The role of metabolism in diclofenac-induced intestinal toxicity in rat and human in vitro

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Abstract

The use of Diclofenac (DCF), a non-steroidal anti-inflammatory drug is associated with severe gastro-intestinal side-effects. The mechanisms of drug-induced intestinal toxicity are largely unknown due to the lack of in vitro models. In vivo rat studies suggested that reactive metabolites of DCF especially diclofenac acyl-glucuronide (DAG) produced by liver played an important role in intestinal toxicity.
Whether DCF is directly toxic to the intestine is not known. In this study, human
as well as rat precision-cut intestinal slices (PCIS) are used as an in vitro model to investigate the mechanism of DCF-induced intestinal toxicity.
PCIS from rats and 4 human individuals were incubated with different concentrations of DCF, metabolite formation as well as toxicity were tested. ATP content and morphology were used as markers for toxicity. Dose-dependent toxicity of DCF was shown for both species: 200 μM DCF caused a significant decrease in ATP and morphological damage in rats. Human intestinal slices were more resistant to DCF and significant damage was induced at concentrations ≥400 μM. Minor amounts of hydroxylated DCF as well as DAG were detected in rat and human PCIS; but with a large variation among human individuals. Drug-protein adducts were detected by immunohistochemistry staining using anti-DCF antibody. To investigate the role of DAG in the mechanism of toxicity, the PCIS were incubated with DCF in the presence of a non-toxic concentration of the glucuronidation inhibitor borneol (0.5mM). Borneol effectively decreased the formation of DAG but did not further reduce the toxicity compared with DCF alone.
In conclusion, using PCIS as an in vitro model we show that DCF is directly toxic
to the human and rat intestine. Human intestine appears less sensitive to DCF-induced toxicity. Similar metabolic profiles are found in rat and human intestinal slices, meanwhile drug-protein adducts are detected. However the role of the reactive metabolite DAG in DCF-induced intestinal toxicity could not be confirmed.
Original languageEnglish
Pages (from-to)393-392
Number of pages1
JournalThe Toxicologist. Supplement to Toxicological Sciences
Volume126
Issue number1
Publication statusPublished - Mar-2012

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