Renal Podocyte Research Articles

Soluble Epoxide Hydrolase Inhibition Attenuates Proteinuria by Alleviating Renal Inflammation and Podocyte Injuries in Adriamycin-Induced Nephropathy.

Soluble epoxide hydrolase (sEH) has previously been demonstrated to play an important part in kidney diseases by hydrolyzing renoprotective epoxyeicosatrienoic acids to their less active diols. However, little is known about the role of sEH in primary glomerular diseases. Here, we investigated the effects of sEH inhibition on proteinuria in primary glomerular diseases and the underlying mechanism. The expression of sEH in the renal tubules of patients with minimal change disease, IgA nephropathy, and membranous nephropathy was significantly increased. Renal sEH expression level was positively correlated with the 24 h urine protein excretion and negatively correlated with serum albumin. In the animal model of Adriamycin (ADR)-induced nephropathy, renal sEH mRNA and protein expression increased significantly. Pharmacological inhibition of sEH with AUDA effectively reduced urine protein excretion and attenuated renal pathological damage. Furthermore, sEH inhibition markedly abrogated the abnormal expressions of nephrin and desmin in glomerular podocytes induced by ADR. More importantly, AUDA treatment inhibited renal NF-κB activation and reduced TNF-α levels in rats with ADR-induced nephropathy. Overall, our findings suggest that sEH inhibition ameliorates renal inflammation and podocyte injury, thus reducing proteinuria and exerting renoprotective effects. Targeting sEH might be a potential strategy for the treatment of proteinuria in primary glomerular diseases.

Poricoic acid a ameliorates high glucose-induced podocyte injury by regulating the AMPKα/FUNDC1 pathway.

Poricoic acid A (PAA), a major triterpenoid component of Poria cocos with anti-tumor, anti-fibrotic, anti-inflammatory, and immune-regulating activities, has been shown to induce podocyte autophagy in diabetic kidney disease (DKD) by downregulating FUN14 domain containing 1 (FUNDC1). This study aimed to identify the role of adenosine monophosphate-activated protein kinase alpha (AMPKα) in PAA-mediated phosphorylation of FUNDC1 in podocyte injury occurring in the pathogenesis of DKD. A cellular model of renal podocyte injury was established by culturing MPC5 cells under high-glucose (HG) conditions. MPC5 cells were subjected to transfection with small interfering RNA (siRNA) targeting AMPKα or siRNA targeting FUNDC1, an AMPKα activator, or PAA. PAA treatment induced the phosphorylation of AMPKα in HG-cultured podocytes. AMPKα activation was implicated in the inhibitory effect of PAA on FUNDC phosphorylation in HG-cultured podocytes. Treatment targeting the AMPKα activator also significantly augmented proliferation, migration, mitochondrial membrane potential, and autophagy levels, while reducing apoptosis levels, inhibiting oxidative stress, and suppressing the release of proinflammatory factors in HG-cultured MPC5 cells. In contrast, insufficient expression of AMPKα reversed the effects of PAA on the proliferation, migration, and apoptosis of podocytes and further exacerbated the reduction of phosphorylated FUNDC1 expression in podocytes under HG conditions. AMPKα is involved in the regulation of FUNDC1 phosphorylation by PAA in HG-induced podocyte injury. Furthermore, the AMPKα/FUNDC1 pathway plays a crucial regulatory role in HG-induced podocyte injury. These findings support AMPKα, FUNDC1, and the AMPKα/FUNDC1 pathway as targets for PAA intervention.

Chinese medicine Linggui Zhugan formula protects against diabetic kidney disease in close association with inhibition of proteinase 3-mediated podocyte apoptosis in mice

