Promotes Foam Cell Formation Research Articles

Diisodecyl phenyl phosphate promotes foam cell formation by antagonizing Liver X receptor alpha

While the cardiovascular system is a primary target of organophosphorus flame retardants (OPFRs), particularly aryl-OPFRs, it is still exclusive whether the diisodecyl phenyl phosphate (DIDPP), widely used and broadly present in the environment at high concentrations, elicits atherosclerosis effects. Liver X receptors (LXRs) play a direct role in regulating the formation of atherosclerotic lesions. This study was the first to demonstrate that DIDPP acts as an LXRα ligand and functions as an LXRα antagonist with a half-maximal inhibitory concentration of 16.2 μM. We showed that treatment of an in vitro macrophage model with 1 to 10 μM of DIDPP resulted in the downregulation of direct targets of LXRα, namely ABCA1, ABCG1 and SR-B1, thereby leading to a 7.9–13.2 % reduction in cholesterol efflux. This caused dose-dependent, 24.1–43.1 % increases in the staining intensity of foam cells in the macrophage model. This atherosclerotic effect of DIDPP was proposed to be due to its antagonism of LXRα activity, as DIDPP treatment did not alter cholesterol influx. In conclusion, the findings of this study demonstrate that exposure to DIDPP may be a risk factor for atherosclerosis due to the LXRα-antagonistic activity of DIDPP and its ubiquity in the environment.

Decreased atherosclerosis and abdominal aortic aneurysm in mice deficient in polymeric immunoglobulin receptor

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): La Caixa Banking Foundation and Comunidad de Madrid Background Polymeric immunoglobulin receptor (PIGR) is a transmembrane protein involved in the transcytosis of polymeric immunoglobulins that is widely expressed in mucosal epithelial cells. Recent data from our group described increased PIGR levels in plasma and tissue of atherosclerotic subjects. However, the role for PIGR in the mechanisms involved in vascular remodeling has not been addressed. Purpose To analyse the role for PIGR in experimental mouse models of atherosclerosis and abdominal aortic aneurysm (AAA). Methods We analyzed PIGR expression, secretion and distribution in early atherosclerotic plaques and AAA tissues compared to healthy aortic samples, as well as in macrophages derived from the human monocytic THP-1 cell line. Next, we studied the effect of global PIGR deficiency in experimental atherosclerosis (Ldlr-/- Pigr-/- mice fed with atherogenic diet for 10 weeks). In addition, the contribution of hematopoietic PIGR was assessed in both experimental atherosclerosis and AAA (Ldlr-/- mice fed with atherogenic diet and 1 µg/Kg/min angiotensin II infusion for 28 days) by bone marrow transplantation experiments. Finally, bone marrow-derived macrophages (BMDMs) from Pigr-/- and control mice were isolated to assess their inflammatory expression profile and modulation of polarization in response to oxidized LDL (ox-LDL), as well as their ability to promote foam cell formation. Results PIGR expression was increased in the intima of early human atherosclerotic lesions and showed colocalization with CD68+ expression. PIGR expression was also increased during the in vitro differentiation of THP-1 monocytes to macrophages with phorbol myristate acetate. Both global and hematopoietic-specific PIGR deficient mice displayed reduced plaque size in the aortic sinuses as well as a strong decrease in macrophage infiltration (CD68+ cells), while no changes in smooth muscle cells (α-SMA+ cells) and collagen content were observed. Regarding AAA, increased PIGR levels were found in human AAA tissues, associated with infiltrating CD68+ cells. PIGR deficiency in hematopoietic cells also showed significantly reduced AAA dilatation and reduced macrophage infiltration. In vitro experiments with BMDMs obtained from Pigr-/- mice and stimulated with ox-LDL showed reduced proinflammatory gene expression (TNF-a and IL-6) and M1 markers (iNOS and CD11c) as well as diminished foam cell formation. Conclusions PIGR deficiency in hematopoietic cells decreases atherosclerosis and AAA progression by modulating macrophage inflammatory responses, suggesting a novel proinflammatory role for PIGR in vascular pathologies. Future experiments will test the potential therapeutic effect of modulating PIGR to dampen the inflammatory profile in vascular diseases.Results in human and mouse studies

Mito-Tempo alleviates ox-LDL-provoked foam cell formation by regulating Nrf2/NLRP3 signaling.

