大鼠脑缺血时紧密连接相关蛋白occludin和claudin-5表达的变化

目的研究脑缺血后血脑屏障通透性和紧密连接相关蛋白occludin和claudin-5的变化。方法线栓法制备大鼠大脑中动脉缺血模型,采用伊文氏兰(EB)法检测缺血后血脑屏障通透性的变化。应用免疫组织化学的方法观察occludin和claudin-5在缺血脑组织中的分布,采用RT-PCR、Wesrern blot法检测大鼠缺血脑组织occludin和claudin-5的mRNA和蛋白的表达变化。结果脑缺血2h后血脑屏障通透性显著增加(P0.01),紧密连接相关蛋白occludin和claudin-5在脑微血管内皮细胞上呈阳性表达,occludin和claudin-5的mRNA和蛋白均比正常对照组显著降低(P0.01)。结论脑缺血时血脑屏障通透性的增加可能与紧密连接相关蛋白occludin和claudin-5的降低相关。     

绿茶多酚对脑缺血大鼠血脑屏障通透性的影响

目的探讨绿茶多酚对局灶性脑缺血大鼠血脑屏障的通透性及紧密连接蛋白occludin、claudin-5和蛋白激酶PKCα表达的影响。方法采用线栓法制作大鼠局灶性脑缺血模型,伊文思蓝法检测血脑屏障通透性的变化,免疫组化方法检测缺血脑组织occludin、claudin-5的表达,western blot方法检测脑缺血组织PKCα蛋白的表达。结果大鼠局灶性脑缺血60min、120min的脑组织血脑屏障通透性显著增加,同时点的脑组织BBB紧密连接开放;而绿茶多酚显著降低血脑屏障的通透性(P0.01),使BBB紧密连接处于关闭状态。大鼠局灶性脑缺血60min及120min脑组织紧密连接相关蛋白occludin、claudin-5的蛋白表达水平显著降低,绿茶多酚显著上调这些蛋白表达水平(P0.01)。大鼠局灶性脑缺血30min至120min脑组织中PKCα的蛋白表达水平显著升高,绿茶多酚显著降低PKCα蛋白的表达水平(P0.01)。结论绿茶多酚降低缺血大鼠脑组织血脑屏障通透性可能与上调紧密连接蛋白occludin、claudin-5的表达及下调蛋白激酶PKCα的表达有关。     

柚皮素通过miR-22抑制NLRP3炎症小体并减轻溃疡性结肠炎大鼠模型肠屏障损伤

目的:探究柚皮素通过调控微小RNA-22(miR-22)的表达,对溃疡性结肠炎(UC)大鼠NLRP3炎症小体的影响以及对肠屏障的保护作用。方法:将SD雄性大鼠随机分成对照组、模型组、低剂量柚皮素组、高剂量柚皮素组和柚皮素+miR-22 antagomiR组,每组10只。除对照组外,其余各组大鼠使用葡聚糖硫酸钠(DSS)诱导UC大鼠模型,并给予药物处理。观察大鼠体重变化和粪便稠度等情况,评估疾病活动性指数(DAI);检测血清中促炎因子白细胞介素1β(IL-1β)水平;HE染色观察肠组织病理学变化;透射电子显微镜观察肠上皮细胞;RT-qPCR技术检测肠组织中miR-22水平;Western blot法检测肠组织中紧密连接相关蛋白ZO-1、occludin和claudin-1表达水平;双萤光素酶报告基因实验检测miR-22与NLRP3靶向关系。结果:对照组大鼠肠组织结构正常;模型组大鼠肠组织黏膜结构破坏严重,有大量炎症细胞浸润,屏障受损,细胞间隙增宽;低、高剂量柚皮素组大鼠肠组织损伤减轻;柚皮素+miR-22 antagomiR组大鼠肠组织损伤较高剂量柚皮素组明显加重,炎症细胞浸润增加。与对照组相比,模型组大鼠DAI、肠黏膜损伤肉眼评分、IL-1β水平及NLRP3蛋白表达水平显著升高(P0.05),miR-22水平及ZO-1、occludin和claudin-1蛋白表达水平显著降低(P0.05);与模型组相比,低、高剂量柚皮素组大鼠DAI、肠黏膜损伤肉眼评分、IL-1β水平及NLRP3蛋白表达水平显著降低(P0.05),miR-22水平及ZO-1、occludin和claudin-1蛋白表达水平显著升高(P0.05);与高剂量柚皮素组相比,柚皮素+miR-22 antagomiR组大鼠DAI、肠黏膜损伤肉眼评分、IL-1β水平及NLRP3蛋白表达水平显著升高(P0.05),miR-22水平及ZO-1、occludin和claudin-1蛋白表达水平显著降低(P0.05)。结论:柚皮素通过上调miR-22水平,抑制NLRP3炎症小体活化,发挥对UC大鼠肠屏障的保护作用。     

