Role of Heat Shock Factor 1 in Doxorubincin-Induced Cardiotoxicity

描述(申请人提供)：接受阿霉素(Dox)为主的化疗药物治疗的癌症患者会发展为扩张型心肌病(DCM)和充血性心力衰竭(CHF)。DCM和CHF的发生原因被认为是心脏中Dox氧化还原循环产生的活性氧(ROS)引起的氧化应激和随后的心肌细胞损失。然而，关于ROS如何引起HF的实际机制尚不完全清楚。在我们的初步研究中，我们发现在Dox治疗的心脏中，热休克因子-1(HSF-1)被ROS激活，热休克蛋白25(HSP25)的表达增加。此外，HSP25的聚集增加及其与P53的关联被发现反式激活了P53，并增加了促凋亡蛋白Bax的转录。这可能是Dox处理的心脏中心肌细胞死亡的主要途径。由于HSF-1是HSP25的转录因子，我们推测HSF-1基因敲除可能对DOX诱导的心脏衰竭具有保护作用。在这项建议中，我们将通过使用HSF-1和HSP25基因敲除的小鼠作为实验动物模型来评估这一假说。目前的建议有两个具体目标。在第一个特定目标中，我们将应用小鼠心脏的高分辨率磁共振心脏显微成像(MRI)(500 MHz，11.7T系统)，在Dox治疗后8-10周内，无创跟踪Dox治疗野生型(BALB/b)、HSF-1基因敲除小鼠、HSP25基因敲除小鼠心力衰竭的进展。核磁共振成像能够在所需的一段时间内重复跟踪同一组动物的心脏功能。这一特定目标的结果将能够定量地确定在Dox治疗的WT和HSF-1或HSP25基因敲除小鼠之间是否存在心力衰竭(或延迟)的发生。在第二个特定目标中，我们建议研究HSF-1或HSP25基因敲除对Dox处理后P53/HSP25关联和Bax表达的影响。为此，我们建议采用免疫沉淀、存活曲线分析、组织化学分析、P53抑制剂的应用等多种实验方法来确定HSF-1或HSP25基因敲除是否降低了Dox处理的心脏中Bax的诱导。这一特定目的的结果将揭示HSP25/P53通路是否是主要途径。总体而言，这项提议的结果将揭示心脏中Dox治疗时HSF-1激活和HSP25诱导的作用及其与观察到的心脏毒性的相关性。 公共卫生相关性：接受阿霉素化疗的癌症患者会出现严重的副作用，如心肌病和充血性心力衰竭。这项拨款提案旨在探索热休克因子1或热休克蛋白25是否在观察到的心力衰竭中发挥任何作用。

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.