Podocyte-Specific Deletion of MCP-1 Fails to Protect against Angiotensin II- or Adriamycin-Induced Glomerular Disease.

Investigating the role of podocytes in proteinuric disease is imperative to address the increasing global burden of chronic kidney disease (CKD). Studies strongly implicate increased levels of monocyte chemoattractant protein-1 (MCP-1/CCL2) in proteinuric CKD. Since podocytes express the receptor for MCP-1 (i.e., CCR2), we hypothesized that podocyte-specific MCP-1 production in response to stimuli could activate its receptor in an autocrine manner, leading to further podocyte injury. To test this hypothesis, we generated podocyte-specific MCP-1 knockout mice (Podo-Mcp-1fl/fl) and exposed them to proteinuric injury induced by either angiotensin II (Ang II; 1.5 mg/kg/d, osmotic minipump) or Adriamycin (Adr; 18 mg/kg, intravenous bolus). At baseline, there were no between-group differences in body weight, histology, albuminuria, and podocyte markers. After 28 days, there were no between-group differences in survival, change in body weight, albuminuria, kidney function, glomerular injury, and tubulointerstitial fibrosis. The lack of protection in the knockout mice suggests that podocyte-specific MCP-1 production is not a major contributor to either Ang II- or Adr-induced glomerular disease, implicating that another cell type is the source of pathogenic MCP-1 production in CKD.

Boerhavia diffusa attenuates podocyte injury in rats with adenine induced chronic kidney disease by enhancing nephrin expression.

Nephrin is a transmembrane protein that maintains the slit diaphragm of renal podocyte. In chronic kidney disease (CKD), podocyte effacement causes damage to glomerular basement membrane barrier leading to proteinuria. Boerhavia diffusa, (BD), an Ayurveda herb, is used in treatment of various diseases particularly in relation to the urinary system. This study attempts to evaluate the effect of ethanolic extract of BD on the expression of nephrin in adenine induced CKD rats. CKD was induced in Wistar albino rats using adenine (600/mg/kg, orally for 10 days). CKD rats were treated with BD (400/mg/kg) and pirfenidone (500/mg/kg) orally for 14 days. The kidneys were harvested from euthanized animals and processed for histopathology, electron microscopy and immunohistochemistry, gene and protein expression of nephrin. Diseased rats treated with BD and pirfenidone showed reduction in the thickening of renal basement membranes and reduced haziness in brush border of PCT and glomeruli. Nephrin gene and protein expressions were higher in BD and pirfenidone treated group when compared to the disease control group. The structural and functional damage brought on by adenine-induced nephrotoxicity was countered by protective action of BD by up regulating the expression of nephrin. Therefore, BD can be utilized as a nutraceutical for the prevention and treatment of CKD.

Genetic or pharmacologic blockade of mPGES-2 attenuates renal lipotoxicity and diabetic kidney disease by targeting Rev-Erbα/FABP5 signaling.

Diabetic kidney disease (DKD) is one of the most common complications of diabetes, and no specific drugs are clinically available. We have previously demonstrated that inhibiting microsomal prostaglandin E synthase-2 (mPGES-2) alleviated type 2 diabetes by enhancing ß cell function and promoting insulin production. However, the involvement of mPGES-2 in DKD remains unclear. Here, we aimed to analyze the association of enhanced mPGES-2 expression with impaired metabolic homeostasis of renal lipids and subsequent renal damage. Notably, global knockout or pharmacological blockage of mPGES-2 attenuated diabetic podocyte injury and tubulointerstitial fibrosis, thereby ameliorating lipid accumulation and lipotoxicity. These findings were further confirmed in podocyte- or tubule-specific mPGES-2-deficient mice. Mechanistically, mPGES-2 and Rev-Erbα competed for heme binding to regulate fatty acid binding protein 5 expression and lipid metabolism in the diabetic kidney. Our findings suggest a potential strategy for treating DKD via mPGES-2 inhibition.

Development and Characterization of a Novel FVB-PrkdcR2140C Mouse Model for Adriamycin-Induced Nephropathy.

