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Background: Decreased expression of α3β1 integrin may contribute to reduction in podocyte adhesion to glomerular basement membrane (GBM), which represents a novel early mechanism leading to diabetic kidney disease (DKD). Here, we examined the protective effects of Notoginsenoside R1 (NR1) on podocyte adhesion and α3β1 integrin expression under diabetic condition in vitro and in vivo. Methods: Conditionally immortalized mouse podocytes were exposed to high glucose (HG) with 10 and 100μg /ml of NR1 for 24 h. Podocyte adhesion, albuminuria, oxidative markers, renal histopathology, podocyte number per glomerular volume, integrin-linked kinase (ILK) activity and α3β1 integrin expression were measured in vitro and in vivo. Results: HG decreased podocyte adhesive capacity and α3β1 integrin expression, the main podocyte anchoring dimer to the GBM. However, NR1 ameliorated impaired podocyte adhesive capacity and partially restored α3β1 integrin protein and mRNA expression. These in vitro observations were confirmed in vivo. In streptozotocin(STZ)-induced diabetic rats, treatment with NR1 (5 and 10 mg· kg-1· d-1) for 12 weeks partially restored the number of podocytes per glomerular volume and glomerular α3β1 integrin expression, as well as ameliorated albuminuria, histopathology and oxidative stress. NR1 also inhibited glomerular ILK activity in diabetic rats. Conclusion: NR1, a novel antioxidant, ameliorated glucose-induced impaired podocyte adhesive capacity and subsequent podocyte depopulation partly through α3β1 integrin upregulation. These findings might provide a potential new therapeutic option for the treatment of DKD.

Background: Decreased expression of α3β1 integrin may contribute to reduction in podocyte adhesion to glomerular basement membrane (GBM), which represents a novel early mechanism leading to diabetic kidney disease (DKD). Here, we examined the protective effects of Notoginsenoside R1 (NR1) on podocyte adhesion and α3β1 integrin expression under diabetic condition in vitro and in vivo. Methods: Conditionally immortalized mouse podocytes were exposed to high glucose (HG) with 10 and 100μg /ml of NR1 for 24 h. Podocyte adhesion, albuminuria, oxidative markers, renal histopathology, podocyte number per glomerular volume, integrin-linked kinase (ILK) activity and α3β1 integrin expression were measured in vitro and in vivo. Results: HG decreased podocyte adhesive capacity and α3β1 integrin expression, the main podocyte anchoring dimer to the GBM. However, NR1 ameliorated impaired podocyte adhesive capacity and partially restored α3β1 integrin protein and mRNA expression. These in vitro observations were confirmed in vivo. In streptozotocin(STZ)-induced diabetic rats, treatment with NR1 (5 and 10 mg· kg-1· d-1) for 12 weeks partially restored the number of podocytes per glomerular volume and glomerular α3β1 integrin expression, as well as ameliorated albuminuria, histopathology and oxidative stress. NR1 also inhibited glomerular ILK activity in diabetic rats. Conclusion: NR1, a novel antioxidant, ameliorated glucose-induced impaired podocyte adhesive capacity and subsequent podocyte depopulation partly through α3β1 integrin upregulation. These findings might provide a potential new therapeutic option for the treatment of DKD. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: In the absence of mutant genes encoding components of the podocyte slit diaphragm, about 30-50 % of children with primary glucocorticoid-resistant focal segmental glomerulosclerosis (FSGS) develop recurrent proteinuria and slowly progressive FSGS lesions following renal transplantation. Recurrence of FSGS in the allograft strongly suggests a circulating factor that disturbs normal podocyte biology. To date, the nature of the circulating factor is unclear, and there is no cure for the recurrent form of FSGS (R-FSGS). Methods: Cultured differentiated human podocytes were exposed to the plasmapheresis effluent or blood plasma samples from pediatric patients with recurrent or primary FSGS; in some cases, podocytes were pre-incubated with specific antibodies to block the tumor necrosis factor-alpha (TNFα) signaling pathway. Integrity of focal adhesion complexes and actin cytoskeleton were investigated by immunofluorescent microscopy. Results: Plasmapheresis effluent from an R-FSGS child or fresh plasma from two children with primary FSGS rapidly disturbed the cytoskeleton of normal human podocytes in vitro. Plasma from a child with R-FSGS also activated β3 integrin and dispersed focal adhesion complexes. The effects were reversed by pre-incubation with antibodies against TNFα or either of the two TNFα receptors. When our patient with R-FSGS became resistant to plasmapheresis, we initiated treatment with twice weekly etanercept injections and then infliximab. Within 3 weeks of regular anti-TNFα therapy, the patient achieved sustained partial remission of proteinuria, allowing us to wean her off plasmapheresis completely. Conclusions: We suggest that in some FSGS patients, disruption of the podocyte cytoskeleton and β3 integrin-mediated podocyte attachment are driven by the TNFα pathway. [ABSTRACT FROM AUTHOR]

