益生菌对胆汁淤积性黄疸大鼠小肠上皮细胞紧密连接蛋白的影响

目的探讨双歧三联活菌(培菲康)对胆汁淤积性大鼠小肠上皮细胞紧密连接蛋白ZO-1(zonula oc-cludens-1)和Occludin表达的调控机制。方法雄性3周龄SD大鼠随机分为对照组、模型组和培菲康组,模型组和培菲康组均给予α-异硫氰酸萘酯(ANIT)50 mg/kg一次性灌胃,建立急性肝内胆汁淤积动物模型,培菲康组于造模前4 d开始给予培菲康4.2×107个活菌数/(kg.d)灌胃大鼠。分别于造模后24、48和72 h三个时间点处死大鼠,取末端回肠黏膜组织,采用免疫组化和Western blots免疫印迹法检测紧密连接蛋白ZO-1、闭锁蛋白(Occludin)的分布和表达,并利用图像分析系统对Western blots图像结果进行定量分析。结果ZO-1和Occludin蛋白主要沿大鼠小肠黏膜上皮细胞膜的顶端呈线状分布,模型组大鼠24 h时ZO-1和Occludin的阳性染色较对照组减少,48 h减少最为明显,72 h阳性染色有所恢复,而培菲康组大鼠各时间点ZO-1和Occludin的阳性染色和模型组相比均明显增多。Western blots结果与免疫组织化学结果相一致,模型组24 h已经开始下降(ZO-1 0.1294±0.0481)、(Oc-cludin 0.1950±0.0441),48 h达到最低(ZO-1 0.0395±0.0095)、(Occludin 0.0137±0.0092),72 h开始恢复(ZO-10.2024±0.0498)、(Occludin 0.1494±0.0355),各时间点与对照组(ZO-1 0.2887±0.0237)、(Occludin 0.4266±0.0670)相比差异有统计学意义(P0.01);而培菲康组各时间点蛋白表达分别为24 h(ZO-1 0.2110±0.0367)、(Occludin 0.3056±0.0572),48 h(ZO-1 0.1173±0.0423)、(Occludin 0.0521±0.0123),72 h(ZO-1 0.2601±0.0191)、(Occludin 0.2050±0.0721),与模型组相应时间点数据相比差异有统计学意义(P0.05)。结论双歧三联活菌能够影响胆汁淤积性大鼠小肠黏膜上皮紧密连接蛋白的分布和表达,可以恢复肠黏膜上皮屏障的完整性。     

骶神经电刺激对脊髓损伤大鼠肠黏膜机械屏障的保护作用

目的：观察骶神经电刺激对脊髓损伤大鼠肠黏膜机械屏障的保护作用。方法：56只Wistar大鼠分7组（n=8）：正常组、急性完全性脊髓损伤（SCI）组和骶神经电刺激组（按24、48、72h各8只）。进行内毒素测定;肠系膜淋巴结、肝脏、脾脏菌培养;肠道形态学观察;紧密连接蛋白zo-1的蛋白表达测定。结果：对照组肠黏膜不同程度损伤;肠道上皮细胞及细胞间连接破坏;内毒素血症和细菌移位明显。实验组肠黏膜得到改善,内毒素水平下降且细菌移位减少。ZO-1蛋白表达无统计学差异。对照组ZO-1的分布出现不同程度的散乱、排列不规则,实验组分布得到改善。结论：骶神经电刺激可促肠蠕动、排肠内容物、减少肠道菌群数量,保护肠黏膜上皮细胞及紧密连接的机械屏障,减少细菌移位和内毒素血症。     

