干扰素调节因子8在吗啡诱导的痛觉过敏中的作用研究

Recent studies indicate that microglia plays an important role in morphine-induced hyperalgesia. However, the underlying mechanism remains largely unknown. Interferon regulatory factor 8 (IRF8) is a multi-functional transcription factor, which is involved in immune regulation. Recently, we found that the expression of IRF8 in activated microglia was increased after morphine treatment. The transfection of pAdeno-siIRF8-eGFP vector in spinal cord significantly inhibited morphine-induced hyperalgesia and the increased level of extracellular glutamate. Furthermore, the increased expression of IL-1β and IL-12 caused by morphine was suppressed by inhibiting IRF8 expression in microglia in vitro. These results suggest that IRF8 in the microglia might modulate the expression of IL-1β and IL-12 and contribute to morphine-induced hyperalgesia. Using behavioral test, microdialysis and molecular biological methods, the present project focuses on IRF8 and explores its role in morphine-induced hyperalgesia. To further examine the mechanism that IRF8 mediates morphine-hyperalgesia, IL-1β and IL-12 signaling pathways are interrupted. Our project will provide novel therapeutic target for morphine-induced hyperalgesia.

近年研究显示小胶质细胞在吗啡诱导的痛觉过敏中发挥重要作用，但是其机制未明。干扰素调节因子8（IRF8）是一种多功能的转录因子，参与免疫调控。我们研究发现，吗啡能激活小胶质细胞，且其表达的IRF8上调；而脊髓内转染干扰IRF8表达的腺病毒显著抑制吗啡诱导的痛觉过敏和细胞外谷氨酸水平增加；进一步研究显示在小胶质细胞中转染干扰IRF8表达的腺病毒明显抑制吗啡诱导的IL-1β和IL-12表达。以上预实验提示脊髓小胶质细胞IRF8可能通过上调IL-1β和IL-12的表达参与吗啡诱导的痛觉过敏。因此本项目拟以IRF8为切入点，结合行为学、微透析及分子生物学技术，明确IRF8在吗啡诱导的痛觉过敏中的作用；并通过进一步干预IL-1β和IL-12的信号通路，揭示IRF8介导吗啡诱导痛觉过敏的分子机制。本项目可为防治吗啡诱导的痛觉过敏提供新颖的作用靶点。

吗啡是临床疼痛治疗的代表性药物，但是反复多次使用会引发痛觉过敏现象，极大地削弱了其临床疗效和应用。小胶质细胞的激活在参与介导吗啡痛觉过敏的形成与维持，但其作用机制尚未完全阐明。干扰素调节因子8 （interferon regulatory factor 8, IRF8）是调节小胶质细胞发育和功能的重要转录因子；在神经损伤引起的疼痛中发挥重要作用，是激活小胶质细胞的“开关”。本研究在整体动物和细胞水平上，采用行为学和分子生物学的技术，研究发现：（1）吗啡激活脊髓内小胶质细胞，且其表达的IRF8被上调；（2）鞘内注射干扰IRF8表达的慢病毒质粒，可显著地降低IRF8的表达，并抑制吗啡诱导的痛觉过敏和耐受的形成；（3）吗啡通过诱导小胶质细胞IRF8 的表达，上调小胶质细胞IL-1β和IL-12 的水平，释放的IL-1β 和IL-12 通过抑制星形胶质细胞谷氨酸转运体的活性，增加脊髓胞外谷氨酸水平，从而引起痛觉过敏。上述研究结果证实了IRF8参与吗啡痛觉过敏的形成，并阐明了其介导的下游信号通路，为有效防治吗啡诱导的痛觉过敏提供了新思路和药物作用的新靶点。