IL-22通过MAPK信号转导通路调控C/EBPα表达对银屑病皮损中角质形成细胞增殖和分化的作用

Psoriasis is an inflammatory skin disorder of inheritance involving the interaction of multiple genes in combination with environmental factors. The common skin disease of psoriasis is characterized by abnormal keratinocyte proliferation. In the pathogenesis of psoriasis, dysfunction of the immune system is known to be an important factor. The complex pathology has been implicated in various cells, immune molecules, cytokines, chemokines and intracellular signal pathways, in which IL-22 is important in the immunity. IL-22 is secreted by subpopulations of T-helper cells called Th17 cells. Studies report that the best characterized IL-22-target cells are keratinocytes not immune cells. IL-22 may be a cytokine that is important for the mediators between immune cells and keratinocytes. C/EBP-α (CCAAT/enhancer binding protein (C/EBP)-α), first member of the C/EBP family, is a key regulator of keratinocyte differentiation and a strong suppressor of proliferation. Thus, in the current study, we investigated the pathophysiology of C/EBP-α in skin disorder in cultured keratinocytes and rat model of psoriasis using techniques of cell and molecular biology. We also investigate the regulation of IL-22 on mitogen-activated protein kinase (MAPK) signalling pathway. Our results will provide potential new therapeutic targets for development of biological therapies, monoclonal antibody-based therapies in individuals with psoriasis.

银屑病是遗传因素与环境因素等多因素相互作用的多基因遗传病，通过免疫介导的共同通路最后引起角质形成细胞发生异常增殖。其病理过程涉及多种细胞、免疫分子、细胞因子、趋化因子、细胞内信号传导通路等因素。IL-22在银屑病的发病过程中发挥至关重要的作用。IL-22通过浸润的Th17细胞分泌而作用于角质形成细胞而不是直接作用于免疫细胞，从而在免疫系统和角质形成细胞之间架起了一座桥梁。CEBP/α对于正常皮肤中表皮角质形成细胞的分化、增殖发挥重要的调控作用。本课题将在分子和细胞水平，利用原代培养的角质形成细胞和动物模型，利用分子生物学、细胞生物学技术，深入研究C/EBPα在银屑病皮损形成中的作用机制，从而促进对C/EBPα生物学功能的认识。本课题还试图阐明角质细胞中IL-22对MAPK信号通路的调控作用，明确信号通路中各分子的相互作用，为单抗的研制、个体化治疗和生物治疗提供有价值的参考靶点。

银屑病是临床常见的一种有遗传背景的与免疫反应异常有关的红斑鳞屑性皮肤病。目前认为银屑病的发病机制与遗传因素、免疫因素、感染因素、内分泌因素、神经精神因素及生活习惯、药物和环境因素等密切相关，多种因素的共同作用最终导致角质形成细胞的增殖、分化、凋亡异常和真皮乳头层血管内皮细胞的异常新生，形成了临床可见的银屑病特征性皮损。CCAAT/增强子结合蛋白α（C/EBPα）是转录因子C/EBP家族中的重要成员， C/EBPα对于正常皮肤中表皮角质形成细胞的增殖、分化发挥重要的调控作用。 . 为明确C/EBPα在银屑病发病中的作用，本研究从mRNA和蛋白水平检测寻常型银屑病皮损中C/EBPα的表达，并与角质形成细胞异常增殖及临床皮损面积和严重程度指数（PASI评分）之间进行相关性分析，结果表明C/EBPαmRNA和蛋白在寻常型银屑病皮损中表达明显下调，其蛋白的表达水平与角质形成细胞的增殖指数及银屑病皮损面积和严重程度指数(PASI评分)呈负相关，由此推测C/EBPα蛋白可能参与了寻常型银屑病皮损中角质形成细胞异常增殖的过程，可作为一种反映寻常型银屑病皮损严重程度的指标。应用针对C/EBPα的siRNA沉默人原代角质形成细胞C/EBPα基因的表达，探究C/EBPα基因对角质形成细胞增殖和分化的影响，结果表明C/EBPαsiRNA能够有效的抑制角质形成细胞中C/EBPα的表达，C/EBPα基因沉默后角质形成细胞的增殖率提高、分化水平降低；C/EBPα基因是治疗角质形成细胞增殖、分化异常性疾病的潜在靶基因。采用银屑病发病过程中Th17和Th22细胞分泌的关键细胞因子IL-22刺激角质形成细胞，检测MAPK信号通路中关键信号分子JNK、ERK、p38的磷酸化水平及C/EBPα的表达水平，探究IL-22是否能够通过MAPK信号通路调控C/EBPα的表达，参与寻常型银屑病皮损的形成过程，结果表明IL-22可以显著调控角质形成细胞的增殖和分化过程；IL-22可显著调控角质形成细胞中MAPK信号通路及C/EBPα的表达水平；IL-22可能通过MAPK信号通路及下游的C/EBPα的表达调控角质形成细胞的增殖和分化。