STAT3通路参与白细胞介素-22促进人结肠癌细胞系HT29紧密连接蛋白的表达

目的探讨白细胞介素-22(IL-22)对肠上皮屏障紧密连接的影响及机制。方法将人结肠癌细胞系HT29分为对照组、IL-22组(100 ng/mL)、FLLL32组(IL-22干预前使用FLLL32预处理)、colivelin组(IL-22干预前使用colivelin预处理)。转染处理组:shNC组、shNC+IL-22组(IL-22干预前转染阴性对照)、shSTAT3组(转染LV-STAT3-RNAi)、shSTAT3+IL-22组(IL-22干预前转染LV-STAT3-RNAi)。用Western blot、real-time PCR检测HT29细胞STAT3、p-STAT3和紧密连接蛋白ZO-1、occludin、claudin-1和claudin-2及其mRNA的表达;用透射电镜观察HT29细胞紧密连接结构。结果相比于对照组,IL-22组的STAT3、p-STAT3、 ZO-1、occludin、claudin-1和claudin-2蛋白及mRNA表达水平明显升高(P0.05),且紧密连接更致密。相比于IL-22组,FLLL32组中上述指标的蛋白及mRNA表达量明显下调(P0.05),紧密连接较差,colivelin组则表达上调(P0.05),紧密连接完好。相比于shNC组,shNC+IL-22组的所有紧密连接的蛋白及mRNA表达量明显增加(P0.05),紧密连接结构更致密;而相比于shSTAT3组,shSTAT3+IL-22组的所有紧密连接的蛋白及mRNA表达量的差异无统计学意义。结论 STAT3通路参与IL-22促进HT29细胞紧密连接蛋白ZO-1、occludin、claudin-1和claudin-2的表达。     

褪黑素通过上调紧密连接蛋白减轻蛛网膜下腔出血大鼠脑水肿

目的:研究褪黑素对蛛网膜下腔出血(SAH)大鼠脑水肿的影响及分子机制。方法:雄性SD大鼠分为假手术组(sham)、SAH组(SAH)和褪黑素预处理组(SAH+Mel)。利用注射自体血液的方法制备SAH大鼠模型,SAH+Mel组大鼠在模型制备前1周通过皮下注射给予褪黑素预处理。利用湿干比方法检测大鼠脑含水量,利用伊文思蓝渗透实验检测血脑屏障的完整性,利用Western Blot检测大鼠皮层中闭合小环蛋白-1(ZO-1)、咬合蛋白(occludin)和闭合蛋白-5(claudin-5)的表达。结果:和假手术组大鼠相比,SAH术后48 h大鼠脑含水量增加明显(P<0.05),脑组织中伊文思蓝含量增加(P<0.05),皮层中ZO-1、occludin和claudin-5的表达下降。然而,经褪黑素预处理后,SAH大鼠脑含水量下降(P<0.05),脑组织中伊文思蓝含量减少(P<0.05),ZO-1、occludin和claudin-5的表达上调,(P<0.05)。结论:褪黑素通过上调紧密连接蛋白表达减轻SAH大鼠脑水肿。     

