Suppression of the inflammatory cytokine IL-18 activity by controlling the receptor function

白介素18(IL-18)是一种细胞因子，可诱导干扰素γ的产生、急性肝炎、风湿病、自身免疫反应等。为了抑制IL-18的炎症作用，我们寻找了控制IL-18活性的化合物。寻找抑制IL-18与其受体结合的抗体，合成了覆盖IL-18受体外胞外域全序列的多肽。用该多肽制备了KHL血蓝和BSA的多肽结合物，并进行了免疫。但未获得抑制IL-18活性的抗原。为了解IL-18受体跨膜区对应片段对细胞内信号转导的影响，合成了几个跨膜区片段。然而，没有一个片段能够被洗涤剂溶解。用pSKAN噬菌体展示系统(MoBiTec)制备具有IL-18受体功能的噬菌体文库。然而，噬菌体本身会诱导干扰素γ的产生。因此，我们不能估计展示在噬菌体上的多肽的效果。寻找抑制IL-18活性的多肽IL-18被预测具有与IL-1β相似的三维结构，IL-1β和IL-1受体的复杂晶体结构已经被解决。根据从三维结构推断的数据，我们合成了IL-18的部分序列，并评价了其对IL-18活性的抑制作用。结果表明，多肽、IL-18(113-157)和IL-18与IL-18的混合物(46-66)对L-18加成产生的干扰素-γ有强烈的抑制作用，IL-18部分序列的混合抑制了IL-18的活性，为设计IL-18的抑制剂提供了坚实的基础。

Interleukin 18 (IL-18) is a cytokine that induces the production of interferon γ, acute hepatitis, rheumatism, self-immune reaction and so on. In order to suppress the inflammatory effect of IL-18, we searched the compounds that control the IL-18 activity.1. Search of antibodies that inhibit IL-18 binding to its receptorPeptides that cover all sequence of the outer cellular domain of IL-18 receptor were synthesized. Using the peptide, peptide conjugates with KHL hemocyanine and BSA were prepared and immunized. However, no antigen that inhibits IL-18 activity was obtained.2. Evaluation of characteristics of trans-membrane domains of IL-18 receptor in terms of interference of the signal transaction through the receptorIn order to know the effect of the segment corresponding to the trans-membrane domain of the receptor to the signal transaction into cell, several segments of the trans-membrane domain were synthesized. However, no segments were able to be dissolved by detergents.3. Search of phages that quench the function of IL-18 receptorPhagemid libraries were prepared by using pSKAN Phagemid Display System (MoBiTec). However, phages themselves induce the production of interferon γ production. Therefore, we could not estimate the effect of peptides displayed on the phages.4. Search of peptides that suppress the IL-18 activityIL-18 is predicted to have a similar 3D structure to that of IL-1β and the complex crystal structure of IL-1β and IL-1 receptor has been solved. Based on the date deduced from the 3D structure, we synthesized partial sequences of IL-18 and evaluated the effects on the inhibition of IL-18 activities. As results, peptide, IL-18(113-157) and a mixture of IL-18(113-157) and IL-18(46-66) strongly inhibit the production of IFN-γ by L-18 addition.In conclusion, the mixture of the partial sequences of IL-18 suppresses the IL-18 activity and this fact will present a solid basis for designing inhibitors against IL-18.