Role of Aspergillus fumigatus in Triggering Protease-Activated Receptor-2 in Airway Epithelial Cells and Skewing the Cells toward a T-helper 2 Bias

Am J Respir Cell Mol Biol. 2016 Jan;54(1):60-70. doi: 10.1165/rcmb.2015-0062OC.

Abstract

Aspergillus fumigatus (AF) infection and sensitization are common and promote Th2 disease in individuals with asthma. Innate immune responses of bronchial epithelial cells are now known to play a key role in determination of T cell responses upon encounter with inhaled pathogens. We have recently shown that extracts of AF suppress JAK-STAT signaling in epithelial cells and thus may promote Th2 bias. To elucidate the impact of AF on human bronchial epithelial cells, we tested the hypothesis that AF can modulate the response of airway epithelial cells to favor a Th2 response and explored the molecular mechanism of the effect. Primary normal human bronchial epithelial (NHBE) cells were treated with AF extract or fractionated AF extract before stimulation with poly I:C or infection with human rhinovirus serotype 16 (HRV16). Expression of CXCL10 mRNA (real-time RT-PCR) and protein (ELISA) were measured as markers of IFN-mediated epithelial Th1-biased responses. Western blot was performed to evaluate expression of IFN regulatory factor-3 (IRF-3), NF-κB, and tyrosine-protein phosphatase nonreceptor type 11 (PTPN11), which are other markers of Th1 skewing. Knockdown experiments for protease-activated receptor-2 (PAR-2) and PTPN11 were performed to analyze the role of PAR-2 in the mechanism of suppression by AF. AF and a high-molecular-weight fraction of AF extract (HMW-AF; > 50 kD) profoundly suppressed poly I:C- and HRV16-induced expression of both CXCL10 mRNA and protein from NHBE cells via a mechanism that relied upon PAR-2 activation. Both AF extract and a specific PAR-2 activator (AC-55541) suppressed the poly I:C activation of phospho-IRF-3 without affecting activation of NF-κB. Furthermore, HMW-AF extract enhanced the expression of PTPN11, a phosphatase known to inhibit IFN signaling, and concurrently suppressed poly I:C-induced expression of both CXCL10 mRNA and protein from NHBE cells. These results show that exposure of bronchial epithelial cells to AF extract suppressed poly I:C and HRV16 signaling via a mechanism shown to involve activation of PAR-2 and PTPN11. This action of AF may promote viral disease exacerbations and may skew epithelial cells to promote Th2 inflammation in allergic airway disorders mediated or exacerbated by AF, such as asthma and chronic rhinosinusitis.

Keywords: Aspergillus fumigatus; CRS; asthma; bronchial epithelial cells; virus.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspergillus fumigatus / immunology*
  • Aspergillus fumigatus / metabolism
  • Aspergillus fumigatus / pathogenicity
  • Cells, Cultured
  • Chemokine CXCL10 / genetics
  • Chemokine CXCL10 / immunology
  • Chemokine CXCL10 / metabolism
  • Epithelial Cells / drug effects
  • Epithelial Cells / immunology*
  • Epithelial Cells / metabolism
  • Epithelial Cells / microbiology
  • Epithelial Cells / virology
  • Gene Expression Regulation
  • Host-Pathogen Interactions
  • Humans
  • Interferon Regulatory Factor-3 / immunology
  • Interferon Regulatory Factor-3 / metabolism
  • Poly I-C / pharmacology
  • Protein Tyrosine Phosphatase, Non-Receptor Type 11 / genetics
  • Protein Tyrosine Phosphatase, Non-Receptor Type 11 / immunology
  • Protein Tyrosine Phosphatase, Non-Receptor Type 11 / metabolism
  • Receptor, PAR-2 / genetics
  • Receptor, PAR-2 / immunology*
  • Receptor, PAR-2 / metabolism
  • Respiratory Mucosa / drug effects
  • Respiratory Mucosa / immunology*
  • Respiratory Mucosa / metabolism
  • Respiratory Mucosa / microbiology
  • Respiratory Mucosa / virology
  • Rhinovirus / immunology
  • Rhinovirus / pathogenicity
  • Signal Transduction
  • Th1 Cells / immunology
  • Th1 Cells / metabolism
  • Th2 Cells / drug effects
  • Th2 Cells / immunology*
  • Th2 Cells / metabolism
  • Th2 Cells / microbiology
  • Th2 Cells / virology
  • Time Factors
  • Transfection

Substances

  • CXCL10 protein, human
  • Chemokine CXCL10
  • IRF3 protein, human
  • Interferon Regulatory Factor-3
  • Receptor, PAR-2
  • PTPN11 protein, human
  • Protein Tyrosine Phosphatase, Non-Receptor Type 11
  • Poly I-C