Cholesterol efflux capacity, macrophage reverse cholesterol transport and cardioprotective HDL

Macrophage polarisation and inflammatory mechanisms in atherosclerosis: Implications for prevention and treatment

Atherosclerosis is a chronic inflammatory disease characterised by plaque accumulation in the arteries. Macrophages are immune cells that are crucial in the development of atherosclerosis. Macrophages can adopt different phenotypes, with the M1 phenotype promoting inflammation while the M2 phenotype counteracting it. This review focuses on the factors that drive the polarisation of M1 macrophages towards a pro-inflammatory phenotype during AS. Additionally, we explored metabolic reprogramming mechanisms and cytokines secretion by M1 macrophages. Hyperlipidaemia is widely recognised as a major risk factor for atherosclerosis. Modified lipoproteins released in the presence of hyperlipidaemia can trigger the release of cytokines and recruit circulating monocytes, which adhere to the damaged endothelium and differentiate into macrophages. Macrophages engulf lipids, leading to the formation of foam cells. As atherosclerosis progresses, foam cells become the necrotic core within the atherosclerotic plaques, destabilising them and triggering ischaemic disease. Furthermore, we discuss recent research focusing on targeting macrophages or inflammatory pathways for preventive or therapeutic purposes. These include statins, PCSK9 inhibitors, and promising nanotargeted drugs. These new developments hold the potential for the prevention and treatment of atherosclerosis and its related complications.

The role of foam cells in spinal cord injury: challenges and opportunities for intervention

Spinal cord injury (SCI) results in a large amount of tissue cell debris in the lesion site, which interacts with various cytokines, including inflammatory factors, and the intrinsic glial environment of the central nervous system (CNS) to form an inhibitory microenvironment that impedes nerve regeneration. The efficient clearance of tissue debris is crucial for the resolution of the inhibitory microenvironment after SCI. Macrophages are the main cells responsible for tissue debris removal after SCI. However, the high lipid content in tissue debris and the dysregulation of lipid metabolism within macrophages lead to their transformation into foamy macrophages during the phagocytic process. This phenotypic shift is associated with a further pro-inflammatory polarization that may aggravate neurological deterioration and hamper nerve repair. In this review, we summarize the phenotype and metabolism of macrophages under inflammatory conditions, as well as the mechanisms and consequences of foam cell formation after SCI. Moreover, we discuss two strategies for foam cell modulation and several potential therapeutic targets that may enhance the treatment of SCI.

Coronary artery disease, its associations with ocular, genetic and blood lipid parameters

BACKGROUND/OBJECTIVES

To investigate the associations between ophthalmic parameters, CYP4F2 (rs2108622) and ABCA1 (rs1883025) polymorphisms and coronary artery disease, considering the accessibility, non-invasive origin of retinal examination and its possible resemblance to coronary arteries.

SUBJECTS/METHODS

Overall 165 participants divided into groups based on the coronary angiography results and clinical status: control group (N = 73), MI group (N = 63), 3VD (three vessel disease) (N = 24). All the participants underwent total ophthalmic examination - optical coherence tomography (OCT) and OCT angiography of the macula region were performed and evaluated. Total cholesterol, high-density lipoprotein, low-density lipoprotein and triglyceride cholesterol (Tg-C) were tested. A standard manufacturer's protocol for CYP4F2 (rs2108622) and ABCA1 (rs1883025) was used for genotyping with TaqMan probes.

RESULTS

GCL+ layer was thicker in control group vs. 3VD group (74.00; 62.67-94.67 (median; min.-max.) vs. 71.06; 51.33-78.44, p = 0.037). T allele carriers under ABCA1 rs1883025 dominant model were shown to have ticker retina and smaller foveal avascular zone in superficial capillary plexus and smaller Tg-C concentration. ABCA1 rs1883025 was associated with retinal thickness (OR = 0.575, 95% CI 0.348-0.948, p = 0.030). Univariate logistic regression showed that ABCA1 rs1883025 CT genotype is associated with decreased risk for coronary artery disease development under overdominant genetic model (OR = 0.498, 95% CI 0.254-0.976; p = 0.042) and codominant genetic model (OR = 0.468, 95% CI 0.232-0.945, p = 0.034).

CONCLUSIONS

Results of this study confirmed that non-invasive methods such as OCT of eye might be used for identification of patients at risk of CAD.

Regulation of toll-like receptor (TLR) signaling pathways in atherosclerosis: from mechanisms to targeted therapeutics

Atherosclerosis, one of the life-threatening cardiovascular diseases (CVDs), has been demonstrated to be a chronic inflammatory disease, and inflammatory and immune processes are involved in the origin and development of the disease. Toll-like receptors (TLRs), a class of pattern recognition receptors that trigger innate immune responses by identifying pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs), regulate numerous acute and chronic inflammatory diseases. Recent studies reveal that TLRs have a vital role in the occurrence and development of atherosclerosis, including the initiation of endothelial dysfunction, interaction of various immune cells, and activation of a number of other inflammatory pathways. We herein summarize some other inflammatory signaling pathways, protein molecules, and cellular responses associated with TLRs, such as NLRP3, Nrf2, PCSK9, autophagy, pyroptosis and necroptosis, which are also involved in the development of AS. Targeting TLRs and their regulated inflammatory events could be a promising new strategy for the treatment of atherosclerotic CVDs. Novel drugs that exert therapeutic effects on AS through TLRs and their related pathways are increasingly being developed. In this article, we comprehensively review the current knowledge of TLR signaling pathways in atherosclerosis and actively seek potential therapeutic strategies using TLRs as a breakthrough point in the prevention and therapy of atherosclerosis.

Inverse Correlation of Cholesterol Efflux Capacity with Peripheral Plaque Volume Measured by 3D Ultrasound

INTRODUCTION

Cardiovascular disease (CVD) is a systemic multifocal illness called atherosclerosis that causes artery constriction and blockage. By causing cholesterol to build up in the artery wall, hypercholesterolemia is a major factor in the pathophysiology of atherosclerotic plaque development. Reverse cholesterol transport is the process of transporting cholesterol from the periphery back to the liver through cholesterol efflux mediated by high-density lipoprotein (HDL). It was suggested that the cholesterol efflux capacity (CEC), which is inversely linked with cardiovascular risk, can serve as a stand-in measure for reverse cholesterol transport. In this work, we sought to investigate a potential link between the peripheral plaque volume (PV) and CEC.

METHODS

Since lipid-lowering therapy interferes with CEC, we performed a cross-sectional study of 176 patients (48.9% females) with one cardiovascular risk factor or known CVD that did not currently take lipid-lowering medication. CEC was determined using cAMP-treated ³H-cholesterol-labeled J774 cells. Cholesterol ester transfer protein (CETP)-mediated cholesterol ester transfer was measured by quantifying the transfer of cholesterol ester from radiolabeled exogenous HDL cholesterol to Apolipoprotein B-containing lipoproteins. PV in the carotid and the femoral artery, defined as the total PV, was measured using a 3D ultrasound system equipped with semi-automatic software.

RESULTS

In our patients, we discovered an inverse relationship between high total PV and CEC (p = 0.027). However, there was no connection between total PV and low-density lipoprotein cholesterol, lipoprotein (a), or CETP-mediated cholesterol ester transfer.

CONCLUSION

In patients not receiving lipid-lowering treatment, CEC inversely correlates with peripheral atherosclerosis, supporting its role in the pathophysiology of atherosclerosis.

Alveolar macrophages in pulmonary alveolar proteinosis: origin, function, and therapeutic strategies

Pulmonary alveolar proteinosis (PAP) is a rare pulmonary disorder that is characterized by the abnormal accumulation of surfactant within the alveoli. Alveolar macrophages (AMs) have been identified as playing a pivotal role in the pathogenesis of PAP. In most of PAP cases, the disease is triggered by impaired cholesterol clearance in AMs that depend on granulocyte-macrophage colony-stimulating factor (GM-CSF), resulting in defective alveolar surfactant clearance and disruption of pulmonary homeostasis. Currently, novel pathogenesis-based therapies are being developed that target the GM-CSF signaling, cholesterol homeostasis, and immune modulation of AMs. In this review, we summarize the origin and functional role of AMs in PAP, as well as the latest therapeutic strategies aimed at addressing this disease. Our goal is to provide new perspectives and insights into the pathogenesis of PAP, and thereby identify promising new treatments for this disease.

Atherosclerosis: The Involvement of Immunity, Cytokines and Cells in Pathogenesis, and Potential Novel Therapeutics

As a leading contributor to coronary artery disease (CAD) and stroke, atherosclerosis has become one of the major cardiovascular diseases (CVD) negatively impacting patients worldwide. The endothelial injury is considered to be the initial step of the development of atherosclerosis, resulting in immune cell migration and activation as well as inflammatory factor secretion, which further leads to acute and chronic inflammation. In addition, the inflammation and lipid accumulation at the lesions stimulate specific responses from different types of cells, contributing to the pathological progression of atherosclerosis. As a result, recent studies have focused on using molecular biological approaches such as gene editing and nanotechnology to mediate cellular response during atherosclerotic development for therapeutic purposes. In this review, we systematically discuss inflammatory pathogenesis during the development of atherosclerosis from a cellular level with a focus on the blood cells, including all types of immune cells, together with crucial cells within the blood vessel, such as smooth muscle cells and endothelial cells. In addition, the latest progression of molecular-cellular based therapy for atherosclerosis is also discussed. We hope this review article could be beneficial for the clinical management of atherosclerosis.

