Publications

2024

Shepherd, Amy, Laurence Feinstein, Svetlana Sabel, Daniella Rastelli, Esther Mezhibovsky, Lynley Matthews, Anoohya Muppirala, et al. (2024) 2024. “RET Signaling Persists in the Adult Intestine and Stimulates Motility by Limiting PYY Release From Enteroendocrine Cells”. Gastroenterology 166 (3): 437-49. https://doi.org/10.1053/j.gastro.2023.11.020.

BACKGROUND & AIMS: RET tyrosine kinase is necessary for enteric nervous system development. Loss-of-function RET mutations cause Hirschsprung disease (HSCR), in which infants are born with aganglionic bowel. Despite surgical correction, patients with HSCR often experience chronic defecatory dysfunction and enterocolitis, suggesting that RET is important after development. To test this hypothesis, we determined the location of postnatal RET and its significance in gastrointestinal (GI) motility.

METHODS: RetCFP/+ mice and human transcriptional profiling data were studied to identify the enteric neuronal and epithelial cells that express RET. To determine whether RET regulates gut motility in vivo, genetic, and pharmacologic approaches were used to disrupt RET in all RET-expressing cells, a subset of enteric neurons, or intestinal epithelial cells.

RESULTS: Distinct subsets of enteric neurons and enteroendocrine cells expressed RET in the adult intestine. RET disruption in the epithelium, rather than in enteric neurons, slowed GI motility selectively in male mice. RET kinase inhibition phenocopied this effect. Most RET+ epithelial cells were either enterochromaffin cells that release serotonin or L-cells that release peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), both of which can alter motility. RET kinase inhibition exaggerated PYY and GLP-1 release in a nutrient-dependent manner without altering serotonin secretion in mice and human organoids. PYY receptor blockade rescued dysmotility in mice lacking epithelial RET.

CONCLUSIONS: RET signaling normally limits nutrient-dependent peptide release from L-cells and this activity is necessary for normal intestinal motility in male mice. These effects could contribute to dysmotility in HSCR, which predominantly affects males, and uncovers a mechanism that could be targeted to treat post-prandial GI dysfunction.

2023

Manion, John, Melissa A Musser, Gavin A Kuziel, Min Liu, Amy Shepherd, Siyu Wang, Pyung-Gang Lee, et al. (2023) 2023. “C. Difficile Intoxicates Neurons and Pericytes to Drive Neurogenic Inflammation”. Nature. https://doi.org/10.1038/s41586-023-06607-2.

Clostridioides difficile infection (CDI) is a major cause of healthcare-associated gastrointestinal infections1,2. The exaggerated colonic inflammation caused by C. difficile toxins such as toxin B (TcdB) damages tissues and promotes C. difficile colonization3-6, but how TcdB causes inflammation is unclear. Here we report that TcdB induces neurogenic inflammation by targeting gut-innervating afferent neurons and pericytes, mediated by receptors including Frizzled 1/2/7 (FZD1/2/7) in neurons and chondroitin sulfate proteoglycan 4 (CSPG4) in pericytes. TcdB action stimulates secretion of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) from neurons and pro-inflammatory cytokines from pericytes. Targeted delivery of the TcdB enzymatic domain, through fusion with a detoxified diphtheria toxin (DT), into peptidergic sensory neurons that express exogeneous DT receptor (an approach we termed toxogenetics) is sufficient to induce neurogenic inflammation and recapitulates major colonic histopathology associated with CDI. Conversely, mice lacking SP, CGRP, or the SP receptor (NK1R) show reduced pathology in both models of cecal TcdB injection and CDI. Blocking SP or CGRP signaling reduces tissue damage and C. difficile burden in mice infected with a standard C. difficile strain or hypervirulent strains expressing the TcdB2 variant. Thus, targeting neurogenic inflammation provides a host-oriented therapeutic approach for treating CDI.

Prochera, Aleksandra, and Meenakshi Rao. (2023) 2023. “Mini-Review: Enteric Glial Regulation of the Gastrointestinal Epithelium”. Neuroscience Letters 805: 137215. https://doi.org/10.1016/j.neulet.2023.137215.

Many enteric glia are located along nerve fibers in the gut mucosa where they form close associations with the epithelium lining the gastrointestinal tract. The gut epithelium is essential for absorbing nutrients, regulating fluid flux, forming a physical barrier to prevent the entry of pathogens and toxins into the host, and participating in immune responses. Disruptions to this epithelium are linked to numerous diseases, highlighting its central importance in maintaining health. Accumulating evidence indicates that glia regulate gut epithelial homeostasis. Observations from glial-epithelial co-cultures in vitro and mouse genetic models in vivo suggest that enteric glia influence several important features of the gut epithelium including barrier integrity, ion transport, and capacity for self-renewal. Here we review the evidence for enteric glial regulation of the intestinal epithelium, with a focus on these three features of its biology.

