Interleukin-38 in atherosclerosis.

Chronic inflammation caused by immune cells and their mediators is a characteristic of atherosclerosis. Interleukin-38 (IL-38), a member of the IL-1 family, exerts multiple anti-inflammatory effects via specific ligand-receptor interactions. Upon recognizing a specific receptor, IL-38 restrains mitogen-activated protein kinase (MAPK), nuclear factor kappa B (NK-κB), or other inflammation-related signaling pathways in inflammatory disease. Further research has shown that IL-38 also displays anti-atherosclerotic effects and reduces the occurrence and risk of cardiovascular events. On the one hand, IL-38 can regulate innate and adaptive immunity to inhibit inflammation, reduce pathological neovascularization, and inhibit apoptosis. On the other hand, it can curb obesity, reduce hyperlipidemia, and restrain insulin resistance to reduce cardiovascular disease risk. Therefore, this article expounds on the vital function of IL-38 in the development of atherosclerosis to provide a theoretical basis for further in-depth studies of IL-38 and insights on the prophylaxis and treatment of atherosclerosis.

MicroRNA-134 Promotes the Development of Atherosclerosis Via the ANGPTL4/LPL Pathway in Apolipoprotein E Knockout Mice.

AIMS: Atherosclerosis is the most common cause of cardiovascular disease, such as myocardial infarction and stroke. Previous study revealed that microRNA (miR)-134 promotes lipid accumulation and proinflammatory cytokine secretion through angiopoietin-like 4 (ANGPTL4)/lipid lipoprotein (LPL) signaling in THP-1 macrophages. METHODS: ApoE KO male mice on a C57BL/6 background were fed a high-fat/high-cholesterol Western diet, from 8 to 16 weeks of age. Mice were divided into four groups, and received a tail vein injection of miR-134 agomir, miR-134 antagomir, or one of the corresponding controls, respectively, once every 2 weeks after starting the Western diet. After 8 weeks we measured aortic atherosclerosis, LPL Activity, mRNA and protein levels of ANGPTL4 and LPL, LPL/ low-density lipoprotein receptor related protein 1 Complex Formation, proinflammatory cytokine secretion and lipid levels. RESULTS: Despite this finding, the influence of miR-134 on atherosclerosis in vivo remains to be determined. Using the well-characterized mouse atherosclerosis model of apolipoprotein E knockout, we found that systemic delivery of miR-134 agomir markedly enhanced the atherosclerotic lesion size, together with a significant increase in proinflammatory cytokine secretion and peritoneal macrophages lipid contents. Moreover, overexpression of miR-134 decreased ANGPTL4 expression but increased LPL expression and activity in both aortic tissues and peritoneal macrophages, which was accompanied by increased formation of LPL/low-density lipoprotein receptor-related protein 1 complexes in peritoneal macrophages. However, an opposite effect was observed in response to miR-134 antagomir. CONCLUSIONS: These findings suggest that miR-134 accelerates atherogenesis by promoting lipid accumulation and proinflammatory cytokine secretion via the ANGPTL4/LPL pathway. Therefore, targeting miR-134 may offer a promising strategy for the prevention and treatment of atherosclerotic cardiovascular disease.

MicroRNA-182 Promotes Lipoprotein Lipase Expression and Atherogenesisby Targeting Histone Deacetylase 9 in Apolipoprotein E-Knockout Mice.

BACKGROUND: Lipoprotein lipase (LPL) expressed in macrophages plays an important role in promoting the development of atherosclerosis or atherogenesis. MicroRNA-182 (miR-182) is involved in the regulation of lipid metabolism and inflammation. However, it remains unclear how miR-182 regulates LPL and atherogenesis.Methods and Results:Using bioinformatics analyses and a dual-luciferase reporter assay, we identified histone deacetylase 9 (HDAC9) as a target gene of miR-182. Moreover, miR-182 upregulated LPL expression by directly targetingHDAC9in THP-1 macrophages. Hematoxylin-eosin (H&E), Oil Red O and Masson's trichrome staining showed that apolipoprotein E (ApoE)-knockout (KO) mice treated with miR-182 exhibited more severe atherosclerotic plaques. Treatment with miR-182 increased CD68 and LPL expression in atherosclerotic lesions in ApoE-KO mice, as indicated by double immunofluorescence staining in the aortic sinus. Increased miR-182-induced increases in LPL expression in ApoE-KO mice was confirmed by real-time quantitative polymerase chain reaction and western blotting analyses. Treatment with miR-182 also increased plasma concentrations of proinflammatory cytokines and lipids in ApoE-KO mice. CONCLUSIONS: The results of the present study suggest that miR-182 upregulates LPL expression, promotes lipid accumulation in atherosclerotic lesions, and increases proinflammatory cytokine secretion, likely through targetingHDAC9, leading to an acceleration of atherogenesis in ApoE-KO mice.

