Cholesterol enrichment upregulates intercellular adhesion molecule-1 in human vascular endothelial cells

Cholesterol Tethered Poly(DL-Lactic Acid) for Promoting Osteoblast Attachment and Growth

In poly(DL-lactic acid)-cholesterol oligomers (LC), a novel cholesterol modified poly(DL-lactic acid) (PLA), was synthesized via bulk polymerization of DL-lactide using cholesterol initiator. Gel permeation chromatography (GPC) and 1H nuclear magnetic resonance spectroscopy (1H-NMR) results indicated a narrow molecular weight distribution of poly (DL-lactic acid)-cholesterol oligomers (LC). Mouse MC3T3 osteoblast-like cells were selected as a model system to test the cell behavior of cholesterol modified PLA substrates. The osteoblast attachment, proliferation, and viability revealed that the cholesterol modified PLA was significantly osteoblast compatible and may have potential as a bone tissue engineering material.

Cholesterol Enrichment Impairs Capacitative Calcium Entry, eNOS Phosphorylation & Shear Stress-Induced NO Production

Endothelial dysfunction, characterized by decreased production or availability of nitric oxide (NO), is widely believed to be the hallmark of early-stage atherosclerosis. In addition, hypercholesterolemia is considered a major risk factor for development of atherosclerosis and is associated with impaired flow-induced dilation. However, the mechanism by which elevated cholesterol levels leads to decreased production of NO is unclear. NO is released in response to shear stress and agonist-evoked changes in intracellular calcium. Although calcium signaling is complex, we have previously shown that NO production by endothelial nitric oxide synthase (eNOS) is preferentially activated by calcium influx via store-operated channels. We hypothesized that cholesterol enrichment altered this signaling pathway (known as capacitive calcium entry; CCE) ultimately leading to decreased NO. Our results show that cholesterol enrichment abolished ATP-induced eNOS phosphorylation and attenuated the calcium response by the preferential inhibition of CCE. Furthermore, cholesterol enrichment also inhibited shear stress-induced NO production and eNOS phosporylation, consistent with our previous results showing a significant role for ATP autocrine stimulation and subsequent activation of CCE in the endothelial flow response.

Correlation between pretreatment serum LDL-cholesterol levels and prognosis in nasopharyngeal carcinoma patients

Purpose

To investigate the correlations between long-term survival outcomes in patients with nasopharyngeal carcinoma (NPC) and pretreatment serum low-density lipoprotein cholesterol (LDL-C) levels.

Patients and methods

Between January 2008 and December 2011, 935 patients with newly diagnosed NPC who were treated with intensity-modulated radiation therapy were included in this retrospective clinical analysis. Patients were divided into two groups based on pretreatment LDL-C levels: normal LDL-C (≤3.64 mmol/L; n=816) and elevated LDL-C (>3.64 mmol/L; n=119). Associations between pretreatment LDL-C levels and treatment outcome were analyzed by univariate and multivariate analyses.

Results

The overall patient follow-up rate was 95.1%, and 726 patients received more than 5 years of follow-up. Five-year overall survival (OS), local control (LC), and distant metastasis-free survival (DMFS) rates of the entire patient population were 87.1%, 91.1%, and 87.2%, respectively. Rates of 5-year OS, LC, and DMFS for the elevated versus normal LDL-C groups were 77.0% vs 89.1% (P<0.001), 85.8% vs 91.9% (P=0.041), and 81.1% vs 88.1% (P=0.038), respectively. Compared with normal LDL-C levels, elevated LDL-C levels were identified as an independent prognostic factor of a poorer OS (hazard ratio [HR] =2.171; 95% confidence interval [CI] =1.424–3.309), LC rate (HR =1.762; 95% CI =1.021–3.942), and DMFS (HR =1.594; 95% CI =1.003–2.532).

Conclusion

This study found that elevated pretreatment LDL-C levels are negative prognostic indicators of NPC. Elevated LDL-C levels may be useful indicators of locoregional control and distant metastasis in NPC patients.

p53 Levels positively correlate with carotid intima-media thickness in patients with subclinical atherosclerosis

BACKGROUND

The level of circulating p53 is related to inflammation in asymptomatic subjects with cardiovascular risk factors. Whether p53 is associated with the severity of atherosclerosis remains to be determined.

