Effect of oxidized low-density lipoprotein concentration polarization on human smooth muscle cells' proliferation, cycle, apoptosis and oxidized low-density lipoprotein uptake

HMGB1 promotes Ox-LDL-induced endothelial cell damage by inhibiting PI3K/Akt signaling pathway

BACKGROUND

Atherosclerosis is the pathological basis of cardio-cerebrovascular diseases. Oxidized low-density lipoprotein (ox-LDL) is an important risk factor for atherosclerosis. Ox-LDL leads to endothelial cell (EC) damage and dysfunction through various processes and promotes the occurrence and deterioration of atherosclerosis. High mobility group box-1 (HMGB1) is a protein associated with cellular damage. In the present study, the effect of HMGB1 on ox-LDL-induced EC damage was determined and the underlying mechanism explored.

MATERIALS AND METHODS

Human umbilical vein ECs (HUVECs) were exposed to ox-LDL to induce endothelial damage and changes in HMGB1 expression level were detected using western blotting analysis and reverse transcription-quantitative PCR. To observe the effect of HMGB1 on ox-LDL-induced damage, the HMGB1 expression was downregulated with siRNA, and cell viability, cytotoxicity, and apoptosis rate were assessed. HUVECs were pretreated with LY294002, an inhibitor of the PI3K/Akt pathway, to determine whether the effect of HMGB1 on damage is via the PI3K-Akt pathway.

RESULTS

The results showed that ox-LDL can upregulate HMGB1 expression in HUVECs and downregulation of HMGB1 expression can prevent ox-LDL-induced damage in HUVECs. Furthermore, the effect of HMGB1 on ox-LDL-induced damage could be promoted by inhibiting the PI3K/Akt signaling pathway.

CONCLUSION

The results indicate HMGB1 may be a promising research target to alleviate ox-LDL-induced EC damage.

Protective Effects of Medicinal Plant Decoctions on Macrophages in the Context of Atherosclerosis

Atherosclerosis is a hallmark of most cardiovascular diseases. The implication of macrophages in this pathology is widely documented, notably for their contribution to lipid accumulation within the arterial wall, associated with oxidative stress and inflammation processes. In order to prevent or limit the atherosclerosis damage, nutritional approaches and medicinal plant-based therapies need to be considered. In Reunion Island, medicinal plant-based beverages are traditionally used for their antioxidant, lipid-lowering and anti-inflammatory properties. The aim of our study was to assess the protective effects of eight medicinal plant decoctions in an in vitro model of RAW 264.7 murine macrophages exposed to pro-atherogenic conditions (oxidized low-density lipoproteins—ox-LDL—E. coli Lipopolysaccharides—LPS). The impact of polyphenol-rich medicinal plant decoctions on cell viability was evaluated by Neutral Red assay. Fluorescent ox-LDL uptake was assessed by flow cytometry and confocal microscopy. Activation of NF-κB was evaluated by quantification of secreted alkaline phosphatase in RAW-Blue™ macrophages. Our results show that medicinal plant decoctions limited the cytotoxicity induced by ox-LDL on macrophages. Flow cytometry analysis in macrophages demonstrated that medicinal plant decoctions from S. cumini and P. mauritianum decreased ox-LDL uptake and accumulation by more than 70%. In addition, medicinal plant decoctions also inhibited NF-κB pathway activation in the presence of pro-inflammatory concentrations of E. coli LPS. Our data suggest that medicinal plant decoctions exert protective effects on ox-LDL-induced cytotoxicity and limited macrophage lipid uptake. Moreover, herbal preparations displayed anti-inflammatory properties on macrophages that can be of interest for limiting the atherosclerotic process.

Long noncoding RNA CASC2 inhibits ox-LDL-mediated vascular smooth muscle cells proliferation and migration via the regulation of miR-532-3p/PAPD5

Background

Studies have demonstrated that long noncoding RNAs (lncRNAs) have essential impacts on the development of atherosclerosis (AS). This study aimed to identify the role and functional mechanism of lncRNA CASC2 in the development and migration of vascular smooth muscle cells (VSMCs).

