Minimal change disease: a CD80 podocytopathy?

Screening core genes for minimal change disease based on bioinformatics and machine learning approaches

Based on bioinformatics and machine learning methods, we conducted a study to screen the core genes of minimal change disease (MCD) and further explore its pathogenesis. First, we obtained the chip data sets GSE108113 and GSE200828 from the Gene Expression Comprehensive Database (GEO), which contained MCD information. We then used R software to analyze the gene chip data and performed functional enrichment analysis. Subsequently, we employed Cytoscape to screen the core genes and utilized machine learning algorithms (random forest and LASSO regression) to accurately identify them. To validate and analyze the core genes, we conducted immunohistochemistry (IHC) and gene set enrichment analysis (GSEA). Our results revealed a total of 394 highly expressed differential genes. Enrichment analysis indicated that these genes are primarily involved in T cell differentiation and p13k-akt signaling pathway of immune response. We identified NOTCH1, TP53, GATA3, and TGF-β1 as the core genes. IHC staining demonstrated significant differences in the expression of these four core genes between the normal group and the MCD group. Furthermore, GSEA suggested that their up-regulation may be closely associated with the pathological changes in MCD kidneys, particularly in the glycosaminoglycans signaling pathway. In conclusion, our study highlights NOTCH1, TP53, GATA3, and TGF-β1 as the core genes in MCD and emphasizes the close relationship between glycosaminoglycans and pathogenesis of MCD.

Relapse of minimal change disease following the third mRNA COVID-19 vaccination: a case report and literature review

Mass vaccination is the most important strategy to terminate the coronavirus disease 2019 (COVID-19) pandemic. Reports suggest the potential risk of the development of new-onset or relapse of minimal change disease (MCD) following COVID-19 vaccination; however, details on vaccine-associated MCD remain unclear. A 43-year-old man with MCD, who had been in remission for 29 years, developed nephrotic syndrome 4 days after receiving the third dose of the Pfizer-BioNTech vaccine. His kidney biopsy revealed relapsing MCD. Intravenous methylprednisolone pulse therapy followed by oral prednisolone therapy was administered, and his proteinuria resolved within 3 weeks. This report highlights the importance of careful monitoring of proteinuria after COVID-19 vaccination in patients with MCD, even if the disease is stable and no adverse events occurred during previous vaccinations. Our case report and literature review of COVID-19 vaccine-associated MCD indicated that MCD relapse tends to occur later after vaccination and slightly more often following the second and subsequent vaccine doses than new-onset MCD.

Understanding the podocyte immune responses in proteinuric kidney diseases: from pathogenesis to therapy

The glomerular filtration barrier, comprising the inner layer of capillary fenestrated endothelial cells, outermost podocytes, and the glomerular basement membrane between them, plays a pivotal role in kidney function. Podocytes, terminally differentiated epithelial cells, are challenging to regenerate once injured. They are essential for maintaining the integrity of the glomerular filtration barrier. Damage to podocytes, resulting from intrinsic or extrinsic factors, leads to proteinuria in the early stages and eventually progresses to chronic kidney disease (CKD). Immune-mediated podocyte injury is a primary pathogenic mechanism in proteinuric glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and lupus nephritis with podocyte involvement. An extensive body of evidence indicates that podocytes not only contribute significantly to the maintenance of the glomerular filtration barrier and serve as targets of immune responses but also exhibit immune cell-like characteristics, participating in both innate and adaptive immunity. They play a pivotal role in mediating glomerular injury and represent potential therapeutic targets for CKD. This review aims to systematically elucidate the mechanisms of podocyte immune injury in various podocyte lesions and provide an overview of recent advances in podocyte immunotherapy. It offers valuable insights for a deeper understanding of the role of podocytes in proteinuric glomerular diseases, and the identification of new therapeutic targets, and has significant implications for the future clinical diagnosis and treatment of podocyte-related disorders.

Urinary CD80 and Serum suPAR as Biomarkers of Glomerular Disease among Adults in Brazil

INTRODUCTION

Urinary CD80 has been shown to have good specificity for minimal change disease (MCD) in children. However, the investigation of circulating factors such as soluble urokinase plasminogen activator receptor (suPAR) as biomarkers of focal segmental glomerulosclerosis (FSGS) is quite controversial. The objective of this study was to determine whether urinary CD80 and serum suPAR can be used for the diagnosis of MCD and FSGS, respectively, in the adult population of Brazil. We also attempted to determine whether those biomarkers assess the response to immunosuppressive treatment.

METHODS

This was a prospective study in which urine and blood samples were collected for analysis of CD80 and suPAR, respectively, only in the moment of renal biopsy, from patients undergoing to diagnostic renal biopsy. At and six months after biopsy, we analyzed serum creatinine, serum albumin, and proteinuria in order to evaluate the use of the CD80 and suPAR collected in diagnosis as markers of response to immunosuppressive treatment. In healthy controls were collected urinary CD80 and proteinuria, serum suPAR, and creatinine.

RESULTS

The results of 70 renal biopsies were grouped, by diagnosis, as follows: FSGS (n = 18); membranous nephropathy (n = 14); MCD (n = 5); and other glomerulopathies (n = 33). There was no significant difference among the groups in terms of the urinary CD80 levels, and serum suPAR was not significantly higher in the FSGS group, as would have been expected. Urinary CD80 correlated positively with nephrotic syndrome, regardless of the type of glomerular disease. Neither biomarker correlated with proteinuria at six months after biopsy.

