Polygala fallax Hemsl. ameliorated high glucose-induced podocyte injury by modulating mitochondrial mPTP opening through the SIRT1/PGC-1α pathway.

This study aimed to investigate the effects and molecular mechanism of PF on high glucose (HG)-induced podocyte injury. Results found that PF increased proliferation activity, decreased apoptosis, LDH, and caspase-3 levels, and increased nephrin and podocin expression in HG-induced cells. Similarly, PF improved HG-induced mitochondrial damage, decreased Ca2+ and ROS content, alleviated oxidative stress, inhibited mPTP opening, increased mitochondrial membrane potential, and decreased the expressions of Drp1, Bak, Bax, and Cytc in cytoplasm, increased the expressions of SIRT1, PGC-1α, HSP70, HK2, and Cytc in mitochondria of podocytes. The use of mPTP agonist/blocker and SIRT1 inhibitor confirmed that PF alleviates HG-induced podocyte injury by regulating mitochondrial mPTP opening through SIRT1/PGC-1α. In addition, PF affected HK2-VDAC1 protein binding to regulate mPTP opening via the SIRT1/PGC-1α pathway. In conclusion, PF-regulated HK2-VDAC1 protein binding affected mitochondrial mPTP opening and improved HG-induced podocyte injury through the SIRT1/PGC-1α pathway.

Podocyte senescence: from molecular mechanisms to therapeutics.

As an important component of the glomerular filtration membrane, the state of the podocytes is closely related to kidney function, they are also key cells involved in aging and play a central role in the damage caused by renal aging. Therefore, understanding the aging process of podocytes will allow us to understand their susceptibility to injury and identify targeted protective mechanisms. In fact, the process of physiological aging itself can induce podocyte senescence. Pathological stresses, such as oxidative stress, mitochondrial damage, secretion of senescence-associated secretory phenotype, reduced autophagy, oncogene activation, altered transcription factors, DNA damage response, and other factors, play a crucial role in inducing premature senescence and accelerating aging. Senescence-associated-ß-galactosidase (SA-ß-gal) is a marker of aging, and ß-hydroxybutyric acid treatment can reduce SA-ß-gal activity to alleviate cellular senescence and damage. In addition, CCAAT/enhancer-binding protein-α, transforming growth factor-ß signaling, glycogen synthase kinase-3ß, cycle-dependent kinase, programmed cell death protein 1, and plasminogen activator inhibitor-1 are closely related to aging. The absence or elevation of these factors can affect aging through different mechanisms. Podocyte injury is not an independent process, and injured podocytes interact with the surrounding epithelial cells or other kidney cells to mediate the injury or loss of podocytes. In this review, we discuss the manifestations, molecular mechanisms, biomarkers, and therapeutic drugs for podocyte senescence. We included elamipretide, lithium, calorie restriction, rapamycin; and emerging treatment strategies, such as gene and immune therapies. More importantly, we summarize how podocyte interact with other kidney cells.

Barleriside A, an aryl hydrocarbon receptor antagonist, ameliorates podocyte injury through inhibiting oxidative stress and inflammation.

Introduction: Increasing evidence shows that hyperactive aryl hydrocarbon receptor (AHR) signalling is involved in renal disease. However, no currently available intervention strategy is effective in halting disease progression by targeting the AHR signalling. Our previous study showed that barleriside A (BSA), a major component of Plantaginis semen, exhibits renoprotective effects. Methods: In this study, we determined the effects of BSA on AHR expression in 5/6 nephrectomized (NX) rats. We further determined the effect of BSA on AHR, nuclear factor kappa B (NF-ƙB), and the nuclear factor erythroid 2-related factor 2 (Nrf2) signalling cascade in zymosan-activated serum (ZAS)-stimulated MPC5 cells. Results: BSA treatment improved renal function and inhibited intrarenal nuclear AHR protein expression in NX-treated rats. BSA mitigated podocyte lesions and suppressed AHR mRNA and protein expression in ZAS-stimulated MPC5 cells. BSA inhibited inflammation by improving the NF-ƙB and Nrf2 pathways in ZAS-stimulated MPC5 cells. However, BSA did not markedly upregulate the expression of podocyte-specific proteins in the ZAS-mediated MPC5 cells treated with CH223191 or AHR siRNA compared to untreated ZAS-induced MPC5 cells. Similarly, the inhibitory effects of BSA on nuclear NF-ƙB p65, Nrf2, and AHR, as well as cytoplasmic cyclooxygenase-2, heme oxygenase-1, and AHR, were partially abolished in ZAS-induced MPC5 cells treated with CH223191 or AHRsiRNA compared with untreated ZAS-induced MPC5 cells. These results indicated that BSA attenuated the inflammatory response, partly by inhibiting AHR signalling. Discussion: Both pharmacological and siNRA findings suggested that BSA mitigated podocyte lesions by improving the NF-ƙB and Nrf2 pathways via inhibiting AHR signalling. Therefore, BSA is a high-affinity AHR antagonist that abolishes oxidative stress and inflammation.