Our previous studies have demonstrated that Mito-Tempol (also known as 4-hydroxy-Tempo), a mitochondrial reactive oxygen species scavenger, alleviates oxidized low-density lipoprotein (ox-LDL)-triggered foam cell formation. Given the effect of oxidative stress on activating the NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome, which promotes foam cell formation, we aimed to explore whether Mito-Tempo inhibits ox-LDL-triggered foam cell formation by regulating NLRP3 inflammasome. The results revealed that Mito-Tempo re-activated Nrf2 and alleviated macrophage foam cell formation induced by ox-LDL, whereas the effects were reversed by ML385 (a specific Nrf2 inhibitor). Mito-Tempo restored the expression and nuclear translocation of Nrf2 by decreasing ox-LDL-induced ubiquitination. Furthermore, Mito-Tempo suppressed ox-LDL-triggered NLRP3 inflammasome activation and subsequent pyroptosis, whereas the changes were blocked by ML385. Mito-Tempo decreased lipoprotein uptake by inhibiting CD36 expression and suppressed foam cell formation by regulating the NLRP3 inflammasome. Taken together, Mito-Tempo exhibits potent anti-atherosclerotic effects by regulating Nrf2/NLRP3 signaling.

Abstract 3046: Macrophage-smooth Muscle Cell Interactions In Atherosclerotic Foam Cell Formation

Background: A hallmark of atherosclerosis is uncontrolled uptake of atherogenic lipoproteins by artery wall cells that accumulate large amounts of cholesteryl esters (“foam cells”). While smooth muscle cells (SMCs) and macrophages are in close proximity in lesions and contribute to cholesterol accumulation, whether these cells influence each other’s tendency to form foam cells is not clearly established. Hypothesis: Direct and indirect interactions between SMCs and macrophages promote foam cell formation by both cell types. Method: Human vascular SMCs were seeded onto macrophages to mimic direct macrophage-SMC interactions (n=5). Alternatively, conditioned media generated from human macrophages or SMCs with or without lipoprotein exposure was incubated with the alternate cell type (n=3). Aggregated lipoproteins were added in both models to induce cellular cholesterol accumulation. Intracellular cholesterol was quantified to compare lipoprotein uptake in cocultures relative to monocultures. Crosstalk based on CellChat analysis using single-cell RNA sequencing data from human coronary samples was performed to identify potential factors responsible for foam cell development (n=3). One-way ANOVA was used for statistical analysis. Result: SMCs showed a 4-fold (+/-0.3, p=0.002) increase in cell cholesterol accumulation when in direct contact with macrophages and a 3-fold (+/- 0.3, p<0.0001) increase when exposed to the conditioned media from macrophage foam cells. In contrast, macrophages showed a 3-fold reduction (+/- 0.3, p=0.001) in intracellular cholesterol accumulation when in direct contact with SMCs and a 2-fold reduction (+/-0.2, p=0.0005) when exposed to SMC foam cell-conditioned media. CellChat analysis suggested macrophage foam cells but not macrophage non-foam cells promote SMC foam cell formation by secretion of inflammatory cytokines, and that SMCs promote macrophage foam cell formation by secretion of extracellular matrix components. Conclusion: Our study provides novel understanding of how macrophage-SMC interactions influence macrophage and SMC foam cell formation. Further studies will be presented examining the role of SMC extracellular matrix proteins and macrophage-secreted cytokines on foam cell formation.

Huanglian Jiedu decoction inhibits vascular smooth muscle cell-derived foam cell formation by activating autophagy via suppressing P2RY12

