Background-The pathology of pediatric severe therapy-resistant asthma (STRA) is little understood.

Exhaled nitric oxide (FE(NO)) has been proposed as a noninvasive marker of airway inflammation in asthma, and may reflect airway eosinophilia. We examined the relationship between FE(NO) and eosinophilic inflammation in endobronchial biopsies from 31 children with difficult asthma (mean age [range] 11.9 [6-17] yr), following 2 wk of prednisolone (40 mg/d). Endobronchial biopsy was also performed in seven children without asthma. Biopsy eosinophils were detected using antibody to major basic protein, and point-counting used to derive an "eosinophil score." FE(NO) readings and suitable biopsies for analysis were both obtained in 21 of 31 children with asthma. Adherence to prednisolone was demonstrated in 17 of these 21. Within this group, there was a correlation between FE(NO) and eosinophil score (r = 0.54, p = 0.03). The relationship was strongest in patients with persistent symptoms after prednisolone, in whom FE(NO) > 7 ppb was associated with a raised eosinophil score. For all patients, FE(NO) < 7 ppb was associated with an eosinophil score within the nonasthmatic range, regardless of symptoms. We propose that FE(NO) is associated with eosinophilic inflammation in children with difficult asthma, following prednisolone, and may help in identifying patients in whom persistent symptoms are associated with airway eosinophilia.

IL-33 is a relatively steroid-resistant mediator that promotes airway remodeling in patients with STRA and is an important therapeutic target.

Asthma is a chronic inflammatory disease that is characterized by increased expression of multiple inflammatory genes. Chromatin modification plays a critical role in the regulation of these genes. Acetyaltion of histones by histone acetyltransferases (HATs) is associated with increased gene transcription, whereas hypocetylation induced by histone deacetylases (HDACs) is associated with suppression of gene expression. We have examined the expression and activity of HATs and HDACs in bronchial biopsies from normal subjects and subjects with asthma. There was no difference in the site of HDAC1-HDAC6 expression between normal subjects and subjects with asthma, but subjects with asthma had reduced HDAC enzymatic activity and reduced HDAC1 and HDAC2 protein expression, as measured by Western blotting. In contrast, subjects with asthma treated with inhaled steroids were found to have greater HDAC activity than untreated subjects with asthma, although still lower than control subjects. In contrast, although there was no change in the site of HAT (CREB binding protein and p300/CREB binding protein-associated factor) expression, HAT activity was increased in subjects with asthma. HAT activity was reduced to control levels in subjects with asthma treated with inhaled steroids. The increase in HAT activity and reduced HDAC activity in asthma may underlie the increased expression of multiple inflammatory genes, and this is reversed, at least in part, by treatment with inhaled steroids.

No abstract