MicroRNA-20a/b regulates cholesterol efflux through post-transcriptional repression of ATP-binding cassette transporter A1

C1q/Tumor Necrosis Factor-Related Protein-9 Enhances Macrophage Cholesterol Efflux and Improves Reverse Cholesterol Transport via AMPK Activation

Cholesterol efflux from foam cells in atherosclerotic plaques is crucial for reverse cholesterol transport (RCT), an important antiatherogenic event. ATP-binding cassette (ABC) transporters, ABCA1 and ABCG1, are key receptors in the cholesterol efflux pathway. C1q/tumor necrosis factor-related protein-9 (CTRP9) is a newly discovered adipokine and exhibits an atheroprotective activity. However, the role of CTRP9 in RCT still remains unknown. In this work, we investigated the effect of subcutaneous administration of CTRP9 protein on RCT and atherosclerotic lesion formation in ApoE-/- mice fed with a high-fat diet. CTRP9-dependent regulation of cholesterol efflux and ABC transporters in RAW 264.7 foam cells was determined. Our results showed that CTRP9 protein decreased atherosclerotic lesions, increased cholesterol efflux, and upregulated liver ABCA1 and ABCG1 expression in ApoE-/- mice. CTRP9 treatment dose-dependently increased mRNA and protein expression of ABCA1, ABCG1, and LXR-α in RAW 264.7 foam cells. Moreover, the expression and phosphorylation of AMPK was potentiated upon CTRP9 treatment. Notably, CTRP9-induced cholesterol efflux and upregulation of ABCA, ABCG1, and LXR-α were impaired when AMPK was knocked down. AMPK depletion restored cholesterol accumulation in CTRP9-treated RAW 264.7 cells. Taken together, subcutaneous injection is an effective novel delivery route for CTRP9 protein, and exogenous CTRP9 can facilitate cholesterol efflux and promote RCT in an animal model of atherosclerosis. The atheroprotective activity of CTRP9 is mediated through the activation of AMPK signaling.

Salidroside: An Overview of Its Promising Potential and Diverse Applications

Salidroside, a phenolic compound isolated from various Rhodiola plants, is the principal active constituent of Traditional Chinese Medicine known for its adaptogenic properties. Due to the challenging environment of Rhodiola species, such as high altitude, high radiation, drought, and hypoxia, the source of salidroside is scarce. However, numerous studies have shown that salidroside has a range of biological activities, including cardiovascular and central nervous system activity, and anti-hypoxia, anti-inflammatory, and anti-aging activities. Although previous studies have partially summarized the pharmacological effects of salidroside, the overall pharmacological effects have not been analyzed. Hence, this review will systematically summarize the isolation, purification, synthesis, derivatization, pharmacological activity, pharmacokinetics, clinical application, and safety of salidroside. It is expected to provide new insights for the further research and pharmaceutical development of salidroside.

MicroRNA-19a-3p inhibits endothelial dysfunction in atherosclerosis by targeting JCAD

OBJECTIVE

To examine the influences and mechanisms of MicroRNA-19a-3p (miR-19a-3p) on endothelial dysfunction in atherosclerosis.

METHODS

An analysis of miR-19a expression was carried out using the Gene Expression Omnibus (GEO) database. The effect of miR-19a-3p on endothelial function in HUVECs was evaluated by miR-19a-3p overexpression under TNF-α treatment. Luciferase assays were performed to explore the potential target genes. Overexpression of junctional protein associated with coronary artery disease (JCAD) was used to examine the effects of miR-19a-3p on cell adhesion, and proliferation.

RESULTS

MiR-19a-3p expression in endothelial cells decreased after exposure to TNF-α and/or oscillatory flow, consistent with the expression change of miR-19a-3p found in atherosclerotic plaques. Additionally, endothelial cell dysfunction and inflammation were significantly diminished by miR-19a-3p overexpression but markedly exacerbated by miR-19a-3p inhibition. MiR-19a-3p transfection significantly decreased the expression of JCAD by binding to the 3'-UTR of JCAD mRNA. Furthermore, the protective effect of miR-19a-3p against endothelial cell dysfunction and inflammation was achieved by regulating JCAD and was closely linked to the Hippo/YAP signaling pathway.

CONCLUSION

MiR-19a-3p expression is a crucial molecular switch in the onset of atherosclerosis and miR-19a-3p overexpression is a possible pharmacological therapeutic strategy for reversing the development of atherosclerosis.

Cholesterol metabolism: physiological regulation and diseases

Cholesterol homeostasis is crucial for cellular and systemic function. The disorder of cholesterol metabolism not only accelerates the onset of cardiovascular disease (CVD) but is also the fundamental cause of other ailments. The regulation of cholesterol metabolism in the human is an extremely complex process. Due to the dynamic balance between cholesterol synthesis, intake, efflux and storage, cholesterol metabolism generally remains secure. Disruption of any of these links is likely to have adverse effects on the body. At present, increasing evidence suggests that abnormal cholesterol metabolism is closely related to various systemic diseases. However, the exact mechanism by which cholesterol metabolism contributes to disease pathogenesis remains unclear, and there are still unknown factors. In this review, we outline the metabolic process of cholesterol in the human body, especially reverse cholesterol transport (RCT). Then, we discuss separately the impact of abnormal cholesterol metabolism on common diseases and potential therapeutic targets for each disease, including CVD, tumors, neurological diseases, and immune system diseases. At the end of this review, we focus on the effect of cholesterol metabolism on eye diseases. In short, we hope to provide more new ideas for the pathogenesis and treatment of diseases from the perspective of cholesterol.

