Glomerular Protein Research Articles

Agnostic Mass Spectrometry Proteomics Identifies Glomerular Adipocyte Enhancer Binding Protein 1 (AEBP1) as a Novel Marker of Diabetic Kidney Disease

Agnostic Mass Spectrometry Proteomics Identifies Glomerular Adipocyte Enhancer Binding Protein 1 (AEBP1) as a Novel Marker of Diabetic Kidney Disease

Glomerular proteomic profiling of kidney biopsies with hypertensive nephropathy reveals a signature of disease progression.

Hypertensive nephropathy (HN) requires a kidney biopsy as diagnostic gold-standard but histological findings are unspecific and specific prognostic markers are missing. We aimed at identifying candidate prognostic markers based on glomerular protein signatures. We studied adult patients (n = 17) with eGFR >30 ml/min/1.73m2 and proteinuria <3 g/d from the Norwegian Kidney Biopsy Registry, including subjects non progressing (NP, n = 9), or progressing (P, n = 8) to end-stage renal disease (ESRD) within an average follow-up of 22 years. Glomerular cross-sections from archival kidney biopsy sections were microdissected and processed for protein extraction. Proteomic analyses were performed using Q-exactive HF mass spectrometer and relative glomerular protein abundances were compared between P and NP patients. Immunohistochemistry (IHC) was used to validate selected data. Amongst 1870 quality filtered proteins, 58 were differentially expressed in P and NP patients' glomeruli, with absolute fold changes (FC) ≥1.5, p ≤ 0.05. Supervised classifier analysis (K nearest neighbor) identified a set of five proteins, including Gamma-butyrobetaine dioxygenase (BBOX1, O75936) and Cadherin 16 (CDH16, O75309), overexpressed in P, and Eosinophil peroxidase (EPX, P11678), DnaJ homolog subfamily B member 1 (DNAJB1, P25685) and Alpha-1-syntrophin (SNTA1, Q13424), overexpressed in NP glomeruli, correctly classifying 16/17 kidney biopsy samples. Geneset Enrichment Analysis (GSEA), showed that metabolic pathways were generally enriched in P, and structural cell pathways in NP. Pathway analysis identified Epithelial Adherens Junction Signaling as most affected canonical pathway. IHC analysis confirmed overexpression of BBOX1 and Cadherin 16 in glomeruli from P patients. In conclusion, glomerular proteomic profiling can be used to discriminate P from NP HN patients.

The modulatory effect of sodium molybdate against cisplatin-induced CKD: Role of TGF-β/Smad signaling pathway

AimsChronic kidney disease (CKD) is a global non-communicable health problem. Fibrosis is considered the base and the fate of CKD; thus, the goal of this study was to evaluate the effects of sodium molybdate on cisplatin-induced CKD model and demonstrate the possible involved mechanisms. Materials and methodsIn cisplatin model, Wistar rats were challenged with cisplatin (1 mg/kg, i.p.) twice weekly for ten weeks. Sodium molybdate (100 and 200 mg/kg, orally) was given one-week prior cisplatin and was continued daily for the next ten weeks. Key findingsAdministration of sodium molybdate amended kidney function and significantly reduced the pathological changes in renal histopathological sections. Moreover, it modulates oxidative stress parameters by increasing the levels of SOD and GSH and decreasing the level of MDA. Likewise, in renal homogenate, sodium molybdate attenuated inflammation that was revealed by NF-κB and TNF-α levels significant reduction. Additionally, it ameliorated fibrosis that was indicated by decreased Masson's trichome staining in cortex and medulla. Immunohistochemical staining of renal sections against TGF-β1 showed reduction of positive glomerular and tubular protein expression. Additionally, it decreased profibrotic Smad3 level and increased antifibrotic Smad7 level. SignificanceAdministration of sodium molybdate demonstrated a hopeful suppressor effect on cisplatin-induced CKD/fibrosis in rat model. This effect may be through the inhibition pof TGF-β/Smad signaling pathway and up-regulation of Smad7 expression leading to decreased extracellular collagen accumulation. Moreover, they could ameliorate the inflammation through NF-κB and TNF-α levels reduction, decrease in ROS, and retrieval of antioxidant defenses.

