Role and therapeutic potential of gelsolin in atherosclerosis.

Atherosclerosis is the major pathophysiological basis of a variety of cardiovascular diseases and has been recognized as a lipid-driven chronic inflammatory disease. Gelsolin (GSN) is a member of the GSN family. The main function of GSN is to cut and seal actin filaments to regulate the cytoskeleton and participate in a variety of biological functions, such as cell movement, morphological changes, metabolism, apoptosis and phagocytosis. Recently, more and more evidences have demonstrated that GSN is Closely related to atherosclerosis, involving lipid metabolism, inflammation, cell proliferation, migration and thrombosis. This article reviews the role of GSN in atherosclerosis from inflammation, apoptosis, angiogenesis and thrombosis.

CTRP1: A novel player in cardiovascular and metabolic diseases.

Cardiovascular diseases (CVDs) are a series of diseases induced by inflammation and lipid metabolism disorders, among others. Metabolic diseases can cause inflammation and abnormal lipid metabolism. C1q/TNF-related proteins 1 (CTRP1) is a paralog of adiponectin that belongs to the CTRP subfamily. CTRP1 is expressed and secreted in adipocytes, macrophages, cardiomyocytes, and other cells. It promotes lipid and glucose metabolism but has bidirectional effects on the regulation of inflammation. Inflammation can also inversely stimulate CTRP1 production. A vicious circle may exist between the two. This article introduces CTRP1 from the structure, expression, and different roles of CTRP1 in CVDs and metabolic diseases, to summarize the role of CTRP1 pleiotropy. Moreover, the proteins which may interact with CTRP1 are predicted through GeneCards and STRING, speculating their effects, to provide new ideas for the study of CTRP1.

Microtubule affinity regulating kinase 4: A promising target in the pathogenesis of atherosclerosis.

Microtubule affinity regulating kinase 4 (MARK4), an important member of the serine/threonine kinase family, regulates the phosphorylation of microtubule-associated proteins and thus modulates microtubule dynamics. In human atherosclerotic lesions, the expression of MARK4 is significantly increased. Recently, accumulating evidence suggests that MARK4 exerts a proatherogenic effect via regulation of lipid metabolism (cholesterol, fatty acid, and triglyceride), inflammation, cell cycle progression and proliferation, insulin signaling, and glucose homeostasis, white adipocyte browning, and oxidative stress. In this review, we summarize the latest findings regarding the role of MARK4 in the pathogenesis of atherosclerosis to provide a rationale for future investigation and therapeutic intervention.

ABCA1, ABCG1, and Cholesterol Homeostasis.

Cholesterol is a major component of mammalian cell membranes and plays important structural and functional roles. However, excessive cholesterol accumulation is toxic to cells and constitutes the molecular basis for many diseases, especially atherosclerotic cardiovascular disease. Thus, cellular cholesterol is tightly regulated to maintain a homeostasis. Reverse cholesterol transport (RCT) is thought to be one primary pathway to eliminate excessive cholesterol from the body. The first and rate-limiting step of RCT is ATP-binding cassette (ABC) transports A1 (ABCA1)- and ABCG1-dependent cholesterol efflux. In the process, ABCA1 mediates initial transport of cellular cholesterol to apolipoprotein A-I (apoA-I) for forming nascent high-density lipoprotein (HDL) particles, and ABCG1 facilitates subsequent continued cholesterol efflux to HDL for further maturation. In this chapter, we summarize the roles of ABCA1 and ABCG1 in maintaining cellular cholesterol homoeostasis and discuss the underlying mechanisms by which they mediate cholesterol export.

Zinc finger E-box binding homeobox 1 and atherosclerosis: New insights and therapeutic potential.