Correlation analysis of cofilin-1 with renal prognosis in primary IgA nephropathy.

PURPOSE: The purpose of this study was to investigate the correlation between podocyte related biomarker cofilin-1 and renal function, and explore the value of cofilin-1 in predicting the risk of renal adverse prognosis in IgA nephropathy (IgAN). METHODS: Patients with primary IgAN diagnosed by initial renal biopsy performed in our hospital from January 2019 to February 2022 were included. This study was a prospective cohort study. All IgAN patients were detected the expression of cofilin-1 and other related biomarkers (RhoA, NGAL) in urine by enzyme-linked immunosorbent assay (ELISA) and follow-up at least 6 months. We also collected baseline clinicopathologial data of IgAN. The decreased renal function group was defined as baseline eGFR < 60 ml/min/1.73m2. Logistic and Cox regression model were used to analyze the correlation among cofilin-1 and renal prognosis. RESULTS: 133 IgAN patients were included, with a male-to-female ratio of 1.25:1 and an age of 37.67 ± 13.78 years, as well as an average of eGFR was 71.63 (40.42,109.33) ml/min/1.73m2. 56 patients (42.1%) had decreased renal function at baseline, with the average of eGFR was 34.07 (16.72, 49.21) ml/min/1.73 m2. 12 of which developed to renal adverse prognosis. The average of follow-up time was 22.035 ± 8.992 months. The multivariate regression analysis showed that increased urinary cofilin-1 was an independent risk factor associated with baseline renal function decline and renal adverse prognosis in IgAN patients (P < 0.05). ROC curves showed great efficacy of urinary cofilin-1 levels in diagnosing baseline renal function decline and predicting renal adverse prognosis (the area under the ROC curve was 0.708 and 0.803). CONCLUSION: Cofilin-1 as a novel biomarker of podocyte lesion is closely related to renal function decline in IgAN. Cofilin-1 has certain clinical value in predicting the risk of renal adverse prognosis. Podocyte fusion affects the renal prognosis of IgAN.

The role of podocyte injury in the pathogenesis of Fabry disease nephropathy / O papel da injúria podocitária na patogênese da nefropatia da doença de Fabry

Abstract Renal involvement is one of the most severe morbidities of Fabry disease (FD), a multisystemic lysosomal storage disease with an X-linked inheritance pattern. It results from pathogenic variants in the GLA gene (Xq22.2), which encodes the production of alpha-galactosidase A (α-Gal), responsible for glycosphingolipid metabolism. Insufficient activity of this lysosomal enzyme generates deposits of unprocessed intermediate substrates, especially globotriaosylceramide (Gb3) and derivatives, triggering cellular injury and subsequently, multiple organ dysfunction, including chronic nephropathy. Kidney injury in FD is classically attributed to Gb3 deposits in renal cells, with podocytes being the main target of the pathological process, in which structural and functional alterations are established early and severely. This configures a typical hereditary metabolic podocytopathy, whose clinical manifestations are proteinuria and progressive renal failure. Although late clinical outcomes and morphological changes are well established in this nephropathy, the molecular mechanisms that trigger and accelerate podocyte injury have not yet been fully elucidated. Podocytes are highly specialized and differentiated cells that cover the outer surface of glomerular capillaries, playing a crucial role in preserving the structure and function of the glomerular filtration barrier. They are frequent targets of injury in many nephropathies. Furthermore, dysfunction and depletion of glomerular podocytes are essential events implicated in the pathogenesis of chronic kidney disease progression. We will review the biology of podocytes and their crucial role in regulating the glomerular filtration barrier, analyzing the main pathogenic pathways involved in podocyte injury, especially related to FD nephropathy.

