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Background: Macrophage-derived foam cells are essential in the progression of atherosclerosis (AS). Based on our previous study, the Huxin Formula (HXF), a traditional Chinese medicine formula, demonstrates potential in anti-atherosclerosis. Nevertheless, it is still unknown how HXF affects the formation of foam cells derived from THP-1 macrophages. Purpose: This research aims to examine the preventive role of HXF in the development of foam cells and its underlying molecular mechanism. Methods: THP-1 derived macrophages and THP-1 cells overexpressing LOX-1 (LV-OLR1) were exposed to ox-LDL to establish foam cell models, and then treated with HXF. Meantime, Oil red O staining was used to detect lipid droplet production. ELISA kit was performed to measure intracellular levels of IL-6 and TGF-β. RT-qPCR and Western Blot were then utilized to determine the LOX-1 and NF-κB mRNA/protein levels. Results: The findings indicated that HXF treatment potently reduced the lipid accumulation, downregulated IL-6 levels and upregulated TGF-β levels. However, this impact was almost reversed when LOX-1 was overexpressed in THP-1 cells stimulated with ox-LDL. Moreover, THP-1 were treated with HXF markedly reduced the levels of LOX-1 and NF-κB mRNA/protein, whereas overexpressing LOX-1 significantly reversed this effect. Conclusion: HXF reduced the formation of foam cell in ox-LDL-stimulated THP-1 macrophages via inhibiting lipid accumulation and inflammation through regulating the LOX-1/ NF-κB pathway. These present findings further indicate a potential beneficial role of HXF in ameliorating atherosclerosis and foam cell formation, while provide a novel potential therapeutic strategy for preventing atherosclerosis. [ABSTRACT FROM AUTHOR]

In our search for bioactive components, various chromatographic separations of the organic fractions from Filipendula glaberrima leaves led to the isolation of a new ellagitannin and a triterpenoid, along with 26 known compounds. The structures of the isolates were determined based on their spectroscopic properties and chemical evidence, which were then evaluated for their antioxidant activities, inhibitory activities on 3-hydroxy-3-methylglutaryl-coenzyme A reductase, and foam cell formation in THP-1 cells to prevent atherosclerosis. Rugosin B methyl ester (1) showed the best HMG-CoA reductase inhibition and significantly reduced ox-low-density lipoprotein-induced THP-1 macrophage-derived foam cell formation at 25 µM. In addition, no cytotoxicity was observed in THP-1 cells at 50 μg/mL of all extracts in the macrophage foam cell formation assay. Therefore, F. glaberrima extract containing 1 is promising in the development of dietary supplements due to its potential behavior as a novel source of nutrients for preventing and treating atherosclerosis. [ABSTRACT FROM AUTHOR]

Abstract Aims Atherosclerosis is a huge threaten to the human health, C1q/TNF‐related protein 9 (CTRP9) has been previously reported possessing vascular protective functions. Our study is aimed to reveal the mechanism of the regulative effects of CTRP9 on the foam cell formation. Methods and results Primary human macrophages were isolated from human monocytes donated by healthy volunteers. CCK‐8 assay was performed for determining the cell viability. Oil Red O staining was employed for measuring the lipid accumulation. Cholesterol ester and cholesterol concentration were detected by commercial kits for evaluating the intracellular cholesterol. Ubiquitination assay was performed to reveal the ubiquitination level of CD36, cycloheximide assay was applied for determining the half‐life of CD36 protein. Quantitative real‐time PCR and western blot assays were performed for detecting the mRNA and protein expression. Pre‐treatment with CTRP9 in primary human macrophages markedly suppressed the cholesterol accumulation concentration after oxidized low‐density lipoprotein treatment. CD36 was significantly increased after oxidized low‐density lipoprotein exposure while was reduced by CTRP9 treatment. Up‐regulation of CD36 significantly reversed the CTRP9‐mediated protective effects in foam cells. The differential expression levels of several deubiquitinating enzymes preliminarily indicated that USP11 was obviously decreased after CTRP9 treatment. USP11 knockdown decreased the CD36 protein expression and pre‐treatment with 10 μg/mL MG132 significantly maintained the CD36 level from USP11 knock down. Up‐regulation of CD36 reversed the alterations on the cholesterol metabolism caused by CTRP9 or USP11 knockdown. Conclusions CTRP9 regulates the USP11/CD36 axis to protect the macrophages form transforming into foam cells by suppressing intracellular lipid and cholesterol accumulation, which is a potential therapeutic agent for atherosclerosis.

In atherosclerosis, macrophage-derived foam cell formation is considered to be a hallmark of the pathological process; this occurs via the uptake of modified lipoproteins. In the present study, we aim to determine the role of transaldolase in foam cell formation and atherogenesis and reveal the mechanisms underlying its role. Bone marrow-derived macrophages (BMDMs) isolated from mice successfully form foam cells after treatment with oxidized low-density lipoprotein (80 μg/mL). Elevated transaldolase levels in the foam cell model are assessed by quantitative polymerase chain reaction and western blot analysis. Transaldolase overexpression and knockdown in BMDMs are achieved via plasmid transfection and small interfering RNA technology, respectively. We find that transaldolase overexpression effectively attenuates, whereas transaldolase knockdown accelerates, macrophage-derived foam cell formation through the inhibition or activation of cholesterol uptake mediated by the scavenger receptor cluster of differentiation 36 (CD36) in a p38 mitogen-activated protein kinase (MAPK) signaling-dependent manner. Transaldolase-mediated glutathione (GSH) homeostasis is identified as the upstream regulator of p38 MAPK-mediated CD36-dependent cholesterol uptake in BMDMs. Transaldolase upregulates GSH production, thereby suppressing p38 activity and reducing the CD36 level, ultimately preventing foam cell formation and atherosclerosis. Thus, our findings indicate that the transaldolase-GSH-p38-CD36 axis may represent a promising therapeutic target for atherosclerosis.

Abstract Background Gastrodin is an effective polyphenol extracted from Chinese natural herbal Gastrodiae elata Blume, which exhibits antioxidant and anti-inflammatory effects. It has been reported to benefit neurodegenerative diseases, but the effect of Gastrodin on atherosclerosis and the underlying mechanisms remain elusive. The aim of this study is to investigate the function and mechanism of Gastrodin in atherosclerosis. Methods Atherosclerosis mouse model was established by fed low density lipoprotein receptor-deficient (Ldlr −/− ) mice with a high fat diet (HFD, 20% fat and 0.5 cholesterol) for 8 weeks and Gastrodin was administered daily via oral gavage. Plasma lipid levels were measured using commercial kits. En face and aortic sinus lipid accumulation were analyzed with Oil Red O staining. In vitro cell models using foam cell formation model and classical atherosclerosis inflammation model, macrophages were incubated with oxygenized low-density lipoproteins (ox-LDL) or lipopolysaccharide (LPS) in the presence of different concentration of Gastrodin or vehicle solution. Foam cell formation and cellular lipid content were evaluated by Oil Red O staining and intracellular lipids extraction analysis. Gene expression and proteins related to cholesterol influx and efflux were examined by quantitative reverse transcription PCR (RT-qPCR) and western blotting analysis. Furthermore, the effect of Gastrodin on LPS induced macrophage inflammatory responses and NF-κB pathway were evaluated by RT-qPCR and western blotting analysis. Results Gastrodin administration reduced the body weight, plasma lipid levels in Ldlr −/− mice after fed a high fat diet. Oil Red O staining showed Gastrodin-treated mice displayed less atherosclerosis lesion area. Furthermore, Gastrodin treatment significantly ameliorated ox-LDL-induced macrophage-derived foam cells formation through suppressing genes expression related to cholesterol efflux including scavenger receptor class B and ATP-binding cassette transporter A1. Moreover, Gastrodin markedly suppressed pro-inflammatory cytokines secretion and LPS induced inflammatory response in macrophage through downregulating NF-κB pathway. Conclusions Our study demonstrated that Gastrodin attenuates atherosclerosis by suppressing foam cells formation and LPS-induced inflammatory response and represents a novel therapeutic target for the treatment of atherosclerosis.

