Nephrosis In Rats Research Articles

Effect of α2-adrenoceptor antagonist on puromycin aminonucleoside-induced nephrosis in rats

Effect of α2-adrenoceptor antagonist on puromycin aminonucleoside-induced nephrosis in rats

Nicorandil protects podocytes via modulation of antioxidative capacity in acute puromycin aminonucleoside-induced nephrosis in rats.

Nephrotic syndrome, characterized by proteinuria and hypoalbuminemia, results from the dysregulation of glomerular podocytes and is a significant cause of end-stage kidney disease. Patients with idiopathic nephrotic syndrome are generally treated with immunosuppressive agents; however, these agents produce various adverse effects. Previously, we reported the renoprotective effects of a stimulator of the mitochondrial ATP-dependent K+ channel (MitKATP), nicorandil, in a remnant kidney model. Nonetheless, the cellular targets of these effects remain unknown. Here, we examined the effect of nicorandil on puromycin aminonucleoside-induced nephrosis (PAN) rats, a well-established model of podocyte injury and human nephrotic syndrome. PAN was induced using a single intraperitoneal injection. Nicorandil was administered orally at 30 mg/kg/day. We found that proteinuria and hypoalbuminemia in PAN rats were significantly ameliorated following nicorandil treatment. Immunostaining and ultrastructural analysis under electron microscopy demonstrated that podocyte injury in PAN rats showed a significant partial attenuation following nicorandil treatment. Nicorandil ameliorated the increase in the oxidative stress markers nitrotyrosine and 8-hydroxy-2-deoxyguanosine in glomeruli. Conversely, nicorandil prevented the decrease in levels of the antioxidant enzyme manganese superoxide dismutase in PAN rats. We found that mitochondrial Ca2+ uniporter levels in glomeruli were higher in PAN rats than in control rats, and this increase was significantly attenuated by nicorandil. We conclude that stimulation of MitKATP by nicorandil reduces proteinuria by attenuating podocyte injury in PAN nephrosis, which restores mitochondrial antioxidative capacity, possibly through mitochondrial Ca2+ uniporter modulation. These data indicate that MitKATP may represent a novel target for podocyte injury and nephrotic syndrome.NEW & NOTEWORTHY Our findings suggest that the mitochondrial Ca2+ uniporter may be an upstream regulator of manganese superoxide dismutase and indicate a biochemical basis for the interaction between the ATP-sensitive K+ channel and Ca2+ signaling. We believe that our study makes a significant contribution to the literature because our results indicate that the ATP-sensitive K+ channel may be a potential therapeutic target for podocyte injury and nephrotic syndrome.

Differential Expression of Renal and Hepatic PCSK9 During Development of Hypercholesterolemia in the Puromycin Aminonucleoside Nephrosis Rat Model of Nephrotic Syndrome

Differential Expression of Renal and Hepatic PCSK9 During Development of Hypercholesterolemia in the Puromycin Aminonucleoside Nephrosis Rat Model of Nephrotic Syndrome

TRPC5 Channel Inhibition Protects Podocytes in Puromycin-Aminonucleoside Induced Nephrosis Models.

Podocyte injury and the appearance of proteinuria are key features of several progressive kidney diseases. Genetic deletion or selective inhibition of TRPC5 channels with small-molecule inhibitors protects podocytes in rodent models of kidney disease, but less is known about the human relevance and translatability of TRPC5 inhibition. Here, we investigate the effect of TRPC5 inhibition in puromycin aminonucleoside (PAN)-treated rats, human iPSC-derived podocytes, and kidney organoids. We first established that systemic administration of the TRPC5 inhibitor AC1903 was sufficient to protect podocyte cytoskeletal proteins and suppress proteinuria in PAN-induced nephrosis rats, an established model of podocyte injury. TRPC5 current was recorded in the human iPSC-derived podocytes and was blocked by AC1903. PAN treatment caused podocyte injury in human iPSC-derived podocytes and kidney organoids. Inhibition of TRPC5 channels reversed the effects of PAN-induced injury in human podocytes in both 2D and 3D culture systems. Taken together, these results revealed the relevance of TRPC5 channel inhibition in puromycin-aminonucleoside induced nephrosis models, highlighting the potential of this therapeutic strategy for patients.

