Traumatic optic neuropathy is a common clinical problem. Damage to the optic nerve leads to shear stress and triggers secondary swelling within the optic canal. The study aims to explore the role of the inflammatory response following optic nerve injury (ONI) in toll-like receptor-9 knockout mice (TLR-9^−/−) compared to wild-type mice (WT). At first, TLR-9^−/− and WT mice were subjected to ONI. We then found that ONI significantly up-regulated TLR-9 expression levels in retinal tissues of WT mice. The retinal degeneration after ONI was alleviated in TLR-9^−/− mice, as evidenced by the increased number of retinal ganglion cells (RGCs) and thickness of inner retinal layer (IRL). TUNEL staining and immunofluorescence staining of BRN3A indicated that TLR-9 knockout effectively improved the survival of RGCs. ONI-enhanced expression of Iba-1 and TMEM119 was markedly reduced in TLR-9^−/− mice, indicating the suppression of microglial activation. Moreover, production of pro-inflammatory regulators, including inducible nitric oxide synthase (iNOS), macrophage chemo-attractant protein (MCP)-1, cyclooxygenase-2 (COX-2), interleukin (IL)-1β, IL-18 and tumor necrosis factor-α (TNF-α), was significantly decreased in TLR-9^−/− mice following ONI. TLR-9 knockout-attenuated inflammation was mainly through repressing myeloid differentiation factor 88 (MyD88) and IL-1 receptor-associated kinase 4 (IRAK4). Furthermore, ONI greatly up-regulated the protein expression levels of phosphorylated (p)-IKKα, p-IκBα and p-nuclear factor (NF)-κB, whereas being repressed in TLR-9^−/− mice. The effects of TLR-9 on ONI were verified in lipopolysaccharide (LPS)-stimulated retinal microglial cells transfected with small interfering RNA TLR-9 (siTLR-9). As expected, promoting TLR-9 with its agonist markedly restored inflammation in TLR-9 knockdown cells stimulated by LPS. Therefore, all findings above suggested that suppressing TLR-9 showed neuroprotective effects against ONI through reducing inflammatory response, and TILR-9 might be a promising therapeutic target to develop effective strategies for the treatment of optic neuropathies.

创伤性视神经病变是常见的临床问题。对视神经的损伤导致剪切应力并触发视神经管内的继发性肿胀。该研究旨在探讨与野生型小鼠（WT）相比，在Toll样受体9敲除小鼠（TLR-9 ^-/-）中视神经损伤（ONI）后炎症反应的作用。首先，对TLR-9 ^-/-和WT小鼠进行ONI。然后，我们发现ONI显着上调了WT小鼠视网膜组织中TLR-9的表达水平。TLR-9 ^-/-减轻了ONI后的视网膜变性视网膜神经节细胞（RGCs）数量增加和视网膜内层（IRL）厚度证明了这一点。TUNEL染色和BRN3A的免疫荧光染色表明，TLR-9敲除有效提高了RGC的存活率。在TLR-9 ^-/-小鼠中，Iba-1和TMEM119的ONI增强表达显着降低，表明抑制了小胶质细胞活化。此外，还产生促炎性调节剂，包括诱导型一氧化氮合酶（iNOS），巨噬细胞化学吸引蛋白（MCP）-1，环氧合酶2（COX-2），白介素（IL）-1β，IL-18和肿瘤坏死因子-α（TNF-α），在TLR-9中显着降低^-/-ONI之后的小鼠。TLR-9敲除减弱的炎症主要是通过抑制髓样分化因子88（MyD88）和与IL-1受体相关的激酶4（IRAK4）。此外，ONI极大地上调了磷酸化（p）-IKKα，p-IκBα和p-核因子（NF）-κB的蛋白表达水平，而在TLR-9 ^-/-中却受到抑制老鼠。在用小干扰RNA TLR-9（siTLR-9）转染的脂多糖（LPS）刺激的视网膜小胶质细胞中证实了TLR-9对ONI的作用。不出所料，用其激动剂促进TLR-9可以明显恢复LPS刺激的TLR-9敲低细胞的炎症。因此，以上所有发现均表明抑制TLR-9通过降低炎症反应对ONI具有神经保护作用，而TILR-9可能是开发有效治疗视神经病变策略的有希望的治疗靶点。