HYPOTHESIS

This study examines the relationship of systemic p53 levels with atherosclerotic risk factors and subclinical atherosclerosis.

METHODS

Circulating levels of p53 and markers of inflammation were measured in 356 subjects with cardiovascular risk factors but who were free from clinical cardiovascular disease. Subclinical atherosclerosis was evaluated by both the mean carotid intima-media thickness (IMT) and the presence of atherosclerotic plaques with the use of B-mode ultrasound in all subjects.

RESULTS

p53 levels were positively correlated with age (r = 0.382, P < 0.001), intercellular adhesion molecular-1 (ICAM-1; r = 0.510, P < 0.01), vascular cell adhesion molecular-1 (VCAM-1; r = 0.497, P < 0.01), E-selectin (r = 0.337, P < 0.01), and carotid IMT (r = 0.594, P < 0.01). The association between p53 and IMT remained significant in multiple regression analysis (P < 0.01) when controlling for traditional atherosclerotic risk factors and inflammatory markers.

CONCLUSION

Higher plasma p53 levels were associated with an increase in inflammatory markers, as well as increased carotid IMT. Circulating p53 may be useful in identifying subclinical atherosclerosis in subjects symptomatically free from cardiovascular disease.

Niacin affects cell adhesion molecules and plasminogen activator inhibitor-1 in HepG2 cells

BACKGROUND

Beyond lipid-modifying actions, niacin lowers the risk of atherothrombotic events by lowering prothrombotic factors like fibrinogen. Plasminogen activator inhibitor type 1 (PAI-1) is a potential factor for atherogenesis and thrombosis, increased in acute myocardial infarctions and restenosis after angioplasty. Cell adhesion molecules (CAM) mediate adhesion, recruitment and migration of white blood cells through vascular surfaces, an essential process in atherogenesis. ICAM-1 is a significant predictor of future coronary events. Whether niacin affects ICAM-1 expression is unknown. We studied the effects of niacin on PAI-1 and CAM using HepG2 cells.

METHODS

HepG2 cells were cultured in DMEM until 90% confluent. After serum starvation, cells were exposed to DME/F12 containing niacin. Transforming growth factor-beta (TGF-beta) was added directly to cell media. Cell lysate and conditioned media were collected for measurement of PAI-1 by ELISA. For measurement of ICAM, cells were treated with tumor necrosis factor-alpha (TNF-alpha) instead. The effect of niacin on mRNA expression of ICAM-1 was studied using RT-PCR.

RESULTS

Niacin reduced the TGF-beta-induced rise by 30% to 55% (p=0.002). The differences in degree of PAI-1 reduction, between different niacin concentrations, were not statistically significant. Niacin reduced TNF-alpha-induced rise in ICAM-1 levels by 66% to 89% (p<0.0001), but did not significantly affect TNF-alpha-induced rise in PECAM-1. Semiquantitative RT-PCR analysis showed that reduced TNF-alpha-induced rise in ICAM-1 mRNA expression significantly by 17% (p=0.001).

CONCLUSIONS

Treatment with niacin suppressed PAI-1 and ICAM-1 levels in HepG2 cells. Further studies to understand the mechanistic pathways of this suppression, could further explain benefits of niacin in prevention of atherosclerotic disease, and offer therapeutic avenues against the rising burden of atherothrombotic disease.

Convergence of genes implicated in Alzheimer's disease on the cerebral cholesterol shuttle: APP, cholesterol, lipoproteins, and atherosclerosis

