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.

Disparity in peripheral and renal B-cell depletion with rituximab in systemic lupus erythematosus: an opportunity for obinutuzumab?

OBJECTIVES: To investigate key factors that may contribute to the variability of rituximab-mediated peripheral and renal B cell depletion (BCD) in SLE. METHODS: We analysed: (i) CD19+ B cell counts in patients with SLE before and 1, 2, 3 and 6 months after treatment with rituximab, comparing them with RA patients; (ii) the presence of B cells in renal biopsies after rituximab therapy; (iii) whether the duration of BCD correlated with patient demographics and B cell expression of CD20 and FcγRIIb; and (iv) the effect of B cell activation factor (BAFF) on the efficiency of rituximab and obinutuzumab at inducing BCD in whole blood assays, in vitro. RESULTS: In SLE (n = 71), the duration of BCD was shorter compared with RA (n = 27). B cells were detectable in renal biopsy samples (n = 6) after treatment with rituximab in all patients with poor response while peripheral blood B cells remained low or undetectable in the same patients. There were no significant relationships between peripheral BCD and patient age, disease duration, serum C3 levels or the level of expression of B cell surface proteins CD20 and FcγRIIb. Obinutuzumab was more efficient than rituximab at inducing BCD in whole blood assays, regardless of excess BAFF. CONCLUSIONS: BCD in SLE is less efficient than in RA. Renal B cell presence following rituximab treatment was associated with poor outcomes. No significant relationships between any measured B cell related, clinical or laboratory parameters and the efficiency of BCD by rituximab was found. Obinutuzumab was superior to rituximab at inducing BCD.

Neutrophils are key mediators in crescentic glomerulonephritis and targets for new therapeutic approaches.

Crescentic glomerulonephritis (CGN) results from a diverse set of diseases associated with immune dysregulation and the breakdown of self-tolerance to a wide range of autoantigens, some known and some that remain unknown. Experimental data demonstrate that neutrophils have an important role in the pathogenesis of CGN. Upon activation, neutrophils generate reactive oxygen species, release serine proteases and form neutrophil extracellular traps (NETs), all of which can induce direct tissue damage. In addition, serine proteases such as myeloperoxidase and proteinase 3, presented on NETs, can be processed and recognized as autoantigens, leading to the generation and maintenance of autoimmune responses in susceptible individuals. The basis of the specificity of autoimmune responses in different patients to NET proteins is unclear, but relates at least in part to differences in human leucocyte antigen expression. Conditions associated with CGN are often characterized by aberrant neutrophil activation and NETosis and, in some, impaired NET degradation. Targeting neutrophil degranulation and NETosis is now possible using a variety of novel compounds and may provide a promising therapeutic alternative to glucocorticoid use, which has been a mainstay of management in CGN for decades and is associated with significant adverse effects. In this review, we discuss the evidence supporting the role of neutrophils in the development of CGN and the pathways identified in neutrophil degranulation and NETosis that may translate to novel therapeutic applications.

Therapeutic Myeloperoxidase Inhibition Attenuates Neutrophil Activation, ANCA-Mediated Endothelial Damage, and Crescentic GN.

BACKGROUND: Myeloperoxidase released after neutrophil and monocyte activation can generate reactive oxygen species, leading to host tissue damage. Extracellular glomerular myeloperoxidase deposition, seen in ANCA-associated vasculitis, may enhance crescentic GN through antigen-specific T and B cell activation. Myeloperoxidase-deficient animals have attenuated GN early on, but augmented T cell responses. We investigated the effect of myeloperoxidase inhibition, using the myeloperoxidase inhibitor AZM198, to understand its potential role in treating crescentic GN. METHODS: We evaluated renal biopsy samples from patients with various forms of crescentic GN for myeloperoxidase and neutrophils, measured serum myeloperoxidase concentration in patients with ANCA-associated vasculitis and controls, and assessed neutrophil extracellular trap formation, reactive oxygen species production, and neutrophil degranulation in ANCA-stimulated neutrophils in the absence and presence of AZM198. We also tested the effect of AZM198 on ANCA-stimulated neutrophil-mediated endothelial cell damage in vitro, as well as on crescentic GN severity and antigen-specific T cell reactivity in the murine model of nephrotoxic nephritis. RESULTS: All biopsy specimens with crescentic GN had extracellular glomerular myeloperoxidase deposition that correlated significantly with eGFR and crescent formation. In vitro, AZM198 led to a significant reduction in neutrophil extracellular trap formation, reactive oxygen species production, and released human neutrophil peptide levels, and attenuated neutrophil-mediated endothelial cell damage. In vivo, delayed AZM198 treatment significantly reduced proteinuria, glomerular thrombosis, serum creatinine, and glomerular macrophage infiltration, without increasing adaptive T cell responses. CONCLUSIONS: Myeloperoxidase inhibition reduced neutrophil degranulation and neutrophil-mediated endothelial cell damage in patients with ANCA-associated vasculitis. In preclinical crescentic GN, delayed myeloperoxidase inhibition suppressed kidney damage without augmenting adaptive immune responses, suggesting it might offer a novel adjunctive therapeutic approach in crescentic GN.

