Hearing loss is the third most common chronic health condition in the United States and largely results from damage to sensory hair cells. Major causes of hair cell damage include aging, noise exposure, and medications such as aminoglycoside antibiotics. Due to their potent antibacterial properties and low cost, aminoglycosides are often used for the treatment of gram-negative bacterial infections, surpassing expensive antibiotics with fewer harmful side effects. However, their use is coupled with permanent hearing loss in over 20% of patients requiring these life-sustaining antibiotics. There are currently no FDA-approved drugs that prevent hearing loss from aminoglycosides. A previous study by our group identified the plant alkaloid berbamine as a strong protectant of zebrafish lateral line hair cells from aminoglycoside damage. This effect is likely due to a block of the mechanotransduction channel, thereby reducing aminoglycoside entry into hair cells. The present study builds on this previous work, investigating 16 synthetic berbamine analogs to determine the core structure underlying their protective mechanisms. We demonstrate that nearly all of these berbamine analogs robustly protect lateral line hair cells from ototoxic damage, with ED₅₀ values nearing 20 nM for the most potent analogs. Of the 16 analogs tested, nine strongly protected hair cells from both neomycin and gentamicin damage, while one conferred strong protection only from gentamicin. These data are consistent with prior research demonstrating that different aminoglycosides activate somewhat distinct mechanisms of damage. Regardless of the mechanism, protection required the entire berbamine scaffold. Phenolic alkylation or acylation with lipophilic groups appeared to improve protection compared to berbamine, implying that these structures may be responsible for mitigating damage. While the majority of analogs confer protection by blocking aminoglycoside uptake, 18% of our analogs also confer protection via an uptake-independent mechanism; these analogs exhibited protection when delivered after aminoglycoside removal. Based on our studies, berbamine analogs represent a promising tool to further understand the pathology of aminoglycoside-induced hearing loss and can serve as lead compounds to develop otoprotective drugs.

听力损失是美国第三种最常见的慢性健康状况，很大程度上是由于感觉毛细胞受损所致。毛细胞受损的主要原因包括衰老，噪音暴露和氨基糖苷类抗生素等药物。由于氨基糖苷具有强效的抗菌性能和低成本，因此它们通常用于治疗革兰氏阴性细菌感染，从而取代了昂贵的抗生素，且副作用更少。然而，在需要这些维持生命的抗生素的患者中，超过20％的患者使用它们会导致永久性听力丧失。当前尚无FDA批准的药物可预防氨基糖苷类药物引起的听力损失。我们小组先前的研究确定了植物生物碱贝巴明是斑马鱼侧线毛细胞免受氨基糖苷损害的强力保护剂。这种作用可能是由于机械转导通道受阻，从而减少了氨基糖苷进入毛细胞。本研究在此之前的工作的基础上，研究了16种合成的贝巴明类似物，以确定其保护机制的核心结构。我们证明，几乎所有这些贝巴明类似物都能通过ED强有力地保护侧线毛细胞免受耳毒性损害最有效的类似物的_50个值接近20 nM。在测试的16种类似物中，有9种强烈保护毛发细胞免受新霉素和庆大霉素的损害，而其中一种仅对庆大霉素具有强保护作用。这些数据与先前的研究一致，表明不同的氨基糖苷激活了不同的损伤机制。无论采用何种机制，保护都需要整个贝巴明支架。与苯巴明相比，酚类烷基化或与亲脂性基团的酰化似乎可以改善保护作用，这表明这些结构可能是减轻损害的原因。尽管大多数类似物通过阻止氨基糖苷的摄取来提供保护，但我们18％的类似物也可以提供保护通过与摄取无关的机制；这些类似物在氨基糖苷去除后递送时显示出保护作用。根据我们的研究，贝巴明类似物代表了一种有前途的工具，可以进一步了解氨基糖苷引起的听力损失的病理学，并且可以作为开发耳保护药物的先导化合物。