peripheral CD4+CD25+Foxp3+ Regulatory T Cells Ameliorates Surgical Stress-Induced Atherosclerotic Plaque Progression in ApoE-Deficient Mice

Systemic inflammation associated with major surgery rapidly accelerates atherosclerotic plaque progression in mice. Regulatory T cells (Tregs) have emerged as important modulators of atherogenesis. In coronary artery disease patients, low frequency of Tregs constitutes an independent risk factor for cardiovascular complications after non-cardiac surgery. In this exploratory analysis, we investigate whether preoperative Treg levels affect surgery-induced atherosclerotic lesion destabilization in a murine model of perioperative stress. After 9 weeks of high-cholesterol diet, atherosclerotic apolipoprotein E-deficient mice with modulated Treg levels were subjected to a 30-minute surgical procedure consisting of general isoflurane anesthesia, laparotomy and moderate blood loss. Controls underwent general anesthesia only. Brachiocephalic arteries were harvested 3 days after the intervention for histomorphological analyses of atherosclerotic plaques. Tregs were depleted by a single dose of anti-CD25 monoclonal antibody (mAb) administered 6 days prior to the intervention. Expansion of Tregs was induced by daily injections of IL-2/anti-IL-2 complex (IL-2C) on three consecutive days starting 3 days before surgery. Isotype-matched antibodies and PBS served as controls. Antibody-mediated modulation was Treg-specific. IL-2C treatment resulted in an eight-fold elevation of peripheral CD4⁺CD25⁺Foxp3⁺ Tregs compared to mice administered with anti-CD25 mAb. In mice treated with PBS and anti-CD25 mAb, surgical stress response caused a significant increase of atherosclerotic plaque necrosis (PBS: p < 0.001; anti-CD25 mAb: p = 0.037). Preoperative Treg expansion abrogated perioperative necrotic core formation (p = 0.556) and significantly enhanced postoperative atherosclerotic plaque stability compared to PBS-treated mice (p = 0.036). Postoperative plaque volume (p = 0.960), stenosis (p = 0.693), lesional collagen (p = 0.258), as well as the relative macrophage (p = 0.625) and smooth muscle cell content (p = 0.178) remained largely unaffected by preoperative Treg levels. In atherosclerotic mice, therapeutic expansion of Tregs prior to major surgery mitigates rapid effects on perioperative stress-driven atherosclerotic plaque destabilization. Future studies will show, whether short-term interventions modulating perioperative inflammation qualify for prevention of cardiovascular events associated with major non-cardiac surgery.

Do Mitochondrial DNA Mutations Play a Key Role in the Chronification of Sterile Inflammation? Special Focus on Atherosclerosis

BACKGROUND

The aim of the elucidation of mechanisms implicated in the chronification of inflammation is to shed light on the pathogenesis of disorders that are responsible for the majority of the incidences of diseases and deaths, and also causes of ageing. Atherosclerosis is an example of the most significant inflammatory pathology. The inflammatory response of innate immunity is implicated in the development of atherosclerosis arising locally or focally. Modified low-density lipoprotein (LDL) was regarded as the trigger for this response. No atherosclerotic changes in the arterial wall occur due to the quick decrease in inflammation rate. Nonetheless, the atherosclerotic lesion formation can be a result of the chronification of local inflammation, which, in turn, is caused by alteration of the response of innate immunity.

OBJECTIVE

In this review, we discussed potential mechanisms of the altered response of the immunity in atherosclerosis with a particular emphasis on mitochondrial dysfunctions.

CONCLUSION

A few mitochondrial dysfunctions can be caused by the mitochondrial DNA (mtDNA) mutations. Moreover, mtDNA mutations were found to affect the development of defective mitophagy. Modern investigations have demonstrated the controlling mitophagy function in response to the immune system. Therefore, we hypothesized that impaired mitophagy, as a consequence of mutations in mtDNA, can raise a disturbed innate immunity response, resulting in the chronification of inflammation in atherosclerosis.

Endothelium-restricted endothelin-1 overexpression in type 1 diabetes worsens atherosclerosis and immune cell infiltration via NOX1

AIMS

NADPH oxidase (NOX) 1 but not NOX4-dependent oxidative stress plays a role in diabetic vascular disease, including atherosclerosis. Endothelin (ET)-1 has been implicated in diabetes-induced vascular complications. We showed that crossing mice overexpressing human ET-1 selectively in endothelium (eET-1) with apolipoprotein E knockout (Apoe-/-) mice enhanced high-fat diet-induced atherosclerosis in part by increasing oxidative stress. We tested the hypothesis that ET-1 overexpression in the endothelium would worsen atherosclerosis in type 1 diabetes through a mechanism involving NOX1 but not NOX4.

METHODS AND RESULTS

Six-week-old male Apoe-/- and eET-1/Apoe-/- mice with or without Nox1 (Nox1-/y) or Nox4 knockout (Nox4-/-) were injected intraperitoneally with either vehicle or streptozotocin (55 mg/kg/day) for 5 days to induce type 1 diabetes and were studied 14 weeks later. ET-1 overexpression increased 2.5-fold and five-fold the atherosclerotic lesion area in the aortic sinus and arch of diabetic Apoe-/- mice, respectively. Deletion of Nox1 reduced aortic arch plaque size by 60%; in contrast, Nox4 knockout increased lesion size by 1.5-fold. ET-1 overexpression decreased aortic sinus and arch plaque alpha smooth muscle cell content by ∼35% and ∼50%, respectively, which was blunted by Nox1 but not Nox4 knockout. Reactive oxygen species production was increased two-fold in aortic arch perivascular fat of diabetic eET-1/Apoe-/- and eET-1/Apoe-/-/Nox4-/- mice but not eET-1/Apoe-/-/Nox1y/- mice. ET-1 overexpression enhanced monocyte/macrophage and CD3+ T-cell infiltration ∼2.7-fold in the aortic arch perivascular fat of diabetic Apoe-/- mice. Both Nox1 and Nox4 knockout blunted CD3+ T-cell infiltration whereas only Nox1 knockout prevented the monocyte/macrophage infiltration in diabetic eET-1/Apoe-/- mice.

CONCLUSION

Endothelium ET-1 overexpression enhances the progression of atherosclerosis in type 1 diabetes, perivascular oxidative stress, and inflammation through NOX1.

