Dusp1 deletion unveils its central role in the regulation of redox homeostasis and inflammation in the mouse cochlea

Stress-activated protein kinases (SAPK) have been associated with sensorineural hearing loss (SNHL) of multiple etiologies. The activity of these kinases is tightly regulated by the dual-specificity phosphatase 1 (DUSP1), thus, DUSP1 loss of function leads to the sustained activation of SAPK. In the hearing organ, DUSP1 is an indispensable component of the stress response machinery, and its deficit accelerates SNHL progression, triggers the inflammatory response and promotes hair cell (HC) and spiral neurons (SGN) death. Here, we have studied the link between inflammation and redox imbalance in the cochlea by further characterizing the transcriptome of the Dusp1-/- mouse. RNAseq and subsequent GSEA indicated that Dusp1-/- mice present a distinct gene expression pattern of key cellular programs, including altered expression of genes of the inflammatory response and glutathione metabolism. To dissociate both components, Dusp1-/- mice were treated with the antioxidant N-acetylcysteine (NAC). Treatment with NAC delayed the onset of SNHL and reduced cochlear damage. Less HC were TUNEL+ and SGN showed less p-H2AX foci. NAC treatment not only improved redox balance but also reduced cytokine production and macrophage recruitment in Dusp1-/ -mice. In conclusion, our data point to DUSP1 as an essential node to control the cross-regulation of oxidative stress and inflammation. Overall design: Cochlear mRNA profiles of 5 and 8-months-old wild type (WT) and Dusp1-/- mice

应激激活蛋白激酶（Stress-activated protein kinases, SAPK）与多种病因导致的感音神经性听力损失（sensorineural hearing loss, SNHL）密切相关。这类激酶的活性受双特异性磷酸酶1（dual-specificity phosphatase 1, DUSP1）严格调控，因此DUSP1功能缺失会导致SAPK持续激活。在听觉器官中，DUSP1是应激反应机制的不可或缺组分，其缺失会加速SNHL进展、触发炎症反应，并促进毛细胞（hair cell, HC）与螺旋神经元（spiral neurons, SGN）凋亡。本研究通过进一步表征Dusp1基因敲除（Dusp1-/-）小鼠的转录组，探究了耳蜗内炎症与氧化还原失衡的关联。RNA测序（RNAseq）及后续的基因集富集分析（Gene Set Enrichment Analysis, GSEA）结果显示，Dusp1-/-小鼠呈现出关键细胞程序的独特基因表达特征，涵盖炎症反应相关基因与谷胱甘肽代谢基因的表达异常。为分离这两类病理效应，本研究对Dusp1-/-小鼠施以抗氧化剂N-乙酰半胱氨酸（N-acetylcysteine, NAC）干预。NAC干预可延缓SNHL的发病进程，并减轻耳蜗损伤：TUNEL阳性毛细胞数量减少，螺旋神经元的磷酸化H2AX焦点数量亦显著降低。NAC干预不仅改善了氧化还原平衡，还降低了Dusp1-/-小鼠的细胞因子生成与巨噬细胞招募。综上，本研究数据表明DUSP1是调控氧化应激与炎症交叉调控的核心节点。实验整体设计：对5月龄与8月龄的野生型（wild type, WT）及Dusp1-/-小鼠开展耳蜗mRNA表达谱分析。