Dexamethasone Prevents Podocyte Apoptosis Induced by Puromycin Aminonucleoside: Role of p53 and Bcl-2–Related Family Proteins

Inhibition of the glucocorticoid receptor attenuates proteinuric kidney diseases in multiple species

BACKGROUND

Glucocorticoids are the treatment of choice for proteinuric patients with minimal change disease (MCD) and primary focal segmental glomerulosclerosis (FSGS). Immunosuppressive as well as direct effects on podocytes are believed to mediate their actions. In this study, we analyzed the anti-proteinuric effects of inhibition of the glucocorticoid receptor (GR) in glomerular epithelial cells, including podocytes.

METHODS

We employed genetic and pharmacological approaches to inhibit the GR. Genetically, we used Pax8-Cre/GRfl/fl mice to specifically inactivate the GR in kidney epithelial cells. Pharmacologically, we utilized a glucocorticoid antagonist called mifepristone.

RESULTS

Genetic inactivation of GR, specifically in kidney epithelial cells, using Pax8-Cre/GRfl/fl mice, ameliorated proteinuria following protein overload. We further tested the effects of pharmacological GR inhibition in three models and species: the puromycin aminonucleoside-induced nephrosis model in rats, the protein overload model in mice and the inducible transgenic NTR/MTZ zebrafish larvae with specific and reversible podocyte injury. In all three models, both pharmacological GR activation and inhibition consistently and significantly ameliorated proteinuria. Additionally, we translated our findings to humans, where three nephrotic adult patients with MCD or primary FSGS with contraindications or insufficient responses to corticosteroids were treated with mifepristone. This treatment resulted in a clinically relevant reduction of proteinuria.

CONCLUSIONS

Thus, across multiple species and proteinuria models, both genetic and pharmacological GR inhibition was at least as effective as pronounced GR activation. While the mechanism remains perplexing, GR inhibition may be a novel and targeted therapeutic approach to treat glomerular proteinuria potentially bypassing adverse actions of steroids.

Podocyte number and glomerulosclerosis indices are associated with the response to therapy for primary focal segmental glomerulosclerosis

Corticosteroid therapy, often in combination with inhibition of the renin-angiotensin system, is first-line therapy for primary focal and segmental glomerulosclerosis (FSGS) with nephrotic-range proteinuria. However, the response to treatment is variable, and therefore new approaches to indicate the response to therapy are required. Podocyte depletion is a hallmark of early FSGS, and here we investigated whether podocyte number, density and/or size in diagnostic biopsies and/or the degree of glomerulosclerosis could indicate the clinical response to first-line therapy. In this retrospective single center cohort study, 19 participants (13 responders, 6 non-responders) were included. Biopsies obtained at diagnosis were prepared for analysis of podocyte number, density and size using design-based stereology. Renal function and proteinuria were assessed 6 months after therapy commenced. Responders and non-responders had similar levels of proteinuria at the time of biopsy and similar kidney function. Patients who did not respond to treatment at 6 months had a significantly higher percentage of glomeruli with global sclerosis than responders (p < 0.05) and glomerulosclerotic index (p < 0.05). Podocyte number per glomerulus in responders was 279 (203-507; median, IQR), 50% greater than that of non-responders (186, 118-310; p < 0.05). These findings suggest that primary FSGS patients with higher podocyte number per glomerulus and less advanced glomerulosclerosis are more likely to respond to first-line therapy at 6 months. A podocyte number less than approximately 216 per glomerulus, a GSI greater than 1 and percentage global sclerosis greater than approximately 20% are associated with a lack of response to therapy. Larger, prospective studies are warranted to confirm whether these parameters may help inform therapeutic decision making at the time of diagnosis of primary FSGS.

Apoptosis-Controlling, Clinical, Laboratory, Anamnestic Factors in Prediction of the Early Stage of Diabetic Nephropathy in Children

Background. The most prevalent microvascular consequence of type 1 diabetes (T1D) is diabetic nephropathy (DN). Aim of the Study. To find the clinical, anamnestic, and genetic markers that characterize and forecast early diabetic nephropathy in T1D children. Methods. One hundred four children with T1D and DN between the ages of 2 and 17 were surveyed. Stepwise logistic regression models and linear regression models were used. Results. BMI, systolic blood pressure, concurrent kidney pathology, anamnesis viral infections, ESR level, serum cholesterol, blood urea, number of DKA episodes/year, and GFR were determined to be predictors of early DN in children with T1D. Bcl-xL, caspase-3, and HIF-1alfa were discovered to predict DN among all previously identified variables influencing apoptosis. Conclusion. BMI, systolic blood pressure, concurrent kidney disease, anamnesis viral infections, ESR level, serum cholesterol, blood urea, number of DKA episodes/year, GFR, apoptotic and hypoxia markers were discovered as variables predicting early DN.

Dexamethasone-Loaded Hydrogels Improve Motor and Cognitive Functions in a Rat Mild Traumatic Brain Injury Model

Functional recovery following traumatic brain injury (TBI) is limited due to progressive neuronal damage resulting from secondary injury-associated neuroinflammation. Steroidal anti-inflammatory drugs, such as dexamethasone (DX), can reduce neuroinflammation by activated microglia and infiltrated macrophages. In our previous work, we developed hydrolytically degradable poly(ethylene) glycol-bis-(acryloyloxy acetate) (PEG-bis-AA) hydrogels with dexamethasone (DX)-conjugated hyaluronic acid (HA-DXM) and demonstrated that dexamethasone-loaded hydrogels (PEG-bis-AA/HA-DXM) can reduce neuroinflammation, apoptosis, and lesion volume and improve neuronal cell survival and motor function recovery at seven days post-injury (DPI) in a rat mild-TBI model. In this study, we investigate the effects of the local application of PEG-bis-AA/HA-DXM hydrogels on motor function recovery at 7 DPI and cognitive functional recovery as well as secondary injury at 14 DPI in a rat mild-CCI TBI model. We observed that PEG-bis-AA/HA-DXM-treated animals exhibit significantly improved motor functions by the rotarod test and cognitive functions by the Morris water maze test compared to untreated TBI animals. We also observed that PEG-bis-AA/HA-DXM hydrogels reduce the inflammatory response, apoptosis, and lesion volume compared to untreated animals at 14 DPI. Therefore, PEG-bis-AA/HA-DXM hydrogels can be promising a therapeutic intervention for TBI treatment.

How immunosuppressive drugs may directly target podocytes in glomerular diseases

Podocytes are the direct target of immunologic injury in many immune-mediated glomerular diseases, leading to proteinuria and subsequent kidney failure. Immunosuppressive agents such as steroids, calcineurin inhibitors, and rituximab are the commonly used treatment strategies in this context for their immunotherapeutic or anti-inflammatory properties. However, in recent years, studies have demonstrated that immunosuppressive agents can have a direct effect on podocytes, introducing the concept of the non-immunologic mechanism of kidney protection by immunomodulators. In this review, we focus on the mechanisms by which these agents may directly target the podocyte independent of their systemic effects and examine their clinical significance.

New Insights into the Treatment of Glomerular Diseases: When Mechanisms Become Vivid

Treatment for glomerular diseases has been extrapolated from the experience of other autoimmune disorders while the underlying pathogenic mechanisms were still not well understood. As the classification of glomerular diseases was based on patterns of juries instead of mechanisms, treatments were typically the art of try and error. With the advancement of molecular biology, the role of the immune agent in glomerular diseases is becoming more evident. The four-hit theory based on the discovery of gd-IgA1 gives a more transparent outline of the pathogenesis of IgA nephropathy (IgAN), and dysregulation of Treg plays a crucial role in the pathogenesis of minimal change disease (MCD). An epoch-making breakthrough is the discovery of PLA2R antibodies in the primary membranous nephropathy (pMN). This is the first biomarker applied for precision medicine in kidney disease. Understanding the immune system’s role in glomerular diseases allows the use of various immunosuppressants or other novel treatments, such as complement inhibitors, to treat glomerular diseases more reasonable. In this era of advocating personalized medicine, it is inevitable to develop precision medicine with mechanism-based novel biomarkers and novel therapies in kidney disease.

