Glomerular C3 Deposition Research Articles

Tris DBA Ameliorates Accelerated and Severe Lupus Nephritis in Mice by Activating Regulatory T Cells and Autophagy and Inhibiting the NLRP3 Inflammasome.

Tris (dibenzylideneacetone) dipalladium (Tris DBA), a small-molecule palladium complex, has been shown to inhibit cell growth and proliferation in pancreatic cancer, lymphocytic leukemia, and multiple myeloma. In the current study, we examined the therapeutic effects of Tris DBA on glomerular cell proliferation, renal inflammation, and immune cells. Treatment of accelerated and severe lupus nephritis (ASLN) mice with Tris DBA resulted in improved renal function, albuminuria, and pathology, including measurements of glomerular cell proliferation, cellular crescents, neutrophils, fibrinoid necrosis, and tubulointerstitial inflammation in the kidneys as well as scoring for glomerulonephritis activity. The treated ASLN mice also showed significantly decreased glomerular IgG, IgM, and C3 deposits. Furthermore, the compound was able to 1) inhibit bone marrow-derived dendritic cell-mediated T cell functions and reduce serum anti-dsDNA autoantibody levels; 2) differentially regulate autophagy and both the priming and activation signals of the NLRP3 inflammasome; and 3) suppress the phosphorylation of JNK, ERK, and p38 MAPK signaling pathways. Tris DBA improved ASLN in mice through immunoregulation by blunting the MAPK (ERK, JNK)-mediated priming signal of the NLRP3 inflammasome and by regulating the autophagy/NLRP3 inflammasome axis. These results suggest that the pure compound may be a drug candidate for treating the accelerated and deteriorated type of lupus nephritis.

SUN-413 C3 GLOMERULOPATHY: 2 YEARS’ EXPERIENCE, NEPHROLOGY DEPARTEMENT MONASTIR

C3 glomerulopathies (C3 G) are rare diseases that share an underlying mechanism of complement dysregulation. Diagnosis relies solely on renal biopsy immunofluorescence findings characterized by glomerular deposits of C3 with minimal or no immunoglobulin (Ig) deposits; light microscopy findings and complement biomarker profiles are heterogeneous, We present in this study our experience about 6 cases of C3 G diagnosed at the nephrology department from Janury 2017 to october 2019 This is a retrospective, descriptive study. We included a group of 6 medical records of patients with C3G with a performed native renal biopsy. In all cases light microscopic and immunofluorescence evaluation were performed. The median age at diagnosis was 58 years,( minimum age 36 years and maximum 66 years), with a female predominance (4 women Vs 2 men ), three patients had a history of high blood pressure, a case of diabetes mellitus, hypothyroidism and the youngest woman had recurrent angina, no history of infection, positive autoimmune findings, or monoclonal gammopathy was identified. Initial presentation was as follow: oedema in three cases, inflammatory polyarthraligia in 2 cases, and only one patient presented oligoanuria. the majority presented sediment anomaly (non-nephrotic Pu + Hu) with renal insufficiency with median Glomerular Filtration Rate(GFR) and proteinuria of 30ml/min/1,73m² and 2,5 /24h, respectively and only one patient had a nephrotic syndrome (defined by a Pu> 3 g / 24h, hypolabuminemia <35 g ), hematuria was always present except one case, a biological inflammatory syndrome was present in all cases, only one had unexplained biological cholestasis, both men had leg purpuric lesions, C3/C4 levels were low in 4 cases however CH50 was low in one, exploration of the alternative complement pathway is in progress (Factor, H and I). The etiological assessment of a MPGN included: a myelogram, cardiac ultrasonography, serology of hepatitis B and C, was negative. Membranoproliferative and mesangial proliferative glomerulonephritis were the common patterns of injury nevertheless one patient had Crescentics. The treatment was as follow 0.5 mg / kg / day of corticosteroid therapy with Mycophenolate mofetil in 5 cases, 4 had a good evolution with a decreased proteinuria and hematuria level and DFG stabilization, in one case the outcome was good with only corticosteroid, this patient presented nephrotic syndrome without renal insufficiency and 1 patient progressed to ESRD. Because clinical courses and prognoses among glomerular diseases with dominant C3 deposition differ, further understanding the background mechanism, particularly complement dysregulation in C3G, is needed. This may resolve current dilemmas in practice and shed light on novel targeted therapies to remedy the dysregulated alternative complement pathway in C3G.

