Elevated Gliotoxin Production By Aspergillus Fumigatus Downregulates Vitamin D Receptor Expression In Cystic Fibrosis Airways

C. A. Coughlan , E. P. Reeves , G. Bergsson , C. M. Greene , K. Kavanagh , S. J. O'Neill , N. G. McElvaney

Author address: 

Royal College of Surgeons in Ireland, Dublin, Ireland, NUI Maynooth, Maynooth, Ireland, RCSI, Dublin, Ireland

Abstract: 

Rationale: Lung disease in cystic fibrosis (CF) is characterized by chronic microbial colonization and repeated acute exacerbations of pulmonary infection. Vitamin D has previously been shown to induce expression of many anti-microbial peptides, thus enhancing innate immunity. The vitamin D receptor (VDR) a nuclear hormone receptor mediates the activity of vitamin D . Recently low mean serum vitamin D levels 3 were found in an allergic bronchopulmonary aspergillosis (ABPA) cohort of CF patients(1). ABPA affects between 4-15 % of CF patients and is characterised by pulmonary infiltrates, wheezing, parenchyma fibrosis, and bronchiectasis together with a heightened T helper type 2 (Th2) response. As the fungal pathogen Aspergillus fumigatus (A. fumigatus) in CF individuals leads to clinical deterioration of the lungs, the aim of this study was to investigate the effect of Aspergillus secreted toxins on VDR expression. Methods: The A. fumigatus clinical strains employed in this study were ATCC 26933 and CAF1. The effect of A. fumigatus on VDR expression was investigated in vitro in human CF bronchial and tracheal epithelial cells (CFBE 41o CFTE 29o ) and in CF bronchial brushings of - , - in vivo, A. fumigatus colonized individuals. The effect of the Aspergillus secondary metabolite gliotoxin, on VDR expression was also examined and levels of gliotoxin in bronchoalveolar lavage fluid (BALF) and culture filtrates were quantified by High-performance liquid chromatography on a reverse phase C-18 column. Results: A. fumigatus culture filtrates down-regulated VDR mRNA expression and reduced the level of VDR protein by 50% in both CFTE (P=0.005) and CFBE (P=0.009) cell lines. Culture filtrates from the Aspergillus strain CAF1 did not contain the immunosuppressive mycotoxin gliotoxin and did not affect VDR expression. Gliotoxin at a concentration of 0.8µM significantly downregulated VDR expression in both CFTE (p=0.002) and CFBE (p=0.02) cells. In vivo, analysis of bronchial brushings of Aspergillus colonized versus non-colonized patients with CF, revealed reduced levels of VDR (p=0.02) gene expression in fungal colonized individuals. In addition, significantly increased gliotoxin levels in BALF of Aspergillus colonised individuals with CF correlated with diminished VDR expression. Conclusion: This data indicates that in CF bronchial and tracheal epithelial cells, A. fumigatus secreted gliotoxin dose-dependently regulates VDR mRNA and protein expression. Aspergillus colonized patients with CF were characterised by distinct down-regulation of VDR gene expression and elevated levels of gliotoxin in vivo. Via inhibition of VDR expression, Aspergillus may directly impact upon the Th2 cytokine (IL-5/IL-13) expression profile thereby altering the inflammatory response within the CF lung. 1. Kreindler JL, Steele C, Nguyen N, Chan YR, Pilewski JM, Alcorn JF, et al. Vitamin D3 attenuates Th2 responses to Aspergillus fumigatus mounted by CD4+ T cells from cystic fibrosis patients with allergic bronchopulmonary aspergillosis. J Clin Invest. 2010 Sep 1;120(9):3242-54.
2011

abstract No: 

D25

Full conference title: 

American Thoracic Society
    • ATS 2011