Novel Glycomimetics Protect against Glycated Low-Density Lipoprotein-Induced Vascular Calcification In Vitro via Attenuation of the RAGE/ERK/CREB Pathway

Heparan sulphate (HS) can act as a co-receptor on the cell surface and alterations in this process underpin many pathological conditions. We have previously described the usefulness of mimics of HS (glycomimetics) in protection against β-glycerophosphate-induced vascular calcification and in the restoration of the functional capacity of diabetic endothelial colony-forming cells in vitro. This study aims to investigate whether our novel glycomimetic compounds can attenuate glycated low-density lipoprotein (g-LDL)-induced calcification by inhibiting RAGE signalling within the context of critical limb ischemia (CLI). We used an established osteogenic in vitro vascular smooth muscle cell (VSMC) model. Osteoprotegerin (OPG), sclerostin and glycation levels were all significantly increased in CLI serum compared to healthy controls, while the vascular calcification marker osteocalcin (OCN) was down-regulated in CLI patients vs. controls. Incubation with both CLI serum and g-LDL (10 µg/mL) significantly increased VSMC calcification vs. controls after 21 days, with CLI serum-induced calcification apparent after only 10 days. Glycomimetics (C2 and C3) significantly inhibited g-LDL and CLI serum-induced mineralisation, as shown by a reduction in alizarin red (AR) staining and alkaline phosphatase (ALP) activity. Furthermore, secretion of the osteogenic marker OCN was significantly reduced in VSMCs incubated with CLI serum in the presence of glycomimetics. Phosphorylation of cyclic AMP response element-binding protein (CREB) was significantly increased in g-LDL-treated cells vs. untreated controls, which was attenuated with glycomimetics. Blocking CREB activation with a pharmacological inhibitor 666-15 replicated the protective effects of glycomimetics, evidenced by elevated AR staining. In silico molecular docking simulations revealed the binding affinity of the glycomimetics C2 and C3 with the V domain of RAGE. In conclusion, these findings demonstrate that novel glycomimetics, C2 and C3 have potent anti-calcification properties in vitro, inhibiting both g-LDL and CLI serum-induced VSMC mineralisation via the inhibition of LDLR, RAGE, CREB and subsequent expression of the downstream osteogenic markers, ALP and OCN.

β-caryophyllene blocks reactive oxygen species-mediated hyperlipidemia in isoproterenol-induced myocardial infarcted rats

Myocardial infarction (MI) is a leading cause of death. Lipid-lowering interventions have been shown to decrease coronary events and mortality of MI and heart failure. In this investigation, we assessed the anti-hyperlipidemic effects of β-caryophyllene in isoproterenol-induced myocardial infarcted rats. β-Caryophyllene (20 mg/kg body weight) pre-and co-treatment was given to rats orally, daily, for 3 weeks. Isoproterenol (100 mg/kg body weight) was administered to rats to induce MI. The levels of serum cardiac troponins T and I, serum and heart total cholesterol, triglycerides, free fatty acids, and the levels of serum low-density and very low-density lipoprotein-cholesterols were augmented, and the level of serum high-density lipoprotein-cholesterol was lessened in myocardial infarcted rats. Further, the activity/levels of liver 3-hydroxy-3-methylglutaryl-coenzyme A reductase and plasma thiobarbituric acid reactive substances were amplified and the activity/levels of heart glutathione -S- transferase, vitamin C, and vitamin E were lessened by isoproterenol. A down-regulated expression of liver sterol regulatory element-binding protein-2 and liver low-density lipoprotein-receptor genes was observed by a reverse transcription-polymerase chain reaction study. Moreover, histopathology of Sudan III staining revealed an accumulation of fats in the heart of isoproterenol-induced rats. Nevertheless, β-caryophyllene pre-and co-treatment blocked alterations in all the parameters examined in isoproterenol-induced rats and inhibited the risk of MI. Moreover, the in vitro study revealed the potent free radical scavenging and antioxidant effects of β-caryophyllene. β-Caryophyllene's antioxidant and anti-hyperlipidemic properties are the possible mechanisms for the observed protective effects in this investigation.

[Danshenxinkun B protects human umbilical vein endothelial cells against ox-LDL-induced injury by inhibiting pyroptosis and the NF-κB/NLRP3 pathway]

OBJECTIVE

To investigate the protective effect of Danshenxinkun B against oxidized low-density lipoprotein (ox-LDL)- induced human umbilical vein endothelial cell (HUVEC) injury and explore the underlying mechanism.

METHODS

HUVECs cultured in the presence of 10% fetal bovine serum were treated with ox-LDL (100 μg/mL), ox-LDL+0.1% dimethyl sulfoxide (DMSO), or ox-LDL+Danshenxinkun B (100 ng/mL, dissolved in DMSO) for 24 h. The changes in lactate dehydrogenase (LDH) release was detected, and qRT-PCR was used to detect the mRNA expressions of nuclear factor-κB1 (NF-κB1), nucleotide binding oligomerization domain-like receptor family pyrin domain protein 3 (NLRP3), gasdermin D (GSDMD) and interleukin- 1β (IL-1β). The protein expressions of NF-κB1, NLRP3, caspase-1, IL-1β and GSDMD-N were detected with Western blotting. Immunofluorescence assay was performed to examine the changes in GSDMD expression in the cells.

RESULTS

Compared with the normal control cells, the cells treated with ox-LDL alone or in combination with DMSO exhibited significantly increased LDH release, mRNA expressions of NF-κB1, NLRP3, GSDMD, and IL- 1β and the protein levels of NF-κB1, NLRP3, IL- 1β, GSDMD-N and caspase-1 (P<0.01), which were all significantly lowered by treatment with Danshenxinkun B (P<0.05 or 0.01). Danshenxinkun B treatment significantly inhibited GSDMD expression on the cell membrane and restricted its entry into the cell nucleus.

CONCLUSION

Danshenxinkun B alleviates ox-LDL-induced HUVEC injury possibly by suppressing pyroptosis mediated by NLRP3 inflammatory bodies and inhibiting the NF-κB/NLRP3 signaling pathway.

Interference with lysophosphatidic acid receptor 5 ameliorates oxidized low-density lipoprotein-induced human umbilical vein endothelial cell injury by inactivating NOD-like receptor family, pyrin domain containing 3 inflammasome signaling

Endothelial cell damage induced by oxidized low-density lipoprotein (ox-LDL) plays an important role in the pathogenesis of atherosclerosis (AS). We aimed to explore the effects of lysophosphatidic acid receptor 5 (LPAR5) on ox-LDL-induced damage of human umbilical vein endothelial cells (HUVECs). After HUVECs exposed to ox-LDL, LPAR5 expression was detected by RT-qPCR and western blotting. Then, LPAR5 was silenced and cell viability was determined with a CCK-8 assay. ELISA was employed to analyze the contents of inflammatory factors. The levels of oxidative stress markers were examined by kits. The expression of proteins related to endothelium function, including CD31, α-SMA, iNOS and eNOS, was evaluated with RT-qPCR and western blotting. Additionally, the effects of LPAR5 deletion on the NLRP3 inflammasome signaling in HUVECs under ox-LDL condition were assessed by determining NLRP3, caspase-1 and ASC expression. Afterward, NLRP3 agonist MSU was adopted for exploring the regulation of LPAR5 on NLRP3 inflammasome signaling in ox-LDL HUVECs injury. Results revealed that ox-LDL led to a significant upregulation in LPAR5 expression. NLRP3 knockdown enhanced cell viability, inhibited inflammation and oxidative stress in HUVECs after ox-LDL exposure. Besides, the expression of CD31 and eNOS was increased while that of α-SMA and iNOS was decreased after LPAR5 silencing. Moreover, interference with LPAR5 remarkably downregulated NLRP3, caspase-1 and ASC expression. Furthermore, MSU addition partially abrogated the inhibitory effects of LPAR5 deletion on the inflammation, oxidative stress and endothelium dysfunction of HUVECs. To conclude, we demonstrated that LPAR5 silencing alleviates ox-LDL-induced HUVECs injury by inhibiting NLRP3 inflammasome signaling.

