Decreased Podocyte Vesicle Transcytosis and Albuminuria in APC C-Terminal Deficiency Mice with Puromycin-Induced Nephrotic Syndrome

In minimal change nephrotic syndrome, podocyte vesicle transport is enhanced. Adenomatous polyposis coli (APC) anchors microtubules to cell membranes and plays an important role in vesicle transport. To clarify the role of APC in vesicle transport in podocytes, nephrotic syndrome was induced by puromycin amino nucleoside (PAN) injection in mice expressing APC1638T lacking the C-terminal of microtubule-binding site (APC1638T mouse); this was examined in renal tissue changes. The kidney size and glomerular area of APC1638T mice were reduced (p = 0.014); however, the number of podocytes was same between wild-type (WT) mice and APC1638T mice. The ultrastructure of podocyte foot process was normal by electron microscopy. When nephrotic syndrome was induced, the kidneys of WT+PAN mice became swollen with many hyaline casts, whereas these changes were inhibited in the kidneys of APC1638T+PAN mice. Electron microscopy showed foot process effacement in both groups; however, APC1638T+PAN mice had fewer vesicles in the basal area of podocytes than WT+PAN mice. Cytoplasmic dynein-1, a motor protein for vesicle transport, and α-tubulin were significantly reduced in APC1638T+PAN mice associated with suppressed urinary albumin excretion compared to WT+PAN mice. In conclusion, APC1638T mice showed reduced albuminuria associated with suppressed podocyte vesicle transport when minimal change nephrotic syndrome was induced.

Excretion Patterns of Urinary Sediment and Supernatant Podocyte Biomarkers in Patients with Chronic Kidney Disease

Background: Podocyte depletion causes glomerulosclerosis, and persistent podocyte loss drives progression to end-stage kidney disease. Urinary sediment podocyte (u-sed Pod) mRNA excretion and urinary supernatant podocyte (u-sup PCX) protein have been used to monitor disease activity in glomerular diseases. However, the differences in these markers among pathologies have not been investigated. We examined the roles of these markers in kidney diseases. Methods: From January 2013 to March 2016, early morning urine samples were collected from 12 healthy controls and 172 patients with kidney disease (minor glomerular abnormality with mild proteinuria and/or microscopic hematuria, n = 15; minimal change nephrotic syndrome [MCNS], n = 15; membranous nephropathy [MN], n = 15; IgA nephropathy [IgAN], n = 60; crescentic glomerulonephritis [Cres GN], n = 19; lupus nephritis [LN], n = 10; others, n = 38). We examined u-sed Pod mRNA excretion, u-sup PCX protein and the urinary protein:creatinine ratio (u-PCR). Results: U-sed Pod mRNA excretion was significantly correlated with u-sup PCX protein (r = 0.37, p < 0.001). Both u-sed Pod mRNA excretion and u-sup PCX protein were significantly correlated with u-PCR (r = 0.53, p < 0.001 and r = 0.35, p < 0.001, respectively). Interestingly, u-sed Pod mRNA excretion was significantly increased in proliferative-type glomerulonephritis-including IgAN with extracapillary proliferative lesions, Cres GN and LN class IV-and significantly correlated with the rate of crescent formation, whereas u-sup PCX protein was significantly increased only in MN and subepithelial dense deposit-type LN compared with controls. Conclusions: Higher u-sed Pod mRNA excretion and u-sup PCX protein were associated with proliferative-type glomerulonephritis indicating podocyte detachment and subepithelial dense deposit-type glomerulonephritis, respectively. The results suggest that u-sed Pod mRNA excretion and u-sup PCX protein have usefulness for the diagnosis and measurement of disease activity with regard to glomerular diseases.

