Calcium blockade versus ACE inhibition in clipped and unclipped kidneys of 2K-1C rats

Comparative Analysis of Hypertensive Tubulopathy in Animal Models of Hypertension and Its Relevance to Human Pathology

Assessment of hypertensive tubulopathy for more than fifty animal models of hypertension in experimental pathology employs criteria that do not correspond to lesional descriptors for tubular lesions in clinical pathology. We provide a critical appraisal of experimental hypertension with the same approach used to estimate hypertensive renal tubulopathy in humans. Four models with different pathogenesis of hypertension were analyzed-chronic angiotensin (Ang) II-infused and renin-overexpressing (TTRhRen) mice, spontaneously hypertensive (SHR), and Goldblatt two-kidney one-clip (2K1C) rats. Mouse models, SHR, and the nonclipped kidney in 2K1C rats had no regular signs of hypertensive tubulopathy. Histopathology in animals was mild and limited to variations in the volume density of tubular lumen and epithelium, interstitial space, and interstitial collagen. Affected kidneys in animals demonstrated lesion values that are significantly different compared with healthy controls but correspond to mild damage if compared with hypertensive humans. The most substantial human-like hypertensive tubulopathy was detected in the clipped kidney of 2K1C rats. For the first time, our study demonstrated the regular presence of chronic progressive nephropathy (CPN) in relatively young mice and rats with induced hypertension. Because CPN may confound the assessment of rodent models of hypertension, proliferative markers should be used to verify nonhypertensive tubulopathy.

Podocyte VEGF-A Knockdown Induces Diffuse Glomerulosclerosis in Diabetic and in eNOS Knockout Mice

Vascular endothelial growth factor-a (VEGF-A) and nitric oxide (NO) are essential for glomerular filtration barrier homeostasis, and are dysregulated in diabetic kidney disease (DKD). While NO availability is consistently low in diabetes, both high and low VEGF-A have been reported in patients with DKD. Here we examined the effect of inducible podocyte VEGF-A knockdown (VEGF^KD) in diabetic mice and in endothelial nitric oxide synthase knockout mice (eNOS^−/−). Diabetes was induced with streptozotocin using the Animal Models of Diabetic Complications Consortium (AMDCC) protocol. Induction of podocyte VEGF^KD led to diffuse glomerulosclerosis, foot process effacement, and GBM thickening in both diabetic mice with intact eNOS and in non-diabetic eNOS^−/−:VEGF^KD mice. VEGF^KD diabetic mice developed mild proteinuria and maintained normal glomerular filtration rate (GFR), associated with extremely high NO and thiol urinary excretion. In eNOS^−/−:VEGF^KD (+dox) mice severe diffuse glomerulosclerosis was associated with microaneurisms, arteriolar hyalinosis, massive proteinuria, and renal failure. Collectively, data indicate that combined podocyte VEGF-A and eNOS deficiency result in diffuse glomerulosclerosis in mice; compensatory NO and thiol generation prevents severe proteinuria and GFR loss in VEGF^KD diabetic mice with intact eNOS, whereas VEGF^KD induction in eNOS^−/−:VEGF^KD mice causes massive proteinuria and renal failure mimicking DKD in the absence of diabetes. Mechanistically, we identify VEGF^KD-induced abnormal S-nitrosylation of specific proteins, including β3-integrin, laminin, and S-nitrosoglutathione reductase (GSNOR), as targetable molecular mechanisms involved in the development of advanced diffuse glomerulosclerosis and renal failure.

Comparative analysis of hypertensive nephrosclerosis in animal models of hypertension and its relevance to human pathology. Glomerulopathy

Current research on hypertension utilizes more than fifty animal models that rely mainly on stable increases in systolic blood pressure. In experimental hypertension, grading or scoring of glomerulopathy in the majority of studies is based on a wide range of opinion-based histological changes that do not necessarily comply with lesional descriptors for glomerular injury that are well-established in clinical pathology. Here, we provide a critical appraisal of experimental hypertensive glomerulopathy with the same approach used to assess hypertensive glomerulopathy in humans. Four hypertensive models with varying pathogenesis were analyzed–chronic angiotensin II infused mice, mice expressing active human renin in the liver (TTRhRen), spontaneously hypertensive rats (SHR), and Goldblatt two-kidney one-clip rats (2K1C). Analysis of glomerulopathy utilized the same criteria applied in humans–hyalinosis, focal segmental glomerulosclerosis (FSGS), ischemic, hypertrophic and solidified glomeruli, or global glomerulosclerosis (GGS). Data from animal models were compared to human reference values. Kidneys in TTRhRen mice, SHR and the nonclipped kidneys in 2K1C rats had no sign of hyalinosis, FSGS or GGS. Glomerulopathy in these groups was limited to variations in mesangial and capillary compartment volumes, with mild increases in collagen deposition. Histopathology in angiotensin II infused mice corresponded to mesangioproliferative glomerulonephritis, but not hypertensive glomerulosclerosis. The number of nephrons was significantly reduced in TTRhRen mice and SHR, but did not correlate with severity of glomerulopathy. The most substantial human-like glomerulosclerotic lesions, including FSGS, ischemic obsolescent glomeruli and GGS, were found in the clipped kidneys of 2K1C rats. The comparison of affected kidneys to healthy control in animals produces lesion values that are numerically impressive but correspond to mild damage if compared to humans. Animal studies should be standardized by employing the criteria and classifications established in human pathology to make experimental and human data fully comparable for comprehensive analysis and model improvements.

Role of (Pro)Renin Receptor in Cyclosporin A-Induced Nephropathy

Calcineurin inhibitors (CNIs) such as cyclosporin A (CsA) have been widely used to improve graft survival following solid-organ transplantation. However, the clinical use of CsA is often limited by its nephrotoxicity. The present study tested the hypothesis that activation of (pro)renin receptor (PRR) contributes to CsA-induced nephropathy by activating the renin-angiotensin system (RAS). Renal injury in male Sprague-Dawley rats was induced by a low-salt diet combined with CsA as evidenced by elevated plasma creatinine and BUN levels, decreased creatinine clearance and induced renal inflammation, apoptosis as well as interstitial fibrosis, elevated urinary N-acetyl-β-D-glucosaminidase activity and urinary kidney injury molecular 1 content. Each index of renal injury was attenuated following a 2-wk treatment with a PRR decoy inhibitor PRO20. While CsA rats with kidney injury displayed increased renal sPRR abundance, plasma sPRR, renin activity, Ang II, and heightened urinary total prorenin/renin content; RAS activation was attenuated by PRO20. Exposure of cultured human renal proximal tubular HK-2 cells to CsA induced expression of fibronectin and sPRR production, but the fibrotic response was attenuated by PRO20 and siRNA-mediated PRR knockdown. These findings support the hypothesis that activation of PRR contributes to CsA-induced nephropathy by activating the RAS in rats. Of importance, we provide strong proof of concept that targeting PRR offers a novel therapeutic strategy to limit nephotoxic effects of immunosuppressant drugs.

Renal effects of the serine protease inhibitor aprotinin in healthy conscious mice

Treatment with aprotinin, a broad-spectrum serine protease inhibitor with a molecular weight of 6512 Da, was associated with acute kidney injury, which was one of the reasons for withdrawal from the market in 2007. Inhibition of renal serine proteases regulating the epithelial sodium channel ENaC could be a possible mechanism. Herein, we studied the effect of aprotinin in wild-type 129S1/SvImJ mice on sodium handling, tubular function, and integrity under a control and low-salt diet. Mice were studied in metabolic cages, and aprotinin was delivered by subcutaneously implanted sustained release pellets (2 mg/day over 10 days). Mean urinary aprotinin concentration ranged between 642 ± 135 (day 2) and 127 ± 16 (day 8) µg/mL . Aprotinin caused impaired sodium preservation under a low-salt diet while stimulating excessive hyperaldosteronism and unexpectedly, proteolytic activation of ENaC. Aprotinin inhibited proximal tubular function leading to glucosuria and proteinuria. Plasma urea and cystatin C concentration increased significantly under aprotinin treatment. Kidney tissues from aprotinin-treated mice showed accumulation of intracellular aprotinin and expression of the kidney injury molecule 1 (KIM-1). In electron microscopy, electron-dense deposits were observed. There was no evidence for kidney injury in mice treated with a lower aprotinin dose (0.5 mg/day). In conclusion, high doses of aprotinin exert nephrotoxic effects by accumulation in the tubular system of healthy mice, leading to inhibition of proximal tubular function and counterregulatory stimulation of ENaC-mediated sodium transport.