EP300/CBP is crucial for cAMP-PKA pathway to alleviate podocyte dedifferentiation via targeting Notch3 signaling

Podocyte injury is the hallmark of proteinuric glomerular diseases. Notch3 is neo-activated simultaneously in damaged podocytes and podocyte's progenitor cells of FSGS, indicating a unique role of Notch3. We previously showed that activation of cAMP-PKA pathway alleviated podocyte injury possibly via inhibiting Notch3 expression. However, the mechanisms are unknown. In the present study, Notch3 signaling was significantly activated in ADR-induced podocytes in vitro and in PAN nephrosis rats and patients with idiopathic FSGS in vivo, concomitantly with podocyte dedifferentiation. In cultured podocytes, pCPT-cAMP, a selective cAMP-PKA activator, dramatically blocked ADR-induced activation of Notch3 signaling as well as inhibition of cAMP-PKA pathway, thus alleviating the decreased cell viability and podocyte dedifferentiation. Bioinformatics analysis revealed EP300/CBP, a transcriptional co-activator, as a central hub for the crosstalk between these two signaling pathways. Additionally, CREB/KLF15 in cAMP-PKA pathway competed with RBP-J the major transcriptional factor of Notch3 signaling for binding to EP300/CBP. EP300/CBP siRNA significantly inhibited these two signaling transduction pathways and disrupted the interactions between the above major transcriptional factors. These data indicate a crucial role of EP300/CBP in regulating the crosstalk between cAMP-PKA pathway and Notch3 signaling and modulating the phenotypic change of podocytes, and enrich the reno-protective mechanisms of cAMP-PKA pathway.

N-acetylglucosamine increases the efficacy of quercetin in the treatment of experimental acute kidney injury

Context: Acute kidney injury (AKI) is a common complication of renal pathology and an adverse drug effect. Mortality caused by AKI reaches 80% in some groups of patients. Therefore, the search of the effective agents for AKI treatment is an important task of the pharmaceutical science. Aims: To evaluate the efficacy of various combinations of N-acetylglucosamine (NAG) and quercetin in rats with AKI. Methods: The study was conducted on the model of acute glycerol nephrosis in rats. Combinations of NAG and quercetin in ratios of 1:2, 1:1, 2:1 and 3:1 were studied at a dose of 50 mg/kg with daily intramuscular injection for a week. The efficacy of the combinations was assessed by the indicators of animal survival, excretory renal function, nitrogen metabolism and nephroprotective activity (NA). Results: The combination of NAG and quercetin in the 1:1 ratio was the most effective. There was a significant increase of excretory renal function and normalization of nitrogen metabolism under the influence of this combination. This determined the NA level up to 69.7%, which was the highest value in the presented study. This combination was statistically superior to all others, as well as to quercetin, by the efficacy level. In addition, the combination exceeded the quercetin in NA index by 2.7 times. Conclusions: Thus, the NAG/quercetin combination in 1:1 ratio in injectable dosage form is the most promising for kidney diseases treatment.

Nephrotic syndrome is associated with increased plasma K+ concentration, intestinal K+ losses, and attenuated urinary K+ excretion: a study in rats and humans.

The present study tested the hypotheses that nephrotic syndrome (NS) leads to renal K+ loss because of augmented epithelial Na+ channel (ENaC) activity followed by downregulation of renal K+ secretory pathways by suppressed aldosterone. The hypotheses were addressed by determining K+ balance and kidney abundance of K+ and Na+ transporter proteins in puromycin aminonucleoside (PAN)-induced rat nephrosis. The effects of amiloride and angiotensin II type 1 receptor and mineralocorticoid receptor (MR) antagonists were tested. Glucocorticoid-dependent MR activation was tested by suppression of endogenous glucocorticoid with dexamethasone. Urine and plasma samples were obtained from pediatric patients with NS in acute and remission phases. PAN-induced nephrotic rats had ENaC-dependent Na+ retention and displayed lower renal K+ excretion but elevated intestinal K+ secretion that resulted in less cumulated K+ in NS. Aldosterone was suppressed at day 8. The NS-associated changes in intestinal, but not renal, K+ handling responded to suppression of corticosterone, whereas angiotensin II type 1 receptor and MR blockers and amiloride had no effect on urine K+ excretion during NS. In PAN-induced nephrosis, kidney protein abundance of the renal outer medullary K+ channel and γ-ENaC were unchanged, whereas the Na+-Cl- cotransporter was suppressed and Na+-K+-ATPase increased. Pediatric patients with acute NS displayed suppressed urine Na+-to-K+ ratios compared with remission and elevated plasma K+ concentration, whereas fractional K+ excretion did not differ. Acute NS is associated with less cumulated K+ in a rat model, whereas patients with acute NS have elevated plasma K+ and normal renal fractional K+ excretion. In NS rats, K+ balance is not coupled to ENaC activity but results from opposite changes in renal and fecal K+ excretion with a contribution from corticosteroid MR-driven colonic secretion.