Zinc finger E-box binding homeobox 1 (ZEB1), an important transcription factor belonging to the ZEB family, plays a crucial role in regulating gene expression required for both normal physiological and pathological processes. Accumulating evidence has shown that ZEB1 participates in the initiation and progression of atherosclerotic cardiovascular disease. Recent studies suggest that ZEB1 protects against atherosclerosis by regulation of endothelial cell angiogenesis, endothelial dysfunction, monocyte-endothelial cell interaction, macrophage lipid accumulation, macrophage polarization, monocyte-vascular smooth muscle cell (VSMC) interaction, VSMC proliferation and migration, and T cell proliferation. In this review, we summarize the recent progress of ZEB1 in the pathogenesis of atherosclerosis and provide insights into the prevention and treatment of atherosclerotic cardiovascular disease.

Astragalin Retards Atherosclerosis by Promoting Cholesterol Efflux and Inhibiting the Inflammatory Response via Upregulating ABCA1 and ABCG1 Expression in Macrophages.

ABSTRACT: Lipid metabolism disorder and inflammatory response are considered to be the major causes of atherosclerogenesis. Astragalin, the most important functional component of flavonoid obtained from persimmon leaves, has the hypolipidemic effects. However, it is unknown, how astragalin protects against atherosclerosis. The aim of this study was to observe the effects of astragalin on cholesterol efflux and inflammatory response and to explore the underlying mechanisms. Our results showed that astragalin upregulated the expression of ATP-binding cassette transporters A1 and G1 (ABCA1 and ABCG1), promoted cholesterol efflux, and suppressed foam cell formation. Inhibition of the PPARγ/LXRα pathway abrogated the promotive effects of astragalin on both transporter expression and cholesterol efflux. In addition, treatment of astragalin markedly decreased the secretion of inflammatory factors, including interleukin 6, monocyte chemotactic protein 1, tumor necrosis factor α, and interleukin 1ß. Mechanistically, astragalin upregulated ABCA1 and ABCG1 expression, which in turn reduced TLR4 surface levels and inhibited NF-κB nuclear translocation. Consistently, astragalin reduced atherosclerotic plaque area in apoE-/- mice. Taken together, these findings suggest that astragalin protects against atherosclerosis by promoting ABCA1- and ABCG1-mediated cholesterol efflux and inhibiting proinflammatory mediator release.

Myristica fragrans promotes ABCA1 expression and cholesterol efflux in THP-1-derived macrophages.

Myristica fragrans is a traditional herbal medicine and has been shown to alleviate the development of atherosclerosis. However, the anti-atherogenic mechanisms of M. fragrans are still to be addressed. In this study, we explored the effect of M. fragrans on lipid metabolism and inflammation and its mechanisms in THP-1-derived macrophages. The quantitative polymerase chain reaction and western blot analysis results showed that M. fragrans promotes cholesterol efflux from THP-1-derived macrophages and reduces intracellular total cholesterol, cholesterol ester, and free cholesterol contents in a dose- and a time-dependent manner. Further study found that liver X receptor alpha (LXRα) antagonist GGPP significantly blocked the upregulation of ABCA1 expression with M. fragrans treatment. In addition, chromatin immunoprecipitation assay confirmed that GATA binding protein 3 (GATA3) can bind to the LXRα promoter, and inhibition of GATA3 led to the downregulation of LXRα and ATP-binding cassette subfamily A member 1 expression. Furthermore, M. fragrans reduced lipid accumulation, followed by decreasing tumor necrosis factor-α, interleukin (IL)-6, and IL-1ß and increasing IL-10 produced by THP-1-derived macrophages. Therefore, M. fragrans is identified as a valuable therapeutic medicine for atherosclerotic cardiovascular disease.

The Long Noncoding RNA Metastasis-Associated Lung Adenocarcinoma Transcript-1 Regulates CCDC80 Expression by Targeting miR-141-3p/miR-200a-3p in Vascular Smooth Muscle Cells.

