B. Amoah-apraku et al., A non-nucleotide-bridged DNA decoy inhibits renal epithelial nitric oxide synthase expression, KIDNEY INT, 57(1), 2000, pp. 83-91
Background. The expression of inducible nitric oxide synthase (iNOS) is sub
ject to strict tissue-specific transcriptional control. In mouse renal epit
helium, an interferon-gamma (IFN-gamma)induced signaling protein, IFN-gamma
regulatory factor 1 (IRF-1), appears to mediate the induction of iNOS expr
ession by cytokines and bacterial lipopolysaccharide (LPS).
Methods. We used a novel technique, namely, blockade of cytosolic IRF-1 act
ivity with a triethyleneglycol-bridged decoy DNA oligonucleotide (ODN) cont
aining the IRF-1 consensus binding sequences present in the iNOS promoter t
o inhibit iNOS gene expression. Cultured mouse renal epithelial cells were
treated with a combination of LPS (11 mu g/mL) and IFN (100 U/mL) in the ab
sence or presence of IRF-1 decoy ODN followed by determinations of NO produ
ction and iNOS protein and mRNA expression.
Results. Treatment with IRF-1 decoy ODN resulted in concentration-dependent
inhibition of NO production and a marked reduction in iNOS protein and mRN
A levels. A scrambled ODN failed to affect LPS/IFN-stimulated NO production
or iNOS protein and mRNA levels. Transcriptional assays showed that the IR
F-1 decoy ODN inhibited transcriptional activity of an iNOS promoter-CAT ge
ne construct.
Conclusions. Decoy ODN-based techniques effectively inhibit iNOS expression
in renal epithelium and represent a potentially useful approach for select
ive blockade of this enzyme in pathologic conditions associated with excess
ive NO production.