The Adriamycin (ADR) nephropathy model, which induces podocyte injury, is limited to certain mouse strains due to genetic susceptibilities, such as the PrkdcR2140C polymorphism. The FVB/N strain without the R2140C mutation resists ADR nephropathy. Meanwhile, a detailed analysis of the progression of ADR nephropathy in the FVB/N strain has yet to be conducted. Our research aimed to create a novel mouse model, the FVB-PrkdcR2140C, by introducing PrkdcR2140C into the FVB/NJcl (FVB) strain. Our study showed that FVB-PrkdcR2140C mice developed severe renal damage when exposed to ADR, as evidenced by significant albuminuria and tubular injury, exceeding the levels observed in C57BL/6J (B6)-PrkdcR2140C. This indicates that the FVB/N genetic background, in combination with the R2140C mutation, strongly predisposes mice to ADR nephropathy, highlighting the influence of genetic background on disease susceptibility. Using RNA sequencing and subsequent analysis, we identified several genes whose expression is altered in response to ADR nephropathy. In particular, Mmp7, Mmp10, and Mmp12 were highlighted for their differential expression between strains and their potential role in influencing the severity of kidney damage. Further genetic analysis should lead to identifying ADR nephropathy modifier gene(s), aiding in early diagnosis and providing novel approaches to kidney disease treatment and prevention.

Zinc oxide nanoparticles prevent the onset of diabetic nephropathy by inhibiting multiple pathways associated with oxidative stress.

BACKGROUND: Zinc deficiency is strongly correlated with prolonged diabetes mellitus and diabetic nephropathy (DN). Previously, glucose-lowering, insulinomimetic, and ß-cell proliferative activities of zinc oxide nanoparticles (ZON) have been reported. Considering these pleiotropic effects, we hypothesized that ZON modulates multiple cellular pathways associated with necroptosis, inflammation, and renal fibrosis, which are involved in progressive loss of renal function. AIM: This study evaluated the effect of ZON on renal function, leading to the alleviation of DN in streptozotocin (STZ)-induced type 1 diabetic Wistar rats and proposed a probable mechanism for its activity. METHODS: Wistar rats (n = 6/group) were used as healthy controls, diabetic controls, diabetic rats treated with ZON (1, 3, and 10 mg/kg), and insulin controls. Urine and serum biochemical parameters, glomerular filtration rate (GFR), and renal histology were also evaluated. Cultured E11 podocytes were evaluated in vitro for markers of oxidative stress, proteins associated with the loss of renal function, and genes associated with renal damage. KEY FINDINGS: STZ-treated rats receiving oral doses of ZON showed enhanced renal function, with no histological alterations in the kidney tissue. ZON inhibited the TGF-ß/Samd3 pathway in renal fibrosis; blocked Ripk1/Ripk3/Mlkl mediated necroptosis and protected against hyperglycemia-induced pyroptosis. In E11 podocytes, ZON reduced oxidative stress under high glucose conditions and retained podocyte-specific proteins. SIGNIFICANCE: A probable mechanism by which ZON prevents DN has been proposed, suggesting its use as a complementary therapeutic agent for the treatment of diabetic complications. To the best of our knowledge, this is the first study to demonstrate the in vitro effects of ZON in cultured podocytes.

Activation of the IL-6/STAT3 pathway contributes to the pathogenesis of membranous nephropathy and is a target for Mahuang Fuzi and Shenzhuo Decoction (MFSD) to repair podocyte damage.