Comparative proteomic analysis of glomerular proteins in primary and bucillamine-induced membranous nephropathy

BackgroundAnti-phospholipase A2 receptor autoantibody (PLA2R Ab)-associated membranous nephropathy (MN) is the most common form of primary MN (pMN). On the other hand, bucillamine (BCL), an antirheumatic drug developed in Japan, was reported to cause a rare form of secondary MN (sMN). Between these MN forms, comparative proteomic analysis of glomerular proteins has not been performed.MethodsWe used renal biopsy specimens from 6 patients with PLA2R Ab (+) pMN, 6 patients with PLA2R Ab (‒) pMN, 6 patients with BCL-induced sMN, and 5 control cases (time 0 transplant biopsies). Proteins were extracted from laser-microdissected glomeruli and analyzed using mass spectrometry. The quantification values of protein abundance in each MN group were compared with those in the control group.ResultsMore than 800 proteins with high confidence were identified. Principal component analysis revealed a different distribution between the pMN and sMN groups. For further analysis, 441 proteins matched with ≥ 3 peptides were selected. Among the pMN and sMN groups, we compared the profiles of several protein groups based on the structural and functional characteristics, such as immunoglobulins, complements, complement-regulating proteins, podocyte-associated proteins, glomerular basement membrane proteins, and several proteins that are known to be associated with kidney diseases, including MN. In all MN groups, increased levels of immunoglobulins (IgG, IgA, and IgM), complements (C3, C4, and C9), complement factor H-related protein 5, type XVIII collagen, calmodulin, polyubiquitin, and ubiquitin ligase were observed. For some proteins, such as type VII collagen and nestin, the fold-change values were significantly different between the pMN and sMN groups.ConclusionsBetween the pMN and BCL-induced sMN groups, we observed common and different alterations in protein levels such as known disease-associated proteins and potential disease marker proteins.

Clinical Significance of Glomerular Autophagy in Evaluation of Diabetic Kidney Disease Progression.

BackgroundDiabetic kidney disease (DKD) is closely associated with the death or survival of resident kidney cells.AimThe purpose of this study was to determine the changes in renal cell survival and death in DKD and their diagnostic values in DKD progression.Materials and MethodsThis study analyzed a dataset of renal tissues from DKD patients to identify changes in genes associated with renal cell death and survival. Our findings were subsequently validated in human kidney tissues. Differential indicators of DKD patients’ clinicopathological data screened by stepwise regression and glomerular P62 protein expression were included in binary logistic regression analysis to assess the impact of these parameters on DKD progression. A receiver operating characteristic (ROC) curve analysis was employed to evaluate the diagnostic value of P62 protein in DKD progression.ResultsBioinformatics analysis results revealed that glomerular autophagy in DKD was more significantly altered, which was consistent with the semi-quantitative results of P62 in glomeruli. Further studies established that P62 expression was mainly increased in podocytes. Stepwise regression analysis indicated that changes in the expressions of glomerular P62 and apolipoprotein A1 (ApoA1) might be involved in the progression of DKD. However, binary logistic regression analysis results suggested that only P62 was significantly associated with DKD development. ROC curve analysis showed that the area under the curve (AUC) of P62 for the detection of DKD was 0.905.ConclusionAutophagy inhibition occurred in both glomeruli and tubules, and was most pronounced in glomerular podocytes. The levels of P62 protein in glomeruli, as an autophagy activity indicator, was one of the predictors of entering the stage of macroalbuminuria in DKD.

POS-032 Human PLA2R-antibodies induce membranous nephropathy in minipigs and activate complement

POS-032 Human PLA2R-antibodies induce membranous nephropathy in minipigs and activate complement

Protocol for a Phase 1, Open-Label, Multiple-Center, Dose-Escalation Study to Evaluate the Safety and Tolerability of ADR-001 in the Treatment of Immunoglobulin A Nephropathy.

