Complement activation in progressive renal disease

The Janus-faced nature of complement in hemodialysis: interplay between complement, inflammation, and bioincompatibility unveiling a self-amplifying loop contributing to organ damage

In hemodialysis (HD), complement activation, bioincompatibility, and inflammation are intricately intertwined. In the 1970s, as HD became a routine therapy, the observation of complement pathway activation and transient leukopenia by cellulosic dialysis membranes triggered the bioincompatibility debate and its clinical relevance. Extensive deliberations have covered definitions, assessment markers, scope, and long-term clinical consequences of membrane-dependent bioincompatibility reactions. While complement pathways' interplay with coagulation and inflammation has been delineated, HD's focus has primarily been on developing more biocompatible membranes using advanced technologies. Recent advances and understanding of the current HD delivery mode (4-hour sessions, thrice weekly) suggest that factors beyond membrane characteristics play a significant role, and a more complex, multifactorial picture of bioincompatibility is emerging. Chronic activation of the complement system and persistent low-grade "uremic inflammation" in chronic kidney disease (CKD) and HD lead to premature inflammaging of the kidney, resembling aging in the general population. Cellular senescence, modulated by complement activation and the uremic milieu, contributes to chronic inflammaging. Additionally, the formation of neutrophil extracellular traps (NETs, process of NETosis) during HD and their biological activity in the interdialytic period can lead to dialysis-induced systemic stress. Thus, complement-inflammation manifestations in HD therapies extend beyond traditional membrane-related bioincompatibility consequences. Recent scientific knowledge is reshaping strategies to mitigate detrimental consequences of bioincompatibility, both technologically and in HD therapy delivery modes, to improve dialysis patient outcomes.

Renal Epithelial Complement C3 Expression Affects Kidney Fibrosis Progression

Kidney fibrosis is a hallmark of chronic kidney diseases. Evidence shows that genetic variability and complement component 3 (C3) might influence tubulointerstitial fibrosis. Still, the role of renal C3 production in the epithelial-to-mesenchymal transition (EMT) and genetically determined fibrosis progression remains undiscovered. The kidneys of fibrosis-resistant C57Bl/6J (B6) and fibrosis-prone CBA/J (CBA) and BALB/cJ (BalbC) mice (n = 4-8/group) were subjected to unilateral ureteral obstruction (UUO) and analyzed after 1, 3, and 7 days, along with human focal glomerular sclerotic (FSGS) and healthy kidneys. Mouse primary tubular epithelial cells (PTECs) were investigated after 24 h of treatment with transforming growth factor β (TGFβ) or complement anaphylatoxin 3a (C3a) agonist (n = 4/group). UUO resulted in delayed kidney injury in fibrosis-resistant B6 mice, but very early renal C3 messenger RNA (mRNA) induction in fibrosis-prone CBA and BalbC mice, along with collagen I (Col1a1) and collagen III (Col3a1). CBA depicted the fastest fibrosis progression with the highest C3, lipocalin-2 (Lcn2), Tgfb1, and chemokine (C-C motif) ligand 2 (Ccl2) expression. Human FSGS kidneys depicted C3 mRNA over-expression and strong tubular C3 immunostaining. In PTECs, C3a agonist treatment induced pro-fibrotic early growth response protein 1 (EGR1) expression and the EMT, independent of TGFβ signaling. We conclude that de novo renal tubular C3 synthesis is associated with the genetically determined kidney fibrosis progression rate in mice and the pathogenesis of FSGS in humans. This tubular C3 overproduction can, through local pro-fibrotic effects, influence the progression of chronic kidney disease.

Tubular insulin-induced gene 1 deficiency promotes NAD+ consumption and exacerbates kidney fibrosis

Profibrotic proximal tubules (PT) were identified as a unique phenotype of proximal tubule cells (PTCs) in renal fibrosis by single-cell RNA sequencing (scRNA-seq). Controlling the process of renal fibrosis requires understanding how to manage the S1 subset's branch to the S3 subset rather than to the profibrotic PT subset. Insulin-induced gene 1 (Insig1) is one of the branch-dependent genes involved in controlling this process, although its role in renal fibrosis is unknown. Here, we discovered that tubular Insig1 deficiency, rather than fibroblast Insig1 deficiency, plays a detrimental role in the pathogenesis of renal fibrosis in vivo and in vitro. Overexpression of Insig1 profoundly inhibited renal fibrosis. Mechanistically, Insig1 deletion in PTCs boosted SREBP1 nuclear localization, increasing Aldh1a1 transcriptional activity, causing excessive NAD+ consumption and ER enlargement, as well as accelerating renal fibrosis. We also identified nicardipine as a selective inhibitor of Aldh1a1, which could restore NAD+ and maintain ER homeostasis, as well as improve renal fibrosis. Together, our findings support tubular Insig1 as a new therapeutic target for chronic kidney disease (CKD).

A Rare Case of Atypical Hemolytic Uremic Syndrome Presenting as Chronic Interstitial Nephritis

Atypical hemolytic uremic syndrome commonly presents as rapidly progressive renal failure and is histologically characterized by thrombotic microangiopathy (TMA). TMA presenting with acute renal failure requires aggressive medical management. Here, we present a case of a 30-year-old man who presented with a history of accelerated hypertension and a strong family history of end-stage renal disease, in September 2023. Upon evaluation, he was found to have a creatinine level of 2 mg/dl, bland urine and normal-sized kidneys; a renal biopsy revealed chronic interstitial nephritis. Genetic analysis for autosomal dominant tubulointerstitial kidney disease and nephronophthisis yielded negative results. The patient was managed with antihypertensive medications. In January 2024, he was admitted with a history of confusion, headache, and alcohol binge. He had a blood pressure of 200/100 mmHg and had grade 3 hypertensive retinopathy. Laboratory tests revealed anemia with thrombocytopenia, bland urine, normal coagulation parameters, indirect hyperbilirubinemia, normal-sized kidneys on ultrasound, and elevated lactate dehydrogenase levels. MRI of the brain revealed symmetrical hyperintensities in bilateral cerebellum and the dorsal brainstem. Complement levels revealed low C3 levels and genetic analysis revealed a homozygous deletion in the complement factor H-related 3 (CFHR3) gene. The autoantibody for complement factor H was negative. The patient was managed conservatively with adequate blood pressure control. This case highlights the effects of complement dysregulation on the renal tubulointerstitium.

The complement system in the pathogenesis and progression of kidney diseases: What doesn't kill you makes you older

The Complement System is an evolutionarily conserved component of immunity that plays a key role in host defense against infections and tissue homeostasis. However, the dysfunction of the Complement System can result in tissue damage and inflammation, thereby contributing to the development and progression of various renal diseases, ranging from atypical Hemolytic Uremic Syndrome to glomerulonephritis. Therapeutic interventions targeting the complement system have demonstrated promising results in both preclinical and clinical studies. Currently, several complement inhibitors are being developed for the treatment of complement-mediated renal diseases. This review aims to summarize the most recent insights into complement activation and therapeutic inhibition in renal diseases. Furthermore, it offers potential directions for the future rational use of complement inhibitor drugs in the context of renal diseases.

Meta-analysis of Transcriptomic Data from Lung Autopsy and Cellular Models of SARS-CoV-2 Infection

Severe COVID-19 is a systemic disorder involving excessive inflammatory response, metabolic dysfunction, multi-organ damage, and several clinical features. Here, we performed a transcriptome meta-analysis investigating genes and molecular mechanisms related to COVID-19 severity and outcomes. First, transcriptomic data of cellular models of SARS-CoV-2 infection were compiled to understand the first response to the infection. Then, transcriptomic data from lung autopsies of patients deceased due to COVID-19 were compiled to analyze altered genes of damaged lung tissue. These analyses were followed by functional enrichment analyses and gene-phenotype association. A biological network was constructed using the disturbed genes in the lung autopsy meta-analysis. Central genes were defined considering closeness and betweenness centrality degrees. A sub-network phenotype-gene interaction analysis was performed. The meta-analysis of cellular models found genes mainly associated with cytokine signaling and other pathogen response pathways. The meta-analysis of lung autopsy tissue found genes associated with coagulopathy, lung fibrosis, multi-organ damage, and long COVID-19. Only genes DNAH9 and FAM216B were found perturbed in both meta-analyses. BLNK, FABP4, GRIA1, ATF3, TREM2, TPPP, TPPP3, FOS, ALB, JUNB, LMNA, ADRB2, PPARG, TNNC1, and EGR1 were identified as central elements among perturbed genes in lung autopsy and were found associated with several clinical features of severe COVID-19. Central elements were suggested as interesting targets to investigate the relation with features of COVID-19 severity, such as coagulopathy, lung fibrosis, and organ damage.

Screening candidate diagnostic biomarkers for diabetic kidney disease

BACKGROUND

There are big differences in treatments and prognosis between diabetic kidney disease (DKD) and non-diabetic renal disease (NDRD). However, DKD patients couldn't be diagnosed early due to lack of special biomarkers. Urine is an ideal non-invasive sample for screening DKD biomarkers. This study aims to explore DKD special biomarkers by urinary proteomics.

