High Glucose-induced Podocyte Research Articles

Silencing of KPNA2 inhibits high glucose-induced podocyte injury via inactivation of mTORC1/p70S6K signaling pathway

Dysregulation of apoptotic and autophagic function are characterized as the main pathogeneses of diabetic nephropathy (DN). It has been reported that Karyopherin Alpha 2 (KPNA2) contributes to apoptosis and autophagy in various cells, but its role in DN development remains unknown. The purpose of present study was to explore the function and underling mechanisms of KPNA2 in development of DN. In this study, 30 mM high glucose (HG)-evoked podocytes were used as DN model. The expression of KPNA2 was detected by qRT-PCR and Western blot assays. The cell viability was tested by CCK-8 kit, the apoptosis was measured using flow cytometry assay, the apoptotic and the autophagy related genes was detected by Western blot. Our results indicated that KPNA2 was significantly increased after HG stimulation. Knockdown of KPNA2 inhibited apoptosis, and promoted cell viability and autophagy in HG-treated podocytes. In addition, silencing of KPNA2 deactivated mTORC1/p70S6K pathway activation via regulating SLC1A5. Further results demonstrated that activating mTORC1/p70S6K pathway strongly ameliorated the effect of KPNA2 on cell viability, apoptosis and autophagy. Therefore, our study suggested that knockdown of KPNA2 rescued HG-induced injury via blocking activation of mTORC1/p70S6K pathway by mediating SLC1A5.

The protective effect and mechanism of catalpol on high glucose-induced podocyte injury

BackgroundCatalpol, a natural iridoid glycoside in Rehmannia glutinosa, can alleviate proteinuria associated with diabetic nephropathy (DN), however, whether catalpol has a protective effect against podocyte injury in DN remains unclear.MethodsIn this study, we used a high glucose (HG)-induced podocyte injury model to evaluate the protective effect and mechanism of catalpol against HG-induced podocyte injury. Cell viability was determined by the 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The levels of lactate dehydrogenase (LDH), superoxide dismutase (SOD) and malondialdehyde (MDA) were measured by commercial assay kits. Cell apoptosis and reactive oxygen species (ROS) were determined by using flow cytometry. Tumour necrosis factor α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) levels were determined by enzyme-linked immunosorbent assay (ELISA). The protein expression levels of B-cell lymphoma-2 (Bcl-2), Bcl2-associated x (Bax), cleaved caspase-3, nicotinamide adenine dinucleotide phosphate oxidase enzyme 4 (NOX4), toll-like receptor 4 (TLR4), myeloid differentiation primary response gene 88 (MyD88), p38 mitogen-activated protein kinase (p38 MAPK), phosphorylated p38 MAPK (p-p38 MAPK), nuclear factor kappa B inhibitor alpha (IκBα) and phosphorylated IκBα (p-IκBα) were measured by western blotting. In addition, Bcl-2, Bax, caspase-3 and nuclear factor kappa B (NF-κB) levels were determined by immunofluorescence staining.ResultsCatalpol significantly increased cell viability and decreased LDH release in HG-induced podocyte injury. Catalpol significantly decreased ROS generation, apoptosis, level of MDA, levels of inflammatory cytokine TNF-α, IL-1β, and IL-6 and increased SOD activity in HG-induced podocyte injury. Moreover, catalpol significantly decreased expression of cleaved caspase-3, Bax, NOX4, TLR4, MyD88, p-p38 MAPK, p-IκBα and NF-κB nuclear translocation, as well as increased Bcl-2 expression in HG-induced podocyte injury.ConclusionCatalpol can protect against podocyte injury by ameliorating apoptosis and inflammation. These protective effects may be attributed to the inhibition of NOX4, which alleviates ROS generation and suppression of the TLR4/MyD88 and p38 MAPK signaling pathways to prevent NF-κB activation. Therefore, catalpol could be a promising drug for the prevention of DN.

Bousigonine A and B, bis- and tri-indole alkaloids from Bousigonia mekongensis and their preventing high glucose-induced podocyte injury activity

Bousigonine A (1), an unprecedented eburnamine-voaphylline type dimeric indole alkaloid, and Bousigonine B (2), the first example of eburnamine-eburnamine-aspidospermine type trimeric indole alkaloid were isolated from Bousigonia mekongensis. Their structures were elucidated mainly by spectroscopic analysis and compared to published data. Their preventing high glucose-induced podocyte injury activity were evaluated for the first time, and compound 1 exhibited significant effect with EC50 value of 2.5 μM.

