Proteinuria In Focal Segmental Glomerulosclerosis Research Articles

Decreased GM3 correlates with proteinuria inminimal change nephrotic syndrome and focal segmental glomerulosclerosis.

Glycolipids on cell membrane rafts play various roles by interacting with glycoproteins. Recently, it was reported that the glycolipid GM3 is expressed in podocytes and may play a role in podocyte protection. In this report, we describe the correlation between changes in GM3 expression in glomeruli and proteinuria in minimal change nephrotic syndrome (MCNS) and focal segmental glomerulosclerosis (FSGS) patients. We performed a case-control study of the correlation between nephrin/GM3 expression levels and proteinuria in MCNS and FSGS patients who underwent renal biopsy at our institution between 2009 and 2014. Normal renal tissue sites were used from patients who had undergone nephrectomy at our institution and gave informed consent. Both MCNS and FSGS had decreased GM3 and Nephrin expression compared with the normal (normal vs. MCNS, FSGS; all p < 0.01). Furthermore, in both MCNS and FSGS, GM3 expression was negatively correlated with proteinuria (MCNS: r = -0.61, p < 0.01, FSGS: r = -0.56, p < 0.05). However, nephrin expression had a trend to correlate with proteinuria in FSGS (MCNS: r = 0.19, p = 0.58, FSGS: r = -0.48, p = 0.06). Furthermore, in a simple linear regression analysis, GM3 expression also correlated with proteinuric change after 12months of treatment (MCNS: r = 0.40, p = 0.38, FSGS: r = 0. 68, p < 0.05). We showed for the first time that decreased GM3 expression correlates with proteinuria in MCNS and FSGS patients. Further studies are needed on the podocyte-protective effects of GM3.

SUN-190 GFB-887, a small molecule inhibitor of TRPC5, protects against podocyte injury and attenuates proteinuria in models of FSGS

Focal segmental glomerulosclerosis (FSGS) is a rare podocytopathy with a high likelihood of progression to end stage renal disease. The Ca2+-permeable transient receptor potential canonical 5 (TRPC5) channel is a critical mediator of proteinuria in FSGS. Activation of the TRPC5 pathway in podocytes culminates in activation of Rac1, which is the primary driver of proteinuria in many forms of familial and sporadic FSGS. Inhibition of TRPC5 channel activity has been shown to protect against proteinuria and podocyte loss in AT1R transgenic and Dahl salt-sensitive rats. We performed high throughput screening of a structurally diverse compound collection followed by lead optimization for the development of several potent TRPC5 inhibitors. We characterized TRPC5 inhibitors in vitrousing a mouse podocyte cell line and podocyte injury models derived from human inducible pluripotent stem cells (hiPSC), and in two in vivomodels of FSGS, the unilaterally nephrectomized deoxycorticosterone acetate (DOCA)-salt rat model and the puromycin aminonucleoside nephrosis (PAN) rat model Here we report the identification of GFB-887, a potent, selective and orally bioavailable small molecule inhibitor of TRPC5. Potency and selectivity across TRP channels were determined using FLIPR based assays and electrophysiology. We show that TRPC5 inhibition protects against loss of stress fibers induced by protamine sulfate, a known activator of TRPC5, and restores stress fibers in podocytes after knockdown of synaptopodin. We further show that inhibition of TRPC5 suppresses pathogenic podocyte motility in a scratch assay. Finally, we demonstrate that inhibition of TRPC5 attenuates proteinuria in hypertension-induced FSGS in DOCA-salt rat model without altering blood pressure, and in non-hypertensive FSGS in the PAN rat model suggesting direct glomerular protection in vivo. We have identified GFB-887 as a new selective small molecule inhibitor of TRPC5 for the treatment of proteinuria in FSGS

1 H NMR-based metabolomics exploring urinary biomarkers correlated with proteinuria in focal segmental glomerulosclerosis: a pilot study.

