Pro-inflammatory responses induced by A. fumigatus and A. versicolor in various human macrophage models

ABSTRACT

Exposure to mold-contaminated indoor air has been associated with various respiratory diseases, and there is a need for experimental data to confirm these associations. The pro-inflammatory properties of well-characterized aerosolized spores and hyphal fragments from Aspergillus fumigatus and Aspergillus versicolor were examined and compared using various human macrophage cell models including phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 macrophages (THP-1 Ma), primary peripheral blood monocyte-derived macrophages (MDM), and primary airway macrophages (AM) from induced sputum. X-ray treated samples of the two mold species induced different responses with A. fumigatus displaying the most potent induction of pro-inflammatory responses. While hyphal fragments from A. fumigatus were more potent than spores, similar responses were produced by the two growth stages of A. versicolor. THP-1 Ma was the most sensitive model releasing a broad range of cytokines/chemokines. MDM exhibited a similar cytokine/chemokine profile as THP-1 Ma, except for a low-quantity release of interleukin-1β (IL-1β). In contrast, AM appeared to be nonresponsive and yielded a different pattern of pro-inflammatory markers. Toll-like receptor (TLR)4, but also to a certain degree TLR2, was involved in several responses induced by spores and aerosolized hyphal fragments of A. fumigatus in MDM. Taken together, MDM seems to be the most promising experimental macrophage model.

Abbreviations: AF: A. fumigatus, Aspergillus fumigatus; AV: A. versicolor, Aspergillus versicolor; AM: Airway Macrophage; CBA: Cytometric Bead Array; CD: Cluster of Differentiation; DTT: dithiothreitol; ELISA: Enzyme Linked Immunosorbent Assay; FBS: fetal bovine serum; GM-CSF: Granulocyte macrophage colony-stimulating factor; IL-1β: Interleukin-1beta; MDM: Monocyte-Derived Macrophages; NF-κB: Nuclear Factor kappa light chain enhancer of activated B cells; NLR: NOD-like Receptor; PAMP: Pathogen Associated Molecular Pattern; PMA: Phorbol 12-myristate 13-acetate; PRR: Pattern Recognition Receptor; THP-1: Human leukemia monocyte cell line; TLR: Toll-like Receptor; TNF-α: Tumor Necrosis Factor- alpha

KEYWORDS:

• Mold
• inflammation
• immune cells
• cytokines
• TLRs

Acknowledgments

The present investigation is a part of the project “Mold particles in indoor air” that is funded by the Research Council of Norway: Grant number NFR196130/H10. Valuable comments from Dr. Wijnand Eduard, the project leader, are gratefully acknowledged. Dr. Liv Ingunn B Sikkeland, Department of Respiratory Medicine, Oslo University Hospital, is acknowledged for technical advice, and providing access to facilities for sputum induction and preparation of AM. The authors wish to thank Ms Leni Ekeren for her skillful technical assistance. Dr. Anette K. Bølling reports grants from the Research Council of Norway (#228129).

Authors’ contributions

JAH and EØ designed and coordinated the study. EØ performed all experiments, and contributed in all experimental planning and design in collaboration with JAH. AAKJ provided the mold particles. RØ made the MDM model available to this study. AS provided technical advice for THP-1 Ma and MDM models. TBS performed the sputum induction and preparation of AM. AKB provided technical advice with AM model. EØ performed all data analysis and statistics in collaboration with JAH, AKB, and AS. EØ and JAH drafted the first version of the manuscript and wrote the final version in collaboration with AS and AKB. All authors read, commented, and approved the final manuscript.

Conflicts of interest

The authors declare that there are no conflicts of interest.

Ethics approval

The MDM (REC; 2014/76) and AM (REC; 2015/1322) studies were approved by the Norwegian Regional Committees for Medical and Health Research Ethics.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Norges Forskningsråd [NFR196130/H10].