Sex-specific molecular signature of mouse podocytes in homeostasis and in response to pharmacological challenge with rapamycin.

BACKGROUND: Sex differences exist in the prevalence and progression of major glomerular diseases. Podocytes are the essential cell-type in the kidney which maintain the physiological blood-urine barrier, and pathological changes in podocyte homeostasis are critical accelerators of impairment of kidney function. However, sex-specific molecular signatures of podocytes under physiological and stress conditions remain unknown. This work aimed at identifying sexual dimorphic molecular signatures of podocytes under physiological condition and pharmacologically challenged homeostasis with mechanistic target of rapamycin (mTOR) inhibition. mTOR is a crucial regulator involved in a variety of physiological and pathological stress responses in the kidney and inhibition of this pathway may therefore serve as a general stress challenger to get fundamental insights into sex differences in podocytes. METHODS: The genomic ROSAmT/mG-NPHS2 Cre mouse model was used which allows obtaining highly pure podocyte fractions for cell-specific molecular analyses, and vehicle or pharmacologic treatment with the mTOR inhibitor rapamycin was performed for 3 weeks. Subsequently, deep RNA sequencing and proteomics were performed of the isolated podocytes to identify intrinsic sex differences. Studies were supplemented with metabolomics from kidney cortex tissues. RESULTS: Although kidney function and morphology remained normal in all experimental groups, RNA sequencing, proteomics and metabolomics revealed strong intrinsic sex differences in the expression levels of mitochondrial, translation and structural transcripts, protein abundances and regulation of metabolic pathways. Interestingly, rapamycin abolished prominent sex-specific clustering of podocyte gene expression and induced major changes only in male transcriptome. Several sex-biased transcription factors could be identified as possible upstream regulators of these sexually dimorphic responses. Concordant to transcriptomics, metabolomic changes were more prominent in males. Remarkably, high number of previously reported kidney disease genes showed intrinsic sexual dimorphism and/or different response patterns towards mTOR inhibition. CONCLUSIONS: Our results highlight remarkable intrinsic sex-differences and sex-specific response patterns towards pharmacological challenged podocyte homeostasis which might fundamentally contribute to sex differences in kidney disease susceptibilities and progression. This work provides rationale and an in-depth database for novel targets to be tested in specific kidney disease models to advance with sex-specific treatment strategies.

The global burden of chronic kidney diseases is rapidly increasing and is projected to become the fifth most common cause of years of life lost worldwide by 2040. Sexual dimorphism in kidney diseases and transplantation is well known, yet sex-specific therapeutic strategies are still missing. One reason is the lack of knowledge due to the lack of inclusion of sex as a biological variable in study designs. This work aimed at identification of molecular signatures of male and female podocytes, gate-keepers of the glomerular filtration barrier. Like cardiomyocytes, podocytes are terminally differentiated cells which are highly susceptible towards pathological challenges. Podocytes are the decisive cell-type of the kidney to maintain the physiological blood-urine barrier, and disturbances of their homeostasis critically accelerate kidney function impairment. By help of a genomic mouse model, highly purified podocytes were obtained from male and female mice with and without pharmacological challenge of the mechanistic target of rapamycin (mTOR) signaling pathway which is known to be deregulated in major kidney diseases. Deep RNA sequencing, proteomics and metabolomics revealed strong intrinsic sex differences in the expression levels of mitochondrial, translation and structural transcripts, protein abundances and regulation of metabolic pathways which might fundamentally contribute to sex differences in kidney disease susceptibilities and progression. Remarkably, high number of previously reported kidney disease genes showed so far unknown intrinsic sexual dimorphism and/or different response patterns towards mTOR inhibition. Our work provides an in-depth database for novel targets to be tested in kidney disease models to advance with sex-specific treatment strategies.

PPAR-α Insufficiency Enhances Doxorubicin-Induced Nephropathy in PPAR-α Knockout Mice and a Murine Podocyte Cell Line.