MATERIALS AND METHODS

According to the result of renal biopsy, 142 type 2 diabetes mellitus (T2DM) patients were divided into 2 groups: DKD (n = 83) and NDRD (n = 59). Ten patients were selected from each group to define urinary protein profiles by label-free quantitative proteomics. The candidate proteins were further verifyied by parallel reaction monitoring (PRM) methods (n = 40). Proteins which perform the same trend both in PRM and proteomics were verified by enzyme-linked immunosorbent assays (ELISA) with expanding the sample size (n = 82). The area under the receiver operating characteristic curve (AUC) was used to evaluate the accuracy of diagnostic biomarkers.

RESULTS

We identified 417 peptides in urinary proteins showing significant difference between DKD and NDRD. PRM verification identified C7, SERPINA4, IGHG1, SEMG2, PGLS, GGT1, CDH2, CDH1 was consistent with the proteomic results and p < 0.05. Three potential biomarkers for DKD, C7, SERPINA4, and gGT1, were verified by ELISA. The combinatied SERPINA4/Ucr and gGT1/Ucr (AUC = 0.758, p = 0.001) displayed higher diagnostic efficiency than C7/Ucr (AUC = 0.632, p = 0.048), SERPINA4/Ucr (AUC = 0.661, p = 0.032), and gGT1/Ucr (AUC = 0.661, p = 0.029) respectively.

CONCLUSIONS

The combined index SERPINA4/Ucr and gGT1/Ucr can be considered as candidate biomarkers for diabetic nephropathy after adjusting by urine creatinine.

Identification and validation of disulfidptosis-related gene signatures and their subtype in diabetic nephropathy

Background: Diabetic nephropathy (DN) is the most common complication of diabetes, and its pathogenesis is complex involving a variety of programmed cell death, inflammatory responses, and autophagy mechanisms. Disulfidptosis is a newly discovered mechanism of cell death. There are little studies about the role of disulfidptosis on DN. Methods: First, we obtained the data required for this study from the GeneCards database, the Nephroseq v5 database, and the GEO database. Through differential analysis, we obtained differential disulfidptosis-related genes. At the same time, through WGCNA analysis, we obtained key module genes in DN patients. The obtained intersecting genes were further screened by Lasso as well as SVM-RFE. By intersecting the results of the two, we ended up with a key gene for diabetic nephropathy. The diagnostic performance and expression of key genes were verified by the GSE30528, GSE30529, GSE96804, and Nephroseq v5 datasets. Using clinical information from the Nephroseq v5 database, we investigated the correlation between the expression of key genes and estimated glomerular filtration rate (eGFR) and serum creatinine content. Next, we constructed a nomogram and analyzed the immune microenvironment of patients with DN. The identification of subtypes facilitates individualized treatment of patients with DN. Results: We obtained 91 differential disulfidptosis-related genes. Through WGCNA analysis, we obtained 39 key module genes in DN patients. Taking the intersection of the two, we preliminarily screened 20 genes characteristic of DN. Through correlation analysis, we found that these 20 genes are positively correlated with each other. Further screening by Lasso and SVM-RFE algorithms and intersecting the results of the two, we identified CXCL6, CD48, C1QB, and COL6A3 as key genes in DN. Clinical correlation analysis found that the expression levels of key genes were closely related to eGFR. Immune cell infiltration is higher in samples from patients with DN than in normal samples. Conclusion: We identified and validated 4 DN key genes from disulfidptosis-related genes that CXCL6, CD48, C1QB, and COL6A3 may be key genes that promote the onset of DN and are closely related to the eGFR and immune cell infiltrated in the kidney tissue.

COVID-19 and Kidney: The Importance of Follow-Up and Long-Term Screening

Renal involvement and kidney injury are common in COVID-19 patients, and the symptoms are more severe if the patient already has renal impairment. Renal involvement in COVID-19 is multifactorial, and the renal tubule is mainly affected, along with podocyte injury during SARS-CoV-2 infection. Inflammation, complement activation, hypercoagulation, and crosstalk between the kidney and lungs, brain, and heart are contributory factors. Kidney injury during the acute phase, termed acute kidney injury (AKI), may proceed to chronic kidney disease if the patient is discharged with renal impairment. Both AKI and chronic kidney disease (CKD) increase mortality in COVID-19 patients. Further, COVID-19 infection in patients suffering from CKD is more severe and increases the mortality rate. Thus, it is important to address both categories of patients, either developing AKI or CKD after COVID-19 or previously having CKD, with proper management and treatment. This review discusses the pathophysiology involved in AKI and CKD in COVID-19 infection, followed by management and treatment of AKI and CKD. This is followed by a discussion of the importance of screening and treatment of CKD patients infected with COVID-19 and future perspectives to improve treatment in such patients.

Challenges in IgA Nephropathy Management: An Era of Complement Inhibition

IgA nephropathy (IgAN) is the most common glomerular disease worldwide, with an estimated annual incidence of 25 per million adults. Despite optimized supportive care, some patients fail to achieve disease control and suffer progressive deterioration of kidney function. In this subpopulation of patients, the Kidney Disease: Improving Global Outcomes 2021 guidelines recommend consideration of corticosteroids; however, their use is associated with significant side effects. Ongoing clinical trials are expected to identify corticosteroid-sparing therapies to help improve treatment and prognosis for patients with IgAN. It has been well-documented that the complement system plays a significant role in IgAN pathogenesis, and several complement inhibitors are now entering late-stage clinical development. This review evaluates what we know about the role of complement in the pathophysiology of IgAN and considers how the availability of targeted complement inhibitors may impact future clinical practice. Key knowledge gaps are evaluated, and research opportunities are recommended to help guide clinical decision-making and optimize patient outcomes. Such gaps include evaluating the relative contribution of the alternative and lectin pathways to disease pathogenesis, and the importance of determining the dominant pathway driving IgAN progression. Continued research into the staining of complement proteins in kidney biopsies and identifying targeted biomarkers to assess disease progression and treatment responses will also be needed to support the implementation of newer therapies in clinical practice. Considering the future horizons for enhancing the care of patients with IgAN, tackling the outstanding challenges now will help prepare for the best possible future outcomes.

Identifying C1QB, ITGAM, and ITGB2 as potential diagnostic candidate genes for diabetic nephropathy using bioinformatics analysis

Background

Diabetic nephropathy (DN), the most intractable complication in diabetes patients, can lead to proteinuria and progressive reduction of glomerular filtration rate (GFR), which seriously affects the quality of life of patients and is associated with high mortality. However, the lack of accurate key candidate genes makes diagnosis of DN very difficult. This study aimed to identify new potential candidate genes for DN using bioinformatics, and elucidated the mechanism of DN at the cellular transcriptional level.

Methods

The microarray dataset GSE30529 was downloaded from the Gene Expression Omnibus Database (GEO), and the differentially expressed genes (DEGs) were screened by R software. We used Gene Ontology (GO), gene set enrichment analysis (GSEA), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis to identify the signal pathways and genes. Protein-protein interaction (PPI) networks were constructed using the STRING database. The GSE30122 dataset was selected as the validation set. Receiver operating characteristic (ROC) curves were applied to evaluate the predictive value of genes. An area under curve (AUC) greater than 0.85 was considered to be of high diagnostic value. Several online databases were used to predict miRNAs and transcription factors (TFs) capable of binding hub genes. Cytoscape was used for constructing a miRNA-mRNA-TF network. The online database 'nephroseq' predicted the correlation between genes and kidney function. The serum level of creatinine, BUN, and albumin, and the urinary protein/creatinine ratio of the DN rat model were detected. The expression of hub genes was further verified through qPCR. Data were analyzed statistically using Student's t-test by the 'ggpubr' package.

Results

A total of 463 DEGs were identified from GSE30529. According to enrichment analysis, DEGs were mainly enriched in the immune response, coagulation cascades, and cytokine signaling pathways. Twenty hub genes with the highest connectivity and several gene cluster modules were ensured using Cytoscape. Five high diagnostic hub genes were selected and verified by GSE30122. The MiRNA-mRNA-TF network suggested a potential RNA regulatory relationship. Hub gene expression was positively correlated with kidney injury. The level of serum creatinine and BUN in the DN group was higher than in the control group (unpaired t test, t = 3.391, df = 4, p = 0.0275, r = 0.861). Meanwhile, the DN group had a higher urinary protein/creatinine ratio (unpaired t test, t = 17.23, df = 16, p < 0.001, r = 0.974). QPCR results showed that the potential candidate genes for DN diagnosis included C1QB, ITGAM, and ITGB2.

Conclusions

We identified C1QB, ITGAM and ITGB2 as potential candidate genes for DN diagnosis and therapy and provided insight into the mechanisms of DN development at transcriptome level. We further completed the construction of miRNA-mRNA-TF network to propose potential RNA regulatory pathways adjusting disease progression in DN.