Ethnopharmacological relevanceLinggui-Zhugan (LGZG) comprises four herbs and is a classic formula in traditional Chinese medicine. There is strong clinical evidence of its pleiotropic effects in the prevention of diabetes and its related complications. Although several classes of drugs are currently available for clinical management of diabetic kidney disease (DKD), tight glycemic and/or hypertension control may not prevent disease progression. This study evaluated the therapeutic effect of the ethnopharmacological agent LGZG on DKD. Aim of the studyThis study aimed to investigate the effects of LGZG formula with standard quality control on experimental DKD and its related metabolic disorders in animal model. Meanwhile, the present study aimed to investigate regulatory effects of LGZG on renal proteinase 3 (PR3) to reveal mechanisms underlying renoprotective benefits of LGZG. Materials and methodsLGZG decoction was fingerprinted by high-performance liquid chromatography for quality control. An experimental model of DKD was induced in C57 BL/6J mice by a combination of high-fat diet feeding, uninephrectomy, and intraperitoneal injection of streptozocin. The LGZG decoction was administrated by daily oral gavage. ResultsTreatment with LGZG formula significantly attenuated DKD-like traits (including severe albuminuria, mesangial matrix expansion, and podocyte loss) and metabolic dysfunction (disordered body composition and dyslipidemia) in mice. RNA sequencing data revealed a close association of LGZG treatment with marked modulation of signaling pathways related to podocyte injury and cell apoptosis. Mechanistically, LGZG suppressed the DKD-triggered increase in renal PR3 and podocyte apoptosis. In-vitro incubation of mouse immortalized podocytes with LGZG-medicated serum attenuated PR3-mediated apoptosis. ConclusionOur data demonstrated that the LGZG formula protected against DKD in mice and was closely associated with its inhibitory effects on PR3-mediated podocyte apoptosis.

Effects of xenogeneic transplantation of umbilical cord-derived mesenchymal stem cells combined with irbesartan on renal podocyte damage in diabetic rats

BackgroundThe leading cause of end-stage renal disease (ESRD) is diabetic nephropathy (DN). Podocyte damage is an early event in the development of DN. Currently, there is no effective treatment strategy that can slow the progression of DN or reverse its onset. The role of mesenchymal stem cells (MSCs) transplantation in diabetes and its complications has been extensively studied, and diabetic nephropathy has been a major focus. Irbesartan exerts reno-protective effects independent of lowering blood pressure, can reduce the incidence of proteinuria in rats, and is widely used clinically. However, it remains undetermined whether the combined utilization of the angiotensin II receptor antagonist irbesartan and MSCs could enhance efficacy in addressing DN.MethodsA commonly used method for modeling type 2 diabetic nephropathy (T2DN) was established using a high-fat diet and a single low-dose injection of STZ (35 mg/kg). The animals were divided into the following 5 groups: (1) the control group (CON), (2) the diabetic nephropathy group (DN), (3) the mesenchymal stem cells treatment group (MSCs), (4) the irbesartan treatment group (Irb), and (5) the combined administration group (MSC + Irb). MSCs (2 × 106 cells/rat) were injected every 10 days through the tail vein for a total of three injections; irbesartan (30 mg/kg/d) was administered by gavage. Additionally, the safety and homing of mesenchymal stem cells were verified using positron emission tomography (PET) imaging.ResultsThe combination treatment significantly reduced the UACR, kidney index, IGPTT, HOMA-IR, BUN, serum creatine, and related inflammatory factor levels and significantly improved renal function parameters and the expression of proteins related to glomerular podocyte injury in rats. Moreover, MSCs can homing target to damaged kidneys.ConclusionsCompared to the administration of MSCs or irbesartan alone, the combination of MSCs and irbesartan exerted better protective effects on glomerular podocyte injury, providing new ideas for the clinical application of mesenchymal stem cells.

Network pharmacology and in vitro experiments reveal the autophagy mechanism of Yanggan-Yishui granules in improving hypertensive renal injury