Resumo O acometimento renal é uma das mais severas morbidades da doença de Fabry (DF), enfermidade multissistêmica de depósito lisossômico com padrão de herança ligada ao cromossomo X, decorrente de variantes patogênicas do gene GLA (Xq22.2), que codifica a produção de alfa-galactosidase A (α-Gal), responsável pelo metabolismo de glicoesfingolipídeos. A atividade insuficiente dessa enzima lisossômica gera depósitos de substratos intermediários não processados, especialmente do globotriaosilceramida (Gb3) e derivados, desencadeando injúria celular e, posteriormente, disfunção de múltiplos órgãos, incluindo a nefropatia crônica. A lesão renal na DF é classicamente atribuída aos depósitos de Gb3 nas células renais, sendo os podócitos o alvo principal do processo patológico, nos quais as alterações estruturais e funcionais são instaladas de forma precoce e severa, configurando uma podocitopatia metabólica hereditária típica, cujas manifestações clínicas são proteinúria e falência renal progressiva. Embora os desfechos clínicos tardios e as alterações morfológicas estejam bem estabelecidos nessa nefropatia, os mecanismos moleculares que deflagram e aceleram a injúria podocitária ainda não estão completamente elucidados. Podócitos são células altamente especializadas e diferenciadas que revestem a superfície externa dos capilares glomerulares, desempenhando papel essencial na preservação da estrutura e função da barreira de filtração glomerular, sendo alvos frequentes de injúria em muitas nefropatias. A disfunção e depleção dos podócitos glomerulares são, além disso, eventos cruciais implicados na patogênese da progressão da doença renal crônica. Revisaremos a biologia dos podócitos e seu papel na regulação da barreira de filtração glomerular, analisando as principais vias patogênicas envolvidas na lesão podocitária, especialmente relacionadas à nefropatia da DF.

Human and Mouse Nephrin and Their Interactions With 13 Proteins: An In Silico Study.

Background Human nephrin (hNeph) (podocyte protein) has been known to be involved in both the formation and maintenance of the slit diaphragm (SD) and also acts as a hub protein in the podocyte by modulating cell polarity, cell survival, cell adhesion, cytoskeletal organization, mechano-sensing, and SD turn-over. Methodology In the present investigation, we aimed to analyse the hNeph and mouse nephrin (mNeph) and their interactions with 13 proteins using the molecular docking method. The 13 selected human proteins which include matrix metalloproteinases (MMP 2 and 9), retinol-binding proteins (RBP 3 and 4), kallikrein 1 (KLK 1), uromodulin, insulin-like growth factor binding protein 7 (IGFBP7), cystatin C, podocin, beta arrestin 1, vang-like protein 2 (VANGL2), dynamin 1, and tensin-like C1 domain-containing phosphatase (TENC1) were studied on the docking analysis of hNeph and mNeph by using the HDOCK (protein-protein) docking method. In addition, the physicochemical (PC) properties of 15 proteins were performed using the ProtParam web server. Results In the present investigation, five chosen human proteins, namely, IGFBP7, cystatin C, podocin, VANGL2, and TENC1, have exhibited theoretical isoelectric point (PI) values greater than 7.0. The protein-protein docking analysis has shown that hKLK and hVANGL2 exhibited the maximum docking score of -206.39 kcal/mol and -329.28 (kcal/mol) with the target proteins mNeph and hNeph, respectively. Conclusions Thus, the current finding highlights the interactions of hNeph and mNeph with 13 chosen proteins, which may help in renal disease management.

Effects of Inonotus obliquus on ameliorating podocyte injury in ORG mice through TNF pathway and prediction of active compounds.

Background: Podocyte injury is a common pathologic mechanism in diabetic kidney disease (DKD) and obesity-related glomerulopathy (ORG). Our previous study confirmed that Inonotus obliquus (IO) improved podocyte injury on DKD rats. The current study explored the pharmacological effects, related mechanisms and possible active components of IO on ORG mice. Methods: Firstly, by combining ultra-high performance liquid chromatography tandem mass spectrometry analysis (UPLC-Q-TOF-MS) with network pharmacology to construct the human protein-protein interaction mechanism and enrich the pathway, which led to discover the crucial mechanism of IO against ORG. Then, ORG mice were established by high-fat diet and biochemical assays, histopathology, and Western blot were used to explore the effects of IO on obesity and podocyte injury. Finally, network pharmacology-based findings were confirmed by immunohistochemistry. The compositions of IO absorbed in mice plasma were analyzed by UPLC-Q-TOF-MS and molecular docking was used to predict the possible active compounds. Results: The network pharmacology result suggested that IO alleviated the inflammatory response of ORG by modulating TNF signal. The 20-week in vivo experiment confirmed that IO improved glomerular hypertrophy, podocyte injury under electron microscopy, renal nephrin, synaptopodin, TNF-α and IL-6 expressions with Western blotting and immunohistochemical staining. Other indicators of ORG such as body weight, kidney weight, serum total cholesterol, liver triglyceride also improved by IO intervention. The components analysis showed that triterpenoids, including inoterpene F and trametenolic acid, might be the pharmacodynamic basis. Conclusion: The research based on UPLC-Q-TOF-MS analysis, network pharmacology and in vivo experiment suggested that the amelioration of IO on podocyte injury in ORG mice via its modulation on TNF signal. Triterpenoids were predicated as acting components.