Subproteomic profiling from renal cortices in OLETF rats reveals mutations of multiple novel genes in diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is a serious threat to human health, but its pathogenesis is not fully understood. Otsuka Long-Evans Tokushima Fatty (OLETF) rats are very similar to human DN in many aspects such as pathological changes and processes, and are deemed to be an ideal rodent model.

OBJECTIVE

This study was aimed to explore the pathogenesis of DN by analyzing the protein expression profile from renal cortices in OLETF rats.

METHODS

Thirty-six-week-old diabetic OLETF rats and normal control Long-Evans Tokushima Otsuka (LETO) rats were nephrectomized, and the renal cortices were isolated. The proteins were separated by soluble and insoluble high-resolution subproteomics methods for the analysis and identification of differential proteins.

RESULTS

Thirty-six differentially expressed proteins were found. Among them, 11 proteins had different isoelectric points and molecular weights between OLETF and LETO rats. Further sequencing identified point mutations in genes encoding eight of these proteins, which are involved in many biological processes closely related to DN, including oxidative stress and inflammation. Five of these eight proteins have not been reported in DN.

CONCLUSION

This study reveals mutations of multiple novel genes in diabetic OLETF rats, providing some new potential targets for the pathogenesis of DN and helping to better understand the pathogenesis of DN.

(Pro)renin receptor antagonist PRO20 attenuates nephrectomy-induced nephropathy in rats via inhibition of intrarenal RAS and Wnt/β-catenin signaling

Introduction

(Pro)renin receptor has emerged as a new member of the renin‐angiotensin system implicated in the pathogenesis of chronic kidney disease (CKD). Herein we report characterization of the therapeutic potential of (pro)renin receptor (PRR) antagonist PRO20 in 5/6 nephrectomy (5/6Nx) rats.

Methods

Male Wistar rats underwent 5/6Nx followed by treatment with vehicle or received daily injections of a PRR inhibitor PRO20 (700 μg/kg) via the 3 s.c. Sham group served as a control.

Results

As compared with the sham control, the 5/6Nx rats exhibited significant increases in proteinuria, glomerulosclerosis, tubular injury, and interstitial inflammation in the remnant kidneys. Treatment with PRO20 significantly attenuated these abnormalities, as evidenced by reduced expression of fibronectin, α‐SMA, collagen 1, TGF‐β1, IL‐6, IL‐8, IL‐1β, MCP‐1 and increased expression of E‐cadherin. Increased urinary/renal levels of renin activity, angiotensinogen (AGT), and Angiotensin II (Ang II) by 5/6Nx, which were all ameliorated by PRO20. Renal PRR, the secreted proteolytic fragment of PRR (sPRR) in renal and urinary, were all elevated in 5/6Nx rats. Moreover, our results revealed that renal Wnt3A and β‐catenin expression were upregulated during 5/6Nx, which were all attenuated by PRO20.

Conclusions

Overall we conclude that in vivo antagonism of PRR with PRO20 will improve 5/6Nx‐induced CKD mainly through inhibition of intrarenal RAS and Wnt/β‐catenin signaling pathway.

Açaí Reverses Adverse Cardiovascular Remodeling in Renovascular Hypertension: A Comparative Effect With Enalapril

ABSTRACT

This study aimed to determine if açai seed extract (ASE) could reverse pre-existing cardiovascular and renal injury in an experimental model of renovascular hypertension (2 kidney, 1 clip, 2K1C). Young male rats (Wistar) were used to obtain 2K1C and sham groups. Animals received the vehicle, ASE (200 mg/kg/d), or enalapril (30 mg/kg/d) in drinking water from the third to sixth week after surgery. We evaluated systolic blood pressure by tail plethysmography, vascular reactivity in the rat isolated mesenteric arterial bed (MAB), serum and urinary parameters, plasma inflammatory cytokines by ELISA, MAB expression of endothelial nitric oxide synthase and its active form peNOS by Western blot, plasma and MAB oxidative damage and antioxidant activity by spectrophotometry, and vascular and cardiac structural changes by histological analysis. ASE and enalapril reduced the systolic blood pressure, restored the endothelial and renal functions, and decreased the inflammatory cytokines and the oxidative stress in 2K1C rats. Furthermore, both treatments reduced vascular and cardiac remodeling. ASE substantially reduced cardiovascular remodeling and recovered endothelial dysfunction in 2K1C rats probably through its antihypertensive, antioxidant, and anti-inflammatory actions, supplying a natural resource for the treatment of renovascular hypertension.

Effect of meloxicam (cyclooygenase-2 inhibitor) versus vitamin D3 (cholecalciferol) as ameliorating agents of progressive doxorubicin-induced nephrotoxicity in rats

Doxorubicin (DOX)-induced nephropathy hampered its antineoplastic efficiency. The objective of the current work is to assess the prospective ameliorating effects of meloxicam versus vitamin D3 (Vit D3, cholecalciferol) against progressive DOX-induced nephropathy in rats trying to ascertain the possible mechanism underlying such amelioration. Ninety Male Wistar rats were randomly distributed to five experimental groups for 3 weeks, with saline, meloxicam (daily), DOX (single dose), Vit D3+DOX, or both meloxicam and DOX. We measured levels of urinary protein, serum creatinine, malondialdehyde (MDA) and renal reduced glutathione (GSH). In addition, tumor necrosis factor-alpha (TNF-α) expression and renal histopathology were assessed. Meloxicam alone treated group revealed no significant difference in urinary protein and serum creatinine. It also presented non-significant reduction in the MDA content while an increase in the reduced GSH content in contrast to the control group, which is more evident after the first week. Renal sections of rats received meloxicam only showed no significant histological changes and negative immunoreactivity compared to the control group. DOX induced a significant increase in urinary protein, serum creatinine, decrease reduced GSH, increased renal MDA and disrupted renal morphometric parameters and histology with increased TNF-α expression. Combination groups of Vit D3+DOX and meloxicam+DOX showed improvement of all DOX disturbed parameters. Meloxicam showed better results most likely due to anti-inflammatory and antioxidant activities superimposing the immune-modulatory effect of Vit D3. So, it is recommended to use meloxicam in patients receiving DOX as a renoprotective agent in addition to its analgesic effects required by cancer patients.

Diabetes-induced upregulation of kallistatin levels exacerbates diabetic nephropathy via RAS activation

Kallistatin is an inhibitor of tissue kallikrein and also inhibits the Wnt pathway. Its role in diabetic nephropathy (DN) is uncertain. Here we reported that serum kallistatin levels were significantly increased in diabetic patients with DN compared to those in diabetic patients without DN and healthy controls, and positively correlated with urinary albumin excretion. In addition, renal kallistatin levels were significantly upregulated in mouse models of type 1 (Akita, OVE26) and type 2 diabetes (db/db). To unveil the effects of kallistatin on DN and its underlying mechanism, we crossed transgenic mice overexpressing kallistatin with OVE26 mice (KS‐tg/OVE). Kallistatin overexpression exacerbated albuminuria, renal fibrosis, inflammation, and oxidative stress in diabetes. Kallikrein activity was inhibited while the renin‐angiotensin system (RAS) upregulated in the kidney of KS‐tg/OVE mice compared to WT/OVE mice, suggesting a disturbed balance between the RAS and kallikrein‐kinin systems. As shown by immunostaining of endothelial makers, renal vascular densities were decreased accompanied by increased HIF‐1α and erythropoietin levels in the kidneys of KS‐tg/OVE mice. Taken together, high levels of kallistatin exacerbate DN at least partly by inducing RAS overactivation and hypoxia. The present study demonstrated a positive correlation between kallistatin levels and DN, suggesting a potential biomarker for prognosis of DN.