Focal segmental glomerulosclerosis (FSGS) is a common glomerulonephritis, and its rates of occurrence are increasing worldwide. Proteinuria is a clinical defining feature of FSGS which correlates with the severity of podocyte injury in patients with nephrotic-range protein excretion. Metabolite biomarkers corresponding with the level of proteinuria could be considered as non-invasive complementary prognostic factors to proteinuria. The urine samples of 15 patients (n = 6 women and n = 9 men) with biopsy-proven FSGS were collected and subjected to nuclear magnetic resonance (NMR) analysis for metabolite profiling. Multivariate statistical analyses, including principal component analysis and orthogonal projection to latent structure discriminant analysis, were applied to construct a predictive model based on patients with proteinuria >3000 mg/day and <3000 mg/day. In addition, random forest was performed to predict differential metabolites, and pathway analysis was performed to find the defective pathways responsible for proteinuria. Ten metabolites, significant in both statistical methods (orthogonal projection to latent structure discriminant analysis and random forest), were considered as prognostic biomarkers for FSGS: citrulline, dimethylamine, proline, acetoacetate, alpha-ketoisovaleric acid, valine, isobutyrate, D-Palmitylcarnitine, histidine, and N-methylnicotinamide. Pathway analysis revealed impairment of the branched-chain amino acid degradation pathways in patients with massive proteinuria. This study shows that metabolomics can reveal the molecular changes corresponding with disease progression in patients with FSGS and provide a new insight for pathogenic pathways. Copyright © 2016 John Wiley & Sons, Ltd.

Podocyte Foot Process Effacement in Postreperfusion Allograft Biopsies Correlates with Early Recurrence of Proteinuria in Focal Segmental Glomerulosclerosis

Background Focal segmental glomerulosclerosis (FSGS) is a relatively prevalent glomerular disorder that often progresses to end-stage renal disease. 30 to 80% of kidney transplant (KT) recipients with FSGS will experience recurrence characterized by proteinuria and podocyte damage. We hypothesized the degree of podocyte foot process (FP) effacement in post-reperfusion transplant biopsies can be used to predict the development of clinical recurrence of FSGS.

Rituximab in idiopathic nephrotic syndrome: does it make sense?

Idiopathic nephrotic syndrome (INS) includes three different entities: minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), and mesangial proliferative glomerulonephritis. Historically, this condition has been attributed to a T-cell disorder resulting in the secretion of a circulating factor that increases glomerular permeability to plasma proteins. The therapeutic approach to control the proteinuria of INS remains the use of drugs that have been considered to suppress the production of the "circulating factor" secreted by T cells. Recently, rituximab (RTX), a chimeric monoclonal antibody directed against the CD20 cell surface receptor expressed on B cells, has emerged as potential therapeutic agent. The number of publications reporting clinical experience with RTX in the treatment of nephrotic syndrome has greatly increased in the last few years. However, there is currently no good evidence from clinical or experimental studies that support a role of RTX in the treatment of MCD and FSGS proteinuria. In summary, there is the need for a better understanding of the pathogenesis of the proteinuria in INS and the potential role of RTX in this condition.

The calcineurin–NFAT pathway allows for urokinase receptor-mediated beta3 integrin signaling to cause podocyte injury

Circulating and podocyte-bound urokinase receptor (uPAR) is a mediator of podocyte injury, proteinuria, and focal segmental glomerulosclerosis (FSGS) allowing pathological activation of the uPAR-β3 integrin signaling axis. Clinically, calcineurin inhibitors (e.g., cyclosporine A, CsA) are known to suppress T cells, yet are also being used to reduce proteinuria in FSGS, suggesting the possibility of signal cross talk between uPAR and calcineurin. Calcineurin is known to facilitate the nuclear translocation of the nuclear factor of activated T cells (NFAT). Accordingly, in vivo conditional NFATc1 activation in podocytes leads to proteinuria in mice, yet the downstream targets of NFAT remain unclear. Here, we show that inducible podocyte-specific expression of constitutively active NFATc1 increased podocyte uPAR expression by binding to the Plaur gene promoter (encoding uPAR) in chromatin immunoprecipitation assays. Pathological uPAR signals in podocytes are independent of T cells and affect cell motility via activation, but not expression, changes of the β3 integrin and can be blocked by CsA, NFAT-siRNA, or the cell-permeable NFAT inhibitor (11R-VIVIT) using rodent models of glomerular disease (LPS; 5/6 nephrectomized rats). Taken together, these findings identify podocyte uPAR as a downstream target of NFAT and provide further insights into the pathogenesis of FSGS.

