Role of Heat Shock Factor 1 in Doxorubincin-Induced Cardiotoxicity

描述（由申请人提供）：接受以阿霉素（Dox）为基础的化疗药物治疗的癌症患者发展为扩张性心肌病（DCM）和充血性心力衰竭（CHF）。DCM和CHF发展的原因已被发现是“氧化应激”和随后心肌细胞的损失，由于活性氧（ROS），由心脏中的Dox氧化还原循环产生。然而，ROS引起HF的实际机制尚不完全清楚。在我们的初步研究中，我们发现热休克因子-1 （HSF-1）被ROS激活，热休克蛋白25 （Hsp25）在dox处理的心脏中表达增加。此外，Hsp25聚集的增加及其与p53的关联被发现可反激活p53和Bax（一种促凋亡蛋白）的更高转录。这可能是Dox处理心脏心肌细胞死亡的主要途径。由于HSF-1是Hsp25的转录因子，我们假设敲除HSF-1可能保护心脏免受DOX诱导的衰竭。在本提案中，我们将使用HSF-1和Hsp25敲除小鼠作为实验动物模型来评估这一假设。目前的建议有两个具体目的。在第一个具体目标中，我们将应用小鼠心脏的高分辨率磁共振微成像（MRI） （500MHz， 11.7 T系统），在阿霉素治疗后8-10周的时间里，无创地跟踪阿霉素治疗野生型（BALB/b）、HSF-1敲除小鼠、Hsp25敲除小鼠的HF进展。核磁共振成像能够在一段时间内反复跟踪同一组动物的心脏功能。这一特定目的的结果将能够定量地确定在dox处理的WT和HSF-1或Hsp25敲除小鼠中HF的发生（或延迟）是否有任何差异。在第二个具体目标中，我们提出研究HSF-1或Hsp25敲除对Dox治疗后p53/Hsp25关联程度和Bax表达的影响。在这个特定的目的中，我们建议使用各种实验方法，如免疫沉淀、生存曲线分析、组织化学分析、p53抑制剂的应用等，来确定HSF-1或Hsp25敲除是否会减少Dox处理心脏中的Bax诱导。这一特定目的的结果将揭示Hsp25/p53通路是否是主要通路。总的来说，本研究的结果将揭示HSF-1激活和Hsp25诱导在心脏Dox治疗中的作用及其与观察到的心脏毒性的相关性。

DESCRIPTION (provided by applicant): Cancer patients, who are treated with Doxorubicin (Dox) based chemotherapeutics, develop dilated cardiomyopathy (DCM) and congestive heart failure (CHF). The cause for the development of DCM and CHF has been found to be the "oxidative stress" and subsequent loss of cardiomyocytes, due to reactive oxygen species (ROS), generated by redox cycling of Dox in the heart. However, the actual mechanism on how the ROS causes HF is not completely understood yet. In our preliminary studies we have found that heat shock factor -1 (HSF-1) is activated by the ROS and heat shock protein 25 (Hsp25) expression is increased in Dox-treated hearts. Further, increased aggregation of Hsp25 and its association with p53 was found to transactivate p53 and higher transcription of Bax, a pro-apoptotic protein. This could be a major pathway of cardiomyocyte death in Dox treated hearts. Since HSF-1 is the transcription factor for Hsp25, we hypothesize that HSF-1 knock out may protect the heart from DOX induced failure. In this proposal we will evaluate this hypothesis by using HSF-1 and Hsp25 knock out mice, as experimental animal models. The present proposal has two specific aims. In the first specific aim we will apply high resolution magnetic resonance cardiac microimaging (MRI) of mouse hearts (500MHz, 11.7 T system), to non-invasively follow the progression of HF in Dox treated wild type (BALB/b), HSF-1 knock out mice, Hsp25 knock out mice, over a period of 8-10 weeks after Dox treatment. MRI enables to repeatedly follow the cardiac function of the same group of animals, over a desired period of time. Results from this specific aim will enable to quantitatively determine whether there is any difference in the occurrence of HF (or delay) among Dox-treated WT and HSF-1 or Hsp25 knock out mice. In the second specific aim, we propose to study the effect of HSF-1 or Hsp25 knock out on the magnitude of p53/Hsp25 association and Bax expression upon treating with Dox. In this specific aim we propose to use various experimental approaches such as immunoprecipitation, survival curve analysis, histochemical analysis, application of p53 inhibitors, etc to determine whether HSF-1 or Hsp25 knock out reduces the Bax induction in Dox treated hearts. Results from this specific aim will reveal, whether Hsp25/p53 pathway is a major pathway. Overall, the results from this proposal will reveal the role of HSF-1 activation and Hsp25 induction upon Dox treatment in the heart and its relevance to the observed cardiotoxicity. PUBLIC HEALTH RELEVANCE: Cancer patients, who are treated with Doxorubicin as chemotherapeutic agent, develop serious side effects such as cardiomyopathy and congestive heart failure. This grant proposal is intended to explore whether heat shock factor 1 or Heat shock protein 25 plays any role in the observed heart failure.