Pathological activation of canonical nuclear-factor kB by synergy of tumor necrosis factor alpha and TNF-like weak inducer of apoptosis in mouse acute colitis

To test the efficacy of TNFR-Fc and anti-TWEAK mAb treatment alone and in combination Tumor necrosis factor (TNF)-alpha is a major effector in various inflammatory conditions. TNF-like weak inducer of apoptosis (TWEAK) is a member of the TNF superfamily that promotes inflammatory tissue damage through its receptor, FGF-inducible molecule 14 (Fn14). Since both TWEAK and TNF-alpha have been shown to mediate pathological responses through inter-dependent or independent pathways by in vitro, the potential interplay of these pathways was investigated in a mouse colitis model. Acute colitis was induced by rectal injection of trinitrobenzene sulfonic acid (TNBS), with administration of control IgG, TNF receptor (TNFR)-Ig chimeric protein, anti-TWEAK monoclonal antibody, or the combination of TNFR-Ig and anti-TWEAK antibody. On day 4, disease severity was evaluated and gene expression profiling was analyzed using whole colon tissue. Levels of transcript of TWEAK, Fn14 and NF-kB-related molecules were measured in purified colon epithelial cells (ECs). NF-kB activation was investigated with Western blot and immunohistochemical analysis. As a result, activation of the canonical, but not noncanonical NF-kB pathway was the hallmark of inflammatory responses in this model. Inflammation induced upregulation of Fn14 only in ECs but not in other cell types. Combination treatment of TNFR-Ig and anti-TWEAK antibody synergistically reduced disease severity in comparison with the control antibody or single agent treatment. Gene expression profile of the colon indicated downregulation of canonical NF-kB pathway with combination treatment. In conclusion, synergistic activation of canonical NF-kB by TWEAK and TNF-alpha is critical for the induction of inflammatory tissue damage in acute inflammation. TNBS colitis was induced by intrarectal administration of a 2 % solution of TNBS in phosphate-buffered saline (PBS): ethanol (1:1). For acute inflammatory responses, 70 μg/g body weight of TNBS was given on day 0 and animals sacrificed on day 4. One hour prior to administration of TNBS, groups of mice were injected i.p. with the control IgG2a mAb (anti-human CD20) (10 mg/kg), TNFR-Ig (0.3 mg/kg), anti-TWEAK (mP2D10, 10 mg/kg), the combination of TNFR-Fc (0.3 mg/kg) and anti-TWEAK mP2D10 (10 mg/kg), or were untreated. For single agent and combination treatments groups, 0.3 mg/kg TNFR-Ig was employed, since 1 mg/kg of TNFR-Ig markedly ameliorated TNBS colitis but 0.3 mg/kg was much less effective as monitored by the effect on colon length and body weight. Colon tissue was rolled and snap-frozen in liquid nitrogen. Specimens for RNA extraction were cut from the frozen rolled colon. A set of experiments using 5-8 mice for each experimental group was performed twice, labelled 7 and 10 in the CEL files. Total number of mice for each experimental condition was as follows; untreated TNBS colitis group, 8; control antibody, 15; TNFR-Ig, 12; anti-TWEAK mAb, 14; combination of TNFR-Ig and anti-TWEAK mAb, 15.