Diaporisoindole B Reduces Lipid Accumulation in THP-1 Macrophage Cells via MAPKs and PPARγ-LXRα Pathways and Promotes the Reverse Cholesterol Transport by Upregulating SR-B1 and LDLR in HepG2 Cells

Diaporisoindole B (DPB), an isoprenylisoindole alkaloid isolated from the mangrove endophytic fungus Diaporthe sp. SYSU-HQ3, has been proved to have a good anti-inflammatory activity in macrophage cells. In this study, we found that DPB was able to reduce lipid accumulation in THP-1 macrophage-derived foam cells. DPB could inhibit the lipid influx-related gene CD36 and increase the expression of lipid efflux-related genes ATP binding cassette transporter A1 (ABCA1), ATP binding cassette transporter G1 (ABCG1), and scavenger receptor B1 (SR-B1). Moreover, DPB elevated low-density lipoprotein receptor (LDLR) protein expression in HepG2 cells, which can increase the transport of LDL. Meanwhile, DPB could downregulate the expression levels of proteins related to cholesterol and fatty acid synthesis. Further study showed that DPB could activate peroxisome proliferator-activated receptor gamma (PPARγ) and inhibit mitogen-activated protein kinase (MAPK) phosphorylation. Taken together, our findings demonstrated that DPB could reduce lipid accumulation in THP-1 macrophage cells by reducing the intake of lipids and promoting the efflux of lipids and also could promote the reverse cholesterol transport (RCT) mechanism by upregulating SR-B1 and LDLR in HepG2 cells.

Regulation of cholesterol homeostasis in health and diseases: from mechanisms to targeted therapeutics

Disturbed cholesterol homeostasis plays critical roles in the development of multiple diseases, such as cardiovascular diseases (CVD), neurodegenerative diseases and cancers, particularly the CVD in which the accumulation of lipids (mainly the cholesteryl esters) within macrophage/foam cells underneath the endothelial layer drives the formation of atherosclerotic lesions eventually. More and more studies have shown that lowering cholesterol level, especially low-density lipoprotein cholesterol level, protects cardiovascular system and prevents cardiovascular events effectively. Maintaining cholesterol homeostasis is determined by cholesterol biosynthesis, uptake, efflux, transport, storage, utilization, and/or excretion. All the processes should be precisely controlled by the multiple regulatory pathways. Based on the regulation of cholesterol homeostasis, many interventions have been developed to lower cholesterol by inhibiting cholesterol biosynthesis and uptake or enhancing cholesterol utilization and excretion. Herein, we summarize the historical review and research events, the current understandings of the molecular pathways playing key roles in regulating cholesterol homeostasis, and the cholesterol-lowering interventions in clinics or in preclinical studies as well as new cholesterol-lowering targets and their clinical advances. More importantly, we review and discuss the benefits of those interventions for the treatment of multiple diseases including atherosclerotic cardiovascular diseases, obesity, diabetes, nonalcoholic fatty liver disease, cancer, neurodegenerative diseases, osteoporosis and virus infection.

Effects of Omega-3 and Antioxidant Cocktail Supplement on Prolonged Bed Rest: Results from Serum Proteome and Sphingolipids Analysis

Physical inactivity or prolonged bed rest (BR) induces muscle deconditioning in old and young subjects and can increase the cardiovascular disease risk (CVD) with dysregulation of the lipemic profile. Nutritional interventions, combining molecules such as polyphenols, vitamins and essential fatty acids, can influence some metabolic features associated with physical inactivity and decrease the reactive oxidative and nitrosative stress (RONS). The aim of this study was to detect circulating molecules correlated with BR in serum of healthy male subjects enrolled in a 60-day BR protocol to evaluate a nutritional intervention with an antioxidant cocktail as a disuse countermeasure (Toulouse COCKTAIL study). The serum proteome, sphingolipidome and nitrosoproteome were analyzed adopting different mass spectrometry-based approaches. Results in placebo-treated BR subjects indicated a marked decrease of proteins associated with high-density lipoproteins (HDL) involved in lipemic homeostasis not found in the cocktail-treated BR group. Moreover, long-chain ceramides decreased while sphingomyelin increased in the BR cocktail-treated group. In placebo, the ratio of S-nitrosylated/total protein increased for apolipoprotein D and several proteins were over-nitrosylated. In cocktail-treated BR subjects, the majority of protein showed a pattern of under-nitrosylation, except for ceruloplasmin and hemopexin, which were over-nitrosylated. Collectively, data indicate a positive effect of the cocktail in preserving lipemic and RONS homeostasis in extended disuse conditions.

Circulating Lipoproteins in Subjects with Morbid Obesity Undergoing Bariatric Surgery with Gastric Bypass or Sleeve Gastrectomy

The efficacy of various bariatric procedures on the mitigation of the obese dyslipidemia remains debated, and the impact of these measures on lipoprotein(a) (Lp(a)) levels is unknown. In this study we aimed to compare the two most commonly used procedures: gastric bypass (RYGB) and sleeve gastrectomy (SG). Adult patients with morbid obesity were assigned to receive either RYGB or SG. The levels of non-HDL cholesterol, LDL/HDL-ratio and Lp(a) at examinations conducted 6 and 12 months postoperatively were determined and compared to preoperative levels to estimate the efficacy of the two surgical methods. All results 6 and 12 months after surgery were used in the comparisons with the preoperative results. A linear mixed regression model for repeated analyses was used. The Lp(a) and the non-HDL cholesterol levels were considerably reduced in the RYGB group, in contrast to the minor changes in the SG group. In addition, the LDL/HDL ratio was significantly more reduced in the RYGB group when compared to the SG group. Conclusively, RYGB was found to be more efficient than SG for the mitigation of obese dyslipidemia, including preoperative high Lp(a)-levels. This might have important individual and societal implications, especially regarding the potential to reduce the risk of cardiovascular disease and the related societal costs.

Circular RNA circ_0001445 alleviates the ox-LDL-induced endothelial injury in human primary aortic endothelial cells through regulating ABCG1 via acting as a sponge of miR-208b-5p

BACKGROUND

Coronary artery disease (CAD) originates from the blockage of the inner walls of the coronary arteries due to a plaque buildup. Circular RNA (circRNA) circ_0001445 has been reported to be downregulated in patients with a higher coronary atherosclerotic burden. This study is designed to explore the role and mechanism of circ_0001445 on the oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell damage.

METHODS

Circ_0001445, microRNA-208b-5p (miR-208b-5p), and ATP-binding cassette sub-family G member 1 (ABCG1) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Inflammatory cytokines levels, cell viability, proliferation, migration were detected by Enzyme-linked immunosorbent assay (ELISA) kits, Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and transwell assays, respectively. Protein levels were determined by western blot assay. The binding between miR-208b-5p and circ_0001445 or ABCG1 was predicted by circBank or TargetScan, and then verified by a dual-luciferase reporter, RNA Immunoprecipitation (RIP), and RNA pull-down assays.

RESULTS

Circ_0001445 and ABCG1 were decreased, and miR-208b-5p was increased in CAD patients and ox-LDL-treated HAECs. Also, circ_0001445 overexpression could weaken ox-LDL-triggered HAEC injury by boosting proliferation, migration, and repressing inflammation and extracellular matrix (ECM). Mechanically, circ_0001445 directly targeted miR-208b-5p. Furthermore, miR-208b-5p mediated the modulation of circ_0001445 in ox-LDL-induced HAEC injury. ABCG1 acted as a direct target of miR-208b-5p, and the downregulation of miR-208b-5p relieved ox-LDL-induced HAEC damage by interacting with ABCG1. Additionally, circ_0001445 regulated ABCG1 expression by sponging miR-208b-5p.

CONCLUSION

Circ_0001445 could abate ox-LDL-mediated HAEC damage by the miR-208b-5p/ABCG1 axis, providing a novel insight into the pathogenesis and treatment of CAD.

Natural Flavonoids Derived From Fruits Are Potential Agents Against Atherosclerosis

Atherosclerosis, as a chronic inflammatory response, is one of the main causes of cardiovascular diseases. Atherosclerosis is induced by endothelial cell dysfunction, migration and proliferation of smooth muscle cells, accumulation of foam cells and inflammatory response, resulting in plaque accumulation, narrowing and hardening of the artery wall, and ultimately leading to myocardial infarction or sudden death and other serious consequences. Flavonoid is a kind of natural polyphenol compound widely existing in fruits with various structures, mainly including flavonols, flavones, flavanones, flavanols, anthocyanins, isoflavones, and chalcone, etc. Because of its potential health benefits, it is now used in supplements, cosmetics and medicines, and researchers are increasingly paying attention to its role in atherosclerosis. In this paper, we will focus on several important nodes in the development of atherosclerotic disease, including endothelial cell dysfunction, smooth muscle cell migration and proliferation, foam cell accumulation and inflammatory response. At the same time, through the classification of flavonoids from fruits, the role and potential mechanism of flavonoids in atherosclerosis were reviewed, providing a certain direction for the development of fruit flavonoids in the treatment of atherosclerosis drugs.

