Role of miRNA-671-5p in Mediating Wnt/β-Catenin-Triggered Podocyte Injury

Podocyte injury and proteinuria are the most common features of glomerular disease, which is the leading cause of end-stage renal failure. Hyperactivated Wnt/β-catenin signaling is closely associated with podocyte injury, but the underlying mechanisms are incompletely understood. Here we show that miRNA-671-5p (miR-671-5p) plays a crucial role in mediating β-catenin-triggered podocyte injury by targeting Wilms tumor 1 (WT1). Microarray-based expression profiling revealed that miR-671-5p was the most upregulated miRNA in podocytes after β-catenin activation. MiR-671-5p was colocalized with β-catenin in the glomeruli of proteinuric CKD in vivo. Bioinformatics analyses and luciferase reporter assays confirmed that miR-671-5p targeted WT1 mRNA. Overexpression of miR-671-5p mimics inhibited WT1 and impaired podocyte integrity, whereas miR-671-5p antagomir preserved the expression of WT1 and other podocyte-specific proteins under basal conditions or after β-catenin activation. In mouse remnant kidney model, overexpression of miR-671-5p aggravated podocyte injury, worsened kidney dysfunction and exacerbated renal fibrosis after 5/6 nephrectomy. In contrast, miR-671-5p antagomir alleviated podocyte injury and attenuated proteinuria and renal fibrotic lesions after glomerular injury in vivo. These studies underscore a pivotal role of miR-671-5p in mediating WT1 depletion and podocyte injury induced by β-catenin. Targeting miR-671-5p may serve as a new approach to prevent podocyte injury and proteinuria in proteinuric CKD.

From membranoproliferative glomerulonephritis to a final diagnosis: Hypocomplementemic urticarial vasculitis syndrome

Membranoproliferative glomerulonephritis describes a glomerular-injury pattern common to a heterogeneous group of diseases. Evaluation based on clinical and laboratory presentation and immunofluorescence staining on kidney biopsy allows identification of underlying pathophysiological processes and may facilitate proper diagnosis and treatment. Hypocomplementemic urticarial vasculitis syndrome is a rare autoimmune disease of multi-organ involvement. The diagnosis is based on well-defined clinical and laboratory criteria. The pathophysiology is not completely understood but the presence of anti-C1q antibody seems to be involved. Renal involvement occurs in up to 50% of cases. It can be heterogeneous and can be indistinguishable from lupus nephritis. Serological findings and skin involvement distinguish these two entities. We report the case of a 40-year-old female who presented with urticarial skin lesions, hypocomplementemia and nephrotic syndrome. Kidney biopsy showed membranoproliferative glomerulonephritis with full house immune complex deposits. The diagnosis of hypocomplementemic urticarial vasculitis syndrome was made and the patient was successfully treated with prednisolone and mycophenolate mofetil.

Efficacy of Plasmapheresis in Nivolumab-Associated ANCA Glomerulonephritis: A Case Report and Pathophysiology Discussion

Immune checkpoint inhibitors (ICIs) have revolutionized solid organ and hematologic cancer treatments by improving overall prognoses. However, they can lead to overactivation of the immune system and several immune-related adverse events and sometimes affecting the renal system. Although acute interstitial nephritis is well described, we know little about ICI-associated glomerular injury. Herein, we report an exceptional case of renal ANCA positive-associated vasculitis (AAV) after nivolumab therapy. Three weeks after the last nivolumab injection, the patient presented with proteinuria at 1.73 g/g of creatininuria, hematuria, and acute kidney injury needing dialysis associated with lung hemorrhage; anti-neutrophil cytoplasmic antibody (ANCA titer ≥1,280 with myeloperoxidase specificity of 780 U/mL) was positive, and kidney biopsy confirmed glomerular injury with crescents. The patient underwent treatment with steroid pulses, rituximab, and plasmapheresis, resulting in an improvement of the renal function and lung hemorrhage and produced a negative ANCA titer. Despite the results of the PEXIVAS study and the absence of clear benefit of plasmapheresis demonstrated in idiopathic AAV, we suggest that drug-induced AAV may be effectively treated by plasmapheresis, steroids, and rituximab.

Effect of Everolimus versus Bone Marrow-Derived Stem Cells on Glomerular Injury in a Rat Model of Glomerulonephritis: A Preventive, Predictive and Personalized Implication

