Hepcidin is widely perceived to act as the master physiological regulator of body iron metabolism (reviewed in Ganz, 2005). Interestingly, a number of studies have shown that hepcidin levels are inappropriately high in inflammatory conditions and this can lead to the development of the anaemia of chronic disease. Elevated production of hepcidin in these pathological situations is thought to be regulated by pro-inflammatory cytokines, in particular IL-6. Our work and that of others suggests that the gut is a target organ for the action of cytokines (Johnson et al. 2004). Therefore, our current study has investigated the link between cytokines, hepcidin production and the effects on intestinal iron transporter expression. Studies were performed on established hepatic (HuH7) and intestinal (Caco-2) cell models. Prior to experimentation, cells were stimulated with either TNFα or IL-6 (10ng/ml). HuH7 cells were then assessed for hepcidin mRNA levels by quantitative PCR. Caco-2 cells were used to measure changes in the expression of the divalent metal transporter (DMT1) and iron regulated transporter (IREG1) protein by Western blotting. In additional experiments, Caco-2 cells were exposed to conditioned medium produced from IL-6 stimulated HuH7 cells. Data are mean ± S.E.M. from 3-6 experiments in each group. Statistical analysis was performed using Student’s unpaired t test and differences were considered significant when P<0.05. Hepcidin levels were significantly increased in HuH7 cells stimulated with IL-6 (415 ± 15%, p<0.002) but not in those exposed to TNFα (110 ± 18%) compared with the unstimulated controls. In Caco-2 cells, TNFα induced a decrease in DMT1 protein levels (-32.1 ± 4.5%, p<0.005) compared with the controls, whereas there was no effect of IL-6 (-5.7 ± 8.0%). IREG1 levels were not altered in Caco-2 cells by either cytokine. Interestingly, exposure of Caco-2 cells to conditioned medium produced from IL-6 stimulated HuH7 cells resulted in a significant decrease in DMT1 protein expression (-33.1 ± 4.9%, p<0.01). Incubation with synthetic hepcidin also decreased Caco-2 cell DMT1 levels (Yamaji et al. 2004). Taken together with our current data, this suggests that hepcidin may be the active agent in the conditioned medium. Importantly for intestinal iron absorption, our data suggest that the response to the cocktail of cytokines released in inflammatory conditions is not uniform. We propose that at least two distinct pathways exist that converge on intestinal enterocytes to regulate the rate of iron absorption. In this model, some cytokines (such as TNFα) have a direct effect on the intestinal mucosa to regulate dietary iron assimilation, whereas others (e.g. IL-6) act indirectly first stimulating the release of hepcidin which then elicits its inhibitory action on intestinal iron transport.