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Biomedical subjects

Yukio Ozaki

Publications and source records attributed to Yukio Ozaki.

12 recordsLinked to original sources
PubMed2003

Sphingosine 1-phosphate induces contraction of coronary artery smooth muscle cells via S1P2.

OBJECTIVES: Sphingosine 1-phosphate (Sph-1-P), a bioactive lipid derived from activated platelets, may play an important role in coronary artery spasm and hence the pathogenesis of ischemic heart diseases, since we reported that a decrease in coronary blood flow was induced by this lysophospholipid in an in vivo canine heart model [Cardiovasc. Res. 46 (2000) 119]. In this study, metabolism related to and cellular responses elicited by Sph-1-P were examined in human coronary artery smooth muscle cells (CASMCs). METHODS AND RESULTS: [3H]Sphingosine (Sph), incorporated into CASMCs, was converted to [3H]Sph-1-P intracellularly, but its stimulation-dependent formation and extracellular release were not observed. Furthermore, the cell surface Sph-1-P receptors of S1P family (previously called EDG) were found to be expressed in CASMCs. Accordingly, Sph-1-P seems to act as an extracellular mediator in CASMCs. Consistent with Sph-1-P-elicited coronary vasoconstriction in vivo, Sph-1-P strongly induced CASMC contraction, which was inhibited by JTE-013, a newly-developed specific antagonist of S1P(2) (EDG-5). Furthermore, C3 exoenzyme or Y-27632 inhibited the CASMC contraction induced by Sph-1-P, indicating Rho involvement. Finally, exogenously-added [3H]Sph-1-P underwent a rapid degradation. Since lipid phosphate phosphatases, ectoenzymes capable of dephosphorylating Sph-1-P, were expressed in CASMCs, Sph-1-P may be dephosphorylated by the ectophosphatases. CONCLUSIONS: Sph-1-P, derived from platelets and dephosphorylated on the cell surface, may induce the contraction of coronary artery smooth muscle cells through the S1P(2)/Rho signaling.

Acute-Phase Proteins↗
PubMed2003

Plasma thioredoxin levels and platelet aggregability in patients with acute myocardial infarction.

BACKGROUND: Oxidative stress is thought to play an important role in atherosclerotic vascular disease. Recently, it has become possible to quantitatively measure thioredoxin, a marker of oxidative stress in human plasma. A platelet aggregometer that uses laser-light scattering enables minimal changes in platelet aggregability to be monitored; however, the relationship between oxidative stress and platelet aggregability in vivo is not well understood. METHODS: We investigated plasma thioredoxin levels and platelet aggregability, in particular small platelet aggregates, in 45 patients with acute myocardial infarction (AMI); we compared the results with 33 patients with stable exertional angina (SEA) and 30 patients with chest pain syndrome (CPS). RESULTS: The plasma thioredoxin levels and the degree of small platelet aggregates were higher in the AMI group than in the SEA and the CPS groups: in the AMI group, at 4 weeks after admission, both of those parameters were significantly decreased (P <.01), but they were still higher (P <.05) than in the SEA or the CPS group. There was a significant positive correlation between small platelet aggregates and plasma thioredoxin levels (rho = 0.354, P =.0002). We divided the AMI patients into 2 groups according to the 75 percentile of plasma thioredoxin levels on admission. At the chronic phase, the left ventricular ejection fraction was significantly higher in the lower thioredoxin group than in the higher thioredoxin group. CONCLUSIONS: We showed that plasma thioredoxin levels and platelet aggregability increased concomitantly in patients with AMI. In these patients, increased plasma thioredoxin was associated with platelet hyperaggregability and lower left ventricular ejection fraction.

Adult↗
PubMed2003

Ceramide 1-phosphate formation in neutrophils.

In this study, we examined the metabolism of [(3)H]N-hexanoylsphingosine [C(6)-ceramide (Cer)] in neutrophils, erythrocytes, platelets and mononuclear cells. [(3)H]C(6)-Cer, exogenously added and incorporated into the inside of the cell, was found to be converted to other radioactive sphingolipids in these differentiated blood cells, except erythrocytes, which were unable to metabolize C(6)-Cer. Only in neutrophils was a specific radioactive band, comigrating with a standard C(6)-Cer 1-phosphate (C(6)-Cer-1-P) on thin layer chromatography, observed in a time-dependent manner. This metabolite was confirmed to be C(6)-Cer-1-P by its sensitivity to acid treatment and resistance to mild alkaline hydrolysis. Neutrophil [(3)H]C(6)-Cer conversion into [(3)H]C(6)-Cer-1-P, reflecting Cer kinase activity, was not affected by cell stimulation. Furthermore, extracellular release of [(3)H]C(6)-Cer-1-P was not observed either. Exogenous addition of C(8)-Cer-1-P failed to induce intracellular Ca(2+) mobilization or affect the response induced by the formyl peptide. Furthermore, neutrophil morphology was not affected by C(8)-Cer-1-P. Although specific expression of Cer kinase suggests an important role for Cer-1-P in neutrophils, its functional role(s) remain to be clarified.