SUN-190 GFB-887, a small molecule inhibitor of TRPC5, protects against podocyte injury and attenuates proteinuria in models of FSGS

Focal segmental glomerulosclerosis (FSGS) is a rare podocytopathy with a high likelihood of progression to end stage renal disease. The Ca2+-permeable transient receptor potential canonical 5 (TRPC5) channel is a critical mediator of proteinuria in FSGS. Activation of the TRPC5 pathway in podocytes culminates in activation of Rac1, which is the primary driver of proteinuria in many forms of familial and sporadic FSGS. Inhibition of TRPC5 channel activity has been shown to protect against proteinuria and podocyte loss in AT1R transgenic and Dahl salt-sensitive rats. We performed high throughput screening of a structurally diverse compound collection followed by lead optimization for the development of several potent TRPC5 inhibitors. We characterized TRPC5 inhibitors in vitrousing a mouse podocyte cell line and podocyte injury models derived from human inducible pluripotent stem cells (hiPSC), and in two in vivomodels of FSGS, the unilaterally nephrectomized deoxycorticosterone acetate (DOCA)-salt rat model and the puromycin aminonucleoside nephrosis (PAN) rat model Here we report the identification of GFB-887, a potent, selective and orally bioavailable small molecule inhibitor of TRPC5. Potency and selectivity across TRP channels were determined using FLIPR based assays and electrophysiology. We show that TRPC5 inhibition protects against loss of stress fibers induced by protamine sulfate, a known activator of TRPC5, and restores stress fibers in podocytes after knockdown of synaptopodin. We further show that inhibition of TRPC5 suppresses pathogenic podocyte motility in a scratch assay. Finally, we demonstrate that inhibition of TRPC5 attenuates proteinuria in hypertension-induced FSGS in DOCA-salt rat model without altering blood pressure, and in non-hypertensive FSGS in the PAN rat model suggesting direct glomerular protection in vivo. We have identified GFB-887 as a new selective small molecule inhibitor of TRPC5 for the treatment of proteinuria in FSGS

In glomerular cells of puromycin aminonucleoside nephrosis rats both phosphorylated and total STAT3 levels increased during proteinuria

Recent studies showed that JAK/STAT pathway plays role in glomerular damages. The fact that STAT3 could be activated also by oxidative stress make Puromycin Aminonucleoside (PAN) Nephrosis model very appropriate for examination of STAT3 expression changes in glomerular pathology. Along with a control group, three PAN groups sacrificed on different days were formed by the i.p. injection of PAN for 5 consecutive days. Throughout the experiment, 24-hour-urines were collected on specific days and proteinuria levels were monitored. At the end of the experiments, tissue specimens were stained immunohistochemically for both total and phosphorylated STAT3 and evaluated subjectively. They were also examined ultrastructurally in transmission electron microscope. The proteinuria levels did not increase significantly on 5th day but showed a dramatic increase on 10th and 15th days. On 20th and 25th days, urinary protein levels gradually decreased. Ultrastructural examinations showed glomerular damages such as significant decrease in slit pore number, a significant gradual increase in glomerular basement membrane thickness and podocyte hypertrophy on 5th and 15th days; besides significant increase in mesangial matrix. The first significant increases in phosphorylated and total STAT3 levels occurred in 5th day and 15th day groups respectively. These increases diminished in 25th day group. Regarding all the findings, it was deduced that STAT3 is one of the active factors in glomerular pathologies.

Modified Huangqi Chifeng decoction inhibits excessive autophagy to protect against Doxorubicin-induced nephrotic syndrome in rats via the PI3K/mTOR signaling pathway.

