The role of NF-κB, IRF-1, and STAT-1α transcription factors in the iNOS gene induction by gliadin and IFN-γ in RAW 264.7 macrophages.

Nitric oxide (NO) plays an important role in the pathogenesis of celiac disease. We have examined the involvement of nuclear factor-κB (NF-κB), interferon regulatory factor-1 (IRF-1), and signal transducer and activator of transcription-1α (STAT-1α) on the synergistic induction of inducible nitric oxide synthase (iNOS) gene expression by gliadin (G) in association with interferon-γ (IFN-γ) in RAW 264.7 macrophages. We found that IFN-γ was efficient in enhancing the basal transcription of the iNOS promoter at 1, 6, and 24 h, whereas G had no effect. The G plus IFN-γ association caused an increase in iNOS promoter activity which was inhibited by pyrrolidine dithiocarbammate (PDTC) at 6 and 24 h as well as by genistein (Gen) and tyrphostine B42 (TB42) at 1 h, inhibitors of NF-κB, IRF-1, and STAT-1α activation, respectively. Similarly, the IFN-γ and G combination treatment led to a higher increase in iNOS mRNA levels at 1, 6, and 24 h compared with IFN-γ alone. Gen and TB42 inhibited iNOS mRNA levels at 1 h, whereas PDTC inhibited iNOS mRNA levels at 6 and 24 h. In addition, the synergistic induction of iNOS gene expression by G plus IFN-γ correlated with the induction of NF-κB, IRF-1, and STAT-1α/DNA binding activity and mRNA expression. In conclusion, our study, which provides evidence that the effect of G on iNOS gene transcription in IFN-γ-stimulated RAW 264.7 cells can be ascribed to all three transcription factors, may contribute to lead to new insights into the molecular mechanisms governing the inflammatory process in celiac disease. [ABSTRACT FROM AUTHOR]