Yiqihuoxue Formula Activates Autophagy and Offers Renoprotection in a Rat Model of Adenine-Induced Kidney Disease

Chronic kidney disease (CKD) is a worldwide health problem for which effective therapeutic methods are still lacking. Traditional Chinese medicine (TCM) has been indicated as an effective alternative treatment for kidney disease. In this study, a clinically effective therapy, yiqihuoxue (YQHX) formula, was administrated to adenine-induced kidney disease rats for 6 weeks. We found that the adenine rats displayed a significant reduction in renal function as evidenced by the increased levels of serum creatinine (Scr), blood urea nitrogen (BUN), and 24-h urinary albumin level, which were attenuated by the YQHX treatment. The glomerulosclerosis, interstitial fibrosis, arteriolosclerosis, interstitial inflammation, and tubular dilatation were reversed by the YQHX treatment in the adenine rats. Furthermore, the hepatic damage characterized by increased levels of aspartate aminotransferase and alanine aminotransferase and inflammatory cell infiltration was improved by YQHX. In addition, the number of apoptotic cells in the adenine rats was obviously reduced by the YQHX treatment as manifested by the lower expression level of cleaved caspase-3 protein. Moreover, the YQHX treatment downregulated the expression levels of fibronectin, type I collagen, α-smooth muscle actin, and TGF-β1 in the adenine rats. Furthermore, autophagy was activated by the YQHX treatment, which manifested as an increased LC3-II and Beclin-1 expression levels and a decreased p62 level. In conclusion, the YQHX formula might retard the progression of kidney disease by activating autophagy.

Effect of fosinopril on the renal cortex protein expression profile of Otsuka Long-Evans Tokushima Fatty rats

Angiotensin-converting enzyme inhibitors (ACEIs) can reduce urinary protein excretion and postpone the deterioration of renal function. However, the mechanisms of renal protection are not yet fully understood. To investigate the mechanisms of ACEIs in the treatment of diabetic nephropathy (DN), the present study determined the effects of the ACEI fosinopril (FP) on the profiling of renal cortex protein expression in Otsuka Long-Evans Tokushima Fatty (OLETF) rats using Long-Evans Tokushima Otsuka (LETO) rats as controls. Urinary protein levels at 24 h were examined using the Broadford method. PAS staining was performed to observe renal histopathological changes. The kidney cortices of OLETF, FP-treated OLETF and LETO rats were examined using soluble and insoluble high-resolution subproteomic analysis methodology at age of 36 and 56 weeks. Differentiated proteins were further confirmed using western blotting analysis. The results demonstrated that FP significantly decreased the glomerulosclerosis index and reduced the 24 h urinary protein excretion of OLETF rats. Additionally, 17 proteins significantly changed following FP-treatment. Amongst these proteins, the abundances of the stress-response protein heat shock protein family A member 9 and the antioxidant glutathione peroxidase 3 were particularly increased. These results indicated that FP ameliorated diabetic renal injuries by inhibiting oxidative stress. In conclusion, the differentially expressed proteins may improve our understanding of the mechanism of ACEIs in the OLETF rats.

Heterogeneous Nuclear Ribonucleoprotein F Mediates Insulin Inhibition of Bcl2-Modifying Factor Expression and Tubulopathy in Diabetic Kidney

We investigated the molecular mechanism(s) by which insulin prevents Bcl2-modifying factor (Bmf)-induced renal proximal tubular cell (RPTC) apoptosis and loss in diabetic mice. Transgenic mice (Tg) mice specifically overexpressing human BMF in RPTCs and non-Tg littermates were studied at 10 to 20 weeks of age. Non-diabetic littermates, diabetic Akita mice +/− insulin implant, Akita Tg mice specifically overexpressing heterogeneous nuclear ribonucleoprotein F (hnRNP F) in their RPTCs and immortalized rat renal proximal tubular cells (IRPTCs) were also studied. BMF-Tg mice exhibited higher systolic blood pressure, urinary albumin/creatinine ratio, RPTC apoptosis and urinary RPTCs than non-Tg mice. Insulin treatment in Akita mice and Akita mice overexpressing hnRNP F suppressed Bmf expression and RPTC apoptosis. In hyperinsulinemic-euglycemic wild type mice, renal Bmf expression was down-regulated with up-regulation of hnRNP F. In vitro, insulin inhibited high glucose-stimulation of Bmf expression, predominantly via p44/42 mitogen-activated protein kinase (MAPK) signaling. Transfection of p44/42 MAPK or hnRNP F small interfering RNA (siRNA) prevented insulin inhibition of Bmf expression. HnRNP F inhibited Bmf transcription via hnRNP F-responsive element in the Bmf promoter. Our results demonstrate that hnRNP F suppression of Bmf transcription is an important mechanism by which insulin protects RPTCs from apoptosis in diabetes.

Role of (pro)renin receptor in albumin overload-induced nephropathy in rats

Proteinuria is not only a common feature of chronic kidney diseases (CKD) but also an independent risk factor promoting CKD progression to end-stage renal failure. However, the underlying molecular mechanisms for protein overload-induced renal injury remain elusive. The present study examined the role of (pro)renin receptor (PRR) in pathogenesis of albumin overload (AO)-induced nephropathy and activation of the intrarenal renin-angiotensin system (RAS) in rats. Wistar rats underwent unilateral nephrectomy and were treated for 7 wk with vehicle, bovine serum albumin (5 g·kg^-1·day^-1 via a single ip injection), alone or in conjunction with the PRR decoy inhibitor PRO20 (500 μg·kg^-1·day^-1 via 3 sc injections). The AO rat model exhibited severe proteinuria, tubular necrosis, and interstitial fibrosis, oxidative stress, and inflammation, accompanied by elevated urinary N-acetyl-β-d-glucosaminidase activity and urinary β₂-microglobulin secretion, all of which were significantly attenuated by PRO20. Urinary and renal levels of renin, angiotensinogen, and ANG II were elevated by AO and suppressed by PRO20, contrasting to largely unaltered plasma levels of the RAS parameters. The AO model also showed increased renal expression of full-length PRR and soluble PRR (sPRR) and urinary excretion of sPRR. Taken together, we conclude that PRR antagonism with PRO20 alleviates AO-induced nephropathy via inhibition of intrarenal RAS.

Endothelin A receptor blocker and calcimimetic in the adenine rat model of chronic renal insufficiency

BACKGROUND

We studied whether endothelin receptor antagonist and calcimimetic treatments influence renal damage and kidney renin-angiotensin (RA) components in adenine-induced chronic renal insufficiency (CRI).

METHODS

Male Wistar rats (n = 80) were divided into 5 groups for 12 weeks: control (n = 12), 0.3% adenine (Ade; n = 20), Ade + 50 mg/kg/day sitaxentan (n = 16), Ade + 20 mg/kg/day cinacalcet (n = 16), and Ade + sitaxentan + cinacalcet (n = 16). Blood pressure (BP) was measured using tail-cuff, kidney histology was examined, and RA components measured using RT-qPCR.

RESULTS

Adenine caused tubulointerstitial damage with severe CRI, anemia, hyperphosphatemia, 1.8-fold increase in urinary calcium excretion, and 3.5-fold and 18-fold increases in plasma creatinine and PTH, respectively. Sitaxentan alleviated tubular atrophy, while sitaxentan + cinacalcet combination reduced interstitial inflammation, tubular dilatation and atrophy in adenine-rats. Adenine diet did not influence kidney angiotensin converting enzyme (ACE) and AT₄ receptor mRNA, but reduced mRNA of renin, AT_1a, AT₂, (pro)renin receptor and Mas to 40-60%, and suppressed ACE2 to 6% of that in controls. Sitaxentan reduced BP by 8 mmHg, creatinine, urea, and phosphate concentrations by 16-24%, and PTH by 42%. Cinacalcet did not influence BP or creatinine, but reduced PTH by 84%, and increased hemoglobin by 28% in adenine-rats. The treatments further reduced renin mRNA by 40%, while combined treatment normalized plasma PTH, urinary calcium, and increased ACE2 mRNA 2.5-fold versus the Ade group (p < 0.001).

CONCLUSIONS

In adenine-induced interstitial nephritis, sitaxentan improved renal function and tubular atrophy. Sitaxentan and cinacalcet reduced kidney renin mRNA by 40%, while their combination alleviated tubulointerstitial damage and urinary calcium loss, and increased kidney tissue ACE2 mRNA.

Post-weaning high-fat diet accelerates kidney injury, but not hypertension programmed by maternal diabetes

BACKGROUND

The aim of this study was to establish the underlying mechanisms by which a post-weaning high-fat diet (HFD) accelerates the perinatal programming of kidney injury occurring in the offspring of diabetic mothers.

