IL-13-induced changes in endogenous glucocorticoid metabolism in the lung regulate the proasthmatic response

Am J Physiol Lung Cell Mol Physiol. 2012 Sep;303(5):L382-90. doi: 10.1152/ajplung.00125.2012. Epub 2012 Jul 6.

Abstract

Endogenous glucocorticoid (GC) activation is regulated by the intracellular GC-activating and -inactivating enzymes 11β-hydroxysteroid dehydrogenase (11β-HSD)1 and 11β-HSD2, respectively, that catalyze interconversion of inert cortisone and its bioactive metabolite cortisol. Because endogenous GCs are critically implicated in suppressing the asthmatic state, this study examined the roles of the 11β-HSD enzymes in regulating GC activation and bronchoprotection during proasthmatic stimulation. Airway hyperresponsiveness to methacholine and inflammation were assessed in rabbits following inhalation of the proasthmatic/proinflammatory cytokine IL-13 with and without pretreatment with the 11β-HSD inhibitor carbenoxolone (CBX). Additionally, IL-13-induced changes in 11β-HSD isozyme expression and GC metabolism were examined in epithelium-intact and -denuded tracheal segments and peripheral lung tissues. Finally, the effects of pretreatment with CBX or 11β-HSD2-targeted siRNAs were investigated with respect to cortisol prevention of IL-13-induced airway constrictor hyperresponsiveness and eotaxin-3 production by airway epithelial cells. IL-13-exposed rabbits exhibited airway hyperresponsiveness, inflammation, and elevated bronchoalveolar lung fluid levels of eotaxin-3. These responses were inhibited by pretreatment with CBX, suggesting a permissive proasthmatic role for 11β-HSD2. Supporting this concept, extended studies demonstrated that 1) IL-13-treated tracheal epithelium and peripheral lung tissues exhibit upregulated 11β-HSD2 activity, 2) the latter impairs cortisone-induced cortisol accumulation and the ability of administered cortisol to prevent both IL-13-induced heightened airway contractility and eotaxin-3 release from epithelial cells, and 3) these proasthmatic responses are prevented by cortisol administration in the presence of 11β-HSD2 inhibition. Collectively, these data demonstrate that the proasthmatic effects of IL-13 are enabled by impaired endogenous GC activation in the lung that is attributed to upregulation of 11β-HSD2 in the pulmonary epithelium.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 11-beta-Hydroxysteroid Dehydrogenase Type 1 / antagonists & inhibitors
  • 11-beta-Hydroxysteroid Dehydrogenase Type 1 / genetics
  • 11-beta-Hydroxysteroid Dehydrogenase Type 1 / metabolism
  • 11-beta-Hydroxysteroid Dehydrogenase Type 2 / antagonists & inhibitors
  • 11-beta-Hydroxysteroid Dehydrogenase Type 2 / genetics
  • 11-beta-Hydroxysteroid Dehydrogenase Type 2 / metabolism
  • Animals
  • Asthma / enzymology
  • Asthma / metabolism*
  • Asthma / pathology
  • Bronchoconstrictor Agents / pharmacology
  • Carbenoxolone / pharmacology
  • Chemokines, CC / genetics
  • Chemokines, CC / metabolism
  • Cortisone / metabolism
  • Gene Expression
  • Glucocorticoids / metabolism*
  • Hydrocortisone / metabolism
  • Interleukin-13 / administration & dosage
  • Interleukin-13 / physiology*
  • Isoenzymes / antagonists & inhibitors
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Lung / enzymology
  • Lung / metabolism*
  • Lung / pathology
  • Methacholine Chloride / pharmacology
  • Muscle, Smooth / enzymology
  • Muscle, Smooth / metabolism
  • Pneumonia / enzymology
  • Pneumonia / metabolism
  • Rabbits
  • Respiratory Mucosa / enzymology
  • Respiratory Mucosa / metabolism
  • Trachea / pathology

Substances

  • Bronchoconstrictor Agents
  • Chemokines, CC
  • Glucocorticoids
  • Interleukin-13
  • Isoenzymes
  • Methacholine Chloride
  • 11-beta-Hydroxysteroid Dehydrogenase Type 1
  • 11-beta-Hydroxysteroid Dehydrogenase Type 2
  • Carbenoxolone
  • Cortisone
  • Hydrocortisone