缺氧增加小鼠小胶质细胞IRAK-4的表达

Hypoxia increases IRAK-4 expression in cultured murine N9 microglia cells

目的观察缺氧后小鼠小胶质细胞株N9对白细胞介素-1受体相关激酶4(interleukin-1 receptor associatedkinase-4,IRAK-4)表达的变化,探讨小胶质细胞内炎症反应的相关机制。方法将培养的N9细胞置于低氧(3%O2,5%CO2,92%N2)条件下培养1、3、6、12、24 h,用Western blot检测蛋白表达的变化,用激光共聚焦技术观察IRAK-4在细胞内表达变化情况,用酶联免疫吸附法检测培养液上清肿瘤坏死因子α(TNF-α)含量。结果N9细胞IRAK-4的蛋白表达随缺氧时间延长而逐渐增高,1 h开始增加,3 h增加明显(P<0.01),6 h达高峰,12 h仍维持在较高水平(P<0.01),24 h下降与常氧无显著性差异(P>0.05)。激光共聚焦也显示随着缺氧时间的延长,荧光强度逐渐加强。培养液上清TNF-α含量的变化也符合相似的变化趋势。IRAK-4蛋白表达水平与培养液上清TNF-α含量的变化呈显著的正相关(r=0.863,P<0.05)。结论缺氧可以增加小鼠小胶质细胞内IRAK-4的蛋白表达,提示中枢神经系统内存在对免疫反应起着调控作用的TLR/IL-1R家族信号转导系统,调控下游炎症反应。

Objective To explore the mechanism of the microglia inflammatory response through observing the changes of interleukin-1 receptor associated kinase-4 （IRAK-4） expression in murine N9 microglia cells under hypoxia. Methods N9 cells were exposed to 3% O2 ,5% CO2, 92% N2 for 1, 3, 6, 12 and 24 h respectively. The IRAK-4 protein level was detected by Western blotting and the celluar change was observed by laser scanning confocal microscope （LSCM）. The TNF-α level was measured by ELISA. Results After hypoxia, the expression of IRAK-4 protein was increased in a time-dependent manner. The elevation began at 1 h after hypoxia, increased significantly at 3 h（P 〈0. 01 ）, peaked at 6 h and remained in higher level at 12 h（P 〈 0. 01 ）. then decreased at 24 h （P 〉0. 05）. The fluorescence intensity of IRAK-4 also increased with the extension of anoxic time. The TNF-α level change were similar. There were significant positive correlations between the expression of IRAK-4 and TNF-α（P 〈0. 05 ）. Conclusion Hypoxia could increase IRAK-4 expression in murine microglia cells. It suggests that TLR/IL-IR signaling may exist in central nervous system and regulate the subsequent inflammation response.