Biomedical subjects

Daisuke Sakurai

Publications and source records attributed to Daisuke Sakurai.

11 recordsLinked to original sources

PubMed2007

TACI regulates IgA production by APRIL in collaboration with HSPG.

Transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) is a member of the tumor necrosis factor (TNF) receptor family that serves as a receptor for B-cell activating factor of the TNF family (BAFF) and as a proliferation-inducing ligand (APRIL). Although TACI is reported to function as a positive or negative regulator for B-cell responses, its roles remain elusive. Experiments using TACI siRNA into B cells indicated that TACI positively regulated APRIL-induced IgA production in collaboration with heparan sulfate proteoglycans (HSPG). Furthermore, TACI negatively regulated BAFF-induced B-cell proliferation and production of IgA and IgG. In addition, B cells treated with heparitinase to denature HSPG showed that HSPG is essential for APRIL-induced B-cell responses such as B-cell proliferation, IgG and IgA production, induction of activation-induced cytidine deaminase (AID), and noncanonical NF-kappaB2. In contrast, phosphorylation of physiological AID kinase, protein kinase A (PKA), was dependent on TACI. Importantly, coligation of TACI and HSPG by specific antibodies, but not by TACI or HSPG ligation itself, could induce the phosphorylation of PKA and IgA production instead of APRIL. Our findings indicate that simultaneous binding of TACI and HSPG on B cells with APRIL is crucial for IgA production.

B-Cell Activating Factor↗

PubMed2007

TACI attenuates antibody production costimulated by BAFF-R and CD40.

B cell activating factor of the TNF family (BAFF), plays critical roles in B cell survival, activation, differentiation, and antibody (Ab) production. BAFF binds to three receptors: BAFF-R, transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) and B cell maturation antigen. While BAFF-R is the primary receptor for B cell costimulation by BAFF, TACI is reported to serve as a positive or negative regulator for B cell responses depending on conditions. To determine the real role of TACI in B cell responses, we examined the functional relationship between TACI and BAFF-R in Ab production from human peripheral blood B cells using agonistic mAb. BAFF-R and CD40 enhanced IgG secretion and B cell proliferation, which were inhibited by TACI. Although TACI induced mild B cell apoptosis, its extent did not correlate with that of TACI-mediated inhibition of IgG secretion. In addition, TACI inhibited B-lymphocyte-induced maturation protein-1 expression, IgG secretion from previously IgG-negative selected B cells, and activation-induced cytidine deaminase expression enhanced by BAFF-R and CD40. Importantly, BAFF-R and CD40 enhanced B cell responsiveness to TACI-mediated suppression. Thus, BAFF may attenuate T cell-independent and -dependent B cell responses by TACI.

Adjuvants, Immunologic↗

PubMed2006

Effects of down-regulating the Id genes in human colorectal cancer cells on early steps of haematogenous metastasis.

Id genes (inhibitor of DNA binding/differentiation) play important roles in tumour growth. We have previously described crucial roles of Id gene over-expression in endothelial cells for tumour angiogenesis. Here, we have evaluated direct effects of Id gene down-regulation on tumour cells, namely on cell proliferation, motility, and adhesion to lung microvasculature during haematogenous metastasis. For this purpose, Id genes were stably down-regulated by RNA interference in human colorectal cancer cells. These cells showed delayed proliferation, inhibited motility and decreased expression of integrin alpha6 and consequently reduced adhesion to lung microvasculature in mice. Static adhesion assays and laminar flow assays revealed decreased laminin binding capacity of these cells, and blocking experiments confirmed that it could be attributed to decreased expression of integrin alpha6. The present results indicate important roles of Id genes in tumour cells during early steps of haematogenous metastasis and suggest dual effects from their therapeutic inhibition.

Animals↗

PubMed2005

Expression of BAFF-R (BR 3) in normal and neoplastic lymphoid tissues characterized with a newly developed monoclonal antibody.

BAFF-receptor (BAFF-R) is required for the successful maturation and survival of B-cells. We developed an anti-human BAFF-R monoclonal antibody (mAb), 8 A 7. The reactivity of 8 A 7 in normal and neoplastic tissue was examined by performing immunohistochemistry on paraffin-embedded sections. 8 A 7 reacted with lymphocytes in the mantle and marginal zones, but not with lymphocytes in the interfollicular area. Lymphocytes in the germinal centers were found to be negative or occasionally weakly positive for 8 A 7. BAFF-R expression was found only in B-cell lymphoma (44/80, positive cases/examined cases): B-lymphoblastic lymphoma 0/3, B-chronic lymphocytic leukemia/small lymphocytic lymphoma 4/4, mantle cell lymphoma 9/11, follicular lymphoma 10/14, diffuse large B-cell lymphoma (DLBCL) 11/25, marginal zone B-cell lymphoma 8/10, lymphoplasmacytic lymphoma 2/2, plasma cell myeloma 0/2, and Burkitt lymphoma 0/9, but not in T/NK cell lymphomas (0/19) or Hodgkin lymphoma (0/10). BAFF-R was expressed in most low-grade B-cell neoplasms and a small number of DLBCL, suggesting that BAFF-R may play an important role in the proliferation of neoplastic lymphoid cells. Thus, the mAb is very useful for further understanding of both healthy B-cell biology and its pathogenic neoplasms.