Mitochondrial Damage-Induced Innate Immune Activation in Vascular Smooth Muscle Cells Promotes Chronic Kidney Disease-Associated Plaque Vulnerability

Chronic kidney disease (CKD) is associated with accelerated atherosclerosis progression and high incidence of cardiovascular events, hinting that atherosclerotic plaques in CKD may be vulnerable. However, its cause and mechanism remain obscure. Here, it is shown that apolipoprotein E-deficient (ApoE-/-) mouse with CKD (CKD/ApoE-/- mouse) is a useful model for investigating the pathogenesis of plaque vulnerability, and premature senescence and phenotypic switching of vascular smooth muscle cells (VSMCs) contributes to CKD-associated plaque vulnerability. Subsequently, VSMC phenotypes in patients with CKD and CKD/ApoE-/- mice are comprehensively investigated. Using multi-omics analysis and targeted and VSMC-specific gene knockout mice, VSMCs are identified as both type-I-interferon (IFN-I)-responsive and IFN-I-productive cells. Mechanistically, mitochondrial damage resulting from CKD-induced oxidative stress primes the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway to trigger IFN-I response in VSMCs. Enhanced IFN-I response then induces VSMC premature senescence and phenotypic switching in an autocrine/paracrine manner, resulting in the loss of fibrous cap VSMCs and fibrous cap thinning. Conversely, blocking IFN-I response remarkably attenuates CKD-associated plaque vulnerability. These findings reveal that IFN-I response in VSMCs through immune sensing of mitochondrial damage is essential for the pathogenesis of CKD-associated plaque vulnerability. Mitigating IFN-I response may hold promise for the treatment of CKD-associated cardiovascular diseases.

Analysis of MicroRNAs Associated With Carotid Atherosclerotic Plaque Rupture With Thrombosis

Atherosclerosis is a progressive vascular wall inflammatory disease, and the rupture of atherosclerotic vulnerable plaques is the leading cause of morbidity and mortality worldwide. This study intended to explore the potential mechanisms behind plaque rupture and thrombosis in ApoE knockout mice. The spontaneous plaque rupture models were established, and left carotid artery tissues at different time points (1-, 2-, 4-, 6-, 8-, 12-, and 16-week post-surgery) were collected. By the extent of plaque rupture, plaque was defined as (1) control groups, (2) atherosclerotic plaque group, and (3) plaque rupture group. Macrophage (CD68), MMP-8, and MMP-13 activities were measured by immunofluorescence. Cytokines and inflammatory markers were measured by ELISA. The left carotid artery sample tissue was collected to evaluate the miRNAs expression level by miRNA-microarray. Bioinformatic analyses were conducted at three levels: (2) vs. (1), (3) vs. (2), and again in seven time series analysis. The plaque rupture with thrombus and intraplaque hemorrhage results peaked at 8 weeks and decreased thereafter. Similar trends were seen in the number of plaque macrophages and lipids, the expression of matrix metalloproteinase, and the atherosclerotic and plasma cytokine levels. MiRNA-microarray showed that miR-322-5p and miR-206-3p were specifically upregulated in the atherosclerotic plaque group compared with those in the control group. Meanwhile, miR-466h-5p was specifically upregulated in the plaque rupture group compared with the atherosclerotic plaque group. The highest incidence of plaque rupture and thrombosis occurred at 8 weeks post-surgery. miR-322-5p and miR-206-3p may be associated with the formation of atherosclerotic plaques. miR-466h-5p may promote atherosclerotic plaque rupture via apoptosis-related pathways.

Association of tumor necrosis factor-alpha and interleukin-10 levels with ultrasound characteristics of atherosclerotic plaques in patients with essential hypertension

Aim. To study the association  of ultrasound characteristics of carotid atherosclerotic  plaques  (ASPs) with the concentration  of tumor necrosis factor-alpha  (TNFα) and interleukin-10 (IL-10) in patients  with essential hypertension.

Material and methods. The study included 117 patients  (men, 75; women, 42) with essential hypertension aged 40 to 75 years (mean age, 55,8±7,5 years). All patients  underwent anthropometric  measurements (height, weight, body mass index, waist circumference),  assessment of blood pressure  and heart rate, blood tests (levels of glucose, creatinine with the calculation of glomerular filtration rate using CKD-EPI equation, lipid profile), duplex ultrasound of the carotid arteries.  Also, the blood concentration  of TNFα and IL-10 by the enzyme-linked immunosorbent assay using CYTOKIN-STIMUL-BEST (Novosibirsk,Russia) kit was determined.

Results.  According to the  results  of carotid  duplex ultrasound,  3 groups of patients  were identified. Group 1 included 48 patients  with homogeneous hyperechoic ASPs; group 2 — 56 patients with dominant hyperechoic  ASPs (>50% of areas);  group 3 — 13 patients  with anechoic, unstable,  low-density ASPs. TNFα concentration  in group 3 patients, amounting to 10,51±2.23 pg/ml, was significantly higher than in patients of group 1 (7,26±0,64 pg/ml (p<0,001)) and group 2 (8,93±0,98 pg/ml (p<0,001)).  Similar results were obtained for IL-10. The logistic regression  showed that the TNFα concentration  is an independent  factor associated with unstable  ASsP (relative risk, 2,72; 95% confidence interval 1,44-5,15  (p<0,02)). It was also revealed that TNFα >10 pg/ml increased the risk of ASP instability by ~8 times.

Conclusion.  An increase  in TNFα >10 pg/ml with a high specificity (95%) was associated with vulnerable unstable carotid ASPs.

Inflammation of carotid plaques and risk of cerebrovascular events

Carotid atherosclerotic plaques represent a risk for ischemic stroke. The data indicate that the risk for distal embolization from atherosclerotic lesions in internal carotid arteries is not related only to the degree of stenosis but also to the composition of plaques. The stability of atherosclerotic plaque depends on the thickness of the fibrous cap and plaque hemorrhage. Recent research indicated that the inflammatory activity of atherosclerotic lesions is pivotal in the progression of atherosclerotic plaques. It also promotes the development of unstable atherosclerotic lesions and is related to thromboembolic cerebrovascular complications. Inflammation destabilizes atherosclerotic plaques through the degradation of their fibrotic structure. Inflammation of atherosclerotic plaques was confirmed by histopathologic findings and levels of circulating inflammatory markers which were correlated to the intensity of the inflammation in atherosclerotic lesions. Recently, new techniques like fluorodeoxyglucose positron emission tomography (18-FDG PET) were developed for the identification of inflammation of atherosclerotic lesions in the vessel wall in vivo. Systemic inflammatory markers, particularly interleukins, tumor necrosis factor-alpha and metalloproteinases were shown to be related to the intensity of the inflammatory process in atherosclerotic lesions and the cerebrovascular events. Identification of inflamed atherosclerotic plaques may help to identify unstable atherosclerotic lesions and subjects at high risk for cerebrovascular incidents who need intensive preventive measures including anti-inflammatory medication.