Curcumin attenuates inflammation of Macrophage-derived foam cells treated with Poly-L-lactic acid degradation via PPARγ signaling pathway

Poly-L-lactic acid (PLLA) is considered to be a promising candidate material for biodegradable vascular scaffolds (BVS) in percutaneous coronary intervention (PCI). But, PLLA-BVS also faces the challenge of thrombosis (ST) and in-stent restenosis (ISR) caused by in-stent neo-atherosclerosis (ISNA) associated with inflammatory reactions in macrophage-derived foam cells. Our previous studies have confirmed that curcumin alleviates PLLA-induced injury and inflammation in vascular endothelial cells, but it remains unclear whether curcumin can alleviate the effect of inflammatory reactions in macrophage-derived foam cells while treated with degraded product of PLLA. In this study, PLLA-BVS was implanted in the porcine coronary artery to examine increased macrophages and inflammatory cytokines such as NF-κb and TNF-α by histology and immunohistochemistry. In vitro, macrophage-derived foam cells were induced by Ox-LDL and observed by Oil Red Staining. Foam cells were treated with pre-degraded PLLA powder, curcumin and PPARγ inhibitor GW9662, and the expression of IL-6, IL-10, TNF-α, NF-κb, PLA2 and PPARγ were investigated by ELISA or RT-qPCR. This study demonstrated that the macrophages and inflammatory factors increased after PLLA-BVS implantation in vivo, and foam cells derived from macrophages promoted inflammation by products of PLLA degradation in vitro. This present study was found that the inflammation of foam cells at the microenvironment of PLLA degraded products were significantly increased, and curcumin can attenuate the inflammation caused by the PLLA degradation via PPARγ signal pathway. In addition, curcumin should be further studied experimentally in vivo experiments on animal models as a potential therapeutic to reduce ISNA of PLLA-BVS. Graphical abstract.

Bioactive components to inhibit foam cell formation in atherosclerosis

BACKGROUND

The production of lipid-laden cells in macrophages after significant ingestion of oxidized low-density lipoprotein is considered the most critical phase in the creation of atherosclerotic lesions, which is known as foam cell formation. Targeting foam cell development to find a potential therapeutic strategy for the management of atherosclerosis has yielded numerous promising outcomes. Multiple variables influence foam cell growth, including scavenger receptor expression, cholesterol transporter expression acyl CoA: cholesterol acyltransferase activity, and neutral cholesteryl ester hydrolase activity. Plants used during herbal therapy have been shown to assist with a variety of ailments.

RESULT

In this study, we found medicinal plants and their bioactive components suppress foam cell formation in a variety of ways; some inhibit cholesterol transporter and lectin-like oxidized low-density lipoprotein receptor-1 upregulation, while others inhibit the function of acyl CoA: cholesterol acyltransferase activity, and neutral cholesteryl ester hydrolase activity.

CONCLUSION

Recent study findings related to the synthesis of the new active component from plant sources by focusing on the typical process involved in the generation of foam cells. We're also looking at using a cellular target-based therapeutic approach to generate novel plant-based medications for the cure of atherosclerosis.

Mechanisms of cardiovascular toxicity induced by PM2.5: a review

An increasing number of studies have shown that exposure to particulate matter with a diameter ≤ 2.5 μm (PM_2.5) could affect the onset and development of cardiovascular diseases. To explore the underlying mechanisms, the studies conducted in vitro investigations using different cell lines. In this review, we examined recently published reports cited by PubMed or Web of Science on the topic of cardiovascular toxicity induced by PM_2.5 that carried the term in vitro. Here, we summarized the suggested mechanisms of PM_2.5 leading to adverse effects and cardiovascular toxicity including oxidative stress; the increase of vascular endothelial permeability; the injury of vasomotor function and vascular reparative capacity in vascular endothelial cell lines; macrophage polarization and apoptosis in macrophage cell lines; and hypermethylation and apoptosis in the AC16 cell line and the related signaling pathways, which provided a new research direction of cardiovascular toxicity of PM_2.5.

Genetics and regulation of HDL metabolism

The inverse association between plasma HDL cholesterol (HDL-C) levels and risk for cardiovascular disease (CVD) has been demonstrated by numerous epidemiological studies. However, efforts to reduce CVD risk by pharmaceutically manipulating HDL-C levels failed and refused the HDL hypothesis. HDL-C levels in the general population are highly heterogeneous and are determined by a combination of genetic and environmental factors. Insights into the causes of HDL-C heterogeneity came from the study of monogenic HDL deficiency syndromes but also from genome wide association and Μendelian randomization studies which revealed the contribution of a large number of loci to low or high HDL-C cases in the general or in restricted ethnic populations. Furthermore, HDL-C levels in the plasma are under the control of transcription factor families acting primarily in the liver including members of the hormone nuclear receptors (PPARs, LXRs, HNF-4) and forkhead box proteins (FOXO1-4) and activating transcription factors (ATFs). The effects of certain lipid lowering drugs used today are based on the modulation of the activity of specific members of these transcription factors. During the past decade, the roles of small or long non-coding RNAs acting post-transcriptionally on the expression of HDL genes have emerged and provided novel insights into HDL regulation and new opportunities for therapeutic interventions. In the present review we summarize recent progress made in the genetics and the regulation (transcriptional and post-transcriptional) of HDL metabolism.

Chemically Modified Biomimetic Carbon-Coated Iron Nanoparticles for Stent Coatings: In Vitro Cytocompatibility and In Vivo Structural Changes in Human Atherosclerotic Plaques

Atherosclerosis, a systematic degenerative disease related to the buildup of plaques in human vessels, remains the major cause of morbidity in the field of cardiovascular health problems, which are the number one cause of death globally. Novel atheroprotective HDL-mimicking chemically modified carbon-coated iron nanoparticles (Fe@C NPs) were produced by gas-phase synthesis and modified with organic functional groups of a lipophilic nature. Modified and non-modified Fe@C NPs, immobilized with polycaprolactone on stainless steel, showed high cytocompatibility in human endothelial cell culture. Furthermore, after ex vivo treatment of native atherosclerotic plaques obtained during open carotid endarterectomy surgery, Fe@C NPs penetrated the inner structures and caused structural changes of atherosclerotic plaques, depending on the period of implantation in Wistar rats, serving as a natural bioreactor. The high biocompatibility of the Fe@C NPs shows great potential in the treatment of atherosclerosis disease as an active substance of stent coatings to prevent restenosis and the formation of atherosclerotic plaques.

Dysfunctional High-Density Lipoproteins in Type 2 Diabetes Mellitus: Molecular Mechanisms and Therapeutic Implications

High density lipoproteins (HDLs) are commonly known for their anti-atherogenic properties that include functions such as the promotion of cholesterol efflux and reverse cholesterol transport, as well as antioxidant and anti-inflammatory activities. However, because of some chronic inflammatory diseases, such as type 2 diabetes mellitus (T2DM), significant changes occur in HDLs in terms of both structure and composition. These alterations lead to the loss of HDLs’ physiological functions, to transformation into dysfunctional lipoproteins, and to increased risk of cardiovascular disease (CVD). In this review, we describe the main HDL structural/functional alterations observed in T2DM and the molecular mechanisms involved in these T2DM-derived modifications. Finally, the main available therapeutic interventions targeting HDL in diabetes are discussed.

L-theanine inhibits foam cell formation via promoting the scavenger receptor A degradation

Atherosclerosis is one of the most common cardiovascular diseases with highly mortality worldwide. The formation of foam cell plays an important role in the early stage of atherosclerosis pathogenesis. L-theanine is the most abundant free amino acid in tea, which possesses anti-inflammatory, anti-tumor and anti-atherosclerosis effects. However, little is known about the effects of L-theanine on the foam cell formation. In our study, RAW264.7 cells and primary mouse peritoneal macrophages were exposed to oxidized low density lipoprotein (ox-LDL) for inducing foam cell formation. We found that L-theanine significantly impeded cholesterol accumulation in macrophages, while inhibiting the formation of foam cell. Our further experiments showed that L-theanine attenuated the cholesterol uptake of RAW264.7 cells and primary mouse peritoneal macrophages by reducing the protein level of macrophage scavenger receptor A (SR-A), but not the level of mRNA suggesting that L-theanine regulates scavenger receptor A at the translational rather than transcriptional level. The present results demonstrated that L-theanine obviously promoted the degradation of scavenger receptor A protein and scavenger receptor A was degraded by ubiquitination dependent manner. Collectively, our research indicates that L-theanine suppresses the formation of macrophage foam cell by promoting the ubiquitination dependent degradation of scavenger receptor A.