OBJECTIVE: Our previous study showed that Coiled-Coil Domain Containing 80 (CCDC80) accelerates the development of atherosclerosis by decreasing lipoprotein lipase (LPL) expression and activity in apoE knockout mice. However, the regulatory mechanism for CCDC80 expression is unclear. This study was designed to evaluate whether noncoding RNAs involved the regulation of CCDC80 expression in vascular smooth muscle cells. METHODS AND RESULTS: Bioinformatics prediction and luciferase reporter gene results showed that miR-141-3p/200a-3p bound to the 3'UTR of CCDC80. Furthermore, miR-141-3p/200a-3p mimics decreased the expression of CCDC80 but increased LPL expression. Opposite results were observed with miR-141-3p/200a-3p inhibitors. We also found that lncRNA metastasis-associated lung adenocarcinoma transcript-1 (MALAT1) interacted with the sequences of miR-141-3p/200a-3p and decreased their expression. RT-qPCR and western blotting results showed that MALAT1 overexpression increased CCDC80 expression and decreased LPL expression, while MALAT1 knockdown displayed an opposite phenotype. The effects of both MALAT1 overexpression and knockdown were blocked by miR-141-3p/200a-3p mimics or inhibitors. CONCLUSIONS: Thus, we demonstrated that lncRNA MALAT1 regulates CCDC80 and LPL expression through miR-141-3p/200a-3p.

The antiatherogenic function of kallistatin and its potential mechanism.

Atherosclerosis is the pathological basis of most cardiovascular diseases, the leading cause of morbidity and mortality worldwide. Kallistatin, originally discovered in human serum, is a tissue-kallikrein-binding protein and a unique serine proteinase inhibitor. Upon binding to its receptor integrin ß3, lipoprotein receptor-related protein 6, nucleolin, or Krüppel-like factor 4, kallistatin can modulate various signaling pathways and affect multiple biological processes, including angiogenesis, inflammatory response, oxidative stress, and tumor growth. Circulating kallistatin levels are significantly decreased in patients with coronary artery disease and show an inverse correlation with its severity. Importantly, both in vitro and in vivo experiments have demonstrated that kallistatin reduces atherosclerosis by inhibiting vascular inflammation, antagonizing endothelial dysfunction, and improving lipid metabolism. Thus, kallistatin may be a novel biomarker and a promising therapeutic target for atherosclerosis-related diseases. In this review, we focus on the antiatherogenic function of kallistatin and its potential mechanism.

Interleukin-5 promotes ATP-binding cassette transporter A1 expression through miR-211/JAK2/STAT3 pathways in THP-1-dervied macrophages.

Interleukin-5 (IL-5) is manifested as its involvement in the process of atherosclerosis, but the mechanism is still unknown. In this study, we explored the effect of IL-5 on lipid metabolism and its underlying mechanisms in THP-1-derived macrophages. The quantitative polymerase chain reaction (qPCR) and western blot analysis results showed that IL-5 significantly up-regulated ATP-binding cassette transporter A1 (ABCA1) expression in a dose-dependent and time-dependent manner. [3H]-labeled cholesterol was used to assess the levels of cholesterol efflux, and the results showed that IL-5 increased ABCA1-mediated cholesterol efflux. A high-performance liquid chromatography assay indicated that cellular cholesterol content was decreased by IL-5 treatment in THP-1-derived macrophages. The selective inhibitor and small interfering RNA were used to block the Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) pathway. The results of the qPCR and western blot analysis showed that IL-5 activated JAK2/STAT3 pathway to up-regulate ABCA1 expression. Meanwhile, IL-5 reduced the expression level of miR-211. Furthermore, we found that JAK2 is a target gene of miR-211 and miR-211 mimic inhibited the expression of JAK2 and reduced the levels of p-STAT3 and ABCA1 as revealed by luciferase reporter assay, qPCR and western blot analysis. In summary, these findings indicated that IL-5 promotes ABCA1 expression and cholesterol efflux through the miR-211/JAK2/STAT3 signaling pathway in THP-1-derived macrophages.

CXCL12 promotes atherosclerosis by downregulating ABCA1 expression via the CXCR4/GSK3ß/ß-cateninT120/TCF21 pathway.

