Puromycin Aminonucleoside Research Articles

Protective Effect of Salvia Przewalskii Extract on Puromycin-Induced Podocyte Injury

Background: To determine the effect of Salvia przewalskii extract (SPE) from total phenolic acids on puromycin aminonucleoside (PAN)-induced rat podocyte injury. Methods: The rats were divided into groups that were treated with either PAN only or PAN followed by tacrolimus or SPE. We evaluated the effects of SPE on podocyte injury 5, 10, 15 and 21 days following treatment. Results: (1) Proteinuria was observed starting on day 5 in all groups. The peak levels of proteinuria differed among the groups with tacrolimus and high-dose SPE, which significantly decreased proteinuria relative to the PAN and low- and medium-dose SPE groups. The proteinuria in each group decreased by day 15 and returned to a normal level by day 21. (2) H&E and PAS staining revealed no abnormality in glomerular morphology. With electron microscopy, we observed foot process effacement in the rats of all groups starting on day 5, but rats in the tacrolimus and high-dose SPE groups exhibited a lower degree. (3) IHC staining of nephrin and podocin revealed unaffected expression and better linear distributions in the high-dose SPE and tacrolimus groups. Western blot analysis confirmed that SPE could improve the expression of proteins. (4) The mRNA levels of nephrin and podocin in the tacrolimus and high-dose SPE groups were significantly higher than that in the others. Conclusion: In our study, we first demonstrated the ability of SPE to reduce proteinuria, preserve the morphology and structure of podocytes and retain the levels of slit diaphragm proteins on PAN-induced rat podocytes injury.

MicroRNA-30 family members regulate calcium/calcineurin signaling in podocytes.

Calcium/calcineurin signaling is critical for normal cellular physiology. Abnormalities in this pathway cause many diseases, including podocytopathy; therefore, understanding the mechanisms that underlie the regulation of calcium/calcineurin signaling is essential. Here, we showed that critical components of calcium/calcineurin signaling, including TRPC6, PPP3CA, PPP3CB, PPP3R1, and NFATC3, are the targets of the microRNA-30 family (miR-30s). We found that these 5 genes are highly expressed as mRNA, but the level of the proteins is low in normal podocytes. Conversely, protein levels were markedly elevated in podocytes from rats treated with puromycin aminonucleoside (PAN) and from patients with focal segmental glomerulosclerosis (FSGS). In both FSGS patients and PAN-treated rats, miR-30s were downregulated in podocytes. In cultured podocytes, PAN or a miR-30 sponge increased TRPC6, PPP3CA, PPP3CB, PPP3R1, and NFATC3 expression; calcium influx; intracellular Ca2+ concentration; and calcineurin activity. Moreover, NFATC3 nuclear translocation, synaptopodin degradation, integrin β3 (ITGB3) activation, and actin fiber loss, which are downstream of calcium/calcineurin signaling, were induced by miR-30 reduction but blocked by the calcineurin inhibitor FK506. Podocyte-specific expression of the miR-30 sponge in mice increased calcium/calcineurin pathway component protein expression and calcineurin activity. The mice developed podocyte foot process effacement and proteinuria, which were prevented by FK506. miR-30s also regulated calcium/calcineurin signaling in cardiomyocytes. Together, our results identify miR-30s as essential regulators of calcium/calcineurin signaling.

Editorial: Podocyte Pathology and Nephropathy.

Editorial: Podocyte Pathology and Nephropathy.

Everolimus Stabilizes Podocyte Microtubules via Enhancing TUBB2B and DCDC2 Expression.

