Meeting report: molecular mechanisms of inflammation: how leukocytes come,see and seize

Inflammation has developed in the course of evolution as a process to defend the body against invading microbes and to respond to injuries. Several mechanisms of interaction between endothelial cells and leukocytes have evolved to render inflammation an effective, tightly controlled, and self-limited process. Imperfect executions of this "game plan" lead to pathological abnormalities resulting in diseases. The meeting on Molecular Mechanisms of Inflammation held at Schloss Elmau, Germany in October 2002 has featured activation of endothelial cells, adhesion and migration of leukocytes, as well as receptor pathways for activation and deactivation of leukocytes and, concomitantly, of the inflammatory response. Thus, a review on some of the presented data casts interesting spotlights on different steps of the inflammatory cascade.     

Isolation and culture of rat microvascular endothelial cells

The purpose of this study is to identify the separation techniques that result in pure cultures of rat microvascular endothelial cells (MECs). A multistep process is used to optimize the separation of the cells from rat epididymal fat pads, obtaining as pure a culture as possible within a relatively short processing time. The process initially employs the digestion, filtration, and density gradient separation steps. We further describe the use of an attachment phase that allows the differential adherence of contaminating cell types. Immunomagnetic purification is the final step in the process and is performed using anti-PECAM-1 (CD31) monoclonal antibody-labeled DynaBeads.     

The unfolding tale of PECAM-1

Platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) is a member of the immunoglobulin (Ig) superfamily that has distinctive features of an immunoreceptor based upon its genomic structure and the presence of intrinsic immunoreceptor tyrosine inhibitory motifs (ITIMs) in its ligand binding polypeptide. This has lead to its subclassification into the Ig-ITIM superfamily. Its amino-terminal Ig-like domain of PECAM-1 is necessary for its homophilic binding, which plays an important role in cell–cell interactions. Its intracellular ITIMs serve as scaffolds for recruitment of signalling molecules including protein-tyrosine phosphatases to mediate its inhibitory co-receptor activity. Increasing evidence has implicated PECAM-1 in a plethora of biological phenomena, including modulation of integrin-mediated cell adhesion, transendothelial migration, angiogenesis, apoptosis, cell migration, negative regulation of immune cell signalling, autoimmunity, macrophage phagocytosis, IgE-mediated anaphylaxis and thrombosis. In this review, we discuss some of the new developments attributed to this molecule and its unique roles in biology.     

体外流动剪切力作用下的白细胞-内皮细胞动态粘附

建立一个用于体外研究特定流动剪切力作用下白细胞和内皮细胞动态相互作用的方法。利用建立的平板流动小室系统可在体外产生特定的流动剪切力。将培养的人脐静脉内皮细胞装入平板流动小室后 ,以 0 .71dynes/cm2 的流动剪切力把含有吖啶橙染色的白细胞的灌流液导入流动小室 ,由此产生了白细胞和内皮细胞的动态粘附过程。整个粘附过程通过OlympusIX70倒置荧光显微系统观察 ,同时通过CCD摄象头录像。然后用图象采集卡将录像采集为数字图象并保存。利用针对实验设计的图象处理和分析方法 ,对采集的数字图象进行处理和测量 ,可以得到粘附白细胞的个数和滚动白细胞的速度。通过研究内毒素脂多糖 (LPS)对内皮细胞粘附功能的促进及地塞米松 (DXM )对该刺激的抑制作用来验证。对于用内毒素脂多糖 (LPS)处理的内皮细胞 ,固定粘附和慢速滚动的白细胞的个数比对照组分别显著增加了 2 3.7倍和 4 .1倍 ,同时白细胞在粘附作用过程中慢速滚动和快速滚动的速度比对照组明显降低了 2 5 .6 %和 2 6 .1%。而对于脂多糖和地塞米松 (DXM)处理过的内皮细胞 ,上述内毒素引起的影响被显著抑制了。该方法可以用于研究不同的化学和物理刺激对内皮细胞功能的影响机制 ,及用来评价各类抑制内皮细胞粘附功能的药物。     

Stimulation of endothelial cell migration in culture by ladsin,a laminin-5-like cell adhesion protein