BACKGROUND: Primary membranous nephropathy (PMN) is an autoimmune glomerular disease. IL-6 is a potential therapeutic target for PMN. Previous clinical studies have demonstrated the effectiveness of Mahuang Fuzi and Shenzhuo Decoction (MFSD) in treating membranous nephropathy. However, the mechanism of action of MFSD remains unclear. METHODS: Serum IL-6 levels were measured in patients with PMN and healthy subjects. The passive Heymann nephritis (PHN) rat model was established, and high and low doses of MFSD were used for intervention to observe the repair effect of MFSD on renal pathological changes and podocyte injury. RNA-seq was used to screen the possible targets of MFSD, and the effect of MFSD targeting IL-6/STAT3 was further verified by combining the experimental results. Finally, the efficacy of tocilizumab in PHN rats was observed. RESULTS: Serum IL-6 levels were significantly higher in PMN patients than in healthy subjects. These levels significantly decreased in patients in remission after MFSD treatment. MFSD treatment improved laboratory indicators in PHN rats, as well as glomerular filtration barrier damage and podocyte marker protein expression. Renal transcriptome changes showed that MFSD-targeted differential genes were enriched in JAK/STAT and cytokine-related pathways. MFSD inhibits the IL6/STAT3 pathway in podocytes. Additionally, MFSD significantly reduced serum levels of IL-6 and other cytokines in PHN rats. However, treatment of PHN with tocilizumab did not achieve the expected effect. CONCLUSION: The IL-6/STAT3 signaling pathway is activated in podocytes of experimental membranous nephropathy. MFSD alleviates podocyte damage by inhibiting the IL-6/STAT3 pathway.

Rutaecarpine protects podocytes in diabetic kidney disease by targeting VEGFR2/NLRP3-mediated pyroptosis.

OBJECTIVE: Diabetic kidney disease (DKD) is the most common cause of the end-stage renal disease, which has limited treatment options. Rutaecarpine has anti-inflammatory effects, however, it has not been studied in DKD. Pyroptosis is a newly discovered mode of podocyte death related to inflammation. This study aimed to explore whether Rutaecarpine can ameliorate DKD and to clarify its possible mechanism. METHODS: In this study, we investigated the effects of Rutaecarpine on DKD using diabetic mice model (db/db mice) and high glucose (HG)-stimulated mouse podocyte clone 5 (MPC5) cells. Quantitative reverse transcription polymerase chain reaction and western blot were performed to detect the related gene and protein levels. We applied pharmacological prediction, co-immunoprecipitation assay, cellular thermal shift assay, surface plasmon resonance to find the target and pathway of the substances. Gene knockdown experiments confirmed this view in HG-stimulated MPC5 cells. RESULTS: Rutaecarpine significantly reduced proteinuria, histopathological damage, and pyroptosis of podocytes in a dose-dependent manner in db/db mice. Rutaecarpine also protected high glucose induced MPC5 injury in vitro experiments. Mechanistically, Rutaecarpine can inhibit pyroptosis in HG-stimulated MPC5 by reducing the expression of VEGFR2. VEGFR2 is a target of Rutaecarpine in MPC5 cells and directly binds to the pyroptosis initiation signal, NLRP3. VEGFR2-knockdown disrupted the beneficial effects of Rutaecarpine in HG-stimulated MPC5 cells. CONCLUSION: Rutaecarpine inhibits renal inflammation and pyroptosis through VEGFR2/NLRP3 pathway, thereby alleviating glomerular podocyte injury. These findings highlight the potential of Rutaecarpine as a novel drug for DKD treatment.

Insulin induces bioenergetic changes and alters mitochondrial dynamics in podocytes.

Diabetic nephropathy (DN) is one of the most frequent complications of diabetes. Early stages of DN are associated with hyperinsulinemia and progressive insulin resistance in insulin-sensitive cells, including podocytes. The diabetic environment induces pathological changes, especially in podocyte bioenergetics, which is tightly linked with mitochondrial dynamics. The regulatory role of insulin in mitochondrial morphology in podocytes has not been fully elucidated. Therefore, the main goal of the present study was to investigate effects of insulin on the regulation of mitochondrial dynamics and bioenergetics in human podocytes. Biochemical analyses were performed to assess oxidative phosphorylation efficiency by measuring the oxygen consumption rate (OCR) and glycolysis by measuring the extracellular acidification rate (ECAR). mRNA and protein expression were determined by real-time polymerase chain reaction and Western blot. The intracellular mitochondrial network was visualized by MitoTracker staining. All calculations were conducted using CellProfiler software. Short-term insulin exposure exerted inhibitory effects on various parameters of oxidative respiration and adenosine triphosphate production, and glycolysis flux was elevated. After a longer time of treating cells with insulin, an increase in mitochondrial size was observed, accompanied by a reduction of expression of the mitochondrial fission markers DRP1 and FIS1 and an increase in mitophagy. Overall, we identified a previously unknown role for insulin in the regulation of oxidative respiration and glycolysis and elucidated mitochondrial dynamics in human podocytes. The present results emphasize the importance of the duration of insulin stimulation for its metabolic and molecular effects, which should be considered in clinical and experimental studies of DN.

