UCP2调节IκB SUMO化抑制缺血性脑卒中后炎性反应

Activated NF-κB plays a key role in inflammatory damage induced by ischemic stroke, which is inhibited by uncoupling protein 2 (UCP2) via regulation of ROS production. The inactive form of NF-κB is due to the interaction with IκB to mask its nuclear localization. Interestingly, SUMO-modified IκB maintains its stability and strongly restrains deconjugation of NF-κB. Our previous study has shown UCP2 protected against cerebral ischemic injury by anti-inflammatory effect depending on suppression of IκB degradation. Based on the previous work, further research will be performed in experimental stroke using UCP2 knockout or overexpress mice in vitro and in vivo. The object of this study is: 1) to verify the anti-inflammatory effect of UCP2 resulting in attenuation of ischemic brain damage; 2) to demonstrate the implication of UCP2 in microglial activation and NF-κB signaling; 3) to assess whether UCP2 modulate SUMOylation of IκB protein in response to cerebral ischemia, and explore the specific lysine residue(s) covalently attached by SUMO. Our research will clarify the mechanism responsible for anti-inflammatory effect of UCP2 after cerebral ischemia, and provide a new therapeutic strategy for clinical treatment.

缺血性脑卒中后炎性反应与NF-κB活性增强密切相关，解偶联蛋白2（UCP2）可通过调控ROS生成抑制NF-κB活性，从而减轻炎症损伤。SUMO化修饰IκB是阻断NF-κB激活途径的关键步骤。我们的前期研究显示UCP2基因敲除使MCAO小鼠皮层促炎因子表达增加，缺血性脑损伤加重，同时抑制IκB SUMO化修饰，促进NF-κB核移位，从而激动NF-κB促炎作用。在此基础上，我们将采用UCP2基因敲除或过表达小鼠制备体内外脑缺血模型，从整体到细胞、分子水平探讨如下问题：1）明确UCP2对缺血性脑卒中的抗炎作用；2）建立UCP2与抑制小胶质细胞活化、阻断NF-κB激活的相关性；3）探讨UCP2调节IκB SUMO化的重要性，探寻UCP2促进的IκB SUMO化的氨基酸位点。通过上述研究，阐明UCP2调控脑缺血后炎症反应的新机制，开拓临床脑保护治疗缺血性脑卒中的新靶点及新思路。

解偶联蛋白2（UCP2）是位于线粒体内膜的载体蛋白，通过介导线粒体内膜的“质子漏”减少ROS生成，能够调节病理状态下的氧化应激和炎性反应。本研究试图探讨UCP2对缺血性脑损伤的神经保护作用及其分子机制。我们采用UCP2基因敲除小鼠制备MCAO模型，应用定量PCR、Western blot 等方法检测小鼠脑缺血后不同脑区的促炎因子及凋亡相关蛋白表达。结果显示与野生型小鼠相比，UCP2基因敲除促使脑缺血后梗死体积增大，缺血侧TNF-γ和IL-6表达明显增加，bcl2表达明显降低。此外，检测UCP2基因敲除小鼠的皮层bcl2蛋白水平，发现明显低于野生型小鼠；反之，高表达UCP2的ob/ob小鼠皮层bcl2表达明显升高，并可被UCP2抑制剂genipin所下调。进一步研究发现缺血再灌注诱使NF-κB激活并移位于胞核内，UCP2基因敲除小鼠NF-κB核移位现象尤著。本研究证实了UCP2能够抑制脑缺血后炎性反应，提升抗凋亡蛋白表达，从而发挥脑保护作用。UCP2的脑保护作用可能是通过抑制NF-κB的活性而实现的。