IntroductionIn China, Yanggan-Yishui granules (YGYSG) have been used to treat hypertensive renal damage (HRD) for over 20 years. Network pharmacology was used to determine whether YGYSG affects HRD via the autophagy pathway, which was verified using in vitro experiments.Material and methodsCommon targets of YGYSG, HRD, and the autophagy pathway were screened using network pharmacology, and effective compounds, core targets, and signaling pathways were identified. The affinity of the compounds for the core targets was evaluated using molecular docking simulations. Angiotensin II (Ang II) was used to generate an in vitro renal podocyte model using MPC-5 cells. Morphological changes in the autophagosomes were observed using transmission electron microscopy (TEM). The expression levels of autophagy-related and pathway proteins were detected using western blotting and reverse transcription quantitative real-time PCR (PCR).ResultsNetwork pharmacology and molecular docking analyses identified eight autophagy-related core targets and ten core components in the YGYSG treatment of HRD. These targets are mainly involved in the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway and autophagy-related biological processes. In vitro experiments showed that Ang II-stimulated renal podocytes exhibited abnormal autophagy, and YGYSG protected renal podocytes from abnormal autophagy. In addition, YGYSG reversed abnormal autophagy and improved HRD by activating the PI3K/AKT/mTOR signaling pathway.ConclusionsYGYSG may regulate abnormal autophagy in renal podocytes by activating the PI3K/AKT/mTOR signaling pathway and may play a role in improving HRD.

Investigating the value of urinary biomarkers in relation to lupus nephritis histopathology: present insights and future prospects.

Lupus nephritis (LN), a leading cause of death in Systemic Lupus Erythematosus (SLE) patients, presents significant diagnostic and prognostic challenges. Although renal pathology offers critical insights regarding the diagnosis, classification, and therapy for LN, its clinical utility is constrained by the invasive nature and limited reproducibility of renal biopsies. Moreover, the continuous monitoring of renal pathological changes through repeated biopsies is impractical. Consequently, there is a growing interest in exploring urine as a non-invasive, easily accessible, and dynamic "liquid biopsy" alternative to guide clinical management. This paper examines novel urinary biomarkers from a renal pathology perspective, encompassing cellular components, cytokines, adhesion molecules, auto-antibodies, soluble leukocyte markers, light chain fragments, proteins, small-molecule peptides, metabolomics, urinary exosomes, and ribonucleic acids. We also discuss the application of combined models comprising multiple biomarkers in assessing lupus activity. These innovative biomarkers and models offer insights into LN disease activity, acute and chronic renal indices, fibrosis, thrombotic microangiopathy, podocyte injury, and other pathological changes, potentially improving the diagnosis, management, and prognosis of LN. These urinary biomarkers or combined models may serve as viable alternatives to traditional renal pathology, potentially revolutionizing the method for future LN diagnosis and observation.

Serum L C3-II levels in type 2 diabetic patients with impaired renal functions

This study was designed to evaluate serum LC3-II, BCL-2, IL-1β, TGF-β1, and podocin levels in.type 2 diabetes (T2DM) patients with renal dysfunction. Materials176 Turkish subjects were enrolled, of whom 26 were healthy, and 150 had T2DM. Patients.were classified according to albumin urea ratio: 88 patients had macroalbuminuria, 20.patients had microalbuminuria, and 42 had normoalbuminuria. T2DM patients were also.classified into three groups according to proteinuria and eGFR stages. ResultsIncreased serum LC3-II levels in patients with T2DM with increased urinary albumin.extraction and impaired renal functions. There was a strong relationship between serum.LC3-II levels and serum BCL-2, IL-1β, TGF-β1, and Podocin levels. The efficiency of LC3-II as a diagnostic biomarker in the differential diagnosis of DM patients with.macroproteinuria from DM patients with normoproteinuria was 75.4%. ConclusionsIt was thought that increased serum LC3-II levels in T2DM patients with impaired renal.functions may cause renal podocyte damage. In these patients, serum LC3-II levels can be.evaluated as a new biomarker to follow the development of renal damage.

Hypoxia-inducible factor-1α attenuates renal podocyte injury in male rats in a simulated high-altitude environment by upregulating Krüppel-like factor 4 expression.