CONCLUSION

In adults, urinary CD80 can serve as a marker of nephrotic syndrome but is not specific for MCD, whereas serum suPAR does not appear to be useful as a diagnostic or treatment response marker.

Second and Third Generational Advances in Therapies of the Immune-Mediated Kidney Diseases in Children and Adolescents

Therapy of immune-mediated kidney diseases has evolved during recent decades from the non-specific use of corticosteroids and antiproliferative agents (like cyclophosphamide or azathioprine), towards the use of more specific drugs with measurable pharmacokinetics, like calcineurin inhibitors (cyclosporine A and tacrolimus) and mycophenolate mofetil, to the treatment with biologic drugs targeting detailed specific receptors, like rituximab, eculizumab or abatacept. Moreover, the data coming from a molecular science revealed that several drugs, which have been previously used exclusively to modify the upregulated adaptive immune system, may also exert a local effect on the kidney microstructure and ameliorate the functional instability of podocytes, reducing the leak of protein into the urinary space. The innate immune system also became a target of new therapies, as its specific role in different kidney diseases has been de novo defined. Current therapy of several immune kidney diseases may now be personalized, based on the detailed diagnostic procedures, including molecular tests. However, in most cases there is still a space for standard therapies based on variable protocols including usage of steroids with the steroid-sparing agents. They are used as a first-line treatment, while modern biologic agents are selected as further steps in cases of lack of the efficacy or toxicity of the basic therapies. In several clinical settings, the biologic drugs are effective as the add-on therapy.

Spectrum of Kidney Injury Following COVID-19 Disease: Renal Biopsy Findings in a Single Italian Pathology Service

The onset of coronavirus disease (COVID-19) as a pandemic infection, has led to increasing insights on its pathophysiology and clinical features being revealed, such as a noticeable kidney involvement. In this study, we describe the histopathological, immunofluorescence, and ultrastructural features of biopsy-proven kidney injury observed in a series of SARS-CoV-2 positive cases in our institution from April 2020 to November 2021. We retrieved and retrospectively reviewed nine cases (two pediatric and seven adults) that experienced nephrotic syndrome (six cases), acute kidney injury (two cases), and a clinically silent microhematuria and leukocyturia. Kidney biopsies were investigated by means of light microscopy, direct immunofluorescence, and electron microscopy. The primary diagnoses were minimal change disease (four cases), acute tubular necrosis (two cases), collapsing glomerulopathy (two cases), and C3 glomerulopathy (one case). None of the cases showed viral or viral-like particles on ultrastructural analysis. Novel and specific histologic features on kidney biopsy related to SARS-CoV-2 infection have been gradually disclosed and reported, harboring relevant clinical and therapeutic implications. Recognizing and properly diagnosing renal involvement in patients experiencing COVID-19 could be challenging (due to the lack of direct proof of viral infection, e.g., viral particles) and requires a proper integration of clinical and pathological data.

Delayed Onset Minimal Change Disease as a Manifestation of Lupus Podocytopathy

Lupus podocytopathy (LP) is an uncommon manifestation of systemic lupus erythematosus (SLE) and is not included in the classification of lupus nephritis. The diagnosis of LP is confirmed by the presence of diffuse foot process effacement in the absence of capillary wall deposits with or without mesangial immune deposits in a patient with SLE. Here we describe a 13-year-old female who presented with nephrotic syndrome (NS) seven years after the diagnosis of SLE. The renal function had been stable for seven years since the SLE diagnosis, as manifested by the normal serum creatinine, serum albumin and absence of proteinuria. Renal biopsy showed evidence of minimal change disease without immune complex deposits or features of membranous nephropathy. Renal function was normal. The patient had an excellent response to steroid therapy with remission within two weeks. The patient remained in remission five months later during the most recent follow-up. This report highlights the importance of renal histology to determine the accurate etiology of NS in patients with SLE. Circulating factors, including cytokines such as interleukin 13, may play a role in the pathophysiology of LP and needs to be studied further in future larger studies.

COVID-19 vaccination and glomerulonephritis

Introduction

mRNA COVID-19 vaccine is more effective than traditional vaccines owing to superior immune activation. Nevertheless, the impact of mRNA COVID-19 vaccine on triggering de novo/relapsing glomerulonephritis (GN) is limited. We report a case series of patients who developed new or relapsing GN postvaccination.

Methods

We evaluated baseline characteristics, vaccine type, and clinical outcomes of 13 patients from our institution who had a new diagnosis or relapse of their GN post–mRNA COVID-19 vaccination.

Results

Of 13 patients, 8 patients were newly diagnosed with having GN and 5 patients had relapse. Median age was 62 years (range 19–83 years). Autoimmune disease (38%) was the most prevalent underlying disease followed by cancer (23%). Most patients were White males. IgA nephropathy (IgAN) was the most common GN in our series (5 patients, 38%) followed by membranous nephropathy (MN) (3 patients, 23%). There was 1 patient with IgAN who had evidence of IgA deposits before vaccination suggesting the immune activation after vaccination triggered a flare of the disease. Our case series also included the first case report of tip-variant focal segmental glomerulosclerosis (FSGS), NELL-1–associated MN, and atypical anti–glomerular basement membrane (GBM) nephritis. A total of 77% developed acute kidney injury (AKI) with most being Kidney Disease: Improving Global Outcomes stage 1 (67%). Outcomes are favorable with 80% responding to therapy.