The aim of the present study was to investigate whether modified Huangqi Chifeng decoction (MHCD) could be an effective treatment against Doxorubicin-induced nephrosis in rats and whether it regulates autophagy via the phosphoinositide-3 kinase/mammalian target of rapamycin (PI3K/mTOR) signaling pathway. A total of 40 male Sprague-Dawley rats were randomly divided into blank, model, telmisartan and MHCD groups. The rat model of nephrosis was induced by intragastric administration of Doxorubicin for 8 weeks. Rats were housed in metabolic cages and urine was collected once every 2 weeks to measure 24-h protein levels. Blood samples were obtained from the abdominal aorta and levels of albumin (ALB), total cholesterol (TCH), triacylglyceride (TG) and serum creatinine (Scr) were assessed. Renal pathological changes were examined using hematoxylin-eosin, Masson's trichome and periodic acid-Schiff staining. Podocytes and autophagosomes were observed using an electron microscope. The expression and distribution of microtubule-associated proteins 1A/1B light chain 3B (LC3), LC3-I, LC3-II, beclin-1, PI3K and mTOR were determined using immunohistochemistry and western blotting. At weeks 6 and 8, 24-h proteinuria significantly decreased in the MHCD group compared with the model group (P<0.05). Compared with the model group, the MHCD group exhibited significantly reduced levels of TG, TCH and Scr, as well as significantly increased ALB levels (P<0.05). MHCD was demonstrated to prevent glomerular and podocyte injury. The number of autophagosomes was significantly decreased and the expression of beclin-1, LC3, LC3-I and LC3-II was inhibited following MHCD treatment compared with the model group (P<0.05). MHCD treatment significantly increased the expression of PI3K and mTOR in Doxorubicin nephrotic rats compared with the model group (P<0.05). In conclusion, MHCD was demonstrated to ameliorate proteinuria and protect against glomerular and podocyte injury by inhibiting excessive autophagy via the PI3K/mTOR signaling pathway.

Trpc6 inactivation confers protection in a model of severe nephrosis in rats

Mutations in canonical transient receptor potential-6 (TRPC6) channels give rise to rare familial forms of focal and segmental glomerulosclerosis (FSGS). Here we examined a possible role for TRPC6 in the progression of chronic puromycin aminonucleoside (PAN) nephrosis in Sprague-Dawley rats, a classic model of acquired nephrotic syndromes. We used CRISPR/Cas9 technology to delete a 239-bp region within exon 2 of the Trpc6 gene (Trpc6del allele). Trpc6del/del rats expressed detectable Trpc6 transcripts missing exon 2, and TRPC6 proteins could be detected by immunoblot of renal cortex. However, the abundance of Trpc6 transcripts and TRPC6 protein in renal cortex was much lower than in Trpc6wt/wt littermates, and functional TRPC6 channels could not be detected in whole-cell recordings from glomerular cells cultured from Trpc6del/del animals, possibly because of disruption of ankyrin repeats 1 and 2. During the chronic phase of PAN nephrosis, Trpc6del/del rats had reduced urine albumin excretion, reduced serum cholesterol and triglycerides, and improved azotemia compared to wild-type Trpc6wt/wt littermates. Glomerulosclerosis was severe during chronic PAN nephrosis in Trpc6wt/wt rats but was markedly reduced in Trpc6del/del littermates. Trpc6del/del animals also had less severe tubulointerstitial fibrosis as assessed by several biochemical and histological analyses, as well as reduced foot process effacement and glomerular basement thickening compared to Trpc6wtt/wt controls. None of the manipulations in this study affected the abundance of TRPC5 channels in renal cortex. TRPC3 was increased in PAN nephrosis and in Trpc6del/del rats. These data support a role for TRPC6 channels in driving an acquired form of secondary FSGS.Key messagesWe examined aminonucleoside nephrosis in rats with wild type and inactivated TRPC6.TRPC6 channels were inactivated by CRISPR/Cas9 editing of the Trpc6 gene.TRPC6 inactivation reduced albuminuria in the chronic but not the acute phase.TRPC6 inactivation reduced glomerulosclerosis and ultrastructural changes.TRPC6 inactivation also reduced interstitial changes and renal fibrosis.

Antiproteinuric effect of an endothelin-1 receptor antagonist in puromycin aminonucleoside-induced nephrosis in rat.

