BACKGROUND/AIMS: Nuclear translocation and DNA binding of NF-kappaB is essential, as interleukin-1beta (IL-1beta) stimulates the induction of inducible nitric oxide synthase (iNOS) gene expression in hepatocytes. However, recent evidence indicates that the activation of NF-kappaB is not sufficient to induce the NF-kappaB-dependent transcription, and the existence of a second signaling is postulated. METHODS: Primary cultured hepatocytes were treated with IL-1beta, and the expression of iNOS and type 1 IL-1 receptor (IL-1R1) was analyzed in the presence of antisense of IL-1R1, phosphatidylinositol 3-kinase (PI3K) inhibitor, proteasome inhibitor and hypoxia. Moreover, the activities of Akt and NF-kappaB were recorded and the cotransfection was carried out. RESULTS: Antisense experiment revealed that IL-1R1 was required for iNOS transcription. IL-1beta markedly stimulated the induction of IL-1R1, which preceded the induction of iNOS. The IL-1R1 induction was found to be PI3K/Akt-dependent but NF-kappaB-independent. The up-regulation of IL-1R1 was associated with the second activation of Akt, which accelerated the phosphorylation of NF-kappaB p65 subunit. Cotransfection experiments revealed that Akt increased the transcriptional activity of iNOS gene promoter. CONCLUSIONS: These results indicate that the up-regulation of IL-1R1 in concert with the activation of NF-kappaB is required for the transcriptional activation of iNOS gene.
BACKGROUND/AIMS: Nuclear translocation and DNA binding of NF-kappaB is essential, as interleukin-1beta (IL-1beta) stimulates the induction of inducible nitric oxide synthase (iNOS) gene expression in hepatocytes. However, recent evidence indicates that the activation of NF-kappaB is not sufficient to induce the NF-kappaB-dependent transcription, and the existence of a second signaling is postulated. METHODS: Primary cultured hepatocytes were treated with IL-1beta, and the expression of iNOS and type 1 IL-1 receptor (IL-1R1) was analyzed in the presence of antisense of IL-1R1, phosphatidylinositol 3-kinase (PI3K) inhibitor, proteasome inhibitor and hypoxia. Moreover, the activities of Akt and NF-kappaB were recorded and the cotransfection was carried out. RESULTS: Antisense experiment revealed that IL-1R1 was required for iNOS transcription. IL-1beta markedly stimulated the induction of IL-1R1, which preceded the induction of iNOS. The IL-1R1 induction was found to be PI3K/Akt-dependent but NF-kappaB-independent. The up-regulation of IL-1R1 was associated with the second activation of Akt, which accelerated the phosphorylation of NF-kappaB p65 subunit. Cotransfection experiments revealed that Akt increased the transcriptional activity of iNOS gene promoter. CONCLUSIONS: These results indicate that the up-regulation of IL-1R1 in concert with the activation of NF-kappaB is required for the transcriptional activation of iNOS gene.
Authors: Wei Li; Jennifer S Moylan; Melissa A Chambers; Jeffrey Smith; Michael B Reid Journal: Am J Physiol Cell Physiol Date: 2009-07-22 Impact factor: 4.249
Authors: Bergthor Björnsson; Anders Winbladh; Linda Bojmar; Tommy Sundqvist; Per Gullstrand; Per Sandström Journal: World J Gastroenterol Date: 2014-07-28 Impact factor: 5.742