Extract of Ginkgo Biloba decreased expression of lectin-like oxidized low density lipoprotein receptor-1 induced by TNF-α in bovine aortic endothelial cells

AIM: To investigate the effects of extract of Ginkgo biloba (EGB) on the expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) induced by tumor necrosis factor a(TNF-α) in bovine aortic endothelial cells(BAECs). METHODS: The BAECs were incubated with TNF-α, followed by EGB treatment. The effect of EGB on LOX-1 expression was investigated by RT-PCR and Western blotting. The content of endothelial nitric oxide synthase (eNOS) was determined by Western blotting. Potential involvement of signaling pathways of the effects was explored by using related inhibitors of the signal molecules. The concentration of NO^-₂/NO^-₃ was also tested. RESULTS: Increased LOX-1 expression was induced by TNF-α. EGB markedly prevented the increase of LOX-1 expression induced by TNF-α (P<0.05), and this effect was inhibited by inhibitor of NOS (P<0.05). EGB significantly prevented the decrease of eNOS expression induced by TNF-α (P<0.05). EGB also significantly prevented the decrease of NO^-₂/NO^-₃ production induced by TNF-α (P<0.05). CONCLUSION: EGB markedly prevents the increase of LOX-1 expression induced by TNF-α and the effect is mediated by eNOS.     

Proliferation and apoptosis of human umbilical vein endothelial cells induced by oxidized low density lipoprotein

AIM:To investigate proliferation and apoptosis of cultured endothelial cell (ECV-304 cell line) induced by varied concentrations of oxidized low density lipoprotein (ox-LDL). METHODS:Cell morphology, Typan blue test, MTT test, LDH release test, flow cytometry and micro-molecular weight DNA fragment gel electrophoresis of apoptosis were used for the detection of the cytotoxic effects of ox-LDL on ECV-304 cell line.RESULTS:0.1, 1, 10 mg/L ox-LDL could promote proliferation of ECV-304 cells. When the concentration of ox-LDL reached up to 100 mg/L and above, the distinct cytotoxic effect appeared. Further study showed that the apoptosis rate of endothelial cells, induced by ox-LDL of 150 mg/L and 200 mg/L for 12 hours, are 15.86% and 21.89%, respectively. 18 h and above hours after incubation, the apoptosis rate began to decrease and rate of necrosis increased. CONCLUSION:ox-LDL has strong cytotoxic effects on endothelial cells and could give rise to different pathologic process, such as proliferation, apoptosis prophase, apoptosis and necrosis.     

XBP-01 accelerated apoptosis induced by oxidized low density lipoprotein in vascular smooth muscle cells

AIM: Previous studies performed with XBP-01 in vitro indicated that XBP-01 could inhibit vascular smooth muscle cells from being transformed into foam cell and could eliminate the atherosclerotic plaque in C57BL/6J mouse. This experiment is to investigate its mechanism of eliminating plaques in vitro. METHODS: The cultured porcine artery smooth muscle cells incubated with XBP-01 of 0.1 mg/L for 24 h after preincubated with oxidized low density lipoprotein of 15 mg/L for 72 h in vitro. The samples were analyzed by fluorescence microscope, confocal microscope system and flow cytometry. RESULTS: Apoptosis was triggered by being incubated with oxidized low density lipoprotein and this process was accelerated additionally by being incubated with XBP-01. CONCLUSION: XBP-01 can be effective in eliminating atherosclerotic plaque by accelerating the process in which oxidized low density lipoprotein induced smooth muscle cell apoptosis.     

Foam cells can be induced by oxidized low density lipoprotein in human monocyte-derived dendritic cells

