IETP2短肽偶联Klotho蛋白跨越血迷路屏障延缓老年性聋及分子机制研究

With the rapid augmentation of elderly population in China, age-related hearing loss (ARHL) or presbycusis inevitably becomes a major public health challenge which significantly hampers the quality of life in this population. Unfortunately, no effective intervention regimens and no inner ear-targeted medicine are currently available, mostly due to the fact that ARHL is an auditory nerve system disease, of which exact pathogenesis remains elusive. Our previous studies affirmed that inflammasomes were activated in the inner ears during the aging process, resulting in excessive accumulation of downstream inflammatory factors, which potentially impairs auditory nerves. This process has been validated to underlie the fundamental pathogenesis of presbycusis, and the development of inhibitors of inflammasomes would bring great prospect for the breakthrough in prophylaxis and therapeutics of presbycusis. In this study, we observed that the expression of Klotho, a life extension protein, in the cochleae in aging mice with ARHL was significantly downregulated, accompanied by aberrant activation of inflammasomes. Our data verified that activation of inflammasomes in the inner ears in young klotho-deficient (klotho-/-) mice with severe hearing loss, with signs highly similar to those in aging mice with presbycusis. Thereby, we postulated that Klotho protein might play a pivotal role in the prophylaxis of the pathogenesis of ARHL via the inhibition of inflammasomal activation in the inner ears. These findings substantiated our prior hypothesis. Meanwhile, the in vivo phage display technique was employed to screen the inner ear-targeted peptide, and IETP2 as a candidate peptide to deliver the secretory Klotho protein into murine inner ear for oto-protection of the ARHL. A priori, the implementation of this project is essential to the elucidation of the molecular mechanism of ARHL and will benefit pharmacological intervention of ARHL.

我国人口老龄化形势严峻，老年性聋严重影响生活质量。该病核心机制不明且内耳给药尚存技术障碍，因此暂无药物干预措施。我课题组证明老年鼠内耳炎性复合体持续激活导致听神经损伤可能是老年性聋的关键病理机制；因此寻找内源性炎性复合体拮抗因子，有望成为防治老年性聋的关键突破口。本研究发现，老年性聋小鼠耳蜗中内源Klotho因子表达下降，并伴随炎性复合体激活；而年轻klotho缺陷小鼠内耳中提前出现炎性复合体激活现象，且听力异常，我们据此提出“Klotho蛋白抑制内耳炎性复合体激活进而缓解老年性聋”的科学假设；同时本研究采用in vivo噬菌体展示技术筛选获得内耳靶向功能肽段IETP2，并与分泌型Klotho蛋白进行融合表达，拟验证该融合分子的内耳靶向、抗炎性复合体激活及延缓老年性聋进程等相关功能。本项目不仅有力阐释了老年性聋的病理机制，而且有望突破药物防治老年性聋的技术瓶颈，意义重大！

老年性聋是常见的因衰老导致神经退行性病变引起的感音神经性聋现象，目前尚无理想的治疗手段；结合以往研究经验，本研究证实，内耳炎性复合体激活是老年性耳聋发生的关键机制，且该过程与Klotho蛋白表达下降密切相关，因此我们考虑通过外源表达klotho蛋白实现内耳听觉保护作用；然而由于血迷路屏障系统阻碍klotho蛋白进入内耳淋巴系统，本研究以LRP1受体为靶点，借助噬菌体展示技术筛选获得了一系列具有跨越BLB功能的特异性内耳靶向肽，并证明其中IETP2效率最优，随后采用融合蛋白表达系统，我们合成IETP2-klotho融合蛋白，并进行了对老年性聋小鼠的预防效果评价，结果充分证明，IETP2内耳靶向肽能够高效递送klotho及其他药物分子到达内耳组织，并起到较为理想的听功能保护效果。本项目不仅有力阐释了老年性聋的病理机制，而且有望突破药物防治老年性聋的技术瓶颈，意义重大！