Conclusion

New cases and relapse of GN can present shortly after mRNA COVID-19 vaccination. New cases of IgAN may result from unmasking of undiagnosed IgAN owing to robust immune activation rather than development of new deposits.

Trends in pediatric nephrotic syndrome

Nephrotic syndrome (NS) is relatively common in children, with most of its histological types being minimal changed disease. Its etiology has long been attributed to lymphocyte (especially T-cell) dysfunction, while T-cell-mediated vascular hyperpermeability increases protein permeability in glomerular capillaries, leading to proteinuria and hypoproteinemia. Based on this etiology, steroids and immunosuppressive drugs that are effective against this disease have also been considered to correct T-cell dysfunction. However, in recent years, this has been questioned. The primary cause of NS has been considered damage to glomerular epithelial cells and podocyte-related proteins. Therefore, we first describe the changes in expression of molecules involved in NS etiology, and then describe the mechanism by which abnormal expression of these molecules induces proteinuria. Finally, we consider the mechanism by which infection causes the recurrence of NS.

Low regulatory T-cells: A distinct immunological subgroup in minimal change nephrotic syndrome with early relapse following rituximab therapy

Rituximab is an important second line therapy in difficult nephrotic syndrome (NS), especially given toxicity of long-term glucocorticoid or calcineurin inhibitor (CNI) use. However, clinical response to rituximab is heterogenous. We hypothesized that this was underpinned by immunological differences amongst patients with NS. We recruited a cohort of 18 subjects with glucocorticoid-dependent or glucocorticoid-resistant childhood-onset minimal change NS who received rituximab either due to CNI nephrotoxicity, or due to persistent glucocorticoid toxicity with inadequate response to cyclophosphamide or CNIs. Immunological subsets, T-cell activation assays and plasma cytokines were measured at baseline and 6-months post-rituximab. Time to relapse was bifurcated: 56% relapsed within one year ("early relapse"), while the other 44% entered remission mainly lasting ≥3 years ("sustained remission"). At baseline, early relapse compared to sustained remission group had lower regulatory T-cells (Tregs) [2.94 (2.25, 3.33)% vs 6.48 (5.08, 7.24)%, P<0.001], PMA-stimulated IL-2 [0.03 (0, 1.85)% vs 4.78 (0.90, 9.18)%, P=0.014] and IFNγ [2.22 (0.18, 6.89)% vs 9.47 (2.72, 17.0)%, P=0.035] levels. Lower baseline Treg strongly predicted early relapse (ROC-AUC 0.99, 95% CI 0.97-1.00, P<0.001). There were no differences in baseline plasma cytokine levels. Following rituximab, there was significant downregulation of Th2 cytokines in sustained remission group (P=0.038). In particular, IL-13 showed a significant decrease in sustained remission group [-0.56 (-0.64, -0.35)pg/ml, P=0.007)], but not in the early relapse group. In conclusion, early relapse following rituximab is associated with baseline reductions in Treg and T-cell hyporesponsiveness, which suggest chronic T-cell activation and may be useful predictive biomarkers. Sustained remission, on the other hand, is associated with downregulation of Th2 cytokines following rituximab.

Identification of a novel genetic locus associated with immune mediated thrombotic thrombocytopenic purpura

Immune thrombotic thrombocytopenic purpura (iTTP) is an ultra-rare, life-threatening disorder, mediated through severe ADAMTS13 deficiency causing multi-system micro-thrombi formation, and has specific human leukocyte antigen associations. We undertook a large genome-wide association study to investigate additional genetically distinct associations in iTTP. We compared two iTTP patient cohorts with controls, following standardized genome-wide quality control procedures for single-nucleotide polymorphisms and imputed HLA types. Associations were functionally investigated using expression quantitative trait loci (eQTL), and motif binding prediction software. Independent associations consistent with previous findings in iTTP were detected at the HLA locus and in addition a novel association was detected on chromosome 3 (rs9884090, P=5.22x10^-10, odds ratio 0.40) in the UK discovery cohort. Meta-analysis, including the French replication cohort, strengthened the associations. The haploblock containing rs9884090 is associated with reduced protein O-glycosyltransferase 1 (POGLUT1) expression (eQTL P<0.05), and functional annotation suggested a potential causative variant (rs71767581). This work implicates POGLUT1 in iTTP pathophysiology and suggests altered post-translational modification of its targets may influence disease susceptibility.