METHODS

Male mice, offspring of nondiabetic and diabetic dams were fed with normal diet (ND) or HFD from 4 to 20 wk of age. Rat renal proximal tubular cells were used in vitro.

RESULTS

On ND, the offspring of dams with severe maternal diabetes had an intrauterine growth restriction (IUGR) phenotype and developed mild hypertension and evidence of kidney injury in adulthood. Exposing the IUGR offspring to HFD resulted in rapid weight gain, catch-up growth, and later to profound kidney injury with activation of renal TGFβ1 and collagen type IV expression, increased oxidative stress, and enhanced renal lipid deposition, but not systemic hypertension. Given our data, we speculate that HFD or free fatty acids may accelerate the process of perinatal programming of kidney injury, via increased CD36 and fatty acid-binding protein 4 expression, which may target reactive oxygen species, nuclear factor-kappa B, and TGFβ1 signaling in vivo and in vitro.

CONCLUSION

Early postnatal exposure to overnutrition with a HFD increases the risk of development of kidney injury, but not hypertension, in IUGR offspring of dams with maternal diabetes.

Renal artery stenosis - an update

Renal artery stenosis (RAS) is a common form of peripheral arterial disease. The most common cause of RAS is atherosclerosis. It is predominantly unilateral. The pathophysiologic mechanism stems from renal underperfusion resulting in the activation of the renin- angiotensin-aldosterone pathway. Even though the majority of patients with RAS are asymptomatic, it can clinically present with hypertension, nephropathy and congestive heart failure. This progressive disease can lead to resistant hypertension and end stage kidney failure. Screening patients for RAS with either Doppler ultrasonography, computed tomographic angiography, or magnetic resonance angiography is preferred. Adequate blood pressure control, goal-directed lipid-lowering therapy, smoking cessation, and other preventive measures form the foundation of management of patients with RAS. Catheter-based percutaneous revascularization with angioplasty and stenting showed modest clinical benefit for patients in small retrospective studies, but data from randomized clinical trials failed to confirm these beneficial results. The current ongoing Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial may provide more concrete data regarding the role of stenting in RAS. Surgical revascularization is considered only if catheter-based revascularization is unsuitable or unsuccessful. The American College of Cardiology/American Heart Association guidelines on evaluation and management of patients with RAS provide the framework for determining individualized assessment and treatment plans for patients with RAS.

Delayed mTOR inhibition with low dose of everolimus reduces TGFβ expression, attenuates proteinuria and renal damage in the renal mass reduction model

Background

The immunosuppressive mammalian target of rapamycin (mTOR) inhibitors are widely used in solid organ transplantation, but their effect on kidney disease progression is controversial. mTOR has emerged as one of the main pathways regulating cell growth, proliferation, differentiation, migration, and survival.

The aim of this study was to analyze the effects of delayed inhibition of mTOR pathway with low dose of everolimus on progression of renal disease and TGFβ expression in the 5/6 nephrectomy model in Wistar rats.

Methods

This study evaluated the effects of everolimus (0.3 mg/k/day) introduced 15 days after surgical procedure on renal function, proteinuria, renal histology and mechanisms of fibrosis and proliferation.

Results

Everolimus treated group (EveG) showed significantly less proteinuria and albuminuria, less glomerular and tubulointerstitial damage and fibrosis, fibroblast activation cell proliferation, when compared with control group (CG), even though the EveG remained with high blood pressure. Treatment with everolimus also diminished glomerular hypertrophy.

Everolimus effectively inhibited the increase of mTOR developed in 5/6 nephrectomy animals, without changes in AKT mRNA or protein abundance, but with an increase in the pAKT/AKT ratio. Associated with this inhibition, everolimus blunted the increased expression of TGFβ observed in the remnant kidney model.

Conclusion

Delayed mTOR inhibition with low dose of everolimus significantly prevented progressive renal damage and protected the remnant kidney. mTOR and TGFβ mRNA reduction can partially explain this anti fibrotic effect. mTOR can be a new target to attenuate the progression of chronic kidney disease even in those nephropathies of non-immunologic origin.

Intrarenal metabolomics reveals the association of local organic toxins with the progression of diabetic kidney disease

The pathological development of diabetic kidney disease (DKD) might involve metabolic perturbations in kidney tissue. The present study was designed to detect the systematic alterations of renal cortex metabolites thereby exploring the related mechanisms of DKD development and fosinopril treatment. Based on combined gas chromatography/time-of-flight mass spectrometry (GC-TOF MS) and liquid chromatography/time-of-flight mass spectrometry (UPLC-TOF MS) data acquiring platform, we have performed a metabolomic analysis of perfused renal cortex samples from the diabetic rats induced by streptozocin and treated with or without fosinopril, a pharmacological inhibitor of angiotensin II converting enzyme (ACEI). We identified a number of abnormal metabolites in the diabetic kidney, including groups of amino acids, carbohydrates, polyols, lyso-phospholipids, glucuronides and other unidentified metabolites. Of them, an increase in intrarenal organic toxins including uremic toxins, glucuronides and glucotocixity-associated metabolites are highly correlated with diabetic kidney injury including 24h urinary protein levels and tubulointerstitial injury index. Treatment with fosinopril significantly attenuated diabetic kidney injury, and simultaneously blocked the intrarenal accumulation of these organic toxins, especially hippurate and glucuronides. These results indicate that intrarenal accumulation of organic toxins may be significant for the development of DKD and the related mechanisms deserve to be further investigated.

Early glomerular alterations in genetically determined low nephron number

An association between low nephron number and subsequent development of hypertension in later life has been demonstrated. The underlying pathomechanisms are unknown, but glomerular and postglomerular changes have been discussed. We investigated whether such changes are already present in prehypertensive “glial cell line-derived neurotrophic growth factor” heterozygous mice (GDNF+/−) with lower nephron number. Twenty-six-week-old mice [22 GDNF+/−, 29 C57B6 wild-type control (wt)] were used for in vivo experiments with intra-arterial and tail cuff blood pressure measurements. After perfusion fixation, kidneys were investigated with morphological, morphometric, stereological, and immunohistochemical techniques and TaqMan PCR analysis. As expected at this age, blood pressure was comparable between GDNF+/− and wt. Nephron number per kidney was significantly lower in GDNF+/− than in wt (−32.8%, P < 0.005), and mean glomerular volume was significantly higher (+49.5%, P < 0.001). Renal damage scores, glomerular and tubular proliferation, analysis of intrarenal arteries and peritubular capillaries, expression of relevant tubular transporter proteins, as well as gene expression of profibrotic, proinflammatory, or prohypertensive markers were not significantly different between GDNF+/− and wt. Compensatory glomerular hypertrophy in GDNF+/− was accompanied by higher numbers of endothelial and mesangial cells as well as PCNA-positive glomerular cells, whereas podocyte density was significantly reduced. Further electron microscopic analysis showed marked thickening of glomerular basement membrane. In conclusion, lower nephron number is associated with marked early glomerular structural changes, in particular lower capillary supply, reduced podocyte density, and thickened glomerular basement membrane, that may predispose to glomerular sclerosis.

Attenuation of Diabetic Nephropathy in Otsuka Long-Evans Tokushima Fatty (OLETF) Rats with a Combination of Chinese Herbs (Tangshen Formula)

Diabetic nephropathy is one of the most significant microvascular complications in patients with type 2 diabetics. The concise mechanism of diabetic nephropathy is unknown and there is no successful treatment. The objective of study was to investigate effects of Chinese herbs (Tangshen Formula) on diabetic nephropathy in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. OLETF rats and LETO rats were divided into four groups: LETO control, OLETF diabetics, OLETF diabetics treated with Tangshen Formula, and OLETF diabetics treated with Monopril. Body weight, blood glucose, and 24 h urinary proteins were measured once every four weeks. Blood samples and kidney tissues were obtained for analyses of total cholesterol, triglyceride, whole blood viscosity, plasma viscosity, and pathohistological examination at 36 and 56 weeksrespectively. Untreated OLETF rats displayed diabetic nephropathy over the study period. Treatment of OLETF rats with Tangshen Formula attenuated the increases in blood glucose, body weight, 24 h urinary protein content, serum total cholesterol, whole blood viscosity and plasma viscosity at certain time. Treatment with Tangshen Formula also reduced glomerulosclerotic index and interstitial fibrotic index seen in OLETF rats. In conclusion, Tangshen Formula could attenuate the development of diabetic nephropathy in OLETF rat diabetic model.