CXC chemokine ligand 12 (CXCL12) is a member of the CXC chemokine family and mainly acts on cell chemotaxis. CXCL12 also elicits a proatherogenic role, but the molecular mechanisms have not been fully defined yet. We aimed to reveal if and how CXCL12 promoted atherosclerosis via regulating lipid metabolism. In vitro, our data showed that CXCL12 could reduce ABCA1 expression, and it mediated cholesterol efflux from THP-1-derived macrophages to apoA-I. Data from the luciferase reporter gene and chromatin immunoprecipitation assays revealed that transcription factor 21 (TCF21) stimulated the transcription of ABCA1 via binding to its promoter region, which was repressed by CXCL12. We found that CXCL12 increased the levels of phosphorylated glycogen synthase kinase 3ß (GSK3ß) and the phosphorylation of ß-catenin at the Thr120 position. Inactivation of GSK3ß or ß-catenin increased the expression of TCF21 and ABCA1. Further, knockdown or inhibition of CXC chemokine receptor 4 (CXCR4) blocked the effects of CXCL12 on TCF21 and ABCA1 expression and the phosphorylation of GSK3ß and ß-catenin. In vivo, the overexpression of CXCL12 in Apoe-/- mice via lentivirus enlarged the atherosclerotic lesion area and increased macrophage infiltration in atherosclerotic plaques. We further found that the overexpression of CXCL12 reduced the efficiency of reverse cholesterol transport and plasma HDL-C levels, decreased ABCA1 expression in the aorta and mouse peritoneal macrophages (MPMs), and suppressed cholesterol efflux from MPMs to apoA-I in Apoe-/- mice. Collectively, these findings suggest that CXCL12 interacts with CXCR4 and then activates the GSK-3ß/ß-cateninT120/TCF21 signaling pathway to inhibit ABCA1-dependent cholesterol efflux from macrophages and aggravate atherosclerosis. Targeting CXCL12 may be a novel and promising strategy for the prevention and treatment of atherosclerotic cardiovascular diseases.

Nobiletin reduces LPL-mediated lipid accumulation and pro-inflammatory cytokine secretion through upregulation of miR-590 expression.

Nobiletin has protective effects on cardiovascular diseases, but the mechanism is not clear. In this study, we examined whether nobiletin affects the expression of miR-590/LPL and its relative effects on lipid accumulation and pro-inflammatory cytokine secretion in human THP-1 macrophages. RT-qPCR analysis showed that nobiletin increased the expression of miR-590. Western blot analysis showed that nobiletin-suppressed LPL expression was enhanced by miR-590 mimic and abrogated by miR-590 inhibitor. Oil Red O staining and high-performance liquid chromatography assays showed that nobiletin attenuated lipid accumulation in macrophages. Treatment with nobiletin and miR-590 mimic decreased cellular lipid accumulation, whereas treatment with miR-590 inhibitor increased cellular lipid accumulation. ELISA illustrated that nobiletin alleviated pro-inflammatory cytokine secretion in macrophages as measured by, which was reduced by miR-590 mimic and increased by miR-590 inhibitor. In conclusion, nobiletin may alleviate lipid accumulation and secretion of pro-inflammatory cytokines by enhancing the inhibitory effect of miR-590 on LPL expression, suggesting a promising strategy for potential drug development for atherosclerosis.

Itaconate: an emerging determinant of inflammation in activated macrophages.

Macrophages play a central role in innate immunity as the first line of defense against pathogen infection. Upon exposure to inflammatory stimuli, macrophages rapidly respond and subsequently undergo metabolic reprogramming to substantially produce cellular metabolites such as itaconate. As a derivate of the tricarboxylic acid cycle, itaconate is derived from the decarboxylation of cis-aconitate mediated by immunoresponsive gene 1 in the mitochondrial matrix. It is well known that itaconate has a direct antimicrobial effect by inhibiting isocitrate lyase. Strikingly, two recent studies published in Nature showed that itaconate markedly decreases the production of proinflammatory mediators in lipopolysaccharide-treated macrophages and ameliorates sepsis and psoriasis in animal models, revealing a novel biological action of itaconate beyond its regular roles in antimicrobial defense. The mechanism for this anti-inflammatory effect has been proposed to involve the inhibition of succinate dehydrogenase, blockade of IκBζ translation and activation of Nrf2. These intriguing discoveries provide a new explanation for how macrophages are switched from a pro- to an anti-inflammatory state to limit the damage and facilitate tissue repair under proinflammatory conditions. Thus, the emerging effect of itaconate as a crucial determinant of macrophage inflammation has important implications in further understanding cellular immunometabolism and developing future therapeutics for the treatment of inflammatory diseases. In this review, we focus on the roles of itaconate in controlling the inflammatory response during macrophage activation, providing a rationale for future investigation and therapeutic intervention.

