Biomedical subjects

Kazuhiro Otani

Publications and source records attributed to Kazuhiro Otani.

4 recordsLinked to original sources

PubMed2006

Nepmucin, a novel HEV sialomucin, mediates L-selectin-dependent lymphocyte rolling and promotes lymphocyte adhesion under flow.

Lymphocyte trafficking to lymph nodes (LNs) is initiated by the interaction between lymphocyte L-selectin and certain sialomucins, collectively termed peripheral node addressin (PNAd), carrying specific carbohydrates expressed by LN high endothelial venules (HEVs). Here, we identified a novel HEV-associated sialomucin, nepmucin (mucin not expressed in Peyer's patches [PPs]), that is expressed in LN HEVs but not detectable in PP HEVs at the protein level. Unlike conventional sialomucins, nepmucin contains a single V-type immunoglobulin (Ig) domain and a mucin-like domain. Using materials affinity-purified from LN lysates with soluble L-selectin, we found that two higher molecular weight species of nepmucin (75 and 95 kD) were decorated with oligosaccharides that bind L-selectin as well as an HEV-specific MECA-79 monoclonal antibody. Electron microscopic analysis showed that nepmucin accumulates in the extended luminal microvillus processes of LN HEVs. Upon appropriate glycosylation, nepmucin supported lymphocyte rolling via its mucin-like domain under physiological flow conditions. Furthermore, unlike most other sialomucins, nepmucin bound lymphocytes via its Ig domain, apparently independently of lymphocyte function-associated antigen 1 and very late antigen 4, and promoted shear-resistant lymphocyte binding in combination with intercellular adhesion molecule 1. Collectively, these results suggest that nepmucin may serve as a dual-functioning PNAd in LN HEVs, mediating both lymphocyte rolling and binding via different functional domains.

Amino Acid Sequence↗

PubMed2005

CXCL13 is an arrest chemokine for B cells in high endothelial venules.

Chemokine receptor signaling is critical for lymphocyte trafficking across high endothelial venules (HEVs), but the exact mode of action of individual chemokines expressed in the HEVs is unclear. Here we report that CXCL13, expressed in a substantial proportion of HEVs in both lymph nodes (LNs) and Peyer patches (PPs), serves as an arrest chemokine for B cells. Whole-mount analysis of mesenteric LNs (MLNs) showed that, unlike T cells, B cellsa dhere poorly to the HEVs of CXCL13-/- mice and that B-cell adhesion is substantially restored in CXCL13-/- HEVs when CXCL13 is added to the MLNs by superfusion, as we have previously observed in PP HEVs by intravital microscopy. In vitro, CXCL13 activated the small guanosine triphosphatase (GTPase) Rap1 in B cells, and corroborating this observation, a deficiency of RAPL, the Rap1 effector molecule, caused a significant reduction in shear-resistant B-cell adhesion to intercellular adhesion molecule 1 (ICAM-1). In addition, CXCL13 induced B-cell adhesion to mucosal addressin cell adhesion molecule 1 (MAdCAM-1) by activating alpha4 integrin. These data identify CXCL13 as an arrest chemokine for B cells in HEVs and show that CXCL13 plays an important role in B-cell entry into not only PPs but also MLNs.

Animals↗

PubMed2005

Hepatitis C virus core protein, cytochrome P450 2E1, and alcohol produce combined mitochondrial injury and cytotoxicity in hepatoma cells.

BACKGROUND & AIMS: Alcohol consumption exacerbates liver injury in chronic hepatitis C, and enhanced mitochondrial oxidative stress is one possible mechanism. The aim of this study was to determine whether hepatitis C virus core protein and alcohol-inducible cytochrome P450 2E1 contribute to reactive oxygen species production and cytotoxicity in human hepatoma cells. METHODS: Huh-7 cells expressing core protein, cytochrome P450 2E1, or both were exposed to 0.1 mmol/L tertiary butyl hydroperoxide, tumor necrosis factor alpha, and/or 25 mmol/L ethanol. Cytotoxicity, reactive oxygen species production, glutathione content, and mitochondrial membrane potential were measured. RESULTS: Expression of core/cytochrome P450 2E1 synergistically enhanced cell death induced by either tertiary butyl hydroperoxide or tumor necrosis factor alpha. After tertiary butyl hydroperoxide treatment, total reactive oxygen species production was increased more than 3-fold compared with cells that did not express core and cytochrome P450 2E1. Mitochondrial depolarization and reduced glutathione depletion occurred as well, and cell death was prevented by inhibition of mitochondrial permeability transition or caspase activity. Confocal microscopy showed that the mitochondria themselves were the origin of the reactive oxygen species. In the absence of core/cytochrome P450 2E1 expression, mitochondrial changes and cell death did not occur. Ethanol treatment further decreased mitochondrial reduced glutathione content and exacerbated mitochondrial reactive oxygen species production, depolarization, and cell death. All these effects were prevented by the antioxidant N -acetylcysteine. CONCLUSIONS: Mitochondrial reactive oxygen species production is induced by hepatitis C virus core and cytochrome P450 2E1, resulting in a reduction of mitochondrial antioxidant capacity and sensitivity to oxidants and tumor necrosis factor alpha. Alcohol further depletes mitochondrial reduced glutathione, which exacerbates depolarization and cell death. Sensitization of mitochondria to oxidative insults is thus a potential mechanism for alcohol-related exacerbation of liver injury in chronic hepatitis C.

Alcohols↗

PubMed2005

Mitochondrial dysfunction in hepatitis C.

Chronic hepatitis C induces a state of hepatic oxidative stress that is more pronounced than that present in many other inflammatory liver diseases. This review summarizes recent information that the hepatitis C virus (HCV) core protein plays an important role in this phenomenon. Core protein localizes to mitochondria, particularly at the points of contact between mitochondrial outer membrane and endoplasmic reticulum. Its expression causes inhibition of electron transport at complex I, increased complex I reactive oxygen species (ROS) production, decreased mitochondrial glutathione, and increased mitochondrial permeability transition in response to exogenous oxidants and tumor necrosis factor-alpha. Possible mechanisms of the core protein effects include direct interaction with electron carriers and indirect effects mediated by changes in mitochondrial calcium. These results suggest that antioxidant approaches may prove beneficial for patients with chronic hepatitis C.

Hepacivirus↗