Use of bioluminescence imaging to track neutrophil migration and its inhibition in experimental colitis.

Inflammatory bowel disease (IBD) is associated with neutrophil infiltration into the mucosa and crypt abscesses. The chemokine interleukin (IL)-8 [murine homologues (KC) and macrophage inflammatory protein (MIP)-2] and its receptor CXCR2 are required for neutrophil recruitment; thus, blocking this engagement is a potential therapeutic strategy. In the present study, we developed a preclinical model of neutrophil migration suitable for investigating the biology of and testing new drugs that target neutrophil trafficking. Peritoneal exudate neutrophils from transgenic β-actin-luciferase mice were isolated 12h after intraperitoneal injection with thioglycollate, and were assessed phenotypically and functionally. Exudate cells were injected intravenously into recipients with dextran sodium sulphate (DSS)-induced colitis followed by bioluminescence imaging of whole-body and ex vivo organs at 2, 4 and 16-22h post-transfer. Anti-KC antibody or an isotype control were administered at 20 µg/mouse 1h before transfer, followed by whole-body and organ imaging 4h post-transfer. The peritoneal exudate consisted of 80% neutrophils, 39% of which were CXCR2(+) . In vitro migration towards KC was inhibited by anti-KC. Ex vivo bioluminescent imaging showed that neutrophil trafficking into the colon of DSS recipients was inhibited by anti-KC 4h post-cell transfer. In conclusion, this study describes a new approach for investigating neutrophil trafficking that can be used in preclinical studies to evaluate potential inhibitors of neutrophil recruitment.