IgG deposits in the mesangium and capillary loops predict poor renal outcome in patients with IgA nephropathy: a single-center retrospective study

Background Glomerular IgG deposition in patients with IgA nephropathy (IgAN) has been shown to be associated with poor renal survival; however, most published studies to date are too small-scale and inconsistent to provide guidance for clinical practice. Methods Based on renal biopsy findings, 742 patients were divided into the following groups: (i) IgA deposition alone (IgA) vs IgA + IgG deposition (IgA + IgG) and (ii) IgG co-deposition confined to the mesangium vs mesangium + capillary loops (CLs). The clinicopathological variables at biopsy and renal outcome were assessed. Results Of the 742 patients, 182 had IgG co-deposition and 51 had IgG deposits in the mesangium + CLs. Patients with IgG co-deposition were associated with severe clinical and pathological lesions, especially those with a location of IgG deposits in the mesangium +CLs. Kaplan–Meier analysis revealed that a lower renal cumulative survival rate was present in both patients with IgG co-deposition and those with a location of IgG deposits in the mesangium + CLs (all p < 0.05). Moreover, patients with a higher intensity of glomerular IgG deposits or C3 deposits or C1q deposits were also associated with a lower survival rate. A multivariate Cox regression model identified the location of IgG deposits in the mesangium + CLs as an independent risk factor for poor prognosis (HR, 2.11; 95% CI: 1.06–4.18; p = 0.005). Conclusions Glomerular IgG co-deposition and the location of glomerular IgG deposits in the mesangium + CLs were both associated with adverse renal outcomes, but only the location of glomerular IgG deposits in the CLs was an independent risk factor for poor prognosis in IgAN.

Development of Murine Systemic Lupus Erythematosus in the Absence of BAFF.

To determine whether systemic lupus erythematosus (SLE) can develop in the absence of BAFF in an SLE-prone host. Starting with C57BL/6 mice that express a human BCL2 transgene (Tg) in their B cells (thereby rendering B cell survival largely independent of BAFF-triggered signals), we introgressed this Tg into NZM 2328 mice genetically deficient in BAFF (NZM.Baff-/- ) to generate NZM.Baff-/- .Bcl2Tg mice. Expression of human Bcl-2 and lymphocyte profiles were assessed by fluorescence-activated cell sorting, and serologic profiles were determined by enzyme-linked immunosorbent assay. Immunofluorescence and histologic analyses were performed to assess renal immunopathologic features in the mice, and clinical disease was assessed according to the outcomes of severe proteinuria and death. In comparison to their non-Tg NZM.Baff-/- littermates (n ≥ 7), NZM.Baff-/- .Bcl2Tg mice (n ≥ 8) overexpressed Bcl-2 in their B cells and developed significantly increased percentages and numbers of B cells and plasma cells, serum levels of IgG autoantibodies, glomerular deposition of IgG and C3, and severity of glomerular and tubulointerstitial inflammation, culminating in severe proteinuria and death (all P < 0.05 versus NZM.Baff-/- littermates). The time course for development of SLE-like features in NZM.Baff-/- .Bcl2Tg mice was more rapid than has been previously observed in NZM 2328 wild-type mice (median age at death 4.5 months versus 7.5 months). NZM.Baff-/- .Bcl2Tg mice remained responsive to BAFF, since reintroduction of the Baff gene into these mice further accelerated the course of disease (median age at death 3 months). The role of BAFF in the development of SLE-like disease may be dispensable as long as B cell survival is preserved via a BAFF-independent pathway. This may help explain the limited and variable clinical success with BAFF antagonists in human SLE. Thus, NZM.Baff-/- .Bcl2Tg mice may serve as a powerful murine model for the study of BAFF-independent SLE.