Functional significance of cholesterol metabolism in cancer: from threat to treatment

Cholesterol is an essential structural component of membranes that contributes to membrane integrity and fluidity. Cholesterol homeostasis plays a critical role in the maintenance of cellular activities. Recently, increasing evidence has indicated that cholesterol is a major determinant by modulating cell signaling events governing the hallmarks of cancer. Numerous studies have shown the functional significance of cholesterol metabolism in tumorigenesis, cancer progression and metastasis through its regulatory effects on the immune response, ferroptosis, autophagy, cell stemness, and the DNA damage response. Here, we summarize recent literature describing cholesterol metabolism in cancer cells, including the cholesterol metabolism pathways and the mutual regulatory mechanisms involved in cancer progression and cholesterol metabolism. We also discuss various drugs targeting cholesterol metabolism to suggest new strategies for cancer treatment.

The emerging crosstalk between atherosclerosis-related microRNAs and Bermuda triangle of foam cells: Cholesterol influx, trafficking, and efflux

In atherosclerosis, the gradual buildup of lipid particles into the sub-endothelium of damaged arteries leads to numerous lipid alterations. The absorption of these modified lipids by monocyte-derived macrophages in the arterial wall leads to cholesterol accumulation and increases the likelihood of foam cell formation and fatty streak, which is an early characteristic of atherosclerosis. Foam cell formation is related to an imbalance in cholesterol influx, trafficking, and efflux. The formation of foam cells is heavily regulated by various mechanisms, among them, the role of epigenetic factors like microRNA alteration in the formation of foam cells has been well studied. Recent studies have focused on the potential interplay between microRNAs and foam cell formation in the pathogenesis of atherosclerosis; nevertheless, there is significant space to progress in this attractive field. This review has focused to examine the underlying processes of foam cell formation and microRNA crosstalk to provide a deep insight into therapeutic implications in atherosclerosis.

TMAO Upregulates Members of the miR-17/92 Cluster and Impacts Targets Associated with Atherosclerosis

Atherosclerosis is a hallmark of cardiovascular disease, and lifestyle strongly impacts its onset and progression. Nutrients have been shown to regulate the miR-17/92 cluster, with a role in endothelial function and atherosclerosis. Choline, betaine, and L-carnitine, found in animal foods, are metabolized into trimethylamine (TMA) by the gut microbiota. TMA is then oxidized to TMAO, which has been associated with atherosclerosis. Our aim was to investigate whether TMAO modulates the expression of the miR-17/92 cluster, along with the impact of this modulation on the expression of target genes related to atherosclerosis and inflammation. We treated HepG-2 cells, THP-1 cells, murine liver organoids, and human peripheral mononuclear cells with 6 µM of TMAO at different timepoints. TMAO increased the expression of all analyzed members of the cluster, except for miR-20a-5p in murine liver organoids and primary human macrophages. Genes and protein levels of SERPINE1 and IL-12A increased. Both have been associated with atherosclerosis and cardiovascular disease (CDVD) and are indirectly modulated by the miR-17-92 cluster. We concluded that TMAO modulates the expression of the miR-17/92 cluster and that such modulation could promote inflammation through IL-12A and blood clotting through SERPINE1 expression, which could ultimately promote atherosclerosis and CVD.

The Role of the miR-17-92 Cluster in Autophagy and Atherosclerosis Supports Its Link to Lysosomal Storage Diseases

Establishing the role of non-coding RNA (ncRNA), especially microRNAs (miRNAs), in the regulation of cell function constitutes a current research challenge. Two to six miRNAs can act in clusters; particularly, the miR-17-92 family, composed of miR-17, miR-18a, miR-19a, miR-20a, miR-19b-1, and miR-92a is well-characterized. This cluster functions during embryonic development in cell differentiation, growth, development, and morphogenesis and is an established oncogenic cluster. However, its role in the regulation of cellular metabolism, mainly in lipid metabolism and autophagy, has received less attention. Here, we argue that the miR-17-92 cluster is highly relevant for these two processes, and thus, could be involved in the study of pathologies derived from lysosomal deficiencies. Lysosomes are related to both processes, as they control cholesterol flux and regulate autophagy. Accordingly, we compiled, analyzed, and discussed current evidence that highlights the cluster's fundamental role in regulating cellular energetic metabolism (mainly lipid and cholesterol flux) and atherosclerosis, as well as its critical participation in autophagy regulation. Because these processes are closely related to lysosomes, we also provide experimental data from the literature to support our proposal that the miR-17-92 cluster could be involved in the pathogenesis and effects of lysosomal storage diseases (LSD).

Downregulation of serum miR-106b: a potential biomarker for Alzheimer disease

Analysis of miRNAs has a strong potential for the identification of novel prognostic or predictive biomarkers in the serum of AD patients. In this study, we investigated the serum levels of miR-106b as a diagnostic biomarker for AD and evaluate its predictive value for therapeutic response to the drug rivastigmine. Patients were divided into either responding (n = 33) or non-responding (n = 23) groups according to rivastigmine treatment and to Mini-Mental State Exam score. The serum concentrations of miR-106b were measured with real-time PCR. Here, we found that miR-106b was significantly down-regulated in the serum samples of AD patients compared with those of controls (p < .001). ROC results showed a specificity of 62% and a sensitivity of 94%. The serum values of miR-106b tended to be positively associated with the therapeutic response but were not significant (p = .15). Taken together, detection of serum miR-106b might be a promising serum biomarker for early diagnosis of AD.

