Abstract:Aim To explore the effects of apolipoprotein AⅠ (ApoAⅠ) and apolipoprotein AⅠ binding protein (AIBP) on THP-1-derived macrophage pyroptosis. Methods The lactate dehydrogenase (LDH) detection kit was used to evaluate cell membrane integrity, Hoechst33342/PI staining was used to observe cell membrane permeability, ELISA was used to detect the levels of inflammatory factors such as interleukin-1β (IL-1β) and interleukin-18 (IL-18), Western blot was used to detect the expression of pyroptosis-related protein nucleotide-binding domain leucine-rich repeat and pyrin domain-containing receptor 3 (NLRP3), gasdermin D (GSDMD), cleaved Caspase-1, IL-1β and IL-18. Results Oxidized low density lipoprotein (ox-LDL) upregulated the expression of NLRP3, GSDMD-N, cleaved Caspase-1, IL-1β and IL-18 in THP-1-derived macrophages in a concentration-dependent manner, and promoted the release of IL-1β, IL-18 and LDH (P＜0.05 or P＜0.01), indicating that ox-LDL induced pyroptosis in THP-1-derived macrophages in a concentration-dependent manner. Co-treatment of macrophages with ApoAⅠand AIBP significantly downregulated the expression of NLRP3, GSDMD-N, cleaved Caspase-1, IL-1β and IL-18, reduced the release of IL-1β, IL-18 and LDH, and inhibited ox-LDL induced pyroptosis (P＜0.05 or P＜0.01). After ATP-binding cassette transporter A1 (ABCA1) siRNA transfection, co-treatment with ApoAⅠ and AIBP had no significant effect on the expression of pyroptosis-related proteins and secretion of inflammatory factors (P＞0.05). Co-treatment of macrophages with ApoAⅠ and AIBP significantly reduced the expression of purinergic 2X7R receptor (P2X7R) on the cell membrane, inhibited P2X7R mediated protein kinase R (PKR) phosphorylation and NLRP3 inflammasome assembly (P＜0.05 or P＜0.01). After P2X7R siRNA transfection, co-treatment with ApoAⅠand AIBP had no significant effect on the expression of pyroptosis-related proteins and secretion of inflammatory factors (P＞0.05). Conclusion ApoAⅠ and AIBP reduce the expression of P2X7R on the cell membrane through ABCA1, inhibiting P2X7R/PKR/NLRP3 mediated macrophage pyroptosis.

Abstract:Aim To explore the effect of Pueraria Lobata Flowers Extract (PFE) on lipid accumulation in macrophage-derived foam cells. Methods The concentration of PFE in THP-1-derived foam cells was screened by MTT, intracellular lipid accumulation was detected by oil red O staining and cholesterol detection kit, intracellular cholesterol efflux levels were detected by cholesterol efflux assay kit, RT-qPCR and Western blot were used to analyze mRNA and protein expression. Results PFE significantly reduced lipid accumulation in THP-1-derived foam cells. PFE did not affect the mRNA expression of CD36, scavenger receptor-AⅠ (SR-AⅠ), sterol regulatory element-binding protein 2 (SREBP2), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), but it could upregulate the mRNA and protein expression levels of ATP-binding cassette transporter A1 (ABCA1) (P＜0.05), and promote the intracellular cholesterol efflux of macrophage-derived foam cells (P＜0.01). PFE could activate the activity of peroxisome proliferator-activated receptor γ (PPARγ) (P＜0.01) and upregulate the mRNA and protein expression levels of PPARγ (P＜0.05). Compared with the PFE control group, the expression of PPARγ and ABCA1 proteins decreased and cholesterol efflux decreased after GW9662 treatment (all P＜0.01). Conclusion PFE could significantly prevent the lipid accumulation in THP-1-derived foam cells and inhibit the formation of foam cells by upregulating ABCA1 expression and cholesterol efflux mediated by PPARγ.

Abstract:Aim To investigate the impact of bakuchiol (BAK) on lipid accumulation in macrophage-derived foam cell and explore the underlying mechanisms. Methods MTT assay was used to determine the non-toxic concentration of BAK on foam cell. Oil red O staining, NBD cholesterol, and Dil-ox-LDL were used to assess lipid accumulation in foam cell. RT-qPCR and Western blot were utilized to measure mRNA and protein expression, respectively. Results BAK promoted cholesterol effux and reduced lipid accumulation in foam cell. BAK upregulated the mRNA and protein expression levels of ATP-binding cassette transporter A1 (ABCA1) and concurrently downregulated the phosphorylation levels of extracellular signal-regulated kinase 1/2 (ERK1/2). Treatment with the ERK1/2 activator Ro 67-7476 resulted in decreased ABCA1 protein expression compared with the BAK-treated group. Conclusion BAK reduced lipid accumulation in foam cell by inhibiting ERK1/2 phosphorylation, upregulating ABCA1 expression, and promoting cholesterol efflux, thereby suppressing foam cell formation.

