The Role of the EGF Receptor in Sex Differences in Kidney Injury

BACKGROUND

Sex differences mediating predisposition to kidney injury are well known, with evidence indicating lower CKD incidence rates and slower decline in renal function in nondiabetic CKD for premenopausal women compared with men. However, signaling pathways involved have not been elucidated to date. The EGF receptor (EGFR) is widely expressed in the kidney in glomeruli and tubules, and persistent and dysregulated EGFR activation mediates progressive renal injury.

METHODS

To investigate the sex differences in response to renal injury, we examined EGFR expression in mice, in human kidney tissue, and in cultured cell lines.

RESULTS

In wild type mice, renal mRNA and protein EGFR levels were comparable in males and females at postnatal day 7 but were significantly lower in age-matched adult females than in adult males. Similar gender differences in renal EGFR expression were detected in normal adult human kidneys. In Dsk5 mutant mice with a gain-of-function allele that increases basal EGFR kinase activity, males had progressive glomerulopathy, albuminuria, loss of podocytes, and tubulointerstitial fibrosis, but female Dsk5 mice had minimal kidney injury. Oophorectomy had no effect on renal EGFR levels in female Dsk5 mice, while castration protected against the kidney injury in male Dsk5 mice, in association with a reduction in EGFR expression to levels seen in females. Conversely, testosterone increased EGFR expression and renal injury in female Dsk5 mice. Testosterone directly stimulated EGFR expression in cultured kidney cells.

CONCLUSIONS

These studies indicate that differential renal EGFR expression plays a role in the sex differences in susceptibility to progressive kidney injury that may be mediated at least in part by testosterone.

[Effect and molecular mechanism of interferon-α on podocyte apoptosis induced by hepatitis B virus X protein]

OBJECTIVE

To investigate the effect and molecular mechanism of interferon-α (INF-α) on the apoptosis of the mouse podocyte cell line MPC5 induced by hepatitis B virus X (HBx) protein.

METHODS

MPC5 cells were transfected with the pEX plasmid carrying the HBx gene. RT-PCR was used to measure the mRNA expression of HBx at different time points. MPC5 cells were divided into 4 groups: control group (MPC5 cells cultured under normal conditions), INF-α group (MPC5 cells cultured with INF-α), HBx group (MPC5 cells induced by HBx), and HBx+INF-α group (MPC5 cells induced by HBx and cultured with INF-α). After 48 hours of intervention under different experimental conditions, flow cytometry was used to measure the apoptosis of MPC5 cells, and quantitative real-time PCR and Western blot were used to measure the mRNA and protein expression of slit diaphragm-related proteins (nephrin, CD2AP, and synaptopodin) and the cytoskeleton-related protein transient receptor potential cation channel 6 (TRPC6).

RESULTS

MPC5 cells transfected by pEX-HBx had the highest expression of HBx mRNA at 48 hours after transfection (P<0.05). Compared with the control, INF-α and HBx+INF-α groups, the HBx group had a significant increase in the apoptosis rate of MPC5 cells (P<0.05). Compared with the control and INF-α groups, the HBx group had significant reductions in the mRNA and protein expression of nephrin, synaptopodin, and CD2AP and significant increases in the mRNA and protein expression of TRPC6 (P<0.05). Compared with the HBx group, the HBx+INF-α group had significant increases in the mRNA and protein expression of nephrin, synaptopodin, and CD2AP and significant reductions in the mRNA and protein expression of TRPC6 (P<0.05).

CONCLUSIONS

INF-α can inhibit the apoptosis of podocytes induced by HBx, possibly through improving the abnormal expression of slit diaphragm-related proteins (CD2AP, nephrin, and synaptopodin) and cytoskeleton-related protein (TRPC6) induced by HBx.

