ATP-binding Cassette Transporter G1 Research Articles

Heat-killed Lactiplantibacillus plantarum Shinshu N-07 exerts antiobesity effects in western diet-induced obese mice.

The aim of this study was to evaluate the antiobesity effects of heat-killed Lactiplantibacillus plantarum Shinshu N-07 (N-07) isolated from fermented Brassica rapa L. Male mice were divided into three groups (n=10/group); normal diet, western diet (WD), or WD+N-07 (N-07) group and administered each diet for 56 days. The N-07 group showed significant suppression of body weight gain and epididymal fat, perirenal fat, and liver weights compared with the WD group. Higher levels of fecal total cholesterol, triglyceride (TG), and free fatty acid (FFA) were observed in the N-07 group than in the WD group. The mRNA expression of the cholesterol transporter ATP-binding cassette transporter G5 (ABCG5) was significantly increased in the small intestine of N-07-fed mice compared with WD-fed mice. Moreover, N-07 supplementation significantly increased the mRNA expression of ABCG5 and ABCG8 in Caco-2 cells. Furthermore, the TG- and FFA-removal ability of N-07 was confirmed to evaluate its soybean oil- and oleic acid-binding capacities in in vitro experiments. The antiobesity effects of N-07 might be due to its ability to promote lipid excretion by regulating cholesterol transporter expression and lipid-binding ability.

Cav3.1 T-type calcium channel blocker NNC 55-0396 reduces atherosclerosis by increasing cholesterol efflux

Calcium channel blockers (CCBs) are commonly used as antihypertensive agents. While certain L-type CCBs exhibit antiatherogenic effects, the impact of Cav3.1 T-type CCBs on antiatherogenesis and lipid metabolism remains unexplored. NNC 55–0396 (NNC) is a highly selective blocker of T-type calcium channels (Cav3.1 channels). We investigated the effects of NNC on relevant molecules and molecular mechanisms in human THP-1 macrophages. Cholesterol efflux, an indicator of reverse cholesterol transport (RCT) efficiency, was assessed using [3H]-labeled cholesterol. In vivo, high cholesterol diet (HCD)-fed LDL receptor knockout (Ldlr-/-) mice, an atherosclerosis-prone model, underwent histochemical staining to analyze plaque burden. Treatment of THP-1 macrophages with NNC facilitated cholesterol efflux and reduced intracellular cholesterol accumulation. Pharmacological and genetic interventions demonstrated that NNC treatment or Cav3.1 knockdown significantly enhanced the protein expression of scavenger receptor B1 (SR-B1), ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1), and liver X receptor alpha (LXRα) transcription factor. Mechanistic analysis revealed that NNC activates p38 and c-Jun N-terminal kinase (JNK) phosphorylation, leading to increased expression of ABCA1, ABCG1, and LXRα-without involving the microRNA pathway. LXRα isrequired for NNC–induced ABCA1 and ABCG1 expression. Administering NNC diminished atherosclerotic lesion area and lipid deposition in HCD-fed Ldlr-/- mice. NNC's anti-atherosclerotic effects, achieved through enhanced cholesterol efflux and inhibition of lipid accumulation, suggest a promising therapeutic approach for hypertensive patients with atherosclerosis. This research highlights the potential of Cav3.1 T-type CCBs in addressing cardiovascular complications associated with hypertension.

Laminaria japonica Aresch-Derived Fucoidan Ameliorates Hyperlipidemia by Upregulating LXRs and Suppressing SREBPs.

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide, and hyperlipidemia is one major inducing factor of CVD. It is worthy to note that fucoidans are reported to have hypolipidemic activity with species specificity; however, the underlying mechanisms of action are far from clarification. This study is aimed at investigating the plasma lipid-lowering mechanisms of the fucoidan from L. japonica Aresch by detecting the levels of hepatic genes that are involved in lipid metabolism. Our results demonstrated that the fucoidan F3 significantly lowered total cholesterol and triglyceride in C57BL/6J mice fed a high-fat diet. In the mouse liver, fucoidan F3 intervention significantly increased the gene expression of peroxisome proliferator-activated receptor (PPAR) α, liver X receptor (LXR) α and β, and ATP-binding cassette transporter (ABC) G1 and G8 and decreased the expression of proprotein convertase subtilisin/kexin type 9 (PCSK9), low-density lipoprotein receptor, cholesterol 7 alpha-hydroxylase A1, and sterol regulatory element-binding protein (SREBP) 1c and SREBP-2. These results demonstrated that the antihyperlipidemic effects of fucoidan F3 are related to its activation of PPARα and LXR/ABC signaling pathways and inactivation of SREBPs. In conclusion, fucoidan F3 may be explored as a potential compound for prevention or treatment of lipid disorders.

