miR320a/IRAK-M在脓毒症免疫麻痹中的调节机制

Immunoparalysis accounts for high mortality for sepsis, but the underlying mechanism remains largely unknown and the therapeutic approach is lacking. IRAK-M is a key negative regulator for endotoxin signaling. In our previous investigation, we found that IRAK-M was highly expressed in the monocytes isolated from patients with severe sepsis. In “two-hit” animal model of immnuoparalysis, silencing expression of IRAK-M can significantly improve animal survival and alleviate pathogen infection, suggesting IRAK-M promote immunparalysis. We therefore explore the regulatory mechanism for IRAK-M expression. The result demonstrated that endotoxin can trigger a rapid increase in IRAK-M expression, but on the contrary, the miR320a expression was accordingly downregulated. Bioinformatic analysis revealed that there are two potential miR320a binding sites in the 3’-untranslated region of IRAK-M, furthermore, miR320a expression was downregulated in monocytes from patients with severe sepsis. All of these results let us presume that miR320a can suppress sepsis-induced immunoparalysis by negatively regulating IRAK-M expression. To prove the above hypothesis, we initiate this project, and the main purpose of this project is to unveil the regulatory mechanism of miR320a/IRAK-M in sepsis-induced immunoparalysis and to evaluate the possibility of using miR320a in the therapy of immuoparalysis. The results of this project will provide more potential biomarkers and approaches for the diagnosis as well as therapy of sepsis.

免疫麻痹是严重脓毒症高死亡率的重要原因，但作用机制不详，治疗手段缺乏。IRAK-M是内毒素通路关键负调控因子，我们发现IRAK-M在严重脓毒症患者单核细胞中高表达，在“二次打击”免疫麻痹动物模型上，干扰IRAK-M表达能明显提高动物存活与抗病原微生物感染，由此推测IRAK-M促进脓毒症免疫麻痹，进而深入探索IRAK-M表达调控机制。内毒素处理后的单核细胞IRAK-M表达快速上升，而相对应的是miR320a表达快速下调，且IRAK-M 3’非翻译区序列上含有多个miR320a潜在结合位点，miR320a在严重脓毒症患者单核细胞中低表达，由此推测miR320a能通过负调控IRAK-M表达，抑制脓毒症免疫麻痹。通过验证上述推测，揭示miR320a/IRAK-M在脓毒症免疫麻痹中的调节机制，探索miR320a在对抗脓毒症免疫麻痹中的应用价值，为临床脓毒症诊疗提供更多潜在生物标志物与治疗手段。

脓毒症是由感染与创伤引起的免疫性疾病，临床发病率与死亡率高。脓毒症免疫麻痹是重症脓毒症高死亡率的重要病理机制，但治疗手段缺乏。本研究围绕IRAK-M在脓毒症中的生物学机制进行探索，发现IRAK-M在脓毒症免疫激活与免疫抑制期均发挥重要的作用。在免疫激活期，IRAK-M通过与NADPH氧化酶重要亚基p22phox相互作用，抑制NADP/NADPH氧化酶的激活与活性氧的产生，从而抑制免疫细胞“呼吸暴发”与杀死病原微生物能力。在免疫麻痹期，IRAK-M进一步促进p22phox蛋白质泛素化降解，抑制免疫细胞在免疫抑制期对病原微生物二次打击的清除，加重免疫麻痹。此外，IRAK-M在脓毒症免疫麻痹期表达升高，其表达水平受转录、转录后与翻译后水平的调控。AP-1是调控IRAK-M转录的重要基础转录因子，而mir320a能结合IRAK-M 3‘-UTR负调控IRAK-M mRNA稳定性，LncLRRC8C-2-1能通过ceRNA调控机制影响IRAK-M的表达等。因此，IRAK-M促进脓毒症免疫麻痹，其表达水平调控的多样性为干预IRAK-M表达，逆转脓毒症免疫麻痹提供了手段。