Ethnopharmacological relevanceHuanglian Jiedu Decoction (HLJDD) is a Chinese medicine with a long history of therapeutic application. It is widely used in treating atherosclerosis (AS) in Chinese medicine theory and clinical practice. However, the mechanism of HLJDD in treating AS remains unclear. Aim of the studyTo investigate the efficacy and mechanism of HLJDD in treating AS. Materials and methodsAS was induced on high-fat diet-fed ApoE−/− mice, with the aorta pathological changes evaluated with lipid content and plaque progression. In vitro, foam cells were induced by subjecting primary mouse aortic vascular smooth muscle cells (VSMCs) to oxLDL incubation. After HLJDD intervention, VSMCs were assessed with lipid stack, apoptosis, oxidative stress, and the expression of foam cell markers. The effects of P2RY12 were tested by adopting clopidogrel hydrogen sulfate (CDL) in vivo and transfecting P2RY12 over-expressive plasmid in vitro. Autophagy was inhibited by Chloroquine or transfecting siRNA targeting ATG7 (siATG7). The mechanism of HLJDD treating atherosclerosis was explored using network pharmacology and validated with molecular docking and co-immunoprecipitation. ResultsHLJDD exhibited a dose-dependent reduction in lipid deposition, collagen loss, and necrosis within plaques. It also reversed lipid accumulation and down-regulated the expression of foam cell markers. P2RY12 inhibition alleviated AS, while P2RY12 overexpression enhanced foam cell formation and blocked the therapeutic effects of HLJDD. Network pharmacological analysis suggested that HLJDD might mediate PI3K/AKT signaling pathway-induced autophagy. P2RY12 overexpression also impaired autophagy. Similarly, inhibiting autophagy counteracted the effect of CDL, exacerbated AS in vivo, and promoted foam cell formation in vitro. However, HLJDD treatment mitigated these detrimental effects by suppressing the PI3K/AKT signaling pathway. Immunofluorescence and molecular docking revealed a high affinity between P2RY12 and PIK3CB, while co-immunoprecipitation assays illustrated their interaction. ConclusionsHLJDD inhibited AS in vivo and foam cell formation in vitro by restoring P2RY12/PI3K/AKT signaling pathway-suppressed autophagy. This study is the first to reveal an interaction between P2RY12 and PI3K3CB.

Triglyceride-rich lipoproteins and cardiovascular diseases.

The global prevalence of cardiovascular diseases (CVD) continues to rise steadily, making it a leading cause of mortality worldwide. Atherosclerosis (AS) serves as a primary driver of these conditions, commencing silently at an early age and culminating in adverse cardiovascular events that severely impact patients' quality of life or lead to fatality. Dyslipidemia, particularly elevated levels of low-density lipoprotein cholesterol (LDL-C), plays a pivotal role in AS pathogenesis as an independent risk factor. Research indicates that abnormal LDL-C accumulation within arterial walls acts as a crucial trigger for atherosclerotic plaque formation. As the disease progresses, plaque accumulation may rupture or dislodge, resulting in thrombus formation and complete blood supply obstruction, ultimately causing myocardial infarction, cerebral infarction, and other common adverse cardiovascular events. Despite adequate pharmacologic therapy targeting LDL-C reduction, patients with cardiometabolic abnormalities remain at high risk for disease recurrence, highlighting the importance of addressing lipid risk factors beyond LDL-C. Recent attention has focused on the causal relationship between triglycerides, triglyceride-rich lipoproteins (TRLs), and their remnants in AS risk. Genetic, epidemiologic, and clinical studies suggest a causal relationship between TRLs and their remnants and the increased risk of AS, and this dyslipidemia may be an independent risk factor for adverse cardiovascular events. Particularly in patients with obesity, metabolic syndrome, diabetes, and chronic kidney disease, disordered TRLs and its remnants levels significantly increase the risk of atherosclerosis and cardiovascular disease development. Accumulation of over-synthesized TRLs in plasma, impaired function of enzymes involved in TRLs lipolysis, and impaired hepatic clearance of cholesterol-rich TRLs remnants can lead to arterial deposition of TRLs and its remnants, promoting foam cell formation and arterial wall inflammation. Therefore, understanding the pathogenesis of TRLs-induced AS and targeting it therapeutically could slow or impede AS progression, thereby reducing cardiovascular disease morbidity and mortality, particularly coronary atherosclerotic heart disease.

TB impairs DNA repair.

A Mycobacterium tuberculosis virulence factor promotes foam cell formation by inhibiting DNA repair.

SLAMF7 Promotes Foam Cell Formation of Macrophage by Suppressing NR4A1 Expression During Carotid Atherosclerosis.