BackgroundGlomerular podocytes are highly differentiated cells that are key components of the kidney filtration units. The podocyte cytoskeleton builds the basis for the dynamic podocyte cytoarchitecture and plays a central role for proper podocyte function. Recent studies implicate that immunosuppressive agents including the mTOR-inhibitor everolimus have a protective role directly on the stability of the podocyte actin cytoskeleton. In contrast, a potential stabilization of microtubules by everolimus has not been studied so far.MethodsTo elucidate mechanisms underlying mTOR-inhibitor mediated cytoskeletal rearrangements, we carried out microarray gene expression studies to identify target genes and corresponding pathways in response to everolimus. We analyzed the effect of everolimus in a puromycin aminonucleoside experimental in vitro model of podocyte injury.ResultsUpon treatment with puromycin aminonucleoside, microarray analysis revealed gene clusters involved in cytoskeletal reorganization, cell adhesion, migration and extracellular matrix composition to be affected. Everolimus was capable of protecting podocytes from injury, both on transcriptional and protein level. Rescued genes included tubulin beta 2B class IIb (TUBB2B) and doublecortin domain containing 2 (DCDC2), both involved in microtubule structure formation in neuronal cells but not identified in podocytes so far. Validating gene expression data, Western-blot analysis in cultured podocytes demonstrated an increase of TUBB2B and DCDC2 protein after everolimus treatment, and immunohistochemistry in healthy control kidneys confirmed a podocyte-specific expression. Interestingly, Tubb2b brdp/brdp mice revealed a delay in glomerular podocyte development as showed by podocyte-specific markers Wilm’s tumour 1, Podocin, Nephrin and Synaptopodin.ConclusionsTaken together, our study suggests that off-target, non-immune mediated effects of the mTOR-inhibitor everolimus on the podocyte cytoskeleton might involve regulation of microtubules, revealing a potential novel role of TUBB2B and DCDC2 in glomerular podocyte development.

Sialic acid supplementation ameliorates puromycin aminonucleoside nephrosis in rats

Defects in sialylation are known to have serious consequences on podocyte function leading to collapse of the glomerular filtration barrier and the development of proteinuria. However, the cellular processes underlying aberrant sialylation in renal disease are inadequately defined. We have shown in cultured human podocytes that puromycin aminonucleoside (PAN) downregulates enzymes involved in sialic acid metabolism and redox homeostasis and these can be rescued by co-treatment with free sialic acid. The aim of the current study was to ascertain whether sialic acid supplementation could improve renal function and attenuate desialylation in an in vivo model of proteinuria (PAN nephrosis) and to delineate the possible mechanisms involved. PAN nephrotic rats were supplemented with free sialic acid, its precursor N-acetyl mannosamine or the NADPH oxidase inhibitor apocynin. Glomeruli, urine, and sera were examined for evidence of kidney injury and therapeutic efficacy. Of the three treatment regimens, sialic acid had the broadest efficacy in attenuating PAN-induced injury. Proteinuria and urinary nephrin loss were reduced. Transmission electron microscopy revealed that podocyte ultrastructure, exhibited less severe foot process effacement. PAN-induced oxidative stress was ameliorated as evidenced by a reduction in glomerular NOX4 expression and a downregulation of urine xanthine oxidase levels. Sialylation dysfunction was improved as indicated by reduced urinary concentrations of free sialic acid, restored electrophoretic mobility of podocalyxin, and improved expression of a sialyltransferase. These data indicate that PAN induces alterations in the expression of enzymes involved in redox control and sialoglycoprotein metabolism, which can be ameliorated by sialic acid supplementation possibly via its properties as both an antioxidant and a substrate for sialylation.

Inhibition of microRNA-30a prevents puromycin aminonucleoside-induced podocytic apoptosis by upregulating the glucocorticoid receptor α