BackgroundThe pathogenesis of idiopathic nephrotic syndrome (INS) remains unclear, although recent studies suggest endothelin 1 (ET-1) and CD80 of podocytes are involved. We investigated the potential of antagonist to ET-1 receptor type A (ETRA) as therapeutic agent through the suppression of CD80 in a rat model of INS.MethodsPuromycin aminonucleoside (PAN) was injected to Wister rats to induce proteinuria: some were treated with ETRA antagonist and others were treated with 0.5% methylcellulose. Blood and tissue samples were collected. Quantitative PCR was used to determine the expression of Toll-like receptor-3 (TLR-3), nuclear factor-κB (NF-κB), CD80, talin, ETRA, and ET-1 in the kidney. To confirm the level of CD80 protein expression, immunofluorescence staining and western blot analysis of the renal tissue were performed.ResultsAmount of proteinuria in the treatment group was significantly lower than the other groups. The same-day body weight, serum creatinine values, and blood pressure were not significantly different. ETRA antagonist restores podocyte foot process effacement as well as the aberrant expression of TLR-3, nuclear factor-κB (NF-κB), and CD80 in PAN-injured kidneys.ConclusionsThe ETRA antagonist may be promising drug for INS as it showed an antiproteinuric effect. Its action was considered to be through suppression of CD80 expression on podocytes.

Adrenomedullin ameliorates podocyte injury induced by puromycin aminonucleoside in vitro and in vivo through modulation of Rho GTPases.

Podocyte injury is a key event in proteinuric kidney disease and eventually glomerular scarring. While adrenomedullin (AM), a potent vasodilatory peptide, has been reported to confer renoprotection in several experimental models of kidney diseases, its effect on injured podocytes and the related mechanism is still largely unknown. Employing Western blotting analysis, immunoprecipitation and immunofluorescence, we investigated the effects of AM on the expressions of podocyte cytoskeletal proteins and Rho-family small GTPases (Rho GTPases) in puromycin aminonucleoside (PAN)-induced podocyte injury, both in cultured podocytes and in PAN nephrosis rats. Urinary protein excretion and the morphologic changes of kidney in PAN nephrosis rats were evaluated. Glutathione-S-transferase pull-down assay was applied for Rho GTPases activity. PAN induced massive albuminuria and morphologic injury, which were significantly mitigated by AM administration. AM significantly antagonized not only the PAN-decreased expressions of synaptopodin, nephrin, CD2AP and podocin, but also the PAN-disrupted interactions between synaptopodin-RhoA, nephrin-CD2AP, and CD2AP-Rac1-cortactin. These effects of AM in cultured podocytes were mostly significantly blocked by H89, a PKA inhibitor. AM dramatically upregulated the PAN-induced Rho GTPases protein expressions and their activities. PAN increased the expressions of endogenous AM and its receptor RAMP2 which was furthermore upregulated by AM administration. AM alleviated podocyte injury induced by PAN both in cell culture and in PAN nephrosis. The beneficial effects of AM on podocytes can be attributable to direct modulation of podocyte cytoskeletal proteins and Rho GTPases, mainly via a PKA-dependent pathway.

Thrombin-Induced Podocyte Injury Is Protease-Activated Receptor Dependent.

Nephrotic syndrome is characterized by massive proteinuria and injury of specialized glomerular epithelial cells called podocytes. Studies have shown that, whereas low-concentration thrombin may be cytoprotective, higher thrombin concentrations may contribute to podocyte injury. We and others have demonstrated that ex vivo plasma thrombin generation is enhanced during nephrosis, suggesting that thrombin may contribute to nephrotic progression. Moreover, nonspecific thrombin inhibition has been shown to decrease proteinuria in nephrotic animal models. We thus hypothesized that thrombin contributes to podocyte injury in a protease-activated receptor-specific manner during nephrosis. Here, we show that specific inhibition of thrombin with hirudin reduced proteinuria in two rat nephrosis models, and thrombin colocalized with a podocyte-specific marker in rat glomeruli. Furthermore, flow cytometry immunophenotyping revealed that rat podocytes express the protease-activated receptor family of coagulation receptors in vivo High-concentration thrombin directly injured conditionally immortalized human and rat podocytes. Using receptor-blocking antibodies and activation peptides, we determined that thrombin-mediated injury depended upon interactions between protease-activated receptor 3 and protease-activated receptor 4 in human podocytes, and between protease-activated receptor 1 and protease-activated receptor 4 in rat podocytes. Proximity ligation and coimmunoprecipitation assays confirmed thrombin-dependent interactions between human protease-activated receptor 3 and protease-activated receptor 4, and between rat protease-activated receptor 1 and protease-activated receptor 4 in cultured podocytes. Collectively, these data implicate thrombinuria as a contributor to podocyte injury during nephrosis, and suggest that thrombin and/or podocyte-expressed thrombin receptors may be novel therapeutic targets for nephrotic syndrome.