[Effects of miR-133b on oxLDL-induced vascular endothelial cell injury by targeting SGTB]

Objective: To investigate the effect of microRNA-133b (miR-133b) on oxidized low density lipoprotein (oxLDL) induced vascular endothelial cell injury by targeting small protein molecules rich in glutamine 34-tetrapeptide repeats (SGTB). Methods: Human umbilical vein endothelial cells (EVC-304) were induced by 100 μg/ml oxLDL for 24 h to construct a vascular endothelial cell injury model. EVC-304 cells were divided into control group, oxLDL group (oxLDL treatment), oxLDL+miR-NC group (transfectted with 20 nmol/L miR-NC+oxLDL treatment), oxLDL+miR-133b group (transfectted with 20 nmol/L miR-133b mimics +oxLDL treatment), oxLDL+si-NC group (transfectted with 20 nmol/L si-NC+oxLDL treatment), oxLDL+si-SGTB group (transfected with 20 nmol/L si-SGTB+oxLDL treatment), oxLDL+miR-133b+ pcDNA group (transfected with 20 nmol/L si-SGTB and pcDNA+oxLDL), oxLDL+miR-133b+pcDNA-SGTB group (transfected with 20 nmol/L si-SGTB and pcDNA-SGTB), 9 wells in each group. Real-time quantitative PCR (qRT-PCR) and Western blot were used to detect the expression levels of miR-133b and SGTB; flow cytometry was used to detect cell apoptosis; kits were used to detect malondialdehyde (MDA) content and the activities of superoxide disproportionation enzyme (SOD) and glutathione peroxidase (GSH-Px). The expression levels of Bcl-2 and Bax protein were detected by Western blot. The dual luciferase reporter gene assay and Western blot were used to verify the targeted and regulatory between miR-133b and SGTB. Results: Compared with the control group, the expressions of miR-133b and Bcl-2 in EVC-304 cells were decreased significantly after oxLDL induction, while the expression levels of SGTB and Bax were sincreased ignificantly (P＜0.05), the MDA content and apoptosis rate were increased significantly (P＜0.05), and the activities of SOD and GSH-Px were decreased significantly (P＜0.05). Over-expression of miR-133b or interfering with SGTB inhibited oxLDL-induced apoptosis and oxidative stress in EVC-304 cells (P＜ 0.05). miR-133b directly bound to SGTB, miR-133b overexpression significantly down-regulated SGTB expression (P＜0.05), miR-133b inhibition significantly up-regulated SGTB expression (P＜0.05) Over-expression of SGTB reversed the effect of over-expressing miR-133b on oxLDL-induced vascular endothelial cell injury (P＜0.05). Conclusion: miR-133b could attenuate oxidative stress damage and apoptosis induced by oxLDL in vascular endothelial cells by targeting and inhibiting SGTB expression.

Rosmarinic Acid Increases Macrophage Cholesterol Efflux through Regulation of ABCA1 and ABCG1 in Different Mechanisms

Lipid dysregulation in diabetes mellitus escalates endothelial dysfunction, the initial event in the development and progression of diabetic atherosclerosis. In addition, lipid-laden macrophage accumulation in the arterial wall plays a significant role in the pathology of diabetes-associated atherosclerosis. Therefore, inhibition of endothelial dysfunction and enhancement of macrophage cholesterol efflux is the important antiatherogenic mechanism. Rosmarinic acid (RA) possesses beneficial properties, including its anti-inflammatory, antioxidant, antidiabetic and cardioprotective effects. We previously reported that RA effectively inhibits diabetic endothelial dysfunction by inhibiting inflammasome activation in endothelial cells. However, its effect on cholesterol efflux remains unknown. Therefore, in this study, we aimed to assess the effect of RA on cholesterol efflux and its underlying mechanisms in macrophages. RA effectively reduced oxLDL-induced cholesterol contents under high glucose (HG) conditions in macrophages. RA enhanced ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) expression, promoting macrophage cholesterol efflux. Mechanistically, RA differentially regulated ABCA1 expression through JAK2/STAT3, JNK and PKC-p38 and ABCG1 expression through JAK2/STAT3, JNK and PKC-ERK1/2/p38 in macrophages. Moreover, RA primarily stabilized ABCA1 rather than ABCG1 protein levels by impairing protein degradation. These findings suggest RA as a candidate therapeutic to prevent atherosclerotic cardiovascular disease complications related to diabetes by regulating cholesterol efflux in macrophages.

LDL‑induced NLRC3 inflammasome activation in cardiac fibroblasts contributes to cardiomyocytic dysfunction

Heart failure (HF) is a progressive myocardial disease that affects pulse rate. Notably, chronic inflammation serves a crucial role in cardiac dysfunction and HF. Appropriate cardiomyocyte‑fibroblast communication is essential for cardiac function. In addition, cardiac fibroblasts (CFs) are the main cellular population in the cardiac microenvironment; therefore, determining the role of CFs in HF progression and the associated molecular basis is important. In the present study, ELISAs were performed to detect inflammatory factors in the sera of patients with HF and their association with CF activation was analyzed using Pearson's correlation coefficient. The mechanism underlying the proinflammatory phenotype of CFs was investigated via western blotting. Notably, the levels of IL10 and TNF‑α were significantly increased in the sera of patients with HF. Further analysis revealed that CFs were extensively activated in the cardiac tissues of patients with HF and released excessive amounts of cytokines, which could impair the viability of cardiomyocytes. Moreover, low‑density lipoprotein (LDL)‑induced NLRC3 inflammasome was activated in CFs, which gave rise to proinflammatory phenotypes. Targeting LDL in CFs significantly improved the functioning of cardiomyocytes and inhibited apoptosis. These findings highlighted the critical role of LDL in inflammasome activation; to the best of our knowledge, the present study is the first to reveal that CF‑induced microenvironmental inflammation may suppress cardiomyocyte viability. The present study established the cellular basis for CF activation during HF progression and provided information on the cellular interactions important for HF treatment.

Identification and functional analysis of a biflavone as a novel inhibitor of transient receptor potential vanilloid 4-dependent atherogenic processes

Atherosclerosis, a chronic inflammatory disease of large arteries, is the major contributor to the growing burden of cardiovascular disease-related mortality and morbidity. During early atherogenesis, as a result of inflammation and endothelial dysfunction, monocytes transmigrate into the aortic intimal areas, and differentiate into lipid-laden foam cells, a critical process in atherosclerosis. Numerous natural compounds such as flavonoids and polyphenols are known to have anti-inflammatory and anti-atherogenic properties. Herein, using a fluorometric imaging plate reader-supported Ca2+ influx assay, we report semi high-throughput screening-based identification of ginkgetin, a biflavone, as a novel inhibitor of transient receptor potential vanilloid 4 (TRPV4)-dependent proatherogenic and inflammatory processes in macrophages. We found that ginkgetin (1) blocks TRPV4-elicited Ca2+ influx into macrophages, (2) inhibits oxidized low-density lipoprotein (oxLDL)-induced foam cell formation by suppressing the uptake but not the binding of oxLDL in macrophages, and (3) attenuates oxLDL-induced phosphorylation of JNK2, expression of TRPV4 proteins, and induction of inflammatory mRNAs. Considered all together, the results of this study show that ginkgetin inhibits proatherogenic/inflammatory macrophage function in a TRPV4-dependent manner, thus strengthening the rationale for the use of natural compounds for developing therapeutic and/or chemopreventive molecules.

Knockdown of LINC00657 inhibits ox-LDL-induced endothelial cell injury by regulating miR-30c-5p/Wnt7b/β-catenin

Long noncoding RNAs (lncRNAs) play pivotal roles in the pathogenesis, development, and treatment of atherosclerosis (AS). The endothelial cell injury is a feature of AS. However, the role and mechanism of lncRNA LINC00657 in oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell injury remain unclear. The serum samples were collected from 32 AS patients and normal volunteers. Ox-LDL-treated human umbilical vein endothelial cells (HUVEC) were used for the experiments in vitro. The levels of LINC00657, microRNA (miR)-30c-5p and Wnt family member 7B (Wnt7b) were measured by quantitative real-time polymerase chain reaction or western blot. The expression levels of proteins in Wnt7b/β-catenin pathway or endothelial-mesenchymal transition (EndMT) were detected by western blot. The secretion of inflammatory cytokine was examined by enzyme linked immunosorbent assay (ELISA). Cell viability and apoptosis were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide, flow cytometry, and western blot. The target association of miR-30c-5p and LINC00657/Wnt7b was analyzed via dual-luciferase reporter assay and RNA pull-down assay. LINC00657 expression was increased in AS serum and ox-LDL-treated HUVEC cells. LINC00657 knockdown suppressed ox-LDL-induced Wnt7b/β-catenin activation, EndMT, inflammatory response, and apoptosis in HUVEC cells. MiR-30c-5p was bound to LINC00657 and it knockdown reversed the role of LINC00657 inhibition in ox-LDL-induced HUVEC cell injury. MiR-30c-5p targeted Wnt7b to inhibit ox-LDL-induced Wnt7b/β-catenin activation, EndMT, inflammatory response, and apoptosis in HUVEC cells. Silence of LINC00657 repressed ox-LDL-induced injury via inhibiting EndMT, inflammatory response, and apoptosis in HUVEC cells by regulating miR-30c-5p/Wnt7b/β-catenin, indicating a potential target for treatment of AS.

