Predictive validity and immune cell involvement in the pathogenesis of piroxicam-accelerated colitis in interleukin-10 knockout mice.

Piroxicam administration is a method for induction of enterocolitis in interleukin-10 knockout (IL-10 k.o.) mice. The piroxicam-accelerated colitis (PAC) IL-10 k.o. model combines a dysregulated immune response against the gut microbiota with a decreased mucosal integrity. The predictive validity and pathogenic mechanisms of the model have not been thoroughly investigated. In this study, IL-10 k.o. mice received piroxicam in the chow, and model qualification was performed by examining the efficacy of prophylactic anti-IL-12/23p40 monoclonal antibody (mAb), anti-TNFα mAb, cyclosporine A (CsA) and oral prednisolone treatment. To evaluate cell involvement in the disease pathogenesis, specific cell subsets were depleted by treatment with anti-CD4 mAb, anti-CD8 mAb or clodronate-encapsulated liposomes. T cell receptor co-stimulation was blocked by CTLA4-Ig. Cytokine profiling ELISAs and calprotectin immunohistochemistry were performed on colon tissue. Treatments with anti-IL-12/23p40 mAb and CsA prevented disease in PAC IL-10 k.o. mice and reduced IFNγ, IL-17A, MPO and calprotectin levels in colon. Anti-TNFα mAb treatment caused amelioration of selected clinical parameters. No effect of prednisolone was detected. Depletion of CD8(+) cells tended to increase mortality, whereas treatment with anti-CD4 mAb or CTLA4-Ig had no significant effect on disease development. Clodronate liposome treatment induced a loss of body weight; nevertheless macrophage depletion was associated with a significant reduction in colonic pathology. In conclusion, reference drugs with known efficacy in severe inflammatory bowel disease were efficacious in the PAC IL-10 k.o. model. Our data indicate that in this model macrophages are a main driver of colitis, whereas CD4(+) cells are not.