Genome-wide expression analysis in a Fabry disease human podocyte cell line.

Fabry disease (FD) is an X-linked lysosomal disease caused by an enzyme deficiency of alpha-galactosidase A (α-gal A). This deficiency leads to the accumulation of glycosphingolipids in lysosomes, resulting in a range of clinical symptoms. The complex pathogenesis of FD involves lysosomal dysfunction, altered autophagy, and mitochondrial abnormalities. Omics sciences, particularly transcriptomic analysis, comprehensively understand molecular mechanisms underlying diseases. This study focuses on genome-wide expression analysis in an FD human podocyte model to gain insights into the underlying mechanisms of podocyte dysfunction. Human control and GLA-edited podocytes were used. Gene expression data was generated using RNA-seq analysis, and differentially expressed genes were identified using DESeq2. Principal component analysis and Spearman correlation have explored gene expression trends. Functional enrichment and Reporter metabolite analyses were conducted to identify significantly affected metabolites and metabolic pathways. Differential expression analysis revealed 247 genes with altered expression levels in GLA-edited podocytes compared to control podocytes. Among these genes, 136 were underexpressed, and 111 were overexpressed in GLA-edited cells. Functional analysis of differentially expressed genes showed their involvement in various pathways related to oxidative stress, inflammation, fatty acid metabolism, collagen and extracellular matrix homeostasis, kidney injury, apoptosis, autophagy, and cellular stress response. The study provides insights into molecular mechanisms underlying Fabry podocyte dysfunction. Integrating transcriptomics data with genome-scale metabolic modeling further unveiled metabolic alterations in GLA-edited podocytes. This comprehensive approach contributes to a better understanding of Fabry disease and may lead to identifying new biomarkers and therapeutic targets for this rare lysosomal disorder.

Loss of Nup155 promotes high fructose-driven podocyte senescence by inhibiting INO80 mRNA nuclear export.

INTRODUCTION: Podocyte senescence causes podocyte loss and glomerulopathy. Excessive fructose intake is a risk factor for podocyte injury. However, whether high fructose promotes podocyte senescence remains unknown. OBJECTIVES: To explore the pathological mechanism by which high fructose drives podocyte senescence and find natural compounds to alleviate podocyte senescence. METHODS: Podocyte senescence was characterized with senescence-associated beta-galactosidase (SA-ß-gal) staining, Western blot, real-time quantitative polymerase chain reaction (qRT-PCR), comet assay and immunofluorescence. Proteomics analysis was performed to identify differentially expressed proteins in high fructose-exposed podocytes. Podocyte nuclear pore complexes (NPCs) and foot processes were observed by transmission electron microscopy. The mRNA and protein levels of nucleoporin 155 (Nup155) and inositol requiring mutant 80 (INO80) were detected by qRT-PCR, Western blot and immunofluorescence. Virtual screening was conducted to find natural compounds that target Nup155. RESULTS: High fructose increased SA-ß-gal activity, protein level of p53, p21, p16 and phosphorylated histone H2AX (γ-H2AX), as well as mRNA expression of interleukin-1ß (IL-1ß), IL-6 and tumor necrosis factor α (TNF-α) in rat glomeruli and podocytes. Proteomic analysis unraveled a crucial molecule Nup155, which was decreased in high fructose-induced podocyte senescence. Meanwhile, the number of podocyte NPCs was also decreased in vivo and in vitro. Consistently, high fructose suppressed nuclear export of INO80 mRNA, thereby down-regulated INO80 protein expression in podocyte senescence. Deletion of Nup155 inhibited INO80 mRNA nuclear export to induce podocyte senescence, whereas overexpression of Nup155 or INO80 alleviated high fructose-induced podocyte senescence. Ferulic acid was found to up-regulate Nup155 by both direct binding to stabilize Nup155 protein and enhancing its transcription, to promote INO80 mRNA nuclear export in the mitigation of high fructose-caused podocyte senescence. CONCLUSION: High fructose induces podocyte senescence by decreasing Nup155 to inhibit INO80 mRNA nuclear export. Ferulic acid targeting Nup155 may be a potential strategy to prevent high fructose-induced podocyte senescence.