Previous studies have shown that podocyte injury is involved in the development of proteinuria in rats under hypobaric hypoxia conditions. Prolyl hydroxylase inhibitors (PHIs) may reduce proteinuria. This study aimed to further investigate whether the protective effects of hypoxia-inducible factor 1α (HIF1α) on podocyte injury induced by hypobaric hypoxia are related to Krüppel-like factor 4 (KLF4). Rats were housed in a low-pressure oxygen chamber to simulate a high-altitude environment (5000m), and a PHI was intraperitoneally injected. Urinary protein electrophoresis was performed and the morphology of the podocytes was observed by electron microscopy. Rat podocytes were cultured under 1% O2, and siRNA was used to interfere with KLF4 expression. The protein expression levels of HIF1α, KLF4, CD2-associated protein (CD2AP) and nephrin were determined by western blotting. Compared with those in the experimental group, the rats in the intervention group on day 14 had lower urinary protein levels, increased protein expression levels of CD2AP and nephrin, and reduced podocyte injury. The results of in vitro experiments showed that the protein expression levels of KLF4, CD2AP and nephrin were greater in the PHI intervention group and lower in the HIF1α inhibitors group than in the low-oxygen group. The protein expression of CD2AP and nephrin in the siKLF4-transfected podocytes treated with PHI and HIF1α inhibitors did not differ significantly from that in the low-oxygen group. HIF1α may be involved in reducing progressive high-altitude proteinuria by regulating KLF4 expression and contributing to the repair of podocyte injury induced by hypobaric hypoxia.

Lipid Toxicity in the Cardiovascular-Kidney-Metabolic Syndrome (CKMS).

Recent studies of Cardiovascular-Kidney-Metabolic Syndrome (CKMS) indicate that elevated concentrations of derivatives of phospholipids (ceramide, sphingosine), oxidized LDL, and lipoproteins (a, b) are toxic to kidney and heart function. Energy production for renal proximal tubule resorption of critical fuels and electrolytes is required for homeostasis. Cardiac energy for ventricular contraction/relaxation is preferentially supplied by long chain fatty acids. Metabolism of long chain fatty acids is accomplished within the cardiomyocyte cytoplasm and mitochondria by means of the glycolytic, tricarboxylic acid, and electron transport cycles. Toxic lipids and excessive lipid concentrations may inhibit cardiac function. Cardiac contraction requires calcium movement from the sarcoplasmic reticulum from a high to a low concentration at relatively low energy cost. Cardiac relaxation involves calcium return to the sarcoplasmic reticulum from a lower to a higher concentration and requires more energy consumption. Diastolic cardiac dysfunction occurs when cardiomyocyte energy conversion is inadequate. Diastolic dysfunction from diminished ATP availability occurs in the presence of inadequate blood pressure, glycemia, or lipid control and may lead to heart failure. Similar disruption of renal proximal tubular resorption of fuels/electrolytes has been found to be associated with phospholipid (sphingolipid) accumulation. Elevated concentrations of tissue oxidized low-density lipoprotein cholesterols are associated with loss of filtration efficiency at the level of the renal glomerular podocyte. Macroscopically excessive deposits of epicardial and intra-nephric adipose are associated with vascular pathology, fibrosis, and inhibition of essential functions in both heart and kidney. Chronic triglyceride accumulation is associated with fibrosis of the liver, cardiac and renal structures. Successful liver, kidney, or cardiac allograft of these vital organs does not eliminate the risk of lipid toxicity. Lipid lowering therapy may assist in protecting vital organ function before and after allograft transplantation.

Tanshinone IIA suppresses ferroptosis to attenuate renal podocyte injury in diabetic nephropathy through the embryonic lethal abnormal visual-like protein 1 and acyl-coenzyme A synthetase long-chain family member 4 signaling pathway.

Tanshinone IIA (TIIA) is one of the main components of the root of the red-rooted Salvia miltiorrhiza Bunge. However, the molecular mechanisms underlying TIIA-mediated protective effects in diabetic nephropathy (DN) are still unclear. High glucose (HG)-induced mouse podocyte cell line (MPC5) cells were used as the in vitro model of DN and treated with TIIA. Cell viability, proliferation and apoptosis were detected using 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide, 5-ethynyl-2'-deoxyuridine and flow cytometry assays. The protein levels were assessed using western blot assay. The levels of inflammatory factors were deleted by enzyme-linked immunoassay. Fe+ level, reactive oxygen species, malondialdehyde and glutathione products were detected using special assay kits. After ENCORI prediction, the interaction between embryonic lethal abnormal visual-like protein 1 (ELAVL1) and acyl-coenzyme A synthetase long-chain family member 4 (ACSL4) was verified using co-immunoprecipitation assay and dual-luciferase reporter assays. ACSL4 messenger ribonucleic acid expression was measured using real-time quantitative polymerase chain reaction. TIIA repressed HG-induced MPC5 cell apoptosis, inflammatory response and ferroptosis. ACSL4 upregulation relieved the repression of TIIA on HG-mediated MPC5 cell injury and ferroptosis. ELAVL1 is bound with ACSL4 to positively regulate the stability of ACSL4 messenger ribonucleic acid. TIIA hindered HG-triggered MPC5 cell injury and ferroptosis by regulating the ELAVL1-ACSL4 pathway. TIIA blocked DN progression in in vivo research. TIIA treatment restrained HG-caused MPC5 cell injury and ferroptosis partly through targeting the ELAVL1-ACSL4 axis, providing a promising therapeutic target for DN treatment.

