Specific inhibition of nitric oxide production in macrophages by phosphorothioate antisense oligonucleotides

The effects of antisense oligonucleotides (ODNs) on nitric oxide (NO) production induced by lipopolysaccharide (LPS) were investigated using thioglycollate-induced mouse peritoneal macrophages. Antisense phosphorothioate ODNs (S-oligo) corresponding to a sequence in the neighborhood of the AUG initiation codon of a mouse inducible nitric oxide synthase (iNOS) mRNA, which has a G-quartet motif in its antisense sequence, inhibited NO induction in a dose-dependent manner. Antisense phosphodiester ODNs (D-oligo), 5'- and 3'-terminal phosphorothioate-modified antisense ODNs and control scramble and missense S-oligos had no such effect. In addition, control nonsense and two mismatched S-oligos, which include G-quartet motif in their sequences, inhibited NO induction to similar to 50% of those in the control. Antisense S-oligo showed the inhibitory effect on NO production by exposure of macrophages to various concentrations of LPS. Western blot analysis using anti-mouse inducible nitric oxide synthase (iNOS) antibody revealed that antisense S-oligo specifically removed an immunoreactive band at 130 kDa. In addition, the results of reverse transcription-polymerase chain reaction (RT-PCR) revealed that the antisense effect originated from a specific reduction of the targeted iNOS mRNA by hybridization with the antisense S-oligo. Furthermore, no ODNs affected beta-actin mRNA and tumor necrosis factor alpha (TNF-alpha) expression in macrophages stimulated by LPS. These findings demonstrated that antisense S-oligo inhibited NO production derived from iNOS expression in macrophages by an antisense mechanism, including the aptameric effect partially mediated by the G-quartet motif.