Macrophage-derived lipid-laden foam cells from the subendothelium play a crucial role in the initiation and progression of atherosclerosis. However, the molecule mechanism that regulates the formation of foam cells is not completely understood. Here, we found that SLAMF7 was upregulated in mice bone marrow-derived macrophages and RAW264.7 cells stimulated with oxidized low-density lipoprotein (ox-LDL). SLAMF7 promoted ox-LDL-mediated macrophage lipid accumulation and M1-type polarization. SLAMF7 deficiency reduced serum lipid levels and improved the lesions area of carotid plaque and aortic arch in high-fat diet-fed ApoE-/- mice. In response to ox-LDL, SLAMF7 downregulated NR4A1 and upregulated RUNX3 through transcriptome sequencing analysis. Overexpression NR4A1 reversed SLAMF7-induced lipid uptake and M1 polarization via inhibiting RUNX3 expression. Furthermore, RUNX3 enhanced foam cell formation and M1-type polarization. Taken together, the study suggested that SLAMF7 play contributing roles in the pro-atherogenic effects by regulating NR4A1-RUNX3.

Hepatic steatosis aggravates atherosclerosis via small extracellular vesicle-mediated inhibition of cellular cholesterol efflux

While it is recognized that non-alcoholic fatty liver disease (NAFLD) is associated with cardiovascular disease (CVD), how NAFLD affects the development and progression of CVD remains unclear and debatable. Hence, we aimed to determine the role of steatotic hepatocyte-derived small extracellular vesicles (sEVs) in foam cell formation and atherosclerosis progression. sEVs from steatotic hepatocytes were isolated and characterized. MicroRNA (miRNA) deep sequencing was utilized to identify functional miRNA in sEVs. Lastly, we conducted a cross-sectional study on patients with NAFLD to validate these findings. Treatment of sEVs from steatotic hepatocytes promoted macrophage-derived foam cell formation and atherosclerosis progression via inhibition of ABCA1-mediated cholesterol efflux. Macrophage-specific deletion of Abca1 in ApoE-/- mice abolished the role of steatotic hepatocyte-derived sEVs in atherosclerosis progression. In addition, hepatocyte-specific deletion of Rab27a, which is the key GTPase regulating sEV release, significantly ameliorated high-fat, high-cholesterol diet-induced atherosclerosis progression in ApoE-/- mice. The miRNA deep sequencing results showed that miR-30a-3p was enriched in sEVs from steatotic hepatocytes. miR-30a-3p directly targeted the 3' untranslated region of ABCA1 to inhibit ABCA1 expression and cholesterol efflux. Treatment with antagomiR-30a-3p significantly attenuated atherosclerosis progression in high-fat, high-cholesterol diet-fed ApoE-/- mice. Moreover, serum sEVs from patients with NAFLD and sEV-miR-30a-3p expression were associated with decreased cholesterol efflux levels in foam cells. Steatotic hepatocyte-derived sEVs promote foam cell formation and facilitate atherogenesis via the miR-30a-3p/ABCA1 axis. Reducing sEV secretion by steatotic hepatocytes or targeting miR-30a-3p may be potential therapeutic approaches to slow the progression of NAFLD-driven atherosclerosis. The presence of hepatic steatosis is strongly correlated with the risk of cardiovascular disease and cardiovascular events, yet the molecular mechanisms linking steatosis to progression of atherosclerosis are unclear. Herein, we identified small extracellular vesicles from steatotic hepatocytes as a trigger that accelerated the progression of atherosclerosis. Steatotic hepatocyte-derived small extracellular vesicles promoted foam cell formation via the miR-30a-3p/ABCA1 axis. Our findings not only provide mechanistic insight into non-alcoholic fatty liver disease-driven atherosclerosis but also provide potential therapeutic targets for patients with atherosclerosis.

Lysophosphatidylglucoside/GPR55 signaling promotes foam cell formation in human M2c macrophages

Atherosclerosis is a major cause of cerebral and cardiovascular diseases. Intravascular plaques, a well-known pathological finding of atherosclerosis, have a necrotic core composed of macrophages and dead cells. Intraplaque macrophages, which are classified into various subtypes, play key roles in maintenance of normal cellular microenvironment. Excessive uptake of oxidized low-density lipoprotein causes conversion of macrophages to foam cells, and consequent progression/exacerbation of atherosclerosis. G-protein-coupled receptor 55 (GPR55) signaling has been reported to associate with atherosclerosis progression. We demonstrated recently that lysophosphatidylglucoside (lysoPtdGlc) is a specific ligand of GPR55, although in general physiological ligands of GPR55 are poorly understood. Phosphatidylglucoside is expressed on human monocytes and can be converted to lysoPtdGlc. In the present study, we examined possible involvement of lysoPtdGlc/GPR55 signaling in foam cell formation. In monocyte-derived M2c macrophages, lysoPtdGlc/GPR55 signaling inhibited translocation of ATP binding cassette subfamily A member 1 to plasma membrane, and cholesterol efflux. Such inhibitory effect was reversed by GPR55 antagonist ML193. LysoPtdGlc/GPR55 signaling in M2c macrophages was involved in excessive lipid accumulation, thereby promoting foam cell formation. Our findings suggest that lysoPtdGlc/GPR55 signaling is a potential therapeutic target for inhibition of atherosclerosis progression.

