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

Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, 54 Shogoin Kawahara-cho Sakyo-ku, Japan.
FEBS Letters (Impact Factor: 3.58). 07/2003; 544(1-3):86-92. DOI: 10.1016/S1567-5688(03)90843-9
Source: PubMed

ABSTRACT 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.

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    ABSTRACT: Adrenomedullin (ADM) is an endogenous peptide first identified as a strong vasodilating molecule. We previously showed that in mice, homozygous knockout of ADM (ADM(-/-)) or its receptor regulating protein, RAMP2 (RAMP2(-/-)), is embryonically lethal due to abnormal vascular development, thereby demonstrating the importance of ADM and its receptor signaling to vascular development. ADM expression in the retina is strongly induced by ischemia; however, its role in retinal pathophysiology remains unknown. Here, we analyzed oxygen-induced retinopathy (OIR) using heterozygous ADM and RAMP2 knockout mice models (ADM(+/-) or RAMP2(+/-), respectively). In addition, we analyzed the role of the ADM-RAMP2 system during earlier stages of retinal angiogenesis using an inducible endothelial cell-specific RAMP2 knockout mouse line (DI-E-RAMP2(-/-)). Finally, we assessed the ability of antibody-induced ADM blockade to control pathological retinal angiogenesis in OIR. In OIR, neovascular tufts, avascular zones, and hypoxic areas were all smaller in ADM(+/-) retinas compared with wild-type mice. ADM(+/-) retinas also exhibited reduced levels of VEGF and eNOS expression. DI-E-RAMP2(-/-) showed abnormal retinal vascular patterns in the early stages of development. However, ADM enhanced the proliferation and migration of retinal endothelial cells. Finally, we found intravitreal injection of anti-ADM antibody reduced pathological retinal angiogenesis. In conclusion, the ADM-RAMP2 system is crucially involved in retinal angiogenesis. ADM and its receptor system are potential therapeutic targets for controlling pathological retinal angiogenesis.
    American Journal Of Pathology 04/2013; · 4.52 Impact Factor
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    ABSTRACT: To investigate the roles of an adrenomedullin receptor antagonist (adrenomedullin22-52) on high-glucose-induced human retinal endothelial cell (HREC) in vitro cell biology. HRECs were cultured with different concentrations of glucose and adrenomedullin22-52. The proliferation of HRECs was evaluated by a cell counting kit-8 assay. Cell migration was assessed by scratch wound assay, and cell sprouting was detected by tube formation assay. The mRNA levels of adrenomedullin (ADM), vascular endothelial growth factor (VEGF), ADAMTS-1, and TSP-1 were measured by reverse-transcription polymerase chain reaction (RT-PCR). The VEGF and phosphatidylinositol 3' kinase (PI3K) pathway protein expression levels were assessed by western blot analysis. Compared with 5 mM normal glucose treatment, 30 mM glucose significantly promoted the migration of HRECs, which was attenuated by 1 μg/ml adrenomedullin22-52. The proliferation of HRECs was also suppressed by 1 μg/ml adrenomedullin22-52. Furthermore, compared with other groups, 5 μg/ml of adrenomedullin22-52 was shown to suppress high-glucose-induced tube formation of HRECs. With adrenomedullin22-52 treatment, the mRNA level of ADAMTS-1 was significantly increased. Moreover, western blot and RT-PCR analyses showed that HRECs treated with 30 mM glucose exhibited increased VEGF and PI3K pathway protein levels, while the expression levels were suppressed by 5 μg/ml of adrenomedullin22-52. Our study indicated that adrenomedullin22-52 mediated the migration, proliferation and tube formation after HRECs were exposed to high levels of glucose, which may be related to its ability to affect the expression of VEGF through the PI3K pathway.
    Molecular vision 01/2014; 20:259-69. · 1.99 Impact Factor
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    ABSTRACT: The anti-inflammatory peptide, adrenomedullin (AM), and its cognate receptor are expressed in lung tissue, but its pathophysiological significance in airway inflammation is unknown. This study investigated whether allergen-induced airway inflammation involves an impaired local AM response. Airway AM expression was measured in acute and chronically sensitized mice following allergen inhalation and in airway epithelial cells of asthmatic and nonasthmatic patients. The effects of AM on experimental allergen-induced airway inflammation and of AM on lung epithelial repair in vitro were investigated. Adrenomedullin mRNA levels were significantly (P < 0.05) reduced in acute ovalbumin (OVA)-sensitized mice after OVA challenge, by over 60% at 24 h and for up to 6 days. Similarly, reduced AM expression was observed in two models of chronic allergen-induced inflammation, OVA- and house dust mite-sensitized mice. The reduced AM expression was restricted to airway epithelial and endothelial cells, while AM expression in alveolar macrophages was unaltered. Intranasal AM completely attenuated the OVA-induced airway hyperresponsiveness and mucosal plasma leakage but had no effect on inflammatory cells or cytokines. The effects of inhaled AM were reversed by pre-inhalation of the putative AM receptor antagonist, AM ((22-52)) . AM mRNA levels were significantly (P < 0.05) lower in human asthmatic airway epithelial samples than in nonasthmatic controls. In vitro, AM dose-dependently (10(-11) -10(-7) M) accelerated experimental wound healing in human and mouse lung epithelial cell monolayers and stimulated epithelial cell migration. Adrenomedullin suppression in T(H) 2-related inflammation is of pathophysiological significance and represents loss of a factor that maintains tissue integrity during inflammation.
    Allergy 06/2012; 67(8):998-1006. · 5.88 Impact Factor

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