Effects of phlebotomy on the growth of ferric nitrilotriacetate-induced renal cell carcinoma.

The ferric nitrilotriacetate-induced carcinogenesis model is unique in that reactive oxygen species-free radicals are involved in the carcinogenic process. But the effects of iron-withdrawal in the progression of renal cell carcinoma are not well understood. We performed repeated phlebotomies on animals that had been administered ferric nitrilotriacetate in the initiation stage of renal cell carcinoma (phlebotomy group), and compared the development of renal tumors with those not receiving repeated phlebotomies (non-phlebotomy group). Ferric nitrilotriacetate-treated male Wistar rats were randomly divided into 2 groups: a phlebotomy group (21 rats) and a non-phlebotomy group (17 rats). Ten age-adjusted normal rats were also observed as a normal group. Hematocrit was maintained under 25% in the phlebotomy group. Hematocrit levels in the normal group and in the non-phlebotomy group were not significantly different. As a result, the incidence of renal cell carcinoma was not significantly different between phlebotomy and non-phlebotomy animals. However, the total weight of the renal cell carcinoma was significantly heavier in the animals from non-phlebotomy group than in those from the phlebotomy group (23.64 g +/- 18.54 vs. 54.40 g +/- 42.40, P &#60; 0.05). The present study demonstrated that phlebotomy after the administration of ferric nitrilotriacetate did not reduce the incidence of renal cell carcinoma. In addition, we showed that iron withdrawal at the promotion stage of carcinogenesis will retard tumor growth.</p

Oxidative modification of IκB by monochloramine inhibits tumor necrosis factor α-induced NF-κB activation

AbstractWe have previously reported that monochloramine (NH2Cl), a neutrophil-derived oxidant, inhibited tumor necrosis factor α (TNFα)-induced expression of cell adhesion molecules and nuclear factor-κB (NF-κB) activation (Free Radical Research 36 (2002) 845–852). Here, we studied the mechanism how NH2Cl inhibited TNFα-induced NF-κB activation, and compared the effects with taurine chloramine (Tau–NHCl). Pretreatment of Jurkat cells with NH2Cl at 70 μM resulted in suppression of TNFα-induced IκB phosphorylation and degradation, and inhibited NF-κB activation. In addition, a slow-moving IκB band appeared on SDS-PAGE. By contrast, Tau–NHCl for up to 200 μM had no effects. Interestingly, NH2Cl did not inhibit IκB kinase activation by TNFα. Protein phosphatase activity did not show apparent change. When recombinant IκB was oxidized by NH2Cl in vitro and phosphorylated by TNFα-stimulated Jurkat cell lysate, its phosphorylation occurred less effectively than non-oxidized IκB. In addition, when NF-κB–IκB complex was immunoprecipitated from NH2Cl-treated cells and phosphorylated in vitro by recombinant active IκB kinase, native IκB but not oxidized IκB was phosphorylated. Amino acid analysis of the in vitro oxidized IκB showed methionine oxidation to methionine sulfoxide. Although Tau–NHCl alone had little effects on TNFα-induced NF-κB activation, simultaneous presence of Tau–NHCl and ammonium ion significantly inhibited the NF-κB activation, probably through the conversion of Tau–NHCl to NH2Cl. These results indicated that NH2Cl inhibited TNFα-induced NF-κB activation through the oxidation of IκB, and that NH2Cl is physiologically more relevant than Tau–NHCl in modifying NF-κB-mediated cellular responses