Wang X, Yue T L, Barone F C, White R F, Clark R K, Willette R N, Sulpizio A C, Aiyar N V, Ruffolo R R, Feuerstein G Z
Department of Cardiovascular Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406, USA.
Proc Natl Acad Sci U S A. 1995 Dec 5;92(25):11480-4. doi: 10.1073/pnas.92.25.11480.
Focal brain ischemia is the most common event leading to stroke in humans. To understand the molecular mechanisms associated with brain ischemia, we applied the technique of mRNA differential display and isolated a gene that encodes a recently discovered peptide, adrenomedullin (AM), which is a member of the calcitonin gene-related peptide (CGRP) family. Using the rat focal stroke model of middle cerebral artery occlusion (MCAO), we determined that AM mRNA expression was significantly increased in the ischemic cortex up to 17.4-fold at 3 h post-MCAO (P < 0.05) and 21.7-fold at 6 h post-MCAO (P < 0.05) and remained elevated for up to 15 days (9.6-fold increase; P < 0.05). Immunohistochemical studies localized AM to ischemic neuronal processes, and radioligand (125I-labeled CGRP) displacement revealed high-affinity (IC50 = 80.3 nmol) binding of AM to CGRP receptors in brain cortex. The cerebrovascular function of AM was studied using synthetic AM microinjected onto rat pial vessels using a cranial window or applied to canine basilar arteries in vitro. AM, applied abluminally, produced dose-dependent relaxation of preconstricted pial vessels (P < 0.05). Intracerebroventricular (but not systemic) AM administration at a high dose (8 nmol), prior to and after MCAO, increased the degree of focal ischemic injury (P < 0.05). The ischemia-induced expression of both AM mRNA and peptide in ischemic cortical neurons, the demonstration of the direct vasodilating effects of the peptide on cerebral vessels, and the ability of AM to exacerbate ischemic brain damage suggests that AM plays a significant role in focal ischemic brain injury.
局灶性脑缺血是导致人类中风的最常见事件。为了解与脑缺血相关的分子机制，我们应用了mRNA差异显示技术，分离出一个编码最近发现的肽——肾上腺髓质素（AM）的基因，肾上腺髓质素是降钙素基因相关肽（CGRP）家族的成员。利用大鼠大脑中动脉闭塞（MCAO）局灶性中风模型，我们确定，在MCAO后3小时，缺血皮层中AM mRNA表达显著增加，高达17.4倍（P < 0.05），在MCAO后6小时增加21.7倍（P < 0.05），并持续升高长达15天（增加9.6倍；P < 0.05）。免疫组织化学研究将AM定位于缺血性神经元突起，放射性配体（125I标记的CGRP）置换显示AM与大脑皮层中的CGRP受体具有高亲和力结合（IC50 = 80.3 nmol）。使用合成AM通过颅窗微量注射到大鼠软脑膜血管上或体外应用于犬基底动脉，研究了AM的脑血管功能。从管腔外施加的AM产生了剂量依赖性的预收缩软脑膜血管舒张（P < 0.05）。在MCAO之前和之后，以高剂量（8 nmol）脑室内（而非全身）给予AM，增加了局灶性缺血损伤的程度（P < 0.05）。缺血诱导缺血性皮层神经元中AM mRNA和肽的表达，该肽对脑血管的直接舒张作用的证明，以及AM加重缺血性脑损伤的能力表明，AM在局灶性缺血性脑损伤中起重要作用。