Inflammatory MicroRNAs and the Pathophysiology of Endometriosis and Atherosclerosis: Common Pathways and Future Directions Towards Elucidating the Relationship

Emerging data indicates an association between endometriosis and subclinical atherosclerosis, with women with endometriosis at a higher risk for cardiovascular disease later in life. Inflammation is proposed to play a central role in the pathophysiology of both diseases and elevated levels of systemic pro-inflammatory cytokines including macrophage migration inhibitory factor (MIF), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) are well documented. However, a thorough understanding on the mediators and mechanisms which contribute to altered cytokine expression in both diseases remain poorly understood. MicroRNAs (miRNAs) are important post-transcriptional regulators of inflammatory pathways and numerous studies have reported altered circulating levels of miRNAs in both endometriosis and atherosclerosis. Potential contribution of miRNA-mediated inflammatory cascades common to the pathophysiology of both diseases has not been evaluated but could offer insight into common pathways and early manifestation relevant to both diseases which may help understand cause and effect. In this review, we discuss and summarize differentially expressed inflammatory circulating miRNAs in endometriosis subjects, compare this profile to that of circulating levels associated with atherosclerosis when possible, and then discuss mechanistic studies focusing on these miRNAs in relevant cell, tissue, and animal models. We conclude by discussing the potential utility of targeting the relevant miRNAs in the MIF-IL-6-TNF-α pathway as therapeutic options and offer insight into future studies which will help us better understand not only the role of these miRNAs in the pathophysiology of both endometriosis and atherosclerosis but also commonality between both diseases.

Regulation of ABCA1 by AMD-Associated Genetic Variants and Hypoxia in iPSC-RPE

Age-related macular degeneration (AMD) is a progressive disease of the macula characterized by atrophy of the retinal pigment epithelium (RPE) and photoreceptor degeneration, leading to severe vision loss at advanced stages in the elderly population. Impaired reverse cholesterol transport (RCT) as well as intracellular lipid accumulation in the RPE are implicated in AMD pathogenesis. Here, we focus on ATP-binding cassette transporter A1 (ABCA1), a major cholesterol transport protein in the RPE, and analyze conditions that lead to ABCA1 dysregulation in induced pluripotent stem cell (iPSC)-derived RPE cells (iRPEs). Our results indicate that the risk-conferring alleles rs1883025 (C) and rs2740488 (A) in ABCA1 are associated with increased ABCA1 mRNA and protein levels and reduced efficiency of cholesterol efflux from the RPE. Hypoxia, an environmental risk factor for AMD, reduced expression of ABCA1 and increased intracellular lipid accumulation. Treatment with a liver X receptor (LXR) agonist led to an increase in ABCA1 expression and reduced lipid accumulation. Our data strengthen the homeostatic role of cholesterol efflux in the RPE and suggest that increasing cellular cholesterol export by stimulating ABCA1 expression might lessen lipid load, improving RPE survival and reducing the risk of developing AMD.

Regulatory Non-coding RNAs in Atherosclerosis

Regulatory RNAs like microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) control vascular and immune cells' phenotype and thus play a crucial role in atherosclerosis. Moreover, the mutual interactions between miRNAs and lncRNAs link both types of regulatory RNAs in a functional network that affects lesion formation. In this review, we deduce novel concepts of atherosclerosis from the analysis of the current data on regulatory RNAs' role in endothelial cells (ECs) and macrophages. In contrast to arterial ECs, which adopt a stable phenotype by adaptation to high shear stress, macrophages are highly plastic and quickly change their activation status. At predilection sites of atherosclerosis, such as arterial bifurcations, ECs are exposed to disturbed laminar flow, which generates a dysadaptive stress response mediated by miRNAs. Whereas the highly abundant miR-126-5p promotes regenerative proliferation of dysadapted ECs, miR-103-3p stimulates inflammatory activation and impairs endothelial regeneration by aberrant proliferation and micronuclei formation. In macrophages, miRNAs are essential in regulating energy and lipid metabolism, which affects inflammatory activation and foam cell formation.Moreover, lipopolysaccharide-induced miR-155 and miR-146 shape inflammatory macrophage activation through their oppositional effects on NF-kB. Most lncRNAs are not conserved between species, except a small group of very long lncRNAs, such as MALAT1, which blocks numerous miRNAs by providing non-functional binding sites. In summary, regulatory RNAs' roles are highly context-dependent, and therapeutic approaches that target specific functional interactions of miRNAs appear promising against cardiovascular diseases.