Clinical and Apoptotic Factors Defining and Predicting Steroid Resistance in Nephrotic Syndrome in Children

Introduction. Nephrotic syndrome (NS) is a kidney disease characterized by albuminuria, hyperlipidemia, edema, and hypoalbuminemia. Above 20 % of nephrotic children do not show response to steroid treatment. Molecular markers controlling apoptosis have not been studied as a predictors of steroid resistant NS (SRNS) and steroid sensitive NS (SSNS) in children. Aim of the Study. To identify clinical and molecular markers which define and predict the steroid-resistance phenomenon in children with NS. Methods. Fifty-six clinical cases of children hospitalized in Pediatric Hospital No. 7 (Kyiv, Ukraine) with NS (26 SSNS and 30 SRNS) studied. Stepwise logistic regression models used to analyze data. Data processed using GraphPad Prism 9.0 Software for Windows (USA, San Diego, CA). Results. Arterial hypertension, WBC and RBC count, serum creatinine, serum urea, serum cholesterol found to be factors defining and predicting SRNS. Apoptosis regulating BcL-xL, Bax but not caspase-8 found to be those defining SRNS. Among transcriptional factors HIF-1alfa selected as a factor predicting steroid resistance phenomenon. For SSNS group significant negative correlation observed between BcL-xL and Bax, BcL-xL and caspase-3, significant positive correlation observed between marker of cellular hypoxia HIF-1alfa and proapoptotic factor caspase-3. For SRNS group significant negative correlation observed between BcL-xL and Bax, BcL-xL and caspase-3 level, significant positive correlation observed between HIF-1alfa and proapoptotic factor caspase-3. Conclusions. Arterial hypertension, serum creatinine level, serum urea level, serum cholesterol level, WBC and RBC count, BcL-xL, Bax, caspase-3, and HIF-1alfa identified as candidate biomarkers to predict and define SRNS in pediatric NS.

Glucocorticoids Inhibit EGFR Signaling Activation in Podocytes in Anti-GBM Crescentic Glomerulonephritis

Glucocorticoids are commonly used to treat anti-GBM crescentic glomerulonephritis, however, the mechanism underlying its therapeutic effectiveness is not completely understood. Since podocyte EGFR/STAT3 signaling is known to mediate the development of anti-GBM glomerulonephritis, we investigated the effect of glucocorticoids on EGFR/STAT3 signaling in podocytes. We found that the levels of phosphorylated (activated) EGFR and STAT3 in podocytes were markedly elevated in anti-GBM patients without glucocorticoids treatment, but were normalized in patients with glucocorticoids treatment. In a rat model of anti-GBM glomerulonephritis, glucocorticoids treatment significantly attenuated the proteinuria, crescent formation, parietal epithelial cell (PEC) activation and proliferation, accompanied by elimination of podocyte EGFR/STAT3 signaling activation. In cultured podocytes, glucocorticoids were found to inhibit HB-EGF-induced EGFR and STAT3 activation. The conditioned medium from podocytes treated with HB-EGF in the absence but not presence of glucocorticoids was capable of activating Notch signaling (which is known to be involved in PEC proliferation and crescent formation) and enhancing proliferative activity in primary PECs, suggesting that glucocorticoids prevent podocytes from producing secreted factors that cause PEC proliferation and crescent formation. Furthermore, we found that glucocorticoids can downregulate the expression of EGFR ligands, EGF and HB-EGF, while upregulate the expression of EGFR inhibitor, Gene 33, explaining how glucocorticoids suppress EGFR signaling. Taken together, glucocorticoids exert therapeutic effect on anti-GBM crescentic glomerulonephritis through inhibiting podocyte EGFR/STAT3 signaling and the downstream pathway that leads to PEC proliferation and crescent formation.

Treatment of idiopathic nephrotic syndrome with two steroid dosing regimens - one-year observational study

Introduction

The aim of the study was to compare the first year of disease in children with idiopathic nephrotic syndrome (INS) treated according to two prednisone dosing regimens: a weight-based schedule (2 mg/kg/24 h in the 1^st month, 2 mg/kg/48 h in the 2^nd month, with dose tapering during the following 4 months), and a body surface area (BSA)-based schedule (60 mg/m²/24 h in the 1^st month, 40 mg/m²/48 h in the 2^nd month, with dose tapering during the following 4 months).

Material and methods

In 2 groups of children treated with weight- and BSA-based regimens (20 patients, 3.13 ±1.01 years, treated in 2010-2013 and 20 patients, 5.13 ±2.86 years, treated in 2014-2016) clinical and anthropometrical parameters, number of INS relapses, total prednisone dose (mg/kg/year), and steroid adverse effects were compared during the first year of disease.

Results

Children treated with the weight-based steroid regimen received a higher total annual prednisone dose (259.06 ±79.54 vs. 185.83 ±72.67 mg/kg/24 h, p = 0.004) and had a shorter (though not significantly) period without prednisone (38.25 ±55.83 vs. 75.90 ±73.06 days, p = 0.062) compared to patients treated with the BSA-based regimen. There was no difference in number of relapses between groups (2.20 ±1.64 vs. 1.60 ±1.67, p = 0.190) but more patients relapsed in the weight-based group (19/20 vs. 13/20, p = 0.044). No differences in Z-score values of height, weight, and body mass index (BMI) were observed. No steroid-related adverse events were noted except for arterial hypertension (4/20 vs. 5/20 patients, p = 1.000).

Conclusions

The BSA-based regimen of prednisone dosing in children with INS reduces exposure to steroids and risk of relapse, as well as increases days off steroids in the first year compared to the weight-based regimen with a high second-month dose.

Levamisole Therapy in COVID-19

Coronavirus disease 2019 (COVID-19) a global infectious disease caused by severe acute respiratory coronavirus 2 (SARS-CoV-2) affects various organs, primarily the respiratory system, and presented with pulmonary manifestations such as acute lung injury (ALI) and acute respiratory distress syndrome. Levamisole (LVM) is an anthelminthic drug; it has immune-modulating effects through induction of type 1 immune response. Based on these findings several recent studies highlighted that LVM might be effective in preventing and treating SARS-CoV-2 infections. The aim of this report is to illustrate the potential role of LVM in SARS-CoV-2 infection and in the management of COVID-19. Different studies proposed that LVM may inhibit proliferation of SARS-CoV-2 through inhibition of papain-like protease. LVM may prevent ALI and acute kidney injury through activation of glucocorticoid receptors. In general, LVM has strong immune stimulant effects by modulating cellular and humoral immune responses. This effect is beneficial in the early phase of COVID-19 and harmful in the late phase. In the early phase, immune stimulation facilitates SARS-CoV-2 clearance and tissue repair, however, in the late phase, immune stimulation in COVID-19 may increase propagation risk of cytokine storm. In conclusion, LVM therapy in COVID-19 has bidirectional effects, beneficial in the early phase and harmful effects in the late phase of COVID-19. Clinical trial and prospective studies are warranted in this regard to confirm the efficacy and timing administration of LVM in the management of COVID-19.

Podocyte Glucocorticoid Receptors Are Essential for Glomerular Endothelial Cell Homeostasis in Diabetes Mellitus

Background Proteinuria and glomerular segmental fibrosis are inevitable complications of diabetic nephropathy though their mechanisms are poorly understood. Understanding the clinical characteristics and pathogenesis of proteinuria and glomerular segmental fibrosis in diabetic nephropathy is, therefore, urgently needed for patient management of this severe disease. Methods and Results Diabetes mellitus was induced in podocyte-specific glucocorticoid receptor knockout (GRPKO) mice and control littermates by administration of streptozotocin. Primary podocytes were isolated and subjected to analysis of Wnt signaling and fatty acid metabolism. Conditioned media from primary podocytes was transferred to glomerular endothelial cells. Histologic analysis of kidneys from diabetic GRPKO mice showed worsened fibrosis, increased collagen deposition, and glomerulomegaly indicating severe glomerular fibrosis. Higher expression of transforming growth factor-βR1 and β-catenin and suppressed expression of carnitine palmitoyltransferase 1A in nephrin-positive cells were found in the kidneys of diabetic GRPKO mice. Podocytes isolated from diabetic GRPKO mice demonstrated significantly higher profibrotic gene expression and suppressed fatty acid oxidation compared with controls. Administration of a Wnt inhibitor significantly improved the fibrotic features in GRPKO mice. The glomerular endothelium of diabetic GRPKO mice demonstrated the features of endothelial-to-mesenchymal transition. Moreover, endothelial cells treated with conditioned media from podocytes lacking GR showed increased expression of α-smooth muscle actin, transforming growth factor-βR1 and β-catenin levels. Conclusions These data demonstrate that loss of podocyte GR leads to upregulation of Wnt signaling and disruption in fatty acid metabolism. Podocyte-endothelial cell crosstalk, mediated through GR, is important for glomerular homeostasis, and its disruption likely contributes to diabetic nephropathy.

