Winge Mårten C G, Ohyama Bungo, Dey Clara N, Boxer Lisa M, Li Wei, Ehsani-Chimeh Nazanin, Truong Allison K, Wu Diane, Armstrong April W, Makino Teruhiko, Davidson Matthew, Starcevic Daniela, Kislat Andreas, Nguyen Ngon T, Hashimoto Takashi, Homey Bernard, Khavari Paul A, Bradley Maria, Waterman Elizabeth A, Marinkovich M Peter
J Clin Invest. 2016 Jul 1;126(7):2661-77. doi: 10.1172/JCI85738. Epub 2016 Jun 13.
Interactions between the epidermis and the immune system govern epidermal tissue homeostasis. These epidermis-immune interactions are altered in the inflammatory disease psoriasis; however, the pathways that underlie this aberrant immune response are not well understood. Here, we determined that Ras-related C3 botulinum toxin substrate 1 (RAC1) is a key mediator of epidermal dysfunction. RAC1 activation was consistently elevated in psoriatic epidermis and primary psoriatic human keratinocytes (PHKCs) exposed to psoriasis-related stimuli, but not in skin from patients with basal or squamous cell carcinoma. Expression of a constitutively active form of RAC1 (RACV12) in mice resulted in the development of lesions similar to those of human psoriasis that required the presence of an intact immune system. RAC1V12-expressing mice and human psoriatic skin showed similar RAC1-dependent signaling as well as transcriptional overlap of differentially expressed epidermal and immune pathways. Coculture of PHKCs with immunocytes resulted in the upregulation of RAC1-dependent proinflammatory cytokines, an effect that was reproduced by overexpressing RAC1 in normal human keratinocytes. In keratinocytes, modulating RAC1 activity altered differentiation, proliferation, and inflammatory pathways, including STAT3, NFκB, and zinc finger protein 750 (ZNF750). Finally, RAC1 inhibition in xenografts composed of human PHKCs and immunocytes abolished psoriasiform hyperplasia and inflammation in vivo. These studies implicate RAC1 as a potential therapeutic target for psoriasis and as a key orchestrator of pathologic epidermis-immune interactions.
表皮与免疫系统之间的相互作用维持着表皮组织的稳态。这些表皮 - 免疫相互作用在炎症性疾病银屑病中会发生改变；然而，这种异常免疫反应背后的途径尚未完全清楚。在这里，我们确定Ras相关的C3肉毒杆菌毒素底物1（RAC1）是表皮功能障碍的关键介质。在银屑病表皮和暴露于银屑病相关刺激的原发性银屑病人类角质形成细胞（PHKC）中，RAC1的激活持续升高，但在基底细胞癌或鳞状细胞癌患者的皮肤中则不然。在小鼠中表达组成型活性形式的RAC1（RACV12）会导致出现类似于人类银屑病的病变，这需要完整免疫系统的存在。表达RAC1V12的小鼠和人类银屑病皮肤显示出相似的RAC1依赖性信号传导以及差异表达的表皮和免疫途径的转录重叠。将PHKC与免疫细胞共培养导致RAC1依赖性促炎细胞因子上调，在正常人角质形成细胞中过表达RAC1可重现这一效应。在角质形成细胞中，调节RAC1活性会改变分化、增殖和炎症途径，包括信号转导和转录激活因子3（STAT3）、核因子κB（NFκB）和锌指蛋白750（ZNF750）。最后，在由人类PHKC和免疫细胞组成的异种移植中抑制RAC1可消除体内的银屑病样增生和炎症。这些研究表明RAC1是银屑病的潜在治疗靶点，也是病理性表皮 - 免疫相互作用的关键协调者。