AIM: The purpose of this study is to investigate the mechanisms related to oxidized low-density lipoprotein (ox-LDL) and dendritic cells (DCs) in the process of atherosclerosis.METHODS: Human DCs were prepared from human CD14+ peripheral blood monocytes using rhGM-CSF (100 μg/L) and rhIL-4 (40 μg/L).Cells were incubated with 100 mg/L native or oxidized LDL for 72 h.The formation of foam cells was investigated by electron microscopy and oil red O staining.Phenotypic and immune functional assays were used with FACS, FITC-dextran phagocytosis, allogeneic mixed T lymphocytes reaction and secretion of Th1/Th2 (IL-12/IL-2) cytokines were also conduced.RESULTS: DCs treated with ox-LDL, but not native LDL were induced into foam cells after cultured for 72 h.Compared with native LDL, ox-LDL-treated DCs were less potent in FITC-dextran phagocytosis.ox-LDL promoted allogeneic T cells proliferation.Moreover, ox-LDL upregulated CD80 (72.4± 9.6 vs 89.5±10.1, P<0.01), CD86 (67.2±8.8 vs 80.2±11.6, P<0.01), HLA-DR (80.6±9.8 vs 86.6±10.8, P<0.01) and CD1a (40.2±10.3 vs 60.2±9.3, P<0.01) expressions, increased IL-12 secretion ［(44.3±8.9)ng/L vs (65.1±10.4)ng/L, P<0.05］ in DCs.However, the secretion of IL-2 was decreased ［(43.6±7.8)ng/L vs (10.0±4.5 )ng/L, P<0.01］ significently.CONCLUSION: DCs were induced into foam cells by ingesting ox-LDL with some functional characteristic of mature DC.DCs seem to be a new source of foam cells and play a key role in immunopathogenesis of atherosclerosis.     

Role of Toll-like receptor 4/MAPKs pathway on monocyte chemoattractant protein-1 secretion induced by oxidized low density lipoprotein in vascular smooth muscle cells

AIM: To investigate the role of Toll-like receptor 4/MAPKs pathway on the secretion of monocyte chemoattractant protein-1 (MCP-1) induced by oxidized low density lipoprotein (ox-LDL) in the vascular smooth muscle cells (VSMCs). METHODS: mRNA and protein expressions of MCP-1 in VSMCs stimulated with oxidized low density lipoprotein were determined by RT-PCR and ELISA, respectively. The phosphorylated forms of ERK1/2 and p38MAPK were determined by Western blotting. TLR4 neutralizing antibodies (a specific TLR4 inhibitor), PD98059 (ERK1/2 specific inhibitor), SB23015 (p38MAPK specific inhibitor) and SP600125 (JNK specific inhibitor) were used to investigate the underlying mechanisms. RESULTS: The mRNA and protein expressions of MCP-1 in VSMCs were up-regulated by ox-LDL (P<0.05), while those were inhibited by TLR4 neutralizing antibodies, PD98059 or SB23015 (P<0.05), but not by SP600125 (P>0.05). TLR4 had regulatory effect on the phosphorylation of ERK1/2 and p38MAPK. CONCLUSION: ox-LDL is an endogenous ligand of TLR4. The secretion of MCP-1 induced by ox-LDL in VSMCs is at least in part via TLR4/ERK1/2 and TLR4/p38MAPKs pathways.     

Effects of captopril on vascular endothelial cell morphological and functional damages induced by oxidized low density lipoproteins

AIM：To evaluate the effects of oxidized low density lipoproteins (ox-LDL) on morphology and secretion of endothelial cells,and whether captopril (CPT) has an impact on it.METHODS：Bovine aortic endothelial cells (BAECs) seeded and grown to confluent monolayers,were incubated with ox-LDL and in the presence or absence of CPT.The cellular morphology and ultrastructure were observed and photographs were taken by light and scanning electron microscope.In addition,BAECs were incubated with ox-LDL or coincubated with different concentrations of CPT for 2,4,8 and 24 h in vitro.ET-1,TXB2 and 6-keto-PGF1α levels in cell culture supernatant were measured.The data were presented as mean±s and were analyzed by ANOVA.Statistical significance was set at P<0.05.RESULTS：1.Morphological changes of BAECs were not apparent by light microscope.By scanning electron microscope,with incubation of ox-LDL for 4 h,the BAEC monolayers produced significant changes observed,such as cell imperfect，detachment，dispersion，and microvilli reduced.Above mentioned changes of BAECs were alleviated by pre-treatment with CPT.2.With ox-LDL treatment,ET-1,6-keto-PGF1α and tromboxan B2 productions were significant higher than those in control.Coincubated with 10-7 mol·L-1 CPT increased ET-1 production at 2 h and 4 h.However,coincubation with 10-9 mol·L-1 CPT,ET-1 production was significant decreased at 8 h.The production of 6-keto-PGF1α was significant increased when coincubated with different concentration of CPT for 24 h.No significant change of tromboxane B2 production was observed.CONCLUSION：These results suggest that ox-LDL induces the morphologic and ultrastructural damage and functional alterations in endothelial cells,at least in part,through angiotensin.     

