Title Steroid resistance of airway type 2 innate lymphoid cells from patients with severe asthma: The role of thymic stromal lymphopoietin.
Author Liu, Sucai; Verma, Mukesh; Michalec, Lidia; Liu, Weimin; Sripada, Anand; Rollins, Donald; Good, James; Ito, Yoko; Chu, HongWei; Gorska, Magdalena M; Martin, Richard J; Alam, Rafeul
Journal J Allergy Clin Immunol Publication Year/Month 2018-Jan
PMID 28433687 PMCID PMC5650571
Affiliation + expend 1.Department of Medicine, Division of Allergy & Immunology, and the Division of Pulmonary and Critical Care Medicine, National Jewish Health, Denver, Colo.

BACKGROUND: Type 2 innate lymphoid cells (ILC2s) represent an important type 2 immune cell. Glucocorticoid regulation of human ILC2s is largely unknown. OBJECTIVE: We sought to assess steroid resistance of human blood and airway ILC2s from asthmatic patients and to examine its mechanism of induction. METHODS: We studied human blood and lung ILC2s from asthmatic patients and control subjects using flow cytometry and ELISA. RESULTS: Dexamethasone inhibited (P = .04) chemoattractant receptor-homologous molecule expressed on TH2 lymphocytes and type 2 cytokine expression by blood ILC2s stimulated with IL-25 and IL-33. However, it did not do so when ILC2s were stimulated with IL-7 and thymic stromal lymphopoietin (TSLP), 2 ligands of IL-7 receptor alpha. Unlike blood ILC2s, bronchoalveolar lavage (BAL) fluid ILC2s from asthmatic patients were resistant to dexamethasone. BAL fluid from asthmatic patients had increased TSLP but not IL-7 levels. BAL fluid TSLP levels correlated (r = 0.74) with steroid resistance of ILC2s. TSLP was synergistically induced in epithelial cells by IL-13 and human rhinovirus. Mechanistically, dexamethasone upregulated ILC2 expression of IL-7 receptor alpha, which augmented and sustained signal transducer and activator of transcription (STAT) 5 signaling by TSLP. TSLP induced mitogen-activated protein kinase kinase (MEK), c-Fos, inhibitor of DNA binding 3, phosphorylated signal transducer and activator of transcription (pSTAT) 3, and pSTAT5, molecules linked to steroid resistance. Dexamethasone inhibited c-Fos, inhibitor of DNA binding 3, and pSTAT3 but not pSTAT5 and MEK. The MEK inhibitor trametinib, the Janus kinase-STAT inhibitor tofacitinib, and the STAT5 inhibitor pimozide reversed steroid resistance of BAL ILC2s. CONCLUSIONS: Dexamethasone inhibited type 2 cytokine production by blood ILC2s. IL-7 and TSLP abrogated this inhibition and induced steroid resistance of ILC2s in a MEK- and STAT5-dependent manner. BAL fluid ILC2s from asthmatic patients with increased TSLP levels were steroid resistant, which was reversed by clinically available inhibitors of MEK and STAT5.

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