Protective effect of silencing Stat1 on high glucose-induced podocytes injury via Forkhead transcription factor O1-regulated the oxidative stress response

BackgroundPodocyte plays an important role in maintaining the integrity and function of the glomerular filtration barrier. Various studies reported that forkhead transcription factor (Fox) O1 played a key role in anti-oxidative signaling. This study aimed to investigate the role of Stat1 in high glucose (HG) -induced podocyte injury.MethodsUnder normal glucose, hypertonic and HG stimulated podocyte conditions, cell counting kit-8 (CCK-8) assay, flow cytometry and western blot and quantitative real-time polymerase chain reaction (qRT-PCR) were respectively carried out to determine cell viability, apoptosis, reactive oxygen species (ROS) production and related genes expressions. We then respectively used silent Stat1, simultaneous silencing Stat1 and FoxO1 and over-expression of FoxO1, to observe whether they/it could reverse the damage of podocytes induced by HG.ResultsHigh glucose attenuated cell survival and promoted cell apoptosis in MPC-5 cells at the same time, and it was also observed to promote the protein expression of Stat1 and the FoxO1 expression inhibition. Silencing Stat1 could reverse HG-induced podocytes injury. Specifically, siStat1 increased cell viability, inhibited cell apoptosis and attenuated ROS level in a high-glucose environment. Cleaved caspase-3 and pro-apoptosis protein Bax was significantly down-regulated, and anti-apoptosis protein Bcl-2 was up-regulated by siStat1. The antioxidant genes Catalase, MnSOD, NQO1 and HO1 were up-regulated by siStat1. We found that silencing FoxO1 reversed the protective effect of siStat1 on the HG-induced podocytes injury.ConclusionsSilencing Stat1 could reverse the effects of high glucose-triggered low cell viability, cell apoptosis and ROS release and the functions of Stat1 might be involved in FoxO1 mediated-oxidative stress in nucleus.

LncRNA SOX2OT alleviates the high glucose-induced podocytes injury through autophagy induction by the miR-9/SIRT1 axis

ObjectivesPodocytes injury is a major contributor to the progression of diabetic nephropathy (DN). This study aims to investigate the role of long non-coding RNA SOX2OT in the high glucose (HG)-induced injury of human podocytes cells (HPCs) and the underlying mechanism. MethodsHPCs proliferation and apoptosis were examined using MTT assay and flow cytometry assay, respectively. The protein levels of SIRT1 and autophagy-associated proteins (Beclin-1, LC3-II, Atg7, and p62) were determined using western blot. The interactions among SOX2OT, miR-9, and SIRT1 were investigated using luciferase activity assay. ResultsSOX2OT overexpression significantly alleviated the HG-induced HPCs injury and induced autophagy, which was abrogated by the autophagy inhibitor 3-MA and SIRT1 knockdown. Mechanistically, SOX2OT acted as a ceRNA by sponging miR-9 to facilitate SIRT1, and thus induce autophagy. ConclusionSOX2OT overexpression alleviates the HG-induced podocytes injury through autophagy induction by the miR-9/SIRT1 axis.

Sulfiredoxin-1 alleviates high glucose-induced podocyte injury though promoting Nrf2/ARE signaling via inactivation of GSK-3β

Hyperglycemia-induced podocyte injury plays a vital role in the development of diabetic nephropathy. Sulfiredoxin-1 (Srxn1) is emerging as a cytoprotective protein that protects from various insults in a wide range of cell types. However, whether Srxn1 is involved in regulating hyperglycemia-induced podocyte injury and participates in diabetic nephropathy remains unknown. In the present study, we aimed to explore the potential role of Srxn1 in regulating high glucose (HG)-induced apoptosis and oxidative stress of podocytes in vitro. Results demonstrated that Srxn1 was induced in HG-stimulated podocytes. The depletion of Srxn1 by Srxn1 siRNA-mediated gene silencing significantly exacerbated HG-induced apoptosis and the production of reactive oxygen species (ROS), while Srxn1 overexpression attenuated HG-induced apoptosis and ROS production. In-depth molecular mechanism research revealed that Srxn1 overexpression promoted the nuclear expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and reinforced antioxidant response element (ARE)-mediated transcription activity. Moreover, results confirmed that Srxn1 increased the activation of Nrf2/ARE signaling associated with inactivating glycogen synthase kinase (GSK)-3β. Notably, the inhibition of GSK-3β significantly reversed Srxn1 silencing-induced adverse effects in HG-treated cells, while the knockdown of Nrf2 abrogated the Srxn1-mediated protective effect against HG-induced podocyte injury. Taken together, our results demonstrated that Srxn1 protects podocytes from HG-induced injury by promoting the activation of Nrf2/ARE signaling associated with inactivating GSK-3β, indicating a potential role of Srxn1 in diabetic nephropathy. Our study suggests that Srxn1 may serve as a potential target for kidney protection.