It is well‑established that steroid‑resistant nephrotic syndrome commonly involves podocytic injury, however, the underlying mechanism remains to be elucidated. Previous studies have demonstrated that glucocorticoids enhance podocytic recovery predominantly through the functional isoform, glucocorticoid receptor (GR)α. Our previous study demonstrated the reduced expression of GRα in podocytes from patients with steroid‑resistant nephrotic syndrome compared with those with steroid‑sensitive syndromes, which suggested that microRNAs (miRNAs) may be a potential therapeutic target in the modulation of steroid sensitivity. The present study screened miRNAs in murine injured podocytes by microarray and identified 10 miRNAs significantly upregulated, including miR‑30a, miR‑30d, miR‑100, miR181c, miR‑5099, miR‑3535, miR‑140‑3p, miR‑148‑3p and miR‑103‑3p. Bioinformatic target prediction indicated that the GR was a candidate target gene of miR‑30a. The data also indicated that miR‑30a negatively regulated GRα in normal and injured podocytes induced by puromycin aminonucleoside (PAN). In addition, the inhibition of miR‑30a prevented podocytic apoptosis induced by PAN. However, luciferase reporter assay data suggested an indirect effect on the transcriptional activity of GRα. The present study indicated that silencing of miR‑30a may improve steroid sensitivity in injured podocytes, although the mechanism cannot be explained by conventional means and remains to be elucidated.

Loss of Epithelial Membrane Protein 2 Aggravates Podocyte Injury via Upregulation of Caveolin-1.

Nephrotic syndrome is a CKD defined by proteinuria with subsequent hypoalbuminemia, hyperlipidemia, and edema caused by impaired renal glomerular filtration barrier function. We previously identified mutations in epithelial membrane protein 2 (EMP2) as a monogenic cause of this disease. Here, we generated an emp2-knockout zebrafish model using transcription activator-like effector nuclease-based genome editing. We found that loss of emp2 in zebrafish upregulated caveolin-1 (cav1), a major component of caveolae, in embryos and adult mesonephric glomeruli and exacerbated podocyte injury. This phenotype was partially rescued by glucocorticoids. Furthermore, overexpression of cav1 in zebrafish podocytes was sufficient to induce the same phenotype observed in emp2 homozygous mutants, which was also treatable with glucocorticoids. Similarly, knockdown of EMP2 in cultured human podocytes resulted in increased CAV1 expression and decreased podocyte survival in the presence of puromycin aminonucleoside, whereas glucocorticoid treatment ameliorated this phenotype. Taken together, we have established excessive CAV1 as a mediator of the predisposition to podocyte injury because of loss of EMP2, suggesting CAV1 could be a novel therapeutic target in nephrotic syndrome and podocyte injury.

Syndecan-4 ectodomain evokes mobilization of podocyte TRPC6 channels and their associated pathways: An essential role for integrin signaling

PodocyteTRPC6 channels have been implicated in glomerular diseases. Syndecan-4 (Sdc4) is a membrane proteoglycan that can be cleaved to release a soluble ectodomain capable of paracrine and autocrine signaling. We have confirmed that overexpression of Sdc4 core protein increases surface abundance of TRPC6 channels in cultured podocytes, whereas Sdc4 knockdown has the opposite effect. Exposure to soluble Sdc4 ectodomain also increased the surface abundance of TRPC6, and increased cationic currents evoked by a diacylglycerol analog in podocytes. Sdc4 ectodomain increased generation of reactive oxygen species (ROS), reduced activation of RhoA, increased activation of Rac1, increased nuclear abundance of NFATc1, and increased total β3-integrin. The effects of Sdc4 ectodomain on cell-surface TRPC6 were blocked by the ROS quencher TEMPOL, and by the Rac1 inhibitor NSC-23766, but were not blocked by inhibition of calcineurin–NFATc1 signaling. The Sdc4 core protein co-immunoprecipitates with β3-integrin in cultured podocytes. Moreover, effects of Sdc4 ectodomain on TRPC6, ROS generation, Rac1 and RhoA modulation, and NFATc1 activation were blocked by cilengitide, a selective inhibitor of outside-in signaling through αv-containing integrins. Exposure to TNF, or serum from three patients with recurrent FSGS in relapse, increased shedding of podocyte Sdc4 ectodomains into the surrounding medium. This was also observed after treating podocytes with the metalloproteinase ADAM17 or after overexpression of the Sdc4 core protein. Increased concentrations of Sdc4 ectodomain were detected in urine of rats during acute puromycin aminonucleoside nephrosis. Locally generated Sdc4 may play a role in regulating TRPC6 channels, and may contribute to glomerular pathology.