The role of ATP-binding cassette transporter G1 (ABCG1) in Alzheimer's disease: A review of the mechanisms.

The maintenance of cholesterol homeostasis is essential for central nervous system function. Consequently, factors that affect cholesterol homeostasis are linked to neurological disorders and pathologies. Among them, ATP-binding cassette transporter G1 (ABCG1) plays a significant role in atherosclerosis. However, its role in Alzheimer's disease (AD) is unclear. There is inconsistent information regarding ABCG1's role in AD. It can increase or decrease amyloid β (Aβ) levels in animals' brains. Clinical studies show that ABCG1 is involved in AD patients' impairment of cholesterol efflux capacity (CEC) in the cerebrospinal fluid (CSF). Lower Aβ levels in the CSF are correlated with ABCG1-mediated CEC dysfunction. ABCG1 modulates α-, β-, and γ-secretase activities in the plasma membrane and may affect Aβ production in the mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) cell compartment. Despite contradictory findings regarding ABCG1's role in AD, this review shows that ABCG1 has a role in Aβ generation via modulation of membrane secretases. It is, however, necessary to investigate the underlying mechanism(s). ABCG1 may also contribute to AD pathology through its role in apoptosis and oxidative stress. As a result, ABCG1 plays a role in AD and is a candidate for drug development.

Evidence for hypoxia-induced dysregulated cholesterol homeostasis in preeclampsia: Insights into the mechanisms from human placental cells and tissues.

Preeclampsia (PE) poses a considerable risk to the long-term cardiovascular health of both mothers and their offspring due to a hypoxic environment in the placenta leading to reduced fetal oxygen supply. Cholesterol is vital for fetal development by influencing placental function. Recent findings suggest an association between hypoxia, disturbed cholesterol homeostasis, and PE. This study investigates the influence of hypoxia on placental cholesterol homeostasis. Using primary human trophoblast cells and placentae from women with PE, various aspects of cholesterol homeostasis were examined under hypoxic and hypoxia/reoxygenation (H/R) conditions. Under hypoxia and H/R, intracellular total and non-esterified cholesterol levels were significantly increased. This coincided with an upregulation of HMG-CoA-reductase and HMG-CoA-synthase (key genes regulating cholesterol biosynthesis), and a decrease in acetyl-CoA-acetyltransferase-1 (ACAT1), which mediates cholesterol esterification. Hypoxia and H/R also increased the intracellular levels of reactive oxygen species and elevated the expression of hypoxia-inducible factor (HIF)-2α and sterol-regulatory-element-binding-protein (SREBP) transcription factors. Additionally, exposure of trophoblasts to hypoxia and H/R resulted in enhanced cholesterol efflux to maternal and fetal serum. This was accompanied by an increased expression of proteins involved in cholesterol transport such as the scavenger receptor class B type I (SR-BI) and the ATP-binding cassette transporter G1 (ABCG1). Despite these metabolic alterations, mitogen-activated-protein-kinase (MAPK) signaling, a key regulator of cholesterol homeostasis, was largely unaffected. Our findings indicate dysregulation of cholesterol homeostasis at multiple metabolic points in both the trophoblast hypoxia model and placentae from women with PE. The increased cholesterol efflux and intracellular accumulation of non-esterified cholesterol may have critical implications for both the mother and the fetus during pregnancy, potentially contributing to an elevated cardiovascular risk later in life.

Cornelian Cherry (Cornus mas L.) Fruit Extract Lowers SREBP-1c and C/EBPα in Liver and Alters Various PPAR-α, PPAR-γ, LXR-α Target Genes in Cholesterol-Rich Diet Rabbit Model.

