Hypoxia regulates iNOS expression in human normal peritoneal and adhesion fibroblasts through nuclear factor kappa B activation mechanism

Objective: To determine the mechanism by which hypoxia increases expression of iNOS in human normal peritoneal and adhesion fibroblasts. Design: Prospective experimental study. Setting: University medical center. Patient(s): Primary cultures of fibroblasts from normal peritoneum and adhesion tissues. Intervention(s): Hypoxia-treated cells. Main Outcome Measure(s): We used real-time reverse transcription-polymerase chain reaction to quantify mRNA levels of iNOS and nuclear factor kappa B (NF-κB). Western blots were used to determine iNOS, NF-κB, IκB-α, and phospho-IκB expression levels in normal peritoneal and adhesion fibroblasts in response to hypoxia. Result(s): Hypoxia resulted in a significant increase in iNOS and NF-κB expression in normal and adhesion fibroblasts. Furthermore, both cell types manifested lower levels of NF-κB, cytoplasmic phospho-IκB-α, and iNOS proteins. In contrast, they manifested higher levels of cytoplasmic IκB-α and IκB-α/NF-κB ratios as well as a phosphorylated-IκB-α/NF-κB ratio. Under hypoxic conditions, both cell types exhibited significantly decreased cytoplasmic NF-κB, IκB-α levels, and significantly increased cytoplasmic phospho-IκB-α, iNOS, and NF-κB protein levels. Conclusion(s): Hypoxia increases iNOS expression by a mechanism involving activation of NF-κB. The ratio of IκB-α/NF-κB or IκB-α/p-IκB-α can be used to monitor activation.