Photobiomodulation therapy promotes the ATP-binding cassette transporter A1-dependent cholesterol efflux in macrophage to ameliorate atherosclerosis

Atherosclerosis is a chronic inflammatory disease related to a massive accumulation of cholesterol in the artery wall. Photobiomodulation therapy (PBMT) has been reported to possess cardioprotective effects but has no consensus on the underlying mechanisms. Here, we aimed to investigate whether PBMT could ameliorate atherosclerosis and explore the potential molecular mechanisms. The Apolipoprotein E (ApoE)^−/− mice were fed with western diet (WD) for 18 weeks and treated with PBMT once a day in the last 10 weeks. Quantification based on Oil red O‐stained aortas showed that the average plaque area decreased 8.306 ± 2.012% after PBMT (P < .05). Meanwhile, we observed that high‐density lipoprotein cholesterol level in WD + PBMT mice increased from 0.309 ± 0.037 to 0.472 ± 0.038 nmol/L (P < .05) compared with WD mice. The further results suggested that PBMT could promote cholesterol efflux from lipid‐loaded primary peritoneal macrophages and inhibit foam cells formation via up‐regulating the ATP‐binding cassette transporters A1 expression. A contributing mechanism involved in activating the phosphatidylinositol 3‐kinases/protein kinase C zeta/specificity protein 1 signalling cascade. Our study outlines that PBMT has a protective role on atherosclerosis by promoting macrophages cholesterol efflux and provides a new strategy for treating atherosclerosis.

Olive oil consumption and its repercussions on lipid metabolism

Consumption of highly processed foods, such as those high in trans fats and free sugars, coupled with sedentarism and chronic stress increases the risk of obesity and cardiometabolic disorders, while adherence to a Mediterranean diet is inversely associated with the prevalence of such diseases. Olive oil is the main source of fat in the Mediterranean diet. Data accumulated thus far show consumption of extra virgin, (poly)phenol-rich olive oil to be associated with specific health benefits. Of note, recommendations for consumption based on health claims refer to the phenolic content of extra virgin olive oil as beneficial. However, even though foods rich in monounsaturated fatty acids, such as olive oil, are healthier than foods rich in saturated and trans fats, their inordinate use can lead to adverse effects on health. The aim of this review was to summarize the data on olive oil consumption worldwide and to critically examine the literature on the potential adverse effects of olive oil and its main components, particularly any effects on lipid metabolism. As demonstrated by substantial evidence, extra virgin olive oil is healthful and should be preferentially used within the context of a balanced diet, but excessive consumption may lead to adverse consequences.

Porphyromonas gingivalis facilitated the foam cell formation via lysosomal integral membrane protein 2 (LIMP2)

OBJECTIVE

The involvement of lysosomal integral membrane protein 2 (LIMP2) in cholesterol transport and formation of foam cells under the infection of Porphyromonas gingivalis (P. gingivalis) is yet to be elucidated. The current study verified the role and explored the mechanism of LIMP2 in promoting foam cell formation by P. gingivalis.

BACKGROUND

An association between periodontitis and atherosclerosis (AS) has been established. P. gingivalis is a key pathogen of periodontitis that promotes foam cell formation by regulating activities of CD36 scavenger receptors expressed on the macrophages. LIMP2, a member of CD36 superfamily, is involved in cholesterol efflux. However, whether LIMP2 is involved in the formation of foam cells promoted by P. gingivalis remains unclear.

METHODS

The formation of foam cells was examined by Oil Red O staining. The knockdown of limp2 was identified by qRT-PCR. The accumulation of cholesterol was monitored by Cholesterol Assay Kit. The location of P. gingivalis was visualized by confocal microscopy. Cathepsin L activity was monitored with Magic Red Cathepsin L Assay Kit. The key genes and pathways in P. gingivalis-infected macrophages were explored by RNA sequencing. The protein level was investigated by Western blotting.

RESULTS

Porphyromonas gingivalis increases foam cells formation and upregulates the expression of LIMP2 in foam cells. The knockdown of limp2 decreases the number of foam cells and increases cholesterol export, which is related to lysosomal functions. In addition, the interaction between LIMP2 and caveolin-1(CAV1) might contribute to this process, and NF-κB and JNK activity is required for increased expression of P. gingivalis-induced LIMP2.

CONCLUSIONS

This study suggested that LIMP2 is involved in the foam cells formation facilitated by P. gingivalis, which favors a close connection between periodontitis and atherosclerosis (AS).

Oxidative Stress Triggers Defective Autophagy in Endothelial Cells: Role in Atherothrombosis Development

Atherothrombosis, a multifactorial and multistep artery disorder, represents one of the main causes of morbidity and mortality worldwide. The development and progression of atherothrombosis is closely associated with age, gender and a complex relationship between unhealthy lifestyle habits and several genetic risk factors. The imbalance between oxidative stress and antioxidant defenses is the main biological event leading to the development of a pro-oxidant phenotype, triggering cellular and molecular mechanisms associated with the atherothrombotic process. The pathogenesis of atherosclerosis and its late thrombotic complications involve multiple cellular events such as inflammation, endothelial dysfunction, proliferation of vascular smooth muscle cells (SMCs), extracellular matrix (ECM) alterations, and platelet activation, contributing to chronic pathological remodeling of the vascular wall, atheromatous plague formation, vascular stenosis, and eventually, thrombus growth and propagation. Emerging studies suggest that clotting activation and endothelial cell (EC) dysfunction play key roles in the pathogenesis of atherothrombosis. Furthermore, a growing body of evidence indicates that defective autophagy is closely linked to the overproduction of reactive oxygen species (ROS) which, in turn, are involved in the development and progression of atherosclerotic disease. This topic represents a large field of study aimed at identifying new potential therapeutic targets. In this review, we focus on the major role played by the autophagic pathway induced by oxidative stress in the modulation of EC dysfunction as a background to understand its potential role in the development of atherothrombosis.

Metabolic reprogramming of the myeloid lineage by Schistosoma mansoni infection persists independently of antigen exposure

Macrophages have a defined role in the pathogenesis of metabolic disease and cholesterol metabolism where alternative activation of macrophages is thought to be beneficial to both glucose and cholesterol metabolism during high fat diet induced disease. It is well established that helminth infection protects from metabolic disease, but the mechanisms underlying protection are not well understood. Here, we investigated the effects of Schistosoma mansoni infection and cytokine activation in the metabolic signatures of bone marrow derived macrophages using an approach that integrated transcriptomics, metabolomics, and lipidomics in a metabolic disease prone mouse model. We demonstrate that bone marrow derived macrophages (BMDM) from S. mansoni infected male ApoE-/- mice have dramatically increased mitochondrial respiration compared to those from uninfected mice. This change is associated with increased glucose and palmitate shuttling into TCA cycle intermediates, increased accumulation of free fatty acids, and decreased accumulation of cellular cholesterol esters, tri and diglycerides, and is dependent on mgll activity. Systemic injection of IL-4 complexes is unable to recapitulate either reductions in systemic glucose AUC or the re-programing of BMDM mitochondrial respiration seen in infected males. Importantly, the metabolic reprogramming of male myeloid cells is transferrable via bone marrow transplantation to an uninfected host, indicating maintenance of reprogramming in the absence of sustained antigen exposure. Finally, schistosome induced metabolic and bone marrow modulation is sex-dependent, with infection protecting male, but not female mice from glucose intolerance and obesity. Our findings identify a transferable, long-lasting sex-dependent reprograming of the metabolic signature of macrophages by helminth infection, providing key mechanistic insight into the factors regulating the beneficial roles of helminth infection in metabolic disease.

Expression levels of miR-27a, miR-329, ABCA1, and ABCG1 genes in peripheral blood mononuclear cells and their correlation with serum levels of oxidative stress and hs-CRP in the patients with coronary artery disease

Atherosclerosis is a chronic inflammatory disease with high mortality worldwide. The reverse cholesterol transport pathway in macrophage plays an important role in the pathogenesis of coronary artery disease (CAD) and is strongly controlled by regulatory factors. The microRNAs can promote or prevent the formation of atherosclerotic lesions by post-transcriptional regulation of vital genes in this pathway. Therefore, this study was conducted to investigate the relationship between the expression levels of miR-27a, miR-329, ABCA1, and ABCG1 genes and serum levels of hs-CRP, ox-LDL, and indices of oxidative stress in the patients with established CAD and controls. A total of 84 subjects (42 patients with CAD and 42 controls) were included in this study. Expression levels of miR-27a-3p, miR-329-3p, ABCA1, and ABCG1 genes in the peripheral blood mononuclear cells (PBMCs) and serum concentration of hs-CRP and ox-LDL were measured by real time-PCR and ELISA, respectively. Also, oxidative stress parameters in the serum were evaluated by ferric-reducing antioxidant power (FRAP) and malondialdehyde (MDA) assays. ABCA1 and ABCG1 gene expression in PBMC and serum concentration of FRAP were significantly lower in the CAD group compared to the control group. Expression levels of miR-27a and miR-329 and serum levels of hs-CRP, ox-LDL, and MDA were significantly higher in the CAD group compared to the control group. Serum levels of hs-CRP, ox-LDL, and expression level of miR-27a have inversely related to ABCA1 and ABCG1 gene expression in all the subjects. An increase in the expression levels of miR-27a and miR-329 may lead to the progression of atherosclerosis plaque by downregulating the expression of ABCA1 and ABCG1 genes.