Cornelian cherry (Cornus mas L.) fruits, abundant in iridoids and anthocyanins, are natural products with proven beneficial impacts on the functions of the cardiovascular system and the liver. This study aims to assess and compare whether and to what extent two different doses of resin-purified cornelian cherry extract (10 mg/kg b.w. or 50 mg/kg b.w.) applied in a cholesterol-rich diet rabbit model affect the levels of sterol regulatory element-binding protein 1c (SREBP-1c) and CCAAT/enhancer binding protein α (C/EBPα), and various liver X receptor-α (LXR-α), peroxisome proliferator-activated receptor-α (PPAR-α), and peroxisome proliferator-activated receptor-γ (PPAR-γ) target genes. Moreover, the aim is to evaluate the resistive index (RI) of common carotid arteries (CCAs) and aortas, and histopathological changes in CCAs. For this purpose, the levels of SREBP-1c, C/EBPα, ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1), fatty acid synthase (FAS), endothelial lipase (LIPG), carnitine palmitoyltransferase 1A (CPT1A), and adiponectin receptor 2 (AdipoR2) in liver tissue were measured. Also, the levels of lipoprotein lipase (LPL), visceral adipose tissue-derived serine protease inhibitor (Vaspin), and retinol-binding protein 4 (RBP4) in visceral adipose tissue were measured. The RI of CCAs and aortas, and histopathological changes in CCAs, were indicated. The oral administration of the cornelian cherry extract decreased the SREBP-1c and C/EBPα in both doses. The dose of 10 mg/kg b.w. increased ABCA1 and decreased FAS, CPT1A, and RBP4, and the dose of 50 mg/kg b.w. enhanced ABCG1 and AdipoR2. Mitigations in atheromatous changes in rabbits' CCAs were also observed. The obtained outcomes were compared to the results of our previous works. The beneficial results confirm that cornelian cherry fruit extract may constitute a potentially effective product in the prevention and treatment of obesity-related disorders.

Up-regulation of ABCG1 is associated with methotrexate resistance in acute lymphoblastic leukemia cells.

Acute lymphoblastic leukemia (ALL) is a prevalent hematologic malignancy in children, and methotrexate (MTX) is a widely employed curative treatment. Despite its common use, clinical resistance to MTX is frequently encountered. In this study, an MTX-resistant cell line (Reh-MTXR) was established through a stepwise selection process from the ALL cell line Reh. Comparative analysis revealed that Reh-MTXR cells exhibited resistance to MTX in contrast to the parental Reh cells. RNA-seq analysis identified an upregulation of ATP-binding cassette transporter G1 (ABCG1) in Reh-MTXR cells. Knockdown of ABCG1 in Reh-MTXR cells reversed the MTX-resistant phenotype, while overexpression of ABCG1 in Reh cells conferred resistance to MTX. Mechanistically, the heightened expression of ABCG1 accelerated MTX efflux, leading to a reduced accumulation of MTX polyglutamated metabolites. Notably, the ABCG1 inhibitor benzamil effectively sensitized Reh-MTXR cells to MTX treatment. Moreover, the observed upregulation of ABCG1 in Reh-MTXR cells was not induced by alterations in DNA methylation or histone acetylation. This study provides insight into the mechanistic basis of MTX resistance in ALL and also suggests a potential therapeutic approach for MTX-resistant ALL in the future.

Multiple bioactivities of choerospondin obtained from blossom of Citrus aurantium L. Var. Amara engl. And its anti-inflammation and anti-atherosclerosis action pathways

Nutritional intervention has been emerged as a popular strategy to improve quality of human life. Here we extracted and identified choerospondin (CHO), a dietary flavonoid glycoside from blossom of Citrus aurantium L. var. amara Engl. Different models were employed to screen the antioxidant, anti-tumor, anti-obesity, anti-inflammation and anti-atherosclerosis effects of CHO. The data showed that CHO displayed enhanced resistance to oxidative stress. Anti-proliferative effects against MCF-7, HepG2 and H1299 cells were also observed by CHO administration. CHO intervention potently inhibited 3 T3-L1 preadipocytes differentiation by suppressing transcription of some key adipogenic factors. Especially, CHO supplementation exhibited marked decreases of nitric oxide production in LPS-induced macrophages, significant reductions of cholesterol uptake and increases of cholesterol efflux in ox-LDL-loaded macrophages. These facts indicated that CHO showed greater anti-inflammation and anti-atherosclerosis potential. Futher, CHO markedly inhibited inflammatory responses through blunting mitogen-activated protein kinase phosphorylation and nuclear factor-kappa B activation. CHO application also reversed foam cell formation by regulating cluster of differentiation 36, phospholipid ATP-binding cassette transporter A1, phospholipid ATP-binding cassette transporter G1 and scavenger receptor class B type 1 expression. In conclusion, these data provided strong evidences that CHO possessed various pharmacological effects, including antioxidant, anti-tumor, anti-obesity and especially anti-inflammation and anti-atherosclerosis properties.

