Proline rich-39 (PR-39) antimicrobial protein alleviated lipopolysaccharide-induced intestinal barrier dysfunction in piglets by altering intestinal flora associated bile acid metabolism and in turn regulating TGR-5/NF-κB/MLCK/MLC pathway

Proline rich-39 (PR-39) is a natural antimicrobial protein with good antibacterial and anti-inflammatory activities. The miniature Wuzhishan pig (WZSP) has important similarities to humans in anatomical structure, physiological characteristics, and nutrient metabolism that make it an important model animal for biomedical research. This study aimed to investigate the protective effect and therapeutic mechanism of PR-39 on intestinal barrier function using the LPS-induced enteritis model in WZSPs. We found that PR-39 treatment reversed the decrease in growth performance and peripheral organ damage, regulated serum indices (IL-1β, IL-6, TNF-α, IL-10, TGF-β, IgA, IgG, DAO, D-LA) and enhanced the antioxidant capacity (MDA, CAT, GSH-Px, T-AOC) of piglets. PR-39 protected the integrity of the jejunal barrier by upregulating the density of goblet cells and the expression of tight junction proteins ZO-1, Claudin-1, and Occludin. Additionally, PR-39 increased the abundance of jejunal probiotics (e.g., Lactococcus), and increased the cecal abundance of Lactobacillus johnsonii, then promoted the production of 7-keto deoxycholic acid to activate the bile acid receptor TGR5, which in turn inhibited the NF-κB-MLCK-MLC signaling pathway and the secretion of proinflammatory factors by macrophages. In summary, these findings suggest that PR-39 supplementation may be an effective strategy to improve the intestinal damage and dysfunction.