Advanced oxidation protein products exacerbates lipid accumulation and atherosclerosis through downregulation of ATP-binding cassette transporter A1 and G1 expression in apolipoprotein E knockout mice.

BACKGROUND: Both clinical data and basic science studies suggest that advanced oxidation protein products (AOPPs) may contribute to the progression of atherosclerosis. The aim of this study was to investigate the effects of AOPPs on ATP-binding cassette transporter (ABC) A1 and ABCG1 expression, lipid accumulation and atherosclerotic lesions in apolipoprotein E knockout (apoE-KO) mice. METHODS AND RESULTS: Male 8-week-old apoE-KO mice were fed a high-fat/high-cholesterol diet. Mice received intraperitoneal injections of AOPPs (5 mg/kg) and/or Janus Kinase (JAK) inhibitor AG-490 (5 mg/kg) once every other day for 8 weeks. As shown in our data, AOPPs increased lipid levels of plasma, and promoted advanced lesions in the aortic regions in apoE-KO mice. The ABCA1, ABCG1 and liver X receptor alpha (LXRα) expression were downregulated in apoE-KO mice treated with AOPPs, whereas the lesions in the aortas were decreased, and the ABCA1, ABCG1 and LXRα expression were upregulated in mice treated with AOPPs plus AG-490, compared to the mice treated with AOPPs only. The ABCA1 and LXRα expressions of aortas, liver and intestine were downregulated in the AOPPs group, while the expressions were upregulated in the AOPPs-plus-AG-490 group when compared to the AOPPs group. The same results can be also observed in peritoneal macrophages. CONCLUSIONS: AOPPs increase accumulation of lipids and exacerbate atherosclerosis through downregulation of ABCA1 and ABCG1 expression, and the JAK-LXRα signaling pathway in apoE-KO mice.

MicroRNA-19b promotes macrophage cholesterol accumulation and aortic atherosclerosis by targeting ATP-binding cassette transporter A1.

RATIONALE: Macrophage accumulation of cholesterol leads to foam cell formation which is a major pathological event of atherosclerosis. Recent studies have shown that microRNA (miR)-19b might play an important role in cholesterol metabolism and atherosclerotic diseases. Here, we have identified miR-19b binding to the 3'UTR of ATP-binding cassette transporter A1 (ABCA1) transporters, and further determined the potential roles of this novel interaction in atherogenesis. OBJECTIVE: To investigate the molecular mechanisms involved in a miR-19b promotion of macrophage cholesterol accumulation and the development of aortic atherosclerosis. METHODS AND RESULTS: We performed bioinformatics analysis using online websites, and found that miR-19b was highly conserved during evolution and directly bound to ABCA1 mRNA with very low binding free energy. Luciferase reporter assay confirmed that miR-19b bound to 3110-3116 sites within ABCA1 3'UTR. MiR-19b directly regulated the expression levels of endogenous ABCA1 in foam cells derived from human THP-1 macrophages and mouse peritoneal macrophages (MPMs) as determined by qRT-PCR and western blot. Cholesterol transport assays revealed that miR-19b dramatically suppressed apolipoprotein AI-mediated ABCA1-dependent cholesterol efflux, resulting in the increased levels of total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) as revealed by HPLC. The excretion of (3)H-cholesterol originating from cholesterol-laden MPMs into feces was decreased in mice overexpressing miR-19b. Finally, we evaluated the proatherosclerotic role of miR-19b in apolipoprotein E deficient (apoE(-/-)) mice. Treatment with miR-19b precursor reduced plasma high-density lipoprotein (HDL) levels, but increased plasma low-density lipoprotein (LDL) levels. Consistently, miR-19b precursor treatment increased aortic plaque size and lipid content, but reduced collagen content and ABCA1 expression. In contrast, treatment with the inhibitory miR-19b antisense oligonucleotides (ASO) prevented or reversed these effects. CONCLUSION: MiR-19b promotes macrophage cholesterol accumulation, foam cell formation and aortic atherosclerotic development by targeting ABCA1.

MicroRNA-590 attenuates lipid accumulation and pro-inflammatory cytokine secretion by targeting lipoprotein lipase gene in human THP-1 macrophages.