Impaired cholesterol efflux capacity in patients with Helicobacter pylori infection and its relation with inflammation

BACKGROUND

Gut microorganisms are associated with atherosclerosis and related cardiovascular disease. Helicobacter pylori (H. pylori) infection is associated with dyslipidemia and inflammation contributing to the progression of atherosclerosis.

OBJECTIVE

Several studies have reported reduced HDL-C levels in H. pylori infected patients, but HDL cholesterol efflux capacity (CEC) as the most important function of HDL has not been evaluated yet.

METHODS

This cross-sectional study was conducted with 44 biopsy confirmed H. pylori patients and 43 controls. ABCA1-mediated, non-ABCA1 and total CEC were measured in ApoB-depleted serum and levels of ApoA-I, ApoB and hsCRP were estimated using ELISA technique.

RESULTS

Total and ABCA1 mediated-CEC were reduced in patients compared to controls, independent of age, sex, body mass index and HDL-C (p < 0.001), while non-ABCA1 CEC indicated no significant change between the groups. In addition, patients showed lower serum levels of ApoA-I but increased levels of hsCRP when compared to controls. Total CEC and ABCA1-mediated CEC positively correlated with ApoA-I and HDL-C, furthermore, ABCA1-mediated CEC as well as ApoA-I inversely correlated with hsCRP.

CONCLUSION

The results of the present study indicate reduced CECs in H. pylori infected patients, especially ABCA1-mediated CEC which is associated with decreased ApoA-I and increased inflammation.

Acidic extracellular pH promotes accumulation of free cholesterol in human monocyte-derived macrophages via inhibition of ACAT1 activity

BACKGROUND AND AIMS

In focal areas of advanced human atherosclerotic lesions, the intimal fluid is acidic. An acidic medium impairs the ABCA1-mediated cholesterol efflux from macrophages, so tending to increase their content of free cholesterol, which is then available for esterification by the macrophage enzyme ACAT1. Here we investigated whether low extracellular pH would affect the activity of ACAT1.

METHODS

- Human monocyte-derived macrophages were first incubated with acetyl-LDL at neutral and acidic conditions (pH 7.5, 6.5, and 5.5) to generate foam cells, and then the foam cells were incubated with [³H]oleate-BSA complexes, and the formation of [³H]oleate-labeled cholesteryl esters was measured. ACAT1 activity was also measured in cell-free macrophage extracts.

RESULTS

- In acidic media, ACAT1-dependent cholesteryl [³H]oleate generation became compromised in the developing foam cells and their content of free cholesterol increased. In line with this finding, ACAT1 activity in the soluble cell-free fraction derived from macrophage foam cells peaked at pH 7, and gradually decreased under acidic pH with a rapid drop below pH 6.5. Incubation of macrophages under progressively more acidic conditions (until pH 5.5) lowered the cytosolic pH of macrophages (down to pH 6.0). Such intracellular acidification did not affect macrophage gene expression of ACAT1 or the neutral CEH.

CONCLUSIONS

Exposure of human macrophage foam cells to acidic conditions lowers their intracellular pH with simultaneous decrease in ACAT1 activity. This reduces cholesterol esterification and thus leads to accumulation of potentially toxic levels of free cholesterol, a contributing factor to macrophage foam cell death.

Inflammasomes: a preclinical assessment of targeting in atherosclerosis

INTRODUCTION

Inflammasomes are central to atherosclerotic vascular dysfunction with regulatory effects on inflammation, immune modulation, and lipid metabolism. The NLRP3 inflammasome is a critical catalyst for atherogenesis thus highlighting its importance in understanding the pathophysiology of atherosclerosis and for the identification of novel therapeutic targets and biomarkers for the treatment of cardiovascular disease.

AREAS COVERED

This review includes an overview of macrophage lipid metabolism and the role of NLRP3 inflammasome activity in cardiovascular inflammation and atherosclerosis. We highlight key activators, signal transducers and major regulatory components that are being considered as putative therapeutic targets for inhibition of NLRP3-mediated cardiovascular inflammation and atherosclerosis.

EXPERT OPINION

NLRP3 inflammasome activity lies at the nexus between inflammation and cholesterol metabolism; it offers unique opportunities for understanding atherosclerotic pathophysiology and identifying novel modes of treatment. As such, a host of NLRP3 signaling cascade components have been identified as putative targets for drug development. We catalog these current discoveries in therapeutic targeting of the NLRP3 inflammasome and, utilizing the CANTOS trial as the translational (bench-to-bedside) archetype, we examine the complexities, challenges, and ultimate goals facing the field of atherosclerosis research.

Atherosclerosis and carcinoma: Two facets of dysfunctional cholesterol homeostasis

Although cholesterol is an essential and necessary component for biological systems; inappropriate accumulation of cholesterol in blood vessels and intracellular territory is also detrimental to living things. On one hand, cholesterol is the acting precursor of many metabolic regulators, a component of the structural veracity and scaffold fluidity of biomembranes, an insulator of electrical transmission in nerves and many more; on the other hand, its deposition in blood vessels induces atherosclerotic plaque and cardiovascular complications with the consequences of heart attack and stroke. It is also an emerging fact that cholesterol is a prelate in the cell nucleus for cell proliferation and any oddity in this venture may be the cause of tumorigenesis. Hence, cholesterol homeostasis is a very crucial element in issues of health management. Cholesterol is now a global target for maintaining quality health, particularly to control the two giants of the present world health tragedy: atherosclerosis and carcinoma, which appear to be the two facets of dysfunctional cholesterol homeostasis.

Short-term High-fat Overfeeding Does Not Induce NF-κB Inflammatory Signaling in Subcutaneous White Adipose Tissue

CONTEXT

It is unclear how white adipose tissue (WAT) inflammatory signaling proteins respond during the early stages of overnutrition.

OBJECTIVE

To investigate the effect of short-term, high-fat overfeeding on fasting abdominal subcutaneous WAT total content and phosphorylation of proteins involved in nuclear factor-κB (NF-κB) inflammatory signaling, systemic metabolic and inflammatory biomarkers.

DESIGN

Individuals consumed a high-fat (65% total energy from total fat), high-energy (50% above estimated energy requirements) diet for 7 days.

RESULTS

Fifteen participants (aged 27 ± 1 years; body mass index 24.4 ± 0.6 kg/m2) completed the study. Body mass increased following high-fat overfeeding (+1.2 ± 0.2 kg; P < 0.0001). However, total content and phosphorylation of proteins involved in NF-κB inflammatory signaling were unchanged following the intervention. Fasting serum glucose (+0.2 ± 0.0 mmol/L), total cholesterol (+0.4 ± 0.1 mmol/L), low-density lipoprotein cholesterol (+0.3 ± 0.1 mmol/L), high-density lipoprotein cholesterol (+0.2 ± 0.0 mmol/L), and lipopolysaccharide-binding protein (LBP; +4.7 ± 2.1 µg/mL) increased, whereas triacylglycerol concentrations (-0.2 ± 0.1 mmol/L) decreased following overfeeding (all P < 0.05). Systemic biomarkers (insulin, soluble cluster of differentiation 14 [CD14], C-reactive protein, interleukin-6, tumor necrosis factor-α and monocyte chemoattractant protein-1) and the proportion and concentration of circulating CD14+ monocytes were unaffected by overfeeding.

CONCLUSION

Acute lipid oversupply did not impact on total content or phosphorylation of proteins involved in WAT NF-κB inflammatory signaling, despite modest weight gain and metabolic alterations. Systemic LBP, which is implicated in the progression of low-grade inflammation during the development of obesity, increased in response to a 7-day high-fat overfeeding period.

Targeting foam cell formation and macrophage polarization in atherosclerosis: The Therapeutic potential of rhubarb

Atherosclerosis, a chronic inflammatory disease associated with high morbidity and mortality, is characterized by the accumulation of foam cells in the arterial wall. It has long been acknowledged that the formation of foam cells is caused by excess lipid uptake and abnormal cholesterol metabolism function. And increasing evidence shows that inhibiting foam cell formation is a promising way to suppress the development of atherosclerotic lesions. In addition to excess foam cells accumulation, inflammation is another major contributor of atherosclerotic lesions. Recently, macrophage polarization has been demonstrated to play a vital role in the regulation of inflammatory response. Generally, macrophages mainly polarized into two phenotypes: either classically activated pro-inflammatory M1 or alternatively activated anti-inflammatory M2. And targeting macrophage polarization has been considered as a feasible approach to prevent the development of atherosclerosis. At present, the anti-atherosclerosis drugs mainly classified into two types: lipid-lowering drugs and anti-inflammatory drugs. A large part of those drugs belong to western medicine, and various side effects are unavoidable. Interestingly, in recent years, Traditional Chinese medicine has attracted growing attention because of its good efficacy and low negative effects. Rhubarb (called Da Huang in Chinese) is a famous folk medicine with a wide spectrum of pharmacological effects, such as lipid-lowering and anti-inflammatory effects. In this review, we summarized current findings about the regulatory effects of Rhubarb on foam cell formation and macrophage polarization, with emphasis on the molecular mechanisms of action that have been revealed during the past two decades, to better understand its pivotal role in the treatment and prevention of atherosclerosis.