Abstract:Atherosclerosis is a chronic vascular inflammation caused by lipid deposition. The onset and progression of atherosclerotic lesions are closely related to the disturbance of cellular cholesterol homeostasis. ATP-binding cassette transporter A1 (ABCA1) mediates active cholesterol efflux to apolipoprotein AⅠ, preβ high density lipoprotein (HDL), and HDL3. The impairment of this cholesterol efflux pathway leads to the intracellular accumulation of cholesterol esters. Importantly, loss-of-function mutations of ABCA1 influence the growth of atherosclerotic plaques and the incidence of coronary heart diseases. Recent studies using transgenic animals have shown that effects of ABCA1 on atherosclerosis are tissue/cell-specific. This paper focuses on the role of tissue/cell-specific ABCA1 in atherosclerosis and underlying mechanisms after briefly introducing reverse cholesterol transport and atherosclerosis.

Abstract:Aim To explore the effect of the compatibility of Alisma and Atractylodes on relieving atherosclerosis(As) in ApoE－/－mice and the correlation with reverse cholesterol transport. Methods ApoE－/－ mice were fed with a high-fat diet to construct an animal model of As and treated with Alisma and Atractylodes. The wall thickness, lumen diameter of common carotid artery were measured by ultrasound. HE staining was used to observe the morphology of the artery, and lipid deposition in the liver was observed by oil red O staining. Inflammatory cytokines such as tumor necrosis factor-α(TNF-α), interleukin-1β(IL-1β), matrix metalloproteinase-2(MMP-2)were test by ELISA,and matrix metalloproteinase-9(MMP-9) and blood lipid components serum total cholesterol(TC), triglyceride(TG), low density lipoprotein(LDL) and high density lipoprotein(HDL)were analyzed by automatic biochemical analyser. Western blot was used to quantify the expression of silent information regulator protein 1(SIRT1), liver X receptor α(LXRα), ATP-binding cassette transporter A1(ABCA1)and scavenger receptor class B type Ⅰ (SR-BⅠ)in the ApoE－/－ mice liver. Results The compatibility of Alisma and Atractylodes not only significantly repressed the wall thickness, lumen diameter of the common carotid in ApoE－/－ mice, but also reduced the deposition of lipids in the ApoE－/－ mice liver. Treatment with Alisma decoction caused a drop in serum MMP-2, MMP-9, TNF-α, IL-1β, TC, TG, LDL and increase in serum HDL. The expression of SIRT1, LXRα, ABCA1 and SR-BⅠ were markedly up-regulated in the ApoE－/－mice liver treated with Alisma and Atractylodes. Conclusion It was suggested that the compatibility of Alisma and Atractylodes promoted reverse cholesterol transport to reduce liver lipid deposition, suppressed inflammation and improved the morphology of artery via SIRT1-LXRα-ABCA1/SR-BⅠ pathway. It exerted the protective effect in the occurrence and development of As.

Abstract:Aim To investigate the effect of ligustrazine (LIG) on inflammatory injury induced by lipopolysaccharide (LPS) in human coronary artery endothelial cells (HCAEC) and explore its possible mechanism. Methods After pretreatment with LIG (1,0, 100 μmol/L) for 12 hours, HCAEC cells were co-treated by LPS (1 mg/L) and LIG for 24 hours. Cell viability was tested by methyl thiazolyl tetrazolium (MTT) assay. Apoptosis rate of HCAEC was detected by flow cytometry. Levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in supernatant of cell culture medium were tested by enzyme linked immunosorbent assay (ELISA). Expression of ATP-binding cassette transporter A1 (ABCA1) protein in HCAEC cells were measured by Western blot. Results Compared with control group, the cell viability of HCAEC was significantly decreased, the apoptosis rate of HCAEC was significantly increased, the levels of IL-6 and TNF-α in supernatant of cell culture medium were significantly increased, expression of ABCA1 protein in HCAEC was significantly down-regulated in LPS group (all P＜0.05). Compared with LPS group, the cell viability of HCAEC was significantly increased, the apoptosis rate of HCAEC was significantly decreased, the levels of IL-6 and TNF-α in supernatant of cell culture medium were significantly decreased, expression of ABCA1 protein in HCAEC were significantly up-regulated in LIG (10 and 100 μmol/L)＋LPS group (all P＜0.05). Conclusion LIG inhibits the inflammatory injury induced by LPS in HCAECs, and its mechanism may be related to LIG up-regulating the expression of ABCA1.

