Scientists have discovered how and why develops diarrhea

© Fotolia / psdesign1Бактериальная infectionScientists have discovered how and why develops diarrhea© Fotolia / psdesign1

Unusual experiments on mice helped the biologists to confirm that the diarrhea is a means of cleaning the body from toxins and pathogens, and to uncover the molecular mechanisms of its development, said in an article published in the journal Cell Host & Microbe.

«The hypothesis that diarrhoea clears the intestines of pathogens, is controversial among scientists for several centuries. We are still very poorly understood how it affects the course of intestinal infections. We tried to find the answer to this question by observing whether pathogens are slower to be excreted from the body in its lock,» says Jerrold Turner (Jerrold Turner) from Harvard University (USA).

To answer this question, Turner and his colleagues acquired a small population of mice that they fed food infected with spores of Citrobacter rodentium – a microbe that causes inflammation of the epithelium and other effects similar to dysentery and other bowel infections in humans.

Having infected rodents spores of bacteria, scientists have observed the development of infection and noted all changes in their intestines before and after the development of diarrhea and inflammation of tissues caused by toxins of the bacterium, which he uses to weaken the walls of the intestine.

These observations showed that the intestines of the mice starts to respond to infection before the onset of inflammation and cell damage, releasing two kinds of proteins — claudin-2 and interleukin-22. The combination of these molecules, as shown by the experiments of scientists, and is the cause of diarrhea.

In particular, claudin-2 causes the epithelium to absorb water from digested food and allocate it back into the intestine in large quantities. Or just wash off microbes or prevent them from normal to multiply. In turn, interleukin-22 causes cells to release more claudin-2, which amplifies this reaction and leads to those consequences that are characteristic of any resurgence of problems with the stomach and intestines.

Opening this connection, the researchers tested what would happen if you turn off the genes responsible for the Assembly of molecules of these proteins. This action prevented the development of diarrhea, but the mouse began it is much harder to cope with the infection and to lose more weight during infection with Citrobacter rodentium. In turn, enhancing the Il-22 or claudin-2 has the opposite effects – this mouse is much faster to cope with infection than their «normal» relatives or rodents with the deleted genes.

Similar results, according to the authors, allowed the centuries-old debate about the benefits of diarrhea and show that it really helps the body to quickly deal with the infections and contact with toxins in the intestines.

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