IntroductionImmunoglobulin A (IgA) nephropathy is a disease that presents with urinary symptoms such as glomerular hematuria and urinary protein positivity, with predominant deposition of IgA in the mesangial region of the glomerulus. Corticosteroids are mainly used for treatment; however, infection is a serious adverse event, and evidence regarding therapeutic efficacy is insufficient, thus new treatments are strongly desired. Mesenchymal stem cells (MSCs) contribute to the amelioration of inflammation and recovery of organ function in inflammatory environments by converting the character of leukocytes from inflammatory to anti-inflammatory and inducing the proliferation and differentiation of organ component cells, respectively. These properties of MSCs have led to their clinical application in various inflammatory diseases, but this study is the first clinical trial of MSCs for refractory glomerulonephritis in the world. This study is registered and assigned the number, jRCT2043200002 and NCT04342325.MethodsThis will be a phase 1, open-label, multiple-center, dose-escalation study of adult patients with refractory IgA nephropathy resistant to or difficult to treat with existing therapies. ADR-001 will be administered intravenously to from three to six patients at a dose of 1 × 108 cells once in the first cohort and to six patients twice at 2-week intervals in the second cohort, and observation will continue until 52 weeks. The primary endpoint will be the evaluation of adverse events up to 6 weeks after the start of ADR-001 administration. Secondary endpoints will be the respective percentages of patients with adverse events, clinical remission, partial remission, remission of urine protein, remission of hematuria, time to remission, changes in urine protein, hematuria, and estimated glomerular filtration rate.ResultsFollowing the administration of ADR-001 to patients with IgA nephropathy, the respective percentages of patients with adverse events, asymptomatic pulmonary emboli, clinical remission, partial remission, urine protein remission, hematuria remission, their time to remission, changes in urine protein, hematuria, and glomerular filtration rate will be determined.ConclusionThis study will evaluate the safety and tolerability of ADR-001 and confirm its therapeutic efficacy in adult patients with refractory IgA nephropathy.

MO523: The Differential Effect of Third-Generation Intravenous Iron Preparations (Ferric Carboxymaltose, Ferric Derisomaltose) on Hematinic and Renal Function Variables in Patients With Non-Dialysis Dependent CKD and Iron Deficiency Anemia

Abstract BACKGROUND AND AIMS Iron deficiency anemia is common in patients with non-dialysis dependent chronic kidney disease (CKD). Guidelines advocate the use of oral or intravenous (IV) iron, with IV iron offering a quicker and potentially more efficacious replenishment. The advent of third-generation IV iron products [such as ferric carboxymaltose (FCM) and ferric derisomaltose (FDI)] has allowed high doses of iron to be provided in a single sitting. Despite good evidence on their efficacy in replenishing iron stores and safety in terms of renal injury and inflammation when compared against placebo, oral iron or older iron compounds (such as iron sucrose and low molecular weight iron dextran), the two compounds have never before been compared head-to-head in CKD. METHOD As part of the single-center double-blinded exploratory randomized controlled trial ‘Iron and Phosphaturia—ExplorIRON-CKD’ that took place in a tertiary center in the UK, patients with iron deficiency with/without anemia and CKD stage 3a–5 but not on dialysis were recruited to receive FCM or FDI in two divided doses—1000 mg at baseline and 500–1000 mg in a 1-month interval to achieve replenishment. Iron deficiency was defined as serum ferritin (SF) &amp;lt;200 µg/L or transferrin saturation (TSAT) ≤20% and SF 200–299 µg/L. Markers of treatment response such as hemoglobin and iron parameters [serum ferritin (SF), transferrin saturation (TSAT)], renal function and injury [serum creatinine, estimated glomerular filtration rate (eGFR) and protein: creatinine ratio (PCR)] and inflammation (CRP) were monitored throughout the study. Hemoglobin, renal function and inflammation were monitored at baseline, 2 weeks, 1 month and 2 months following initial infusion. Iron response was assessed at baseline, 1–2 days, 2 weeks, 1 month post-initial infusion (and time of second infusion), 1–2 days after the second infusion and 2 months after initial administration. RESULTS A total of 26 patients were recruited; 14 were randomized to receive FDI and 12 to receive FCM. All patients received at least one iron dose (1000 mg), 10 patients received two FDI doses and 11 received two FCM doses. There was an increase in hemoglobin in both groups, with no significant difference between the groups at any given time point in the study [baseline: FDI: 99.2 (12.2) g/L versus FCM: 101.6 (15.3) g/L; P = .67; 2 months: FDI: 106.0 (13.3) g/L versus FCM: 109.1 (8.3) g/L; P = .526). Both groups had a median baseline SF &amp;lt;100 µg/L and TSAT &amp;lt;20%, and by the end of follow-up, iron repletion was similarly successful in both groups as indicated by a median SF &amp;gt; 400 µg/L and a TSAT &amp;gt;20% (Figure 1). A small numerical reduction was noted in median eGFR in the FCM group from baseline to the end of the study (baseline: 18.0 (11.3) mL/min/1.73 m2 versus 2 months: 16.5 (8.5) mL/min/1.73 m2); however, there was no significant difference between the two groups at any time point in the study (Figure 2). Urinary PCR, serum creatinine and CRP remained stable throughout the study and did not differ significantly between the two groups. CONCLUSION Third-generation IV iron preparations are efficacious in replenishing iron stores. There was no adverse short-term impact on renal function, injury or inflammation. In our cohort, the two compounds were equivocal for the parameters studied, with no significant difference identified in any of the areas examined. The population was small, therefore the results should be interpreted with caution; nonetheless, newer IV iron compounds appear to be equally efficacious in the treatment of iron deficiency anemia in non-dialysis-dependent CKD.