Yi Qi Qing Re Gao formula ameliorates puromycin aminonucleoside-induced nephrosis by suppressing inflammation and apoptosis.

BackgroundYi Qi Qing Re Gao (YQQRG) formula is a traditional Chinese herbal medicine used to treat chronic nephritis. This study was designed to evaluate the underlying mechanism in the use of YQQRG formula to treat nephrosis induced by puromycin aminonucleoside (PAN).MethodsThirty-six male Wistar rats were randomly divided into 3 groups of 12 rats each: a sham group, a vehicle-treated PAN model group (PAN), and a group treated with YQQRG (PAN + YQQRG). The PAN model was established by a single intravenous injection of PAN at a dose of 40 mg/kg body weight; rats in the sham group received the same volume of saline. Twenty-four hour urinary protein was measured 0, 3, 5, 10, and 15 days after the injection. The rats were sacrificed on day 10 and day 15 and the serum lipid profile examined. The renal cortex of each rat was stained with periodic acid–Schiff reagent and the pathologic alterations and ultrastructural changes were examined by transmission electron microscopy. In situ cell apoptosis was detected by a terminal deoxynucleotidyl transferase-mediated uridine 5′-triphosphate-biotin nick end-labeling (TUNEL) assay. Transcriptive levels of inflammatory markers and molecules associated with apoptosis were detected by a real-time polymerase chain reaction and expression of proteins was examined by either immunohistochemistry or Western blot analysis.ResultsYQQRG significantly decreased urinary protein level, and lowered serum lipid level. YQQRG also attenuated histologic lesions in the rat kidneys. Activation of inflammatory markers was largely restored by the administration of YQQRG. TUNEL assay showed that YQQRG decreased the number of apoptotic cells. Both mRNA and protein levels of caspase-3 were significantly reduced in the group treated with YQQRG, whereas expression of the Bcl-2 protein increased in the YQQRG group.ConclusionsYQQRG alleviated kidney injury in PAN-treated rats, possibly through anti-inflammatory and anti-apoptotic effects.

Inhibition of the metabolic degradation of filtered albumin is a major determinant of albuminuria.

Inhibition of the degradation of filtered albumin has been proposed as a widespread, benign form of albuminuria. There have however been recent reports that radiolabeled albumin fragments in urine are not exclusively generated by the kidney and that in albuminuric states albumin fragment excretion is not inhibited. In order to resolve this controversy we have examined the fate of various radiolabeled low molecular weight protein degradation products (LMWDPs) introduced into the circulation in rats. The influence of puromycin aminonucleoside nephrosis on the processing and excretion of LMWDPs is also examined. The status and destinies of radiolabeled LMWDPs in the circulation are complex. A major finding is that LMWDPs are rapidly eliminated from the circulation (>97% in 2 h) but only small quantities (<4%) are excreted in urine. Small (<4%) but significant amounts of LMWDPs may have prolonged elimination (>24 h) due to binding to high molecular weight components in the circulation. If LMWDPs of albumin seen in the urine are produced by extra renal degradation it would require the degradation to far exceed the known catabolic rate of albumin. Alternatively, if an estimate of the role of extra renal degradation is made from the limit of detection of LMWDPs in plasma, then extra renal degradation would only contribute <1% of the total excretion of LMWDPs of albumin. We confirm that the degradation process for albumin is specifically associated with filtered albumin and this is inhibited in albuminuric states. This inhibition is also the primary determinant of the massive change in intact albuminuria in nephrotic states.

Aberrant glomerular filtration of urokinase-type plasminogen activator in nephrotic syndrome leads to amiloride-sensitive plasminogen activation in urine.