Proteomic signature associated with chronic kidney disease (CKD) progression identified by data-independent acquisition mass spectrometry

BACKGROUND

Halting progression of chronic kidney disease (CKD) to established end stage kidney disease is a major goal of global health research. The mechanism of CKD progression involves pro-inflammatory, pro-fibrotic, and vascular pathways, but pathophysiological differentiation is currently lacking.

METHODS

Plasma samples of 414 non-dialysis CKD patients, 170 fast progressors (with ∂ eGFR-3 ml/min/1.73 m2/year or worse) and 244 stable patients (∂ eGFR of - 0.5 to + 1 ml/min/1.73 m2/year) with a broad range of kidney disease aetiologies, were obtained and interrogated for proteomic signals with SWATH-MS. We applied a machine learning approach to feature selection of proteins quantifiable in at least 20% of the samples, using the Boruta algorithm. Biological pathways enriched by these proteins were identified using ClueGo pathway analyses.

RESULTS

The resulting digitised proteomic maps inclusive of 626 proteins were investigated in tandem with available clinical data to identify biomarkers of progression. The machine learning model using Boruta Feature Selection identified 25 biomarkers as being important to progression type classification (Area Under the Curve = 0.81, Accuracy = 0.72). Our functional enrichment analysis revealed associations with the complement cascade pathway, which is relevant to CKD as the kidney is particularly vulnerable to complement overactivation. This provides further evidence to target complement inhibition as a potential approach to modulating the progression of diabetic nephropathy. Proteins involved in the ubiquitin-proteasome pathway, a crucial protein degradation system, were also found to be significantly enriched.

CONCLUSIONS

The in-depth proteomic characterisation of this large-scale CKD cohort is a step toward generating mechanism-based hypotheses that might lend themselves to future drug targeting. Candidate biomarkers will be validated in samples from selected patients in other large non-dialysis CKD cohorts using a targeted mass spectrometric analysis.

Metalloporphyrins as Tools for Deciphering the Role of Heme Oxygenase in Renal Immune Injury

Renal immune injury is a frequent cause of end-stage renal disease, and, despite the progress made in understanding underlying pathogenetic mechanisms, current treatments to preserve renal function continue to be based mainly on systemic immunosuppression. Small molecules, naturally occurring biologic agents, show considerable promise in acting as disease modifiers and may provide novel therapeutic leads. Certain naturally occurring or synthetic Metalloporphyrins (Mps) can act as disease modifiers by increasing heme oxygenase (HO) enzymatic activity and/or synthesis of the inducible HO isoform (HO-1). Depending on the metal moiety of the Mp employed, these effects may occur in tandem or can be discordant (increased HO-1 synthesis but inhibition of enzyme activity). This review discusses effects of Mps, with varying redox-active transitional metals and cyclic porphyrin cores, on mechanisms underlying pathogenesis and outcomes of renal immune injury.

C3 glomerulopathy associated with both hypertensive retinopathy and purtscher-like retinopathy

Purpose

This article reports the case of a 21-year-old woman with both hypertensive retinopathy and Purtscher-like retinopathy in association with C3 glomerulopathy.

Observations

The patient was referred for bilateral painless vision loss with posterior pole cotton wool spots, optic disc edema, and confluent retinal whitening suggesting a mixed picture of hypertensive retinopathy, with initial blood pressure 236/152, and Purtscher-like retinopathy. She was subsequently diagnosed with C3 glomerulopathy which likely caused her severe hypertension and which likely occurred alongside Purtscher-like retinopathy due to a shared pathogenesis of complement dysregulation. Follow up examination and imaging revealed gradual improvement in visual acuity, almost complete resolution of fundus exam abnormalities, improvement in macular nonperfusion, resolution of disc leakage and choroidal leakage, resolution of macular edema, and residual outer retinal hyperreflective foci in both eyes.

Conclusion and importance

This case represents the first report of both Purtscher-like retinopathy and hypertensive retinopathy occurring in association with C3 glomerulopathy. It supports investigation of anti-complement therapy as a potential treatment for Purtscher-like retinopathy.

Experimental Study on Danggui Shaoyao San Improving Renal Fibrosis by Promoting Autophagy

Renal fibrosis could lead to chronic kidney disease (CKD) developing into the end-stage with its pathological manifestation is the deposition of extracellular matrix (ECM). Danggui Shaoyao San (DSS) is one of the widely used herbal formulas in ancient China, which has been proven to have efficacy in the treatment of CKD. The experiment employed TGF-β1 to stimulate the NRK-52E cells to establish a renal fibrosis model. With rapamycin (RAPA) used as the positive control, we detected the expression of fibronectin (FN), caspase-3, and autophagy-related proteins in the NRK-52E cells treated with DSS by Western blot and immunofluorescence assay. In order to further verify autophagy-promoting effects of DSS, we adopted 3-MA to inhibit autophagy. The experiment has found that DSS can lower the protein levels of FN and caspase-3 in the NRK-52E cells induced by TGF-β1. After TGF-β1 stimulation, the expression of LC3 II/I and Beclin 1 has decreased, and the protein levels of mTOR and p62 have increased. Consistent with rapamycin, DSS has significantly reduced these effects of TGF-β1. It has also been found that DSS can increase the expression of LC3 II/I and Beclin 1 proteins and can reduce the level of mTOR in cells treated with 3-MA, suggesting that DSS can promote autophagy. In conclusion, DSS has been proved to reduce the apoptosis and fibrosis of NRK-52E cells induced by TGF-β1, which may be achieved by promoting autophagy.

Purtscher-like retinopathy: Ocular findings in a young woman with chronic kidney disease

Purpose

To report a case of Purtscher-like retinopathy treated with systemic steroids in a young woman with chronic kidney disease.

Observations

An 18-year-old female with a stage 3b chronic kidney disease presented with bilateral, sudden vision loss during an influenza-like syndrome. Best corrected visual acuity (BCVA) was 20/32 bilaterally and fundoscopic examination revealed cotton-wool spots, Purtscher flecken and intraretinal haemorrhages. Flourescein angiography showed areas of retinal ischemia with vascular leakage and optical coherence tomography showed cystoid macular oedema. The patient completed a short-course treatment with high-dose oral steroids. After 1 week, BCVA was 20/20 bilaterally. After 1 month, fundoscopy and imaging evaluation revealed complete resolution of the retinal injury. This favorable outcome remained stable throughout the 1-year follow-up.

Conclusions

AND IMPORTANCE: Purtscher-like retinopathy is a rare, sight-threatening retinal disorder. We described a case of retinal injury presumably related to chronic kidney disease and possibly triggered by an influenza-like syndrome, with a favorable visual recovery.

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Purtscher-like retinopathy is a rare, sight-threatening retinal disorder.

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There is a possible association to chronic kidney disease.

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It frequently leads to sudden but reversible visual loss.

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Fundoscopy reveals posterior pole cotton-wool spots, haemorrhages and Purtscher flecken.

Total coumarin derivates from Hydrangea paniculata attenuate renal injuries in cationized-BSA induced membranous nephropathy by inhibiting complement activation and interleukin 10-mediated interstitial fibrosis

BACKGROUND

Total coumarins extracted from Hydrangea. Paniculata, Sieb (HP) have showed renal protective effect in several experimental acute and chronic kidney diseases.

PURPOSE

The aim of current study is to evaluate renal protective effect of HP against cationized-BSA (c-BSA) induced experimental membranous nephritis (MN), and further investigate its underlying mechanisms.

METHODS

Rat MN model was established by intravenous injection of 5 mg c-BSA for consecutive 14 days, and after albuminuria confirmed, HP was orally administrated with 7.5, 15, 30 mg/kg for nine weeks. The renal function was measured and histopathological injuries were observed. RNA sequencing was used to analyze the altered signaling pathways in kidneys. Pharmacokinetics was performed to investigate the pharmacodynamics of major ingredients in HP and possible metabolites. Discover X platform helped to clarify the possible molecular mechanisms of major compound in HP.

RESULTS

HP administration could significantly improve the renal function, and ameliorate the dyslipidemia and histopathological injuries. mRNA sequencing demonstrated that HP had anti-inflammation and anti-fibrosis effects possible through down-regulating the complement activation and PI3K-AKT pathways. Pharmacokinetics demonstrated that skimmin and 7-hydoxycoumarin (7-HC) were major compound or metabolite in plasma after oral administration. Based on Discover X platform, we confirmed that skimmin and 7-HC inhibited the   IL10 production by inflammatory macrophages through blocking PI3K-AKT and NFκB signaling pathways. Finally, we demonstrated that HP protected tubulointerstitium from complement attack by reducing the C3 self-production and auto-cleavage in tubular cells.

CONCLUSIONS

HP has a renal protective effect, and its drug development may provide one alternative strategy to treat immune-mediated nephropathy.