Polymorphic genes associated with Alzheimer's disease (see ) delineate a clearly defined pathway related to cerebral and peripheral cholesterol and lipoprotein homoeostasis. They include all of the key components of a glia/neurone cholesterol shuttle including cholesterol binding lipoproteins APOA1, APOA4, APOC1, APOC2, APOC3, APOD, APOE and LPA, cholesterol transporters ABCA1, ABCA2, lipoprotein receptors LDLR, LRP1, LRP8 and VLDLR, and the cholesterol metabolising enzymes CYP46A1 and CH25H, whose oxysterol products activate the liver X receptor NR1H2 and are metabolised to esters by SOAT1. LIPA metabolises cholesterol esters, which are transported by the cholesteryl ester transport protein CETP. The transcription factor SREBF1 controls the expression of most enzymes of cholesterol synthesis. APP is involved in this shuttle as it metabolises cholesterol to 7-betahydroxycholesterol, a substrate of SOAT1 and HSD11B1, binds to APOE and is tethered to LRP1 via APPB1, APBB2 and APBB3 at the cytoplasmic domain and via LRPAP1 at the extracellular domain. APP cleavage products are also able to prevent cholesterol binding to APOE. BACE cleaves both APP and LRP1. Gamma-secretase (PSEN1, PSEN2, NCSTN) cleaves LRP1 and LRP8 as well as APP and their degradation products control transcription factor TFCP2, which regulates thymidylate synthase (TS) and GSK3B expression. GSK3B is known to phosphorylate the microtubule protein tau (MAPT). Dysfunction of this cascade, carved out by genes implicated in Alzheimer's disease, may play a major role in its pathology. Many other genes associated with Alzheimer's disease affect cholesterol or lipoprotein function and/or have also been implicated in atherosclerosis, a feature of Alzheimer's disease, and this duality may well explain the close links between vascular and cerebral pathology in Alzheimer's disease. The definition of many of these genes as risk factors is highly contested. However, when polymorphic susceptibility genes belong to the same signaling pathway, the risk associated with multigenic disease is better related to the integrated effects of multiple polymorphisms of genes within the same pathway than to variants in any single gene [Wu, X., Gu, J., Grossman, H.B., Amos, C.I., Etzel, C., Huang, M., Zhang, Q., Millikan, R.E., Lerner, S., Dinney, C.P., Spitz, M.R., 2006. Bladder cancer predisposition: a multigenic approach to DNA-repair and cell-cycle-control genes. Am. J. Hum. Genet. 78, 464-479.]. Thus, the fact that Alzheimer's disease susceptibility genes converge on a clearly defined signaling network has important implications for genetic association studies.

In vivo low-density lipoprotein exposure induces intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 correlated with activator protein-1 expression

OBJECTIVE

We tested the hypothesis that direct native low-density lipoprotein (LDL) injection into LDL receptor-deficient (LDLR(-/-)) mice would induce the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in their aortic endothelial cells, and that transcriptional regulation of this pathway involved activator protein-1 (AP-1) but not nuclear factor kappaB (NF-kappaB).

METHODS AND RESULTS

Using tail vein injection of LDL into LDLR(-/-) mice, we were able to maintain atherogenic LDL blood levels, which induced ICAM-1 and VCAM-1 expression in their aortic endothelial cells after 24 hours. We were able to visualize and quantify this expression using immunohistochemistry and confocal microscopy. Under conditions in which ICAM-1 and VCAM-1 were expressed, the regulatory AP-1 proteins c-Fos and c-Jun were also highly expressed in the endothelial cell cytoplasm and observed within the cell nucleus. The NF-kappaB protein P65, although expressed in the endothelial cell cytoplasm after LDL injection, was not observed within the cell nucleus.

CONCLUSIONS

Elevated LDL blood levels, maintained in vivo, increased the expression of the adhesion molecules ICAM-1 and VCAM-1 in aortic endothelial cells. This effect appeared to correlate with AP-1 but not NF-kappaB.

Rho GTPases and Leukocyte Adhesion Receptor Expression and Function in Endothelial Cells

Rho family GTPases are key signal transducers that regulate cell adhesion and migration and a variety of other cellular responses, including changes in gene expression. In this review, we discuss how Rho GTPases regulate signaling by endothelial cell receptors involved in leukocyte extravasation. First, Rho GTPases affect the expression of some leukocyte adhesion molecules on endothelial cells, such as intracellular adhesion molecule-1 and E-selectin, that can be induced by proinflammatory mediators, hypoxia, or shear stress. Second, Rho GTPases are activated by engagement of several leukocyte adhesion receptors and contribute to both early morphological changes and subsequent alterations in gene expression. Rho GTPases are therefore candidate targets for inhibiting leukocyte transendothelial migration in heart disease and chronic inflammatory disorders.