In nephrotic syndrome, aberrant glomerular filtration of plasminogen and conversion to active plasmin in preurine are thought to activate proteolytically epithelial sodium channel (ENaC) and contribute to sodium retention and edema. The ENaC blocker amiloride is an off-target inhibitor of urokinase-type plasminogen activator (uPA) in vitro. It was hypothesized that uPA is abnormally filtered to preurine and is inhibited in urine by amiloride in nephrotic syndrome. This was tested by determination of Na(+) balance, uPA protein and activity, and amiloride concentration in urine from rats with puromycin aminonucleoside (PAN)-induced nephrotic syndrome. Urine samples from 6 adult and 18 pediatric patients with nephrotic syndrome were analyzed for uPA activity and protein. PAN treatment induced significant proteinuria in rats which coincided with increased urine uPA protein and activity, increased urine protease activity, and total plasminogen/plasmin concentration and Na(+) retention. Amiloride (2 mg·kg(-1)·24 h(-1)) concentration in urine was in the range 10-20 μmol/l and reduced significantly urine uPA activity, plasminogen activation, protease activity, and sodium retention in PAN rats, while proteinuria was not altered. In paired urine samples, uPA protein was significantly elevated in urine from children with active nephrotic syndrome compared with remission phase. In six adult nephrotic patients, urine uPA protein and activity correlated positively with 24 h urine protein excretion. In conclusion, nephrotic syndrome is associated with aberrant filtration of uPA across the injured glomerular barrier. Amiloride inhibits urine uPA activity which attenuates plasminogen activation and urine protease activity in vivo. Urine uPA is a relevant target for amiloride in vivo.

Alteration in the podoplanin-ezrin-cytoskeleton linkage is an important initiation event of the podocyte injury in puromycin aminonucleoside nephropathy, a mimic of minimal change nephrotic syndrome.

Podoplanin was identified as a protein associated with the transformation of arborized foot processes of glomerular epithelial cells (podocytes) to flat feet. However, the function of podoplanin in the podocyte is not yet fully clarified. In this study, we analyzed the molecular nature of podoplanin, and its expression in rat nephrotic models and patients with minimal change nephrotic syndrome (MCNS). We demonstrated here that podoplanin has two forms: one contains abundant sialic acid and the other a lesser amount of sialic acid. Podoplanin bound ezrin to interact with the cytoskeleton. The silencing of podoplanin in cultured podocytes caused a change in the cell shape and the distribution of ezrin and actin. The expression of podoplanin was clearly reduced before the onset of proteinuria in puromycin aminonucleoside (PAN) nephropathy, a mimic of MCNS, and the decrease in the expression of podoplanin became more evident at the proteinuric stage. Podoplanin was detected in normal urine samples, and the amount of urinary podoplanin markedly increased on day 1 of PAN nephropathy. Urinary ezrin was also detected. The amount of the phosphorylated ezrin was reduced, while the amount of the podoplanin-interacting ezrin increased. The podoplanin expression was reduced in a patient with active-phase MCNS. It is conceivable that the alteration of the podoplanin-ezrin-cytoskeleton linkage is an important event of the podocyte injury in MCNS.

CXCL10 induces the recruitment of monocyte-derived macrophages into kidney, which aggravate puromycin aminonucleoside nephrosis.

The mechanism responsible for trafficking of monocyte-derived macrophages into kidney in the puromycin aminonucleoside model of nephrotic syndrome in rats (PAN-NS), and the significance of this infiltration, remain largely unknown. CXCL10, a chemokine secreted in many T helper type 1 (Th1) inflammatory diseases, exhibits important roles in trafficking of monocytes and activated T cells. We hypothesized that induction of circulating interferon (IFN)-γ and glomerular tumour necrosis factor (TNF)-α during PAN-NS would stimulate the release of CXCL10 by podocytes, leading to infiltration of activated immune cells and greater glomerular injury. We found that serum IFN-γ, glomerular Cxcl10 mRNA and intra- and peri-glomerular macrophage infiltration were induced strongly during the late acute phase of PAN-NS in Wistar rats, but not in nude (Foxn1(rnu/rnu) ) rats lacking functional effector T lymphocytes. Wistar rats also developed significantly greater proteinuria than nude rats, which could be abolished by macrophage depletion. Stimulation of cultured podocytes with both IFN-γ and TNF-α markedly induced the expression of Cxcl10 mRNA and CXCL10 secretion. Together, these data support our hypothesis that increased circulating IFN-γ and glomerular TNF-α induce synergistically the production and secretion of CXCL10 by podocytes, attracting activated macrophages into kidney tissue. The study also suggests that IFN-γ, secreted from Th1 lymphocytes, may prime proinflammatory macrophages that consequently aggravate renal injury.