Deletion or Inhibition of NOD1 Favors Plaque Stability and Attenuates Atherothrombosis in Advanced Atherogenesis †

Atherothrombosis, the main cause of acute coronary syndromes (ACS), is characterized by the rupture of the atherosclerotic plaque followed by the formation of thrombi. Fatal plaque rupture sites show large necrotic cores combined with high levels of inflammation and thin layers of collagen. Plaque necrosis due to the death of macrophages and smooth muscle cells (SMCs) remains critical in the process. To determine the contribution of the innate immunity receptor NOD1 to the stability of atherosclerotic plaque, Apoe^-/- and Apoe^-/- Nod1^-/- atherosclerosis prone mice were placed on a high-fat diet for 16 weeks to assess post-mortem advanced atherosclerosis in the aortic sinus. The proliferation and apoptosis activity were analyzed, as well as the foam cell formation capacity in these lesions and in primary cultures of macrophages and vascular SMCs obtained from both groups of mice. Our results reinforce the preeminent role for NOD1 in human atherosclerosis. Advanced plaque analysis in the Apoe^-/- atherosclerosis model suggests that NOD1 deficiency may decrease the risk of atherothrombosis by decreasing leukocyte infiltration and reducing macrophage apoptosis. Furthermore, Nod1^-/- SMCs exhibit higher proliferation rates and decreased apoptotic activity, contributing to thicker fibrous caps with reduced content of pro-thrombotic collagen. These findings demonstrate a direct link between NOD1 and plaque vulnerability through effects on both macrophages and SMCs, suggesting promising insights for early detection of biomarkers for treating patients before ACS occurs.

Diabetic atherosclerosis: is there a role for the hypoxia-inducible factors?

Atherosclerosis is a major cause of mortality worldwide and is driven by multiple risk factors, including diabetes. Diabetes is associated with either an insulin deficiency in its juvenile form or with insulin resistance and obesity in Type 2 diabetes mellitus, and the latter is clustered with other comorbidities to define the metabolic syndrome. Diabetes and metabolic syndrome are complex pathologies and are associated with cardiovascular risk via vascular inflammation and other mechanisms. Several transcription factors are activated upon diabetes-driven endothelial dysfunction and drive the progression of atherosclerosis. In particular, the hypoxia-inducible factor (HIF) transcription factor family is a master regulator of endothelial biology and is raising interest in the field of atherosclerosis. In this review, we will present an overview of studies contributing to the understanding of diabetes-driven atherosclerosis, integrating the role of HIF in this disease with the knowledge of its functions in metabolic syndrome and diabetic scenario.

Role of Nrf2 and Its Activators in Cardiocerebral Vascular Disease

Cardiocerebral vascular disease (CCVD) is a common disease with high morbidity, disability, and mortality. Oxidative stress (OS) is closely related to the progression of CCVD. Abnormal redox regulation leads to OS and overproduction of reactive oxygen species (ROS), which can cause biomolecular and cellular damage. The Nrf2/antioxidant response element (ARE) signaling pathway is one of the most important defense systems against exogenous and endogenous OS injury, and Nrf2 is regarded as a vital pharmacological target. The complexity of the CCVD pathological process and the current difficulties in conducting clinical trials have hindered the development of therapeutic drugs. Furthermore, little is known about the role of the Nrf2/ARE signaling pathway in CCVD. Clarifying the role of the Nrf2/ARE signaling pathway in CCVD can provide new ideas for drug design. This review details the recent advancements in the regulation of the Nrf2/ARE system and its role and activators in common CCVD development.

Parallel Murine and Human Plaque Proteomics Reveals Pathways of Plaque Rupture

RATIONALE

Plaque rupture is the proximate cause of most myocardial infarctions and many strokes. However, the molecular mechanisms that precipitate plaque rupture are unknown.

OBJECTIVE

By applying proteomic and bioinformatic approaches in mouse models of protease-induced plaque rupture and in ruptured human plaques, we aimed to illuminate biochemical pathways through which proteolysis causes plaque rupture and identify substrates that are cleaved in ruptured plaques.

METHODS AND RESULTS

We performed shotgun proteomics analyses of aortas of transgenic mice with macrophage-specific overexpression of urokinase (SR-uPA^+/0 mice) and of SR-uPA^+/0 bone marrow transplant recipients, and we used bioinformatic tools to evaluate protein abundance and functional category enrichment in these aortas. In parallel, we performed shotgun proteomics and bioinformatics studies on extracts of ruptured and stable areas of freshly harvested human carotid plaques. We also applied a separate protein-analysis method (protein topography and migration analysis platform) to attempt to identify substrates and proteolytic fragments in mouse and human plaque extracts. Approximately 10% of extracted aortic proteins were reproducibly altered in SR-uPA^+/0 aortas. Proteases, inflammatory signaling molecules, as well as proteins involved with cell adhesion, the cytoskeleton, and apoptosis, were increased. ECM (Extracellular matrix) proteins, including basement-membrane proteins, were decreased. Approximately 40% of proteins were altered in ruptured versus stable areas of human carotid plaques, including many of the same functional categories that were altered in SR-uPA^+/0 aortas. Collagens were minimally altered in SR-uPA^+/0 aortas and ruptured human plaques; however, several basement-membrane proteins were reduced in both SR-uPA^+/0 aortas and ruptured human plaques. Protein topography and migration analysis platform did not detect robust increases in proteolytic fragments of ECM proteins in either setting.

CONCLUSIONS

Parallel studies of SR-uPA^+/0 mouse aortas and human plaques identify mechanisms that connect proteolysis with plaque rupture, including inflammation, basement-membrane protein loss, and apoptosis. Basement-membrane protein loss is a prominent feature of ruptured human plaques, suggesting a major role for basement-membrane proteins in maintaining plaque stability.

Atherosclerosis is aggravated by iron overload and ameliorated by dietary and pharmacological iron restriction

AIMS

Whether and how iron affects the progression of atherosclerosis remains highly debated. Here, we investigate susceptibility to atherosclerosis in a mouse model (ApoE-/- FPNwt/C326S), which develops the disease in the context of elevated non-transferrin bound serum iron (NTBI).

METHODS AND RESULTS

Compared with normo-ferremic ApoE-/- mice, atherosclerosis is profoundly aggravated in iron-loaded ApoE-/- FPNwt/C326S mice, suggesting a pro-atherogenic role for iron. Iron heavily deposits in the arterial media layer, which correlates with plaque formation, vascular oxidative stress and dysfunction. Atherosclerosis is exacerbated by iron-triggered lipid profile alterations, vascular permeabilization, sustained endothelial activation, elevated pro-atherogenic inflammatory mediators, and reduced nitric oxide availability. NTBI causes iron overload, induces reactive oxygen species production and apoptosis in cultured vascular cells, and stimulates massive MCP-1-mediated monocyte recruitment, well-established mechanisms contributing to atherosclerosis. NTBI-mediated toxicity is prevented by transferrin- or chelator-mediated iron scavenging. Consistently, a low-iron diet and iron chelation therapy strongly improved the course of the disease in ApoE-/- FPNwt/C326S mice. Our results are corroborated by analyses of serum samples of haemochromatosis patients, which show an inverse correlation between the degree of iron depletion and hallmarks of endothelial dysfunction and inflammation.

