Nitric oxide induces DNA mutations that are repaired by the MMR pathway.

<p>(A) Measurements of the amounts of nitric oxide in culture medium generated by various concentrations of SNAP or by macrophages that were stimulated by LPS and IFN-γ. (B) The mutant frequency at the <i>lac</i>I gene in Msh2^+/− (WT, n = 3) and Msh2^−/− (n = 3) SNAP-treated or non-treated macrophages was measured by the Big Blue mutagenesis screen. Bone marrow-derived macrophages were cultured in presence of 150 µM SNAP for 20 hrs. Genomic DNA was isolated and the mutant frequency at <i>lac</i>I gene was calculated. (C) Mutation spectrum in SNAP-treated macrophages as determined by sequencing analysis. The C:G → T:A transitions are shown. The tranversion mutations include C:G → A:T, C:G → G:C, T:A → G:C and T:A → A:T substitutions. The insertions and deletions are presents as other mutations. (D) The mutant frequency at the <i>hprt</i> gene in Msh2^+/− (WT, n = 8) and Msh2^−/− (n = 8) SNAP-treated or non-treated Pre-B cells. (E) The mutant frequency at the <i>hprt</i> gene in SW680 (n = 8) and DLD-1 (n = 8) SNAP-treated or non-treated human colorectal cancer cell lines.