Abstract Background Atherosclerosis is driven by synergistic interactions between pathological biomechanical and lipid metabolic factors. Long noncoding RNAs (LncRNAs) have been implicated in atherogenesis. The purpose of this study was to investigate the potential mechanism of lncRNA AI662270 on macrophage cholesterol transport in atherosclerosis. Methods Apolipoprotein E deficiency (ApoE −/−) mice were fed a high fat diet for 16 weeks to construct atherosclerotic model, and the mice were injected with recombinant lentivirus carrying AI662270 gene to overexpress AI662270. Macrophages were cleared by liposomal clondronate in vivo. Fundamental experiments and functional assays, hematoxylin and eosin staining, oil red O staining and others, were performed to evaluate the function of AI662270 on atherogenesis. Peritoneal macrophages were treated with oxidized low density lipoprotein (ox-LDL) to simulate in vitro model. Mechanism assays, RNA-interacting protein immunoprecipitation, RNA–protein pulldown and others, were performed to study the regulatory mechanism of AI662270 in macrophages. Results The novel AI662270 was mainly enriched in macrophages, but not in endothelial cells, smooth muscle cells and fibroblasts of mouse atherosclerotic lesions and was upregulated by ox-LDL. Overexpression of AI662270 resulted in lipid accumulation, larger atherosclerotic plaques and cardiac dysfunction in vivo. After macrophages were removed, the pro-atherogenic effect of AI662270 disappeared. Downregulation of AI662270 in macrophages protected against foam cell formation by potentiating cholesterol efflux and reducing intracellular total cholesterol. The opposite effect was observed in macrophage-specific AI662270-overexpressed cells in vitro. AI662270 bound to adenosine triphosphate-binding cassette transporter A1 (Abca1) responsible for regulating cholesterol efflux in macrophages. Forced expression of AI662270 in macrophages decreased Abca1 expression. The reverse occurred when expression of AI662270 was repressed. Conclusion These findings reveal an essential role for AI662270 in atherosclerosis progression by regulating cholesterol efflux from macrophages.

Atherosclerosis is a complex inflammatory disease that affects the arteries and can lead to severe complications such as heart attack and stroke. Macrophages, a type of immune cell, play a crucial role in atherosclerosis initiation and progression. Emerging studies revealed that ion channels regulate macrophage activation, polarization, phagocytosis, and cytokine secretion. Moreover, macrophage ion channel dysfunction is implicated in macrophage-derived foam cell formation and atherogenesis. In this context, exploring the regulatory role of ion channels in macrophage function and their impacts on the progression of atherosclerosis emerges as a promising avenue for research. Studies in the field will provide insights into novel therapeutic targets for the treatment of atherosclerosis. [ABSTRACT FROM AUTHOR]

Aims: Atherosclerosis is a huge threaten to the human health, C1q/TNF‐related protein 9 (CTRP9) has been previously reported possessing vascular protective functions. Our study is aimed to reveal the mechanism of the regulative effects of CTRP9 on the foam cell formation. Methods and results: Primary human macrophages were isolated from human monocytes donated by healthy volunteers. CCK‐8 assay was performed for determining the cell viability. Oil Red O staining was employed for measuring the lipid accumulation. Cholesterol ester and cholesterol concentration were detected by commercial kits for evaluating the intracellular cholesterol. Ubiquitination assay was performed to reveal the ubiquitination level of CD36, cycloheximide assay was applied for determining the half‐life of CD36 protein. Quantitative real‐time PCR and western blot assays were performed for detecting the mRNA and protein expression. Pre‐treatment with CTRP9 in primary human macrophages markedly suppressed the cholesterol accumulation concentration after oxidized low‐density lipoprotein treatment. CD36 was significantly increased after oxidized low‐density lipoprotein exposure while was reduced by CTRP9 treatment. Up‐regulation of CD36 significantly reversed the CTRP9‐mediated protective effects in foam cells. The differential expression levels of several deubiquitinating enzymes preliminarily indicated that USP11 was obviously decreased after CTRP9 treatment. USP11 knockdown decreased the CD36 protein expression and pre‐treatment with 10 μg/mL MG132 significantly maintained the CD36 level from USP11 knock down. Up‐regulation of CD36 reversed the alterations on the cholesterol metabolism caused by CTRP9 or USP11 knockdown. Conclusions: CTRP9 regulates the USP11/CD36 axis to protect the macrophages form transforming into foam cells by suppressing intracellular lipid and cholesterol accumulation, which is a potential therapeutic agent for atherosclerosis. [ABSTRACT FROM AUTHOR]

To explore the sesquiterpenoids in Curcuma longa L. and their activity related to anti-atherosclerosis. The chemical compounds of the rhizomes of C. longa were separated and purified by multiple chromatography techniques. Their structures were established by a variety of spectroscopic experiments. The absolute configurations were determined by comparing experimental and calculated NMR chemical shifts and electronic circular dichroism (ECD) spectra. Their anti-inflammatory effects and inhibitory activity against macrophage-derived foam cell formation were evaluated by lipopolysaccharide (LPS) and oxidized low-density lipoprotein (ox-LDL)-injured RAW264.7 macrophages, respectively. This study resulted in the isolation of 10 bisabolane-type sesquiterpenoids (1–10) from C. longa, including two pairs of new epimers (curbisabolanones A–D, 1–4). Compound 4 significantly inhibited LPS-induced nitric oxide (NO), interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and prostaglandin E2 (PGE2) production in RAW264.7 cells. Furthermore, compound 4 showed inhibitory activity against macrophage-derived foam cell formation, which was represented by markedly reducing ox-LDL-induced intracellular lipid accumulation as well as total cholesterol (TC), free cholesterol (FC), and cholesterol ester (CE) contents in RAW264.7 cells. These findings suggest that bisabolane-type sesquiterpenoids, one of the main types of components in C. longa, have the potential to alleviate the atherosclerosis process by preventing inflammation and inhibiting macrophage foaming. [ABSTRACT FROM AUTHOR]

Monocyte-to-macrophage differentiation and subsequent foam cell formation are key processes that contribute to plaque build-up during the progression of atherosclerotic lesions. Palmitoylation enzymes are known to play pivotal roles in the development and progression of inflammatory diseases. However, their specific impact on atherosclerosis development remains unclear. In this study, we discovered that the knockout of zDHHC1 in THP-1 cells, as well as Zdhhc1 in mice, markedly reduces the uptake of oxidized low-density lipoprotein (ox-LDL) by macrophages, thereby inhibiting foam cell formation. Moreover, the absence of Zdhhc1 in ApoE−/− mice significantly suppresses atherosclerotic plaque formation. Mass spectrometry coupled with bioinformatic analysis revealed an enrichment of the PI3K-Akt-mTOR signaling pathway. Consistent with this, we observed that knockout of zDHHC1 significantly decreases the palmitoylation levels of p110α, a crucial subunit of PI3K. Notably, the deletion of Zdhhc1 facilitates the nuclear translocation of p110α in macrophages, leading to a significant reduction in the downstream phosphorylation of Akt at Ser473 and mTOR at Ser2448. This cascade results in a decreased number of macrophages within plaques and ultimately mitigates the severity of atherosclerosis. These findings unveil a novel role for zDHHC1 in regulating foam cell formation and the progression of atherosclerosis, suggesting it as a promising target for clinical intervention in atherosclerosis therapy. • ZDHHC1 deficiency significantly reduces foam cell formation by inhibiting the uptake of ox-LDL; • The absence of Zdhhc1 in ApoE–/– mice markedly suppresses atherosclerotic plaque formation; • Zdhhc1 deficiency mitigates atherosclerosis by inhibiting PI3K-Akt-mTOR via promoting p110α nuclear translocation. [ABSTRACT FROM AUTHOR]