Clinical Response to Intestine-targeted Steroid Therapy in Biopsy-proven Immunoglobulin A Nephropathy.

Primary immunoglobulin A (IgA) nephropathy is associated with a dysfunctional mucosal immune system, leading to renal deposition of IgA and injury. Fifty patients with biopsy-proven IgA nephropathy were included. All patients were initiated on renin-angiotensin-aldosterone system (RAAS) inhibitors, polyunsaturated fatty acids, and a controlled release formulation (CRF) of budesonide. All drugs were started together, as isolated RAAS inhibitors will not prevent the immunological damage caused by the ongoing deposition of IgA. Depending on the histology (mesangial hypercellularity, endocapillary proliferation, segmental glomerulosclerosis, tubular atrophy/interstitial fibrosis, and crescents score), the patients received 9 mg or 12 mg of budesonide. All patients were followed up every 4 weeks to monitor renal function, 24-h urinary protein, and adverse effects. Our primary outcome was a mean change in the estimated glomerular filtration rate (eGFR) and 24-h urinary protein from the baseline to the end of 6 months. The percentage of decline in mean 24-h protein at 6 months from the baseline was 33%. The mean decrease in serum creatinine from the baseline was 0.73 mg/dL. The mean gain in eGFR from the baseline was an increase of 9 mL/min/1.73 m2. Of 50 patients, 11 (22%) achieved complete remission, 20 (40%) achieved partial remission, and 16 (32%) were non-responders. Three patients (6%) were lost to follow-up. The early initiation of CRF budesonide with optimized supportive care led to reductions in proteinuria and improvements in eGFR at 6 months in patients with IgA nephropathy. Early lesions with minimal chronicity showed an excellent response to budesonide.

Sex Differences in Glomerular Protein Expression and Effects of Soy-Based Diet on Podocyte Signaling.

Background:Kidney disease is a major public health issue arising from loss of glomerular podocyte function, and there are considerable sex differences in its prognosis. Evidence suggests a renoprotective effect of estrogen and soy diet-derived phytoestrogens, although the molecular basis for this is poorly understood.Objective:Here, we aim to assess sex differences in expression of key proteins associated with podocyte survival and determine the effects of dietary soy on glomerular and podocyte signaling.Methods:Male and female FVB mice were fed control, low (1%), and high (20%) doses of isolated soy protein (ISP) in utero and until 100 days of age. Spot urine was collected to measure proteinuria and isolated glomeruli were used to quantify activated and total levels of nephrin, Akt, and ERK1/2. To investigate protective effects of specific soy phytoestrogens, cultured podocytes were treated with or without daidzein and subject to control or high glucose as a model of podocyte injury.Results:Nephrin and Akt were elevated at baseline in glomeruli from females compared to males. Both sexes that were fed 1% and 20% ISP displayed robust increases in total glomerular Akt compared to controls, and these effects were more prominent in females. A similar trend at both doses in both sexes was observed with activated Akt and total nephrin. Notably, males exclusively showed increased phosphorylation of nephrin and extracellular signal-regulated kinase (ERK) at the 1% ISP dose; however, no overt changes in urinary albumin excretion or podocin levels were observed, suggesting that the soy diets did not impair podocyte function. Finally, in cultured male and female podocytes, daidzein treatment suppressed high glucose-induced ERK activation.Conclusions:Together, our findings reveal a putative mechanism to explain the protective influence of sex on kidney disease progression, and they provide further evidence to support a beneficial role for dietary soy in preserving glomerular function.