A systematic review of the impact of Porphyromonas gingivalis on foam cell formation: Implications for the role of periodontitis in atherosclerosis

BackgroundThe current literature suggests the significant role of foam cells in the initiation of atherosclerosis through the formation of a necrotic core in atherosclerotic plaques. Moreover, an important periodontal pathogen called Porphyromonas gingivalis (P. gingivalis) is indicated to play a significant role in this regard. Thus, the aim of this systematic review was to comprehensively study the pathways by which P. gingivalis as a prominent bacterial species in periodontal disease, can induce foam cells that would initiate the process of atherosclerosis formation.MethodsAn electronic search was undertaken in three databases (Pubmed, Scopus, and Web of Science) to identify the studies published from January 2000 until March 2023. The risk of bias in each study was also assessed using the QUIN risk of bias assessment tool.ResultsAfter the completion of the screening process, 11 in-vitro studies met the inclusion criteria and were included for further assessments. Nine of these studies represented a medium risk of bias, while the other two had a high risk of bias. All of the studies have reported that P. gingivalis can significantly induce foam cell formation by infecting the macrophages and induction of oxidized low-density lipoprotein (oxLDL) uptake. This process is activated through various mediators and pathways. The most important factors in this regard are the lipopolysaccharide of P. gingivalis and its outer membrane vesicles, as well as the changes in the expression rate of transmembrane lipid transportation channels, including transient receptor potential channel of the vanilloid subfamily 4 (TRPV4), lysosomal integral protein 2 (LIMP2), CD36, etc. The identified molecular pathways involved in this process include but are not limited to NF-κB, ERK1/2, p65.ConclusionBased on the results of this study, it can be concluded that P. gingivalis can effectively promote foam cell formation through various pathogenic elements and this bacterial species can affect the expression rate of various genes and the function of specific receptors in the cellular and lysosomal membranes. However, due to the moderate to high level of risk of bias among the studies, further studies are required in this regard.

IRE1α: from the function to the potential therapeutic target in atherosclerosis.

Inositol requiring enzyme 1 (IRE1) is generally thought to control the most conserved pathway in the unfolded protein response (UPR). Two isoforms of IRE1, IRE1α and IRE1β, have been reported in mammals. IRE1α is a ubiquitously expressed protein whose knockout shows marked lethality. In contrast, the expression of IRE1β is exclusively restricted in the epithelial cells of the respiratory and gastrointestinal tracts, and IRE1β-knockout mice are phenotypically normal. As research continues to deepen, IRE1α was showed to be tightly linked to inflammation, lipid metabolism regulation, cell death and so on. Growing evidence also suggests an important role for IRE1α in promoting atherosclerosis (AS) progression and acute cardiovascular events through disrupting lipid metabolism balance, facilitating cells apoptosis, accelerating inflammatory responses and promoting foam cell formation. In addition, IRE1α was recognized as novel potential therapeutic target in AS prevention. This review provides some clues about the relationship between IRE1α and AS, hoping to contribute to further understanding roles of IRE1α in atherogenesis and to be helpful for the design of novel efficacious therapeutics agents targeting IRE1α-related pathways.

Macrophage Gpx4 deficiency aggravates foam cell formation by regulating the expression of scavenger receptors, ABCA1, and ABCG1.

Macrophage-derived foam cell formation is critical for the initiation and development of atherosclerosis, which contributes to atherosclerotic cardiovascular disease (ASCVD). Glutathione peroxidase 4 (GPX4), a crucial ferroptosis regulator, protects cells from excessive oxidative stress by neutralizing lipid peroxidation. However, the role of macrophage GPX4 in foam cell formation remains unknown. We reported that oxidized low-density lipoprotein (oxLDL) upregulated GPX4 expression in macrophages. Using the Cre-loxP system, we generated myeloid cell-specific Gpx4 knockout (Gpx4myel-KO ) mice. Bone marrow-derived macrophages (BMDMs) were isolated from WT and Gpx4myel-KO mice and incubated with modified low-density lipoprotein (LDL). We found that Gpx4 deficiency promoted foam cell formation and increased the internalization of modified LDL. Mechanistic studies unveiled that Gpx4 knockout upregulated scavenger receptor type A and LOX-1 expression and downregulated ABCA1 and ABCG1 expression. Collectively, our study lends a novel insight into the role of GPX4 in suppressing macrophage-derived foam cell formation and suggests GPX4 as a promising therapeutic target to interfere with atherosclerosis-related diseases.