QiShenYiQi pill inhibits atherosclerosis by promoting TTC39B-LXR mediated reverse cholesterol transport in liver

BackgroundTetranucleotide repeat domain protein 39B (TTC39B) was found to combine with ubiquitin ligase E3, and promote the ubiquitination modification of liver X receptor (LXR), which led to the inhibition of reverse cholesterol transport and development of atherosclerosis. QiShenYiQi pill (QSYQ) is a modern Chinese patent drug for treating ischemic cardiovascular diseases, the underlying mechanism is found to promote the expression of LXR-α/ ATP-binding cassette transporter G5 (ABCG5) in the liver of atherosclerotic mice. PurposeThe aim of this study is to investigate the effect of QSYQ on TTC39B-LXR mediated reverse cholesterol transport in atherosclerotic mice. Study design and methodsMale apolipoprotein E gene knockout mice (7 weeks old) were fed with high-fat diet and treated with low dose of QSYQ (QSYQ-l, 0.3 g/kg·d), high dose of QSYQ (QSYQ-H, 1.2 g/kg·d) and LXR-α agonist (LXR-A, GW3965 10 mg/kg·d) for 8 weeks. C57BL/6 J mice were fed with normal diet and used as negative control. Oil red O staining, HE staining, ELISA, RNA sequencing, western blot, immunohistochemistry, RT-PCR, cell culture and RNA interference were performed to analyze the effect of QSYQ on atherosclerosis. ResultsHE staining showed that QSYQ reduced the atherosclerotic lesion significantly when compared to the control group. ELISA measurement showed that QSYQ decreased serum VLDL and increased serum ApoA1. Oil Red O staining showed that QSYQ reduced the lipid content of liver and protect liver function. Comparative transcriptome RNA-sequence of liver showed that DEGs after QSYQ treatment enriched in high-density lipoprotein particle, ubiquitin ligase complex, bile secretion, etc. Immunohistochemical staining and western blot proved that QSYQ increased the protein expression of hepatic SR-B1, LXR-α, LXR-β, CYP7A1 and ABCG5. Targeted inhibiting Ttc39b gene in vitro further established that QSYQ inhibited the gene expression of Ttc39b, increased the protein expression of SR-B1, LXR-α/β, CYP7A1 and ABCG5 in rat hepatocyte. ConclusionOur results demonstrated the new anti-atherosclerotic mechanism of QSYQ by targeting TTC39B-LXR mediated reverse cholesterol transport in liver. QSYQ not only promoted reverse cholesterol transport, but also improved fatty liver and protected liver function.

Gypenosides and capsaicinoids in combination ameliorates high-fat-diet- induced rat hyperlipidemia via the PPARγ-LXRα-ABCA1/ABCG1 pathway