Spontaneous remission of minimal change nephrotic syndrome in an elderly man

Minimal change nephrotic syndrome (MCNS) cases achieving spontaneous remission without external factors are rarely reported. We report a case of MCNS that achieved spontaneous remission without external factors that triggered its onset. An 82-year-old male patient was admitted to the hospital for close examination of nephrotic syndrome. Renal biopsy was performed and MCNS was diagnosed. Owing to the patient's age and history of foot and microvascular arteriovenous thrombosis, we did not start immunosuppressive drugs, including steroids, and opted for conservative management. After conservative treatment, proteinuria gradually decreased, and the patient achieved complete remission. Given that the patient had a history of urinary protein and thrombosis, recurrence of MCNS was considered again this time. In addition, the involvement of external factors that trigger the onset of MCNS was not found. In conclusion, in elderly-onset MCNS, clinicians generally hesitate to initiate treatment with an immunosuppressive drug, containing steroids, because of its many complications. Thus, our data provide valuable insight into MCNS.

Toll-Like Receptor as a Potential Biomarker in Renal Diseases

One of the major challenges faced by modern nephrology is the identification of biomarkers associated with histopathological patterns or defined pathogenic mechanisms that may assist in the non-invasive diagnosis of kidney disease, particularly glomerulopathy. The identification of such molecules may allow prognostic subgroups to be established based on the type of disease, thereby predicting response to treatment or disease relapse. Advances in understanding the pathogenesis of diseases, such as membranous nephropathy, minimal change disease, focal segmental glomerulosclerosis, IgA (immunoglobulin A) nephropathy, and diabetic nephropathy, along with the progressive development and standardization of plasma and urine proteomics techniques, have facilitated the identification of an increasing number of molecules that may be useful for these purposes. The growing number of studies on the role of TLR (toll-like receptor) receptors in the pathogenesis of kidney disease forces contemporary researchers to reflect on these molecules, which may soon join the group of renal biomarkers and become a helpful tool in the diagnosis of glomerulopathy. In this article, we conducted a thorough review of the literature on the role of TLRs in the pathogenesis of glomerulopathy. The role of TLR receptors as potential marker molecules for the development of neoplastic diseases is emphasized more and more often, as prognostic factors in diseases on several epidemiological backgrounds.

CD80 expression and infiltrating regulatory T cells in idiopathic nephrotic syndrome of childhood

BACKGROUND

CD80 (also known as B7-1) is a co-stimulatory molecule that is expressed in biopsies and also excreted in urine in patients with minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). CD80 is inhibited by the cytotoxic T-lymphocyte-associated-antigen 4 (CTLA4), which is mainly expressed on regulatory T cells (Tregs). Ineffective circulating Treg response is involved in the pathogenesis of nephrotic syndrome. In this study, we evaluated CD80 expression and infiltrating Tregs in children with MCD and FSGS.

METHODS

Evaluation of CD80 expression and semi-quantitative evaluation of Tregs (FOXP3-positive CD4 T cells) were carried out in 31 kidney biopsies (12 MCD, 19 FSGS) with immunofluorescence and immunohistochemistry staining.

RESULTS

All MCD sections were stained negative; whereas six out of 19 FSGS sections (all from steroid-resistant (SR) patients), including one from a Wilms' tumor 1 (WT1) mutation-positive FSGS patient, stained positive for anti-CD80 goat antibody, and negative for anti-CD80 rabbit antibody. FSGS biopsy specimens had significantly higher FOXP3-positive cells/mm² compared with MCD and control samples (P < 0.001). Biopsy samples from SR-FSGS patients (n = 12) with positive CD80 staining (n = 6) had significantly less Tregs (FOXP3-positive CD4 T cells) compared with CD80 (-) biopsies (n = 6; P = 0.004).

CONCLUSION

CD80 expression was not detected in the majority of the archival biopsy sections and the results were not consistent across the different antibodies. In the SR-FSGS sections, however, CD80-positive biopsies had decreased FOXP3-positive CD4 T cells, suggesting that a decreased anti-inflammatory milieu may be the cause of increased CD80 expression.

Role of Podocyte Injury in Glomerulosclerosis

Finding new therapeutic targets of glomerulosclerosis treatment is an ongoing quest. Due to a living environment of various stresses and pathological stimuli, podocytes are prone to injuries; moreover, as a cell without proliferative potential, loss of podocytes is vital in the pathogenesis of glomerulosclerosis. Thus, sufficient understanding of factors and underlying mechanisms of podocyte injury facilitates the advancement of treating and prevention of glomerulosclerosis. The clinical symptom of podocyte injury is proteinuria, sometimes with loss of kidney functions progressing to glomerulosclerosis. Injury-induced changes in podocyte physiology and function are actually not a simple passive process, but a complex interaction of proteins that comprise the anatomical structure of podocytes at molecular levels. This chapter lists several aspects of podocyte injuries along with potential mechanisms, including glucose and lipid metabolism disorder, hypertension, RAS activation, micro-inflammation, immune disorder, and other factors. These aspects are not technically separated items, but intertwined with each other in the pathogenesis of podocyte injuries.

Cytotoxic T- Lymphocyte Antigen-4 (CTLA4) Gene Expression and Urinary CTLA4 Levels in Idiopathic Nephrotic Syndrome

OBJECTIVES

To detect Cytotoxic T- Lymphocyte Antigen-4 (CTLA4) single nucleotide polymorphisms (SNPs) at +49A/G (rs231775) and -318C/T (rs5742909) positions in children with idiopathic nephrotic syndrome (INS) and also assay urinary soluble CTLA4 (sCTLA4) levels in children with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS) and steroid sensitive nephrotic syndrome (SSNS) in remission.