Inhibition of the soluble epoxide hydrolase promotes albuminuria in mice with progressive renal disease

Epoxyeicotrienoic acids (EETs) are cytochrome P450-dependent anti-hypertensive and anti-inflammatory derivatives of arachidonic acid, which are highly abundant in the kidney and considered reno-protective. EETs are degraded by the enzyme soluble epoxide hydrolase (sEH) and sEH inhibitors are considered treatment for chronic renal failure (CRF). We determined whether sEH inhibition attenuates the progression of CRF in the 5/6-nephrectomy model (5/6-Nx) in mice. 5/6-Nx mice were treated with a placebo, an ACE-inhibitor (Ramipril, 40 mg/kg), the sEH-inhibitor cAUCB or the CYP-inhibitor fenbendazole for 8 weeks. 5/6-Nx induced hypertension, albuminuria, glomerulosclerosis and tubulo-interstitial damage and these effects were attenuated by Ramipril. In contrast, cAUCB failed to lower the blood pressure and albuminuria was more severe as compared to placebo. Plasma EET-levels were doubled in 5/6 Nx-mice as compared to sham mice receiving placebo. Renal sEH expression was attenuated in 5/6-Nx mice but cAUCB in these animals still further increased the EET-level. cAUCB also increased 5-HETE and 15-HETE, which derive from peroxidation or lipoxygenases. Similar to cAUCB, CYP450 inhibition increased HETEs and promoted albuminuria. Thus, sEH-inhibition failed to elicit protective effects in the 5/6-Nx model and showed a tendency to aggravate the disease. These effects might be consequence of a shift of arachidonic acid metabolism into the lipoxygenase pathway.

Role of FTY720 on M1 and M2 macrophages, lymphocytes, and chemokines in 5/6 nephrectomized rats

Renal injury is accompanied by the presence of infiltrating inflammatory cells in the glomerulus and tubulointerstitium. FTY720 modifies lymphocyte migration into injured tissues by lymphocyte sequestration to secondary lymphoid organs. The purpose of this study was to examine the potential of FTY720 to influence the inflammatory response in a nonimmunological model of renal failure. Sham-operated and 5/6 nephrectomized (SNX) Sprague-Dawley rats received two different doses of FTY720 or vehicle orally for 14 wk. Treatment with FTY720 reduced glomerular and tubulointerstitial damage in SNX rats but failed to stabilize creatinine clearance. The increase in gene expression of chemokine receptors CCR1, CCR2, and CCR5 in kidneys of vehicle-treated SNX rats was significantly attenuated by high-dose FTY720. Treatment with high-dose FTY720 tended to normalize RANTES and MCP-1 renal gene expression. FTY720 affected not only glomerular and tubulointerstitial lymphocytes, but M1 and M2 phenotype macrophages were also reduced. FTY720 significantly reduced key mediators of renal inflammation and fibrosis. FTY720 also decreased immunoregulation of M2 macrophages, which are beneficial for tissue remodeling and repair.

Lack of nidogen-2 increases blood pressure, glomerular and tubulointerstitial damage in DOCA-salt hypertension

BACKGROUND

Nidogen-2, an extracellular matrix protein, is ubiquitous in renal basement membranes linking the laminin and collagen IV networks. Nidogen-2-deficient (nidogen-2(-/-)) mice do not exhibit a phenotype, and renal basement membranes appear normal. The functional role of nidogen-2 in the adult kidney under pathological conditions however remains unclear. We tested the hypothesis that nidogen-2 mediated cell-matrix interactions are important to maintain glomerular integrity and structure in renal hyperperfusion and hypertension.

MATERIALS AND METHODS

Two weeks after unilateral nephrectomy (UNX), desoxycorticosterone (DOCA)-salt hypertension was induced in nidogen-2(-/-) mice and their wild type littermates for 6 weeks. Renal damage was assessed by means of semiquantitative scoring, morphometric analysis, immunohistochemistry and measurement of serum creatinine and albumin excretion.

RESULTS

UNX alone resulted in a very mild increase in renal damage in nidogen-2(-/-) mice compared to wild type animals. Following DOCA-salt treatment, blood pressure, serum creatinine and albumin excretion were significantly higher in nidogen-2(-/-) than in wild type mice. In addition, nidogen-2(-/-) mice showed increased mesangial cell hyperplasia and matrix expansion with higher expression of fibronectin and its receptor alpha8 integrin. Glomerular capillaries were significantly reduced in size and number.

CONCLUSIONS

We demonstrate that in both mild and severe glomerular damage, lack of nidogen-2 is associated with: (i) increased mesangioproliferation; (ii) higher mesangial matrix expansion; and (iii) reduction in glomerular capillary supply. These findings suggest a critical role for nidogen-2 in the maintenance of glomerular structure in the diseased kidney.

Divergences in antihypertensive therapy in special situations in nephrology

CONTEXT AND OBJECTIVE

The choice of an antihypertensive drug is based on several criteria and specific situations give rise to doubt and controversy. The aim here was to evaluate physicians approaches towards treatment with antihypertensive agents in specific situations.

DESIGN AND SETTING

Cross-sectional study, at Universidade Federal de São Paulo, São Paulo.

METHODS

A questionnaire was applied during a nephrology meeting to evaluate individual approaches towards each hypothetical clinical situation. The questionnaire consisted of five multiple-choice questions (clinical cases) concerning controversial aspects of antihypertensive therapy.

RESULTS

A total of 165 questionnaires were analyzed. Most participants were nephrologists (93.2%). There was a preference for angiotensin-converting enzyme (ACE) inhibitors in at least two of the cases. Only 57.2% of the physicians were correct in choosing beta-blockers as the first-line drugs for patients with ischemic coronary disease. Moreover, 66.2% chose ACE inhibitors as the first-line drugs for patients with chronic kidney disease and proteinuria. About 5% of the physicians did not follow the current recommendations for the use of ACE inhibitors in diabetic patients with microalbuminuria. The most controversial question concerned the first-line drug for advanced chronic kidney disease. Most physicians were correct in choosing calcium channel blockers and avoiding ACE inhibitors in renovascular hypertension in the case of a patient with a single functioning kidney.

CONCLUSIONS

Most physicians adopted the correct approach, but some had an alternative strategy for the same situations that was not based on evidence.

Blockade of cannabinoid CB1 receptors improves renal function, metabolic profile, and increased survival of obese Zucker rats

Obesity is a major risk factor in the development of chronic renal failure. Rimonabant, a cannabinoid CB1 receptor antagonist, improves body weight and metabolic disorders; however, its effect on mortality and chronic renal failure associated with obesity is unknown. Obese Zucker rats received either rimonabant or vehicle for 12 months and were compared to a pair-fed but untreated group of obese rats. Mortality in the obese rats was significantly reduced by rimonabant along with a sustained decrease in body weight, transient reduction in food intake, and an increase in plasma adiponectin. This was associated with significant reduction in plasma total cholesterol, low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio, triglycerides, glucose, norepinephrine, plasminogen activator inhibitor 1, and preservation of pancreatic weight and beta-cell mass index. The cannabinoid antagonist attenuated the increase in proteinuria, urinary N-acetylglucosaminidase excretion, plasma creatinine, and urea nitrogen levels while improving creatinine clearance. Renal hypertrophy along with glomerular and tubulointerstitial lesions were reduced by rimonabant. Although the drug did not modify hemodynamics, it normalized the pressor response to angiotensin II. Our study suggests that in a rat model of chronic renal failure due to obesity, rimonabant preserves renal function and increases survival.

