MicroRNA-126 regulates endothelial expression of vascular cell adhesion molecule 1

Adhesion molecules expressed by activated endothelial cells play a key role in regulating leukocyte trafficking to sites of inflammation. Resting endothelial cells normally do not express adhesion molecules, but cytokines activate endothelial cells to express adhesion molecules such as vascular cell adhesion molecule 1 (VCAM-1), which mediate leukocyte adherence to endothelial cells. We now show that endothelial cells express microRNA 126 (miR-126), which inhibits VCAM-1 expression. Transfection of endothelial cells with an oligonucleotide that decreases miR-126 permits an increase in TNF-alpha-stimulated VCAM-1 expression. Conversely, overexpression of the precursor to miR-126 increases miR-126 levels and decreases VCAM-1 expression. Additionally, decreasing endogenous miR-126 levels increases leukocyte adherence to endothelial cells. These data suggest that microRNA can regulate adhesion molecule expression and may provide additional control of vascular inflammation.     

Low-density lipoprotein augments interleukin-1-induced vascular adhesion molecule expression in human endothelial cells.

In this study, the effect of low density lipoproteins (LDL) on the ability of the vascular endothelium to respond to vascular cell adhesion molecule 1 (VCAM-1) activation by a cytokine was investigated. After a 4-day pre-exposure to 240 mg/dl of LDL, human umbilical vein endothelial cells (HUVECs) were hyperresponsive to minute amounts of interleukin 1 alpha (IL-1 alpha) as demonstrated by an augmentation of VCAM-1 gene expression. Furthermore, in response to LDL exposure, endothelial recruitment of monocytes induced by minute amounts of IL-1 alpha was increased. This enhancing effect was blocked by an anti-VCAM antibody. The increased response appears not to be due to changes in IL-1 binding affinity or induction of endogenous IL-1 alpha. Transient transfection of HUVECs with a reporter driven by the VCAM promoter showed that LDL increased cellular response to IL-1 alpha by 46%. LDL itself does not increase NF-kappa B binding in endothelial cells (ECs). However, after a 2-day LDL incubation, NF-kappa B binding could be induced by over 63% with a very low dose of IL-1 alpha. IL-1 alpha at this dose (which activates NF-kappa B, but not AP-1) also enhanced LDL-activated AP-1 binding. This cross-enhanced effect may be an important intracellular signaling mechanism for EC activation. The results from this study provide new clues to understanding the mechanisms governing combined risk factors for atherosclerosis.     

Anti-inflammatory drugs and endothelial cell adhesion molecule expression in murine vascular beds

Background—Inflammatory boweldiseases (IBD) are characterised by an intense infiltration ofleucocytes that is mediated by adhesion molecules expressed on thesurface of activated endothelial cells.
Aims—To determine whether drugsused in the treatment of IBD, specifically dexamethasone (DEX),5-aminosalicylic acid (5-ASA), methotrexate (MTX), and 6-mercaptopurine(6-MP), alter the expression of endothelial cell adhesion molecules (ECAMs).
Methods—The expression ofP-selectin, E-selectin, intercellular adhesion molecule 1 (ICAM-1), andvascular CAM 1(VCAM-1) in different vascular beds of C57Bl/6J mice wasmeasured using the dual radiolabelled monoclonal antibody technique.
Results—Lipopolysaccharide (LPS)elicited a profound increase in the expression of all ECAMs in themesentery, small intestine, caecum, and distal colon. The LPS inducedincrease in CAM expression was not significantly affected by priortreatment with either MTX or 6-MP. However, pretreatment with eitherDEX or 5-ASA significantly attenuated LPS induced increases inexpression of P- and E-selectin, and VCAM-1 in the majority of tissuesevaluated. DEX also blunted the LPS induced increase in ICAM-1expression in the caecum and distal colon. DEX, but not 5-ASA, largelyabolished the rise in plasma tumour necrosis factor α elicited by LPS.
Conclusions—These findings suggestthat DEX and 5-ASA may exert their beneficial therapeutic action inIBD, at least in part, by inhibiting the expression of ECAMs whichmediate leucocyte adhesion and transmigration in the microvasculature.