Noncanonical immunomodulatory activity of complement regulator C4BP(β-) limits the development of lupus nephritis

Lupus nephritis is a chronic autoimmune-inflammatory condition that can lead to end-stage kidney disease. Presently available immunosuppressive treatments for lupus nephritis are suboptimal and can induce significant side effects. Recently, we characterized a novel immunomodulatory activity of the minor isoform of the classical pathway complement inhibitor, C4BP(β-). We show here that C4BP(β-) treatment prevented the development of proteinuria and albuminuria, decreased significantly the formation of anti-dsDNA antibodies and, locally, mitigated renal glomerular IgG and C3 deposition and generation of apoptotic cells. There was a consequent histological improvement and increased survival in lupus-prone mice. The therapeutic efficacy of C4BP(β-) was analogous to that of the broad-acting immunosuppressant cyclophosphamide. Remarkably, a comparative transcriptional profiling analysis revealed that the kidney gene expression signature resulting from C4BP(β-) treatment turned out to be 10 times smaller than that induced by cyclophosphamide treatment. C4BP(β-) immunomodulation induced significant downregulation of transcripts relevant to lupus nephritis indicating immunopathogenic cell infiltration, including activated T cells (Lat), B cells (Cd19, Ms4a1, Tnfrsf13c), inflammatory phagocytes (Irf7) and neutrophils (Prtn3, S100a8, S100a9). Furthermore, cytokine profiling and immunohistochemistry confirmed that C4BP(β-), through systemic and local CXCL13 downregulation, was able to prevent ectopic lymphoid structures neogenesis in aged mice with lupus nephritis. Thus, due to its anti-inflammatory and immunomodulatory activities and high specificity, C4BP(β-) could be considered for further clinical development in patients with systemic lupus erythematosus.

Clinicopathological features of C3 glomerulopathy in children: a single-center experience.

C3 glomerulopathy (C3G) is defined by dominant glomerular deposition of C3 and minimal or no immunoglobulin, with two subtypes-dense deposit disease (DDD) and C3 glomerulonephritis (C3GN)-distinguished by features on electron microscopy (EM). Given that this rare disease has generally unfavorable yet highly variable outcomes, we sought out to review the histopathology, complement/genetic studies, and renal outcomes of pediatric patients with C3G at our institution. All native kidney biopsies performed in a single pediatric hospital over a 10-year period were reviewed for features of C3G. Of 589 biopsy reports, we identified 9 patients fulfilling the diagnostic criteria for C3G and retrospectively reviewed their clinical chart and renal biopsy findings. We identified 4 patients with DDD, 4 with C3GN, and 1 indeterminate case, with features of both C3GN and DDD. Five patients were positive for one or more nephritic factors (C3NeF, C4NeF, C5NeF) with 1 patient additionally positive for complement factor H (CFH) autoantibody. Genetic testing done in 5 of the 9 patients failed to identify any causative mutations. Three patients showed progressive renal dysfunction over a mean follow-up period of 33 months. Complement and genetic studies are now routinely recommended for patients with a histopathological diagnosis of C3G. Careful interpretation of these studies and their prognostic and therapeutic implications in conjunction with biopsy findings is needed to further understand the pathophysiology of this rare disease in children.

Blockade of the kallikrein-kinin system reduces endothelial complement activation in vascular inflammation.

BackgroundThe complement and kallikrein-kinin systems (KKS) are activated during vascular inflammation. The aim of this study was to investigate if blockade of the KKS can affect complement activation on the endothelium during inflammation.MethodsComplement deposition on endothelial microvesicles was assayed in vasculitis patient plasma samples and controls. Plasma was perfused over glomerular endothelial cells and complement deposition assayed by flow cytometry. The effect of the kinin system was assessed using kinin receptor antagonists and C1-inhibitor. The in vivo effect was assessed in kidney sections from mice with nephrotoxic serum-induced glomerulonephritis treated with a kinin receptor antagonist.FindingsVasculitis patient plasma had significantly more C3- and C9-positive endothelial microvesicles than controls. Perfusion of patient acute-phase plasma samples over glomerular endothelial cells induced the release of significantly more complement-positive microvesicles, in comparison to remission or control plasma. Complement activation on endothelial microvesicles was reduced by kinin B1- and B2-receptor antagonists or by C1-inhibitor (the main inhibitor of the classical pathway and the KKS). Likewise, perfusion of glomerular endothelial cells with C1-inhibitor-depleted plasma induced the release of complement-positive microvesicles, which was significantly reduced by kinin-receptor antagonists or C1-inhibitor. Mice with nephrotoxic serum-induced glomerulonephritis exhibited significantly reduced glomerular C3 deposition when treated with a B1-receptor antagonist.InterpretationExcessive complement deposition on the endothelium will promote endothelial injury and the release of endothelial microvesicles. This study demonstrates that blockade of the KKS can reduce complement activation and thereby the inflammatory response on the endothelium.FundingFull details are provided in the Acknowledgements/Funding section.