METHODS

The study included 59 patients of INS (MCD-23, FSGS-15 and SSNS in remission-21) and 35 healthy controls. The CTLA4 SNPs profiling was done in peripheral blood mononuclear cells and urinary sCTLA4 level was assayed by ELISA kit.

RESULTS

Although frequency of homozygous +49 GG (rs4553808) genotype (26.3% vs. 11.4%; p = 0.231) and G allele (52.6% vs. 40%; p = 0.216) were found to be higher in INS as compared to controls, the differences were statistically non-significant. Genotypes GG, AG, AA and alleles A and G frequencies were comparable among MCD, FSGS and controls. SNP at -318 C/T (rs5742909) did not show homozygous TT genotype both in INS as well as controls. Median urinary sCTLA4/creatinine level was significantly higher in MCD as compared to FSGS (p = 0.027), SSNS in remission (p = 0.001) and controls (p = 0.003).

CONCLUSIONS

The positive associations of +49 GG genotype and G allele in patients with nephrotic syndrome were not observed. The frequencies did not differ significantly among MCD, FSGS and controls. Urinary sCTLA4 level was significantly increased in MCD; suggesting its possible role in the pathogenesis of disease.

Spontaneous remission of adult-onset minimal change nephrotic syndrome associated with influenza B infection: a case report

Background

While the majority of adult-onset minimal change nephrotic syndrome (MCNS) is a primary or an idiopathic form of disease, it can also occur as a secondary form. Reports on the spontaneous remission of MCNS are rare since the condition is typically treated with corticosteroids. We herein describe the spontaneous remission of adult-onset MCNS in a patient who developed nephrotic syndrome after type B influenza infection.

Case presentation

A 50-year-old woman experienced fever, cough, malaise, and low back pain, which had persisted for 6 days before she presented to our hospital, and edema of the face and limbs, which had persisted for 5 days before her presentation. She was diagnosed with type B influenza infection and later exhibited an exacerbation of facial edema, decreased urine output, and a high level of proteinuria. She was referred to our department after the diagnosis of nephrotic syndrome. On admission, her proteinuria level was 20.88 g/gCr and her selectivity index value was 0.13. The examination of a kidney biopsy specimen obtained on the fourth day of hospitalization under a light microscope revealed minor abnormalities. An immunofluorescence showed only nonspecific granular IgM deposits in the mesangium. Electron microscopy showed extensive foot process effacement without any immune complex deposits. Based on these findings, the patient was diagnosed with MCNS. After admission, the proteinuria decreased to 0.06 g/gCr with rest and sodium restriction (6 g/day) alone; a complete remission from nephrotic syndrome was observed at approximately 2 weeks after the onset of symptoms. There have been no signs of recurrence of nephrotic syndrome in the one years since.

Conclusion

We experienced a rare case in which spontaneous remission of MCNS occurred within a short period of 2 weeks after influenza B infection. When patients present with nephrotic syndrome after an infection, it is necessary to consider MCNS in the differential diagnosis, which also includes post-infectious glomerulonephritis and the acute exacerbation of IgA nephropathy.

Remaining Physiological Barriers in Porcine Kidney Xenotransplantation: Potential Pathways behind Proteinuria as well as Factors Related to Growth Discrepancies following Pig-to-Kidney Xenotransplantation

Considerable shortages in the supply of available organs continue to plague the field of solid organ transplantation. Despite changes in allocation, as well as the utilization of extended criteria and living donors, the number of patients waiting for organs continues to grow at an alarming pace. Xenotransplantation, cross-species solid organ transplantation, offers one potential solution to this dilemma. Previous extensive research dedicated to this field has allowed for resolution of xenograft failure due to acute rejection, leaving new areas of unresolved challenges as barriers to success in large animal models. Specific to kidney xenotransplantation, recent data seems to indicate that graft compromise can occur due to discrepancies in growth between breeds of donors and significant proteinuria leading to nephrotic syndrome in the recipient. Given these potential limitations, herein, we review potential pathways behind proteinuria, as well as potential causative factors related to growth discrepancies. Control of both of these has the potential to allow xenotransplantation to become clinically applicable in an effort to resolve this organ shortage crisis.

TLR-mediated albuminuria needs TNFα-mediated cooperativity between TLRs present in hematopoietic tissues and CD80 present on non-hematopoietic tissues in mice

Transient albuminuria induced by pathogen-associated molecular patterns (PAMPs) in mice through engagement of Toll-like receptors (TLRs) is widely studied as a partial model for some forms of human nephrotic syndrome (NS). In addition to TLRs, CD80 has been shown to be essential for PAMP-mediated albuminuria. However, the mechanistic relationships between TLRs, CD80 and albuminuria remain unclear. Here, we show that albuminuria and CD80-uria induced in mice by many TLR ligands are dependent on the expression of TLRs and their downstream signalling intermediate MyD88 exclusively in hematopoietic cells and, conversely, on CD80 expression exclusively in non-hematopoietic cells. TNFα is crucial for TLR-mediated albuminuria and CD80-uria, and induces CD80 expression in cultured renal podocytes. IL-10 from hematopoietic cells ameliorates TNFα production, albuminuria and CD80-uria but does not prevent TNFα-mediated induction of podocyte CD80 expression. Chitohexaose, a small molecule originally of parasite origin, mediates TLR4-dependent anti-inflammatory responses, and blocks TLR-mediated albuminuria and CD80-uria through IL-10. Thus, TNFα is a prominent mediator of renal CD80 induction and resultant albuminuria in this model, and small molecules modulating TLR-mediated inflammatory activation might have contributory or adjunct therapeutic potential in some contexts of NS development.

