Rationale: Optic neuritis is one of main symptoms in multiple sclerosis (MS) that causes visual disability. Astrocytes are pivotal regulators of neuroinflammation in MS, and astrocytic yes-associated protein (YAP) plays a critical role in neuroinflammation. Meanwhile, YAP signaling is involved in visual impairment, including glaucoma, retinal choroidal atrophy and retinal detachment. However, the roles and underlying mechanisms of astrocytic YAP in neuroinflammation and demyelination of MS-related optic neuritis (MS-ON) remains unclear./nMethods: To assess the functions of YAP in MS-ON, experimental autoimmune encephalomyelitis (EAE, a common model of MS) was established, and mice that conditional knockout (CKO) of YAP in astrocytes, YAP^GFAP-CKO mice, were successfully generated. Behavior tests, immunostaining, Nissl staining, Hematoxylin-Eosin (HE) staining, TUNEL staining, Luxol Fast Blue (LFB) staining, electron microscopy (EM), quantitative real-time PCR (qPCR), gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) by RNA sequencing were used to examine the function and mechanism of YAP signaling based on these YAP^GFAP-CKO mice and EAE model mice. To further explore the potential treatment of YAP signaling in EAE, EAE mice were treated with various drugs, including SRI-011381 that is an agonist of transforming growth factor-β (TGF-β) pathway, and XMU-MP-1 which inhibits Hippo kinase MST1/2 to activate YAP./nResults: We found that YAP was significantly upregulated and activated in the astrocytes of optic nerve in EAE mice. Conditional knockout of YAP in astrocytes caused more severe inflammatory infiltration and demyelination in optic nerve, and damage of retinal ganglion cells (RGCs) in EAE mice. Moreover, YAP deletion in astrocytes promoted the activation of astrocytes and microglia, but inhibited the proliferation of astrocytes of optic nerve in EAE mice. Mechanically, TGF-β signaling pathway was significantly down-regulated after YAP deletion in astrocytes. Additionally, both qPCR and immunofluorescence assays confirmed the reduction of TGF-β signaling pathway in YAP^GFAP-CKO EAE mice. Interestingly, SRI-011381 partially rescued the deficits in optic nerve and retina of YAP^GFAP-CKO EAE mice. Finally, activation of YAP signaling by XMU-MP-1 relieved the neuroinflammation and demyelination in optic nerve of EAE mice./nConclusions: These results suggest astrocytic YAP may prevent the neuroinflammatory infiltration and demyelination through upregulation of TGF-β signaling and provide targets for the development of therapeutic strategies tailored for MS-ON.

中文翻译：

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星形细胞 YAP 通过 TGF-β 信号传导保护实验性自身免疫性脑脊髓炎模型中的视神经和视网膜

理由：视神经炎是导致视力障碍的多发性硬化症 (MS) 的主要症状之一。星形胶质细胞是 MS 中神经炎症的关键调节因子，星形胶质细胞相关蛋白 (YAP) 在神经炎症中起关键作用。同时，YAP 信号与视力障碍有关，包括青光眼、视网膜脉络膜萎缩和视网膜脱离。然而，星形细胞 YAP 在 MS 相关视神经炎（MS-ON）的神经炎症和脱髓鞘中的作用和潜在机制仍不清楚。/n方法：为了评估 YAP 在 MS-ON 中的功能，实验性自身免疫性脑脊髓炎（EAE，a建立了 MS 的通用模型），并在星形胶质细胞中条件性敲除（CKO） YAP、YAP ^{GFAP的小鼠}-CKO小鼠，成功生成。行为测试、免疫染色、Nissl 染色、苏木精-伊红 (HE) 染色、TUNEL 染色、Luxol Fast Blue (LFB) 染色、电子显微镜 (EM)、定量实时 PCR (qPCR)、基因集富集分析 (GSEA) 和基于这些 YAP ^GFAP -CKO 小鼠和 EAE 模型小鼠，通过 RNA 测序的基因组变异分析 (GSVA) 来检查 YAP 信号传导的功能和机制。为了进一步探索 EAE 中 YAP 信号传导的潜在治疗方法，EAE 小鼠接受了多种药物治疗，包括作为转化生长因子-β (TGF-β) 通路激动剂的 SRI-011381 和抑制 Hippo 的 XMU-MP-1激酶 MST1/2 激活 YAP./n结果：我们发现 YAP 在 EAE 小鼠视神经星形胶质细胞中显着上调和激活。星形胶质细胞中 YAP 的条件性敲除导致更严重的视神经炎症浸润和脱髓鞘，以及 EAE 小鼠视网膜神经节细胞 (RGC) 的损伤。此外，星形胶质细胞中的YAP缺失促进了星形胶质细胞和小胶质细胞的活化，但抑制了EAE小鼠视神经星形胶质细胞的增殖。机械地，在星形胶质细胞中 YAP 缺失后，TGF-β 信号通路显着下调。^{此外，qPCR 和免疫荧光测定均证实了 YAP GFAP} -CKO EAE 小鼠中 TGF-β 信号通路的减少。^{有趣的是，SRI-011381 部分挽救了 YAP GFAP}的视神经和视网膜缺陷-CKO EAE 小鼠。最后，XMU-MP-1 激活 YAP 信号可缓解 EAE 小鼠视神经的神经炎症和脱髓鞘。/n结论：这些结果表明星形细胞 YAP 可能通过上调 TGF-β 信号来预防神经炎症浸润和脱髓鞘，并提供靶点用于开发针对 MS-ON 的治疗策略。