Deoxynivalenol impairs the intestinal barrier by disrupting the tight junction network

INTRODUCTION: Mycotoxins are toxic secondary metabolites produced by fungi that may contaminate animal and human food at all stages of the food chain. Deoxynivalenol (DON) is one of the most abundant mycotoxins in Europe and North America found in raw and processed foods and feeds with well-documented enteropathogenic activities. The gastrointestinal tract represents the first barrier against food contaminants as well as the first target for toxicants. Tight junctions as multi-protein complex at the luminal end of the intracellular space, regulate the permeability of the intestinal barrier. An adequate intestinal epithelial barrier function is essential not only for the maintenance of the physiological functions but it also prevents the translocation of potentially harmful toxins, bacteria and viruses from the gut lumen into the circulation. The aim of this study is to apply an in vitro model for gut barrier function and to elucidate the role of tight junction proteins in a DON-induced increase in the intestinal permeability. MATERIALS AND METHODS: Using the human epithelial intestinal cell-line Caco2 in a transwell system as in vitro model, the effect of DON on cell viability, transepithelial electrical resistance (TEER), paracellular tracer flux, tight junction proteins (mRNA expression, protein concentration and their localization) was measured. RESULTS: Transepithelial electrical resistance of Caco-2 monolayers gradually dropped over 24 h in a concentration- and time-dependent manner. In parallel a significant increase in lucifer yellow (LY) and 4 kDa FITC-Dextran permeability could be observed. These alterations of the intestinal barrier function were associated with an increase in the mRNA expression of occludin, claudin1, claudin3, claudin4, ZO-1 and ZO-2 after 6 h of incubation with DON. All these tight junction proteins were delocalized after 24 h incubation with DON as demonstrated by immuno-fluorescence staining (Fig. 1). The concentrations of the tight junction protein claudin-1 and occludin were reduced, while the concentrations of the other tight junction proteins were unchanged after 24 h DON stimulation in spite of their delocalization. CONCLUSIONS: Taken together, these data suggest that DON decreases the barrier function of the intestinal epithelium, which is most probably related to alterations in tight junction protein expression. Loss of (Figure presented) barrier integrity by DON may account for an increased level of antigen translocation that has been observed in farm animals.