Background: Gastrodin is an effective polyphenol extracted from Chinese natural herbal Gastrodiae elata Blume, which exhibits antioxidant and anti-inflammatory effects. It has been reported to benefit neurodegenerative diseases, but the effect of Gastrodin on atherosclerosis and the underlying mechanisms remain elusive. The aim of this study is to investigate the function and mechanism of Gastrodin in atherosclerosis. Methods: Atherosclerosis mouse model was established by fed low density lipoprotein receptor-deficient (Ldlr−/−) mice with a high fat diet (HFD, 20% fat and 0.5 cholesterol) for 8 weeks and Gastrodin was administered daily via oral gavage. Plasma lipid levels were measured using commercial kits. En face and aortic sinus lipid accumulation were analyzed with Oil Red O staining. In vitro cell models using foam cell formation model and classical atherosclerosis inflammation model, macrophages were incubated with oxygenized low-density lipoproteins (ox-LDL) or lipopolysaccharide (LPS) in the presence of different concentration of Gastrodin or vehicle solution. Foam cell formation and cellular lipid content were evaluated by Oil Red O staining and intracellular lipids extraction analysis. Gene expression and proteins related to cholesterol influx and efflux were examined by quantitative reverse transcription PCR (RT-qPCR) and western blotting analysis. Furthermore, the effect of Gastrodin on LPS induced macrophage inflammatory responses and NF-κB pathway were evaluated by RT-qPCR and western blotting analysis. Results: Gastrodin administration reduced the body weight, plasma lipid levels in Ldlr−/− mice after fed a high fat diet. Oil Red O staining showed Gastrodin-treated mice displayed less atherosclerosis lesion area. Furthermore, Gastrodin treatment significantly ameliorated ox-LDL-induced macrophage-derived foam cells formation through suppressing genes expression related to cholesterol efflux including scavenger receptor class B and ATP-binding cassette transporter A1. Moreover, Gastrodin markedly suppressed pro-inflammatory cytokines secretion and LPS induced inflammatory response in macrophage through downregulating NF-κB pathway. Conclusions: Our study demonstrated that Gastrodin attenuates atherosclerosis by suppressing foam cells formation and LPS-induced inflammatory response and represents a novel therapeutic target for the treatment of atherosclerosis. [ABSTRACT FROM AUTHOR]

Background: Atherosclerosis is driven by synergistic interactions between pathological biomechanical and lipid metabolic factors. Long noncoding RNAs (LncRNAs) have been implicated in atherogenesis. The purpose of this study was to investigate the potential mechanism of lncRNA AI662270 on macrophage cholesterol transport in atherosclerosis. Methods: Apolipoprotein E deficiency (ApoE−/−) mice were fed a high fat diet for 16 weeks to construct atherosclerotic model, and the mice were injected with recombinant lentivirus carrying AI662270 gene to overexpress AI662270. Macrophages were cleared by liposomal clondronate in vivo. Fundamental experiments and functional assays, hematoxylin and eosin staining, oil red O staining and others, were performed to evaluate the function of AI662270 on atherogenesis. Peritoneal macrophages were treated with oxidized low density lipoprotein (ox-LDL) to simulate in vitro model. Mechanism assays, RNA-interacting protein immunoprecipitation, RNA–protein pulldown and others, were performed to study the regulatory mechanism of AI662270 in macrophages. Results: The novel AI662270 was mainly enriched in macrophages, but not in endothelial cells, smooth muscle cells and fibroblasts of mouse atherosclerotic lesions and was upregulated by ox-LDL. Overexpression of AI662270 resulted in lipid accumulation, larger atherosclerotic plaques and cardiac dysfunction in vivo. After macrophages were removed, the pro-atherogenic effect of AI662270 disappeared. Downregulation of AI662270 in macrophages protected against foam cell formation by potentiating cholesterol efflux and reducing intracellular total cholesterol. The opposite effect was observed in macrophage-specific AI662270-overexpressed cells in vitro. AI662270 bound to adenosine triphosphate-binding cassette transporter A1 (Abca1) responsible for regulating cholesterol efflux in macrophages. Forced expression of AI662270 in macrophages decreased Abca1 expression. The reverse occurred when expression of AI662270 was repressed. Conclusion: These findings reveal an essential role for AI662270 in atherosclerosis progression by regulating cholesterol efflux from macrophages. [ABSTRACT FROM AUTHOR]

Nonalcoholic steatohepatitis (NASH) is the progressive form of nonalcoholic fatty liver disease (NAFLD), and the dysregulation of lipid metabolism and oxidative stress are the typical features. Subsequent dyslipidemia and oxygen radical production may render the formation of modified lipids. Macrophage scavenger receptor 1 (MSR1) is responsible for the uptake of modified lipoprotein and is one of the key molecules in atherosclerosis. However, the unrestricted uptake of modified lipoproteins by MSR1 and the formation of cholesterol-rich foamy macrophages also can be observed in NASH patients and mouse models. In this review, we highlight the dysregulation of lipid metabolism and oxidative stress in NASH, the alteration of MSR1 expression in physiological and pathological conditions, the formation of modified lipoproteins, and the role of MSR1 on macrophage foaming and NASH development and progression. [ABSTRACT FROM AUTHOR]

Atherosclerosis (AS) is the main pathological basis for the development of cardiovascular diseases. Vascular inflammation is an important factor in the formation of AS, and macrophage pyroptosis plays a key role in AS due to its unique inflammatory response. Guizhitongluo Tablet (GZTLT) has shown clinically effective in treating patients with AS, but its mechanism is elusive. This study was to determine the effects of GZTLT on atherosclerotic vascular inflammation and pyroptosis and to understand its underlying mechanism. The active constituents of GZTLT were analysed by means of UPLC-HRMS. In vivo experiments were performed using ApoE−/− mice fed a high fat diet for 8 weeks, followed by treatment with varying concentrations of GZTLT orally by gavage and GsMTx4 (GS) intraperitoneally and followed for another 8 weeks. Oil red O, Haematoxylin-eosin (HE) and Masson staining were employed to examine the lipid content, plaque size, and collagen fibre content of the mouse aorta. Immunofluorescence staining was utilised to identify macrophage infiltration, as well as the expression of Piezo1 and NLRP3 proteins in aortic plaques. The levels of aortic inflammatory factors were determined using RT-PCR and ELISA. In vitro, foam cell formation in bone marrow-derived macrophages (BMDMs) was observed using Oil Red O staining. Intracellular Ca2+ measurements were performed to detect the calcium influx in BMDMs, and the expression of NLRP3 and its related proteins were detected by Western blot. The UPLC-HRMS analysis revealed 31 major components of GZTLT. Our data showed that GZTLT inhibited aortic plaque formation in mice and increased plaque collagen fibre content to stabilise plaques. In addition, GZTLT could restrain the expression of serum lipid levels and suppress macrophage foam cell formation. Further studies found that GZTLT inhibited macrophage infiltration in aortic plaques and suppressed the expression of inflammatory factors. It is noteworthy that GZTLT can restrain Piezo1 expression and reduce Ca2+ influx in BMDMs. Additionally, we found that GZTLT could regulate NLRP3 activation and pyroptosis by inhibiting Piezo1. The present study suggests that GZTLT inhibits vascular inflammation and macrophage pyroptosis through the Piezo1/NLRP3 signaling pathway, thereby delaying AS development. Our finding provides a potential target for AS treatment and drug discovery. [Display omitted] [ABSTRACT FROM AUTHOR]

Macrophages are key inflammatory immune cells that display dynamic phenotypes and functions in response to their local microenvironment. In different conditions, macrophage polarization can be induced by high-mobility group box 1 (HMGB1), a nuclear DNA-binding protein that activates innate immunity via the Toll-like receptor (TLR) 4, the receptor for advanced glycation end products (RAGE), and C-X-C chemokine receptor (CXCR) 4. This study investigated the phenotypes of murine bone-marrow-derived macrophages (BMDMs) stimulated with different HMGB1 redox isoforms using bulk RNA sequencing (RNA-Seq). Disulfide HMGB1 (dsHMGB1)-stimulated BMDMs showed a similar but distinct transcriptomic profile to LPS/IFNγ- and LPS-stimulated BMDMs. Fully reduced HMGB1 (frHMGB1) did not induce any significant transcriptomic change. Interestingly, compared to LPS/IFNγ- and LPS-, dsHMGB1-stimulated BMDMs showed lipid metabolism and foam cell differentiation gene set enrichment, and oil red O staining revealed that both dsHMGB1 and frHMGB1 alleviated oxidized low-density lipoprotein (oxLDL)-induced foam cells formation. Overall, this work, for the first time, used transcriptomic analysis by RNA-Seq to investigate the impact of HMGB1 stimulation on BMDM polarization. Our results demonstrated that dsHMGB1 and frHMGB1 induced distinct BMDM polarization phenotypes compared to LPS/IFNγ- and LPS- induced phenotypes. [ABSTRACT FROM AUTHOR]