Genomic Variants and Multilevel Regulation of ABCA1, ABCG1, and SCARB1 Expression in Atherogenesis

Atheroprotective properties of human plasma high-density lipoproteins (HDLs) are determined by their involvement in reverse cholesterol transport (RCT) from the macrophage to the liver. ABCA1, ABCG1, and SR-BI cholesterol transporters are involved in cholesterol efflux from macrophages to lipid-free ApoA-I and HDL as a first RCT step. Molecular determinants of RCT efficiency that may possess diagnostic and therapeutic meaning remain largely unknown. This review summarizes the progress in studying the genomic variants of ABCA1, ABCG1, and SCARB1, and the regulation of their function at transcriptional and post-transcriptional levels in atherosclerosis. Defects in the structure and function of ABCA1, ABCG1, and SR-BI are caused by changes in the gene sequence, such as single nucleotide polymorphism or various mutations. In the transcription initiation of transporter genes, in addition to transcription factors, long noncoding RNA (lncRNA), transcription activators, and repressors are also involved. Furthermore, transcription is substantially influenced by the methylation of gene promoter regions. Post-transcriptional regulation involves microRNAs and lncRNAs, including circular RNAs. The potential biomarkers and targets for atheroprotection, based on molecular mechanisms of expression regulation for three transporter genes, are also discussed in this review.

Foam Cells as Therapeutic Targets in Atherosclerosis with a Focus on the Regulatory Roles of Non-Coding RNAs

Atherosclerosis is a major cause of human cardiovascular disease, which is the leading cause of mortality around the world. Various physiological and pathological processes are involved, including chronic inflammation, dysregulation of lipid metabolism, development of an environment characterized by oxidative stress and improper immune responses. Accordingly, the expansion of novel targets for the treatment of atherosclerosis is necessary. In this study, we focus on the role of foam cells in the development of atherosclerosis. The specific therapeutic goals associated with each stage in the formation of foam cells and the development of atherosclerosis will be considered. Processing and metabolism of cholesterol in the macrophage is one of the main steps in foam cell formation. Cholesterol processing involves lipid uptake, cholesterol esterification and cholesterol efflux, which ultimately leads to cholesterol equilibrium in the macrophage. Recently, many preclinical studies have appeared concerning the role of non-encoding RNAs in the formation of atherosclerotic lesions. Non-encoding RNAs, especially microRNAs, are considered regulators of lipid metabolism by affecting the expression of genes involved in the uptake (e.g., CD36 and LOX1) esterification (ACAT1) and efflux (ABCA1, ABCG1) of cholesterol. They are also able to regulate inflammatory pathways, produce cytokines and mediate foam cell apoptosis. We have reviewed important preclinical evidence of their therapeutic targeting in atherosclerosis, with a special focus on foam cell formation.

MicroRNA-320b Modulates Cholesterol Efflux and Atherosclerosis

Aim: ATP-binding cassette (ABC) transporters and endonuclease-exonuclease-phosphatase family domain containing 1 (EEPD1) are reported to regulate cellular cholesterol efflux in macrophages. Bioinformatics analysis has revealed that ABCG1 and EEPD1 might be potential targets of microRNA (miR)-320b. This study aimed to elucidate the roles of miR-320b in cholesterol efflux from macrophages and the pathogenesis of atherosclerosis.

Methods: Microarray was conducted to profile microRNA (miRNA) expression, and quantitative real-time PCR (qPCR) was used to validate the differentially expressed miRNAs in peripheral blood mononuclear cells of coronary artery disease (CAD) patients and healthy controls. Luciferase assay was conducted to evaluate the activity of reporter construct containing the 3´-untranslated region (3´-UTR) of target genes. Besides, NBD-cholesterol efflux induced by high-density lipoprotein (HDL) and lipid-free apolipoprotein A1 (apoA1) was detected using fluorescence intensity, respectively. Apoe^−/− mice were injected with adeno-associated virus (AAV)2-miR-320b or control via tail vein, thereafter fed with 14 week atherogenic diet to study the roles of miR-320b in vivo .

Results: MiR-320b was highly expressed in CAD patients compared with that in the healthy controls in both the microarray analysis and qPCR analysis. In vitro study showed that miR-320b decreased HDL- and apoA1-mediated cholesterol efflux from macrophages partly by directly targeting ABCG1 and EEPD1 genes and partly via suppressing the LXRα-ABCA1/G1 pathway. Consistently, in vivo administration of AAV2-miR-320b into Apoe^−/− mice attenuated cholesterol efflux from peritoneal macrophages, which showed reduced expression of ABCA1/G1 and EEPD1, and increased lipid LDL-C level, with a down-regulation of hepatic LDLR and ABCA1. AAV2-miR-320b treatment also increased atherosclerotic plaque size and lesional macrophage content and enhanced pro-inflammatory cytokines levels through the elevated phosphorylation level of nuclear factor-κB p65 in macrophages.

Conclusion: We identify miR-320b as a novel modulator of macrophage cholesterol efflux and that it might be a promising therapeutic target for atherosclerosis treatment.

MicroRNA regulation of cholesterol metabolism

MicroRNAs are small noncoding RNAs that regulate gene expression at the posttranscriptional level. Since many microRNAs have multiple mRNA targets, they are uniquely positioned to regulate the expression of several molecules and pathways simultaneously. For example, the multiple stages of cholesterol metabolism are heavily influenced by microRNA activity. Understanding the scope of microRNAs that control this pathway is highly relevant to diseases of perturbed cholesterol metabolism, most notably cardiovascular disease (CVD). Atherosclerosis is a common cause of CVD that involves inflammation and the accumulation of cholesterol-laden cells in the arterial wall. However, several different cell types participate in atherosclerosis, and perturbations in cholesterol homeostasis may have unique effects on the specialized functions of these various cell types. Therefore, our review discusses the current knowledge of microRNA-mediated control of cholesterol homeostasis, followed by speculation as to how these microRNA-mRNA target interactions might have distinctive effects on different cell types that participate in atherosclerosis.

