Chapter 3 Effect of the Anti-Tumor Necrosis Factor-Antibody Infliximab on the ex vivo Mucosal Matrix Metalloproteinase-Proteolytic Phenotype in Inflammatory Bowel Disease ( IBD ) Short title : Infliximab and MMPs in IBD

Background/aims. Previous studies have shown an upregulation of matrix metalloproteinases (MMPs) in intestinal tissue of patients with inflammatory bowel disease (IBD) and significant clinical improvement after administration of the antiTNFantibody infliximab. The aims of our study were to determine expression and secretion of MMP-1, -2, -3, -9, and their inhibitors TIMP-1, -2 by IBD versus control intestinal mucosa ex vivo and to assess the regulatory capacity by infliximab of the proteolytic phenotype. Methods. Intestinal mucosal explants from 20 IBD and 15 control patients were cultured with or without infliximab and/or the T-cell activator pokeweed mitogen (PWM). Explants and culture supernatants were analyzed for MMPs, TIMPs, and TNFprotein, activity and/or mRNA levels. All patients were genotyped for functional TNF, MMP, and TIMP single nucleotide polymorphism (SNP) loci. Results. Expression of MMP and TIMP protein/activity in basal medium was higher in IBD versus control explants. Dependent on genotype at SNP loci, infliximab downregulated MMP-1, -3, and -9 relative to TIMP-1 and -2 and also decreased MMP-1 and -3 activities, while PWM enhanced these levels, partly counteracted again by infliximab. The expression of MMP-2 relative to TIMP did not change by treatment with infliximab and/or PWM. Conclusions. The high expression of MMPs in patients with IBD suggests a role for these proteinases in the pathogenesis of this disease. Infliximab seems to induce a genotype-associated matrix protective phenotype, which may contribute to the observed therapeutic efficacy of this drug in IBD, particularly at the mucosal surface. Infliximab and MMPs in IBD 81