探討Aliskiren對心肌梗塞的保護效果

Abstract

心肌梗塞 (myocardial infarction, MI)已經成為現代化國家最主要的健康問題之一，根據世界衛生組織在2011年的報告指出，每年約有570萬人死於心肌梗塞。Aliskiren是一個腎素的抑制劑（direct renin inhibitor, DRI），由瑞士藥廠Novartis所開發的抗高血壓藥，在2007由美國FDA核准上市。近年來一些研究指出Aliskiren可以減緩心肌梗塞後心臟傷害的情形，但詳細機制仍尚未明瞭，因此我們在此論文中，探討Aliskiren對於心肌梗塞後心臟的保護作用與其相關的機轉。我們使用8到12週大的C57BL/6小鼠，藉由結紮心臟的左前降支冠狀動脈(left anterior descending coronary artery, LAD)做為心肌梗塞的動物模式。動物被分為三組:(1)控制組，(2)心肌梗塞組，(3)Aliskiren治療組(劑量為經由皮下注射25 mg/kg/day)。在術前，術後1、3、7與14天，使用心臟超音波進行短軸掃瞄，測量FS (fractional shortening)%與EF (ejection fraction)%，以評估小鼠的心臟功能。結果顯示FS%會33.4±5.2% (控制組)下降到9.7±0.8% (MI後14天)，EF%也會從62.2±7.3%下降至21.4±1.5%，但Aliskiren治療組可以顯著的恢復MI後14天的心功能(FS%=16.9±0.5%，EF%=35.4±1.1%)。另外，心臟纖維化的面積與TGF-β表現量相對於心肌梗塞組，Aliskiren治療組都會比較低；TUNEL assay 也證明Aliskiren治療組會有較少的細胞凋亡數目。使用免疫組織化學染色法標定血管內皮細胞，結果顯示隨著心肌梗塞後的天數增加，心臟組織中微血管的數量會顯著減少，Aliskiren治療組則會有恢復的趨勢。進一步不論在動物模式與細胞模式中，可以觀察使用Aliskiren處理組，其細胞自噬量比傷害組皆會顯著的增加，同時經由細胞實驗證實細胞自噬量的增加是透過活化AMPK的訊息傳遞。綜合我們的實驗結果， Aliskiren是一有潛能當為抑制心肌梗塞惡化的有效藥物。

Myocardial infarction (MI) is a major health problem and the leading cause of death and disability in both industrialized and developing nations. According to the report from World Health Organization (WHO), it showed that there were 5.7 million people died from MI in 2011. The efficacy of Aliskiren, a direct renin inhibitor (DRI), is first to develope as an antihypertensive drug. Several studies have indicated that Aliskiren treatment may attenuate cardiac remodeling after MI. However, the mechanisms remain unclear. Here we investigated the protective effects of Aliskiren and elucidated its related mechanism. Myocardial infarction (MI) was induced in 8 to 12-week old C57BL/6 mice by ligating the left descending coronary artery. After MI, mice were randomly divided into 3 groups: (1) the control group, (2) the MI group, and (3) the Aliskiren treated group (25 mg/kg/day via subcutaneous injection). The trans- thoracic echocardiographic assay was performed before surgery, and at 1, 3, 7, and 14 days after MI with a dynamically focused 40 MHz linear-array transducer (Prospect, S-Sharp, Taipei, Taiwan). M-mode tracings were recorded from the short axis at the level of the papillary muscle in the left ventricle. The percentages of fractional shortening (FS%) and the ejection fraction (EF%) were measured. FS% reduced from 33.4±5.2% (control mice) to 9.7±0.8% (14 days after MI) and EF% decreased from 62.2±7.3% to 21.4±1.5%, respectively. But the Aliskiren-treated group showed a significant improvement of cardiac function at 14 days after MI. (FS% and EF% are increased to 16.9±0.5% and 35.4±1.1%, respectively). Furthermore, fibrosis area and TGF-β expression were lowered in Aliskiren-treated group compared to those in MI group. The decreased number of apoptotic cells was also observed in Aliskiren-treated group by TUNEL assay. In addition, the capillary density in Aliskiren-treated group was higher than in MI group by immunohistochemistry. We also found that the level of autophagy was upregulated in Aliskiren-treated group in vitro and in vivo. The increased autophagy was mediated by the activation of AMPK. Based on these findings, Aliskiren could be served as an effective drug for the prevention of the progression of myocardial infarction.