In Vitro Characterization of Gut Microbiota-Derived Commensal Strains: Selection of Parabacteroides distasonis Strains Alleviating TNBS-Induced Colitis in Mice

Abstract

Alterations in the gut microbiota composition and diversity seem to play a role in the development of chronic diseases, including inflammatory bowel disease (IBD), leading to gut barrier disruption and induction of proinflammatory immune responses. This opens the door for the use of novel health-promoting bacteria. We selected five Parabacteroides distasonis strains isolated from human adult and neonates gut microbiota. We evaluated in vitro their immunomodulation capacities and their ability to reinforce the gut barrier and characterized in vivo their protective effects in an acute murine model of colitis. The in vitro beneficial activities were highly strain dependent: two strains exhibited a potent anti-inflammatory potential and restored the gut barrier while a third strain reinstated the epithelial barrier. While their survival to in vitro gastric conditions was variable, the levels of P. distasonis DNA were higher in the stools of bacteria-treated animals. The strains that were positively scored in vitro displayed a strong ability to rescue mice from colitis. We further showed that two strains primed dendritic cells to induce regulatory T lymphocytes from naïve CD4+ T cells. This study provides better insights on the functionality of commensal bacteria and crucial clues to design live biotherapeutics able to target inflammatory chronic diseases such as IBD.

Identification of New Potential Biotherapeutics from Human Gut Microbiota-Derived Bacteria

“…First, we verified that the bacteria were catalase-negative i.e., were not able to degrade H 2 O 2 when put in contact with it (data not shown). Second, the ability of the selected strains to modulate the H 2 O 2 -induced increase in paracellular permeability was evaluated using an in vitro epithelial barrier model as previously described [ 40 , 46 , 47 ]. As expected, the addition of H 2 O 2 reduced the TransEpithelial Electrical Resistance (TEER) indicating an increased permeability ( Figure 3 , H 2 O 2 ) reflecting the sensitization of the cell monolayers in the control.…”

“…The bacterial survival to gastric stress was strain-dependent and only P. distasonis PF-BaE7 among the seven strains combining several probiotic functions was tolerant to that stress condition. However, we previously showed that adding sodium bicarbonate to the bacterial suspensions to neutralize the gastric pH, improved the strain survival during the in vitro stress assay (data not shown) and could also allow significant protection against intestinal inflammation after in vivo administration of gastric-stress sensitive strains [ 40 ].…”

“…B. coprocola AS101 and B. uniformis PF-BaE8 and PF-BaE13 which combined anti-inflammatory profile and barrier protection abilities together with R. intestinalis AS6 and P. distasonis AS93 which showed the 3 probiotic activities are highlighted by our work as appealing NGP candidates to target intestinal inflammation. Indeed, based on the in vitro barrier and immunomodulation tests, we were previously able to identify P. distasonis strains including AS93, with the ability to alleviate intestinal inflammation in a murine model of colitis [ 40 ]. In the present study, we included two of these P. distasonis strains to complete their functional characterization with their effect on GLP1 production.…”

“…Bacteroides have been shown to be decreased in obese patients and the protective effect of selected strains has been shown in animal models [ 38 , 39 ]. We and others have also highlighted the probiotic potential of Parabacteroides distasonis [ 40 , 41 ].…”

Severity of Experimental Autoimmune Uveitis Is Reduced by Pretreatment with Live Probiotic Escherichia coli Nissle 1917

“…Interestingly, flagellin also induces IRAK3 expression in cultured intestinal epithelial cells, which is associated with tolerance induction [ 80 ]. Microbiota-induced strengthening of the gut barrier is a mechanism that can influence different pathological processes in the gut and liver and may even be employed in fundamental processes, such as age-related “leaky gut” [ 81 , 82 , 83 ]. Therefore, we analyzed ileal and colonic expression of the flagellin sensor Tlr5 , the negative regulator of TLR signaling Irak3 , the gene for tight junction protein ZO-1 ( Tjp1 ), Muc13, and a set of anti-microbial peptides, including the murine functional orthologue of human beta-defensin 2, Defb4 [ 84 ].…”