Renal effects of S18886 (Terutroban), a TP receptor antagonist, in an experimental model of type 2 diabetes

Thromboxane A(2) (TxA(2)) is assumed to contribute to the development of diabetes complications, including nephropathy. We investigated whether the selective thromboxane-prostanoid endoperoxide receptor antagonist, S18886, ameliorates renal damage in uninephrectomized (UNX) obese Zucker rats (OZR). S18886, at doses of 10 (S18886-10) and 30 (S18886-30) mg x kg(-1) x day(-1), was administered to UNX-OZR by gavage over 8 weeks (n = 8 each group). UNX lean rats (n = 12) and OZR rats that received placebo (OZR-PLAC, n = 8) served as controls. As compared with the OZR-PLAC, S18886 had no significant effect on the elevated blood pressure and the enhanced creatinine clearance, while augmented proteinuria was partially prevented (-12 and -37%, low and high dose, respectively; NS). The increased excretion of transforming growth factor beta(1) (TGF-beta(1)) and of the thromboxane metabolite 2,3-dinor thromboxane B(2) (TxB(2)) was lowered (P < 0.05). S18886 prevented both the enhanced mesangiolysis (P < 0.01) in the OZR-PLAC as well as enlargement and degeneration of podocytes. In the blood, S18886-30 augmented the antioxidant enzymes (P < 0.01) and lessened the increase of plasma advanced oxidation protein products (-25%, NS). Body weight, hyperglycemia, and dyslipidemia remained uninfluenced under both doses of treatment. S18886 has renoprotective properties in the model of UNX-OZR. It prevents mesangiolysis, reduces urinary TGF-beta(1) and 2,3-dinor-TxB(2) excretion, and enhances the antioxidative defense.

Adult hypertension in intrauterine growth-restricted offspring of hyperinsulinemic rats: evidence of subtle renal damage

In humans, intrauterine growth-restricted newborns are prone to develop hypertension as adults. We studied a rat model of pregnancy-induced hypertension associated with intrauterine growth restriction (IUGR) produced by chronic administration of insulin. Fetuses of hyperinsulinemic dams (HDs) were smaller than those of normal dams (5.1+/-0.4 g versus 5.6+/-0.1 g, respectively; P<0.05). At 16 weeks of age, tail-cuff systolic blood pressure was measured, the rats were placed in metabolic cages and euthanized, and the kidneys were examined. Male but not female offspring of HDs (n=9) had higher blood pressure than normal-pregnancy offspring (n=12; 148+/-11 mm Hg versus 118+/-14 mm Hg; P<0.004). In contrast to other models, there was no difference in ours in the number and volume of glomeruli. However, there were significantly greater glomerular, tubulointerstitial, and vascular damage indices in the kidneys of male HD offspring versus controls (2.01+/-0.34 versus 1.08+/-0.16, 1.80+/-0.34 versus 0.76+/-0.12, and 2.13+/-0.81 versus 0.78+/-0.16, respectively; P<0.0001), with similar tubulointerstitial findings in females. Increased expression of collagen type IV, a kidney damage marker indicating fibrosis, was found in the tubulointerstitium. This may be associated with downregulation of bone morphogenetic protein 6, a presumptive antifibrogenic agent, at the end of gestation. In conclusion, male offspring of HDs displayed IUGR and adult hypertension accompanied by several indices of renal fibrosing damage, mainly in the renal tubulointerstitium. Our findings suggest that there is >1 pathway of fetal programming leading from IUGR to development of hypertension in later life.

Long-term blockade of angiotensin AT1 receptors increases survival of obese Zucker rats

Despite the well-documented effect of irbesartan, an angiotensin AT1 receptor antagonist, on diabetic nephropathy, its effect on mortality related to multiple metabolic risk factors is unknown. To address this question, obese fa/fa Zucker rats were submitted to a 13-month treatment by irbesartan (30 mg/kg/day p.o.). Vehicle-treated obese fa/fa Zucker rats exhibited an important mortality (72%), which was markedly reduced by irbesartan (22%, P<0.05). Mortality in control lean fa/+ rats attained 12%. Irbesartan diminished the elevation in urinary protein excretion, plasma creatinine and urea nitrogen levels, and reduced the extent of glomerular and tubulo-interstitial lesions together with a reduction of urinary monocyte chemoattractant protein-1 excretion in fa/fa Zucker rats. Irbesartan treatment prevented the rise in plasma total cholesterol, triglycerides and glucose levels, and partially corrected low-density lipoprotein/high-density lipoprotein (LDL/HDL) cholesterol ratio in fa/fa Zucker rats. Therefore, prolonged irbesartan treatment preserves renal function and metabolic profile, and substantially increases survival in obese fa/fa Zucker rats.

Renoprotective effect of a dopamine D3 receptor antagonist in experimental type II diabetes

Diabetic nephropathy is the leading cause of end-stage renal disease. Dopamine receptors are involved in the regulation of renal hemodynamics and may play a role in diabetes-induced hyperfiltration. To test this hypothesis, we investigated the renal effect of a dopamine D3 receptor antagonist (D3-RA) in hypertensive type II diabetic SHR/N-cp rats. Lean and obese SHR/N-cp rats were randomly assigned to D3-RA, angiotensin-converting enzyme inhibitor (ACE-i), or D3-RA+ACE-i treatment or control conditions. Treated animals were given the D3-RA A-437203 (10 mg/kg/body weight (BW)/day) or the ACE-i trandolapril (0.3 mg/kg BW/day) or a combination of both. At 6 months following perfusion, fixed kidneys were analyzed by morphological and stereological methods. Indices of renal damage (glomerulosclerosis, glomerulosclerosis damage index (GSI), tubulointerstitial and vascular damage), glomerular geometry and functional variables such as urinary albumin excretion, glomerular filtration rate, blood pressure, blood chemistry and BW were determined. The GSI (score 0-4) was significantly higher (P<0.05) in untreated diabetic animals (1.62+/-0.3) compared to nondiabetic controls (0.4+/-0.2) and the treatment groups (D3-RA: 0.31+/-0.12; ACE-i: 0.29+/-0.1; combination treatment: 0.12+/-0.01). Urinary albumin excretion (mg/24 h) was higher in untreated diabetic controls (102+/-19) compared to nondiabetic controls (31+/-12) and the treatment groups (D3-RA: 44+/-15; ACE-i: 41+/-13; combination treatment: 15+/-8). Mean glomerular volume was higher in untreated diabetic animals compared to nondiabetic controls and to the treatment groups. Desmin expression, a marker of podocyte damage, was elevated in untreated diabetic controls and diminished in all treatment groups. These data suggest that in a model of type II diabetes, the dopamine D3-RA had a beneficial effect on renal morphology and albuminuria, which was comparable in magnitude to that of ACE-i treatment.

Effects of calcium channel blockade on angiotensin II-induced peritubular ischemia in rats

Recent studies have indicated that derangement of peritubular capillary (PTC) circulation with consequent tubulointerstitial hypoxia plays a pivotal role in the pathogenesis of renal injury. The present study was performed to determine whether azelnidipine, a new dihydropyridine calcium channel blocker, attenuates angiotensin II (AngII)-induced peritubular ischemia in anesthetized rats. The superficial PTCs were visualized directly using an intravital fluorescence videomicroscope system, and the PTC blood flow was evaluated by analyzing the velocity of fluorescein isothiocyanate-labeled erythrocytes. Intravenous infusion of AngII (50 ng/kg/min, 10 min) significantly increased mean arterial pressure (MAP) and renal vascular resistance (RVR) (by 35 +/- 3% and 110 +/- 32%, respectively), and decreased total renal blood flow (RBF) and PTC erythrocyte velocity (by -34 +/- 4 and -37 +/- 1%, respectively). Treatment with azelnidipine (5 microg/kg/min i.v., 10 min) had no effect on basal MAP, RBF, RVR, or PTC erythrocyte velocity. However, azelnidipine markedly attenuated the AngII-induced increases in MAP (7 +/- 3%) and RVR (40 +/- 4%) and decreases in RBF (-24 +/- 1%) and PTC erythrocyte velocity (-22 +/- 1%). Similar attenuation in the AngII-induced responses of MAP, RBF, RVR, and PTC erythrocyte velocity were observed in rats treated with a higher dose of azelnidipine (20 microg/kg/min i.v., 10 min), which significantly decreased basal MAP and RVR and increased RBF and PTC erythrocyte velocity. These data suggest that calcium channel blockade attenuates AngII-induced peritubular ischemia, which may be involved in its beneficial effects on renal injury.

p27Kip1 knockout mice are protected from diabetic nephropathy: Evidence for p27Kip1 haplotype insufficiency11See editorial by Qi and Breyer, p. 1896

BACKGROUND

High glucose up-regulates the mesangial cell expression of p27(Kip1), an inhibitor of cyclin-dependent kinases/cyclin complexes. Previous in vitro studies using cultured mesangial cells from p27(Kip1-/-) mice demonstrated that these cells do not undergo high glucose-mediated cellular hypertrophy. Since glomerular hypertrophy is an early feature of diabetic nephropathy and may precede the development of glomerulosclerosis, interference with p27(Kip1) expression may attenuate diabetic nephropathy. However, it is unclear whether deletion of p27(Kip1) protects the kidneys of diabetic nephropathy in vivo.