Complement Blockade in Recipients Prevents Delayed Graft Function and Delays Antibody-mediated Rejection in a Nonhuman Primate Model of Kidney Transplantation

BACKGROUND

Complement activation in kidney transplantation is implicated in the pathogenesis of delayed graft function (DGF). This study evaluated the therapeutic efficacy of high-dose recombinant human C1 esterase inhibitor (rhC1INH) to prevent DGF in a nonhuman primate model of kidney transplantation after brain death and prolonged cold ischemia.

METHODS

Brain death donors underwent 20 h of conventional management. Procured kidneys were stored on ice for 44-48 h, then transplanted into ABO-compatible major histocompatibility complex-mismatched recipients. Recipients were treated with vehicle (n = 5) or rhC1INH 500 U/kg plus heparin 40 U/kg (n = 8) before reperfusion, 12 h, and 24 h posttransplant. Recipients were followed up for 120 d.

RESULTS

Of vehicle-treated recipients, 80% (4 of 5) developed DGF versus 12.5% (1 of 8) rhC1INH-treated recipients (P = 0.015). rhC1INH-treated recipients had faster creatinine recovery, superior urinary output, and reduced urinary neutrophil gelatinase-associated lipocalin and tissue inhibitor of metalloproteinases 2-insulin-like growth factor-binding protein 7 throughout the first week, indicating reduced allograft injury. Treated recipients presented lower postreperfusion plasma interleukin (IL)-6, IL-8, tumor necrosis factor-alpha, and IL-18, lower day 4 monocyte chemoattractant protein 1, and trended toward lower C5. Treated recipients exhibited less C3b/C5b-9 deposition on day 7 biopsies. rhC1INH-treated animals also trended toward prolonged mediated rejection-free survival.

CONCLUSIONS

Our results recommend high-dose C1INH complement blockade in transplant recipients as an effective strategy to reduce kidney injury and inflammation, prevent DGF, delay antibody-mediated rejection development, and improve transplant outcomes.

The influences of α-hemolytic Streptococcus on class switching and complement activation of human tonsillar cells in IgA nephropathy

While β-hemolytic streptococcus (β-HS) infections are known to predispose patients to acute poststreptococcal glomerulonephritis, there is evidence that implicates α-hemolytic streptococcus (α-HS) in IgA nephropathy (IgAN). The alternative pathway of the complement system has also been implicated in IgAN. We aimed to explore the association between α-HS and complement activation in human tonsillar mononuclear cells (TMCs) in IgAN. In our study, α-HS induced higher IgA levels than IgG levels, while β-HS increased higher IgG levels than IgA levels with more activation-induced cytidine deaminase, in TMCs in the IgAN group. Aberrant IgA1 O-glycosylation levels were higher in IgAN patients with α-HS. C3 and C3b expression was decreased in IgAN patients, but in chronic tonsillitis control patients, the expression decreased only after stimulation with β-HS. Complement factor B and H (CFH) mRNA increased, but the CFH concentration in culture supernatants decreased with α-HS. The percentage of CD19 + CD35 + cells/complement receptor 1 (CR1) decreased with α-HS more than with β-HS, while CD19 + CD21 + cells/complement receptor 2 (CR2) increased more with β-HS than with α-HS. The component nephritis-associated plasmin receptor (NAPlr) of α-HS was not detected on tonsillar or kidney tissues in IgAN patients and was positive on cultured TMCs and mesangial cells. We concluded that α-HS induced the secretion of aberrantly O-glycosylated IgA while decreasing the levels of the inhibitory factor CFH in culture supernatants and CR1 + B cells. These findings provide testable mechanisms that relate α-HS infection to abnormal mucosal responses involving the alternative complement pathway in IgAN.

Effect of dipeptidyl peptidase-4 inhibitors on complement activation

BACKGROUND

Adverse activation of the complement cascade in the innate immune system appears to be involved in development of vascular complications in diabetes. Dipeptidyl peptidase-4 (DPP-4) is a cell surface serine protease expressed in a variety of tissues. DPP-4 inhibitors are widely used in treatment of type 2 diabetes and appear to yield beneficial pleiotropic effects beyond their glucose-lowering action, for example, renoprotective and anti-inflammatory properties, but the exact mechanisms remain unknown. We hypothesised that DPP-4 inhibitors block adverse complement activation by inhibiting complement-activating serine proteases.

MATERIALS AND METHODS

We analysed the effects of 7 different DPP-4 inhibitors on the lectin and classical pathway of the complement system in vitro by quantifying complement factor C4b deposition onto mannan or IgG coated surfaces, respectively. Furthermore, plasma concentrations of mannan-binding lectin (MBL), soluble membrane attack complex (sMAC), and C4b deposition were quantified in 71 patients with a recent acute coronary syndrome and glucose disturbances, randomly assigned to sitagliptin 100 mg (n = 34) or placebo (n = 37) for 12 weeks.

RESULTS

All the 7 DPP-4 inhibitors tested in the study directly inhibited functional activity of the lectin pathway in a dose-dependent manner with varying potency in vitro. In vivo, MBL, sMAC, and C4b declined significantly during follow-up in both groups without significant effect of sitagliptin.

CONCLUSIONS

We demonstrated an inhibitory effect of DPP-4 inhibitors on the lectin pathway in vitro. The clinical relevance of this effect of DPP-4 inhibitors remains to be fully elucidated.

Diabetic retinopathy in the Eastern Morocco: Different stage frequencies and associated risk factors

Diabetes is a major cause of morbidity and mortality worldwide. It can affect many organs and, over time, leads to serious complications. Diabetic retinopathy (DR), a specific ocular complication of diabetes, remains the leading cause of vision loss and vision impairment in adults. This work is the first in Eastern Morocco aimed at identifying the different stages of DR and to determine their frequencies and associated risk factors. It is a case-control study conducted from December 2018 to July 2019 at the ophthalmology department of Al-Irfane Clinic (Oujda). Data were obtained from a specific questionnaire involving 244 diabetic patients (122 cases with retinopathy vs 122 controls without retinopathy). All results were analyzed by the EPI-Info software. This study shows a predominance of proliferative diabetic retinopathy (PDR) with 57.4% of cases (uncomplicated proliferative diabetic retinopathy (UPDR): 23.8%; complicated proliferative diabetic retinopathy (CPDR): 33.6%). The non-proliferative diabetic retinopathy (NPDR) represents 42.6% (minimal NPDR: 8.2%; moderate NPDR: 26.2%; severe NPDR: 8.2%). The determinants of DR were insulin therapy, high blood pressure, poor glycemic control and duration of diabetes. Regarding the chronological evolution, retinopathy precedes nephropathy. Diabetic nephropathy (DN) was present in 10.6% of cases especially in patients with PDR. In summary, the frequency of PDR was higher than that of NPDR. DR appears before DN with a high frequency of DN in patients with PDR. Good glycemic control and blood pressure control, as well as early diagnosis are the major preventive measures against DR.

Uromodulin aggravates renal tubulointerstitial injury through activation of the complement pathway in rats

Uromodulin (Umod) is the most abundant constituent of urine in humans and exclusively found in the kidney tubular epithelium. However, the specific role of Umod in renal tubulointerstitial injury is yet to be understood. The present study was conducted with aim of investigating the potential therapeutic mechanism of Umod in the regulation of renal tubulointerstitial injury. Protein expression of Umod in renal tubular epithelial cells was measured with the conduction of Western blot analysis. Enzyme-linked immunosorbent assay and immunofluorescence assay were performed to detect the complement activation products and the activation products of surface deposition. The expression of C1q, C2, C4, B factor, C3, C5, H factor, CD46, CD55, C3aR, and C5aR were determined with the use of reverse-transcription quantitative polymerase chain reaction and Western blot analyses. Subsequently, the unilateral ureteral obstruction (UUO) rat model was established. Renal tubulointerstitial injury was assessed with the application of hematoxylin-eosin staining and Masson staining in rats. UUO rats and normal rats were injected with si-NC or si-Umod and complement inhibitor. UUO rats were observed to have serious impairment of kidney tubule, renal tubular dilation, and epithelial atrophy, with downregulated Umod and activated complement pathway. Silencing of Umod resulted in the activation of complement system while promoting interstitial fibrosis in renal tubules. Moreover, addition of complement inhibitor significantly alleviated the renal tubule injury and fibrosis. Collectively, our study suggests that silencing of Umod mediates the complement pathway, exacerbating renal tubulointerstitial injury in rats, which provides insight into the development of novel therapeutic agents for renal tubulointerstitial injury.

Identification of key signaling pathways induced by SARS-CoV2 that underlie thrombosis and vascular injury in COVID-19 patients

The SARS-CoV-2 pandemic has led to hundreds of thousands of deaths and billions of dollars in economic damage. The immune response elicited from this virus is poorly understood. An alarming number of cases have arisen where COVID-19 patients develop complications on top of the symptoms already associated with SARS, such as thrombosis, injuries of vascular system, kidney, and liver, as well as Kawasaki disease. In this review, a bioinformatics approach was used to elucidate the immune response triggered by SARS-CoV-2 infection in primary human lung epithelial and transformed human lung alveolar. Additionally, examined the potential mechanism behind several complications that have been associated with COVID-19 and determined that a specific cytokine storm is leading to excessive neutrophil recruitment. These neutrophils are directly leading to thrombosis, organ damage, and complement activation via neutrophil extracellular trap release.

