Project description:Podocyte injury is a major determinant in proteinuric kidney disease and identification of potential therapeutic targets for preventing podocyte injury has clinical importance. Here, we show that histone deacetylase Sirt6 protects against podocyte injury through epigenetic regulation of Notch signaling. Sirt6 is downregulated in renal biopsies from patients with podocytopathies and its expression negatively correlates withglomerular filtration rate. Podocyte-specific deletion of Sirt6 exacerbates podocyte injury and proteinuria in two independent mouse models including diabetic nephropathy and adriamycin-induced nephropathy. Sirt6 has pleiotropic protective actions in podocytes including anti-inflammatory and anti-apoptotic effects, is involved in actin cytoskeleton maintenance, and promotes autophagy. Sirt6 also reduces urokinase plasminogen activator receptor expression, which is a key factor for podocyte foot process effacement and proteinuria. Mechanistically, Sirt6 inhibits Notch1 and Notch4 transcription by deacetylating the histone H3K9. We suggest Sirt6 as a potential therapeutic target in proteinuric kidney disease.
Project description:Arctigenin (ATG) is a major component of Fructus Arctii, which as a traditional herbal remedy reduced proteinuria in diabetic patients. However, whether ATG specifically provided renoprotection in DKD was not known. Here we report that ATG administration is sufficient to attenuate proteinuria and podocyte injury in mouse models of diabetes. Transcriptomic analysis of diabetic mouse glomeruli showed that cell adhesion and inflammation are two key pathways affected by ATG treatment, and mass spectrometry analysis identified protein phosphatase 2A (PP2A) as one of the top ATG-interacting proteins in renal cells. Enhanced PP2A activity by ATG reduces p65 NF-κB-mediated inflammatory response and high glucose-induced migration in cultured podocytes via its interaction with Drebrin-1. Importantly, podocyte-specific Pp2a deletion in mice exacerbates DKD injury and abrogates the ATG-mediated renoprotection. Collectively, our results clearly demonstrate a renoprotective mechanism of ATG via PP2A activation and establish PP2A as a potential target for DKD progression.
Project description:Arctigenin (ATG) is a major component of Fructus Arctii, which as a traditional herbal remedy reduced proteinuria in diabetic patients. However, whether ATG specifically provided renoprotection in DKD was not known. Here we report that ATG administration is sufficient to attenuate proteinuria and podocyte injury in mouse models of diabetes. Transcriptomic analysis of diabetic mouse glomeruli showed that cell adhesion and inflammation are two key pathways affected by ATG treatment, and mass spectrometry analysis identified protein phosphatase 2A (PP2A) as one of the top ATG-interacting proteins in renal cells. Enhanced PP2A activity by ATG reduces p65 NF-κB-mediated inflammatory response and high glucose-induced migration in cultured podocytes via its interaction with Drebrin-1. Importantly, podocyte-specific Pp2a deletion in mice exacerbates DKD injury and abrogates the ATG-mediated renoprotection. Collectively, our results clearly demonstrate a renoprotective mechanism of ATG via PP2A activation and establish PP2A as a potential target for DKD progression.
Project description:We found that podocyte-specific bPIX deficient (KO) mice developed progressive proteinuria starting at ~8 weeks of age, and glomerulosclerosis and podocyte loss by 13 weeks of age. To investigate the mechanism of podocyte loss induced by bPIX deficiency, we analyzed mRNA expression by RNA-sequence using isolated glomeruli from control (CTRL) and KO mice.
Project description:Podocyte histone deacetylases (HDAC) are essential in maintaining a normal glomerular filtration barrier by modulating podocyte quiescence. Podocyte-specific loss Hdac1 and 2 in mice results in severe proteinuria and sustained DNA damage, likely caused by epigenetic alterations and deficient DNA repair, that result in podocyte senescence. Through glomeruli isolation and RNA-seq profiling from the mutant mice, we demonstrated that senescent podocytes develop a senescence-associated secretory phenotype (SASP) that contribute to the loss of podocytes. The role of HDACs in senescence may provide important clues in our understanding of how podocytes are lost following injury.
Project description:Podocytes are terminally differentiated cells at the kidney filtration barrier and exposed to considerable mechanical strain. Podocyte injury causes morphological changes as a result of cytoskeletal reorganizations and failure of the filtration barrier. The transcriptional co-activators YAP/TAZ are tightly controlled through hippo signaling and responsive to mechanical cues. Here, we show that YAP is upregulated upon podocyte injury to activate YAP-dependent target genes. This activation preceded the development of proteinuria. In contrast, similar perturbations of cells in culture did not reveal increased YAP activity but showed a downregulation of YAP/TAZ activity when cells were grown on stiff surface. However, culture of cells on soft matrix or inhibition of stress fiber formation allowed recapitulation of the damage-induced YAP upregulation indicating a mechanotransduction-dependent mechanism of YAP over-activity. Interestingly, increased expression of YAP targets was confirmed in renal biopsies from patients with glomerular disease. Consistently, pharmacological inhibition of YAP/TEAD activity ameliorated glomerular disease in vivo. These data suggest that perturbation of the mechanosensitive hippo signaling pathway may be a therapeutic principle in podocyte disease.