Maternal alloimmune IgG causes anti-glomerular basement membrane disease in perinatal transgenic mice that express human laminin α5

Mammalian immune systems are not mature until well after birth. However, transfer of maternal IgG to the fetus and newborn usually provides immunoprotection from infectious diseases. IgG transfer occurs before birth in humans across the placenta and continues after birth across the intestine in many mammalian species, including rodents. Transfer, which is mediated by the neonatal IgG Fc receptor, occurs by transcytosis across placental syncytiotrophoblasts and intestinal epithelium. Although maternal IgG is generally beneficial, harmful maternal allo- and autoantibodies can also be transferred to the fetus/infant, resulting in serious disease. To test this we generated transgenic mice that widely express human laminin α5 in their basement membranes. When huLAMA5 transgenic males were crossed with wild-type females, there was a maternal anti-human laminin α5 immune response. Maternal IgG alloantibody crossed the yolk sac and post-natal intestine invivo and bound in bright, linear patterns to kidney glomerular basement membranes of transgenic fetuses/neonates but not those of wild-type siblings. By postnatal day 18, most transgenic mice were proteinuric, had glomerular C3 deposits and inflammatory cell infiltrates, thickened and split glomerular basement membranes, and podocyte foot process effacement. Thus, our novel model of perinatal anti-glomerular basement membrane disease may prove useful for studying pediatric glomerulopathies, formation of the fetomaternal interface, and maternal alloimmunization.

SAT-148 TLR AGONISTS EXACERBATE COMPLEMENT-ASSOCIATED KIDNEY DISEASE AND THE DEVELOPMENT OF AAV THERAPY IN A MOUSE MODEL OF KNOWN HUMAN CFH MUTATION

Atypical haemolytic uremic syndrome (aHUS) is commonly associated with complement factor H (CFH) mutation. CFH is a liver-secreted glycoprotein and a negative regulator of the alternative complement pathway. aHUS patients rapidly progress to acute kidney injury (AKI) due to complement-mediated renal insult. CFH mutation is predisposing, and additional infections are required to exacerbate disease. However, the role of infection in triggering disease remains elusive. Recombinant Adeno-Associated Virus (rAAV) have shown immense therapeutic potential and AAV8, in particular, transduce murine hepatocyte potently.The aim of the study is to evaluate whether lipopolysaccharide (LPS) induces acute kidney injury in CFH mutant mice and to assess the therapeutic potential of a liver-mediated AAV therapy. C57BL/6 mice carrying a single nucleotide polymorphism in CFH resembling human aHUS was generated by N-Ethyl-N-Nitrosourea mutagenesis. Homozygous (HOM), heterozygous (HET) and wildtype (WT) mice were treated with LPS via intraperitoneal injection. Renal function, histology and C3 immunofluorescence were assessed post-treatment. Serum and liver CFH levels were also measured. A rAAV8 containing a liver-specific promoter and functional CFH has been administered intravenously into susceptible CFH mutant mice. Hepatic vector transduction was assessed by assessing the vector copy number and a therapeutic outcome was evaluated by renal function, serum CFH levels and C3 deposition in kidney. Homozygous mice showed spontaneous deposition of glomerular C3 and had minimal serum concentrations of CFH compared to WT and heterozygous mice. Following LPS treatment, homozygous mice showed significantly higher levels of proteinuria (3.1±0.2mg/16h) and serum creatinine (28.3±3umol/L) compared to heterozygous (1.3±0.4mg/16h, 20.3±2umol/L, p<0.01 and p<0.05 respectively) and WT mice (1.2±0.2mg/16h, 17.6±1.6umol/L, p<0.01 and p<0.05 respectively). LPS-treated homozygous mice exhibited significantly more glomerulosclerosis, tubular damage and interstitial inflammation than heterozygous and WT mice (p<0.01). Furthermore, rAAV therapy successfully delivered CFH into the liver of CFH-mutant mice demonstrated by higher level of vector copy number (VCN) from liver tissue for gene therapy mice compared with saline treated mice. Mice homozygous for the aHUS-associated CFH mutation develop glomerular C3 deposition and are sensitive to LPS, developing acute kidney injury and renal histological damage. This suggests a significant role for infection in triggering aHUS in susceptible individuals. Gene therapy using rAAV has potential to treat genetic kidney diseases.