Long-Term Preservation of Renal Function in Septic Shock Burn Patients Requiring Renal Replacement Therapy for Acute Kidney Injury.

Background. The real impact of septic shock-associated acute kidney injury (AKI) on the long-term renal outcome is still debated, and little is known about AKI-burn patients. In a cohort of burn survivors treated by continuous renal replacement therapy (CRRT) and sorbent technology (CPFA-CRRT), we investigated the long-term outcome of glomerular and tubular function. Methods. Out of 211 burn patients undergoing CRRT from 2001 to 2017, 45 survived, 40 completed the clinical follow-up (cumulative observation period 4067 months, median 84 months, IR 44-173), and 30 were alive on 31 December 2020. Besides creatinine and urine albumin, in the 19 patients treated with CPFA-CRRT, we determined the normalized GFR by 99mTc-DTPA (NRI-GFR) and studied glomerular and tubular urine protein markers. Results. At the follow-up endpoint, the median plasma creatinine and urine albumin were 0.99 (0.72–1.19) and 0.0 mg/dL (0.0–0.0), respectively. NRI-GFR was 103.0 mL/min (93.4–115). Four patients were diabetic, and 22/30 presented at least one risk factor for chronic disease (hypertension, dyslipidemia, and overweight). Proteinuria decreased over time, from 0.47 g/day (0.42–0.52) at 6 months to 0.134 g/day (0.09–0.17) at follow-up endpoint. Proteinuria positively correlated with the peak of plasma creatinine (r 0.6953, p 0.006) and the number of CRRT days (r 0.5650, p 0.035) during AKI course, and negatively with NRI–GFR (r −0.5545, p 0.049). In seven patients, urine protein profile showed a significant increase of glomerular marker albumin and glomerular/tubular index. Conclusions. Burn patients who experienced septic shock and AKI treated with CRRT had a long-term expectation of preserved renal function. However, these patients were more predisposed to microalbuminuria, diabetes, and the presence of risk factors for intercurrent comorbidities and chronic renal disease.

Glypican-4 in pregnancy and its relation to glucose metabolism, insulin resistance and gestational diabetes mellitus status

Glypican-4 (GPC-4) is an adipokine that enhances insulin receptor signaling. Plasma concentrations were found to be elevated in patients with prediabetes but reduced in type 2 diabetes mellitus. No study on Glypican-4 in pregnancy and pregnancy-related insulin resistance has been published yet. GPC-4 levels were investigated in 59 overweight women throughout their pregnancy at the Medical University of Vienna. GPC-4 levels, fasting insulin, fasting glucose, estradiol, liver and renal parameters, and markers of bone development were assessed before the < 21st week of gestation (GW), and at GW 35–37. GPC-4 levels increased from < 21 GW (mean = 2.38 pg/ml, SD = 0.68 pg/ml) to GW 35–37 (mean = 2.96 pg/ml, SD = 0.77 pg/ml, p < 0.001). At the same time, GPC-4 levels correlated negatively with estimated glomerular filtration rate (eGFR), serum protein and serum albumin levels and were positively related to creatinine and uric acid levels at GW 35–37. Concerning glucose metabolism, GPC-4 levels were inversely related to ISSI-2, fasting insulin and HOMA-IR, however, not significantly different between women with normal glucose tolerance (NGT) and GDM (p = 0.239). In conclusion, GPC-4 levels rose significantly during pregnancy, correlated negatively with fasting insulin and HOMA-IR but might not be related to gestational diabetes mellitus status.

Associations between measurements of central blood pressure and target organ damage in high-risk patients

BackgroundIt is not well-known which components of central blood pressure (CBP) are more influential to target organ damage (TOD). This study aimed to determine the relationship between CBP measurements and various types of TOD in high-risk patients.MethodsA total of 148 patients who had documented atherosclerotic cardiovascular disease or its multiple risk factors were prospectively enrolled. CBP was measured by using applanation tonometry of the radial artery. The following nine TOD parameters were evaluated: left ventricular mass index, relative wall thickness, septal e′ velocity, septal E/e′, brachial-ankle pulse wave velocity, ankle-brachial index, estimated glomerular filtration rate, urine protein and obstructive coronary artery disease.ResultsThe mean age of the study population was 67.1 ± 9.0 years and 108 (73 %) were male. Among four CBP measurements (systolic, diastolic, mean, and pulse pressures), central pulse pressure (CPP) was associated with the largest number of TOD parameters. As CPP increased, the number of TOD increased (P = 0.010), but this association was not observed in other CBP measurements (P > 0.05 for each).ConclusionsCPP had a stronger correlation with TOD than other CBP measurements. Non-invasive CPP could be a useful indicator for predicting TOD in patients at high coronary risk.