Lower level of low-density lipoprotein cholesterol by statin prevents progression of coronary restenosis after successful stenting in acute myocardial infarction

OBJECTIVE

It is unclear whether the reduction of coronary restenosis by statins is due to a decrease in low-density lipoprotein (LDL) cholesterol and/or pleiotropic effects. Therefore, we performed quantitative coronary angiography (QCA) and analyzed the lipid profile and changes in adhesion molecules and chemokines caused by statin in patients with acute myocardial infarction (AMI).

METHODS

The subjects included AMI patients who had initial coronary angiograms and significant coronary stenosis and were implanted with a stent. After stent implantation, patients were treated either with (n = 36) or without (n = 14) statin. The primary end-point for this study was the absolute changes in the lipid profile, C-reactive protein (CRP), adhesion molecules, chemokines and stenosis measured by QCA between the post-stent and follow-up angiogram at 6 months after stenting.

RESULTS

Treatment with statin reduced % coronary diameter stenosis (DS) and was associated with a greater reduction in LDL cholesterol at 6 months after stenting in patients with acute myocardial infarction (AMI), while there were no differences in adhesion molecules, chemokines, CC chemokine receptor or CXC chemokine receptor. Interestingly, changes in % DS between before and after statin treatment at 6 months (Delta%DS) were positively correlated with DeltaLDL cholesterol, and patients who had an LDL cholesterol level of less than 80 mg/dl had a significantly lower Delta%DS. In addition, Delta%DS was significantly related only to the reduction in LDL cholesterol as assessed by a stepwise multivariable regression analysis.

CONCLUSION

These results suggest that the lower level of LDL cholesterol is the most critical factor in preventing coronary restenosis.

Lysophospholipids increase ICAM-1 expression in HUVEC through a Gi- and NF-kappaB-dependent mechanism

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S-1-P) are both low molecular weight lysophospholipid (LPL) ligands that are recognized by the Edg family of G protein-coupled receptors. In endothelial cells, these two ligands activate Edg receptors, resulting in cell proliferation and cell migration. The intercellular adhesion molecule-1 (ICAM-1, CD54) is one of many cell adhesion molecules belonging to the immunoglobulin superfamily. This study showed that LPA and S-1-P enhance ICAM-1 expression at both the mRNA and protein levels in human umbilical cord vein endothelial cells (HUVECs). This enhanced ICAM-1 expression in HUVECs was first observed at 2 h postligand treatment. Maximal expression appeared at 8 h postligand treatment, as detected by flow cytometry and Western blotting. Furthermore, the effects of S-1-P on ICAM-1 expression were shown to be concentration dependent. Prior treatment of HUVECs with pertussis toxin, a specific inhibitor of G(i), ammonium pyrrolidinedithiocarbamate and BAY 11-7082, inhibitors of the nuclear factor (NF)-kappaB pathway, or Clostridium difficile toxin B, an inhibitor of Rac, prevented the enhanced effect of LPL-induced ICAM-1 expression. However, pretreatment of HUVECs with exoC3, an inhibitor of Rho, had no effect on S-1-P-enhanced ICAM-1 expression. In a static cell-cell adhesion assay system, pretreatment of LPL enhanced the adhesion between HUVECs and U-937 cells, a human mononucleated cell line. The enhanced adhesion effect could be prevented by preincubation with a functional blocking antibody against human ICAM-1. These results suggest that LPLs released by activated platelets might enhance interactions of leukocytes with the endothelium through a G(i)-, NF-kappaB-, and possibly Rac-dependent mechanism, thus facilitating wound healing and inflammation processes.

