Indirect down‐regulation of nuclear NF‐κB levels by cobalamin in the spinal cord and liver of the rat

Abstract

We used electrophoretic mobility shift assays to investigate the effects of cobalamin (Cbl) deficiency on the levels of activated nuclear factor-kappa B (NF-kappaB) in the spinal cords (SCs) and livers of rats made Cbl-deficient (Cbl-D) by total gastrectomy or a Cbl-D diet. We chose the SC and liver because they are severely or scarcely affected, respectively, by Cbl deficiency in terms of histological damage. We found permanently increased NF-kappaB levels (particularly the p50 and p65 subunits) in the SCs and livers of both types of Cbl-D rats, and Western blot analysis demonstrated increased p65 levels. NF-kappaB and p65 protein levels normalized when the totally gastrectomized (TGX) rats were treated with Cbl replacement. As we have previously demonstrated that Cbl deficiency increases tumor necrosis factor (TNF)-alpha and nerve growth factor (NGF) levels in the SC (each of which is a known NF-kappaB activator), we redetermined NF-kappaB levels in the SCs and livers of TGX rats treated with anti-TNF-alpha or anti-NGF antibodies and found that NF-kappaB levels normalized in both tissues after either treatment. These results demonstrate that: (1) Cbl physiologically and indirectly down-regulates NF-kappaB levels in rat SC and liver, and (2) NF-kappaB is an important signaling molecule after Cbl deficiency injury.