Search PubMed⌕ Search

Biomedical subjects

I Kudo

Publications and source records attributed to I Kudo.

At least 91 records · Page 5Linked to original sources
PubMed1995

Detection and purification of two 14 kDa phospholipase A2 isoforms in rat kidney: their role in eicosanoid synthesis.

Phospholipase A2 (PLA2) activity in the soluble fraction of rat kidney yielded three peaks on DEAE cellulose column chromatography. From these three, we purified two PLA2 isoforms to near-homogeneity. Both had a molecular weight of approx. 14,000 on SDS-PAGE, and immunochemical and enzymological studies indicated that one is a 14 kDa type I PLA2 and the other a 14 kDa type II PLA2. RNA blot analysis confirmed that rat kidney contains both types of PLA2 and that administration of lipopolysaccharides and mercury chloride into rats increased type II PLA2 mRNA levels in kidney. When cultured rat mesangial cells were incubated with purified type I or type II PLA2 in combination with the calcium ionophore A23187 at suboptimal condition, augmentation of prostaglandin E2 production was observed. Type I and type II forms of PLA2 may play a role in arachidonate metabolism in rat kidney.

Animals↗
PubMed1995

Lipoxygenase-catalyzed oxygenation of arachidonylethanolamide, a cannabinoid receptor agonist.

Various purified lipoxygenases were incubated with [14C]arachidonylethanolamide which is an endogenous ligand for cannabinoid receptors. When radioactive products were analyzed by thin-layer chromatography, porcine leukocyte 12-lipoxygenase and rabbit reticulocyte and soybean 15-lipoxygenases produced polar compounds at about the same reaction rates as that of oxygenation of free arachidonic acid. In contrast, the reaction of human platelet 12-lipoxygenase proceeded at a much lower rate, and porcine leukocyte 5-lipoxygenase was totally inactive. The result indicated that the lipoxygenases, which had been shown previously to be capable of oxygenating esterified polyunsaturated fatty acids, were also active with the arachidonylethanolamide. High-performance liquid chromatography, ultraviolet and mass spectrometry and nuclear magnetic resonance spectroscopy identified the major product by leukocyte 12-lipoxygenase as 12-hydroperoxy-5,8,10,14-eicosatetraenoylethanolamide and that by 15-lipoxygenases as 15-hydroperoxy-5,8,11,13-eicosatetraenoylethanolamide. The 15-hydroxy derivative inhibited electrically-evoked contraction of mouse vas deferens with an IC50 of 0.63 microM as well as arachidonylethanolamide (0.17 microM), but the 12-hydroxy derivative was much less effective.

Animals↗
PubMed1995

Exogenous type-II phospholipase A2 stimulates prostaglandin synthesis in rat liver-derived BRL-3A cells in the presence of tumor necrosis factor alpha.

The effect of extracellular type-II phospholipase A2 (PLA2) on prostaglandin (PG) synthesis has been studied using rat liver-derived BRL-3A cells. The addition of type-II PLA2 to the medium of BRL-3A cells resulted in a marked decrease in the enzymatic activity in the medium. An immunochemical study involving an anti-(type-II PLA2) antibody revealed that a significant amount of PLA2 was attached to the surface of type-II PLA2-treated BRL-3A cells. Heparin inhibited the binding of PLA2 almost completely. Only modest release of PGE2 over the control value was observed when cells were treated with PLA2 alone or tumor necrosis factor alpha (TNF alpha) alone, whereas PGE2 production as well as arachidonic acid release from phospholipids was augmented more than additively in the presence of both type-II PLA2 and TNF alpha. Furthermore, pretreatment of cells with type-II PLA2 followed by subsequent stimulation by TNF alpha caused an appreciable increase in PGE2 production. Thus, type-II PLA2 bound to cell-surface heparin-like molecules may exert its activity and participate in eicosanoid generation only in the presence of TNF alpha.

Animals↗
PubMed1995

Phospholipid degradation in rat calcium ionophore-activated platelets is catalyzed mainly by two discrete secretory phospholipase As.

An "A1 type" phospholipase activity with serine-phospholipid preference was released by rat activated platelets. It was distinct from the secretory type II phospholipase A2 [Horigome, K., Hayakawa, M., Inoue, K., and Nojima, S. (1987) J. Biochem. 101, 625-631] and co-purified with the secretory lysophosphatidylserine-selective lysophospholipase activity [Higashi, S., Kobayashi, T., Kudo, I., and Inoue, K. (1988) J. Biochem. 103, 442-447]. Several lines of evidence indicated that a single protein was responsible for the phospholipase A1 and lysophospholipase activities. Marked accumulation of lysophospholipids was observed in rat calcium ionophore-activated washed platelets and both phospholipase A1/lysophospholipase and type II phospholipase A2 were shown to contribute to this phospholipid degradation. A selective inhibitor of type II phospholipase A2 reduced the phospholipid degradation and enhanced the clotting time and prothrombinase activity. These results indicate that secretory platelet phospholipases may play a role in regulation of blood clotting.