Hyperlipidemia is a risk factor for lymphatic metastasis in superficial esophageal carcinoma

Although increased dietary fat or cholesterol has been reported to be a risk factor for the development of certain cancers, the effect of the serum lipid level on tumor metastasis has not been well documented. Fasting serum levels of total cholesterol (TC) and triglycerides (TG) were examined in 54 patients with superficial esophageal cancer (SEC) invading lamia musucularis or submucosal layer who underwent esophagectomy with classical lymphadenectomy. The association between lymph node metastasis and the preoperative serum lipid levels as well as the pathological findings was retrospectively analyzed. The levels of TC and TG were significantly higher in 18 node-positive than in 36 node-negative patients (TC: 205.4+/-38.9 vs. 174.5+/-26.8 mg/dl, P<0.01; TG: 152.0+/-68.5 vs. 88.7+/-28.6 mg/dl, P<0.001). Patients with hypercholesterolemia (TC >/= 220 mg/dl) and hypertriglyceridemia (TG >/= 150 mg/dl) showed extremely high rates of nodal metastasis (80 and 91%, respectively), that were significantly higher than those of patients with normal lipid levels (P<0.01 and P<0.001). When hyperlipidemia was defined as the presence of either hypertriglyceridemia or hypercholesterolemia, hyperlipidemia was an independent risk factor for nodal metastasis in SEC. Elevated serum lipid levels might bring favorable circumstances for the development of lymph node metastasis in the early stage of EC. Hyperlipidemia might prompt us to perform more studies to investigate possible metastasis.

Hyperlipidaemia is positively correlated with lymph node metastasis in men with early gastric cancer

BACKGROUND

Although increased dietary fat or cholesterol has been reported to be a risk factor for the development of certain cancers, the effect of serum lipid levels on tumour metastasis is not clearly understood.

METHODS

The association between lymph node metastasis and preoperative serum levels of total cholesterol (TC) and triglyceride (TG) as well as various pathological findings for tumours was examined in 353 patients with early gastric cancer who underwent gastrectomy with classical lymphadenectomy.

RESULTS

The rate of lymph node metastasis was significantly higher in patients with early gastric cancer who had hypercholesterolaemia (TC 220 mg/dl or greater) or hypertriglyceridaemia (TG 150 mg/dl or greater). The tendency was more prominent in men, and multivariate analysis showed that hypertriglyceridaemia was an independent risk factor for nodal metastasis in men, in addition to pathological invasion to the submucosal layer or to lymphatic vessels. In contrast, neither hypercholesterolaemia nor hypertriglyceridaemia showed a significant association with nodal status in women with early gastric cancer.

CONCLUSION

Raised serum lipid levels might favour the development of lymph node metastasis in men with early-stage gastric cancer. In patients with early gastric cancer serum lipid levels should be checked before operation, and the use of minimal local treatments must be considered carefully in male patients with hyperlipidaemia.

Detection of nuclear factor-kappaB in IgA nephropathy using Southwestern histochemistry

BACKGROUND

The transcription factor nuclear factor-kappaB (NF-kappaB) is involved in inflammatory and immune responses through induction of various cytokines and growth factors. The aim of this study is to examine the correlation between NF-kappaB expression and severity of tissue injury in immunoglobulin A (IgA) nephropathy and the mechanism of such correlation.

METHODS

The study included 43 renal tissue samples from 28 patients, including 28 samples of IgA nephropathy, 5 samples of non-IgA mesangial proliferative glomerulonephritis (non-IgA nephropathy), and 10 samples with nonproliferative glomerulonephritis (membranous nephropathy [MN] n = 5; minimal change nephrotic syndrome [MCNS]; n = 5). Tissue sections were examined by Southwestern histochemistry and immunohistochemistry for monocyte chemoattractant protein-1 (MCP-1), granulocyte-macrophage colony-stimulating factor (GM-CSF), and intercellular cell adhesion molecule-1 (ICAM-1), which are regulated by NF-kappaB. Normal portions of surgically resected kidney with adenocarcinoma served as controls.

RESULTS

In normal kidney, MCNS, and MN sections, NF-kappaB expression was detected in a few mesangial cells and tubular epithelial cells. In IgA nephropathy and non-IgA nephropathy samples, NF-kappaB was expressed in mesangial, glomerular endothelial and epithelial cells, tubular epithelial cells, and infiltrating cells. Expression in both glomeruli and interstitium correlated with progression of tissue injury. In IgA nephropathy samples, MCP-1 and GM-CSF expression was increased in both glomeruli and interstitium and correlated with progression of tissue injury. Glomerular ICAM-1 expression was weaker in severe lesions, whereas interstitial expression correlated with progression of tissue injury.

