Papers of the Week

Luminal distention and abdominal pain are major clinical hallmarks of obstructive bowel disorders and functional bowel disorders linked to gut dysbiosis. Our recent studies found that chronic lumen distention increased visceral sensitivity and decreased abundance of gut commensal Lactobacillus reuteri in a rodent model of partial colon obstruction (OB). To establish causation, we performed precision microbial therapy to assess whether recolonization of L. reuteri prevents visceral hypersensitivity in lumen distention, and if so, to identify the gut-microbiota mechanism. Lumen distention was induced in Sprague-Dawley rats by implanting an obstruction band in the distal colon for up to 7 days. L. reuteri strains or vehicle were gavage ingested 1X10 CFU/g daily starting 2 days prior to obstruction. L. reuteri rat strains that were able to recolonize obstructed colon significantly improved food intake and body weight in OB rats, and attenuated referred visceral hyperalgesia measured by the withdrawal response to von Frey filament applications to the abdomen. Mechanistically, L. reuteri treatment attenuated hyper-excitability of the dorsal root ganglia neurons projecting to the distended colon by promoting opioid receptor function in affected tissues. The expression of µ, δ, and κ opioid receptors was significantly downregulated in colonic muscularis externae and sensory neurons in OB rats. However, L. reuteri treatment prevented the loss of opioid receptors. Further, administration of peripheral opioid receptor antagonist naloxone methiodide abolished the analgesic effect of L. reuteri in OB. In conclusion, precision L. reuteri therapy prevents lumen distention-associated visceral hypersensitivity by local bacterial induction of opioid receptors.