BACKGROUND: Accumulating evidence suggests that microRNA-590 (miR-590) has protective effects on cardiovascular diseases, but the mechanism is unknown. Interestingly, previous studies from our laboratory and others have shown that macrophage-derived lipoprotein lipase (LPL) might accelerate atherosclerosis by promoting lipid accumulation and inflammatory response. However, the regulation of LPL at the post-transcriptional level by microRNAs has not been fully understood. In this study, we explored whether miR-590 affects the expression of LPL and its potential subsequent effects on lipid accumulation and pro-inflammatory cytokine secretion in human THP-1 macrophages. METHODS AND RESULTS: Using bioinformatics analyses and dual-luciferase reporter assays, we found that miR-590 directly inhibited LPL protein and mRNA expression by targeting LPL 3'UTR. LPL Activity Assays showed that miR-590 reduced LPL activity in the culture media. Oil Red O staining and high-performance liquid chromatography assays showed that miR-590 had inhibitory effects on the lipid accumulation in human THP-1 macrophages. We also illustrated that miR-590 alleviated pro-inflammatory cytokine secretion in human THP-1 macrophages as measured by ELISA. With the method of small interfering RNA, we found that LPL siRNA can inhibit the miR-590 inhibitor-induced increase in lipid accumulation and secretion of pro-inflammatory cytokines in oxLDL-treated human THP-1 macrophages. CONCLUSIONS: MiR-590 attenuates lipid accumulation and pro-inflammatory cytokine secretion by targeting LPL gene in human THP-1 macrophages. Therefore, targeting miR-590 may offer a promising strategy to treat atherosclerotic cardiovascular diseases.

Chlamydia pneumoniae negatively regulates ABCA1 expression via TLR2-Nuclear factor-kappa B and miR-33 pathways in THP-1 macrophage-derived foam cells.

OBJECTIVES: ATP-binding cassette transporter A1 (ABCA1) is critical in exporting cholesterol from macrophages and plays a protective role in the development of atherosclerosis. This study was to determine the effects and potential mechanisms of Chlamydia pneumoniae (C. pneumoniae) on ABCA1 expression and cellular cholesterol efflux in THP-1 macrophage-derived foam cells. METHODS AND RESULTS: C. pneumoniae significantly decreased the expression of ABCA1 and reduced cholesterol efflux. Furthermore, we found that C. pneumoniae suppressed ABCA1 expression via up-regulation of miR-33s. The inhibition of C. pneumoniae-induced NF-κB activation decreased miR-33s expression and enhanced ABCA1 expression. In addition, C. pneumoniae increased Toll-like receptor 2 (TLR2) expressions, inhibition of which by siRNA could also block NF-κB activation and miR-33s expression, and promot the expression of ABCA1. CONCLUSION: Taken together, these results reveal that C. pneumoniae may negatively regulate ABCA1 expression via TLR2-NF-κB and miR-33 pathways in THP-1 macrophage-derived foam cells, which may provide new insights for understanding the effects of C. pneumoniae on the pathogenesis of atherosclerosis.

MicroRNA-27a/b regulates cellular cholesterol efflux, influx and esterification/hydrolysis in THP-1 macrophages.

RATIONALE: Macrophage cholesterol homeostasis maintenance is the result of a balance between influx, endogenous synthesis, esterification/hydrolysis and efflux. Excessive accumulation of cholesterol leads to foam cell formation, which is the major pathology of atherosclerosis. Previous studies have shown that miR-27 (miR-27a and miR-27b) may play a key role in the progression of atherosclerosis. OBJECTIVE: We set out to investigate the molecular mechanisms of miR-27a/b in intracellular cholesterol homeostasis. METHODS AND RESULTS: In the present study, our results have shown that the miR-27 family is highly conserved during evolution, present in mammals and directly targets the 3' UTR of ABCA1, LPL, and ACAT1. apoA1, ABCG1 and SR-B1 lacking miR-27 bind sites should not be influenced by miR-27 directly. miR-27a and miR-27b directly regulated the expression of endogenous ABCA1 in different cells. Treatment with miR-27a and miR-27b mimics reduced apoA1-mediated cholesterol efflux by 33.08% and 44.61% in THP-1 cells, respectively. miR-27a/b also regulated HDL-mediated cholesterol efflux in THP-1 macrophages and affected the expression of apoA1 in HepG2 cells. However, miR-27a/b had no effect on total cellular cholesterol accumulation, but regulated the levels of cellular free cholesterol and cholesterol ester. We further found that miR-27a/b regulated the expression of LPL and CD36, and then affected the ability of THP-1 macrophages to uptake Dil-oxLDL. Finally, we identified that miR-27a/b regulated cholesterol ester formation by targeting ACAT1 in THP-1 macrophages. CONCLUSION: These findings indicate that miR-27a/b affects the efflux, influx, esterification and hydrolysis of cellular cholesterol by regulating the expression of ABCA1, apoA1, LPL, CD36 and ACAT1.