Antibodies, Monoclonal↗

PubMed2005

Targeting Id1 and Id3 inhibits peritoneal metastasis of gastric cancer.

Inhibitor of DNA binding (Id) proteins are essential for cell differentiation, proliferation, migration, invasion and angiogenesis. Recently, they have been shown to correlate with less differentiated phenotypes, high malignant potential and poor clinical outcome in various kinds of tumors. In an attempt to develop new strategies for the treatment of peritoneal metastasis of gastric cancer, we prepared an Id1, 3 double-knockdown gastric cancer cell line, MKN45, by RNA interference and investigated its effects on the development of metastatic nodules in the peritoneal cavity. Both cell proliferation and migration capabilities were decreased in Id1, 3 double-knockdown cells, as was their ability to bind to laminin, which could be explained by the decreased expression of integrin alpha6. These are important steps in the metastatic process. In a mouse model, the number of peritoneal metastatic nodules formed by Id1, 3 double-knockdown cells was reduced compared to mock-transfected control cells, as was the size of individual tumors. In this study, we clearly demonstrated that Id1, 3 double-knockdown significantly impaired the ability of gastric cancer cells to form peritoneal metastasis. Id should be considered an ideal target for the treatment and prevention of gastric cancer, and RNA interference is an attractive and promising strategy to achieve it.

Animals↗

PubMed2004

Crucial role of inhibitor of DNA binding/differentiation in the vascular endothelial growth factor-induced activation and angiogenic processes of human endothelial cells.

Angiogenesis plays a pivotal role in the aggressive proliferation of synovial cells in rheumatoid arthritis. We have previously reported the overexpression of inhibitor of DNA binding/differentiation (Id) in the endothelial cells within the synovial tissues of rheumatoid arthritis. In this study, we investigated the role of Id in inflammation and angiogenesis in an in vitro model using HUVECs. Vascular endothelial growth factor (VEGF) and TGFbeta induced the expression of Id1 and Id3 in HUVECs. Forced expression of Id induced proliferative activity in HUVECs accompanied by down-regulation of p16INK4a. Overexpression of Id enhanced expression of ICAM-1 and E-selectin, and induced angiogenic processes such as transmigration, matrix metalloproteinase-2 and -9 expression, and tube formation. In contrast, knockdown of Id1 and Id3 with RNA interference abolished proliferation, activation, and angiogenic processes of HUVECs induced by VEGF. These results indicated that Id plays a crucial role in VEGF-induced signals of endothelial cells by causing activation and potentiation of angiogenic processes. Based on these findings, it was proposed that inhibition of expression and/or function of Id1 and Id3 may potentially be of therapeutic value for conditions associated with pathological angiogenesis.

Angiogenesis Inhibitors↗

PubMed2004

The role of pigment cells in the brain of ascidian larva.

The functions of melanin in the pigment cells, the ocellus and the otolith, of ascidian larvae were studied by their swimming behavior and cell morphology with and without 1-phenyl-2-thiourea (PTU), an inhibitor of vertebrate tyrosinase. Melanin formation in both the otolith and the ocellus of PTU-treated larvae at 12 hours of development was completely inhibited. These larvae were unable to swim because of abnormal tail development, but expression of rhodopsin in the outer segments of the photoreceptor was normal. In the PTU-treated larvae at 15 hours of development, melanin formation in the ocellus was inhibited, but that in the otolith seemed to be normal. The photic behavior of these larvae was normal, as was rhodopsin expression in the outer segments. However, the treated larvae lost upward swimming behavior. Synchrotron radiation X-ray fluorescence images showed that metallic elements of K, Ca, and Zn in the statocyte of larva were greatly decreased by PTU treatment, which may result in lowering the specific gravity of the pigment mass. SEM observations showed that the statocyte of Ciona intestinalis was supported by three parts, a foot-piece of the statocyte itself and two fibrous spring-like structures produced from protuberances. All three structures were synaptotagmin-positive. Movement of the statocyte would be detected by these three structures and thus would be responsible for the gravitational orientation.

Animals↗

PubMed2004

Identification of neuron-specific promoters in Ciona intestinalis.