CONCLUSION

Our data demonstrate that NTBI-triggered iron overload aggravates atherosclerosis and unravel a causal link between NTBI and the progression of atherosclerotic lesions. Our findings support clinical applications of iron restriction in iron-loaded individuals to counteract iron-aggravated vascular dysfunction and atherosclerosis.

Cholesterol: A new game player accelerating vasculopathy caused by SARS-CoV-2?

The pandemic of coronavirus disease (COVID-19) has become a global threat to public health. Functional impairments in multiple organs have been reported in COVID-19, including lungs, heart, kidney, liver, brain, and vascular system. Patients with metabolic-associated preconditions, such as hypertension, obesity, and diabetes, are susceptible to experiencing severe symptoms. The recent emerging evidence of coagulation disorders in COVID-19 suggests that vasculopathy appears to be an independent risk factor promoting disease severity and mortality of affected patients. We recently found that the decreased levels of low-density lipoprotein cholesterols (LDL-c) correlate with disease severity in COVID-19 patients, indicating pathological interactions between dyslipidemia and vasculopothy in patients with COVID-19. However, this clinical manifestation has been unintentionally underestimated by physicians and scientific communities. As metabolic-associated morbidities are generally accompanied with endothelial cell (EC) dysfunctions, these pre-existing conditions may make ECs more vulnerable to SARS-CoV-2 attack. In this mini-review, we summarize the metabolic and vascular manifestations of COVID-19 with an emphasis on the association between changes in LDL-c levels and the development of severe symptoms as well as the pathophysiologic mechanisms underlying the synergistic effect of LDL-c and SARS-CoV-2 on EC injuries and vasculopathy.

Association Between HMGB1 and Thrombogenesis in a Hyperlipaemia-induced Microminipig Model of Atherosclerosis

BACKGROUND/AIM

An appropriate animal model is essential to investigate the relationship between inflammation, atherosclerosis, and thrombogenesis, and the development of preventive measures and therapies for atherosclerosis.

MATERIALS AND METHODS

Atherosclerosis was induced in Microminipigs (MMPs) using a high-fat diet. We assessed high mobility group box 1 (HMGB1) expression levels and measured thrombus formation using a Total Thrombus Formation Analysis System (T-TAS). MMPs were divided into a normal diet (control) group and four high-fat diet groups, with differing amounts of cholesterol. After 8 weeks, blood was collected for analysis.

RESULTS

HMGB1 levels increased with increasing dietary cholesterol, and a negative correlation was found between HMGB1 levels and thrombus formation time.

CONCLUSION

T-TAS is useful in the assessment of thrombogenesis in MMPs and HMGB1 is associated with thrombus formation.

Small rodent models of atherosclerosis

The ease of breeding, low cost of maintenance, and relatively short period for developing atherosclerosis make rodents ideal for atherosclerosis research. However, none of the current models accurately model human lipoprotein profile or atherosclerosis progression since each has its advantages and disadvantages. The advent of transgenic technologies much supports animal models' establishment. Notably, two classic transgenic mouse models, apoE-/- and Ldlr-/-, constitute the primary platforms for studying underlying mechanisms and development of pharmaceutical approaches. However, there exist crucial differences between mice and humans, such as the unhumanized lipoprotein profile, and the different plaque progression and characteristics. Among rodents, hamsters and guinea pigs might be the more realistic models in atherosclerosis research based on the similarities in lipoprotein metabolism to humans. Studies involving rat models, a rodent with natural resistance to atherosclerosis, have revealed evidence of atherosclerotic plaques under dietary induction and genetic manipulation by novel technologies, notably CRISPR-Cas9. Ldlr-/- hamster models were established in recent years with severe hyperlipidemia and atherosclerotic lesion formation, which could offer an alternative to classic transgenic mouse models. In this review, we provide an overview of classic and innovative small rodent models in atherosclerosis researches, including mice, rats, hamsters, and guinea pigs, focusing on their lipoprotein metabolism and histopathological changes.

eNOS-Nitric Oxide System Contributes to a Novel Antiatherogenic Effect of Leonurine via Inflammation Inhibition and Plaque Stabilization

Leonurine (LEO) is a bioactive small molecular compound that has protective effects on the cardiovascular system and prevents the early progression of atherosclerosis; however, it is not clear whether LEO is effective for plaque stability. A novel mouse atherosclerosis model involving tandem stenosis (TS) of the right carotid artery combined with western diet (WD) feeding was used. Apolipoprotein E gene-deficient mice were fed with a WD and received LEO administration daily for 13 weeks. TS was introduced 6 weeks after the onset of experiments. We found that LEO enhanced plaque stability by increasing fibrous cap thickness and collagen content while decreasing the population of CD68-positive cells. Enhanced plaque stability by LEO was associated with the nitric oxide synthase (NOS)-nitric oxide (NO) system. LEO restored the balance between endothelial NOS(E)- and inducible NOS(iNOS)-derived NO production; suppressed the NF-κB signaling pathway; reduced the level of the inflammatory infiltration in plaque, including cytokine interleukin 6; and downregulated the expression of adhesion molecules. These findings support the distinct role of LEO in plaque stabilization. In vitro studies with oxidized low-density lipoprotein-challenged human umbilical vein endothelial cells revealed that LEO balanced NO production and inhibited NF-κB/P65 nuclear translocation, thus mitigating inflammation. In conclusion, the restored balance of the NOS-NO system and mitigated inflammation contribute to the plaque-stabilizing effect of LEO. SIGNIFICANCE STATEMENT: LEO restored the balance between endothelial NOS and inducible NOS in NO production and inhibited excessive inflammation in atherosclerotic "unstable" and rupture-prone plaques in apolipoprotein E gene-deficient mice. The protective effect of LEO for stabilizing atherosclerotic plaques was due to improved collagen content, increased fibrous cap thickness, and decreased accumulation of macrophages/foam cells. So far, LEO has passed the safety and feasibility test of phase I clinical trial.

Possible Role of Mitochondrial DNA Mutations in Chronification of Inflammation: Focus on Atherosclerosis

Chronification of inflammation is the process that lies at the basis of several human diseases that make up to 80% of morbidity and mortality worldwide. It can also explain a great deal of processes related to aging. Atherosclerosis is an example of the most important chronic inflammatory pathology in terms of public health impact. Atherogenesis is based on the inflammatory response of the innate immunity arising locally or focally. The main trigger for this response appears to be modified low-density lipoprotein (LDL), although other factors may also play a role. With the quick resolution of inflammation, atherosclerotic changes in the arterial wall do not occur. However, a violation of the innate immunity response can lead to chronification of local inflammation and, as a result, to atherosclerotic lesion formation. In this review, we discuss possible mechanisms of the impaired immune response with a special focus on mitochondrial dysfunction. Some mitochondrial dysfunctions may be due to mutations in mitochondrial DNA. Several mitochondrial DNA mutations leading to defective mitophagy have been identified. The regulatory role of mitophagy in the immune response has been shown in recent studies. We suggest that defective mitophagy promoted by mutations in mitochondrial DNA can cause innate immunity disorders leading to chronification of inflammation.