Complement C7 is Specifically Expressed in Mesangial Cells and is a Potential Diagnostic Biomarker for Diabetic Nephropathy and is Regulated by miR-494-3p and miR-574-5p

BACKGROUND

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease, but it remains relatively underdiagnosed.

OBJECTIVE

In this study, we aimed to explore the key regulatory pathways and potential biomarkers related to DN using integrated bioinformatics analysis and validation.

METHODS

First, the microarray data of the GSE30528 and GSE96804 datasets were downloaded from the Gene Expression Omnibus (GEO) database, and differentially expressed genes (DEGs) were screened. Then, weighted gene coexpression network analysis (WGCNA), gene ontology (GO) annotation, gene set enrichment analysis (GSEA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to identify key pathways and genes. qRT-PCR and receiver operating characteristic (ROC) curves were used to validate our results. Furthermore, single-cell RNA sequencing (scRNA-seq) data were reanalyzed to investigate the expression specificity of C7 in DN cells. An online database search and luciferase reporter assay identified the target relationship between miRNAs and C7.

RESULTS

The "complement and coagulation cascades" were significantly enriched, and complement C3 and C7 were candidate markers. The receiver operating characteristic (ROC) curve revealed that C7 had significant diagnostic value (AUC=0.865) in DN. Through scRNA-seq reanalysis, we found that C7 was specifically elevated in mesangial (MES) cells of DN. Moreover, we found that the expression of C7 was regulated by miR-494-3p and miR-574-5p.

CONCLUSION

This is the first study to reveal that C7 is specifically expressed in mesangial cells, is a potential diagnostic biomarker for diabetic nephropathy, and is regulated by miR-494-3p and miR-574-5p.

Quality assessment of unsaturated iron-binding protein capacity in Iraqi patients undergoing hemodialysis

Hemodialysis is autoimmune disease result from inflammation, oxidative stress, and fibrosis. It is characterized by renal glomeruli damage, podocyte injury, tubule interstitial, and proteinuria. Electrolyte balance is the main function of the renal and any form of electrolyte disorders may lead to excess blood volume, hypertension, and difficulty in maintaining natural blood sodium. Renal erythropoietin has an important role in the balance of vascular active substances, such as prostaglandins and thromboxanes; therefore, patients undergoing hemodialysis observe decreased production of erythropoietin with iron loss through hemodialysis machine as well as weakened iron absorption and mobilization from the intestine to the bloodstream. Ferritin, total iron-binding capacity (TIBC), unsaturated iron-binding protein capacity (UIBC), iron free, and transferrin are used to confirm iron status. According the clinical characterization of the results, no normality was observed in patients undergoing hemodialysis. There was hypertension, anemia, lean symptoms and equal distribution of age parallel with developed disease, there was significant increased in renal function except albumin, it was decreased in the patients compared with control groups. In addition, there was a decreased level of iron status in all parameters such as packed cell volume (%), TIBC, UIBC, iron free, and transferrin except ferritin; there was an increased level of iron status in all parameters in patients compared with control groups.

Circadian Clock and Complement Immune System-Complementary Control of Physiology and Pathology?

Mammalian species contain an internal circadian (i.e., 24-h) clock that is synchronized to the day and night cycles. Large epidemiological studies, which are supported by carefully controlled studies in numerous species, support the idea that chronic disruption of our circadian cycles results in a number of health issues, including obesity and diabetes, defective immune response, and cancer. Here we focus specifically on the role of the complement immune system and its relationship to the internal circadian clock system. While still an incompletely understood area, there is evidence that dysregulated proinflammatory cytokines, complement factors, and oxidative stress can be induced by circadian disruption and that these may feed back into the oscillator at the level of circadian gene regulation. Such a feedback cycle may contribute to impaired host immune response against pathogenic insults. The complement immune system including its activated anaphylatoxins, C3a and C5a, not only facilitate innate and adaptive immune response in chemotaxis and phagocytosis, but they can also amplify chronic inflammation in the host organism. Consequent development of autoimmune disorders, and metabolic diseases associated with additional environmental insults that activate complement can in severe cases, lead to accelerated tissue dysfunction, fibrosis, and ultimately organ failure. Because several promising complement-targeted therapeutics to block uncontrolled complement activation and treat autoimmune diseases are in various phases of clinical trials, understanding fully the circadian properties of the complement system, and the reciprocal regulation by these two systems could greatly improve patient treatment in the long term.

Inflammaging and Complement System: A Link Between Acute Kidney Injury and Chronic Graft Damage

The aberrant activation of complement system in several kidney diseases suggests that this pillar of innate immunity has a critical role in the pathophysiology of renal damage of different etiologies. A growing body of experimental evidence indicates that complement activation contributes to the pathogenesis of acute kidney injury (AKI) such as delayed graft function (DGF) in transplant patients. AKI is characterized by the rapid loss of the kidney's excretory function and is a complex syndrome currently lacking a specific medical treatment to arrest or attenuate progression in chronic kidney disease (CKD). Recent evidence suggests that independently from the initial trigger (i.e., sepsis or ischemia/reperfusions injury), an episode of AKI is strongly associated with an increased risk of subsequent CKD. The AKI-to-CKD transition may involve a wide range of mechanisms including scar-forming myofibroblasts generated from different sources, microvascular rarefaction, mitochondrial dysfunction, or cell cycle arrest by the involvement of epigenetic, gene, and protein alterations leading to common final signaling pathways [i.e., transforming growth factor beta (TGF-β), p16 ink4a , Wnt/β-catenin pathway] involved in renal aging. Research in recent years has revealed that several stressors or complications such as rejection after renal transplantation can lead to accelerated renal aging with detrimental effects with the establishment of chronic proinflammatory cellular phenotypes within the kidney. Despite a greater understanding of these mechanisms, the role of complement system in the context of the AKI-to-CKD transition and renal inflammaging is still poorly explored. The purpose of this review is to summarize recent findings describing the role of complement in AKI-to-CKD transition. We will also address how and when complement inhibitors might be used to prevent AKI and CKD progression, therefore improving graft function.

A Randomized Trial of Recombinant Human C1-Esterase-Inhibitor in the Prevention of Contrast-Induced Kidney Injury

OBJECTIVES

This study sought to determine the efficacy profile and safety of recombinant human C1 esterase inhibitor (rhC1INH) in the prevention of contrast-associated acute kidney injury after elective coronary angiography.

BACKGROUND

Contrast-associated acute kidney injury is caused by tubular cytotoxicity and ischemia/reperfusion injury. rhC1INH is effective in reducing renal ischemia/reperfusion injury in experimental models.

METHODS

In this placebo-controlled, double-blind, single-center trial 77 patients with chronic kidney disease were randomized to receive 50 IU/kg rhC1INH before and 4 h after elective coronary angiography or placebo. The primary outcome was the peak change of urinary neutrophil gelatinase-associated lipocalin within 48 h, a surrogate marker of kidney injury.

RESULTS

Median peak change of urinary neutrophil gelatinase-associated lipocalin was lower in the rhC1INH group (4.7 ng/ml vs. 22.5 ng/ml; p = 0.038) in the per-protocol population but not in the modified intention-to-treat analysis, and in patients with percutaneous coronary interventions (median, 1.8 ng/ml vs. 26.2 ng/ml; p = 0.039 corresponding to a median proportion peak change of 11% vs. 205%; p = 0.002). The incidence of a cystatin C increase ≥10% within 24 h was lower in the rhC1INH group (16% vs. 33%; p = 0.045), whereas the frequency of contrast-associated acute kidney injury was comparable. Adverse events during a 3-month follow-up were similarly distributed.

CONCLUSIONS

Administration of rhC1INH before coronary angiography may attenuate renal injury as reflected by urinary neutrophil gelatinase-associated lipocalin and cystatin C. The safety profile of rhC1INH was favorable in a patient population with multiple comorbidities. (Recombinant Human C1 Esterase Inhibitor in the Prevention of Contrast-induced Nephropathy in High-risk Subjects [PROTECT]; NCT02869347).

Complement C5a inhibition moderates lipid metabolism and reduces tubulointerstitial fibrosis in diabetic nephropathy

Background

Complement C5 mediates pro-inflammatory responses in many immune-related renal diseases. Given that the C5a level is elevated in diabetes, we investigated whether activation of C5a/C5aR signalling plays a pathogenic role in diabetic nephropathy (DN) and the therapeutic potential of C5a inhibition for renal fibrosis.

Methods

Human renal biopsies from patients with DN and control subjects were used for immunohistochemical staining of complement C5 components. Renal function and tubulointerstitial injury were compared between db/m mice, vehicle-treated mice and C5a inhibitor-treated db/db mice. A cell culture model of tubule epithelial cells (HK-2) was used to demonstrate the effect of C5a on the renal fibrotic pathway.