Nephrotic syndrome: immunological mechanisms

Nephrotic Syndrome (NS) is a rare diseases (around 2-7 cases per 100.000 children per year) characterized by proteinuria ≥50 mg/kg/day (or ≥40 mg/m2/h) or a proteinuria/creatininuria ratio >2 (mg/mg); hypoalbuminaemia less than 25 g/l and edema. The protein leakage, with the consequent hypoalbunaemia and edema, due to podocyte alterations may be caused by genetic diseases, immunological mechanisms, infections, toxins or malignancy. However, most commonly the exact etiology is unknow. The idiopathic NS may be classified based on response to corticosteroid therapy or the hytological appearance. The first classification identifies steroid-resistant NS (no response after 4 weeks of steroid therapy); frequently relapsing NS (≥ 2 relapses in first 6 months or ≥4 relapses in 1-year); steroid dependent NS (relapses during steroid decalage or within 2 weeks from steroid therapy interruption). The hystological classification is based on light and electron microscopy after renal biopsy, which is indicated in case of onset disease before 1 year or after 12 years of age. Macroscopic hematuria: persistent hypertension and/or microscopic hematuria and/or low plasma C3 renal failure not related to hypovolemia; steroid resistence: secondary or relatedsyndromes NS. Minimal change disease (MCD) is the most common form of idiopahtic NS in children, with good response to steroid treatment, and it is characterized by normal glomerular appearance on light microscopy and evidence of podocyte foot alterations on electron microscopy, due to immunological related damage. Focal segmental glomerulosclerosis (FSGS) is described inidiopahtic NS, particularly in steroiddependent or steroid-resistant forms, and is characterized by evidence of focal glomerular damage with secondary sclerosis and adhesion with Bowman's capsule; the electron appearance is the same of MCD one. Recent authors hypotizethat the FSGS is an evolution of MCD. These 2 idiopathic NS forms may be expression of the same immunological disease, with 2 different severity grades; so they may be considered different moments of the same disease spectrum. Less common idiopathic NS forms are membrano proliferative glomerulonephritis; membranous nephropathy; IgM-nephropathy; C1q nephropathy and thin basement membrane disease (1, 2, 3).

ATP-binding cassette A1 deficiency causes cardiolipin-driven mitochondrial dysfunction in podocytes

Fibroblasts from patients with Tangier disease carrying ATP-binding cassette A1 (ABCA1) loss-of-function mutations are characterized by cardiolipin accumulation, a mitochondrial-specific phospholipid. Suppression of ABCA1 expression occurs in glomeruli from patients with diabetic kidney disease (DKD) and in human podocytes exposed to DKD sera collected prior to the development of DKD. We demonstrated that siRNA ABCA1 knockdown in podocytes led to reduced oxygen consumption capabilities associated with alterations in the oxidative phosphorylation (OXPHOS) complexes and with cardiolipin accumulation. Podocyte-specific deletion of Abca1 (Abca1fl/fl) rendered mice susceptible to DKD, and pharmacological induction of ABCA1 improved established DKD. This was not mediated by free cholesterol, as genetic deletion of sterol-o-acyltransferase-1 (SOAT1) in Abca1fl/fl mice was sufficient to cause free cholesterol accumulation but did not cause glomerular injury. Instead, cardiolipin mediates ABCA1-dependent susceptibility to podocyte injury, as inhibition of cardiolipin peroxidation with elamipretide improved DKD in vivo and prevented ABCA1-dependent podocyte injury in vitro and in vivo. Collectively, we describe a pathway definitively linking ABCA1 deficiency to cardiolipin-driven mitochondrial dysfunction. We demonstrated that this pathway is relevant to DKD and that ABCA1 inducers or inhibitors of cardiolipin peroxidation may each represent therapeutic strategies for the treatment of established DKD.

Role of TRPC6 in Progression of Diabetic Kidney Disease

PURPOSE OF REVIEW

The underlining goal of this review is to offer a concise, detailed look into current knowledge surrounding transient receptor potential canonical channel 6 (TRPC6) in the progression of diabetic kidney disease (DKD).

RECENT FINDINGS

Mutations and over-activation in TRPC6 channel activity lead to the development of glomeruli injury. Angiotensin II, reactive oxygen species, and other factors in the setting of DKD stimulate drastic increases in calcium influx through the TRPC6 channel, causing podocyte hypertrophy and foot process effacement. Loss of the podocytes further promote deterioration of the glomerular filtration barrier and play a major role in the development of both albuminuria and the renal injury in DKD. Recent genetic manipulation with TRPC6 channels in various rodent models provide additional knowledge about the role of TRPC6 in DKD and are reviewed here. The TRPC6 channel has a pronounced role in the progression of DKD, with deviations in activity yielding detrimental outcomes. The benefits of targeting TRPC6 or its upstream or downstream signaling pathways in DKD are prominent.