Peroxisome proliferator-activated receptor-alpha (PPAR-α) and its exogenous activators (fibrates) promote autophagy. However, whether the deleterious effects of PPAR-α deficiency on doxorubicin (DOX)-induced podocytopathy are associated with reduced autophagy remains to be clarified. We investigated the mechanisms of PPAR-α in DOX-induced podocytopathy and tubular injury in PPAR-α knockout (PAKO) mice and in a murine podocyte cell line. DOX-treated PAKO mice showed higher serum levels of triglycerides and non-esterified fatty acids and more severe podocytopathy than DOX-treated wild-type mice, as evidenced by higher urinary levels of proteins and podocalyxin at 3 days to 2 weeks and higher blood urea nitrogen and serum creatinine levels at 4 weeks. Additionally, there was an increased accumulation of p62, a negative autophagy marker, in the glomerular and tubular regions in DOX-treated PAKO mice at Day 9. Moreover, DOX-treated PAKO mice showed more severe glomerulosclerosis and tubular damage and lower podocalyxin expression in the kidneys than DOX-treated control mice at 4 weeks. Furthermore, DOX treatment increased p-p53, an apoptosis marker, and cleaved the caspase-3 levels and induced apoptosis, which was ameliorated by fenofibrate, a PPAR-α activator. Fenofibrate further enhanced AMPK activation and autophagy under fed and fasting conditions. Conclusively, PPAR-α deficiency enhances DOX-induced podocytopathy, glomerulosclerosis, and tubular injury, possibly by reducing autophagic activity in mouse kidneys.

Mechanism of Kemeng Fang's Inhibition of Podocyte Apoptosis in Rats with Membranous Nephropathy through the PI3K/AKT Signaling Pathway.

Membranous nephropathy (MN) is a common pathological type of adult nephrotic syndrome. Up to 20% of patients with MN develop end-stage renal disease (ESRD). Podocytes have an important function in maintaining the glomerular filtration barrier and play a crucial role in the occurrence and development of proteinuria and MN. PI3K/AKT signaling pathway is involved in the entire process of podocyte growth, differentiation, and apoptosis. Kemeng Fang (KMF) is a traditional Chinese medicine formula that has been used to delay kidney injury. However, the therapeutic mechanism of KMF in MN is unclear. Here, the MN rat model was established by axillary, inguinal, and tail vein injections of cationized bovine serum albumin (C-BSA), and then KMF and PI3K inhibitor (LY294002) were administered. The data of liver function, kidney function, blood lipid, renal pathology, podocyte function, expression level of PI3K/AKT signaling pathway, and transcriptomics of rats demonstrated that KMF has a protective effect on the podocytes of MN rats by activating the PI3K/AKT signaling pathway, and it can effectively prevent the progression of MN.

Urine-derived podocytes from steroid resistant nephrotic syndrome patients as a model for renal-progenitor derived extracellular vesicles effect and drug screening.

BACKGROUND: Personalized disease models are crucial for evaluating how diseased cells respond to treatments, especially in case of innovative biological therapeutics. Extracellular vesicles (EVs), nanosized vesicles released by cells for intercellular communication, have gained therapeutic interest due to their ability to reprogram target cells. We here utilized urinary podocytes obtained from children affected by steroid-resistant nephrotic syndrome with characterized genetic mutations as a model to test the therapeutic potential of EVs derived from kidney progenitor cells (nKPCs). METHODS: EVs were isolated from nKPCs derived from the urine of a preterm neonate. Three lines of urinary podocytes obtained from nephrotic patients' urine and a line of Alport syndrome patient podocytes were characterized and used to assess albumin permeability in response to nKPC-EVs or various drugs. RNA sequencing was conducted to identify commonly modulated pathways after nKPC-EV treatment. siRNA transfection was used to demonstrate the involvement of SUMO1 and SENP2 in the modulation of permeability. RESULTS: Treatment with the nKPC-EVs significantly reduced permeability across all the steroid-resistant patients-derived and Alport syndrome-derived podocytes. At variance, podocytes appeared unresponsive to standard pharmacological treatments, with the exception of one line, in alignment with the patient's clinical response at 48 months. By RNA sequencing, only two genes were commonly upregulated in nKPC-EV-treated genetically altered podocytes: small ubiquitin-related modifier 1 (SUMO1) and Sentrin-specific protease 2 (SENP2). SUMO1 and SENP2 downregulation increased podocyte permeability confirming the role of the SUMOylation pathway. CONCLUSIONS: nKPCs emerge as a promising non-invasive source of EVs with potential therapeutic effects on podocytes with genetic dysfunction, through modulation of SUMOylation, an important pathway for the stability of podocyte slit diaphragm proteins. Our findings also suggest the feasibility of developing a non-invasive in vitro model for screening regenerative compounds on patient-derived podocytes.

