心臟衰竭是心血管疾病的死亡率主要的原因之一。阿黴素Doxorubicin (DOX)為一治療癌症的化療藥物，但其副作用會造成心肌病變最後導致心臟衰竭。DOX所引發之心臟衰竭的動物模型常被用來探討其在心臟的作用機轉及發展新的治療方法。先前研究指出當自噬作用被抑制時，DOX所引發的心肌死亡現象會被大幅下降。CCAAT/增強子結合蛋白δ --CCAAT/enhancer binding protein (C/EBP)家族中的其中一員—C/EBP δ為一轉錄因子，一般條件下，其在細胞的表現量低，但一但受到刺激，便會大量表現。在我們之前的研究中，我們發現cebpd-/-的老鼠在經過DOX的施打之後心臟的傷害相較於WT老鼠輕。在先前的研究也有指出在施予metformin 後C/EBP δ可以活化癌症細胞的自噬作用。因此，我們將研究在DOX若引發了自噬作用時，C/EBP δ在H9c2細胞株及老鼠心肌細胞所扮演的角色。我們發現在H9c2細胞株施予DOX之後，C/EBP δ的表現量會隨著AMP-activated protein kinase (AMPK)失去活性而降低，而自噬作用則會被DOX所誘發。動物實驗上，在施打了DOX之後，cebpd-/-的老鼠心肌則表現了較少的自噬作用，我們認為有其他器官的回饋調控的可能性會影響到心肌細胞自噬作用的表現。Metformin被認為是一個AMPK的活化劑，其可以拮抗C/EBP δ降低表現量的現象，並且讓細胞免於受到自噬作用甚至細胞凋亡。在AMPK的抑制劑實驗中，C/EBP δ表現量隨著AMPK或性下降而降低，因此我們認為AMPK可能是C/EBP δ的上游調控因子。在未來的研究與應用方面，應著重於動物實驗中metformin對C/EBP δ的影響，單一使用metformin或合併使用其他可調控C/EBP δ之藥物時，將能否提升DOX治療癌症病患的穩定性。

Heart failure is one of the leading causes of cardiovascular mortality in the world. Doxorubicin (DOX), though a useful medicine for chemotherapy for cancer treatment, can also induce cardiomyopathy and finally heart failure. Besides that, DOX-induced heart failure in mice is a commonly used animal model to explore the mechanism and therapeutic tools. DOX-induced autophagy in cardiomyocytes was shown to be detrimental, and inhibiting autophagy with a chemical or genetic approach dramatically attenuated DOX-induced cardiomyocyte death. C/EBP δ belongs to the CCAAT/enhancer binding protein (C/EBP) family of transcription factors. In our lab, we showed that cebpd-/- mice encountered less cardiac injury in the first 2 weeks after last doxorubicin treatment. Previous studies also characterized the role of C/EBP δ in autophagy activation by metformin treatment. Our research aim is to study the DOX-induced autophagy in H9c2 and mouse cardiomyocytes, thus to test the role of C/EBP δ in DOX-associated cardiomyopathy. We found that C/EBP δ was down-regulated in doxorubicin treatment through AMPK inactivation and led to autophagy and apoptosis increased. In animal experiment, cebpd-/- mice showed less autophagy. We consider that feedback regulation of other organs in cebpd-/- mice could control autophagy in cardiomyocyte. Metformin, as an AMPK activator, could reverse the attenuation of C/EBP δ and rescue H9c2 from autophagy then apoptosis. In AMPK inhibitor experiment, C/EBP δ was down regulated in a dosage-depend manner. This indicated that AMPK is an up-stream regulator of C/EBP δ. In future research and application, animal experiment should be focus on the regulation of C/EBP δ by metformin. In addition, we hoped to demonstrate the treatment with metformin or combined with other C/EBP δ-regulation drug would increase the stability of cancer therapy with DOX.

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