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

BackgroundPrimary 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. MethodsSerum 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. ResultsSerum 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. ConclusionThe IL-6/STAT3 signaling pathway is activated in podocytes of experimental membranous nephropathy. MFSD alleviates podocyte damage by inhibiting the IL-6/STAT3 pathway.

Exosomal miR-223-3p from bone marrow mesenchymal stem cells targets HDAC2 to downregulate STAT3 phosphorylation to alleviate HBx-induced ferroptosis in podocytes.

Background: Hepatitis B virus associated-glomerulonephritis (HBV-GN) is one of the major secondary renal diseases in China, and microRNAs (miRNAs) in bone marrow mesenchymal stem cell-derived exosomes (BMSC-Exo) can attenuate HBV-X protein (HBx)-induced ferroptosis in renal podocytes, but the exact mechanism remains unclear. This study aimed to investigate the protective mechanism of miR-223-3p in BMSC-Exo in HBx-induced ferroptosis in podocytes. Methods: The study employed human renal podocyte cells (HPCs), bone marrow-derived mesenchymal stem cells (BMSCs), as well as kidney tissue from C57BL/6 mice and HBx transgenic mice. Initially, the correlation between STAT3 phosphorylation and ferroptosis was authenticated through the administration of signal transducer and activator of transcription 3 (STAT3) phosphorylation inhibitors in both in vivo and in vitro settings. Furthermore, the effect of HDAC2 overexpression on STAT3 phosphorylation was examined. Subsequently, the association between BMSC-Exo carrying miR-223-3p, HDAC2, and the phosphorylation of STAT3 in HPCs ferroptosis and injury induced by HBx was assessed. The interaction between miR-223-3p and HDAC2 was confirmed via RNA immunoprecipitation assay. Various techniques such as cell counting kit-8 assay, western blot, RT-qPCR, immunofluorescence, flow cytometry, lipid peroxidation assay kit, iron assay kit, transmission electron microscopy, and hematoxylin-eosin staining were employed to visualize the extent of HBx-induced podocyte injury and ferroptosis in both in vivo and in vitro. Results: The attenuation of podocyte ferroptosis can be achieved by inhibiting the phosphorylation of STAT3 in podocytes induced by HBx. Conversely, the upregulation of HDAC2 can enhance STAT3 phosphorylation, thereby promoting podocyte ferroptosis. MiR-223-3p was capable of directly exerting negative regulation on HDAC2 expression. BMSC-Exo carrying miR-223-3p can effectively suppress the expression of HDAC2, ultimately leading to reduce HBx-induced ferroptosis in podocytes by targeting HDAC2 with miR-223-3p and downregulating STAT3 phosphorylation. Conclusion: This study evidences the potential of BMSC-Exo mediated delivery of miR-223-3p in mitigating HBx-induced ferroptosis in podocytes, thereby offering a novel therapeutic target and approach for treating HBV-GN and alleviating renal injury.