Differing sensitivities to angiotensin converting enzyme inhibition of kidney disease mediated by APOL1 high-risk variants G1 and G2.

Apolipoprotein L1 (APOL1) variants G1 and G2 contribute to the excess risk of kidney disease in individuals of recent African ancestry. Since disease mechanisms and optimal treatments remain controversial, we study the effect of current standard-of-care drugs in mouse models of APOL1 kidney disease. Experiments were performed in APOL1 BAC-transgenic mice, which develop proteinuria and glomerulosclerosis following injection with a pCpG-free IFNɤ plasmid. Proteinuric, plasmid injected G1/G1 and G2/G2 mice were randomized to drug treatment or no treatment. Lisinopril, dapagliflozin, and hydralazine were administered in drinking water starting day seven. The urine albumin/creatinine ratio was measured twice weekly, and the kidneys examined histologically with the focal segmental glomerulosclerosis score computed from periodic acid-Shiff-stained sections. The angiotensin converting enzyme inhibitor lisinopril, at standard dose, reduced proteinuria by approximately 90-fold and reduced glomerulosclerosis in the APOL1 G1/G1 BAC-transgenic mice. These effects were independent of blood pressure. Dapagliflozin did not alter disease progression in either G1/G1 or G2/G2 mice. Proteinuria reduction and glomerulosclerosis in G2/G2 BAC-transgenic mice required lisinopril doses two times higher than were effective in G1/G1 mice but achieved a much smaller benefit. Therefore, in these BAC-transgenic mouse models of APOL1 disease, the anti-proteinuric and anti-glomerulosclerotic effects of standard dose lisinopril were markedly effective in G1/G1 compared with G2/G2 APOL1 mice. Comparable reduction in blood pressure by hydralazine treatment provided no such protection. Neither G1/G1 or G2/G2 mice showed improvement with the sodium-glucose cotransporter-2 inhibition dapagliflozin. Thus, it remains to be determined if similar differences in ACE inhibitor responsiveness are observed in patients.

Podocyte Infolding Glomerulopathy Masquerading as Membranous Nephropathy - A Shared Pathogenesis?

Podocyte infolding glomerulopathy (PIG) is a rare pathological entity, diagnosed by electron microscopic demonstration of diffuse infolding of the podocytes into the glomerular basement membranes. We report the first case from United Kingdom exhibiting typical ultrastructural features of PIG in a male with Type II diabetes mellitus, hypertension and common variable immune deficiency. Renal biopsy revealed phospholipase A2 receptor (PLA2R) immunostain positive membranous nephropathy (MN) but no serum PLA2R antibodies. Diffuse infolding of the podocytes into the glomerular basement membranes along with pathognomonic microspherular and microtubular intra basement membrane clusters distributed diffusely and globally were noted on electron microscopy, diagnostic of PIG. We postulate a shared pathomechanistic link between PIG and MN, highlighting the overlapping features of both conditions.

Renal Protective Effect of Boeravinone B against Diabetic Nephropathy Rats via Inhibition of The Inflammatory and JAK2/STAT3 Signalling Pathway.

OBJECTIVE: Chronic inflammation is a common feature in diabetes, especially when blood sugar levels are poorly controlled. This chronic low-grade inflammation can affect various organs, including the kidneys. Podocyte damage play a key role in the development of diabetic nephropathy (DN). The aim of the study was to evaluate the nephroprotective effect of Boeravinone B (BB) against streptozotocin (STZ) induced DN in rats and explore the underlying mechanism. MATERIALS AND METHODS: In this experimental study, the rats received intraperitoneal injections of STZ (60 mg/kg) to induce DN. Various doses of BB (2.5, 5, and 7.5 mg/kg) were administered orally. Glucose levels, body weights, and organ weights (hepatic and renal) were assessed. Renal, histomorphological, antioxidant, hepatic, and cytokine levels were determined, as were the mRNA expression levels of JAK2 and STAT3. At end of the experimental study, the rats were sacrificed and their renal tissues were removed for histopathological assessment. RESULTS: BB treatment decreased glucose levels and increased body weights. This treatment suppressed hepatic weights, increased renal tissue weights, and also decreased renal parameters like uric acid, urea, bilirubin, creatinine (Cr) and, albumin. There was a decrease (P<0.001) in histomorphological parameters such as kidney hypertrophy index (KHI), mean glomerular volume (MGV), foot process fusion ratio (FPFR), and glomerular basement membrane thickness (GBMT) after treatment with BB. In addition, this treatment improved the levels of renal podocin, renal CD2- associated protein (CD2AP) and suppressed hepatic parameter levels. BB treatment (P<0.001) altered antioxidant parameters and cytokine levels, and suppressed mRNA expressions of JAK2, STAT3, RAGE, KIM-1, NAGL, and S100A8. CONCLUSION: Administration of BB showed renal protective effects against STZ-induced DN in rats via the reduction of oxidative stress and inflammatory reactions.

