Yasuhiko Miyazaki

Platelet-derived microparticles may influence the development of atherosclerosis in diabetes mellitus.

We investigated the association between low-density lipoprotein (LDL), triglycerides, and platelet activation in 18 patients with hypertension age 41-64 years and 18 with diabetes mellitus aged 43-70 years. Platelet P-selectin positivity and the microparticle level (indicators of activation) were both significantly higher in the diabetics than in healthy controls (P-selectin: 28.0% +/- 7.5% vs. 7.3% +/- 4.2%, P < 0.001; microparticles: 1900 +/- 966 vs. 526 +/- 158/10(4) platelets, P < 0.01). In contrast, there was no significant increase of either parameter in the patients with hypertension. Plasma microparticle levels were also significantly greater in the diabetics with high LDL levels than in those with low LDL levels (2375 +/- 949 vs. 1519 +/- 796/10(4) platelets, P < 0.05), and in those with high rather than low triglyceride levels (2188 +/- 845 vs. 1492 +/- 783/10(4) platelets, P < 0.05). However, platelet positivity for P-selectin was not significantly different between these two subgroups. Microparticle and P-selectin levels both showed no significant difference between the hypertensive patients with high and low LDL or triglyceride levels. These results suggest that platelet-derived microparticles may participate in the development or progression of atherosclerosis in patients with diabetes mellitus.

Expression of Functional Tissue Factor on Small Vesicles of Lipopolysaccharide- Stimulated Human Vascular Endothelial Cells

We examined tissue factor expression on lipopolysaccharide-stimulated endothelial cells and their small vesicles by using specific antibodies and flow cytometry. Tissue factor functional activity was also assessed by activation of factor X. Endothelial cells were stimulated with 10 microg/ml of lipopolysaccharide in M-199/bovine serum albumin. Flow cytometry showed that expression of tissue factor on endothelial cells reached a maximum at 6 hours after stimulation, whereas that on small vesicles reached a maximum after 12 hours. Factor X activation mediated by factor VIIa and tissue factor was observed over a similar time course and was inhibited by the addition of antitissue factor antibody. Immunoelectron microscopy suggested that small vesicles with expression of some tissue factor were produced from the surface of endothelial cells. Our findings thus showed that tissue factor on endothelial cells produced by lipopolysaccharide stimulation was partly released to small vesicles. This may cause disseminated intravascular coagulation and related coagulation disorders.

Relationship of microparticles withβ2-glycoprotein I and P-selectin positivity to anticardiolipin antibodies in immune thrombocytopenic purpura

We investigated the association ofβ2-glycoprotein I and P-selectin with platelet-derived microparticles in 48 patients with immune thrombocytopenic purpura and 20 normal controls using two-color flow cytometric analysis. In addition, anticardiolipin antibodies were detected by an enzyme-linked immunosorbent assay. Platelet microparticles from the patients showed a higher positivity forβ2-glycoprotein I than those from the normal controls (23.1±15.4% vs. 5.3±3.1%, p<0.01), but this positivity was not related to the presence of platelet-associated IgG or to the severity of thrombocytopenia. In the 18 patients with more than 20% P-selectin-positive microparticles,β2-glycoprotein I positivity was significantly higher than in the 30 patients with less than 20% P-selectin-positive microparticles (37.1±20.5% vs. 21.5±17.3%, p<0.01). In addition, anticardiolipin antibodies were detected in eight patients, and they had a significantly higher level ofβ2-glycoprotein I-positive microparticles than the patients without such antibodies (42.0±22.9% vs. 22.6±18.9%, p<0.05). Our results suggest that anticardiolipin antibodies activate platelets in immune throm bocytopenic purpura and cause the generation of microparticles rich inβ2-glycoprotein I and P-selectin. These microparticles may then act to regulate coagulation abnormalities in patients with anticardiolipin antibodies.

Participation of αIIbβ3 in platelet microparticle generation by collagen plus thrombin

We investigated the role of αIIbβ3 in microparticle generation by normal and thrombasthenic platelets stimulated with collagen plus thrombin. Microparticle generation by normal p

Significance of cytokines and CD68‐positive microparticles in immune thrombocytopenic purpura

Abstract: We investigated the significance of cytokines (soluble interleukin‐2 receptor, granulocyte‐macrophage colony‐stimulating factor, interleukin‐6, and interferon‐gamma) and CD68‐positive microparticles in immune thrombocytopenic purpura. Cytokines were measured by enzyme‐linked immunosorbent assay and microparticles were detected by flow cytometry. CD68 expression by histiocytic U937 cells incubated with lipopolysaccharide or cytokines was also assessed in a control study. The level of CD68‐positive microparticles was significantly higher in the patients with thrombocytopenia than in normal controls (p<0.01). The soluble interleukin‐2 receptor level was also significantly higher in patients than in controls (p<0.01), but the other cytokines did not show a significant difference. However, patients with severe thrombocytopenia (platelet count >20000/μl) had significantly higher levels of granulocyte‐macrophage colony‐stimulating factor and interleukin‐6 than the controls (p<0.05). When opsonized platelets were incubated with activated U937 cells, lipopolysaccharide and granulocyte‐macrophage colony‐stimulating factor caused an increase of CD68‐positive microparticles in the supernatant. These results suggest that granulocyte‐macrophage colony‐stimulating factor is released by activated T cells in immune thrombocytopenic purpura and activates monocyte/macrophage phagocytosis, resulting in an increase of circulating CD68‐positive microparticles and enhanced platelet destruction.