Using Quality Improvement Methodology to Reduce Costs while Improving Efficiency and Provider Satisfaction in a Busy, Academic Musculoskeletal Radiology Division.

Within an everchanging healthcare system, continuous evaluation of standard operating procedures must be performed to ensure optimization of system level organization, communication, and efficiency. Using the Lean management approach, our institution introduced modifications to our musculoskeletal (MSK) radiology workflow in order to facilitate beneficial change that improved clinical workflow efficiency, reduced moonlighting costs, and improved radiologist satisfaction without sacrificing quality of care. The scope of our study included the MSK division of adult inpatient and outpatient populations at three hospitals in a single academic medical center. A root cause analysis was executed to determine the causative factors contributing to clinical inefficiency. Five main factors were identified, and appropriate countermeasures were introduced. Efficiency was measured via the turnaround time (TAT) for radiographic examinations, measured from exam completion to final report submission. Moonlighting expenses were monitored for the fiscal year in which the modifications were implemented. Surveys were administered to MSK radiologists before and after the countermeasures were introduced to determine subjective ratings of efficiency and satisfaction. The average TAT within our MSK division decreased from 40 h to 12 h after introducing changes to our workflow. During one fiscal year, moonlighting expenses decreased from $26,000 to $5000. Post-study survey results indicated increased efficiency of and satisfaction with our implemented modifications to the scheduling and clinical workflow. Optimization of our radiology department's workflow led to increased productivity, efficiency, and radiologist satisfaction, as well as a reduction in moonlighting costs. This project leveraged Lean management principles to combat clinical inefficiency, waste time, and high costs.

Diagnostic and management challenges in Goodpasture's (anti-glomerular basement membrane) disease.

Goodpasture's or anti-glomerular basement membrane (GBM) disease is classically characterized by the presence of circulating autoantibodies directed against the non-collagenous domain of the α3 chain of type IV collagen, targeting glomerular and alveolar basement membranes, and associated with rapidly progressive crescentic glomerulonephritis, with alveolar haemorrhage in over half the patients. However, there are increasing examples of variants or atypical presentations of this disease, and novel therapeutic options have been proposed, which nephrologists should be aware of. The pathophysiology of this condition has been understood through molecular analysis of the antibody-antigen interactions and the use of human leucocyte antigen-transgenic animals, while the association of anti-GBM antibodies with anti-neutrophil cytoplasm antibodies and their combined impact on disease phenotype is increasingly recognized, providing some insights into the basis of glomerular damage and autoimmunity.

Cocaine-induced granulomatosis with polyangiitis-an under-recognized condition.

Objectives: Cocaine and cocaine mixed with levamisole are increasingly used in the UK and result in significant direct nasal damage in addition to promoting vasculitis. Our aims were as follows: (1) to identify the main symptoms and presentation of cocaine-induced vasculitis; (2) to provide evidence regarding the best practice for the investigation and diagnosis of cocaine-induced vasculitis; and (3) to analyse the clinical outcomes of patients in order to understand the optimal management for the condition. Methods: We performed a retrospective case series analysis of patients presenting with cocaine-induced midline destructive lesions or vasculitis compatible with granulomatosis with polyangiitis (GPA) from two large tertiary vasculitis clinics between 2016 and 2021. Results: Forty-two patients (29 Birmingham, 13 London) with cocaine-induced midline lesions or systemic disease were identified. The median age was 41 years (range 23-66 years). Current cocaine use was common, and 20 of 23 samples provided were positive when routine urine toxicology was performed; 9 patients who denied ever using cocaine were identified as using cocaine based on urine toxicology analysis, and 11 who stated they were ex-users still tested positive. There was a high incidence of septal perforation (75%) and oronasal fistula (15%). Systemic manifestations were less common (27%), and only one patient had acute kidney injury. Fifty-six per cent of our patients were PR3-ANCA positive, with none testing positive for MPO-ANCA. Symptom remission required cocaine discontinuation even when immunosuppression was administered. Conclusion: Patients with destructive nasal lesions, especially young patients, should have urine toxicology performed for cocaine before diagnosing GPA and considering immunosuppressive therapy. The ANCA pattern is not specific for cocaine-induced midline destructive lesions. Treatment should be focused on cocaine cessation and conservative management in the first instance in the absence of organ-threatening disease.

