Statin引起斑馬魚肌肉病變之研究

Abstract

HMG-CoA reductase抑制劑，又被稱為statins，被廣泛用於治療高膽固醇血症(hypercholesterolemia)。然而，這類藥物會導致一系列肌肉相關的副作用，並且副作用與用量有劑量效應 (dose-dependent) 關係。這些症狀包含較輕微的肌痛 (myalgia)、肌炎 (myositis) 及嚴重的橫紋肌溶解症 (rhabdomyolysis)。雖然橫紋肌溶解症發生的比率不高，但有報告指出，對一名肝臟移植患者同時施以Simvastatin與免疫抑制劑Rapamycin時，引發了致死性橫紋肌溶解症。 在本實驗中，我們建立了一個以statin誘發肌肉病變 (myopathy) 的斑馬魚模型。首先，比較Simvastatin、Atorvastatin和Lovastatin引發肌肉病變的效果，並選出Simvastatin進行進一步分析，發現處理時間、濃度與肌肉病變有正向關係。接著在進行Rapamycin與Simvastatin共同處理時，卻發現Rapamycin能抑制肌肉病變現象。由於Rapamycin主要的功能是抑制TOR (target of rapamycin) 的活性，為了確認其對肌肉病變的保護能力是否與TOR有關，我們另外使用morpholino (MO) 將TOR基因knockdown。結果注射tor MO的胚胎在Simvastatin處理後依舊產生肌肉病變，而對注射tor MO的胚胎以Rapamycin 與Simvastatin共同處理仍能防止肌肉病變。由此推論，Rapamycin可能不是透過抑制TOR而達到對肌肉病變的保護效果。

HMG-CoA reductase inhibitors, also known as statins, are widely used to treat hypercholesterolemia. However, they can lead to a number of dose-dependent and muscle-associated side effects, ranging from myalgia to myositis and rhabdomyolysis. The frequency of rhabdomyolysis incidence is low, however, it is reported that concomitant use of Simvastatin with Rapamycin, an immunosuppressor which inhibits TOR (target of rapamycin) activity, in liver transplant patient resulted in severe rhabdomyolysis. In this study, we generated a zebrafish statin-induced myopathy model. At first, we compare the adverse effect induced by Simvastatin, Lovastatin and Atorvastatin in zebrafish. Then, we found that Simvastatin could induce visible muscle damage in zebrafish embryos, with degree of damage proportionate to Simvastatin concentration and length of exposure. We further investigated the effect of Rapamycin and Simvastatin co-treatment on zebrafish. Surprisingly, the results showed that the muscle toxicity induced by Simvastatin can be rescued by Rapamycin. To confirm this phenomenon is related to TOR signaling, we also knocked down the zebrafish TOR gene (ztor) using splicing morpholino. However, the morphants with reduced expression of TOR still demonstrated muscle damage upon Simvastatin administration, and the effect can be blocked by Rapamycin as well. These results indicate that Rapamycin may exert its protective effect against Simvastatin-induced myopathy via a TOR-independent mechanism.