Ulinastatin ameliorates podocyte ferroptosis via regulating miR-144-3p/SLC7A11 axis in acute kidney injury.

Ferroptosis is a newly discovered form of cell death characterized by intracellular iron accumulation and subsequent lipid peroxidation, which has been identified in various pathological processes, such as acute kidney injury (AKI). Ulinastatin (UTI), known as an antioxidant and anti-inflammatory, has been reported to prevent kidney injury. Here, we investigated the protective effects of UTI on LPS-induced podocyte ferroptosis in vivo and in vitro. Conditionally immortalized mouse podocyte was exposed to LPS in the presence or absence of UTI in vitro for 48 h. The levels of reactive oxygen species (ROS) and intracellular Fe2+ were detected to value the effect of UTI treatment on the podocyte cell ferroptosis. We also evaluated the influence of UTI on kidney injury in vivo. LPS-induced mice were treated with vehicle or UTI at 50 U/g/d for 6 wk. We identified the important function of UTI in repressing ferroptosis and ameliorating podocyte injury. The treatment of UTI reduced accumulation of Fe2+ and lipid ROS in podocyte. The cell proliferation was induced by UTI compared with the LPS-treated group in vitro. UTI attenuated the podocyte cytoskeletal as well. Regarding the mechanism, we found that UTI upregulated solute carrier family 7 member 11 (SLC7A11) expression by reducing miR-144-3p in the cells. The overexpression of miR-144-3p blocked the protective role of UTI in podocyte ferroptosis. MiR-144-3p/SLC7A11 axis was involved in UTI-mediated podocyte cell proliferation in vitro. Furthermore, the treatment of UTI repressed podocyte injury and proteinuria in vivo, and the level of miR-144-3p was decreased while SLC7A11 expression was increased in comparison with the model mice. UTI prevents LPS-induced podocyte ferroptosis and subsequent renal dysfunction through miR-144-3p/SLC7A11 axis. These findings might provide a potential novel therapeutic option for AKI and other renal diseases affecting podocyte.

Astragaloside IV Inhibited Podocyte Pyroptosis in Diabetic Kidney Disease by Regulating SIRT6/HIF-1α Axis.

To investigate the effect of astragaloside IV (AS) on podocytes pyroptosis in diabetic kidney disease (DKD). Forty male Sprague-Dawley rats were randomly divided into normal group (n = 10) and model group (n = 30). Rats in model group were intraperitoneally injected streptozotocin (60 mg/kg) for 3 days to induce DKD. Then rats were divided into DKD group, AS group, and UBCS group. The AS group was given 40 mg/kg/d of AS by gavage, and UBCS group was given 50 mg/kg/d of UBCS039 by gavage, and normal group and DKD group were given the same amount saline for 8 weeks, once a day. Hematoxylin-eosin and masson staining were used to observe pathology of kidney. Rat podocytes were divided into normal group, mannitol hypertonic group, high-glucose group, UBCS group, OSS group, and AS group. Western blotting, quantitative real-time polymerase chain reaction, immunofluorescence, and flow cytometry were used to analyze pyroptosis-related markers and reactive oxygen species (ROS) levels. Results showed that AS inhibited ROS and alleviated podocytes pyroptosis in rats by increasing expression of sirtuin 6 (SIRT6) and decreasing expression of hypoxia inducible factor 1 subunit alpha (HIF-1α). UBCS039 and AS enhanced SIRT6 level, decreased HIF-1α level, and finally improved pyroptosis of podocytes in vitro, whereas OSS-128167 showed the opposite effect for podocytes pyroptosis. AS improved podocytes pyroptosis in DKD by regulating SIRT6/HIF-1α pathway, thereby alleviating injury of DKD.

The effect of mycophenolate mofetil on podocytes in nephrotoxic serum nephritis.