Adult↗
PubMed2003

Expression of the LIM proteins paxillin and Hic-5 in human tissues.

The LIM domain is a protein-protein interaction motif critically involved in a variety of fundamental biological processes, including cytoskeletal organization, cell lineage specification, and organ development. In this study we examined the expression of the LIM proteins paxillin and Hic-5 in adult human tissues by immunohistochemistry and immunoblotting. Paxillin expression was widespread and observed both in non-muscle and muscle tissues. Of the latter, paxillin was mainly expressed in multinuclear striated muscle. In contrast, Hic-5 showed restricted expression and was expressed in muscle tissues, mainly in mononuclear smooth muscle. Taken together with previous findings, it appears likely that the counterbalance between paxillin and Hic-5 may be deeply involved in muscle differentiation.

Adult↗
PubMed2003

Formation of platelet microaggregates correlates with adverse clinical outcome in patients with coronary artery disease.

Platelet activation plays a pivotal role in the pathogenesis of acute coronary syndromes. Laser-light scattering in a platelet aggregometer was used to evaluate aggregate size and number quantitatively. Small platelet aggregates ultimately develop into medium and then large platelet aggregates. Thus the measurement of small platelet aggregates is important in the evaluation of thrombus formation. We examined the relationship between small platelet aggregates and the occurrence of subsequent cardiovascular events. We followed-up 204 patients (149 men and 55 women, mean age 68 +/- 9 years) with coronary artery disease (CAD) for 48 months. Blood sampling to determine platelet aggregation was performed on the day of hospital discharge. The degree of small platelet aggregates [relative risk 4.34, 95% confidence interval (1.62-11.7), p = 0.004] and low left-ventricular ejection fraction [relative risk 2.88, 95% confidence interval (1.23-6.73), p = 0.015] were independent predictors of the occurrence of cardiovascular events in multivariate Cox hazard analysis. In Kaplan-Meier analysis, the degree of small platelet aggregates correlated with the probability of cardiovascular event occurrence. In patients with CAD, an increase in small platelet aggregates is closely correlated with the future occurrence of cardiovascular events

Adult↗
PubMed2002

Enhancement of sphingosine 1-phosphate-induced migration of vascular endothelial cells and smooth muscle cells by an EDG-5 antagonist.

Sphingosine 1-phosphate (Sph-1-P), a bioactive lysophospholipid capable of inducing a wide spectrum of biological responses, acts as an intercellular mediator, through interaction with the endothelial differentiation gene (EDG)/S1P family of G protein-coupled receptors. In this study, the effects of JTE-013, a specific antagonist of the migration-inhibitory receptor EDG-5, on Sph-1-P-elicited responses were examined in human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (SMCs), which expressed EDG-5 protein weakly and abundantly, respectively. This pyrazolopyridine compound reversed the inhibitory effect of Sph-1-P on SMC migration and further enhanced Sph-1-P-stimulated HUVEC migration. In contrast, its effect on Sph-1-P-induced intracellular Ca(2+) mobilization was marginal. Our results indicate that specific regulation of Sph-1-P-modulated migration responses in vascular cells can be achieved by EDG-5 antagonists and that manipulation of Sph-1-P biological activities by each EDG antagonist may lead to a therapeutical application to control vascular diseases.

Calcium Signaling↗
PubMed2002

Interaction between von Willebrand factor and glycoprotein Ib activates Src kinase in human platelets: role of phosphoinositide 3-kinase.

