engleski

Aflatoxin production and in vitro toxicity of Aspergilli section Flavi isolated from air samples collected from different environments

Aspergilli section Flavi, originally isolated from air samples collected from inhabited apartments (AP), unoccupied basements (BS), and from the processing facilities of a grain mill (GM), were analysed for their potential to produce aflatoxin B1 (AFB1) on solid media. The isolates were further characterized with regard to their cytotoxic, genotoxic and pro- inflammatory properties in vitro. Aspergilli were identified based on partial calmodulin (CaM) gene sequencing ; the producing capacities of isolates were analysed by HPLC/FLD and confirmed by genes in biosynthesis (aflR, norA, omtA). In the grain mill, the Aspergilli section Flavi (up to 1.3x106 cfu/m3) dominated by AFB1-producing A. flavus (71%, 4.5-5254 ng/ml) that showed a serious health risk for workers. Living environments were not relevant sources of exposure. After 24 h, AFB1 (1-100 µmol/l) reduced cell viability (MTT test) in both A549 cells and THP-1 macrophage- like cells without reaching IC50. In A549 cells, the extract of the AFB1-producing A. flavus significantly decreased cell viability but not below 50%. THP-1 macrophage-like cells were more sensitive to both extracts but IC50 was obtained only for the AFB1-producing strain (0.37 mg/ml ; AFB1 2.78 µmol/l). AFB1 (1 and 10 µmol/l) induced significant DNA damage (tail intensity, alkaline comet assay) in A549 cells in contrast to Aspergilli extracts. AFB1 elevated IL-6 and IL-8 while Aspergilli extracts increased IL-1b, TNF-a and IL-17 release in THP-1 macrophages (ELISA). Chronic exposure to AFB1 and/or other metabolites in airborne A. flavus from occupational environments may stimulate epithelial damage of airways accompanied by lowered macrophage viability.

airborne fungi, aflatoxin B1, cytotoxicity, DNA damage, cytokines

This work was financially supported by the University of Zagreb (Grant No. 1126)