Characteristics of membranoproliferative glomerulonephritis based on a new classification at a single center.

Recently, a new classification has been established for membranoproliferative glomerulonephritis (MPGN). However, the effect of the new classification on MPGN treatment is not fully understood. We conducted a retrospective study of 87 patients with biopsies diagnosed as MPGN. We reclassified 87 MPGN patients diagnosed between 1977 and 2014at our hospital, according to the new classification, and analyzed both primary immune complex (IC)- and Alternative pathway (AP)-mediated MPGN [corrected] in terms of clinicopathological features, treatment, and renal prognosis. Proteinuria was abundant in the IC-mediated MPGN group (p = 0.0063), and the serum albumin level was significantly lower in the IC-mediated MPGN group (p = 0.0186). The serum C3 value was significantly lower in the CP-mediated MPGN group (p = 0.0317). Serum CH50 values were also lower in the CP-mediated MPGN group (p = 0.0404). However, glomerular deposition of C3 showed no significant differences in immunofluorescence findings. The 148.6-month renal survival rate was similar in both groups (p = 0.445). These results suggested no significant differences in complement activation of the solid phase in local glomeruli and therefore equivalent in renal prognosis [corrected].

Glomerular C3 Deposition Is an Independent Risk Factor for Allograft Failure in Kidney Transplant Recipients With Transplant Glomerulopathy

IntroductionTransplant glomerulopathy (TG) becomes increasingly prevalent in kidney transplant recipients over time, and it is strongly associated with allograft failure. To date, our prognostic biomarkers and understanding of the processes of immunologic injury in TG are limited.MethodsThis is a retrospective cohort analysis of kidney transplant recipients with TG (double contours of the glomerular basement membrane as defined by the chronic glomerulopathy score). Glomerular deposition of the complement protein C3 was determined, and its association with allograft survival was analyzed by Cox regression analysis.ResultsOf the 111 patients with TG, 72 (65%) had allograft failure, with a median follow-up time of 3 years from biopsy diagnosis of TG. C3-positive compared to C3-negative patients did not differ with respect to cause of end-stage renal disease, induction or maintenance immunosuppression, or sensitization. A greater proportion of patients with glomerular C3 deposition developed allograft failure compared to those with no C3 deposition (78% vs. 55%, P = 0.01). C3 deposition was independently associated with allograft failure in multivariate analyses (adjusted hazard ratio [HR] = 1.38, 95% confidence interval [CI] = 1.13−1.69, P = 0.002). There was no association between C4d or C1q deposition and allograft failure. Chronicity score was also associated with allograft failure in multivariate analysis (adjusted HR 1.26, 95% CI 1.12-1.41, P = 0.0001).ConclusionIn this cohort of patients with TG, glomerular C3 deposition was independently associated with a higher risk of allograft failure. These findings identify glomerular C3 as a novel prognostic indicator in patients with TG.

Corticosteroid therapy alone for the treatment of C3 glomerulonephritis in association with monoclonal gammopathy .

C3 glomerulonephritis (C3GN) is a form of proliferative glomerulonephritis characterized by dominant glomerular C3 deposition. There is currently no consensus guideline on therapy for this disease. Experience with corticosteroids alone is scant in C3GN. We report the experience of treating patients with C3GN in association with monoclonal gammopathy with corticosteroid at a single center. Corticosteroid therapy alone was used to treat 6 patients with C3GN who were also found to have monoclonal gammopathy at the time of presentation. Median age of this cohort was 65 years. Median estimated glomerular filtration rate (eGFR) by MDRD equation was 31.6 mL/min/1.73m2 at presentation. After a median duration of follow-up of 23.5 months, all patients showed improvement in proteinuria: median proteinuria reduced from 2.3 to 0.5 g/d. Four of 6 patients showed improvement in kidney function. One patient who had required renal replacement therapy recovered renal function. Median eGFR at follow-up was 38.7 mL/min/1.73m2. In patients with C3GN in association with monoclonal gammopathy, corticosteroid therapy alone may be a viable treatment option. Work-up should be done to exclude a hematologic neoplasm and inherited complement abnormalities before proceeding to corticosteroid therapy. .

