Am. J. Respir. Crit. Care Med., Volume 165, Number 7, April 2002, 1010-1014

Clinical Relevance of Airway 11-Hydroxysteroid Dehydrogenase Type II Enzyme in Asthma

BERNADETTE E. ORSIDA, ZYGMUNT S. KROZOWSKI, and E. HAYDN WALTERS

Department of Respiratory Medicine, The Alfred Hospital and Monash University Medical School; Laboratory of Molecular Hypertension, Baker Medical Research Institute, Melbourne; and Department of Clinical Sciences, University of Tasmania Medical School, Royal Hobart Hospital, Tasmania, Australia

11-Hydroxysteroid dehydrogenases (11-HSD) are responsible for the conversion of bioactive glucocorticoids to and from inactive metabolites. 11-HSD2 is generally considered a high-affinity inactivator of natural glucocorticoids, although its activity with synthetic compounds in vivo is unknown. Inhaled corticosteroids (ICS) remain the primary antiinflammatory agents for treating asthma, but little is known about their metabolism in the lung. The aims of this study were to determine whether the 11-HSD2 enzyme can be localized to human airway tissue and whether differential expression of this enzyme relates to asthma severity and ICS needs. We studied airway biopsy specimens from 22 asthmatic subjects, in two groups: (1) a group not treated with ICS (n = 7); and (2) a group treated with ICS (range: 200 to 1,500 µg/d; n = 15). A control population consisted of nine nonasthmatic subjects. Immunostaining was done with an immunopurified antibody to human 11-HSD2. Immunoreactivity was generally localized to the endothelium of vessels in the lamina propria and to airway epithelium both in asthmatic patients and nonasthmatic controls. There was a statistically significant inverse relationship between the ICS dose required for effective treatment and the extent of epithelial 11-HSD2 staining (r = 0.44; p = 0.04). This is consistent with 11-HSD2 acting as an oxidoreductase that regenerates rather than inactivates ICS. This study suggests that glucocorticoid sensitivity in the lung is not determined by ICS breakdown, but may be related to 11-HSD2 sustaining the activation of synthetic glucocorticoids.

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