青蒿素减轻LPS诱导的肠上皮细胞屏障功能损伤的实验研究

目的:探究青蒿素对脂多糖(lipopolysaccharide,LPS)诱导的大鼠肠上皮IEC-6细胞屏障功能损伤的影响。方法:体外培养IEC-6细胞,随机分为5组:对照组、LPS(100 mg/L)组和LPS+青蒿素(30、50和100μmol/L)组,MTT法检测各组细胞毒性变化,ELISA检测各组细胞分泌炎性因子TNF-α、IL-1β和IL-6水平的变化,电阻仪检测肠上皮细胞跨上皮电阻(TER),酶标仪检测单层细胞对辣根过氧化物酶(HRP)的通透性,RT-qPCR和Western blot检测各组细胞紧密连接蛋白(ZO-1、claudin-1和occludin)以及TLR4/My D88/NF-κB mRNA和蛋白表达的变化。结果:LPS与青蒿素在本实验浓度范围对IEC-6细胞均无毒性。与对照组相比,LPS处理下,细胞分泌TNF-α、IL-1β和IL-6水平以及TLR4/My D88/NF-κB的mRNA和蛋白表达明显增加,ZO-1、claudin-1和occludin的mRNA和蛋白表达降低。而青蒿素干预下,细胞分泌TNF-α、IL-1β和IL-6水平以及TLR4/My D88/NF-κB mRNA和蛋白表达明显降低,ZO-1、claudin-1和occludin的mRNA和蛋白表达升高(P0.05),均呈现浓度依赖性。结论:青蒿素可能通过抑制TLR4/My D88/NF-κB通路减轻LPS诱导的肠上皮细胞屏障功能损伤。     

RNA干扰沉默神经轴突导向因子受体4基因增加血肿瘤屏障通透性

目的研究神经轴突导向因子受体(Robo4)对血肿瘤屏障(BTB)通透性的影响。方法建立了体外BTB模型,应用Real-time PCR和Western blot检测Robo4在正常人脑微血管内皮细胞和胶质瘤微血管内皮细胞中的表达变化。设计合成针对Robo4基因的小干扰RNA,转染至人脑微血管内皮h CMEC/D3细胞,下调体外血肿瘤屏障模型内皮细胞中Robo4的表达,跨内皮电阻测量系统和辣根过氧化物酶渗透试验分析血肿瘤屏障通透性变化;Western blot和免疫荧光法检测h CMEC/D3细胞中紧密连接相关蛋白occludin和ZO-1的表达和分布变化。结果和正常人脑微血管内皮细胞相比,Robo4在胶质瘤微血管内皮细胞中的表达显著上调。下调体外血肿瘤屏障模型内皮细胞Robo4的表达后,TEER值显著降低,辣根过氧化物酶透过率显著增高;同时胶质瘤微血管内皮细胞中紧密连接相关蛋白occludin和ZO-1的表达显著降低,在细胞膜上呈不连续分布。结论 RNA干扰沉默Robo4表达能够显著降低紧密连接相关蛋白occludin和ZO-1的表达,增加BTB通透性。     

真人养脏汤对溃疡性结肠炎大鼠肠道黏膜屏障功能的保护作用

目的:观察真人养脏汤(ZRYZ)对三硝基苯磺酸(TNBS)诱导的溃疡性结肠炎(UC)大鼠肠道黏膜屏障功能的保护作用以及紧密连接相关蛋白闭锁小带蛋白1(zonula occludens-1,ZO-1)和闭锁蛋白(occludin)的表达变化,探讨其可能作用机制。方法:将Wistar雄性大鼠随机分为正常组、模型组、柳氮磺吡啶(SASP)阳性对照组、ZRYZ高剂量组和ZRYZ低剂量组。除正常组外,其它各组用TNBS/50%乙醇混合溶液局部灌肠法复制溃疡性结肠炎大鼠模型。造模成功后阳性对照组给予SASP混悬液灌胃;ZRYZ高剂量组和ZRYZ低剂量组分别按生药30.4 g/kg和15.2 g/kg剂量灌胃;正常组与模型组等量生理盐水灌胃,共21 d。给药结束后,考察大鼠疾病活动指数(DAI)变化,进行大体损伤评分,测定肠道黏膜通透性(以尿中乳果糖/甘露醇的比值表示,即L/M值),测定结肠组织髓过氧化物酶(MPO)活性,计数结肠组织杯状细胞数量,测定血清二胺氧化酶(DAO)及D-乳酸(D-LA)水平,检测ZO-1和occludin的表达。结果:与正常组相比,模型组DAI、大体损伤评分、L/M值、结肠组织MPO活性以及血清D-LA和DAO水平明显升高(P0.05),结肠组织杯状细胞数量以及ZO-1和occludin表达明显降低(P0.05);与模型组相比,ZRYZ高剂量组和ZRYZ低剂量组DAI、大体损伤评分、L/M值、结肠组织MPO活性以及血清DAO和D-LA水平明显降低(P0.05),结肠组织杯状细胞数量以及ZO-1和occludin表达明显升高(P0.05)。结论:真人养脏汤可通过降低肠道黏膜通透性,保护溃疡性结肠炎大鼠肠道上皮细胞黏膜屏障功能,其机制可能与升高ZO-1和occludin表达有关。     