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic hepatic disease characterized by excessive fat accumulation, and is the major risk for cardiovascular and metabolic disorders. We explored the therapeutic effect of gypenosides (Gyps) in combination with capsaicinoids (Caps) against high-fat-diet (HFD)-induced rat hyperlipidemia and oxidized low-density lipoprotein (ox-LDL)-treated Raw264.7 cells. Network pharmacology analysis predicted that the potential molecular mechanism of Gyps/Caps combination against hyperlipidemia was mainly associated with steroid metabolism, lipid synthesis and inflammatory response. Animal experiment demonstrated that Gyps/Caps combination lowered the liver weight, liver index, serum lipid profile and hepatic cholesterol content, improved liver function by reducing the serum markers of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), thereby relieving the hepatic injury. Moreover, Gyps/Caps combination inhibited oxidative stress by decreasing the lactic dehydrogenase (LDH) activity and increasing the superoxide dismutase (SOD) activity. Western blotting result suggested that Gyps/Caps combination could upregulate the expressions of peroxisome proliferator-activated receptors γ (PPARγ), liver X receptor α (LXRα), ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1) in the liver tissue. Cellular experiment revealed that the combination treatment protected RAW264.7 cells from ox-LDL induction through inhibiting apoptosis, lipid-decreasing and anti-inflammation, and caused the dramatic enhancement on PPARγ expression. Notably, the combined use of Gyps and Caps did not influence the pharmacological outcomes of each other, but significantly enhanced the overall therapeutic effect in ameliorating HFD-induced hyperlipidemia. Our research provided an experimental basis for advanced research and clinical application of Gyps/Caps combination. Importantly, our cumulative data indicated that combination use of Gyps and Caps may be an effective therapeutic strategy for alleviating hyperlipidemia-induced NAFLD.

ATP-binding cassette transporter G1 (ABCG1) polymorphisms in pregnant women with gestational diabetes mellitus

Context and objectivesGestational diabetes mellitus (GDM) is the most common metabolic disorder in pregnancy, and it often leads to adverse pregnancy outcomes and seriously harms the health of mothers and infants. ATP-binding cassette transporter G1 (ABCG1) plays critical roles in high-density lipoprotein (HDL) metabolism and reverse cholesterol transport. This study was designed to explore the relevance of the ABCG1 polymorphisms in the atherometabolic risk in GDM. Study designThe case-control population consists of 1504 subjects. The rs2234715 and rs57137919 single nucleotide polymorphisms (SNPs) were genotyped using PCR and DNA sequencing, and clinical and metabolic parameters were determined. ResultsThe genotype distributions of the two SNPs showed no difference between the GDM patient and control groups. However, the rs57137919 polymorphism was associated with total cholesterol (TC), and diastolic blood pressure (DBP) levels in patients with GDM. Moreover, subgroup analysis showed that this polymorphism was associated with ApoA1 and DBP levels in overweight/obese patients with GDM, while it was associated with TC, and gestational weight gain (GWG) in non-obese patients with GDM. Meanwhile, the rs2234715 polymorphism was found to be associated with neonatal birth height in non-obese patients with GDM. ConclusionsThe two polymorphisms in the ABCG1 have an influence on atherometabolic traits, GWG, and fetal growth in GDM, depending on the BMI of the patients.

OxLDL-Induced Foam Cell Formation Inhibitory Activity of Pepsin Hydrolysate of Ark Shell (Scapharca subcrenata (Lischke, 1869)) in RAW264.7 Macrophages

Inhibitory effect of ark shell (Scapharca subcrenata (Lischke, 1869)) proteolytic hydrolysates (ASHs) on oxidized low-density lipoprotein (oxLDL)-induced macrophage foam cell formation was investigated. Two types of ASHs were prepared by Alcalase® and pepsin, ASAH (ark shell-Alcalase® hydrolysates), and ASPH (ark shell-pepsin hydrolysate). Oil Red O staining results showed that ASPH suppressed foam cell formation and lipid accumulation more than ASAH in oxLDL-induced foam cell formation of RAW264.7 macrophages. ASPH reduced the levels of total cholesterol, cholesterol ester, and free cholesterol in oxLDL-treated RAW264.7 macrophages. It was found that ASPH increased cholesterol efflux and decreased cholesterol influx rate. In this regard, protein expressions of CD36 and scavenger receptor class A1 (SR-A1) for cholesterol influx and ATP-binding cassette transporter A1 and G1 (ABCA1 and ABCG1) for cholesterol efflux were investigated. ASPH treatment resulted in an increase of ABCA1 and ABCG1 expression but downregulated CD36 and SR-A1 expression. Furthermore, ASPH suppressed production of proinflammatory cytokines, including tumor necrosis factor-α and interleukin-6 and -1β, through regulating nuclear factor-kappa B (NF-κB) in oxLDL-induced foam cell formation of RAW264.7 macrophages. Taken together, our data indicate that ASPH might be a useful ingredient in functional foods for ameliorating atherosclerosis by preventing foam cell formation.