Abstract Background Premature atherosclerosis occurs in patients with SLE; however, the mechanisms remain unclear. Both mitochondrial machinery and proinflammatory cytokine interferon alpha (IFN-α) potentially contribute to atherogenic processes in SLE. Here, we explore the roles of the mitochondrial protein cytidine/uridine monophosphate kinase 2 (CMPK2) in IFN-α-mediated pro-atherogenic events. Methods Foam cell measurements were performed by oil red O staining, Dil-oxLDL uptake and the BODIPY approach. The mRNA and protein levels were measured by qPCR and Western blotting, respectively. Isolation of CD4+ T cells and monocytes was performed with monoclonal antibodies conjugated with microbeads. Manipulation of protein expression was conducted by either small interference RNA (siRNA) knockdown or CRISPR/Cas9 knockout. The expression of mitochondrial reactive oxygen species (mtROS) was determined by flow cytometry and confocal microscopy. Results IFN-α enhanced oxLDL-induced foam cell formation and Dil-oxLDL uptake by macrophages. In addition to IFN-α, several triggers of atherosclerosis, including thrombin and IFN-γ, can induce CMPK2 expression, which was elevated in CD4+ T cells and CD14+ monocytes isolated from SLE patients compared to those isolated from controls. The analysis of cellular subfractions revealed that CMPK2 was present in both mitochondrial and cytosolic fractions. IFN-α-induced CMPK2 expression was inhibited by Janus kinase (JAK)1/2 and tyrosine kinase 2 (Tyk2) inhibitors. Both the knockdown and knockout of CMPK2 attenuated IFN-α-mediated foam cell formation, which involved the reduction of scavenger receptor class A (SR-A) expression. CMPK2 also regulated IFN-α-enhanced mtROS production and inflammasome activation. Conclusions The study suggests that CMPK2 plays contributing roles in the pro-atherogenic effects of IFN-α.

Atherosclerosis, accompanied by inflammation and metabolic disorders, is the primary cause of clinical cardiovascular death. In recent years, unhealthy lifestyles (e.g., sedentary lifestyles) have contributed to a worldwide epidemic of atherosclerosis. Exercise is a known treatment of atherosclerosis, but the precise mechanisms are still unknown. Here, we show that 12 weeks of regular exercise training on a treadmill significantly decreased lipid accumulation and foam cell formation in ApoE−/− mice fed with a Western diet, which plays a critical role in the process of atherosclerosis. This was associated with an increase in β-hydroxybutyric acid (BHB) levels in the serum. We provide evidence that BHB treatment in vivo or in vitro increases the protein levels of cholesterol transporters, including ABCA1, ABCG1, and SR-BI, and is capable of reducing lipid accumulation. It also ameliorated autophagy in macrophages and atherosclerosis plaques, which play an important role in the step of cholesterol efflux. Altogether, an increase in serum BHB levels after regular exercise is an important mechanism of exercise inhibiting the development of atherosclerosis. This provides a novel treatment for atherosclerotic patients who are unable to undertake regular exercise for whatever reason. They will gain a benefit from receiving additional BHB. [ABSTRACT FROM AUTHOR]

Abstract Background Macrophages that accumulate in atherosclerotic plaques contribute to progression of the lesions to more advanced and complex plaques. Although iron deposition was found in human atherosclerotic plaques, clinical and pre-clinical studies showed controversial results. Several epidemiological studies did not show the positive correlation between a systemic iron status and an incidence of cardiovascular diseases, suggesting that the iron involvement occurs locally, rather than systemically. Results To determine the direct in vivo effect of iron accumulation in macrophages on the progression of atherosclerosis, we generated Apoe −/− mice with a macrophage-specific ferroportin (Fpn1) deficiency (Apoe −/− Fpn1 LysM/LysM ). Fpn1 deficiency in macrophages dramatically accelerated the progression of atherosclerosis in mice. Pathophysiological evidence showed elevated levels of reactive oxygen species, aggravated systemic inflammation, and altered plaque-lipid composition. Moreover, Fpn1 deficiency in macrophages significantly inhibited the expression of ABC transporters (ABCA1 and ABCG1) by decreasing the expression of the transcription factor LXRα, which reduced cholesterol efflux and therefore promoted foam cell formation and enhanced plaque formation. Iron chelation relieved the symptoms moderately in vivo, but drastically ex vivo. Conclusions Macrophage iron content in plaques is a critical factor in progression of atherosclerosis. The interaction of iron and lipid metabolism takes place in macrophage-rich atherosclerotic plaques. And we also suggest that altering intracellular iron levels in macrophages by systemic iron chelation or dietary iron restriction may be a potential supplementary strategy to limit or even regress the progression of atherosclerosis.

Macrophages are critical components of atherosclerotic lesions and their pro- and anti-inflammatory responses influence atherogenesis. Type-I interferons (IFNs) are cytokines that play an essential role in antiviral responses and inflammatory activation and have been shown to promote atherosclerosis. Although the impact of type-I IFNs on macrophage foam cell formation is well-documented, the effect of lipid accumulation in monocytes and macrophages on type-I IFN responses remains unknown. Here we examined IFN stimulated (ISG) and non-ISG inflammatory gene expression in mouse and human macrophages that were loaded with acetylated LDL (acLDL), as a model for foam cell formation. We found that acLDL loading in mouse and human macrophages specifically suppressed expression of ISGs and IFN-β secretion, but not other pro-inflammatory genes. The down regulation of ISGs could be rescued by exogenous IFN-β supplementation. Activation of the cholesterol-sensing nuclear liver X receptor (LXR) recapitulated the cholesterol-initiated type-I IFN suppression. Additional analyses of murine in vitro and in vivo generated foam cells confirmed the suppressed IFN signaling pathways and suggest that this phenotype is mediated via down regulation of interferon regulatory factor binding at gene promoters. Finally, RNA-seq analysis of monocytes of familial hypercholesterolemia (FH) patients also showed type-I IFN suppression which was restored by lipid-lowering therapy and not present in monocytes of healthy donors. Taken together, we define type-I IFN suppression as an athero-protective characteristic of foamy macrophages. These data provide new insights into the mechanisms that control inflammatory responses in hyperlipidaemic settings and can support future therapeutic approaches focusing on reprogramming of macrophages to reduce atherosclerotic plaque progression and improve stability.

Protein phosphatase 2A (PP2A), a crucial serine/threonine phosphatase, has recently been reported to play an important role in cardiovascular disease. Previous studies have hinted that PP2A is involved in atherosclerosis formation, but the associated mechanisms remain poorly understood. In this study, we investigate the role of PP2A in the pathogenesis of atherosclerosis. In human atherosclerotic coronary arteries, we found that the expression and activity of PP2A decreased significantly when compared to non-atherosclerotic arteries. Additional experiments demonstrated that pharmacological inhibition of PP2A aggravated atherosclerosis of ApoE−/− mice. Considering the central role of macrophages in atherosclerosis, mice with conditional knockout of the PP2A-Cα subunit in myeloid cells were produced to investigate the function of PP2A in macrophages. Results showed that PP2A deficiency in myeloid cells aggravated atherosclerotic lesions in mice. in vitro experiments indicated that PP2A-deficient macrophages had an enhanced ability of lipid uptake and foam cell formation. Mechanistically, the deficiency of the PP2A in macrophages led to an increase in the phosphorylation level of p38, which contributed to the elevated expression of scavenger receptor CD36, a key factor involved in lipoprotein uptake. Our data suggest that PP2A participates in the pathophysiological process of atherosclerosis. The decrease of PP2A expression and activity in macrophages is a crucial determinant for foam cell formation and the initiation of atherosclerosis. Our study may provide a potential novel approach for the treatment of atherosclerosis.

Vascular smooth muscle cells (SMCs) are important vascular components that are essential for the regulation of vascular functions during vascular atherosclerogenesis and vascular injury. Oxidized low-density lipoprotein (oxLDL) is known to induce SMC activation and foam cell transformation. This study characterized the role of hepatoma-derived growth factor (HDGF) in oxLDL-induced foam cell formation in cultured primary rat aortic SMCs. OxLDL exposure significantly increased HDGF expression and extracellular release. It also upregulated atherogenic regulators in SMCs, including TLR4, MyD88, LOX-1, and CD36. Exogenous HDGF stimulation not only increased the expression of cognate receptor nucleolin, but also the innate immunity regulators TLR4/MyD88 and lipid metabolism regulators, including LOX-1 and CD36. Oil red O staining showed that HDGF did not initiate, but enhanced oxLDL-driven foam cell formation in SMCs. Further signaling characterization demonstrated that oxLDL evoked activation of PI3K/Akt and p38 MAPK signaling pathways, both of which were involved in the upregulation of HDGF, LOX-1, and CD36 induced by oxLDL. Gene knockdown experiments using LOX-1 targeted siRNA demonstrated that LOX-1 expression was critical for oxLDL-induced HDGF upregulation, while HDGF gene depletion completely abolished oxLDL-triggered TLR4, LOX-1, and CD36 overexpression and foam cell formation in SMCs. These findings strongly suggest that oxLDL-induced HDGF upregulation participates in subsequent LOX-1 and CD36 expression in aortic SMCs and mechanistically contributes to the formation of SMC-derived foam cells. The oxLDL/LOX-1/HDGF axis may serve as a target for anti-atherogenesis therapy.