MiR-124a enhances therapeutic effects of bone marrow stromal cells transplant on diabetic nephropathy-related epithelial-to-mesenchymal transition and fibrosis.

Epithelial-to-mesenchymal transition (EMT) has beengradually considered as one of the major pathways that causes the production of interstitial myofibroblasts in diseased kidneys. The study was done to investigate the effect of a bone marrow stromal cell(BMSCs) transplant on rat podocytes and diabetic nephropathy (DN) rats in high-glucose concentration, and to explore the effect of miR-124a on BMSCtherapy. High glucose-injured podocytes and streptozotocin-induced DN rats have beenrespectively used as injury models in in vitro and in vivo studies. Podocyte viability was measured using the Cell Counting Kit-8 assay. Renal pathological examination was observed by HE staining and Masson staining. The messenger RNA and protein levels were determined via real-time polymerase chain reaction and Western blotting, respectively. By mediating the activation of caveolin-1 (cav-1) and β-catenin and affecting the expression levels of EMT biomarkers including p-cadherin, synaptopodin, fibroblast-specific protein-1, α-smooth muscle actin and snail, our in vitro study confirmed that miR-124a played a significant role in the treatment of high glucose-induced podocyte injury by BMSCs. The therapeutic effects of the BMSCtransplant on DN rats were also proved to be further enhanced by miR-124a overexpression in BMSCs, and such a phenomenon was accompanied by the improvement of renal fibrosis and mitigation of DN-related kidney impairment. Regulation of fibronectin, collagen1, and EMT-related proteins was closely implicated with the mechanism, and the activation of cav-1 and β-catenin was also possibly involved. The study demonstrated thepivotal effect of miR-124a on BMSCtherapy for DN rats via mitigating EMT and fibrosis. Our results provide a novel insight into how therapeutic effects of BMSCs can be improved at theposttranscriptional level.

Effects of transcription factor EB on oxidative stress and apoptosis induced by high glucose in podocytes.

The aim of the present study was to investigate the effects of transcription factor EB (TFEB) overexpression on oxidative stress, mitochondrial function and apoptosis in podocytes induced with high glucose. High glucose-induced time-dependent changes in TFEB expression were identified and nuclear translocation of TFEB was observed in podocytes. Overexpression of TFEB markedly reduced high glucose-induced oxidative stress in podocytes, and increased the expression of superoxide dismutase 2 and heme oxygenase 1 antioxidant enzymes. It was further observed that TFEB overexpression could partially restore the expression of peroxisome proliferator-activated receptor-γ coactivator-1α, transcription factor A, mitochondrial, and cytochrome c oxidase subunit 4, thereby enhancing mitochondrial biosynthesis. Furthermore, overexpression of TFEB reduced mitochondrial swelling and fragmentation, restored mitochondrial membrane potential, and contributed to the restoration of mitochondrial function. By overexpressing TFEB, it was revealed that TFEB increased the ratios of phosphorylated (p)-Akt/Akt and p-Bad/Bad, and the expression of downstream Bcl-xl, and reduced the ratio of Bax/Bcl-2 and the expression of cleaved-caspase-3 compared with high glucose-treatment. Furthermore, when the Akt phosphorylation inhibitor Ly294002 was added, the improvement by TFEB to high glucose-induced apoptosis was significantly reduced. These findings suggest that overexpressing TFEB could reduce the production of reactive oxygen species in podocytes in a high glucose environment, relieve oxidative stress, promote mitochondrial biogenesis and renewal functions, and reduce high glucose-induced podocyte apoptosis by activating the Akt/Bad pathway.