Glomerular endothelial injury and effectiveness of glomerular endothelial repair play a crucial role in the progression of glomerulonephritis. Although the potent immune suppressive everolimus is increasingly used in renal transplant patients, adverse effects of its chronic use have been reported clinically in human glomerulonephritis and experimental renal disease. Recent studies suggest that progenitor stem cells could enhance glomerular endothelial repair with minimal adverse effects. Increasing evidence supports the notion that stem cell therapy and regenerative medicine can be effectively used in pathological conditions within the predictive, preventive and personalized medicine (PPPM) paradigm. In this study, using an experimental model of glomerulonephritis, we tested whether bone marrow-derived stem cells (BMDSCs) could provide better effect over everolimus in attenuating glomerular injury and improving the repair process in a rat model of glomerulonephritis. Anti-Thy1 glomerulonephritis was induced in male Sprague Dawley rats by injection of an antibody against Thy1, which is mainly expressed on glomerular mesangial cells. Additional groups of rats were treated with the immunosuppressant everolimus daily after the injection of anti-Thy1 or injected with single bolus dose of BMDSCs after one week of injection of anti-Thy1 (n = 6–8). Nine days after injection of anti-Thy1, glomerular albumin permeability and albuminuria were significantly increased when compared to control group (p < 0.05). Compared to BMDSCs, everolimus was significantly effective in attenuating glomerular injury, nephrinuria and podocalyxin excretion levels as well as in reducing inflammatory responses and apoptosis. Our findings suggest that bolus injection of BMDSCs fails to improve glomerular injury whereas everolimus slows the progression of glomerular injury in Anti-Thy-1 induced glomerulonephritis. Thus, everolimus could be used at the early stage of glomerulonephritis, suggesting potential implications of PPPM in the treatment of progressive renal injury.

A Hypercaloric Diet Induces Early Podocyte Damage in Aged, Non-Diabetic Rats

Background/Aims: The number of patients of older age with metabolic syndrome, obesity, and associated kidney disease, which is characterized by podocyte damage, glomerular hypertrophy, and focal segmental glomerulosclerosis (FSGS), is increasing worldwide. Animal models that would reflect the development of such kidney diseases could facilitate the testing of drugs. We investigated the renal effects of a long-term high caloric diet in aged rats and the potential effects of drugs used to treat metabolic syndrome. Methods: We analyzed nine-month-old male and female Sprague Dawley rats fed five months with a normal diet (control group) or high-fat-high-carbohydrate diet (HFHCD group). Two additional groups were fed with HFHCD and treated with drugs used in patients with metabolic syndrome, i.e., the glucagon-like peptide receptor 1 agonist liraglutide (HFHCD+liraglutide group) or metformin (HFHCD+metformin group). Results: Except an increase of waist circumference as a sign of visceral obesity, the HFHCD diet did not induce metabolic syndrome or obesity. There were no significant changes in kidney function and all groups showed similar indices of glomerular injury, i.e., no differences in glomerular size or the number of glomeruli with FSGS or with FSGS-precursor lesions quantified by CD44 expression as a marker of parietal epithelial cell (PEC) activation. Analysis of ultrastructural morphology revealed mild podocyte stress and a decrease of glomerular nestin expression in the HFHCD group, whereas podocin and desmin were not altered. HFHCD did not promote fibrogenesis, however, treatment with liraglutide led to a slightly increased tubulointerstitial damage, immune cell infiltration, and collagen IV expression compared to the control and HFHCD groups. Conclusion: A five-month feeding with HFHCD in aged rats induced mild podocyte injury and microinflammation, which was not alleviated by liraglutide or metformin.

Treatment With Lisinopril Prevents the Early Progression of Glomerular Injury in Obese Dahl Salt-Sensitive Rats Independent of Lowering Arterial Pressure

Recently, we reported that obese Dahl salt-sensitive leptin receptor mutant (SSLepRmutant) rats develop glomerular injury and progressive proteinuria prior to puberty. Moreover, this early progression of proteinuria was associated with elevations in GFR. Therefore, the current study examined whether treatment with lisinopril to reduce GFR slows the early progression of proteinuria in SSLepRmutant rats prior to puberty. Experiments were performed on 4-week-old SS and SSLepRmutant rats that were either treated with vehicle or lisinopril (20 mg/kg/day, drinking water) for 4 weeks. We did not observe any differences in MAP between SS and SSLepRmutant rats treated with vehicle (148 ± 5 vs. 163 ± 6 mmHg, respectively). Interestingly, chronic treatment with lisinopril markedly reduced MAP in SS rats (111 ± 3 mmHg) but had no effect on MAP in SSLepRmutant rats (155 ± 4 mmHg). Treatment with lisinopril significantly reduced proteinuria in SS and SSLepRmutant rats compared to their vehicle counterparts (19 ± 5 and 258 ± 34 vs. 71 ± 12 and 498 ± 66 mg/day, respectively). Additionally, nephrin excretion was significantly elevated in SSLepRmutant rats versus SS rats, and lisinopril reduced nephrin excretion in both strains. GFR was significantly elevated in SSLepRmutant rats compared to SS rats, and lisinopril treatment reduced GFR in SSLepRmutant rats by 30%. The kidneys from SSLepRmutant rats displayed glomerular injury with increased mesangial expansion and renal inflammation versus SS rats. Chronic treatment with lisinopril significantly decreased glomerular injury and renal inflammation in the SSLepRmutant rats. Overall, these data indicate that inhibiting renal hyperfiltration associated with obesity is beneficial in slowing the early development of glomerular injury and renal inflammation.