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

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

Synbindin Downregulation Participates in Slit Diaphragm Dysfunction

<b><i>Introduction:</i></b> Synbindin, originally identified as a neuronal cytoplasmic molecule, was found in glomeruli. The cDNA subtractive hybridization technique showed the mRNA expression of synbindin in glomeruli was downregulated in puromycin aminonucleoside (PAN) nephropathy, a mimic of minimal-change nephrotic syndrome. <b><i>Methods:</i></b> The expression of synbindin in podocytes was analyzed in normal rats and 2 types of rat nephrotic models, anti-nephrin antibody-induced nephropathy, a pure slit diaphragm injury model, and PAN nephropathy, by immunohistochemical analysis and RT-PCR techniques. To elucidate the function of synbindin, a gene silencing study with human cultured podocytes was performed. <b><i>Results:</i></b> Synbindin was mainly expressed at the slit diaphragm area of glomerular epithelial cells (podocytes). In both nephrotic models, decreased mRNA expression and the altered staining of synbindin were already detected at the early phase when proteinuria and the altered staining of nephrin, a key molecule of slit diaphragm, were not detected yet. Synbindin staining was clearly reduced when severe proteinuria was observed. When the cultured podocytes were treated with siRNA for synbindin, the cell changed to a round shape, and filamentous actin structure was clearly altered. The expression of ephrin-B1, a transmembrane protein at slit diaphragm, was clearly lowered, and synaptic vesicle-associated protein 2B (SV2B) was upregulated in the synbindin knockdown cells. <b><i>Conclusion:</i></b> Synbindin participates in maintaining foot processes and slit diaphragm as a downstream molecule of SV2B-mediated vesicle transport. Synbindin downregulation participates in slit diaphragm dysfunction. Synbindin can be an early marker to detect podocyte injury.

Rifampicin-Associated Secondary Minimal Change Disease Presenting with Nephrotic Syndrome in a Pulmonary Tuberculosis Patient

Various extraglomerular disease processes have been associated with drug-induced secondary minimal change disease (MCD). In a majority of cases, preferably, a hypersensitivity reaction appears to be involved, and in some cases, there is direct toxic effect over glomerular capillaries. There are several reports to demonstrate that rifampicin has been associated with various nephrotoxic adverse effects, but rifampicin-induced secondary minimal change disease (MCD) is very rare. Here, we report the case of a young adult male who presented with nephrotic proteinuria with bland urine sediment after one month of initiation of rifampicin treatment for pulmonary tuberculosis. The patient had no proteinuria before the start of antituberculosis treatment. Renal biopsy showed nonproliferative glomerulopathy and immunofluorescence did not show significant glomerular immune deposits. Electron microscopy showed diffuse effacement of visceral epithelial cell foot processes and did not show any presence of glomerular immune complexes and thickening of glomerular basement membrane, promoting the diagnosis of minimal change nephrotic syndrome. The patient got complete remission after discontinuation of rifampicin.

The Effect of Interleukin-4 and Dexamethasone on RNA-Seq-Based Transcriptomic Profiling of Human Podocytes: A Potential Role in Minimal Change Nephrotic Syndrome

Interleukin-4 (IL-4) expression is implicated in the pathogenesis of nephrotic syndrome (NS). This study aimed to investigate the changes in the transcriptomes of human podocytes induced by IL-4 treatment and to analyze whether these changes could be affected by simultaneous steroid treatment. Three groups of human podocytes were treated with control, IL-4, and IL-4 plus dexamethasone (DEX), respectively. We performed whole-transcriptome sequencing to identify differentially expressed genes (DEGs) between the groups. We investigated relevant biological pathways using Gene Ontology (GO) enrichment analyses. We also attempted to compare and validate the DEGs with the genes listed in PodNet, a literature-based database on mouse podocyte genes. A total of 176 genes were differentially expressed among the three groups. GO analyses showed that pathways related to cytoskeleton organization and cell signaling were significantly enriched. Among them, 24 genes were listed in PodNet, and 12 of them were previously reported to be associated with IL-4-induced changes in human podocytes. Of the 12 genes, the expression levels of BMP4, RARB, and PLCE1 were reversed when podocytes were simultaneously treated with DEX. In conclusion, this study explored changes in the transcriptome profiles of human podocytes treated with IL-4. Few genes were reported in previous studies and were previously validated in experiments with human podocytes. We speculate that IL-4 may exert pathogenic effects on the transcriptome of human podocytes, and a few genes may be involved in the pathogenesis.