Podocyte Cell-Specific Npr1 is Required for Blood Pressure and Renal Homeostasis in Male and Female Mice: Role of Sex-Specific Differences.

Atrial and brain natriuretic peptides (ANP and BNP) bind to guanylyl cyclase-A/natriuretic peptide receptor-A (GC-A/NPRA), stimulating natriuresis and diuresis and reducing blood pressure (BP), but the role of ANP/NPRA signaling in podocytes (highly specialized epithelial cells covering the outer surfaces of renal glomerular capillaries) remains unclear. This study aimed to determine the effect of conditional deletion of podocyte (PD)-specific Npr1 (encoding NPRA) gene knockout (KO) in male and female mice. Tamoxifen-treated wild-type control (PD Npr1 f/f; WT), heterozygous (PD-Cre-Npr1 f/+; HT), and knockout (PD-Cre-Npr1 f/-; KO) mice were fed a normal-, low-, or high-salt diet for 4 weeks. Podocytes isolated from HT and KO male and female mice showed complete absence of Npr1 mRNA and NPRA protein compared to WT mice. BP, plasma creatinine, plasma sodium, urinary protein, and albumin/creatinine ratio were significantly increased, while plasma total protein, albumin, creatinine clearance, and urinary sodium levels were significantly reduced in the HT and KO male and female mice compared to WT mice. These changes were significantly greater in males than females. On a normal-salt diet, glomerular filtration rate (GFR) was significantly decreased in PD Npr1 HT and KO male and female mice compared with WT mice. Immunofluorescence of podocin and synaptopodin were also significantly reduced in HT and KO mice compared to WT mice. These observations suggest that in podocytes, ANP/NPRA signaling may be crucial in the maintenance and regulation of glomerular filtration and BP and serve as a biomarker of renal function in a sex-dependent manner.

A molecular mechanism for angiotensin II receptor blocker-mediated slit membrane protection: Angiotensin II increases nephrin endocytosis via AT1-receptor-dependent ERK 1/2 activation.

Albuminuria is characterized by a disruption of the glomerular filtration barrier, which is composed of the fenestrated endothelium, the glomerular basement membrane, and the slit diaphragm. Nephrin is a major component of the slit diaphragm. Apart from hemodynamic effects, Ang II enhances albuminuria by ß-Arrestin2-mediated nephrin endocytosis. Blocking the AT1 receptor with candesartan and irbesartan reduces the Ang II-mediated nephrin-ß-Arrestin2 interaction. The inhibition of MAPK ERK 1/2 blocks Ang II-enhanced nephrin-ß-Arrestin2 binding. ERK 1/2 signaling, which follows AT1 receptor activation, is mediated by G-protein signaling, EGFR transactivation, and ß-Arrestin2 recruitment. A mutant AT1 receptor defective in EGFR transactivation and ß-Arrestin2 recruitment reduces the Ang II-mediated increase in nephrin ß-Arrestin2 binding. The mutation of ß-Arrestin2K11,K12, critical for AT1 receptor binding, completely abrogates the interaction with nephrin, independent of Ang II stimulation. ß-Arrestin2K11R,K12R does not influence nephrin cell surface expression. The data presented here deepen our molecular understanding of a blood-pressure-independent molecular mechanism of AT-1 receptor blockers (ARBs) in reducing albuminuria.

Obtusifolin inhibits podocyte apoptosis by inactivating NF-κB signaling in acute kidney injury.