The Diabetes Mellitus-Atherosclerosis Connection: The Role of Lipid and Glucose Metabolism and Chronic Inflammation

Diabetes mellitus comprises a group of carbohydrate metabolism disorders that share a common main feature of chronic hyperglycemia that results from defects of insulin secretion, insulin action, or both. Insulin is an important anabolic hormone, and its deficiency leads to various metabolic abnormalities in proteins, lipids, and carbohydrates. Atherosclerosis develops as a result of a multistep process ultimately leading to cardiovascular disease associated with high morbidity and mortality. Alteration of lipid metabolism is a risk factor and characteristic feature of atherosclerosis. Possible links between the two chronic disorders depending on altered metabolic pathways have been investigated in numerous studies. It was shown that both types of diabetes mellitus can actually induce atherosclerosis development or further accelerate its progression. Elevated glucose level, dyslipidemia, and other metabolic alterations that accompany the disease development are tightly involved in the pathogenesis of atherosclerosis at almost every step of the atherogenic process. Chronic inflammation is currently considered as one of the key factors in atherosclerosis development and is present starting from the earliest stages of the pathology initiation. It may also be regarded as one of the possible links between atherosclerosis and diabetes mellitus. However, the data available so far do not allow for developing effective anti-inflammatory therapeutic strategies that would stop atherosclerotic lesion progression or induce lesion reduction. In this review, we summarize the main aspects of diabetes mellitus that possibly affect the atherogenic process and its relationship with chronic inflammation. We also discuss the established pathophysiological features that link atherosclerosis and diabetes mellitus, such as oxidative stress, altered protein kinase signaling, and the role of certain miRNA and epigenetic modifications.

miR-532-3p-CSF2RA Axis as a Key Regulator of Vulnerable Atherosclerotic Plaque Formation

BACKGROUND

The most dangerous atherosclerotic plaques, referred to as "vulnerable," are most likely to trigger acute atherothrombotic events such as myocardial infarction (heart attack) and stroke. Our goal was to uncover the molecular drivers of vulnerable plaque formation.

METHODS

To elucidate the functional gene modules that drive vulnerable plaque formation, we performed a weighted gene coexpression network analysis integrated with a protein-protein interaction network analysis in human atherosclerotic carotid samples, which identified the candidate gene granulocyte-macrophage colony-stimulating factor 2 (GM-CSF) receptor alpha subunit (CSF2RA). Follow-up in vitro experiments were performed to elucidate the regulatory relationship between CSF2RA and the microRNA miR-532-3p as well as modifiers of macrophagic miR-532-3p-CSF2RA axis expression. Microarray and quantitative reverse transcription polymerase chain reaction (qRT-PCR) studies elucidated the effect of statins on carotid miR-532-3p-CSF2RA axis expression in patients with carotid atherosclerotic disease. Apoe^-/-, Ldlr^-/-, and Csf2ra mutant Apoe^-/- mouse models of atherosclerosis were employed to assess the effects of agomiR-532-3p therapy in vivo.

RESULTS

The integrated weighted gene coexpression network analysis/protein-protein interaction network analysis revealed that the macrophagic GM-CSF receptor CSF2RA is significantly upregulated in macrophage-rich vulnerable plaques. Follow-up analysis identified the miR-532-3p-CSF2RA axis, as miR-532-3p downregulates CSF2RA via binding to CSF2RA's 3'UTR. Macrophagic miR-532-3p-CSF2RA dysregulation was enhanced via modified low-density lipoprotein or tumor necrosis factor α exposure in vitro. Moreover, this miR-532-3p-CSF2RA dysregulation was observed in human vulnerable plaques and Apoe^-/- mouse plaques, effects rescued by statin therapy. In vivo, agomiR-532-3p therapy suppressed murine plaque formation and promoted plaque stabilization in a Csf2ra-dependent manner.

CONCLUSION

Macrophagic miR-532-3p-CSF2RA axis dysregulation is a key driver in vulnerable plaque formation.

Local intravascular delivery of low-density-lipoprotein cholesterol corresponds with increased intimal thickening in a healthy porcine coronary model. A prelude to development of a model of atherosclerosis

Introduction

Preclinical, vascular response studies are limited due to lack of underlying disease. The available cholesterol-diet-based and genetic atherosclerotic models are not satisfactory due to long breeding, unpredictable lesion formation, low plaque volume and degree of stenosis.

Aim

To evaluate the vascular response to local, intramural delivery of human, highly atherogenic lipids into healthy domestic swine (DS) coronary arteries.

Material and methods

A total of 24 coronary artery segments of 10 DS were enrolled. Following balloon injury (plain old balloon angioplasty – POBA), segments were assigned to local delivery of 2 ml of human LDL from apheresis (400 mg/dl, n = 9), 0.9% NaCl (control, n = 7) or to POBA alone. The solutions were infused with a modified, triple micro-needle catheter into the vessel wall. After 28 days, optical coherence tomography (OCT), virtual histology IVUS (VH-IVUS) and near-infra-red spectroscopy (NIRS) were performed. Following euthanasia, vessel segments were harvested for pathological evaluation.

Results

At 28 days the % area stenosis in OCT was highest in the LDL group (23.6 ±13 vs. 10.8 ±7 vs. 8.1 ±7%; p = 0.02). The presence of necrotic core (LDL: 55.5%, control: 37.5% and POBA: 42.8%; p = 0.77) and dense calcium (LDL: 33.3%, control: 28.5%, POBA: 37.5%; p = 0.94) in VH-IVUS were comparable between groups. The lipid core burden index in NIRS was negative in all cases. In pathology, the injury was comparable between groups (LDL: 1.6 ±0.4, control: 1.7 ±0.8, POBA: 1.7; p = 0.8) and specimens showed no signs of necrotic or lipid core. The tissue consisted of smooth muscle cells (SMC)/proteoglycan-rich lesions and inflammatory cells.

Conclusions

Local delivery of saturated human LDL into the coronary artery wall was feasible and resulted in a higher degree of stenosis caused by intimal thickening. A discrepancy between histopathological findings and virtual histology intravascular ultrasound (VH-IVUS) was also noted.

