Effects of tumor necrosis factor type 1 and 2 receptor deficiencies on anorexia, growth and IgA dysregulation in mice exposed to the trichothecene vomitoxin

Abstract

Dietary exposure of mice to vomitoxin (VT), a trichothecene mycotoxin, causes anorexia and impaired growth as well as inducing elevated serum IgA and kidney mesangial IgA deposition in a manner analogous to human IgA nephropathy. Based on the observations that TNF-alpha is induced by in vitro and in vivo VT exposure, it was hypothesized that this cytokine plays a role in the nutritional and immunological effects of this toxin. To test this hypothesis, the effects of dietary VT on feed intake, weight gain, serum IgA levels and kidney mesangial IgA deposition in mice homozygous for targeted disruption of the two known TNF-alpha cell surface receptors, TNFR1(p55) or TNFR2(p75), were compared to effects in corresponding C57BL/6J wild-type (WT) mice with normal receptor function. The capacity of VT to cause feed refusal or impair weight gain over a 12-week feeding period was not impaired in TNFR1 knockout (KO) or TNFR2-KO as compared to WT mice. Both WT and TNFR-KO mice fed VT exhibited reduced (P<0.05) feed conversion efficiency, but surprisingly, feed conversion efficiency was significantly higher (P<0.05) in TNFR1-KO and TNFR2-KO fed either control or VT diets than in corresponding WT mice. By week 12, serum IgA concentrations in all three mouse groups fed VT were significantly higher than those for corresponding mice fed control diets (P<0.05). Serum IgA levels in the VT-fed TNFR1-KO group were significantly less (P<0.05) than those for the VT-fed WT mice at 4, 8 and 12 weeks, whereas no differences in this parameter were found between the TNFR2-KO and WT groups. Serum IgA immune complex concentrations were measured at wk 12 and found to follow an identical pattern to IgA. Kidneys taken from VT-fed TNFR2-KO and WT mice after 12 weeks had significantly increased mesangial IgA deposition as compared to controls. While slight increases in mesangial IgA were also observed in VT-fed TNFR1-KO mice, these levels were significantly less (P<0.05) than that found in VT-fed TNFR2-KO and WT mice. Taken together, the data suggest that while VT-mediated anorexic and growth effects were largely independent of TNF-alpha, VT-induced dysregulation of IgA production was dependent, in part, on the interaction of TNF-alpha with TNFR1.