New Lactobacillus plantarum membrane proteins (LpMPs) towards oral anti-inflammatory agents against dextran sulfate sodium-induced colitis

Inflammatory bowel disease (IBD), a progressive and unpredictable colorectal inflammatory disease, is a global health problem. Currently, therapeutic strategies for the management of the disease are limited. Results from our previous studies indicated that probiotic Lactobacillus plantarum exhibits therapeutic effects against IBD, and through screening, we obtained an active 61-amino-acid long protein, L. plantarum membrane protein 1 (LpMP-1). Based on druggability-guided strategies, the search for LpMPs with lower molecular weights and better bioactivities contributes to the development of new anti-inflammatory agents to overcome the limitations of existing therapies against IBD. We used amino-acid-truncation strategies to obtain modified LpMPs (LpMP-2 - LpMP-9) using LpMP-1 as the parent template. Furthermore, we systematically evaluated the anti-colitis pharmacodynamics of these LpMPs in terms of symptomatology, histopathology, and cytokine levels in DSS-induced ulcerative colitis mice. Their possible targets of action against IBD was investigated under an iTRAQ-based pharmacoproteomic system and a docking-guided receptor-ligand relationship frame. We found a new active protein, LpMP-8, which had a lower molecular weight than LpMP-1. LpMP-8 was found to exhibit anti-colitis activity following oral administration in vivo (50 μg/kg) by improving symptoms of colitis, colonic ulcerations, and cytokine disorders. TLRs and TGF-β were found to be involved in the action of LpMP-8 against colitis; LpMP-8 was to compete with TLR4-MD2-bound LPS and reverse TGF-β and Smad2/7 disorders. Our probiotic-derived LpMP-8 was shown to elicit oral anti-colitis activity, and its significant efficacy is probably associated with TLR4 and TGF-β.