Results

Increased levels of C5a, but not of its receptor C5aR, were detected in renal tubules from patients with DN. The intensity of C5a staining was positively correlated with the progression of the disease. In db/db mice, administration of a novel C5a inhibitor, NOX-D21, reduced the serum triglyceride level and attenuated the upregulation of diacylglycerolacyltransferase-1 and sterol-regulatory element binding protein-1 expression and lipid accumulation in diabetic kidney. NOX-D21-treated diabetic mice also had reduced serum blood urea nitrogen and creatinine levels with less glomerular and tubulointerstitial damage. Renal transforming growth factor beta 1 (TGF-β1), fibronectin and collagen type I expressions were reduced by NOX-D21. In HK-2 cells, C5a stimulated TGF-β production through the activation of the PI3K/Akt signalling pathway.

Conclusions

Blockade of C5a signalling by NOX-D21 moderates altered lipid metabolism in diabetes and improved tubulointerstitial fibrosis by reduction of lipid accumulation and TGF-β-driven fibrosis in diabetic kidney.

Ischaemia reperfusion injury: mechanisms of progression to chronic graft dysfunction

The increasing use of extended criteria organs to meet the demand for kidney transplantation raises an important question of how the severity of early ischaemic injury influences long-term outcomes. Significant acute ischaemic kidney injury is associated with delayed graft function, increased immune-associated events and, ultimately, earlier deterioration of graft function. A comprehensive understanding of immediate molecular events that ensue post-ischaemia and their potential long-term consequences are key to the discovery of novel therapeutic targets. Acute ischaemic injury primarily affects tubular structure and function. Depending on the severity and persistence of the insult, this may resolve completely, leading to restoration of normal function, or be sustained, resulting in persistent renal impairment and progressive functional loss. Long-term effects of acute renal ischaemia are mediated by several mechanisms including hypoxia, HIF-1 activation, endothelial dysfunction leading to vascular rarefaction, sustained pro-inflammatory stimuli involving innate and adaptive immune responses, failure of tubular cells to recover and epigenetic changes. This review describes the biological relevance and interaction of these mechanisms based on currently available evidence.

Danggui Shaoyao San Ameliorates Renal Fibrosis via Regulation of Hypoxia and Autophagy

Danggui Shaoyao San (DSS), a traditional Chinese medicinal prescription, was widely used to reinforce earth to activate collaterals in ancient times. Recently, many clinical studies found that DSS had a renoprotection. In this study, we evaluated the effect of DSS on unilateral ureteral obstruction- (UUO-) induced renal fibrosis in rats and investigated the mechanisms underlying the effect. Sprague Dawley (SD) rats were randomized to UUO or Sham operation. After 1 day, the rats that underwent UUO were randomized to treatment for four experimental groups (n=10 each group): Sham, UUO only, UUO+ benazepril (Bena), and UUO+DSS. After 4 weeks, we demonstrated that DSS significantly suppressed UUO-induced renal hypertrophy by gravimetric. In addition, DSS obviously prevented UUO-induced disorder in renal structure and renal function by HE and biochemistry test. We also found that DSS abrogated UUO-induced renal fibrosis by Masson's staining and collagen volume fraction (CVF) analysis; this is consistent with the western blot analysis that showed DSS abrogated the UUO-induced enhanced TGF-β1 and weakened BMP-7. Compared with the UUO only group, rats treated with DSS exhibited significant increase in vascular density, followed by decrease in hypoxia and HIF-1α protein level through western blot and immunofluorescence analysis. Furthermore, we also determined proteins of autophagy and DSS enhanced autophagy to prevent the damage-induced by UUO. Taken together, our findings demonstrated that DSS had a renoprotection effect in ameliorating renal fibrosis possibly via attenuating tissue hypoxia and regulating autophagy.

Diagnostic Indicators of Superimposed Preeclampsia in Women With CKD

Introduction

Diagnosis of superimposed preeclampsia in women with chronic kidney disease (CKD) is complicated by the presence of hypertension and proteinuria due to renal disease. The aims of this study were to determine mechanistic links between superimposed preeclampsia and renin-angiotensin system activation, endothelial pathology, complement dysfunction, and tubular injury, and to explore the role of diagnostic indicators of superimposed preeclampsia.

Methods

Plasma and urinary biomarkers derived from the renin-angiotensin system (active renin, angiotensinogen), endothelial glycocalyx (hyaluronan, intercellular adhesion molecule, vascular cell adhesion molecule [VCAM], P-selectin, E-selectin), complement activation (C3a, C5a, complement factor H, C5b-9), and tubular injury (kidney injury molecule-1, urinary lipocalin-2) were quantified in 60 pregnant women with CKD including 15 women at the time of superimposed preeclampsia diagnosis and 45 women who did not develop superimposed preeclampsia, 18 women with preeclampsia, and 20 normal pregnancies. Correlation with placental growth factor was assessed.

Results

Plasma concentrations of hyaluronan (67.5 ng/ml vs. 27.5 ng/ml, P = 0.0017, receiver operating characteristic area 0.80) and VCAM (1132 ng/ml vs. 659 ng/ml, P < 0.0001, receiver operating characteristic area 0.86) distinguished women with CKD and superimposed preeclampsia from those without superimposed preeclampsia, and correlated with placental growth factor concentration. The diagnostic discrimination of markers of the renin-angiotensin system was reduced by adjustment for chronic hypertension, antihypertensive drug use, and black ethnicity. Other markers offered limited or no diagnostic discrimination for superimposed preeclampsia.

Conclusion

This study suggests that endothelial dysfunction contributes to the pathophysiology of superimposed preeclampsia and a diagnostic role for plasma hyaluronan and VCAM is hypothesized.

Intrarenal Complement System Transcripts in Chronic Antibody-Mediated Rejection and Recurrent IgA Nephropathy in Kidney Transplantation

Background: The complement system activation and regulation have been linked to post-transplant pathologies including chronic antibody mediated rejection (cAMR) and the recurrence of IgA nephropathy (ReIgAN) but distinct mechanisms remain to be elucidated.

Methods: In this retrospective single center study, the outcome of kidney transplantation was studied in 150 patients with late histological diagnosis to be either cAMR or ReIgAN, 14 stable kidney grafts at 3 months and finally 11 patients with native kidney IgAN nephropathy. To study a role of complement cascade and regulation in cAMR and ReIgAN, the RNA was extracted from available frozen kidney biopsy samples and using RT-qPCR transcripts of 11 target genes along with clinical data were determined and compared with stable grafts at 3 months protocol biopsies or IgAN native kidney nephropathy. Immunohistologically, CD46 (MCP), and C5 proteins were stained in biopsies.

Results: Interestingly, there were no differences in kidney graft survival between cAMR and ReIgAN since transplantation. cAMR was associated with significantly higher intragraft transcripts of C3, CD59, and C1-INH as compared to ReIgAN (p < 0.05). When compared to normal stable grafts, cAMR grafts exhibited higher C3, CD55, CD59, CFH, CFI, and C1-INH (p < 0.01). Moreover, ReIgAN was associated with the increase of CD46, CD55, CD59 (p < 0.01), and CFI (p < 0.05) transcripts compared with native kidney IgAN. Rapid progression of cAMR (failure at 2 years after biopsy) was observed in patients with lower intrarenal CD55 expression (AUC 0.77, 78.6% sensitivity, and 72.7 specificity). There was highly significant association of several complement intrarenal transcripts and the degree of CKD regardless the diagnosis; C3, CD55, CFH, CFI, and C1-INH expressions positively correlated with eGFR (for all p < 0.001). Neither the low mRNA transcripts nor the high mRNA transcripts biopsies were associated with distinct trend in MCP or C5 proteins staining.

Conclusions: The intrarenal complement system transcripts are upregulated in progressively deteriorated kidney allografts.

Complement 7 Is Up-Regulated in Human Early Diabetic Kidney Disease

There is a temporal window from the time diabetes is diagnosed to the appearance of overt kidney disease during which time the disease progresses quietly without detection. Currently, there is no way to detect early diabetic nephropathy (EDN). Herein, we performed an unbiased assessment of gene-expression analysis of postmortem human kidneys to identify candidate genes that may contribute to EDN. We then studied one of the most promising differentially expressed genes in both kidney tissue and blood samples. Differential transcriptome analysis of EDN kidneys and matched nondiabetic controls showed alterations in five canonical pathways, and among them the complement pathway was the most significantly altered. One specific complement pathway gene, complement 7 (C7), was significantly elevated in EDN kidney. Real-time PCR confirmed more than a twofold increase of C7 expression in EDN kidneys compared with controls. Changes in C7 gene product level were confirmed by immunohistochemistry. C7 protein levels were elevated in proximal tubules of EDN kidneys. Serum C7 protein levels were also measured in EDN and control donors. C7 levels were significantly higher in EDN serum than control serum. This latter finding was independently confirmed in a second set of blood samples from a previously collected data set. Together, our data suggest that C7 is associated with EDN, and can be used as a molecular target for detection and/or treatment of EDN.