非酒精性脂肪性肝病大鼠肠粘膜紧密连接蛋白ZO-1及肌球蛋白轻链激酶的变化

目的:研究不同阶段非酒精性脂肪性肝病(NAFLD)大鼠肠粘膜紧密连接蛋白ZO-1及肌球蛋白轻链激酶(MLCK)的变化。方法:将60只雄性清洁级SD大鼠随机分为两组:正常饮食组(NDG)和高脂饮食组(FDG)。于4周、8周、12周时观察各组大鼠肝脏病理学改变;应用ELISA方法测定各阶段大鼠血清谷丙转氨酶(ALT)、谷草转氨酶(AST)、甘油三酯(TG)、胆固醇(CHOL)的变化;应用鲎实验测定各阶段大鼠门静脉血中内毒素(ET)水平;应用免疫组化方法检测肠道粘膜肌球蛋白轻链激酶(MLCK)及紧密连接蛋白(ZO-1)的表达及分布情况。结果:随着高脂饮食时间增长,高脂饮食组大鼠肝脏脂肪变性程度逐渐加重;血清ALT、AST、TG、CHOL水平逐渐升高(4周时,P0.05,8周和12周时P0.05);大鼠血浆内毒素的水平逐渐上升(0.11±0.01比0.11±0.01,P0.05;0.36±0.01比0.11±0.01,P0.05;0.44±0.15比0.18±0.03,P0.05);高质饮食组较正常饮食组大鼠紧密连接蛋白ZO-1表达逐渐下降(3.6±0.7比3.9±0.32,P0.05;2.8±0.63比3.8±0.42,P0.05;1.8±0.79比3.7±0.48,P0.05),MLCK表达逐渐增多(0.5±0.53比0.3±0.48,P0.05;1.3±0.48比0.4±0.52,P0.05;1.9±0.74比0.5±0.53,P0.05)。结论:肠粘膜紧密连接蛋白ZO-1及MLCK可通过影响肠粘膜屏障功能,改变肠粘膜的通透性,促进非酒精性脂肪肝病发生发展。     

整肠生对溃疡性结肠炎 小鼠肠上皮屏障的保护作用

目的探讨整肠生对溃疡性结肠炎小鼠肠道紧密连接蛋白表达以及对氧化应激反应的影响。方法选用雄性8~10周龄C57BL/6小鼠40只,随机分为4组:对照组、模型组(3%DSS)、5-ASA组(3%DSS+5-ASA 200mg/kg灌胃)和整肠生组(3%DSS+联合整肠生及5-ASA灌胃),每组10只,造模7d。观察各组小鼠便血程度、组织学损伤情况,通过投射电镜观察各组肠道上皮间紧密连接改变情况,应用Western blot和RT-PCR的方法,检测小鼠结肠黏膜紧密连接蛋白Occludin、ZO-1、Claudin-2的表达情况。结果 (1)与模型组比较,5-ASA组和整肠生组小鼠便血程度明显减轻,DAI评分显著降低(P0.05)。整肠生组与5-ASA组比较,便血减轻,DAI评分降低(P0.05)。(2)电镜显示,对照组肠上皮间紧密连接呈一条致密条带,结构完整,见细胞桥粒,微绒毛光滑、排列整齐,细胞间隙狭窄;模型组肠上皮间紧密连接结构松散、模糊、密度降低,桥粒结构消失,微绒毛稀疏,短缩且长短不一,细胞间隙增宽;各治疗组的紧密连接的破坏情况较模型组有不同程度的改善,整肠生组紧密连接清晰,细胞间隙缩窄,微绒毛排列整齐,出现细胞桥粒。(3)应用Western blot和Real time-PCR法检测,与正常组相比,模型组Occludin、ZO-1蛋白和mRNA表达显著下降,Claudin-2表达显著上调(P0.05);各治疗组较模型组Occludin、ZO-1蛋白表达上调,Claudin-2蛋白表达下调(P0.05),整肠生组较单用5-ASA组更明显提高Occludin、ZO-1蛋白和mRNA表达。(4)与正常组相比,模型组MDA含量增高,SOD活性降低,与5-ASA组相比,整肠生组能更显著地降低MDA含量,提高SOD活性(P0.05)。结论联合应用整肠生通过调节紧密连接蛋白Occludin、ZO-1的表达和降低氧化应激反应,来改善溃疡性结肠炎小鼠肠上皮屏障功能。     

添加益生元对急进高原大鼠肠黏膜屏障紧密连接蛋白Occludin的作用研究

目的探讨通过灌胃的方式给予益生元(低聚半乳糖)对急进高原大鼠肠黏膜屏障紧密连接Occludin蛋白的表达及作用。方法在3848米建立高原缺氧模型大鼠共48只,随机选24只为高原缺氧对照组,另24只为添加益生元组,再按2 d、4 d和6 d时间点,分为6组,每组8只。采用免疫组织化学法检测Occludin蛋白表达,用ELISA法测定回肠组织肿瘤坏死因子-α(TNF-α)、白介素-10(IL-10)。结果和高原缺氧组各时间点比较,添加益生元组Occludin蛋白表达显著升高(P<0.01),TNF-α水平降低、IL-10水平升高(P<0.05)。结论益生元可以增加急进高原缺氧大鼠肠黏膜紧密连接蛋白Occludin的表达,改善高原缺氧对大鼠肠黏膜屏障的破坏。     

