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Kazutoshi Miyashita

Publications and source records attributed to Kazutoshi Miyashita.

10 recordsLinked to original sources
PubMed2005

The neuroprotective and vasculo-neuro-regenerative roles of adrenomedullin in ischemic brain and its therapeutic potential.

Adrenomedullin (AM) is a vasodilating hormone secreted mainly from vascular wall, and its expression is markedly enhanced after stroke. We have revealed that AM promotes not only vasodilation but also vascular regeneration. In this study, we focused on the roles of AM in the ischemic brain and examined its therapeutic potential. We developed novel AM-transgenic (AM-Tg) mice that overproduce AM in the liver and performed middle cerebral artery occlusion for 20 min (20m-MCAO) to examine the effects of AM on degenerative or regenerative processes in ischemic brain. The infarct area and gliosis after 20m-MCAO was reduced in AM-Tg mice in association with suppression of leukocyte infiltration, oxidative stress, and apoptosis in the ischemic core. In addition, vascular regeneration and subsequent neurogenesis were enhanced in AM-Tg mice, preceded by increase in mobilization of CD34(+) mononuclear cells, which can differentiate into endothelial cells. The vasculo-neuro-regenerative actions observed in AM-Tg mice in combination with neuroprotection resulted in improved recovery of motor function. Brain edema was also significantly reduced in AM-Tg mice via suppression of vascular permeability. In vitro, AM exerted direct antiapoptotic and neurogenic actions on neuronal cells. Exogenous administration of AM in mice after 20m-MCAO also reduced the infarct area, and promoted vascular regeneration and functional recovery. In summary, this study suggests the neuroprotective and vasculo-neuro-regenerative roles of AM and provides basis for a new strategy to rescue ischemic brain through its multiple hormonal actions.

Adrenomedullin↗
PubMed2003

Adrenomedullin provokes endothelial Akt activation and promotes vascular regeneration both in vitro and in vivo.

We previously reported that adrenomedullin (AM), a vasodilating hormone secreted from blood vessels, promotes proliferation and migration of human umbilical vein endothelial cells (HUVECs). In this study, we examined the ability of AM to promote vascular regeneration. AM increased the phosphorylation of Akt in HUVECs and the effect was inhibited by the AM antagonists and the inhibitors for protein kinase A (PKA) or phosphatidylinositol 3-kinase (PI3K). AM promoted re-endothelialization in vitro of wounded monolayer of HUVECs and neo-vascularization in vivo in murine gel plugs. These effects were also inhibited by the AM antagonists and the inhibitors for PKA or PI3K. The findings suggest that AM plays significant roles in vascular regeneration, associated with PKA- and PI3K-dependent activation of Akt in endothelial cells, and possesses therapeutic potential for vascular injury and tissue ischemia.

Adrenomedullin↗
PubMed2003

Different differentiation kinetics of vascular progenitor cells in primate and mouse embryonic stem cells.

BACKGROUND: We demonstrated that vascular endothelial growth factor receptor 2 (VEGF-R2)-positive cells derived from mouse embryonic stem (ES) cells can differentiate into both endothelial cells and mural cells to suffice as vascular progenitor cells (VPCs). Here we examined whether VPCs occur in primate ES cells and investigated the differences in VPC differentiation kinetics between primate and mouse ES cells. METHODS AND RESULTS: In contrast to mouse ES cells, undifferentiated monkey ES cells expressed VEGF-R2. By culturing these undifferentiated ES cells for 4 days on OP9 feeder layer, VEGF-R2 expression disappeared, and then reappeared after 8 days of differentiation. We then isolated these VEGF-R2-positive and vascular endothelial cadherin (VEcadherin)-negative cells by flow cytometry sorting. Additional 5-day reculture of these VEGF-R2+ VEcadherin- cells on OP9 feeder layer resulted in the appearance of platelet endothelial cell adhesion molecule-1 (PECAM1)-positive, VEcadherin-positive, endothelial nitric oxide synthase (eNOS)-positive endothelial cells. On a collagen IV-coated dish in the presence of serum, these cells differentiated into smooth muscle actin (SMA)-positive and calponin-positive mural cells (pericytes or vascular smooth muscle cells). Addition of 50 ng/mL VEGF to the culture on a collagen IV-coated dish resulted in the appearance of PECAM1+ cells surrounded by SMA+ cells. In addition, these differentiated VEGF-R2+ cells can form tube-like structures in a 3-dimensional culture. CONCLUSIONS: Our findings indicate that differentiation kinetics of VPCs derived from primate and mouse ES cells were different. Differentiated VEGF-R2+ VEcadherin- cells can act as VPCs in primates. To seek the clinical potential of VPCs for vascular regeneration, investigations of primate ES cells are indispensable.

