Connections between gut, brain, and immune system strengthened


OVER recent years, researchers have given the common phrase “gut feeling” scientific backing. The interplay between the two systems is slowly being unraveled. New research finds that the gut-brain interaction might also play a role in immunity. The guts of C. elegans, highlighted by fluorescent proteins produced when the nervous system is targeted by drugs. Image credit: Alejandro Aballay Lab, Duke University The gut and brain are connected by a dense network of neurons. These connections are responsible, unsurprisingly, for signaling hunger and satiety. More surprisingly, gut-brain connections also play a role in signaling love, fear, safety, and danger.
As with other networks, they utilize a cocktail of neurotransmitters; one of the chemicals commonly used is dopamine, known for its role in reward and addiction. The interaction between gut and brain has recently been implicated in a number of brain-based disorders, including Parkinson’s disease, autism, Alzheimer’s disease, depression, and anxiety. It is only now that the complexity and ramifications of these relationships are coming to light. Antipsychotics and the gut A study, published this week in Current Biology, investigated whether drugs designed to manipulate dopamine signaling, such as antipsychotics, could have an effect on inflammation.
In other words, could drugs that work on the nervous system affect the immune system, two biological systems that, until recently, were considered to be separate entities. The research group was headed up by Alejandro Aballay, Ph.D., a professor of molecular genetics and microbiology at Duke School of Medicine in Durham, NC. He believes that the nematode worm Caenorhabditis elegans is a useful model to study the gut-brain interaction. C. elegans’ nervous system contains just 302 neurons, compared with a fruit fly’s 250,000 or a human brain’s 100 billion; they also have a very basic immune system.
Aballay and his team first noted a gut-brain-immune interaction in C. elegans during a study they carried out in 2009. The team bombarded the nematodes with a range of chemicals in the search for compounds that would help protect the creatures from bacterial infection. Of more than 1,000 drugs, 45 were found to switch on the immune pathway.
Half of these drugs worked on the nervous system, and a few of them blocked dopamine activity. This finding provided the basis for the current study. Dopamine influencing immunity For this next phase, the team set out to investigate the effects of dopamine and dopamine signaling pathways on the nematodes and their immune system. They blocked dopamine’s effects using a drug normally used for manic depression and schizophrenia, called chlorpromazine.

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