Summary: Systemic TNFα mediates myeloid cell and podocyte cross-talk to cause LPS-induced mouse microalbuminuria, a partial model of human nephrotic syndrome, pointing to potential adjunct therapeutic approaches.

Urine and serum ghrelin, sCD80 and sCTLA-4 levels in doxorubicin-induced experimental nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is an immune-mediated disorder associated with hyperlipidemia. NS has been proposed to be mediated through CD80-related T cell immune response, which could be blocked using soluble cytotoxic T lymphocyte-associated s(CTLA)-4. Although ghrelin is a hormone-modulating lipid metabolism and suppressing immune system, the precise role of ghrelin in NS is not well established.

METHODS

We evaluated the levels of ghrelin, soluble CD80 (sCD80) and sCTLA4 in serum and urine in doxorubicin-induced NS in rats. We also investigated the relation between their levels and the levels of serum total cholesterol (TC), triglyceride, albumin and urine protein.

RESULTS

While urinary ghrelin levels were significantly lower in the nephrotic rats compared to the control group, serum ghrelin levels were comparable in the nephrotic and control rats. In contrast, serum and urinary sCD80 and sCTLA4 levels were higher in the nephrotic rats than the controls. The urinary ghrelin levels were negatively correlated with the levels of serum triglyceride, TC and urine protein, sCD80 and sCTLA4. The urine sCD80 levels were positively correlated with the TC, urine protein and urine sCTLA4 levels, and negatively correlated with the serum albumin. The urine sCTLA4 levels were positively correlated with the TC and urine protein levels and negatively correlated with the serum albumin levels. In regression analysis, the urine ghrelin levels significantly relate to urine sCD80 levels. Besides, hyperlipidemia in NS did not appear to be related to serum ghrelin levels.

CONCLUSION

Low urine ghrelin levels might be relevant to pathogenesis of doxorubicin-induced NS. The reduction in urine ghrelin levels might also be associated with increased levels of urine sCTLA4 and sCD80 which reflect proteinuria.

Costimulatory blockade: A novel approach to the treatment of glomerular disease?

Costimulatory pathways (Cluster of differentiation 28, tumor necrosis factor-related, adhesion and T Cell Ig- and mucin-domain molecules) regulating the interactions between receptors on the T cells and their ligands expressed on several cell types, have a key role in controlling many immunological and non immunological processes. Indeed, accumulating evidence indicate that these molecules are involved in the pathogenesis of numerous conditions, such as allograft rejection, atherosclerosis, rheumatoid arthritis, psoriasis and renal diseases, including glomerulonephritis. Primary or secondary (i.e., associated with infections, drugs or systemic diseases, such as systemic lupus erythematosus, diabetes, etc.) glomerulonephritis represent a group of heterogeneous diseases with different pathogenic mechanisms. Since costimulatory molecules, in particular CD80 and CD40, have been found to be expressed on podocytes in the course of different experimental and clinical glomerulonephritis, costimulation has been thought as a new therapeutic target for patients with glomerular diseases. However, although experimental data suggested that the blockade of costimulatory pathways is effective and safe in the prevention and treatment of glomerular diseases, clinical trials reported contrasting results. So, at this moment, there is not a strong evidence for the general use of costimulatory blockade as an alternative treatment strategy in patients with primary or secondary glomerulonephritis. Here, we critically discuss the current data and the main issues regarding the development of this innovative therapeutic approach.

Minimal change nephrotic syndrome associated with non-Hodgkin lymphoid disorders: a retrospective study of 18 cases

Few studies have examined the occurrence of minimal change nephrotic syndrome (MCNS) in patients with non-Hodgkin lymphoma (NHL). We report here a series of 18 patients with MCNS occurring among 13,992 new cases of NHL. We analyzed the clinical and pathologic characteristics of this association, along with the response of patients to treatment, to determine if this association relies on a particular disorder. The most frequent NHLs associated with MCNS were Waldenström macroglobulinemia (33.3%), marginal zone B-cell lymphoma (27.8%), and chronic lymphocytic leukemia (22.2%). Other lymphoproliferative disorders included multiple myeloma, mantle cell lymphoma, and peripheral T-cell lymphoma. In 4 patients MCNS occurred before NHL (mean delay, 15 mo), in 10 patients the disorders occurred simultaneously, and in 4 patients MCNS was diagnosed after NHL (mean delay, 25 mo). Circulating monoclonal immunoglobulins were present in 11 patients. A nontumoral interstitial infiltrate was present in renal biopsy specimens from 3 patients without significant renal impairment. Acute kidney injury resulting from tubular lesions or renal hypoperfusion was present in 6 patients. MCNS relapse occurred more frequently in patients treated exclusively by steroid therapy (77.8%) than in those receiving steroids associated with chemotherapy (25%). In conclusion, MCNS occurs preferentially in NHL originating from B cells and requires an aggressive therapeutic approach to reduce the risk of MCNS relapse.