Losing their footing: Rac1 signaling causes podocyte detachment and FSGS

Selective modulation of Rho GTPase activity in podocytes recapitulates characteristic features of human nephrosis. Using a mouse model, Robins et al. found that high levels of Rac1 activation in podocytes caused podocyte detachment and glomerulosclerosis. Podocyte Rac1 activity was enhanced in biopsy specimens from patients with nephrosis, and serum from this patient population activated Rac1 in cultured podocytes. These data provide a causal link between podocyte Rac1 activation and human nephrotic diseases.

c-Src is in the effector pathway linking uPAR and podocyte injury

The role of urokinase-type plasminogen activator receptor (uPAR) in kidney physiology and pathology has attracted considerable attention. The protein uPAR has dual functions: as a key regulator of plasmin generation and a component of the innate immune system. In the current issue, Wei and colleagues describe a transgenic mouse expressing Plaur RNA in glomerular podocytes. The mice manifested podocyte injury, including c-Src phosphorylation, proteinuria, and focal segmental glomerulosclerosis (FSGS). Plaur-transgenic mice on a β3 integrin-deficient background were protected from podocyte injury. Renal biopsies from subjects with FSGS, but not those with other glomerular diseases, manifested increased c-Src phosphorylation in podocytes. These findings suggest a novel injury mechanism in FSGS, with possible implications for new treatment strategies.

The natural drug DIAVIT is protective in a type II mouse model of diabetic nephropathy

There is evidence to suggest that abnormal angiogenesis, inflammation, and fibrosis drive diabetic nephropathy (DN). However, there is no specific treatment to counteract these processes. We aimed to determine whether DIAVIT, a natural Vaccinium myrtillus (blueberry) and Hippophae Rhamnoides (sea buckthorn) extract, is protective in a model of type II DN. Diabetic db/db mice were administered DIAVIT in their drinking water for 14 weeks. We assessed the functional, structural, and ultra-structural phenotype of three experimental groups (lean+vehicle, db/db+vehicle, db/db+DIAVIT). We also investigated the angiogenic and fibrotic pathways involved in the mechanism of action of DIAVIT. Diabetic db/db mice developed hyperglycaemia, albuminuria, and an increased glomerular water permeability; the latter two were prevented by DIAVIT. db/db mice developed fibrotic glomeruli, endothelial insult, and glomerular ultra-structural changes, which were not present in DIAVIT-treated mice. Vascular endothelial growth factor A (VEGF-A) splicing was altered in the db/db kidney cortex, increasing the pro-angiogenic VEGF-A₁₆₅ relative to the anti-angiogenic VEGF-A₁₆₅b. This was partially prevented with DIAVIT treatment. Delphinidin, an anthocyanin abundant in DIAVIT, increased the VEGF-A₁₆₅b expression relative to total VEGF-A₁₆₅ in cultured podocytes through phosphorylation of the splice factor SRSF6. DIAVIT, in particular delphinidin, alters VEGF-A splicing in type II DN, rescuing the DN phenotype. This study highlights the therapeutic potential of natural drugs in DN through the manipulation of gene splicing and expression.

Pregnancy in renal transplant patients: Renal function markers and maternal-fetal outcomes

OBJECTIVES

We aimed to evaluate laboratory markers in women who got pregnant after renal transplantation.

STUDY DESIGN

Cross-sectional prospective study.

MAIN OUTCOME MEASURES

Renal function parameters and maternal and fetal data were assessed in renal transplant recipients.

RESULTS

Forty-three women who got pregnant after renal transplantation (mean age, 28.5 years; mean gestational age, 35.6 weeks) were included. Most patients (53.5%) received a renal transplant from a deceased donor. Podocyturia was not significantly correlated with other renal function markers. Mean period from transplantation to pregnancy was approximately 5 years; this period was not associated with obstetric complications or changes in renal markers. A gradual increase was observed in the following parameters during pregnancy and puerperium: serum creatinine levels (P < 0.001), proteinuria (P < 0.001), urinary protein/creatinine ratio (P < 0.001), and albumin/creatinine ratio (P < 0.001). The sensitivity and specificity of protein/creatinine ratio in predicting preeclampsia were high (96.0% and 94.0%, respectively). Elevated serum creatinine levels, urinary albumin/creatinine ratio, and retinol-binding protein levels in the third trimester were associated with prematurity (P < 0.001). Preeclampsia was the main cause of renal function decline at the end of pregnancy (65.0% of cases). Approximately four (9.5%) pregnant women presented with premature rupture of membranes and 18 (42.0%) with a urinary tract infection.

