ATF6调控TLR4信号通路在肝脏缺血再灌注损伤中的作用及机制研究

Liver ischemia reperfusion injury (IRI) is a complex Pathophysiological processes. Many factors, especially inflammatory responses, can lead to liver IRI, but the exact pathogenesis is not very clear. Studies indicated that Toll-like receptor 4 (TLR4) was involved in hepatic IRI. Our group has demonstrated that endoplasmic reticulum stress (ERS) has a synergy with TLR4 during liver IRI, but the exact mechanisms need be further investigated. Our previous experiments have showed that ischemia directly activates Kupffer cells, enhances reactivity of Kupffer cells to TLR4 ligand (LPS), strengthen inflammatory responses. Interestingly, our pre-experiments also indicated that only ATF6 pathway was activated in three ERS pathways during ischemia. In addition, an ERS inhibitor (or ATF6siRNA)significantly reduced activation of TLR4 induced by ischemia. Herein, we suppose that ATF6 activation triggered by ischemia has a synergy with TLR4 innate immune responses and increased liver IRI; and further investigate exact mechanisms of this hypothesis. The success of the project will be an important significance in ischemia diseases, and provide a new target to molecular therapy of liver IRI.

肝脏缺血再灌注损伤(Ischemia-reperfusion injury，IRI)是一个复杂的病理生理过程，导致肝脏IRI的因素很多，其中炎症反应起关键作用，确切机制尚不清楚。研究证实Toll样受体4(Toll like receptor 4，TLR4)参与肝脏IRI，本组证实内质网应激(Endoplasmic reticulum stress，ERS)协同TLR4参与肝脏IRI，其机制有待进一步研究。预实验显示热缺血可以直接激活Kupffer细胞，提高TLR4的反应性，促进炎症反应。有趣的是，缺血阶段三条ERS通路仅ATF6被激活，且ERS抑制剂或ATF6siRNA预处能理明显抑制缺血激活TLR4。该项目将研究该假设"缺血激活ATF6协同TLR4促进炎症反应，增加肝脏IRI损伤程度"，且分析其确切机制。本项目的实现对缺血性疾病具有一定的普遍意义，且为肝脏IRI提供新的分子治疗靶点。

肝脏缺血再灌注损伤(ischemia reperfusion injury，IRI)是一个复杂的病理生理过程，导致肝脏IRI的因素很多，其中炎症反应起关键作用，研究发现TLR4参与肝脏IRI。通过建立小鼠肝脏部分热缺血模型，本组实验研究实验显示热缺血可以直接激活肝脏Kupffer细胞内质网应激(Endoplasmic Reticulum Stress， ER stress)反应，特别是缺血阶段可直接激活三条ERS通路中的ATF6通路，并提高TLR4的反应性，促进炎症反应。缺血激活的Kupffer细胞能增强促炎性细胞因子的产生而抑制抑炎细胞因子的产生。通过ERS抑制剂PBA或ATF6siRNA预处理能明显抑制缺血启动Kupffer细胞促炎症作用，从而抑制缺血过程中的炎症反应，实现对肝脏IRI的保护作用。此外，在体外实验中发现ATF6干扰能通过抑制AKT-Gsk3b信号通路同时增强NF-kB信号通路消除ER stress介导的对TLR4反应的炎症增强作用。因此，缺血通过ATF6介导的ERstress来启动肝脏天然免疫细胞。IR诱导的代谢应激与TLR激活协同作用，共同激活组织炎症免疫反应。随着生活水平的提高，糖尿病及糖耐量异常的患者越来越多，我们发现肝切除或肝移植中约有1/5-1/4患者存在糖耐量异常，这些患者在术后肝脏损伤往往较重，且于高血糖恶化的肝脏的IRI密切相关，但其作用的确切机制目前未得到明确阐述。项目组发现高血糖也可特异性的激活ER stress中ATF6-CHOP通路，从而加重炎症反应，参与高血糖恶性化肝脏IRI。我们的发现为临床高血糖或DM恶化肝脏IRI防治提供新的思路和理论依据。