Atrasentan alleviates high glucose-induced podocyte injury by the microRNA-21/forkhead box O1 axis

Diabetic nephropathy (DN) is the most common complication of diabetes mellitus. Atrasentan (Atr) has potential therapeutic values for DN. MicroRNAs (miRNAs) function as vital regulators in the pathophysiology of kidney diseases including DN. Our present study aimed to further explore whether Atr could alleviate kidney injury by regulating microRNA-21(miR-21)/forkhead box O1 (FOXO1) in DN mouse models and cell models. Blood glucose concentration and ACR ratio were determined by matching commercial kits. MiR-21 and FOXO1 mRNA level was measured by RT-qPCR assay. Protein levels of FOXO1, LC3Ⅰ, LC3Ⅱ and p62 were measured by western blot assay. Cell apoptotic index was examined by flow cytometry. The interaction of miR-21 and FOXO1 was tested by bioinformatics analysis, luciferase assay and RIP assay. We found that Atr alleviated kidney injury by inhibiting miR-21 expression and promoting autophagy in DN mice. Moreover, miR-21 loss suppressed apoptosis and induced autophagy in high glucose (HG)-treated podocytes. And, Atr inhibited cell apoptosis and improved cell autophagic activity by downregulating miR-21 in HG-cultured podocytes. Moreover, FOXO1 was identified as a target of miR-21. MiR-21 exerted its pro-apoptosis and anti-autophagy effects by targeting FOXO1 in HG-cultured podocytes. Atr enhanced FOXO1 expression by downregulating miR-21 in HG-cultured podocytes. We concluded that Atr mitigated kidney injury in DN mice and alleviated HG-mediated apoptosis increase and autophagy inhibition in podocytes by regulating miR-21/FOXO1 axis, further elucidating the molecular basis by which Atr hampered DN progression.

Vitamin D3 Ameliorates High Glucose-Induced Podocyte Apoptosis

Vitamin D3 Ameliorates High Glucose-Induced Podocyte Apoptosis

Vitamin D3 Ameliorates High Glucose-Induced Podocyte Apoptosis

Objective: Diabetic kidney disease (DKD) is a severe kidney disease characterized by podocyte apoptosis, injury, and accumulation of extracellular matrices that ultimately lead to end-stage renal disease. Vitamin D3 was reported to provide renal protection in DKD through the Vitamin D receptor (VDR), however there was limited data on whether it has a protective effect on podocytes of DKD induced by high glucose. Methods: The experimental subjects were conditionally immortalized mouse podocytes (MPC-5), which were divided into 4 groups: NG (normal glucose) group, HM (Hypertonic) group, HG (high glucose) group, VD3 (HG +1,25-dihydroxyvitamin D3 (1,25-D3)) group. Western-blot analysis was performed to detect the expression of Bcl-2, Bax and Caspase-3 in podocytes. The mRNA Expression of Bcl-2, Bax and Caspase-3 in the three groups were detected by RT-PCR method. Results: Compared with the NG group, the expression of apoptosis proteins Caspase-3 and Bax in the podocytes of HG group increased, and the expression of Bcl-2 decreased. Pretreatment with vitamin D3 attenuated these abnormalities in podocytes in HG group. Conclusion: Vitamin D can alleviate the apoptosis of podocytes induced by high glucose in vitro.

Septin 7 mediates high glucose-induced podocyte apoptosis

Podocyte depletion is a central pathological mechanism of diabetic nephropathy (DN). Hyperglycemia induced podocyte apoptosis, resulting in podocyte depletion. However, the crucial mechanism of hyperglycemia-induced podocyte apoptosis remains poorly understood. In this study, we evaluated the expression of septin 7, a GTP-binding protein, in glomerular podocytes of patients and mice with DN, and investigated the pro-apoptotic effect of septin 7 on high glucose (HG) induced podocyte apoptosis in vitro. We found septin 7 expression was markedly increased not only in glomerular podocytes of patients and db/db mice with DN but also in cultured podocytes with HG stimulation. Knocking down septin 7 with siRNA could attenuate HG induced podocytes apoptosis and excessive intracellular Ca2+ concentration. This study revealed septin7 may potentially play a proapoptotic role in podocyte under diabetic conditions and may provide a potential target for preventing podocyte apoptosis in DN.

