Bifidobacterium Longum Inhibit The Ileum Mucous Immune Of PI-IBS Through Down-regulation Of NLRP6Inflammasome

AIM: The aim of this study is to investigate whether NLRP6inflammasomeparticipates in the activation of intestinal mucosal immune in post infectious irritablebowel syndrome (PI-IBS) models, and whether intragastric administration ofBifidobacterium longum has some effect on NLRP6inflammasome signal pathway.METHOD:40NIH mice were randomly divided into five groups: normal controls of2weeks (NC-2w) group,2weeks after infection group (PI-2w), normal control of8weeks (NC-8w),8weeks after infection group (PI–8w) and Bifidobacterium longumintervention group (PI-B). Gastrointestinal infection was achieved by intragastricadministration of Trichinella spiralis. For the control models, saline was used insteadof the trichinella spiralis. Mice were sacrificed at the2th week after infection for theNC-2w and PI-2w groups and at the8th week for the NC-8w and PI–8w groups.Mice of PI-B group were sacrificed after infection for eight weeks and thenintervention with Bifidobacterium longum for one week. Visceral sensation evaluationof abdominal withdrawal reflex score was performed for all mice before they weresacrificed. The terminal ileum tissue of each mouse was removed for detecting theexpression of CD172a, NLRP6, ASC, CARD8, caspase-1, IL-18and IL-1β.RESULT:1. The change of visceral sensitivity (AWR score): the visceral sensitivity ofPI-2W and PI-8W increased significantly in40mmHg and60mmHg pressurecompared with their control groups (NC-2W and NC-8W)（P＜0.05）; but in20mmHg and80mmHg pressure, there was no significant difference（P>0.05）. Thevisceral sensitivity of PI–B group had a significant decline when compared to PI-8W group in40mmHg and60mmHg pressure（P＜0.05）, but had no significantdecline when compared to PI-8W group in20mmHg and80mmHg pressure 2. The expression level of CD172a: The expression level of PI-2W groupincreased significantly compared with NC-2W group（P＜0.05）; but The expressionlevel of PI-8W group had no significant difference compared with PI-8W（P>0.05）.3. The expression position of NLRP6, ASC and caspase-1: Immunofluorescenceresults showed that NLRP6, ASC and caspase-1only expressed in mucous membranelayer， mainly expressed in cytoplasm and rich in intestinal epithelial cells. AndNLRP6, ASC and caspase-1all expressed in same position.4. The expression level of NLRP6and NLRP6related protein4.1The expression level of NLRP6: The expression level of PI-2w and PI-8Wgroup increased significantly when compared with their control groups （NC-2W andNC-8W group）. Because there was no statistical difference between NC-2W andNC-8W group, we can compare PI-8W to PI-2W, the results showed that there was nostatistical differences between them (P>0.05). The expression level of PI-B groupexpression level decreased significantly when compared with PI–8W group (P <0.05).4.2The expression level of CARD8、ASC and caspase-1: The expression level ofCARD8、ASC and caspase-1in PI-2W and PI-8W group increased significantly whencompared with their control groups （NC-2W and NC-8W group）, and the expressionlevel of the CARD8、ASC and caspase-1in PI-2W group had no statistical differencewith the expression level PI-8W group (P>0.05). The expression level of CARD8、ASC and caspase-1in PI-B group decreased significantly when compared withPI–8W group (P <0.05). 4.3The expression level of downstream cytokines: The expression level of IL–18in PI-2w and PI-8W group increased significantly when compared with theircontrol groups （NC-2W and NC-8W group）, and the expression level of IL–18inPI-8W declined significantly when compared to PI-2W. The expression of IL-18inPI-B group declined significantly when compared to PI-8W (P <0.05). But, theexpression level of IL-1β just increased remarkably in PI-2W (P <0.05).CONCLUSION: NLRP6inflammasome participates in immune activation ofintestinal mucosa in PI-IBS models, and Bifidobacterium longum is a negativegreulate factor to NLRP6inflammasome signal pathway.