Increased antigen and bacterial uptake in follicle associated epithelium induced by chronic psychological stress in rats

Background: Chronic stress affects the course of inflammatory bowel disease and experimental colitis, and may also initiate intestinal inflammation in rats. Aim: To investigate the effects of stress on the M cell containing follicle associated epithelium, specialised in antigen uptake. Subjects and methods: Wistar rats were submitted to acute water avoidance stress for one hour or chronic water avoidance stress for 1 hour/day for 10 consecutive days. Permeability to Cr-51-EDTA, horseradish peroxidase, and chemically killed Escherichia coli K-12 was studied in both villus and follicle associated epithelium in Ussing chambers. Segments were further examined by light, electron, and confocal microscopy. Results: Acute stress increased horseradish peroxidase flux in villus as well as in follicle associated epithelium. Chronic stress further increased permeability to horseradish peroxidase in villus and follicle associated epithelium, in the latter by almost fourfold. Moreover, chronic stress induced over 30 times increased E coli passage in follicle associated epithelium whereas there was no significant increase in villus epithelium. Bacterial uptake was confirmed by confocal microscopy showing fluorescent bacteria penetrating and passing through the epithelial surface. Conclusions: These results show that the barrier function of follicle associated epithelium can be modulated, and that chronic stress enhances the uptake of luminal antigens and bacteria via the follicle associated epithelium. This can increase antigen exposure in Peyer's patches thereby having implications in the initiation of proinflammatory immune responses within the intestinal mucosa.