     

Human eosinophil adherence to vascular endothelium mediated by binding to vascular cell adhesion molecule 1 and endothelial leukocyte adhesion molecule 1.

Adherence of human eosinophils to cytokine-stimulated endothelial cells, which was only partially due to CD18-dependent pathways, was also mediated by binding to endothelial leukocyte adhesion molecule 1 (ELAM-1) and vascular cell adhesion molecule 1 (VCAM-1). Eosinophils bound specifically to both recombinant soluble ELAM-1 and recombinant soluble VCAM-1. Eosinophil binding to recombinant soluble VCAM-1 and to transfected CHO cells expressing VCAM-1 was inhibited with anti-VCAM-1 (4B9) and anti-very late activation antigen 4 (anti-VLA-4; HP1/2 or HP2/1) monoclonal antibodies. Eosinophils, but not neutrophils, expressed VLA-4 detected by cytofluorography. Eosinophil adherence to tumor necrosis factor alpha-stimulated human umbilical vein endothelial cells was partially blocked by monoclonal antibodies against ELAM-1 (BB11) and VCAM-1 (4B9) and against VLA-4 (HP2/1). Thus, while both eosinophils and neutrophils can bind to activated endothelial cells by adherence to ICAM-1 and ELAM-1, only eosinophils expressed VLA-4 and adhered to VCAM-1 on activated endothelial cells. Eosinophil adherence to VCAM-1 might provide a mechanism contributing to the selective recruitment of eosinophils into tissue sites of inflammation.     

Tibolone inhibits leukocyte adhesion molecule expression in human endothelial cells

Tibolone is a synthetic steroid with mixed estrogenic and progestogenic/androgenic activity used for post-menopausal hormone replacement therapy. Since its cardiovascular effects are still not clear, and no data have been published on possible direct actions on the vessel wall, we studied the effects of tibolone and its metabolites on lipopolysaccharide (LPS)-induced expression of leukocyte adhesion molecules on human endothelial cells. Tibolone and its two estrogenic 3alpha-OH and 3beta-OH metabolites, but not the progestogenic/androgenic Delta(4)-isomer, concentration-dependently decreased LPS-induced vascular cell adhesion molecule-1 protein expression. This effect was estrogen receptor dependent, since it was completely blocked by the pure estrogen receptor antagonist ICI 182780. Furthermore, only tibolone, the 3alpha-OH and the 3beta-OH metabolites decreased endothelial expression of E-selectin, while none of the compounds changed the levels of intercellular adhesion molecule-1. These findings were associated with parallel changes in mRNA levels for the three adhesion molecules. Our data show that tibolone and its estrogenic metabolites exert direct actions on the vascular wall, decreasing the expression of endothelial-leukocyte adhesion molecules, thus producing potentially important direct anti-atherogenic effects.     

青藤碱对肿瘤坏死因子-α诱导人脐静脉内皮细胞VCAM-1表达影响初步研究

目的 进一步研究青藤碱(SIN)对肿瘤坏死因子(TNF)-α诱导脐静脉内皮细胞(HUVECs)血管细胞黏附分子(VCAM)-1表达的影响.方法 从新鲜脐带中分离培养HUVECs.用TNF-α诱导HUVECs表达VCAM-1,实验组加入不同浓度的SIN(0.25、0.0和1.0 mol/L)或地塞米松(1.0×106mol/L)分别进行或联合进行干预,用流式细胞仪检测细胞表面VCAM-1表达.结果 与TNF-α刺激组相比,SIN干预组细胞表面VCAM-1表达下降,抑制作用以1.0 mol/L最为显著.联合地塞米松(1.0x106 mol/L)进行干预,可加强SIN对TNF-α诱导的VCAM-1表达的抑制作用.结论 SIN可抑制TNF-α诱导的脐静脉内皮细胞VCAM-1的表达.青藤碱与地塞米松对TNF-α诱导的VCAM-1表达的抑制有协同作用.     