2022

Rastelli, Daniella, Ariel Robinson, Valentina Lagomarsino, Lynley Matthews, Rafla Hassan, Kristina Perez, William Dan, et al. 2022. “Diminished androgen levels are linked to irritable bowel syndrome and cause bowel dysfunction in mice”. J Clin Invest 132 (2). https://doi.org/10.1172/JCI150789.
Functional gastrointestinal disorders (FGIDs) have prominent sex differences in incidence, symptoms, and treatment response that are not well understood. Androgens are steroid hormones present at much higher levels in males than females and could be involved in these differences. In adults with irritable bowel syndrome (IBS), a FGID that affects 5% to 10% of the population worldwide, we found that free testosterone levels were lower than those in healthy controls and inversely correlated with symptom severity. To determine how this diminished androgen signaling could contribute to bowel dysfunction, we depleted gonadal androgens in adult mice and found that this caused a profound deficit in gastrointestinal transit. Restoring a single androgen hormone was sufficient to rescue this deficit, suggesting that circulating androgens are essential for normal bowel motility in vivo. To determine the site of action, we probed androgen receptor expression in the intestine and discovered, unexpectedly, that a large subset of enteric neurons became androgen-responsive upon puberty. Androgen signaling to these neurons was required for normal colonic motility in adult mice. Taken together, these observations establish a role for gonadal androgens in the neural regulation of bowel function and link altered androgen levels with a common digestive disorder.

2021

Dan, William, Ga Hyun Park, Shruti Vemaraju, Amy Wu, Kristina Perez, Meenakshi Rao, Dan Berkowitz, Richard Lang, and Peter Yim. (2021) 2021. “Light-Mediated Inhibition of Colonic Smooth Muscle Constriction and Colonic MotilityOpsin 3”. Front Physiol 12: 744294. https://doi.org/10.3389/fphys.2021.744294.
Opsin photoreceptors outside of the central nervous system have been shown to mediate smooth muscle photorelaxation in several organs. We hypothesized that opsin receptor activation in the colon would have a similar effect and influence colonic motility. We detected Opsin 3 (OPN3) protein expression in the colonic wall and demonstrated that OPN3 was present in enteric neurons in the muscularis propria of the murine colon. Precontracted murine colon segments demonstrated blue light (BL) -mediated relaxation ex vivo. This photorelaxation was wavelength specific and was increased with the administration of the chromophore 9-cis retinal and a G protein receptor kinase 2 (GRK2) inhibitor. Light-mediated relaxation of the colon was not inhibited by L-NAME or tetrodotoxin (TTX). Furthermore, BL exposure in the presence of 9-cis retinal decreased the frequency of colonic migrating motor complexes (CMMC) in spontaneously contracting mouse colons ex vivo. These results demonstrate for the first time a receptor-mediated photorelaxation of colonic smooth muscle and implicate opsins as possible new targets in the treatment of spasmodic gastrointestinal dysmotility.
Rao, Meenakshi, and Milena Bogunovic. 2021. “Enteric glia worm their way into gut immunity”. Immunity 54 (12): 2698-2700. https://doi.org/10.1016/j.immuni.2021.11.014.
The gut houses one of the largest populations of glia in the nervous system, yet their essential functions remain unclear. New work by Progatzky et al. (2021) in Nature reveals that these enteric glia orchestrate an IFNγ-dependent immune response to helminth infection that promotes tissue repair.
Rosenberg, Harry, and Meenakshi Rao. 2021. “Enteric glia in homeostasis and disease: From fundamental biology to human pathology”. IScience 24 (8): 102863. https://doi.org/10.1016/j.isci.2021.102863.
Glia, the non-neuronal cells of the nervous system, were long considered secondary cells only necessary for supporting the functions of their more important neuronal neighbors. Work by many groups over the past two decades has completely overturned this notion, revealing the myriad and vital functions of glia in nervous system development, plasticity, and health. The largest population of glia outside the brain is in the enteric nervous system, a division of the autonomic nervous system that constitutes a key node of the gut-brain axis. Here, we review the latest in the understanding of these enteric glia in mammals with a focus on their putative roles in human health and disease.
Yan, Yiqing, Deepshika Ramanan, Milena Rozenberg, Kelly McGovern, Daniella Rastelli, Brinda Vijaykumar, Omar Yaghi, et al. 2021. “Interleukin-6 produced by enteric neurons regulates the number and phenotype of microbe-responsive regulatory T cells in the gut”. Immunity 54 (3): 499-513.e5. https://doi.org/10.1016/j.immuni.2021.02.002.
The immune and enteric nervous (ENS) systems monitor the frontier with commensal and pathogenic microbes in the colon. We investigated whether FoxP3 regulatory T (Treg) cells functionally interact with the ENS. Indeed, microbe-responsive RORγ and Helios subsets localized in close apposition to nitrergic and peptidergic nerve fibers in the colon lamina propria (LP). Enteric neurons inhibited in vitro Treg (iTreg) differentiation in a cell-contact-independent manner. A screen of neuron-secreted factors revealed a role for interleukin-6 (IL-6) in modulating iTreg formation and their RORγ proportion. Colonization of germfree mice with commensals, especially RORγ Treg inducers, broadly diminished colon neuronal density. Closing the triangle, conditional ablation of IL-6 in neurons increased total Treg cells but decreased the RORγ subset, as did depletion of two ENS neurotransmitters. Our findings suggest a regulatory circuit wherein microbial signals condition neuronal density and activation, thus tuning Treg cell generation and immunological tolerance in the gut.

2020

Jazayeri, Amir, Dieudonne Nonga, and Meenakshi Rao. 2020. “The Key to a Boy’s Heart Is Through His Intestine”. Gastroenterology 158 (5): 1226-28. https://doi.org/10.1053/j.gastro.2019.08.056.