Method

The serum of 40 pairs of AS patients and healthy volunteers were collected and the expression of CASC2 was evaluated. qRT-PCR and western blotting were carried out to examine the expression levels of at mRNA and protein level, repectively. Cell proliferation assay, colony formation assay, transwell migration assay, dual-luciferase reporter assay, and wound healing assay were conducted to evaluate cell proliferation, colony formation, migration, transcription, targeting, and self-restoration.

Results

The expression levels of CASC2 were decreased, while the expression levels of miR-532-3p were elevated in AS patient samples and VSMCs. Overexpression of CASC2 inhibited the proliferation and migration of VSMCs and enhanced cell apoptosis. CASC2 inhibited the expression of miR-532-3p, and inversely upregulated the expression of PAPD5, which was a target of miR-532-3p. In addition, knockdown of miR-532-3p-mimic and PAPD5 could attenuate the impact of overexpression of CASC2 on proliferation, migration, and apoptosis in ox-LDL-VSMCs.

Conclusion

CASC2 suppressed cell reproduction and promoted cell apoptosis by regulating the miR-532-3p/PAPD5 axis in ox-LDL-mediated VSMCs. This might be important for AS therapeutics.

Transfer of Low-Density Lipoproteins in Coronary Artery Bifurcation Lesions with Stenosed Side Branch: Numerical Study

Evidence from clinical data suggests that the stenotic side branch (SB) is one of the key predictors for SB occlusion-based adverse events. In this study, we hypothesized that coronary bifurcations with stenotic SB might lead to severe concentration polarization of atherogenic lipids, such as the low-density lipoproteins (LDL), motivating the adverse events in the clinic. To confirm this hypothesis, this work numerically investigated the transport of LDL in different bifurcation lesions based on the Medina classification with various location and stenosis severities. The results showed that the coronary bifurcations with stenotic SB might be suffering more serious concentration polarization of LDL on the luminal surface of the SB due to higher level of LDL concentrations. Moreover, compared to the other bifurcation lesion types, the type (1,0,1) had the highest luminal surface LDL concentration along the SB and the highest degree of risk to enhance the process of atherosclerosis. In addition, this study also showed that the luminal surface LDL concentration increased with elevated stenosis severity. The type (1,0,1) with the severe stenosis (75% diameter reduction) had the highest concentration at the SB. In conclusion, these results suggested that both location of lesions and stenosis severities had great influence on the distribution of LDL on the luminal surface of the SB. Therefore, the estimation of disease severity and the interventional therapy should be carried out not only according to the stenosis severities in clinic. Moreover, compared to the other bifurcation lesion types, the type (1,0,1), rather than the type (1,1,1) as usually considered, had the highest luminal surface LDL concentration along the SB and the highest degree of risk to enhance the process of atherosclerosis.

SIRT7 Regulates the Vascular Smooth Muscle Cells Proliferation and Migration via Wnt/β-Catenin Signaling Pathway

A huge amount of evidence indicates that sirtuin 7 (SIRT7), a key mediator of many cellular activities, plays a crucial role in the pathogenesis of various diseases. However, little is known about the role of SIRT7 in atherosclerosis. This study investigated the potential role of SIRT7 in regulating the proliferation and migration of human vascular smooth muscle cells (HAVSMCs) and its possible molecular mechanism. In this study, human vascular smooth muscle cells (HAVSMCs) were induced by oxidized low-density lipoprotein (ox-LDL) to establish atherosclerosis (AS) cell model. Immunofluorescence staining and Western blot were used to detect the level of α-SMA expression, which was a marker protein in AS. In addition, RT-qPCR and Western blot assay were applied for exploring the mRNA and protein expression levels of SIRT7, Wnt, β-catenin, and cyclin D1 after knockdown or overexpression of SIRT7. And, furthermore, Cell Counting Kit-8 assay, flow cytometry, and wound-healing assay were used to assess HAVSMCs proliferation, cell cycle, and migration. Dickkopf-1 (DKK-1), a secretory glycoprotein that can block Wnt/β-catenin pathway, was used in SIRT7 overexpression HAVSMCs; subsequently cells proliferation and migration were assessed by Cell Counting Kit-8 assay, flow cytometry analysis, and wound-healing assay. We found that knockdown of SIRT7 significantly promoted cell proliferation and migration, decreased the percentages of cells in the G1 and G2 phases, and increased those in the S phase and downregulated the protein expression levels of Wnt, β-catenin, and cyclin D1, while overexpression of SIRT7 had reverse results. After treatment with Wnt/beta-catenin pathway inhibitor DKK-1 in SIRT7 overexpression HAVSMCs, cell proliferation and migration were increased, respectively. In conclusion, SIRT7 inhibited HAVSMCs proliferation and migration via enhancing Wnt/β-catenin activation, which provided a novel therapeutic strategy for antiatherosclerosis.