Diabetic retinopathy may predict the renal outcomes of patients with diabetic nephropathy

BACKGROUND

The patients with Type 2 diabetes mellitus (T2DM) and diabetic retinopathy (DR) are prone to develop diabetic nephropathy (DN). In this study, we aimed to clarify the relationship between DR and the progression of DN in patients with T2DM.

METHODS

In the cross-section study, 250 patients with T2DM and biopsy-proven DN were divided into two groups: 130 in the DN without DR group (DN group) and 120 in the DN + DR group. Logistic regression analysis was performed to identify risk factors for DR. Of the above 250 patients, 141 were recruited in the cohort study who received follow-up for at least 1 year and the influence of DR on renal outcome was assessed using Cox regression. Renal outcome was defined as the progression to end-stage renal disease (ESRD).

RESULTS

In the cross-section study, the severity of glomerular lesions (class IIb + III) and DM history >10 years were significantly associated with the odds of DR when adjusting for baseline proteinuria, hematuria, e-GFR, and interstitial inflammation. In the cohort study, a multivariate COX analysis demonstrated that the DR remained an independent risk factor for progression to ESRD when adjusting for important clinical variables and pathological findings (p < .05).

CONCLUSIONS

These findings indicated that the severity of glomerular lesions was significantly associated with DR and DR was an independent risk factor for the renal outcomes in patients with DN, which suggested that DR may predict the renal prognosis of patients with T2DM and DN.

Endothelial Microparticles and Systemic Complement Activation in Patients With Chronic Kidney Disease

BACKGROUND

Endothelial microparticles are associated with chronic kidney disease (CKD) and complement activation. We hypothesized that the complement pathway is activated in patients with CKD via endothelial microparticles and that complement activation correlates with endothelial dysfunction in CKD.

METHODS AND RESULTS

We analyzed complement data of 30 healthy subjects, 30 patients with stage III/IV CKD, and 30 renal transplant recipients with stage III/IV CKD, evaluating the potential correlation of complement fragments with brachial artery flow-mediated dilation, Chronic Kidney Disease Epidemiology Collaboration glomerular filtration rate, and urinary albumin/creatinine ratio. Endothelial microparticles were characterized via proteomic analysis and compared between study groups. Complement fragment Ba was significantly increased in CKD and post-kidney transplant CKD. Plasma Ba levels correlated significantly with lower brachial artery flow-mediated dilation, lower Chronic Kidney Disease Epidemiology Collaboration glomerular filtration rate, and higher urinary albumin/creatinine ratio. Factor D levels were significantly higher in the plasma microparticles of patients with CKD versus healthy controls. Plasma microparticles isolated from patients with CKD and containing factor D activated the alternative pathway in vitro.

CONCLUSION

The alternative complement pathway is activated in CKD and correlates with endothelial dysfunction and markers of CKD. Future studies are needed to evaluate whether endothelial microparticles with increased factor D play a pathologic role in CKD-associated vascular disease.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02230202.

Cellular and molecular mechanisms of kidney fibrosis

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. It is considered as the underlying pathological process of chronic kidney disease (CKD), which affects more than 10% of world population and for which treatment options are limited. Renal fibrosis is defined by excessive deposition of extracellular matrix, which disrupts and replaces the functional parenchyma that leads to organ failure. Kidney's histological structure can be divided into three main compartments, all of which can be affected by fibrosis, specifically termed glomerulosclerosis in glomeruli, interstitial fibrosis in tubulointerstitium and arteriosclerosis and perivascular fibrosis in vasculature. In this review, we summarized the different appearance, cellular origin and major emerging processes and mediators of fibrosis in each compartment. We also depicted and discussed the challenges in translation of anti-fibrotic treatment to clinical practice and discuss possible solutions and future directions.

Celastrol alleviates renal fibrosis by upregulating cannabinoid receptor 2 expression

Renal fibrosis is the final manifestation of various chronic kidney diseases, and no effective therapy is available to prevent or reverse it. Celastrol, a triterpene that derived from traditional Chinese medicine, is a known potent anti-fibrotic agent. However, the underlying mechanisms of action of celastrol on renal fibrosis remain unknown. In this study, we found that celastrol treatment remarkably attenuated unilateral ureteral obstruction (UUO)-induced mouse renal fibrosis. This was evidenced by the significant reduction in tubular injury; collagen deposition; accumulation of fibronectin, collagen I, and α-smooth muscle actin; and the expression levels of pro-fibrotic factors Vim, Cola1, and TGF-β1 mRNA, as well as inflammatory responses. Celastrol showed similar effects in a folic acid-induced mouse renal fibrosis model. Furthermore, celastrol potentiated the expression of the anti-fibrotic factor cannabinoid receptor 2 (CB2R) in established mouse fibrotic kidney tissues and transforming growth factor β1 (TGF-β1)-stimulated human kidney 2 (HK-2) cells. In addition, the CB2R antagonist (SR144528) abolished celastrol-mediated beneficial effects on renal fibrosis. Moreover, UUO- or TGF-β1-induced activation of the pro-fibrotic factor SMAD family member 3 (Smad3) was markedly inhibited by celastrol. Inhibition of Smad3 activation by an inhibitor (SIS3) markedly reduced TGF-β1-induced downregulation of CB2R expression. In conclusion, our study provides the first direct evidence that celastrol significantly alleviated renal fibrosis, by contributing to the upregulation of CB2R expression through inhibiting Smad3 signaling pathway activation. Therefore, celastrol could be a potential drug for treating patients with renal fibrosis.

Murine Nephrotoxic Nephritis as a Model of Chronic Kidney Disease

Using the nonaccelerated murine nephrotoxic nephritis (NTN) as a model of chronic kidney disease (CKD) could provide an easily inducible model that enables a rapid test of treatments. Originally, the NTN model was developed as an acute model of glomerulonephritis, but in this study we evaluate the model as a CKD model and compare CD1 and C57BL/6 female and male mice. CD1 mice have previously showed an increased susceptibility to CKD in other CKD models. NTN was induced by injecting nephrotoxic serum (NTS) and evaluated by CKD parameters including albuminuria, glomerular filtration rate (GFR), mesangial expansion, and renal fibrosis. Both strains showed significant albuminuria on days 2-3 which remained significant until the last time point on days 36-37 supporting dysfunctional filtration also observed by a significantly declined GFR on days 5-6, 15–17, and 34–37. Both strains showed early progressive mesangial expansion and significant renal fibrosis within three weeks suggesting CKD development. CD1 and C57BL/6 females showed a similar disease progression, but female mice seemed more susceptible to NTS compared to male mice. The presence of albuminuria, GFR decline, mesangial expansion, and fibrosis showed that the NTN model is a relevant CKD model both in C57BL/6 and in CD1 mice.

Clinical risk stratification of paediatric renal transplant recipients using C1q and C3d fixing of de novo donor-specific antibodies

INTRODUCTION

We have previously shown that children who developed de novo donor-specific human leukocyte antigen (HLA) antibodies (DSA) had greater decline in allograft function. We hypothesised that patients with complement-activating DSA would have poorer renal allograft outcomes.

METHODS

A total of 75 children developed DSA in the original study. The first positive DSA sample was subsequently tested for C1q and C3d fixing. The primary event was defined as 50% reduction from baseline estimated glomerular filtration rate and was analysed using the Kaplan-Meier estimator.

RESULTS

Of 65 patients tested, 32 (49%) and 23 (35%) tested positive for C1q and C3d fixing, respectively. Of the 32 C1q-positive (c1q+) patients, 13 (41%) did not show concomitant C3d fixing. The mean fluorescence intensity values of the original immunoglobulin G DSA correlated poorly with complement-fixing positivity (C1q: adjusted R ² 0.072; C3d: adjusted R ² 0.11; p < 0.05). C1q+ antibodies were associated with acute tubulitis [0.75 ± 0.18 (C1q+) vs. 0.25 ± 0.08 (C1q-) episodes per patient (mean ± standard error of the mean; p < 0.05] but not with worse long-term renal allograft dysfunction (median time to primary event 5.9 (C1q+) vs. 6.4 (C1q-) years; hazard ratio (HR) 0.74; 95% confidence ratio (CI) 0.30-1.81; p = 0.58]. C3d-positive (C3d+) antibodies were associated with positive C4d histological staining [47% (C3d+) vs. 20% (C3d-); p = 0.04] and with significantly worse long-term allograft dysfunction [median time to primary event: 5.6 (C3d+) vs. 6.5 (C3d-) years; HR 0.38; 95% CI 0.15-0.97; p = 0.04].

CONCLUSION

Assessment of C3d fixing as part of prospective HLA monitoring can potentially aid stratification of patients at the highest risk of long-term renal allograft dysfunction.