Oleacein is a polyphenol and can be found in unfiltered extra virgin olive oil and leaves Ligustrum vulgare L. (Oleaceae). The aim of the present study was to investigate whether oleacein could increase efflux cholesterol from macrophages.Oleacein in dose-dependent manner (OLEA20, OLEA50) significantly reduced lipid deposits in macrophages. The increase of SRB1 expression was found for OLEA50 and OLEA20 compared to oxLDL-induced macrophages. Oleacein significantly up-regulated protein expression of ABCA1 and ABCG1 transporter. Moreover, oleacein increased of HO-1 intracellular secretion, as well as increased activation of Nrf2. Whereas, the level of NF-κB protein was almost completely inhibited by oleacein at the same concentrations. For OLEA10, no significant changes were observed for the parameters tested.Our study demonstrated that oleacein may reduce foam cell formation. Therefore, we propose a novel explanation for the oleacein, that can be used to develop new therapeutic strategies for the treatment of atherosclerosis.

The persistence of macrophage-derived foam cells in the artery wall fuels atherosclerosis development. However, the mechanism of foam cell formation regulation remains elusive. We are committed to determining the role that CD147 might play in macrophage foam cell formation during atherosclerosis. In this study, we found that CD147 expression was primarily increased in mouse and human atherosclerotic lesions that were rich in macrophages and could be upregulated by ox-LDL. High-throughput compound screening indicated that ox-LDL-induced CD147 upregulation in macrophages was achieved through PI3K/Akt/mTOR signaling. Genetic deletion of macrophage CD147 protected against foam cell formation by impeding cholesterol uptake, probably through the scavenger receptor CD36. The opposite effect was observed in primary macrophages isolated from macrophage-specific CD147-overexpressing mice. Moreover, bioinformatics results indicated that CD147 suppression might exert an atheroprotective effect via various processes, such as cholesterol biosynthetic and metabolic processes, LDL and plasma lipoprotein clearance, and decreased platelet aggregation and collagen degradation. Our findings identify CD147 as a potential target for prevention and treatment of atherosclerosis in the future.

Gynostemma pentaphyllum was widely consumed in China because of its various pharmacological activities. Numerous studies have confirmed the beneficial effects of G. pentaphyllum. However, the ultimate compounds responsible for its inhibitory effects on foam cell formation were still unknown. Gypenoside LVI (GPLVI), a dammarane-type gynosaponin was isolated and identified from G. pentaphyllum. Treatment of GPLVI successfully attenuated foam cell formation, as evidenced by Oil Red O staining, TG and cholesterol contents, and Dil-ox-LDL uptake analyses. GPLVI displayed significant inhibitory effects on secretion of IL-6 and IL-1β. In contrast, production of TNF-α was not markedly reduced. GPLVI also markedly induced ABCG1, SRB1 and LXRα expression. Additionally, GPLVI significantly blocked phosphorylation of ERK and JNK. Taken together, our results suggested that GPLVI might be responsible for the inhibitory effect of G. pentaphyllum on ox-LDL-induced foam cell formation mainly by promoting cholesterol efflux and inhibiting inflammatory response.

Background/Aims: High mobility group B-1 (HMGB-1)-induced endoplasmic reticulum stress (ERS) has been implicated in inflammation and dendritic cell maturation. C/EBP-homologous protein (CHOP) is a vital component of ERS and apoptosis and plays a critical role in atherosclerosis. However, only a little information is available about the role of HMGB-1 in foam cell formation. Thus, the role of HMGB-1-induced ERS/CHOP pathway in apoptosis and formation of macrophage-derived foam cells is investigated. Methods: RAW264.7 cells were treated with oxidized low-density lipoprotein (oxLDL) in the absence and/or presence of HMGB-1, N-acetylcysteine (NAC, an antioxidant), glycyrrhizin (Gly, an HMGB-1 inhibitor), tunicamycin (TM, an ERS inducer), and 4-phenylbutyrate (4-PBA, an ERS inhibitor). Reactive oxygen species (ROS) production was examined by dihydroethidium (DHE) staining. Oil Red O staining, intracellular total cholesterol assay, and Dil-oxLDL uptake assay evaluated the accumulation of lipids in macrophages. Cell apoptosis was measured by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Western blot detected the expression of HMGB-1/ERS/CHOP pathway. Results: oxLDL induced HMGB-1 translocation and secretion in a dose- and time-dependent manner, which was inhibited by NAC. oxLDL-induced lipid accumulation in macrophages was promoted synergistically by HMGB-1 that was attenuated by Gly. Moreover, TM synergized with oxLDL induced lipid accumulation and apoptosis of macrophages; however, 4-PBA alleviated the oxLDL-induced apoptotic foam cells. Additionally, the inhibition of ERS with 4-PBA suppressed the expression of HMGB-1-induced CHOP. Conclusions: OxLDL triggered HMGB-1 secretion in macrophages via oxidative stress. Furthermore, HMGB-1 promoted the formation and apoptosis of macrophage-derived foam cells via activation of ERS/CHOP pathway.

(1) Background: The cholinergic anti-inflammatory pathway (CAP) has been implicated in the regulation of various diseases, including chronic inflammatory cardiovascular disorders such as atherosclerosis (AS). This study aims to explore the underlying regulatory mechanisms of CAP activity in the progression of AS. (2) Methods: The Apoe-/- mice were subjected to sham, bilateral cervical vagotomy surgery (VGX), and VGX supplemented with Gainesville Tokushima scientists (GTS)-21 (4 mg/kg/d) and then fed with a high-fat diet for 10 weeks. Atherosclerotic lesion size and inflammation levels were investigated by histology and inflammatory cytokines analysis. The blood M1/M2 macrophages were analyzed by flow cytometry. Primary mouse bone marrow-derived macrophages (BMDM), peritoneal macrophages, and RAW264.7 cells were treated with CAP agonists acetylcholine (Ach) and GTS-21 to study their effects on macrophage functions. (3) Results: Compared with the sham group, inhibition of CAP by the VGX resulted in growing aortic lipid plaque area, deteriorated inflammatory levels, and aberrant quantity of M1/M2 macrophages in Apoe-/- mice. However, these detrimental effects of VGX were significantly ameliorated by the reactivation of CAP through GTS-21 treatment. The in vitro study using macrophages revealed that stimulation with CAP agonists suppressed M1, but promoted M2 macrophage polarization through the upregulation of TNFAIP3 and phosphorylation STAT3 levels, respectively. Moreover, the activation of CAP inhibited the formation of macrophage foam cells in the peritoneal cavity by regulating genes related to cholesterol metabolism. (4) Conclusions: This study provides novel evidence and mechanisms that the CAP plays an important role in the regulation of AS development by controlling macrophage functions, implying a potential use of CAP activation as a therapeutic strategy for AS treatment.

Gynostemma pentaphyllum (Thunb.) Makino was traditionally used as antiatherogenic foods in China but ingredients responsible for the effects remained unexplored. Here, kaempferol 3-O-[2G-(E)-Coumaroyl-3G-O-β-D-glucosyl-3R-O-β-D-glucosylrutinoside] (KCGG), gypenoside XLVI (GPXLVI), gypenoside LI (GPLI), gypenoside L (GPL), ginsenoside Rd (GSRd) and 2α, 3β, 12β, 20 (S)-tetrahydroxy-25-hydroperoxy-dammar-23-ene-20-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranoside (GLUP) were isolated, among which KCGG, GPLI and GLUP exhibited greater antioxidant potential. The predominant inhibitory effects of KCGG, GPLI and GLUP on oxidized low-density lipoproteins (ox-LDL)-induced foam cell formation and intracellular lipid accumulation were further confirmed at non-cytotoxic concentrations. KCGG mainly decreased interleukin-6 (IL-6) production, while GPLI and GLUP were more powerful in inhibiting interleukin-1β (IL-1β) accumulation. KCGG, GPLI and GLUP significantly inhibited extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) phosphorylation. They also dramatically promoted cholesterol efflux through up-regulating scavenger receptor class B type I (SRB1) expression. In conclusion, KCGG, GPLI and GLUP acted through different pathways that acted simultaneously.

