Inflammatory cytokine gene expression in THP‐1 cells exposed to Stachybotrys chartarum and Aspergillus versicolor

Very little is known about the mechanisms which occur in human cells upon exposure to fungi as well as their mycotoxins. A better understanding of toxin-regulated gene expression would be helpful to identify safe levels of exposure and could eventually be the basis for establishing guidelines for remediation scenarios following a water intrusion event. In this research, cytokine mRNA expression patterns were investigated in the human monocytic THP-1 cell line exposed to fungal extracts of various fragment sizes obtained from Stachybotrys chartarum RTI 5802 and/or Aspergillus versicolor RTI 3843, two common and well studied mycotoxin producing fungi. Cytokine mRNA expression was generally upregulated 2 to 10 times following a 24-hour exposure to fungal extracts. Expression of the proinflammatory interleukin-1β (IL-1β), Interleukin-8 (IL-8) and tumor necrosis factor-α (TNFα) genes increased while the anti-inflammatory gene Interleukin-10 (IL-10) also increased albeit at very low level, suggesting that negative feedback regulation mechanism of production of pro-inflammatory cytokines initiated upon 24 hours of incubation. In addition, submicron size extracts of A. versicolor caused significant death of THP-1 cells whereas extracts of S. chartarum caused no cell death while the mixture of the two fungi had an intermediate effect. There was no general correlation between gene expression and fragment sizes, which suggests that all submicron fragments may contribute to inflammatory response.