Construction and evaluation of novel αvβ3 integrin ligand-conjugated ultrasmall star polymer micelles targeted glomerular podocytes through GFB permeation

As glomerular cells, podocytes are the last line of defense for glomerular filtration barriers (GFB) and play a critical role in chronic kidney disease (CKD). Podocyte-targeted drug delivery is a promising direction in the treatment of CKD. In this study, we constructed four-arm star polymers conjugated with a novel linear RWrNM peptide. And poly ε-caprolactone (PCL) hydrophobic core and brush poly (2-hydroxyethyl methacrylate) (PHEMA) hydrophilic shell were synthesized by ROP and SET LRP polymerization. The PHEMA modified by succinic anhydride was coupled with the novel linear RWrNM peptide, and then the PCL hydrophobic core was loaded with dexamethasone acetate (Dexac) to form micelles with stable dimensions. Our findings showed that the novel micelles had an ultrasmall particle size of 16-30 nm. We, for the first time, showed that the specific affinity of the novel linear RWrNM peptide to primary podocytes (24.9 ± 1.7 times of the free RhB uptake) through the αvβ3 integrin receptor mediation was comparable to that of B16F10 cells (24.4 ± 1.2 times of the free RhB uptake). In vivo studies showed that the novel ultrasmall micelles possessed a significant kidney-targeted effect, excellent podocyte colocalization effect, and GFB permeability at 49%-60 % in normal SD rats. Besides, the novel ultrasmall micelles decreased the plasma elimination half-life of Dexac to 1.62-2.09 h and showed good safety in vitro and in vivo. Both in vitro and in vivo results demonstrated the novel ultrasmall micelles could be used as a promising drug delivery strategy for actively targeted therapy of CKD.

Podocyte apoptosis in diabetic nephropathy by BASP1 activation of the p53 pathway via WT1

AIMS

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease. BASP1 (brain acid-soluble protein) is up-regulated in podocyte-specific protein phosphatase 2A knockout mice (Pod-PP2A-KO) that develop kidney dysfunction. Here, we explore the role of BASP1 for podocytes in DN.

METHODS

BASP1 was assessed in kidneys from DN patients and DN mouse models, podocyte specific BASP1 knockout mice (Pod-BASP1-KO mice) were generated and studied in vivo. Furthermore, podocyte injury and apoptosis were measured after BASP1 knockdown and overexpression in a mouse podocyte cell line (MPC5). Potential signalling pathways involved in podocyte apoptosis were detected.

RESULTS

BASP1 expression was up-regulated in DN patients compared to normal controls. BASP1 specific deletion in podocytes protected against podocyte injury by reducing the loss of expression of slit diaphragm molecules and foot process effacement in the DN model. BASP1 promoted actin cytoskeleton rearrangements and apoptosis in the MPC5 podocyte line. Molecules involved in the p53 pathway were down-regulated in BASP1 knockdown podocytes treated with high glucose compared to controls. BASP1 promoted podocyte apoptosis and P53 pathway activation through co-repression with Wilms' tumour 1 transcription factor (WT1).

CONCLUSION

BASP1 activates the p53 pathway through modulation of WT1 to induce podocyte apoptosis in diabetic nephropathy.

Dysfunction of the Klotho-miR-30s/TRPC6 axis confers podocyte injury

Klotho deficiency was observed in virtually all kinds of kidney disease and is thought to play a critical role in podocyte injury. However, the underline mechanisms involved in podocyte injury remain unknown. miRNAs have diverse regulatory roles, and miR-30 family members were essential for podocyte homeostasis. Our study revealed that Klotho and miR-30s were downregulated in PAN-treated podocytes. The ectopic expression of Klotho ameliorates PAN induced podocyte apoptosis through upregulating miR-30a and downregulating Ppp3ca, Ppp3cb, Ppp3r1, and Nfact3 expression, which are the known targets of miR-30s. We also found that Klotho regulates TRPC6 via miR-30a to activate calcium/calcineurin signaling. Further, glucocorticoid (Dexamethasone, DEX) was found to sustain Klotho and miR-30a levels during PAN treatment in vitro. Eventually, in rats, PAN treatment substantially downregulated Klotho and miR-30a levels, lead to podocyte injury and increased proteinuria. The transfer of exogenous Klotho to podocytes of PAN-treated rats could increase miR-30a expression, reduce TRPC6 expression, and also ameliorated podocyte injury and proteinuria. In conclusion, Klotho, acting on miR-30s, which directly regulates its target genes, contributes to podocyte apoptosis induced by PAN. It is a novel mechanism underlying PAN-induced podocyte injury.

Injectable hydrogels of newly designed brush biopolymers as sustained drug-delivery vehicle for melanoma treatment

Novel biocompatible and brush copolymers have been developed for cancer treatment using its controlled drug-release potential. Polyurethane graft on linear dextrin has been synthesized to control the hydrophilic-hydrophobic balance for regulated drug delivery. The properties of the graft copolymers have been tuned through graft density. The prepared grafts are thermally stable and mechanically strong. An injectable hydrogel has been developed by embedding the drug-loaded brush copolymers in methyl cellulose to better control the release for a prolonged period, importantly by keeping the drug release at a constant rate. Cellular studies indicate the biocompatible nature of the brush copolymers whose controlled and slow release of drug exhibit significant cytotoxic effects on cancer cells. Endocytosis of drug tagged contrast agent indicates greater transport of biologically active material inside cell as observed through cellular uptake studies. In vivo studies on melanoma mice exhibit the real efficacy of the controlled drug release from the injectable hydrogel with significant melanoma suppression without any side effects as opposed to severe toxic effects observed in conventional chemotherapy. Special application method of drug-loaded hydrogel just beneath the tumor makes this system incredibly effective through confinement. Thus, brush copolymer injectable hydrogel is a promising vehicle for control release of drug for cancer treatment in future.

The podocyte as a direct target of glucocorticoids in nephrotic syndrome

Nephrotic syndrome (NS) is characterized by massive proteinuria; podocyte loss or altered function is a central event in its pathophysiology. Treatment with glucocorticoids is the mainstay of therapy. However, many patients experience one or multiple relapses and prolonged use may be associated with severe adverse effects. Recently, the beneficial effects of glucocorticoids have been attributed to a direct effect on podocytes in addition to the well-known immunosuppressive effects. The molecular effects of glucocorticoid action have been studied using animal and cell models of NS. This review provides a comprehensive overview of different molecular mediators regulated by glucocorticoids including an overview of the model systems that were used to study them. Glucocorticoids are described to stimulate podocyte recovery by restoring pro-survival signaling of slit diaphragm related proteins and limiting inflammatory responses. Of special interest is the effect of glucocorticoids on stabilizing the cytoskeleton of podocytes, since these effects are also described for other therapeutic agents used in NS, such as cyclosporin. Current models provide much insight, but do not fully recapitulate the human condition since the pathophysiology underlying NS is poorly understood. New and promising models include the glomerulus-on-a-chip and kidney organoids, which have the potential to be further developed into functional NS models in the future.

CD80 Insights as Therapeutic Target in the Current and Future Treatment Options of Frequent-Relapse Minimal Change Disease

Minimal change disease (MCD) is the most common cause of idiopathic nephrotic syndrome in children, and it is well known for its multifactorial causes which are the manifestation of the disease. Proteinuria is an early consequence of podocyte injury and a typical sign of kidney disease. Steroid-sensitive patients react well with glucocorticoids, but there is a high chance of multiple relapses. CD80, also known as B7-1, is generally expressed on antigen-presenting cells (APCs) in steroid-sensitive MCD patients. Various glomerular disease models associated with proteinuria demonstrated that the detection of CD80 with the increase of urinary CD80 was strongly associated closely with frequent-relapse MCD patients. The role of CD80 in MCD became controversial because one contradicts finding. This review covers the treatment alternatives for MCD with the insight of CD80 as a potential therapeutic target. The promising effectiveness of CD20 (rituximab) antibody and CD80 inhibitor (abatacept) encourages further investigation of CD80 as a therapeutic target in frequent-relapse MCD patients. Therapeutic-based antibody towards CD80 (galiximab) had never been investigated in MCD or any kidney-related disease; hence, the role of CD80 is still undetermined. A new therapeutic approach towards MCD is essential to provide broader effective treatment options besides the general immunosuppressive agents with gruesome adverse effects.