Complement Recognition Pathways in Renal Transplantation

The complement system, consisting of soluble and cell membrane-bound components of the innate immune system, has defined roles in the pathophysiology of renal allograft rejection. Notably, the unavoidable ischemia-reperfusion injury inherent to transplantation is mediated through the terminal complement activation products C5a and C5b-9. Furthermore, biologically active fragments C3a and C5a, produced during complement activation, can modulate both antigen presentation and T cell priming, ultimately leading to allograft rejection. Earlier work identified renal tubule cell synthesis of C3, rather than hepatic synthesis of C3, as the primary source of C3 driving these effects. Recent efforts have focused on identifying the local triggers of complement activation. Collectin-11, a soluble C-type lectin expressed in renal tissue, has been implicated as an important trigger of complement activation in renal tissue. In particular, collectin-11 has been shown to engage L-fucose at sites of ischemic stress, activating the lectin complement pathway and directing the innate immune response to the distressed renal tubule. The interface between collectin-11 and L-fucose, in both the recipient and the allograft, is an attractive target for therapies intended to curtail renal inflammation in the acute phase.

Excretions/secretions from medicinal larvae (Lucilia sericata) inhibit complement activation by two mechanisms

Larvae of the blowfly Lucilia sericata facilitate wound healing by removing dead tissue and biofilms from non-healing and necrotic wounds. Another beneficial action of larvae and their excretions/secretions (ES) is down-regulation of excessive inflammation. As prolonged complement activation is key to excessive inflammation, the aim of this study was to elucidate the mechanisms underlying the anti-complement activities of ES. Results revealed that heat sensitive serine proteases in ES degrade multiple complement proteins in all steps of the three complement activation pathways. Importantly, C3a and C5a-major activators of inflammation-were also degraded by ES and pretreatment of these factors with ES completely blocked their ability to induce activation of human neutrophils. Pre-exposure of the neutrophils to ES did not affect their responsiveness to C3a/C5a and fMLP, indicating that the receptors for these activators on neutrophils were not affected by ES. Surprisingly, heat and serine protease inhibitor pretreatment did not affect the ability of ES to inhibit C5b-9 complex formation despite degrading complement proteins, indicating a second complement-inhibiting molecule in ES. Heated ES was as effective as intact ES in inhibiting C3 deposition upon activation of the alternative pathway, but was significantly less effective in wells with a classical or lectin pathway-specific coating. Unfortunately, the molecules affecting the complement system could not be identified due to an insufficient database for L. sericata. Together, larval ES inhibit complement activation by two different mechanisms and down-regulate the C3a/C5a-mediated neutrophil activation. This attenuates the inflammatory process, which may facilitate wound healing.

Urine Proteome Specific for Eye Damage Can Predict Kidney Damage in Patients With Type 2 Diabetes: A Case-Control and a 5.3-Year Prospective Cohort Study

OBJECTIVE

The predictive value of microalbuminuria (MAU) for kidney damage is limited in type 2 diabetes (T2D). We studied whether a urine proteome specific for sight-threatening proliferative diabetic retinopathy (PDR) is an indicator to predict chronic renal insufficiency (CRI) in patients with T2D.

RESEARCH DESIGN AND METHODS

A shotgun urine proteomic analysis was performed in patients with MAU and PDR (case subjects) and in patients with MAU and a duration of T2D for >10 years but without any degree of retinopathy (control subjects). In the cohort study, 210 patients with T2D with an estimated glomerular filtration rate (eGFR) ≥80 mL/min/1.73 m² were followed for a median of 5.3 years. Urine proteins specific for PDR were used for predicting CRI (eGFR <60 mL/min/1.73 m²).

RESULTS

The top two urine proteins with the highest difference in ratio of case subjects to control subjects were haptoglobin (8.7 times; P < 0.0001) and α-2-macroglobulin (5.7 times; P < 0.0001). In the cohort study, patients with baseline urinary haptoglobin ≥20 ng/min (haptoglobinuria) had a higher incidence of CRI than those without (hazard ratio [95% CI] 3.27 [1.41-7.58]; P = 0.006). The overall CRI rate was 3.2% for patients without haptoglobinuria or MAU, 9.5% for those with MAU, and 13.3% for those with haptoglobinuria. The highest rate for CRI (22.4%) was in patients with both MAU and haptoglobinuria (P < 0.001).

CONCLUSIONS

Urine haptoglobin, which is specific for PDR, is a novel biomarker and complement to urine albumin for predicting kidney damage in patients with T2D.

Transcriptome analysis reveals manifold mechanisms of cyst development in ADPKD

Background

Autosomal dominant polycystic kidney disease (ADPKD) causes progressive loss of renal function in adults as a consequence of the accumulation of cysts. ADPKD is the most common genetic cause of end-stage renal disease. Mutations in polycystin-1 occur in 87% of cases of ADPKD and mutations in polycystin-2 are found in 12% of ADPKD patients. The complexity of ADPKD has hampered efforts to identify the mechanisms underlying its pathogenesis. No current FDA (Federal Drug Administration)-approved therapies ameliorate ADPKD progression.

Results

We used the de Almeida laboratory’s sensitive new transcriptogram method for whole-genome gene expression data analysis to analyze microarray data from cell lines developed from cell isolates of normal kidney and of both non-cystic nephrons and cysts from the kidney of a patient with ADPKD. We compared results obtained using standard Ingenuity Volcano plot analysis, Gene Set Enrichment Analysis (GSEA) and transcriptogram analysis. Transcriptogram analysis confirmed the findings of Ingenuity, GSEA, and published analysis of ADPKD kidney data and also identified multiple new expression changes in KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways related to cell growth, cell death, genetic information processing, nucleotide metabolism, signal transduction, immune response, response to stimulus, cellular processes, ion homeostasis and transport and cofactors, vitamins, amino acids, energy, carbohydrates, drugs, lipids, and glycans. Transcriptogram analysis also provides significance metrics which allow us to prioritize further study of these pathways.

Conclusions

Transcriptogram analysis identifies novel pathways altered in ADPKD, providing new avenues to identify both ADPKD’s mechanisms of pathogenesis and pharmaceutical targets to ameliorate the progression of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s40246-016-0095-x) contains supplementary material, which is available to authorized users.

Role of the lectin complement pathway in kidney transplantation

In the last 15 years two major advances in the role of complement in the kidney transplant have come about. The first is that ischaemia reperfusion injury and its profound effect on transplant outcome is dependent on the terminal product of complement activation, C5b-9. The second key observation relates to the function of the small biologically active fragments C3a and C5a released by complement activation in increasing antigen presentation and priming the T cell response that results in transplant rejection. In both cases local synthesis of C3 principally by the renal tubule cells plays an essential role that overshadows the role of the circulating pool of C3 generated largely by hepatocyte synthesis. More recent efforts have investigated the molecules expressed by renal tissue that can trigger complement activation. These have revealed a prominent effect of collectin-11 (CL-11), a soluble C-type lectin that is expressed in renal tissue and aligns with its major ligand L-fucose at sites of complement activation following ischaemic stress. Biochemical studies have shown that interaction between CL-11 and L-fucose results in complement activation by the lectin complement pathway, precisely targeting the innate immune response to the ischaemic tubule surface. Therapeutic approaches to reduce inflammatory and immune stimulation in ischaemic kidney have so far targeted C3 or its activation products and several are in clinical trials. The finding that lectin-fucose interaction is an important trigger of lectin pathway complement activation within the donor organ opens up further therapeutic targets where intervention could protect the donor kidney against complement.

C5b-9 does not mediate tubulointerstitial injury in experimental acute glomerular disease characterized by selective proteinuria

AIM: To determine whether complement membrane attack complex (C5b-9) has a pathogenic role in tubulointerstitial injury in a renal disease model characterized by acute highly selective proteinuria.

METHODS: Protein-overload nephropathy (PON) was induced in adult female Piebald-Viral-Glaxo rats with or without complement C6 deficiency (C6^- and C6⁺) by daily intraperitoneal injections of bovine serum albumin (BSA, 2 g/d), and examined on days 2, 4 and 8.

RESULTS: Groups with PON developed equivalent levels of heavy proteinuria within 24 h of BSA injection. In C6⁺ rats with PON, the tubulointerstitial expression of C5b-9 was increased and localized predominantly to the basolateral surface of tubular epithelial cells (TECs), whereas it was undetectable in C6^- animals. TEC proliferation (as assessed by the number of BrdU+ cells) increased by more than 50-fold in PON, peaking on day 2 and declining on days 4 to 8. There was a trend for a reduction in the number of BrdU+ TECs on day 4 in the C6^- PON group (P = 0.10 compared to C6⁺) but not at any other time-point. Kidney enlargement, TEC apoptosis (TUNEL⁺ cells) and markers of tubular injury (tubule dilatation, loss of TEC height, protein cast formation) were not altered by C6 deficiency in PON. Interstitial monocyte (ED-1+ cell) accumulation was partially reduced in C6^- animals with PON on day 4 (P = 0.01) but there was no change in myofibroblast accumulation.

CONCLUSION: These data suggest that C5b-9 does not mediate tubulointerstitial injury in acute glomerular diseases characterized by selective proteinuria.