Effects of low molecular weight fungal compounds on inflammatory gene transcription and expression in mouse alveolar macrophages

Abstract

The inflammatory potential and molecular mechanisms underscoring inflammatory responses of lung cells to compounds from fungi that grow on damp building materials is poorly understood in vitro. In this study we evaluated the effect of pure fungal compounds on potentiating acute inflammatory response in primary mouse alveolar macrophages (AMs) and tested the hypothesis that AM responses to low molecular weight fungal compounds exhibit temporal and compound specificity that mimic that observed in the whole lung. Transcriptional responses of 13 inflammation/respiratory burst-associated genes (KC=Cxcl1, Cxcl2, Cxcl5, Cxcl10, Ccl3, Ccl112, Ccl20, IL-1β, Il-6, ifi27 Tnfα, iNOS and Blvrb) were evaluated in mouse AMs exposed to a 1ml (10(-8)mol) dose of either pure atranone C, brevianimide, cladosporin, curdlan, LPS, neoechinulin A & B, sterigmatocystin or TMC-120A for 2h, 4h and 12h PE using customized reverse transcription (RT)-PCR based arrays. Multianalyte ELISA was used to measure expression of 6 pro-inflammatory cytokines common to the transcriptional assays (Cxcl1, Cxcl10, Ccl3, IL1β, Ifn-λ and Tnf-α) to determine whether gene expression corresponded to the transcription data. Compared to controls, all of these compounds induced significant (≥2.5-fold or ≤-2.5-fold change at p≤0.05) time- and compound-specific transcriptional gene alterations in treatment AMs. The highest number of transcribed genes were in LPS treatment AMs at 12h PE (12/13) followed by neoechinulin B at 4h PE (11/13). Highest fold change values (>30) were associated with KC, Cxcl2, Cxcl5 and IL1β genes in cells exposed to LPS. Compound exposures also induced significant (p≤0.05) time- and compound-specific pro-inflammatory responses manifest as differentially elevated Cxcl1, Cxcl10, Ccl3, Ifn-λ and Tnf-α concentrations in culture supernatant of treatment AMs. Dissimilarity in transcriptional responses in AMs and our in vivo model of lung disease is likely attributable to whole lung vs. isolated cell responsive and dose differences between the two studies. The results not only indicate that low molecular weight compounds from fungi that grow in damp built environments are potently pro-inflammatory in vitro, it further highlights the important role AMs play in innate lung defence, and against exposure to low molecular weight fungal compounds. These observations further support our position that exposure to low molecular weight compounds from indoor-associated fungi may provoke some of the inflammatory health effects reported from humans in damp building environments. They also open up a hypothesis building process that could explain the rise of non-atopic asthma associated with fungi.

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