Abstract:The abnormality of reverse cholesterol transport (RCT) induces the disorder of lipid metabolism, which is a key factor in the pathogenesis of atherosclerosis. It is important to explore the roles and regulatory mechanisms of key proteins mediated RCT in lipid metabolism. These are also important significance to elucidate the molecular mechanism of atherosclerosis. In this topic collection papers, we discuss the effects of liraglutide, momordicin and growth differentiation factor 11 on cholesterol efflux and the expressions of key proteins ATP-binding cassette transporter A1 (ABCA1), ABCG1 and scavenger receptor class B type Ⅰ in RCT. From different angles, we explain the molecular mechanism of RCT key proteins involved in the regulation of cholesterol efflux by drugs or small molecules.

Abstract:Aim To explore the effect of growth differentiation factor 11 (GDF11) on macrophage reverse cholesterol transport and uncover the potential mechanism. Methods Mouse peritoneal macrophages were treated with oxidized low density lipoprotein (ox-LDL), GDF11 and activin receptor-like kinase 7 (ALK7) inhibitor SB431542 for 24 hours. The lipid accumulation was observed with oil red O staining, and the mRNA and protein expression levels of GDF11, ABCA1 and ABCG1 were determined by real-time PCR and Western blot. Mice were given intraperitoneal injection of exogenous GDF11. Peritoneal macrophages were labeled with 3H-cholesterol, then the labeled macrophages were injected into mice intraperitoneally. The mice feces were collected every 8 hours and the liver and blood samples of mice were gathered after 48 hours since cell injection. The radioactivity of 3H was detected to measure the reverse cholesterol transport level. Results After treated with ox-LDL for 24 hours, ox-LDL induced the accumulation of lipid in macrophage and inhibited the GDF11 mRNA and protein expression level. GDF11 treatment effectively inhibited the lipid accumulation in macrophage induced by ox-LDL. Exogenous GDF11 effectively induced macrophage ABCA1 mRNA expression and increased the cholesterol reverse transport level in vivo. However, after treated with GDF11 and ALK7 inhibitor SB431542, the inhibitory effect of GDF11 on intracellular lipid accumulation induced by ox-LDL was antagonized, and the upregulation of ABCA1 expression was also inhibited. Conclusion GDF11 regulates the expression of ABCA1 through ALK7, thus promoting the reverse transport of cholesterol in macrophage.

Abstract:Aim To investigate the effects of liraglutide on cholesterol efflux in HepG2 cells under high glucose condition, and to detect the expression of related protein and further to explore its mechanism of action. Methods HepG2 cells were cultured in vitro, stimulating with high glucose and intervening with different concentrations of liraglutide.Effect of liraglutide on cholesterol efflux in HepG2 cells under high glucose condition was detected by using BODIPY-cholesterol fluorescence assay. Western blot was used to analyze the protein expressions of ATP-binding cassette transporter A1 (ABCA1), ABCG1 and scavenger receptor B1 and the change of extracellular regulated protein kinase 1/2 (ERK1/2) signaling pathway. Results Liraglutide could significantly reduce the fluorescence density of HepG2 cells in high glucose (50 mmol/L) condition, increase the expression of ABCA1 protein and enhance the phosphorylation level of ERK1/2.Conclusion Liraglutide can promote cholesterol efflux in HepG2 cells under high glucose condition, and its mechanism may be related to the regulation of ERK1/2 signaling pathway and the up-regulation of ABCA1 expression.

Abstract:Reverse cholesterol transport (RCT) is a process that promotes the efflux of cholesterol from the cells and transports it to the liver for metabolism. Its dysfunction plays a key role in the development of atherosclerosis (As). Chronic metabolic inflammatory diseases including diabetes, obesity promote the progress of As, in which pro-inflammatory cytokines and adipokines are important regulatory mechanisms for the regulation of RCT in vivo. The research papers and review collected in this issue studied the effect of nuclear factor κB (NF-κB), glycosylation end products Nε-carboxymethyllysine, adipokines Visfatin, etc. on the cholesterol efflux and the expression of key proteins such as adenosine triphosphate binding cassette transporter A1, Sortilin, and acyl-coenzyme A:cholesterol acyltransferase (ACAT) in RCT, which would clarify the molecular mechanism of chronic metabolic inflammatory diseases regulating RCT and cardiovascular disease development from different perspectives.