Mechanism of crocin I on ANIT-induced intrahepatic cholestasis by combined metabolomics and transcriptomics.

Background: Intrahepatic cholestasis (IC) is a disorder of bile production, secretion, and excretion with various causes. Crocin I (CR) is effective in the treatment of IC, but its underlying mechanisms need to be further explored. We aimed to reveal the therapeutic mechanism of crocin I for IC by combining an integrated strategy of metabolomics and transcriptomics. Methods: The hepatoprotective effect of CR against cholestasis liver injury induced by α-naphthylisothiocyanate (ANIT) was evaluated in rats. The serum biochemical indices, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bile acid (TBA), total bilirubin (TBIL), direct bilirubin (DBIL), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β), as well as the liver oxidative stress indexes and the pathological characteristics of the liver were analyzed. In addition, we also performed a serum metabolomics study using UPLC-Q Exactive HF-X technology to investigate the effect of CR on the serum of rats with ANIT-induced IC and screened potential biomarkers. The enrichment analysis of differential expressed genes (DEGs) was performed by transcriptomics. Finally, the regulatory targets of CR on potential biomarkers were obtained by combined analysis, and the relevant key targets were verified by western blotting. Results: CR improved serum and liver homogenate indexes and alleviated liver histological injury. Compared with ANIT group, the CR group had 76 differential metabolites, and 10 metabolic pathways were enriched. There were 473 DEGs significantly changed after CR treatment, most of which were enriched in the retinol metabolism, calcium signaling pathway, PPAR signaling pathway, circadian rhythm, chemokine signaling pathway, arachidonic acid metabolism, bile secretion, primary bile acid biosynthesis, and other pathways. By constructing the "compound-reaction-enzyme-gene" interaction network, three potential key-target regulation biomarkers were obtained, including 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), ATP-binding cassette transporter G5 (ABCG5), and sulfotransferase2A1(SULT2A1), which were further verified by western blotting. Compared with the ANIT group, the CR group significantly increased the expression of ABCG5 and SULT2A1, and the expression of HMGCR significantly decreased. Conclusion: Combined metabolomic and transcriptomic analyses show that CR has a therapeutic effect on IC through regulation of the biosynthesis of bile acids and bilirubin in the bile secretion pathway and regulation of the expression of HMGCR, ABCG5, and SULT2A1.

Diaporisoindole B Reduces Lipid Accumulation in THP-1 Macrophage Cells via MAPKs and PPARγ-LXRα Pathways and Promotes the Reverse Cholesterol Transport by Upregulating SR-B1 and LDLR in HepG2 Cells.

Diaporisoindole B (DPB), an isoprenylisoindole alkaloid isolated from the mangrove endophytic fungus Diaporthe sp. SYSU-HQ3, has been proved to have a good anti-inflammatory activity in macrophage cells. In this study, we found that DPB was able to reduce lipid accumulation in THP-1 macrophage-derived foam cells. DPB could inhibit the lipid influx-related gene CD36 and increase the expression of lipid efflux-related genes ATP binding cassette transporter A1 (ABCA1), ATP binding cassette transporter G1 (ABCG1), and scavenger receptor B1 (SR-B1). Moreover, DPB elevated low-density lipoprotein receptor (LDLR) protein expression in HepG2 cells, which can increase the transport of LDL. Meanwhile, DPB could downregulate the expression levels of proteins related to cholesterol and fatty acid synthesis. Further study showed that DPB could activate peroxisome proliferator-activated receptor gamma (PPARγ) and inhibit mitogen-activated protein kinase (MAPK) phosphorylation. Taken together, our findings demonstrated that DPB could reduce lipid accumulation in THP-1 macrophage cells by reducing the intake of lipids and promoting the efflux of lipids and also could promote the reverse cholesterol transport (RCT) mechanism by upregulating SR-B1 and LDLR in HepG2 cells.

Metformin suppresses foam cell formation, inflammation and ferroptosis via the AMPK/ERK signaling pathway in ox‑LDL‑induced THP‑1 monocytes.

