Biomedical subjects

Hirotoshi Tobioka

Publications and source records attributed to Hirotoshi Tobioka.

9 recordsLinked to original sources

PubMed2004

Expression of occludin, a tight-junction-associated protein, in human lung carcinomas.

Occludin is a tight-junction-associated transmembrane protein, and previous observations suggested that occludin might play a crucial role in the formation and maintenance of organized tubular structures. Based on these observations, we explored the possible role of occludin immunostaining in the diagnosis of lung carcinomas. A total of 68 lung carcinomas and surrounding normal lung tissues were studied. A formalin-fixed, paraffin-embedded section from each tumor was stained with a new anti-occludin monoclonal antibody raised in our laboratory. In normal lung tissues, the anti-occludin antibody strongly stained the apicoluminal borders of the bronchial/bronchiolar epithelia and bronchial glands as a dot or short line. The antibody also stained the intercellular borders of alveolar epithelia. In cancer cells that faced lumina of all adenocarcinomas, regardless of grade, including bronchioloalveolar carcinomas, occludin showed an expression pattern identical to that of the normal bronchial and alveolar epithelia. Occludin reactivity was not noted in any cases of squamous cell carcinoma, large cell carcinoma, small cell carcinoma, or large cell neuroendocrine carcinoma. The results of the present study suggest that occludin can serve as an immunohistochemical indicator of the "true" glandular differentiation that forms tubulo-papillary structures in human lung carcinoma tissues.

Humans↗

PubMed2004

Occludin expression decreases with the progression of human endometrial carcinoma.

The tight junctions of the glandular epithelium are crucial for the maintenance of cell polarity, separating the plasma membrane into apical and basolateral domains. Thus abnormalities of the tight junctions may result in the structural disturbances of glandular epithelial neoplasia. In this study we introduced an anti-occludin monoclonal antibody for semiquantitative assay of the occludin expression in tissue sections of human normal and neoplastic endometrial epithelia using the Adobe Photoshop and NIH Image programs. Normal endometrial glands and samples of endometrial hyperplasia and endometrioid carcinoma grade 1 fully expressed occludin at the apical cell border. In endometrioid carcinomas grades 2 and 3, however, occludin disappeared in solid areas of the carcinomatous tissues. Occludin was also found at the apical borders of the cancer cells that formed glandular structures. Occludin expression decreased progressively in parallel with the increase in carcinoma grade, and the decreased occludin expression correlated with myometrial invasion and lymph node metastasis. These results suggest that the loss of tight junctions has a close relationship with structural atypia in the progression of human endometrial carcinomas and their malignant potential.

Adenocarcinoma↗

PubMed2004

Localization and function in endoplasmic reticulum stress tolerance of ERdj3, a new member of Hsp40 family protein.

Heat shock protein 40 (Hsp40) family proteins are known to bind to Hsp70 through their J-domain and regulate the function of Hsp70 by stimulating its adenosine triphosphatase activity. In the endoplasmic reticulum (ER), there are 5 Hsp40 family proteins known so far, 3 of which were recently identified. In this report, one of the novel Hsp40 cochaperones, ERdj3, was characterized in terms of its subcellular localization, stress response, and stress tolerance of cells. By using ERdj3-specific polyclonal antibody, endogenous ERdj3 protein was shown to reside in the ER as gene transfer-mediated exogenous ERdj3. Analysis of the expression level of endogenous ERdj3 protein revealed its moderate induction in response to various ER stressors, indicating its possible action as a stress protein in the ER. Subsequently, we analyzed whether this molecule was involved in ER stress tolerance of cells, as was the case with the ER-resident Hsp70 family protein BiP. Although overexpression of ERdj3 by gene transfection could not strengthen ER stress tolerance of neuroblastoma cells, reduction of ERdj3 expression by small interfering ribonucleic acid decreased the tolerance of cells, indicating that ERdj3 might have just a marginal role in the ER stress resistance of neuroblastoma cells. In contrast, overexpression of ERdj3 notably suppressed vero toxin-induced cell death. These data suggest that ERdj3 might have diverse roles in the ER, including that of the molecular cochaperone of BiP and an as yet unknown protective action against vero toxin.