Apolipoprotein L1 (APOL1) renal risk variant-mediated podocyte cytotoxicity depends on African haplotype and surface expression

Homozygous Apolipoprotein L1 (APOL1) variants G1 and G2 cause APOL1-mediated kidney disease, purportedly acting as surface cation channels in podocytes. APOL1-G0 exhibits various single nucleotide polymorphisms, most commonly haplotype E150K, M228I and R255K (“KIK”; the Reference Sequence is “EMR”), whereas variants G1 and G2 are mostly found in a single “African” haplotype background (“EIK”). Several labs reported cytotoxicity with risk variants G1 and G2 in KIK or EIK background haplotypes, but used HEK-293 cells and did not verify equal surface expression. To see if haplotype matters in a more relevant cell type, we induced APOL1-G0, G1 and G2 EIK, KIK and EMR at comparable surface levels in immortalized podocytes. G1 and G2 risk variants (but not G0) caused dose-dependent podocyte death within 48h only in their native African EIK haplotype and correlated with K+ conductance (thallium FLIPR). We ruled out differences in localization and trafficking, except for possibly greater surface clustering of cytotoxic haplotypes. APOL1 surface expression was required, since Brefeldin A rescued cytotoxicity; and cytoplasmic isoforms vB3 and vC were not cytotoxic. Thus, APOL1-EIK risk variants kill podocytes in a dose and haplotype-dependent manner (as in HEK-293 cells), whereas unlike in HEK-293 cells the KIK risk variants did not.

Cosentyx alleviates psoriasis-induced podocyte injury by inhibiting the tlr/nf-κb signaling pathway.

Pathological studies have shown an association between psoriasis and renal podocyte injury, and the specific mechanism of podocyte injury in psoriasis remains unclear, with no effective treatments currently available. This study aimed to investigate the underlying mechanisms of podocyte and epidermal cell injury in psoriasis and evaluate the therapeutic effect of Cosentyx. A psoriasis-like mouse model was established using BALB/C mice, and Cosentyx treatment was administered via intraperitoneal injection. Various parameters, including skin lesions, urinary protein, kidney/serum inflammatory cytokines, kidney function, podocyte membrane proteins, and Toll-like receptors/nuclear factor kappa-b (TLR/NF-κB) pathway-associated proteins, were analyzed to explore the mechanisms of podocyte and epidermal cell injury in psoriasis and the potential ameliorative effects of Cosentyx. Treatment with Cosentyx significantly reduced the increased levels of urinary protein, creatinine, and blood urea nitrogen caused by psoriasis. Cosentyx inhibited the upregulation of kidney/serum inflammatory factors (IL-17, IL-1β, IL-6, TNF-α, and IL-22) and TLR/NF-κB-related proteins (TLR2, TLR4, MyD88, and NF-κBp65) in both psoriatic skin and kidney tissues, while also reducing the accumulation of oxidative products. Moreover, Cosentyx treatment suppressed podocyte apoptosis and promoted epidermal cell apoptosis. The experimental data demonstrated that psoriasis-like inflammation impaired renal podocytes through the TLR/NF-κB signaling pathway. Cosentyx treatment effectively inhibited the expression of TLR/NF-κB-related proteins, providing a therapeutic effect for psoriasis-induced kidney and skin injuries.

Metformin inhibits high glucose-induced apoptosis of renal podocyte through regulating miR-34a/SIRT1 axis.

Previous studies have reported SIRT1 was inversely modulated by miR-34a, However, mechanism of metformin (MFN)'srenal podocyte protection under high glucose (HG)conditions and the connection between miR-34a and SIRT1 expression in diabetic nephropathy (DN)remain unclear. We aimed to further elucidate the role of miR-34a in HG-treated podocytes in DN. A conditionally immortalized human podocyte cell line was cultivated in d-glucose (30 mM). Microarray and RT-qPCRrevealed that miR-34a was downregulated in HG-treatedpodocytes. Additionally, miR-34a levels increased in MFN-treated HG-induced podocytes. CCK-8assay, colony formation assay,flow cytometry,and Western blotdetection showed that HG treatment reduced cell viability and promoted via HG treatment, and MFN treatment reversed this phenotypic change. MiR-34a upregulation caused restored cell viability and suppressed cell apoptosis in HG-treated podocytes, and miR-34a downregulation led to damaged cell survival and induced apoptosis in MFN-administered and HG-treated podocytes. The dual luciferase reporter assay showed that SIRT1 3'-UTR was a direct miR-34a target. Further studies demonstrated an elevation in SIRT1 levels in HG-exposed podocytes, whereas MFN treatment decreased SIRT1 levels. In addition, miR-34a upregulation led to reduced SIRT1 expression, whereas miR-34a inhibition increased SIRT1 levels in cells. MFN-induced miR-34a suppresses podocyte apoptosis under HG conditions by acting on SIRT1. This study proposes a promising approach to interpret the mechanisms of action of the MFN-miR-34a axis involved in DN.