不同途径下MIMP对 炎症性肠病小鼠肠道菌群结构的影响

目的通过葡聚糖硫酸钠诱导小鼠炎症性肠病(IBD)模型并观察不同途经下乳杆菌微小膜蛋白(MIMP)对炎症性肠病小鼠的紧密连接蛋白及菌群结构的影响。方法 C57BL/6小鼠24只根据DSS和MIMP不同干预组合将其分为4组:MIMP腹腔注射组(n=6)、MIMP灌胃组(n=6)、诱导肠炎组(n=6)和健康对照组(n=6),利用Western blot对各组小鼠肠道中紧密连接蛋白(Occludin、JAM-1和ZO-1)的表达进行检测,采用16SrRNA测序技术检测V4区鉴定细菌,并进行菌群差异分析。结果 MIMP腹腔注射及灌胃均可显著提高IBD小鼠肠道中紧密连接蛋白的表达水平,灌胃组效果更为显著;MIMP干预后小鼠肠道中拟杆菌门(Bacteroidetes)丰度增高、厚壁菌门(Firmicutes)及变形菌门(Proteobacteria)丰度降低,LEfSe分析、PCoA分析和PCA分析提示4组小鼠肠道菌群结构差异显著。结论不同途径下MIMP均可显著提高IBD小鼠肠道中紧密连接蛋白的表达水平,改善肠黏膜屏障功能,纠正小鼠肠道菌群结构紊乱。     

不同剂量乌司他汀对急性重症胆管炎大鼠肝屏障的保护作用

目的:探讨不同剂量乌司他汀对急性重症胆管炎(ACST)大鼠肝屏障的保护作用。方法:60只雄性SD大鼠通过手术造成胆总管梗阻并注射细菌内毒素造成ACST模型,造模48 h后处死,随机分成5组,每组12只,分别进行假手术(SN组)、ACST造模手术(ACST组)、ACST造模手术+乌司他汀治疗,依据乌司他汀浓度分为低(20000 U/kg·d)(ASCT-L组)、中(40000 U/kg·d)(ASCT-M组)、高(80000 U/kg·d)(ASCT-H组)三组,采集血液进行总胆红素(TB)、谷丙转氨酶(ALT)、白细胞介素-6(IL-6)、白细胞介素-10(IL-10)和肿瘤坏死因子-α(TNF-α)的检测,采集部分肝组织进行组织染色,检测肝细胞凋亡率并分析紧密连接蛋白Occludin和ZO-1基因表达水平。结果:与SN组比较,造模后各组大鼠TB和ALT水平均显著升高(均P0.05),乌司他汀治疗后各组大鼠TB和ALT水平随剂量增加而明显降低,各组间差异均有统计学意义(均P0.05);造模后大鼠IL-6、IL-10和TNF-α水平均显著升高,乌司他汀治疗后各组大鼠IL-6和TNF-α水平随剂量增加而降低,IL-10水平随剂量增加而升高,不同剂量间差异有统计学意义(均P0.05);ACST组肝细胞凋亡率显著高于SN组,Occludin和ZO-1基因表达水平显著降低(P0.05);乌司他汀治疗后各组大鼠肝细胞凋亡率有不同程度的降低,Occludin和ZO-1基因表达水平有不同程度的升高(P0.05)。结论:乌司他汀治疗ACST大鼠疗效显著,对肝屏障功能有良好的保护作用,其治疗效果与剂量呈现明显的相关性,其机制及合适的给药剂量值得进一步研究。     

闭锁小带蛋白1研究进展

闭锁小带蛋白1（ZO-1）属于膜结合鸟苷酸激酶（MAGUK）家族,存在于所有脊椎动物的紧密连接中,起中介作用。它把闭锁蛋白和细胞内骨架系统连接在一起,构成稳定的连接系统。ZO-1在维持正常胞旁屏障通透性、细胞信号转导、基因转录及调节细胞增殖分化和周期中发挥着非常巨大的作用。ZO-1基因表达沉默和蛋白缺失与肿瘤及非肿瘤疾病的发生发展密切相关。     