Alcoholic and Non-Alcoholic Beer Modulate Plasma and Macrophage microRNAs Differently in a Pilot Intervention in Humans with Cardiovascular Risk

Beer is a popular beverage and some beneficial effects have been attributed to its moderate consumption. We carried out a pilot study to test if beer and non-alcoholic beer consumption modify the levels of a panel of 53 cardiometabolic microRNAs in plasma and macrophages. Seven non-smoker men aged 30–65 with high cardiovascular risk were recruited for a non-randomised cross-over intervention consisting of the ingestion of 500 mL/day of beer or non-alcoholic beer for 14 days with a 7-day washout period between interventions. Plasma and urine isoxanthohumol were measured to assess compliance with interventions. Monocytes were isolated and differentiated into macrophages, and plasma and macrophage microRNAs were analysed by quantitative real-time PCR. Anthropometric, biochemistry and dietary parameters were also measured. We found an increase in plasma miR-155-5p, miR-328-3p, and miR-92a-3p after beer and a decrease after non-alcoholic beer consumption. Plasma miR-320a-3p levels decreased with both beers. Circulating miR-320a-3p levels correlated with LDL-cholesterol. We found that miR-17-5p, miR-20a-5p, miR-145-5p, miR-26b-5p, and miR-223-3p macrophage levels increased after beer and decreased after non-alcoholic beer consumption. Functional analyses suggested that modulated microRNAs were involved in catabolism, nutrient sensing, Toll-like receptors signalling and inflammation. We concluded that beer and non-alcoholic beer intake modulated differentially plasma and macrophage microRNAs. Specifically, microRNAs related to inflammation increased after beer consumption and decreased after non-alcoholic beer consumption.

Inhibition of long non-coding RNA MALAT1 elevates microRNA-429 to suppress the progression of hypopharyngeal squamous cell carcinoma by reducing ZEB1

OBJECTIVE

Hypopharyngeal squamous cell carcinoma (HSCC) is a common type of malignant tumor. Long non-coding RNAs (lncRNAs) are known to participate in HSCC development, while the role of lncRNA MALAT1 in HSCC remains largely unknown. We aimed to explore function of the lncRNA MALAT1/miR-429/ZEB1 axis in HSCC progression.

METHODS

Levels of MALAT1, miR-429 and ZEB1 in HSCC tissues samples were assessed. The FaDu cells were respectively treated with relative sequence or plasmid of MALAT1, miR-429, or ZEB1. Then, CCK-8 assay, colony formation assay, flow cytometry and Transwell assay were used to determine the cell proliferation, apoptosis, cell cycle, migration and invasion of the cells. The PI3K/Akt/mTOR signaling pathway-related proteins, proliferation-related proteins, cell cycle-related proteins, apoptosis-related proteins, and migration-related proteins were detected using Western blot analysis. The cell growth in vivo was observed. The targeting relationships between MALAT1 and miR-429, and between miR-429 and ZEB1 were confirmed.

RESULTS

MALAT1 and ZEB1 expression in HSCC was upregulated while miR-429 expression was downregulated. Reduced MALAT1 and ZEB1, and upregulated miR-429 inactivated the PI3K/Akt/mTOR signaling pathway, suppressed in vitro viability, colony formation ability, migration and invasion, as well as cell growth in vivo, and promoted the apoptosis of FaDu cells. Downregulated miR-429 reversed the role of MALAT1 inhibition in FaDu cell growth. LncRNA MALAT1 served as a sponge of miR-429, thus regulating ZEB1 expression.

CONCLUSION

Inhibition of MALAT1 was able to elevate miR-429 to suppress the progression of HSCC via reducing ZEB1. Our research provided a potential therapeutic target for HSCC.

The impact of ATP-binding cassette transporters on metabolic diseases

Currently, many people worldwide suffer from metabolic diseases caused by heredity and external factors, such as diet. One of the symptoms of metabolic diseases is abnormal lipid metabolism. ATP binding cassette (ABC) transporters are one of the largest transport protein superfamilies that exist in nearly all living organisms and are mainly located on lipid-processing cells. ABC transporters have been confirmed to be closely related to the pathogenesis of diseases such as metabolic diseases, cancer and Alzheimer's disease based on their transport abilities. Notably, the capability to transport lipids makes ABC transporters critical in metabolic diseases. In addition, gene polymorphism in ABC transporters has been reported to be a risk factor for metabolic diseases, and it has been reported that relevant miRNAs have significant roles in regulating ABC transporters. In this review, we integrate recent studies to examine the roles of ABC transporters in metabolic diseases and aim to build a network with ABC transporters as the core, linking their transport abilities with metabolic and other diseases.