Diagnosis and treatment of glomerular diseases in elderly patients

Glomerular diseases are common in elderly patients and are a major cause of kidney failure. Most glomerular diseases in the elderly are caused by chronic systemic diseases, including arterial hypertension, diabetes, and atherosclerotic vascular diseases, although acute systemic vasculitis, especially anti-neutrophil-cytoplamic-antibody-mediated vasculitis, and membranous nephropathy related to malignancy, drug toxicity, and idiopathic form also occur often. Complex age-related changes and sensitivity to drug toxicity can render diagnosis and treatment for elderly patients challenging. As the general population is aging and the rate of CKD rising, updating knowledge on managing these patients is critical for care providers. We provide a comprehensive review and update of the diagnosis and treatment of glomerular diseases in the elderly.

Effects of melanocortin 1 receptor agonists in experimental nephropathies

Nephrotic syndrome, characterized by massive proteinuria, is caused by a large group of diseases including membranous nephropathy (MN) and focal segmental glomerulosclerosis (FSGS). Although the underlying mechanisms are beginning to unravel, therapy is unspecific and far from efficient. It has been suggested that adrenocorticotropic hormone (ACTH) has beneficial effects in patients with MN and possibly in other nephrotic diseases. We have previously reported that ACTH may act directly on podocytes through the melanocortin 1 receptor (MC1R). In the present study, we evaluate the effect of highly specific MC1R agonists in two different nephrotic disease models. Experimental MN: Passive Heymann nephritis (PHN) was induced in rats that were treated for four weeks with MS05, a selective MC1R agonist, or saline. The degree of albuminuria was significantly reduced over time and the effect was sustained one week after treatment withdrawal (p<0.05). Experimental FSGS: Based on a dose-response study, two doses of adriamycin were used for induction of nephropathy in Balb/c mice. Mice were treated with either a synthetic MC1R agonist (BMS-470539), with α-melanocyte stimulating hormone (α-MSH) or with saline. There was no beneficial effect of treatment. In summary, MC1R agonists reduce albuminuria and improve morphology in experimentally induced MN whereas they have no effect in experimental FSGS. The results illustrate the differences in these podocytopathies in terms of signaling mechanisms underlying proteinuria, and progression of disease.

The interplay between MDV and HVT affects viral miRNa expression

It is well established that herpesviruses encode numerous microRNAs (miRNAs) and that these virally encoded small RNAs play multiple roles in infection. The present study was undertaken to determine how co-infection of a pathogenic MDV serotype one (MDV1) strain (MD5) and a vaccine strain (herpesvirus of turkeys [HVT]) alters viral miRNA expression in vivo. We first used small RNA deep sequencing to identify MDV1-encoded miRNAs that are expressed in tumorigenic spleens of MDV1-infected birds. The expression patterns of these miRNAs were then further assessed at an early time point (7 days postinfection [dpi]) and a late time point (42 dpi) in birds with and without HVT vaccination using real-time PCR (RT-PCR). Additionally, the effect of MDV1 co-infection on HVT-encoded miRNAs was determined using RT-PCR. A diverse population of miRNAs was expressed in MDV-induced tumorigenic spleens at 42 dpi, with 18 of the 26 known mature miRNAs represented. Of these, both mdv1-miR-M4-5p and mdv1-miR-M2-3p were the most highly expressed miRNAs. RT-PCR analysis further revealed that nine MDV miRNAs were differentially expressed between 7 dpi and 42 dpi infected spleens. At 7 dpi, three miRNAs were differentially expressed between the spleens of birds co-infected with HVT and MD5 compared with birds singly infected with MD5, whereas at 42 dpi, nine miRNAs were differentially expressed. At 7 dpi, the expression of seven HVT-encoded miRNAs was affected in the spleens of co-infected birds compared with birds only receiving the HVT vaccine. At 42 dpi, six HVT-encoded miRNAs were differentially expressed between the two groups. Target prediction analysis suggests that these differentially expressed viral miRNAs are involved in regulating several cellular processes, including cell proliferation and the adaptive immune response.

Therapy of relapsing minimal-change disease in adults: a new approach?

Multiple-relapsing minimal-change disease (MCD) often requires exposure to potentially toxic agents in an attempt to achieve a lasting remission of nephrotic syndrome. Munyentwali and co-workers describe an experience using rituximab in adults with multiple-relapsing MCD that supports both efficacy and safety of this agent. However, the optimal dosing regimen and mechanism of action remain unclear. Thus, randomized controlled trials are warranted in both adults and children to better define the role of rituximab in multiple-relapsing MCD.

