Background:
The expression of inducible nitric oxide synthase (iNOS) contributes to the systemic manifestations of sepsis.
Objective:
To determine whether nitric oxide (NO) can exert negative feedback regulation on iNOS gene expression.
Setting:
Molecular biology research laboratory of the department of surgery.
Study Design:
Isolated rat hepatocytes were cultured with a cytokine mix consisting of tumor necrosis factor α, interleukin 1β, and interferon γ in the presence or absence of the NO donor S-nitroso-N-acetyl-d,l-penicillamine.
Main Outcome Measures:
Nitrite and nitrate (NO2− and NO3−) levels were assayed. Hepatocyte iNOS messenger RNA and protein levels were assessed. Electromobility shift assays were performed for NF-κB DNA binding activity. Finally, iNOS enzyme activity was determined using high-performance liquid chromatography.
Results:
Cytokine mix–induced hepatocyte iNOS mRNA and protein production and the addition of the NO donor S-nitroso-N-acetyl-d,l-penicillamine markedly attenuated iNOS mRNA and protein levels. Gel shift assays of the nuclear extracts disclosed that decreased cytokine mix–induced DNA binding activity for NF-κB in a concentration-dependent manner. Finally, NO failed to significantly inhibit iNOS enzyme activity.
Conclusions:
These data indicate that NO down-regulates iNOS gene transcription, and that the effect is mediated in part by inhibiting NF-κB activity. These results identify a novel negative feedback mechanism whereby NO down-regulates iNOS gene expression, possibly to limit overproduction during the septic response.Arch Surg. 1997;132:1177-1183