重症急性胰腺炎患者血清IL-6水平与内毒素移位及肠黏膜紧密连接蛋白表达关系的研究

目的：大量研究表明重症急性胰腺炎（SAP）患者血清中高浓度IL-6 和肠黏膜低表达的紧密连接蛋白可促进内毒素移位的发生。本文主要研究重症胰腺炎患者血清IL-6 水平对内毒素移位和肠黏膜紧密连接蛋白表达的影响。方法：50 例重症胰腺炎患者,其中12 例在患病早期因结肠受累合并腹胀,对12 例结肠受累患者应用结肠镜行结肠灌洗进行腹腔减压,同时取结肠黏膜进行活组织检查。所有病人在治疗的第3 天,第7天,第10 天,第14 天抽取外周静脉血。40 例健康志愿者作为对照组。应用ELISA方法检测血清IL-6 水平,鲎试验（LAL）方法检测血清内毒素含量,应用免疫荧光和Western blotting 方法检测肠黏膜紧密连接蛋白表达水平。结果：SAP 患者血清IL-6 和内毒素含量明显高于健康对照组,而结肠黏膜紧密连接蛋白表达低于对照组;在临床治疗过程中,早期SAP 患者血清IL-6 和内毒素水平高于晚期（P 值均＜0.05）。SAP 早期血清高浓度的IL-6 与结肠黏膜紧密连接蛋白的低表达具有相关性,差异有统计学意义（r=0.735,P＜0.05）。结论：血清IL-6 水平可作为早期评价重症急性胰腺炎严重程度的一项指标,IL-6 水平与重症急性胰腺炎临床病程有相关性,可能导致肠道内毒素移位。     

重症急性胰腺炎患者血清IL-6水平与内毒素移位及肠黏膜紧密连接蛋白表达关系的研究(英文)

目的:大量研究表明重症急性胰腺炎(SAP)患者血清中高浓度IL-6和肠黏膜低表达的紧密连接蛋白可促进内毒素移位的发生。本文主要研究重症胰腺炎患者血清IL-6水平对内毒素移位和肠黏膜紧密连接蛋白表达的影响。方法:50例重症胰腺炎患者,其中12例在患病早期因结肠受累合并腹胀,对12例结肠受累患者应用结肠镜行结肠灌洗进行腹腔减压,同时取结肠黏膜进行活组织检查。所有病人在治疗的第3天,第7天,第10天,第14天抽取外周静脉血。40例健康志愿者作为对照组。应用ELISA方法检测血清IL-6水平,鲎试验(LAL)方法检测血清内毒素含量,应用免疫荧光和Western blotting方法检测肠黏膜紧密连接蛋白表达水平。结果:SAP患者血清IL-6和内毒素含量明显高于健康对照组,而结肠黏膜紧密连接蛋白表达低于对照组;在临床治疗过程中,早期SAP患者血清IL-6和内毒素水平高于晚期(P值均0.05)。SAP早期血清高浓度的IL-6与结肠黏膜紧密连接蛋白的低表达具有相关性,差异有统计学意义(r=0.735,P0.05)。结论:血清IL-6水平可作为早期评价重症急性胰腺炎严重程度的一项指标,IL-6水平与重症急性胰腺炎临床病程有相关性,可能导致肠道内毒素移位。     

Keeping it tight: The relationship between bacterial dysbiosis,septate junctions,and the intestinal barrier in Drosophila

Maladaptive changes in the intestinal flora, typically referred to as bacterial dysbiosis, have been linked to intestinal aging phenotypes, including an increase in intestinal stem cell (ISC) proliferation, activation of inflammatory pathways, and increased intestinal permeability^1,2. However, the causal relationships between these phenotypes are only beginning to be unravelled. We recently characterized the age-related changes that occur to septate junctions (SJ) between adjacent, absorptive enterocytes (EC) in the fly intestine. Changes could be observed in the overall level of SJ proteins, as well as the localization of a subset of SJ proteins. Such age-related changes were particularly noticeable at tricellular junctions (TCJ)³. Acute loss of the Drosophila TCJ protein Gliotactin (Gli) in ECs led to rapid activation of stress signalling in stem cells and an increase in ISC proliferation, even under axenic conditions; a gradual disruption of the intestinal barrier was also observed. The uncoupling of changes in bacteria from alterations in ISC behaviour and loss of barrier integrity has allowed us to begin to explore the interrelationship of these intestinal aging phenotypes in more detail and has shed light on the importance of the proteins that contribute to maintenance of the intestinal barrier.     

