The intestines of mice which have been subjected to stress, overreact to certain nutritional substances. Ph.D. biologist Annette van Kalkeren from the University of Amsterdam has investigated the relationship between stress and the occurrence of food allergies and various intestinal disorders.
The biologist investigated the reaction of pieces of mouse intestine to egg albumin, a substance found in eggs. Just like humans, mice can become allergic to the substance. However, mice only become allergic if they are injected with the substance and not as a result of eating it.
The aim of the study was to investigate whether mice could become allergic to egg albumin if they ate it whilst stressed. The intestinal wall becomes more permeable under stressful conditions. Harmful substances penetrate the permeable intestinal wall where they then cause a panic response by the immune system. That could be the start of an allergy. The intestines of allergic mice demonstrate, just as in humans, a diarrhoea response if they come into contact with egg albumin. The cells in the intestinal wall then excrete salt and water.
Research revealed that the intestines of non-allergic mice also sometimes exhibited a localised diarrhoea reaction if they came into contact with egg albumin. However, the localised diarrhoea occurred much more frequently in the intestines of mice which had been deliberately stressed prior to the experiment. Furthermore, the intestines of mice subjected to prolonged stress were much more sensitive for neurotransmitters from nerve cells which cause diarrhoea and the contraction of the intestinal muscles. Annette van Kalkeren used a systematic treatment to stress the mice. The mice had to spend several hours in a narrow tube. Sometimes they were also placed in a cold environment.
A number of mice were subjected to a maximum of three days of social isolation. Some also had to swim for three minutes. The excretion of salt and water is a response of the intestines to wash out unwanted substances. However, the intestinal wall is then much more permeable to allergens. Whether or not this has a function is not known. The Amsterdam researcher suspects that a higher permeability promotes the immune response.
Antigens from the body can then get closer to the intestinal content. The defence of the body is then pushed forward so to speak. However, during chronic stress the defence of the body is weakened and allergens can penetrate to deep into the body. Food allergies and various intestinal diseases, such as Crohn’s disease, ulcerative colitus and irritable bowel syndrome can in part be caused or enhanced by chronic stress. The mechanism behind this has yet to be elucidated.
Further information can be obtained from Annette van Kalkeren (Swammerdam Institute for Life Sciences, University of Amsterdam, and now employed by ZON/MW), tel. +31 (0)70 3495199 (work) or +31 (0)6 18085140 (home), fax +31 (0)70 3495100 e-mail email@example.com. The defence of the doctoral thesis will take place on 24 April 2002. Ms Van Kalkeren’s supervisors are Prof. M. Joëls and Prof. J. Koolhaas.