Involvement of ABC-transporters and acyltransferase 1 in intracellular cholesterol-mediated autophagy in bovine alveolar macrophages in response to the Bacillus Calmette-Guerin (BCG) infection

Background

Understanding pathogenic mechanisms is imperative for developing novel treatment to the tuberculosis, an important public health burden worldwide. Recent studies demonstrated that host cholesterol levels have implications in the establishment of Mycobacterium tuberculosis (M. tuberculosis, Mtb) infection in host cells, in which the intracellular cholesterol-mediated ATP-binding cassette transporters (ABC-transporters) and cholesterol acyltransferase1 (ACAT1) exhibited abilities to regulate macrophage autophagy induced by Mycobacterium bovis bacillus Calmette–Guérin (BCG).

Results

The results showed that a down-regulated expression of the ABC-transporters and ACAT1 in primary bovine alveolar macrophages (AMs) and murine RAW264.7 cells in response to a BCG infection. The inhibited expression of ABC-transporters and ACAT1 was associated with the reduction of intracellular free cholesterol, which in turn induced autophagy in macrophages upon to the Mycobacterial infection. These results strongly suggest an involvement of ABC-transporters and ACAT1 in intracellular cholesterol-mediated autophagy in AMs in response to BCG infection.

Conclusion

This study thus provides an insight into into a mechanism by which the cholesterol metabolism regulated the autophagy in macrophages in response to mycobacterial infections.

Association Between LOX-1, LAL, and ACAT1 Gene Single Nucleotide Polymorphisms and Carotid Plaque in a Northern Chinese Population

Objective: Carotid atherosclerosis is one of the major risk factors for ischemic stroke. The presence of carotid plaque has been widely used to assess the risk of clinical atherosclerotic disease. Lectin-type oxidized LDL (low-density lipoprotein) receptor 1 (LOX-1), lysosomal acid lipase (LAL), and acyl-CoA:cholesterol acyltransferase 1 (ACAT1) are important for lipid accumulation in atherosclerosis. The objective of this study was to investigate the relationship between single nucleotide polymorphisms (SNPs) in the LOX-1, LAL, and ACAT1 genes and the presence of carotid plaque in a Northern Chinese population. Methods: Three polymorphisms in LOX-1 (rs1050286), LAL (rs11203042), and ACAT1 (rs11576517) were identified and genotyped in 215 patients with carotid plaque and 252 controls using the polymerase chain reaction with high-resolution melting analysis. Results: The LOX-1 (rs1050286) AA and LAL (rs11203042) TT genotypes were significantly associated with increased risk of carotid plaque, whereas a ACAT1 (rs11576517) TT genotype was shown to be protective against carotid plaque in a Northern Chinese population (p < 0.05). Even after the Bonferroni correction, the LAL (rs11203042) TT genotype (odds ratio = 3.838, 95% confidence interval = 1.748-8.426, p < 0.001) was still associated with an increased risk for carotid plaque. Conclusions: These results suggest that the LAL (rs11203042) TT genotype is associated with increased risk for carotid plaque in a Northern Chinese population, and that the LOX-1 (rs1050286) AA genotype shows a nonstatistically significant trend towards association. However, no association was found between the ACAT1 (rs11576517) polymorphisms and carotid plaque presence.

Socioeconomic deprivation and blood lipids in first-episode psychosis patients with minimal antipsychotic exposure: Implications for cardiovascular risk

BACKGROUND

The influence of socioeconomic deprivation on the cardiovascular health of patients with psychosis-spectrum disorders (PSD) has not been investigated despite the growing recognition of social factors as determinants of health, and the disproportionate rates of cardiovascular mortality observed in PSD. Discordant results have been documented when studying dyslipidemia -a core cardiovascular risk factor- in first-episode psychosis (FEP), before chronic exposure to antipsychotic medications. The objective of the present study is to determine the extent to which socioeconomic deprivation affects blood lipids in patients with FEP, and examine its implications for cardiovascular risk in PSD.

METHODS

Linear regression models, controlling for age, sex, exposure to pharmacotherapy, and physical anergia, were used to test the association between area-based measures of material and social deprivation and blood lipid levels in a sample of FEP patients (n = 208).

RESULTS

Social, but not material deprivation, was associated with lower levels of total and HDL cholesterol. This effect was statistically significant in patients with affective psychoses, but not in schizophrenia-spectrum disorders.

CONCLUSIONS

Contrary to other reports from the literature, the relationship between socioeconomic disadvantage and blood lipid levels was contingent on the social rather than the material aspects of deprivation. Furthermore, this association also depended on the main diagnostic category of psychosis, suggesting a complex interaction between the environment, psychopathology, and physical health. Future studies exploring health issues in psychosis might benefit from taking these associations into consideration. A better understanding of the biology of blood lipids in this context is necessary.

LCK inhibitor attenuates atherosclerosis in ApoE-/- mice via regulating T cell differentiation and reverse cholesterol transport

Lots of studies demonstrated that CD4⁺ T cells regulate the development of atherosclerosis (AS). Previously, we reported that LCK, a key molecule in activation of T cell receptor (TCR) signalling and T cells, adversely affects reverse cholesterol transport (RCT), which ameliorates AS in vitro. To investigate the effect of LCK on AS in vivo, we injected the LCK inhibitor, PP2, into ApoE^-/- mice fed a chow diet or a high-fat diet (HFD). Although, AS plaques were not affected by PP2 in chow diet-fed mice, PP2 significantly reduced the lesion percentage and necrotic core areas in HFD-fed mice. We further analysed the plaque contents and found that the accumulation of lipids and macrophages were decreased, while the contents of collagen and smooth muscle cells were increased by the LCK inhibitor. Thus, inhibiting LCK enhanced the plaque stability. We also found the LCK inhibitor improved cholesterol efflux capacity of HDL and up-regulated RCT regulatory proteins in the spleen. Moreover, inhibiting LCK regulated differentiation of T cells by increasing regulatory T (Treg) cells and decreasing the number of T helper 1 (Th1) cells in the aorta, thymus and spleen. Consistent with these results, infiltration of CD4⁺ T cells in plaques, secretion of pro-atherosclerotic cytokines, INF-γ and TNF-α synthesized mostly by Th1 cells, and the activation of PI3K/AKT/mTOR signalling were inhibited by the LCK inhibitor. Moreover, the effect of LCK inhibitor on the ratio of Th1 to Treg cells were compromised by activation of mTOR. Together, these data indicate that inhibiting LCK in TCR signalling attenuated the development of AS and promoted plaque stability. Improving RCT by upregulating RCT regulatory proteins and decreasing the Th1/Treg ratio by inhibiting PI3K/AKT/mTOR signalling may contribute to the anti-atherosclerotic effects of LCK inhibition.

Dysfunctional High-Density Lipoproteins Are Associated With a Greater Incidence of Acute Coronary Syndrome in a Population at High Cardiovascular Risk: A Nested Case-Control Study

BACKGROUND

Studies have failed to establish a clear link between high-density lipoprotein (HDL) cholesterol and cardiovascular disease, leading to the hypothesis that the atheroprotective role of HDL lies in its biological activity rather than in its cholesterol content. However, to date, the association between HDL functional characteristics and acute coronary syndrome has not been investigated comprehensively.

METHODS

We conducted a case-control study nested within the PREDIMED (Prevención con Dieta Mediterránea) cohort, originally a randomized trial in which participants followed a Mediterranean or low-fat diet. Incident acute coronary syndrome cases (N=167) were individually matched (1:2) to control patients by sex, age, intervention group, body mass index, and follow-up time. We investigated 2 individual manifestations (myocardial infarction, unstable angina) as secondary outcomes. We measured the following functional characteristics: HDL cholesterol concentration (in plasma); cholesterol efflux capacity; antioxidant ability, measured by the HDL oxidative-inflammatory index; phospholipase A2 activity; and sphingosine-1-phosphate, apolipoproteins A-I and A-IV, serum amyloid A, and complement 3 protein (in apolipoprotein B-depleted plasma). We used conditional logistic regression models adjusted for HDL cholesterol levels and cardiovascular risk factors to estimate odds ratios (ORs) between 1-SD increments in HDL functional characteristics and clinical outcomes.

RESULTS

Low values of cholesterol efflux capacity (OR_1SD, 0.58; 95% CI, 0.40-0.83) and low levels of sphingosine-1-phosphate (OR_1SD, 0.70; 95% CI, 0.52-0.92) and apolipoprotein A-I (OR_1SD, 0.58; 95% CI, 0.42-0.79) were associated with higher odds of acute coronary syndrome. Higher HDL oxidative inflammatory index values were marginally linked to acute coronary syndrome risk (OR_1SD, 1.27; 95% CI, 0.99-1.63). Low values of cholesterol efflux capacity (OR_1SD, 0.33; 95% CI, 0.18-0.61), sphingosine-1-phosphate (OR_1SD: 0.60; 95% CI: 0.40-0.89), and apolipoprotein A-I (OR_1SD, 0.59; 95% CI, 0.37-0.93) were particularly linked to myocardial infarction, whereas high HDL oxidative-inflammatory index values (OR_1SD, 1.53; 95% CI, 1.01-2.33) and low apolipoprotein A-I levels (OR_1SD, 0.52; 95% CI, 0.31-0.88) were associated with unstable angina.

