The ELISA results show that 24 h after co-incubation, WT V. parahaemolyticus is a powerful activator of IL-8
secretion by Caco-2 cells, as there was a 15-fold increase in IL-8 concentrations KU55933 purchase after WT V. parahaemolyticus co-incubation in comparison to untreated Caco-2 cells (Figure 5C). Similar IL-8 concentrations were detected with the Caco-2 cells alone and in the presence of heat-killed WT V. parahaemolyticus. A dramatic reduction of IL-8 secretion was observed in response to ΔvscN1, showing an involvement of the TTSS1 GSK461364 apparatus in the activation of IL-8 secretion. Moreover, the use of the Δvp1680 strain showed an intermediate level of IL-8 secretion when compared to the WT and ΔvscN1 strains, suggesting that the effector protein VP1680 is involved in the IL-8 secretion activation by the Caco-2 cells in response to the bacteria but it is not the only TTSS1 effector responsible for this activation. With the ΔvscN2 strain there was a higher level of IL-8 secretion by the Caco-2 cells than that observed with the WT V. parahaemolyticus, suggesting that TTSS2 is involved in the inhibition of the IL-8
secretion by the Caco-2 cells in response to the bacteria 24 h after the addition of the bacteria. These results demonstrate that V. parahaemolyticus actively induces the transcription and production of IL-8 by the host cell. TTSS1 is involved in the activation of IL-8 production by the host while TTSS2 is involved in its inhibition. Moreover, we have demonstrated that the TTSS1 effector VP1680 is involved in the stimulation of IL-8 secretion by the host. CHIR98014 mw The ERK signalling pathway is activated by
V. parahaemolyticus and leads to IL-8 secretion by intestinal epithelial cells In order to obtain a better overview of the signalling pathways leading to IL-8 activation in response to V. parahaemolyticus, the pharmacologic inhibitors of the MAPK signalling pathways were added during co-incubation and IL-8 secretion was quantified by ELISA (Figure 6). Addition of the inhibitors SB203580 and SP600125 had no influence on the level of IL-8 secreted by the Caco-2 cells co-incubated with WT V. parahaemolyticus, while the use of the ERK inhibitor PD98059 led to a significant decrease in the concentration of secreted IL-8. In fact a decrease of about 25% was seen in the IL-8 Acyl CoA dehydrogenase level secreted by the Caco-2 cells co-incubated with the WT V. parahaemolyticus when the cells have been pre-treated with PD98059. This result suggests that the inhibition of ERK signalling leads to inhibition of the resulting IL-8 secretion level. ERK signalling is a major signalling pathway activated by the WT V. parahaemolyticus and leads to the activation of IL-8 secretion by the eukaryotic cells. Figure 6 p38 and ERK are involved in the stimulation of IL-8 secretion by V. parahaemolyticus. A: ELISA to detect secreted IL-8 6 h and 24 h after co-incubation with V. parahaemolyticus in presence of MAPK inhibitors.