Acute kidney injury (AKI) is a common clinical condition and is associated with unacceptable morbidity and mortality. Obtusifolin is an anthraquinone extracted from the seeds of Cassia obtusifolia with anti-inflammatory properties. This study focused on the role and mechanism of obtusifolin in AKI. The mouse podocyte cell line MPC5 was exposed to lipopolysaccharide (LPS) to establish a cell model of AKI. The viability of MPC5 cells treated with obtusifolin and/or LPS was detected by 3-(4, 5-Dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay. Cell apoptosis was analyzed by flow cytometry. The levels of podocyte injury- and apoptosis-related proteins as well as the nuclear factor-kappaB (NF-κB) signaling pathway was examined using western blotting analysis. The renal protective effects of obtusifolin were determined using an LPS-induced mouse model of AKI. Serum creatinine and blood urea nitrogen levels were measured. Hematoxylin-eosin staining of kidney sections was performed to evaluate renal histology. We found that MPC5 cells treated with LPS showed suppressed cell viability (p < 0.01) and increased cell apoptosis (p < 0.001). LPS reduced the protein expression of Bcl-2, nephrin, and synaptopodin as well as increased the protein levels of Bax and Cleaved Caspase-3 in podocytes in a concentration-dependent manner (p < 0.01). In addition, 10 µg/ml LPS-repressed cell viability was rescued by obtusifolin in a concentration-dependent manner (p < 0.01). Moreover, LPS-induced increase in MPC5 cell apoptosis was reversed by obtusifolin treatment (p < 0.01). Obtusifolin administration ameliorated LPS-induced kidney injury and reduced blood urea nitrogen and serum creatinine levels in mice (p < 0.001). Additionally, obtusifolin inhibited LPS-induced activation of NF-κB signaling in vitro and in vivo (p < 0.01). Overall, obtusifolin was effective in protecting renal function against LPS-induced AKI via inactivation of NF-κB signaling, which suggested that obtusifolin may act as a valuable agent for AKI therapy.

Renal protective effects of helix B surface polypeptide in rats with puromycin aminonucleoside nephropathy.

BACKGROUND: Recent studies have reported that helix B surface polypeptide (HBSP), an erythropoietin derivative, exhibits strong tissue protective effects, independent of erythropoietic effects, in a renal ischemia-reperfusion (IR) injury model. Meanwhile, the transforming growth factor-ß (TGF-ß) superfamily member glial cell line-derived neurotrophic factor (GDNF) demonstrated protective effect on podocytes in vitro. Using a rat puromycin aminonucleoside nephropathy (PAN) model, this study observed the renal protective effect of HBSP and investigated its renal protective effect on podocytes and mechanism related to GDNF. METHODS: Rats nephropathy model was induced by injection of 60 mg/kg of PAN via the tail vein. Rats in the PAN + HBSP group were injected intraperitoneally with HBSP (8 nmol/kg) 4 h before the model was induced, followed by intraperitoneal injections of HBSP once every 24 h for 7 consecutive days. The 24-hour urinary protein level was measured once every other day, and blood and renal tissue samples were collected on the 7th day for the examination of renal function, complete blood count, renal pathological changes and the expression levels of GDNF. RESULTS: Compared with the control group, the PAN nephropathy rat model showed a large amount of urinary protein. The pathological manifestations were mainly extensive fusion and disappearance of foot processes, along with vacuolar degeneration of podocytes and their separation from the glomerular basement membrane. GDNF expression was upregulated. Compared with the PAN + vehicle group, the PAN + HBSP group showed decreased urinary protein (p < 0.05). Pathological examination revealed ameliorated glomerular injury and vacuolar degeneration of podocytes. The expression of GDNF in the PAN nephropathy group was increased, when compared with the control group. The greatest expression of GDNF observed in the PAN + HBSP group (p < 0.05). CONCLUSIONS: The expression of GDNF in the kidney of PAN rat model was increased. HBSP reduced urinary protein, ameliorated pathological changes in renal podocytes, increased the expression of GDNF in the PAN rat model. HBSP is likely to exert its protective effects on podocytes through upregulation of GDNF expression.

Ultrastructural analysis of whole glomerulus using array tomography.

The renal glomerulus produces primary urine from blood plasma by ultrafiltration. The ultrastructure of the glomerulus is closely related to filtration function and disease development. The ultrastructure of the glomeruli has mainly been evaluated using transmission electron microscopy. However, the volume that can be observed using transmission electron microscopy is extremely limited relative to the total volume of the glomerulus. Consequently, observing structures that exist in only one location in each glomerulus, such as the vascular pole, and evaluating low-density or localized lesions are challenging tasks. Array tomography (AT) is a technique used to analyze the ultrastructure of tissues and cells via scanning electron microscopy of serial sections. In this study, we propose an AT workflow optimized for observing complete serial sections of the whole glomerulus, shared several analytical examples using the optimized AT workflow, and demonstrate the usefulness of this approach. Overall, this AT workflow can be a powerful tool for structural and pathological evaluation of the glomerulus. This workflow is also expected to provide new insights into the ultrastructure of the glomerulus and its constituent cells.