Co-Deposition of IgM and C3 May Indicate Unfavorable Renal Outcomes in Adult Patients with Primary Focal Segmental Glomerulosclerosis

Background/Aims: We aimed to investigate the effects of glomerular IgM and C3 deposition on outcomes of adult patients with primary focal segmental glomerulosclerosis (FSGS). Methods: In this retrospective analysis, 86 consecutive adult patients with biopsy-proven primary FSGS were stratified into 3 groups according to their histopathological features: IgM– C3–, IgM+ C3–, and IgM+ C3+. Primary outcome was defined as at least a 50% reduction in baseline estimated glomerular filtration rate (eGFR) or development of kidney failure, while complete or partial remission rates were secondary outcomes. Results: Glomerular IgM deposits were found in 44 (51.1%) patients, 22 (25.5%) of which presented with accompanying C3 deposition. Patients in IgM+ C3+ group had higher level of proteinuria (5.6 g/24 h [3.77–8.5], p = 0.073), higher percentage of segmental glomerulosclerosis (20% [12.3–27.2], p = 0.001), and lower levels of eGFR (69 ± 37.2 mL/min/1.73 m2, p = 0.029) and serum albumin (2.71 ± 0.85 g/dL, p = 0.045) at the time of diagnosis. Despite 86.3% of patients in IgM+ C3+ group (19/22) received immunosuppressive treatment, the primary outcome was more common in patients in the IgM+ C3+ group compared with patients in IgM+ C3– and IgM– C3– groups (11 [50%] vs. 2 [9%] and 11 [26.1%] respectively [p = 0.010]). Complete or partial remission rates were lower in patients in the IgM+ C3+ group (5/22, 22.7%), as well (p = 0.043). Multivariate Cox regression analysis revealed that IgM and C3 co-deposition was an independent risk factor associated with primary outcome (hazard ratio 3.355, 95% CI 1.349–8.344, p = 0.009). Conclusions: Glomerular IgM and C3 co-deposition is a predictor of unfavorable renal outcomes in adult patients with primary FSGS.

Properdin binds independent of complement activation in an in vivo model of anti–glomerular basement membrane disease

Properdin is the only known positive regulator of complement activation by stabilizing the alternative pathway convertase through C3 binding, thus prolonging its half-life. Recent invitro studies suggest that properdin may act as a specific pattern recognition molecule. To better understand the role of properdin invivo, we used an experimental model of acute anti-glomerular basement membrane disease with wild-type, C3- and properdin knockout mice. The model exhibited severe proteinuria, acute neutrophil infiltration and activation, classical and alternative pathway activation, and progressive glomerular deposition of properdin, C3 and C9. Although the acute renal injury was likely due to acute neutrophil activation, we found properdin deposition in C3-knockout mice that was not associated with IgG. Thus, properdin may deposit in injured tissues invivo independent of its main ligand C3.

Accelerated Glomerular Cell Senescence in Experimental Lupus Nephritis.

BackgroundThe aim of this study was to determine whether senescence in renal glomeruli is involved in lupus nephritis (LN); the expression of senescence-associated β-galactosidase (SA-β-Gal) and its association with glomerular lesions were investigated in a mouse model of LN.Material/MethodsEighteen MRL/lpr mice with severe proteinuria were randomly divided into 2 equal groups and intraperitoneally injected with dexamethasone (DEX) or saline; 4 age-matched mice with mild proteinuria served as controls. Serum creatinine and urinary protein levels were analyzed, and kidney histological changes were observed by periodic acid–Schiff and Sirius Red staining. SA-β-Gal was detected via histochemistry. Glomerular expression of collagen IV, α-SMA, and nephrin was analyzed by immunohistochemistry, and glomerular complement C3 deposition was tested by immunofluorescence. The relationships between SA-β-Gal expression and renal function or glomerular lesion markers were determined by Spearman’s correlation analysis.ResultsMice with severe proteinuria exhibited glomerular segmental sclerosis and endothelial cell proliferation. DEX administration suppressed these lesions but had no significant effect on 24-hour urinary protein levels. The elevated glomerular expression of SA-β-Gal in proteinuric mice was attenuated by DEX treatment. In addition, DEX treatment markedly downregulated glomerular C3 deposition and collagen IV and α-SMA expression, while significantly increasing nephrin expression. Furthermore, SA-β-Gal expression was positively correlated with urinary protein levels and expression of α-SMA.ConclusionsAccelerated senescence of glomerular cells may contribute to glomerular injury in LN.