Emerging Insights Into Chronic Renal Disease Pathogenesis in Hypertension From Human and Animal Genomic Studies.

The pathogenic links between elevated blood pressure and chronic kidney disease remain obscure. This article examines progress in population genetics and in animal models of hypertension and chronic kidney disease. It also provides a critique of the application of genome-wide association studies to understanding the heritability of renal function. Emerging themes identified indicate that heritable risk of chronic kidney disease in hypertension can arise from genetic variation in (1) glomerular and tubular protein handling mechanisms; (2) autoregulatory capacity of the renal vasculature; and (3) innate and adaptive immune mechanisms. Increased prevalence of hypertension-associated chronic kidney disease that occurs with aging may reflect amplification of heritable risks by normal aging processes affecting immunity and autoregulation.

PGLYRP2 as a novel biomarker for the activity and lipid metabolism of systemic lupus erythematosus

BackgroundTo assess the value of peptidoglycan recognition protein 2 (PGLYRP2) in assessing the disease activity and lipid metabolism in patients with systemic lupus erythematosus (SLE).MethodsSLE patients with stable disease (n = 15), active lupus nephritis (LN) (n = 15) and neuropsychiatric systemic lupus erythematosus (NP-SLE) (n = 15) admitted to Northern Jiangsu People’s Hospital (Jiangsu, China) in 2019–2020 were recruited. In addition, volunteers with matched age and sex (n = 15) were enrolled as controls. The level of PGLYRP2 in the serum and its expression in peripheral blood mononuclear cells (PBMCs) were measured. The link between PGLYRP2 level and clinical parameters (including lipid profile) was described.ResultsSerum PGLYRP2 level in SLE cases exceeded that in healthy volunteers (3938.56 ± 576.07 pg/mL), and significantly higher in active LN (5152.93 ± 446.13 pg/mL) and NP-SLE patients (5141.52 ± 579.61 pg/mL). As shown by quantitative real-time PCR results, the expression of PGLYRP2 in PBMCs of SLE patients with active LN and NP-SLE surpassed that in healthy volunteers (P < 0.01). Receiver operating characteristic (ROC) curves demonstrated that PGLYRP2 was capable of distinguishing stable SLE from active LN (AUC = 0.841, 95%CI = 0.722–0.960, P = 0.000). PGLYRP2 level positively correlated with SLEDAI of SLE patients (r = 0.5783, P < 0.01). Moreover, its level varied with serological and renal function parameters (complement 3, complement 4, estimated glomerular filtration rate and 24-h urine protein) and immunoglobulin A (IgA) of SLE. A potential correlation between PGLYRP2 level and lipid profile (HLD-c, Apo-A1 and Apo B/A1) was determined in SLE patients. The linear regression analysis indicated SLEDAI as an independent factor of PGLYRP2 level, with a positive correlation in between (P < 0.05).ConclusionsSerum PGLYRP2 level significantly increases in SLE patients, and is positively correlated to SLEDAI. Moreover, serum PGLYRP2 level is correlated with renal damage parameters and the abnormal lipid profile of SLE. PGLYRP2 could be used to predict SLE activity, dyslipidemia and cardiovascular disease risks in SLE patients.

Transforming Growth Factor Beta Receptor 3 (TGFBR3)-Associated Membranous Nephropathy.

