iTRAQ-based proteomic analysis of the interaction of A549 human lung epithelial cells with Aspergillus fumigatus conidia

Severe invasive aspergillosis infection occurs when human immune function is impaired. The interaction between Aspergillus fumigatus (A. fumigatus) conidia and type II lung epithelial cells serves an important role in disease progression. The present study compared the proteomes of A549 human lung epithelial cells with and without A. fumigatus infection. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein interaction analyses were performed, and differential protein expression was verified by western blotting and reverse transcription-quantitative PCR (RT-qPCR). In addition, the RNA interference method, an internalization assay and ELISA were performed. Isobaric tags for relative and absolute quantification analysis detected a total of 1,582 proteins, from which 111 proteins with differential expression were obtained (fold change >1.5 or <0.75). Among them, 18 proteins were upregulated and 93 proteins were downregulated in A549 cells challenged with A. fumigatus. GO and KEGG analyses revealed that the altered proteins were mainly involved in biological functions, such as cell metabolism, synthesis, the cellular stress response, metabolic pathways and pyruvate metabolism. N-myc downstream-regulated gene 1 (NDRG1) expression was upregulated 1.88-fold, while CD44 expression was downregulated 0.47-fold following A. fumigatus infection. The expression levels of specific proteins were verified by western blotting and RT-qPCR. The internalization efficiency was affected by NDRG1 gene silencing. The secretion of IL-6 and IL-8 was affected when CD44 was inhibited. These results indicated that A. fumigatus affects lung epithelial cell metabolism and biological synthetic functions. A number of novel molecules, including NDRG1 and CD44, were found to be related to A. fumigatus infection.