Abstract
The influence of pro-inflammatory cytokines on alpha class glutathione S-transferase A1 and A2 (GSTA1/A2) expression was examined in human colonic epithelial cells (Caco-2) in culture. Dose-dependent reductions in GSTA1/A2 mRNA, protein, and activity levels occurred in Caco-2 cells cultured in conditioned medium (CM) from lipopolysaccharide-stimulated murine monocyte-macrophage cells (RAW 264.7). Neutralizing anti-interleukin-1β (IL-1β) antibodies attenuated this repression of GSTA1/A2 expression by CM. Moreover, recombinant human IL-1β reduced GSTα expression at the mRNA, protein, and activity levels in a dose-related fashion. Reduction of GSTA1/A2 mRNA levels by IL-1β was attenuated by pretreatment with IL-1 receptor antagonist. GSTA1/A2 mRNA half-lives were similar in control and IL-1β-treated cells, indicating that IL-1β has no effect on mRNA stability. In reporter gene studies, IL-1β caused a dose-related reduction of luciferase activity in Caco-2 cells transfected with the full-length GSTA1 promoter-luciferase construct. Using truncated constructs, IL-1β responsiveness was mapped to a region 286 base pairs upstream to the coding region. Deletion of a hepatic nuclear factor 1 (HNF-1) site in this region abrogated the IL-1β-mediated repression of GSTA1 promoter activity. These results demonstrate that IL-1β down-regulates GSTA1/A2 expression in cultured human enterocytes by a transcriptional mechanism involving an HNF-1 site.
Footnotes
-
Supported by funding from the Medical Research Council of Canada (Grant MT-13757).
- Abbreviations used are::
- GST
- glutathioneS-transferase
- IL-1β
- interleukin-1β
- IL-6
- interleukin-6
- TNFα
- tumor necrosis factor-α
- GSTA1/A2
- alpha class glutathione S-transferase A1 and A2
- HNF-1
- hepatic nuclear factor-1
- CM
- conditioned medium
- LPS
- lipopolysaccharide
- FBS
- fetal bovine serum
- IL-1ra
- interleukin-1 receptor antagonist
- bp
- base pair(s)
- LUC
- luciferase
- PCR
- polymerase chain reaction
- AP-1
- activating protein-1
- IBD
- inflammatory bowel disease
- Received May 29, 2002.
- Accepted August 2, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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