IL-8 negatively regulates ABCA1 expression and cholesterol efflux via upregulating miR-183 in THP-1 macrophage-derived foam cells.

OBJECTIVE: Previous studies suggest that IL-8 has an important role in the regulation of cholesterol efflux, but whether miRNAs are involved in this process is still unknown. The purpose of this study is to explore whether IL-8 promotes cholesterol accumulation by enhancing miR-183 expression in macrophages and its underlying mechanism. METHODS AND RESULTS: Treatment of THP-1 macrophage-derived foam cells with IL-8 decreased ABCA1 expression and cholesterol efflux. Using bioinformatics analyses and dual-luciferase reporter assays, we found that miR-183 was highly conserved during evolution and directly inhibited ABCA1 protein and mRNA expression by targeting ABCA1 3'UTR. MiR-183 directly regulated endogenous ABCA1 expression levels. Furthermore, IL-8 enhanced the expression of miR-183 and decrease ABCA1 expression. Cholesterol transport assays confirmed that IL-8 dramatically inhibited apolipoprotein AI-mediated ABCA1-dependent cholesterol efflux by increasing miR-183 expression. In contrast, treatment with anti-IL-8 antibody reversed these effects. CONCLUSION: IL-8 enhances the expression of miR-183, which then inhibits ABCA1 expression and cholesterol efflux. Our studies suggest that the IL-8-miR-183-ABCA1 axis may play an intermediary role in the development of atherosclerosis.

Pregnancy-Associated Plasma Protein-A Accelerates Atherosclerosis by Regulating Reverse Cholesterol Transport and Inflammation.

BACKGROUND: Recent studies have suggested that pregnancy-associated plasma protein-A (PAPP-A) is involved in the pathogenesis of atherosclerosis. This study aim is to investigate the role and mechanisms of PAPP-A in reverse cholesterol transport (RCT) and inflammation during the development of atherosclerosis. Methods and Results: PAPP-A was silenced in apolipoprotein E (apoE-/-) mice with administration of PAPP-A shRNA. Oil Red O staining of the whole aorta root revealed that PAPP-A knockdown reduced lipid accumulation in aortas. Oil Red O, hematoxylin and eosin (HE) and Masson staining of aortic sinus further showed that PAPP-A knockdown alleviated the formation of atherosclerotic lesions. It was found that PAPP-A knockdown reduced the insulin-like growth factor 1 (IGF-1) levels and repressed the PI3K/Akt pathway in both aorta and peritoneal macrophages. The expression levels of LXRα, ABCA1, ABCG1, and SR-B1 were increased in the aorta and peritoneal macrophages from apoE-/-mice administered with PAPP-A shRNA. Furthermore, PAPP-A knockdown promoted RCT from macrophages to plasma, the liver, and feces in apoE-/-mice. In addition, PAPP-A knockdown elevated the expression and secretion of monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), tumor necrosis factor-α, and interleukin-1ß through the nuclear factor kappa-B (NF-κB) pathway. CONCLUSIONS: The present study results suggest that PAPP-A promotes the development of atherosclerosis in apoE-/-mice through reducing RCT capacity and activating an inflammatory response.

Sortilin promotes macrophage cholesterol accumulation and aortic atherosclerosis through lysosomal degradation of ATP-binding cassette transporter A1 protein.

