Benzo[a]pyrene (B[a]P) is present in environmental pollution and cigarette smoke. B[a]P has been shown to induce apoptosis in hepatoma cells, human B cells, human ectocervical cells, macrophages, and rat lungs. Nitrogen oxides (NOx) are the other important indoor and outdoor air pollutants. Many studies have indicated that NO gas causes lung tissue damage both by its oxidative properties and free radicals. In our previous study we demonstrated that NO gas induced proliferation of human lung fibroblast MRC-5 cells. In this study we showed that NO gas inhibits B[a]P-induced MRC-5 cells apoptosis by cell cycle analysis. Western blot data revealed that NO gas increased the expressions of anti-apoptosis proteins (Bcl-2 and Mcl-1) and decreased the expression of apoptosis proteins (Bax, t-Bid, cytochrome c, FasL, and caspases) after B[a]P treatment. We further clarified that B[a]P-induced MRC-5 cell apoptosis via JNK1/FasL and JNK1/p53 signals. In conclusion, NO gas inhibited B[a]P-induced MRC-5 cells apoptosis via inhibition of JNK1 apoptosis pathway and induction of Bcl-2 and Mcl-1 anti-apoptosis pathway.
