WTAP介导的甲基转移酶复合物METTL3-METTL14激活调控脓毒症肺微血管内皮损伤中hnRNP A2/B1 mRNA m6A甲基化修饰

Sepsis-induced lung injury, as the main cause of death in ICU patients, is an important clinical issue to be managed. However, the pathophysiological mechanism of sepsis-induced lung injury remains unclear. Pulmonary microvascular endothelial injury is critical to the pathogenesis of ALI during sepsis. Our previous work found that hnRNP A2/B1 could protect pulmonary microvascular endothelial cells against the impairment from sepsis-induced lung injury in mice (under review). Moreover, we also found that hnRNP A2/B1 expression in pulmonary endothelial cells was significantly induced by sepsis, and then quickly declined, suggesting that negative feedback regulatory loop is important for the regulation of hnRNP A2/B1 expression. Our pilot data showed that down-regulation of hnRNP A2/B1 expression in the late phase of sepsis-induced lung injury was significantly inverse-correlated with m6A modification of its mRNA, but it remains unknown for the regulatory mechanisms. Thus, we intend to investigate the underlying mechanisms responsible for the hnRNP A2/B1 mRNA m6A modification, so as to suggest new mechanisms and therapeutic targets for sepsis-induced lung injury.

脓毒症肺损伤是ICU患者的重要死因，降低脓毒症肺损伤的死亡率是亟待解决的临床问题，但其相关的病理生理机制尚不明确。肺微血管内皮损伤在脓毒症肺损伤中发挥关键作用，我们前期研究发现：hnRNP A2/B1在脓毒症肺损伤小鼠的肺微血管内皮细胞中发挥保护作用（待发表）。此外，我们还发现，肺微血管内皮细胞中hnRNP A2/B1的表达在脓毒症肺损伤早期显著增高，随后迅速降低，提示hnRNP A2/B1的表达存在负反馈调控机制。我们预实验发现，脓毒症肺损伤后期hnRNP A2/B1表达下调与其mRNA发生m6A甲基化修饰相关，但具体的调控机制目前未知。因此，本研究拟探讨hnRNP A2/B1 mRNA m6A甲基化修饰的可能机制，从而为脓毒症肺损伤的病生理机制研究提供基础，为脓毒症肺损伤的治疗提供新的靶点。

脓毒症是由于宿主对感染的反应失调引起的危及生命的器官功能障碍。其中，急性肺损伤是严重脓毒症患者最常见的并发症之一。其病理生理机制的关键环节是肺微血管内皮损伤，导致肺微血管内皮及肺组织炎症反应加重，从而影响血管内皮粘附分子活化及迁移，破坏血管内皮屏障功能。但是，脓毒症肺损伤具体的发病机制仍不清楚。本课题组围绕“hnRNP A2/B1 mRNA m6A甲基化修饰调控脓毒症肺微血管内皮损伤”的主题，通过构建脓毒症肺损伤模型以及分离纯化肺微血管内皮细胞的方法，探究hnRNP A2/B1 mRNA 发生m6A甲基化修饰时其蛋白的表达变化以及关键的作用酶，由于METTL3-METTL14 复合物并未在hnRNP A2/B1 mRNA m6A甲基化修饰中发挥重要作用。因此，我们探寻m6A甲基化修饰相关的酶在脓毒症诱导肺微血管内皮损伤中的作用及其可能的作用机制，为脓毒症肺微血管内皮损伤提供潜在的治疗靶点。研究发现：（1）hnRNP A2/B1对脓毒症肺损伤时肺微血管内皮细胞功能具有保护作用, 具体调控的机制为hnRNPA2/B1抑制NF-κB以及VE-cadherin/β-catenin信号通路。（2）m6A甲基化参与脓毒症诱导的急性呼吸窘迫综合征，并且甲基转移酶METTL3在脓毒症诱导的肺血管内皮损伤中的保护作用，其具体作用机制为METTL3介导靶基因TRIM59与识别蛋白YTHDF1结合，抑制TLR4/NF-κB通路。其中，TRIM59作为关键作用分子，有望成为脓毒症介导的肺微血管内皮损伤新的干预靶点和治疗策略，从而降低严重脓毒症患者的死亡率。