<i>Lactiplantibacillus plantarum</i> strengthens the intestinal barrier: involvement of the endocannabinoidome

Probiotics have been suggested to ameliorate intestinal epithelial homeostasis and barrier function. They also modulate several mediators and receptors of the expanded endocannabinoid system, or endocannabinoidome (eCBome), potentially explaining their beneficial effects on intestinal function. We aimed to study the effects of probiotic strains on gut barrier functions and the possible involvement of the eCBome in these effects. We cocultured three strains of <i>Lactiplantibacillus plantarum</i> with murine small intestine epithelial organoids and explored the involvement of eCBome signaling and inflammation in mediating the beneficial effects of the probiotics on the epithelial barrier function. All three <i>L. plantarum</i> strains reduced the transepithelial permeability of organoids and increased mRNA expression of several tight junction proteins (<i>Clnd1</i>, <i>Clnd2</i>, <i>Ocln</i>, <i>Tjp1</i>, and <i>Cdh1</i>) and intestinal barrier proteins (<i>Muc2</i>, <i>Lyz1</i>, <i>Reg3a</i>, and <i>Defa20</i>). Concomitantly, the three strains increased the expression of genes encoding eCBome receptors while decreasing the expression of two catabolic enzymes (<i>Faah</i> and <i>Naaa</i>), and increasing one anabolic enzyme (<i>Daglb</i>). Altogether, these changes led to an overall increase in levels of eCBome mediators, namely <i>N</i>-acyl-ethanolamines (NAEs) and, particularly, 2-monoacylglycerols (2-MAGs), as measured by LC-MS/MS. URB 597 and JZL 184, two selective inhibitors of NAE and 2-MAG catabolism, reduced the transepithelial permeability of organoids, as observed with <i>L. plantarum</i> strains. Interestingly, both inhibitors also reversed inflammation-induced transepithelial permeability in organoids. Elevated endogenous levels of NAEs or 2-MAGs promote improvement in small intestine transepithelial permeability, and <i>L. plantarum</i> strains may exploit this mechanism to exert this same beneficial effect.<b>NEW & NOTEWORTHY</b> <i>Lactiplantibacillus plantarum</i> strains improve transepithelial permeability and concomitantly increase the levels of eCBome mediators in murine small intestine epithelial organoids. Pharmacological elevation of NAE or 2-MAG levels enhances the expression of intestinal epithelial barrier genes and reduces the transepithelial permeability of murine small intestine epithelial organoids, suggesting that <i>L. plantarum</i> may exploit eCBome signaling to exert its beneficial effects.