Comprehensive study of dexamethasone on albumin biogenesis during normal and pathological renal conditions

CONTEXT

Dexamethasone (DXM) has an anti-immunoinflammatory effect, and is often used in acute kidney injury (AKI). However, the effects of DXM on albumin (ALB) have not been fully studied.

OBJECTIVE

To investigate the effects of DXM on ALB production and renal function.

MATERIALS AND METHODS

Male Wistar rats were divided into normal and DXM groups (0.25, 0.5, 1 mg/kg for 5 days) (n = 15) for a dose-dependent study. Rats were divided into normal group and DXM groups (0.5 mg/kg for 3, 5, 7 days) (n = 9) for a time-dependent study. In AKI experiment, rats were divided into normal (saline), cisplatin (CP, 5 mg/kg, i.v.), CP + DXM groups (0.25, 0.5 and 1 mg/kg, i.m.) (n = 16). The blood and the organs were isolated for analysis.

RESULTS

In normal, serum ALB (sALB) and serum total protein (sTP) increased in DXM group with sALB increased 19.8-32.2% (from small to large dosages); and 30.2-32.5.6% (from 3 to 7 days of DXM); sTP 15.7-22.6% and 14.2-24.3%; urine ALB (uALB) 31.5-392.3%, and 1047.2-1390.8%; urine TP (uTP) 0.68-173.1% and 98.0-504.9%, compared with normal groups. DXM increased the mRNA expression of Cebp and Hnf, suppressing podocin. In AKI, DXM decreased serum BUN (53.7%), serum Cre (73.4%), sALB (30.0%), sTP (18.7%), uALB (74.5%), uTP (449.3%), rescuing the suppressed podocin in kidney.

CONCLUSIONS

DXM acts on Cebp and Hnf and promotes ALB production. This finding helps to evaluate the rationale of DXM for kidney injury.

Hydrogel-mediated local delivery of dexamethasone reduces neuroinflammation after traumatic brain injury

Excessive and prolonged neuroinflammation leads to neuronal cell death and limits functional recovery after traumatic brain injury (TBI). Dexamethasone (DX) is a steroidal anti-inflammatory agent that is known to attenuate early expression of pro-inflammatory cytokines associated with activated microglia/macrophages. In this study, we investigated the effect of dexamethasone-conjugated hyaluronic acid (HA-DXM) incorporated in a hydrolytically degradable, photo-cross-linkable PEG-bis-(acryloyloxy acetate) (PEG-bis-AA) hydrogel on the inflammatory response, apoptosis, and functional recovery in a controlled cortical impact (CCI) rat TBI model. In vitro, DX release from PEG-bis-AA/HA-DXM hydrogel was slow in PBS without enzymes, but significantly increased in the presence of hyauronidase/esterase enzymes. TBI was generated by a CCI device armed with a 3 mm tip (3.5 m/sec, depth: 2 mm) and treated immediately with PEG-bis-AA/HA-DXM hydrogel. PEG-bis-AA/HA hydrogel without DX was used for comparison and untreated TBI group was used as a control. Significant reductions in cavity size, inflammatory response, and apoptosis were observed in animals treated with PEG-bis-AA/HA-DXM compared to those receiving PEG-bis-AA/HA and untreated. Animals receiving the PEG-bis-AA/HA-DXM hydrogel also exhibited higher neuronal cell survival and improved motor functional recovery compared to the other two groups.

In situ evaluation of podocytes in patients with focal segmental glomerulosclerosis and minimal change disease

Podocyte injury in focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) results from the imbalance between adaptive responses that maintain homeostasis and cellular dysfunction that can culminate in cell death. Therefore, an in situ analysis was performed to detect morphological changes related to cell death and autophagy in renal biopsies from adult patients with podocytopathies. Forty-nine renal biopsies from patients with FSGS (n = 22) and MCD (n = 27) were selected. In situ expression of Wilms Tumor 1 protein (WT1), light chain microtubule 1-associated protein (LC3) and caspase-3 protein were evaluated by immunohistochemistry. The foot process effacement and morphological alterations related to podocyte cell death and autophagy were analyzed with transmission electronic microscopy. Reduction in the density of WT1-labeled podocytes was observed for FSGS and MCD cases as compared to controls. Foot process width (FPW) in control group was lower than in cases of podocytopathies. In FSGS group, FPW was significantly higher than in MCD group and correlated with proteinuria. A density of LC3-labeled podocytes and the number of autophagosomes in podocytes/ pedicels were higher in the MCD group than in the FSGS group. The number of autophagosomes correlated positively with the estimated glomerular filtration rate in cases of MCD. The density of caspase-3-labeled podocytes in FSGS and MCD was higher than control group, and a higher number of podocytes with an evidence of necrosis was detected in FSGS cases than in MCD and control cases. Podocytes from patients diagnosed with FSGS showed more morphological and functional alterations resulting from a larger number of lesions and reduced cell adaptation.

The Krüppel-like factor 15-NFATc1 axis ameliorates podocyte injury: a novel rationale for using glucocorticoids in proteinuria diseases

Podocyte injury and loss contribute to proteinuria, glomerulosclerosis and eventually kidney failure. Recent studies have demonstrated that the loss of Kruppel-like factor 15 (KLF15) in podocytes increases the susceptibility to injury; however, the mechanism underlying the protective effects on podocyte injury remains incompletely understood. Herein, we showed that KLF15 ameliorates podocyte injury through suppressing NFAT signaling and the salutary effects of the synthetic glucocorticoid dexamethasone in podocyte were partially mediated by the KLF15-NFATc1 axis. We found that KLF15 was significantly reduced in glomerular cells of proteinuric patients and in ADR-, LPS- or HG-treated podocyets in vitro. Overexpression of KLF15 attenuated podocyte apoptosis induced by ADR, LPS or HG and resulted in decreased expression of pro-apoptotic Bax and increased expression of anti-apoptotic Bcl-2. Conversely, the flow cytometry analysis and TUNEl assay demonstrated that loss of KLF15 accelerated podocyte apoptosis and we further found that 11R-VIVIT, a specific NFAT inhibitor, and NFATc1-siRNA rescued KLF15-deficient induced podocyte apoptosis. Meanwhile, Western blot and RT-qPCR showed that the expression of NFATc1 was up-regulated in KLF15 silenced podocytes and reduced in KLF15 overexpressed podocytes. Mechanistically, ChIP analysis showed that KLF15 bound to the NFATc1 promoter region -1984 to -1861base pairs upstream of the transcription start site and the binding amount was decreased after treatment with LPS. The dual-luciferase reporter assay indicated that NFATc1 was a direct target of KLF15. In addition, we found that in vitro treatment with dexamethasone induced a decrease of NFATc1 expression in podocytes and was abrogated by knockdown of KLF15. Hence, our results identify the critical role of the KLF15-NFATc1 axis in podocyte injury and loss, which may be involved in mediating the salutary effects of dexamethasone in podocytes.

Nuclear receptors in podocyte biology and glomerular disease

Nuclear receptors have a broad spectrum of biological functions in normal physiology and in the pathology of various diseases, including glomerular disease. The primary therapies for many glomerular diseases are glucocorticoids, which exert their immunosuppressive and direct podocyte protective effects via the glucocorticoid receptor (GR). As glucocorticoids are associated with important adverse effects and a substantial proportion of patients show resistance to these therapies, the beneficial effects of selective GR modulators are now being explored. Peroxisome proliferator-activated receptor-γ (PPARγ) agonism using thiazolidinediones has potent podocyte cytoprotective and nephroprotective effects. Repurposing of thiazolidinediones or identification of novel PPARγ modulators are potential strategies to treat non-diabetic glomerular disease. Retinoic acid receptor-α is the key mediator of the renal protective effects of retinoic acid, and repair of the endogenous retinoic acid pathway offers another potential therapeutic strategy for glomerular disease. Vitamin D receptor, oestrogen receptor and mineralocorticoid receptor modulators regulate podocyte injury in experimental models. Further studies are needed to better understand the mechanisms of these nuclear receptors, evaluate their synergistic pathways and identify their novel modulators. Here, we focus on the role of nuclear receptors in podocyte biology and non-diabetic glomerular disease.