Animals↗
PubMed1995

Activation of phospholipase A2 and acylation of lysophospholipids: the major regulators for platelet activating factor production in rat neutrophils.

Rat inflammatory neutrophils induced arachidonic acid release and platelet-activating factor (PAF) production in response to opsonized zymosan (OPZ) dose-dependently. Phospholipase A2 activity also increased dose-dependently, paralleling the increases in arachidonic acid and PAF. The time courses of the activities of phospholipase A2 and acetyltransferase, and the amounts of free arachidonic acid, lyso-PAF, and PAF demonstrated that activation of the enzymes in the remodeling pathway could be required for PAF production in rat neutrophils, which agrees with the documented fact for macrophages. Phospholipase A2 could be a rate-limiting enzyme for PAF production, since an increased lyso-PAF amount or addition of exogenous lyso-PAF reflected the increase in PAF formation in the cells. This phospholipase A2 activity in rat neutrophils could be attributed to cytosolic type phospholipase A2, because the activity was mostly suppressed by a specific antibody to cytosolic phospholipase A2. As previously reported, pretreatment of neutrophils with the acyl-CoA synthetase inhibitor, triacsin C, or the acyltransferase inhibitor, merthiolate, enhanced PAF production as well as arachidonic acid release by the cells in response to OPZ. Triacsin C inhibited arachidonoyl-CoA production and merthiolate suppressed the transacylation of lyso-PAF to 1-alkyl-2-arachidonoyl-GPC. These results suggest that these inhibitors of acylation of lyso-PAF caused accumulation of lyso-PAF, which resulted in enhancement of PAF production when phospholipase A2 and acetyltransferase were activated by OPZ. Thus the activation of cytosolic phospholipase A2 and the acylation of lyso-PAF by such as arachidonic acid could be regulating factors for PAF production in stimulated rat neutrophils.

Acylation↗
PubMed1995

A case of osteoporosis with bilateral defects in the mandibular processes.

We carried out a detailed total body examination of a 62-year-old woman with osteoporosis who had bilateral defects in the mandibular processes. It was inferred that the defects in both articular heads were caused by resorption of small bone fragments following fracture. The quantity of bone salt was determined by microdensitometry, and a diagnosis of osteoporosis was then established. An improved bite was obtained by treatment consisting of tooth extraction and the preparation of partial dentures.

Absorptiometry, Photon↗
PubMed1994

Dual regulation of cytosolic phospholipase A2 in mast cells after cross-linking of FC epsilon-receptor.

We have reported previously that cultured mast cells (MC) express three discrete phospholipases A2 (PLA2s), one of which corresponds to arachidonoyl-preferential cytosolic PLA2 (cPLA2). In the present study, we investigated the possible role of cPLA2 in eicosanoid synthesis by activating mouse bone marrow-derived mast cells (BMMC) through cross-linking of the high affinity IgE receptor (Fc epsilon RI) with a specific Ag. BMMC released arachidonic acid within 2 min after Fc epsilon RI cross-linking. A rapid, transient phosphorylation of cPLA2 was observed after Fc epsilon RI cross-linking, reaching the maximum within 2 min, and accompanied by an increase of cPLA2 activity in the cell lysate. Exposure of BMMC to the IgE-Ag for longer periods resulted in a time-dependent increase of the cPLA2 protein. The increase was detected within 10 h after stimulation and reached the maximum within 30 h. Dexamethasone inhibited the Ag-stimulated cPLA2 induction significantly. cPLA2 activity in cells stimulated for 24 h was increased significantly, and suppressed in cells treated with dexamethasone. When the cells were exposed to IgE-Ag for 36 h and then challenged with a secondary agonist, thrombin, arachidonate release was augmented significantly in comparison with cells without the Ag pretreatment. Thus, cPLA2 activation in BMMC by short term exposure to the Ag might be regulated by post-Fc epsilon RI modification (phosphorylation) of pre-existing enzyme, whereas that observed after long term exposure might be explained by the increase in cPLA2 protein.

Animals↗
PubMed1994

A possible role for extracellular bicarbonate in U-46619-induced rat platelet aggregation.

