Suppression of epithelial signal transducer and activator of transcription 1 activation by extracts of Aspergillus fumigatus

Bharat Bhushan, Tetsuya Homma, James E. Norton, Quan Sha, Jason Siebert, Dave S. Gupta, James W. Schroeder, Robert P. Schleimer*

*Corresponding author for this work

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Aspergillus fumigatus (AF) is often pathogenic in immune-deficient individuals and can cause life-threatening infections such as invasive aspergillosis. The pulmonary epithelial response to AF infection and the signaling pathways associated with it have not been completely studied. BEAS-2B cells or primary human bronchial epithelial cells were exposed to extracts of AF and challenged with IFN-β or the Toll-like receptor 3 agonist double-stranded RNA (dsRNA). Cytokine release (B-cell activating factor of the TNF family [BAFF], IFN-γ-induced protein-10 [IP-10], etc.) was assessed. AF extract was separated into low-molecular-weight (LMW) and highmolecular-weight (HMW) fractions using ultra 4 centrifugal force filters to characterize the activity. Real-time PCR was performed with a TaqMan method, and protein estimation was performed using ELISA techniques. Western blot was performed to assess phosphorylation of signal transducer and activator of transcription 1 (STAT1). IFN-β and dsRNA induced messenger RNA (mRNA) expression of BAFF (350- and 452-fold, respectively [n = 3]) and IP-10 (1,081- and 3,044-fold, respectively [n = 3]) in BEAS-2B cells. When cells were pretreated with AF extract for 1 hour and then stimulated with IFN-b or dsRNA for 6 hours, induction of BAFF and IP-10 mRNA was strongly suppressed relative to levels produced by IFN-b and dsRNA alone. When compared with control, soluble BAFF and IP-10 protein levels were maximally suppressed in dsRNA-stimulated wells treated with 1:320 wt/vol AF extract (P < 0.005). Upon molecular size fractionation, a LMW fraction of AF extract had no measurable suppressive effect on IP-10 mRNA expression. However, a HMW fraction of the AF extract significantly suppressed IP-10 expression in BEAS-2B cells that were stimulated with dsRNA or IFN-β. When BEAS-2B cells were pretreated with AF extract and then stimulated with IFN-β, reduced levels of pSTAT1 were observed, with maximum suppression at 4 and 6 hours. Our results show that AF extracts suppressed expression of inflammatory cytokines in association with inhibition of the IFN-β signaling pathway and suppression of the formation of pSTAT1.

Original languageEnglish (US)
Pages (from-to)87-95
Number of pages9
JournalAmerican journal of respiratory cell and molecular biology
Volume53
Issue number1
DOIs
StatePublished - Jul 1 2015

Keywords

  • Aspergillus fumigatus
  • BAFF
  • Epithelial cells
  • IP-10

ASJC Scopus subject areas

  • Molecular Biology
  • Pulmonary and Respiratory Medicine
  • Clinical Biochemistry
  • Cell Biology

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