Project description:Podocytes are terminally differentiated cells at the kidney filtration barrier and exposed to considerable mechanical strain. Podocyte injury causes morphological changes as a result of cytoskeletal reorganizations and failure of the filtration barrier. The transcriptional co-activators YAP/TAZ are tightly controlled through hippo signaling and responsive to mechanical cues. Here, we show that YAP is upregulated upon podocyte injury to activate YAP-dependent target genes. This activation preceded the development of proteinuria. In contrast, similar perturbations of cells in culture did not reveal increased YAP activity but showed a downregulation of YAP/TAZ activity when cells were grown on stiff surface. However, culture of cells on soft matrix or inhibition of stress fiber formation allowed recapitulation of the damage-induced YAP upregulation indicating a mechanotransduction-dependent mechanism of YAP hyper-activity. Interestingly, increased expression of YAP targets was confirmed in renal biopsies from patients with glomerular disease. Consistently, pharmacological inhibition of YAP/TEAD activity ameliorated glomerular disease in vivo. These data suggest that perturbation of the mechanosensitive hippo signaling pathway may be a therapeutic principle in podocyte disease.
Project description:High fructose diet has been proposed as a major contributor to metabolic syndrome, which is usually accompanied with proteinuria due to glomerular podocyte injury. However, the underlying pathological mechanisms of fructose-induced podocyte injury remain elusive. In this study, we have used an iTRAQ based quantitative proteomic strategy to comprehensively characterize the dynamic proteome changes in glomeruli of high fructose-fed rats, and revealed global fructose-induced glomerular metabolic reprogramming at four different stages during the progression of high fructose modeling.
Project description:Calcimimetic agents allosterically increase the calcium (Ca2+) sensitivity of the calcium-sensing receptor (CaSR), which is expressed in the tubular system and to a lesser extent in podocytes. Activation of this receptor can reduce glomerular proteinuria and structural damage in proteinuric animal models. However, the precise role of the podocyte CaSR is still unclear. A CaSR knockdown in cultured murine podocytes and a podocyte-specific CaSR knockout in BALB/c mice were generated to study its role in proteinuria and kidney function. Podocyte CaSR knockdown abolished the calcimimetic R-568 mediated Ca2+-influx, disrupted the actin cytoskeleton, reduced cellular attachment and migration velocity. Adriamycin (ADR)-induced proteinuria enhanced glomerular CaSR expression in wild type mice. Albuminuria, podocyte foot process effacement, podocyte loss and glomerular sclerosis were significantly more pronounced in ADR-treated podocyte-specific CaSR knockout mice compared to wild type littermates. The co-treatment of WT mice with ADR and the calcimimetic cinacalcet reduced the proteinuria in WT, but not in podocyte specific CaSR knockout mice. In addition, four children with nephrotic syndrome, objecting glucocorticoid therapy, were treated with cinacalcet for 1 to 33 days. Proteinuria declined transiently by up to 96% and edema resolved. The activation of podocyte CaSR regulates key podocyte functions in vitro and reduces toxin induced proteinuria and glomerular damage in mice. Our findings suggest a potential novel role of CaSR signaling in control of glomerular disease. Proteomic samples: two backgrounds (CaSR Knockdown vs WT) two conditions (Treatment = 1µM R568 vs untreated control) two timepoints (24h and 48h) five replicates each 2 x 2 x 2 x 5 = 40 samples
Project description:Evidence for reduced expression of cyclin-G associated kinase (GAK) in glomeruli of chronic kidney disease patients was observed in the Nephroseq human database and was found to be associated with the decline in kidney function. To examine the role of GAK, a protein that functions to uncoat clathrin during endocytosis, we generated podocyte-specific Gak knockout mice (Gak KO) which developed progressive proteinuria and kidney failure with global glomerulosclerosis. We isolated glomeruli from the mutant mice to perform messenger RNA profiling and unearthed evidence for dysregulated podocyte calpain protease activity as an important contributor to this process. Treatment with calpain inhibitor III specifically inhibited calpain-1/-2 activities, mitigated the degree of proteinuria and glomerulosclerosis, and led to a striking increase in survival in the Gak KO mice. Podocyte-specific deletion of Capns1, essential for calpain-1 and calpain-2 activities, also improved proteinuria and glomerulosclerosis in Gak KO mice. Increased podocyte calpain activity mediated proteolysis of IkB resulted in increased NF-kBp65 induced Gadd45b expression in the Gak KO mice. Our results suggest that loss of podocyte associated Gak induces glomerular injury secondary to calcium dysregulation and aberrant calpain activation, which when inhibited, can provide a protective role.