Targeting Inflammation for the Amelioration of Cisplatin-Hearing Loss

描述（由申请人提供）：耳毒性是顺铂的常见副作用，顺铂是一种广泛用于治疗各种实体肿瘤的药物。顺铂耳毒性是不可逆的，对儿科人群尤其具有创伤性，因为它阻碍了他们的沟通技巧和社会发展。与卡铂和奥沙利铂的有限活性相比，顺铂在铂基化疗中具有广泛的抗多种不同癌症的活性，这在铂基化疗中是独一无二的。顺铂的持续临床使用表明，耳毒性将继续是一个问题，除非采取实质性的努力来开发有效的耳保护疗法。目前的一种治疗策略是使用抗氧化剂来减少活性氧（ROS），这与顺铂耳毒性有关。虽然这种方法提供了耳部保护，但人们担心抗氧化剂可能会限制顺铂的疗效。其他治疗方法针对参与细胞凋亡的蛋白，导致外毛细胞（OHCs）死亡。然而，抑制caspase、p53或激活DNA修复酶可能促进肿瘤的发展或促进肿瘤的化疗耐药。更合理的方法应该针对ROS产生的来源或与肿瘤发生无关的下游信号分子，并利用耳保护剂的局部（鼓室内）递送。我们已经确定了两个这样的分子，即NADPH氧化酶异构体，NOX3（耳蜗中ROS生成的主要来源）和瞬时受体电位香草样蛋白1通道（与顺铂耳毒性有关）。这些蛋白的敲除减少了ohc的损伤，减少了顺铂引起的听力损失。我们实验室最近的研究结果表明，TRPV1和NOX3可以增加信号转导和转录激活因子（STAT1）的活性，STAT1是炎症的重要介质。STAT1的敲低降低了炎症基因（如TNF-a）的表达，并防止顺铂引起的听力损失。这导致了炎症是顺铂诱导耳毒性的一个重要组成部分的假设。此外，我们提出STAT1是NOX3和TRPV1的下游靶点，因此代表了耳保护药物的新靶点。该项目的总体目标是研究STAT1在顺铂耳毒性中的作用，并确定STAT1是否代表耳保护治疗的可行靶点。具体来说，我们将(1)确定ROS激活STAT1的机制，(2)更详细地表征鼓室内注射STAT1 siRNA抑制顺铂诱导的听力损失的能力，(3)确定顺铂诱导的炎症基因的表达谱，(4)确定鼓室内注射TNF-a选择性抑制剂（依那西普）是否可以防止顺铂耳毒性。总的来说，从本研究中获得的数据将扩大我们对耳蜗中STAT1激活的理解，并为靶向这种转录因子对抗顺铂耳毒性和其他形式的听力损失提供依据。我们的研究结果有望直接转化应用于癌症患者听力损失的治疗。

DESCRIPTION (provided by applicant): Ototoxicity is a common side effect of cisplatin, a drug widely used for the treatment of a various solid tumor. Cisplatin ototoxicity is irreversible and is especially traumatic for the pediatric population since it hampers their communication skills and social development. Cisplatin is unique among platinum-based chemotherapy by having a broad spectrum of activity against a number of different cancers compared to more limited activity for carboplatin and oxaliplatin. The continued clinical use of cisplatin suggests ototoxicity will continue to be a problem unless a substantial effort is undertaken to develop effective otoprotective therapies. One current treatment strategy uses antioxidants to decrease reactive oxygen species (ROS), which has been implicated in cisplatin ototoxicity. While this approach provides otoprotection, there are concerns that antioxidants could limit the efficacy of cisplatin. Other treatment approaches target proteins involved in apoptosis which contribute to death of outer hair cells (OHCs). However, inhibition of caspases, p53, or activation of DNA repair enzymes may promote the development of tumors or promote tumor chemoresistance. A more rational approach should target the source of ROS generation or downstream signaling molecules which are not linked to oncogenesis and utilize localize (intra-tympanic) delivery of otoprotective agents. We have identified two such molecules, namely the NADPH oxidase isoform, NOX3 (a major source of ROS generation in the cochlea) and transient receptor potential vanilloid 1 channel (implicated in cisplatin ototoxicity). Knockdown of these proteins reduced damage to OHCs and reduced hearing loss induced by cisplatin. Recent findings from our laboratories indicate that TRPV1 and NOX3 can increase the activity of signal transducers and activators of transcription (STAT1), an important mediator of inflammation. Knockdown of STAT1 reduced the expression of inflammatory genes (such as TNF-a) and protected against cisplatin-induced hearing loss. This has led to the hypothesis that inflammation is a significant component of cisplatin-induced ototoxicity. Furthermore, we proposed that STAT1 is a downstream target of NOX3 and TRPV1 and thereby represents a novel target for otoprotective drugs. The overall goal of this project is to examine a role of STAT1 in cisplatin ototoxicity and determine whether it represents a viable target for otoprotective therapies. Specifically, we will (1) determine the mechanism(s) underlying ROS activation of STAT1, (2) characterize in more detail the ability of intra-tympanic injection of STAT1 siRNA to inhibit cisplatin-induced hearing loss, (3) determine the expression profile of inflammatory genes induced by cisplatin and (4) to determine whether intra-tympanic injection of a selective inhibitor of TNF-a (etanercept) protects against cisplatin ototoxicity. Overall, the data obtained from this study would expand our understanding of STAT1 activation in the cochlea and provide the rationale for targeting this transcription factor for combating cisplatin ototoxicity and other forms of hearing loss. Our findings are expected to have direct translational application to the treatment of hearing loss in cancer patients. PUBLIC HEALTH RELEVANCE: The current research proposal focuses on hearing loss observed clinically in patients being treated with the anticancer drug, cisplatin. Research from our laboratory indicates that cisplatin produces inflammation in the inner ear and this leads to death of cells responsible for transmission of sound in the inner ear. We will test the ability of anti-inflammatory agents to protect against cisplatin-mediated hearing loss when administered directly through the ear drum. We believe the information gained from this study will lead to potentially new treatments for treating hearing loss.