title: Increased corticosteroid sensitivity by a long acting β2 agonist formoterol via β2 adrenoceptor independent protein phosphatase 2A activation.
abstract: Long-acting β2-adrenoceptor agonists (LABAs) are reported to enhance anti-inflammatory effects of corticosteroids in vitro and in vivo, although the molecular mechanisms have not yet been elucidated. We investigated the role of serine/threonine protein phosphatase 2A (PP2A) on regulation of corticosteroid sensitivity via inhibition of glucocorticoid receptor (GR) phosphorylation as the target of formoterol, an LABA. Corticosteroid sensitivity was determined as IC50 to dexamethasone (Dex) on TNFα-induced IL-8 release in a U937 monocytic cell line (Dex-IC50). Phosphorylation levels of GR-Ser226 and c-Jun N-terminal kinase (JNK) were determined by western-blotting. Phosphatase activity of immunopurified PP2A was measured by fluorescence-based assay. Exposure to IL-2/IL-4 for 48 h decreased Dex sensitivity with a concomitant increase of GR phosphorylation at Ser226 with JNK1 activation. Formoterol restored Dex sensitivity by inhibiting phosphorylation of GR-Ser226 and JNK1. PP2A inhibition by okadaic acid, a phosphatase inhibitor, abrogated formoterol-mediated effects. In addition, formoterol enhanced PP2A activity in intact or IL-2/IL-4 treated U937 cells and human peripheral blood mononuclear cells. In addition, PP2A activation by formoterol was not antagonized by ICI-118551, and formoterol could activate PP2A directly in cell free system. Taken together, formoterol increases corticosteroid sensitivity via activation of PP2A in receptor independent manner, explaining its benefits as add-on therapy for the treatment of corticosteroid-insensitive diseases, such as severe asthma.
authors.affiliation: Airway Disease Section, National Heart and Lung Institute, Imperial College London, Guy Scadding Building, Royal Brompton Campus, Dovehouse Street, London SW3 6LY, UK.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mercado
authors.forename: Anna
authors.initials: A
authors.lastname: Miller-Larsson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barnes
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ito
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists / Q000494:pharmacology*; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology*; D004983:Ethanolamines / Q000494:pharmacology*; D000068759:Formoterol Fumarate; D005938:Glucocorticoids / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D020128:Inhibitory Concentration 50; D016209:Interleukin-8 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054648:Protein Phosphatase 2 / Q000187:drug effects* / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D020298:U937 Cells
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D004983:Ethanolamines; D005938:Glucocorticoids; D016209:Interleukin-8; D011965:Receptors, Glucocorticoid; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; D054648:Protein Phosphatase 2; D000068759:Formoterol Fumarate