Trimetazidine Protects Against Atherosclerosis by Changing Energy Charge and Oxidative Stress

BACKGROUND This study investigated the effect and the possible mechanism of trimetazidine in atherosclerosis. MATERIAL AND METHODS We established an atherosclerotic rat model by high-fat diet and vitamin D injection. Rats were separated into 3 different groups: control, atherosclerosis, and trimetazidine (n=10). The aortic artery was isolated and its morphological features were examined by hematoxylin and eosin (HE) staining. Serum low-density lipoprotein cholesterol (LDL-c), total cholesterol (TC), and triglycerides (TG) were analyzed using an automatic biochemical analyzer. Human aortic smooth muscle cells (HASMCs) were cultured and divided into 5 groups: no treatment, H₂O₂ treatment only, trimetazidine preincubation before H₂O₂ treatment, oxidized low-density lipoprotein (oxLDL) treatment only, and trimetazidine preincubation before oxLDL treatment. HASMCs proliferation was tested using the Cell Counting Kit-8. Reactive oxygen species (ROS) and malondialdehyde (MDA) levels, superoxide dismutase (SOD) activity of the aortic artery, and HASMCs were measured using commercially available kits. RESULTS HE staining assay showed that trimetazidine suppressed the progression of atherosclerosis and reduced foam cell formation in the aortic artery without affecting serum lipid levels. HASMCs proliferation assay revealed that trimetazidine alleviated the inhibitory effect of H₂O₂ on HASMCs proliferation and inhibited oxLDL-induced proliferation of HASMCs. Moreover, trimetazidine ameliorated ROS up-regulation elicited by H₂O₂ or oxLDL in HASMCs. Additionally, trimetazidine restored SOD activity and reduced MDA content of HASMCs. CONCLUSIONS Trimetazidine suppressed the progression of atherosclerosis by enhancing energy value, decreasing ROS level of aortic artery, modulating HASMCs proliferation, and reducing oxidative stress in HASMCs.

Expression status and clinical significance of lncRNA APPAT in the progression of atherosclerosis

Background

Long non-coding RNAs (lncRNAs) have been reported to modulate cardiovascular diseases, and expression dynamics of lncRNAs in the bloodstream were proposed to be potential biomarkers for clinical diagnosis. However, few cardiovascular diseases-related circulating lncRNAs were identified and their prediction power has not been investigated in depth. Here we report a new circulating lncRNA, atherosclerotic plaque pathogenesis associated transcript (APPAT), and evaluated its role and predicting ability in atherosclerotic development.

Methods

APPAT was analyzed and screened by high-throughput sequencing, and then detected in vitro and in vivo. Immunofluorescence-fluorescence in situ hybridization (IF-FISH) was utilized to explore distribution and subcellular location of APPAT. The expressing alteration of APPAT in samples of healthy and pathological coronary artery was explored further. We also assessed the level of circulating APPAT in blood samples from healthy individuals, and patients with angina pectoris (AP) or myocardial infarction (MI). Additionally, we predicted and validated microRNA targets of APPAT, then showed the expression level of a candidate target which was primarily measured in human VSMCs cell line, coronary artery, and blood samples. Lastly, we examined the potential indicating ability of APPAT for the risk of AP or MI.

Results

APPAT showed significant reduction in ox-LDL treated human VSMCs in vitro. It enriched in contractile VSMCs of artery tunica media and mainly existed in cytoplasm. Significant down-regulation of APPAT was found in coronary artery samples with severe stenosis. More importantly, we observed decreased expression of APPAT in blood samples accompanying disease progression. ROC and correlation analyses further verified the relatively high predicting ability of APPAT. We also observed the predicted miRNA exhibited opposite expression direction to that of APPAT.

Conclusions

This study revealed that circulating lncRNA-APPAT may perform an important function and have some indicating ability on the development of atherosclerosis.