The Clinical Impact of Glomerular Immunoglobulin M Deposition in Patients with Type 2 Diabetic Nephropathy

Glomerular immunoglobulin M (IgM) deposition is common in diabetic kidney disease. The clinical implication of IgM deposition in the renal tissues of type 2 diabetes mellitus patients with biopsy-proven diabetic nephropathy remains unclear. One hundred thirty-two patients with type 2 diabetes and biopsy-proven pure diabetic nephropathy were enrolled retrospectively. Clinicopathological features and renal outcomes were compared between patients with and without glomerular capillary IgM deposition. A Cox proportional hazards model was employed to identify the risk factors associated with renal survival. Fifty-two patients had positive linear glomerular capillary IgM staining. Patients with glomerular capillary IgM deposition presented with heavier proteinuria, and lower serum albumin. During 35.5 (12, 107) months of follow-up, patients with glomerular tuft IgM deposition had shorter renal survival than those with negative IgM deposition (39 [23.74, 54.26] versus (vs.) 64 [45.82, 82.18] months, P = 0.01). Patients with glomerular complement 1q (C1q) deposition showed worse renal survival than those lacking glomerular C1q deposition (36 [23.82, 48.18] vs. 60 [50.27, 69.74] months, P = 0.001). Worse renal outcome was observed in patients with glomerular C3 deposition than in those without glomerular C3 deposition (37 [22.43, 51.56] vs. 63 [51.75, 74.25] months, P = 0.001). Multivariate Cox proportional analysis demonstrated that combined glomerular capillary IgM and C1q deposition was an independent predictor of end-stage renal disease (hazard ratio 3.75, 95% CI[ 1.68,8.35], P = 0.001). Patients with diabetic nephropathy and combined glomerular capillary IgM and C1q deposition had unfavorable renal outcome, which indicates that IgM derived from B cells might be involved in diabetic kidney injury.

Autoimmune abnormalities of the alternative complement pathway in membranoproliferative glomerulonephritis and C3 glomerulopathy

Membranoproliferative glomerulonephritis (MPGN) is a rare chronic kidney disease associated with complement activation. Recent immunofluorescence-based classification distinguishes between immune complex (IC)-mediated MPGN, with glomerular IgG and C3 deposits, and C3 glomerulopathies (C3G), with predominant C3 deposits. Genetic and autoimmune abnormalities causing hyperactivation of the complement alternative pathway have been found as frequently in patients with immune complex-associated MPGN (IC-MPGN) as in those with C3G. In the last decade, there have been great advances in research into the autoimmune causes of IC-MPGN and C3G. The complement-activating autoantibodies called C3-nephritic factors (C3NeFs), which are present in 40-80% of patients, form a heterogeneous group of autoantibodies that stabilise the C3 convertase or the C5 convertase of the alternative pathway or both. A few patients, mainly with IC-MPGN, carry autoantibodies directed against the two components of the alternative pathway C3 convertase, factors B and C3b. Finally, autoantibodies against factor H, the main regulator of the alternative pathway, have been reported in a small proportion of patients with IC-MPGN or C3G. The identification of distinct pathogenetic patterns leading to kidney injury and of targets in the complement cascade may pave the way for tailored therapies for IC-MPGN and C3G, with specific complement inhibitors in the development pipeline.

Essential Roles for Mannose-Binding Lectin-Associated Serine Protease-1/3 in the Development of Lupus-Like Glomerulonephritis in MRL/lpr Mice.

