Mast cell corticotropin-releasing factor subtype 2 suppresses mast cell degranulation and limits the severity of anaphylaxis and stress-induced intestinal permeability. Permalink https://escholarship.org/uc/item/8t3660m4 Journal Abstract 33 34 Background: Psychological stress and heightened MC activation are linked with important 35 immunological disorders including allergy, anaphylaxis, asthma, and functional bowel 36diseases, but the mechanisms remain poorly defined. We have previously demonstrated that 37 activation of the corticotropin releasing factor (CRF) system potentiates MC degranulation 38 responses during IgE-mediated anaphylaxis and psychological stress, via CRF receptor 39 subtype 1 (CRF 1 ) expressed on MCs. 40 41 Objective: In this study, we investigated the role of CRF receptor subtype 2 (CRF 2 ) as a 42 modulator of stress-induced MC degranulation and associated disease pathophysiology. 43 44 Methods: In vitro MC degranulation assays were performed with bone marrow derived MCs 45 (BMMCs) derived from WT and CRF 2 -deficient (CRF 2 -/-) mice and RBL-2H3 MCs transfected 46 with CRF 2 -overexpressing plasmid or CRF 2 -siRNA. In vivo MC responses and associated 47 pathophysiology in IgE-mediated passive systemic anaphylaxis (PSA) and acute 48 psychological restraint stress were measured in WT, CRF 2 -/-, and MC-deficient Kit W-sh/W-sh 49 knock-in mice. 50 51 Results: Compared with WT mice, CRF 2 -/exhibited heightened serum histamine levels and 52 exacerbated PSA-induced anaphylactic responses and colonic permeability. In addition, 53 CRF 2 -/mice exhibited increased serum histamine and colonic permeability following acute 54 restraint stress. Experiments with BMMCs and RBL-2H3 MCs demonstrated that CRF 2 55 expressed on MCs suppresses store-operated Ca 2+ entry (SOCE) signaling and MC 56 M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 degranulation induced by diverse MC stimuli. Experiments with MC-deficient Kit W-sh/W-sh mice 57 systemically engrafted with WT and CRF 2 -/-BMMCs demonstrated the functional importance 58 of MC-CRF 2 in modulating stress-induced pathophysiology. 59 60 Conclusions: MC CRF 2 is a negative, global modulator of stimuli-induced MC degranulation 61 and limits the severity of IgE-mediated anaphylaxis and stress-related disease pathogenesis. 62 63 Key messages 64 • Loss of CRF 2 function induces exacerbated MC degranulation, IgE-mediated 65 anaphylaxis and psychological stress-induced intestinal barrier dysfunction. 66 • MC-specific CRF 2 suppresses degranulation induced by diverse MC stimuli via 67 negative regulation of SOCE. 68 • Further characterization of the mechanisms by which CRF 2 negatively modulates MC 69 activation could lead to novel therapeutic approaches for stress-related immunological 70 disorders associated with MC hyperactivity. 71 72

Although females suffer twice as much as males from stress-related disorders, sex-specific participating and pathogenic cellular stress mechanisms remain uncharacterized. Using corticotropin-releasing factor receptor 2-deficient (Crhr2−/−) and wild-type (WT) mice, we show that CRF receptor type 2 (CRF2) and its high-affinity ligand, urocortin 1 (Ucn1), are key mediators of the endoplasmic reticulum (ER) stress response in a murine model of acute pancreatic inflammation. Ucn1 was expressed de novo in acinar cells of male, but not female WT mice during acute inflammation. Upon insult, acinar Ucn1 induction was markedly attenuated in male but not female Crhr2r−/− mice. Crhr2−/− mice of both sexes show exacerbated acinar cell inflammation and necrosis. Electron microscopy showed mild ER damage in WT male mice and markedly distorted ER structure in Crhr2−/− male mice during pancreatitis. WT and Crhr2−/− female mice showed similarly distorted ER ultrastructure that was less severe than distortion seen in Crhr2−/− male mice. Damage in ER structure was accompanied by increased ubiquitination, peIF2, and mis-targeted localization of vimentin in WT mice that was further exacerbated in Crhr2−/− mice of both sexes during pancreatitis. Exogenous Ucn1 rescued many aspects of histological damage and cellular stress response, including restoration of ER structure in male WT and Crhr2−/− mice, but not in females. Instead, females often showed increased damage. Thus, specific cellular pathways involved in coping and resolution seem to be distinct to each sex. Our results demonstrate the importance of identifying sex-specific pathogenic mechanisms and their value in designing effective therapeutics.

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