Essential role of the JAK/STAT1 signaling pathway in the expression of inducible nitric-oxide synthase in intestinal epithelial cells and its regulation by butyrate.
Nitric oxide (NO) is a highly reactive free radical that modulates tumorigenesis through its ability to regulate cell proliferation, cell death, migration and angiogenesis. Although the role of NO has been well studied in inflammatory cells, much less is known about the regulation of NO production in epithelial cells. We demonstrated that in intestinal epithelial cells the expression of inducible NO synthase (iNOS), the critical enzyme in the synthesis of NO, is synergistically stimulated by bacterial lipopolysaccharide (LPS) and interferon gamma (IFNgamma) or by the combination of tumor necrosis factor (TNF) and IFNgamma at the transcriptional level. Expression of iNOS and the production of NO in response to LPS/IFNgamma were significantly increased upon induction of oncogenic K-Ras, underlying frequently elevated expression of iNOS in colon cancer. Silencing of STAT1, a major transcription factor involved in signaling by IFNgamma, or pharmacological inhibition of JAKs, kinases that phosphorylate STATs, prevented the induction of iNOS and the production of NO in response to stimulation of cells with LPS/IFNgamma or TNF/IFNgamma, underscoring the importance of the intact JAK/STAT signaling in the regulation of iNOS expression in intestinal epithelial cells. Butyrate, a histone deacetylase (HDAC) inhibitor and a dietary chemopreventive agent, decreased NO production in macrophages and in intestinal myofibroblasts, consistent with its anti-inflammatory activity. In contrast, in intestinal epithelial cells, butyrate significantly enhanced the expression of iNOS and the production of NO in response to treatment with LPS/IFNgamma. Despite the fact that, like butyrate, three structurally unrelated inhibitors of HDAC activity, trichostatin A, suberoylanilide hydroxamic acid, and apicidin, induced acetylation of H3 and H4 in epithelial cells, they failed to increase the production of NO, demonstrating that butyrate regulates NO production in epithelial cells in an HDAC-independent manner. The ability of butyrate to regulate the production of NO in a variety of cell types is likely to underlie its potent chemopreventive and anti-inflammatory activity.
Stempelj
Mateja
M
Department of Oncology, Albert Einstein Cancer Center, Montefiore Medical Center, Bronx, New York 10467.
Kedinger
Michele
M
INSERM U682, Université Louis Pasteur, 67200 Strasbourg, France.
Augenlicht
Leonard
L
Department of Oncology, Albert Einstein Cancer Center, Montefiore Medical Center, Bronx, New York 10467.
Klampfer
Lidija
L
Department of Oncology, Albert Einstein Cancer Center, Montefiore Medical Center, Bronx, New York 10467. Electronic address: lklampf@aecom.yu.edu.
D000818:Animals; D002087:Butyrates / Q000494:pharmacology*; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology*; D007371:Interferon-gamma / Q000502:physiology; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D053612:Janus Kinases / Q000502:physiology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D050794:STAT1 Transcription Factor / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects
D002087:Butyrates; D008070:Lipopolysaccharides; D050794:STAT1 Transcription Factor; C494081:Stat1 protein, rat; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II; D053612:Janus Kinases