CONCLUSIONS

Proteinuria, urinary protein/creatinine ratio, and retinol-binding protein levels were elevated in patients with preeclampsia. Using these markers to assess renal function during pregnancy may be clinically useful for detecting and monitoring renal injury in renal transplant recipients.

Podocytes: Way to Go

This commentary highlights the article by Hara et al that discusses the clinical implications of mitotic catastrophe in podocyte health during diabetic kidney disease.

Mutations in six nephrosis genes delineate a pathogenic pathway amenable to treatment

No efficient treatment exists for nephrotic syndrome (NS), a frequent cause of chronic kidney disease. Here we show mutations in six different genes (MAGI2, TNS2, DLC1, CDK20, ITSN1, ITSN2) as causing NS in 17 families with partially treatment-sensitive NS (pTSNS). These proteins interact and we delineate their roles in Rho-like small GTPase (RLSG) activity, and demonstrate deficiency for mutants of pTSNS patients. We find that CDK20 regulates DLC1. Knockdown of MAGI2, DLC1, or CDK20 in cultured podocytes reduces migration rate. Treatment with dexamethasone abolishes RhoA activation by knockdown of DLC1 or CDK20 indicating that steroid treatment in patients with pTSNS and mutations in these genes is mediated by this RLSG module. Furthermore, we discover ITSN1 and ITSN2 as podocytic guanine nucleotide exchange factors for Cdc42. We generate Itsn2-L knockout mice that recapitulate the mild NS phenotype. We, thus, define a functional network of RhoA regulation, thereby revealing potential therapeutic targets.

Advances and unmet needs in genetic, basic and clinical science in Alport syndrome: report from the 2015 International Workshop on Alport Syndrome

Alport syndrome (AS) is a genetic disease characterized by haematuric glomerulopathy variably associated with hearing loss and anterior lenticonus. It is caused by mutations in the COL4A3, COL4A4 or COL4A5 genes encoding the α3α4α5(IV) collagen heterotrimer. AS is rare, but it accounts for >1% of patients receiving renal replacement therapy. Angiotensin-converting enzyme inhibition slows, but does not stop, the progression to renal failure; therefore, there is an urgent requirement to expand and intensify research towards discovering new therapeutic targets and new therapies. The 2015 International Workshop on Alport Syndrome targeted unmet needs in basic science, genetics and diagnosis, clinical research and current clinical care. In three intensive days, more than 100 international experts including physicians, geneticists, researchers from academia and industry, and patient representatives from all over the world participated in panel discussions and breakout groups. This report summarizes the most important priority areas including (i) understanding the crucial role of podocyte protection and regeneration, (ii) targeting mutations by new molecular techniques for new animal models and potential gene therapy, (iii) creating optimal interaction between nephrologists and geneticists for early diagnosis, (iv) establishing standards for mutation screening and databases, (v) improving widespread accessibility to current standards of clinical care, (vi) improving collaboration with the pharmaceutical/biotech industry to investigate new therapies, (vii) research in hearing loss as a huge unmet need in Alport patients and (viii) the need to evaluate the risk and benefit of novel (including 'repurposing') therapies on an international basis.

Klotho May Ameliorate Proteinuria by Targeting TRPC6 Channels in Podocytes

Klotho is a type-1 membrane protein predominantly produced in the kidney, the extracellular domain of which is secreted into the systemic circulation. Membranous and secreted Klotho protect organs, including the kidney, but whether and how Klotho directly protects the glomerular filter is unknown. Here, we report that secreted Klotho suppressed transient receptor potential channel 6 (TRPC6)-mediated Ca2+ influx in cultured mouse podocytes by inhibiting phosphoinositide 3-kinase-dependent exocytosis of the channel. Furthermore, soluble Klotho reduced ATP-stimulated actin cytoskeletal remodeling and transepithelial albumin leakage in these cells. Overexpression of TRPC6 by gene delivery in mice induced albuminuria, and exogenous administration of Klotho ameliorated the albuminuria. Notably, immunofluorescence and in situ hybridization revealed Klotho expression in podocytes of mouse and human kidney. Heterozygous Klotho-deficient CKD mice had aggravated albuminuria compared with that in wild-type CKD mice with a similar degree of hypertension and reduced clearance function. Finally, disrupting the integrity of glomerular filter by saline infusion-mediated extracellular fluid volume expansion increased urinary Klotho excretion. These results reveal a potential novel function of Klotho in protecting the glomerular filter, and may offer a new therapeutic strategy for treatment of proteinuria.

