Isoorientin Modulates Gut Microbes and Their Metabolites to Alleviate Caco-2 Cell Monolayer Inflammation by Reducing Intestinal Permeability via P-Gp/eCBs.

INTRODUCTION: Isoorientin (ISO) is a naturally occurring flavonoid that studies have shown to have strong experimental antioxidant, anti-inflammatory, anti-diabetic and anti-obesity properties. It has been shown that ISO alleviates Dextran sodium sulfate (DSS) induced colitis in mice by modulating gut microbes and their metabolites. The aim of this study was to modulate gut microbes and their metabolism by ISO to investigate its anti-inflammatory effects and its specific molecular mechanisms in a lipopolysaccharide (LPS)-induced monolayer inflammation model in Caco-2 cells. METHODS: Feces from ISO-treated DSS colitis mice were collected and gut flora culture supernatants were prepared. Detection of the effect of intestinal flora supernatants on the monolayer barrier of Caco-2 cells by inoculation of Caco-2 cells into the Transwell transmembrane culture system to simulate the intestinal mucosal barrier. RESULTS: The results revealed that ISO-conditioned intestinal flora supernatant significantly increased TEER values, decreased intestinal epithelial FITC-dextran flux permeability, and restored LPS-induced occludin, ZO-1 protein expression in Caco-2 cells. Meanwhile, intestinal flora supernatant significantly ameliorated the LPS-induced inflammatory response. In addition, ISO further enhanced its protective effect on intestinal permeability by regulating the expression of P-glycoprotein (P-gp) and endogenous cannabinoid system (eCB)-related proteins, which may attenuate the inflammatory response by activating the P-gp/eCB signaling pathway. CONCLUSION: The present study offers fresh perspectives into the application of ISO-conditioned intestinal flora supernatant as a potential anti-inflammatory agent and intestinal barrier protector in vitro. The unique regulation of the P-gp/eCBs pathway by ISO-conditioned intestinal flora supernatant was the novel mechanistic insights provided in this study.