Electronegative LDL Promotes Inflammation and Triglyceride Accumulation in Macrophages

Electronegative low-density lipoprotein (LDL) (LDL(−)), a modified LDL that is present in blood and exerts atherogenic effects on endothelial cells and monocytes. This study aimed to determine the action of LDL(−) on monocytes differentiated into macrophages. LDL(−) and in vitro-modified LDLs (oxidized, aggregated, and acetylated) were added to macrophages derived from THP1 monocytes over-expressing CD14 (THP1-CD14). Then, cytokine release, cell differentiation, lipid accumulation, and gene expression were measured by ELISA, flow cytometry, thin-layer chromatography, and real-time PCR, respectively. LDL(−) induced more cytokine release in THP1-CD14 macrophages than other modified LDLs. LDL(−) also promoted morphological changes ascribed to differentiated macrophages. The addition of high-density lipoprotein (HDL) and anti-TLR4 counteracted these effects. LDL(−) was highly internalized by macrophages, and it was the major inductor of intracellular lipid accumulation in triglyceride-enriched lipid droplets. In contrast to inflammation, the addition of anti-TLR4 had no effect on lipid accumulation, thus suggesting an uptake pathway alternative to TLR4. In this regard, LDL(−) upregulated the expression of the scavenger receptors CD36 and LOX-1, as well as several genes involved in triglyceride (TG) accumulation. The importance and novelty of the current study is that LDL(−), a physiologically modified LDL, exerted atherogenic effects in macrophages by promoting differentiation, inflammation, and triglyceride-enriched lipid droplets formation in THP1-CD14 macrophages, probably through different receptors.

CTRP3 Alleviates Ox-LDL-Induced Inflammatory Response and Endothelial Dysfunction in Mouse Aortic Endothelial Cells by Activating the PI3K/Akt/eNOS Pathway

C1q/tumor necrosis factor-related protein-3 (CTRP3) is a novel, certified, adipokine that beneficially regulates metabolism and inflammation in the cardiovascular system. Atherosclerotic plaque rupturing and secondary thrombosis cause vascular disorders, such as myocardial infarction and unstable angina. However, the underlying role of CTRP3 in atherosclerosis remains unclear. In this study, we aimed to elucidate whether and how CTRP3 ameliorates inflammation and endothelial dysfunction caused by oxidized low-density lipoprotein (ox-LDL). We first confirmed that CTRP3 expression was inhibited in ApoE-/- mice, compared to normal mice. Then, pcDNA-CTRP3 and siCTRP3 were transfected into mouse aortic endothelial cells after ox-LDL stimulation, and we observed that enhanced CTRP3 remarkably downregulated CRP, TNF-α, IL-6, CD40, and CD40L. We also observed that overexpression of CTRP3 elevated cell activity and decreased lactated hydrogenase release, accompanied by a marked reduction in cell apoptosis induced by ox-LDL. Meanwhile, overexpressed CTRP3 caused a decrease in Ang II, ICAM-1, and VCAM-1 expression, and it restored the balance between ET-1 and NO. Mechanism analysis confirmed that incremental CTRP3 upregulated p-PI3K, p-Akt, and p-eNOS expression, indicating that CTRP3 facilitated activation of the PI3K/Akt/eNOS pathway. On the contrary, siCTRP3 exerted the opposite effect to this activation. Blocking these pathways using LY294002 or L-NAME attenuated the protective role of CTRP3. Overall, these results suggest that CTRP3 can efficiently inhibit the inflammatory response and endothelial dysfunction induced by ox-LDL in mouse aortic endothelial cells, perhaps by activating the PI3K/Akt/eNOS pathway, indicating a promising strategy against atherosclerosis.

Diet-Modulated Lipoprotein Metabolism and Vascular Inflammation Evaluated by 18F-fluorodeoxyglucose Positron Emission Tomography

Vascular inflammation plays a central role in atherosclerosis, from initiation and progression to acute thrombotic complications. Modified low-density lipoproteins (LDLs) and apoB-containing particles stimulate plaque inflammation by interacting with macrophages. Loss of function of high-density lipoprotein (HDL) for preventing LDL particles from oxidative modification in dyslipidemic states may amplify modified LDL actions, accelerating plaque inflammation. Diets are one of the most important factors that can affect these processes of lipoprotein oxidation and vascular inflammation. Recently, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a reliable noninvasive imaging modality for identifying and quantifying vascular inflammation within atherosclerotic lesions based on the high glycolytic activity of macrophages infiltrating active atherosclerotic plaques. Vascular inflammation evaluated by FDG PET has been positively related to metabolic syndrome components and traditional risk factors of cardiovascular disease, including high-sensitivity C-reactive protein, body mass index, and insulin resistance. A positive association of vascular inflammation with endothelial dysfunction, resistin levels, pericardial adipose tissue, and visceral fat area has also been reported. In contrast, HDL cholesterol and adiponectin have been inversely related to vascular inflammation detected by FDG PET. Because of its reproducibility, serial FDG PET shows potential for tracking the effects of dietary interventions and other systemic and local antiatherosclerotic therapies for plaque inflammation.

[Effects of thyroid hormone on macrophage dysfunction induced by oxidized low-density lipoprotein]

It has been recognized that patients with hypothyroidism have higher risks of atherosclerosis and coronary heart disease, however, the mechanisms are largely unknown. Considering that macrophage dysfunction plays an important role in the formation and development of atherosclerosis plaques, this study aimed to investigate the direct effects of thyroid hormone on macrophage functions and to provide new insight for the mechanism of hypothyroid atherosclerosis. RAW264.7 cells (mouse leukaemic monocyte macrophage cell line) were incubated with oxidized low-density lipoprotein (oxLDL) to establish macrophage foam cells model in vitro, and the protective effects of different concentration of thyroxine (T4) on the macrophage foam cells function were explored. The proliferation, migration and cell aging of macrophages were detected by MTT method, scratch test and β-galactosidase staining respectively. The ELISA method was used to detect the secretion of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and interleukin-1β (IL-1β). Western blot analysis was applied to measure the phosphorylation of focal adhesion kinase (FAK), which was required for the process of proliferation and migration of macrophages. The results showed that oxLDL significantly inhibited the macrophage proliferation and migration, induced cell senescence, and promoted the secretion of TNF-α, MCP-1, and IL-1β; while T4 reversed those effects of oxLDL on macrophage in a concentration-dependent manner. Moreover, oxLDL increased the phosphorylation of FAK in macrophage, while T4 concentration-dependently reversed the effect. These results suggest that T4 modulates macrophage proliferation, migration, senescence, and secretion of inflammation factors in a concentration-dependent way.

SIRT6 reduces macrophage foam cell formation by inducing autophagy and cholesterol efflux under ox-LDL condition

SIRT6 is a pivotal regulator of lipid metabolism. It is also closely connected to cardiovascular diseases, which are the main cause of death in diabetic patients. We observed a decrease in the expression of SIRT6 and key autophagy effectors (ATG5, LC3B, and LAMP1) in ox-LDL-induced foam cells, a special form of lipid-laden macrophages. In these cells, SIRT6 WT but not SIRT6 H133Y overexpression markedly reduced foam cell formation, as shown by Oil Red O staining, while inducing autophagy flux, as determined by both mRFP-GFP-LC3 labeling and transmission electron microscopy. Silencing the key autophagy initiation gene ATG5, reversed the autophagy-promoting effect of SIRT6 in ox-LDL-treated THP1 cells, as evidenced by an increase in foam cells. Cholesterol efflux assays indicated that SIRT6 overexpression in foam cells promoted cholesterol efflux, increased the levels of ABCA1 and ABCG1, and reduced miR-33 levels. By transfecting miR-33 into cells overexpressing SIRT6, we observed that reduced foam cell formation and autophagy flux induction were largely reversed. These data imply that SIRT6 plays an essential role in protecting against atherosclerosis by reducing foam cell formation through an autophagy-dependent pathway.