Podocyte Autophagy: A Potential Therapeutic Target to Prevent the Progression of Diabetic Nephropathy

Diabetic nephropathy (DN), a leading cause of end-stage renal disease (ESRD), becomes a worldwide problem. Ultrastructural changes of the glomerular filtration barrier, especially the pathological changes of podocytes, lead to proteinuria in patients with diabetes. Podocytes are major components of glomerular filtration barrier, lining outside of the glomerular basement membrane (GBM) to maintain the permeability of the GBM. Autophagy is a high conserved cellular process in lysosomes including impaired protein, cell organelles, and other contents in the cytoplasm. Recent studies suggest that activation of autophagy in podocytes may be a potential therapy to prevent the progression of DN. Here, we review the mechanisms of autophagy in podocytes and discuss the current studies about alleviating proteinuria via activating podocyte autophagy.

The Effects of Extensive Glomerular Filtration of Thin Graphene Oxide Sheets on Kidney Physiology

Understanding how two-dimensional (2D) nanomaterials interact with the biological milieu is fundamental for their development toward biomedical applications. When thin, individualized graphene oxide (GO) sheets were administered intravenously in mice, extensive urinary excretion was observed, indicating rapid transit across the glomerular filtration barrier (GFB). A detailed analysis of kidney function, histopathology, and ultrastructure was performed, along with the in vitro responses of two highly specialized GFB cells (glomerular endothelial cells and podocytes) following exposure to GO. We investigated whether these cells preserved their unique barrier function at doses 100 times greater than the dose expected to reach the GFB in vivo. Both serum and urine analyses revealed that there was no impairment of kidney function up to 1 month after injection of GO at escalating doses. Histological examination suggested no damage to the glomerular and tubular regions of the kidneys. Ultrastructural analysis by transmission electron microscopy showed absence of damage, with no change in the size of podocyte slits, endothelial cell fenestra, or the glomerular basement membrane width. The endothelial and podocyte cell cultures regained their full barrier function after >48 h of GO exposure, and cellular uptake was significant in both cell types after 24 h. This study provided a previously unreported understanding of the interaction between thin GO sheets with different components of the GFB in vitro and in vivo to highlight that the glomerular excretion of significant amounts of GO did not induce any signs of acute nephrotoxicity or glomerular barrier dysfunction.

Mechanisms underpinning remission of albuminuria following bariatric surgery

PURPOSE OF REVIEW

Albuminuria is a biomarker of renal injury commonly used to monitor progression of diabetic kidney disease. The appearance of excess albumin in the urine reflects alterations in the structure and permeability of the glomerular filtration barrier. The present article summarizes the clinical evidence base for remission of albuminuria after bariatric surgery. It furthermore focuses on how beneficial impacts on glomerular podocyte structure and function may explain this phenomenon.

RECENT FINDINGS

A coherent clinical evidence base is emerging demonstrating remission of albuminuria following bariatric surgery in patients with obesity and diabetes. The impaired metabolic milieu in diabetic kidney disease drives podocyte dedifferentiation and death through glucotoxic, lipotoxic proinflammatory, and pressure-related stress. Improvements in these parameters after surgery correlate with improvements in albuminuria and preclinical studies provide mechanistic data that support the existence of cause-effect relationship.

SUMMARY

The benefits of bariatric surgery extend beyond weight loss in diabetes to encompass beneficial effects on diabetic renal injury. Attenuation of the toxic metabolic milieu that the podocyte is exposed to postbariatric surgery suggests that the restitution of podocyte health is a key cellular event underpinning remission of albuminuria.

[Regulatory Effect of Chinese Drugs for Stasis Removing and Collaterals Dredging on the Expres- sions of podocin and CD2AP in Podocyte Slit Diaphragm of Diabetic Nephropathy Rats]

OBJECTIVE

To observe the regulatory effect of Chinese drugs for stasis removing and collaterals dredging (CDSRCD) on the expressions of podocin and CD2AP in podocyte slit diaphragm (SD) of diabetic nephropathy (DN) rats.

