School of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan West Road, Wenzhou, Zhejiang 325027, China.
Department of Biological Sciences, College of Optometry, State University of New York, New York, NY 10036, USA.
Exp Eye Res. 2014 Aug;125:1-8. doi: 10.1016/j.exer.2014.05.001. Epub 2014 May 14.
Tear film hyperosmolarity along with exposure to oxidant stress are factors that can induce chronic ocular surface inflammation and pain. However, there is limited information on how increases in reactive oxygen species (ROS) generated by oxidant exposure can induce inflammation. There is emerging evidence in other tissues that innate immune responses to a variety of environmental stresses stem from ROS-induced cytosolic NLRP3 inflammasome activation. Once this occurs, pro-caspase-1 is converted into its catalytic active form, which in turn cleaves pro-IL-1β thereby generating its bioactive form. We determined the role of ROS generation in mediating increases in IL-1β secretion through caspase-1 activation caused by NLRP3 inflammasome activation in an environment-induced murine dry eye (DE) model. An intelligently controlled environmental system (ICES) induced evaporative DE in female 4-6 week old C57BL/6J mice. Increases in ROS production preceded rises in corneal and conjunctival gene expression of NLRP3 inflammasome components and IL-1β that were identified using real-time PCR. Confocal microscopy evaluated concomitant increases in NLPR3, caspase-1 and IL-1β immunostaining. Increases in caspase-1 activity were used as an indicator of inflammasome activation. Rises in ROS generation occurred after 1 week of ICES exposure, which preceded increases in gene expression of three NLRP3 inflammasome components (i.e. NLRP3, ASC and caspase-1) leading to rises in bioactive IL-1β release. Increases in caspase-1 activity occurred after 2 weeks of ICES exposure. Eyedrops containing 0.3% N-acetyl-l-cysteine (NAC) were applied to quench ROS generation by mice kept in the ICES for 2 weeks. This scavenger reduced corneal fluorescein staining and decreased ROS production. NAC also down-regulated both increases in NLRP3, ASC, caspase-1 and IL-1β mRNA levels, along with their immunostaining. It robustly attenuated rises in inflammasome mediated increases in caspase-1 catalytic activity. We show in a dessicating DE disease murine model that rises in ROS generation trigger NLRP3 inflammasome complexation and activation leading to increases in bioactive IL-1β secretion. These results prompt us to suggest that the ROS-NLRP3-IL-1β signaling pathway might play a priming role in environment-induced DE progression. Finally, our findings provide a basis for developing novel strategies that may improve the management of patients requiring treatment for environment-induced dry eye disease.
泪膜高渗以及暴露于氧化应激是可引起慢性眼表面炎症和疼痛的因素。然而,关于氧化剂暴露产生的活性氧(ROS)增加如何引起炎症的信息有限。在其他组织中,有新的证据表明,对各种环境应激的先天免疫反应源自 ROS 诱导的细胞质 NLRP3 炎性体激活。一旦发生这种情况,前胱天蛋白酶-1 就会转化为其催化活性形式,反过来又将前白细胞介素-1β(pro-IL-1β)切割成其生物活性形式。我们通过 NLRP3 炎性体激活引起的 caspase-1 激活,确定了 ROS 生成在介导环境诱导的干燥性眼病(DE)模型中 IL-1β 分泌增加中的作用。智能控制环境系统(ICES)在 4-6 周龄 C57BL/6J 雌性小鼠中诱导蒸发性 DE。通过实时 PCR 鉴定,在用角膜和结膜 NLRP3 炎性体成分和 IL-1β 的基因表达升高之前,ROS 产生增加。共聚焦显微镜评估了 NLPR3、胱天蛋白酶-1 和 IL-1β 免疫染色的同时增加。半胱天冬酶-1 活性的增加被用作炎性体激活的指标。在 ICE 暴露 1 周后,ROS 生成增加,这先于三个 NLRP3 炎性体成分(即 NLRP3、ASC 和胱天蛋白酶-1)的基因表达增加,导致生物活性 IL-1β 的释放增加。在 ICE 暴露 2 周后,半胱天冬酶-1 活性增加。将含有 0.3% N-乙酰-L-半胱氨酸(NAC)的眼药水滴入在 ICE 中保持 2 周的小鼠中,以淬灭 ROS 的产生。这种清除剂减少了角膜荧光素染色并减少了 ROS 的产生。NAC 还下调了 NLRP3、ASC、胱天蛋白酶-1 和 IL-1β mRNA 水平及其免疫染色的增加。它强烈减弱了炎性体介导的半胱天冬酶-1 催化活性的增加。我们在干燥性眼病疾病的小鼠模型中表明,ROS 生成的增加触发 NLRP3 炎性体复合物的形成和激活,导致生物活性 IL-1β 的分泌增加。这些结果促使我们提出,ROS-NLRP3-IL-1β 信号通路可能在环境诱导的 DE 进展中起启动作用。最后,我们的发现为开发可能改善需要治疗环境诱导的干眼症的患者的治疗方法提供了基础。
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