The pro-inflammatory cytokines, IL-1beta and TNF-alpha, inhibit intestinal alkaline phosphatase gene expression.
High levels of the pro-inflammatory cytokines, interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), are present in the gut mucosa of patients suffering form various diseases, most notably inflammatory bowel diseases (IBD). Since the inflammatory milieu can cause important alterations in epithelial cell function, we examined the cytokine effects on the expression of the enterocyte differentiation marker, intestinal alkaline phosphatase (IAP), a protein that detoxifies bacterial lipopolysaccharides (LPS) and limits fat absorption. Sodium butyrate (NaBu), a short-chain fatty acid and histone deacetylase (HDAC) inhibitor, was used to induce IAP expression in HT-29 cells and the cells were also treated +/- the cytokines. Northern blots confirmed IAP induction by NaBu, however, pretreatment (6 h) with either cytokine showed a dose-dependent inhibition of IAP expression. IAP Western analyses and alkaline phosphatase enzyme assays corroborated the Northern data and confirmed that the cytokines inhibit IAP induction. Transient transfections with a reporter plasmid carrying the human IAP promoter showed significant inhibition of NaBu-induced IAP gene activation by the cytokines (100 and 60% inhibition with IL-1beta and TNF-alpha, respectively). Western analyses showed that NaBu induced H4 and H3 histone acetylation, and pretreatment with IL-1beta or TNF-alpha did not change this global acetylation pattern. In contrast, chromatin immunoprecipitation showed that local histone acetylation of the IAP promoter region was specifically inhibited by either cytokine. We conclude that IL-1beta and TNF-alpha inhibit NaBu-induced IAP gene expression, likely by blocking the histone acetylation within its promoter. Cytokine-mediated IAP gene silencing may have important implications for gut epithelial function in the setting of intestinal inflammatory conditions.
Malo
Madhu S
MS
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Biswas
Shaluk
S
Abedrapo
Mario A
MA
Yeh
Lisa
L
Chen
Alexander
A
Hodin
Richard A
RA
D000107:Acetylation / Q000187:drug effects; D000123:Acetyltransferases / Q000187:drug effects; D000469:Alkaline Phosphatase; D000951:Antigens, Neoplasm / Q000378:metabolism*; D002087:Butyrates / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D058851:GPI-Linked Proteins; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D017930:Genes, Reporter / Q000187:drug effects; D045325:HCT116 Cells; D019073:HT29 Cells; D051548:Histone Acetyltransferases / Q000187:drug effects; D006801:Humans; D018836:Inflammation Mediators / Q000494:pharmacology; D053583:Interleukin-1beta / Q000494:pharmacology*; D008156:Luciferases / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000951:Antigens, Neoplasm; D002087:Butyrates; D058851:GPI-Linked Proteins; D018836:Inflammation Mediators; D053583:Interleukin-1beta; D014409:Tumor Necrosis Factor-alpha; D008156:Luciferases; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; C063088:ALPI protein, human; D000469:Alkaline Phosphatase