Modified peptide nucleic acids are internalized in mouse macrophages RAW 264.7 and inhibit inducible nitric oxide synthase

Overexpression of inducible nitric oxide synthase causes the production of high levels of nitric oxide, which, under pathological conditions, leads to immunosuppression and tissue damage. The results recently obtained using p eptide nucleic acids, rather than traditional oligonucleotides as antigen a nd antisense molecules, prompted us to test their efficacy in the regulatio n of nitric oxide production, thereby overcoming the obstacle of cellular i nternalization. The cellular permeability of four inducible nitric oxide sy nthase antisense peptide nucleic acids of different lengths was evaluated. These peptide nucleic acids were covalently linked to a hydrophobic peptide moiety to increase internalization and to a tyrosine to allow selective I- 125 radiolabelling. Internalization experiments showed a 3-25-fold increase in the membrane permeability of the modified peptide nucleic acids with re spect to controls. inducible nitric oxide synthase inhibition experiments o n intact stimulated macrophages RAW 264.7 after passive permeation of the t wo antisense peptide nucleic acids 3 and 4 demonstrated a significant decre ase (43-44%) in protein enzymatic activity with respect to the controls. Th ese data offer a basis for developing a good alternative to conventional dr ugs directed against inducible nitric oxide synthase overexpression. (C) 19 99 Federation of European Biochemical Societies.