Mechanisms of Sensory Hair Cell Survival and Death

我们的基础科学研究集中在毛细胞应激所激活的信号转导和细胞间通讯通路上。我们之前研究了热休克蛋白(HSPs)在促进应激下毛细胞存活方面的作用。我们发现，HSP诱导是内耳的一种关键应激反应，可以保护毛细胞免受主要应激的影响，包括暴露于两种耳毒性药物(即氨基糖苷类抗生素和顺铂)。我们发现HSP表达的促生存诱导在毛细胞中相对较低，在支持细胞和驻留巨噬细胞中更强劲。这些数据表明，毛细胞在应激反应中诱导自主促生存信号的能力可能降低，当毛细胞处于应激状态时，来自支持细胞和巨噬细胞的非自主信号发挥着促生存信号的关键中介作用。 我们之前已经证明，神经胶质样支持细胞在应激诱导的反应中分泌HSP70，保护毛细胞免受耳毒性药物的影响。今年，我们已经证明了分泌性外切体作为支持细胞和毛细胞之间发生的非自主细胞信号的中介。胞外体是一类携带蛋白质和核酸的胞外小泡，可以影响受体细胞的功能。我们的数据表明，热休克的保护作用需要外切体的释放，而分离的外切体可以减少耳毒性药物诱导的毛细胞死亡。我们已经证明HSP70与毛细胞上的TLR4相互作用来介导这种保护。这些数据发表在《临床调查杂志》上。 我们的翻译研究包括临床前实验，旨在开发治疗方法，以保护暴露于耳毒性药物或其他毛细胞压力下的人类的听力。为了实现这一目标，我们目前正在研究外切体是否可以被设计成临床治疗听力损失的输送载体。 在第二项翻译研究中，我们研究了以铂为基础的化疗药物的药代动力学，以确定铂在内耳的摄取与顺铂耳毒性之间的关系。我们的初步数据表明，顺铂很容易进入耳蜗并无限期地留在那里，而卡铂在很大程度上被排除在耳蜗外，不会导致听力损失。奥沙利铂治疗导致耳蜗铂的部分摄取，但没有听力损失。这些数据发表在《耳鼻喉科研究协会杂志》上。 临床研究：我们正在研究他汀类药物在多大程度上减少顺铂引起的人类听力损失。我们最近完成了一项与罗切斯特大学耳鼻喉科和沃尔特里德国家军事医学中心合作的回顾性研究，以检查这个问题。我们还完成了我们的前瞻性研究，我们测试了头颈部癌症患者在顺铂治疗开始前和停止顺铂治疗后的听力，以确定他汀类药物是否降低了顺铂在该患者群体中的耳毒性。我们对前瞻性和回溯性研究相结合的分析表明，与未服用他汀类药物的受试者相比，同时服用阿托伐他汀的接受顺铂治疗的头颈部癌症患者发生顺铂所致听力损失的发生率和严重程度有所降低。这些数据被描述在一篇手稿中，这篇手稿在临床调查杂志上获得了好评。基于这些数据，我们启动了一项3期、随机、安慰剂对照研究，以确定阿托伐他汀在多大程度上减少该人群中顺铂引起的听力损失。这项研究的人类受试者方案已经完成了NIDCD科学审查，目前正在等待NIH中央IRB的审查。

Our basic science studies are focused on the signal transduction and intercellular communication pathways that are activated in response to hair cell stress. We previously examined the roles of heat shock proteins (HSPs) in promoting survival of hair cells under stress. We showed that HSP induction is a critical stress response in the inner ear that can protect hair cells against major stresses, including exposure to both classes of ototoxic drugs (i.e., the aminoglycoside antibiotics and cisplatin). We showed that pro-survival induction of HSP expression is relatively low in hair cells and is more robust in supporting cells and resident macrophages. These data indicate that hair cells may have a reduced capacity to induce autonomous pro-survival signaling in response to stress, and that non-autonomous signals from supporting cells and macrophages function as critical mediators of pro-survival signaling when hair cells are under stress. We showed previously that glia-like supporting cells secrete HSP70 in a stress-induced response that protects hair cells against death caused by exposure to ototoxic drugs. This year we have demonstrated that secretory exosomes act as mediators of the non-autonomous cellular signaling that occurs between supporting cells and hair cells. Exosomes are a class of extracellular vesicles that carry protein and nucleic acid cargo and can influence function of recipient cells. Our data indicate that exosome release is required for the protective effect of heat shock, and isolated exosomes reduce ototoxic drug-induced hair cell death. We have shown that HSP70 interacts with TLR4 on hair cells to mediate this protection. These data were published in Journal of Clinical Investigation. Our translational studies consist of preclinical experiments aimed at developing therapies to preserve hearing in humans exposed to ototoxic drugs or other hair cell stresses. Toward this goal we are currently examining whether exosomes can be engineered as therapeutic delivery vehicles for clinical treatment of hearing loss. In a second translational study we have examined the pharmacokinetics of platinum-based chemotherapy drugs to determine the relationship between platinum uptake in the inner ear and cisplatin ototoxicity. Our preliminary data suggest that cisplatin readily enters the cochlea and remains there indefinitely, while carboplatin is largely excluded from the cochlea and does not cause hearing loss. Oxaliplatin treatment results in some cochlear uptake of platinum but no hearing loss. These data were published in Journal of the Association for Research in Otolaryngology. Clinical studies: We are examining the extent to which statins reduce cisplatin-induced hearing loss in humans. We recently completed a retrospective study in collaboration with University of Rochester Otolaryngology Department and Walter Reed National Military Medical Center to examine this question. We also completed our prospective study in which we tested the hearing of head and neck cancer patients before onset of cisplatin therapy and after cessation of cisplatin therapy to determine if statins reduce cisplatin ototoxicity in this patient population. Our analyses of the combined prospective and retrospective studies indicate that subjects undergoing cisplatin therapy to treat head and neck cancer who are concurrently taking atorvastatin experience reduced incidence and severity of cisplatin-induced hearing loss compared to subjects not taking a statin. These data are described in a manuscript that has received favorable reviews at Journal of Clinical Investigation. Based on these data, we have initiated development of a phase 3, randomized, placebo-controlled study to determine the extent to which atorvastatin reduces cisplatin-induced hearing loss in this population. The human subjects protocol for this study has completed NIDCD scientific review and is currently awaiting review by the NIH Central IRB.