Oxidation of low-density lipoprotein (LDL) plays a crucial role in the pathogenesis of atherosclerosis. Hemin (iron (III)-protoporphyrin IX) is a degradation product of hemoglobin that can be found in thalassemia patients. Hemin is a strong oxidant that can cause LDL oxidation and contributes to atherosclerosis in thalassemia patients. Lusianthridin from Dendrobium venustrum is a phenolic compound that possesses antioxidant activity. Hence, lusianthridin could be a promising compound to be used against hemin-induced oxidative stress. The major goal of this study is to evaluate the protective effect of lusianthridin on hemin-induced low-density lipoprotein oxidation (he-oxLDL). Here, various concentrations of lusianthridin (0.25, 0.5, 1, and 2 µM) were preincubated with LDL for 30 min, then 5 µM of hemin was added to initiate the oxidation, and oxidative parameters were measured at various times of incubation (0, 1, 3, 6, 12, 24 h). Lipid peroxidation of LDL was measured by thiobarbituric reactive substance (TBARs) assay and relative electrophoretic mobility (REM). The lipid composition of LDL was analyzed by using reverse-phase HPLC. Foam cell formation with he-oxLDL in RAW 264.7 macrophage cells was detected by Oil Red O staining. The results indicated that lusianthridin could inhibit TBARs formation, decrease REM, decrease oxidized lipid products, as well as preserve the level of cholesteryl arachidonate and cholesteryl linoleate. Moreover, He-oxLDL incubated with lusianthridin for 24 h can reduce the foam cell formation in RAW 264.7 macrophage cells. Taken together, lusianthridin could be a potential agent to be used to prevent atherosclerosis in thalassemia patients.

Background/Aims: Hyperuricemia is part of the metabolic-syndrome cluster of abdominal obesity, impaired glucose tolerance, insulin resistance, dyslipidemia, and hypertension. Monocytes/macrophages are critical in the development of metabolic syndrome, including gout, obesity and atherosclerosis. However, how high uric acid (HUA) exposure affects monocyte/macrophage function remains unclear. In this study, we investigated the molecular mechanism of HUA exposure in monocytes/macrophages and its impact on oxidized low-density lipoprotein (oxLDL)-induced foam-cell formation in a human monocytic cell line, THP-1. Methods: We primed THP-1 cells with phorbol-12-myristate-13-acetate (PMA) for differentiation, then exposed cells to HUA and detected the production of reactive oxygen species (ROS) and analyzed the level of phospho-AMPKα. THP-1 cells were pre-incubated with Compound C, an AMPK inhibitor, or N-acetyl-L-cysteine (NAC), a ROS scavenger, or HUA before PMA, to assess CD68 expression and phospho-AMPKα level. PMA-primed THP-1 cells were pre-treated with oxLDL before Compound C and HUA treatment. Western blot analysis was used to examine the levels of phospho-AMPKα, CD68, ABCG1, ABCA1, cyclooxygenase-2 (COX-2) and NF-κB (p65). Flow cytometry was used to assess ROS production and CD68 expression in live cells. Oil-red O staining was used to observe oxLDL uptake in cells. Results: HUA treatment increased ROS production in PMA-primed THP-1 cells; NAC blocked HUA-induced oxidative stress. HUA treatment time-dependently increased phospho-AMPKα level in PMA-primed THP-1 cells. The HUA-induced oxidative stress increased phospho-AMPKα levels, which was blocked by NAC. HUA treatment impaired CD68 expression during cell differentiation by activating the AMPK pathway, which was reversed by Compound C treatment. Finally, HUA treatment inhibited oxLDL uptake in the formation of foam cells in THP-1 cells, which was blocked by Compound C treatment. HUA treatment significantly increased the expression of ABCG1 and reversed the oxLDL-reduced ABCG1 expression but did not affect the expression of ABCA1, NF-κB (p65) or COX-2. Conclusions: HUA exposure activated the ROS-AMPK pathway, impaired CD68 expression, and inhibited oxLDL-induced foam-cell formation in a human monocytic cell line, THP-1.

Background: Oleacein is a secoiridoid group polyphenol found mostly in Olea europea L. and Ligustrum vulgare L. (Oleaceae). The aim of the present study was to investigate a potential role of oleacein in prevention of the foam cell formation. Materials and Methods: Oleacein was isolated from Ligustrum vulgare leaves. Human monocyte-derived macrophages were obtained from monocytes cultured with Granulocyte-macrophage colony-stimulating factor (GM-CSF). Then, cells were incubated with 20 μM or 50 μM of oleacein and with oxidized low-density lipoprotein (oxLDL) (50 μg/mL). Visualization of lipid deposition within macrophages was carried out using Oil-Red-O. Expression of CD36, Scavenger receptor A1 (SRA1) and Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) was determined by Reverse transcription polymerase chain reaction (RT-PCR) and by flow cytometry. Apoptosis was determined by flow cytometry using Annexin V assay. STAT3 and Acyl-coenzyme A: cholesterol acyltransferase type 1 (ACAT1) levels were determined by ELISA. P-STAT3, P-JAK1, P-JAK2 expressions were determined by Western blot (WB). Results: Oleacein in dose-dependent manner significantly reduced lipid deposits in macrophages as well as their expression of selected scavenger receptors. The highest decrease of expression was found for CD36 and SRA1 receptors, from above 20% to more than 75% compared to oxLDL and the lowest for LOX-1 receptor, from approx. 8% to approx. 25% compared to oxLDL-stimulated macrophages. Oleacein significantly reduced (2.5-fold) early apoptosis of oxLDL-stimulated macrophages. Moreover, oleacein significantly increased the protein expression of JAK/STAT3 pathway and had no effect on ACAT1 level. Conclusions: Our study demonstrates, for the first time, that oleacein inhibits foam cell formation in human monocyte-derived macrophages and thus can be a valuable tool in the prevention of early and advanced atherosclerotic lesions.

Pine (Pinus morrisonicola Hay, PM) needles have been used as folk medicine for their antihypertension and lipid-lowering effects. As supercritical fluid extraction (SFE) is considered an ideal technique for the extraction of essential oil from plant materials, the present work investigated the optimal SFE conditions and the protective effects of different resulting fractions of PM needles on lipid peroxidation and foam cell production in macrophages. Nine PM needle extracts (PME1–9) were obtained in 1%–4% yields using different SFE conditions, of which PME1 had the lowest yield (1.1%) and PME3 the highest (3.9%). PME3 exhibited lower cytotoxic effects and stronger inhibition of lipid peroxidation and formation of foam cell in RAW 264.7 macrophages than those of other PME extracts. PME3-1 purified from PME3 by column and thin layer chromatography inhibited LDL oxidation more effectively than did PME3 in a cell-free system oxidized by Cu2+. PME3-1 dose-dependently (25–100 μg/mL) decreased conjugated diene levels and foam cell formation induced by ox-LDL. GC/MS analyses revealed that 1-docosene, neophytadiene, and methyl abietate were increased 5.2-, 1.7- and 4.3-fold in PME3-1 relative to PME3. A new hydrocarbon compound, cedrane-8,13-diol, was identified in PME3-1. Overall, the present study demonstrates the optimal extraction conditions of SFE of PM and identifies the most potent antioxidant fractions and possible active compounds in PM.

Abstract Conjugated linoleic acid (CLA) has the unique property of inducing regression of pre‐established murine atherosclerosis. Understanding the mechanism(s) involved may help identify endogenous pathways that reverse human atherosclerosis. Here, we provide evidence that CLA inhibits foam cell formation via regulation of the nuclear receptor coactivator, peroxisome proliferator‐activated receptor (PPAR)‐γ coactivator (PGC)‐1α, and that macrophage PGC‐1α plays a role in atheroprotection in vivo. PGC‐1α was identified as a hub gene within a cluster in the aorta of the apoE−/− mouse in the CLA‐induced regression model. PGC‐1α was localized to macrophage/foam cells in the murine aorta where its expression was increased during CLA‐induced regression. PGC‐1α expression was also detected in macrophages in human atherosclerosis and was inversely linked to disease progression in patients with the disease. Deletion of PGC‐1α in bone marrow derived macrophages promoted, whilst over expression of the gene inhibited foam cell formation. Importantly, macrophage specific deletion of PGC‐1α accelerated atherosclerosis in the LDLR−/− mouse in vivo. These novel data support a functional role for PGC‐1α in atheroprotection.