Non-enzymatic glycation and diabetic kidney disease.

Chronic diabetes leads to various complications including diabetic kidney disease (DKD). DKD is a major microvascular complication and the leading cause of morbidity and mortality in diabetic patients. Varying degrees of proteinuria and reduced glomerular filtration rate are the cardinal clinical manifestations of DKD that eventually progress into end-stage renal disease. Histopathologically, DKD is characterized by renal hypertrophy, mesangial expansion, podocyte injury, glomerulosclerosis, and tubulointerstitial fibrosis, ultimately leading to renal replacement therapy. Amongst the many mechanisms, hyperglycemia contributes to the pathogenesis of DKD via a mechanism known as non-enzymatic glycation (NEG). NEG is the irreversible conjugation of reducing sugars onto a free amino group of proteins by a series of events, resulting in the formation of initial Schiff's base and an Amadori product and to a variety of advanced glycation end products (AGEs). AGEs interact with cognate receptors and evoke aberrant signaling cascades that execute adverse events such as oxidative stress, inflammation, phenotypic switch, complement activation, and cell death in different kidney cells. Elevated levels of AGEs and their receptors were associated with clinical and morphological manifestations of DKD. In this chapter, we discussed the mechanism of AGEs accumulation, AGEs-induced cellular and molecular events in the kidney and their impact on the pathogenesis of DKD. We have also reflected upon the possible options to curtail the AGEs accumulation and approaches to prevent AGEs mediated adverse renal outcomes.

Roles of the mechanosensitive ion channel Piezo1 in the renal podocyte injury of experimental hypertensive nephropathy.

Glomerular podocyte injury plays an essential role in proteinuria pathogenesis, a hallmark of chronic kidney disease, including hypertensive nephropathy. Although podocytes are susceptible to mechanical stimuli, their mechanotransduction pathways remain elusive. Piezo proteins, including Piezo1 and 2, are mechanosensing ion channels that mediate various biological phenomena. Although renal Piezo2 expression and its alteration in rodent dehydration and hypertension models have been reported, the role of Piezo1 in hypertensive nephropathy and podocyte injury is unclear. In this study, we examined Piezo1 expression and localization in the kidneys of control mice and in those of mice with hypertensive nephrosclerosis. Uninephrectomized, aldosterone-infused, salt-loaded mice developed hypertension, albuminuria, podocyte injury, and glomerulosclerosis. RNAscope in situ hybridization revealed that Piezo1 expression was enhanced in the podocytes, mesangial cells, and distal tubular cells of these mice compared to those of the uninephrectomized, vehicle-infused control group. Piezo1 upregulation in the glomeruli was accompanied by the induction of podocyte injury-related markers, plasminogen activator inhibitor-1 and serum/glucocorticoid regulated kinase 1. These changes were reversed by antihypertensive drug. Exposure of Piezo1-expressing cultured podocytes to mechanical stretch activated Rac1 and upregulated the above-mentioned markers, which was antagonized by the Piezo1 blocker grammostola mechanotoxin #4 (GsMTx4). Administration of Piezo1-specific agonist Yoda1 mimicked the effects of mechanical stretch, which was minimized by the Yoda1-specific inhibitor Dooku1 and Rac inhibitor. Rac1 was also activated in the above-mentioned hypertensive mice, and Rac inhibitor downregulated gene expression of podocyte injury-related markers in vivo. Our results suggest that Piezo1 plays a role in mechanical stress-induced podocyte injury.

T-2 Toxin-Mediated β-Arrestin-1 O-GlcNAcylation Exacerbates Glomerular Podocyte Injury via Regulating Histone Acetylation.

