Targeting Inflammation for the Amelioration of Cisplatin-Hearing Loss

描述(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。顺铂的耳毒性是不可逆转的，对儿科人群尤其是创伤，因为它阻碍了他们的沟通技能和社会发展。顺铂在以铂为基础的化疗中是独一无二的，它对许多不同的癌症具有广泛的活性，而卡铂和奥沙利铂的活性更有限。顺铂的持续临床应用表明，除非做出实质性努力来开发有效的耳保护疗法，否则耳毒性仍将是一个问题。目前的一种治疗策略是使用抗氧化剂来减少活性氧物种(ROS)，ROS已被认为与顺铂的耳毒性有关。虽然这种方法提供了耳部保护，但有人担心抗氧化剂可能会限制顺铂的疗效。其他治疗方法以参与细胞凋亡的蛋白质为靶点，这些蛋白质有助于外毛细胞(OHC)的死亡。然而，抑制caspase、p53或激活DNA修复酶可能会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与肿瘤发生无关的ROS产生或下游信号分子的来源，并利用局部(鼓室内)传递耳保护剂。我们已经确定了两个这样的分子，即NADPH氧化酶亚型NOX3(耳蜗内ROS产生的主要来源)和瞬时受体电位香草素1通道(与顺铂耳毒性有关)。这些蛋白质的敲除减少了对内皮层细胞的损害，并减少了顺铂引起的听力损失。我们实验室的最新发现表明，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基因的敲除减少了炎症基因(如肿瘤坏死因子-a)的表达，并对顺铂诱导的听力损失具有保护作用。这导致了一种假设，即炎症是顺铂引起的耳毒性的重要组成部分。此外，我们认为STAT1是NOX3和TRPV1的下游靶点，因此是耳科保护药物的新靶点。该项目的总体目标是研究STAT1在顺铂耳毒性中的作用，并确定它是否代表了耳保护治疗的可行靶点。具体地说，我们将(1)确定STAT1激活ROS的机制(S)，(2)更详细地表征鼓室内注射STAT1siRNA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，以及(4)确定鼓室内注射肿瘤坏死因子-α的选择性抑制剂(依那西普)是否具有对抗顺铂耳毒性的作用。总体而言，这项研究获得的数据将扩大我们对耳蜗中STAT1激活的理解，并为靶向该转录因子对抗顺铂耳毒性和其他形式的听力损失提供理论基础。我们的发现有望直接应用于癌症患者听力损失的治疗。 公共卫生相关性：目前的研究方案侧重于临床上观察到的接受抗癌药物顺铂治疗的患者的听力损失。我们实验室的研究表明，顺铂会在内耳产生炎症，导致负责内耳声音传输的细胞死亡。我们将测试抗炎药直接通过鼓膜给药时，对顺铂介导的听力损失的保护能力。我们相信，从这项研究中获得的信息将导致潜在的治疗听力损失的新方法。

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.