We isolated 5' flanking regions of four genes, Ci-Galphai1, Ci-arr, Ci-vAChTP, and Ci-vGAT, each of which is expressed in distinct sets of neurons in the central nervous system of the ascidian Ciona intestinalis, and we examined their function by introducing green fluorescent protein (GFP)-fusion constructs into Ciona embryos. The reporter gene driven by the 5' flanking region of Ci-Galphai1, Ci-arr, and Ci-vAChTP recapitulated the endogenous gene expression patterns, while that of Ci-vGAT can drive GFP expression in particular subsets of neurons expressing the endogenous gene. Deletion analysis revealed that the Ci-Galphai1 promoter consists of multiple regulatory modules controlling the expression in different types of cells. The GFP fluorescence enabled visualization of cell bodies and axons of different sets of neurons in ascidian larvae. These promoters can be a powerful tool for studying molecular mechanisms of neuronal development as well as neuron networks and functions in ascidians.

Amino Acid Sequence↗

PubMed2004

A novel method for isolation of endothelial cells and macrophages from murine tumors based on Ac-LDL uptake and CD16 expression.

Analysis of specific properties of tumor endothelium should be useful for development of novel antiangiogenic strategies. However, the isolation of pure endothelial cells from tumor tissues is still a fundamental problem. In this study, we have attempted to develop a reliable method for the isolation of endothelial cells from murine tumors. We found that the labeling with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate-acetylated-low density lipoprotein (Dil-Ac-LDL), commonly used for this purpose, can result in the contamination of isolated endothelium by macrophages due to the overlapping staining patterns of these two distinct cell types. Therefore, we chose the CD16, which is expressed on macrophages but not endothelial cells, to better distinguish them when labeled with Dil-Ac-LDL. By using this method, we obtained pure populations of endothelial cells and macrophages from murine colorectal cancer tissues, showing characteristic morphological and functional properties of the either cell type. The endothelial cells were long spindle-shaped, spread on gelatin, formed tube-like structures on Matrigel and expressed MECA-32 but not CD68. In contrast, the macrophages were round-shaped, partially spread on gelatin, formed unorganized aggregates on Matrigel and expressed CD68 but not MECA-32. The additional analysis of normal and tumor tissues revealed a positive correlation between the relative numbers of tumor endothelial cells and macrophages, calculated as % total cells, as well as the respective relative number and tumor weight. The present method is hoped to be useful for the evaluation of tumor angiogenesis and antitumor immunity.

Animals↗

PubMed2003

BAFF/BLyS can potentiate B-cell selection with the B-cell coreceptor complex.

The tumor necrosis factor (TNF)-like ligand BAFF/BLyS (B-cell activating factor of the TNF family/B-lymphocyte stimulator) is a potent B-cell survival factor, yet its functional relationship with other B-cell surface molecules such as CD19 and CD40 is poorly understood. We found that follicular dendritic cells (FDCs) in human lymph nodes expressed BAFF abundantly. BAFF up-regulated a B cell-specific transcription factor Pax5/BSAP (Pax5/B cell-specific activator protein) activity and its target CD19, a major component of the B-cell coreceptor complex, and synergistically enhanced CD19 phosphorylation by B-cell antigen receptor (BCR). BAFF further enhanced B-cell proliferation, immunoglobulin G (IgG) production, and reactivity to CD154 by BCR/CD19 coligation and interleukin-15 (IL-15). Our results suggest that BAFF may play an important role in FDC-B-cell interactions through the B-cell coreceptor complex and a possibly sequential link between the T cell-independent and -dependent B-cell responses in the germinal centers.

Antibodies, Monoclonal↗

PubMed2003

Direct evidence for the role of pigment cells in the brain of ascidian larvae by laser ablation.

The anterior sensory vesicle of ascidian larvae contains a single large vesicle in which lie two distinct types of pigment cells, anterior and posterior. The ultrastructure of these pigment cells suggests that the anterior pigment cell is an otolith, presumably used for gravity detection, and the posterior pigment cell is an ocellus, used for photoreception. However, there is no direct experimental evidence for this assignment of function. Upward swimming behaviour occurring during the initial period of larval life was examined before and after laser ablation of the anterior pigment and posterior pigment cells. Posterior pigment cell-ablated larvae retained the upward swimming behaviour, but anterior pigment cell-ablated larvae lost it. These results suggest that the anterior pigment acts as a gravity sensor. The negatively phototactic swimming during the latter part of larval life was also examined before and after laser ablation of the anterior pigment or posterior pigment cells. Anterior pigment cell-ablated larvae retained the phototactic response, but posterior pigment cell-ablated larvae lost it. These results suggest that the posterior pigment of the sensory vesicle is involved in the negatively phototactic, downward swimming behavior. The effect of pressure on swimming behaviour was studied, and a putative pressure-detection organ was found not to be involved in the larval swimming behaviour. These are the first published experimental results that permit a functional role in ascidian larval behavior to be assigned to the sensory organs.

Animals↗