Nanoparticles exhibit greater accumulation in kidney glomeruli during experimental glomerular kidney disease

Loss and dysfunction of glomerular podocytes result in increased macromolecule permeability through the glomerular filtration barrier and nephrotic syndrome. Current therapies can induce and maintain disease remission, but cause serious and chronic complications. Nanoparticle drug carriers could mitigate these side effects by delivering drugs to the kidneys more efficiently than free drug through tailoring of carrier properties. An important extrinsic factor of nanoparticle biodistribution is local pathophysiology, which may drive greater nanoparticle deposition in certain tissues. Here, we hypothesized that a "leakier" filtration barrier during glomerular kidney disease would increase nanoparticle distribution into the kidneys. We examined the effect of nanoparticle size and disease state on kidney accumulation in male BALB/c mice. The effect of size was tested using a panel of fluorescent polystyrene nanoparticles of size 20-200 nm, due to the relevance of this size range for drug delivery applications.Experimental focal segmental glomerulosclerosis was induced using an anti-podocyte antibody that causes abrupt podocyte depletion. Nanoparticles were modified with carboxymethyl-terminated poly(ethylene glycol) for stability and biocompatibility. After intravenous injection, fluorescence from nanoparticles of size 20 and 100 nm, but not 200 nm, was observed in kidney glomeruli and peritubular capillaries. During conditions of experimental focal segmental glomerulosclerosis, the number of fluorescent nanoparticle punctae in kidney glomeruli increased by 1.9-fold for 20 and 100 nm nanoparticles compared to normal conditions. These findings underscore the importance of understanding and leveraging kidney pathophysiology in engineering new, targeted drug carriers that accumulate more in diseased glomeruli to treat glomerular kidney disease.

Tripterygium glycoside fraction n2 ameliorates adriamycin-induced nephrotic syndrome in rats by suppressing apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium wilfordii Hook F. (TwHF), a traditional Chinese herb medicine, has been widely used for clinical treatment of various rheumatic immune diseases. Tripterygium glycosides (TG) extracted from TwHF has been verified to process multiple bioactivities, including immunosuppressive, anti-inflammatory and anti-cancer effects. However, the clinical application of TG is limited due to its severe toxicity and narrow therapeutic window. For the clinical safety of TG usage, attenuation of toxicity is the key issue to be solved.

PURPOSE

Tripterygium glycoside fraction n2 (TG-n2) is a detoxified mixture obtained from TG using a new preparation method. In our previous study, we have demonstrated that TG-n2 has a lower toxicity than TG. The aim of the present study was to screen the renal protective effect of TG-n2 in nephrotic syndrome (NS) induced by adriamycin (ADR) in rats and its effect on apoptosis, as well as the effective difference between TG-n2 and TG.

MATERIALS AND METHODS

The ADR-induced NS rat model was established. Rats were intravenously injected with ADR (6 mg/kg), then treated with either TG-n2 (10 mg/kg/day) or TG (10 mg/kg/day) by oral gavage for 4 weeks. Clinical indexes in each group were determined. HE staining and electron microscopic analysis were used to evaluate renal histopathological damage. Caspase-3 activity reagent and TUNEL staining were used to estimate renal apoptosis. Protein levels of caspase-3, caspase-9, caspase-8, caspase-12, Bax, Bcl-2, p53, TNF-R1, FLIP and podocin were measured by Western Blot.

RESULTS

TG-n2 and TG intervention ameliorated renal function as assessed by the levels of 24-h proteinuria, Cr, BUN, TC, TG, ALB and LDL-c. TG-n2 and TG alleviated the decrease of podocin protein expression and morphological injury of podocyte as screened by Western Blot and electron microscopic analysis. Besides, renal tubular injury was reduced as inspected by light microscopic analysis. TG-n2 and TG could significantly inhibit the apoptosis and activity of caspase-3 in kidney tissues as examined by fluorescence microscopic analysis and reagent. After intervention of TG-n2 and TG, protein levels of cleaved caspase-3, cleaved caspase-8, cleaved caspase-9, Bax, p53 and TNF-R1 in renal issues were significantly decreased compared with ADR group. In contrast, protein level of Bcl-2 was elevated remarkedly.

CONCLUSIONS

Our data suggested that attenuated TG-n2 may have a similar protective effect with TG in ADR-induced NS in rats by inhibiting activation of apoptosis.

Transcription factor 21 expression in injured podocytes of glomerular diseases

Transcription factor 21 (TCF21) is one of the essential transcription factors in kidney development. To elucidate its influence on glomerular disease, we have investigated TCF21 expression in human and rat kidney tissue, and its urinary concentration. Immunohistological analysis suggested the highest TCF21 expression in nephrotic syndrome along with the urinary protein level. Urinary TCF21 concentration in human showed a positive correlation with its podocyte expression level. In nephrotic rat models, TCF21 expression in podocytes increased along with the severity of nephrotic syndrome. Next, in vitro experiments using Tcf21-expressing murine podocyte cell line, we could observe some Tcf21-dependent effects, related with actin cytoskeleton dysregulation and apoptosis. Our study illustrated TCF21 expression changes in vivo and its in vitro-functional significance injured podocytes.

Treatment of nephrotic syndrome: going beyond immunosuppressive therapy

It is indisputable that immunosuppressive therapy and pathological diagnosis of renal biopsy have greatly improved the prognosis of childhood nephrotic syndrome. Unfortunately, there is no "one-size-fits-all" approach for precise patient stratification and treatment when facing the huge challenges posed by steroid-resistant nephrotic syndrome (SRNS). But genomic medicine has brought a glimmer of light, and the cognition of SRNS has entered a new stage. Based on this, identification of single genetic variants of SRNS has recognized the key role of podocyte injury in its pathogenesis. Targeted treatment of podocyte injury is paramount, and immunosuppressant with podocyte-targeted therapy seems to be more suitable as the first choice for SRNS, that is, we need to pay attention to their additional non-immunosuppressive effects. In the same way, other effect factors of nephrotic syndrome and the related causes of immunosuppressive therapy resistance require us to select reasonable and targeted non-immunosuppressive therapies, instead of only blindly using steroids and immunosuppressants, which may be ineffective and bring significant side effects. This article provides a summary of the clinical value of identification of genetic variants in podocytes and non-immunosuppressive therapy for nephrotic syndrome in children.

Melatonin inhibits apoptosis in mouse Leydig cells via the retinoic acid-related orphan nuclear receptor α/p53 pathway

Melatonin is an endogenous indoleamine hormone involved in various physiological processes. However, the mechanism of melatonin in mediating Leydig cells function has not been fully explained. In this study, we investigated the mechanism through which melatonin inhibits apoptosis in mouse Leydig cells by activating the retinoic acid-related orphan nuclear receptor (ROR) α/p53 signaling pathway. We confirmed the expression and localization of RORα in mouse Leydig cells using immunofluorescence. After treatment with 10 ng/mL melatonin for 36 h, RORα mRNA and protein levels were significantly increased (P < 0.01). TUNEL and flow cytometry showed that melatonin significantly decreased the TUNEL-positive cell ratio and apoptosis rate (P < 0.05). Moreover, melatonin decreased BAX expression and increased BCL-2 expression (P < 0.05). However, the RORα inhibitor SR1001 reversed the inhibitory effects of melatonin on apoptosis (P < 0.05). Additionally, analysis of p53 expression showed that melatonin inhibited p53 mRNA and protein expression (P < 0.05), whereas SR1001 reversed these effects. p53 reversed the anti-apoptotic process involving RORα-mediated melatonin in mouse Leydig cells. Collectively, our findings suggested that melatonin inhibited apoptosis via the RORα/p53 pathway.

The impact of steroids on the injured podocytes in nephrotic syndrome

Nephrotic syndrome (NS), a common chronic kidney disease, embraces a variety of kidney disorders. Though Glucocorticoids (GCs) are generally used in the treatment of NS, their mechanism of action is poorly understood. A plethora of evidence indicates that podocytes are considered as the main target cells for the therapeutic strategies to prevent NS. GCs regulate the transactivation and transrepression of genes in podocytes that affect their morphological and cytoskeletal features, motility, apoptosis and survival rate. Moreover, they prevent protein leakage through the glomerular barrier membrane by affecting the synthesis, trafficking and posttranslational modifications of slit diaphragms components, podocytes' intercellular junctions. The response to the treatment is variable among different ethnics and populations and resistance to the steroids is detected in almost 50% of adult patients. Not only do pharmacokinetics and pharmacogenetics of steroids play a role in GC resistance but also the genetic variations in one or more podocyte related genes are connected with the steroid resistance in cases with NS. The focus of this review is to explain the underlying cellular and molecular mechanisms of GCs in podocytes. Understanding the mechanisms by which the GCs and GCs receptors in podocytes regulate the gene expression network and crosstalk with other molecular pathways would guarantee an optimum therapeutic benefit of steroid treatment.

