Background-In our previous study, adrenomedullin (AM) overexpression could limit the arterial intimal hyperplasia induced by cuff injury in rats. However, it remains to be elucidated whether endogenous AM plays a role against vascular injury. Methods and Results-We used the AM knockout mice to investigate the effect of endogenous AM. Compared with wild-type (AM ϩ/ϩ ) mice, heterozygous AM knockout (AM ϩ/Ϫ ) mice had the increased intimal thickening of the cuff-injured femoral artery, concomitantly with lesser AM staining. In AM ϩ/Ϫ mice, cuff placement increased both the production of superoxide anions (O 2 Ϫ ) measured by coelentarazine chemiluminescence and the immunostaining of p67 phox and gp91 phox , subunits of NAD(P)H oxidase in the adventitia, associated with the increment of CD45-positive leukocytes, suggesting that the stimulated formation of radical oxygen species accompanied chronic adventitial inflammation. Not only the AM gene transfection but also the treatment of NAD(P)H oxidase inhibitor apocynin and membrane-permeable superoxide dismutase mimetic tempol could limit cuff-induced intimal hyperplasia in AM

Abstract-Adrenomedullin (AM) inhibits vascular smooth muscle cell proliferation stimulated by fetal calf serum and platelet-derived growth factor in vitro. In this study, an adenovirus expressing AM (AxCAAM) was created to examine the in vivo action of AM. Femoral arteries of Wistar rats were wrapped with a silicone cuff and treated with adenovirus expressing Escherichia coli ␤-galactosidase (AxCALacZ) or AxCAAM. Immunoreactivity for endothelial nitric oxide synthase (eNOS) was reduced in the endothelium of cuff-injured arteries and was associated with increased local DNA synthesis. Consequently, the intimal formation measured by the intimal-to-medial ratio was significantly increased at 14 and 28 days after the cuff placement. AxCAAM-infected arteries increased the expression of eNOS in the endothelium and inducible NOS in the media and the adventitia. AxCAAM significantly decreased the intimal-to-medial ratio by 40% at 14 days and 51% at 28 days, whereas AxCALacZ showed no changes compared with cuff-injured control arteries. AM overexpression effectively limits intimal hyperplasia by reducing cell proliferation through a nitric oxide-dependent pathway of eNOS. Key Words: adrenomedullin Ⅲ muscle, smooth, vascular Ⅲ endothelium Ⅲ nitric oxide synthase A drenomedullin (AM) was first isolated from the acid extract of human pheochromocytoma as a potent hypotensive peptide. 1 This peptide, consisting of 52 amino acids, has been shown to have several actions other than its vasodilatory effect. AM inhibits the proliferation and migration of cultured rat aortic smooth muscle cells (SMCs) and rat mesangial cells. [2][3][4] This peptide stimulates cAMP formation in cultured cells; 2,3 however, some actions are not solely through the elevation of intracellular cAMP. AM acts not only on cells of mesenchymal origin such as SMC or mesangial cells but also on other cell types. It was demonstrated that AM stimulates the proliferation of fibroblasts 5 and certain tumor cell lines. 6 Therefore, it seems that the effect of AM on mitogenesis might depend on the particular cell type. Considering that the actions of AM are so diverse, it is very important to examine the effect of AM in the setting of multicellular circumstances such as in in vivo models to further elucidate the actions of AM.Intimal thickening is an early, essential stage in the development of atherosclerotic lesions. In experimental animals, several models have been established to mimic this pathologic condition and to assess the efficacy of therapeutic strategies. Intimal thickening can be induced by balloon denudation of the endothelium, by ligation of the vessel, or by electrical injury. Recently, it has been reported that placement of a nonconstrictive cuff around an arterial segment in rodents results in a reproducible, concentric intimal hyperplasia within 14 days. 7-10 Intimal thickening induced by these techniques results from the excessive accumulation of SMC and the deposition of extracellular matrix in the intimal layer of the vessel wall. The cellular c...

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To investigate whether hyperthermic preconditioning can actually protect skin flaps against ischemia/reperfusion injury, the authors first developed a new skin-flap model in 15 mice, a dorsal bipedicle island skin-flap model. Then, another 75 mice were separated into five groups. Mice in Groups 1 to 4 received the same hyperthermic preconditioning, but had different recovery times of 6 hr, 24 hr, 48 hr, and 72 hr, respectively. Mice in Group 5 served as control. Island skin flaps were elevated in all groups, and then were subjected to 8 hr of ischemia and subsequent reperfusion. Flap survival was statistically significantly higher than in controls in animals in Groups 1 and 3, with recovery times of 6 hr and 48 hr, respectively. Mice in Groups 2 and 4 had recovery times of 24 hr and 72 hr, respectively. Hyperthermic preconditioning could thus protect skin flaps against ischemia/reperfusion injury, and there were two optimal periods for such a protective effect.

P190 Objectives Adrenomedullin(AM) is not only a potent vasodilator but also regulates several hormone release such as aldosterone, NO and also regulates inflammatory reactions. In order to clarify its physiological role, we generated AM knock-out mouse and investigated its cardiac and vascular changes. Method A point mutation to stop AM translation were induced and by conventional method, AM knock-out mouse was generated. As homozygote was lethal we used heterozygote for this study. In heterozygote plasma and tissue AM level were as half as wild type. Angiotensin II were continuously administered and 8% NaCl diet were loaded to 8 weeks old male heterozygote and wild type for 2 weeks. In some mice, we wrapped silicone tube around the femoral artery and transferred adrenomedullin gene via adenovirus vector topically. Blood pressure were monitored by tail cuff method. After 2 weeks, heart weight were measured and pathological changes were observed. Results Baseline SBP were comparable between heterozygote and wild type (150±10 mmHg vs 142±8 mmHg). One week after angiotensin II and salt loading both mice increased blood pressure to 170±9 mmHg in heterozygote and 168±10 mmHg in wild type. At the end of the study SBP of heterozygote were 160±13 mmHg and that of wild type were 173±9 mmHg. Heart weight/BW were significantly larger in heterozygote (0.0068±0.0003) than in wild (0.0061±0.0002). Perivascular area of coronary artery from heterozygote was full of inflammatory cells and fibrosis. In severe case, coronary aretery showed fibrinoid necrosis. These findings were not found in kidney or other arterioles.The femoral artery from heterozygote showed marked medial proliferation and stenosis compared to wild type. And this change was rescued by AM administration. Conclusion AM is protective against coronary artery injury and cardiomegaly.