Increased GADD gene expression in human colon epithelial cells exposed to deoxycholate.
The colonic epithelium is often exposed to high concentrations of secondary bile acids, which stresses the epithelial cells, leading potentially to activation of stress-response genes. To examine this possibility in vitro, the purpose of this study was to determine if expression of certain growth arrest and DNA damage-inducible genes (GADD) is upregulated in human colonic epithelial cells exposed to deoxycholate (DOC). DNA macroarray screening of a small cluster of stress/apoptosis-related genes in DOC-treated HCT-116 colonocytes revealed clearly higher expression of only GADD45, which was confirmed by gene-specific relative RT-PCR analysis. Subsequently, it was found that DOC also increased GADD34 mRNA expression. However, mRNA expression of GADD153 was increased most markedly in DOC-treated HCT-116 colonocytes, which express wild-type p53. However, the upregulation of GADD34, GADD45, and GADD153 mRNA expression apparently did not require p53, based on the finding that DOC increased expression of all three GADD genes in HCT-15 colonocytes, which express mutant p53. In further studying GADD153 in particular, the effect of DOC on GADD153 mRNA was prevented by actinomycin-D (Act-D), but not by antioxidants or MAPK inhibitors. DOC also caused GADD153 protein to be expressed in close parallel with increased GADD153 mRNA expression. Induction of GADD153 protein by DOC was prevented by either anisomycin or cycloheximide. These findings suggest that DOC-induced upregulation of GADD153 mRNA expression occurred at the level of transcription without involving reactive oxygen species and MAPK signaling, and that the expression of GADD153 protein was due also to translation of pre-existing, and not just newly synthesized, mRNA.
Cellular and Molecular Nutrition Research Laboratory, Graduate Program in Nutrition, University of North Carolina at Greensboro, Greensboro, North Carolina 27403-6170, USA.
David W
DW
Scott
Sophia
S
Mutamba
Robin G
RG
Hopkins
George
G
Loo
D000943:Antigens, Differentiation; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003106:Colon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics*; D003609:Dactinomycin / Q000494:pharmacology; D003840:Deoxycholic Acid / Q000378:metabolism* / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D018816:Genes, cdc / Q000187:drug effects; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects / Q000235:genetics; D054645:Protein Phosphatase 1; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D013312:Stress, Physiological / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D000097642:GADD45 Proteins
D000943:Antigens, Differentiation; D022762:CCAAT-Enhancer-Binding Proteins; D018797:Cell Cycle Proteins; D003609:Dactinomycin; D003840:Deoxycholic Acid; D009687:Nuclear Proteins; D054645:Protein Phosphatase 1; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D012333:RNA, Messenger; D051742:Transcription Factor CHOP; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; C497249:DDIT3 protein, human; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C087519:PPP1R15A protein, human