Mycophenolate mofetil (MMF) is applied in proteinuric kidney diseases, but the exact mechanism of its effect on podocytes is still unknown. Our previous in vitro experiments suggested that MMF can ameliorate podocyte damage via restoration of the Ca2+-actin cytoskeleton axis. The goal of this study was to characterize podocyte biology during MMF treatment in nephrotoxic serum (NTS) nephritis (NTN). NTN was induced in three-week old wild-type mice. On day 3, half of the mice were treated with MMF (100 mg/kgBW/d p.o.) for one week. On day 10, we performed proteomic analysis of glomeruli as well as super-resolution imaging of the slit diaphragm. For multiphoton imaging of Ca2+ concentration ([Ca2+]i), the experimental design was repeated in mice expressing podocyte-specific Ca2+ sensor. MMF ameliorated the proteinuria and crescent formation induced by NTS. We identified significant changes in the abundance of proteins involved in Ca2+ signaling and actin cytoskeleton regulation, which was further confirmed by direct [Ca2+]i imaging in podocytes showing decreased Ca2+ levels after MMF treatment. This was associated with a tendency to restoration of podocyte foot process structure. Here, we provide evidence that MPA has a substantial direct effect on podocytes. MMF contributes to improvement of [Ca2+]i and amelioration of the disorganized actin cytoskeleton in podocytes. These data extend the knowledge of direct effects of immunosuppressants on podocytes that may contribute to a more effective treatment of proteinuric glomerulopathies with the least possible side effects.

Jiedu Tongluo Baoshen formula enhances podocyte autophagy and reduces proteinuria in diabetic kidney disease by inhibiting PI3K/Akt/mTOR signaling pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Traditional Chinese medicine (TCM) has been applied to diabetic kidney disease (DKD). A large number of animal trials each year focus on TCM for DKD, but the evidence for these preclinical studies is not clear. AIM OF THE STUDY: The aim of this study was to study the therapeutic effect of Jiedu Tongluo Baoshen formula (JTBF) on DKD proteinuria and renal protection. At the same time, it is verified that JTBF can reduce podocyte injury by enhancing autophagy function, and then achieve the effect of proteinuria. MATERIALS AND METHODS: We use high performance liquid chromatography to detect and analyze the fingerprint of JTBF to find the chemical composition. Subsequently, we constructed a DKD rat model induced by high-fat diet and streptozocin (HFD + STZ). Urine and blood biochemical automatic analyzer were used to detect 24-h urine protein quantification (24 h-UP) and renal function. The renal pathological changes were observed by H&E and transmission electron microscopy (TEM), and the levels of autophagy-related proteins and mRNA in podocytes were detected by immunohistochemistry, RT-qPCR and Western Blot. The chemical composition of JTBF was screened from traditional Chinese medicine systems pharmacol (TCMSP) and PubChem databases, and the potential targets and associated pathways of JTBF were predicted using kyoto encyclopedia of genes and genomes (KEGG) and protein-protein interaction (PPI) network analysis in network pharmacology, and confirmed in animal experiments and histopathological methods. RESULTS: We discovered 77 active ingredients of JTBF. Through animal experiments, it was found that JTBF reduced 24 h-UP and promoted the expression of podocin, nephrin, and WT-1 in podocytes, thereby reducing podocyte damage. At the same time, JTBF activates the expression of podocyte autophagy-related proteins (beclin-1, LC3 and P62). Subsequently, through network pharmacology predictions, 208 compounds were obtained from JTBF, and phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) was a potential signal pathway. JTBF was obtained in DKD rat kidney tissue to inhibit the expression of PI3K, Akt and mTOR related proteins. CONCLUSIONS: JTBF enhance podocyte autophagy to reduce podocyte damage, thereby effectively treating DKD proteinuria and protecting kidney function.

Discovery of pyrroledione analogs as potent transient receptor potential canonical channel 5 inhibitors.