Focal segmental glomerulosclerosis in a boy with Dent-2 disease

Sirs, Proximal tubular dysfunction is, in general, more common when the nephrotic syndrome is associated with focal segmental glomerulosclerosis (FSGS) than with minimal-change nephrotic syndrome. Although it has been considered that the nonselective proteinuria in FSGS causes proximal tubular cell injury with the resultant tubulointerstitial damage and scarring, Copelovitch et al. have recently postulated that the tubular dysfunction or damage is the primary renal insult and that FSGS may be a secondary epiphenomenon in some patients with congenital tubulopathies [1]. We encountered a patient who fits into this concept. The patient was a 4-year-old Japanese boy referred to us for further evaluation of significant proteinuria detected by a mass screening program for renal disease in Japan at 3 years of age. He was first referred to a local hospital where renal biopsy was performed because of persistent proteinuria for several months. Pathological diagnosis of FSGS was made (Fig. 1). His past medical history and family history were unremarkable. Physical examination on admission showed that the boy’s height was 95.2 cm (−2.4 S.D.), his weight was 15.1 kg (−1 S.D.), and his blood pressure was 102/ 68 mmHg. There were no dysmorphic features. Initial serum concentrations were all normal: sodium 139 mEq/L, potassium 3.8 mEq/L, chloride 103 mEq/L, carbon dioxide 25 mEq/L, calcium 9.9 mg/dl, phosphorous 3.8 mg/dl, albumin 4.5 g/dl, and creatinine 0.27 mg/dl. Twenty-fourhour protein excretion varied from 892 mg/day to 1,242 mg/day. Repeated urinalysis did not detect glucosuria or hematuria. From these findings, the presumptive diagnosis of idiopathic FSGS was made and the treatment consisting of steroid and cyclosporine A had been initiated without a significant reduction in the amount of proteinuria. During the treatment over the following 11 months, quantitative analysis of the low-molecular weight protein in urine, such as beta-2-microglobulin (BMG), was repeatedly performed and showed extraordinarily high values (BMG: 84,800 μg/l–185,000 μg/l, normal T, p.P509S). This same mutation has been neither previously described nor observed in 200 control chromosomes from healthy individuals. No mutations were detected in CLCN5. Our patient was diagnosed as having Dent-2 and was weaned off steroids and cyclosporine A over the following month. He is now 6 years old and otherwise healthy without any medication, although a significant amount of proteinuria is still present. K. Kaneko (*) :M. Hasui Department of Pediatrics, Kansai Medical University, 2-3-1 Shin-machi, Hirakata-shi, Osaka 573-1191, Japan e-mail: kanekok@hirakata.kmu.ac.jp

Direct effect of plasma permeability factors from patients with idiopatic FSGS on nephrin and podocin expression in human podocytes

The presence of circulating plasma factors (PF) altering renal permeability to proteins has been previously described in patients with focal segmental glomerulosclerosis (FSGS). Since these patients show reduced nephrin and podocin expression at renal biopsy, we evaluated the effect of serum and PF from patients with FSGS on nephrin and podocin expression in human podocytes. We studied 7 sera from patients with steroid-resistant FSGS, 3 from patients with nephrotic syndrome caused by non-immune disease, and 6 from healthy subjects. PF was prepared from plasmapheresis eluates of 2 patients with post-transplant recurrence of FSGS. Purification procedure was based on protein A Sepharose chromatography and differential precipitation in ammonium sulphate. Nephrin and podocin expression was semi-quantitatively evaluated by immunofluorescence. We found that serum and PF from FSGS patients rapidly induced redistribution and loss of nephrin in podocytes. This effect was associated with cytoskeleton redistribution and inhibited by cytochalasin B and sodium azide. On the contrary, podocin expression was unchanged after incubation with serum and PF from FSGS patients for short periods, but markedly reduced at 24 h. Our results demonstrate that serum and PF from FSGS patients may directly affect nephrin and podocin in human podocytes, thus providing new insights into the mechanisms causing proteinuria in FSGS.

Early use of plasmapheresis for recurrent post-transplant FSGS.

Recurrence of focal segmental glomerulosclerosis (FSGS) in an allograft is a challenging clinical situation because it frequently results in graft loss. We report our experience with early use of plasmapheresis in recurrent FSGS. Of the 18 (33%) children with biopsy-proven FSGS (in their native kidneys) transplanted at our institution, 6 had recurrence (elevated urine protein/creatinine ratios) post transplant and were treated with plasmapheresis. Patients who received treatment within 1 day of the recurrence (4/6) went into remission after 5-13 plasmapheresis treatments, within 5-27 days of starting treatment. Patients who did not respond to plasmapheresis (2/6) were treated 7 and 17 days after onset of proteinuria; 1 of these had acute tubular necrosis and acute rejection leading to graft loss and the other developed acute rejections, ongoing proteinuria, and subsequent graft loss. All 4 patients who went into remission have maintained good graft function, 22-53 months post transplant. In our experience early institution of plasmapheresis for recurrent post-transplant proteinuria in FSGS is effective.