Piperazine ferulate inhibits diabetic nephropathy by suppressing AGE/RAGE-mediated inflammatory signaling in rats and podocytes.

Objective: Diabetic nephropathy (DN) is a serious complication that may occur during the later stages of diabetes, and can be further exacerbated by podocyte damage. Piperazine ferulate (PF) has well-defined nephroprotective effects and is used clinically in the treatment of chronic nephritis and other kidney diseases. However, the renoprotective effects and mechanisms of PF on DN are not clear. This study aims to investigate the protective effect of PF on DN and its mechanism of action, to inform the clinical application of PF in DN treatment. Methods: Network pharmacology was performed to predict the mechanism of action of PF in DN. Male Sprague Dawley rats were intraperitoneally injected with STZ (60 mg/kg) to establish a DN model, and then assessed for renal injury after 12 weeks of administration. In vitro, rat podocytes were treated with 25 mmol/L glucose and cultured for 24 h, followed by an assessment of cell injury. Results: Our results showed that PF significantly improved renal function, reduced renal pathological changes, decreased inflammatory response, and alleviated podocyte damage in DN rats. PF also attenuated glucose-induced podocyte injury in vitro. Regarding molecular mechanisms, our study demonstrated that PF downregulated the expression of genes and proteins related to AGE-RAGE-mediated inflammatory signaling. Conclusion: In summary, PF exerts its renoprotective effects by decreasing inflammation and protecting against podocyte injury through the inhibition of the AGE/RAGE/NF-κB/NLRP3 pathway. Overall, these data support the clinical potential of PF as a renoprotective agent in DN.

THSD7A-associated membranous nephropathy involves both complement-mediated and autonomous podocyte injury.

Membranous nephropathy (MN) continues to be a leading cause of nephrotic syndrome in non-diabetic adults. As a unique subtype in the serology-based classification of MN, thrombospondin type 1 domain containing 7A (THSD7A)-associated MN has attracted increasing interest, because, unlike other autoantigens, THSD7A is also expressed in preclinical species, facilitating the study of its role in MN. A heterologous mouse model of THSD7A-associated MN was previously established using a proprietary in-house antibody that was unfortunately not available to the research community. Here, we developed a mouse model of THSD7A-associated MN by administering a commercially available antibody targeting the most N-terminal part of THSD7A. Our model was characterized by heavy proteinuria and pathological features of human MN without sex differences. Complement depletion with cobra venom factor only partially attenuated proteinuria and glomerular injury in this model, entailing that complement-independent pathomechanisms also contribute. Consistently, in vitro in primary podocytes, exposure to the anti-THSD7A antibody caused evident podocytopathic changes, including disruption of actin cytoskeleton integrity, podocyte hypermobility, oxidative stress, and apoptotic cell death. These signs of podocytopathy were preserved, albeit to a lesser extent, after complement inactivation, indicating autonomous podocyte injury. Furthermore, as the first FDA-approved treatment for primary MN, adrenocorticotropic hormone therapy with repository corticotropin injection (Purified Cortrophin Gel®) appeared to be beneficial and significantly attenuated proteinuria and glomerular injury, suggesting that this model may be useful for developing novel treatments or understanding the pathogenesis of MN. Collectively, our model, based on the use of a commercially available anti-THSD7A antibody, will be an important tool for MN research.

Podocyte Death in Diabetic Kidney Disease: Potential Molecular Mechanisms and Therapeutic Targets.

Cell deaths maintain the normal function of tissues and organs. In pathological conditions, the abnormal activation or disruption of cell death often leads to pathophysiological effects. Diabetic kidney disease (DKD), a significant microvascular complication of diabetes, is linked to high mortality and morbidity rates, imposing a substantial burden on global healthcare systems and economies. Loss and detachment of podocytes are key pathological changes in the progression of DKD. This review explores the potential mechanisms of apoptosis, necrosis, autophagy, pyroptosis, ferroptosis, cuproptosis, and podoptosis in podocytes, focusing on how different cell death modes contribute to the progression of DKD. It recognizes the limitations of current research and presents the latest basic and clinical research studies targeting podocyte death pathways in DKD. Lastly, it focuses on the future of targeting podocyte cell death to treat DKD, with the intention of inspiring further research and the development of therapeutic strategies.