Activation of Nrf2/HO-1 Pathway and Human Atherosclerotic Plaque Vulnerability:an In Vitro and In Vivo Study

Reactive oxygen species (ROS) induce nuclear factor erythroid 2-related factor 2 (Nrf2) activation as an adaptive defense mechanism, determining the synthesis of antioxidant molecules, including heme-oxygenase-1 (HO-1). HO-1 protects cells against oxidative injury, degrading free heme and inhibiting ROS production. HO-1 is highly expressed in macrophages during plaque growth. Macrophages are morpho-functionally heterogeneous, and the prevalence of a specific phenotype may influence the plaque fate. This heterogeneity has also been observed in monocyte-derived macrophages (MDMs), a model of macrophages infiltrating tissue. The study aims to assess oxidative stress status and Nrf2/HO-1 axis in MDM morphotypes obtained from healthy subjects and coronary artery disease (CAD) patients, in relation to coronary plaque features evaluated in vivo by optical coherence tomography (OCT). We found that MDMs of healthy subjects exhibited a lower oxidative stress status, lower Nrf2 and HO-1 levels as compared to CAD patients. High HO-1 levels in MDMs were associated with the presence of a higher macrophage content, a thinner fibrous cap, and a ruptured plaque with thrombus formation, detected by OCT analysis. These findings suggest the presence of a relationship between in vivo plaque characteristics and in vitro MDM profile, and may help to identify patients with rupture-prone coronary plaque.

Hydrogen sulfide stabilizes atherosclerotic plaques in apolipoprotein E knockout mice

Hydrogen sulfide gas (H₂S) has protective effects in the cardiovascular system that includes preventing the development of atherosclerosis when tested in several in vivo models. Plaque instability is a major risk factor for thromboembolism, myocardial infarction, and stroke, so we examined if H₂S can promote plaque stability and the potential underlying mechanisms. Apolipoprotein E knockout mice fed an atherogenic diet were administered the exogenous H₂S donor sodium hydrosulfide (NaHS) or pravastatin as a positive control daily for 14 weeks. NaHS significantly enhanced plaque stability by increasing fibrous cap thickness and collagen content compared to vehicle-treated controls. NaHS treatment also reduced blood lipid levels and plaque formation. Preservation of plaque stability by NaHS was associated with reductions in vascular smooth muscle cells (VSMCs) apoptosis and expression of the collagen-degrading enzyme matrix metallopeptidase-9 (MMP-9) in plaque. While pravastatin also increased fibrous cap thickness and reduced VSMC apoptosis, but did not enhance plaque collagen or reduce MMP-9 significantly, suggesting distinct mechanisms of plaque stabilization. in vitro, NaHS also decreased MMP-9 expression in macrophages stimulated with tumor necrosis factor-α by inhibiting ERK/JNK phosphorylation and activator protein 1 nuclear translocation. Moreover, H₂S reduced caspase-3/9 activity, Bax/Bcl-2 ratio, and LOX-1 mRNA expression in VSMCs stimulated with oxidized low-density lipoprotein. These results suggest that H₂S enhances plaque stability and protects against atherogenesis by increasing plaque collagen content and VSMC count. In conclusion, H₂S exerts protective effects against atherogenesis at least partly by stabilizing atherosclerotic plaque.

An update on clonality: what smooth muscle cell type makes up the atherosclerotic plaque?

Almost 50 years ago, Earl Benditt and his son John described the clonality of the atherosclerotic plaque. This led Benditt to propose that the atherosclerotic lesion was a smooth muscle neoplasm, similar to the leiomyomata seen in the uterus of most women. Although the observation of clonality has been confirmed many times, interest in the idea that atherosclerosis might be a form of neoplasia waned because of the clinical success of treatments for hyperlipemia and because animal models have made great progress in understanding how lipid accumulates in the plaque and may lead to plaque rupture. Four advances have made it important to reconsider Benditt's observations. First, we now know that clonality is a property of normal tissue development. Second, this is even true in the vessel wall, where we now know that formation of clonal patches in that wall is part of the development of smooth muscle cells that make up the tunica media of arteries. Third, we know that the intima, the "soil" for development of the human atherosclerotic lesion, develops before the fatty lesions appear. Fourth, while the cells comprising this intima have been called "smooth muscle cells", we do not have a clear definition of cell type nor do we know if the initial accumulation is clonal. As a result, Benditt's hypothesis needs to be revisited in terms of changes in how we define smooth muscle cells and the quite distinct developmental origins of the cells that comprise the muscular coats of all arterial walls. Finally, since clonality of the lesions is real, the obvious questions are do these human tumors precede the development of atherosclerosis, how do the clones develop, what cell type gives rise to the clones, and in what ways do the clones provide the soil for development and natural history of atherosclerosis?

Overexpression of tissue factor induced atherothrombosis in apolipoprotein E-/- mice via both enhanced plaque thrombogenicity and plaque instability

The mechanisms leading to atherothrombosis from "vulnerable plaque" are more complex than initially proposed. We aimed to clarify whether plaque thrombogenicity is critical in atherothrombosis in mice. In a murine model of plaque destabilization, we enhanced plaque thrombogenicity by systemically overexpressing murine tissue factor (TF) by adenovirus-mediated gene transfer. The potential effects and mechanisms of TF on plaque destabilization were examined in cultured human aortic smooth muscle cells (HASMCs), RAW264.7 cells and human umbilical vein endothelial cells (HUVECs). To elucidate the TF noncoagulant effects on plaque destabilization, TF-overexpressed mice were treated with the protease-activated receptor 2 (PAR-2) antagonist ENMD-1068. In TF-overexpressing apolipoprotein (E)-deficient (ApoE-/-) mice, 67% (8 of 12) of carotid plaques exhibited plaque disruption and atherothrombosis. Moreover, 58% (7 of 12) showed plaque hemorrhage, including 1 due to plaque disruption, 4 neovascularization and 2 both. In contrast, only 17% (2 of 12) of control mice showed atherothrombosis, both with plaque hemorrhage but no neovascularization. On PCR, TF overexpression increased the expression of inflammatory factors. In cultured cells, the TF-FVIIa complex enhanced the expression of inflammatory factors and a vicious cycle of inflammation. Also, TF-FVIIa complex induced intra-plaque angiogenesis via PAR-2. ENMD-1068 treatment significantly inhibited the expression of inflammatory factors and neovascularization, and the incidence of intra-plaque hemorrhage decreased in TF-overexpressing mice. In conclusions, TF overexpression enhanced plaque thrombogenicity, which played a pivotal role in atherothrombosis in ApoE-/- mice. In addition, TF promoted plaque instability by activating inflammatory and proangiogenic effects via TF-FVIIa/PAR-2 signaling.