AL-amyloidosis of the kidney initially presenting as minimal change glomerulonephritis

Small amounts of amyloid in kidney biopsy specimens may be missed on routine examination unless specifically targeted. Occasionally, this oversight results in a diagnosis of minimal change glomerulonephritis (MCGN). This misdiagnosis may be facilitated by the fact that typical “minimal changes” with flattening and effacement of the epithelial foot processes can be found in capillary loops directly affected by amyloid deposition as well as in capillary loops of glomeruli with only mild amyloid deposition in the mesangium. Repeatedly, the diagnosis of MCGN had to be corrected to renal amyloidosis when re-examination by special techniques succeeded in detecting even small amounts of amyloid fibrils. We present the case of a previously healthy 49-year-old man who suddenly developed nephrotic syndrome. A first renal biopsy showed MCGN. Proteinuria remained refractory to immunosuppressive treatments, and creatinine clearance deteriorated rapidly. Two years later, a repeat renal biopsy showed AL-amyloidosis. In this case, re-examination of the first biopsy in the light of the final diagnosis again did not show any deposition of amyloid fibrils. We suspect that proteinuria and epithelial podocyte changes in amyloidosis are caused by factors other than deposition of amyloid fibrils itself. Possibly a cytokine release during the early fibril formation leads to abnormalities even before the typical structural changes of renal amyloidosis can be detected. This is analogous to the hypothesis of a circulating factor that leads to proteinuria in focal segmental glomerulosclerosis or the speculation of altered lymphokine expression associated with the development of MCGN in Hodgkin’s disease.

Effects of cyclosporin A on glomerular barrier function in the nephrotic syndrome.

1. To elucidate the mechanisms by which cyclosporin A diminishes proteinuria, we studied 20 patients with severe nephrotic syndrome. Biopsy-established pathologies included minimal change disease (n = 5), membranous glomerulopathy (n = 6), membranoproliferative glomerulonephritis (n = 5) and focal segmental glomerulosclerosis (n = 4). Before, at the end of a 90 day course of cyclosporin A, and finally 1 month after stopping cyclosporin A we determined 24 h protein excretion. Measurements of glomerular filtration rate, effective renal plasma flow, fractional clearance rates of albumin and immunoglobulins with different charges and the transglomerular sieving of uncharged dextrans of broad size distribution were used to study the effects of cyclosporin A on renal perfusion and the glomerular filtration barrier. The findings were analysed with a theoretical model of solute transport. 2. Among the different forms of glomerulopathy the response to low-dose cyclosporin A (trough levels 32.0-36.9 ng/ml) varied markedly. In minimal change disease, proteinuria decreased from 9.5 +/- 3.1 to 1.3 +/- 0.2 g/24 h (mean +/- SEM, P less than 0.01). This response was due to restoration of the charge selectivity of the glomerular barrier. The depressed value of the glomerular permeability coefficient also returned to normal. Glomerular filtration rate, effective renal plasma flow and renal vascular resistance did not change. Proteinuria returned after stopping cyclosporin A, although it did not reach pretreatment levels. In membranous glomerulopathy, proteinuria fell from 9.9 +/- 1.5 to 1.8 +/- 0.3 g/24 h (P less than 0.01). Changes in protein excretion and dextran sieving were compatible with an increase in glomerular permselectivity and a decrease in filtrate flow through the 'shunt' pathway. Glomerular filtration rate was maintained, although effective renal plasma flow fell significantly. Proteinuria relapsed after stopping cyclosporin A. In membranoproliferative glomerulonephritis and focal segmental glomerulosclerosis proteinuria did not respond to cyclosporin A, although cyclosporin A exerted important haemodynamic effects. 3. In minimal change disease and membranous glomerulopathy cyclosporin A exerts its beneficial effects on proteinuria through changes in the properties of the glomerular barrier, resulting in increased charge and size selectivity, respectively.