Membranous lupus nephritis (MLN) comprises 10%-15% of lupus nephritis and increases morbidity and mortality of patients with SLE through complications of nephrotic syndrome and chronic kidney failure. Identification of the target antigens in MLN may enable noninvasive monitoring of disease activity, inform treatment decisions, and aid in prognostication, as is now possible for idiopathic MN caused by antibodies against the phospholipase A2 receptor. Here, we show evidence for type III TGF-β receptor (TGFBR3) as a novel biomarker expressed in a subset of patients with MLN. Mass spectrometry was used for protein discovery through enrichment of glomerular proteins by laser capture microdissection and through elution of immune complexes within MLN biopsy specimens. Colocalization with IgG within glomerular immune deposits from patients and disease controls was evaluated by confocal microscopy. Immunostaining of consecutive case series was used to determine the overall frequency in MN and MLN. TGFBR3 was found to be enriched in glomeruli and coimmunoprecipitated with IgG within a subset of MLN biopsy specimens by mass spectrometry. Staining of consecutive MN cases without clinical evidence of SLE did not show TGFBR3 expression (zero of 104), but showed a 6% prevalence in MLN (11 of 199 cases). TGFBR3 colocalized with IgG along the glomerular basement membranes in TGFBR3-associated MN, but not in controls. Positive staining for TGFBR3 within glomerular immune deposits represents a distinct form of MN, substantially enriched in MLN. A diagnosis of TGFBR3-associated MN can alert the clinician to search for an underlying autoimmune disease.

Serine Protease HTRA1 as a Novel Target Antigen in Primary Membranous Nephropathy.

Identification of target antigens PLA2R, THSD7A, NELL1, or Semaphorin-3B can explain the majority of cases of primary membranous nephropathy (MN). However, target antigens remain unidentified in 15%-20% of patients. A multipronged approach, using traditional and modern technologies, converged on a novel target antigen, and capitalized on the temporal variation in autoantibody titer for biomarker discovery. Immunoblotting of human glomerular proteins followed by differential immunoprecipitation and mass spectrometric analysis was complemented by laser-capture microdissection followed by mass spectrometry, elution of immune complexes from renal biopsy specimen tissue, and autoimmune profiling on a protein fragment microarray. These approaches identified serine protease HTRA1 as a novel podocyte antigen in a subset of patients with primary MN. Sera from two patients reacted by immunoblotting with a 51-kD protein within glomerular extract and with recombinant human HTRA1, under reducing and nonreducing conditions. Longitudinal serum samples from these patients seemed to correlate with clinical disease activity. As in PLA2R- and THSD7A- associated MN, anti-HTRA1 antibodies were predominantly IgG4, suggesting a primary etiology. Analysis of sera collected during active disease versus remission on protein fragment microarrays detected significantly higher titers of anti-HTRA1 antibody in active disease. HTRA1 was specifically detected within immune deposits of HTRA1-associated MN in 14 patients identified among three cohorts. Screening of 118 "quadruple-negative" (PLA2R-, THSD7A-, NELL1-, EXT2-negative) patients in a large repository of MN biopsy specimens revealed a prevalence of 4.2%. Conventional and more modern techniques converged to identify serine protease HTRA1 as a target antigen in MN.

Organ-Specific Monitoring of Solitary Kidney after Living Donation by Using Markers of Glomerular Filtration Rate and Urinary Proteins

Background: Effective follow-up after living kidney donation is important for maintaining the renal function of the donor. We investigated whether the estimated glomerular filtration rate (eGFR) and urinary protein and enzyme levels can provide important information regarding the state of the remaining kidney after donor nephrectomy. Methods: Seventy-five living donations were included (prospective/retrospective) in the study. The following parameters were measured up to 1 year after donor nephrectomy: serum creatinine and cystatin C as markers of the GFR; the high-molecular-weight urinary proteins as markers of glomerular injury; and the low-molecular-weight urinary proteins and urinary enzymes as markers of tubular function. Results: One year after kidney donation, the creatinine and cystatin C values were 1.38-fold increased than their initial values, while the eGFR was 32% lower. At that time, 38% of donors had a moderate or high risk of CKD progression. The biochemical urinary glomerular and tubular kidney markers examined showed different behaviors. After a transient increase, the glomerular proteins normalized. Conversely, the detection of low-molecular-weight urinary proteins and enzymes reflected mild tubular damage at the end of the study period. Conclusions: Our findings suggest that for the evaluation of mild tubular damage, low-molecular-weight marker proteins should be included in the urine diagnostic of a personalized living kidney donor follow-up.

Antiproteinuric and Hyperkalemic Mechanisms Activated by Dual Versus Single Blockade of the RAS in Renovascular Hypertensive Rats.

