Apical exposure to dietary non-digestible oligosaccharides and bacterial CpG DNA suppresses Th2 type chemokine release by activated intestinal epithelial cells

Background: Dietary short chain galactoand long chain fructo-oligosaccharides (scGOS/lcFOS) and TLR9 ligand CpG DNA affect intestinal epithelial cell (IEC) function. Epithelial derived IL-1a is known to contribute to allergic sensitization in the lung. To study the effect of IL-1a on Th2 polarizing chemokine release by IEC and the modulatory effect of scGOS/lcFOS and CpG DNA in presence or absence of monocyte derived dendritic cells (moDC). Method: HT-29 cells (IEC) cultured in transwells were pre-incubated basolaterally with IL-1a ± IFNg/TNFa and apically with scGOS/lcFOS ± CpG DNA for 6 hours, washed and basolaterally exposed to immature moDC or medium while apically exposed to scGOS/lcFOS ± CpG for 24-48 hours. Th2 driving IL-25, CCL2, CCL22 and regulatory galectin-9 and TGFβ were measured in basolateral supernatants. After 48 h of co-culture, moDC were added to allogenic naïve T-cells for 6 days (MLR) and cytokines were measured. Results: Combined IFNg/TNFa activation induced the release of CCL2 and CCL22 by IEC, which was further enhanced by IL-1a. IFNg/TNFa ± IL-1a activation also increased galectin-9 and TGFb (24 h). Exposure to scGOS/lcFOS ± CpG DNA reduced CCL2 and CCL22, while galectin- 9 and TGFb remained high. In the 48 h supernatants of IEC/moDC co-cultures, scGOS/lcFOS enhanced galectin-9 in presence or absence of CpG DNA. scGOS/ lcFOS plus CpG DNA reduced IL-25 in co-cultures pre-exposed to IFNg/TNFa/IL- 1a while increasing IFNg concentrations in the MLR. Conclusion: IL-1a enhances Th2 polarizing chemokine release by IFNg/TNFa activated IEC. Combined exposure to dietary scGOS/lcFOS plus CpG DNA suppresses this response skewing away from the allergic phenotype.