Chemical chaperones to the rescue of Alport syndrome?

Alport syndrome is a hereditary kidney disease caused by collagen IV mutations that interfere with the formation and deposition of the α3α4α5 protomer into the glomerular basement membrane. In this issue, Yu et al. show that the chemical chaperone tauroursodeoxycholic acid prevented kidney structural changes and function decline in mice with a pathogenic missense Col4a3 mutation by increasing mutant α3α4α5 protomer glomerular basement membrane deposition and preventing podocyte apoptosis induced by endoplasmic reticulum stress.

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.

Therapeutic Potential of Blocking Nephrin Phosphorylation to Improve Pancreatic ß-cell Function.

The phosphorylation of the transmembrane protein nephrin has been shown to play an important role in signaling in kidney podocytes, and it has now been shown to also play a key role in regulating pancreatic ß-cell function. Williamson et al have recently shown that the loss of nephrin tyrosine phosphorylation on its 3 cytoplasmic YDxV motifs can enhance insulin release in aged female mice. These studies suggest that blocking nephrin phosphorylation may be an effective treatment option for improving ß-cell function.

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.

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

ETHNOPHARMACOLOGICAL RELEVANCE: Linggui-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 STUDY: This 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 METHODS: LGZG 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. RESULTS: Treatment 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. CONCLUSION: Our data demonstrated that the LGZG formula protected against DKD in mice and was closely associated with its inhibitory effects on PR3-mediated podocyte apoptosis.

Supplemented Gegen Qinlian Decoction Formula attenuates podocyte mitochondrial fission and renal fibrosis in diabetic kidney disease by inhibiting TNF-α-mediated necroptosis, compared with empagliflozin.

ETHNOPHARMACOLOGICAL RELEVANCE: Recently, podocyte mitochondrial dysfunction and necroptosis have been shown to play critical roles in renal fibrosis (RF) in diabetic kidney disease (DKD); however, these conditions lack effective treatment. In China, the supplemented Gegen Qinlian Decoction Formula (SGQDF), which originates from the classical prescription Gegen Qinlian Decoction, has been widely used to treat patients with DKD. However, it remains unclear whether SGQDF alleviates podocyte injury-associated RF in patients with DKD. AIM OF STUDY: This study aimed to clarify the therapeutic effects of SGQDF compared with those of empagliflozin (EMPA) on podocyte mitochondrial fission and RF in DKD and its necroptosis-related mechanisms. MATERIALS AND METHODS: Modified DKD rat models were developed through a combination of uninephrectomy, streptozotocin administration through intraperitoneal injection, and exposure to a high-fat diet. Following RF formation, the DKD rat models received either a high dose of SGQDF (H-SGQDF), a low dose of SGQDF (L-SGQDF), EMPA, or vehicle for 4 weeks. In our in vitro study, we subjected cultured murine podocytes to a high-glucose environment and various treatments including Mdivi-1, adalimumab, and necrostatin-1, with or without H-SGQDF or EMPA. SGQDF target prediction and molecular docking verification were performed. For the in vivo study, we focused on examining changes in the parameters associated with renal injury, RF, and oxidative stress (OS)-induced injuries in podocytes. Both in vivo and in vitro studies included an analysis of changes in podocyte mitochondrial fission, TNF-α-induced podocyte necroptosis, and the RIPK1/RIPK3/MLKL signaling pathway activation. RESULTS: SGQDF improved renal injury markers, including body weight, blood glucose, serum creatinine, blood urea nitrogen, and urinary albumin, in a dose-dependent manner. The beneficial effects of H-SGQDF in vivo were greater than those of L-SGQDF alone in vivo. Interestingly, similar to EMPA, H-SGQDF ameliorated RF and reduced OS-induced podocyte injury in diabetic kidneys. Furthermore, TNF-α signaling was shown to be important in the network construction of "the SGQDF-component-target." Based on this, we also showed that the beneficial effects in vivo and in vitro of H-SGQDF were closely related to the improvement in mitochondrial dysfunction and the inhibition of TNF-α-induced necroptosis in podocytes. CONCLUSION: In the present study, we showed that H-SGQDF, similar to EMPA, attenuates podocyte mitochondrial fission and RF, and that the underlying therapeutic mechanisms are closely related to inhibiting the activation of the RIPK1/RIPK3/MLKL signaling axis in diabetic kidneys. Our findings provide new pharmacological evidence for the application of H-SGQDF in the RF treatment of DKD.