A deepening understanding of the relationship between transient receptor potential canonical channel 5 (TRPC5) and chronic kidney disease (CKD), has led to the emergence of several types of TRPC5 inhibitors displaying clear therapeutic effect. Herein, we report the synthesis and biological evaluation of a series of pyrroledione TRPC5 inhibitors, culminating in the discovery of compound 16g with subtype selectivity. Compared with GFB-8438, a potent TRPC5 inhibitor (Goldfinch Bio), compound 16g showed improved inhibition of TRPC5 and enhanced protective effect against protamine sulfates (PS)-induced podocyte injury in vitro. In addition, compound 16g did not induce cell death in primary cultured hepatocytes and immortalized podocytes in a preliminary toxicity assessment, indicating its utility as a potent and safe inhibitor for studying the function of TRPC5.

Wogonin protects glomerular podocytes by targeting Bcl-2-mediated autophagy and apoptosis in diabetic kidney disease.

Diabetic kidney disease (DKD) is one of the microvascular complications of diabetes mellitus and a major cause of end-stage renal disease with limited treatment options. Wogonin is a flavonoid derived from the root of Scutellaria baicalensis Georgi, which has shown a potent renoprotective effect. But the mechanisms of action in DKD are not fully elucidated. In this study, we investigated the effects of wogonin on glomerular podocytes in DKD using mouse podocyte clone 5 (MPC5) cells and diabetic mice model. MPC5 cells were treated with high glucose (30 mM). We showed that wogonin (4, 8, 16 µM) dose-dependently alleviated high glucose (HG)-induced MPC5 cell damage, accompanied by increased expression of WT-1, nephrin, and podocin proteins, and decreased expression of TNF-α, MCP-1, IL-1ß as well as phosphorylated p65. Furthermore, wogonin treatment significantly inhibited HG-induced apoptosis in MPC5 cells. Wogonin reversed HG-suppressed autophagy in MPC5 cells, evidenced by increased ATG7, LC3-II, and Beclin-1 protein, and decreased p62 protein. We demonstrated that wogonin directly bound to Bcl-2 in MPC5 cells. In HG-treated MPC5 cells, knockdown of Bcl-2 abolished the beneficial effects of wogonin, whereas overexpression of Bcl-2 mimicked the protective effects of wogonin. Interestingly, we found that the expression of Bcl-2 was significantly decreased in biopsy renal tissue of diabetic nephropathy patients. In vivo experiments were conducted in STZ-induced diabetic mice, which were administered wogonin (10, 20, 40 mg · kg-1 · d-1, i.g.) every other day for 12 weeks. We showed that wogonin administration significantly alleviated albuminuria, histopathological lesions, and p65 NF-κB-mediated renal inflammatory response. Wogonin administration dose-dependently inhibited podocyte apoptosis and promoted podocyte autophagy in STZ-induced diabetic mice. This study for the first time demonstrates a novel action of wogonin in mitigating glomerulopathy and podocytes injury by regulating Bcl-2-mediated crosstalk between autophagy and apoptosis. Wogonin may be a potential therapeutic drug against DKD.

Steroid-sensitive nephrotic syndrome candidate gene CLVS1 regulates podocyte oxidative stress and endocytosis.

We performed next-generation sequencing in patients with familial steroid-sensitive nephrotic syndrome (SSNS) and identified a homozygous segregating variant (p.H310Y) in the gene encoding clavesin-1 (CLVS1) in a consanguineous family with 3 affected individuals. Knockdown of the clavesin gene in zebrafish (clvs2) produced edema phenotypes due to disruption of podocyte structure and loss of glomerular filtration barrier integrity that could be rescued by WT CLVS1 but not the p.H310Y variant. Analysis of cultured human podocytes with CRISPR/Cas9-mediated CLVS1 knockout or homozygous H310Y knockin revealed deficits in clathrin-mediated endocytosis and increased susceptibility to apoptosis that could be rescued with corticosteroid treatment, mimicking the steroid responsiveness observed in patients with SSNS. The p.H310Y variant also disrupted binding of clavesin-1 to α-tocopherol transfer protein, resulting in increased reactive oxygen species (ROS) accumulation in CLVS1-deficient podocytes. Treatment of CLVS1-knockout or homozygous H310Y-knockin podocytes with pharmacological ROS inhibitors restored viability to control levels. Taken together, these data identify CLVS1 as a candidate gene for SSNS, provide insight into therapeutic effects of corticosteroids on podocyte cellular dynamics, and add to the growing evidence of the importance of endocytosis and oxidative stress regulation to podocyte function.