Numerous studies have shown that the formation of foam cells is of vital importance in the process of atherosclerosis. The aim of the present study was to assess the effects of metformin on foam cell formation in oxidized low-density lipoprotein (ox-LDL)-treated THP-1 cells and explore its associated mechanism of action. Human monocytic THP-1 cells were pretreated with metformin for 2 h and subsequently treated with ox-LDL for 24 h. The data indicated that metformin significantly inhibited lipid accumulation in ox-LDL-treated THP-1 cells by decreasing the expression of scavenger receptor A, cluster of differentiation 36 and adipocyte enhancer-binding protein 1. In addition, metformin increased the expression levels of scavenger receptor B1 and ATP binding cassette transporter G1 and suppresses the esterification of free cholesterol. Furthermore, it markedly inhibited ferroptosis (reflected by the upregulation of glutathione peroxidase glutathione peroxidase 4 and the downregulation of Heme oxygenase-1). In addition, it caused a marked suppression in the expression levels of cysteinyl aspartate specific proteinase-1, IL-1β, NOD-like receptor protein 3, IL-18 secretion and in the levels of oxidative stress. Metformin attenuated the activation of ERK and facilitated the phosphorylation of 5' adenosine monophosphate-activated protein kinase (AMPK). Treatment of THP-1 cells with an ERK inhibitor reversed these effects, while inhibition of AMPK activity exacerbated the effects noted in ox-LDL-treated THP-1 cells. In conclusion, the present study suggested that metformin suppressed foam cell formation, inflammatory responses and inhibited ferroptosis in ox-LDL-treated macrophages via the AMPK/ERK signaling pathway.

Three polymethoxyflavones from the peel of Citrus reticulata "Chachi" inhibits oxidized low-density lipoprotein-induced macrophage-derived foam cell formation.

Foam cell formation is the hallmark of the development and progression of atherosclerosis. The aim of this study was to investigate the regulatory effects of three polymethoxyflavones (PMFs), namely, tangeretin (TAN), 5,6,7,3′,4′,5′-hexamethoxyflavone (HxMF), and 3,5,6,7,8,3′,4′-heptamethoxyflavone (HpMF) on macrophage-derived foam cell formation and to further explore the molecular mechanisms. The RAW264.7 macrophage-derived foam cell model was successfully induced by oxidized low-density lipoprotein (ox-LDL) (80 μg/ml). It showed that TAN, HxMF, and HpMF alleviated ox-LDL-induced NO release while also inhibiting the expression of IL-1β, IL-6, and TNF-α in RAW264.7 cells. Uptake of excess ox-LDL was inhibited by TAN, HxMF, and HpMF, resulting in the reduction of its foam cell formation. Moreover, TAN, HxMF, and HpMF promoted HDL-mediated cholesterol efflux. Western blot experiment showed that TAN, HxMF, and HpMF inhibited the expression of scavenger receptor class A type I (SRA1) and cluster of differentiation 36 (CD36), while upregulating peroxisome proliferator-activated receptor γ (PPARγ), liver X receptor α (LXRα), phospholipid ATP-binding cassette transporter G1 (ABCG1), and scavenger receptor class B type I (SRB1) expression. Together, our findings suggested that PMFs inhibited foam cell formation might inhibit lipid uptake via downregulating SRA1/CD36 expression and promote cholesterol efflux from foam cells via upregulating PPARγ/LXRα/ABCG1/SRB1 expression. This antiatherosclerotic activity is expected to provide new insights into the development of healthcare uses for PMFs.

Different Pathways of Cellular Cholesterol Efflux.

Cholesterol efflux is the first and rate-limiting step of reverse cholesterol transport (RCT) from peripheric cells to the liver. The involvement of high-density lipoprotein (HDL) in RCT determines the atheroprotective properties of HDL. Cholesterol efflux from different membrane pools includes both passive and energy-dependent processes. The first type of route consists of cholesterol desorption from the cell membrane into the unstirred layer adjacent to the cell surface and diffusion in the water phase. Moreover, the selective uptake and facilitated diffusion of cholesterol and cholesteryl ester molecules through the hydrophobic tunnel in the scavenger receptor BI molecule does not require energy consumption. The second type of route includes active cholesterol export by the ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1). Several cholesterol acceptors specifically bind cholesterol and phospholipid molecules, and cholesterol binding to the albumin molecule, which acts as a shuttle, significantly increases cholesterol movement between acceptors and red blood cells, thus functioning as a sink for cholesterol. Cholesterol and phospholipid molecules effluxed from macrophages by ABCA1 are accepted exclusively by the lipid-free apolipoprotein apoA-I, which is the major protein moiety of HDL, whereas those effluxed by ABCG1 are accepted by HDL. ABCA1- and ABCG1-mediated cholesterol transport, together with cholesterol diffusion, largely determine cholesterol turnover at the physiological level of intracellular cholesterol. However, at cholesterol overload, ABCA1-mediated efflux prevails over other routes. The exchange of apoA-I between lipid-free and lipid-associated states and the synergism of nascent and mature HDL contribute to cholesterol efflux efficiency. Moreover, extracellular cholesterol deposits and microvesicles may be involved in RCT.