Effects of glycated serum albumin on expression of MCP-1 in cultured human umbilical vein endothelial cells

AIM: To investigate the effects of glycated serum albumin (GSA) on the expression of monocyte chemoattratant protein-1 (MCP-1) in endothelial cells.METHODS: Human umbilical vein endothelial cells (HUVECs) were cultured with GSA at different concentrations in the presence or absence of glycosylation-product inhibitor aminoguanidine (AG) and anti-oxidant N-acetylcysteine (NAC). The expression of MCP-1 was evaluated by the methods of immunocytochemistry and sandwich ELISA.Malondialdehyde(MDA) content and superoxide dismutase(SOD) activity were determined by the technique of thiobarbituric acid(TBA) and xanthine oxidase(XOD),respectively. RESULTS: GSA stimulated HUVECs to produce and release MCP-1. After HUVECs were treated with 50 mg/L GSA, the expression of MCP-1 at 4 h, 8 h and 12 h was 1.3, 1.9 and 2.8 folds higher than that in control group (P<0.01), respectiuely.The significant difference among the experiment groups (P<0.01) was observed, indicating that GSA took effect in a concentration-dependent manner. The release of MCP-1 in cultured supernatants in the experiment groups with 3 different concentrations of GSA was 1.6, 2.4 and 3.0 folds as much as that in control group (P<0.01), and the significant difference among the experiment groups (P<0.01) was also observed. GSA decreased the activity of SOD (P<0.05) and increased the content of MDA (P<0.01). AG and NAC obviously inhibited the upregulation of MCP-1 expression in HUVECs by GSA (P<0.01). NAC also inhibited the effect of GSA on SOD activity and MDA content in HUVECs (P<0.05). CONCLUSION: GSA stimulates the expression of MCP-1 by inducing oxidative stress in endothelial cells.     

Effect of peroxisome proliferator activated receptor δ on mRNA expression of MCP-1 induced by homocysteine in cultured human umbilical vein endothelial cells

AIM: To investigate the effects of peroxisome proliferator activated receptor δ (PPARδ) on the mRNA expression of monocyte chemoattractant protein 1 (MCP-1) induced by homocysteine (Hcy) in human umbilical vein endothelial cells (HUVECs). METHODS: Collagenase was used to isolate endothelial cells from human umbilical vein, and the cells were cultured in vitro . The HUVECs were divided into blank control group, Hcy group, GW0742 (a specific agonist of PPARδ) group and diphenyleneiodonium (DPI,a specific inhibitor of NADPH oxidase) group. RT-PCR was used to examine the mRNA expression of MCP-1 and PPARδ. The protein level of PPARδ was detected by Western blotting.2',7'-Dichlorofluorescin diacetate(DCFH-DA) was added to monitor intracellular production of reactive oxygen species (ROS). RESULTS: Compared with control group, Hcy promoted the mRNA expression of MCP-1 in a concentration-dependent manner, and decreased the mRNA expression of PPARδ in HUVECs. The mRNA expression of MCP-1 was significantly elevated by Hcy at the concentration of 10^-5 mol/L, and the mRNA expression of PPARδ was decreased remarkably (P<0.01). GW0742 decreased the mRNA expression of MCP-1 compared with Hcy group (P<0.01). Hcy remarkably increased the production of ROS compared with control group. Hcy-induced production of ROS was also significantly attenuated by GW0742. CONCLUSION: The activation of PPARδ decreases the Hcy-induced mRNA expression of MCP-1 by suppressing Hcy-stimulated production of ROS.     

Native and oxidized low density and very low density lipoprotein enhance the expression of MIP-1α mRNA in aortic smooth muscle cells

