Activation of transcription factor IL-6 (NF-IL-6) and nuclear factor- [kappa]B (NF-[kappa]B) by lipid ozonation products is crucial to interleukin-8 gene expression in human airway epithelial cells

Ozone (O sub(3)) is a major component of smog and an inhaled toxicant to the lung. O sub(3) rapidly reacts with the airway epithelial cell membrane phospholipids to generate lipid ozonation products (LOP). 1-Hydroxy-1- hydroperoxynonane (HHP-C9) is an important LOP, produced from the ozonation of 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphatidylcholine. This LOP, at a biologically relevant concentration (100 [mu]M), increases the activity of phospholipase C, nuclear factors-[kappa]B (NF-[kappa]B), and interleukin-6 (NF- IL-6) and the expression of the inflammatory gene, interleukin-8 (IL-8) in a cultured human bronchial epithelial cell line (BEAS-2B). The signaling pathways of ozone and its biologically-active products are as yet undefined. In the present study, we report that the HHP LOP, HHP-C9 (100 [mu]M X 4 h), activated the expression of IL-8 (218 +/- 26% increase over control, n = 4, P < 0.01) through an apparent interaction between the two transcription factors, NF- [kappa]B and NF-IL-6. Transfection studies using luciferase reporter assays demonstrated that HHP-C9 induced a significant increase in NF-[kappa]B-DNA binding activity (37 +/- 7% increase over control, n = 6, P < 0.05). Inhibition of NF-[kappa]B showed a statistically significant but modest decrease in IL-8 release, which suggested a role for another transcription factor, NF-IL- 6. Exposure of BEAS-2B cells to HHP-C9 induced a significant increase in the DNA binding activity of NF-IL-6 (45 +/- 11% increase over control, n = 6, P < 0.05). The results of the present study indicate that NF-IL-6 interacts with NF-[kappa]B in regulating the expression of IL-8 in cultured human airway epithelial cells exposed to LOP, the biological products of ozone in the lung. Environ Toxicol 22: 159-168, 2007.