evolution: gut nerve controls (Introduction)

by David Turell , Wednesday, May 15, 2024, 17:53 (115 days ago) @ David Turell

Glial cells in the gut:

https://www.quantamagazine.org/in-the-guts-second-brain-key-agents-of-health-emerge-202...

"Breaking down food requires coordination across dozens of cell types and many tissues — from muscle cells and immune cells to blood and lymphatic vessels. Heading this effort is the gut’s very own network of nerve cells, known as the enteric nervous system, which weaves through the intestinal walls from the esophagus down to the rectum. This network can function nearly independently from the brain; indeed, its complexity has earned it the nickname “the second brain.” And just like the brain, it’s made up of two kinds of nervous system cells: neurons and glia.

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"...Neuroscientists have increasingly discovered that glia play physiological roles in the brain and nervous system that once seemed reserved for neurons.

"A similar glial reckoning is now happening in the gut. A number of studies have pointed to the varied active roles that enteric glia play in digestion, nutrient absorption, blood flow and immune responses. Others reveal the diversity of glial cells that exist in the gut, and how each type may fine-tune the system in previously unknown ways. One recent study, not yet peer-reviewed, has identified a new subset of glial cells that senses food as it moves through the digestive tract, signaling to the gut tissue to contract and move it along its way.

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"Thanks to some of these newer technologies, scientists now know that enteric glia are among the first responders to injury or inflammation in gut tissue. They help maintain the gut’s barrier to keep toxins out. They mediate the contractions of the gut that allow food to flow through the digestive tract. Glia regulate stem cells in the gut’s outer layer, and are critical for tissue regeneration. They chat with the microbiome, neurons and immune-system cells, managing and coordinating their functions.

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"Those methods allowed her to get the “first glimpse into the diversity of these glial cells” across all tissues of the duodenum, Scavuzzo said. In June, in a paper published on the biorxiv.org preprint server that has not yet been peer-reviewed, she reported her team’s discovery of six subtypes of glial cells, including one that they named “hub cells.”

"Hub cells express genes for a mechanosensory channel called PIEZO2 — a membrane protein that can sense force and is typically found in tissues that respond to physical touch. Other researchers recently found PIEZO2 present in some gut neurons; the channel allows neurons to sense food in the intestines and move it along. Scavuzzo hypothesized that glial hub cells can also sense force and instruct other gut cells to contract. She found evidence that these hub cells existed not only in the duodenum, but also in the ileum and colon, which suggests they’re likely regulating motility throughout the digestive tract.

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"Glia are likely involved because of their central role in communicating between the microbiome, immune cells and other gut cells. Healthy glia strengthen the intestines’ epithelial barrier, a layer of cells that keeps out toxins and pathogens and absorbs nutrients. But in patients with Crohn’s disease, glial cells don’t function properly, resulting in a weaker barrier and inappropriate immune response.

“Different subtypes of glia can be functioning differently or dysfunctioning in a wide range of diseases and disorders where motility is impacted,” Scavuzzo said. They have also been linked to neural inflammation, hypersensitivity in the organs and even neuron death.

"For instance, Gulbransen and his team recently discovered that glia contribute to gut pain by secreting molecules that sensitize neurons. This is likely an adaptive response intended to draw the gut’s attention to damaging substances to dispose of them, Gulbransen said, which as a side effect causes pain."

Comment: glia were ignored for a long time. It just shows everything is there for a reason.