Octanoylated ghrelin attenuates angiogenesis induced by oxLDL in human coronary artery endothelial cells via the GHSR1a-mediated NF-κB pathway

OBJECTIVE

Low concentrations of oxidized low-density lipoprotein (oxLDL) promote the in vitro angiogenesis of endothelial cells and play an important role in plaque angiogenesis, which may cause plaque vulnerability and enhance the risk of intravascular thrombosis. The aim of this research was to investigate the effects of octanoylated ghrelin on oxLDL-induced angiogenesis and the underlying molecular mechanisms involved in this process.

MATERIALS/METHODS

Human coronary artery endothelial cells (HCAECs) were incubated with 5 μg/ml oxLDL and treated with various concentrations of octanoylated ghrelin (10(-9)-10(-6)M) with or without inhibitors for 24h. Cell proliferation, migration, and in vitro angiogenesis were analyzed by bromodeoxyuridine (BrdU) staining and BrdU enzyme-linked immunosorbent assay (ELISA), transwell assay, and tube formation on Matrigel, respectively. NF-κB (nuclear factor κB) expression was determined by Western-blot analysis.

RESULTS

Treatment with oxLDL at 5 μg/ml enhanced the proliferation, migration and tube formation of HCAECs. In contrast, pretreatment with octanoylated ghrelin significantly attenuated in vitro angiogenesis in oxLDL-induced HCAECs. In addition, Western blot analysis indicated that NF-κB expression was increased after oxLDL treatment, and that this effect was significantly reversed by pretreatment with octanoylated ghrelin. However, the NF-κB inhibitor PDTC or the GHSR1a inhibitor [D-Lys3]-GHRP-6 abolished the effects of octanoylated ghrelin on the inhibition of angiogenesis and NF-κB p65 expression induced by oxLDL.

CONCLUSIONS

These findings suggest that octanoylated ghrelin attenuates angiogenesis induced by oxLDL in HCAECs via the inhibition of GHSR1a-mediated NF-κB pathway. Furthermore, octanoylated ghrelin may promote the stability of vulnerable plaques by inhibiting plaque angiogenesis.

Tripterine treatment improves endothelial progenitor cell function via integrin-linked kinase

BACKGROUND/AIMS

Atherosclerosis is associated with dysfunction of endothelial progenitor cells (EPCs). Tripterine, a chemical compound derived from the Chinese medicinal plant Tripterygium wilfordii Hook, displays anti-inflammatory properties in several animal models. We hypothesized that tripterine can improve EPC function and thus the efficiency of EPC transplantation.

METHODS AND RESULTS

Tripterine preconditioning (2.5 μM, 4 h) improved EPC proliferation, tube formation, migration, and adhesion, and reduced apoptosis in cells cultured in ox-LDL (200 µg/ml). Tripterine restored integrin-linked kinase (ILK) levels downregulated by ox-LDL in EPCs, suggesting the involvement of the ILK/Akt pathway. Small interfering RNA-mediated depletion of ILK and dominant-negative ILK transduction inhibited the phosphorylation of the ILK downstream signaling targets protein kinase B/Akt and glycogen synthase kinase 3-beta (GSK-3β), and reduced β-catenin and cyclin D1 expression. In atherosclerotic mice injected with green fluorescent protein-labeled EPCs to evaluate EPC function, tripterine decreased aortic lesions and plaque deposition, and injection of tripterine-treated EPCs restored ILK levels.

CONCLUSION

The present results suggest that tripterine improves vascular function in atherosclerosis by enhancing EPC function through a mechanism involving the ILK signaling pathway.

Rutaecarpine prevented dysfunction of endothelial gap junction induced by Ox-LDL via activation of TRPV1

Gap junctions, which is formed by connexins, has been proved to play an important role in the atherogenesis development. Rutaecarpine was reported to inhibited monocyte migration, which indicates its potential for anti-atherosclerosis activity. This study evaluated the effect of rutaecarpine on endothelial dysfunction, and focused on the regulation of connexin expression in endothelial cells by rutaecarpine. Endothelia damage was induced by exposing HUVEC-12 to Ox-LDL (100mg/l) for 24h, which decreased the expression of protective proteins Cx37 and Cx40, but induced atherogenic Cx43 expression, in both mRNA and protein levels, concomitant with the impaired propidium iodide diffusion through the gap junctions. Pretreatment with rutaecarpine effectively recovered the expression of Cx37 and Cx40, but inhibited Cx43 expression, thereby improving gap junction communication and significantly prevented the endothelial dysfunction. Consequently, the cell viability and nitric oxide production were increased, lactate dehydrogenase production was decreased and monocyte adhesion was inhibited. These protective effects of rutaecarpine were remarkably attenuated by pretreatment with capsazepine, a competitive antagonist of transient receptor potential vanilloid subtype 1 (TRPV1). In summary, this study is the first to report that rutaecarpine prevents endothelial injury and gap junction dysfunction induced by Ox-LDL in vitro, which is related to regulation of connexin expression patterns via TRPV1 activation. These results suggest that rutaecarpine has the potential for use as an anti-atherosclerosis agent with a novel mechanism.

[The estrogen-like protective effect of ginsenoside Rb3 on oxidative stress and dysfunction of endothelial cells induced by oxidized low-density lipoprotein]

Ginsenoside Rb3 (GRb3) is one of the main components in plasma of Panax quinquefolius Saponin of stem and leaf (PQS), which can be into human plasma. Previous studies have found PQS has estrogen-like vascular protective effects. In the present study, we investigated the estrogen-like protective effect of GRb3 on oxidative stress and dysfunction of endothelial cells induced by oxidized low-density lipoprotein. The activities of SOD, NOS and the contents of MDA in the cell lysate were examined by enzyme method or spectrophotometry. The NO and ET-1 concentrations in the cell culture supernatant were measured by ELISA method. The iNOS and eNOS mRNA expression were measured by real time RT-PCR, while the phosphorylation levels of Akt was measured by Western blotting. The results showed that GRb3 could enhance the activity of SOD, reduce the content of MDA, increase the level of NOS, NO, ET-1 and iNOS mRNA expression while decrease the eNOS mRNA expression and the phosphorylation level of Akt. These effects were blocked by estrogen receptor antagonist ICI182780. GRb3 can play a role in protecting vascular endothelial cells by estrogen receptors, the protective mechanism is similar to 17-β estrodiol.

β-Glucan attenuates inflammatory responses in oxidized LDL-induced THP-1 cells via the p38 MAPK pathway

AIM

To investigate the immunomodulatory effects of β-(1,3/1,6)-d-glucan on atherosclerosis as well as on the molecular mechanisms of its transition.

METHODS AND RESULTS

Human monocytic leukemia (THP-1) cells were differentiated into the macrophage phenotype by incubation with oxLDL in the absence or presence of β-glucan. β-glucan attenuated CD86 and CD80 expression and simultaneously reduced secretion of the inflammatory cytokines IL-2, IL-8, IL-12, TNF-α and IFN-γ. Western blot analysis showed that oxLDL treatment induced phosphorylation of p38 MAPK and ERK1/2 in PMA-differentiated THP-1 cells. However, β-glucan inhibited p38 MAPK activation. In experiments with monocytes derived from healthy donors, β-glucan inhibited IL-8, IL-12 and TNF-α production. The anti-inflammatory effects of β-glucan were also observed in atherosclerotic plaque cells.

CONCLUSIONS

β-glucan inhibited oxLDL-induced pro-inflammatory effects in macrophages via regulation of p38 MAPK phosphorylation. This novel finding may provide insight for new therapeutic strategies.

