Ehlers Lisa, Wouters Marjon, Pillay Bethany, Delafontaine Selket, Dzhus Mariia, Baggio Marco, Niehues Tim, Dückers Gregor, Sevenants Lieve, Casteels Kristina, De Somer Lien, Schrijvers Rik, Vanderschueren Steven, Jacquemyn Maarten, Daelemans Dirk, Hombrouck Anneleen, Chambers Eugene P, Tousseyn Thomas, Bucciol Giorgia, Agostinis Patrizia, Moens Leen, Meyts Isabelle
Department of Microbiology, Immunology and Transplantation, Laboratory for Inborn Errors of Immunity, KU Leuven, Leuven, Belgium; Department of Pediatric Respiratory Medicine, Immunology and Critical Care Medicine, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany; Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Berlin, Germany; German Center for Child and Adolescent Health, partner site Berlin, Berlin, Germany; Deutsches Rheuma-Forschungszentrum, an Institute of the Leibniz Association, Berlin, Germany.
Department of Microbiology, Immunology and Transplantation, Laboratory for Inborn Errors of Immunity, KU Leuven, Leuven, Belgium.
J Allergy Clin Immunol. 2025 Jun 20. doi: 10.1016/j.jaci.2025.06.009.
Deficiency of adenosine deaminase 2 (DADA2) is an inborn error of immunity causing vasculitis and bone marrow failure. Bone marrow failure is mostly unresponsive to TNF-α inhibitors. The limited understanding of the pathomechanisms driving the disease impedes the development of new treatment options. Unlike cellular model systems expressing pathogenic ADA2 variants, primary monocytes from patients with DADA2 lack ADA2 protein expression.
This study aimed to analyze the role of protein degradation in the pathogenesis of DADA2 and the therapeutic potential of the lysosomotropic drug hydroxychloroquine in the treatment of patients with DADA2.
ADA2 protein expression in CD14 monocytes from healthy controls (n = 8) and patients with DADA2 (n = 11) was determined by Western blot after inhibition of lysosomal and proteasomal degradation, as well as after hydroxychloroquine treatment in vivo in 1 patient with DADA2. Lipidation of microtubule associated protein 1 light chain 3 beta (LC3B) was analyzed as a measure of autophagic activity. Clinical and laboratory data were recorded in cytopenic patients with DADA2 treated with hydroxychloroquine, 200 mg per day.
We demonstrated that inhibition of lysosomal degradation restores ADA2 protein expression in DADA2 monocytes in vitro. DADA2 monocytes exhibited increased autophagic activity. We observed clinical improvement in 2 cytopenic patients with DADA2 who were treated with hydroxychloroquine, and we showed a concomitant increase in ADA2 protein levels in monocytes from one of these patients in vivo.
We identified lysosomal protein degradation of ADA2 as a pathomechanism of DADA2 and introduced hydroxychloroquine as a potential treatment option in patients with DADA2 with refractory cytopenia.
腺苷脱氨酶2（DADA2）缺乏是一种导致血管炎和骨髓衰竭的先天性免疫缺陷病。骨髓衰竭对肿瘤坏死因子-α抑制剂大多无反应。对驱动该疾病的发病机制了解有限阻碍了新治疗方案的开发。与表达致病性ADA2变体的细胞模型系统不同，DADA2患者的原代单核细胞缺乏ADA2蛋白表达。
本研究旨在分析蛋白质降解在DADA2发病机制中的作用以及溶酶体亲和性药物羟氯喹治疗DADA2患者的治疗潜力。
在抑制溶酶体和蛋白酶体降解后，通过蛋白质印迹法测定健康对照者（n = 8）和DADA2患者（n = 11）的CD14单核细胞中ADA2蛋白表达，以及在1例DADA2患者体内进行羟氯喹治疗后进行测定。分析微管相关蛋白1轻链3β（LC3B）的脂化作为自噬活性的指标。记录每日服用200 mg羟氯喹治疗的DADA2血细胞减少患者的临床和实验室数据。
我们证明抑制溶酶体降解可在体外恢复DADA2单核细胞中ADA2蛋白表达。DADA2单核细胞表现出自噬活性增加。我们观察到2例接受羟氯喹治疗的DADA2血细胞减少患者临床症状改善，并且我们显示其中1例患者体内单核细胞中ADA2蛋白水平随之升高。
我们确定ADA2的溶酶体蛋白降解是DADA2的发病机制，并引入羟氯喹作为治疗难治性血细胞减少的DADA2患者的潜在治疗选择。