Platelet endothelial cell adhesion molecule-1 and mechanotransduction in vascular endothelial cells

Endothelial cells are known to respond to mechanical forces such as fluid shear stress and cyclic stretch, but elucidating the mechanism for mechanosensing has been difficult. Experimental data indicate that there are probably several sensing mechanisms. We have recently proposed a novel mechanoresponse mechanism that involves platelet endothelial cell adhesion molecule-1 (PECAM-1). When endothelial cells are stimulated by fluid shear stress, PECAM-1 is tyrosine phosphorylated and activates the extracellular signal-regulated kinase 1 and 2 (ERK1/2) signalling cascade. The same signalling events occurred when we applied pulling force directly on PECAM-1 on the endothelial cell surface using magnetic beads coated with antibodies against the external domain of PECAM-1. These results appear to indicate that PECAM-1 is a mechanotransduction molecule. To our knowledge, this is the first mammalian molecule that is shown to respond to mechanical force directly exerted to it.     

Simvastatin alters human endothelial cell adhesion molecule expression and inhibits leukocyte adhesion under flow

Hypercholesterolaemia is implicated as an independent risk factor in the pathogenesis of atherosclerosis. HMG-CoA reductase inhibitors (statins) are prescribed for their lipid-lowering effects but recent evidence suggests they have pleiotropic effects independent of lipid balance regulation that may explain their role in dramatically decreasing cardiovascular mortality and morbidity. The mechanisms responsible are unclear but endothelial cell (EC) dysfunction is critical. To investigate potential anti-inflammatory properties of statins on EC, functional responses of human umbilical vein endothelial cells (HUVEC) and human neutrophils under physiological flow conditions were studied. These interactions were quantified in response to inflammatory mediators following pre-treatment with statin.Histamine stimulation resulted in significant (p < 0.001) increases in transient interactions between neutrophils and EC (tethering). These effects were significantly reduced (p < 0.001) on pre-treatment with statin. TNF-α stimulation resulted in significant (p < 0.001) increases in rolling interactions. These effects were significantly (p < 0.001) reduced following pre-treatment of EC with statin. Mevalonate pre-treatment of EC significantly reversed the effects of statin pre-treatment on both tethering and rolling (p < 0.001).Reductions in surface expression of P- and E-selectin were confirmed by ELISA. EC exposed to histamine demonstrated significantly increased (p < 0.01) levels of P-selectin, abrogated (p < 0.001) by pre-treatment with statin. EC exposed to TNF-α demonstrated a significant increase (p < 0.001) in levels of E-selectin, reduced (p < 0.05) by pre-treatment with statin.     

Vascular endothelial platelet endothelial cell adhesion molecule 1 (PECAM-1) regulates advanced metastatic progression

Most patients who die from cancer succumb to treatment-refractory advanced metastatic progression. Although the early stages of tumor metastasis result in the formation of clinically silent micrometastatic foci, its later stages primarily reflect the progressive, organ-destructive growth of already advanced metastases. Early-stage metastasis is regulated by multiple factors within tumor cells as well as by the tumor microenvironment (TME). In contrast, the molecular determinants that control advanced metastatic progression remain essentially uncharacterized, precluding the development of therapies targeted against it. Here we show that the TME, functioning in part through platelet endothelial cell adhesion molecule 1 (PECAM-1), drives advanced metastatic progression and is essential for progression through its preterminal end stage. PECAM-1-KO and chimeric mice revealed that its metastasis-promoting effects are mediated specifically through vascular endothelial cell (VEC) PECAM-1. Anti-PECAM-1 mAb therapy suppresses both end-stage metastatic progression and tumor-induced cachexia in tumor-bearing mice. It reduces proliferation, but not angiogenesis or apoptosis, within advanced tumor metastases. Because its antimetastatic effects are mediated by binding to VEC rather than to tumor cells, anti-PECAM-1 mAb appears to act independently of tumor type. A modified 3D coculture assay showed that anti-PECAM-1 mAb inhibits the proliferation of PECAM-1-negative tumor cells by altering the concentrations of secreted factors. Our studies indicate that a complex interplay between elements of the TME and advanced tumor metastases directs end-stage metastatic progression. They also suggest that some therapeutic interventions may target late-stage metastases specifically. mAb-based targeting of PECAM-1 represents a TME-targeted therapeutic approach that suppresses the end stages of metastatic progression, until now a refractory clinical entity.