The Anti-atherosclerotic Effect of Paeonol against Vascular Smooth Muscle Cell Proliferation by Up-regulation of Autophagy via the AMPK/mTOR Signaling Pathway

Introduction: Paeonol (2′-hydroxy-4′-methoxyacetophenone), isolated from moutan cortex, is an active component and has been shown to have anti-atherosclerotic and anti-proliferation effects on vascular smooth muscle cells (VSMCs). However, the possible role of Paeonol in protecting against VSMC proliferation as related to autophagy has yet to be elucidated.

Materials and Methods: The athero-protective effects of Paeonol were evaluated in apoE^-/- mice. The effects of Paeonol on VSMC proliferation and autophagy were examined by staining α-SMA and LC3II spots in the media layer of apoE^-/- mice, respectively. CCK8 and BrdU assays were used to investigate the effects of Paeonol on cell proliferation in vitro. The autophagic levels in VSMCs were evaluated by detecting LC3II accumulation and p62 degradation by immunoblot analysis. To investigate if Paeonol could prevent VSMCs proliferation through autophagy induction, we tested the change in autophagy and cell proliferation by inhibition of autophagy. The levels of the AMPK/mTOR pathway in autophagy regulation were detected by immunoblot analysis. An AMPK inhibitor and si-AMPK transfection in VSMCs was used to confirm whether AMPK activity plays a key role in autophagy regulation of Paeonol.

Results:In vivo experiments confirmed that Paeonol restricted atherosclerosis development and decreased the amount of VSMCs in the media layer of apoE^-/- mice. Paeonol increased protein levels of LC3II and the presence of autophagosomes in the media layer of arteries, which implies that Paeonol may induce VSMCs autophagy in vivo. Paeonol showed potential in inhibiting ox-LDL-induced proliferation in vitro experiments. Paeonol dose-dependently enhanced the formation of acidic vesicular organelles and autophagosmomes, up-regulated the expression of LC3II and increased p62 degradation. The autophagy inhibitor CQ obviously attenuated Paeonol-induced autophagy and the anti-proliferation effect in VSMCs. In addition, Paeonol induced phosphorylation of AMPK and reduced phosphorylation of mTOR. An AMPK inhibitor reversed the Paeonol-induced p-mTOR/mTOR decrease. Paeonol induced LC3II conversion, increased p62 degradation and inhibited cell proliferation in VSMCs, the effects of which were abolished by si-AMPK.

Conclusion: These results imply that Paeonol inhibits proliferation of VSMCs by up-regulating autophagy, and activating the AMPK/mTOR signaling pathway, providing new insights into the anti-atherosclerosis activity of Paeonol.

Numerical simulation of haemodynamics and low-density lipoprotein transport in the rabbit aorta and their correlation with atherosclerotic plaque thickness

Two mechanisms of shear stress and mass transport have been recognized to play an important role in the development of localized atherosclerosis. However, their relationship and roles in atherogenesis are still obscure. It is necessary to investigate quantitatively the correlation among low-density lipoproteins (LDL) transport, haemodynamic parameters and plaque thickness. We simulated blood flow and LDL transport in rabbit aorta using computational fluid dynamics and evaluated plaque thickness in the aorta of a high-fat-diet rabbit. The numerical results show that regions with high luminal LDL concentration tend to have severely negative haemodynamic environments (HEs). However, for regions with moderately and slightly high luminal LDL concentration, the relationship between LDL concentration and the above haemodynamic indicators is not clear cut. Point-by-point correlation with experimental results indicates that severe atherosclerotic plaque corresponds to high LDL concentration and seriously negative HEs, less severe atherosclerotic plaque is related to either moderately high LDL concentration or moderately negative HEs, and there is almost no atherosclerotic plaque in regions with both low LDL concentration and positive HEs. In conclusion, LDL distribution is closely linked to blood flow transport, and the synergetic effects of luminal surface LDL concentration and wall shear stress-based haemodynamic indicators may determine plaque thickness.

