Inducible NO synthase expression is low in airway epithelium from young children with cystic fibrosis

Alexander Moeller ^1*, Fritz Jr Horak ², Catherine Lane ³, Darryl Knight ⁴, Anthony Kicic ⁵, Siobhain Brennan ⁶, Peter Franklin ⁷, Jason Terpolilli ⁵, Johannes H Wildhaber ⁸ and Stephen M Stick ⁹

¹ University Children's Hospital Zuerich, Switzerland
² Princess Margaret Hospital for Children, Perth,, Australia
³ Princess Margaret Hospital for Children, Perth, Australia
⁴ James Hogg iCAPTURE centre for cardiovascular and Respiratory Research, St.Pauls Hospital, Vancouver, Canada
⁵ Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth,, Australia
⁶ Telethon Institute for Child Health Research, Centre for Child Health Research,, Australia
⁷ School of Paediatrics and Child Health, University of Western Australia, Australia
⁸ University Children's Hospital, Switzerland
⁹ Princess Margaret Hospital, Australia

^* To whom correspondence should be addressed. E-mail: alexander.moeller{at}kispi.unizh.ch.

Accepted 19 February 2006

Abstract

Background: This is the first study to measure inducible nitric oxide synthase gene (iNOS) and protein expression quantitatively in primary epithelial cells from very young children with cystic fibrosis (CF). Low levels of exhaled nitric oxide in CF suggest dysregulation of NO production in the airway. Due to the importance of NO in cell homeostasis and innate immunity any defect in the pathway associated with CF would be a potential target for therapeutic intervention.

Methods: Cells were obtained by tracheo-bronchial brushing from 40 children with CF (mean age ± SD, 2.1 ± 1.5 years) and from 12 healthy, non-atopic Children (3.4 ± 1.2 years). Expression of iNOS mRNA was measured using quantitative PCR and iNOS protein by immunofluorescence and Western blot.

Results: Inducible NOS mRNA expression was significantly lower in CF patients with and without bacterial infection in broncho-alveolar lavage (BAL) compared to healthy children (0.22 and 0.23 vs 0.76; p=0.002 and p=0.01, respectively). Low levels of iNOS gene expression were accompanied by low levels of iNOS protein expression as detected by Western blot.

Conclusions: These results support the findings of previous studies in adult patients with advanced disease, cell lines and animal models. Our findings reflect the situation in children mild lung disease. They indicate that low iNOS expression may be an innate defect in CF with potential consequences for local anti-microbial defense and epithelial cell function and provide evidence for an approach to therapy based upon increasing epithelial NO production or the sensitivity of NO-dependent cellular processes.

Keywords: cystic fibrosis, inducible NO synthase, primary epithelial cells, young children

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