NFAT2 mediates high glucose-induced apoptosis in glomerular podocytes in vitro

To determine whether hyperglycemia activates NFAT2 in cultured podocytes to cause podocyte apoptosis and explore the role of NFAT2 in high glucose-induced podocyte apoptosis. Immortalized mouse podocytes were cultured in the presence of normal (5.3 mmol/L) or high glucose (10, 20, 30, and 40 mmol/L) or pretreated with 11R-vivit (100 nmol/L) or cyclosporine A (500 nmol/L) before exposure to 20 mmol/L glucose for different durations (0.5-48 h). The activation of NFAT2 in the podocytes was detected using Western blotting and immunofluorescence assay. The role of NFAT2 in hyperglycemia-induced podocyte apoptosis was explored by observing the inhibition of NFAT2 activation by 11R-vivit using flow cytometry. Intracellular Ca2+ was monitored in high glucose-treated podocytes using Fluo-3/AM. The mRNA and protein expressions of the apoptosis gene Bax were detected using real time-qPCR and Western blotting. Exposure to high glucose in the medium time- and dose-dependently activated NFAT2 in cultured podocytes. Pretreatment with cyclosporine A or 11R- VIVIT completely blocked nuclear accumulation of NFAT2. Treatment with 11R- vivit also inhibited high glucoseinduced apoptosis in cultured podocytes. Exposure to high glucose obviously increased [Ca2 +]I in the podocytes to cause activation of calcineurin and the subsequent increment of nuclear accumulation of NFAT2 and Bax expression. High glucose-induced apoptosis in podocytes is mediated by calcineurin/NFAT2/Bax signaling pathway, which may serve as a potential target for therapeutic intervention.

MiR-370 promotes high glucose-induced podocyte injuries by inhibiting angiotensin II type 1 receptor-associated protein.

miRNAs expression profiles in podocyte injuries have been reported in different models in vivo and in vitro. In the present study, miR-370 was elevated in high glucose-stimulated podocyte, and the post-transcriptional mechanism of miR-370 was investigated in high glucose-induced podocyte injuries. The gene and protein levels were assayed by RT-qPCR and Western blotting, respectively. Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining was used to evaluate the apoptosis in high glucose-stimulated podocyte. The targeted genes were predicted by a bioinformatics algorithm and confirmed by a dual luciferase reporter assay. The results demonstrated that over-activation of miR-370 was verified in high glucose-treated podocytes, while miR-370 repression protected against high glucose-induced apoptosis, cell membrane, and DNA damage in podocytes. We also found that AGTRAP as a direct target of miR-370 served as an opposite effect to miR-370, and overexpression of AGTRAP blocked high glucose-induced podocytes dysfunction. In conclusions, high glucose-induced podocytes damage by activating miR-370 signaling targeted to inhibit the expression of AGTRAP, representing a novel and promising therapeutic target for the treatment of DN.

Knockdown of TLR4 attenuates high glucose-induced podocyte injury via the NALP3/ASC/Caspase-1 signaling pathway

Diabetic nephropathy (DN) is one of the most common syndromes of the diabetic mellitus, and is the leading cause of end-stage renal disease. TLR4 (Toll-like receptor 4) has been shown to be implicated in the progression of DN. However, the role of TLR4 in DN and its underlying mechanism remain elusive. In this study, we found that high glucose (HG) activated nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NALP3) inflammasome, as shown by elevated NALP3, apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC) and cleaved caspase-1 protein levels, and increased caspase-1 activity in mouse podocytes in vitro. Simultaneously, HG decreased the mRNA and protein expression of Wilm’s tumor-1 and synaptopodin, and increased the mRNA and protein expression levels of desmin in podocytes, in a dose-dependent manner. Administration of HG increased the number of TUNEL-positive cells, inhibited the viability of podocytes, elevated the intracellular level of ROS, and increased the levels of IL-1β, IL-18, TNF-α and TGF-β1. Moreover, the effects of HG were effectively blocked by repression of NALP3 or ASC. Furthermore, TLR4 was upregulated in HG-stimulated podocytes. TLR4 knockdown inhibited the activation of NALP3 inflammasome in HG-treated podocytes, as indicated by the decrease in NALP3, ASC and cleaved caspase-1 protein levels and the reduction in caspase-1 activity. Additionally, knockdown of TLR4 attenuated the HG-induced increase of cell apoptosis and reduction of cell viability in podocytes. TLR4 knockdown reduced the intracellular level of ROS in conjunction with reduced IL-1β, IL-18, TNF-α and TGF-β1 levels in podocytes in the presence of HG. In conclusion, knockdown of TLR4 attenuates HG-induced podocyte injury via the NALP3/ASC/Caspase-1 signaling pathway.