MicroRNA let-7g alleviates atherosclerosis via the targeting of LOX-1 in vitro and in vivo

Atherosclerosis is a chronic arterial disease and the leading cause of stroke and myocardial infarction. Micro-RNAs (miRNAs or miRs) have been reported to act as essential modulators during the progression of atherosclerosis. Although miR-let-7g has been demonstrated to contribute to maintaining endothelial function and vascular homeostasis, it is not known whether miR-let-7g exerts a therapeutic effect on experimental atherosclerosis. The aim of this study was to investigate the effects of miR-let-7g on atherosclerosis in vivo and in vitro and to explore its underlying mechanisms. Data from our study showed that exogenous lectin‑like oxidized low‑density lipoprotein receptor‑1 (LOX-1 or OLR1) overexpression resulted in the significant promotion of proliferation and migration of human aortic smooth muscle cells (ASMCs), whereas such changes induced by LOX-1 were obviously suppressed by transfection of miR‑let‑7g. We later confirmed that LOX-1 is a potential target of miR-let-7g, and miR-let-7g markedly inhibited LOX-1 expression in ASMCs by directly binding to the 3' untranslated region of LOX-1. Furthermore, in a hyperlipidemic apolipoprotein E knockout (ApoE-/-) mouse model, intravenous delivery of miR-let-7g mimics obviously attenuated high-fat diet-induced neointima formation and atherosclerotic lesions, accompanied by the significant downregulation of LOX-1, which was consistent with the effect of miR-let-7g on ASMCs. Taken together, our data revealed that miR-let-7g exhibits anti-atherosclerotic activity, at least partially by targeting the LOX-1 signaling pathway. This study suggests that miR-let-7g may be a therapeutic candidate for treating atherosclerosis, and provides novel insight into miRNA-based therapy for this disease.

Suppression of EC-SOD by oxLDL During Vascular Smooth Muscle Cell Proliferation

Reactive oxygen species (ROS) produced by endothelial cells and macrophages play important roles in atherogenesis because they promote the formation of oxidized low-density lipoproteins (oxLDL). Extracellular-superoxide dismutase (EC-SOD) is mainly produced by vascular smooth muscle cells (VSMCs), is secreted into the extracellular space, and protects cells from the damaging effects of the superoxide anion. Thus, the expression of EC-SOD in VSMCs is crucial for protecting cells against atherogenesis; however, oxLDL-induced changes in the expression of EC-SOD in VSMCs have not yet been examined. We herein showed that oxLDL decreased EC-SOD mRNA and protein levels by binding to lectin-like oxidized LDL receptor-1 (LOX-1). Moreover, we demonstrated the significant role of mitogen-activated protein kinase (MEK)/extracellular-regulated protein kinase (ERK) signaling in oxLDL-elicited reductions in the expression of EC-SOD and proliferation of VSMCs. The results obtained with the FCS treatment indicate that oxLDL-elicited reductions in the expression of EC-SOD are related to the proliferation of VSMCs. We herein showed for the first time that luteolin, a natural product, restored oxLDL-induced decreases in the expression of EC-SOD and proliferation of VSMCs. Collectively, the results of the present study suggest that oxLDL accelerates the development of atherosclerosis by suppressing the expression of EC-SOD and also that luteolin has potential as a treatment for atherosclerosis. J. Cell. Biochem. 117: 2496-2505, 2016. © 2016 Wiley Periodicals, Inc.

Galectin-3-induced oxidized low-density lipoprotein promotes the phenotypic transformation of vascular smooth muscle cells

Oxidized low-density lipoprotein (oxLDL) is involved in the pathological phenotypic transformation of vascular smooth muscle cells in atherosclerosis. Galectin‑3 also has an important role in atherosclerosis. However, little is currently known regarding the effects of galectin‑3 on the oxLDL‑induced phenotypic transformation of vascular smooth muscle cells. In the present study, primary culture human umbilical vascular smooth muscle cells were treated with various oxLDL concentrations (0‑50 µg/ml) for 72 h, and phenotypic changes were subsequently recorded. The results of the present study suggested that oxLDL increases the expression levels of galectin‑3, and induces the phenotypic transformation of vascular smooth muscle cells. The oxLDL‑induced cells exhibited increased expression levels of osteopontin, a smooth muscle synthetic protein, and calponin and α‑actin, smooth muscle contractile proteins. The oxLDL‑induced changes in cellular phenotype were associated with increased migration, proliferation, and phagocytosis. Concordant with these results, oxLDL‑treated smooth muscle cells exhibited activation of canonical Wnt signaling, as determined by an increase in the protein expression levels of β‑catenin. Silencing of galectin‑3 by small interfering RNA reversed the phenotypic transformation and functional changes observed in the oxLDL‑treated cells, suggesting these changes were dependent on the activation of galectin‑3. In addition, galectin‑3 knockdown decreased the protein expression levels of β‑catenin in both the cytoplasm and nucleus; however, the mRNA expression levels of β‑catenin remained unchanged. These results suggest that galectin‑3 is responsible for the phenotypic transformation of human umbilical vascular smooth muscle cells, and the canonical Wnt/β-catenin signaling pathway may be involved in this process.