A Podocyte-Based Automated Screening Assay Identifies Protective Small Molecules.

Podocyte injury and loss mark an early step in the pathogenesis of various glomerular diseases, making these cells excellent targets for therapeutics. However, cell-based high-throughput screening assays for the rational development of podocyte-directed therapeutics are currently lacking. Here, we describe a novel high-content screening-based phenotypic assay that analyzes thousands of podocytes per assay condition in 96-well plates to quantitatively measure dose-dependent changes in multiple cellular features. Our assay consistently produced a Z' value >0.44, making it suitable for compound screening. On screening with >2100 pharmacologically active agents, we identified 24 small molecules that protected podocytes against injury in vitro (1% hit rate). Among the identified hits, we confirmed an β1-integrin agonist, pyrintegrin, as a podocyte-protective agent. Treatment with pyrintegrin prevented damage-induced decreases in F-actin stress fibers, focal adhesions, and active β1-integrin levels in cultured cells. In vivo, administration of pyrintegrin protected mice from LPS-induced podocyte foot process effacement and proteinuria. Analysis of the murine glomeruli showed that LPS administration reduced the levels of active β1 integrin in the podocytes, which was prevented by cotreatment with pyrintegrin. In rats, pyrintegrin reduced peak proteinuria caused by puromycin aminonucleoside-induced nephropathy. Our findings identify pyrintegrin as a potential therapeutic candidate and show the use of podocyte-based screening assays for identifying novel therapeutics for proteinuric kidney diseases.

Disease Severity Correlates with Thrombotic Capacity in Experimental Nephrotic Syndrome.

Thrombotic disease, a major life-threatening complication of nephrotic syndrome, has been associated with proteinuria and hypoalbuminemia severity. However, it is not fully understood how disease severity correlates with severity of the acquired hypercoagulopathy of nephrotic syndrome. Without this knowledge, the utility of proteinuria and/or hypoalbuminemia as biomarkers of thrombotic risk remains limited. Here, we show that two well established ex vivo hypercoagulopathy assays, thrombin generation and rotational thromboelastometry, are highly correlated with proteinuria and hypoalbuminemia in the puromycin aminonucleoside and adriamycin rat models of nephrotic syndrome. Notably, in the puromycin aminonucleoside model, hyperfibrinogenemia and antithrombin deficiency were also correlated with proteinuria severity, consistent with reports in human nephrotic syndrome. Importantly, although coagulation was not spontaneously activated in vivo with increasing proteinuria, vascular injury induced a more robust thrombotic response in nephrotic animals. In conclusion, hypercoagulopathy is highly correlated with nephrotic disease severity, but overt thrombosis may require an initiating insult, such as vascular injury. Our results suggest that proteinuria and/or hypoalbuminemia could be developed as clinically meaningful surrogate biomarkers of hypercoagulopathy to identify patients with nephrotic syndrome at highest risk for thrombotic disease and potentially target them for anticoagulant pharmacoprophylaxis.

Gq signaling causes glomerular injury by activating TRPC6.