MicroRNA sequences modulating inflammation and lipid accumulation in macrophage “foam” cells: Implications for atherosclerosis

Accumulation of macrophage “foam” cells, laden with cholesterol and cholesteryl ester, within the intima of large arteries, is a hallmark of early “fatty streak” lesions which can progress to complex, multicellular atheromatous plaques, involving lipoproteins from the bloodstream and cells of the innate and adaptive immune response. Sterol accumulation triggers induction of genes encoding proteins mediating the atheroprotective cholesterol efflux pathway. Within the arterial intima, however, this mechanism is overwhelmed, leading to distinct changes in macrophage phenotype and inflammatory status. Over the last decade marked gains have been made in understanding of the epigenetic landscape which influence macrophage function, and in particular the importance of small non-coding micro-RNA (miRNA) sequences in this context. This review identifies some of the miRNA sequences which play a key role in regulating “foam” cell formation and atherogenesis, highlighting sequences involved in cholesterol accumulation, those influencing inflammation in sterol-loaded cells, and novel sequences and pathways which may offer new strategies to influence macrophage function within atherosclerotic lesions.

Lipid efflux mechanisms, relation to disease and potential therapeutic aspects

Lipids are hydrophobic and amphiphilic molecules involved in diverse functions such as membrane structure, energy metabolism, immunity, and signaling. However, altered intra-cellular lipid levels or composition can lead to metabolic and inflammatory dysfunction, as well as lipotoxicity. Thus, intra-cellular lipid homeostasis is tightly regulated by multiple mechanisms. Since most peripheral cells do not catabolize cholesterol, efflux (extra-cellular transport) of cholesterol is vital for lipid homeostasis. Defective efflux contributes to atherosclerotic plaque development, impaired β-cell insulin secretion, and neuropathology. Of these, defective lipid efflux in macrophages in the arterial walls leading to foam cell and atherosclerotic plaque formation has been the most well studied, likely because a leading global cause of death is cardiovascular disease. Circulating high density lipoprotein particles play critical roles as acceptors of effluxed cellular lipids, suggesting their importance in disease etiology. We review here mechanisms and pathways that modulate lipid efflux, the role of lipid efflux in disease etiology, and therapeutic options aimed at modulating this critical process.

Diagnostic and theranostic microRNAs in the pathogenesis of atherosclerosis

MicroRNAs (miRNAs) are a group of small single strand and noncoding RNAs that regulate several physiological and molecular signalling pathways. Alterations of miRNA expression profiles may be involved with pathophysiological processes underlying the development of atherosclerosis and cardiovascular diseases, including changes in the functions of the endothelial cells and vascular smooth muscle cells, such as cell proliferation, migration and inflammation, which are involved in angiogenesis, macrophage function and foam cell formation. Thus, miRNAs can be considered to have a crucial role in the progression, modulation and regulation of every stage of atherosclerosis. Such potential biomarkers will enable us to predict therapeutic response and prognosis of cardiovascular diseases and adopt effective preclinical and clinical treatment strategies. In the present review article, the current data regarding the role of miRNAs in atherosclerosis were summarized and the potential miRNAs as prognostic, diagnostic and theranostic biomarkers in preclinical and clinical studies were further discussed. The highlights of this review are expected to present opportunities for future research of clinical therapeutic approaches in vascular diseases resulting from atherosclerosis with an emphasis on miRNAs.

Brothers in Arms: ABCA1- and ABCG1-Mediated Cholesterol Efflux as Promising Targets in Cardiovascular Disease Treatment

Atherosclerosis is a leading cause of cardiovascular disease worldwide, and hypercholesterolemia is a major risk factor. Preventive treatments mainly focus on the effective reduction of low-density lipoprotein cholesterol, but their therapeutic value is limited by the inability to completely normalize atherosclerotic risk, probably due to the disease complexity and multifactorial pathogenesis. Consequently, high-density lipoprotein cholesterol gained much interest, as it appeared to be cardioprotective due to its major role in reverse cholesterol transport (RCT). RCT facilitates removal of cholesterol from peripheral tissues, including atherosclerotic plaques, and its subsequent hepatic clearance into bile. Therefore, RCT is expected to limit plaque formation and progression. Cellular cholesterol efflux is initiated and propagated by the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. Their expression and function are expected to be rate-limiting for cholesterol efflux, which makes them interesting targets to stimulate RCT and lower atherosclerotic risk. This systematic review discusses the molecular mechanisms relevant for RCT and ABCA1 and ABCG1 function, followed by a critical overview of potential pharmacological strategies with small molecules to enhance cellular cholesterol efflux and RCT. These strategies include regulation of ABCA1 and ABCG1 expression, degradation, and mRNA stability. Various small molecules have been demonstrated to increase RCT, but the underlying mechanisms are often not completely understood and are rather unspecific, potentially causing adverse effects. Better understanding of these mechanisms could enable the development of safer drugs to increase RCT and provide more insight into its relation with atherosclerotic risk. SIGNIFICANCE STATEMENT: Hypercholesterolemia is an important risk factor of atherosclerosis, which is a leading pathological mechanism underlying cardiovascular disease. Cholesterol is removed from atherosclerotic plaques and subsequently cleared by the liver into bile. This transport is mediated by high-density lipoprotein particles, to which cholesterol is transferred via ATP-binding cassette transporters ABCA1 and ABCG1. Small-molecule pharmacological strategies stimulating these transporters may provide promising options for cardiovascular disease treatment.