Estradiol, acting through estrogen receptor alpha, restores dimethylarginine dimethylaminohydrolase activity and nitric oxide production in oxLDL-treated human arterial endothelial cells

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase. ADMA accumulation, mainly due to a decreased dimethylarginine dimethylaminohydrolase (DDAH) activity, has been related to the development of cardiovascular diseases. We investigate whether estradiol prevents the changes induced by oxidized low density lipoprotein (oxLDL) on the DDAH/ADMA/NO pathway in human umbilical artery endothelial cells (HUAEC). HUAEC were exposed to estradiol, native LDL (nLDL), oxLDL and their combinations for 24 h. In some experiments, cells were also exposed to the unspecific estrogen receptor (ER) antagonist ICI 182780, the specific ERα antagonist MPP or specific agonists for ERα, ERβ and GPER. ADMA concentration was measured by HPLC and concentration of NO by amperometry. Protein expression and DDAH activity were measured by immunoblotting and an enzymatic method, respectively. oxLDL, but not nLDL, increased ADMA concentration with a concomitant decrease on DDAH activity. oxLDL reduced eNOS protein and NO production. Estradiol alone had no effects on DDAH/ADMA/NO pathway, but increased the attenuated endothelial NO production induced by oxLDL by reduction in ADMA and preventing loss of eNOS protein levels. ICI 182780 and MPP completely abolished these effects of estradiol on oxLDL-exposed cells. ERα agonist, but not ERβ and GPER agonists, mirrored estradiol effects on NO production. In conclusion, estradiol restores (1) DDAH activity, and therefore ADMA levels, and (2) NO production impaired by oxLDL in HUAEC acting through ERα.

[Resolvin E1 protects against ox-LDL-induced injury on vascular endothelial cells]

OBJECTIVE

To investigate whether Resolvin E1 (RvE1) could protect against ox-LDL-induced injury on human vein vascular endothelial cells and reveal related molecular mechanisms.

METHODS

Human vein vascular endothelial cells were randomly assigned to six groups, which were treated with saline, RvE1, wortmanin, ox-LDL, ox-LDL and RvE1, ox-LDL and RvE1 and wortmanin, respectively. After 48 h, survival rates were determined by MTT, apoptosis rate of cells were determined by flow cytometry, TNF-α contents were assayed by ELISA, caspase 3 and 9 activities were measured by microplate reader, and the expression of p-AKT and LOX-1 were determined by Western blot.

RESULT

Compared with normal saline group, survival rate was markedly decreased and apoptosis rate, TNF-α content, caspase 3 and 9 activities, and the expression of LOX-1 were significantly increased in ox-LDL group (P < 0.01). Survival rate was significantly increased and apoptosis rate, TNF-α content, caspase 3 and 9 activities, and the expression of LOX-1 were significantly decreased in ox-LDL + RvE1 group compared to ox-LDL group (P < 0.01), these beneficial effects of RvE1 could be blocked by PI3K inhibitor wortmanin (P < 0.05).

CONCLUSION

The present data showed that RvE1 could effectively protect against ox-LDL-induced endothelial cell injury, which might be mediated by PI3K-AKT signaling pathway.

[Effect of valsartan on cyclooxygenase-2 expression in cultured human umbilical vein endothelial cells stimulated by ox-LDL]

OBJECTIVE

To investigate the effects of valsartan on cyclooxygenase-2 (COX-2) in cultured human umbilical vein endothelial cells (HUVECs) stimulated by ox-LDL.

METHODS

HUVECs were cultured in endothelial basal medium and divided into four groups (n = 5 each): group I, control group without any treatment; group II: HUVECs stimulated with ox-LDL (100 mg/L) in endothelial basal medium for 24 hours; group III: HUVECs treated with ox-LDL (100 mg/L) and valsartan (10 µmol/L) in endothelial basal medium for 24 hours; group IV: HUVECs treated with ox-LDL (100 mg/L) and valsartan (30 µmol/L) in endothelial basal medium for 24 hours. Expression of COX-1 and COX-2 mRNA were determined by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Expression of and COX-2 mRNA was significantly higher in ox-LDL-treated HUVECs than in control group (1.478 ± 0.104 vs. 0.366 ± 0.104, P < 0.05), while expression of COX-1 mRNA was similar between the 2 groups (P > 0.05). Valsartan dose-dependently decreased the COX-2 mRNA expression (group III vs. group II: 1.074 ± 0.112 vs. 1.478 ± 0.104, P < 0.05; group IV vs. group II: 0.664 ± 0.104 vs. 1.478 ± 0.104, P < 0.05). Expression of COX-1 mRNA in ox-LDL-treated HUVECs was not affected by valsartan.

CONCLUSIONS

COX-2 mRNA expression in ox-LDL-treated HUVECs could be reduced by valsartan suggesting valsartan might attenuate atherosclerosis by reducing ox-LDL-induced inflammatory responses.

[Effects of mixed-tocopherols and eicosapentaenoic acid on oxidized LDL-induced oxidative damage and inflammatory cytokine secretion in human umbilical vein endothelial cells]

OBJECTIVE

To observe the influence of either alone or combined mixed-tocopherols combined with eicosapentaenoic acid (EPA) and α-Tocopherol use on oxidized LDL (oxLDL) induced 8-hydroxy-2'-deoxyguanosine (8-OHDG) and interleukin-6 (IL-6) secretion by human umbilical vein endothelial cells (HUVECs) and to explore the potential mechanism.

METHOD

Cultured HUVECs in vitro were incubated with oxLDL, oxLDL + α-tocopherol, oxLDL + mixed-tocopherols, oxLDL + EPA, oxLDL + α-tocopherol + EPA, oxLDL + mixed-tocopherols + EPA for 24 hours, respectively. Secretion of 8-OHDG and IL-6 were detected by cell enzyme linked immunosorbent assay (ELISA). The expressions of superoxide dismutase (SOD), protein kinase C-δ (PKC-δ), phosphorylated PKC-δ (p-PKC-δ) were analyzed by Western blot.

RESULTS

8-OHDG and IL-6 secretion of HUVECs was significantly increased significantly after incubated with oxLDL for 24 hours which could be significantly attenuated in the presence of tocopherols and EPA (alone or in combination, all P < 0.05) while the strongest inhibition effects were seen with combined use of mixed-tocopherols and EPA. Moreover, combination of mixed-tocopherols and EPA could also significantly increase SOD activity and decrease PKC activity (all P < 0.05). However, the protein expression of SOD and PKC-was similar among groups.

CONCLUSION

Combined mixed-tocopherols + EPA use enhanced the inhibiting effects on the secretion of 8-OHDG and IL-6 in oxLDL stimulated HUVECs which might be linked with increased SOD activity and reduced p-PKC activity.

[Protective effects of autophagy against oxidized LDL-induced injury in endothelial cells]

OBJECTIVE

To investigate the role of autophagy in oxidized low density lipoprotein (ox-LDL) induced injury of human umbilical vein endothelial cells (HUVEC).

METHODS

The cultured HUVECs were randomly divided into four groups of control, ox-LDL, ox-LDL + rapamycin and ox + 3-methyladenine (3-MA). The cells were used to detect the ratio of LC3-II/LC3-I by Western blot while the proliferation and apoptosis of cells measured by MTT and flow cytometry. The lactate dehydrogenase (LDH) activity and endothelin-1 (ET-1) content in the supernatant were detected with enzyme linked immunosorbent assay.

RESULTS

The Ox-LDL treatment up-regulated the ratio of LC3-II/LC3-I in HUVEC (P < 0.01). It increased the activity of LDH (P < 0.01)and content of ET-1 (P < 0.05) in the supernatant. Also it induced the proliferation (P = 0.028) and apoptosis (P < 0.05) of cells. The autophagic inducer rapamycin increased the up-regulation of autophagic level induced by ox-LDL, decreased the activity of LDH and content of ET-1 (P < 0.05) and inhibited the ox-LDL-induced proliferation of cells. Conversely, the autophagic inhibitor 3-MA decreased the elevation of LC3-II/LC3-I induced by ox-LDL (P < 0.01) and increased the cell apoptosis and death.

CONCLUSION

Ox-LDL exposure can increase the secretion of LDH and ET-1 and induce the proliferation and apoptosis of cells so as to cause a harmful effect in the survival of HUVEC. The injury may be reduced by rapamycin, an autophagic inducer, and elevated by the autophagic inhibitor 3-MA.

Dyslipidemia-induced neuropathy in mice: the role of oxLDL/LOX-1

OBJECTIVE

Neuropathy is a frequent and severe complication of diabetes. Multiple metabolic defects in type 2 diabetic patients result in oxidative injury of dorsal root ganglia (DRG) neurons. Our previous work focused on hyperglycemia clearly demonstrates induction of mitochondrial oxidative stress and acute injury in DRG neurons; however, this mechanism is not the only factor that produces neuropathy in vivo. Dyslipidemia also correlates with the development of neuropathy, even in pre-diabetic patients. This study was designed to explore the contribution of dyslipidemia in neuropathy.