Investigating FSGS-like injury in zebrafish larvae by nifurpirinol: efficacy and molecular insight.

Identifying effective drugs for focal segmental glomerulosclerosis (FSGS) treatment holds significant importance. Our high-content drug screening on zebrafish larvae relies on nitroreductase/metronidazole (NTR/MTZ)-induced podocyte ablation to generate FSGS-like injury. A crucial factor for successful drug screenings is minimizing variability in injury induction. For this, we introduce nifurpirinol (NFP) as a more reliable prodrug for targeted podocyte depletion. NFP showed a 2.3-fold increase in efficiency at concentrations 1,600-fold lower compared with MTZ-mediated injury induction. Integration into the screening workflow validated its suitability for the high-content drug screening. The presence of crucial FSGS hallmarks, such as podocyte foot process effacement, proteinuria, and activation of parietal epithelial cells, was observed. After the isolation of the glomeruli from the larvae, we identified essential pathways by proteomic analysis. This study shows that NFP serves as a highly effective prodrug to induce the FSGS-like disease in zebrafish larvae and is well-suited for a high-content drug screening to identify new candidates for the treatment of FSGS.NEW & NOTEWORTHY This research investigated the use of nifurpirinol in nanomolar amounts as a prodrug to reliably induce focal segmental glomerulosclerosis (FSGS)-like damage in transgenic zebrafish larvae. Through proteomic analysis of isolated zebrafish glomeruli, we were further able to identify proteins that are significantly regulated after the manifestation of FSGS. These results are expected to expand our knowledge of the pathomechanism of FSGS.

Rhodojaponin VI ameliorates podocyte injury related with MDM2/Notch1 pathway in rat experimental membranous nephropathy.

AIM: Rhodojaponin VI (R-VI) is the key compound of Rhododendron molle G. Don (Ericaceae) (RM) with effective clinical application in rheumatoid arthritis and chronic glomerulonephritis. In our study, we tried to explore the effect of R-VI on the rat model of membranous nephropathy. METHODS: The rat model of passive heymann nephritis (PHN) was established by injecting sheep anti-rat Fx1A serum at a single dose through the tail. The rats were orally administered R-VI (0.02 mg/kg) or FK506 (1 mg/kg) 1 day before PHN induction, which was kept for 4 weeks. Urine and blood samples as well as kidney tissue were collected for analysis. C5b-9-induced human podocyte cell (HPC) was employed for experiments in vitro. RESULTS: R-VI could alleviate glomerulonephritis progression and podocyte injury in PHN rats, as indicated by the decreased proteinuria and the elevated level of albumin, accompanied with reduced immune deposits, reversed podocyte injury in the kidneys. Furthermore, R-VI suppressed murine double minute 2 (MDM2) expression without the alteration in the protein level of p53 and decreased Notch1 expression independent of Numb regulation. Pre-treatment with R-VI in C5b-9-induced HPC blocked MDM2/Notch1 signalling pathway. CONCLUSION: Thus, R-VI ameliorates podocyte injury in rats with PHN, which was probably related with MDM2/Notch1 signalling pathway.