MicroRNAs as Therapeutic Targets and Clinical Biomarkers in Atherosclerosis

Atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality worldwide. Atherosclerosis develops over several decades and is mediated by a complex interplay of cellular mechanisms that drive a chronic inflammatory milieu and cell-to-cell interactions between endothelial cells, smooth muscle cells and macrophages that promote plaque development and progression. While there has been significant therapeutic advancement, there remains a gap where novel therapeutic approaches can complement current therapies to provide a holistic approach for treating atherosclerosis to orchestrate the regulation of complex signalling networks across multiple cell types and different stages of disease progression. MicroRNAs (miRNAs) are emerging as important post-transcriptional regulators of a suite of molecular signalling pathways and pathophysiological cellular effects. Furthermore, circulating miRNAs have emerged as a new class of disease biomarkers to better inform clinical diagnosis and provide new avenues for personalised therapies. This review focusses on recent insights into the potential role of miRNAs both as therapeutic targets in the regulation of the most influential processes that govern atherosclerosis and as clinical biomarkers that may be reflective of disease severity, highlighting the potential theranostic (therapeutic and diagnostic) properties of miRNAs in the management of cardiovascular disease.

Interplay between Exosomes and Autophagy in Cardiovascular Diseases: Novel Promising Target for Diagnostic and Therapeutic Application

Exosome, is identified as a nature nanocarrier and intercellular messenger that regulates cell to cell communication. Autophagy is critical in maintenance of protein homeostasis by degradation of damaged proteins and organelles. Autophagy and exosomes take pivotal roles in cellular homeostasis and cardiovascular disease. Currently, the coordinated mechanisms for exosomes and autophagy in the maintenance of cellular fitness are now garnering much attention. In the present review, we discussed the interplay of exosomes and autophagy in the context of physiology and pathology of the heart, which might provide novel insights for diagnostic and therapeutic application of cardiovascular diseases.

Potential microRNA-related targets in clearance pathways of amyloid-β: novel therapeutic approach for the treatment of Alzheimer's disease

Imbalance between amyloid-beta (Aβ) peptide synthesis and clearance results in Aβ deregulation. Failure to clear these peptides appears to cause the development of Alzheimer's disease (AD). In recent years, microRNAs have become established key regulators of biological processes that relate among others to the development and progression of neurodegenerative diseases, such as AD. This review article gives an overview on microRNAs that are involved in the Aβ cascade and discusses their inhibitory impact on their target mRNAs whose products participate in Aβ clearance. Understanding of the mechanism of microRNA in the associated signal pathways could identify novel therapeutic targets for the treatment of AD.

Characterization of Redox-Responsive LXR-Activating Nanoparticle Formulations in Primary Mouse Macrophages

Activation of the transcription factor liver X receptor (LXR) has beneficial effects on macrophage lipid metabolism and inflammation, making it a potential candidate for therapeutic targeting in cardiometabolic disease. While small molecule delivery via nanomedicine has promising applications for a number of chronic diseases, questions remain as to how nanoparticle formulation might be tailored to suit different tissue microenvironments and aid in drug delivery. In the current study, we aimed to compare the in vitro drug delivering capability of three nanoparticle (NP) formulations encapsulating the LXR activator, GW-3965. We observed little difference in the base characteristics of standard PLGA-PEG NP when compared to two redox-active polymeric NP formulations, which we called redox-responsive (RR)1 and RR2. Moreover, we also observed similar uptake of these NP into primary mouse macrophages. We used the transcript and protein expression of the cholesterol efflux protein and LXR target ATP-binding cassette A1 (ABCA1) as a readout of GW-3956-induced LXR activation. Following an initial acute uptake period that was meant to mimic circulating exposure in vivo, we determined that although the induction of transcript expression was similar between NPs, treatment with the redox-sensitive RR1 NPs resulted in a higher level of ABCA1 protein. Our results suggest that NP formulations responsive to cellular cues may be an effective tool for targeted and disease-specific drug release.

Bta-miR-152 affects intracellular triglyceride content by targeting the UCP3 gene

According to our previous studies, bta-miR-152, PRKAA1 and UCP3 are differentially expressed in mammary gland tissues of high milk fat and low milk fat cows, and the trend in bta-miR-152 expression is opposite from those of PRKAA1 and UCP3. To further identify the function and regulatory mechanism of bta-miR-152 in milk fat metabolism, we investigated the effect of bta-miR-152 on cellular triglyceride content in bovine mammary epithelial cells cultured in vitro, on the basis of bta-miR-152 overexpression and inhibition assays. The target genes of bta-miR-152 were identified through qPCR, Western blotting and dual luciferase reporter gene detection. Compared with that in the control group, the expression of UCP3 was significantly lower in the bta-miR-152 mimic group, the expression of PRKAA1 was decreased, and the intracellular TAG content was significantly increased. After transfection with bta-miR-152 inhibitor, the expression of UCP3 increased significantly, and the expression of PRKAA1 decreased, but the difference was not significant; in addition, the intracellular TAG content decreased significantly. Therefore, we concluded that bta-miR-152 affects the intracellular TAG content by targeting UCP3.