Morphological Features of Minimal Change Disease and Focal Segmental Glomerulosclerosis Using Repeat Biopsy and Parietal Epithelial Cell Marker

Introduction

Minimal change disease (MCD) and primary focal segmental glomerulosclerosis (FSGS) are representative podocyte diseases. The clinical cause of MCD and FSGS has not been clearly elucidated yet. However, it is important to distinguish MCD and FSGS because their prognoses and responses to treatment are quite different.

Objective

This study aimed to examine whether parietal epithelial cell (PEC) marker and repeat biopsy are useful for diagnosing primary FSGS.

Methods

Clinicopathological features of 17 patients with the nephrotic syndrome, who underwent kidney biopsy ≥2 times from 1975 to 2017, and had MCD or FSGS were analyzed using PAX8. We defined patients with PAX8+ cells as PAX8+ and the remainder as PAX8- patients. Three cases of sample insufficiency and 1 non-steroid-resistant or frequently relapsing case indicated for repeat biopsy were excluded.

Results

Among the 13 patients studied, 4 were PAX8+ and 9 were PAX8- (median age: 41 and 46 years, -respectively, at first biopsy). PAX8+ and PAX8- patients showed no significant differences in clinical data and histological diagnosis except for a significant difference in histological diagnosis at the second biopsy. The number of PAX8+ patients increased to 6. Unlike the first biopsy results, FSGS was present in 5 of 6 (83.3%) PAX8+ patients; MCD occurred in all 7 (100%) PAX8- patients. Three of 6 (50.0%) PAX8+ patients undergoing repeat biopsy were steroid resistant; no (0%) PAX8- patient was steroid resistant. All cases of final FSGS diagnosis were PAX8+ at the first or second biopsy. Only 1 PAX8+ MCD patient was steroid resistant. All PAX8- MCD patients were frequently relapsing.

Conclusions

More PAX8+ patients were diagnosed with FSGS than PAX8- patients. Clinical presentation of MCD in PAX8- patients was frequently relapsing. PEC marker staining in patients with the nephrotic syndrome, e.g., MCD, may help to diagnose FSGS.

Treatment of steroid-resistant nephrotic syndrome in the genomic era

The pathogenesis of steroid-resistant nephrotic syndrome (SRNS) is not completely known. Recent advances in genomics have elucidated some of the molecular mechanisms and pathophysiology of the disease. More than 50 monogenic causes of SRNS have been identified; however, these genes are responsible for only a small fraction of SRNS in outbred populations. There are currently no guidelines for genetic testing in SRNS, but evidence from the literature suggests that testing should be guided by the genetic architecture of the disease in the population. Notably, most genetic forms of SRNS do not respond to current immunosuppressive therapies; however, a small subset of patients with monogenic SRNS will achieve partial or complete remission with specific immunomodulatory agents, presumably due to non-immunosuppressive effects of these agents. We suggest a pragmatic approach to the therapy of genetic SRNS, as there is no evidence-based algorithm for the management of the disease.

Geniposide alleviates lipopolysaccharide-caused apoptosis of murine kidney podocytes by activating Ras/Raf/MEK/ERK-mediated cell autophagy

Proteinuria is one of the most important clinical features of nephrotic syndrome (NS). Injury of podocyte has been proved to contribute to the occurrence of proteinuria. This study explored the effects of geniposide (GEN) on lipopolysaccharide (LPS)-caused murine kidney podocyte MPC5 apoptosis and autophagy. Viability and apoptosis of MPC5 cells were respectively detected with the help of CCK-8 assay and Guava Nexin assay. 3-Methyladenine (3-MA) was used as an autophagy inhibitor, while rapamycin as autophagy activator. Si-Beclin-1 was transfected in MPC5 cells to down-regulate the expression of Beclin-1. We found that LPS stimulation significantly caused MPC5 cell viability reduction, apoptosis and autophagy (P < .05 or P < .01). GEN treatment remarkably alleviated the LPS-caused MPC5 cell viability reduction and apoptosis, but promoted cell autophagy (P < .05). Moreover, 3-MA incubation or si-Beclin-1 transfection notably weakened the effects of GEN on LPS-caused MPC5 cell apoptosis and autophagy (P < .05), while rapamycin had opposite effects (P < .05). Furthermore, GEN activated Ras/Raf/MEK/ERK pathway in LPS-treated MPC5 cells (P < .05). In conclusion, this research verified the protective effects of GEN on podocytes damage. GEN alleviates LPS-caused apoptosis of murine kidney podocytes by activating Ras/Raf/MEK/ERK-mediated cell autophagy. Highlights: LPS causes podocyte MPC5 apoptosis and autophagy. GEN alleviates LPS-caused MPC5 cell apoptosis, but promotes cell autophagy. 3-MA or si-Beclin-1 weakens the effects of GEN on LPS-treated MPC5 cells. Rapamycin strengthens the effects of GEN on LPS-treated MPC5 cells. GEN activates Ras/Raf/MEK/ERK pathway in LPS-treated MPC5 cells.

Levamisole in Children with Idiopathic Nephrotic Syndrome: Clinical Efficacy and Pathophysiological Aspects

Steroid sensitive nephrotic syndrome is one of the most common pediatric glomerular diseases. Unfortunately, it follows a relapsing and remitting course in the majority of cases, with 50% of all cases relapsing once or even more often. Most children with idiopathic nephrotic syndrome respond initially to steroid therapy, nevertheless repeated courses for patients with relapses induce significant steroid toxicity. Patients with frequent relapses or steroid dependency thus require alternative treatment, such as cyclophosphamide, cyclosporine, tacrolimus, mycophenolate mofetil, levamisole, or rituximab. To reduce the relapse rate, several drugs have been used. Among these, levamisole has been considered the least toxic and least expensive therapy. Several randomized controlled trials (RCT) showed that levamisole is effective in reducing the relapse risk in steroid sensitive forms of nephrotic syndrome with a low frequency of side effects. Levamisole is a synthetic imidazothiazole derivative with immune-modulatory properties. In this article, we review recent data from randomized trials and observational studies to assess the efficacy of levamisole in frequently relapsing nephrotic syndrome and steroid-dependent nephrotic syndrome.

Pharmacology and pharmacogenetics of prednisone and prednisolone in patients with nephrotic syndrome

Nephrotic syndrome is one of the most common glomerular disorders in childhood. Glucocorticoids have been the cornerstone of the treatment of childhood nephrotic syndrome for several decades, as the majority of children achieves complete remission after prednisone or prednisolone treatment. Currently, treatment guidelines for the first manifestation and relapse of nephrotic syndrome are mostly standardized, while large inter-individual variation is present in the clinical course of disease and side effects of glucocorticoid treatment. This review describes the mechanisms of glucocorticoid action and clinical pharmacokinetics and pharmacodynamics of prednisone and prednisolone in nephrotic syndrome patients. However, these mechanisms do not account for the large inter-individual variability in the response to glucocorticoid treatment. Previous research has shown that genetic factors can have a major influence on the pharmacokinetic and dynamic profile of the individual patient. Therefore, pharmacogenetics may have a promising role in personalized medicine for patients with nephrotic syndrome. Currently, little is known about the impact of genetic polymorphisms on glucocorticoid response and steroid-related toxicities in children with nephrotic syndrome. Although the evidence is limited, the data summarized in this study do suggest a role for pharmacogenetics to improve individualization of glucocorticoid therapy. Therefore, studies in larger cohorts with nephrotic syndrome patients are necessary to draw final conclusions about the influence of genetic polymorphisms on the glucocorticoid response and steroid-related toxicities to ultimately implement pharmacogenetics in clinical practice.

