title: Nortriptyline reverses corticosteroid insensitivity by inhibition of phosphoinositide-3-kinase-δ.
abstract: Corticosteroid insensitivity represents a major barrier to the treatment of chronic obstructive pulmonary disease (COPD) and severe asthma. It is caused by oxidative stress, leading to reduced histone deacetylase-2 (HDAC2) function through activation of phosphoinositide-3-kinase-δ (PI3Kδ). The tricyclic antidepressant nortriptyline has been identified in high-throughput screens as an agent that increases corticosteroid responsiveness. The aim of this study was to identify the molecular mechanism whereby nortriptyline increases corticosteroid sensitivity. Phosphorylation of Akt, a footprint of PI3K activation, and HDAC activity were evaluated by Western blotting and fluorescent activity assay in U937 monocytic cells. Corticosteroid sensitivity was evaluated by the inhibition of tumor necrosis factor α (TNFα)-induced interleukin 8 (IL-8) production by budesonide. Hydrogen peroxide (H(2)O(2)) or cigarette smoke extract (CSE) increased the level of phosphorylated Akt (pAkt) and reduced HDAC activity. Pretreatment with nortriptyline inhibited pAkt induced by CSE and H(2)O(2) as well as restored HDAC activity that had been decreased by H(2)O(2) and CSE. In addition, nortriptyline inhibited PI3Kδ activity, but had no effect on the PI3Kα and PI3Kγ isoforms. Although CSE reduced the effects of budesonide on TNFα-induced IL-8 production in U937 cells, nortriptyline reversed CSE-induced corticosteroid insensitivity. Nortriptyline restores corticosteroid sensitivity induced by oxidative stress via direct inhibition of PI3Kδ and is a potential treatment for corticosteroid-insensitive diseases such as COPD and severe asthma.
authors.affiliation: Airway Disease Section, National Heart and Lung Institute, Dovehouse St., London, SW3 6LY, United Kingdom.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mercado
authors.forename: Yasuo
authors.initials: Y
authors.lastname: To
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ito
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barnes
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology*; D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology*; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D019819:Budesonide / Q000494:pharmacology; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D058534:Class I Phosphatidylinositol 3-Kinases; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D056464:Histone Deacetylase 2 / Q000037:antagonists & inhibitors; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D016209:Interleukin-8 / Q000096:biosynthesis; D009025:Morpholines / Q000494:pharmacology; D009661:Nortriptyline / Q000494:pharmacology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy; D017382:Reactive Oxygen Species / Q000378:metabolism; D012907:Smoking / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000494:pharmacology; D020298:U937 Cells
chemical_list: D000305:Adrenal Cortex Hormones; D018759:Adrenergic Uptake Inhibitors; D000893:Anti-Inflammatory Agents; D002867:Chromones; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D016209:Interleukin-8; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019819:Budesonide; D006861:Hydrogen Peroxide; D009661:Nortriptyline; D058534:Class I Phosphatidylinositol 3-Kinases; C486018:PIK3CD protein, human; D051057:Proto-Oncogene Proteins c-akt; D056464:Histone Deacetylase 2