ZEB2 transduces HIF1α dependent regulation of Transglutaminase 2 in glomerular podocytes

Glomerular podocytes are instrumental in ensuring glomerular permselectivity and regulating the integrity of glomerular biology. However, podocytes are vulnerable to various noxious stimuli such as hypoxia, and podocyte injury presented with glomerulosclerosis and impaired kidney function. The mechanism of hypoxia-induced podocyte injury vis-a-vis glomerulosclerosis has remained enigmatic. Hypoxia inducible factor 1α (HIF1α) that transduces hypoxic adaptations, induces Transglutaminase 2 (TG2), a calcium dependent enzyme that catalyzes intramolecular ε-(γ-glutamyl) lysine cross-links of extracellular matrix (ECM) proteins. In this study, we investigated the mechanism of regulation of TG2 by HIF1α. Stabilization of HIF1⍺ by FG4592 (Roxadustat) and physiological hypoxia, resulted in elevated expression of ZEB2 (zinc-finger E-box-homeobox 2) and its downstream target TRPC6 (transient receptor potential channel 6). ZEB2 transcriptionally activates TG2 expression, whereas, via TRPC6, it induces calcium influx, inturn it increases the TG2 activity. Blocking the TRPC6 action or suppressing its expression only partially attenuated FG4592 induced TG2 activity, whereas suppression of ZEB2 expression significantly abolished TG2 activity. This study demonstrates that stabilization of HIF1α stimulates both TG2 expression and activity, whereas abrogation of HIF1⍺ by metformin prevented HIF1⍺ regulated TG2 and consequent glomerular injury.

A case of immune-complex mediated glomerulonephritis associated with pembrolizumab

Introduction: Immune checkpoint inhibitors (ICI) are changing the way we treat cancer. However, these novel agents have various systemic adverse events that may preclude its use and cause poor patient outcomes. ICI-associated acute kidney injury is an emerging complication of this treatment. While tubulointerstitial disease is the most common pathologic finding of patients with ICI-associated AKI, there is sparse data in medical literature describing its association with glomerular disease. Case report: Here, we present a patient with metastatic lung adenocarcinoma who developed acute kidney injury and significant proteinuria after receiving pembrolizumab. The kidney biopsy revealed a membranoproliferative and diffuse segmental endocapillary proliferative pattern of glomerular injury. Management and outcome: Pembrolizumab was then held and high-dose prednisone was initiated, resulting in a rapid and dramatic improvement in kidney function and proteinuria. Discussion: We highlight a report of a patient diagnosed with immune-complex mediated glomerulonephritis associated with the use of pembrolizumab, who was successfully treated with drug withdrawal and corticosteroids.

IL-1 receptor signaling in podocytes limits susceptibility to glomerular damage

IL-1 receptor (IL-1R1) activation triggers a proinflammatory signaling cascade that can exacerbate kidney injury. However, the functions of the podocyte IL-1R1 in glomerular disease remain unclear. To study the role of IL-1R1 signaling in podocytes, we selectively ablated the podocyte IL-1R1 in mice (PKO). We then subjected PKO mice and wild-type (WT) controls to 2 glomerular injury models: nephrotoxic serum (NTS)- and adriamycin (ADR)-induced nephropathy. Surprisingly, we found IL-1R1 activation in podocytes limited albuminuria and podocyte injury during NTS- and ADR-induced nephropathy. Moreover, deletion of IL-1R1 in podocytes drove podocyte apoptosis and glomerular injury through diminishing Akt activation. Activation of Akt signaling abrogated the differences in albuminuria and podocyte injury between WT and PKO mice during NTS. Thus, IL-1R1 signaling in podocytes limits susceptibility to glomerular injury via an Akt-dependent signaling pathway. These data identify an unexpected protective role for IL-1R1 signaling in podocytes in the pathogenesis of glomerular disease.

Redefining the Role of ADAM17 in Renal Proximal Tubular Cells and Its Implications in an Obese Mouse Model of Pre-Diabetes

Acute and chronic kidney lesions induce an increase in A Disintegrin And Metalloproteinase domain 17 (ADAM17) that cleaves several transmembrane proteins related to inflammatory and fibrotic pathways. Our group has demonstrated that renal ADAM17 is upregulated in diabetic mice and its inhibition decreases renal inflammation and fibrosis. The purpose of the present study was to analyze how Adam17 deletion in proximal tubules affects different renal structures in an obese mice model. Tubular Adam17 knockout male mice and their controls were fed a high-fat diet (HFD) for 22 weeks. Glucose tolerance, urinary albumin-to-creatinine ratio, renal histology, and pro-inflammatory and pro-fibrotic markers were evaluated. Results showed that wild-type mice fed an HFD became obese with glucose intolerance and renal histological alterations mimicking a pre-diabetic condition; consequently, greater glomerular size and mesangial expansion were observed. Adam17 tubular deletion improved glucose tolerance and protected animals against glomerular injury and prevented podocyte loss in HFD mice. In addition, HFD mice showed more glomerular macrophages and collagen accumulation, which was prevented by Adam17 deletion. Galectin-3 expression increased in the proximal tubules and glomeruli of HFD mice and ameliorated with Adam17 deletion. In conclusion, Adam17 in proximal tubules influences glucose tolerance and participates in the kidney injury in an obese pre-diabetic murine model. The role of ADAM17 in the tubule impacts on glomerular inflammation and fibrosis.