Background: Vascular disease in diabetes is initiated by monocyte adhesion to vascular endothelium, transmigration and formation of foam cells. Increasing clinical evidence supports a role for the secretory protein, cyclophilin A in diabetic vascular disease. The means by which cyclophilin A contributes to vascular lesion development in diabetes is however largely unknown. Methods: In this study we investigated using THP1 cells and human monocytes whether cyclophilin A under hyperglycemic conditions, functions in the inflammatory cascade as a chemoattractant and increases lipid uptake by formation of foam cells invitro. We developed an invitro model of monocytes cultured in 20 mm glucose (high glucose) equivalent to 360 mg/dL of plasma glucose levels. These monocytes were then differentiated into macrophages using PMA and subsequently transformed to lipid laden foam cells using oxidized low density lipoproteins in the presence and absence of cyclophilin A. This cellular model was used to study monocyte to macrophage differentiation, transmigration and foam cell formation. A similar cellular model using siRNA mediated transient elimination of the cyclophilin A gene as well as chemical inhibitors were used to further confirm the role of cyclophilin A in the differentiation and foam cell formation process. Results: Cyclophilin A effectively increased migration of high glucose treated monocytes to the endothelial cell monolayer (p < 0.0001). In the presence of cyclophilin A, differentiated macrophages, when treated with oxLDL had a 36 percent increase in intracellular lipid accumulation (p = 0.01) when compared to cells treated with oxLDL alone. An increased flux of reactive oxygen species was also observed (p = 0.01). Inflammatory cytokines such as TNF-α, MCP-1 and cyclophilin A were significantly increased. Silencing cyclophilin A in THP-1 cells and human monocytes using siRNA or chemical inhibitor, TMN355 resulted in decrease in lipid uptake by 65-75% even after exposure to oxidized LDL. The expression of scavenger receptors expressed during differentiation process, CD36 and LOX-1 were decreased (p < 0.0001). Levels of extracellular cyclophilin A and other inflammatory cytokines such as TNF-α and MCP-1 also significantly reduced. Conclusions: Taken together, we describe here a possible cellular basis by which cyclophilin A may accelerate atherogenesis in diabetes mellitus. [ABSTRACT FROM AUTHOR]

The nuclear receptor superfamily is composed of transcription factors that positively and negatively regulate gene expression in response to the binding of a diverse array of lipid-derived hormones and metabolites. Intense efforts are currently being directed at defining the biological roles and mechanisms of action of liver X receptors (LXRs) and peroxisome proliferator-activated receptors (PPARs). LXRs have been found to play essential roles in the regulation of whole body cholesterol absorption and excretion, in the efflux of cholesterol from peripheral cells, and in the biosynthesis and metabolism of very low density lipoproteins. PPARs have been found to regulate diverse aspects of lipid metabolism, including fatty acid oxidation, fat cell development, lipoprotein metabolism, and glucose homeostasis. Intervention studies indicate that activation of PPARα, PPARγ, and LXRs by specific synthetic ligands can inhibit the development of atherosclerosis in animal models.Here, we review recent studies that provide new insights into the mechanisms by which these subclasses of nuclear receptors act to systemically influence lipid and glucose metabolism and regulate gene expression within the artery wall.

Phagocytosis of oxidized low-density lipoprotein (OxLDL) by macrophages yields "foam cells" and serves as a hallmark of atherosclerotic lesion. Adipsin is a critical component of the complement activation pathway. Recent evidence has indicated an obligatory role for Adipsin in pathological models including ischemia-reperfusion and sepsis. Adipsin levels are significantly decreased in patients with asymptomatic carotid atherosclerosis, implying the role for Adipsin as a potential marker of asymptomatic carotid atherosclerosis. This study was designed to evaluate the role for Adipsin in atherosclerosis and the mechanisms involved using both in vivo and in vitro experiments. ApoE−/−/AdipsinTg mice were constructed and were fed a high-fat diet for 12 weeks. Compared with ApoE−/− mice, area of the sclerotic plaques was reduced, along with lower macrophage deposition within the plaque in ApoE−/−/AdipsinTg mice. RAW264.7 cells and bone marrow-derived macrophages (BMDMs) were stimulated with oxLDL (50 μg/ml). Adenovirus vectors containing the Adipsin gene were transfected into macrophages. Lipid accumulation was observed by Oil red O staining. Western blot and reverse transcription-polymerase chain reaction data revealed that Adipsin overexpression inhibited oxLDL-induced lipid uptake and foam cell formation and upregulation of CD36 and PPARγ in Ad-Adipsin-transfected macrophages. In addition, the PPARγ-specific agonist GW1929 reversed Adipsin overexpression-evoked inhibitory effect on lipid uptake. These results demonstrate unequivocally that Adipsin inhibits lipid uptake in a PPARγ/CD36-dependent manner and prevents the formation of foam cells, implying that Adipsin may be a potential therapeutic target against atherosclerosis. • Adipsin inhibits atherosclerotic plaque formation in ApoE−/− mice fed with a high-cholesterol diet. • Adipsin overexpression inhibited oxLDL-induced lipid uptake and foam cell formation. • Adipsin inhibits lipid uptake in a PPARγ/CD36-dependent manner. [ABSTRACT FROM AUTHOR]

Foam cell formation occurs in vitro at lipoprotein concentrations above 50 μg/ml in pigeon macrophages. Hypothetically, intracellular trafficking of lipoproteins at higher concentrations may differ from uptake of lipoproteins associated with low concentrations, revealing a separate atherogenic endocytic pathway. Macrophage intracellular trafficking of pigeon β-very low density lipoprotein (β-VLDL) and low density lipoprotein (LDL) at low concentrations (12 μg/ml) near the saturation of high affinity binding sites and high lipoprotein concentrations (50–150 μg/ml) used to induce foam cell formation were examined. Pigeon β-VLDL and LDL, differentially labeled with colloidal gold, were added simultaneously to contrast trafficking of β-VLDL, which causes in vitro foam cell formation, with LDL, which does not. The binding of lipoproteins to cell surface structures, distribution of lipoproteins in endocytic organelles, and the extent of colabeling in the endocytic organelles were determined by thin-section transmission electron microscopy. At low concentrations, the intracellular trafficking of pigeon LDL and β-VLDL was identical. At high concentrations, LDL was removed more rapidly from the plasma membrane and reached lysosomes more quickly than β-VLDL. No separate endocytic route was present at high concentrations of β-VLDL; rather, an increased residence on the plasma membrane, association with nonmicrovillar portions of the plasma membrane, and slower trafficking in organelles of coated-pit endocytosis reflected a more atherogenic trafficking pattern.—Jones, N. L., J. A. Saunders, and R. R. Mallory. Intracellular trafficking of pigeon β-very low density lipoprotein and low density lipoprotein at low and high concentrations in pigeon macrophages. J. Lipid Res. 2000. 41: 1823–1831.

