NF-κB1调节放射致机体造血功能损伤的作用机制研究

Radiation-induced hematopoietic injury is the primary pathological changes of acute radiation sickness (ARS). Meanwhile, the primary pathogenesis of ARS mainly attributes to the functional failure of hematopoietic reconstitution. The mechanisms of radiation-induced hematopoietic injury should be investigated in depth. Based on this, it is one of the important contents of ARS prevention research to reveal the pathogenesis of ARS and discover the therapeutic targets. Preliminary work of this study discovered for the first time an important role for NF-κB1 in the regulation of hematopoietic injury upon radiation exposure. In this context, Eriocalyxin B, an NF-κB1 inhibitor, was found to have a significant radioprotective effect, suggesting that NF-κB1 might be a potent target for the prophylaxis and treatment of ARS. Hence, in this project, NF-κB1-/- mice will be used to systematically investigate the effect of NF-κB1 on the regulation of hematopoietic function injury induced by irradiation. As a starting point, regulation of NF-κB1 on the function of hematopoietic stem cells (HSCs) will be firstly dissected. It will then be thoroughly explored that the role and mechanisms of NF-κB1 in regulating the HSCs injury induced by irradiation. On this account the mechanisms underlying the regulation of NF-κB1 on the hematopoietic function reconstitution after irradiation injury will be uncovered. Based upon this, it will be found and confirmed that NF-κB1 acts as a molecular target for the prophylaxis and treatment of ARS by means of NF-κB1 inhibitors and knockout mice models. New theoretical basis and research direction will eventually be provided for the study on the prophylaxis and treatment of ARS.

造血损伤是急性放射病（ARS）的基本损伤，造血功能重建障碍是ARS的主要发病原因。深入研究放射所致机体造血损伤的作用机制，据此揭示ARS发病机制并发现其防治靶点是ARS防治研究的重要内容。课题前期首次发现了NF-κB1对放射所致造血损伤具有重要调节作用，并由此发现NF-κB1抑制剂Eriocalyxin B具备显著的抗放效果，提示NF-κB1可能是一个潜在的ARS防治靶点。据此，本课题拟应用NF-κB1-/-小鼠系统研究NF-κB1调节放射致机体造血功能损伤的效应；并以NF-κB1对造血干细胞（HSC）功能的调控研究为切入点，深入探讨NF-κB1对放射所致HSC损伤的调节作用及其机制，以此揭示NF-κB1调节放射损伤后造血功能重建的机制；在此基础上，采用NF-κB1抑制剂和敲除小鼠模型等手段，发现并确证以NF-κB1为靶分子的ARS防治靶点，最终为ARS防治研究提供新的理论依据和研究方向。

前期工作中，我们首次发现了NF-κB1对放射所致造血损伤具有重要调节作用，并由此发现NF-κB1特异性抑制剂Eriocalyxin B具有显著的抗放效果，提示NF-κB1可能是潜在的急性放射病（ARS）防治靶点。据此，本课题系统研究了NF-κB1对放射致造血损伤的调控作用与机制，并探索了NF-κB1作为ARS防治靶点的可能性。. 采用全身NF-κB1基因缺失小鼠（NF-κB1-/-）、造血细胞NF-κB1缺失小鼠（NF-κB1flox/flox-Vav1 Cre+）、内皮细胞NF-κB1缺失小鼠（NF-κB1flox/flox-Tek Cre+）及其同窝野生型对照小鼠（NF-κB1+/+，WT），比较分析稳态及照射条件下NF-κB1缺失基因缺失对小鼠外周血成熟细胞、造血祖细胞、造血干细胞（HSC）数量、重建造血能力、HSC细胞周期、增殖、凋亡等指标的影响。. 结果表明，稳态条件下，与WT相比，NF-κB1-/-小鼠各系造血祖细胞MEP、CMP、GMP、CLP及成熟血细胞WBC、RBC和PLT的数量无明显差异，HSC数量和长期造血能力显著提高（p<0.05）；NF-κB1-/-小鼠CD34-LSK G0 期比例下降、G1期和G2/S/M期比例明显升高（p<0.05）。照射小鼠实验结果显示，NF-κB1基因缺失明显减轻6.5Gy γ射线全身照射小鼠外周血细胞、HSPC数量减少，改善HSC重建造血功能下降，并显著提高9.0Gyγ射线致死性照射小鼠存活率（70% vs.10%）。机制研究表明，造血细胞NF-κB1基因缺失对造血放射损伤的影响与全身NF-κB1基因缺失结果一致，但微环境NF-κB1基因缺失对其无明显影响，提示NF-κB1通过对HSC内源性调节来改善放射诱导的造血损伤，调控HSC静息/增殖状态是其重要途径。NF-κB1（p50）特异性抑制剂 Eriocalyxin B 照前2次给药明显改善6.5Gy γ射线全身照射小鼠HSPC数量减少，促进其外周血象恢复（p<0.05），并能将8.5Gy γ射线全身照射小鼠30天存活率提高100%。这提示，NF-κB1可能是防治ARS的新靶点，NF-κB1抑制剂Eriocalyxin B等可能是潜在的抗放药物。本研究将为急性放射病防治靶点及防治药物研究提供实验依据。