Critical role of the CD40-CD40-ligand pathway in regulating mucosal inflammation-driven angiogenesis in inflammatory bowel disease

Background and aims: Angiogenesis is a novel component in inflammatory bowel disease (IBD) pathogenesis. We have previously shown that immune - nonimmune interactions through the CD40 - CD40-ligand (CD40L) pathway might sustain gut inflammation, although their effect on regulating inflammation-driven angiogenesis is unknown. The present study evaluated the role of the CD40 - CD40L interaction in the promotion of immune-mediated angiogenesis in IBD. Methods: Human nonimmune cells of colonic origin - namely, human intestinal fibroblasts (HIFs) and human intestinal microvascular endothelial cells (HIMECs) - were activated with either soluble CD40L (sCD40L), or CD40(+) D1.1 cells or CD40L-activated lamina propria T (LPT) cells before measuring pro-angiogenic cytokine release. Blocking antibodies to either CD40 or CD40L were used to disrupt the CD40 - CD40L interaction. The dextran sodium sulphate (DSS) model of experimental colitis in CD40 and CD40L knockout mice was established to assess whether the CD40 - CD40L pathway was implicated in controlling inflammation-driven angiogenesis in vivo. Results: Engagement of CD40 on HIFs promoted the release of vascular endothelial growth factor (VEGF), interleukin-8 (IL-8) and hepatocyte growth factor (HGF). LPT cells were potent inducers of pro-angiogenic cytokine secretion by HIFs. Supernatants from sCD40L-activated HIFs induced migration of HIMECs and tubule formation, both of which were inhibited by blocking antibodies to either VEGF, IL-8 or HGF. Both CD40- and CD40L-deficient mice were protected from DSS-induced colitis and displayed a significant impairment of gut inflammation-driven angiogenesis, as assessed by microvascular density. Conclusions: The CD40 - CD40L pathway appears to be crucially involved in regulating inflammation-driven angiogenesis, suggesting that strategies aimed at blocking CD40 - CD40L interactions might be beneficial in acute and chronic intestinal injury.