Amino Acid Sequence↗

PubMed2003

Tight junctions and human diseases.

Tight junctions are intercellular junctions adjacent to the apical end of the lateral membrane surface. They have two functions, the barrier (or gate) function and the fence function. The barrier function of tight junctions regulates the passage of ions, water, and various macromolecules, even of cancer cells, through paracellular spaces. The barrier function is thus relevant to edema, jaundice, diarrhea, and blood-borne metastasis. On the other hand, the fence function maintains cell polarity. In other words, tight junctions work as a fence to prevent intermixing of molecules in the apical membrane with those in the lateral membrane. This function is deeply involved in cancer cell biology, in terms of loss of cell polarity. Of the proteins comprising tight junctions, integral membrane proteins occludin, claudins, and JAMs have been recently discovered. Of these molecules, claudins are exclusively responsible for the formation of tight-junction strands and are connected with the actin cytoskeleton mediated by ZO-1. Thus, both functions of tight junctions are dependent on the integrity of the actin cytoskeleton as well as ATP. Mutations in the claudin14 and the claudin16 genes result in hereditary deafness and hereditary hypomagnesemia, respectively. Some pathogenic bacteria and viruses target and affect the tight-junction function, leading to diseases. In this review, the relationship between tight junctions and human diseases is summarized.

Claudins↗

PubMed2002

Polarized distribution of carcinoembryonic antigen is associated with a tight junction molecule in human colorectal adenocarcinoma.

This study we presents a novel anti-occludin monoclonal antibody that can be used for formalin-fixed, paraffin-embedded tissue sections. The relationships between aberrant localization of carcinoembryonic antigen (CEA) and abnormalities of tight junctions were studied in human colorectal cancers by this antibody. Abnormalities in the cell surface expression of CEA have been shown to be characteristic of human colorectal cancer cells. Cancer cells that participated in the formation of glandular structures expressed occludin at the apical cell border and CEA was expressed more apically than occludin. Where cancer cells showed solid nests without glandular structures, occludin was completely lost and CEA was demonstrated in a diffuse pattern throughout the cells. These findings suggest that the polarized apical expression of CEA in neoplastic glandular structures depends on the expression of occludin and the fence function of tight junctions. During tumour progression, loss of occludin may lead to the loss of membrane polarity and the non-polarized expression of CEA. The antibody described provides a powerful tool for the study of tight junctions in surgically resected human tissue.

Adenocarcinoma↗

PubMed2002

Barrier function of microvessels and roles of glial cell line-derived neurotrophic factor in the rat testis.

The expression and localization of glial cell line-derived neurotrophic factor (GDNF) and its receptor GFR alpha1 in the testis were examined, because the blood-testis barrier is a well-known tissue barrier and we previously reported that GDNF reduced the endothelial permeability of the blood-brain barrier (BBB). Five minutes after intravenous injection of Evans blue (molecular weight, 960.6) or fluorescent dextran (molecular weight 10000 and 70000), Evans blue was observed outside microvessels of the testis, whereas the fluorescent dextran was not. Immunohistochemically, GDNF was detected in alpha-smooth muscle actin-positive cells around the seminiferous tubules and in microvessels. On the other hand, GFR alpha1 was detected in endothelial cells in the interstitial space, as well as in spermatocytes. Although occludin was positive in Sertoli cells and endothelium, claudin-5 was localized only in the endothelium of the microvessels. Thus, it became very clear that the microvessels in the testis possessed relatively impermeable tight junctions, and that the alpha-smooth muscle actin-positive cells secreted GDNF, which receptor was expressed in endothelial cells. Because this relation between GDNF and GFR alpha1 is similar to that observed in the BBB, we hypothesize that GDNF is a general regulator of tight junctions of the endothelium forming a blood-tissue barrier in a paracrine fashion.