Sortilin is closely associated with hyperlipidemia and the risk of atherosclerosis (AS). The role of sortilin and the underlying mechanism in peripheral macrophage are not fully understood. In this study, we investigated the effect of macrophage sortilin on ATP-binding cassette transporter A1 (ABCA1) expression, ABCA1-mediated cholesterol efflux, and aortic AS. Macrophage sortilin expression was upregulated by oxidized low-density lipoproteins (ox-LDLs) in both concentration- and time-dependent manners. Its expression reached the peak level when cells were incubated with 50 µg/ml ox-LDL for 24 h. Overexpression of sortilin in macrophage reduced cholesterol efflux, leading to an increase in intracellular total cholesterol, free cholesterol, and cholesterol ester. Sortilin was found to bind with ABCA1 protein and suppress macrophage ABCA1 expression, resulting in a decrease in cholesterol efflux from macrophages. The inhibitory effect of sortilin in cholesterol efflux was partially reversed by treatment with chloroquine, a lysosomal inhibitor. On the contrary, the ABCA1 protein level and ABCA1-mediated cholesterol efflux is increased by sortilin short hairpin RNA transfection. The fecal and biliary cholesterol 3H-sterol from cholesterol-laden mouse peritoneal macrophage was reduced by sortilin overexpression through lentivirus vector (LV)-sortilin in low-density lipoprotein receptor knockout mice, which was prevented by co-treatment with chloroquine. Treatment with LV-sortilin reduced plasma high-density lipoprotein and increased plasma ox-LDL levels. Accordingly, aortic lipid deposition and plaque area were exacerbated, and ABCA1 expression was reduced in mice in response to infection with LV-sortilin alone. These effects of LV-sortilin were partially reversed by chloroquine. Sortilin enhances lysosomal degradation of ABCA1 protein and suppresses ABCA1-mediated cholesterol efflux from macrophages, leading to foam cell formation and AS development.

Visceral adipose tissue-derived serine protease inhibitor accelerates cholesterol efflux by up-regulating ABCA1 expression via the NF-κB/miR-33a pathway in THP-1 macropahge-derived foam cells.

Atherosclerosis is a dyslipidemia disease characterized by foam cell formation driven by the accumulation of lipids. Visceral adipose tissue-derived serine protease inhibitor (vaspin) is known to suppress the development of atherosclerosis via its anti-inflammatory properties, but it is not yet known whether vaspin affects cholesterol efflux in THP-1 macrophage-derived foam cells. Here, we investigated the effects of vaspin on ABCA1 expression and cholesterol efflux, and further explored the underlying mechanism. We found that vaspin decreased miR-33a levels, which in turn increased ABCA1 expression and cholesteorl efflux. We also found that inhibition of NF-κB reduced miR-33a expression and vaspin suppressed LPS-mediated NF-κB phosphorylation. Our findings suggest that vaspin is not only a regular of inflammasion but also a promoter of cholesterol efflux.

Heat shock protein 70 accelerates atherosclerosis by downregulating the expression of ABCA1 and ABCG1 through the JNK/Elk-1 pathway.

BACKGROUND AND AIMS: Recent studies have suggested that heat shock protein 70 (HSP70) may play critical roles in cardiovascular disease. However, the effects of HSP70 on the development of atherosclerosis in apoE-/- mice remain largely unknown. This study was to investigate the role and potential mechanism of HSP70 in atherosclerosis. METHODS: HSP70 was overexpressed in apoE-/- mice and THP-1-derived macrophages with lentiviral vectors. Oil Red O, hematoxylin-eosin, and Masson staining were performed to evaluate atherosclerotic plaque in apoE-/- mice fed the Western type diet. Moreover, immunostaining was employed to detect the expression of relative proteins in aortic sinus. Reporter gene and chromatin immunoprecipitation were performed to analyze the effect of Elk-1 on the promoter activity of ABCA1 and ABCG1; [3H] labeled cholesterol was used to assess the capacity of cholesterol efflux and reverse cholesterol transport (RCT). RESULTS: Our results showed that HSP70 increased lipid accumulation in arteries and promoted the formation of atherosclerotic lesion. The capacity of cholesterol efflux was reduced in peritoneal macrophages isolated from HSP70-overexpressed apoE-/- mice. The levels of ABCA1 and ABCG1 expression were also reduced in the peritoneal macrophages and the aorta from apoE-/- mice in response to HSP70. The c-Jun N-terminal kinase (JNK) and ETS transcription factor (Elk-1) played a critical role in HSP70-induced downregulation ABCA1 and ABCG1. Further, HSP70 reduced RCT from macrophages to plasma, liver, and feces in apoE-/- mice. CONCLUSIONS: HSP70 promotes the progression of atherosclerosis in apoE-/- mice by suppressing the expression of ABCA1 and ABCG1 through the JNK/Elk-1 pathway.

