Neuropods

Abstract

Enteroendocrine cells (EECs) are sensory cells of the gut that communicate by releasing hormones locally through paracrine action or into the blood stream. Recently it has been discovered that EECs possess cytoplasmic processes known as neuropods that extend to distant cells including nerves. Thus, EECs regulate ingestive behavior through local, hormonal and neural signaling. Enteroendocrine cells (EECs) are sensory cells of the gastrointestinal tract. Most EECs reside in the mucosal lining of the stomach or intestine and sense food in the gut lumen. Food signals stimulate the release of hormones into the paracellular space where they either act locally or are taken up into the blood and circulate to distant organs. It recently was recognized that many EECs possess basal processes known as neuropods that not only contain hormones but also connect to nerves. This review describes how neuropods contribute to EEC function beyond typical hormonal actions. For example, gastrointestinal hormones not only act on distant organs, but, through neuropods, some act locally to stimulate other mucosal cells such as intestinal stem cells, enterocytes, or other EECs. With the recent discovery that EECs communicate directly with enteric nerves, EECs not only have the ability to sense food and bacteria in the gastrointestinal tract, but can communicate these signals directly to the nervous system.

Functional circuits and signal processing in the enteric nervous system

“…While chemosensory transduction in the epithelium has been extensively examined, our knowledge of the specific molecules involved in EEC signaling to the ENS is surprisingly lacking. EECs make specialized contacts via their ‘neuropod’ with extrinsic sensory afferents innervating the epithelium [ 70 – 72 ], but the specificity of the intrinsic enteric circuitry involved in detecting different luminal stimuli remains unclear. The local application of various nutrient stimuli, and acidic or basic solutions to the mucosa can activate enteric neurons [ 43 ], but the exact mucosal mediators involved in the communication between EECs and enteric neurons remain elusive.…”

The Gut and Parkinson's Disease—A Bidirectional Pathway

“…Enteroendocrine cells have diverse phenotypes and express a variety of peptides/hormones that can act as signaling molecules on distinct targets, both local and distant, and some are chemoreceptors responding to a variety of luminal stimuli (84, 85). As other intestinal epithelial cells, enteroendocrine cells express toll-like receptors (86), allowing them to detect bacterial products, and activate vagal afferents through basal processes called neuropods (see Figure 1) (20, 87).…”

Inflammatory Bowel Diseases: Host-Microbial-Environmental Interactions in Dysbiosis

“…Secreted neurotransmitters from these bacteria may induce host epithelial cells to release factors that regulate neural signaling within the enteric nervous system or may act directly upon it [ 124 , 125 ]. Their actions may occur through the neuro-epithelial link (neuropods) between enteroendocrine cells and neuron and glial cells in the intestine [ 126 ]. Intestinal enteroendocrine cells produce an array of hormones, including GLP-1, GLP-2, cholecystokinin, somatostatin, and serotonin, which control many critical aspects of metabolism in the intestine and associated tissues.…”