KALP BAĞIRSAK EKSENİ

Many interactions play a role in the gut-heart axis. These include intestinal epithelial dysfunction, dysbiosis, butyrate-producing bacteria, bile acids, and intestinal microbe-derived metabolites. In patients with heart failure (HF), mucosal malabsorption, intestinal wall edema and barrier dysfunction develop as a result of microcirculation disorders in the gut due to decreased perfusion, increased congestion and sympathetically mediated vasoconstriction. Toxic, pathogenic, immunogenic and inflammatory factors, through the increase in intestinal permeability as a result of damaged tight junctions in the intestine, pass through the mucosa and reach the systemic circulation, causing local-systemic inflammation. Many factors that cause dysbiosis by changing the intestinal flora, which are frequently seen in HF, lead to bacterial overgrowth, bacterial translocation and formation of many toxic substances, including lipopolysaccharide (LPS), trimethylamine N-oxide (TMAO), p-cresylsulfate (PCS) and indoxyl sulfate (IS). Depending on the increase in intestinal permeability, these toxic substances reach the systemic circulation; it increases the risk of atherosclerosis by playing a role in thrombosis, platelet invasion, foam cell formation and inflammation processes. Decreased levels of butyrate, one of the short-chain fatty acids that have many effects on the gastrointestinal tract, including maintaining intestinal barrier integrity; It promotes foam cell formation, exacerbates dysbiosis, and plays a role in the disruption of intestinal barrier function, causing endotoxins to reach the general circulation. With this review, it is aimed to inform about the physiopathological processes in the gut-heart axis, in the light of the current literature.

Nε-(carboxymethyl)lysine promotes lipid uptake of macrophage via cluster of differentiation 36 and receptor for advanced glycation end products.

Advanced glycation end products (AGEs) are diabetic metabolic toxic products that cannot be ignored. Nε-(carboxymethyl)lysine (CML), a component of AGEs, could increase macrophage lipid uptake, promote foam cell formation, and thereby accelerate atherosclerosis. The receptor for AGEs (RAGE) and cluster of differentiation 36 (CD36) were the receptors of CML. However, it is still unknown whether RAGE and CD36 play key roles in CML-promoted lipid uptake. Our study aimed to explore the role of RAGE and CD36 in CML-induced mac-rophage lipid uptake. In this study, we examined the effect of CML on lipid uptake by Raw264.7 macrophages. After adding 10 mmol/L CML, the lipid accumulation in macro-phages was confirmed by oil red O staining. Expression changes of CD36 and RAGE were detected with immunoblotting and quantitative real-time polymerase chain reaction. The interaction between CML with CD36 and RAGE was verified by immunoprecipitation. We synthesized a novel N-succinimidyl-4-18F-fluorobenzoate-CML radioactive probe. Radioactive receptor-ligand binding assays were performed to test the binding affinity between CML with CD36 and RAGE. The effects of blocking CD36 or RAGE on CML-promoting lipid uptake were also detected. The study revealed that CML significantly promoted lipid uptake by macro-phages. Immunoprecipitation and radioactive receptor-ligand binding assays indicated that CML could specifically bind to both CD36 and RAGE. CML had a higher affinity for CD36 than RAGE. ARG82, ASN71, and THR70 were the potential interacting amino acids that CD36 binds to CML Anti-CD36 and anti-RAGE could block the uptake of CML by macrophages. The lipid uptake promotion effect of CML was significantly attenuated after blocking CD36 or RAGE. Our results suggest that the binding of CML with CD36 and RAGE promotes macrophage lipid uptake.

Contribution of Trimethylamine N-Oxide (TMAO) to Chronic Inflammatory and Degenerative Diseases.