Concentration polarization of ox-LDL activates autophagy and apoptosis via regulating LOX-1 expression

Here we demonstrate that “concentration polarization” of ox-LDL enhances LOX-1 expression and ox-LDL uptake. It damages cell surface heparan sulfate proteoglycans (HSPG) and activates LOX-1 dependent autophagy and apoptosis. We also show that ox-LDL concentration polarization occurs on the surface of rabbit thoracic aorta and induces autophagy and apoptosis. In order to investigate the significance of swirling flow on LOX-1 expression, HSPG damage, autophagy and apoptosis in the arterial system, an ex vivo model of swirling flow was developed. We observed that swirling flow decreases relative wall concentration of ox-LDL, inhibits LOX-1 expression, protects HSPG from damage, and decreases both autophagy and apoptosis. Taken together, our data suggest that ox-LDL concentration polarization plays an important role in the localization of atherosclerotic lesions concomitant with LOX-1 dependent autophagy and apoptosis. These observations also suggest a novel mechanism by which swirling flow in the arterial system protects arterial wall from atherogenesis.

The accelerated atherogenesis of venous grafts might be attributed to aggravated concentration polarization of low density lipoproteins: a numerical study

We hypothesize that after implantation the much elevated water filtration rate of venous grafts may cause aggravated concentration polarization of low density lipoproteins (LDLs), in turn lead to the accelerated atherogenesis of the grafts. To verify the hypothesis, we numerically simulated the transport of LDLs in various models of arterial bypasses with different grafts (veins or arteries) and geometrical configurations. The results showed that the venous grafts might endure abnormally high lipid infiltration/accumulation within the vessel wall due to severely elevated luminal surface LDL concentration. When compared to the conventional bypass models, the S-type bypass had the lowest luminal surface LDL concentration along its host artery floor, but the highest degree of risk to develop atherosclerotic lesions in its venous graft. Among the three conventional bypass models, the one with 30° anastomosis had the lowest risk to develop atherosclerosis in the venous graft. In conclusion, when compared with the bypass models with arterial grafts, the venous bypass models had rather high levels of LDL concentration polarization (cw) in the vein grafts, especially at the early stages of implantation. This might result in high infiltration/accumulation of LDLs within the walls of the venous grafts, leading to a fast genesis/development of atherosclerosis there.

MicroRNA hsa-let-7g targets lectin-like oxidized low-density lipoprotein receptor-1 expression and inhibits apoptosis in human smooth muscle cells

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) has been identified as a major receptor for oxidatively modified low density lipoprotein (ox-LDL) in endothelial cells and smooth muscle cells (SMCs). MicroRNAs are small non-coding RNAs that regulate gene expression. Very few studies have reported regulation of LOX-1 expression by microRNAs in SMCs. The present study demonstrates that the microRNA hsa-let-7g can inhibit LOX-1 expression in a time- and dose-dependent fashion, and subsequently inhibit ox-LDL uptake in and proliferation of human aortic SMCs. We also show that hsa-let-7g can reduce SMC apoptosis by down-regulation of cytochrome c and Smac/Diablo and upregulation of Bcl-xL and Bcl-2 expression. Furthermore, we show that hsa-let-7g reduces ox-LDL-induced increase in the expression of NADPH oxidase (p22(phox) and p47(phox) subunits) and subsequent intracellular reactive oxygen species generation, phosphorylation of p44/42 mitogen-activated protein kinase and nuclear factor-kappaB p65 expression. These observations suggest that hsa-let-7g is a critical regulator of SMC apoptosis, and may be suitable for therapeutic intervention in disease states characterized by LOX-1 over-expression.