Neutrophils associate with Bowman’s capsule rupture specifically in PR3-ANCA glomerulonephritis

Background Renal involvement is a common and severe complication of ANCA (antineutrophil cytoplasmic antibody) associated vasculitis (AAV) potentially resulting in a pauci-immune necrotizing and crescentic antineutrophil cytoplasmic antibody (ANCA) glomerulonephritis (GN) with acute kidney injury (AKI), end-stage renal disease (ESRD) or death. We recently described that Bowman’s capsule rupture links glomerular damage to tubulointerstitial inflammation in ANCA-associated glomerulonephritis. Herein we provide a comprehensive histological subtyping of immune cell infiltrates in association with Bowman’s capsule rupture in ANCA GN. Methods A total of 44 kidney biopsies with ANCA GN were retrospectively included in a single-center observational study. Within a renal biopsy specimen, each glomerulus was scored separately for the presence of extensive and focal Bowman’s capsule rupture in injured glomeruli. Infiltrates of neutrophils, eosinophils, plasma cells, and mononucleated cells (macrophages, lymphocytes) were quantified as a fraction of the area of total cortical inflammation. Results Extensive Bowman’s capsule rupture was associated with tubulointerstitial inflammation containing infiltrates of neutrophils, eosinophils and plasma cells. A similar association was observed for the presence of focal Bowman’s capsule rupture, correlating with tubulointerstitial inflammation containing neutrophils, eosinophils and plasma cells. Multiple logistic regression confirmed that extensive Bowman’s capsule rupture correlated with tubulointerstitial inflammation containing neutrophils, and focal Bowman’s capsule rupture correlated with neutrophil and plasma cell infiltration. Furthermore, this association was specifically observed in PR3-ANCA GN. Conclusion To our knowledge, this is the first report linking Bowman’s capsule rupture directly to tubulointerstitial inflammation by immune cell subtypes. This underscores a pathomechanistic link between tubulointerstitial and glomerular lesions in ANCA GN and needs further investigation. Graphical abstract

Non-albumin proteinuria in lupus nephritis with tubulointerstitial inflammation and its clinical significance

Background Tubulointerstitial inflammation (TI) associated with systemic lupus erythematosis is an increasing finding in lupus nephritis. TI severity may have prognostic significance in the renal outcomes of lupus nephritis. Here, we aimed to determine whether non-albumin proteinuria is associated with TI severity and with the renal response in lupus nephritis. Objective To investigate the possible association between non-albumin proteinuria, tubulointerstial inflammation severity and poor renal response after immunosuppressive treatment. Patients and Methods This is a case series study which was conducted on 100 patients with systemic lupus erythematosis recruited from the outpatient clinic of Clinical Immunology at Ain Shams University Hospitals. Subject ages were between 13-53 years old, each one was subjected to detailed history, physical examination, laboratory investigations including serum creatinine before and after treatment, protein/creatinine ratio before and after treatment, albumin/creatinine ratio, ESR, CRP, CBC, C3 C4, anti DNA, eGFR and renal biopsy Results Our results showed that non-albumin proteinuria (uPCR − uACR) was significantly higher in patients with moderate-to-severe TI than in patients with no-tomild TI. Further, higher uPCR − uACR levels at baseline were associated with poor renal response after 6 months of treatment. Conclusion we found that non-albumin proteinuria (uPCR-uACR) is associated with severe tubulointerstitial inflammation (TI) in lupus nephritis.

Nephrotic syndrome and acute kidney injury following CoronaVac anti-SARS-CoV-2 vaccine

A 67-year-old female with type 2 diabetes mellitus developed nephrotic syndrome with in one week of receiving the first dose of SARS-CoV-2 CoronaVac vaccine. A kidney biopsy was consistent with minimal change nephrotic syndrome and treatment was symptomatic with antiproteinurik therapy and improvement in proteinuria. Edema returned within one week of the second dose of CoronaVac. In this occasion acute kidney injury and massive proteinuria were noted. In kidney biopsy, glomeruli were normal, but tubulointerstitial inflammation consistent with acute tubulointerstitial nephritis were noted. Pulse followed by oral steroids were followed by recovery of kidney function. Proteinuria decreased after initiation of cyclosporine A.

