NADPH oxidase and nitric oxide synthase-dependent superoxide production is increased in proliferative lupus nephritis

Abstract

Objective Lupus nephritis (LN) is an immune complex-mediated glomerulonephritis. Proliferative LN (PLN, International Society of Nephrology and Renal Pathology Society (ISN/RPS) classes III and IV)) often leads to renal injury or failure despite traditional induction and maintenance therapy. Successful targeted therapeutic development requires insight into mediators of inflammation in PLN. Superoxide (SO) and its metabolites are mediators of the innate immune response through their ability to mediate reduction-oxidation signaling. Endothelial nitric oxide synthase (eNOS) modulates inflammatory responses in endothelial cells. We hypothesized that markers of SO production would be increased in active PLN and that SO production would be dependent on the activity of select enzymes in the renal cortex. Methods Patients with systemic lupus erythematosus were enrolled at the time of renal biopsy for active LN of all classes. Serum collected at baseline was analyzed by HPLC with electrochemical detection for markers of SO production (durable modifications of serum protein Tyr ultimately requiring SO as a substrate). Renal cortex from MRL/MpJ-FASlpr (MRL/lpr) mice with and without functional eNOS was analyzed during active disease for superoxide (SO) production with and without inhibitors of SO producing enzymes. Results Serum protein modifications indicative of total SO production were significantly higher in patients with PLN. These markers were increased in association with more active, inflammatory PLN. Mice lacking functional eNOS had 80% higher levels of renal cortical SO during active disease, and inhibitors of nitric oxide synthase and NADPH oxidase reduced these levels by 60% and 77%, respectively. Conclusion These studies demonstrate that SO production is unique to active PLN in a NOS and NADPH oxidase-dependent fashion. These findings suggest the emulating or augmenting eNOS activity or inhibiting NADPH oxidase SO production may be targets of therapy in patients with PLN. The markers of SO production used in this study could rationally be used to select SO-modulating therapies and serve as pharmacodynamic indicators for dose titration.

Genomic dissection of Systemic Lupus Erythematosus: Distinct Susceptibility, Activity and Severity Signatures

“…To this end, we selected the DEGs from the comparison of inactive versus active SLE that are not included in the 'core' disease signature. A total 365 DEGs were identified, which were enriched for KEGG pathways such as oxidative phosphorylation, consistent with the described alterations in mitochondrial mass and membrane potential in lupus T cells [32][33][34] and the enhanced oxidative stress [35][36][37] . Other enriched pathways included ribosomes and cell cycle.…”

Lipopolysaccharide induces inducible nitric oxide synthase-dependent podocyte dysfunction via a hypoxia-inducible factor 1α and cell division control protein 42 and Ras-related C3 botulinum toxin substrate 1 pathway

“…This suggests that eNOS is uncoupled in this setting, and evidence suggests similar uncoupling of iNOS can occur in lupus nephritis [45]. It is not yet clear from where the ROS that oxidize BH 4 originate; however, both iNOS and NADPH oxidase are important candidates in lupus nephritis [46]. NOS ${\mathrm{normalO}}_2^{•-}$, NOX ${\mathrm{normalO}}_2^{•-}$, and exogenous ${\mathrm{normalO}}_2^{•-}$ all had no immediate effect on podocyte permeability in these studies, suggesting that ${\mathrm{normalO}}_2^{•-}$ itself is not a mediator of the podocyte phenotype described in this study.…”

Lupus nephritis

“…Reactive oxygen species released by phagocytes are another mediator of immunopathology inside the kidney. Oates et al [42] reported that super oxide production in proliferative lupus nephritis patients depends on NADPH oxidase and that endothelial nitric oxide synthase (eNOS) is a negative regulator of this process. Oxidative stress activates the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which serves as a master regulator of oxidative stress-induced gene transcription.…”