Transcriptional suppression of cytokine-induced iNOS gene expression by IL-13 through IRF-1/ISRE signaling.
IL-13 has been reported as one of the major down-regulators of iNOS expression in various tissues and cells. The molecular mechanism of iNOS suppression by IL-13 remains unclear, especially at the transcriptional stage. In this study, we found that IL-13 inhibited the expression of iNOS mRNA, protein, and NO product in a concentration-dependent manner for cytokine-stimulated rat hepatocytes. The most effective dose for IL-13 inhibitory effect is approximately 5 ng/ml. IL-13 also decreased the rat iNOS transcriptional activity by promoter analysis, but had no effect on iNOS mRNA stability. By using TranSignal Protein/DNA Combo Array, we identified cytokine-stimulated IRF-1/ISRE binding that was decreased by the addition of IL-13. Gel shift assay confirmed that IL-13 reduced the IRF-1/ISRE binding at nucleotides -913 to -923 of the rat iNOS promoter. Western blot revealed that IL-13 diminished the relative amount of IRF-1 protein translocated to the nucleus. Our data demonstrate that IL-13 down-regulates the cytokine-induced iNOS transcription by decreasing iNOS specific IRF-1/ISRE binding activity.
Shao
Lifang
L
Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Guo
Zhong
Z
Geller
David A
DA
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D022781:Hepatocytes / Q000378:metabolism; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism*; D018793:Interleukin-13 / Q000096:biosynthesis* / Q000378:metabolism; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis*; D010957:Plasmids / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D014158:Transcription, Genetic
D016207:Cytokines; D050856:Interferon Regulatory Factor-1; D018793:Interleukin-13; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II