Investigating the role of myeloperoxidase as a key mediator of renal damage in crescentic glomerulonephritis and renocardiac disease

Crescentic glomerulonephritis (CGN) describes a severe form of glomerular inflammation, which results from various systemic or renal specific diseases, including anti-neutrophil cytoplasm antibody (ANCA) associated vasculitis (AAV) characterised by glomerular neutrophil and monocyte activation and neutrophil extracellular trap deposition. Diseases associated with CGN are frequently associated with increased cardiovascular disease, which represents a significant cause of premature mortality. Myeloperoxidase (MPO), a heme containing peroxidase stored in neutrophils and monocytes, is a key component of innate immune defence, generating hydrochlorous acid and free radicles that can also lead to host tissue damage. Additionally, MPO has been shown to contribute to vascular inflammation and atherosclerosis through oxidation of lipoproteins and catabolism of nitrous oxide leading to endothelial damage. In humans, MPO deficiency does not appear to lead to an immunodeficient phenotype. In this thesis, the role of selective MPO inhibition using AZM198, as a therapeutic target in CGN and associated reno-cardiac disease is explored. Our data demonstrate that free MPO levels are elevated in patients with active AAN and reduced when disease reaches remission. Renal biopsies of patients with diverse forms of CGN had extracellular glomerular MPO deposition that correlated significantly with clinical and histological disease severity. In vitro, AZM198 led to a significant reduction in neutrophil extracellular trap (NET) formation, reactive oxygen species (ROS) production and neutrophil degranulation and attenuated neutrophil-mediated endothelial cell damage. In vivo, delayed AZM198 treatment at two different doses reduced glomerular inflammation. Combining a murine model of chronic glomerular inflammation and atheroma formation showed that the presence of nephritis enhances atheroma formation. This model will be used in future work to compare treatment with AZM198 with corticosteroid therapy, currently used to treat most conditions associated with CGN

Proteinase 3 promotes formation of multinucleated giant cells and granuloma-like structures in patients with granulomatosis with polyangiitis

OBJECTIVES: Granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) are autoimmune vasculitides associated with antineutrophil cytoplasm antibodies that target proteinase 3 (PR3) or myeloperoxidase (MPO) found within neutrophils and monocytes. Granulomas are exclusively found in GPA and form around multinucleated giant cells (MGCs), at sites of microabscesses, containing apoptotic and necrotic neutrophils. Since patients with GPA have augmented neutrophil PR3 expression, and PR3-expressing apoptotic cells frustrate macrophage phagocytosis and cellular clearance, we investigated the role of PR3 in stimulating giant cell and granuloma formation. METHODS: We stimulated purified monocytes and whole peripheral blood mononuclear cells (PBMCs) from patients with GPA, patients with MPA or healthy controls with PR3 or MPO and visualised MGC and granuloma-like structure formation using light, confocal and electron microscopy, as well as measuring the cell cytokine production. We investigated the expression of PR3 binding partners on monocytes and tested the impact of their inhibition. Finally, we injected zebrafish with PR3 and characterised granuloma formation in a novel animal model. RESULTS: In vitro, PR3 promoted monocyte-derived MGC formation using cells from patients with GPA but not from patients with MPA, and this was dependent on soluble interleukin 6 (IL-6), as well as monocyte MAC-1 and protease-activated receptor-2, found to be overexpressed in the cells of patients with GPA. PBMCs stimulated by PR3 formed granuloma-like structures with central MGC surrounded by T cells. This effect of PR3 was confirmed in vivo using zebrafish and was inhibited by niclosamide, a IL-6-STAT3 pathway inhibitor. CONCLUSIONS: These data provide a mechanistic basis for granuloma formation in GPA and a rationale for novel therapeutic approaches

Risk Factors for Severe Outcomes in Patients With Systemic Vasculitis and COVID‐19: A Binational, Registry‐Based Cohort Study

Funder: Vifor Pharma; Id: http://dx.doi.org/10.13039/501100006484Objective: COVID‐19 is a novel infectious disease with a broad spectrum of clinical severity. Patients with systemic vasculitis have an increased risk of serious infections and may be at risk of severe outcomes following COVID‐19. We undertook this study to establish the risk factors for severe COVID‐19 outcomes in these patients, including the impact of immunosuppressive therapies. Methods: A multicenter cohort was developed through the participation of centers affiliated with national UK and Ireland vasculitis registries. Clinical characteristics and outcomes are described. Logistic regression was used to evaluate associations between potential risk factors and a severe COVID‐19 outcome, defined as a requirement for advanced oxygen therapy, a requirement for invasive ventilation, or death. Results: The cohort included 65 patients with systemic vasculitis who developed COVID‐19 (median age 70 years, 49% women), of whom 25 patients (38%) experienced a severe outcome. Most patients (55 of 65 [85%]) had antineutrophil cytoplasmic antibody–associated vasculitis (AAV). Almost all patients required hospitalization (59 of 65 [91%]), 7 patients (11%) were admitted to intensive care, and 18 patients (28%) died. Background glucocorticoid therapy was associated with severe outcomes (adjusted odds ratio [OR] 3.7 [95% confidence interval 1.1–14.9]; P = 0.047), as was comorbid respiratory disease (adjusted OR 7.5 [95% confidence interval 1.9–38.2]; P = 0.006). Vasculitis disease activity and nonglucocorticoid immunosuppressive therapy were not associated with severe outcomes. Conclusion: In patients with systemic vasculitis, glucocorticoid use at presentation and comorbid respiratory disease were associated with severe outcomes in COVID‐19. These data can inform clinical decision‐making relating to the risk of severe COVID‐19 in this vulnerable patient group