RESEARCH DESIGN AND METHODS

Mice (n = 10) were fed a control (10% kcal %fat) or high-fat (45% kcal %fat) diet to explore the impact of plasma lipids on the development of neuropathy. We also examined oxidized lipid-mediated injury in cultured DRG neurons from adult rat using oxidized LDLs (oxLDLs).

RESULTS

Mice on a high-fat diet have increased oxLDLs and systemic and nerve oxidative stress. They develop nerve conduction velocity (NCV) and sensory deficits prior to impaired glucose tolerance. In vitro, oxLDLs lead to severe DRG neuron oxidative stress via interaction with the receptor lectin-like oxLDL receptor (LOX)-1 and subsequent NAD(P)H oxidase activity. Oxidative stress resulting from oxLDLs and high glucose is additive.

CONCLUSIONS

Multiple metabolic defects in type 2 diabetes directly injure DRG neurons through different mechanisms that all result in oxidative stress. Dyslipidemia leads to high levels of oxLDLs that may injure DRG neurons via LOX-1 and contribute to the development of diabetic neuropathy.

[Tanshinone IIA down-regulates the expression of MMP-12 and TF in RAW 264.7 cells]

OBJECTIVE

To investigate the effect of tanshinone IIA (TanIIA) on the expression of tissue factor (TF) and matrix metalloproteinase-12 (MMP-12) in RAW264.7 cells and explore the possible mechanism.

METHODS

RAW 264.7 cells were incubated with ox-LDL in the presence or absence of different concentrations of tanshinone IIA. At the end of the incubation, the cell proliferation was assessed by MTT assay, and superoxide dismutase (SOD) activity and malondialdehyde (MDA) and TF concentrations in the supernatant were detected by xanthine oxidase method, thiobarbituric acid method and ELISA, respectively. Western blotting was employed to determine MMP-12 expression in the cells.

RESULTS

The cell proliferation was dose-dependently inhibited by TanIIA. SOD activity in the supernatant was increased significantly, while the MDA and TF concentration and MMP-12 expression in cells decreased after treatment of the cells with different concentrations of TanIIA.

CONCLUSION

TanIIA inhibits the cell proliferation and TF and MMP-12 expressions in RAW264.7 cells stimulated by ox-LDL, and these effects may be related with the anti-oxidation property of TanIIA.

[Effects of danshensu on function of EPCs which were damaged by Ox-LDL and study its possible mechanism]

OBJECTIVE

To observe the effects of danshensu on function of endothelial progenitor cells (EPCs) from peripheral blood which were damaged by oxidative low density lipoprotein (Ox-LDL). And study its possible mechanism.

METHOD

Total mononuclear cells (MNCs) were isolated from peripheral blood by ficoll density gradient centrifugation, and were identified by demonstrating the expression of CD34, VEGFR-2 and AC133 with flow cytometry, to sure that all the cells needed were EPCs. Then the cells were plated on fibronectin-coated culture dishes. After incubation for 7 days, attached cells were collected and divided into three groups: Control group, Ox-LDL group, danshensu intervention group, stimulated with different cencentrations of danshensu (2, 10 and 50 mg x L(-1)), adhesion assay respectively. EPCs adhesion assay were performed by replating those on fibronectin-coated dishes, then adherent cells were counted. And take cell supernate of each group to carry on the SOD, MDA content examination.

RESULT

Ox-LDL impaired EPC proliferative and adhesive capacity. In Ox-LDL group, The SOD content obviously drops, the MDA content obviously elevates. After danshensu interventing for 24 h, adhesive EPCs and migratory EPCs were significantly increased. Compared with Ox-LDL group, the SOD content of Danshensu intervention group obviously increased and the MDA content obviously reduced.

CONCLUSION

danshensu could improve proliferative and adhesive capacity of EPCs that were impaired by Ox-LDL. The mechanism might relate to the oxidation resistance damage.

Retention of Low-Density Lipoprotein in Atherosclerotic Lesions of the Mouse

Direct binding of apolipoprotein (apo)B-containing lipoproteins to proteoglycans is the initiating event in atherosclerosis, but the processes involved at later stages of development are unclear. Here, we investigated the importance of the apoB–proteoglycan interaction in the development of atherosclerosis over time and investigated the role of lipoprotein lipase (LPL) to facilitate low-density lipoprotein (LDL) retention at later stages of development. Atherosclerosis was analyzed in apoB transgenic mice expressing LDL with normal (control LDL) or reduced proteoglycan-binding (RK3359-3369SA LDL) activity after an atherogenic diet for 0 to 40 weeks. The initiation of atherosclerosis was delayed in mice expressing RK3359-3369SA LDL, but they eventually developed the same level of atherosclerosis as mice expressing control LDL. Retention studies in vivo showed that although higher levels of 131 I-tyramine cellobiose–labeled control LDL ( 131 I-TC-LDL) were retained in nonatherosclerotic aortae compared with RK3359-3369SA 131 I-TC-LDL, the retention was significantly higher and there was no difference between the groups in atherosclerotic aortae. Lower levels of control 125 I-TC-LDL and RK3359-3369SA 125 I-TC-LDL were retained in atherosclerotic aortae from ldlr −/− mice transplanted with lpl −/− compared with lpl +/+ bone marrow. Uptake of control LDL or RK3359-3369SA LDL into macrophages with specific expression of human catalytically active or inactive LPL was increased compared with control macrophages. Furthermore, transgenic mice expressing catalytically active or inactive LPL developed the same extent of atherosclerosis. Thus, retention of LDL in the artery wall is initiated by direct LDL–proteoglycan binding but shifts to indirect binding with bridging molecules such as LPL.

[Effect of melatonin on the proliferation, apoptosis, and expression of bcl-2 in oxidized low-density lipoprotein-induced endothelial progenitor cells]

OBJECTIVE

To explore the effect of melatonin(Mel) on the proliferation, apoptosis and expression of bcl-2 in oxidized low-density lipoprotein(ox-LDL)-induced endothelial progenitor cells (EPC) from human umbilical cord blood in vitro.

METHODS

Total mononuclear cells were isolated from human umbilical cord blood in vitro by Ficoll density gradient centrifugation, and the cells were plated on fibronectin-coated culture dishes. After 7 days, the attached cells were divided into 7 groups: a control group (normal cells), 3 ox-LDL groups[the attached cells were incubated with different concentrations of ox-LDL(5,10,and 20mg/L) for 24 hours], and 3 Mel groups[the attached cells were incubated with different concentrations of Mel (0.5,1.0, and 2.0 mmol/L) respectively for 24 hours before incubation with 10 mg/L ox-LDL]. EPC was identified by examining the expression of CD34, vascular endothelial growth factor receptor-2(VEGFR-2) and CD133 under a laser scanning confocal microscope. We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to detect the effect of Mel and ox-LDL on the multiplication ability of EPC. Flow cytometry was used to detect the apoptosis. The expressions of Bcl-2 mRNA and protein were detected respectively by RT-PCR and immunohistochemistry technology.

RESULTS

After being exposed to the ox-LDL, the proliferation of EPC in the 3 ox-LDL groups was lower, and the apoptosis rate was higher than that in the control group in a dose-dependent manner (P<0.01); Mel was added at different concentrations before the ox-LDL incubation, and the cells in the 3 Mel groups showed higher proliferation and lower apoptosis rate than those of the 3 ox-LDL groups (P<0.01). Expression of Bcl-2 mRNA and protein of EPC in the 3 Mel groups was higher than that in the 3 ox-LDL groups (P<0.01).

CONCLUSION

Ox-LDL can inhibit the proliferation of EPC and promote the apoptosis of the cells by down-regulating the bcl-2 expression. Mel can inhibit these effects of ox-LDL.

High-density lipoprotein prevents organ damage in endotoxemia

High-density lipoprotein (HDL) may decrease organ injury in sepsis. This study was designed using an animal model to mimic people who had a high HDL level and to test HDL effects on preventing organ damage in endotoxemia. Endotoxemia was induced by an infusion of lipopolysac-charide (LPS) after HDL or LDL administration. Levels of blood biochemical substances, nitrate/nitrite, and TNF-alpha in sera were measured. Pathological examinations were performed 72 hours after LPS infusion. HDL decreased the endotoxin-induced elevation of AST, ALT, BUN, creatinine, LDH, CPK, nitrate/nitrite, and TNF-alpha. On histological examination, neutrophil infiltration was lower in the HDL group. HDL had a significant effect in preventing endotoxin-induced organ damage.