Induction of Atherosclerotic Plaques Through Activation of Mineralocorticoid Receptors in Apolipoprotein E-deficient Mice

Atherosclerosis is due to a chronic inflammatory response affecting vascular endothelium and is promoted by several factors such as hypertension, dyslipidemia, and diabetes. To date, there is evidence to support a role for circulating aldosterone as a risk factor for the development of cardiovascular disease. Transgenic mouse models have been generated to study cellular and molecular processes leading to atherosclerosis. In this manuscript, we describe a protocol that takes advantage of continuous infusion of aldosterone in ApoE^-/- mice and generates atherosclerotic plaques in the aortic root after 4 weeks of treatment. We, therefore, illustrate a method for quantification and characterization of atherosclerotic lesions at the aortic root level. The added value of aldosterone infusion is represented by the generation of atherosclerotic lesions rich in lipid and inflammatory cells after 4 weeks of treatment. We describe in detail the staining procedures to quantify lipid and macrophage content within the plaque. Notably, in this protocol, we perform heart tissue-embedding in OCT in order to preserve the antigenicity of cardiac tissue and facilitate detectability of antigens of interest. Analysis of the plaque phenotype represents a valid approach to study the pathophysiology of atherosclerosis development and to identify novel pharmacological targets for the development of anti-atherogenic drugs.

Anionic nanoliposomes reduced atherosclerosis progression in Low Density Lipoprotein Receptor (LDLR) deficient mice fed a high fat diet

Atherosclerosis is a systemic disease characterized by the deposition of cholesterol and inflammatory cells within the arterial wall. Removal of cholesterol from the vessel wall may have an impact on the size and composition of atherosclerotic lesions. Anionic phospholipids or liposome vesicles composed of a lipid bilayer such as nanoliposomes have been suggested as treatments for dyslipidemia. In this study, we investigated the effect of anionic nanoliposomes on atherosclerosis in a mouse model. Low-density lipoprotein receptor knockout mice (Ldlr^-/- ) were fed with an atherosclerosis promoting high fat and cholesterol (HFC) diet for 12 weeks. Anionic nanoliposomes including hydrogenated soy phosphatidylcholine (HSPC) and distearoyl phosphatidylglycerol (DSPG) (molar ratio: 1:3) were injected intravenously into HFC-fed Ldlr^-/- mice once a week for 4 weeks. Mice receiving nanoliposomes had significantly reduced atherosclerosis within the aortic arch as assessed by Sudan IV staining area (p = 0.007), and reduced intima/media ratio (p = 0.030) and greater collagen deposition within atherosclerosis plaques within the brachiocephalic artery (p = 0.007), compared to control mice. Administration of nanoliposomes enhanced markers of reverse cholesterol transport (RCT) and increased markers of plaque stability in HFC-fed Ldlr^-/- mice. Reduced cholesterol accumulation was observed in the liver along with the up-regulation of the major genes involved in the efflux of cholesterol such as hepatic ATP-binding cassette transporters (ABC) including Abc-a1, Abc-g1, Abc-g5, and Abc-g8, Scavenger receptor class B, member 1 (Scarb1), and Liver X receptor alpha (Lxr)-α. Lecithin Cholesterol Acyltransferase activity within the plasma was also increased in mice receiving nanoliposomes. Anionic nanoliposome administration reduced atherosclerosis in HFC-fed Ldlr^-/- mice by promoting RCT and upregulating the ABC-A1/ABC-G1 pathway.

Animal models for plaque rupture: a biomechanical assessment

Rupture of atherosclerotic plaques is the main cause of acute cardiovascular events. Animal models of plaque rupture are rare but essential for testing new imaging modalities to enable diagnosis of the patient at risk. Moreover, they enable the design of new treatment strategies to prevent plaque rupture. Several animal models for the study of atherosclerosis are available. Plaque rupture in these models only occurs following severe surgical or pharmaceutical intervention. In the process of plaque rupture, composition, biology and mechanics each play a role, but the latter has been disregarded in many animal studies. The biomechanical environment for atherosclerotic plaques is comprised of two parts, the pressure-induced stress distribution, mainly - but not exclusively – influenced by plaque composition, and the strength distribution throughout the plaque, largely determined by the inflammatory state. This environment differs considerably between humans and most animals, resulting in suboptimal conditions for plaque rupture. In this review we describe the role of the biomechanical environment in plaque rupture and assess this environment in animal models that present with plaque rupture.

Potential role of insulin receptor isoforms and IGF receptors in plaque instability of human and experimental atherosclerosis

BACKGROUND

Clinical complications associated with atherosclerotic plaques arise from luminal obstruction due to plaque growth or destabilization leading to rupture. We previously demonstrated that overexpression of insulin receptor isoform A (IRA) and insulin-like growth factor-I receptor (IGF-IR) confers a proliferative and migratory advantage to vascular smooth muscle cells (VSMCs) promoting plaque growth in early stages of atherosclerosis. However, the role of insulin receptor (IR) isoforms, IGF-IR or insulin-like growth factor-II receptor (IGF-IIR) in VSMCs apoptosis during advanced atherosclerosis remains unclear.

METHODS

We evaluated IR isoforms expression in human carotid atherosclerotic plaques by consecutive immunoprecipitations of insulin receptor isoform B (IRB) and IRA. Western blot analysis was performed to measure IGF-IR, IGF-IIR, and α-smooth muscle actin (α-SMA) expression in human plaques. The expression of those proteins, as well as the presence of apoptotic cells, was analyzed by immunohistochemistry in experimental atherosclerosis using BATIRKO; ApoE^-/- mice, a model showing more aggravated vascular damage than ApoE^-/- mice. Finally, apoptosis of VSMCs bearing IR (IRLoxP^+/+ VSMCs), or not (IR^-/- VSMCs), expressing IRA (IRA VSMCs) or expressing IRB (IRB VSMCs), was assessed by Western blot against cleaved caspase 3.

RESULTS

We observed a significant decrease of IRA/IRB ratio in human complicated plaques as compared to non-complicated regions. Moreover, complicated plaques showed a reduced IGF-IR expression, an increased IGF-IIR expression, and lower levels of α-SMA indicating a loss of VSMCs. In experimental atherosclerosis, we found a significant decrease of IRA with an increased IRB expression in aorta from 24-week-old BATIRKO; ApoE^-/- mice. Furthermore, atherosclerotic plaques from BATIRKO; ApoE^-/- mice had less VSMCs content and higher number of apoptotic cells. In vitro experiments showed that IGF-IR inhibition by picropodophyllin induced apoptosis in VSMCs. Apoptosis induced by thapsigargin was lower in IR^-/- VSMCs expressing higher IGF-IR levels as compared to IRLoxP^+/+ VSMCs. Finally, IRB VSMCs are more prone to thapsigargin-induced apoptosis than IRA or IRLoxP^+/+ VSMCs.

CONCLUSIONS

In advanced human atherosclerosis, a reduction of IRA/IRB ratio, decreased IGF-IR expression, or increased IGF-IIR may contribute to VSMCs apoptosis, promoting plaque instability and increasing the risk of plaque rupture and its clinical consequences.