Ractopamine, a synthetic β-adrenoreceptor agonist, is used as an animal feed additive to increase food conversion efficiency and accelerate lean mass accretion in farmed animals. The U.S. Food and Drug Administration claimed that ingesting products containing ractopamine residues at legal dosages might not cause short-term harm to human health. However, the effect of ractopamine on chronic inflammatory diseases and atherosclerosis is unclear. Therefore, we investigated the effects of ractopamine on atherosclerosis and its action mechanism in apolipoprotein E-null (apoe −/− ) mice and human endothelial cells (ECs) and macrophages. Daily treatment with ractopamine for four weeks increased the body weight and the weight of brown adipose tissues and gastrocnemius muscles. However, it decreased the weight of white adipose tissues in apoe −/− mice. Additionally, ractopamine exacerbated hyperlipidemia and systemic inflammation, deregulated aortic cholesterol metabolism and inflammation, and accelerated atherosclerosis. In ECs, ractopamine treatment induced endothelial dysfunction and increased monocyte adhesion and transmigration across ECs. In macrophages, ractopamine dysregulated cholesterol metabolism by increasing oxidized low-density lipoprotein (oxLDL) internalization and decreasing reverse cholesterol transporters, increasing oxLDL-induced lipid accumulation. Collectively, our findings revealed that ractopamine induces EC dysfunction and deregulated cholesterol metabolism of macrophages, which ultimately accelerates atherosclerosis progression. [Display omitted] • Ractopamine (RAC) accelerates the progression of atherosclerosis. • RAC increases hyperlipidemia and inflammatory response in apoe −/− mice. • RAC induces endothelial dysfunction and increases foam cell formation. [ABSTRACT FROM AUTHOR]

CD226 is a costimulatory molecule that regulates immune cell functions in T cells, natural killer cells, and macrophages. Because macrophage-derived foam cell formation is a crucial factor contributing to the development of atherosclerosis, we aimed to evaluate the potential roles of CD226 in the pathogenesis of atherosclerosis. The effects of CD226 on atherosclerosis were investigated in CD226 and apolipoprotein E double-knockout (CD226−/− ApoE−/−) mice fed with a high-cholesterol atherogenic diet. CD226 expression in macrophages was evaluated using flow cytometry. Histopathological analysis was performed to evaluate the atherosclerotic lesions. Inflammatory cell infiltration was detected using immunofluorescence staining. Bone marrow-derived macrophages (BMDMs) and peritoneal macrophages (PEMs) were isolated from the mice and used to explore the mechanism in vitro. The in vivo results indicated that CD226 knockdown protected against atherosclerosis in ApoE−/− mice, evidenced by reduced plaque accumulation in the brachiocephalic artery, aortic roots, and main aortic tree. CD226 gene-deficient macrophages showed reduced foam cell formation under ox-low density lipoprotein stimulation compared with wild-type (WT) cells. CD226 deficiency also decreased the expression of CD36 and scavenger receptor (SR)-A (responsible for lipoprotein uptake) but increased the expression of ATP-binding cassette transporter A1 and G1 (two transporters for cholesterol efflux). Therefore, loss of CD226 hinders foam cell formation and atherosclerosis progression, suggesting that CD226 is a promising new therapeutic target for atherosclerosis. • Absence of CD226 inhibits atherosclerotic plaque formation in ApoE−/− mice fed with a high-cholesterol diet. • CD226 knockout macrophages exhibits attenuated foam cell formation in response to oxidized LDL. • CD226 deficiency may hinder lipoprotein uptake but promote cholesterol efflux to reduce lipid accumulation in macrophages. [ABSTRACT FROM AUTHOR]

Background: Atherosclerosis, the underlying cause of heart attack and strokes, is a progresive dyslipidemic and inflammatory disease where monocyte-derived macrophage cells play a pivotal role. Although most of the mechanisms that contribute to the progression of atherosclerosis have been identified, there is limited information on those governing regression. Conjugated linoleic acid (CLA) is a group of isomers of linoleic acid that differ in the position and/or geometry of their double bonds. We have previously shown that a specific CLA blend (80:20 cis-9,trans-11:trans-10,cis-12-CLA) induces regression of pre-established atherosclerosis in vivo, via modulation of monocyte/macrophage function. However, the exact mechanisms through which CLA mediates this effect remain to be elucidated. Methods: Here, we address if CLA primes monocytes towards an anti-inflammatory MΦ2 macrophage and examine the effect of individual CLA isomers and the atheroprotective blend on monocyte-macrophage differentiation, cytokine generation, foam cell formation and cholesterol metabolism in human peripheral blood monocyte (HPBMC)-derived macrophages. Results: cis-9,trans-11-CLA and the atheroprotective 80:20 CLA blend regulates expression of pro-inflammatory mediators and modulates the inflammatory cytokine profile of macrophages and foam cells. In addition, cis-9,trans-11-CLA and CLA blend primes HPBMCs towards an anti-inflammatory MΦ2 phenotype, characterised by increased scavenger receptor (CD36) and efflux protein (ABCA-1) expression. Furthermore, this altered macrophage phenotype impacts on foam cell formation, inhibiting ox-LDL accumulation and promoting cholesterol efflux via both PPAR? and LXRa dependent pathways. Conclusion: The data increases the understanding of the pathways regulated by CLA in atheroprotection, namely, inhibiting the progressive acquisition of a pro-inflammatory macrophage phenotype. [ABSTRACT FROM AUTHOR]

After a period of relative senescence in the field of vascular smooth muscle cell (VSMC) research with particular regards to atherosclerosis, the last few years has witnessed a resurgence, with extensive research re-assessing potential molecular mechanisms and pathways that modulate VSMC behaviour within the atherosclerotic-prone vessel wall and the atherosclerotic plaque itself. Attention has focussed on the pathological contribution of VSMC in plaque calcification; systemic and local mediators such as inflammatory molecules and lipoproteins; autocrine and paracrine regulators which affect cell–cell and cell to matrix contacts alongside cytoskeletal changes. In this brief focused review, recent insights that have been gained into how a myriad of recently identified factors can influence the pathological behaviour of VSMC and their subsequent contribution to atherosclerotic plaque development and progression has been discussed. An overriding theme is the mechanisms involved in the alterations of VSMC function during atherosclerosis. [ABSTRACT FROM AUTHOR]

Aim MicroRNAs (miRNAs) play key roles in inflammatory responses of macrophages. However, the function of miRNAs in macrophage-derived foam cell formation is unclear. Here, we investigated the role of miRNAs in macrophage-derived foam cell formation and atherosclerotic development. Methods and results Using quantitative reverse transcription-PCR (qRT–PCR), we found that the level of miR-155 expression was increased significantly in both plasma and macrophages from atherosclerosis (ApoE−/−) mice. We identified that oxidized low density lipoprotein (oxLDL) induced the expression and release of miR-155 in macrophages, and that miR-155 was required to mediate oxLDL-induced lipid uptake and reactive oxygen species (ROS) production of macrophages. Furthermore, ectopic overexpression and knockdown experiments identified that HMG box-transcription protein1 (HBP1) is a novel target of miR-155. Knockdown of HBP1 enhanced lipid uptake and ROS production in oxLDL-stimulated macrophages, and overexpression of HBP1 repressed these effects. Furthermore, bioinformatics analysis identified three YY1 binding sites in the promoter region of pri-miR-155 and verified YY1 binding directly to its promoter region. Detailed analysis showed that the YY1/HDAC2/4 complex negatively regulated the expression of miR-155 to suppress oxLDL-induced foam cell formation. Importantly, inhibition of miR-155 by a systemically delivered antagomiR-155 decreased clearly lipid-loading in macrophages and reduced atherosclerotic plaques in ApoE−/− mice. Moreover, we observed that the level of miR-155 expression was up-regulated in CD14+ monocytes from patients with coronary heart disease. Conclusion Our findings reveal a new regulatory pathway of YY1/HDACs/miR-155/HBP1 in macrophage-derived foam cell formation during early atherogenesis and suggest that miR-155 is a potential therapeutic target for atherosclerosis. [ABSTRACT FROM PUBLISHER]

Atherosclerosis and its complications are characterized by lipid-laden foam cell formation. Recently, an obvious up-regulation of BMP4 was observed in atherosclerotic plaque, however, its function and the underlying mechanism remains unknown. In our study, BMP4 pretreatment induced macrophage foam cell formation. Furthermore, a dramatic increase in the ratio of cholesteryl ester (CE) to total cholesterol (TC) was observed in BMP4-treated macrophages, accompanied by the reduction of cholesterol outflow. Importantly, BMP4 stimulation inhibited the expression levels of the two most important cellular cholesterol transporters ABCA1 and ABCG1, indicating that BMP4 may induce formation of foam cells by attenuating transporters expression. Further mechanism analysis showed that BMPR-2, one of the BMP4 receptors, was significantly increased in BMP4 treated macrophage foam cells. That blocking its expression using specific siRNA significantly increased ABCA1 and ABCG1 levels. Additionally, BMP4 treatment triggered the activation of Smad1/5/8 pathway by BMPR-2 signaling. After blocking the Smad1/5/8 with its inhibitor, ABCA1 and ABCG1 expression levels were up-regulated significantly, suggesting that BMP4 inhibited the expression of ABCA1 and ABCG1 through the BMPR-2/Smad1/2/8 signaling pathway. Therefore, our results will provide a new insight about how BMP4 accelerate the progressio of atherosclerosis, and it may become a potential target against atherosclerosis and its complications. [ABSTRACT FROM AUTHOR]