[Protective effect of losartan on injury induced by ox-LDL in endothelial cells and the relationship with asymmetric dimethylarginine]

OBJECTIVE

To investigate the protective effect of losartan against on injury induced by ox-LDL in endothelial cells and the relationship with asymmetric dimethylarginine (ADMA).

METHODS

Endothelial injury was induced by incubation with ox-LDL 100 mg/L in cultured HUVECs for 24 h, and the levels of ADMA, lactate dehydrogenase (LDH), nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha) in the conditioned medium were measured. The activity of dimethylarginine dimethylaminohydrolase (DDAH) of cultured endothelial cells was also determined.

RESULTS

Incubation of endothelial cells with ox-LDL 100 mg/L for 24 h induced a marked elevation of the levels of ADMA, LDH and TNF-alpha in the conditioned medium and a significant decrease in the activity of DDAH and the content of NO (P < 0.05). Pretreatment with losartan (10(-8) - 10(-6) mmol/L) significantly inhibited the increased levels of ADMA, LDH and TNF-alpha, attenuated the decreased levels of NO and the decreased activity of DDAH induced by ox-LDL (P < 0.05).

CONCLUSION

Losartan may preserve ox-LDL-induced endothelial cell injury by increasing the DDAH activity and decreasing the ADMA level.

Effects of vitamin E on the toxicity of oxidized LDL on endothelial cells in vitro in smokers vs nonsmokers on diets rich in fish

OBJECTIVE

To clarify whether supplementation of vitamin E can alter the low density lipoprotein (LDL) oxidation properties and thereby affect endothelial cell function and prostacyclin production in smokers compared to nonsmokers on diets rich in fish in a pilot study.

DESIGN

The LDL of six smokers and six nonsmokers on habitual high fish diet was isolated before and after an 8-week supplementation of vitamin E (800 IU/day). LDL was oxidized by incubation with CuSO4. Cytotoxicity of LDL oxidized to different degrees on endothelial cells was investigated in vitro in these two groups.

SETTING

Helsinki University Central Hospital; Institute of Biomedicine, Pharmacology, University of Helsinki.

RESULTS

At baseline, the rate of oxidation was higher in nonsmokers than in smokers. The lag phase increased significantly after the supplementation of vitamin E both in smokers and nonsmokers. Native LDL dose dependently tended to reduce the viability of endothelial cells in vitro more markedly when isolated from smokers than from nonsmokers. Vitamin E supplementation had no beneficial effect on the cytotoxicity of oxidized LDLs in endothelial cell culture. On the other hand, simultaneous administration of Trolox, the water-soluble analogue of vitamin E, attenuated the LDL cytotoxicity on endothelial cells. The vitamin E supplementation to LDL donors attenuated the increase in prostacyclin production both in smokers and nonsmokers.

CONCLUSION

Supplementation of LDL donors (healthy male volunteers on habitual fish diet) with vitamin E increased the lag phase of LDL oxidation, but, on the other hand, did not influence in vitro cytotoxicity of LDL, or prostacyclin production.

In face of the increasing efficacy of lipid-lowering therapy, is there still a place for LDL-apheresis?

Based on a large body of evidence, high LDL-cholesterol concentrations in blood is a key factor of coronary heart disease (CHD). Overall, the observational studies show a curvilinear relationship between blood cholesterol level and coronary heart disease risk. Even more relevant are the randomised trials, firmly establishing that within just a few years a cholesterol-lowering therapy confers a dramatic effect on cardiovascular morbidity and mortality. More recent studies indicate that there is a greater risk reduction in those subjects achieving lower low-density lipoprotein cholesterol (LDL-C) levels--i.e. lower is better. While this favours aggressive therapy, it is nevertheless imperative to precise patients selection for every therapy that entails a major commitment for the patient and medical community. Therefore, well-defined criteria for use of LDL-apheresis have yet to be established in the light of the expanding therapeutic armamentarium. Based on the current knowledge of the impact of statin therapy and anticipating that new options will further optimize the management of dyslipidemia in high-risk patients, we propose a reliable assessment of the effects of LDL-apheresis.

[Effects of lysophosphatidylcholine on expression of monocyte chemoattractant protein-1 in glomerular endothelial cells]

Glomerular endothelial cells(GEC) produce monocyte chemoattractant protein-1(MCP-1), which is considered to be an important factor for the recruitment of macrophages into the glomeruli. Recent reports have suggested an association between oxidized low-density lipoprotein(ox-LDL) and progression of glomerular disease. In this study, the effects of lysophosphatidylcholine(LysoPC), a modified phospholipid produced during LDL oxidation, on MCP-1 mRNA expression in cultured bovine GEC were examined. GEC from the 8th through 10th passages were used. LysoPC substantially increased expression of MCP-1 mRNA when compared to the control. These findings led us to examine the mechanism of LysoPC-induced MCP-1 expression in GEC. LysoPC-induced MCP-1 mRNA expression in GEC was suppressed by genistein and staurosporine. It was suggested that both the tyrosinekinase(TK) and proteinkinase C(PKC) pathways were involved in LysoPC-induced MCP-1 expression in GEC. MCP-1 mRNA induction by LysoPC was also attenuated by Vitamin E. This effect may be related to the beneficial effects of Vitamin E on experimental glomerular disease models. In conclusion, LysoPC increased MCP-1 expression in GEC. This phenomenon is believed to be mediated by both the TK and PKC signaling pathways, in contrast with other vascular endothelial cells. Vitamin E also attenuated LysoPC-induced MCP-1 expression in GEC.

[Effect of oxidated low-density lipoprotein on early apoptosis of vascular smooth muscle cell]

OBJECTIVE

To investigate the apoptosis in vascular smooth muscle cell (VSMC) induced by oxidated low-density lipoprotein cholesterol (ox-LDL), and to discuss the relative mechanism of the apoptosis of VSMC.

METHODS

The growth index of VSMC of Wistar rat was determined. By using trypan blue to count sustaining cells, the proliferative effect of ox-LDL on culturing VSMC was observed. With flow cytometer, the apoptosis of VSMC induced by ox-LDL and the inhibitory effect of cyclooxygenase-2 (COX-2) inhibitor NS-398 on apoptosis were determined.

RESULTS

After VSMC grew normally in culture, ox-LDL in concentrations of 35 mg/L and 50 mg/L could advance the growth period of VSMC to between 12 and 24 hours, and the proliferation of VSMC were obvious. The proliferation of VSMC induced by ox-LDL were inhibited by NS-398. The rate of apoptosis of VSMC in ox-LDL and NS-398 groups were higher than that of normal control.

CONCLUSION

ox-LDL could induce an obvious proliferation of VSMC in culture. Although NS-398 can decrease the proliferation of VSMC, it could enhance ox-LDL to induce apoptosis.

Small, dense low-density lipoprotein: risk or myth?

Based on the particle diameter of the major subpopulation of low-density lipoprotein (LDL) in plasma, an individual may be classified either as having phenotype A (desirable phenotype; large, buoyant LDL) or phenotype B (high risk; small, dense LDL). This article reviews the clinical significance of LDL particle diameter determination and proposes a strategy for incorporating this information in the new guidelines of the National Cholesterol Education Program's Adult Treatment Panel III.

Recombinant human endostatin is beneficial to endothelial cell growth exposed to mildly oxidized low-density lipoproteins

Endostatin significantly reduced atherosclerosis in genetically susceptible mice. One of the main factors associated with atherogenesis is oxidized low-density lipoproteins (LDL), which also causes apoptosis of endothelial cells. Therefore, we proposed that the antiatherogenic effect of endostatin was partly associated with its protective effect on the endothelial injury induced by oxidized LDL. To confirm such a hypothesis, we studied the effects of recombinant human endostatin (rhEndo) on the proliferation of cultured endothelial cells exposed to mildly oxidized LDL (mox-LDL), rhEndo did not show an obvious inhibitory effect on the proliferation of rabbit aorta endothelial cells (RAEC) (p > 0.05), while mox-LDL inhibited their proliferation (p < 0.01 or p < 0.05). Interestingly, rhEndo seemed to antagonize the role of mox-LDL in inhibiting the proliferation of RAEC. rhEndo seemed, thus, to be beneficial to the proliferating endothelial cells, suggesting that it protects RAECs from the injury caused by mox-LDL. The activity of rhEndo in endothelial cells may possibly result from the interaction of different factors in cell signaling, which remains to be further elucidated.