The effects of miR-467b on lipoprotein lipase (LPL) expression, pro-inflammatory cytokine, lipid levels and atherosclerotic lesions in apolipoprotein E knockout mice.

Atherosclerosis is a lipid disorder disease characterized by chronic blood vessel wall inflammation driven by the subendothelial accumulation of macrophages. Studies have shown that lipoprotein lipase (LPL) participates in lipid metabolism, but it is not yet known whether post-transcriptional regulation of LPL gene expression by microRNAs (miRNAs) occurs in vivo. Here, we tested that miR-467b provides protection against atherosclerosis by regulating the target gene LPL which leads to reductions in LPL expression, lipid accumulation, progression of atherosclerosis and production of inflammatory cytokines in apolipoprotein E knockout (apoE(-/-)) mice. Treatment of apoE(-/-) mice with intra-peritoneal injection of miR-467b agomir led to decreased blood plasma levels of total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-1ß and monocyte chemotactic protein-1 (MCP-1). Using Western blots and real time PCR, we determined that LPL expression in aorta and abdominal cavity macrophages were significantly down-regulated in the miR-467b agomir group. Furthermore, systemic treatment with miR-467b antagomir accelerated the progression of atherosclerosis in the aorta of apoE(-/-) mice. The present study showed that miR-467b protects apoE(-/-) mice from atherosclerosis by reducing lipid accumulation and inflammatory cytokine secretion via downregulation of LPL expression. Therefore, targeting miR-467b may offer a promising strategy to treat atherosclerotic vascular disease.

Apelin and its receptor APJ in cardiovascular diseases.

Apelin is an adipokine that has been identified as an endogenous ligand for the orphan receptor APJ. Apelin and APJ are expressed in a diverse range of tissues with particular preponderance for the heart and vasculature. Apelin has powerful positive inotropic actions and causes endothelium- and nitric oxide-dependent vasodilatation. Growing evidence shows that apelin/APJ system functions as a critical mediator of cardiovascular homeostasis and is involved in the pathophysiology of cardiovascular diseases. Targeting apelin/APJ axis produces protection against cardiovascular diseases. In the current review we have summarized recent data concerning the role and therapeutic potential of apelin/APJ in several major cardiovascular diseases. An increased understanding of the cardiovascular actions of apelin/APJ system will help to develop novel therapeutic interventions for cardiovascular diseases.

MicroRNA-467b targets LPL gene in RAW 264.7 macrophages and attenuates lipid accumulation and proinflammatory cytokine secretion.

LPL (lipoprotein lipase) is a rate-limiting enzyme involved in the hydrolysis of triglycerides. Previous studies have shown that microRNA (miR)-467b regulates hepatic LPL expression and plays a role in the progression of steatosis or abnormal lipid retention in obese mice. Macrophage-derived LPL has been shown to promote atherosclerosis. However, if miR-476b influences macrophage LPL expression and the subsequent effects are unknown. Here, we utilized oxLDL-treatment RAW 264.7 macrophages that were transfected with miR-467b mimics or inhibitors to investigate the potential roles of macrophage miR-476b. We found that miR-467b significantly decreased lipid accumulation and IL-6, IL-1ß, TNF-α and MCP-1 secretions. Furthermore, our studies suggested an additional explanation for the regulatory mechanism of miR-467b on its functional target, LPL in RAW 264.7 macrophages. Thus, our findings indicate that miR-467b may regulate lipid accumulation and proinflammatory cytokine secretion in oxLDL-stimulated RAW 264.7 macrophages by targeting the LPL gene.

[Current progress in lipoprotein lipase and atherosclerosis].

Lipoprotein lipase (LPL) which is the rate-limiting enzyme for the hydrolysis of the triglyceride (TG) core of circulating TG-rich lipoproteins, chylomicrons, low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL) play an important role in reducing TG deposition in vivo. Recent advances indicate that LPL gene structure, synthesis, secretion and degradation had complexity, and it is regulated by many transcription factors, miRNA, interactive proteins and hormonal. Its role in atherosclerosis in the current studies is still controversial. So we focus the LPL on the structure, synthesis and degradation, function, regulation and contribution to atherosclerosis to clarify its role in cardiovascular disease (CVD).