Patients with Alport's syndrome develop a number of pro-inflammatory cytokine and matrix metalloproteinase (MMP) abnormalities that contribute to progressive renal failure. Changes in the composition and structure of the glomerular basement membranes likely alter the biomechanics of cell adhesion and signaling in these patients. To test if enhanced strain on the capillary tuft due to these structural changes contributes to altered gene regulation, we subjected cultured podocytes to cyclic biomechanical strain. There was robust induction of interleukin (IL)-6, along with MMP-3, -9, -10, and -14, but not MMP-2 or -12 by increased strain. Neutralizing antibodies against IL-6 attenuated the strain-mediated induction of MMP-3 and -10. Alport mice treated with a general inhibitor of nitric oxide synthase (L-NAME) developed significant hypertension and increased IL-6 and MMP-3 and -10 in their glomeruli relative to those of normotensive Alport mice. These hypertensive Alport mice also had elevated proteinuria along with more advanced histological and ultrastructural glomerular basement membrane damage. We suggest that MMP and cytokine dysregulation may constitute a maladaptive response to biomechanical strain in the podocytes of Alport patients, thus contributing to glomerular disease initiation and progression. [ABSTRACT FROM AUTHOR]

Abstract: Impaired podocyte adhesion to glomerular basement membrane (GBM) may contribute to podocyte detachment from GBM, which represents a novel early mechanism leading to diabetic nephropathy (DN). Here, we examined the effects of Astragaloside IV (AS-IV), a saponin purified from Astragalus membranaceus (Fisch) Bge, on high glucose-induced cell adhesion dysfunction in cultured mouse podocytes. Cells were seeded into 96-well plates coated with basement membrane protein complex (BMC). The cells were incubated for 12h in media containing 30mM glucose (HG) with 10, 50 and 100μg/ml of AS-IV. The cells were also exposed to HG media with 100μg/ml of AS-IV for 3, 6, 12 and 24h. Cell adhesion assays were performed by fluorescence and centrifugation methods, respectively. Levels of mRNA were determined by quantitative reverse transcriptase real-time PCR and protein expression was analyzed by immunoblotting. HG strongly inhibited adhesion of podocytes to BMC, accompanied by reduction in α3β1 integrin mRNA and protein expression, as well as increase in integrin-linked kinase (ILK) activity and expression. When podocytes under HG stimulation were treated with AS-IV, a dose- and time-dependent increase in cell–matrix adhesion was observed, which was significant from 10μg/ml of AS-IV and from 6h of incubation of AS-IV with 100μg/ml. This was accompanied by significant increases in α3β1 integrin mRNA and protein expression, as well as inhibition of ILK activation and overexpression. These results suggest that AS-IV improve HG-induced podocyte adhesion dysfunction, which is partly attributed to α3β1 integrin upregulation and ILK inhibition. [Copyright &y& Elsevier]