Prediction of remodeling of arteries of kidneys of small diameter in patients with chronic glomerulonephritis

Objective: to determine the significance of clinical, laboratory and morphometric indicators of structural restructuring of kidney tissue in the prognosis of remodeling of small-diameter kidney arteries in patients with primary chronic glomerulonephritis. Materials and methods: the study included 97 patients with primary chronic glomerulonephritis and indications for puncture nephrobiopsy. In all patients, anamnestic and clinical and laboratory risk factors were recorded, and nephrobiopsy was performed. When performing morphometric analysis of nephrobiopsy, the state of the tissue and vessels of the kidneys of small diameter was studied. To achieve this goal, all patients were divided into two groups, the ranking of which was carried out according to the median wall thickness of the interlobular artery. Results: Among all the risk factors studied, a statistically significant effect of an increase in the stages of hypertension (χ2 criterion = 4.24, p = 0.03) and a decrease in GFR (χ2 criterion = 5.92, p = 0.015) on the risk of increasing the thickness of the interlobular artery was found. The indicators of structural reconstruction of the renal tissue did not have a statistically significant effect on the likelihood of remodeling of the arterial wall. However, a direct correlation of weak strength was found between the severity of tubulointerstitial inflammation and the thickness of the wall of the interlobular artery (r = 0.23, p = 0.02). Conclusions: this work shows the paramount importance of hypertension, accompanied by damage to target organs, as a marker of remodeling of the vascular wall of the interlobular artery in patients with chronic glomerulonephritis.

CD36 promotes NLRP3 inflammasome activation via the mtROS pathway in renal tubular epithelial cells of diabetic kidneys

Tubulointerstitial inflammation plays a key role in the pathogenesis of diabetic nephropathy (DN). Interleukin-1β (IL-1β) is the key proinflammatory cytokine associated with tubulointerstitial inflammation. The NLRP3 inflammasome regulates IL-1β activation and secretion. Reactive oxygen species (ROS) represents the main mediator of NLRP3 inflammasome activation. We previously reported that CD36, a class B scavenger receptor, mediates ROS production in DN. Here, we determined whether CD36 is involved in NLRP3 inflammasome activation and explored the underlying mechanisms. We observed that high glucose induced-NLRP3 inflammasome activation mediate IL-1β secretion, caspase-1 activation, and apoptosis in HK-2 cells. In addition, the levels of CD36, NLRP3, and IL-1β expression (protein and mRNA) were all significantly increased under high glucose conditions. CD36 knockdown resulted in decreased NLRP3 activation and IL-1β secretion. CD36 knockdown or the addition of MitoTempo significantly inhibited ROS production in HK-2 cells. CD36 overexpression enhanced NLRP3 activation, which was reduced by MitoTempo. High glucose levels induced a change in the metabolism of HK-2 cells from fatty acid oxidation (FAO) to glycolysis, which promoted mitochondrial ROS (mtROS) production after 72 h. CD36 knockdown increased the level of AMP-activated protein kinase (AMPK) activity and mitochondrial FAO, which was accompanied by the inhibition of NLRP3 and IL-1β. The in vivo experimental results indicate that an inhibition of CD36 could protect diabetic db/db mice from tubulointerstitial inflammation and tubular epithelial cell apoptosis. CD36 mediates mtROS production and NLRP3 inflammasome activation in db/db mice. CD36 inhibition upregulated the level of FAO-related enzymes and AMPK activity in db/db mice. These results suggest that NLRP3 inflammasome activation is mediated by CD36 in renal tubular epithelial cells in DN, which suppresses mitochondrial FAO and stimulates mtROS production.

POS0722 HISTOPATHOLOGICAL ANALYSIS OF LUPUS NEPHRITIS INCORPORATING BANFF CRITERIA EMPHASIZES THE IMPORTANCE OF TUBULOINTERSTITIAL CHANGES FOR CREATININE AND PROTEINURIA AT 12 MONTHS AFTER RENAL BIOPSY

