Gut microbial products regulate murine gastrointestinal motility via toll-like receptor 4 signaling

BACKGROUND & AIMS: Altered gastrointestinal motility is associated with significant morbidity and health care costs. Toll-like receptors (TLR) regulate intestinal homeostasis. We examined the roles of TLR4 signaling in survival of enteric neurons and gastrointestinal motility. METHODS: We assessed changes in intestinal motility by assessing stool frequency, bead expulsion, and isometric muscle recordings of colonic longitudinal muscle strips from mice that do not express TLR4 (Tlr4^Lps-d or TLR4^-/-) or Myd88 (Myd88 ^-/-), in wild-type germ-free mice or wild-type mice depleted of the microbiota, and in mice with neural crest-specific deletion of Myd88 (Wnt1Cre^+/-/Myd88^fl/fl). We studied the effects of the TLR4 agonist lipopolysaccharide (LPS) on survival of cultured, immortalized fetal enteric neurons and enteric neuronal cells isolated from wild-type and Tlr4^Lps-d mice at embryonic day 13.5. RESULTS: There was a significant delay in gastrointestinal motility and reduced numbers of nitrergic neurons in TLR4^Lps-d, TLR4^-/-, and Myd88^-/- mice compared with wild-type mice. A similar phenotype was observed in germ-free mice, mice depleted of intestinal microbiota, and Wnt1Cre^+/-/ Myd88^fl/fl mice. Incubation of enteric neuronal cells with LPS led to activation of the transcription factor nuclear factor (NF)-κB and increased cell survival. CONCLUSIONS: Interactions between enteric neurons and microbes increases neuron survival and gastrointestinal motility in mice. LPS activation of TLR4 and NF-κB appears to promote survival of enteric neurons. Factors that regulate TLR4 signaling in neurons might be developed to alter gastrointestinal motility.