CONCLUSIONS

Low cholesterol efflux capacity values, pro-oxidant/proinflammatory HDL particles, and low HDL levels of sphingosine-1-phosphate and apolipoprotein A-I were associated with increased odds of acute coronary syndrome and its manifestations in individuals at high cardiovascular risk.

CLINICAL TRIAL REGISTRATION

URL: https://www.controlled-trials.com/ISRCTN35739639. Unique identifier: ISRCTN35739639.

Lyso-diacylglyceryltrimethylhomoserine (lyso-DGTS) isolated from Nannochloropsis microalgae improves high-density lipoprotein (HDL) functions

Many population studies have shown that blood concentrations of high-density lipoprotein (HDL) cholesterol are inversely correlated with risk of cardiovascular disease (CVD). However, in recent studies, increasing blood HDL cholesterol concentrations failed to reduce CVD events. On the other hand, studies suggest that improving HDL quality can be a more efficient tool for assessing atherosclerotic risk than simply measuring blood HDL cholesterol concentration. Thus, improving HDL activity using natural substances might be a useful therapeutic approach to reducing CVD risk. We previously isolated a novel active compound from Nannochloropsis microalgae termed lyso-diacylglyceryltrimethylhomoserine (lyso-DGTS), which increased activity of paraoxonase 1, the main antioxidant enzyme associated with HDL. Here we examined the effect of lyso-DGTS on HDL quality and function. Tryptophan-fluorescence-quenching assay showed that lyso-DGTS interacts spontaneously with the entire HDL lipoprotein and with apolipoprotein A1 (ApoA1), the major structural and functional HDL protein, with high affinity (K_a = 2.17 × 10⁴  M^-1 at 37°C). Lyso-DGTS added to HDL and to ApoA1 increased cholesterol efflux from macrophage cells, the main antiatherogenic function of HDL, dose-dependently, and significantly increased HDL's ability to induce nitric oxide production from endothelial cells. In-vivo supplementation of lyso-DGTS to the circulation of mice fed a high-fat diet via osmotic mini-pumps implanted subcutaneously enhanced HDL anti-inflammatory effect significantly as compared to controls. Our findings suggest that lyso-DGTS may have a beneficial effect in decreasing atherosclerosis risk by interacting with HDL particles and improving their quality and antiatherogenic functions.

CCAAT/enhancer-binding protein beta (C/EBPβ) knockdown reduces inflammation, ER stress, and apoptosis, and promotes autophagy in oxLDL-treated RAW264.7 macrophage cells

Atherosclerosis is associated with deregulated cholesterol metabolism and formation of macrophage foam cells. CCAAT/enhancer-binding protein beta (C/EBPβ) is a transcription factor, and its inhibition has recently been shown to prevent atherosclerosis development and foam cell formation. However, whether C/EBPβ regulates inflammation, endoplasmic reticulum (ER) stress, and apoptosis, in macrophage foam cells and its underlying molecular mechanism remains unknown. Here, we investigated the effect of C/EBPβ knockdown on proteins and genes implicated in inflammation, ER stress, apoptosis, and autophagy in macrophage foam cells. RAW264.7 macrophage cells were transfected with control and C/EBPβ-siRNA and then treated with nLDL and oxLDL. Key proteins and genes involved in inflammation, ER stress, apoptosis, and autophagy were analyzed by western blot and qPCR. We found that short interfering RNA (siRNA)-mediated knockdown of C/EBPβ attenuated atherogenic lipid-mediated induction of proteins and genes implicated in inflammation (P-NFkB-p65, NFkB-p65, and TNFα), ER stress (ATF4 and ATF6), and apoptosis (CHOP, caspase 1, 3, and 12). Interestingly, C/EBPβ knockdown upregulated the expression of autophagy proteins (LC3A/B-II, ATG5) and genes (LC3B, ATG5) but decreased the mammalian target of rapamycin (mTOR) protein phosphorylation and mTORC1 gene expression in oxLDL-loaded RAW264.7 macrophage cells. More importantly, treatment with rapamycin (inhibitor of mTOR) increased expression of proteins implicated in autophagy and cholesterol efflux in oxLDL-loaded RAW 264.7 macrophage cells. The present results suggest that C/EBPβ inactivation regulates macrophage foam cell formation in atherogenesis by reducing inflammation, ER stress, and apoptosis and by promoting autophagy and inactivating mTOR.

Macrophage iron retention aggravates atherosclerosis: Evidence for the role of autocrine formation of hepcidin in plaque macrophages

Iron accumulation has been frequently found in atherosclerotic lesions, especially in macrophages/foam cells, but the exact mechanisms by which hepcidin induces iron retention in plaque macrophages and its roles in atherogenesis remain unknown. Double immunofluorescence staining showed colocalization of hepcidin-positive macrophages with ox-LDL, TLR4, p-p65 and ferritin light chain (ferritin-L) both in human and murine atherosclerotic lesions. RAW264.7 macrophages incubated with ox-LDL showed elevated expression of TLR4, p-p65, hepcidin, ferritin-L/H, CYP27A1, CD36, PPARγ, liver X receptor α (LXRα), and ATP binding cassette transporter A1/G1 (ABCA1/G1), as well as increased intracellular labile iron pool level and lipid accumulation. Ox-LDL-induced iron retention and lipid accumulation were aggravated by lipopolysaccharide but blocked by TAK-242, an antagonist of TLR4. Moreover, macrophage TLR4/NF-κB pathway activation and foaming triggered by ox-LDL was enhanced by ferric ammonium citrate or exogenous hepcidin but attenuated by hepcidin silencing or the use of iron chelator. Meanwhile, the addition of hepcidin stimulated CD36-mediated Dil-labeled-ox-LDL uptake and inhibited the LXRα-ABCA1/G1 pathway-dependent cholesterol efflux in macrophages, which was significantly reversed by 27-hydroxycholesterol but further exacerbated by cyclosporin A, a selective inhibitor of CYP27A1. Our study provided the evidence that iron trapped in atherosclerosis plaque macrophages contributes to cholesterol disequilibrium-initiated foam cell formation, which is provoked by the unique but largely unknown autocrine formation of hepcidin in plaque macrophages via activating the TLR4/NF-κB pathway when exposed to ox-LDL. Such findings, considering the intricate vicious cycle between macrophage hepcidin autocrine-triggered iron retention and cholesterol disequilibrium, may shed new light on the "iron hypothesis" of atherosclerosis.

Immunobiology of Atherosclerosis: A Complex Net of Interactions

Cardiovascular disease is the leading cause of mortality worldwide, and atherosclerosis the principal factor underlying cardiovascular events. Atherosclerosis is a chronic inflammatory disease characterized by endothelial dysfunction, intimal lipid deposition, smooth muscle cell proliferation, cell apoptosis and necrosis, and local and systemic inflammation, involving key contributions to from innate and adaptive immunity. The balance between proatherogenic inflammatory and atheroprotective anti-inflammatory responses is modulated by a complex network of interactions among vascular components and immune cells, including monocytes, macrophages, dendritic cells, and T, B, and foam cells; these interactions modulate the further progression and stability of the atherosclerotic lesion. In this review, we take a global perspective on existing knowledge about the pathogenesis of immune responses in the atherosclerotic microenvironment and the interplay between the major innate and adaptive immune factors in atherosclerosis. Studies such as this are the basis for the development of new therapies against atherosclerosis.

Allergic asthma aggravated atherosclerosis increases cholesterol biosynthesis and foam cell formation in apolipoprotein E-deficient mice

Several studies have demonstrated that allergic asthma can induce atherosclerosis formation in mice. Moreover, allergic asthma and atherosclerosis have been shown to be strongly associated with dyslipidemia. In this study, we investigated the underlying mechanism of allergic asthma-aggravated atherosclerosis-induced cholesterol metabolism disorder in asthmatic apoE^-/- mice. We found that allergic asthma increased the expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the liver and CD36 in the aorta during the acute and advanced stages of atherosclerosis, respectively. These results indicate that cholesterol biosynthesis is increased during acute atherosclerosis and cholesterol uptake and foam cell formation is increased during advanced atherosclerosis. Simvastatin administration significantly ameliorated the aortic root lesion size of asthmatic mice and significantly decreased HMGCR and CD36 expression. However, the expression of the low-density lipoprotein receptor and ATP-binding cassette transporter A1 was markedly increased, indicating that the beneficial effect of statins in allergic asthma and coronary artery disease was mediated, at least in part, by decreasing cholesterol biosynthesis and foam cell formation. In conclusion, allergic asthma aggravates atherosclerosis by regulating cholesterol metabolism in apoE^-/- mice. Allergic asthma selectively promotes cholesterol biosynthesis in acute atherosclerosis and increases foam cell formation in advanced atherosclerosis.