METHODS

Type 1 diabetes mellitus was induced in p27(Kip1+/+), p27(Kip1+/-), and p27(Kip1-/-) mice by injection of streptozotocin (STZ). Mice were studied for 6 weeks. Animals injected with citrate buffer only served as controls. At the end of the experiments, urine was collected, albuminuria was determined with an enzyme-linked immunosorbent assay (ELISA), and blood glucose concentrations were measured. Kidneys were perfusion-fixed for quantitative morphologic analysis with glutaraldehyde and for immunohistochemical studies with formaldehyde. Glomerular cell number and volume were analyzed. Glomerulosclerosis, tubulointerstitial, and vascular damage indices were semiquantitatively assessed according to standard methodology. Quantitative glomerular parameters (cell numbers and volumes of endothelial, mesangial, and epithelial cells) were measured on semithin sections. Expression of transforming growth factor-beta1 (TGF-beta1), laminin, and collagen type IV were determined by immunohistochemical staining.

RESULTS

In contrast to animals only injected with citrate buffer, mice that received STZ developed hyperglycemia. There was no significant difference in the degree of hyperglycemia among p27(Kip1+/+), p27(Kip1+/-), and p27(Kip1-/-) mice. Diabetic p27(Kip1+/+), but not control p27(Kip1+/+) animals, developed albuminuria. Albuminuria was significantly reduced in diabetic p27(Kip1+/-) and more profoundly in p27(Kip1-/-) animals. Diabetic p27(Kip1+/+) mice revealed a significant increase in mean glomerular volume at 6 weeks. The volumes of mesangial and endothelial cells and podocytes all increased, whereas cell numbers were reduced, consistent with cell hypertrophy. Glomerular, endothelial, mesangial and podocyte hypertrophy were reduced in diabetic p27(Kip1+/-) and p27(Kip1-/-) animals. Diabetic p27(Kip1) (+/+) animals had significantly increased glomerulosclerosis, tubulointerstium, and vascular damage indices compared to nondiabetic p27(Kip1+/+) controls. Diabetic p27(Kip1-/-) mice exhibited significantly less structural damage than diabetic wild-type animals. Diabetic p27(Kip1+/-) animals revealed intermediate glomerulosclerosis, tubulointerstium, and vascular damage values. Immunohistological stainings demonstrated increases in TGF-beta1, collagen type IV, and laminin expression in kidneys of diabetic p27(Kip1+/+) animals compared to nondiabetic p27(Kip1+/+) controls. Staining intensity for type IV collagen and laminin, but not for TGF-beta1, was significantly lower in diabetic p27(Kip1-/-) mice.

CONCLUSION

Deletion of p27(Kip1) attenuates the functional and morphologic features of diabetic nephropathy. Although deletion of p27(Kip1) abolished some parameters of diabetic glomerular hypertrophy, the significant reduction of TGF-beta1 expression in the tubulointerstitium indicates that other protective mechanisms could be operative. The p27(Kip1) gene is haplo-insufficient because diabetic p27(Kip1)+/- mice exhibited an intermediate degree of functional and structural renal injury. Our data shows that p27(Kip1) plays an important role in diabetic nephropathy.

Mibefradil (Ro 40-5967): the first selective T-type Ca2+ channel blocker

Mibefradil is a novel Ca2+ antagonist acting on both L- and T-type Ca2+ channels, with a ten-fold selectivity for T-type Ca2+ channels. It belongs to a chemical class different from other Ca2+ antagonists (tetralol derivative), and binds to a new receptor site on the L-type Ca2+ channel, where it does not affect dihydropyridine (DHP) binding but appears to overlap the verapamil and fantofarone sites. In vitro and in vivo studies indicate that mibefradil has a high selectivity for the coronary vasculature over the peripheral vasculature and the myocardium. It has no relevant negative inotropic effects in various animal models, in normotensive patients, and patients with hypertension or angina pectoris. Instead, treatment with mibefradil slightly decreases heart rate and improves cardiac function. Clinical studies confirm that mibefradil is an effective antihypertensive and anti-ischaemic drug, which may be beneficial in the treatment of heart failure. Its excellent pharmacological and safety profile combined with high bioavailability makes it a promising new drug. Many of the unique pharmacological properties of mibefradil may derive from its selective block of T-type Ca2+ channels.

Renovascular Hypertension: Current Concepts

Hypertension produced by renal artery occlusive disease is an important secondary form of hypertension. Clinicians commonly encounter forms of renal arterial disease of varying severity, many of which are of little hemodynamic significance when first detected. Experimental studies emphasize that transient activation of the renin-angiotensin-aldosterone system is necessary for initiation of renovascular hypertension. At some point, angiotensin II activates additional mechanisms responsible for sustained increased blood pressure including sodium retention, endothelial dysfunction, and vasoconstriction related to production of reactive oxygen species. Widespread application of agents that block the renin-angiotensin system, including angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers, render many patients with unilateral renal arterial disease manageable primarily by medical means for many years. In the setting of high a priori likelihood of renovascular disease, recognizing the potential for disease progression during medical therapy and individually evaluating the risks and benefits of renal revascularization are important tasks. Recent prospective studies show limited, but real, benefit regarding blood pressure control for patients with atherosclerotic disease. Whether earlier renal revascularization offers benefits regarding improved morbidity and mortality from cardiovascular end point reduction is an important question to be addressed in multicenter, prospective, randomized trials. Our paradigm stresses the fact that patients with renovascular hypertension require intensive blood pressure control and cardiovascular risk factor intervention, both before and after revascularization. Hence, management of such patients requires close attention and periodic review regarding restenosis and progression of vascular disease.

Neonatal renovascular hypertension due to prenatal traumatic retroperitoneal hematoma

This report describes severe hypertension in a 7-week-old male infant found to have renovascular disease from an organized hematoma due to prenatal trauma. As such, this case illustrates a novel acquired, congenital mechanism of renovascular hypertension. The importance of considering prenatal as well as postnatal etiologies of acquired renovascular hypertension in neonates is emphasized. Likewise, attention must be drawn to the classic presentation of congestive heart failure in a child with severe hypertension.

Calcium citrate ameliorates the progression of chronic renal injury

BACKGROUND

Metabolic acidosis is a consequence of chronic renal failure and it may produce bone demineralization, muscle proteolysis, and progression of chronic renal failure. The aim of this study was to evaluate the effects of correction of metabolic acidosis with calcium citrate in an experimental model of renal mass ablation.

METHODS

Wistar rats were subjected to 5/6 nephrectomy and were randomly assigned to one of 4 groups: nontreated (NFX); treated with calcium citrate (1.45 g/100 g feed) (NFX-CIT); treated with captopril (500 mg/L water) (NFX-CAP); or treated with both (NFX-CAP-CIT) during 1, 10, or 20 weeks. Body weight, systolic blood pressure, proteinuria, arterial bicarbonate concentration, urine citrate excretion, plasma calcium, and inulin clearance were measured. Histologic glomerular and tubulointerstitial damage scores were measured at 1, 10, and 20 weeks, and glomerular and tubular proliferating cell nuclear antigen (PCNA)-positive cells, alpha-smooth muscle actin, and desmin staining were studied by immunohistochemistry at 1 and 10 weeks.

RESULTS

The treated groups showed significantly less glomerular and tubulointerstitial cellular proliferation in the first week (P < 0.05), less glomerular cell transdifferentiation and higher plasma bicarbonate at 10 weeks (P < 0.05), as well as diminished histologic glomerular and tubulointerstitial damage scores at 20 weeks (P < 0.05). Inulin clearances were higher (P < 0.05), and urine protein excretion rates were lower (P < 0.05) than in the NFX non-treated group, but arterial blood pressure was not significantly different in the NFX-CIT group.

CONCLUSION

Calcium citrate slows the progression of chronic renal injury in the 5/6 NFX model. It improves metabolic acidosis and diminishes cell proliferation and transdifferentiation without changes in systolic blood pressure.