Albuminuria is associated with an increased prostasin in urine while aldosterone has no direct effect on urine and kidney tissue abundance of prostasin.

The proteinase prostasin is a candidate mediator for aldosterone-driven proteolytic activation of the epithelial sodium channel (ENaC). It was hypothesized that the aldosterone-mineralocorticoid receptor (MR) pathway stimulates prostasin abundance in kidney and urine. Prostasin was measured in plasma and urine from type 2 diabetic patients with resistant hypertension (n=112) randomized to spironolactone/placebo in a clinical trial. Prostasin protein level was assessed by immunoblotting in (1) human and rat urines with/without nephrotic syndrome, (2) human nephrectomy tissue, (3) urine and kidney from aldosterone synthase-deficient (AS-/-) mice and ANGII- and aldosterone-infused mice, and in (4) kidney from adrenalectomized rats. Serum aldosterone concentration related to prostasin concentration in urine but not in plasma. Plasma prostasin concentration increased significantly after spironolactone compared to control. Urinary prostasin and albumin related directly and were reduced by spironolactone. In patients with nephrotic syndrome, urinary prostasin protein was elevated compared to controls. In rat nephrosis, proteinuria coincided with increased urinary prostasin, unchanged kidney tissue prostasin, and decreased plasma prostasin while plasma aldosterone was suppressed. Prostasin protein abundance in human nephrectomy tissue was similar across gender and ANGII inhibition regimens. Prostasin urine abundance was not different in AS-/- and aldosterone-infused mice. Prostasin kidney level was not different from control in adrenalectomized rats and AS-/- mice. We found no evidence for a direct relationship between mineralocorticoid receptor signaling and kidney and urine prostasin abundance. The reduction of urinary prostasin in spironolactone-treated patients is most likely the result of an improved glomerular filtration barrier function and generally reduced proteinuria.

Effects of Shenkangling intervention on the MAPK pathway in rats with doxorubicin-induced nephropathy.

Shenkangling plays a role of Yishenhuoxue effect for the treatment of children with nephrotic syndrome. The aim of this study was to investigate the effects of Shenkangling intervention on the mitogen-activated protein kinase (MAPK) pathway in rats with Adriamycin-induced nephropathy (AN) and its underlying mechanism of action. Nephrosis was induced in healthy Sprague-Dawley rats by doxorubicin and the rats were untreated or treated with prednisone, simvastatin, Shenkangling, or a combination thereof. Using real-time PCR, the mRNA expression levels of Chemokine (C-X-C motif) ligand 16 (CXCL16), A Disintegrin and metalloproteinase domain-containing protein 10 (ADAM10), and ADAM17 in the renal tissues of these rats were found to be decreased by the various treatments compared to those in the untreated doxorubicin-induced nephrosis rats. To quantify the activation of the MAPK pathway, western blotting was used to detect the phosphorylation levels of MAPK pathway-associated proteins (p38, ERK1/2, SAPK/JNK) and nuclear factor (NF)-κB p65, which were reduced by the various treatments compared to those in the untreated doxorubicin-induced rats. Serum levels of transforming growth factor (TGF)-β1, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, quantified by ELISA, were decreased by the various treatments compared to the levels in the untreated doxorubicin-induced nephrosis rats. The rats treated with prednisone, simvastatin, and Shenkangling showed the best outcome. The Chinese medicine Shenkangling that is known for nourishing the kidney and promoting blood circulation reduced urinary protein levels, increased serum albumin levels, and reduced cholesterol levels by reducing the release of CXCL16, ADAM10, ADAM17, TGF-β1, TNF-α, IL-1β, IL- 6, and other inflammatory mediators and inhibiting the activation of the MAPK signaling pathway, thereby effectively improving the state of nephropathy in AN rats. These results indicate that Shenkangling can be used clinically to treat nephropathy.

Editorial: Podocyte Pathology and Nephropathy.

Editorial: Podocyte Pathology and Nephropathy.

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.

Podocin is translocated to cytoplasm in puromycin aminonucleoside nephrosis rats and in poor-prognosis patients with IgA nephropathy.

