Meisgen Florian, Xu Landén Ning, Wang Aoxue, Réthi Bence, Bouez Charbel, Zuccolo Michela, Gueniche Audrey, Ståhle Mona, Sonkoly Enikö, Breton Lionel, Pivarcsi Andor
Dermatology and Venereology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
Dermatology and Venereology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden; Department of Dermatology, The Second Affiliated Hospital of Dalian Medical University, Dalian, China.
J Invest Dermatol. 2014 Jul;134(7):1931-1940. doi: 10.1038/jid.2014.89. Epub 2014 Feb 13.
Keratinocytes represent the first line of defense against pathogens in the skin and have important roles in initiating and regulating inflammation during infection and autoimmunity. Here we investigated the role of miR-146a in the regulation of the innate immune response of keratinocytes. Toll-like receptor 2 (TLR2) stimulation of primary human keratinocytes resulted in an NF-κB- and mitogen-activated protein kinase-dependent upregulation of miR-146a expression, which was surprisingly long lasting, contrasting with the rapid and transient induction of inflammatory mediators. Overexpression of miR-146a significantly suppressed the production of IL-8, CCL20, and tumor necrosis factor-α, which functionally suppressed the chemotactic attraction of neutrophils by keratinocytes. Inhibition of endogenous miR-146a induced the production of inflammatory mediators even in nonstimulated keratinocytes, and potentiated the effect of TLR2 stimulation. Transcriptomic profiling revealed that miR-146a suppresses the expression of a large number of immune-related genes in keratinocytes. MiR-146a downregulated interleukin-1 receptor-associated kinase 1 and TNF receptor-associated factor 6, two key adapter molecules downstream of TLR signaling, and suppressed NF-κB promoter-binding activity as shown by promoter luciferase experiments. Together, these data identify miR-146a as a regulatory element in keratinocyte innate immunity, which prevents the production of inflammatory mediators under homeostatic conditions and serves as a potent negative feedback regulator after TLR2 stimulation.
角质形成细胞是皮肤抵御病原体的第一道防线，在感染和自身免疫过程中启动和调节炎症反应方面发挥着重要作用。在此，我们研究了miR-146a在调节角质形成细胞固有免疫反应中的作用。用Toll样受体2（TLR2）刺激原代人角质形成细胞，导致miR-146a表达呈核因子κB（NF-κB）和丝裂原活化蛋白激酶依赖性上调，令人惊讶的是这种上调持续时间很长，这与炎症介质的快速短暂诱导形成对比。miR-146a的过表达显著抑制白细胞介素-8（IL-8）、CC趋化因子配体20（CCL20）和肿瘤坏死因子-α（TNF-α）的产生，这在功能上抑制了角质形成细胞对中性粒细胞的趋化吸引作用。抑制内源性miR-146a即使在未受刺激的角质形成细胞中也能诱导炎症介质的产生，并增强TLR2刺激的效果。转录组分析显示，miR-146a抑制角质形成细胞中大量免疫相关基因的表达。miR-146a下调白细胞介素-1受体相关激酶1（IRAK1）和TNF受体相关因子6（TRAF6），这是TLR信号下游的两个关键衔接分子，并如启动子荧光素酶实验所示抑制NF-κB启动子结合活性。总之，这些数据确定miR-146a是角质形成细胞固有免疫中的一个调节元件，它在稳态条件下阻止炎症介质的产生，并在TLR2刺激后作为一种有效的负反馈调节因子发挥作用。