siRNA-Tie1下调紧密连接相关蛋白claudin-5、occludin和ZO-1增加血肿瘤屏障通透性

目的研究Tie1 AS和Tie1表达变化对血肿瘤屏障通透性的影响和相关机制。方法建立体外血脑屏障和血肿瘤屏障模型,Real-time PCR检测h CMEC/D3细胞中Tie1 AS和Tie1的表达水平。转染p IRES2-EGFPTie1 AS表达载体上调体外血肿瘤屏障模型h CMEC/D3细胞中Tie1 AS的表达,Western blot检测Tie1的表达变化。将si RNA-Tie1转染人h CMEC/D3细胞并建立体外血肿瘤屏障模型,跨内皮电阻测量系统分析血肿瘤屏障通透性变化;Western blot和免疫荧光法检测h CMEC/D3细胞中紧密连接相关蛋白claudin-5、occludin和ZO-1的表达和分布变化。结果和正常脑微血管内皮细胞相比,体外血肿瘤屏障模型h CMEC/D3细胞中Tie1的表达显著增加,而Tie1 AS的表达显著降低。上调体外血肿瘤屏障模型内皮细胞中Tie1 AS的表达水平,能够显著降低Tie1的表达。下调体外血肿瘤屏障模型内皮细胞中Tie1的表达后屏障通透性显著下降,伴有claudin-5、occludin和ZO-1的表达下调以及在细胞膜上呈不连续分布。结论体外血肿瘤屏障模型内皮细胞中低表达的Tie1 AS能够负性调控Tie1的表达,进而通过调节紧密连接相关蛋白的表达和分布影响屏障的通透性。     

袖状胃切除术对高脂饮食诱导肥胖大鼠肠道屏障的影响

目的研究袖状胃切除术对高脂饮食诱导肥胖大鼠肠道屏障的影响。方法建立高脂饮食诱导肥胖大鼠模型共30只,随机分为普通饮食组(CD,n=10)、假手术组(SO,n=10)和袖状胃切除组(SG,n=10),术后4周时分别检测24 h尿乳果糖/甘露醇比值(L/M)、门静脉血清内毒素水平和小肠黏膜紧密连接蛋白claudin-1和occludin表达水平。结果术后4周时,SG组大鼠体质量明显低于CD组(P0.001)和SO组(P0.001)。SG组大鼠24 h尿L/M值明显低于CD组(P0.001)和SO组(P0.01)。SG组门静脉血清内毒素水平明显低于CD组(P0.01)和SO组(P0.05)。术后4周时,SG组大鼠小肠黏膜中claudin-1表达水平明显高于CD组(P0.001)和SO组(P0.01),occludin表达水平明显高于CD组(P0.001)和SO组(P0.001)。结论袖状胃切除术可使高脂饮食诱导的肥胖大鼠体质量下降,降低24 h尿L/M值和门静脉血清内毒素水平,提高小肠黏膜中claudin-1和occludin蛋白的表达水平。     

Aberrant expression of tight junction-related proteins ZO-1, claudin-1 and occludin in synovial sarcoma: an immunohistochemical study with ultrastructural correlation.

