K M O’SULLIVAN1, P GAN1, R A KITCHING1,2, S R HOLDSWORTH1,2
1Monash University, 2Monash Health
Background and Aims: Neutrophil extracellular traps (NETs) are implicated in the pathogenesis of myeloperoxidase anti neutrophil cytoplasmic antibody (MPO-ANCA) vasculitis. Neutrophil elastase (NE), initiates NET formation through proteolytic degradation of the nuclear envelope, histone degradation and chromatin decondensation facilitating DNA release. NE bound to NET derived DNA provides a reservoir of proteolytic NE protected from endogenous anti proteases- which enables tissue destruction, and further recruitment of neutrophils. This study aims to assess the therapeutic benefit of inhibiting NET formation in experimental MPO-ANCA vasculitis using animals deficient in NE and NE inhibitors (NEi).
Methods: A 20 day experimental model of anti-MPO glomerulonephritis was induced in B6.129X1-Elanetm1Sds/J mice and wild-type (WT) litter mate controls by myeloperoxidase immunisation and GN triggered using a sub-nephritogenic dose of anti-glomerular basement membrane globulin. Further experiments using NE inhibitors Alvelestat and BAY 85-8501 given daily by oral gavage were administered to prevent NET formation.
Results: Elane-/- animals were protected from excessive NET production and glomerular injury with significantly reduced kidney proinflammatory gene expression (IL-6, IL-1β. MCP-1 and CXCL2) segmental necrosis, glomerular neutrophils, extracellular MPO deposition, CD4 T cells, and macrophage influx (all, P <0.05, vs WT). NE inhibition yielded similar results as the Elane -/- animals with a significant reduction in: the frequency of MPO specific CD4 effector T cells from the draining lymph nodes, ANCA titre and albuminuria (all P<0.05, vs vehicle control). NE inhibitors prevented NET formation with no detriment in neutrophil function (phagocytosis).
Conclusions: NE inhibition attenuates inflammation through the reduction of pathological NETs. This data provides proof of concept evidence that targeting NE therapeutically with BAY-85-8501 or Alvelestat could be of potential benefit in MPO-ANCA vasculitis.
Dr Kim O’Sullivan is an Early Career Research Fellow in the Autoimmune Kidney Disease and Vasculitis Research Group at Monash University. Kim’s main research area is investigating the pro-inflammatory role of Neutrophil Extracellular Traps (NETs) in anti-neutrophil cytoplasmic antibody vasculitis (AAV), with a particular focus on looking for potential therapeutics which will prevent NET formation and ameliorate disease. Current research is concentrated on modulating the function of neutrophils to keep their phagocytotic function whilst preventing injurious NET formation.