Trimethylamine N-oxide (TMAO) is a metabolite produced by the gut microbiota and has been mainly associated with an increased incidence of cardiovascular diseases (CVDs) in humans. There are factors that affect one's TMAO level, such as diet, drugs, age, and hormones, among others. Gut dysbiosis in the host has been studied recently as a new approach to understanding chronic inflammatory and degenerative diseases, including cardiovascular diseases, metabolic diseases, and Alzheimer's disease. These disease types as well as COVID-19 are known to modulate host immunity. Diabetic and obese patients have been observed to have an increase in their level of TMAO, which has a direct correlation with CVDs. This metabolite is attributed to enhancing the inflammatory pathways through cholesterol and bile acid dysregulation, promoting foam cell formation. Additionally, TMAO activates the transcription factor NF-κB, which, in turn, triggers cytokine production. The result can be an exaggerated inflammatory response capable of inducing endoplasmic reticulum stress, which is responsible for various diseases. Due to the deleterious effects that this metabolite causes in its host, it is important to search for new therapeutic agents that allow a reduction in the TMAO levels of patients and that, thus, allow patients to be able to avoid a severe cardiovascular event. The present review discussed the synthesis of TMAO and its contribution to the pathogenesis of various inflammatory diseases.

Administration of an LXR agonist promotes atherosclerotic lesion remodelling in murine inflammatory arthritis.

The leading cause of mortality in patients with rheumatoid arthritis is atherosclerotic cardiovascular disease (CVD). We have shown that murine arthritis impairs atherosclerotic lesion regression, because of cellular cholesterol efflux defects in haematopoietic stem and progenitor cells (HSPCs), causing monocytosis and impaired atherosclerotic regression. Therefore, we hypothesised that improving cholesterol efflux using a Liver X Receptor (LXR) agonist would improve cholesterol efflux and improve atherosclerotic lesion regression in arthritis. Ldlr -/- mice were fed a western-type diet for 14 weeks to initiate atherogenesis, then switched to a chow diet to induce lesion regression and divided into three groups; (1) control, (2) K/BxN serum transfer inflammatory arthritis (K/BxN) or (3) K/BxN arthritis and LXR agonist T0901317 daily for 2 weeks. LXR activation during murine inflammatory arthritis completely restored atherosclerotic lesion regression in arthritic mice, evidenced by reduced lesion size, macrophage abundance and lipid content. Mechanistically, serum from arthritic mice promoted foam cell formation, demonstrated by increased cellular lipid accumulation in macrophages and paralleled by a reduction in mRNA of the cholesterol efflux transporters Abca1, Abcg1 and Apoe. T0901317 reduced lipid loading and increased Abca1 and Abcg1 expression in macrophages exposed to arthritic serum and increased ABCA1 levels in atherosclerotic lesions of arthritic mice. Moreover, arthritic clinical score was also attenuated with T0901317. Taken together, we show that the LXR agonist T0901317 rescues impaired atherosclerotic lesion regression in murine arthritis because of enhanced cholesterol efflux transporter expression and reduced foam cell development in atherosclerotic lesions.

The effect of ox-LDL and platelets on macrophages, M2 macrophage polarization, and foam cell formation.

The accumulation of oxidized LDL (ox-LDL) in macrophages in association with platelet activity leads to the formation of foam cells, which play a key role in the pathophysiology of atherosclerosis and coronary artery diseases (CAD). Here, in this study, we aimed to investigate the simultaneous effect of ox-LDL and platelets on foam cell formation, as well as modification in cell markers. First, the U937, a human monocytic cell line, was cultured in RPMI-1640. Then, isolated platelets were co-cultured with the U937 and exposed to ox-LDL (80 µg/ml) to evaluate the impact of ox-LDL on foam cell formation using Oil red O (ORO) staining. Also, the expression of foam cells' surface markers and CD36, ABCA1, SR-B1, ACAT1, and LXRα genes, which are involved in macrophage metabolism and ox-LDL uptake, was measured by flow cytometry and real-time PCR, respectively. Our findings suggest that platelets promoted foam cell formation (ORO-positive cells), accompanied by a higher level of CD163+ M2 macrophages. Furthermore, the expression of CD36, ABCA1, SR-B1, ACAT1, and LXRα genes, which are implicated in cholesterol accumulation in macrophages, was significantly upregulated in the ox-LDL+ platelets group compared to the control (P < 0.05). Moreover, the up-regulation of CD36, ABCA1, and SR-B1 genes in the ox-LDL+ platelets group was more accentuated compared to the ox-LDL group (P < 0.05). Owing to the positive effector role of platelets in the formation of foam cells and CD163+ cells, it could be assumed that platelets play a dual role in the development of these cells.

