Data Sheet 1_ARHGAP25: a novel player in the Pathomechanism of allergic contact hypersensitivity.pdf

ObjectiveContact hypersensitivity (CHS), or allergic contact dermatitis (ACD), is an inflammatory skin disorder characterized by an exaggerated allergic reaction to specific haptens. During this delayed-type allergic reaction, the first contact with the allergen initiates the sensitization phase, forming memory T cells. Upon repeated contact with the hapten, the elicitation phase develops, activating mostly macrophages, cytotoxic T cells, and neutrophilic granulocytes. Our group previously demonstrated that the leukocyte-specific GTPase-activating protein ARHGAP25 regulates phagocyte effector functions and is crucial in the pathomechanism of autoantibody-induced arthritis. Here, we investigate its role in the pathogenesis of the more complex inflammatory process of contact hypersensitivity.
MethodsFor sensitization, the abdomens of wild-type and ARHGAP25 deficient (KO) mice on a C57BL/6 background, as well as bone marrow chimeric mice, were coated with 3% TNCB (2-chloro-1,3,5-trinitrobenzene) or acetone in the control group. After five days, ears were treated with 1% TNCB for elicitation. Swelling of the ears caused by edema formation was evaluated by measuring the ear thickness. Afterward, ears were harvested, and histological analysis, investigation of leukocyte infiltration, cytokine production, and changes in relevant signaling pathways were carried out. ARHGAP25 expression at the mRNA and protein levels was measured using murine ear and human skin samples.
ResultsARHGAP25 expression increased in human patients suffering from contact dermatitis and in contact hypersensitivity induced in mice. Our data suggest that ARHGAP25 expression is infinitesimal in keratinocytes. In the CHS mouse model, the absence of ARHGAP25 mitigated the severity of inflammation in a leukocyte-dependent manner by reducing the infiltration of phagocytes and cytotoxic T cells. ARHGAP25 altered cytokine composition in the sensitization and elicitation phase of the disease. However, this protein did not affect T cell homing and activation in the sensitization phase.
ConclusionOur findings suggest that ARHGAP25 is essential in developing contact hypersensitivity by modulating the cytokine environment and leukocyte infiltration. Based on these findings, we propose ARHGAP25 as a promising candidate for future therapeutic approaches and a potential ACD biomarker.

接触性超敏反应（contact hypersensitivity, CHS），又称变应性接触性皮炎（allergic contact dermatitis, ACD），是一类以对特定半抗原产生过度变态反应为特征的炎症性皮肤疾病。在该迟发型变态反应过程中，首次接触过敏原会启动致敏阶段，形成记忆性T细胞；再次接触半抗原则触发激发阶段，主要激活巨噬细胞、细胞毒性T细胞及中性粒细胞。本团队此前的研究证实，白细胞特异性GTP酶激活蛋白（GTPase-activating protein）ARHGAP25可调控吞噬细胞效应功能，并在自身抗体诱导性关节炎的发病机制中发挥关键作用。本研究旨在探讨其在更为复杂的接触性超敏炎症过程的发病机制中的作用。
方法：将C57BL/6背景下的野生型小鼠、ARHGAP25敲除（KO）小鼠以及骨髓嵌合小鼠的腹部涂抹3%的TNCB（2-氯-1,3,5-三硝基苯），对照组则涂抹丙酮。5天后，用1% TNCB处理小鼠耳部以激发反应。通过测量耳厚度评估水肿形成所致的耳部肿胀程度。随后摘取耳部组织，开展组织学分析、白细胞浸润检测、细胞因子产生检测以及相关信号通路变化分析。采用小鼠耳部及人皮肤样本，检测ARHGAP25的信使RNA（messenger RNA, mRNA）及蛋白水平表达情况。
结果：变应性接触性皮炎患者及小鼠接触性超敏反应模型中，ARHGAP25的表达均出现上调。本研究数据显示，角质形成细胞中ARHGAP25的表达量极低。在CHS小鼠模型中，ARHGAP25缺失可通过减少吞噬细胞与细胞毒性T细胞的浸润，以白细胞依赖性方式减轻炎症严重程度。ARHGAP25可改变疾病致敏阶段与激发阶段的细胞因子组成，但该蛋白并不会影响致敏阶段T细胞的归巢与激活。
结论：本研究结果表明，ARHGAP25可通过调控细胞因子环境与白细胞浸润，在接触性超敏反应的发生发展中发挥核心作用。基于上述发现，我们提出ARHGAP25可作为未来治疗策略的潜在候选靶点，同时亦是ACD的潜在生物标志物。