Comparison of renal morphology in the Streptozotocin and the SHR/N-cp models of diabetes

The Streptozotocin (STZ) model of diabetes is commonly used for studies of diabetic nephropathy although the histological lesions of the kidney are mild and do not resemble those seen in diabetic patients. The SHR/N-cp rat model of type II diabetes spontaneously develops pronounced abnormalities in renal histology. In the present study, we compared renal morphology in the STZ rat and the diabetic SHR/N-cp rat. Sprague-Dawley rats received STZ, developed diabetes after 2 days and were treated with insulin. In the SHR/N-cp rat, obesity is inherited as an autosomal recessive trait. The progeny are either lean (used as controls) or obese and diabetic. After 6 months of observation, STZ and SHR/N-cp rats were killed. The renal damage was evaluated by assessing damage indices and by using stereological techniques. In addition, immunohistochemistry and electron microscopy were performed. The glomerular and tubulointerstitial changes were much more pronounced in the diabetic SHR/N-cp compared to the STZ model. In parallel glomerular PCNA+cells were significantly more frequent and expression of TGF-beta and PDGF by immunohistochemistry in glomeruli and in the tubulointerstitial space was more pronounced in SHR/N-cp compared to STZ rats. The glomeruli of SHR/N-cp contained less and larger podocytes as well as smaller mesangial cells embedded in more mesangial matrix compared to STZ. Similarly, less, but larger endothelial cells were found in SHR/N-cp than in STZ rats. The mean glomerular volume was similarly increased in the two models. Albumin excretion was only modestly increased in STZ diabetes, but pronounced in the SHR/N-cp rat. Although the STZ model of diabetes exhibits numerous biochemical sequelae of hyperglycemia, the morphological lesions are unimpressive. In contrast, the diabetic SHR/N-cp exhibits marked structural lesions, particularly podocyte damage and mesangial expansion that promise to make it a more suitable model for investigation of diabetic glomerulosclerosis.

Renal damage in the SHR/N-cp type 2 diabetes model: comparison of an angiotensin-converting enzyme inhibitor and endothelin receptor blocker

SUMMARY

The pathomechanisms that cause renal damage in diabetes have not been completely clarified. Treatment with angiotensin-converting enzyme inhibitors (ACE-i) is highly effective but fails to completely prevent end-stage renal disease. The effects of ET(A)-receptor blockers (ET(A)-RB) on renal damage are controversial and have rarely been investigated in type 2 diabetes. We compared the influence of the selective ET(A)-RB LU135252 and the ACE-i Trandolapril on renal structure in the SHR/N-cp rat model of type 2 diabetes. Three-month-old male SHR/N-cp rats were left untreated or received daily either Trandolapril or LU135252. The experiment was terminated after 6 months. The glomerulosclerosis index; tubulointerstitial damage index; and glomerular geometry, glomerular cell number, and capillary density were investigated. Proliferating cell nuclear antigen and desmin expression of podocytes, renal mRNA expression of endothelin (ET-1) and transforming growth factor-beta, blood pressure, and urine albumin excretion were measured. The glomerulosclerosis index was significantly higher in untreated diabetic animals than in the groups that were treated with ACE-i and ET(A)-RB. There were analogous changes in tubulointerstitial damage index. Treatment with either substance comparably lowered urinary albumin excretion in diabetic SHR/N-cp. Podocyte and endothelial cell numbers per glomerulus decreased in untreated diabetic animals; this was prevented by the ACE-i but not by the ET(A)-RB. Glomerular capillary length density was lower in SHR/N-cp, and this was normalized by ACE-i only. Increased expression of desmin and proliferating cell nuclear antigen expression of podocytes in the SHR/N-cp was abrogated by ACE-i but not by ET(A)-RB. Treatment with ACE-i or ET(A)-receptor antagonist resulted in less structural and functional alterations, but the ET(A)-RB was inferior to the ACE-i. This is particularly the case for podocyte changes pointing to angiotensin II-dependent pathomechanisms.

Chronic endothelin receptor blockade prevents both early hyperfiltration and late overt diabetic nephropathy in the rat

Diabetic nephropathy is associated with enhanced renal synthesis of endothelin (ET)-1. The goal of this study was to investigate the effects of dual ET receptor antagonism in the early phase (2 months) and in the late phase (5 months) of diabetic nephropathy in rats, and to compare this approach to angiotensin-converting enzyme inhibition. Four groups of uninephrectomized streptozotocin-induced diabetic rats were assigned to receive orally vehicle, bosentan, enalapril, or their combination. A fifth group consisted of nondiabetic, uninephrectomized rats. At 2 weeks, untreated diabetic rats exhibited increased glomerular filtration rate and renal plasma flow. Bosentan, enalapril, and the combination all prevented hyperfiltration and hyperperfusion. By 5 months, diabetic rats developed marked increases in mean arterial pressure and renal vascular resistance, progressive proteinuria, and renal structural damage with glomerular sclerosis and hypertrophy. Bosentan completely prevented the development of hypertension and renal vasoconstriction, and largely prevented the development of proteinuria and renal structural injury. The renal protective effect of bosentan was comparable to that of enalapril or the combination, although its anti-proteinuric effect was less. Clinical studies are warranted to assess whether ET receptor antagonism can have additive effects on top of ACE inhibition, the current treatment of choice in diabetic nephropathy.

Angiotensin type 2 receptor antagonism confers renal protection in a rat model of progressive renal injury

The role of the angiotensin type 2 (AT(2)) receptor in the pathogenesis of progressive renal injury has not been previously elucidated. The renal expression of the AT(1) and AT(2) receptors in subtotally nephrectomized rats (STNx) and the effects of AT(2) receptor blockade on renal injury were explored. Reduced renal expression of the AT(1) but not the AT(2) receptor was observed in STNx by reverse transcription-PCR, by in vitro autoradiography, and by immunohistochemical staining. The STNx rats were randomly assigned to AT(1) receptor antagonist valsartan, AT(2) receptor antagonist PD123319, or the combination of both for 4 wk. Increased proteinuria in STNx rats was reduced by PD123319 but to a lesser degree when compared with valsartan. Reduced gene and protein expression of the slit diaphragm protein nephrin was prevented by either valsartan or PD123319. Expression of osteopontin, proliferating cell nuclear antigen, and monocyte/macrophage infiltration was increased in STNx rats and was reduced by both AT(1) and AT(2) receptor antagonists. These effects of AT(2) receptor antagonism were observed in the presence of increased BP in STNx rats. These findings suggest that blockade of the AT(2) receptor alone confers a degree of renal protection; in particular, it seems that the combination of the AT(1) and AT(2) receptor antagonists may confer additive renal effects than either receptor antagonist as monotherapy.

Isotretinoin alleviates renal damage in rat chronic glomerulonephritis

BACKGROUND

Retinoids, derivatives of vitamin A, have strong anti-inflammatory and antiproliferative properties. We previously demonstrated that the pan-agonists all-transretinoic acid (RA) and isotretinoin (13-cis RA) alleviate renal damage in rat acute glomerulonephritis (GN) induced by anti-Thy-1.1 mAb OX-7.

METHODS

The present study examined the effects of low dose and high dose treatment with isotretinoin in the chronic glomerulonephritis model, Thy-GN. Thy-GN was induced by a single intravenous injection of monoclonal antibody (mAb) 1-22-3 in uninephrectomized Wistar rats (N = 7 to 10 per group). Control and nephritic groups were treated with vehicle (veh), low dose isotretinoin (2 mg/kg body wt), or high dose isotretinoin (10 mg/kg body wt). The experiment was terminated 60 days after induction of Thy-GN.

RESULTS

In animals with Thy-GN, isotretinoin abrogated the increase in blood pressure and significantly reduced albuminuria. Glomerulosclerosis index, glomerular and interstitial cell counts, as well as the area of the interstitial space were significantly lower in nephritic rats treated with low and high dose isotretinoin compared to vehicle-treated nephritic controls. Treatment with isotretinoin also significantly reduced the number of glomerular and interstitial macrophages. The increase of transforming growth factor (TGF)-beta1, TGF receptor II and prepro-endothelin-1 gene expression in vehicle-treated nephritic rats was significantly attenuated by isotretinoin.

CONCLUSIONS

Treatment with isotretinoin significantly reduces glomerular and interstitial damage in rats with chronic glomerulonephritis as indicated by different functional and histological markers. Retinoids may provide a novel therapeutic option for the treatment of glomerulonephritis.