Familial forms of focal segmental glomerulosclerosis (FSGS) have been linked to gain-of-function mutations in the gene encoding the transient receptor potential channel C6 (TRPC6). GPCRs coupled to Gq signaling activate TRPC6, suggesting that Gq-dependent TRPC6 activation underlies glomerular diseases. Here, we developed a murine model in which a constitutively active Gq α subunit (Gq(Q209L), referred to herein as GqQ>L) is specifically expressed in podocytes and examined the effects of this mutation in response to puromycin aminonucleoside (PAN) nephrosis. We found that compared with control animals, animals expressing GqQ>L exhibited robust albuminuria, structural features of FSGS, and reduced numbers of glomerular podocytes. Gq activation stimulated calcineurin (CN) activity, resulting in CN-dependent upregulation of TRPC6 in murine kidneys. Deletion of TRPC6 in GqQ>L-expressing mice prevented FSGS development and inhibited both tubular damage and podocyte loss induced by PAN nephrosis. Similarly, administration of the CN inhibitor FK506 reduced proteinuria and tubular injury but had more modest effects on glomerular pathology and podocyte numbers in animals with constitutive Gq activation. Moreover, these Gq-dependent effects on podocyte injury were generalizable to diabetic kidney disease, as expression of GqQ>L promoted albuminuria, mesangial expansion, and increased glomerular basement membrane width in diabetic mice. Together, these results suggest that targeting Gq/TRPC6 signaling may have therapeutic benefits for the treatment of glomerular diseases.

Reactive Oxygen Species and NFkB Increase Peritoneal Filtration and Generate Ascites in Nephrotic Syndrome

Clinical and experimental observations suggest that nephrotic ascites is not accounted for by hypoalbuminemia but by changes of the capillary endothelium permeability. We investigated the mechanism of these changes in puromycin aminonucleoside (PAN) nephrotic rats. The peritoneal filtration coefficient (Kf) was estimated by the slope of the regression line connecting the trans‐peritoneal gradient of osmotic pressure which was varied experimentally to the trans‐peritoneal water flux measured by osmotic dilution.Kf doubled and expression of aquaporin 1 (AQP1) increased in peritoneum of PAN rats. PAN rats displayed peritoneal oxidative stress attested by ROS accumulation and dysregulation of NADPH oxidase and ROS detoxifying enzymes expression. The ROS scavenger N‐acetyl cysteine (NAC) prevented the increase in Kf and in AQP1 expression. It also reduced by half the volume of ascites without changing renal sodium handling, albuminuria or hypoalbuminemia. PAN rats peritoneum also displayed activation of NFkB attested by increased nuclear labeling with anti‐p50 antibody. Activation of NFkB was blunted in NAC‐treated PAN rats. JSH‐23, an inhibitor of NFkB transcriptional activity, mimicked all the effects of NAC.These results show that nephrotic syndrome is associated with increased filtration coefficient of the peritoneal barrier which stems in part from increased expression of AQP1. These changes are triggered by oxidative stress and subsequent activation of NFkB. They account for at least half of increased filtration rate, the remaining stemming possibly from decreased plasma oncotic pressure.

Improvement of nephrotic syndrome by Banggihwanggitang.

Nephrotic syndrome is associated with altered renal handling of sodium along with changes of renal epithelial Na channel (ENaC), leading to the development of edema and ascites.The dried sclerotia of Banggihwanggitang (BHT) has been used for the treatment of chronic kidney disease. This study was conducted to evaluate the effects of BHT on puromycin aminonucleoside (PAN)‐induced renal functional derangement and the change of ENaC expression. The nephrotic syndrome animal models were constructed by PAN 75 mg/kg injection and then were treated with losartan (30 mg/kg/day) or BHT (200 mg/kg/day) for 7 days. Consequently, BHT group was significantly improved the proteinuria and ascites. In addition, the plasma level of triglyceride, total cholesterol, and low density lipoprotein (LDL)‐cholesterol were significantly decreased in BHT. Besides, BHT group attenuated the PAN‐induced increase in ENaC protein expression. BHT was significantly suppressed PAN‐induced organic osmolytes regulator such as serum‐ and glucocorticoid‐inducible protein kinase (Sgk1), and mineralocorticoid receptor (MR) mRNA expression.Taken together, BHT improve nephrotic syndrome including proteinuria and ascites, through inhibition of ENaC. Thus, Banggihwanggitang is involved in the body‐fluid regulation via inhibition of water and sodium channels against renal disorder such as edema or nephrosis.

