B-Raf inhibitor vemurafenib counteracts sulfur mustard-induced epidermal impairment through MAPK/ERK signaling

The chemical warfare agent sulfur mustard (SM) causes severe cutaneous lesions characterized by epidermal cell death, apoptosis, and inflammation. At present, the molecular mechanisms underlying SM-induced injury are not well understood, and there is no standard treatment protocol for SM-exposed patients. Here, we conducted a high-content screening of the Food and Drug Administration (FDA)-approved drug library of 1018 compounds against SM injury on an immortal human keratinocyte HaCaT cell line, focusing on cell survival. We found that the B-Raf inhibitor vemurafenib had an apparent therapeutic effect on HaCaT cells and resisted SM toxicity. Other tested B-Raf inhibitors, both type-I (dabrafenib and encorafenib) and type-II (RAF265 and AZ628), also exhibited potent therapeutic effects on SM-exposed HaCaT cells. Both SM and vemurafenib triggered extracellular signal-related kinase (ERK) activation. The therapeutic effect of vemurafenib in HaCaT cells during SM injury was ERK-dependent, indicating a specific role of ERK in keratinocyte regulatory mechanisms. Furthermore, vemurafenib partially improved cutaneous damage in a mouse ear vesicant model. Collectively, our results provide evidence that the B-Raf inhibitor vemurafenib is a potential therapeutic agent against SM injury, and oncogenic B-Raf might be an exciting new therapeutic target following exposure to mustard vesicating agents.

化学战剂芥子气（sulfur mustard, SM）可引发以表皮细胞死亡、细胞凋亡及炎症反应为特征的严重皮肤损伤。目前，芥子气诱导损伤的潜在分子机制尚未得到充分阐明，且尚无针对芥子气暴露患者的标准治疗方案。本研究以永生化人角质形成细胞HaCaT细胞系为模型，针对美国食品药品监督管理局（Food and Drug Administration, FDA）批准的1018种化合物库开展高内涵筛选，以评估其对抗芥子气损伤的效果，筛选指标聚焦于细胞存活水平。研究发现，B-Raf抑制剂维莫非尼（vemurafenib）对HaCaT细胞具有显著的治疗活性，可拮抗芥子气的细胞毒性。其余受试的B-Raf抑制剂，包括I型（dabrafenib与encorafenib）及II型（RAF265与AZ628）制剂，同样对芥子气暴露后的HaCaT细胞展现出强效治疗活性。芥子气与维莫非尼均可诱导细胞外信号调节激酶（extracellular signal-related kinase, ERK）的激活。维莫非尼在芥子气损伤模型中对HaCaT细胞的治疗活性依赖于ERK信号通路，这提示ERK在角质形成细胞的调控机制中扮演特定角色。此外，维莫非尼可在小鼠耳囊泡模型中部分缓解皮肤损伤。综上，本研究结果证实，B-Raf抑制剂维莫非尼是对抗芥子气损伤的潜在治疗药物，而致癌性B-Raf或可成为芥子气类发疱剂暴露后的新型治疗靶点。