Histological comparison of arterial thrombi in mice and men and the influence of Cl-amidine on thrombus formation

Aims

Medical treatment of arterial thrombosis is mainly directed against platelets and coagulation factors, and can lead to bleeding complications. Novel antithrombotic therapies targeting immune cells and neutrophil extracellular traps (NETs) are currently being investigated in animals. We addressed whether immune cell composition of arterial thrombi induced in mouse models of thrombosis resemble those of human patients with acute myocardial infarction (AMI).

Methods and results

In a prospective cohort study of patients suffering from AMI, 81 human arterial thrombi were harvested during percutaneous coronary intervention and subjected to detailed histological analysis. In mice, arterial thrombi were induced using two distinct experimental models, ferric chloride (FeCl₃) and wire injury of the carotid artery. We found that murine arterial thrombi induced by FeCl₃ were highly concordant with human coronary thrombi regarding their immune cell composition, with neutrophils being the most abundant cell type, as well as the presence of NETs and coagulation factors. Pharmacological treatment of mice with the protein arginine deiminase (PAD)-inhibitor Cl-amidine abrogated NET formation, reduced arterial thrombosis and limited injury in a model of myocardial infarction.

Conclusions

Neutrophils are a hallmark of arterial thrombi in patients suffering from acute myocardial infarction and in mouse models of arterial thrombosis. Inhibition of PAD could represent an interesting strategy for the treatment of arterial thrombosis to reduce neutrophil-associated tissue damage and improve functional outcome.

Comparison of two murine models of thrombosis induced by atherosclerotic plaque injury

Arterial thrombosis occurs at sites of erosion or rupture of atherosclerotic vascular lesions. To better study the pathophysiology of this complex phenomenon, there is a need for animal models of localised thrombosis at sites of atherosclerotic lesions with closer resemblance to the human pathology as compared to commonly used thrombosis models in healthy vessels. In the present study, we describe and compare a new model of thrombosis induced by atherosclerotic plaque rupture in the carotid artery from ApoE-/- mice using a suture needle to a milder model of ultrasound-induced plaque injury. Needle injury induces atherosclerotic plaque rupture with exposure of plaque material and formation of a thrombus that is larger, nearly occlusive and more stable as compared to that formed by application of ultrasounds. These two models have common features such as the concomitant involvement of platelet activation, thrombin generation and fibrin formation, which translates into sensitivity toward both antiplatelet drugs and anticoagulants. On the other hand, they display differences with respect to the role of the platelet collagen receptor GPVI, the plaque rupture model being less sensitive to its inhibition as compared to the ultrasound-induced injury, which may be related to the amount of thrombin generated. These models represent an improvement as compared to models in healthy vessels and may help identify specific plaque triggers of thrombosis. They should therefore be useful to evaluate new antithrombotic targets.

Stabilisation of atherosclerotic plaques

Plaque rupture and subsequent thrombotic occlusion of the coronary artery account for as many as three quarters of myocardial infarctions. The concept of plaque stabilisation emerged about 20 years ago to explain the discrepancy between the reduction of cardiovascular events in patients receiving lipid lowering therapy and the small decrease seen in angiographic evaluation of atherosclerosis. Since then, the concept of a vulnerable plaque has received a lot of attention in basic and clinical research leading to a better understanding of the pathophysiology of the vulnerable plaque and acute coronary syndromes. From pathological and clinical observations, plaques that have recently ruptured have thin fibrous caps, large lipid cores, exhibit outward remodelling and invasion by vasa vasorum. Ruptured plaques are also focally inflamed and this may be a common denominator of the other pathological features. Plaques with similar characteristics, but which have not yet ruptured, are believed to be vulnerable to rupture. Experimental studies strongly support the validity of anti-inflammatory approaches to promote plaque stability. Unfortunately, reliable non-invasive methods for imaging and detection of such plaques are not yet readily available. There is a strong biological basis and supportive clinical evidence that low-density lipoprotein lowering with statins is useful for the stabilisation of vulnerable plaques. There is also some clinical evidence for the usefulness of antiplatelet agents, beta blockers and renin-angiotensin-aldosterone system inhibitors for plaque stabilisation. Determining the causes of plaque rupture and designing diagnostics and interventions to prevent them are urgent priorities for current basic and clinical research in cardiovascular area.

Loss of SPRR3 in ApoE-/- mice leads to atheroma vulnerability through Akt dependent and independent effects in VSMCs

Vascular smooth muscle cells (VSMCs) represent important modulators of plaque stability in advanced lesions. We previously reported that loss of small proline-rich repeat protein 3 (Sprr3), leads to VSMC apoptosis in a PI3K/Akt-dependent manner and accelerates lesion progression. Here, we investigated the role of Sprr3 in modulating plaque stability in hyperlipidemic ApoE^-/- mice. We show that loss of Sprr3 increased necrotic core size and reduced cap collagen content of atheromas in brachiocephalic arteries with evidence of plaque rupture and development of intraluminal thrombi. Moreover, Sprr3^-/-ApoE^-/- mice developed advanced coronary artery lesions accompanied by intraplaque hemorrhage and left ventricle microinfarcts. SPRR3 is known to reduce VSMC survival in lesions by promoting their apoptosis. In addition, we demonstrated that Sprr3^-/- VSMCs displayed reduced expression of procollagen in a PI3K/Akt dependent manner. SPRR3 loss also increased MMP gelatinase activity in lesions, and increased MMP2 expression, migration and contraction of VSMCs independently of PI3K/Akt. Consequently, Sprr3 represents the first described VSMC modulator of each of the critical features of cap stability, including VSMC numbers, collagen type I synthesis, and protease activity through Akt dependent and independent pathways.

Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association

Animal studies are a foundation for defining mechanisms of atherosclerosis and potential targets of drugs to prevent lesion development or reverse the disease. In the current literature, it is common to see contradictions of outcomes in animal studies from different research groups, leading to the paucity of extrapolations of experimental findings into understanding the human disease. The purpose of this statement is to provide guidelines for development and execution of experimental design and interpretation in animal studies. Recommendations include the following: (1) animal model selection, with commentary on the fidelity of mimicking facets of the human disease; (2) experimental design and its impact on the interpretation of data; and (3) standard methods to enhance accuracy of measurements and characterization of atherosclerotic lesions.

Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association

Animal studies are a foundation for defining mechanisms of atherosclerosis and potential targets of drugs to prevent lesion development or reverse the disease. In the current literature, it is common to see contradictions of outcomes in animal studies from different research groups, leading to the paucity of extrapolations of experimental findings into understanding the human disease. The purpose of this statement is to provide guidelines for development and execution of experimental design and interpretation in animal studies. Recommendations include the following: (1) animal model selection, with commentary on the fidelity of mimicking facets of the human disease; (2) experimental design and its impact on the interpretation of data; and (3) standard methods to enhance accuracy of measurements and characterization of atherosclerotic lesions.