Nitric oxide production in Caco-2 cells exposed to different inducers, inhibitors and natural toxins

The involvement of the NO pathway in several intestinal inflammatory diseas es is under investigation. In vitro models may provide a useful approach to better characterise this pathway at the cellular level. For this purpose, we have used Caco-2 cells, which are able to spontaneously differentiate in long-term culture to small intestine enterocytes. The effect of different NO pathway inducers [gamma -interferon (IFN-gamma) and phorbol myristate ac etate (PMA)] has been studied. Our results demonstrate that Caco-2 cells co nstitutively express NOS at very low levels, while the induction with PMA+I FN-gamma triggers the expression of the inducible isoform with a stronger e ffect starting from day 14 of differentiation. The use of specific inhibito rs of gene expression, at transcriptional and translational level, suggests that new synthesis of iNOS mRNA is required, through direct activation of the gene or new synthesis of transcription-required factors, as indicated b y CHX inhibition. The morphological alteration induced by PMA+IFN-gamma is reversed by iNOS inhibitor, suggesting that the NO pathway may be involved in the cytoskeletal alterations. The DSP toxins, OA and DTX-1, induce NO pr oduction at levels corresponding to their different toxicity, previously de tected in Caco-2 cells. (C) 2001 Elsevier Science Ltd. All rights reserved.