AIM: To understand whether native and oxidized low density and very low density lipoprotein (n-LDL, n-VLDL, ox-LDL, ox-VLDL) enhance the expression of macrophage inflammatory protein (MIP)1α mRNA in cultured aortic smooth muscle cells (SMCs). METHODS: Native low density and very low density lipoprotein were isolated from normal blood donors by density gradient ultracentrifugation, and were oxidatively modified by adding CuCl2. After a 24 h-exposure of the cultured SMCs to n-LDL， n-VLDL， ox-LDL and ox-VLDL, respectively, the expression of MIP-1α mRNA was determined by in situ hybridization and RT-PCR. RESULTS: Cultured aortic SMCs expressed MIP-1α mRNA at low level. N-LDL， n-VLDL， ox-LDL and ox-VLDL enhanced the expression of MIP-1α mRNA in SMCs, ox-LDL and ox-VLDL showed stronger effect than n-LDL and n-VLDL, respectively. The effect of ox-VLDL was most striking. There was a significant difference between groups (P<0.01). CONCLUSION: N-LDL, n-VLDL, especially ox-LDL and ox-VLDL, may play an important role in the formation of early atherosclerotic lesion by inducing SMCs to express MIP-1α.     

Effects of oxidized HDL on the levels of MCP-1, ICAM-1 and free calcium in cultured human umbilical venous endothelial cells

AIM:To study the effects of oxidized high-density lipoprotein (oxHDL) on the expression of monocyte chemoattractant protein-1(MCP-1) and intercellular adhesion molecule-1(ICAM-1) and intracellular free calcium concentration ([Ca²⁺]i) level in cultured human umbilical venous endothelial cells(HUVECs). METHODS:The MCP-1 protein content in the medium of conditioned HUVEC was measured by ELISA, and the ICAM-1 on HUVECs was detected by indirect immunofluorescence, and [Ca²⁺]i was determined by Fluo-3/AM, the injury of cells was observed by scanning electron microscopy (SEM).RESULTS:oxHDL could induce the expression of MCP-1 and ICAM-1 in HUVECs. In oxHDL group (HUVECs were incubated with 100 mg protein/L oxHDL for 24 h), the levels of MCP-1, ICAM-1 and [Ca²⁺]i increased by 160%, 60% and 70% respectively compared with the control group (P＜0.01). When HUVECs were incubated with 300 mg protein/L oxHDL for 24 h, cells were injured obviously. CONCLUSION:By inducing the expression of ICAM-1 and MCP-1 in endothelial cells, oxHDL may promote monocyte-endothelium adhesion and monocyte migration to intima, it may promote atherosclerosis as oxidized low-density lipoprotein (oxLDL).     

Effect of 27nt-miRNA on apoptosis of human umbilical vein endothelial cells induced by oxidized low-density lipoprotein

AIM To investigate the effect of 27nt-miRNA （27nt-miR） on apoptosis of human umbilical vein endothelial cells （HUVECs） induced by oxidized low-density lipoprotein （Ox-LDL） and its underlying mechanism. METHODS HUVECs were cultured in vitro and grouped as below： normal control group, Ox-LDL group, 27nt-miR+Ox-LDL group, anti-27nt-miR+Ox-LDL group and negative control+Ox-LDL group. The cells in Ox-LDL group were treated with Ox-LDL at 40 mg/L for 48 h, while those in normal control group were untreated but cultured normally. The cells in 27nt-miR+Ox-LDL group, anti-27nt-miR+Ox-LDL group and negative control+Ox-LDL group were transfected with their corresponding lentiviral vectors under the same procedure, followed by treatment with Ox-LDL at 40 mg/L for 48 h to induce apoptosis. The cell viability was measured by CCK-8 assay. The migration capacity was detected by scratch assay. The caspase-3 activity was measured by caspase-3 activity assay kit. The apoptotic rate was analyzed by Hoechst 33258 and flow cytometry. The mRNA and protein expression levels of Bcl-2, Bax and caspase-3 were determined by RT-qPCR and Western blot. RESUITS： Compared with negative control+Ox-LDL group, the cell viability and migration ability were significantly decreased by over-expression of 27nt-miR in the HUVECs （P<0.05）, while the activity of caspase-3 and apoptosis induced by Ox-LDL were significantly increased （P<0.05）. Furthermore, the mRNA and protein expression levels of Bax and caspase-3 were significantly up-regulated （P<0.05）, and the mRNA and protein expression level of Bcl-2 was down-regulated in 27nt-miR+Ox-LDL group （P<0.05）. Meanwhile, all the above indexes showed an opposite tendency in anti-27nt-miR+Ox-LDL group. CONCLUSION 27nt-miR promotes Ox-LDL-induced apoptosis and inhibits the viability and migration of HUVECs in vitro, possibly through regulating the expression of apoptotic/anti-apoptotic proteins such as Bax,caspase-3 and Bcl-2.     

