(570) Neutrophil Elastase Inhibition Prevents Neutrophil extracellular trap (NETs) Driven Autoimmune Glomerulonephritis Without Off Target Immunosuppression

Introduction/Rationale: Neutrophils release Neutrophil Extracellular Traps (NETs) as a final defense to trap and kill pathogens. In sterile inflammation, however, NETs become injurious, exposing over 70 autoantigens that drive tissue damage. This study evaluated pharmacologic neutrophil elastase (NE) inhibition using Bay 85-8501 in a NET-driven model of anti-neutrophil cytoplasmic antibody vasculitis (AAV), a major cause of glomerulonephritis and kidney failure. We aimed to determine whether targeted NET inhibition could match the efficacy of standard immunosuppression while preserving host defense.

Methods: A 20-day murine AAV model was induced in C57BL/6 mice. NE was inhibited using Bay 85-8501 via daily oral gavage (n=8 vs vehicle) and compared to mice treated with cyclophosphamide or prednisolone. Kidney NETs were visualized by confocal microscopy, while histology, serum ANCA, RT-PCR for inflammatory mediators, and leukocyte infiltration were assessed. In additional experiments, NE-deficient (NE-/-) mice and inhibitor-treated groups were analyzed for off-target and antimicrobial effects.

Results: Bay 85-8501 significantly reduced renal NET deposition, glomerular injury, and leukocyte infiltration (all P< 0.01 vs WT). RT-PCR showed decreased IL-1β, MCP-1, CXCL2, and IL-4 expression. NE inhibition provided disease protection equivalent to prednisolone and cyclophosphamide but without the immunosuppressive burden. NE-/- mice mirrored the protection seen with pharmacologic inhibition, confirming specificity. Phagocytosis assays showed NE inhibition did not impair neutrophil antimicrobial function.

Conclusion: Bay 85-8501 precisely targets NET formation, achieving efficacy comparable to standard immunosuppression while preserving innate defense. These findings highlight NE inhibitors as a promising therapeutic strategy for NET-mediated diseases such as AAV, offering targeted disease control without the risks of broad immunosuppression.