Synovial sarcoma demonstrates epithelial differentiation, either by light microscopy (biphasic synovial sarcoma) or by immunohistochemical/ultrastructural methods only (monophasic) and poorly differentiated synovial sarcoma. Although the glands of synovial sarcoma are known to have tight junction-like structures, far less is known about junction formation in the spindled component of synovial sarcomas. Additionally, it is unknown whether the tight junctions of synovial sarcoma are normally constituted. The tight junction is a multiprotein complex consisting of numerous proteins that include ZO-1, claudin-1 and occludin. A total of 35 cases of synovial sarcoma (13 biphasic, 14 monophasic and eight poorly differentiated) were immunostained for ZO-1, claudin-1 and occludin using commercially available antibodies, heat-induced epitope retrieval and standard avidin-biotin technique. When available, corresponding electron micrographs were reviewed. For five cases, the presence of either an SYT-SSX1 (three cases) or SYT-SSX2 (two cases) gene fusion was known. Positive cases showed particulate membrane staining. The glands of biphasic synovial sarcomas expressed ZO-1 (13/13), claudin-1 (12/13) and occludin (11/13) in a manner identical to normal glandular epithelia, at the apical portion of the lateral membrane. The spindle cells of biphasic synovial sarcomas showed abnormal circumferential membranous expression of ZO-1 (12/13), claudin-1 (6/13) and occludin (3/13). Monophasic synovial sarcomas expressed ZO-1 in a circumferential pattern (13/14) but less often claudin-1 (4/14) or occludin (3/14). Poorly differentiated synovial sarcomas expressed ZO-1 (8/8) and claudin-1 (6/8) but only rarely occludin (2/8). By electron microscopy, recognizable tight junctions were seen only in glands. No correlation was seen between histologic subtype or fusion type and expression of tight junction proteins. We conclude that the glands of biphasic synovial sarcomas show well-organized, true epithelial tight junctions. In contrast, the spindled cells of all synovial sarcomas show significant abnormalities in the expression and localization of tight junction proteins, suggesting partial and/or aberrant epithelial differentiation.     

IL-8对血管内皮细胞紧密连接的影响

目的 研究白细胞介素-8(IL-8)对血管内皮细胞紧密连接的影响.方法 采用免疫荧光染色检测经不同浓度和时间IL-8处理后EA.hy926细胞的3种紧密连接蛋白occludin、claudin-5和ZO-1的形态和分布;逆转录PCR(RT-PCR)检测3种蛋白mRNA的表达水平.结果 IL-8可改变内皮细胞紧密连接蛋白...     

Claudin-1 is a strong prognostic indicator in stage II colonic cancer: a tissue microarray study.

Tight junction associated proteins are key molecular components governing cellular adhesion, polarity and glandular differentiation. Tight junction proteins also play critical roles in cellular proliferation and neoplastic pathways via their functions as couplers of the extracellular milieu to intracellular signaling pathways and the cytoskeleton. Neoplastic cells frequently exhibit structural and functional deficiencies in the tight junction. The purpose of this study was to determine the pattern of expression and prognostic value of four tight junction associated proteins, claudin-1, claudin-4, occludin and ZO-1 in a cohort of TNM stage II colon cancer using tissue microarray technology. In this study, we retrospectively analyzed, resected and otherwise untreated paraffin embedded specimens from 129 consecutive patients with TNM stage II colonic carcinomas for claudin-1, claudin-4, occludin and ZO-1 protein expression by immunohistochemistry. Seventy-five, 58, 56 and 44% of the tumors exhibited normal to elevated expression levels (+2 and +3 immunopositivity) of claudin-1, claudin-4, occludin and ZO-1 respectively. Low expression levels of claudin-1 and ZO-1 were directly associated with higher tumor grade (P=0.05 and 0.03 respectively). Multivariate analysis indicated that lymphovascular invasion (P=0.01) and low levels of claudin-1 (P=0.0001) expression were independent predictors of recurrence and that reduced claudin-1 expression (P=0.0001) was associated with poor survival. This study is the first to comprehensively examine the expression of several tight junction associated proteins in colonic neoplasms and to correlate their expression with disease progression. Loss of claudin-1 expression proved to be a strong predictor of disease recurrence and poor patient survival in stage II colon cancer.     