Identifying prognostic risk factors for poor outcome following COVID-19 disease among in-centre haemodialysis patients: role of inflammation and frailty

Introduction: The pandemic of coronavirus disease (COVID-19) has highly affected patients with comorbidities and frailty who cannot self-isolate, such as individuals undergoing haemodialysis. The aim of the study was to identify risk factors for mortality and hospitalisation, which may be useful in future disease spikes. Methods: We collected data retrospectively from the electronic medical records of all patients receiving a diagnosis of COVID-19 between 11th March and 10th May 2020 undergoing maintenance haemodialysis at four satellite dialysis units from the Royal Free London NHS Foundation Trust, London, UK. Mortality was the primary outcome, and the need for hospitalization was the secondary one. Results: Out of 746 patients undergoing regular haemodialysis, 148 symptomatic patients tested positive for SARS-CoV-2 by RT-PCR and were included in the analysis. The overall mortality rate was 24.3%. By univariate analysis, older age, ischaemic heart disease, lower systolic blood pressure, lower body mass index (BMI) and higher frailty scores were associated with higher rates of mortality (all p value < 0.05). The laboratory factors associated with mortality were higher values of WBC, neutrophil counts, neutrophil to lymphocyte ratios (NLR), C-reactive protein (CRP), bilirubin, ferritin, troponin, and lower serum albumin level (all p value < 0.05). In the logistic regression, mortality was associated with older age and higher CRP, while high levels of NLR and CRP were associated with the need for hospitalization. Discussion: Haemodialysis patients are susceptible to COVID-19 and have a high mortality rate. Our study identifies prognostic risk factors associated with poor outcome including age, frailty and markers of inflammation, which may support more informed clinical decision-making. Graphic abstract: [Figure not available: see fulltext.

Inherited salt-losing tubulopathies are associated with immunodeficiency due to impaired IL-17 responses

Salt levels in culture affect the polarisation of Th17 cells, which normally protect the host from fungal and bacterial infections. Here, the authors study patients with salt-losing tubulopathies (SLT) to find that, while Th17 immunity is dampened in SLT patients, their Th17-inducing signaling pathways are intact and can be reinvigorated by exogenous salt

Risk Factors for Severe Outcomes in Patients With Systemic Vasculitis and COVID-19: A Binational, Registry-Based Cohort Study.

OBJECTIVE: COVID-19 is a novel infectious disease with a broad spectrum of clinical severity. Patients with systemic vasculitis have an increased risk of serious infections and may be at risk of severe outcomes following COVID-19. We undertook this study to establish the risk factors for severe COVID-19 outcomes in these patients, including the impact of immunosuppressive therapies. METHODS: A multicenter cohort was developed through the participation of centers affiliated with national UK and Ireland vasculitis registries. Clinical characteristics and outcomes are described. Logistic regression was used to evaluate associations between potential risk factors and a severe COVID-19 outcome, defined as a requirement for advanced oxygen therapy, a requirement for invasive ventilation, or death. RESULTS: The cohort included 65 patients with systemic vasculitis who developed COVID-19 (median age 70 years, 49% women), of whom 25 patients (38%) experienced a severe outcome. Most patients (55 of 65 [85%]) had antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Almost all patients required hospitalization (59 of 65 [91%]), 7 patients (11%) were admitted to intensive care, and 18 patients (28%) died. Background glucocorticoid therapy was associated with severe outcomes (adjusted odds ratio [OR] 3.7 [95% confidence interval 1.1-14.9]; P = 0.047), as was comorbid respiratory disease (adjusted OR 7.5 [95% confidence interval 1.9-38.2]; P = 0.006). Vasculitis disease activity and nonglucocorticoid immunosuppressive therapy were not associated with severe outcomes. CONCLUSION: In patients with systemic vasculitis, glucocorticoid use at presentation and comorbid respiratory disease were associated with severe outcomes in COVID-19. These data can inform clinical decision-making relating to the risk of severe COVID-19 in this vulnerable patient group