METHODS

DN rat model was duplicated in 40 male Sprague- Dawley rats by feeding high fat high glucose diet combined with intraperitoneally injecting 1 % streptozoto- cin (STZ, 35 mg/kg). Totally 36 successfully modeled rats were divided into the model group, the CD- SRCD group,- and the irbesartan group according to random digit table, 12 in each group. Besides, anoth- er 10 normal rats were recruited as a normal group. Rats in the CDSRCD group and the irbesartan group were intragastrically fed with CDSRCD and irbesartan respectively. Rats in the normal group and the mod- el group were fed with equal volume of distilled water at the same time. 24 h urine protein quantitation was detected using ELISA at various time points. Body weight (BW) , kidney weight ( KW), kidney index (KI) , fasting blood glucose (FBG) , serum creatinine (SCr), blood urea nitrogen (BUN), and uric acid (UA) in each group were detected after 16 weeks of intervention. The pathomorphological changes of re- nal tissue were observed under light microscope and electron microscope respectively. The protein and mRNA expressions of podocin and CD2AP were detected by Western blot and Real-time PCR respectively.

RESULTS

(1) Compared with the normal group, 24 h urine protein quantitation significantly increased at week 4, 8, 12, and 16, respectively (P <0. 01). BW was decreased; KI and levels of FBG, SCr, BUN, and UA all increased after modeling (P <0. 01). Compared with the model group, 24 h urine protein quan- titation significantly decreased in the CDSRCD group and the irbesartan group at week 4, 8, 12, and 16, respectively (P <0. 01). Besides, it was more obviously reduced in the CDSRCD group than in the irbe- sartan group (P <0. 05, P <0.01). BUN level obviously decreased both in the CDSRCD group and the irbesartan group after modeling (P <0. 05, P <0. 01). (2) Results of renal pathology showed that disar- ranged renal structure, obviously thickened basement membrane, severely proliferated mesenteria, widely fused foot processes in the model group. All these pathological changes were attenuated in the CD- SRCD group and the irbesartan group to some degree. (3) Results of Western blot and Real-time PCR showed, compared with the normal group, protein and mRNA expressions of podocin and CD2AP decreased in the model group (P <0. 01). Compared with the model group, protein and mRNA expressions of podocin and CD2AP increased in the CDSRCD group and the irbesartan group (P <0. 01). Protein and mRNA expressions of podocin and CD2AP increased more in the CDSRCD group than in the irbesartan group (P <0. 05).

CONCLUSIONS

CDSRCD could protect renal function by lowering urinary protein in DN rats, improve renal pathological changes. Its mechanism might be related to up-regulating mRNA and protein expressions of podocin and CD2AP.

Vascular Endothelial Growth Factor and Podocyte Protection in Chronic Hypoxia: Effects of Endothelin-A Receptor Antagonism

BACKGROUND

Podocytes are major components of the filtration barrier and a renal source of vascular endothelial growth factor (VEGF). Chronic renovascular disease (RVD) progressively degrades the renal function, accompanied by podocyte damage and a progressive reduction in VEGF. We showed that the endothelin (ET) pathway contributes to this pathological process and ET-A (but not ET-B) receptor antagonism protects the kidney in RVD. We hypothesize that ET-A-induced renoprotection is largely driven by the protection of podocyte integrity and function.

METHODS

To mimic the renal environment of chronic RVD, human podocytes were incubated under chronic hypoxia for 96 h and divided in untreated or treated with an ET-A or ET-B receptor antagonist. Cells were quantified after 96 h. Cell homogenates and media were obtained after 1, 24 and 96 h to quantify production of VEGF, anti-VEGF soluble receptor s-Flt1, and the expression of apoptotic mediators. A separate set of similar experiments was performed after addition of a VEGF-neutralizing antibody (VEGF-NA).

RESULTS

Hypoxia decreased podocyte number, which was exacerbated by ET-B but improved after ET-A antagonism. Production of VEGF was preserved by ET-A antagonism, whereas s-Flt1 increased in hypoxic cells after ET-B antagonism only, accompanied by a greater expression of pro-apoptotic mediators. On the other hand, treatment with VEGF-NA diminished ET-A-induced protection of podocytes.

