Our guts are lined with an essential barrier that has some important functions; it keeps the microbes in the gastrointestinal tract away from the rest of the body, and helps us absorb nutrients, for example. The cells of this barrier play a variety of crucial roles, and scientists have now shown how one of those cell types can contribute to chronic gut pain. These cells, called enterochromaffin (EC) cells can act as important sensors that can monitor for potentially damaging or harmful substances, and send signals about what they sense. But these cells may also continue sending those signals after the threat has passed, which may contribute to the chronic pain felt by people with issues like irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). The findings have been reported in Nature.
There are two important kinds of EC cells, which each react to different types of stimuli in the gut. One cell type is the villus EC cells, and they are situated higher in the gut lining. They can send early warning signals about damage like oxidative stress, which can harm tissue.
The villus EC cells can release high levels of the neurotransmitter serotonin, and a molecular fuel called ATP, which triggers the pathways that deliver pain signals to the brain.
"Villus EC cells act like guards, releasing both serotonin and ATP as an alarm system for the body, alerting it that there's a problem in the gut," explained senior study author Professor Stuart Brierley of South Australian Health and Medical Research Institute (SAHMRI).
The other EC cell type is known as crypt EC cells and they are found deeper in the gut lining. If the protective barrier of the gut is weakened, the crypt EC cells react to irritants, which can include some compounds that are found in spicy foods such as wasabi and mustard. The crypt EC cells then release serotonin which activates nerves to signal pain, explained Brierley.
"Normally, these crypt EC cells help regulate secretions in the gut, aiding digestion, but when they are exposed to harmful irritants or during inflammation, they flood the system with serotonin, thereby activating nerves, and triggering discomfort or pain," added Brierley.
A better understanding of this phenomenon could help scientists develop better therapeutics for the gut discomfort and pain that happens so often in gastrointestinal disorders.
"We now have a much clearer picture of how gut pain is generated and maintained," said Brierley. "If we can find ways to regulate how EC cells are activated, it could be instrumental in finding more effective treatments for chronic gut pain, which affects millions of people around the world."
Sources: South Australian Health and Medical Research Institute (SAHMRI), Nature