U-46619, a thromboxane A2 agonist, has been believed not to induce aggregation of rat platelets. However, we have found that U-46619 evoked rat platelet aggregation when the cells were suspended in HCO3-containing medium, whereas it was inactive in medium lacking HCO3-. 4,4'-Diisothiocyanostilbene-2,2'-disulfonate (DIDS), selective inhibitor of the HCO3/Cl- exchanger, inhibited the aggregation of rat platelets induced by U-46619 as well as by collagen and ADP. Thrombin-induced aggregation was also inhibited by DIDS, although to a much lesser extent. Several inhibitors of anion transporters, such as phloretin, pyridoxal phosphate and ethacrynic acid, suppressed U-46619-induced aggregation. These observations indicate that HCO3-influx via an anion exchanger may be involved in the signal transduction pathway of U-46619 in rat platelets.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1994

Complete discrimination of docosahexaenoate from arachidonate by 85 kDa cytosolic phospholipase A2 during the hydrolysis of diacyl- and alkenylacylglycerophosphoethanolamine.

In our previous report (Shikano, M., Masuzawa, Y. and Yazawa, K. (1993) J. Immunol. 150, 3525-3533), we described that the enrichment of docosahexaenoic acid (DHA, 22:6(n - 3)) reduces both arachidonic acid (AA, 20:4(n - 6)) release and platelet-activating factor (PAF) synthesis in human eosinophilic leukemia cells, Eol-1. Since no DHA release was observed in response to Ca-ionophore stimulation, we presumed that the phospholipase A2 (PLA2) responsible for AA release and PAF synthesis can not hydrolyze the DHA moiety of phospholipids. In the present paper, we examined whether DHA-containing diacyl- and alkenylacylglycerophosphoethanolamine (DHA-diacylGPE and DHA-alkenylacyGPE) are susceptible to the action of AA-preferential 85 kDa cytosolic phospholipase A2 (cPLA2) from rabbit platelets in comparison with AA and eicosapentaenoic acid (EPA, 20:5(n - 3)) derivatives. When diacylGPE was used as a substrate, DHA release was almost negligible under the assay condition that allowed AA and EPA to be liberated at the rates of 4.3 mumol/min per mg protein and 2.5 mumol/min per mg protein, respectively. On the other hand, 14 kDa type II PLA2 hydrolyzed DHA-diacylGPE as well as AA-diacylGPE and EPA-diacylGPE. When DHA-diacylGPE and AA-diacylGPE were mixed at equimolar concentrations, DHA release by cPLA2 was not observed and AA release was reduced to 32% in the case without DHA-diacylGPE. This indicated that DHA-diacylGPE is a poor substrate but possesses the inhibitory activity for cPLA2. cPLA2 does not clearly discriminate between AA-alkenylacylGPE and AA-diacylGPE. As in the case using diacylGPE as a substrate, DHA-alkenylacylGPE was completely discriminated from AA-alkenylacylGPE by cPLA2. The roles of DHA and cPLA2 in the synthesis of lipid mediators will be discussed in relation to the new aspects of the substrate specificity of cPLA2 provided here.

Animals↗
PubMed1994

Role of type II phospholipase A2 in the inflammatory process of carrageenan-induced pleurisy in rats.

In order to investigate the role of type II phospholipase A2 (PLA2) in the inflammatory process, the effect of a monoclonal antibody specific to type II PLA2 on carrageenan-induced pleurisy was studied in rats. Intravenous injection of the antibody (MB5.2), which inhibits the catalytic activity of type II PLA2, significantly reduced both the pleural exudate volume and the intrapleural leukocyte count, while a control antibody did not have any appreciable effect. MB5.2 caused no change in the level of type II PLA2 in the pleural fluid. These results suggest that type II PLA2 generated at inflamed sites, at least in part, have a crucial role in the pathogenesis of acute inflammation.

Animals↗
PubMed1994

Suppressive effects of the anti-allergic drugs, tranilast and azelastine, on the lysophosphatidylserine-dependent activation of rat mast cells.

Anti-allergic drugs, tranilast and azelastine, were examined for their effects on lysophosphatidylserine (lysoPS)-dependent histamine release from rat mast cells. Although both compounds suppressed the histamine release in a dose-dependent manner, the inhibition was affected by lysoPS concentration differently. In the presence of an increasing concentration of lysoPS, the suppressive effect of tranilast decreased. The inhibition by azelastine, however, was independent of the concentration of lysoPS. The findings suggest that these two drugs inhibit lysoPS-depedent histamine release through essentially different routes.

Animals↗