Enterocytic differentiation is modulated by lipid rafts-dependent assembly of adherens junctions

Integrity of the epithelial barrier is determined by apical junctional complexes which also participate in the signalling pathways inducing intestinal cell differentiation. Lipid rafts (LR) have been proposed to play a role in the organization and the function of these intercellular complexes. This study investigated potential mechanisms by which LR could participate in the establishment of adherens junctions (AJ) and the initiation of enterocytic differentiation.We showed that the differentiation of epithelial cells in rat colons correlates with the emergence of LR. Using HT-29 cells we demonstrated that during the differentiation process, LR are required for the recruitment and the association of p120ctn to E-cadherin. Silencing of flotillin-1, a LR component, alters the recruitment of AJ proteins in LR and delays the expression of differentiation markers. Furthermore, the ability of p120ctn/E-cadherin complexes to support cell differentiation is altered in HT-29 Rac1N17 cells. These results show a contributory role of LR in the enterocytic differentiation process, which serve as signalling platforms for Rac1-mediated organization of AJ. A better understanding of the mechanism involved in the establishment of junctional complex and their role in enterocytic differentiation provides new insights into the regulation of intestinal homeostasis.     

Organization and signaling of endothelial cell-to-cell junctions in various regions of the blood and lymphatic vascular trees

Adhesive intercellular junctions between endothelial cells are formed by tight junctions and adherens junctions. In addition to promoting cell-to-cell adhesion, these structures regulate paracellular permeability, contact inhibition of endothelial cell growth, cell survival, and maintenance of cell polarity. Furthermore, adherens junctions are required for the correct organization of new vessels during embryo development or during tissue proliferation in the adult. Extensive research on cultured epithelial and endothelial cells has resulted in the identification of many molecular components of tight junctions and adherens junctions. Such studies have revealed the complexity of these structures, which are formed by membrane-associated adhesion proteins and a network of several intracellular signaling partners. This review focuses on the structural organization of junctional structures and their functional interactions in the endothelium of blood vessels and lymphatics. We emphasize the way that these structures regulate endothelial cell homeostasis by transferring specific intracellular signals and by modulating activation and signaling of growth factor receptors. This work was supported by the Associazione Italiana per la Ricerca sul Cancro, Association for International Cancer Research, European Community (Integrated Project Contract no. LSHG-CT-2004–503573; NoE MAIN 502935; NoE EVGN 503254; EUSTROKE consortium; Angioscaff consortium; Optistem consortium), Istituto Superiore di Sanità, Italian Ministry of Health, MIUR (COFIN prot: 2006058482_002), and Fondation Leducq Transatlantic Network of Excellence (E.D.). Additional support came from US National Institutes of Health grants HL24136 and HL59157 from the National Heart, Lung, and Blood Institute and CA82923 from the National Cancer Institute and AngelWorks Foundation (D.McD.).     

Interplay between Anakonda,Gliotactin, and M6 for Tricellular Junction Assembly and Anchoring of Septate Junctions in Drosophila Epithelium

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Intermitochondrial junctions in the extraocular muscle of the rat

Summary Intermitochondrial junctions with a spacing of 17–21 nm were observed in the superior rectus muscle of a rat. Periodic rounded densities are aligned midway between the apposed outer mitochondrial membranes at some of these junctions. Such densities have a diameter of about 8–10 nm and a center-to-center spacing of about 26–30 nm. These junctions occur in cases where one mitochondrial profile is enclosed within another or where two profiles are interlocked so that their combined overall form has a smoothly contoured profile. Intermitochondrial junctions seem not to have been previously described in muscle, but have been reported in other kinds of tissues. In agreement with those previous reports, the presently observed intermitochondrial junctions usually involve mitochondria that display atypical features indicative of tissue abnormality or stress. Such junctions were never observed in normal extraocular muscle.This study was supported by Grants EY-00309, EY-01297 and EY-01842 from the National Eye Institute (USPHS) and in part by a grant from the Eye Surgery Fund, Inc. and an unrestricted grant to the Department of Ophthalmology from Research to Prevent Blindness, Inc.     

Cell Adhesion Structures in Epithelial Cells Are Formed in Dynamic and Cooperative Ways

There are many morphologically distinct membrane structures with different functions at the surface of epithelial cells. Among these, adherens junctions (AJ) and tight junctions (TJ) are responsible for the mechanical linkage of epithelial cells and epithelial barrier function, respectively. In the process of new cell–cell adhesion formation between two epithelial cells, such as after wounding, AJ form first and then TJ form on the apical side of AJ. This process is very complicated because AJ formation triggers drastic changes in the organization of actin cytoskeleton, the activity of Rho family of small GTPases, and the lipid composition of the plasma membrane, all of which are required for subsequent TJ formation. In this review, the authors focus on the relationship between AJ and TJ as a representative example of specialization of plasma membrane regions and introduce recent findings on how AJ formation promotes the subsequent formation of TJ.     