CONCLUSION

ET-A antagonism preserves podocyte viability and integrity under chronic hypoxia, whereas ET-B antagonism exacerbates podocyte dysfunction and death. Enhanced bioavailability of VEGF after ET-A antagonism could be a pivotal mechanism of podocyte protection that significantly contributes to ET-A receptor blockade-induced renal recovery in chronic RVD.

[Protective effects of metformin on glomerular podocytes of type 2 diabetes model rats]

OBJECTIVE

To observe the effects of metformin (MET) on podocalyxin (PCX) expression in renal tissue from type 2 diabetes mellitus (T2DM) model rats and investigate its protective effects against glomerular podocyte injury.

METHOD

The rat model of T2DM was established by feeding with high-fat diet and intraperitoneal injection of low dose of streptozotocin (STZ). All the rats were divided into four groups: diabetic group (n=9), metformin group (300 mg·kg(-1)·d(-1), n=8), glibenclamide group (5 mg·kg(-1)·d(-1), n=8 ) and normal group (n=8). After 8 weeks, urinary PCX and creatinine, blood glucose (BG) and glycated hemoglobin (HbA1c) were detected in all the rats. Immunohistochemistry was used to observe the protein expression of PCX in renal tissue. Real-time polymerase chain reaction (PCR) was performed to detect mRNA expression of PCX. Pathological changes of renal tissue were observed by electron microscope.

RESULTS

Metformin and glyburide treatment decreased the levels of BG and HbA1c [(9.6±1.1) and (9.9±1.1) vs (15.6±1.6) mmol/L, (7.0±0.3)% and (8.0±1.0)% vs (12.4±0.6)%, all P<0.05], compared with diabetes group, while there was no statistically significant difference between the two intervention groups (P>0.05). The level of urinary PCX/urinary creatinine (UPCR) in diabetic rats were higher than that of normal group [(697±136) vs (94±25 ) ng/g, P<0.05), meanwhile the levels of protein and mRNA expression of PCX in kidney tissue reduced remarkably [(0.75±0.11) vs (3.18±0.14), (0.08±0.09) vs (1.00±0.02), both P<0.05]. Above-mentioned indicators could be ameliorated by metformin and glyburide treatment compared to normal group (P<0.05), and there were statistically significant difference between the two intervention groups [(404±83) vs (516±38) ng/g, (1.54±0.06) vs(1.06±0.10), (0.23±0.01) vs (0.16±0.04), all P<0.05)]. Further observation found that basement membrane thickness of kidney [(267±22) vs (106±10)nm )] and fusion rate of foot process (0.80±0.07 vs 0) increased in the rats of diabetic group, and metformin or glyburide treatment can significantly reduced the above changes (P<0.05), additionally, the changes were remarkable different between metformin and glyburide group [(151±17) vs (204±22 ) nm, (0.49±0.04) vs (0.57±0.03), both P<0.05)].

CONCLUSION

Metformin has protective effect on glomerular podocytes by regulating the expression of PCX in renal tissue, independent of its hypoglycemic effect.

Detection of podocyturia in patients with lupus nephritis

INTRODUCTION

The podocyturia has been detected in glomerular diseases, such as lupus nephritis (LN), in which proteinuria is an important manifestation, and its occurrence seems to be limited to the active phase of the disease.

OBJECTIVE

To evaluate podocyturia in LN patients, and the possible association with clinical disease activity.

METHODS

We evaluated 56 patients with LN, that were classified in three groups according to the degree of clinical activity: Group B, no activity (n = 17), Group C with mild (n = 29) and Group D, moderate to severe activity (n = 10). The control group was composed by 29 healthy subjects (Group A). The podocyturia was studied by indirect immunofluorescence using primary antibodies to podocyte: anti-podocin, nephrin and synaptopodin, and a secondary antibody conjugated with FITC. We also evaluated serum creatinine levels, urinary protein/creatinine (P/C) ratio, hematuria and leucocituria.

RESULTS

The podocyturia with anti-podocin and anti-sinaptopodin correlated statistically with the P/C ratio (p = 0.001 and p = 0.013, respectively). The podocyturia with anti-podocin, as well as the P/C ratio showed significant correlation (p < 0.001) with the degree of lupus disease activity, unlike the other two antibodies, anti-nephrin and anti-synaptopodin.

CONCLUSION

Our findings show that podocyturia with anti-podocin could be useful in monitoring disease activity in LN patients.