Podocytes serve as the final barrier to urinary protein loss through a highly specialized structure called a slit membrane and maintain foot process and glomerular basement membranes. Podocyte injury results in progressive glomerular damage and accelerates sclerotic changes, although the exact mechanism of podocyte injury is still obscure. We focus on the staining gap (podocin gap) defined as the staining difference between podocin and synaptopodin, which are normally located in the foot process. In puromycin aminonucleoside nephrosis rats, the podocin gap is significantly increased (p < 0.05) and podocin is translocated to the cytoplasm on days 7 and 14 but not on day 28. Surprisingly, the gap is also significantly increased (p < 0.05) in human kidney biopsy specimens of poor-prognosis IgA nephropathy patients. This suggests that the podocin gap could be a useful marker for classifying the prognosis of IgA nephropathy and indicating the translocation of podocin to the cytoplasm. Next, we find more evidence of podocin trafficking in podocytes where podocin merges with Rab5 in puromycin aminonucleoside nephrosis rats at day 14. In immunoelectron microscopy, the podocin positive area was significantly translocated from the foot process areas to the cytoplasm (p< 0.05) on days 7 and 14 in puromycin aminonucleoside nephrosis rats. Interestingly, podocin is also translocated to the cytoplasm in poor-prognosis human IgA nephropathy. In this paper, we demonstrate that the translocation of podocin by endocytosis could be a key traffic event of critical podocyte injury and that the podocin gap could indicate the prognosis of IgA nephropathy.

MiRNAs Expression and Role of Dicer on Podocyte Injury in PAN Nephrosis Rats

Objective: microRNAs (miRNAs) are regulatory RNAs that act as important players in diverse biologic and pathologic processes. Under circumstance as podocye-injury triggering proteinuria, which miRNAs are up-regulated or down-regulated? This experiment aims at detecting miRNAs changes in PAN nephrosis rats based on miRNA arrays and exploring the therapeutic targets of Leizhi capsule. Methods: Fifty male wistar rats were randomly divided into five groups, including control group, model group, leizhi capsule group, Tripterygium glucosides group, and valsartan group. PAN nephrosis models were made by jugular vein injection of PAN (100 mg/kg body weight, dissolve in physiological saline), while control group rats were made by jugular vein injection of physiological saline with equal volume. Other groups rats had been given medicines by irrigating stomach once a day for ten days. Blood and urine samples were collected, and renal tissues were processed after rats being euthanasised. The 24 h urinary protein excretion and blood biochemistry parameters were measured by routine methods. The glomerular morphology and podocyte ultrastructure were observed with light microscopy and transmission electron microscopy respectively. miRNA expression profile was detected by Exiqon miRNA Array. Real time RT-PCR analysis for mature miRNAs was used to validate differentially expressed miRNAs. Results: 1) In day 3 - 5, model rats had decreased urine volume, ascites, malnutrition and wight loss. From day 7 to day 10, the nephrotic syndromes were worst in model rats, but which had no skin edema. Some rats died in serious ascites, the mortality is 3/10. 2) miRNA array detection shows 106 miRNAs up regulated and 62 miRNAs down regulated in PAN nephrosis rats. Fold change (model vs. control group) varies from 1.8 to 7.0. For leizhi capsule group and model sample, there are 90 miRNAs differentially expressed, with 65 miRNAs up and 25 miRNAs down. The most important finding in our research is the discovery of the specific miRNAs related to PAN nephrosis (rno-miR23a, rno-miR-24, rno-miR-30c and rno-miR-300-3p), which have been validated by Real time RT-PCR analysis. 3) Compared with control sample, immune fluorescence intensity of dicer, expression profile of nephrin, podocin and synaptopodin mRNA and protein decrease in PAN nephrosis rats. After treated with Leizhi Capsule, immune fluorescence intensity of the above molecules improved. Conclusion: 1) Characteristic miRNAs of PAN nephrosis were screening. Up-regulated miRNAs (rno-miR-23a, rno-miR-300-3p) may trigger podocyte injury and proteinuria, while down-regulated miRNAs (rno-miR-24, rno-miR-30c) may be protective factors by anti-apoptosis. 2) Dicer and these miRNAs (rno-miR-24, rno-miR-30c, rno-miR-23a) may be are probably key molecules therapeutic targets of Leizhi capsule.