Role of cholesterol homeostasis and its efflux pathways in cancer progression

Tumor cells show high avidity for cholesterol in order to support their inherent nature to divide and proliferate. This results in the rewiring of cholesterol homeostatic pathways by influencing not only de novo synthesis but also uptake or efflux pathways of cholesterol. Recent findings have pointed towards the importance of cholesterol efflux in tumor pathogenesis. Cholesterol efflux is the first and foremost step in reverse cholesterol transport and any perturbation in this pathway may lead to the accumulation of intracellular cholesterol, thereby altering the cellular equilibrium. This review addresses the different mechanisms of cholesterol efflux from the cell and highlights their role and regulation in context to tumor development. There are four different routes by which cholesterol can be effluxed from the cell namely, 1) passive diffusion of cholesterol to mature HDL particles, 2) SR-B1 mediated facilitated diffusion, 3) Active efflux to apo A1 via ABCA1 and 4) ABCG1 mediated efflux to mature HDL. These molecular players facilitating cholesterol efflux are engaged in a complex interplay with different signaling pathways. Thus, an understanding of the efflux pathways, their regulation and cross-talk with signaling molecules may provide novel prognostic markers and therapeutic targets to combat the onset of carcinogenesis.

Relationship between porcine miR-20a and its putative target low-density lipoprotein receptor based on dual luciferase reporter gene assays

Objective

Mutations in low-density lipoprotein receptor (LDLR), which encodes a critical protein for cholesterol homeostasis and lipid metabolism in mammals, are involved in cardiometabolic diseases, such as familial hypercholesterolemia in pigs. Whereas microRNAs (miRNAs) can control LDLR regulation, their involvement in circulating cholesterol and lipid levels with respect to cardiometabolic diseases in pigs is unclear. We aimed to identify and analyze LDLR as a potential target gene of SSC-miR-20a.

Methods

Bioinformatic analysis predicted that porcine LDLR is a target of SSC-miR-20a. Wild-type and mutant LDLR 3′-untranslated region (UTR) fragments were generated by polymerase chain reaction (PCR) and cloned into the pGL3-Control vector to construct pGL3 Control LDLR wild-3′-UTR and pGL3 Control LDLR mutant-3′-UTR recombinant plasmids, respectively. An miR-20a expression plasmid was constructed by inserting the porcine pre-miR-20a-coding sequence between the HindIII and BamHI sites in pMR-mCherry, and constructs were confirmed by sequencing. HEK293T cells were co-transfected with the miR-20a expression or pMR-mCherry control plasmids and constructs harboring the corresponding 3′-UTR, and relative luciferase activity was determined. The relative expression levels of miR-20a and LDLR mRNA and their correlation in terms of expression levels in porcine liver tissue were analyzed using reverse-transcription quantitative PCR.

Results

Gel electrophoresis and sequencing showed that target gene fragments were successfully cloned, and the three recombinant vectors were successfully constructed. Compared to pMR-mCherry, the miR-20a expression vector significantly inhibited wild-type LDLR-3′-UTR-driven (p<0.01), but not mutant LDLR-3′-UTR-driven (p>0.05), luciferase reporter activity. Further, miR-20a and LDLR were expressed at relatively high levels in porcine liver tissues. Pearson correlation analysis revealed that porcine liver miR-20a and LDLR levels were significantly negatively correlated (r = −0.656, p<0.05).

Conclusion

LDLR is a potential target of miR-20a, which might directly bind the LDLR 3′-UTR to post-transcriptionally inhibit expression. These results have implications in understanding the pathogenesis and progression of porcine cardiovascular diseases.

The long noncoding RNA CHROME regulates cholesterol homeostasis in primate

The human genome encodes thousands of long non-coding RNAs (lncRNAs), the majority of which are poorly conserved and uncharacterized. Here we identify a primate-specific lncRNA (CHROME), elevated in the plasma and atherosclerotic plaques of individuals with coronary artery disease, that regulates cellular and systemic cholesterol homeostasis. LncRNA CHROME expression is influenced by dietary and cellular cholesterol via the sterol-activated liver X receptor transcription factors, which control genes mediating responses to cholesterol overload. Using gain- and loss-of-function approaches, we show that CHROME promotes cholesterol efflux and HDL biogenesis by curbing the actions of a set of functionally related microRNAs that repress genes in those pathways. CHROME knockdown in human hepatocytes and macrophages increases levels of miR-27b, miR-33a, miR-33b and miR-128, thereby reducing expression of their overlapping target gene networks and associated biologic functions. In particular, cells lacking CHROME show reduced expression of ABCA1, which regulates cholesterol efflux and nascent HDL particle formation. Collectively, our findings identify CHROME as a central component of the non-coding RNA circuitry controlling cholesterol homeostasis in humans.

Non-coding RNAs in lipid metabolism

Cardiovascular disease (CVD), the leading cause of death and morbidity in the Western world, begins with lipid accumulation in the arterial wall, which is the initial step in atherogenesis. Alterations in lipid metabolism result in increased risk of cardiometabolic disorders, and treatment of lipid disorders remains the most common strategy aimed at reducing the incidence of CVD. Work done over the past decade has identified numerous classes of non-coding RNA molecules including microRNAs (miRNAs) and long-non-coding RNAs (lncRNAs) as critical regulators of gene expression involved in lipid metabolism and CVD, mostly acting at post-transcriptional level. A number of miRNAs, including miR-33, miR-122 and miR-148a, have been demonstrated to play important role in controlling the risk of CVD through regulation of cholesterol homeostasis and lipoprotein metabolism. lncRNAs are recently emerging as important regulators of lipid and lipoprotein metabolism. However, much additional work will be required to fully understand the impact of lncRNAs on CVD and lipid metabolism, due to the high abundance of lncRNAs and the poor-genetic conservation between species. This article reviews the role of miRNAs and lncRNAs in lipid and lipoprotein metabolism and their potential implications for the treatment of CVD.