Summary Ladsin is a laminin-like cell-adhesive scatter factor with potent cell motility-stimulating ability and was purified from serum-free conditioned medium of a malignant human gastric adenocarcinoma cell line STKM-1. To test its possible role in tumor angiogenesis, we investigated its effect on primary culture of endothelial cells (human umbilical vein endothelial cells) and endothelial cell line ECV304 in this study. Cell adhesion and motility effects of ladsin were observed in both types of endothelial cells. In cell-attachment assay, ladsin interacted with integrin α3β1 that was expressed on the endothelial cell surface. In Boyden chambers, ladsin stimulated both directed and random migration of ECV304 cells. Ladsin induced repair of artificial wounds generated in ECV304 cell monolayers by stimulating cell migration. Ladsin did not affect the growth rate of ECV304 cells at a low cell density but significantly increased the saturation cell density. These results suggest that ladsin may be involved in the adhesion and migration of endothelial cells under some physiological and pathological conditions.     

Junctional adhesion molecules are required for melanoma cell lines transendothelial migration in vitro

One of the main steps of metastasis is extravasation, a phenomenon well described in lymphocytes but remaining to be fully uncovered for melanoma. Junctional adhesion molecules (JAMs) control the transendothelial migration of leukocytes. To date, the role of the JAM proteins, notably JAM-A and JAM-C, has not been examined in melanoma. Here, we compared two melanoma tumor cell lines, A375 and SLM8 cells, the A375 cell line being four times more efficient than the SLM8 cells in the crossing of the endothelial monolayer. We show evidence of the differential expression of JAM-A and JAM-C in these cell lines with JAM-C mainly expressed in the A375 cell line, and JAM-A detected preferentially in the SLM8 cells. To further dissect the respective roles of these proteins, we used both siRNA and blocking antibodies to decrease JAM-A and JAM-C expression.     

长链非编码RNA GAS5抑制内皮细胞功能

最新研究表明,长链非编码RNA GAS5（lncRNA GAS5）可调节血管内皮细胞的凋亡,但对内皮细胞其他功能的调控并不明确。本研究旨在了解lncRNA GAS5对内皮细胞的增殖、成血管、NO分泌及内皮标志分子CD31和vWF表达的影响及可能机制。将LncRNA GAS5干扰慢病毒（LV-GAS5-RNAi）转染人脐静脉内皮细胞株（EA.hy926）后,采用CCK8及Matrigel胶分别检测EA.hy926的增殖和成血管能力;硝酸还原酶法检测NO的分泌情况;real-time RT-PCR检测CD31、vWF及miR-21的表达;Western印迹检测PTEN在蛋白质水平的表达。结果显示：与对照组比较,LV-GAS5-RNAi组EA.hy926增殖能力无明显变化(0.34±0.01 vs. 0.34±0.04,P>0.05),而其成血管能力升高(133.70±12.64 vs. 100.00±4.65,P<0.05),NO的分泌量亦增加(28.54±2.75 μmol/L vs.15.11±1.19 μmol/L,P<0.01);内皮标志分子CD31（是对照组的1.46倍）及vWF（是对照组的2.94倍)的基因表达量均显著升高。同时,miR-21表达亦明显升高(是对照组的1.42倍),而miR-21下游靶基因PTEN蛋白质的表达量则显著降低（0.13±0.05 vs. 0.38±0.03,P<0.01）。以上结果提示,LncRNA GAS5抑制了内皮细胞的功能,miR-21、PTEN信号分子可能参与其中的调节。     

Knockdown of CD146 reduces the migration and proliferation of human endothelial cells

Our previous study has demonstrated that CD 146 molecule is a biomarker on vascular endothelium,which is involvedin angiogenesis and tumor growth.However the mechanism behind is not clear.Here we have for the first time devel-oped a novel CD146 blockade system using CD146 siRNA to study its function on endothelial cells.Our data showedthat CD146 siRNA specifically blocked the expression of CD146 on both mRNA and protein levels,leading to thesignificant suppression of HUVEC proliferation,adhesion and migration.These results demonstrate that CD146 playsa key role in vascular endothelial cell activity and angiogenesis,and CD146 siRNA can be used as a new inhibitor foranti-angiogenesis therapy.     

