Toxicological and immunological effects of DON and LPS at the intestinal barrier

The objectives of this study were to examine the effect of DON either in feed or in vitro as well as intraperitoneal LPS on the short circuit currents and tissue conductances across the small intestines of growing pigs in vitro, evaluation of DON transport in vitro across jejunal mucosa of growing pigs and estimation of the immunological effect of DON as well as LPS to induce cytokine secretion. The study was done in two series, in the first series the effect of different in vitro DON concentrations on Isc and Gt was investigated in six animals across duodenum, mid jejunum and ileum using Ussing technique. In the second series segments from mid jejunum were collected from 16 animals. The animals were divided into two groups, control and DON-fed groups. In DON-fed group, the animals were kept on diet containing 2.901 mg DON/kg feed for about 5 weeks. From each group four animals were injected intraperitoneally with 5 µg LPS/kg BW 3h before slaughtering. Blood samples were collected from all animals directly after slaughtering for plasma DON and cytokine analysis. Buffer samples were collected at 30 and 90 min after addition of DON from both, mucosal and serosal sides of Ussing chambers for measuring of DON concentrations using LC-ESI-MS/MS technique. Under basal conditions, duodenum and jejunum showed higher Isc compared with ileum which expressed higher Isc values under nutrient stimulated conditions. Among the examined concentrations, in vitro DON at 4000 and 8000 ng/ml reduced the electrogenic transport of both alanine and glucose across jejunal mucosa of growing pigs. Feeding DON at 2.901 mg/kg feed did not affect significantly the Isc or Gt across porcine intestinal segments. In LPS groups the Isc values were higher compared with non-injected groups, but without significant effect of LPS. Plasma analysis revealed higher TNF-α concentrations in LPS-injected groups compared with control and DON groups. As expected, higher plasma DON concentrations were found in DON-fed groups compared with controls. In DON transport study, lower mucosal amount of DON was observed at 4000 ng/ml compared to that at 8000 ng/ml in all groups. The mucosal uptake of DON in DON-fed groups was significantly higher than that in control groups. Intraperitoneal LPS did not affect on DON transport. Results of the first series showed that the response of porcine small intestines to the electrogenic nutrient transport varied with the type of the intestinal segments particularly ileum. In the second series, DON inhibited the electrogenic transport of alanine and glucose across jejunal mucosa of growing pigs. Both DON and LPS could induce secretion of the proinflammatory cytokines especially TNF-α. Systemic LPS tend to increase the Isc propably via the action of TNF-α, the point which is recommended to be evaluated in pigs. DON transport was proportional to its initial concentrations, with a respective effect of DON in feed on DON transport.