TLRs信号负调控因子SIGIRR在仔猪免疫应激中的作用及其营养调控

Nutritional modulation is one of the most important methods in alleviating immunological stress in pigs. However, its efficacy is limited because the regulatory mechanisms of immunological stress are not clear. Single immunoglobulin IL-1R-related molecule (SIGIRR), an important negative regulator of Toll-like receptors (TLRs) signaling, plays an important role in inflammation regulation, which provides us an important idea to investigate the regulatory mechanisms of immunological stress. In the current study, firstly, we will explore the effect of immunological stress on distribution and expression of SIGIRR in tissues of the weaned pigs. Secondly, we will further investigate the effect of over-expression or RNA interference of SIGIRR, and SIGIRR agonist or antagonist on the responses of immunological stress in weaned pigs. Our aims will be to explore whether SIGIRR is involved in modulation of immunological stress via negative regulation of TLRs signaling. Thirdly, we will investigate the interactions between SIGIRR and the key signaling molecules of TLRs signaling pathway in order to elucidate the mechanism by which SIGIRR inhibits TLRs signaling pathway. Finally, we will explore the regulatory role of n-3 polyunsaturated fatty acid (PUFA) on SIGIRR in weaned pigs. Our aims are to demonstrate if n-3 PUFA can alleviate immunological stress via positive regulation of SIGIRR. The results will be of great significance for us to understand the regulatory mechanism of immunological stress and to explore the methods of nutritional modulation to prevent the immunological stress in weaned pigs.

营养调控是缓解猪免疫应激的重要手段，但由于免疫应激调控机制尚不清楚，致使营养措施针对性不强。免疫学和生物物理学等基础学科研究发现，SIGIRR是TLRs信号重要负调控因子，对炎症发挥着重要调节作用，这为探索猪免疫应激调控机制提供了崭新思路。本项目研究免疫应激对SIGIRR在仔猪组织中的分布和基因表达水平的影响，并进一步研究SIGIRR过表达或RNA干扰、SIGIRR激活剂或抑制剂对免疫应激反应的影响，以探索SIGIRR是否通过抑制TLRs信号参与免疫应激的调控。在此基础上，研究SIGIRR与TLRs信号通路关键分子之间的相互作用，以探索SIGIIRR抑制TLRs信号通路的机制。最后，研究n-3PUFA对SIGIRR的调节作用，以探索n-3PUFA是否可通过正调控SIGIRR从而缓解免疫应激。本研究将为揭示猪免疫应激的调控机制，以及为通过营养调控SIGIRR来克服免疫应激提供重要理论依据。

本项目探讨了Toll样受体（TLRs）负调控因子—单免疫球蛋白IL-1受体相关分子（SIGIRR）在仔猪免疫应激中的作用及其营养调控。（1）采用脂多糖（LPS）刺激仔猪建立免疫应激模型，研究了免疫应激对SIGIRR在仔猪组织中的分布和基因表达水平的影响，为探索SIGIRR是否参与仔猪免疫应激的调控提供理论依据。结果表明：SIGIRR mRNA在回肠中的表达量最高，显著高于脾脏、空肠、胸腺、垂体、肝脏和下丘脑，在肾上腺、腓肠肌和背最长肌等组织表达量相对较低。免疫应激导致所有组织中SIGIRR的mRNA表达下降，这表明SIGIRR可能参与仔猪免疫应激的调控。在此基础上，研究干扰SIGIRR对LPS诱导的猪巨噬细胞系炎性细胞因子及TLR4信号通路相关基因mRNA表达的影响，旨在探究SIGIRR是否参与巨噬细胞免疫应激反应的调控。结果表明，SIGIRR siRNA导致巨噬细胞TLR4信号通路关键基因表达量和炎性细胞因子的表达量进一步上升。这表明SIGIRR可通过抑制TLR4信号通路，从而抑制巨噬细胞炎症反应，SIGIRR可能为控制猪免疫应激的正调控靶点。（2）探讨了营养素，包括脂肪酸[n-3多不饱和脂肪酸（PUFA）、中链脂肪酸]、功能性氨基酸[天冬氨酸（Asp）和谷氨酸（Glu）]是否可通过调控SIGIRR，从而缓解仔猪免疫应激。结果表明：（1）鱼油（富含n-3PUFA）、中链脂肪酸（主要为辛酸和癸酸）可通过促进肠道或肝脏SIGIRR的mRNA表达，抑制TLR4信号通路关键基因的表达，从而缓解LPS导致的肠道或肝脏损伤。（2）在LPS刺激早期和晚期，Asp对TLR4信号通路相关基因的mRNA表达、炎性介质的产生发挥相反的调控作用，并改善了肝脏结构和功能。Asp对肝脏的影响与SIGIRR无关。（3）Glu可通过激活mTOR信号通路，抑制TLR4信号通路，促进蛋白质合成，降低肠道炎性细胞因子的产生，从而缓解了LPS诱导的肠道损伤。Glu对肠道的影响与SIGIRR无关。