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

BACKGROUND: The 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. METHODS: A 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. RESULTS: The 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. CONCLUSIONS: Compared 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.

Quercetin-4'-O-ß-D-glucopyranoside inhibits podocyte injury by SIRT5-mediated desuccinylation of NEK7.

Diabetic kidney disease (DKD) is a complication of diabetic mellitus. New treatments need to be developed. This study aimed to investigate the effects of quercetin-4'-O-ß-D-glucopyranoside (QODG) on podocyte injury. Podocytes were cultured in high glucose (HG) medium, treated with QODG, and overexpressing or knocking down SIRT5. Oxidative stress indicators were assessed using corresponding kits. Pyroptosis was detected by flow cytometry and western blot analysis. Succinylation modification was detected using immunoprecipitation (IP) and western blot analysis. The interaction between NEK7 and NLRP3 was determined by co-IP. The results indicated that QODG inhibited oxidative stress and pyroptosis of podocytes induced by HG. Besides, QODG suppressed succinylation levels in HG-induced podocytes, with the upregulation of SIRT5. Knockdown of SIRT5 reversed the effects of QODG on oxidative stress and pyroptosis. Moreover, SIRT5 inhibited the succinylation of NEK7 and the interaction between NLRP3 and NEK7. In conclusion, QODG upregulates SIRT5 to inhibit the succinylation modification of NEK7, impedes the interaction between NEK7 and NLRP3, and then inhibits the pyroptosis and oxidative stress injury of podocytes under HG conditions. The findings suggested that QODG has the potential to treat DKD and explore a novel underlying mechanism of QODG function.

Cyclosporine A Protects Podocytes by Regulating Transgelin in Adriamycin-Induced Podocyte Injury.

INTRODUCTION: The calcineurin inhibitor cyclosporine A (CsA) has been shown to effectively reduce proteinuria. However, its precise mechanism is still not fully understood. Our previous study showed that CsA reduced proteinuria by directly stabilizing the foot process (FP) cytoskeletal structure via cofilin-1, suggesting that synaptopodin, a podocyte-specific actin protein, is not the sole target of CsA in podocytes. METHODS: In this study, we established an adriamycin (ADR)-induced nephropathy rat model and a cultured podocyte injury model. We employed Western blotting and immunofluorescence techniques to assess the expression and distribution of transgelin, Krüppel-like factor-4 (KLF-4), nephrin, and synaptopodin. RESULTS: We observed a significant increase in proteinuria levels accompanied by loss of normal FP structure in the ADR-induced nephropathy rat model. The levels of the actin cross-linking protein transgelin were increased significantly, while those of the podocyte-specific molecules nephrin and synaptopodin were decreased in vivo. Treatment with CsA effectively reduced proteinuria while restoring FP effacement stability in ADR-induced nephropathy models and restoring the expression of transgelin, nephrin, and synaptopodin both in vivo and in vitro. Furthermore, CsA treatment dose-dependently decreased transgelin levels while significantly increasing KLF-4 expression in injured podocytes. In addition, CsA failed to downregulate transgelin when KLF-4 was specifically knocked down. CONCLUSION: Our findings suggest that CsA protects against podocyte injury by downregulating abnormally high levels of transgelin via upregulation of KLF-4 expression.

Ursolic Acid Alleviates Mitotic Catastrophe in Podocyte by Inhibiting Autophagic P62 Accumulation in Diabetic Nephropathy.

