Selective intestinal epithelial loss of Junctional Adhesion Molecule‐A results in enhanced intestinal permeability and increased susceptibility to colitis

Abstract

Junctional Adhesion Molecule‐A (JAM‐A) is a transmembrane protein that is expressed in epithelial cells and leukocytes. JAM‐A has been proposed to regulate epithelial barrier function and leukocyte transendothelial migration. Since the tissue specific functions of JAM‐A in the intestinal epithelium have not been elucidated yet, we generated epithelial‐targeted JAM‐A deficient mice (Villin‐cre; JAM‐A fl/fl) and tamoxifen‐inducible epithelial‐targeted JAM‐A deficient mice (Villin‐creERT2; JAM‐A fl/fl) to gain insights into the relative contributions of JAM‐A in regulating intestinal barrier function under steady state and inflammatory conditions. Intestinal epithelial‐targeted loss of JAM‐A resulted in compromised intestinal epithelial barrier function with increased paracellular permeability to 4kDa FITC‐dextran under steady state conditions indicating epithelial JAM‐A as major contributor in epithelial barrier homeostasis. Interestingly, neither mice with constitutive loss of epithelial JAM‐A (Villin‐cre; JAM‐A fl/fl) nor mice with acute loss of JAM‐A (Villin‐creERT2; JAM‐A fl/fl) developed spontaneous colitis. Challenge of Villin‐cre; JAM‐A fl/fl mice with pro‐inflammatory cytokines (TNFa and IFNg) led to a further significant increase in epithelial paracellular permeability, supporting the role of epithelial JAM‐A in barrier compromise during mucosal inflammation. To further confirm the crucial role of epithelial JAM‐A in regulating epithelial barrier function under inflammatory conditions, we performed experiments using an acute DSS induced injury model of colitis and observed that Villin‐cre; JAM‐A fl/fl showed increased susceptibility to colitis as has been reported for JAM‐A −/− mice. Given the increase in sensitivity to development of colitis observed in the JAM‐A deficient mice, we established an intestinal loop model of acute inflammation to analyze the contribution of JAM‐A in regulating neutrophil transepithelial migration (TEpM). With this model, we quantified transmigrated PMNs in an isolated segment of the ileum or colon by flow cytometry and immunofluorescence staining. In JAM‐A −/− mice, we observed delayed neutrophil recruitment into the intestinal lumen with accumulation of neutrophils in the mucosal subepithelial space in response to the chemoattractant leukotriene B4 despite significantly increased paracellular permeability. Analogous studies using mice with epithelial and leukocyte targeted loss of JAM‐A are underway. These findings provide novel insight on the pivotal role of epithelial‐specific loss of JAM‐A in regulation of mucosal barrier function under steady state and inflammatory conditions and highlight a novel contribution of JAM‐A in the process of PMN transepithelial migration.Support or Funding InformationRO1 DK072564‐21DFG FL870/1‐1