Serum levels of IL-37 and correlation with inflammatory cytokines and clinical outcomes in patients with coronary artery disease

Coronary artery disease (CAD) due to atherosclerosis is one of the important reasons for death worldwide. Recent evidence has suggested the essential role of inflammation in the progression of atherosclerosis....

Loss of CD226 protects apolipoprotein E-deficient mice from diet-induced atherosclerosis

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.

Role of cannabinoids and vitamin E analogues in macrophages foam cells formation

Recently, macrophages foam cells have gained attention in cases of electronic‐cigarette or vaping product use‐associated lung injury (EVALI). An increased number of foam cells was detected in bronchoalveolar lavages and lungs after inhaling e‐cigarette smoke from products containing cannabinoids and the vitamin E analogue, alpha‐tocopherol acetate (αTA), that was present as vape‐cartridge additive. Increased levels of intact αTA are reportedly detected in EVALI indicating that conversion of αTA to αT may less occur in lungs upon inhaling vapors from e‐cigarettes containing αTA.HypothesisWhereas the molecular mechanisms by which macrophages foam cells are formed after vaping are unclear, it appears possible that cannabinoid receptors play a role, as lung‐resident macrophages express cannabinoid receptors. Dysregulation of cannabinoid receptors by αTA and cannabinoids may induce the CD36 scavenger receptor/fatty acids transporter (CD36/FAT) and/or reduce the ATP binding cassette transporters A1 and G1 (ABCA1/G1) expression leading to lipid accumulation. Therefore, we analyzed the regulatory effects on lipid homeostasis of natural alpha‐tocopherol (RRR‐αT), natural RRR‐αTA (αTAn) and synthetic racemic all‐rac‐αTA (αTAr) with and without co‐treatment with cannabinoids (cannabinol (CBD), Δ9‐tetrahydrocannabinol (THC)) in THP‐1 monocytes and macrophages (differentiated for 48 h with 100 ng/ml phorbol‐12‐myristate‐13‐acetate (PMA)).ResultsQuantification of lipids in macrophages indicated that more lipids accumulate with αT, less with αTAn and αTAr, whereas control alpha‐tocopheryl phosphate (αTP) clearly inhibited. Co‐treatment with THC increased lipid accumulation with αT, αTAn as well as with CBD, whereas αTP again clearly inhibited. In THP‐1 monocytes, CD36 scavenger receptor was stimulated with αTAn and THC and with co‐treatment with THC and αTAn or CBD. In THP‐1 macrophages, CD36 was only up‐regulated by CBD and co‐treatment with αTAn or αTAr reduced it. In THP‐1 monocytes, cell cycle progression was only affected by CBD (increased G1, decreased S) and co‐treatment with αTAn and αTAr restored it. In macrophages, no significant toxicity was measured with lactate dehydrogenase (LDH) release assay by these treatments at 24 h, 48 h and 72 h at αTA concentrations below 50 μM.SummaryAlthough the mechanisms by which intact αTA may affect lungs in cases of EVALI are still unclear it may disrupt the pulmonary surfactant, act as linactant, and/or dysregulate lipid homeostasis and contribute to formation of macrophages foam cells and inflammation. Lipid accumulation in monocytes/macrophages and foam cells formation were modulated by cannabinoids and αTA but the involvement of lipid homeostasis genes such as CD36/FAT and ABCA1/G1 remains to be further elucidated. A detailed analysis of the molecular mechanisms by which foam cells are formed will not only be important to understand EVALI but also for atherosclerosis and non‐alcoholic steatohepatitis (NASH).