Immunoglobulin-E/Dinitrophenyl Complexes Induce Nitric Oxide Synthesis in Rat Peritoneal Macrophages by a Mechanism Involving CD23 and NF-κB Activation

Abstract

The production of nitric oxide (NO) by rat adherent peritoneal cells stimulated with preformed IgE/Dinitrophenyl-BSA (DNP-BSA) complexes and its dependence on the activation of the transcription factor NF-κB were studied. Stimulation with IgE/DNP-BSA complexes at equivalence induced both the production of NO and an increased expression of the inducible isoform of NO synthase (iNOS) protein. Both events were also elicited by a rabbit polyclonal F(ab′) 2anti-CD23 cross-reacting with rat CD23, thus suggesting FcϵRII/CD23 antigen as the IgE-binding structure involved in the triggering of the response and ruling out an interaction of the antibody via its Fc portion. Inhibition of redox-sensitive signaling mechanisms by the antioxidant pyrrolidine dithiocarbamate (PDTC) blocked NO production, iNOS expression, and NF-κB activation elicited by both IgE/DNP-BSA complexes and anti-CD23 F(ab′) 2, thus suggesting the involvement of NF-κB in the signaling pathway leading to the transcriptional activation of iNOS. These results show the existence in rat peritoneal macrophages of a signaling pathway triggered by CD23 engagement that promotes nuclear translocation of NF-κB and transcriptional activation of the inducible isoform of NO synthase.