Soluble aggregates of the amyloid-beta protein activate endothelial monolayers for adhesion and subsequent transmigration of monocyte cells

Increasing evidence suggests that the deposition of amyloid plaques, composed primarily of the amyloid-β protein (Aβ), within the cerebrovasculature is a frequent occurrence in Alzheimer's disease and may play a significant role in disease progression. Accordingly, the pathogenic mechanisms by which Aβ can alter vascular function may have therapeutic implications. Despite observations that Aβ elicits a number of physiological responses in endothelial cells, ranging from alteration of protein expression to cell death, the Aβ species accountable for these responses remains unexplored. In the current study, we show that isolated soluble Aβ aggregation intermediates activate human brain microvascular endothelial cells for both adhesion and subsequent transmigration of monocyte cells in the absence of endothelial cell death and monolayer disruption. In contrast, unaggregated Aβ monomer and mature Aβ fibril fail to induce any change in endothelial adhesion or transmigration. Correlations between average Aβ aggregate size and observed increases in adhesion illustrate that smaller soluble aggregates are more potent activators of endothelium. These results support previous studies demonstrating heightened neuronal activity of soluble Aβ aggregates, including Aβ-derived diffusible ligands, oligomers, and protofibrils, and further show that soluble aggregates also selectively exhibit activity in a vascular cell model.     

肿瘤细胞粘附、迁移与转移的相关性

肿瘤细胞的粘附、迁移能力与癌转移密切相关. 细胞粘附分子选择素、整合素、免疫球蛋白超家族及钙粘素介导同型或异型细胞间以及细胞与基质间的粘附,其在肿瘤细胞表面表达数量或分布方式的改变直接或间接影响着转移潜能,是肿瘤细胞从原发瘤脱落以及着床的关键性环节.肿瘤细胞的迁移能力被认为是癌转移的限速环节.一般情况下,肿瘤细胞在体内或体外的迁移能力与其转移潜能呈正相关性,肿瘤细胞通过对迁移刺激物的趋化性及趋触性应答而完成向远离器官的转移,其具体分子机制目前还不清楚.     

Cell growth in vitro directed by handmade patterns

Summary In this report, we show how the in vitro model of mechanically injured confluent monolayers of cultured mammalian cells, consisting in denudation by gentle scraping of areas in the monolayer, can be extended to obtain patterned cell cultures without using preadded attaching matrices. This work was done with a sinusoidal endothelial liver cell line. Patterns for cell growth were drawn in confluent monolayers by cell detaching with the aid of pipette tips followed by reincubation of the culture. In one or some d, acellular patterns were closed by cell migration and proliferation. For unveiling the pattern formed by migration and cell duplication, an enzymatic digestion with trypsin-collagenase solution was applied; after some min, only the migrating and younger cells filling the previous acellular pattern remained attached to the dish, and the now cellular pattern was clearly depicted. After stopping and recovering from the enzymatic treatment, the culture was ready for starting studies such as those related to migration, proliferation, cell-cell interactions. This method allows us to create simple and complex patterns, does not require preparation of the dishes with attaching matrices, and extracellular matrices in acellular areas are absent because of the enzymatic treatment, thus, potentially having many applications in cell culture techniques.     

The adhesion receptor CD-31 can be primed to rapidly adjust the neutrophil cytoskeleton

The adhesion receptor CD-31 is expressed on neutrophils and endothelial cells and participates in transendothelial migration of neutrophils. Although necessary, information on CD-31-induced signaling and its influence on the shape-forming actin network is scarce. Here, we found that antibody engagement of CD-31 on suspended neutrophils triggered a prompt intracellular Ca(2+) signal, providing the cells had been primed with a chemotactic factor. Inhibition of Src-tyrosine kinases blocked this Ca(2+) signal, but not a fMet-Leu-Phe-induced Ca(2+) signal. Despite the ability of fMet-Leu-Phe to activate Src-tyrosine kinases, it did not per se induce tyrosine phosphorylation of CD-31. However, fMet-Leu-Phe did enable such a phosphorylation following an antibody-induced engagement of CD-31. This clustering also triggered a Ca(2+)-dependent depolymerization of actin and, surprisingly enough, a simultaneous polymerization. The ability of CD-31 to signal dynamic alterations in the cytoskeleton, particularly the Ca(2+)-induced actin depolymerization, further explains how neutrophils can squeeze themselves out between adjacent endothelial cells.