Alterations in tight junction molecules of uterine epithelial cells during early pregnancy in the rat

Distribution patterns of the tight junction associated proteins ZO-1, claudin-1 and occludin were investigated in rat uterine epithelial cells during early pregnancy. Light microscopy and immunohistochemical labelling were used to detect these proteins on days 1, 3, 6 and 7 of pregnancy. Intense staining of claudin-1 at the apical region of the lateral plasma membrane accompanied diffuse staining throughout the cytoplasm. ZO-1 was also localised in the apical region, but ZO-1 was not present in the lower two thirds of the lateral plasma membrane or in the cytoplasm. Occludin was present only on days 6 and 7 of pregnancy. Labelling was also localised in the apical region of the lateral plasma membrane where tight junctions are known to be present. Our results show that ZO-1, claudin-1 and occludin are present in the apical region of uterine epithelial cells, and appear to play a role in the very dynamic tight-junctional network of uterine epithelial cells during early pregnancy. In particular, occludin appears only during uterine receptivity for implantation.     

Amyloid beta-peptide1-42 alters tight junction protein distribution and expression in brain microvessel endothelial cells

Alzheimer's disease is characterised by neuronal loss, numerous intraneuronal deposits of neurofibrillary tangles, senile plaques, and cerebrovascular amyloid deposits. The major component of senile plaques and cerebrovascular deposits is the 39-43 amino acid beta-amyloid peptide (Abeta). The effects of Abeta on cerebral endothelium and thus the blood-brain barrier remain unclear. Utilising endothelial cells isolated from rat cerebral cortex microvessels, we have examined effects of Abeta peptides on tight junction protein behaviour. The transmembrane tight junction proteins occludin, claudin-1 and claudin-5, as well as the cytoplasmic accessory proteins ZO-1 and ZO-2 displayed a continuous distribution at cell boundaries. Endothelial cells exposed to Abeta1-42 (20 microM) for 3 days showed a disrupted plasma membrane pattern of claudin-5 and ZO-2 with relocation to the cytoplasm. These effects were not seen with Abeta25-35 or Abeta1-40[Gln22] (Dutch type). Abeta1-42 treatment altered also protein expression: occludin was lower at 1st day, claudin-1 increased at all times, and ZO-2 increased after 1 day and then decreased. These data suggest that Abeta1-42 effects on tight junction protein complexes may alter blood-brain barrier integrity and contribute to the neuropathological sequelae of Alzheimer's disease.     

Neutrophil Transmigration in Inflammatory Bowel Disease Is Associated with Differential Expression of Epithelial Intercellular Junction Proteins

Inflammatory bowel disease (IBD) consisting of ulcerative colitis (UC) and Crohn's (CD) typically displays a waxing and waning course punctuated by disease flares that are characterized by transepithelial migration of neutrophils (PMN) and altered barrier function. Since epithelial barrier function is primarily regulated by the apical most intercellular junction referred to as the tight junction (TJ), our aim was to examine expression of TJ and adherens junction (AJ) proteins in relation to PMN infiltration in mucosal tissue samples from patients with active IBD. Expression of epithelial intercellular TJ proteins (occludin, ZO-1, claudin-1, and JAM) and subjacent AJ (beta-catenin and E-cadherin) proteins were examined by immunoflourescence/confocal microscopy, immunohistochemistry, and Western blotting. Colonic mucosa from patients with UC revealed dramatic, global down-regulation of the key TJ transmembrane protein occludin in regions of actively transmigrating PMN and in quiescent areas in the biopsy samples. Significant decreases in occludin expression were observed at the protein and mRNA levels by Western and Northern blotting. In contrast, expression of other TJ and AJ proteins such as ZO-1, claudin-1, JAM, beta-catenin, and E-cadherin were down-regulated only in epithelial cells immediately adjacent to transmigrating PMN. Analysis of inflamed mucosa from Crohn's disease patients mirrored the results obtained with UC patients. No change in TJ and AJ protein expression was observed in colonic epithelium from patients with collagenous colitis or lymphocytic colitis that are respectively characterized by a thickened subepithelial collagen plate and increased intraepithelial lymphocytes. These results suggest that occludin expression is diminished in IBD by mechanisms distinct from those regulating expression of other intercellular junction proteins. We speculate that down-regulation of epithelial occludin may play a role in enhanced paracellular permeability and PMN transmigration that is observed in active inflammatory bowel disease.     