Effects of oxidized low density lipoprotein and vitamin E on the levels of IL-6,IL-8 and TNF-α in cultured human umbilical vein endothelial cells

AIM:To investigate effects of OX-LDL and VitE on the levels of IL-6,IL-8 and TNF-α in human umbilical vein endothelial cells(HUVEC).METHODS: Human umbilical vein endothelial cells were obtained by in vitro culture. HUVEC treated with or without Vit E was incubated with OX-LDL, and the levels of IL-6, IL-8 and TNF-α were determined by enzyme-linked immunosorbent assy technique. RESULTS:50 μg/L,100 μg/L, 200 μg/L OX-LDL induced the release of IL-6,IL-8 and TNF-α by HUVEC in a dose-dependent manner. Compared with the control group , the levels of IL-6 and IL-8 were significantly increased at 6-12 h of stimulation with OX-LDL . Maximal levels of IL-6 and IL-8 occurred after 24-36 h, reaching a plateau maintained for at least 48 h. TNF-α rose after 2-6 h in HUVEC, and reached a maximum after 12 h. In contrast to IL-6 and IL-8, TNF-α declined after 48 h. However, when VitE (50 mg/L,100 mg/L,200 mg/L)was added, it can significant inhibited the release of IL-6, IL-8 and TNF-α in a dose-dependent manner, and after 48 h these cytokines have no diference between OX-LDL+VitE groups and OX-LDL groups. CONCLUSION: OX-LDL can obviously stimulate the production of IL-6,IL-8 and TNF-α in vascular endothelial cells, which can significantly be inhibited by VitE in a short time.     

Effect of lipid peroxidation on expression of vascular cell adhesion molecule-1 in cultured human endothelial cells

AIM:To observe the expression of vascular cell adhesion molecule-1 (VCAM-1) in cultured human umbilical vein endothelial cells (HUVEC) by lipid peroxidation injury induced by exposure to diamide.METHODS:Expression of VCAM-1 mRNA and protein in HUVEC was determined by in situ hybridization and a cell enzyme-linked immunosorbent essay (cell ELISA), respectively.RESULTS:The HPIAS-1000 image analytic system in situ hybridization detected that the mean absorbance values in experiment groups(1, 5 and 10 μmol/L diamide for 8 hours) were 0.147±0.013, 0.292±0.020 and 0.396±0.022, which were 1.91-fold, 3.79-fold and 5.14-fold as much as that of the control group (0.077±0.011), respectively. There was significant statistical difference between groups (P＜0.01). The cell ELISA showed that the mean absorbance values of VCAM-1 proteins in experiment groups were 0.158±0.008, 0.220±0.017 and 0.321±0.023, which were 1.53-fold, 2.12-fold and 3.09-fold as much as that of the control group (0.104±0.016), respectively. The analysis of variance proved the significant difference between groups (P<0.01).CONCLUSION:The results suggest that the increased expression of VCAM-1 is integral in promoting adhesion of monocytes to the vascular endothelium.     

Effect of oxidized LDL on expression of connexin43 in cultured human umbilical vein endothelial cells

AIM: To investigate the effect of oxidized LDL (ox-LDL) on the expression of gap junction protein connexin43 in cultured human umbilical vein endothelial cells (HUVECs) in vitro. METHODS: Human umbilical vein endothelial cells cultured in normal condition were divided into blank control group, 50 mg/L,100 mg/L and 200 mg/L ox-LDL intervention groups. The mRNA expression of connexin43 in cultured HUVECs was detected with RT-PCR method; while the protein level of connexin43 was determined by the method of immunocytochemistry in the control and 100 mg/L ox-LDL intervention groups 24 h after ox-LDL was given. RESULTS: Different concentrations (50 mg/L, 100 mg/L, 200 mg/L) of ox-LDL up-regulated mRNA expression of connexin43 in cultured HUVECs after 24 h intervention (P<0.01). The protein level of connexin43 in cultured HUVECs intervened with 100 mg/L Ox-LDL for 24 h was up-regulated as compared to the control cells (P<0.01).CONCLUSION: Ox-LDL may up-regulate the expression of connexin43 at mRNA and protein levels in cultured human umbilical vein endothelial cells within short time, indicating that connexin43 plays an important role in the pro-atherosclerotic effect of Ox-LDL.