Differential toxicities of triptolide to immortalized podocytes and the podocytes in vivo

Triptolide (TP) has an anti-proteinuric effect and is used for the treatment of podocytopathies. TP has also been shown to act directly on immortalized podocytes in culture to protect them from injury. In the present study, we examined the effect of TP on healthy podocytes both in vitro and in vivo to better understand the action of TP on podocytes. We found that treatment of TP at 10 ng/ml, a concentration that is routinely used for podocyte protection, was sufficient to activate pro-apoptotic signaling of MAPK p38, p53 and BAX and induced apoptosis in cultured podocytes; and higher concentrations of TP exacerbated the p38, p53 and BAX activations and apoptosis. Moreover, TP severely downregulated the genes that are essential for podocyte structure and function. Interestingly, in contrast with other agents TP-induced podocyte injury was not prevented by glucocorticoids. In vivo, high-dose TP treatment for prolonged time did not cause podocyte injury, essential genes downregulation, and proteinuria in mice. TP was also not toxic to the podocytes with isolated glomeruli ex vivo. In summary, TP is toxic to immortalized podocytes in culture but not to the podocytes in animals or isolated glomeruli ex vivo. Our study suggests that immortalized podocytes might have genetically evolved to become sensitive to TP toxicity and thus caution should be taken in interpreting data from immortalized podocytes. Nevertheless, in vivo TP could be as safe as glucocorticoids in treating podocytopathies. Finally, TP may be used as a unique in vitro model for studying steroid-resistant podocytopathies.

The Role of Glucocorticoid Receptors in Podocytes and Nephrotic Syndrome

Glucocorticoid receptor (GC), a founding member of the nuclear hormone receptor superfamily, is a glucocorticoid-activated transcription factor that regulates gene expression and controls the development and homeostasis of human podocytes. Synthetic glucocorticoids are the standard treatment regimens for proteinuria (protein in the urine) and nephrotic syndrome (NS) caused by kidney diseases. These include minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), membranous nephropathy (MN) and immunoglobulin A nephropathy (IgAN) or subsequent complications due to diabetes mellitus or HIV infection. However, unwanted side effects and steroid-resistance remain major issues for their long-term use. Furthermore, the mechanism by which glucocorticoids elicit their renoprotective activity in podocyte and glomeruli is poorly understood. Podocytes are highly differentiated epithelial cells that contribute to the integrity of kidney glomerular filtration barrier. Injury or loss of podocytes leads to proteinuria and nephrotic syndrome. Recent studies in multiple experimental models have begun to explore the mechanism of GC action in podocytes. This review will discuss progress in our understanding of the role of glucocorticoid receptor and glucocorticoids in podocyte physiology and their renoprotective activity in nephrotic syndrome.

Effects of Panax notoginseng saponins on severe acute pancreatitis through the regulation of mTOR/Akt and caspase-3 signaling pathway by upregulating miR-181b expression in rats

BACKGROUND

In China, Panax notoginseng has been used to treat oxidative stress-related diseases for a long time. Panax notoginseng saponins is an extract from Panax notoginseng Ledeb. Its therapeutic potential is related to antioxidant activity, but related mechanisms are still unclear. The study aims to assess the protection effects of Panax notoginseng saponins in the taurocholate-induced rat model of acute pancreatitis (AP) and explore underlying mechanisms.

METHODS

A rat model of severe acute pancreatitis (SAP) was established in rats induced with taurocholate. Panax notoginseng saponins was firstly administered in the treatment group via intravenous injection. After 2 h, taurocholate administration was performed. After 24 h, the expression levels of miR-181b, Beclin1, LC3-II, Akt and mTOR from pancreas tissues were measured by Western Blotting and RT-PCR. Then the expression levels of Caspase-3 and Blc-2 were determined by immunohistochemistry. Apoptosis was assessed by the TUNEL assay. Amylase and lipase in serum were determined by ELISA and pancreatic water contents in pancreatic tissue were measured. After eosin and hematoxylin staining, the histologic analysis was performed.

RESULTS

After SAP induction by taurocholate and the treatment with Panax notoginseng saponins for 24 h, we detected the up-regulated miR-181b, the reduced Bcl-2 expression, the increased activity of mTOR/Akt, the blocked Beclin1 and LC3-II expressions, and the enhanced Caspase-3 expression. Serum lipase and amylase levels were significantly decreased in the treatment group of Panax notoginseng saponins compared to the control group. Histological analysis results verified the attenuation effects of Panax notoginseng saponins on taurocholate-induced pancreas injury, apoptosis, and autophagy.

CONCLUSION

By up-regulating the miR-181b expression level, Panax notoginseng saponins significantly reduced taurocholate-induced pancreas injury and autophagy and increased apoptosis. The significant protection effects of Panax notoginseng saponins suggested its potential in treating taurocholate induced-acute pancreatitis.

HIV Infection in the Native and Allograft Kidney: Implications for Management, Diagnosis, and Transplantation

The native kidney is a reservoir for human immunodeficiency virus (HIV)-1 and a site of viral replication, similar to lymphoid tissue, gut-associated lymphoid tissue or semen. The ability of the virus to persist may result from either a true latency or sequestration in an anatomic site that is not effectively exposed to antiretroviral therapy. The presence of HIV in kidney epithelial cells will lead progressively to end-stage renal disease. For decades, HIV-infected patients were excluded from consideration for kidney transplantation. Hemodialysis and peritoneal dialysis were the only forms of treatment available to these patients. The introduction of combined antiretroviral therapy has changed the overall prognosis of these patients and allowed them to benefit from kidney transplantation without an increased risk of opportunistic infections or cancer. However, we recently established that HIV-1 can infect kidney transplant epithelial cells in the absence of detectable viremia. The presence of HIV in kidney cells can manifest itself in multiple ways, ranging from indolent nephropathy and inflammation to proteinuria with glomerular abnormalities. Because the tools that are available to diagnose the presence of HIV in kidney cells are complex, the rate of infection is certainly underestimated. This finding will certainly have implications in the management of patients, particularly for HIV-positive donors. The purpose of this review is to highlight recent evidence that the allograft kidney can be infected by the virus after transplantation as well as the associated consequences.

Loss of the podocyte glucocorticoid receptor exacerbates proteinuria after injury

Nephrotic syndrome is a common disorder in adults and children whose etiology is largely unknown. Glucocorticoids remain the mainstay of therapy in most cases, though their mechanism of action remains poorly understood. Emerging evidence suggests that immunomodulatory therapies used in nephrotic syndrome directly target the podocytes. To study how steroids directly affect the podocytes in the treatment of proteinuria, we created a mouse model with podocyte-specific deletion of the glucocorticoid receptor. The podocyte-specific glucocorticoid receptor (GR) knockout mice had similar renal function and protein excretion compared to wild type. However, after glomerular injury induced by either LPS or nephrotoxic serum, the podocyte GR knockout mice demonstrated worsened proteinuria compared to wild type. Ultrastructural examination of podocytes confirmed more robust foot process effacement in the knockout animals. Expression of several key slit diaphragm protein was down regulated in pGR KO mice. Primary podocytes isolated from wild type and podocyte GR knockout mice showed similar actin stress fiber staining patterns in unstimulated conditions. Yet, when exposed to LPS, GR knockout podocytes demonstrated fewer stress fibers and impaired migration compared to wild type podocytes. We conclude that the podocyte glucocorticoid receptor is important for limiting proteinuria in settings of podocyte injury.

p53/Drp1-dependent mitochondrial fission mediates aldosterone-induced podocyte injury and mitochondrial dysfunction

Mitochondrial dysfunction is increasingly recognized as an important factor in glomerular diseases. Previous study has shown that mitochondrial fission contributed to mitochondrial dysfunction. However, the mechanism of mitochondrial fission on mitochondrial dysfunction in aldosterone-induced podocyte injury remains ambiguous. This study aimed to investigate the pathogenic effect of mitochondrial fission both in vivo and in vitro. In an animal model of aldosterone-induced nephropathy, inhibition of the mitochondrial fission protein dynamin-related protein 1 (Drp1) suppressed aldosterone-induced podocyte injury. In cultured podocytes, aldosterone dose dependently induced Drp1 expression. Knockdown of Drp1 inhibited aldosterone-induced mitochondrial fission, mitochondrial dysfunction, and podocyte apoptosis. Furthermore, aldosterone dose dependently induced p53 expression. Knockdown of p53 inhibited aldosterone-induced Drp1 expression, mitochondrial dysfunction, and podocyte apoptosis. These findings implicated that aldosterone induced mitochondrial dysfunction and podocyte injury mediated by p53/Drp1-dependent mitochondrial fission, which may provide opportunities for therapeutic intervention for podocyte injury.