Animals↗
PubMed2003

Significance and therapeutic potential of the natriuretic peptides/cGMP/cGMP-dependent protein kinase pathway in vascular regeneration.

Natriuretic peptides (NPs), which consist of atrial, brain, and C-type natriuretic peptides (ANP, BNP, and CNP, respectively), are characterized as cardiac or vascular hormones that elicit their biological effects by activation of the cGMPcGMP-dependent protein kinase (cGK) pathway. We recently reported that adenoviral gene transfer of CNP into rabbit blood vessels not only suppressed neointimal formation but also accelerated reendothelialization, a required step for endothelium-dependent vasorelaxation and antithrombogenicity. Accordingly, we investigated the therapeutic potential of the NPscGMPcGK pathway for vascular regeneration. In transgenic (Tg) mice that overexpress BNP in response to hindlimb ischemia, neovascularization with appropriate mural cell coating was accelerated without edema or bleeding, and impaired angiogenesis by the suppression of nitric oxide production was effectively rescued. Furthermore, in BNP-Tg mice, inflammatory cell infiltration in ischemic tissue and vascular superoxide production were suppressed compared with control mice. Ischemia-induced angiogenesis was also significantly potentiated in cGK type I Tg mice, but attenuated in cGK type I knockout mice. NPs significantly stimulated capillary network formation of cultured endothelial cells by cGK stimulation and subsequent Erk12 activation. Furthermore, gene transfer of CNP into ischemic muscles effectively accelerated angiogenesis. These findings reveal an action of the NPscGMPcGK pathway to exert multiple vasculoprotective and regenerative actions in the absence of apparent adverse effects, and therefore suggest that NPs as the endogenous cardiovascular hormone can be used as a strategy of therapeutic angiogenesis in patients with tissue ischemia.

Animals↗
PubMed2003

Adrenomedullin promotes proliferation and migration of cultured endothelial cells.

Adrenomedullin (AM) is a vasoactive hormone which exerts its action through cyclic adenosine monophosphate(cAMP) /cAMP-dependent protein kinase (PKA) cascade and intracellular Ca2+ mobilization. Recently, evidence has accumulated that AM plays a critical role in the regulation of vascular tone, remodeling and morphogenesis. And although numerous reports have examined the action of AM on cultured vascular cells, the results have not been consistent and have depended on the experimental conditions used. Accordingly, the purpose of this study was to clarify the effect of AM on the proliferation and migration of cultured endothelial cells. Our results revealed that AM promoted the growth and migration of endothelial cells (ECs). AM significantly promoted the proliferation of human umbilical vein endothelial cells (HUVECs) (56.0 +/- 8.7% over the controls at 10(-9) mol/l) and this stimulative effect was inhibited by two AM antagonists, AM(22-52) and calcitonin gene-related peptide (CGRP) (8-37). The number of HUVECs migrated to the lower surface of the transwell apparatus was also increased dose-dependently in the AM group (30.4 +/- 4.2% over the controls at 10(-7) mol/l), and this increase was suppressed by the two AM antagonists and by two PKA antagonists, adenosine 3'5'-cyclic monophosphorothioate Rp-isomer and myristoylated protein kinase A inhibitor amide 14-22. The promoting action of AM on endothelial migration was also suppressed by LY294002, an inhibitor for phosphatidylinositol 3-kinase, but not by N(G)-nitro-L-arginine-methyl ester (L-NAME), an antagonist for nitric oxide synthase (NOS). These results indicate that AM promotes proliferation and migration of ECs via a cAMP/PKA dependent pathway and lend support to the idea that AM exerts beneficial effects on vascular regeneration and might be used as a novel therapeutic strategy for patients with vascular disease.

Adrenomedullin↗