High Glucose-Induced Podocyte Injury Involves Activation of Mammalian Target of Rapamycin (mTOR)-Induced Endoplasmic Reticulum (ER) Stress

Background/Aims: The mechanisms by which high glucose (HG) results in podocyte damage remains unclear. We investigated the potential role of endoplasmic reticulum (ER) stress and mTOR signaling in HG injured podocyte. Methods: In cultured mouse podocytes, cellular apoptosis was assessed using FITC-Annexin V and propidium iodide staining followed by flow cytometry analysis. Apoptosis-related proteins as well as the ER stress and the mTOR signals were evaluated using immunoblot assay. Results: Compared to normal glucose (NG) and osmotic mannitol (MN) control, the percentage of apoptotic cells was increased significantly in HG-treated podocytes. The levels of CHOP, Grp78, phospho-PERKThr982, and caspase-12 were increased significantly following HG treatment. The downstream effects of ER stress were obtained in HG-treated podocytes, showing upregulation of Bax, Bak and cytochrome c, and downregulation of Bcl-2. HG-induced increase of cytochrome c, Bax and active caspase-3 was prevented by both ER inhibitor sodium 4-phenylbultyrate (PBA) and CHOP siRNA (siCHOP). PBA and CHOP knockdown remarkably decreased HG-induced apoptosis. In addition, the levels of phospho-mTORSer2448 and phospho- p70S6kThr389 as well as phospho-AMPKα (a sensor of energy consumption) were increased significantly in HG-treated cells. Moreover, the Erk inhibitor U0126 prevented HG-induced mTOR activation. Increased phospho-AMPKα, CHOP and Grp78 as well as cellular apoptosis were prevented by mTOR inhibitor rapamycin in HG-treated podocytes. Conclusion: Our data demonstrate that the activated mTOR by Erk1/2 results in energy consumption, which in turn leads to ER stress signaling and thus induces apoptosis in HG-treated podocytes.

Mechanism of NHX1 Inhibiting TRPV5-Mediated Podocyte Injury in Diabetic Nephropathy

To observe the effect of high glucose stimulation on the expression of guanylate exchange factor NHX1 in mouse kidney cells, and to explore the role of NHX1 in high glucose-induced podocyte injury and its possible molecular mechanism. The expression of NHX1 in podocytes of diabetic nephropathy patients was observed by immunofluorescence staining and laser confocal microscopy. The immortalized podocytes were cultured in vitro, and the podocytes were stimulated with high glucose for 48 h. RT-PCR, Western blot and immunization were used. Fluorescence detection of mRNA and protein expression of NHX1 in podocytes stimulated by high glucose; Western blot, immunofluorescence and scratch assay were used to detect the expression of NHX1 and the expression of podocin, the activity of podocytes and the nuclear access of TRPV5. The transcription of the target gene downstream of TRPV5 was detected by RT-PCR. NHX1 expression was significantly decreased in podocytes and high glucose-stimulated podocytes of diabetic nephropathy patients (P<0.05). After silencing NHX1, podocyte marker protein podocin expression was significantly decreased and podocyte activity was increased. The nuclear translocation of TRPV5 increased, and the transcription of the target gene downstream of TRPV5 increased (P < 0.05). In contrast, the expression of overexpressed NHX1 group was significantly increased, the activity of podocytes was decreased, the nuclear access of TRPV5 was decreased, and the transcription of the target gene downstream of TRPV5 was decreased (P<0.05). NHX1 may reduce podocyte injury in diabetic nephropathy by inhibiting TRPV5 entry into the nucleus.

MicroRNA-20b contributes to high glucose-induced podocyte apoptosis by targeting SIRT7.

