Activation of sympathetic nervous system drives dry eye onset via norepinephrine-ß2-adrenergic receptor signaling in mice

Dry eye disease (DED) and sympathetic nervous system (SNS) activation have clear association with chronic environmental and psychogenic stress. However, the relationship and mechanism of SNS activation in dry eye pathogenesis remains elusive. Here we first found that the DED mice induced by chronic desiccating stress and scopolamine exhibited the SNS activation and elevated corneal norepinephrine (NE) contents. However, systemic SNS ablation with 6-OHDA and local NE depletion with DSP-4 treatment markedly alleviated the dry eye severity. More directly, topical application of NE phenocopied the dry eye syndrome in healthy mice, but not in mice with Adrb2 gene knockout, the dominant adrenergic receptor in cornea. In contrast, topical administration of selective Adrb2 antagonist ICI 118551 significantly attenuated the dry eye severity, including the increased tear secretion, improved corneal epithelial barrier function, and the reduced expressions of matrix-metalloproteinases, chemokines and inflammatory cytokines. Transcriptomic analysis and experimental validations underscored the strong links of top 10 downregulated pathways and dry eye-related inflammatory and immune responses, including TNF, NF-?B, chemokines and IL-17 signaling. Taken together, these results provide direct evidence of SNS activation in driving dry eye onset through NA-Adrb2 signaling pathway, which offers potential preventative and therapeutic approach for dry eye diseases. Overall design: RNA-seq profiling of corneas from dry eye mice, with or without ICI 118551 treatment (four corneas pooled per sample) at day14 of scopolamine injection.

干眼症（dry eye disease, DED）与交感神经系统（sympathetic nervous system, SNS）激活均与慢性环境及心理应激存在明确关联。然而，交感神经系统激活在干眼症发病机制中的具体关联与作用机制仍有待阐明。本研究首次发现，由慢性干燥应激与东莨菪碱诱导的干眼症模型小鼠，可出现交感神经系统激活及角膜去甲肾上腺素（norepinephrine, NE）水平升高的现象。采用6-OHDA进行系统性交感神经系统损毁，或使用DSP-4进行局部去甲肾上腺素耗竭，均可显著减轻干眼症的严重程度。更为直接的是，在健康小鼠眼部局部滴用去甲肾上腺素可模拟干眼症表型，但在角膜优势表达的肾上腺素能受体β2（Adrb2）基因敲除小鼠中则无此效应。与之相反，局部给予选择性Adrb2拮抗剂ICI 118551可显著缓解干眼症病情，具体表现为泪液分泌增加、角膜上皮屏障功能改善，以及基质金属蛋白酶、趋化因子与炎症细胞因子表达水平降低。转录组分析与实验验证结果证实，排名前十的下调通路与干眼症相关炎症及免疫应答（包括TNF、NF-κB、趋化因子及IL-17信号通路）存在紧密关联。综上，本研究结果直接证实交感神经系统激活可通过去甲肾上腺素-Adrb2信号通路驱动干眼症的发生，为干眼症的预防与治疗提供了潜在策略。实验整体设计：在东莨菪碱注射第14天时，对经或未经ICI 118551处理的干眼症模型小鼠的角膜组织（每样本混合4个角膜）进行RNA测序转录组分析。