Membranous Nephropathy Associated with Donor Lymphocyte Infusion following Allogeneic Bone Marrow Transplantation

Nephrotic syndrome after hematopoietic stem cell transplantation (HSCT) followed by donor lymphocyte infusion (DLI) has never been described. We report the case of a myelodysplastic syndrome (MDS) patient who developed nephrotic syndrome with membranous nephropathy 18 months after allogeneic HSCT and 4 months after DLI. A 50-year-old woman with MDS underwent allogeneic bone marrow transplantation from her HLA-matched brother. MDS relapsed 55 days after transplantation, donor lymphocytes were infused as adoptive immunotherapy, and complete remission was achieved. Four months after the third DLI, the patient developed nephrotic syndrome with proteinuria up to 9 g/day. Renal biopsy revealed granular deposits of immunoglobulin G along the glomerular basement membrane, and subepithelial electron-dense deposits. A diagnosis of membranous nephropathy was made. For maintenance of the immunotherapeutic effect of DLI, minimum doses of immunosuppressive therapy for decreasing proteinuria were administered, and improvement of nephrotic syndrome and persistent complete remission of MDS were achieved.

Platelet-derived microparticles in alloxan-induced diabetes in rabbits.

To study platelet-derived microparticle generation in diabetes mellitus, we injected alloxan into male Japanese white rabbits. Injection of alloxan induced diabetes, but did not cause any significant change in various biochemical and hematological parameters. However, diabetic rabbits showed a significant elevation of platelet-derived microparticles from 8 weeks after alloxan injection (week 0: 0.45 +/- 0.24%; week 8: 1.12 +/- 0.61%, p < 0.005). These microparticles are known to have prothrombinase activity, suggesting that they may promote vascular complications in diabetes and may be used as a marker of vascular disease.

EFFECT OF CEPHARANTHIN AND CYTOCHALASIN D ON PLATELET INTERNALIZATION OF ANTI-GLYCOPROTEIN IIb/IIIa ANTIBODIES

The effects of cepharanthin and cytochalasin D on the internalization of anti-glycoprotein IIb/IIIa antibodies by platelets were investigated in 13 patients with chronic immune thrombocytopenic purpura who had circulating anti-glycoprotein IIb/IIIa autoantibodies. Unfixed platelets were incubated with a monoclonal anti-glycoprotein IIb/IIIa antibody (NNKY1-32) or with platelet-binding IgG from the patients (which contained anti-glycoprotein IIb/IIIa antibodies). Flow cytometry showed that the binding of NNKY1-32 to platelets was markedly decreased after incubation for 120 min compared with incubation for 10 min. This decrease was inhibited by cepharanthin but not by cytochalasin D. Platelet-binding IgG also showed markedly reduced binding after incubation for 120 min compared with 10 min, and this decrease was inhibited by both cepharanthin and cytochalasin D. Cytochalasin D inhibits platelet cytoskeletal activity while cepharanthin does not. Therefore, our results suggest that the internalization of anti-glycoprotein IIb/IIIa antibodies from the plasma of patients with immune thrombocytopenic purpura is related to platelet cytoskeletal reorganization, while the cytoskeleton did not participate in internalization of the monoclonal anti-glycoprotein IIb/IIIa antibody (NNKY1-32). Cepharanthin may be useful for studying the internalization and cycling of glycoprotein IIb/IIIa in human platelets, and it may also be potentially useful for the treatment of immune thrombocytopenic purpura.

Expression of prothrombinase activity and CD9 antigen on the surface of small vesicles from stimulated human endothelial cells

We employed flow cytometry and monoclonal antibodies (MoAb) to study the surface membrane protein of shed particles (small vesicles, SV) that were released from vascular endothelial cells (EC) by agonists such as a Ca ionophore (A23187) and thrombin. After stimulation of EC by A23187, CD9 antigens disappeared entirely from the EC surface in a time- and concentration-dependent manner; they subsequently moved onto the SV surface. Von Willebrand factor (vWF) and P-selectin from Weibel-Palade (W-P) bodies were expressed rapidly on the EC surface after thrombin stimulation, but not on the SV surface. P-selectin may have some effect on maintenance of hemostasis on the EC surface. We demonstrated that the surfaces of SV and EC significantly supported prothrombinase activity and confirmed that A23187-induced SV from EC express binding sites for factors IXa and Xa. These results suggest that the SV are an important factor in a novel controlling mechanism of the coagulation system on the EC surface.

Relationship between HMGB1 and PAI-1 after allogeneic hematopoietic stem cell transplantation

Background Conditioning regimens including total body irradiation (TBI) or cyclophosphamide can mobilize high-mobility group box 1 (HMGB1) to peripheral blood. Additionally, increased plasminogen activator inhibitor (PAI)-1 levels are associated with post-allogeneic hematopoietic stem cell transplantation (aHSCT). However, changes to circulating levels of HMGB1 after aHSCT are poorly understood. Materials and methods The study cohort included 289 patients who underwent aHSCT at one of 25 institutions in Japan. We have investigated the relationship between HMGB1 and PAI-1 following aHSCT. A significant increase in HMGB1 levels occurred after conditioning treatment. Additionally, levels of HMGB1 at day 0 were significantly increased in TBI+ patients and cyclophosphamide/TBI patients. Conclusion Our data revealed that an increased level of HMGB1 at day 0 following aHSCT correlates with increased PAI-1 after aHSCT, which is consistent with previous reports. Increased HMGB1 at day 0 after a conditioning regimen may play a role in transplantation-associated coagulopathy following aHSCT, because PAI-1 can accelerate procoagulant activity.