Age-related changes in rat cerebral occludin and zonula occludens-1 (ZO-1)

The endothelial or epithelial tight junctions create a rate-limiting barrier to diffusion of solutes. A major determinant of the barrier function is the density of tight junction proteins. Since aging is associated with significant alterations in the blood-brain barrier (BBB) it is possible that specific tight junction proteins may be altered in the cerebrum of aging rats. To test this hypothesis, Western and Northern blot analysis were carried out to measure the steady-state level of occludin and zonula occludens-one (ZO-1) proteins and their mRNA in cerebral tissue of 3-, 12- and 24-month-old rats. The cerebral occludin content in 24-month-old rats (732.5+/-99.9 arbitrary units) was significantly reduced compared to 12-month-old rats (1043.4+/-131.8) or 3-month-old rats (1021.4+/-62.8), P<0.01. The cerebral ZO-1 protein content in 24-month-old rats (161.7+/-8.1 arbitrary units) and 12-month-old rats (144.3+/-35.9) were not significantly reduced compared to 4-month-old rats (189.0+/-27.2). The occludin mRNA content relative to G3PDH mRNA was 1.11+/-0.05, 1.11+/-0.07 and 1.00+/-0.05 in 3-, 12- and 24-month-old rats, respectively. The differences did not achieve statistical significance. The ZO-1 mRNA content of cerebral tissue relative to G3PDH mRNA was significantly increased in 24-month-old rats compared to 3-month-old rats (1.280+/-0.030 vs. 0.956+/-0.038), P<0.001. It is concluded that aging in rats may alter the molecular anatomy of the BBB by altering the content of select structural proteins of tight junctions.     

Intercellular junctions in Ewing sarcoma/primitive neuroectodermal tumor: additional evidence of epithelial differentiation.

Ewing sarcoma/primitive neuroectodermal tumor (ES/PNET) has recently been shown to frequently express cytokeratins, suggesting partial epithelial differentiation. Older ultrastructural studies have documented primitive cell-cell junctions in ES/PNET, reportedly resembling poorly formed desmosomes. Recently, paraffin-reactive antibodies have become available to proteins found in a variety of intercellular junctions indicative of epithelial differentiation, including tight junctions, desmosomes and adherens junctions. We examined intercellular junction protein expression in a large number of genetically confirmed ES/PNET. Formalin-fixed, paraffin-embedded sections from 23 primary and seven recurrent or metastatic cases of genetically confirmed ES/PNET were immunostained for claudin-1 and occludin (tight junction structural proteins), zonula occludens-1 (ZO-1, tight junction linker protein), desmoglein 1/2 (desmosomal adherens protein), desmoplakin (desmosomal structural protein) and E-cadherin (epithelial adherens junction protein), using steam heat-induced epitope retrieval and the Dako Envision system. Cases with >5% positive cells were scored as 'positive'. Normal colonic epithelium and skin served as external positive controls. Claudin-1 was expressed by 19 of 30 specimens (63%), ZO-1 was expressed by 15 of 29 specimens (51%), and occludin was expressed by three of 28 specimens (11%). In 28 specimens all three tight junction markers were evaluable. In all, 15 samples (54%) expressed only one tight junction marker, and 10 samples (36%) expressed two tight junction markers. No case expressed all three tight junction markers. Desmoglein was expressed in one of 30 (3%) samples. Desmoplakin was expressed in two of 28 (7%) samples. E-cadherin was negative in all cases. Our data suggest that many of the previously described cell-cell junctions in ES/PNET are poorly formed tight junctions, given the high frequency of claudin-1 and ZO-1 expression. This may underestimate the true frequency of tight junction protein expression in ES/PNET, as there are at least 20 different claudins and other ZO proteins. These tight junctions are almost certainly abnormal, given the absence of occludin expression in most cases. Desmosomal and adherens junction protein expression was rare to absent. Our findings provide additional evidence that ES/PNET frequently show partial epithelial differentiation.