O-037 Modulation of Inflammatory Processes in DSS-induced Colitis Models versus Gastrointestinal Acute Radiation Syndrome with AVX-470m, an Oral Polyclonal Anti-TNF Antibody

Abstract

Development of improved therapies for inflammatory bowel disease (IBD) requires animal models that elucidate underlying mechanisms of disease. Acute radiation syndrome (ARS) has devastating consequences in the gastrointestinal (GI) tract driven in part by cytokine-mediated inflammation that closely resembles the pathophysiology of IBD. Tumor Necrosis Factor (TNF) is central to the dysregulated inflammatory response in IBD, and is strongly implicated in GI ARS. In this study AVX-470 m, a bovine polyclonal neutralizing antibody for murine TNF, is used to characterize the pathogenesis of GI damage in models of GI ARS and IBD. Colitis was induced in C57BL/6 mice by including 3% DSS in drinking water for 5 days. Other C57BL/6 mice were irradiated with 15.9 Gy (∼LD80/30) from a 60Co gamma source, with partial bone marrow shielding. Animals were dosed BID with AVX-470 m (10 mg/day) or saline by oral gavage for up to 14 days. In colon and jejunum tissues, relative mRNA expression levels of cytokines and immune markers was measured by qPCR (Taqman), and protein expression was analyzed by immunohistochemistry (IHC) in paraffin embedded, formalin fixed tissue sections. Both mRNA and protein levels of TNF were increased in colon and jejunum tissue, respectively, in the colitis and GI ARS models. IL-1β, IL-6, MMP9, ICAM-1, and TNFR2 mRNA levels were increased in both models, but IL12p40 was increased only in the colitis model, and no change in TNFR1 mRNA levels was detected in either model. Protein expression of MPO was increased in both the colitis and GI ARS models. These data show a remarkable correlation of inflammatory responses between these 2 models of GI injury. In contrast, CD68 and CD3 protein were increased in colon tissue in the colitis model, but neither protein was detected in jejunum in the GI ARS model, suggesting a reduced T-cell component in GI ARS, perhaps due to destruction of these cells by the high levels of ionizing radiation. In both colitis and GI ARS models, treatment with AVX-470 m resulted in a significant decrease in TNF mRNA and protein expression in colon and jejunum tissues, respectively. AVX-470 m also decreased MPO protein expression, and reduced MMP9 mRNA expression, in both models. In the colitis model, IL-6 mRNA levels were decreased by AVX-470 m treatment in colon tissue, while in the GI ARS model IL-6 mRNA levels were transiently increased in jejunum tissue. No change in mRNA levels for ICAM-1 or TNFR1 were seen in either model following AVX-470 m treatment. These studies show that inflammatory responses in colitis and GI ARS models share a common TNF-mediated neutrophilic component in the colon and jejunum, respectively, but differ with respect to immune cell involvement in response to injury. Further studies will reveal whether these differences reflect variability in timing, tissue localization, or response to the different insults. The fact that AVX-470 m is effective in both models highlights the central role of TNF in inflammation in the GI tract, and supports the therapeutic potential of an oral anti-TNF antibody as a gut-targeted treatment for multiple GI inflammatory diseases.