The glomerular podocyte, a terminally differentiated cell, is crucial for the integrity of the glomerular filtration barrier. The re-entry of podocytes into the mitotic phase results in injuries or death, known as mitotic catastrophe (MC), which significantly contributes to the progression of diabetic nephropathy (DN). Furthermore, P62-mediated autophagic flux has been shown to regulate DN-induced podocyte injury. Although previous studies, including ours, have demonstrated that ursolic acid (UA) mitigates podocyte injury by enhancing autophagy under high glucose conditions, the protective functions and potential regulatory mechanisms of UA against DN have not been fully elucidated. For aiming to investigate the regulatory mechanism of podocyte injuries in DN progression, and the protective function of UA treatment against DN progression, we utilized db/db mice and high glucose (HG)-induced podocyte models in vivo and in vitro, with or without UA administration. Our findings indicate that UA treatment reduced DN progression by improving biochemical indices. P62 accumulation led to Murine Double Minute gene 2 (MDM2)-regulated MC in podocytes during DN, which was ameliorated by UA through enhanced P62-mediated autophagy. Additionally, the overexpression of NF-κB p65 or TNF-α abolished the protective effects of UA both in vivo and in vitro. Overall, our results provide strong evidence that UA could be a potential therapeutic agent for DN, regulated by inhibiting podocyte MC through the NF-κB/MDM2/Notch1 pathway by targeting autophagic-P62 accumulation.

Ramulus Mori (Sangzhi) Alkaloids Alleviate Diabetic Nephropathy through Improving Gut Microbiota Disorder.

Diabetic nephropathy (DN), one of the leading causes of end-stage kidney failure worldwide, is closely associated with high mortality in diabetic patients. However, therapeutic drugs for DN are still lacking. Ramulus Mori alkaloids (SZ-A), an effective component of alkaloids extracted from Ramulus Mori, have been found to improve glucose and lipid metabolism to mitigate diabetes and obesity; however, few studies have focused on their effects on DN progression. Thus, we investigated the protective role of SZ-A on DN through 16S rRNA sequencing, non-targeted metabolomics, and fecal microbiota transplantation (FMT) experiments. To address our hypothesis, we established the DN mouse model by combining a high-fat diet (HFD) with streptozotocin (STZ) injection. Herein, we demonstrated that SZ-A supplementation was recalcitrant to renal injury in DN mice, improving glomerular morphology, reversing the blood biochemistry parameters, and ameliorating podocyte injury. Importantly, the composition of the gut microbiota altered after SZ-A treatment, especially with the elevated abundance of Dubosiella and the increased level of serum pentadecanoic acid. FMT experiments further revealed that the gut microbiota exerted critical effects in mediating the beneficial roles of SZ-A. In vitro experiments proved that pentadecanoic acid administration improved podocyte apoptosis induced by AGEs. Taken together, SZ-A play a renoprotective role, possibly through regulating the gut microbiota and promoting pentadecanoic acid production. Our current study lends support to more extensive clinical applications of SZ-A.

Proteomic Changes Induced by the Immunosuppressant Everolimus in Human Podocytes.

mTOR inhibitors (mTOR-Is) may induce proteinuria in kidney transplant recipients through podocyte damage. However, the mechanism has only been partially defined. Total cell lysates and supernatants of immortalized human podocytes treated with different doses of everolimus (EVE) (10, 100, 200, and 500 nM) for 24 h were subjected to mass spectrometry-based proteomics. Support vector machine and partial least squares discriminant analysis were used for data analysis. The results were validated in urine samples from 28 kidney transplant recipients receiving EVE as part of their immunosuppressive therapy. We identified more than 7000 differentially expressed proteins involved in several pathways, including kinases, cell cycle regulation, epithelial-mesenchymal transition, and protein synthesis, according to gene ontology. Among these, after statistical analysis, 65 showed an expression level significantly and directly correlated with EVE dosage. Polo-Like Kinase 1 (PLK1) content was increased, whereas osteopontin (SPP1) content was reduced in podocytes and supernatants in a dose-dependent manner and significantly correlated with EVE dose (p < 0.0001, FDR < 5%). Similar results were obtained in the urine of kidney transplant patients. This study analyzed the impact of different doses of mTOR-Is on podocytes, helping to understand not only the biological basis of their therapeutic effects but also the possible mechanisms underlying proteinuria.