Background:Lupus nephritis (LN) occurs in about 30-60% of patients with systemic lupus erythematosus (SLE). LN is associated with increased mortality. Currently, the diagnosis relies on histopathologic characteristics according to the ISN/RPS classification (1). This classification relies heavily on glomerular changes and may not accurately reflect all changes occurring in LN. For the description of transplanted kidney, the BANFF classification has been established which, in addition to glomerular changes, also incorporates tubular pathologies (2).Objectives:With the present study, we aim to describe histopathologic changes according to the BANFF classification in a single-center cohort of LN patients.Methods:We retrospectively recorded epidemiological, clinical and laboratory data of 58 patients with LN over a ten-year period. Histopathologic diagnoses according to ISN/RPS classification or the former WHO classification were also documented. We then re-analyzed representative kidney samples according to the BANFF classification and performed Spearman rank correlation for BANFF findings and creatinine at biopsy and 12 months as well as proteinuria at biopsy and at 12 months.Results:We analyzed 58 patients with LN. 9 were male, 49 were female. Median age was 38 (15-78) years. According to ISN/RPS, 3 had class I LN, 6 had class II, 14 had class III, 16 had class IV, 6 had class V, and 0 had class VI. Median eGFR at biopsy was 60 ml/min/1.73m2 (13-137). According to the BANFF classification, tubulointerstitial inflammation (ti) was associated with creatinine at 12 months. Proteinuria at 12 months was associated with interstitial fibrosis (ci) (Figure 1).Conclusion:In LN, the current ISN/RPS classification puts emphasis on glomerular changes. Nevertheless, for the long-term outcome, tubulointerstitial changes (tubulointerstitial inflammation and interstitial fibrosis) may at least be as important as glomerular changes. These findings have to be corroborated in larger cohorts with prespecified renal endpoints.References:[1]Weening et al. The classification of glomerulonephritis in systemic lupus erythematosus revisited. JASN 2004.[2]Jeong HY. Diagnosis of renal transplant rejection: Banff classification and beyond. Kidney Res Clin Pract 2020.Disclosure of Interests:Marlene Plüß: None declared, Samy Hakroush: None declared, Noah Niebusch: None declared, Björn Tampe: None declared, PETER KORSTEN Speakers bureau: Abbvie, Pfizer, Chugai, Sanofi, Boehringer-Ingelheim, GSK, Novartis, Consultant of: Abbvie, Pfizer, Chugai, Sanofi, Boehringer-Ingelheim, GSK, Novartis, Lilly, Gilead, Grant/research support from: GSK

Machine Learning to Quantify In Situ Humoral Selection in Human Lupus Tubulointerstitial Inflammation

In human lupus nephritis, tubulointerstitial inflammation (TII) is associated with in situ expansion of B cells expressing anti-vimentin antibodies (AVAs). The mechanism by which AVAs are selected is unclear. Herein, we demonstrate that AVA somatic hypermutation (SHM) and selection increase affinity for vimentin. Indeed, germline reversion of several antibodies demonstrated that higher affinity AVAs can be selected from both low affinity B cell germline clones and even those that are strongly reactive with other autoantigens. While we demonstrated affinity maturation, enzyme-linked immunosorbent assays (ELISAs) suggested that affinity maturation might be a consequence of increasing polyreactivity or even non-specific binding. Therefore, it was unclear if there was also selection for increased specificity. Subsequent multi-color confocal microscopy studies indicated that while TII AVAs often appeared polyreactive by ELISA, they bound selectively to vimentin fibrils in whole cells or inflamed renal tissue. Using a novel machine learning pipeline (CytoSkaler) to quantify the cellular distribution of antibody staining, we demonstrated that TII AVAs were selected for both enhanced binding and specificity in situ. Furthermore, reversion of single predicted amino acids in antibody variable regions indicated that we could use CytoSkaler to capture both negative and positive selection events. More broadly, our data suggest a new approach to assess and define antibody polyreactivity based on quantifying the distribution of binding to native and contextually relevant antigens.

Inhibition of Yes-Associated Protein by Verteporfin Ameliorates Unilateral Ureteral Obstruction-Induced Renal Tubulointerstitial Inflammation and Fibrosis

Yes-associated protein (YAP) activation after acute ischemic kidney injury might be related to interstitial fibrosis and impaired renal tubular regeneration. Verteporfin (VP) is a photosensitizer used in photodynamic therapy to treat age-related macular degeneration. In cancer cells, VP inhibits TEA domain family member (TEAD)-YAP interactions without light stimulation. The protective role of VP in unilateral ureteral obstruction (UUO)-induced renal fibrosis and related mechanisms remains unclear. In this study, we investigate the protective effects of VP on UUO-induced renal tubulointerstitial inflammation and fibrosis and its regulation of the transforming growth factor-β1 (TGF-β1)/Smad signaling pathway. We find that VP decreased the UUO-induced increase in tubular injury, inflammation, and extracellular matrix deposition in mice. VP also decreased myofibroblast activation and proliferation in UUO kidneys and NRK-49F cells by modulating Smad2 and Smad3 phosphorylation. Therefore, YAP inhibition might have beneficial effects on UUO-induced tubulointerstitial inflammation and fibrosis by regulating the TGF-β1/Smad signaling pathway.