How the gut influences neurologic disease

Indigophoton · May 16, 2018

Possibly relevant to ME given the potential involvement of both microglia in the brain and the microbiome in the illness.

A study published this week in Nature sheds new light on the connection between the gut and the brain, untangling the complex interplay that allows the byproducts of microorganisms living in the gut to influence the progression of neurodegenerative diseases. Investigators from Brigham and Women's Hospital (BWH) have been using both animal models and human cells from patients to tease out the key players involved in the gut-brain connection as well as in the crosstalk between immune cells and brain cells. Their new publication defines a pathway that may help guide therapies for multiple sclerosis and other neurologic diseases.

"These findings provide a clear understanding of how the gut impacts central nervous system resident cells in the brain," said corresponding author Francisco Quintana, Ph.D., of the Ann Romney Center for Neurologic Diseases at BWH. "Now that we have an idea of the players involved, we can begin to go after them to develop new therapies."

The new research focuses on the influence of gut microbes on two types of cells that play a major role in the central nervous system: microglia and astrocytes. Microglia are an integral part of the body's immune system, responsible for scavenging the CNS and getting rid of plaques, damaged cells and other materials that need to be cleared. But microglia can also secrete compounds that induce neurotoxic properties on the star-shaped brain cells known as astrocytes. This damage is thought to contribute to many neurologic diseases, including multiple sclerosis.
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The article, https://medicalxpress.com/news/2018-05-gut-neurologic-disease.amp

Abstract

Microglia and astrocytes modulate inflammation and neurodegeneration in the central nervous system (CNS)1,2,3. Microglia modulate pro-inflammatory and neurotoxic activities in astrocytes, but the mechanisms involved are not completely understood4,5. Here we report that TGFα and VEGF-B produced by microglia regulate the pathogenic activities of astrocytes in the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis. Microglia-derived TGFα acts via the ErbB1 receptor in astrocytes to limit their pathogenic activities and EAE development. Conversely, microglial VEGF-B triggers FLT-1 signalling in astrocytes and worsens EAE. VEGF-B and TGFα also participate in the microglial control of human astrocytes. Furthermore, expression of TGFα and VEGF-B in CD14+ cells correlates with the multiple sclerosis lesion stage. Finally, metabolites of dietary tryptophan produced by the commensal flora control microglial activation and TGFα and VEGF-B production, modulating the transcriptional program of astrocytes and CNS inflammation through a mechanism mediated by the aryl hydrocarbon receptor. In summary, we identified positive and negative regulators that mediate the microglial control of astrocytes. Moreover, these findings define a pathway through which microbial metabolites limit pathogenic activities of microglia and astrocytes, and suppress CNS inflammation. This pathway may guide new therapies for multiple sclerosis and other neurological disorders.
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https://www.nature.com/articles/s41586-018-0119-x

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