FK506介导的噪声性听力损失预防与内质网应激反应减弱相关。

文献信息

中文摘要

背景： 噪声性永久性听力损失主要源于耳蜗感觉毛细胞的不可逆丢失，而成体哺乳动物的这些毛细胞不能再生。内质网（ER）应激可能在噪声诱导的外毛细胞（OHC）丢失中起主要作用。我们此前报道，FK506可预防成年CBA/J小鼠的噪声性听力损失（NIHL）；然而，这种预防作用的分子机制仍不完全清楚。结果：在此，我们显示，FK506治疗可减轻成年FVB/NJ小鼠（雌雄均有）的NIHL，并且这种预防作用与噪声诱导的内质网应激受到抑制相关。使用可可靠诱导OHC丢失的永久性阈移噪声模型，探索性RNA-seq分析发现，未折叠蛋白结合和蛋白质加工是FK506介导预防作用相关的最富集通路之一，这指导了随后针对内质网应激相关标志物的验证研究。噪声暴露在暴露后1-3小时内显著增加耳蜗匀浆中BiP（Grp78）表达并降低FKBP8水平，而FK506预处理可阻止这些变化。FK506还阻断了基底转OHC中CHOP的上调，而该区域通常是声创伤后变性开始之处。在生理条件下，FKBP8表达于感觉毛细胞、螺旋神经节神经元和血管纹，并在OHC中与内质网标志物KDEL呈现主要共定位。在HEI-OC1细胞中，FK506同样阻止了毒胡萝卜素诱导的BiP和CHOP升高以及相关的FKBP8水平下降，进一步支持FK506治疗与内质网应激调节之间的关联。结论：总之，这些发现表明，FK506介导的NIHL预防与内质网应激抑制和OHC完整性保存相关，并提示FKBP8可能参与FK506相关的耳蜗内质网稳态调节。然而，目前的数据支持内质网应激抑制在FK506介导的NIHL预防中是一种关联，而非直接因果关系。

英文摘要

Noise-induced permanent hearing loss results primarily from the irreversible loss of cochlear sensory hair cells, which do not regenerate in adult mammals. Endoplasmic reticulum (ER) stress may play a major role in noise-induced outer hair cell (OHC) loss. We previously reported that FK506 prevents noise-induced hearing loss (NIHL) in adult CBA/J mice; however, the molecular mechanisms underlying this preventive effect remain incompletely understood. Here, we show that treatment with FK506 attenuates NIHL in adult FVB/NJ mice of both sexes and that this preventive effect is associated with suppression of noise-induced ER stress. Using a permanent threshold shift noise model that reliably induces OHC loss, exploratory RNA-seq analysis identified unfolded protein binding and protein processing among the top enriched pathways associated with FK506-mediated prevention, which guided subsequent validation studies focused on ER-stress-related markers. Noise exposure significantly increased BiP (Grp78) expression and decreased FKBP8 levels in cochlear homogenates within 1-3 h after exposure, whereas FK506 pretreatment prevented these changes. FK506 also blocked CHOP upregulation in basal- turn OHCs, where degeneration typically begins after acoustic trauma. Under physiological conditions, FKBP8 was expressed in sensory hair cells, spiral ganglion neurons, and the stria vascularis and showed predominant colocalization with the ER marker KDEL in OHCs. In HEI-OC1 cells, FK506 similarly prevented thapsigargin-induced increases in BiP and CHOP and the associated decrease in FKBP8 levels, further supporting the association between FK506 treatment and modulation of ER stress. Together, these findings indicate that FK506-mediated prevention of NIHL is associated with suppression of ER stress and preservation of OHC integrity and suggest that FKBP8 may contribute to FK506-associated regulation of ER homeostasis in the cochlea. However, the present data support an association rather than a direct causal role of ER-stress suppression in FK506-mediated prevention of NIHL.