Comparison of gene expression profiles induced by fresh or ozone-oxidized black carbon particles in A549 cells

Epidemiological studies have showed an association between black carbon (BC) exposure and adverse health effects. This study intends to investigate the influence of oxidation processes in atmosphere on the initial cellular responses of BC. The changes of gene expressions induced by fresh BC (FBC) and ozone-oxidized BC (OBC) in human lung epithelial A549 cells were analyzed. And their toxic effects presented by viability, LDH release and DNA damage were compared. Totally 47, 000 genes in A549 cells were examined using Affymetrix Human U133 plus 2.0 chips. Some of the differentially expressed genes were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The results showed that 1446 genes (including 756 up-regulated and 690 down-regulated) and 1594 genes (including 788 up-regulated and 806 down-regulated genes) were significantly changed by FBC and OBC respectively. Only 4 of 14 (FBC)/15 (OBC) oxidative stress related genes, up- or down-regulated by FBC and OBC, were identical; 13 of 29 (FBC)/31 (OBC) inflammation related genes, and 6 of 20 (FBC)/18 (OBC) autophagy related genes were identical. No obvious differences were observed between the toxic effects of FBC and OBC. The cytotoxicity of OBC and FBC in A549 cells is at least partially induced by oxidative stress and consequent inflammation or autophagy process. Previous studies indicated that OBC may be more toxic than FBC. However, our results suggested that FBC and OBC might lead to diverse toxic endpoints through activating different molecular pathways.