ApoA-1 Mimetic Peptide ELK-2A2K2E Decreases Inflammatory Factor Levels Through the ABCA1-JAK2-STAT3-TTP Axis in THP-1-Derived Macrophages.

OBJECTIVE: The aim of this study was to determine whether the apolipoprotein A-1 (apoA-1) mimetic peptide ELK-2A2K2E regulates inflammatory cytokine expression through activating the adenosine triphosphate-binding cassette transporter A1 (ABCA1)-janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3)-tristetraprolin (TTP) signaling pathway in THP-1 macrophage-derived foam cells. METHODS AND RESULTS: The cells were treated with the apoA-1 mimetic peptide ELK-2A2K2E at different concentrations (0, 20, 40, and 80 µg/mL) or incubated with ELK-2A2K2E (40 µg/mL) for different times (0, 6, 12, and 24 hours). Our results showed that the levels of the cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1), were decreased at both concentration- and time-dependent manners. When the cells were exposed to lipopolysaccharides and actinomycin D, ELK-2A2K2E significantly decreased the mRNA stability of inflammatory cytokines at different time points (0, 30, 60, and 120 minutes) by increasing TTP expression as analyzed by real-time quantitative polymerase chain reaction. The effect of ELK-2A2K2E on TTP was obviously blocked by the inhibition of the JAK-STAT3 pathway. Furthermore, we found that ELK-2A2K2E activated the JAK-STAT3-TTP pathway through the upregulation of ABCA1 and then decreased inflammatory cytokine expression. CONCLUSIONS: ApoA-I mimetic peptide ELK-2A2K2E increases the degradation of TNF-α, IL-6, and MCP-1 mRNA and reduces the levels of inflammatory cytokines through activating the JAK2-STAT3-TTP signaling pathway that is dependent on the upregulation of ABCA1.

Apolipoprotein A-1 Binding Protein Inhibits Inflammatory Signaling Pathways by Binding to Apolipoprotein A-1 in THP-1 Macrophages.

BACKGROUND: It has previously been demonstrated that apolipoprotein A-1 (apoA-1) binding protein (AIBP) promotes apoA-1 binding to ATP-binding cassette transporter A1 (ABCA1) and prevents ABCA1 protein degradation so as to inhibit foam cell formation. Because apoA-1 inhibits inflammatory signaling pathways, whether AIBP has an inhibitory effect on inflammatory signaling pathways in THP-1-derived macrophages is investigated.Methods and Results:Analysis of inflammation-related gene expression indicated that AIBP decreased lipopolysaccharide (LPS)-mediated macrophage inflammation. AIBP significantly prevented NF-κB nuclear translocation. Further, AIBP prevented the activation of mitogen-activated protein kinases (MAPKs), including p38 MAPK, extracellular-signal regulated kinase and c-Jun N-terminal kinase. AIBP decreased MyD88 expression at both mRNA and protein levels, but did not have any effect on TLR4 expression. Moreover, treatment with both AIBP and apoA-1 decreased the abundance of TLR4 in the lipid raft fraction. AIBP lacking 115-123 amino acids (∆115-123), however, did not have such effects as described for intact AIBP. In addition, knockdown of ABCA1 inhibited the effects of AIBP on inflammatory factor secretion. CONCLUSIONS: These results suggest that AIBP inhibits inflammatory signaling pathways through binding to apoA-1 and stabilizing ABCA1, and subsequent alteration of lipid rafts and TLR4 in the cell membrane.