P147 NOVEL JUNCTIONAL ADHESION MOLECULE-LIKE (JAML) REGULATES NEUTROPHIL TRANSEPITHELIAL MIGRATION DURING INTESTINAL INFLAMMATION

Abstract

Neutrophil (PMN) migration in the intestine is an essential component of host defense and wound repair. However, dysregulated PMN recruitment is a hallmark of chronic active inflammatory bowel disease (IBD) characterized by persistent inflammation. Disease flares in IBD are associated with marked recruitment of PMN into the intestinal mucosa that results in crypt abscess formation and mucosal ulcerations. Despite the strong association with IBD, the process of PMN transepithelial migration (TEpM) represents a significantly understudied area. PMN migration into the intestinal mucosa requires multiple adhesive interactions between migrating PMN and intestinal epithelial cells (IECs). PMN TEpM is a multi-step process facilitated by complex interactions between PMN and IEC expressed proteins including members of the Juntional Adhesion Molecules (JAMs) family. We have reported that the novel JAM-like protein termed JAML expressed on PMN, associates with the coxsackie and adenovirus receptor (CAR) on epithelial cells. Binding of recombinant JAML ectodomains disrupts JAML-CAR interactions and reduces PMN TEpM. To define the molecular mechanism of JAML regulation of PMN TEpM during intestinal inflammation in-vivo, we generated JAML knockout mice (JAML-/-). PMN TEpM was evaluated using a small intestinal loop model, and PMN migration into the intestinal lumen in response to the chemoattractant LTB4(1nM) for 1h was quantified by flow cytometry. While WT and JAML-/- mice had similar numbers of circulating leukocytes, we observed reduced PMN migration into the intestinal lumen in response to LTB4 in JAML-/- mice compared to WT animals. In addition, there were increased PMN in the epithelial cell fractions derived from intestines of JAML-/- mice suggesting that JAML regulates PMN TEpM in vivo. We also assessed the role of JAML on susceptibility to DSS induced colitis and recovery. Markedly increased disease activity index, inflammation and mucosal ulceration were observed in JAML-/- mice compared to controls. These observations suggest that JAML represents an important adhesion molecule that regulates PMN TEpM. Furthermore, loss of JAML increases susceptibility to colitis. JAML may thus represent a new therapeutic target to dampen excessive PMN migration during intestinal inflammation as seen in IBD.