GPR97 triggers inflammatory processes in human neutrophils via a macromolecular complex upstream of PAR2 activation.

Neutrophils play essential anti-microbial and inflammatory roles in host defense, however, their activities require tight regulation as dysfunction often leads to detrimental inflammatory and autoimmune diseases. Here we show that the adhesion molecule GPR97 allosterically activates CD177-associated membrane proteinase 3 (mPR3), and in conjugation with several protein interaction partners leads to neutrophil activation in humans. Crystallographic and deletion analysis of the GPR97 extracellular region identified two independent mPR3-binding domains. Mechanistically, the efficient binding and activation of mPR3 by GPR97 requires the macromolecular CD177/GPR97/PAR2/CD16b complex and induces the activation of PAR2, a G protein-coupled receptor known for its function in inflammation. Triggering PAR2 by the upstream complex leads to strong inflammatory activation, prompting anti-microbial activities and endothelial dysfunction. The role of the complex in pathologic inflammation is underscored by the finding that both GPR97 and mPR3 are upregulated on the surface of disease-associated neutrophils. In summary, we identify a PAR2 activation mechanism that directs neutrophil activation, and thus inflammation. The PR3/CD177/GPR97/PAR2/CD16b protein complex, therefore, represents a potential therapeutic target for neutrophil-mediated inflammatory diseases.

Pig trotters lung--novel domestic transmission of Pasteurella multocida.

Pasteurella multocida is a non-motile, faculatively-anaerobic, gram-negative bacillus associated with a spectrum of human disease. Direct and indirect zoonotic transmission is recognised with animal bites being most frequently encountered as a result of salivary colonisation in farm and domestic animals. Despite the prevalence of P. multocida in swine herds, the relationship between porcine colonisation and human disease is poorly established. This lesson reports a previously unrecognised mode of zoonotic transmission in respiratory pasteurellosis; domestic cooking of pig trotters.

Prolonged B cell depletion with rituximab is effective in treating refractory pulmonary granulomatous inflammation in granulomatosis with polyangiitis (GPA).

Pulmonary nodule formation is a frequent feature of granulomatosis with polyangiitis (GPA). Traditional induction therapy includes methotrexate or cyclophosphamide, however, pulmonary nodules generally respond slower than vasculitic components of disease. Efficacy of rituximab (RTX) solely for the treatment of pulmonary nodules has not been assessed. In this observational cohort study, we report patient outcomes with RTX in GPA patients with pulmonary nodules who failed to achieve remission following conventional immunosuppression. Patients (n = 5) with persistent pulmonary nodules were identified from our clinic database and retrospectively evaluated. Systemic manifestations, inflammatory markers, disease activity, concurrent immunosuppression, and absolute B cell numbers were recorded pre-RTX and at 6 monthly intervals following treatment. Chest radiographs at each time point were scored by an experienced radiologist, blinded to clinical details. Five patients with GPA and PR3-ANCA were evaluated (2 male, 3 female), mean age 34 (22-52) years. Pulmonary nodules (median 4, range 2-6), with or without cavitation were present in all patients. RTX induced initial B cell depletion (<5 cells/µL) in all patients but re-population was observed in 3 patients. Repeated RTX treatment in these 3 and persistent B cell depletion in the whole cohort was associated with further significant radiological improvement. Radiographic scoring at each time interval showed reduction in both number of nodules (P =  <0.0001) and largest nodule diameter (P =  <0.0001) in all patients for at least 18 months following B cell depletion. In summary, RTX therapy induces resolution of pulmonary granulomatous inflammation in GPA following prolonged B cell depletion.