Genome-wide association analysis of HDL-C in a Lebanese cohort

Low serum levels of high-density lipoprotein cholesterol (HDL-C) have been shown to be a risk factor for coronary artery disease independent of low-density lipoprotein cholesterol (LDL-C) in different populations. In this study, we investigated genetic variants through genome-wide association studies to determine their association with HDL-C levels in a sample of 2,700 patients. We identified several SNPs associated with HDL-C levels in the Lebanese population using unadjusted and adjusted by biological factors models. We replicated the association of rs3764261 within CETP with HDL-C levels in the study population, and found other previously unidentified SNPs to be significant at the suggestive level, in both previously identified and unidentified genes. This paper reports the first genome-wide analysis of HDL-C in the Lebanese, Middle Eastern, population and supports the importance of genome-wide association studies across different and minor ethnicities to understand better the etiology of complex human diseases.

PM2.5 aggravates the lipid accumulation, mitochondrial damage and apoptosis in macrophage foam cells

Epidemiological evidence showed that the particulate matter exposure is associated with atherosclerotic plaque progression, which may be related to foam cell formation, but the mechanism is still unknown. The study was aimed to investigate the toxic effects and possible mechanism of PM_2.5 on the formation of macrophage foam cells induced by oxidized low density lipoprotein (ox-LDL). Results showed that PM_2.5 induced cytotoxicity by decreasing the cell viability and increasing the LDH level in macrophage foam cells. PM_2.5 aggravated the lipid accumulation in ox-LDL-stimulated macrophage RAW264.7 within markedly increasing level of intracellular lipid by Oil red O staining. The level of ROS increased obivously after co-exposure to PM_2.5 and ox-LDL than single exposure group. In addition, serious mitochondrial damage such as the mitochondrial swelling, cristae rupturing and disappearance were observed in macrophage foam cells. The loss of the mitochondrial membrane potential (MMP) further exacerbated the mitochondrial damage in PM_2.5-induced macrophage foam cells. The apoptotic rate increased more severely via up-regulated protein level of Bax, Cyt C, Caspase-9, Caspase-3, and down-regulated that of Bcl-2, indicating that PM_2.5 activated the mitochondrial-mediated apoptosis pathway. In summary, our results demonstrated that PM_2.5 aggravated the lipid accumulation, mitochondrial damage and apoptosis in macrophage foam cells, suggesting that PM_2.5 was a risk factor of atherosclerosis progression.

Is there a relationship between vitamin D nutritional status and metabolic syndrome in childhood acute lymphoblastic leukemia survivors? A PETALE study

BACKGROUND

Treatment of childhood acute lymphoblastic leukemia (cALL) has reached unprecedented success leading to survival rates reaching 90%. This is regrettably linked to increased risk of developing long-term health-related sequels into early adulthood.

OBJECTIVE

This study aims at assessing the relationship between the vitamin D status and metabolic biomarkers in PETALE, a well-characterized cohort of cALL survivors.

RESULTS

We demonstrate that 15.9% of the study participants exhibited 3 or more metabolic syndrome (MetS) risk factors. We also show a direct relationship between s25OHD₃ and plasma HDL-Cholesterol concentrations in female but not male participants.

CONCLUSION

Our data, from a metabolically well-described cohort, support a modest role for vitamin D in lipid metabolism in childhood leukemia survivors. The major outcome of this study is the strong association between HDL-Cholesterol concentration and s25OHD₃ only in female subjects, thereby conveying vitamin D a gender-specific cardio-protective effect. cALL survivors represent a population at higher risk for secondary diseases. For this reason thorough nutritional evaluation, including vitamin D should be part of the regular follow-up.

ZAP70 deficiency promotes reverse cholesterol transport through MAPK/ERK pathway in Jurkat cell

BACKGROUND

Lots of studies have demonstrated that immune cells could regulate reverse cholesterol transport (RCT). However, neither T cell receptor (TCR) signalling nor Zeta-chain associated protein 70 (ZAP70) have been demonstrated to be associated with RCT. To investigate this association, we used a ZAP70-deficient Jurkat-derived mutant, P116 cell line, to detect the effect of ZAP70 on RCT and inflammatory response. ZAP70 deficiency improved cholesterol efflux capacity by 14%. Meanwhile, mRNA and proteins expression of RCT regulatory proteins such as ABCA1, ABCG1 and SR-BI were increased in P116 cells. ZAP70-deficiency had no influence on LXR-α and PPAR-γ. Regarding the inflammatory response, the mRNA expression and secretion of pro-atherosclerotic cytokines, TNF-α, IFN-γ, IL-2 and IL-6, were significantly decreased in the ZAP70-deficient cell line. Activation of MAP kinases cascades, as determined by of ERK, JNK and p38 MAPK phosphorylation, were found to be inhibited in the absence of ZAP70. Specific inhibition of ERK, JNK and p38 MAPK activity was also found to decreased TNF-α, IFN-γ, and IL-6 secretion. However, only the ERK inhibition was observed to reduce IL-2 secretion, improve cholesterol efflux capacity and increase expression of ABCA1, ABCG1 and SR-BI without increasing LXR-α and PPAR-γ. Using ChIP assay to detect the binding of LXR-α to LXRE, which promotes the expression of ABCG1, we found that inhibiting ERK improved binding without increasing LXR-α levels. Thus, we speculate that ZAP70-deficiency may improve RCT and decrease the inflammatory response of T cells. Furthermore, these effects are probably achieved via ERK signalling pathway.

Association of lecithin-cholesterol acyltransferase activity and low-density lipoprotein heterogeneity with atherosclerotic cardiovascular disease risk: a longitudinal pilot study

BACKGROUND

Lecithin-cholesterol acyltransferase (LCAT) is believed to be involved in reverse cholesterol transport, which is known to play a key role in suppression of atherosclerosis. However, recent investigations have demonstrated that higher LCAT activity, measured in terms of the serum cholesterol esterification rate by an endogenous substrate method, is associated with increased formation of triglyceride (TG)-rich lipoproteins (TRLs), leading to a decrease in the low-density lipoprotein (LDL) particle size. The purpose of this hospital-based longitudinal study was to clarify the causal relationship between changes in the LCAT activity and changes in the LDL-particle size.

METHODS

The subjects were a total of 335 patients, derived from our previous study cohort, with one or more risk factors for atherosclerotic cardiovascular disease (ASCVD). For this study, we measured the LDL-particle size (relative LDL migration [LDL-Rm value]) by polyacrylamide gel electrophoresis in the subjects, along with the changes in the LCAT activity, at the end of a follow-up period of at least 1 year.

RESULTS

The results revealed that the absolute change (Δ) in the LDL-particle size increased significantly as the quartile of Δ LCAT activity increased (p = 0.01). A multi-logistic regression adjusted-analysis revealed that Δ LCAT activity in the fourth quartile as compared to that in the first quartile was independently predictive of an increased LDL-particle size (odds ratio [95% confidence interval]: 2.03 [1.02/4.04], p = 0.04). Moreover, the ∆ LCAT activity was also positively correlated with ∆ TRL-related markers (i.e., TG, remnant particle-like cholesterol [RLP-C], apolipoprotein B, apolipoprotein C-2, and apolipoprotein C-3).

CONCLUSIONS

The results lend support to the hypothesis that increased LCAT activity may be associated with increased formation of TRLs, leading to a reduction in the LDL-particle size in patients at a high risk for ASCVD. To reduce the risk of ASCVD, it may be important to focus not only on the quantitative changes in the serum LDL-cholesterol levels, but also on the LCAT activity.

TRIAL REGISTRATION

UMIN ( https://upload.umin.ac.jp/cgi-bin/ctr/ctr_reg_list.cgi ) Study ID: UMIN000033228 retrospectively registered 2 July 2018.

Elevated high density lipoprotein cholesterol and low grade systemic inflammation is associated with increased gut permeability in normoglycemic men

BACKGROUND & AIMS

Serum lipids and lipoproteins are established biomarkers of cardiovascular disease risk that could be influenced by impaired gut barrier function via effects on the absorption of dietary and biliary cholesterol. The aim of this study was to examine the potential relationship between gut barrier function (gut permeability) and concentration of serum lipids and lipoproteins, in an ancillary analysis of serum samples taken from a previous study.

METHODS AND RESULTS

Serum lipids, lipoproteins and functional gut permeability, as assessed by the percentage of the urinary recovery of ⁵¹Cr-labelled EDTA absorbed within 24 h, were measured in a group of 30 healthy men. Serum lipopolysaccharide, high sensitivity C-reactive protein and interleukin-6 were also measured as markers of low-grade inflammation. The group expressed a 5-fold variation in total gut permeability (1.11-5.03%). Gut permeability was unrelated to the concentration of both serum total and low density lipoprotein (LDL)-cholesterol, but was positively associated with serum high density lipoprotein (HDL)-cholesterol (r = 0.434, P = 0.015). Serum HDL-cholesterol was also positively associated with serum endotoxaemia (r = 0.415, P = 0.023).

CONCLUSION

The significant association between increased gut permeability and elevated serum HDL-cholesterol is consistent with the role of HDL as an acute phase reactant, and in this situation, potentially dysfunctional lipoprotein. This finding may have negative implications for the putative role of HDL as a cardio-protective lipoprotein.