A High-Content Screening Technology for Quantitatively Studying Podocyte Dynamics

Podocytes form the visceral layer of a kidney glomerulus and express a characteristic octopus-like cellular architecture specialized for the ultrafiltration of blood. The cytoskeletal dynamics and structural elasticity of podocytes rely on the self-organization of highly interconnected actin bundles, and the maintenance of these features is important for the intact glomerular filtration. Development of more differentiated podocytes in culture has dramatically increased our understanding of the molecular mechanisms regulating podocyte actin dynamics. Podocytes are damaged in a variety of kidney diseases, and therapies targeting podocytes are being investigated with increasing efforts. Association between podocyte damage and disease severity-or between podocyte recovery and the performance of therapeutic molecules-have been the venues of research for years. In this perspective, more standardized high--content screening has emerged as a powerful tool for visualization and analysis of podocyte morphology. This high-throughput fluorescence microscopy technique is based on an automated image analysis with simultaneous detection of various phenotypes (multiplexing) across multiple phenotypic parameters (multiparametric). Here, we review the principles of high-content screening technology and summarize efforts to carry out small compound screen using podocytes.

Albumin-based nanoparticles as methylprednisolone carriers for targeted delivery towards the neonatal Fc receptor in glomerular podocytes

Glucocorticoids (GCs) are commonly used in the treatment of nephrotic syndrome. However, high doses and long periods of GC therapy can result in severe side effects. The present study aimed to selectively deliver albumin-methylprednisolone (MP) nanoparticles towards glomerular podocytes, which highly express the specific neonatal Fc receptor (FcRn) of albumin. Bovine serum albumin (BSA) was labeled with a fluorescent dye and linked with modified MP via an amide bond. The outcome nanoparticle named BSA633-MP showed a uniform size with a diameter of approximately 10 nm and contained 12 drug molecules on average. The nanoconjugates were found to be stable at pH 7.4 and acid-sensitive at pH 4.0, with approximately 72% release of the MP drug after 48 h of incubation. The nanoparticle demonstrated a 36-fold uptake in receptor-specific cellular delivery in the FcRn-expressing human podocytes compared to the uptake in the non-FcRn-expressing control cells. Co-localization further confirmed that uptake of the nanoconjugates involved receptor-mediated endocytosis followed by lysosome associated transportation. In vitro cellular experiments indicated that the BSA633-MP ameliorated puromycin aminonucleoside-induced podocyte apoptosis. Moreover, in vivo fluorescence molecular imaging showed that BSA633-MP was mainly accumulated in the liver and kidney after intravenous dosing for 24 h. Collectively, this study may provide an approach for the effective and safe therapy of nephrotic syndrome.

Notoginsenoside R1 attenuates glucose-induced podocyte injury via the inhibition of apoptosis and the activation of autophagy through the PI3K/Akt/mTOR signaling pathway

Injury to terminally differentiated podocytes contributes ignificantly to proteinuria and glomerulosclerosis. The aim of this study was to examine the protective effects of notoginsenoside R1 (NR1) on the maintenance of podocyte number and foot process architecture via the inhibition of apoptosis, the induction of autophagy and the maintenance pf podocyte biology in target cells. The effects of NR1 on conditionally immortalized human podocytes under high glucose conditions were evaluated by determining the percentage apoptosis, the percentage autophagy and the expression levels of slit diaphragm proteins. Our results revealed that NR1 protected the podocytes against high glucose-induced injury by decreasing apoptosis, increasing autophagy and by promoting cytoskeletal recovery. The phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway was further investigated in order to elucidate the mechanisms responsible for the protective effects of NR1 on podocytes. Our data indicated that treatment with NR increased the phosphorylation levels of PI3K, Akt and mTOR, leading to the activation of the PI3K/Akt/mTOR signaling pathway in podocytes. To the best of our knowledge, this is the first in vitro study to demonstrate that NR1 protects podocytes by activating the PI3K/Akt/mTOR pathway.

α Actinin 4 (ACTN4) Regulates Glucocorticoid Receptor-mediated Transactivation and Transrepression in Podocytes

Glucocorticoids are a general class of steroids that possess renoprotective activity in glomeruli through their interaction with the glucocorticoid receptor. However, the mechanisms by which glucocorticoids ameliorate proteinuria and glomerular disease are not well understood. In this study, we demonstrated that α actinin 4 (ACTN4), an actin-cross-linking protein known to coordinate cytoskeletal organization, interacts with the glucocorticoid receptor (GR) in the nucleus of human podocytes (HPCs), a key cell type in the glomerulus critical for kidney filtration function. The GR-ACTN4 complex enhances glucocorticoid response element (GRE)-driven reporter activity. Stable knockdown of ACTN4 by shRNA in HPCs significantly reduces dexamethasone-mediated induction of GR target genes and GRE-driven reporter activity without disrupting dexamethasone-induced nuclear translocation of GR. Synonymous mutations or protein expression losses in ACTN4 are associated with kidney diseases, including focal segmental glomerulosclerosis, characterized by proteinuria and podocyte injury. We found that focal segmental glomerulosclerosis-linked ACTN4 mutants lose their ability to bind liganded GR and support GRE-mediated transcriptional activity. Mechanistically, GR and ACTN4 interact in the nucleus of HPCs. Furthermore, disruption of the LXXLL nuclear receptor-interacting motif present in ACTN4 results in reduced GR interaction and dexamethasone-mediated transactivation of a GRE reporter while still maintaining its actin-binding activity. In contrast, an ACTN4 isoform, ACTN4 (Iso), that loses its actin-binding domain is still capable of potentiating a GRE reporter. Dexamethasone induces the recruitment of ACTN4 and GR to putative GREs in dexamethasone-transactivated promoters, SERPINE1, ANGPLT4, CCL20, and SAA1 as well as the NF-κB (p65) binding sites on GR-transrepressed promoters such as IL-1β, IL-6, and IL-8 Taken together, our data establish ACTN4 as a transcriptional co-regulator that modulates both dexamethasone-transactivated and -transrepressed genes in podocytes.

Investigations of Glucocorticoid Action in GN

For several decades, glucocorticoids have been used empirically to treat rapid progressive GN. It is commonly assumed that glucocorticoids act primarily by dampening the immune response, but the mechanisms remain incompletely understood. In this study, we inactivated the glucocorticoid receptor (GR) specifically in kidney epithelial cells using Pax8-Cre/GR^fl/fl mice. Pax8-Cre/GR^fl/fl mice did not exhibit an overt spontaneous phenotype. In mice treated with nephrotoxic serum to induce crescentic nephritis (rapidly progressive GN), this genetic inactivation of the GR in kidney epithelial cells exerted renal benefits, including inhibition of albuminuria and cellular crescent formation, similar to the renal benefits observed with high-dose prednisolone in control mice. However, genetic inactivation of the GR in kidney epithelial cells did not induce the immunosuppressive effects observed with prednisolone. In vitro, prednisolone and the pharmacologic GR antagonist mifepristone each acted directly on primary cultures of parietal epithelial cells, inhibiting cellular outgrowth and proliferation. In wild-type mice, pharmacologic treatment with the GR antagonist mifepristone also attenuated disease as effectively as high-dose prednisolone without the systemic immunosuppressive effects. Collectively, these data show that glucocorticoids act directly on activated glomerular parietal epithelial cells in crescentic nephritis. Furthermore, we identified a novel therapeutic approach in crescentic nephritis, that of glucocorticoid antagonism, which was at least as effective as high-dose prednisolone with potentially fewer adverse effects.

The critical role of Krüppel-like factors in kidney disease

Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors critical to mammalian embryonic development, regeneration, and human disease. There is emerging evidence that KLFs play a vital role in key physiological processes in the kidney, ranging from maintenance of glomerular filtration barrier to tubulointerstitial inflammation to progression of kidney fibrosis. Seventeen members of the KLF family have been identified, and several have been well characterized in the kidney. Although they may share some overlap in their downstream targets, their structure and function remain distinct. This review highlights our current knowledge of KLFs in the kidney, which includes their pattern of expression and their function in regulating key biological processes. We will also critically examine the currently available literature on KLFs in the kidney and offer some key areas in need of further investigation.