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Ingestion of a commensal bacteria, Lactobacillus rhamnosus JB-1, has potent immunoregulatory effects, and changes nerve-dependent colon migrating motor complexes (MMCs), enteric nerve function, and behavior. How these alterations occur is unknown. JB-1 microvesicles (MVs) are enriched for heat shock protein components such as chaperonin 60 heat-shock protein isolated from Escherichia coli (GroEL) and reproduce regulatory and neuronal effects in vitro and in vivo. Ingested labeled MVs were detected in murine Peyer's patch (PP) dendritic cells (DCs) within 18 h. After 3 d, PP and mesenteric lymph node DCs assumed a regulatory phenotype and increased functional regulatory CD4+25+Foxp3+ T cells. JB-1, MVs, and GroEL similarly induced phenotypic change in cocultured DCs via multiple pathways including C-type lectin receptors specific intercellular adhesion molecule-3 grabbing non-integrin-related 1 and Dectin-1, as well as TLR-2 and -9. JB-1 and MVs also decreased the amplitude of neuronally dependent MMCs in an ex vivo model of peristalsis. Gut epithelial, but not direct neuronal application of, MVs, replicated functional effects of JB-1 on in situ patch-clamped enteric neurons. GroEL and anti-TLR-2 were without effect in this system, suggesting the importance of epithelium neuron signaling and discrimination between pathways for bacteria-neuron and -immune communication. Together these results offer a mechanistic explanation of how Gram-positive commensals and probiotics may influence the host's immune and nervous systems. [ABSTRACT FROM AUTHOR]

It is generally accepted that intestinal sensory vagal fibers are primary afferent, responding nonsynaptically to luminal stimuli. The gut also contains intrinsic primary afferent neurons (IPANs) that respond to luminal stimuli. A psychoactive Lactobacillus rhamnosus (JB-1) that affects brain function excites both vagal fibers and IPANs. We wondered whether, contrary to its primary afferent designation, the sensory vagus response to JB-1 might depend on IPAN to vagal fiber synaptic transmission. We recorded ex vivo single- and multiunit afferent action potentials from mesenteric nerves supplying mouse jejunal segments. Intramural synaptic blockade with Ca2+ channel blockers reduced constitutive or JB-1-evoked vagal sensorydischarge. Firing of 60% of spontaneously active units was reduced by synaptic blockade. Synaptic or nicotinic receptor blockade reduced firing in 60% of vagal sensory units that were stimulated by luminal JB-1. In control experiments, increasing or decreasing IPAN excitability, respectively increased or decreased nerve firing that was abolished by synaptic blockade or vagotomy. We conclude that >50% of vagal afferents function as interneurons for stimulation by JB-1, receiving input from an intramural functional "sensory synapse." This was supported by myenteric plexus nicotinicreceptor immunohistochemistry. These data offer a novel therapeutic target to modify pathological gut-brain axis activity. [ABSTRACT FROM AUTHOR]

Gut commensals modulate host immune, endocrine, and metabolic functions. They also affect peripheral and central neural reflexes and function. We have previously shown that daily ingestion of Lactobacillus reuteri (LR) for 9 d inhibits the pseudoaffective cardiac response and spinal single-fiber discharge evoked by visceral distension, and decreases intestinal motility and myenteric AH cell slow afterhyperpolarization (sAHP) by inhibiting a Ca-activated K (IKCa) channel. We tested whether luminal LR could acutely decrease motility in an ex vivo perfusion model of naive Balb/c jejunum. Live LR dose dependently decreased motor complex pressure wave amplitudes with 9- to 16-min onset latency and an IC50 of 5 x 107 cells/ml Krebs. Heat-killed LR or another live commensal, Lactobacillus salivarius, were without effect. The IKCa channel blocker TRAM-34, but neither the opener (DCEBIO) nor the hyperpolarization-activated cationic channel inhibitor ZD7288 (5 µM) (or TTX 1 µM), mimicked the LR effect on motility acutely ex vivo. We provide evidence for a rapid, strain-specific, dosedependent action of a live Lactobacillus on small intestinal motility reflexes that recapitulates the long-term effects of LR ingestion. These observations may be useful as a first step to unraveling the pathways involved in bacteria to the nervous system communication. [ABSTRACT FROM AUTHOR]