Molecular Endocrinological Studies of Adrenomedullin in Cardiovascular

肾上腺髓质素（AM）是从人嗜铬细胞瘤组织中分离出来的一种强效血管舒张肽，结构上属于CGRP家族成员。AM的mRNA在心、肺、肾、血管壁和肾上腺髓质等多种组织中均有高表达。本课题研究了AM及其受体在心力衰竭和脓毒症中的基因表达及其病理生理意义。进一步研究了AM静脉滴注对心力衰竭大鼠和患者的影响，心肌AM在肥厚和心力衰竭中的病理生理意义，以及AM对心肌细胞和成纤维细胞的直接作用。静脉输注AM可明显改善心衰大鼠和病人的全身血流动力学、肾功能及内分泌激素。在压力和容量诱导的心肌肥厚中， 关于我们 与骨骼肌肌动蛋白、β-肌球蛋白重链等分子标记物相比，S的增加更为迅速。在培养的心肌细胞和成纤维细胞中，AM只有在内皮素-1刺激心肌细胞时才具有较弱但显著的肥大作用。AM对心肌成纤维细胞增殖和胶原合成有抑制作用。上述结果提示，AM静脉输注可能是心力衰竭的一种新的治疗手段，心肌AM可能是心肌肥厚和心力衰竭的一种新的生化标志物，脓毒症时血浆AM浓度明显升高，但其作用尚不清楚。降钙素受体样受体（CRLR）和受体活性修饰蛋白（RAMP）2或3共表达可形成肾上腺髓质素（AM）特异性受体。为了阐明小鼠AM受体的基因表达，我们克隆了小鼠AM受体组分的cDNA，并检测了CRLR和RAMP 1，2和3在脂多糖（LPS）诱导的脓毒症模型小鼠几种组织中的表达。CRLR和RAMP 2 mRNA在正常小鼠肺组织中高表达，内毒素血症小鼠肺组织CRLR和RAMP 2 mRNA表达明显降低。结果提示，健康人肺组织中AM的结合位点主要由CRLR和RAMP 2形成，而CRLR和RAMP 2的减少可能是脓毒症时血浆AM浓度升高的原因之一。相反，LPS处理显著增加肺、脾和胸腺中RAMP 3基因的表达。结果表明，脓毒症时AM受体或结合位点的分布发生了变化，提示AM在脓毒症的临床过程中起着重要作用。少

Adrenomedullin (AM) is a potent vasorelaxant peptide isolated from human pheochromocytoma tissue, and is structurally a member of CGRP family. mRNA of AM is highly expressed in several tissues including heart, lung, kidney and vascular wall as well as adrenal medulla. In this project, we have studied the gene expression of AM and its receptor(s), and also examined their pathophysiological significance in heart failure and sepsis.We have previously reported pathophysiological significance of AM in heart failure. We further investigated (1) the effects of intravenous infusion of AM in heart failure of rats and patients, (2) pathophysiological significance of myocardial AM in hypertrophy and failing heart, and (3) direct effect of AM on cultured cardiac myocytes and fibroblasts. Intravenous infusion of AM significantly improved systemic hemodynamics, renal function and endocrine hormones in heart failure of rats and patients. In pressure and volume induced hypertrophy, myocardial AM level … More s more rapidly increased compared with other molecular markers such as skeletal actin and β-myosin heavy chain. In the cultured cardiac myocytes and fibroblasts, AM had weak, but significant hypertrophic effects only when cardiac myocytes were stimulated by endothelin- 1. AM had inhibitory effects of cardiac fibroblasts proliferation and collagen production. These results suggest that intravenous infusion of AM may be a new therappeutic approach in heart failure and that myocardial AM may be a new biochemical marker in cardiac hypertrophy and failing heart.Plasma concentrations of AM are markedly increased during sepsis, but the role of AM has not been clarified. Coexpression of calcitonin receptor- like receptor (CRLR) and receptor activity modifying protein (RAMP) 2 or 3 have been reported to form the adrenomedullin (AM) specific receptor. To elucidate the gene expression of mouse AM receptor, we cloned cDNAs of mouse AM receptor components and examined the expression of CRLR and RAMP1, 2 and 3 in several tissues from mice in a sepsis model induced by lipopolysaccharide (LPS). High expression of CRLR and RAMP2 mRNA was observed in lungs of normal mice, but it was markedly decreased in endotoxemic mice. It is suggested that the abundant binding sites of AM in lungs are formed by CRLR and RAMP2 in healthy subjects, and that their reduction should contribute to the increase of plasma AM concentrations during sepsis. In contrast, LPS treatment markedly increased RAMP3 gene expression in lungs, spleen and thymus. It is revealed that the distributions of receptor or binding sites of AM are changed in sepsis, and it is suggested that AM plays distinct roles in the clinical course of this syndrome. Less