Sealing junctions in a number of arachnid tissues

The junctions present in the central nervous system (CNS), midgut, silk gland and venom gland of arachnids have been investigated. Special care was taken to try to locate tight junctions in tissue other than CNS but they were not found in any of the other tissues. The detailed structure of the junctions present are discussed. The tight junctions present in CNS are somewhat different in appearance and fracturing behaviour to most vertebrate tight junctions and closely resemble only those found in Urochordates (a non-vertebrate chordate). The two types of septate junctions found in the other tissues belong to the pleated septate and smooth septate classes but show some interesting differences. It appears probable that the septate junctions in Arachnida, Merostomata and Myriopoda have different fracturing properties from those found in other arthropods. The finding that only septate junctions are present in most arachnid tissues, although tight junctions are present in CNS, is discussed in the context of the sealing function of septate junctions in invertebrate tissues.     

Regulation by nectin of the velocity of the formation of adherens junctions and tight junctions

Cadherins are key Ca(2+)-dependent cell-cell adhesion molecules at adherens junctions (AJs) in fibroblasts and epithelial cells, whereas claudins are key Ca(2+)-independent cell-cell adhesion molecules at tight junctions (TJs) in epithelial cells. The formation and maintenance of TJs are dependent on the formation and maintenance of AJs. Nectins are Ca(2+)-independent immunoglobulin-like cell-cell adhesion molecules which comprise a family of four members, nectin-1, -2, -3, and -4, and are involved in the formation of AJs in cooperation with cadherins, and the subsequent formation of TJs. We show here that the velocity of the formation of the E-cadherin-based AJs is increased by overexpression of nectin-1 and is reduced by addition of the nectin-1 inhibitors to the medium in L cells stably expressing E-cadherin and Madin-Darby canine kidney cells. Moreover, the velocity of the formation of the claudin-based TJs is increased by overexpression of nectin-1 and is reduced by addition of the nectin-1 inhibitors to the medium in Madin-Darby canine kidney cells. These results indicate that nectins regulate the velocity of the formation of the E-cadherin-based AJs and the subsequent formation of the claudin-based TJs.     

Poly(ADP-ribose) polymerase cleavage during apoptosis: when and where?

On freeze-fracture replicas, gap junctions are frequently colocalized with tight junctions. In this study, to elucidate the relationship between gap- and tight-junction proteins, we investigated the localization of gap-junction proteins Cx32 and Cx26 and tight-junction proteins occludin, claudin-1, ZO-1, and ZO-2 in primary cultured rat hepatocytes, using confocal laser microscopy. In hepatocytes cultured in 2% DMSO and 10(-7) M glucagon medium, Cx32- but not Cx26-immunoreactive lines were observed on the most subapical plasma membrane at cell borders, while on the basolateral membrane both Cx32- and Cx26-positive spots were colocalized. Occludin-, claudin-1-, ZO-1-, and ZO-2-immunoreactive lines were also linearly observed on the most subapical plasma membrane and were colocalized with only Cx32-immunoreactive lines. In freeze-fracture analysis, many small gap-junction plaques were observed within a well-developed tight-junction strand network. The fence function of tight junctions in the cells, as examined by diffusion of labeled sphingomyelin, was well maintained. We also carried out Western blotting for Cx32 following immunoprecipitation with anti-occludin, anti-claudin-1, or anti-ZO-1 antibodies. Cx32 was detectable in all immunoprecipitates. These results suggest that Cx32 gap junctions, but not those with Cx26, are closely coordinated with the expression and function of tight junctions in hepatocytes and that Cx32 gap-junction formation may affect cell polarity through modification of tight-junction expression.     

Deciphering the functional role of endothelial junctions by using in vivo models

Endothelial cell-to-cell junctions are vital for the formation and integrity of blood vessels. The main adhesive junctional complexes in endothelial cells, adherens junctions and tight junctions, are formed by transmembrane adhesive proteins that are linked to intracellular signalling partners and cytoskeletal-binding proteins. Gene inactivation and blocking antibodies in mouse models have revealed some of the functions of the individual junctional components in vivo, and are increasing our understanding of the functional role of endothelial cell junctions in angiogenesis and vascular homeostasis. Adherens-junction organization is required for correct vascular morphogenesis during embryo development. By contrast, the data available suggest that tight-junction proteins are not essential for vascular development but are necessary for endothelial barrier function.