The processes associated with lipid peroxidation in human embryonic lung fibroblasts, treated with polycyclic aromatic hydrocarbons and organic extract from particulate matter

Polycyclic aromatic hydrocarbons (PAHs) may cause lipid peroxidation via reactive oxygen species generation. 15-F2t-isoprostane (IsoP), an oxidative stress marker, is formed from arachidonic acid (AA) by a free-radical induced oxidation. AA may also be converted to prostaglandins (PG) by prostaglandin-endoperoxide synthase (PTGS) induced by NF-κB. We treated human embryonic lung fibroblasts (HEL12469) with benzo[a]pyrene (B[a]P), 3-nitrobenzanthrone (3-NBA) and extractable organic matter (EOM) from ambient air particulate matter <2.5 µm for 4 and 24 h. B[a]P and 3-NBA induced expression of PAH metabolising, but not antioxidant enzymes. The concentrations of IsoP decreased, whereas the levels of AA tended to increase. Although the activity of NF-κB was not detected, the tested compounds affected the expression of prostaglandin-endoperoxide synthase 2 (PTGS2). The levels of prostaglandin E2 (PGE2) decreased following exposure to B[a]P, whereas 3-NBA exposure tended to increase PGE2 concentration. A distinct response was observed after EOM exposure: expression of PAH-metabolising enzymes was induced, IsoP levels increased after 24-h treatment but AA concentration was not affected. The activity of NF-κB increased after both exposure periods, and a significant induction of PTGS2 expression was found following 4-h treatment. Similarly to PAHs, the EOM exposure was associated with a decrease of PGE2 levels. In summary, exposure to PAHs with low pro-oxidant potential results in a decrease of IsoP levels implying 'antioxidant' properties. For such compounds, IsoP may not be a suitable marker of lipid peroxidation.