Lactobacillus crispatus M247-Derived H2O2 Acts as a Signal Transducing Molecule Activating Peroxisome Proliferator Activated Receptor-γ in the Intestinal Mucosa

Background & Aims: Accumulating evidence indicates that the peroxisome proliferator activated receptor (PPAR)-γ is a major player in maintaining intestinal mucosa homeostasis, but whether PPAR-γ is directly involved in probiotic-mediated effects and the molecular events involved in its activation are not known. Methods: We investigated the role of PPAR-γ in the immunomodulatory effects of Lactobacillus crispatus M247 on intestinal epithelial cells (IEC) and the role of probiotic-derived H2O2 on PPAR-γ activity. Results: L crispatus M247 supplementation in mice significantly increased PPAR-γ levels and transcriptional activity in the colonic mucosa. L crispatus M247 induced PPAR-γ nuclear translocation and enhanced transcriptional activity in epithelial (CMT-93) cells, as demonstrated by the increased luciferase activity of a PPAR-γ-responsive element, PPAR-γ-responsive gene up-regulation, and reduced activity of an nuclear factor-κB-responsive element. Pharmacologic PPAR-γ inhibition or silencing by small interfering RNA cancelled the L crispatus M247-mediated effects in CMT-93 cells. Because Lactobacillus strains producing little H2O2 failed to activate PPAR-γ, we investigated the role of L crispatus M247-derived H2O2 in PPAR-γ activation. L crispatus M247 induced a transient rise in intracellular H2O2 and PPAR-γ transcriptional activity was cancelled by antioxidant or H2O2 scavenger. Toll-like receptor (TLR)-2 was not required for PPAR-γ up-regulation mediated by L crispatus M247 in mice, although the protective effects of L crispatus M247 on dextran sodium sulfate-induced colitis were less pronounced in TLR-2−/− mice. Conclusions: L crispatus M247 uses H2O2 as a signal transducing molecule to induce PPAR-γ activation in IEC, directly modulating epithelial cell responsiveness to inflammatory stimuli.