This study aimed to investigate the antiproteinuric and hyperkalemic mechanisms activated by dual renin-angiotensin system (RAS) blockade in renovascular hypertensive rats (2-kidney 1-clip model [2K-1C]). Six weeks after clipping the left renal artery or sham operation (2K), rats were treated with losartan, enalapril, or both drugs for two weeks. We found that 2K-1C rats displayed higher tail-cuff blood pressure (BP), increased non-clipped kidney Ang II concentration, and more pronounced urinary albumin excretion than 2K. BP was decreased by the treatment with either enalapril or losartan, and the combination of both drugs promoted an additional antihypertensive effect in 2K-1C rats. Renal Ang II content and albuminuria were reduced by either enalapril or losartan in monotherapy and restored to control levels by dual RAS blockade. Albuminuria in 2K-1C rats was accompanied by downregulation of the glomerular slit protein podocin, reduction of the endocytic receptors megalin and cubilin, and a marked decrease in the expression of the ClC-5 chloride channel, compared to 2K animals. Treatment with losartan and enalapril in monotherapy or combination increased the expression of podocin, cubilin, and ClC-5. However, only the combined therapy normalized podocin, cubilin, and ClC-5 protein abundance in the non-clipped kidney of 2K-1C rats. Renovascular hypertensive 2K-1C rats had a lower concentration of plasma potassium compared to 2K rats. Single RAS blockade normalized potassium plasma concentration, whereas 2K-1C rats treated with dual RAS blockade exhibited hyperkalemia. Hypokalemia in 2K-1C rats was accompanied by an increase in the cleaved activated forms of α-ENaC and γ-ENaC and the expression of β-ENaC. Combined RAS blockade but not monotherapy significantly reduced the expression of these ENaC subunits in 2K-1C rats. Indeed, double RAS blockade reduced the abundance of cleaved-α-ENaC to levels lower than those of 2K rats. Collectively, these results demonstrate that the antiproteinuric effect of dual RAS blockade in 2K-1C rats is associated with the restored abundance of podocin and cubilin, and ClC-5. Moreover, double RAS blockade-induced hyperkalemia may be due, at least partially, to an exaggerated downregulation of cleaved α-ENaC in the non-clipped kidney of renovascular hypertensive rats.

Patients\u2019 treatment limitations as predictive factor for mortality in COVID-19: results from hospitalized patients of a hotspot region for SARS-CoV-2 infections

BackgroundIn hospitalized patients with SARS-CoV-2 infection, outcomes markedly differ between locations, regions and countries. One possible cause for these variations in outcomes could be differences in patient treatment limitations (PTL) in different locations. We thus studied their role as predictor for mortality in a population of hospitalized patients with COVID-19.MethodsIn a region with high incidence of SARS-CoV-2 infection, adult hospitalized patients with PCR-confirmed SARS-CoV-2 infection were prospectively registered and characterized regarding sex, age, vital signs, symptoms, comorbidities (including Charlson comorbidity index (CCI)), transcutaneous pulse oximetry (SpO2) and laboratory values upon admission, as well as ICU-stay including respiratory support, discharge, transfer to another hospital and death. PTL assessed by routine clinical procedures comprised the acceptance of ICU-therapy, orotracheal intubation and/or cardiopulmonary resuscitation.ResultsAmong 526 patients included (median [quartiles] age 73 [57; 82] years, 47% female), 226 (43%) had at least one treatment limitation. Each limitation was associated with age, dementia and eGFR (p < 0.05 each), that regarding resuscitation additionally with Charlson comorbidity index (CCI) and cardiac disease. Overall mortality was 27% and lower (p < 0.001) in patients without treatment limitation (12%) compared to those with any limitation (47%). In univariate analyses, age and comorbidities (diabetes, cardiac, cerebrovascular, renal, hepatic, malignant disease, dementia), SpO2, hemoglobin, leucocyte numbers, estimated glomerular filtration rate (eGFR), C-reactive protein (CRP), Interleukin-6 and LDH were predictive for death (p < 0.05 each). In multivariate analyses, the presence of any treatment limitation was an independent predictor of death (OR 4.34, 95%-CI 2.10–12.30; p = 0.001), in addition to CCI, eGFR < 55 ml/min, neutrophil number > 5 G/l, CRP > 7 mg/l and SpO2 < 93% (p < 0.05 each).ConclusionIn hospitalized patients with SARS-CoV-2, the percentage of patients with treatment limitations was high. PTL were linked to age, comorbidities and eGFR assessed upon admission and strong, independent risk factors for mortality. These findings might be useful for further understanding of COVID-19 mortality and its regional variations.Clinical trial registration ClinicalTrials.gov Identifier: NCT04344171