Thrombomodulin inhibits the activation of eosinophils and mast cells Ziaurahman Roeen a , Masaaki Toda a , Corina N. D’Alessandro-Gabazza a , Masahiro Onishi b , Tetsu Kobayashi b , Taro Yasuma c , Masahito Urawa a,b , Osamu Taguchi b , Esteban C. Gabazza a,⇑ a Department of Immunology, Mie University Graduate School of Medicine, Edobashi 2-174, Tsu City, Mie Prefecture 514-8507, Japan b Department of Pulmonary and Critical Care Medicine, Mie University Graduate School of Medicine, Edobashi 2-174, Tsu City, Mie Prefecture 514-8507, Japan c Department of Endocrinology, Diabetes and Metabolism, Mie University Graduate School of Medicine, Edobashi 2-174, Tsu City, Mie Prefecture 514-8507, Japan article info Article history: Received 30 July 2014 Accepted 13 November 2014 Available online 5 December 2014 Keywords: Asthma Eosinophils Mast cells Coagulation Protein C pathway abstract Eosinophils and mast cells play critical roles in the pathogenesis of bronchial asthma. Activation of both cells leads to the release of pro-inflammatory mediators in the airway of asthmatic patients. Recently, we have shown that inhaled thrombomodulin inhibits allergic bronchial asthma in a mouse model. In the present study, we hypothesize that thrombomodulin can inhibit the activation of eosinophils and mast cells. The effect of thrombomodulin on the activation and release of inflammatory mediators from eosin- ophils and mast cells was evaluated. Thrombomodulin inhibited the eotaxin-induced chemotaxis, upreg- ulation of CD11b and degranulation of eosinophils. Treatment with thrombomodulin also significantly suppressed the degranulation and synthesis of inflammatory cytokines and chemokines in eosinophils and mast cells. Mice treated with a low-dose of inhaled thrombomodulin have decreased number of eosinophils and activated mast cells and Th2 cytokines in the lungs compared to untreated mice. The results of this study suggest that thrombomodulin may modulate allergic responses by inhibiting the activation of both eosinophils and mast cells. Ó 2014 Elsevier Inc. All rights reserved. 1. Introduction Eosinophils and mast cells are the key mediators of allergic inflammatory responses in the airways of asthmatic patients [1,2]. A large body of evidence gained from clinical and experimen- tal studies has shown that excessive infiltration and secreted prod- ucts of both cells in the airways are associated with disease severity and enhanced airway hyperresponsiveness [1–4]. Eosino- phils can be activated by several ligands of CCR3 including eotaxin, which is secreted by airway epithelial cells [4]. Activated eosino- phils secrete proinflammatory factors including cytokines (IL-13, IL-5, osteopontin), chemokines (CCL11 or eotaxin, CCL22), leukotri- enes, matrix metalloproteinases and granule molecules such as eosinophil peroxidase (EPO), eosinophil cationic protein, major basic protein and eosinophil-derived neurotoxin [1,4]. Mast cells are activated by antigen-mediated cross-linking of immunoglobu- lin E (IgE)-bound Fce receptors (FceR) leading to the release of inflammatory mediators including histamine, serotonin, proteogly- cans, lipid mediators (prostaglandins, leukotrienes), Th2 cytokines (IL-4, IL-5) and chemokines (CCL2, CCL5) [2,3]. Thrombomodulin (TM) is a cell membrane-bound protein also known as CD141 or blood dendritic cell antigen (BDCA)-3 [5,6]. When TM binds thrombin, a critical pro-coagulant protease of the clotting system, thrombin is converted to an anticoagulant and antifibrinolytic factor. TM-bound thrombin is unable to cleave fibrinogen, protease-activated receptor (PAR)-1, and other sub- strates of the coagulation cascade, but it is able to cleave protein C to activated protein C, an anticoagulant and antiinflammatory protein and thrombin-activatable fibrinolysis inhibitor (TAFI) to activated TAFI, an antifibrinolytic and anti-inflammatory factor [5–7]. In addition, TM can exhibit direct antiinflammatory proper- ties by inhibiting the pro-inflammatory activity of high-mobility group protein B-1 (HMGB-1), and recently, we discovered that sol- uble and membrane-bound TM is protective in allergic diseases by modulating the pro-inflammatory activity of dendritic cells (DCs) [8,9]. In the current study we hypothesized that TM may also exert protective effect in allergic conditions by modulating the activation of eosinophils and mast cells. http://dx.doi.org/10.1016/j.cellimm.2014.11.005 0008-8749/Ó 2014 Elsevier Inc. All rights reserved. Abbreviations: EPO, eosinophil peroxidase; ECP, eosinophil cationic protein; MBP, major basic protein; EDN, eosinophil-derived neurotoxin; TM, thrombomod- ulin; BSA, bovine serum albumin; BMMCs, bone marrow-derived mast cells; TNP, trinitrophenyl; OVA, ovalbumin; IL, interleukin; rh, recombinant human; TNFa, tumor necrosis factor-a. ⇑ Corresponding author. Fax: +81 59 231 5225. E-mail address: gabazza@doc.medic.mie-u.ac.jp (E.C. Gabazza). Cellular Immunology 293 (2015) 34–40 Contents lists available at ScienceDirect Cellular Immunology journal homepage: www.elsevier.com/locate/ycimm