Fc-receptor-mediated intracellular delivery of Cu/Zn-superoxide dismutase (SOD1) protects against redox-induced apoptosis through a nitric oxide dependent mechanism

Background: Using specific antibodies against bovine Cu/Zn-superoxide dismu tase (EC 1.15.1.1, SOD1) we demonstrated that anti-SOD antibodies (IgG(1)) are able to promote the intracellular translocation of the antioxidant enzy me. The transduction signalling mediated by IgG(1) immune complexes are kno wn to promote a concomitant production of superoxide and nitric oxide leadi ng to the production of peroxynitrites and cell death by apoptosis. The Fc- mediated intracellular delivery of SOD1 thus limited the endogenous product ion of superoxide. It was thus of interest to confirm that in the absence o f superoxide anion, the production of nitric oxide protected cells against apoptosis. Study in greater detail clearly stated that under superoxide ani on-free conditions, nitric oxide promoted the cell antioxidant armature and thus protected cells against redox-induced apoptosis. Materials and Methods: The murine macrophage cell-lines J774 Al were preact ivated or not with interferon-gamma and were then stimulated by Igc, immune complexes (IC), free SOD1 or SOD1 IC and superoxide anion, nitric oxide, p eroxynitrite, and tumor necrosis factor-alpha (TNF-alpha) production was ev aluated. The redox consequences of these activation processes were also eva luated on mitochondrial respiration and apoptosis as well as on the control led expression of the cellular antioxidant armature. Results: We demonstrated that SOD1 IC induced a Fc gamma receptor (Fc gamma R)-dependent intracellular delivery of the antioxidant enzyme in IFN-gamma activated murine macrophages (the J774 Al cell line). The concomitant stimu lation of the Fc gammaR and the translocation of the SOD1 in the cytoplasm of IFN-gamma -activated macrophages not only reduced the production of supe roxide anion but also induced the expression of the inducible form of nitri c oxide synthase (iNOS) and the related NO production. This inducing effect in the absence of superoxide anion production reduced mitochondrial damage s and cell death by apoptosis and promoted the intracellular antioxidant ar mature. Conclusions: To define the pharmacologic mechanism of action of bovine SOD1 , we attempted to identify the second messengers that are induced by SOD1 I C. In this work, we propose that Fc-mediated intracellular delivery of the SOD1 that reduced the production of superoxide anion and of peroxynitrite, promoted a NO-induced protective effect in inducing the antioxidant armatur e of the cells. Taken together, these data suggested that specific immune r esponses against antigenic SOD1 could promote the pharmacological propertie s of the antioxidant enzyme likely via a NO-dependent mechanism.