T-2 toxin causes renal dysfunction with proteinuria and glomerular podocyte damage. This work explores the role of metabolic disorder/reprogramming-mediated epigenetic modification in the progression of T-2 toxin-stimulated podocyte injury. A metabolomics experiment is performed to assess metabolic responses to T-2 toxin infection in human podocytes. Roles of protein O-linked-N-acetylglucosaminylation (O-GlcNAcylation) in regulating T-2 toxin-stimulated podocyte injury in mouse and podocyte models are assessed. O-GlcNAc target proteins are recognized by mass spectrometry and co-immunoprecipitation experiments. Moreover, histone acetylation and autophagy levels are measured. T-2 toxin infection upregulates glucose transporter type 1 (GLUT1) expression and enhances hexosamine biosynthetic pathway in glomerular podocytes, resulting in a significant increase in β-arrestin-1 O-GlcNAcylation. Decreasing β-arrestin-1 or O-GlcNAc transferase (OGT) effectively prevents T-2 toxin-induced renal dysfunction and podocyte injury. Mechanistically, O-GlcNAcylation of β-arrestin-1 stabilizes β-arrestin-1 to activate the mammalian target of rapamycin (mTOR) pathway as well as to inhibit autophagy during podocyte injury by promoting H4K16 acetylation. To sum up, OGT-mediated β-arrestin-1 O-GlcNAcylation is a vital regulator in the development of T-2 toxin-stimulated podocyte injury via activating the mTORpathway to suppress autophagy. Targeting β-arrestin-1 or OGT can be a potential therapy for T-2 toxin infection-associated glomerular injury, especially podocyte injury.

Irisin ameliorates diabetic kidney disease by restoring autophagy in podocytes.

Many studies have highlighted the importance of moderate exercise. While it can attenuate diabetic kidney disease, its mechanism has remained unclear. The level of myokine irisin in plasma increases during exercise. We found that irisin was decreased in diabetic patients and was closely related to renal function, proteinuria, and podocyte autophagy injury. Muscle-specific overexpression of PGC-1α (mPGC-1α) in a mouse model is known to increase plasma irisin levels. The mPGC-1α mice were crossed with db/m mice to obtain db/db mPGC-1α+ mice in the present study. Compared to db/db mice without mPGC-1α, plasma irisin was increased, and albuminuria and glomerular pathological damage were both alleviated in db/db mPGC-1α+ mice. Impaired autophagy in podocytes was restored as well. Irisin inhibited the activation of the PI3K/AKT/mTOR signaling pathway in cultured human podocytes and improved damaged autophagy induced by high glucose levels. Then, db/db mice were treated with recombinant irisin, which had similar beneficial effects on the kidney as those in db/db mPGC-1α+ mice, with alleviated glomerular injury and albuminuria. Moreover, the autophagy in podocytes was also significantly restored. These results suggest that irisin secreted by skeletal muscles protects the kidney from diabetes mellitus damage. It also restores autophagy in podocytes by inhibiting the abnormal activation of the PI3K/AKT/mTOR signaling pathway. Thus, irisin may become a new drug for the prevention and treatment of diabetic nephropathy.

Immune podocytes in the immune microenvironment of lupus nephritis (Review).

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder caused by the loss of tolerance to endogenous nuclear antigens such as double‑stranded DNA, leading to the proliferation of T cells and subsequent activation of B cells, which results in serious organ damage and life‑threatening complications such as lupus nephritis. Lupus nephritis (LN) develops as a frequent complication of SLE, accounting for >60% of SLE cases, and is characterized by proteinuria and heterogeneous histopathological findings. Glomerular injury serves a role in proteinuria as podocyte damage is the leading contributor. Numerous studies have reported that podocytes are involved in the immune response that promotes LN progression. In LN, immune complex deposition stimulates dendritic cells to secrete inflammatory cytokines that activate T cells and B cells. B cells secrete autoantibodies that attack and damage the renal podocytes, leading to renal podocyte injury. The injured podocytes trigger inflammatory cells through the expression of toll‑like receptors and trigger T cells through major histocompatibility complexes and CD86, thereby participating in the local immune response and the exacerbation of podocyte injury. Based on the existing literature, the present review summarizes the research progress of podocytes in LN under the local immune microenvironment of the kidney, explores the mechanism of podocyte injury under the immune microenvironment, and evaluates podocytes as a potential therapeutic target for LN.