The complement system, composed of the three activation pathways, has both protective and pathogenic roles in the development of systemic lupus erythematosus (or lupus), a prototypic autoimmune disease. The classical pathway contributes to the clearance of immune complexes (ICs) and apoptotic cells, whereas the alternative pathway (AP) exacerbates renal inflammation. The role of the lectin pathway (LP) in lupus has remained largely unknown. Mannose-binding lectin (MBL)-associated serine proteases (MASPs), which are associated with humoral pattern recognition molecules (MBL or ficolins), are the enzymatic constituents of the LP and AP. MASP-1 encoded by the Masp1 gene significantly contributes to the activation of the LP. After the binding of MBL/ficolins to pathogens or self-altered cells, MASP-1 autoactivates first, then activates MASP-2, and both participate in the formation of the LP C3 convertase C4b2a, whereas, MASP-3, the splice variant of the Masp1 gene, is required for the activation of the zymogen of factor D (FD), and finally participates in the formation of the AP C3 convertase C3bBb. To investigate the roles of MASP-1 and MASP-3 in lupus, we generated Masp1 gene knockout lupus-prone MRL/lpr mice (Masp1/3−/− MRL/lpr mice), lacking both MASP-1 and MASP-3, and analyzed their renal disease. As expected, sera from Masp1/3−/− MRL/lpr mice had no or markedly reduced activation of the LP and AP with zymogen forms of complement FD. Compared to their wild-type littermates, the Masp1/3−/− MRL/lpr mice had maintained serum C3 levels, little-to-no albuminuria, as well as significantly reduced glomerular C3 deposition levels and glomerular pathological score. On the other hand, there were no significant differences in the levels of serum anti-dsDNA antibody, circulating ICs, glomerular IgG and MBL/ficolins deposition, renal interstitial pathological score, urea nitrogen, and mortality between the wild-type and Masp1/3−/− MRL/lpr mice. Our data indicate that MASP-1/3 plays essential roles in the development of lupus-like glomerulonephritis in MRL/lpr mice, most likely via activation of the LP and/or AP.

Coding and Noncoding Variants in CFH Act Synergistically for Complement Activation in Immunoglobulin A Nephropathy

BackgroundIn immunoglobulin A nephropathy (IgAN), complement activation occurs in both the systemic circulation and in situ (glomerular). A recent IgAN-genome-wide association study (GWAS) identified 1q32 as an IgAN susceptible locus that contained the complement regulatory protein coding gene complement factor H (CFH). Here, we explored the combined genetic effects of coding and noncoding variants in CFH, rs6677604 and rs800292 on complement activation in IgAN. MethodsIn total, 1,194 IgAN patients and 900 healthy controls who were the same as the Beijing Discovery Cohort in our recent IgAN-GWAS were recruited. The genotyping information of rs800292 and rs6677604 were extracted from GWAS data, while the information regarding plasma C3 levels and mesangial C3 deposits were collected from medical records. ResultsWe found both rs800292-GG and rs6677604-GG were risk genotypes for complement activation in IgAN patients, as represented by lower plasma C3 levels in IgAN patients with rs800292-GG and a higher intensity of glomerular C3 deposits in those with rs6677604-GG, respectively. Additionally, IgAN patients with 2 risk genotypes (rs800292-GG and rs6677604-GG) showed a higher degree of complement activation compared to those with no risk genotypes (rs800292-AA/AG and rs6677604-AA/AG), as represented by both lower plasma C3 levels and a higher intensity of glomerular C3 deposits. Moreover, when compared to rs800292 or rs6677604 alone, the combined genetic effects of rs800292 and rs6677604 showed a stronger association with IgAN susceptibility. ConclusionsOur findings suggested that both coding and noncoding variants in CFH acted synergistically to regulate the degree of complement activation and thereby contributed to IgAN susceptibility.

The MFHR1 Fusion Protein Is a Novel Synthetic Multitarget Complement Inhibitor with Therapeutic Potential.

The complement system is essential for host defense, but uncontrolled complement system activation leads to severe, mostly renal pathologies, such as atypical hemolytic uremic syndrome or C3 glomerulopathy. Here, we investigated a novel combinational approach to modulate complement activation by targeting C3 and the terminal pathway simultaneously. The synthetic fusion protein MFHR1 links the regulatory domains of complement factor H (FH) with the C5 convertase/C5b-9 inhibitory fragment of the FH-related protein 1. In vitro, MFHR1 showed cofactor and decay acceleration activity and inhibited C5 convertase activation and C5b-9 assembly, which prevented C3b deposition and reduced C3a/C5a and C5b-9 generation. Furthermore, this fusion protein showed the ability to escape deregulation by FH-related proteins and form multimeric complexes with increased inhibitory activity. In addition to substantially inhibiting alternative and classic pathway activation, MFHR1 blocked hemolysis mediated by serum from a patient with aHUS expressing truncated FH. In FH-/- mice, MFHR1 administration augmented serum C3 levels, reduced abnormal glomerular C3 deposition, and ameliorated C3 glomerulopathy. Taking the unique design of MFHR1 into account, we suggest that the combination of proximal and terminal cascade inhibition together with the ability to form multimeric complexes explain the strong inhibitory capacity of MFHR1, which offers a novel basis for complement therapeutics.