Ginsenoside Rb1 alleviates diabetic kidney podocyte injury by inhibiting aldose reductase activity.

Panax notoginseng, a traditional Chinese medicine, exerts beneficial effect on diabetic kidney disease (DKD), but its mechanism is not well clarified. In this study we investigated the effects of ginsenoside Rb1 (Rb1), the main active ingredients of Panax notoginseng, in alleviating podocyte injury in diabetic nephropathy and the underlying mechanisms. In cultured mouse podocyte cells, Rb1 (10 µM) significantly inhibited high glucose-induced cell apoptosis and mitochondrial injury. Furthermore, Rb1 treatment reversed high glucose-induced increases in Cyto c, Caspase 9 and mitochondrial regulatory protein NOX4, but did not affect the upregulated expression of aldose reductase (AR). Molecular docking analysis revealed that Rb1 could combine with AR and inhibited its activity. We compared the effects of Rb1 with eparestat, a known aldose reductase inhibitor, in high glucose-treated podocytes, and found that both alleviated high glucose-induced cell apoptosis and mitochondrial damage, and Rb1 was more effective in inhibiting apoptosis. In AR-overexpressing podocytes, Rb1 (10 µM) inhibited AR-mediated ROS overproduction and protected against high glucose-induced mitochondrial injury. In streptozotocin-induced DKD mice, administration of Rb1 (40 mg·kg-1·d-1, ig, for 7 weeks) significantly mitigated diabetic-induced glomerular injuries, such as glomerular hypertrophy and mesangial matrix expansion, and reduced the expression of apoptotic proteins. Collectively, Rb1 combines with AR to alleviate high glucose-induced podocyte apoptosis and mitochondrial damage, and effectively mitigates the progression of diabetic kidney disease.

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

Interleukin (IL)-1 receptor type 1 (IL-1R1) activation triggers a proinflammatory signaling cascade that can exacerbate kidney injury. However, the functions of podocyte IL-1R1 in glomerular disease remain unclear. To study the role of IL-1R1 signaling in podocytes, we selectively ablated podocyte IL-1R1 in mice (PKO mice). We then subjected PKO mice and wild-type controls to two glomerular injury models: nephrotoxic serum (NTS)- and adriamycin-induced nephropathy. Surprisingly, we found that IL-1R1 activation in podocytes limited albuminuria and podocyte injury during NTS- and adriamycin-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 wild-type 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.NEW & NOTEWORTHY The present study establishes that activation of the receptor for interleukin-1 limits susceptibility to damage to the kidney glomerulus in preclinical mouse models by stimulating Akt signaling cascades inside the podocyte.

Structural modulation of gut microbiota during alleviation of experimental passive Heymann nephritis in rats by a traditional Chinese herbal formula.

BACKGROUND: Jianpi-Qushi-Heluo formula (JQHF) has been used to treat idiopathic membranous nephropathy (IMN) in hospitals for many years. PURPOSE: Elucidating the protective effect and exploring the potential mechanism of JQHF against IMN. METHODS: Passive Heymann nephritis (PHN) was induced in rats by a single tail vein injection of anti-Fx1A antiserum. Then, the animals were treated with JQHF at 16.2 g/kg or 32.4 g/kg, with benzepril (10 mg/kg) as a positive control. Renal function was evaluated by biochemical measurements and pathological testing. Fecal samples were collected before and after treatment to analyze the gut microbiota composition by shotgun whole metagenome sequencing. RESULTS: JQHF exhibited potent efficacy in ameliorating PHN at both doses, as revealed by decreasing the deposition of IgG and C5b-9, relieving podocyte injury, and reducing glomerular and tubular cell apoptosis. The lower dose was corresponding to the clinical dosage and showed better therapeutic effects than the higher dose. Metagenomic analysis showed that gavage with 16.2 g/kg of JQHF shifted the structure of the gut microbiota in PHN rats and significantly increased the relative abundances of Prevotella copri, Lactobacillus vaginalis and Subdoligranulum variabile. Particularly, S. variabile was strongly negatively correlated with serum levels of TC and TG, the deposition of IgG and C5b-9, and apoptosis of glomerular cells. CONCLUSIONS: The JQHF is an effective agent for the treatment of experimental PHN. The PHN-allevating effect of JQHF is associated with specific alternation of gut microbiota.