Lipoprotein oxidation and its significance for atherosclerosis: a mathematical approach

Atherosclerosis is a chronic disease which involves the build up of cholesterol and fatty deposits within the arterial wall. This results in the narrowing of the vessel lumen, which eventually restricts blood flow to vital organs such as the heart and lungs. These events may culminate in a heart attack or stroke, the commonest causes of death in the U.K. population. In this paper we study the early stages of atherosclerosis which include the build up of cholesterol within subendothelial cells to form what is known as a fatty streak, the earliest identifiable evidence of atherosclerosis. The deposition of cholesterol is believed to be a consequence of oxidation of circulating cholesterol-rich lipoproteins, in particular low density lipoproteins (LDLs). Via a mathematical model we investigate this process of oxidation within the context of an in vitro framework. We first recreate existing experimental results and then extend the model to investigate phenomenon not studied by current experimental protocols. We find that the model displays hysteresis which reveals some interesting insights into possible in vivo events. Mathematical analysis of this behaviour predicts that vitamin E supplementation is not as beneficial as high density lipoproteins (HDLs) and vitamin C. Furthermore, the scavenging of oxidants by HDL can provide an important first line of defence against LDL oxidation.

Vitamin E: murine studies versus clinical trials

Vitamin E is the most effective lipid-soluble antioxidant present in mammalian cells. The hypothesis that links vitamin E to atherogenesis postulates that oxidative modifications of unsaturated fatty acids in the low-density lipoprotein particles play a crucial role in the pathogenesis of this chronic disease. Therefore, vitamin E supplementation should reduce the extent of oxidation and, thus, be protective against atherosclerosis. This hypothesis is strongly supported by studies in murine models of atherosclerosis. In contrast, clinical trials using this vitamin have been giving a more confused picture than expected, with results ranging from a significant protective action to the absence of any effect. However, these findings do not reduce the validity of the "oxidative hypothesis" and of the large body of experimental evidence accumulated so far in its favor. Several differences between animal studies and clinical trials, and among clinical trials themselves are taken into account in order to explain the conflicting findings. Finally, insights into what might be the most appropriate nature of future trials in humans are given.

Small, dense low density lipoprotein (LDL) and the insulin resistance syndrome (IRS)

The preponderance of small, dense LDL particles has been termed a conditional cardiovascular risk factor, indicating that data derived from experimental, clinical and intervention studies suggest a strong relation of LDL size and cardiovascular (atherosclerotic) disease (77). However, the lack of randomized, controlled trials showing a beneficial effect of increasing LDL size on cardiovascular disease independent of other known risk factors (including hypertriglyceridemia) precludes the inclusion of small, dense LDL into the category of "causal" risk factors. Accordingly, as of today, LDL particle size can not (yet) be considered a primary target of risk factor intervention, and neither can its routine assessment for clinical purposes be recommended. Numerous studies have unanimously shown that components of the IRS, including insulin resistance itself, constitute major environmental determinants of LDL size. Therefore, therapies aiming at improving insulin resistance have the potential to modify small, dense LDL towards larger, more buoyant particles. Randomized controlled trials investigating the effect of these therapies not only on LDL size but also on clinical (cardiovascular) endpoints will be of particular interest.

[Metabolism of atherogenic lipoproteins]

Early development of atherosclerosis results from a complex multifactorial process where lipoprotein anomalies play a predominant role. The metabolism of lipoproteins is regulated by numerous reactions between the structural components of the lipoproteins and the receptors and/or enzymes with which they interact. Among the well-characterized anomalies, the elevation of small and dense LDL and/or the diminution of HDL levels are in first line of the factors involved in the formation of atheromatous plaques. LDL play a direct role by penetrating the intima of the arteries and HDL play an reverse transport of cholesterol from cells to the liver. There has been a long debate concerning risk related to triglyceride rich lipoproteins (TGRL), and more particularly the increase in VLDL. However, a large number of studies have demonstrated that these ephemeral lipoproteins can acquire major atherogenic potential when their level is increased and/or they are associated with perturbed metabolism leading to an accumulation of remnants. Current investigation methods have shown that LDL and HDL-cholesterol levels are excellent markers of LDL and HDL concentrations. Inversely, triglyceride levels provide little information concerning the nature of the elevated TGRL and fasting hypertriglyceridemia, even if moderate, should therefore be considered as a warning sign of persistent atherogeneous remnants in the fasting state.

Oxidized LDL-induced injury and apoptosis in atherosclerosis. Potential roles for oxysterols

The cell injury caused by oxidized lipoproteins was among the first findings that led to the theory that it is the oxidation of low-density lipoprotein (LDL), not just LDL concentration, that leads to arterial disease. Voluminous studies have now revealed that oxidized lipoproteins and their constituents can induce numerous effects on cells that can be construed to be atherogenic. Cell injury is but one of these, and it is these injurious effects that are the focus of this brief review. Cell injury and death appear to play multiple roles in lesion development and the toxic lipid constituents of oxidized lipoproteins, including a variety of oxysterols, are candidates for the in vivo effectors of this cytotoxicity. Recent studies have focused on the mechanisms of oxidized lipoprotein-induced cell death, whether the cells die by apoptosis or necrosis, and the identities of the toxins that induce injury. Understanding the roles of these agents in lesion development could lead to therapies that modulate cell death and inhibit lesion formation.

Macrophage death and the role of apoptosis in human atherosclerosis

The arterial disease atherosclerosis is responsible for severe morbidity and is the most common cause of death in the Western population. The complete pathogenesis of the disease is unknown, but multiple risk factors have been identified that correlate with the development of its complications such as heart attack and stroke. Evidence suggests that atherosclerosis is an inflammatory disease and the major cell types involved are smooth muscle cells, macrophages, and T lymphocytes. In this paper, we review the function of macrophages in the context of atherosclerosis and we also discuss the role and significance of macrophage death, including apoptosis. There is much evidence, certainly in vitro, suggesting that low-density lipoprotein becomes atherogenic when it undergoes cell-mediated oxidation within the artery wall. Besides inducing apoptosis in vitro, oxidized low-density lipoprotein may also cause extensive DNA damage in intimal cells, which might presage apoptosis. We review the results of experimental and clinical studies, which may indicate how the complications of atherosclerosis could be prevented by using different therapeutical strategies including bone marrow transplantation and gene therapy.

Oxidants and antioxidants in atherogenesis. An appraisal

Oxidized low density lipoprotein (Ox-LDL) has a plethora of components that are not present in native LDL. Their presence and quantity depends on the nature, type, and extent of oxidation. Lipids esterified to oxidized fatty acids are the major components formed during the early phase of oxidation and these show a number of proatherogenic properties in in vitro cell culture systems. Recently, evidence has been forthcoming to suggest that some of these oxidized lipids also could elicit "antioxidant;-antiatherogenic" responses from cells. Moreover, some of the cellular effects of Ox-LDL that were previously interpreted as atherogenic could also be reinterpreted to suggest an antiatherogenic cellular response. In addition to the above, the antioxidants that are carried in lipoproteins could have anomalous behavior attributable to their metabolism, ability to be internalized by arterial cells, and the presence of oxidative systems that could render them prooxidants. In conclusion, there are numerous contributing factors that need to be studied and understood before antioxidant therapy becomes an option for the treatment for cardiovascular diseases.

Lipoproteins, atherogenicity, age and risk of myocardial infarction

OBJECTIVE

To perform basic statistical analysis of laboratory lipoprotein data, i.e. the measures of very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL), to assist in their interpretation. In particular, to find any difference in male and female data that might explain the known difference in atherogenic susceptibility between the sexes.

METHOD

The study subjects were patients of doctors in city and country New South Wales. Statistical methodology to find the inter-relations of the lipoproteins was the construction of the matrix of correlation, then by matrix algebra to display the independent trends in the data.

RESULTS AND CONCLUSIONS

The findings have been an atherogenicity function involving LDL and HDL and a risk function of myocardial infarction (MI) involving LDL, HDL and age, confirmed by reference to the age and sex incidence of MI in the Australian population. The principal conclusion is a simple mathematical model of the incidence of MI.

IMPLICATIONS

The means given for identification of at-risk individuals before symptoms appear, also the means given of lowering whole population risk of MI by health education and lifestyle change with increased longevity for all. These concepts call for a prospective trial.