Dallabrida Susan M, Ismail Nesreen S, Pravda Elke A, Parodi Emily M, Dickie Renee, Durand Ellen M, Lai Jean, Cassiola Flavia, Rogers Rick A, Rupnick Maria A
Division of Vascular Biology, Children's Hospital, Boston, Massachusetts 02115, USA.
FASEB J. 2008 Aug;22(8):3010-23. doi: 10.1096/fj.07-100966. Epub 2008 May 23.
Angiopoietins were thought to be endothelial cell-specific via the tie2 receptor. We showed that angiopoietin-1 (ang1) also interacts with integrins on cardiac myocytes (CMs) to increase survival. Because ang1 monomers bind and activate integrins (not tie2), we determined their function in vivo. We examined monomer and multimer expressions during physiological and pathological cardiac remodeling and overexpressed ang1 monomers in phenylephrine-induced cardiac hypertrophy. Cardiac ang1 levels (mRNA, protein) increased during postnatal development and decreased with phenylephrine-induced cardiac hypertrophy, whereas tie2 phosphorylations were unchanged. We found that most or all of the changes during cardiac remodeling were in monomers, offering an explanation for unchanged tie2 activity. Heart tissue contains abundant ang1 monomers and few multimers (Western blotting). We generated plasmids that produce ang1 monomers (ang1-256), injected them into mice, and confirmed cardiac expression (immunohistochemistry, RT-PCR). Ang1 monomers localize to CMs, smooth muscle cells, and endothelial cells. In phenylephrine-induced cardiac hypertrophy, ang1-256 reduced left ventricle (LV)/tibia ratios, fetal gene expressions (atrial and brain natriuretic peptides, skeletal actin, beta-myosin heavy chain), and fibrosis (collagen III), and increased LV prosurvival signaling (akt, MAPK(p42/44)), and AMPK(T172). However, tie2 phosphorylations were unchanged. Ang1-256 increased integrin-linked kinase, a key regulator of integrin signaling and cardiac health. Collectively, these results suggest a role for ang1 monomers in cardiac remodeling.
血管生成素被认为通过Tie2受体对内皮细胞具有特异性。我们发现血管生成素-1（Ang1）也与心肌细胞（CMs）上的整合素相互作用以提高细胞存活率。由于Ang1单体结合并激活整合素（而非Tie2），我们确定了它们在体内的功能。我们研究了生理和病理性心脏重塑过程中单体和多聚体的表达情况，并在苯肾上腺素诱导的心脏肥大模型中过表达Ang1单体。出生后发育过程中心脏Ang1水平（mRNA、蛋白质）升高，而苯肾上腺素诱导的心脏肥大时其水平降低，而Tie2磷酸化水平未发生变化。我们发现心脏重塑过程中的大多数或所有变化都发生在单体中，这就解释了Tie2活性为何未改变。心脏组织含有丰富的Ang1单体和少量多聚体（蛋白质免疫印迹法）。我们构建了产生Ang1单体（Ang1-256）的质粒，将其注射到小鼠体内，并证实其在心脏中的表达（免疫组织化学、逆转录-聚合酶链反应）。Ang1单体定位于心肌细胞、平滑肌细胞和内皮细胞。在苯肾上腺素诱导的心脏肥大中，Ang1-256降低了左心室（LV）/胫骨比值、胎儿基因表达（心房利钠肽、脑利钠肽、骨骼肌肌动蛋白、β-肌球蛋白重链）以及纤维化（胶原蛋白III），并增加了左心室促存活信号（Akt、丝裂原活化蛋白激酶（p42/44））和腺苷酸活化蛋白激酶（T172）。然而，Tie2磷酸化水平未发生变化。Ang1-256增加了整合素连接激酶的表达，这是整合素信号传导和心脏健康的关键调节因子。总体而言，这些结果表明Ang1单体在心脏重塑中发挥作用。