Amino Acid Sequence↗

PubMed2001

Bile canalicular barrier function and expression of tight-junctional molecules in rat hepatocytes during common bile duct ligation.

Tight junctions of hepatocytes form the intercellular barrier between the blood circulation and bile flow. We focused on early stages of common bile duct ligation to observe changes in tight junctions without the irreversible changes seen after lengthy ligation. Common bile ducts of 12-week-old male rats were ligated for 6 h because, at this time point, no histological changes were observed. Serum bilirubin and bile acid levels began to increase 3 h after ligation and were restored to the control level immediately after surgical removal of the ligation. To examine the barrier of hapatocytes, horseradish peroxidase was injected via the femoral vein, and bile was collected for the first 10 min. A four-fold elevation of the secretion and concentration was observed in the bile of ligated rats compared with that of control animals. We next examined lanthanum permeability by perfusion fixation of the liver. At 6 h after ligation, both dilation of the bile canaliculi and partial loss of microvilli were commonly observed. There were dense deposits of lanthanum in almost all bile canaliculi of ligated rats. In control animals, neither dilation of the bile canaliculi nor loss of microvilli was detected, and only 44% of bile canaliculi exhibited deposits. An apparent increase of occludin mRNA expression was detected in livers after 6 h ligation, whereas the expression of claudin-1, -2, and -3 was not influenced by ligation. These results indicate that regulation of occludin gene expression is different from that of claudin-1, -2, and -3. The early phase of bile stasis employed in this study is thought to be an indispensable approach for understanding the precise regulation of tight junctions.

Animals↗

PubMed1999

Occludin modulates organization of perijunctional circumferential actin in rat endothelial cells.

The tight junction is not a constitutional junctional apparatus in endothelial cells, but develops in a particular lineage of endothelia, such as the capillary endothelia in the brain and retina, and thus is considered to be pivotal for the maintenance of the blood-tissue barrier. Occludin is an integral membrane component of tight junctions, but the role of occludin in the endothelial cell function remains to be elucidated. We have cloned and transfected rat full-length occludin cDNA into a rat endothelial cell line (RLE) that expressed only a trace amount of occludin with no fine circumferential actin bundles at the cell border in native conditions. Occludin was expressed at the cell border of RLE cells, and circumferential fine actin bundles developed in close relation to the sites of occludin localization. Even under subconfluent culture conditions, fine circumferential actin bundles were formed at the sites where occludin-positive cell-cell contact was achieved. In immunoelectron microscopy, occludin was localized at distinct areas of the plasma membrane, always in association with the cytoplasmic actin filaments. On the other hand, actin bundles were not seen in occludin-negative juxtaposing plasma membranes. Collectively, these data strongly suggested a possible determinant function of occludin for the organization of actin in endothelial cells.

Journal Article↗

PubMed1999

Electron microscopic and immunohistochemical studies of gastrointestinal stromal tumors.

Sixteen gastrointestinal stromal tumors (GISTs) were studied by immunohistochemical analysis and an ultrastructural procedure. The tumor locations were as follows: esophagus (2), stomach (7), small intestine (3), and large intestine (4). Four of the lesions were classified as malignant, 2 as borderline, and 10 as benign. On the basis of the immunohistochemical analysis, the tumors were classified as follows: 1 as myogenic type, 2 as Schwann cell type, 8 as Cajal cell type (including 2 gastrointestinal autonomic nerve tumors, GANTs), and 5 as mixed-cell type. In each subtype the phenotype was compared to the ultrastructural findings. Myogenic and Schwann cell type revealed ultrastructurally smooth muscle differentiation and schwannian tumor. All 8 tumors of the Cajal cell type revealed interdigitating cytoplasmic processes with occasional clusters of filopodia. Two tumors were subdivided as GANT. Five tumors of mixed-cell type were composed of a mixture of cells with variable myogenic features or variable neural differentiation. We confirmed in this study that immunohistochemical analysis reflected electron microscopic findings.

Journal Article↗