Serotonin and dopamine modulate aging in response to food perception and availability

An organism’s ability to perceive and respond to changes in its environment is crucial for its health and survival. Here we reveal how the most well-studied longevity intervention, dietary restriction (DR), acts in-part through a cell non-autonomous signaling pathway that is inhibited by the perception of attractive smells. Using an intestinal reporter for a key gene induced by DR but suppressed by attractive smells, we identify three compounds that block food perception in C. elegans, thereby increasing longevity as DR mimetics. These compounds clearly implicate serotonin and dopamine in limiting lifespan in response to food perception. We further identify an enteric neuron in this pathway that signals through the serotonin receptor 5-HT1A/ser-4 and dopamine receptor DRD2/dop-3. Aspects of this pathway are conserved in D. melanogaster and mammalian cells. Thus, blocking food perception through antagonism of serotonin or dopamine receptors is a plausible approach to mimic the benefits of dietary restriction.

Genetic background-dependent abnormalities of the enteric nervous system and intestinal function in Kif26a-deficient mice

The Kif26a protein-coding gene has been identified as a negative regulator of the GDNF-Ret signaling pathway in enteric neurons. The aim of this study was to investigate the influence of genetic background on the phenotype of Kif26a-deficient (KO, −/−) mice. KO mice with both C57BL/6 and BALB/c genetic backgrounds were established. Survival rates and megacolon development were compared between these two strains of KO mice. Functional bowel assessments and enteric neuron histopathology were performed in the deficient mice. KO mice with the BALB/c genetic background survived more than 400 days without evidence of megacolon, while all C57BL/6 KO mice developed megacolon and died within 30 days. Local enteric neuron hyperplasia in the colon and functional bowel abnormalities were observed in BALB/c KO mice. These results indicated that megacolon and enteric neuron hyperplasia in KO mice are influenced by the genetic background. BALB/c KO mice may represent a viable model for functional gastrointestinal diseases such as chronic constipation, facilitating studies on the underlying mechanisms and providing a foundation for the development of treatments.

Ebselen prevents cigarette smoke-induced gastrointestinal dysfunction in mice

Gastrointestinal (GI) dysfunction is a common comorbidity of chronic obstructive pulmonary disease (COPD) for which a major cause is cigarette smoking (CS). The underlying mechanisms and precise effects of CS on gut contractility, however, are not fully characterised. Therefore, the aim of the present study was to investigate whether CS impacts GI function and structure in a mouse model of CS-induced COPD. We also aimed to investigate GI function in the presence of ebselen, an antioxidant that has shown beneficial effects on lung inflammation resulting from CS exposure. Mice were exposed to CS for 2 or 6 months. GI structure was analysed by histology and immunofluorescence. After 2 months of CS exposure, ex vivo gut motility was analysed using video-imaging techniques to examine changes in colonic migrating motor complexes (CMMCs). CS decreased colon length in mice. Mice exposed to CS for 2 months had a higher frequency of CMMCs and a reduced resting colonic diameter but no change in enteric neuron numbers. Ten days cessation after 2 months CS reversed CMMC frequency changes but not the reduced colonic diameter phenotype. Ebselen treatment reversed the CS-induced reduction in colonic diameter. After 6 months CS, the number of myenteric nitric-oxide producing neurons was significantly reduced. This is the first evidence of colonic dysmotility in a mouse model of CS-induced COPD. Dysmotility after 2 months CS is not due to altered neuron numbers; however, prolonged CS-exposure significantly reduced enteric neuron numbers in mice. Further research is needed to assess potential therapeutic applications of ebselen in GI dysfunction in COPD.

Microbiota–modulated enteric neuron translational profiling uncovers a CART+ glucoregulatory subset

Microbial density and diversity increase towards the distal intestine, affecting tissue physiology, metabolism, and function of both immune and nervous systems. Intrinsic enteric–associated neurons (iEAN) continuously monitor and modulate intestinal functions, including nutrient absorption and motility. Through molecular, anatomic and functional approaches, we characterized the influence of the microbiota on iEAN. We found that iEAN are functionally adapted to the intestinal segment they occupy, with a stronger microbiota influence on distal intestine neurons. Chemogenetic characterization of microbiota-influenced iEAN identified a subset of viscerofugal CART+ neurons, enriched in the distal intestine, able to modulate feeding through insulin-glucose levels. Retro- and anterograde tracing revealed that CART+ viscerofugal neurons send axons to the gut sympathetic ganglion and are synaptically connected to the liver and pancreas. Our results demonstrate a region-specific adaptation of enteric neurons and indicate that specific iEAN subsets are capable of regulating host physiology independently from the central nervous system.One Sentence SummaryMicrobes impact regionally defined intrinsic enteric neuron translatomes, including a novel CART+ glucoregulatory viscerofugal population.

Diversification of molecularly defined myenteric neuron classes revealed by single cell RNA-sequencing

ABSTRACTAutonomous functions of the gastrointestinal tract require the combined activity of functionally distinct neurons of the enteric nervous system (ENS). However, the range of enteric neuron diversity and how it emerges during development remain largely unknown. We here make a novel molecular definition of 12 enteric neuron classes (ENCs) within the myenteric plexus of the mouse small intestine. We identify communication features and provide histochemical markers for discrete motor, sensory, and interneurons together with genetic tools for class-specific targeting. Transcriptome analysis of embryonic ENS reveals a largely post-mitotic principle of diversification, where only ENC1 or ENC8 phenotypic traits arise through a binary neurogenic trajectory, and other identities form through subsequent differentiation. We propose generic and class-specific transcriptional regulators and functionally connect the transcription factor Pbx3 to one post-mitotic identity conversion. Our results offers a conceptual and molecular resource for dissecting ENS circuits, and predicting key regulators for the directed differentiation of distinct enteric neuron classes.