Astaxanthin attenuates diabetic kidney injury through upregulation of autophagy in podocytes and pathological crosstalk with mesangial cells.

Objectives: Astaxanthin (ATX) is a strong antioxidant drug. This study aimed to investigate the effects of ATX on podocytes in diabetic nephropathy and the underlying renal protective mechanism of ATX, which leads to pathological crosstalk with mesangial cells.Methods: In this study, diabetic rats treated with ATX exhibited reduced 24-h urinary protein excretion and decreased blood glucose and lipid levels compared to vehicle-treated rats. Glomerular mesangial matrix expansion and renal tubular epithelial cell injury were also attenuated in ATX-treated diabetic rats compared to control rats.Results: ATX treatment markedly reduced the α-SMA and collagen IV levels in the kidneys of diabetic rats. Additionally, ATX downregulated autophagy levels. In vitro, compared with normal glucose, high glucose inhibited LC3-II expression and increased p62 expression, whereas ATX treatment reversed these changes. ATX treatment also inhibited α-SMA and collagen IV expression in cultured podocytes. Secreted factors (vascular endothelial growth factor B and transforming growth factor-ß) generated by high glucose-induced podocytes downregulated autophagy in human mesangial cells (HMCs); however, this downregulation was upregulated when podocytes were treated with ATX.Conclusions: The current study revealed that ATX attenuates diabetes-induced kidney injury likely through the upregulation of autophagic activity in podocytes and its antifibrotic effects. Crosstalk between podocytes and HMCs can cause renal injury in diabetes, but ATX treatment reversed this phenomenon.

Morroniside attenuates podocytes lipid deposition in diabetic nephropathy: A network pharmacology, molecular docking and experimental validation study.

BACKGROUND: Dysregulation of lipid metabolism is a key factor influencing the progression of diabetic nephropathy (DN). Morroniside (MOR) is a major active compound isolated from the traditional Chinese herb Cornus officinalis, our previous research found that it can improve the lipid deposition of renal tubular epithelial cells. The purpose of this study is to explore whether MOR can improve podocyte lipid deposition and its mechanism of reducing DN. METHODS: Initially, we used network pharmacology and bioinformatics techniques to predict the relationship between renal lipid metabolism of MOR and DN. Subsequently, the binding activity of MOR with lipid-related proteins was studied by molecular docking to determine how MOR acts through these proteins. After determining the target of MOR, animal experiments and cell tests were carried out to verify it. RESULTS: Using network pharmacology, bioinformatics, and molecular docking, target proteins for MOR treatment of DN were predicted and screened, including PGC-1α, LXRs, ABCA1, PPARY, CD36, and nephrin. It is particularly noted that MOR effectively binds to PGC-1α, while LXRs, ABCA1, PPARY and CD36 are downstream molecules of PGC-1α. Silencing the PGC-1α gene significantly reduced the therapeutic effects of MOR. Conversely, in groups without PGC-1α knockdown, MOR was able to increase the expression levels of PGC-1α and influence the expression of downstream proteins. Furthermore, through in vivo and in vitro experiments, utilizing techniques such as lipid droplet staining, PAS, MASSON staining, immunofluorescence, and Western blot, we found that MOR effectively elevated the expression levels of the podocyte protein nephrin and lipid metabolism-regulating proteins PGC-1α, PPARY, and ABCA1, while significantly inhibiting the expression of the lipid accumulation promoter CD36. CONCLUSION: MOR can regulate the cholesterol efflux in podocytes via the PGC-1α/LXRs/ABCA1 signaling pathway, and control cholesterol intake via the PGC-1α/PPARY/CD36 signaling pathway, thereby ameliorating lipid deposition in DN.