Pancreatitis-associated protein (pap) produced by different lactic acid bacteria can protect mice in an acute colitis model after oral delivery.

Inflammatory bowel disease (IBD) is a group of chronic, complex and relapsing inflammatory conditions of GIT that has been a global health problem, with an increasing incidence. It includes two main forms, Crohn's disease (CD) and ulcerative colitis (UC), which are characterized by alternating phases of clinical relapse and remission. One of the molecules that has been studied by our research group in the treatment of IBD is the Pancreatitis Associated Protein I (PAP). PAP has a variety of activities, which includes anti-apoptotic, anti-inflammatory, antibacterial effects and proliferative, maintaining host-bacterial homeostasis in the mammalian gut. Several new strategies using lactic acid bacteria (LAB) for the expression or ability to metabolize molecules capable of reducing inflammation in inflammatory bowel diseases have been studied in recent years. Here, we first sought to determine whether PAP delivered at intestinal membrane by recombinant Lactococcus lactis strain, LL-PAP, is able to modulate the microbiota community and reduce the chemically induced intestinal inflammation. After a DiNitro-BenzeneSulfonic-acid (DNBS) challenge, mice treated with LL-PAP showed a decrease in the colitis severity compared to those treated with the control L. lactis strain. This effect was characterized by: protection against weight loss; lower macroscopical and histological scores; and down-regulation of pro-inflammatory cytokines secreted by lymphocytes in Mesenteric Lymph Node (MLN). Moreover after 5 days of treatment LL-PAP was able to increase the diversity of the microbiota and relative abundance of Eubacterium plexicaudatum, a bacterium producing an anti-inflammatory molecule, the butyrate. This modification of the microbiota could participate to the anti-inflammatory properties of LL-PAP. Then, we compared LL-PAP and a recombinant strain of Lactobacillus casei, LC-PAP, producing PAP in the treatment of acute colitis induced by DNBS. Beyond the comparison between both strains we also compared two different protocols of administration: i) a daily administration; or ii) an administration every 3 days. The analysis of weight loss, macroscopic score and cytokines showed us that Lactococcus lactis should be administered every day to confer protection, while Lactobacillus casei should be administered every 3 days to show a tendency to protect mice. Our data showed the importance of the vector and the timing of the treatment. We also performed the evaluation of the protection induced by a L. lactis strain delivering a plasmid for PAP expression by epithelial cells, LL-PAP cDNA, compared with LL-PAP in a murine model of DNBS acute colitis. We hypothesized that the use of the two different strains could modifiy the PAP concentration at different places. Administration of LL-PAP increases PAP into the lumen whereas the use of LL-PAP cDNA enhances the level of PAP produced by epithelial cells. Our results showed that both groups of recombinant L. lactis showed the same protective effect compared with LL empty group. Nevertheless, PAP-cDNA was able to induce the production of anti-inflammatory cytokines and this result may suggest an activation of Treg cells differentiation. Taken altogether, we can infer that the location of PAP delivery may influence its anti-inflammatory properties but not regarding weight loss and macroscopic scores. These results confirmed the choice of the strategy used to deliver the molecule is as important as the choice of the molecule per se.