Truncated Variant of ASIC2b Confers Epithelial Sodium Channel Properties to ASIC2: Role in Nephrotic Syndrome

Sodium retention responsible for nephrotic edema stems from epithelial sodium channel (ENaC) and Na,K‐ATPase induction in cortical collecting ducts (CCD) of puromycin aminonucleoside (PAN) nephrotic rats. However PAN rats show hyper‐aldosteronemia whereas most nephrotic patients do not. Aldosterone‐clamped (AC) PAN rats still retain sodium in ASDN although ENaC is no longer expressed. We searched for an alternate sodium entry pathway in CCD from AC‐PAN rats, a more relevant model of human disease.By RACE we isolated from AC‐PAN rat kidney a cDNA identical to that of ASIC2b except that it lacks the 207 3′‐most nucleotides. This truncated sequence contains an ATG within the reading frame of the full length sequence. Heterologous expression in OKP cells demonstrated that it is translated in a protein lacking the 71 N‐ter amino acids. Two‐electrode voltage clamp analysis in Xenopus ovocytes showed that co‐expression of truncated ASIC2b and ASIC2a induces an acid‐stimulated cation current which, instead of being transient, lasts as long as the stimulus is maintained. ASIC2a and truncated‐ASIC2b thus constitute heteromeric channels potentially supporting epithelial sodium transport. ASIC2b expression is induced in CCD of AC‐PAN rats where it localizes at the apical pole. ASIC2b was detected in kidney biopsies from 5/8 patients with idiopathic nephrotic syndrome but not in 26/26 patients with other renal diseases. In ASIC2b‐positive nephrotic patients, ASIC2b was located in CCD.Results suggest that truncated ASIC2b/ASIC2a mediates sodium retention in nephrotic syndrome and appears as a new therapeutic target.

A vital role for Angptl3 in the PAN-induced podocyte loss by affecting detachment and apoptosis in vitro.

BackgroundPodocyte detachment and apoptosis are two risk factors causing podocyte loss, F-actin rearrangement is involved in detachment and apoptosis. However, the nature of events that promote detachment and apoptosis of podocytes and whether detachment occurred simultaneously with apoptosis are still unclear. Previously, it was found that angiopoietin-like3 (Angptl3) induces F-actin rearrangement in podocytes. In this study we investigate whether Angptl3 influences podocyte loss (detachment and apoptosis) and the process through which Angptl3 exactly influenced the podocyte loss.MethodsIn conditionally immortalized mice podocytes, recombinant mice Angptl3 protein (rm-Angptl3) was used to mimic Angptl3 overexpression model and transfection with small interfering RNA (siRNA) to knockdown the expression of Angptl3. Both flow cytometry analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay were used to detect apoptosis. Rearrangement of F-actin was assessed using confocal microscopy. Western blot assay was used to measure levels of Angptl3, integrin α3β1, integrin-linked kinase (ILK), p53, caspase 3, and phosphorylation of integrin β1.ResultsIn a puromycin aminonucleoside (PAN)-induced podocyte injury model, rm-Angptl3 accelerated the loss of podocytes, both detachment and apoptosis occurred, and F-actin rearrangement is involved in the process. However, knockdown of Angptl3 by siRNA markedly ameliorated these injuries. Observed effects were partially correlated with the altered integrin α3β1, ILK and p53, rather than caspase 3.ConclusionsAngptl3 is a novel factor involved in the PAN-induced podocyte loss by affecting detachment and apoptosis in vitro. This study helps to deepen the understanding of the mechanisms of podocyte loss and lays the foundation for developing a new successful therapy for podocyte injury via lower expression of Angptl3.