Barrier Permeability / Intestinal Permeability

FXR deficiency has been linked to increased intestinal permeability because of reduced inhibition of cytokine expression by Farnesoid X receptor (FXR)
Verbeke et al. 2015 Am. J. Pathol. 185: 409–419

Gut permeability is also regulated via Farnesoid X receptor (FXR / NR1H4), is most commonly activated by primary bile acids
Fiorucci et al. 2009 Trends Pharm. Sci. 30: 570-580
Yoneno et al. 2013 Immunology 139: 19-29

Two cytokines known to be increasing the permeability in the intestinal epithelial monolayer are IL-4 and IL-13
Adams et al. 1993 J Immunol 150: 2356-63.
Ceponis et al. 2000 J Biol Chem 275: 29132-7

Both increase intestinal epithelial permeability by a phosphatidylinositol 3-kinase pathway within IECs
Ceponis et al. 2000 J Biol Chem 275: 29132-7

see also:
Dysbiosis & Leaky Gut Syndrome / Leaky Gut