The binding of von Willebrand factor (VWF) to glycoprotein (GP) Ib-IX-V stimulates transmembrane signaling events that lead to platelet adhesion and aggregation. Recent studies have implied that activation of Src family kinases is involved in GPIb-mediated platelet activation, although the related signal transduction pathway remains poorly defined. This study presents evidence for an important role of Src and GPIb association. In platelet lysates containing Complete, a broad-spectrum protease inhibitor mixture, Src and Lyn dynamically associated with GPIb on VWF-botrocetin stimulation. Cytochalasin D, which inhibits translocation of Src kinases to the cytoskeleton, further increased Src and GPIb association. Similar results were obtained with botrocetin and monomeric A1 domain, instead of intact VWF, with induction of both Src activation and association between GPIb and Src. These findings suggest that ligand binding of GPIb, without receptor clustering, is sufficient to activate Src. Immunoprecipitation studies demonstrated that Src, phosphoinositide 3- kinase (PI 3-kinase), and GPIb form a complex in GPIb-stimulated platelets. When the p85 subunit of PI 3-kinase was immunodepleted, association of Src with GPIb was abrogated. However, wortmannin, a specific PI 3-kinase inhibitor, failed to block complex formation between Src and GPIb. The Src-SH3 domain as a glutathione S-transferase (GST)-fusion protein coprecipitated the p85 subunit of PI 3-kinase and GPIb. These findings taken together suggest that the p85 subunit of PI 3-kinase mediates GPIb-related activation signals and activates Src independently of the enzymatic activity of PI 3- kinase.

Androstadienes↗
PubMed2002

Small aggregates of platelets can be detected sensitively by a flow cytometer equipped with an imaging device: mechanisms of epinephrine-induced aggregation and antiplatelet effects of beraprost.

BACKGROUND: Although cross-talks between platelets and other blood cells are important in vivo, laboratory platelet aggregation tests have been performed mainly with the use of platelet-rich plasma (PRP) as samples. Methods that enable an efficient and sensitive detection of platelet aggregates in whole blood are being developed. METHODS: A flow cytometer equipped with an imaging device, the flow imaging cytometer 2 (FIC2), was used to detect platelet aggregates in whole blood. RESULTS: The FIC2 provides a resolution that is high enough to differentiate platelet aggregates from single platelets or other blood cells. Epinephrine elicited platelet aggregate formation in hirudin plus argatroban-treated whole blood, but not in PRP. The reconstitution study revealed that a small amount of adenosine diphosphate (ADP) from erythrocytes may play an important role in epinephrine-induced platelet aggregation (in whole blood), through mediation of P2Y1 receptors. When the inhibitory effect of beraprost, an antiplatelet agent, on platelet aggregation was assessed, analysis of whole blood samples with FIC2 proved to be the most sensitive among the methods available. CONCLUSIONS: FIC2 is a promising device for detection of platelet aggregates in whole blood, with wide basic and clinical applications.

Epinephrine↗
PubMed2002

An involvement of granulocyte medullasin in phenytoin-induced gingival overgrowth in rats.

To investigate the relationship between histological changes and distributions of medullasin, a neutrophil elastase-like serine proteinase, in phenytoin-induced gingival overgrowth, we established a rat model of gingival overgrowth. Thirty-two, 20-day-old male Fischer 344 rats were fed a diet containing phenytoin and sacrificed at 1, 2, 4 and 8 weeks. Control rats (n = 40) were fed the same diet, but without the drug and killed at the same weeks as experimental rats (n = 32) and 0 week (n = 8). The mandible specimens were resected and sectioned bucco-lingually between the first and second molars. A marked inflammatory-cell infiltration and elongated rete pegs were seen in the phenytoin-treated group. The extent of the overgrowth assessed by computer image analysis and the density of medullasin-positive cells by immunohistochemistry in the approximal gingiva showed a significant increase in the phenytoin-treated group compared to the control group. A marked infiltration of the positive cells in experimental rats was observed as early as 2 weeks when gingival overgrowth was not fully established. Medullasin-positive cells were mostly neutrophils and partly macrophage-like cells. These findings suggest that medullasin may be involved in mainly host defense and secondarily collagen metabolism in the phenytoin-induced rat model of gingival overgrowth.

Animals↗
PubMed2002

[Detection method for platelet activation markers].

The assessment of platelet activation levels may be useful for identifying patients who would benefit from antiplatelet therapy and prediction of ischemic events. Laboratory markers of platelet activation include activation-dependent changes in glycoprotein (GP) IIb/IIIa complex, exposure of granule membrane proteins, binding of secreted platelet proteins, and development of procoagulant surfaces. Whole blood flow cytometry is a popular and useful method for the detection of these markers of platelet activation. Monoclonal antibodies against platelet surface glycoproteins are used to identify activated platelets.

Biomarkers↗