Previous reports have indicated that microRNAs (miRNAs) have an important role in the pathogenesis of diabetic nephropathy (DN). Podocyte apoptosis induced by high glucose (HG) is characteristic of DN. However, the role of miRNAs in HG‑induced podocyte apoptosis remains poorly understood. The present study investigated the role and potential underlying mechanism of miRNA‑20b (miR‑20b) in podocyte apoptosis induced by HG. The results demonstrated that miR‑20b was significantly upregulated in HG‑treated podocytes, as determined by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Caspase‑3 activity and TUNEL assays indicated that suppression of miR‑20b using miR‑20b inhibitors significantly inhibited the podocyte apoptosis induced by HG. Sirtuin 7 (SIRT7) was identified as a functional target of miR‑20b by a Dual‑Luciferase activity reporter assay, RT‑qPCR and western blot analysis. Silencing SIRT7 promoted HG‑induced podocyte apoptosis, as determined by the caspase‑3 activity, while SIRT7 overexpression attenuated HG‑induced podocyte apoptosis. However, SIRT7 silencing significantly blocked the protective effect of miR‑20b suppression against HG‑induced apoptosis. In conclusion, these results indicate that miR‑20b may contribute to HG‑induced podocyte apoptosis by targeting SIRT7, providing a potential therapeutic target for the treatment of DN.

PKC-α Triggers EGFR Ubiquitination, Endocytosis and ERK Activation in Podocytes Stimulated with High Glucose

Background: Protein Kinase C-α (PKC-α) and epidermal growth factor receptor (EGFR) are both involved in diabetic kidney disease; however, the connection between these two proteins during high glucose-induced podocyte injury remains uncertain. Methods: Diabetes was induced in SD rats by streptozotocin (STZ). Fourteen days later, the kidney cortex was removed and subjected to plasma membrane isolation and lipid raft fractionation. In vitro study human podocyte cell line was differentiated and subjected to various treatments. The levels of membranous protein and endocytosis were assessed by biotinylation and sodium 2-mercaptoethane sulfonate (MesNa) treatment. Gö6976 and PYR-41 were used as inhibitors of PKC-α and ubiquitin activating E1 enzyme, respectively. Results: In diabetic rats, the abundance of PKC-α in the membranous fraction and the lipid raft domain is elevated, whereas the EGFR level is reduced. Consistently, in vitro high glucose treated podocytes, membranous EGFR is downregulated with increased PKC-α. Furthermore, the ubiquitination and endocytosis of EGFR are enhanced accompanied by extracellular signal–regulated kinase (ERK) signaling activation and podocyte damage during hyperglycemia. However, these processes can be ameliorated by inhibition of either PKC-α or ubiquitin activating E1 enzyme. Conclusion: During hyperglycemia, PKC-α mediates podocytic EGFR ubiquitination, endocytosis from cell surface and the subsequent ERK activation, which contributes to podocyte injury.

Repression of miR-217 protects against high glucose-induced podocyte injury and insulin resistance by restoring PTEN-mediated autophagy pathway

Podocyte damage is the initial hallmark of diabetic nephropathy (DN), leading to the increasing morbidity and mortality in diabetic patients. Recent researches have corroborated the critical roles of miRNAs in the pathological progression of DN. Here, elevation of miR-217 was verified in high glucose (HG)-stimulated podocytes. Moreover, blocking miR-217 expression antagonized HG-induced cell injury by attenuating the adverse role of HG on cell viability and inhibiting ROS levels and cell apoptosis. Simultaneously, miR-217 repression restored HG-disrupted insulin resistance by elevating glucose uptake and nephrin expression, an essential component for insulin-induced glucose uptake. Mechanism assay substantiated the defective autophagy in HG-treated podocytes, which was resumed by miR-217 cessation. Importantly, suppressing autophagy pathway with 3-MA alleviated the protective roles of miR-217 down-regulation in podocyte injury and insulin resistance. Luciferase reporter analysis confirmed that PTEN was a target of miR-217 in podocytes. Additionally, blocking PTEN expression restrained autophagy restoration in miR-217-decreased cells. Furthermore, PTEN down-regulation attenuated the beneficial role of miR-217 suppression in HG-induced injury and insulin resistance. Together, this study manifests that miR-217inhibition can protectively antagonize HG-induced podocyte damage and insulin resistance by restoring the defective autophagy pathway via targeting PTEN, representing a novel and promising therapeutic target against diabetic nephropathy.