Novel Effects of Combination Therapy Through Inhibition of Caspase-1/Gasdermin D Induced-Pyroptosis in Lupus Nephritis.

Objectives: Combination therapy with mycophenolate mofetil, tacrolimus and steroids are effective in achieving complete remission in lupus nephritis (LN). Combination therapy uniquely downregulated caspase-1 compared with monotherapies, which can cleave gasdermin D (GSDMD) and was recently identified as the pyroptosis executioner. We therefore investigated whether combination therapy enabled the suppression of caspase-1/GSDMD-mediated pyroptosis in LN. Methods: Expression and activation of GSDMD were detected in kidney specimens of the human and mouse with LN using immunohistochemical staining and immunoblotting. Primary podocytes isolated from MRL/lpr mice were incubated with LPS+ATP, and pretreated with monotherapy or combination therapy. Inhibition of caspase-1/GSDMD-induced pyroptosis by combination therapy were assessed in MRL/lpr mice and human specimens. Pyroptosis was examined using a FAM caspase-1 kit and flow cytometry. The correlation between pyroptosis in peripheral blood and the systemic lupus erythematosus disease activity index (SLEDAI) was analyzed. Results: Kidney tissue specimens from LN patients and mice exhibited greatly increased expression levels and cleavage of GSDMD. In cultured podocytes, combination treatment significantly suppressed the activation of NLRP3 and caspase-1 and reduced GSDMD N-terminal levels. Combination therapy repressed disease progression through inhibition of caspase-1/GSDMD-mediated pyroptosis in both humans and MRL/lpr mice. Caspase-1/PI positive cell numbers in peripheral blood were positively correlated with SLE-DAI. LN patients with complete remission and partial remission had remarkably reduced caspase-1/PI positive cell numbers compared to baseline. Ac-FLTD-CMK, a GSDMD-derived inhibitor, prevented the development of LN. Conclusion: Combination therapy suppressed caspase-1/GSDMD-mediated pyroptosis in vitro and in vivo and reduced disease progression.

MAD2B-mediated cell cycle reentry of podocytes is involved in the pathogenesis of FSGS.

Rationale: Focal segmental glomerulosclerosis (FSGS) is characterized by the dysfunction of "post-mitotic" podocytes. The reentry of podocytes in the cell cycle will ultimately result in cell death. Mitotic arrest deficient 2-like protein 2 (MAD2B), an inhibitor of anaphase-promoting complex (APC)/cyclosome, precisely controls the metaphase to anaphase transition and ordered cell cycle progression. However, the role of MAD2B in FSGS podocyte injury remains unknown. Methods: To explore MAD2B function in podocyte cell cycle reentry, we used conditional mutant mice lacking MAD2B selectively in podocytes in ADR-induced FSGS murine model. Additionally, KU-55933, a specific inhibitor of ataxia-telangiectasia mutated (ATM) was utilized in vivo and in vitro to explore the role of ATM in regulating MAD2B. Results: The expression of MAD2B in podocytes was dramatically increased in patients with FSGS and ADR-treated mice along with podocyte cell cycle reentry. Podocyte-specific knockout of MAD2B effectively attenuated proteinuria, podocyte injury, and prevented the aberrant cell cycle reentry. By bioinformatics analysis we revealed that ATM kinase is a key upstream regulator of MAD2B. Furthermore, inhibition of ATM kinase abolished MAD2B-driven cell cycle reentry and alleviated podocyte impairment in FSGS murine model. In vitro studies by site-directed mutagenesis and immunoprecipitation we revealed ATM phosphorylated MAD2B and consequently hampered the ubiquitination of MAD2B in a phosphorylation-dependent manner. Conclusions: ATM kinase-MAD2B axis importantly contributes to the cell cycle reentry of podocytes, which is a novel pathogenic mechanism of FSGS, and may shed light on the development of its therapeutic approaches.