CONCLUSION

Our results indicate that NF-kappaB is involved in the progression of tissue injury in IgA nephropathy through the induction of transcriptionally regulated genes.

Effect of oxidized low-density lipoprotein on differential gene expression in primary human endothelial cells

Oxidative modification of low-density lipoprotein (LDL) plays an important role in the initiation and progression of atherosclerosis. It has been proposed that the biological action of oxidized LDL (ox-LDL) may be partially attributed to its effect on a shift of the pattern of gene expression in endothelial cells. To examine the transcriptional response to ox-LDL, we applied cDNA array technology to cultured primary human endothelial cells challenged with oxidized human LDL. A twofold or greater difference in the expression of a particular gene was considered a significant difference in transcript abundance. Seventy-eight of the 588 genes analyzed were differentially expressed in response to the treatment. Ox-LDL significantly affected the expression of genes encoding for transcription factors, cell receptors, growth factors, adhesion molecules, extracellular matrix proteins, and enzymes involved in cholesterol metabolism. The alteration of the expression pattern of several genes was substantiated post hoc using RT-PCR. The experimental strategy identified several novel ox-LDL-sensitive genes associated with a "response to injury" providing a conceptual background to be utilized for future studies addressing the molecular basis of the early stages of atherogenesis.

p53 activates ICAM-1 (CD54) expression in an NF-kappaB-independent manner

Intercellular adhesion molecule-1 (ICAM-1) is a crucial receptor in the cell-cell interaction, a process central to the reaction to all forms of injury. Its expression is upregulated in response to a variety of inflammatory/immune mediators, including cellular stresses. The NF-kappaB signalling pathway is known to be important for activation of ICAM-1 transcription. Here we demonstrate that ICAM-1 induction represents a new cellular response to p53 activation and that NF-kappaB inhibition does not prevent the effect of p53 on ICAM-1 expression after DNA damage. Induction of ICAM-1 is abolished after treatment with the specific p53 inhibitor pifithrin-alpha and is abrogated in p53-deficient cell lines. Furthermore, we map two functional p53-responsive elements to the introns of the ICAM-1 gene, and show that they confer inducibility to p53 in a fashion similar to other p53 target genes. These results support an NF-kappaB-independent role for p53 in ICAM-1 regulation that may link p53 to ICAM-1 function in various physiological and pathological settings.

Simvastatin reduces the expression of adhesion molecules in circulating monocytes from hypercholesterolemic patients

OBJECTIVE

The intercellular adhesion molecule-1 (ICAM-1/CD54) and its ligand, CD11a/CD18, mediate endothelial adhesion of leukocytes and their consecutive transmigration. Anti-inflammatory effects of statins are considered to be exerted in part through inhibition of leukocyte-endothelial interactions. We investigated the in vivo effects of simvastatin treatment in hypercholesterolemic patients and the influence of various statins on expression of cellular adhesion molecules in vitro.

METHODS AND RESULTS

A total number of 107 hypercholesterolemic patients were treated with 20 mg (n=52) or 40 mg (n=55) of simvastatin daily. After 6 weeks of treatment, peripheral blood mononuclear cells (PBMCs) expressed lower amounts of CD54-, CD18-, and CD11a-mRNA compared with pretreatment values. Surface expression of CD54 and CD18/CD11a on CD14+-monocytes also decreased significantly in both groups of patients. Moreover, simvastatin, atorvastatin, and cerivastatin were found to downregulate tumor necrosis factor (TNF)-alpha-induced expression of CD54 and CD18/CD11a in isolated PBMCs obtained from normal donors as well as TNF-alpha-dependent expression of these CAMs in cultured human umbilical vein endothelial cells (HUVECs). Furthermore, all three statins were found to reduce the binding of PBMCs to TNF-alpha-stimulated HUVECs in vitro.

CONCLUSIONS

Statin-induced inhibition of expression of CD54 and CD18/CD11a in PBMCs and HUVECs with consecutive loss of adhesive function may contribute to the anti-inflammatory effects of these drugs and some of their beneficial clinical activities.