MiR-186-5p Dysregulation in Serum Exosomes from Patients with AMI Aggravates Atherosclerosis via Targeting LOX-1.

The formation of macrophage-derived foam cells via the uptake of modified lipoproteins is a pivotal development event in atherosclerosis. It has been reported that clinical and experimental myocardial infarction could accelerate atherosclerosis. Several studies have suggested the critical role of exosomes in cardiovascular diseases. However, the role of exosomes from patients with acute myocardial infarction (AMI) patients in atherogenesis remains unclear. Serum exosomes from AMI patients (AMI-Exo) and control individuals (Con-Exo) were isolated and characterized. These exosomes were studied in vitro and in vivo to determine their impact on macrophage foaming and atherogenesis. Our results showed that AMI-Exo promoted foam cell formation in oxidized low-density lipoprotein (ox-LDL)-treated macrophages and progression of atherosclerosis in high-fat/cholesterol diet-fed ApoE-/- mice together with a significantly upregulated levels of lectin-like ox-LDL receptor-1 (LOX-1). The miR-186-5p was found to be downregulated in AMI-Exo and macrophages administered with AMI-Exo. Moreover, serum exosomal miR-186-5p achieved high diagnostic performance for AMI. Luciferase reporter assay indicated that miR-186-5p directly inhibited LOX-1. The endogenous or exogenous miR-186-5p deficiency enhanced lipid accumulation by upregulating LOX-1, whereas miR-186-5p mimics had a reverse effect. In conclusion, the current findings suggest that dysregulated miR-186-5p in AMI-Exo may explain the contribution of acute ischemia events to the advancement of atherosclerosis by enhancing macrophage foaming via its target, LOX-1.

Abstract 15024: High Concentration Mineral Oil, Corn Oil and Their Constitutive Fatty Acids Do Not Influence Low-Density Lipoprotein (LDL) Oxidation Rates in vitro

Introduction: LDL transports dietary long chain fatty acids, constituents that may influence rates of lipid oxidation. Modified LDL promotes foam cell formation during atherosclerosis. The omega-3 fatty acid (n3-FA) eicosapentaenoic acid (EPA) administered as icosapent ethyl (IPE), reduced cardiovascular events in REDUCE-IT compared to mixed n3-FAs in similar high-risk patients (STRENGTH). Some have attributed these discordant outcomes, in part, to placebo choice (mineral versus corn oil) despite very limited oral absorption. We compared the effects of these oils and various FAs on rates of LDL oxidation at supra-pharmacologic doses. Methods: LDL was isolated from human plasma by isopycnic centrifugation, separated into test samples of 100 μg/mL before being incubated at 37°C for 30 min with pharmaceutical grade mineral or corn oil at high concentrations (100 μg/mL) that are comparable to treatment achieved n3-FAs (4 g/d) that have high oral absorption. We also tested FAs contained in these oils, including stearic acid (18:0), arachidic acid (20:0), and linoleic acid (18:2, n-6) as well as ascorbic acid (10 μM) and a water-soluble analog of vitamin E (Trolox, 10 μM) as controls. All samples then underwent copper-induced oxidation (20 μM) monitored by formation of malondialdehyde (MDA). Results: MDA formation increased from 0.28 ± 0.03 to 9.96 ± 0.58 μM ( p &lt;0.001) with vehicle treatment from 0-2 h. Addition of either mineral or corn oil at 100 μg/mL did not significantly influence rates of MDA formation at 2 h (0.02% and 1.93% change vs vehicle, respectively). Nor did we observe any antioxidant activity with constituent FAs stearic acid, arachidic acid, or linoleic acid, FAs with no or two double bonds. As antioxidant controls, ascorbic acid and Trolox both reduced LDL oxidation by 93% and 94% (0.71 ± 0.11 and 0.62 ± 0.04 to 9.96 ± 0.58 μM, p &lt;0.001) after 2 h. Conclusions: Neither mineral nor corn oils affected LDL oxidation even at supra-pharmacologic concentrations. Beyond poor oral absorption, mineral oil and its constituent fatty acids did not affect LDL oxidation, a property related to mechanisms of atherosclerosis.