Suppression by Δ(9)-tetrahydrocannabinol of the primary immunoglobulin M response by human peripheral blood B cells is associated with impaired STAT3 activation

This study was undertaken to gain insights into the mechanism for Δ(9)-tetrahydrocannabinol (Δ(9)-THC)-mediated suppression of primary immunoglobulin M (IgM) responses in humans. An in vitro activation model, which employs cell surface-expressed CD40 ligand (CD40L) and recombinant cytokines (interleukin (IL)-2, -6, and -10), was used to differentiate human peripheral blood (HPB) naïve B cells into IgM secreting cells. Pretreatment with Δ(9)-THC significantly decreased the number of IgM secreting cells as determined by ELISPOT. The attenuation of IgM secretion by Δ(9)-THC involved, at least in part, the impairment of plasma cell differentiation as evidenced by suppression of immunoglobulin joining chain (IgJ) mRNA expression. The analysis at each of two different stages critically involved in plasma cell differentiation indicates that Δ(9)-THC impaired both the primary activation stage and proliferation of B cells. Interestingly, Δ(9)-THC selectively suppressed the surface expression of CD80, but not other measured B-cell activation markers (CD69, CD86, and ICAM1). Furthermore, pretreatment with Δ(9)-THC was accompanied by a robust decrease of STAT3 phosphorylation, whereas the phosphorylation of the p65 NFκB subunit was not affected. Collectively, these data provide new insights into the mechanisms for impaired B cell function by Δ(9)-THC.

The podocyte's response to stress: the enigma of foot process effacement

Progressive loss of podocytes is the most frequent cause accounting for end-stage renal failure. Podocytes are complex, terminally differentiated cells incapable of replicating. Thus lost podocytes cannot be replaced by proliferation of neighboring undamaged cells. Moreover, podocytes occupy a unique position as epithelial cells, adhering to the glomerular basement membrane (GBM) only by their processes, whereas their cell bodies float within the filtrate in Bowman's space. This exposes podocytes to the danger of being lost by detachment as viable cells from the GBM. Indeed, podocytes are continually excreted as viable cells in the urine, and the rate of excretion dramatically increases in glomerular diseases. Given this situation, it is likely that evolution has developed particular mechanisms whereby podocytes resist cell detachment. Podocytes respond to stress and injury by undergoing tremendous changes in shape. Foot process effacement is the most prominent and, yet in some ways, the most enigmatic of those changes. This review summarizes the various structural responses of podocytes to injury, focusing on foot process effacement and detachment. We raise the hypothesis that foot process effacement represents a protective response of podocytes to escape detachment from the GBM.

LPS and PAN-induced podocyte injury in an in vitro model of minimal change disease: changes in TLR profile

Minimal change disease (MCD), the most common idiopathic nephrotic syndrome in children, is characterized by proteinuria and loss of glomerular visceral epithelial cell (podocyte) ultrastructure. Lipopolysaccharide (LPS) and puromycin aminonucleoside (PAN) are used to study podocyte injury in models of MCD in vivo and in vitro. We hypothesized that LPS and PAN influence components of the innate immune system in podocytes such as the Toll-Like Receptor (TLRs), TLR adapter molecules, and associated cytokines. Our results show that cultured human podocytes constitutively express TLRs 1-6 and TLR-10, but not TLRs 7-9. LPS (25 μg/ml) or PAN (60 μg/ml) caused comparable derangement of the actin cytoskeleton in podocytes. Quantitative RT-PCR analysis show that LPS differentially up-regulated the expression of genes for TLRs (1 > 4 ≥ 2 > 3 > 6 > 5), the adapter molecule, MyD88, and transcription factor NF-κB within one hour. LPS also caused increased levels of IL-6, IL-8 and MCP1 without exerting any effect on TNF-α, IFN-α or TGF-β1 at 24 h. Immunofluorescence intensity analysis of confocal microscopy images showed that LPS induced a significant increase in nuclear translocation of NF-κB by 6 h. In contrast, PAN-induced only small changes in the expression of TLRs 2-6 that included a persistent increase in TLRs 2 and 5, a transient increase in TLR-4, and a gradual increase in TLRs 3 and 6 between 1 and 6 h. Correspondingly, it did not alter pro-inflammatory cytokine levels in podocytes. However, PAN induced a low but significant increase in NF-κB nuclear translocation within one hour that remained unchanged up to 6 h. In summary, these novel findings show that LPS, a known TLR-4 ligand, induced the gene expression of multiple TLRs with maximum effect on the expression of TLR-1 suggesting a loss of receptor selectivity and induction of receptor interactions in podocytes. A comparable derangement of the podocyte cytoskeleton and significant increase in the nuclear translocation of NF-κB by PAN suggest that disparate but complementary mechanisms may contribute to the development of podocytopathy in MCD.

Relapse of minimal change disease following infection with the 2009 pandemic influenza (H1N1) virus

We report a case of relapse of minimal change disease following infection with the influenza A (H1N1) virus responsible for the 2009 pandemic. A 22-year-old man who had been diagnosed with minimal change disease presented with systemic edema. He had achieved complete remission with an oral steroid (prednisolone 1 mg/kg/day) by the 17th day of administration. On the 27th day of prednisolone administration, he presented with a new onset of generalized edema after several days of productive coughing. His urine showed proteinuria (4+) with a protein/creatinine ratio (PCR) of 2852.1 mg/g. His nasal swab sample was positive for the 2009 pandemic influenza (H1N1) virus by real-time reverse-transcriptase polymerase chain reaction (RT-PCR). He received oseltamivir (150 mg/day) for 5 days. A day after completing the oseltamivir therapy, his proteinuria returned to a normal range; urinalysis was negative for protein with PCR 79.2 mg/g. One month later, the patient remained normal with no proteinuria.