Chronic Unilateral Ureteral Obstruction Research Articles

Evaluation of Diuretic Renal Doppler Ultrasonography Findings in Chronic Unilateral Partial Ureteral Obstruction in Rabbits

Evaluation of Diuretic Renal Doppler Ultrasonography Findings in Chronic Unilateral Partial Ureteral Obstruction in Rabbits

Using 2-Photon Microscopy to Quantify the Effects of Chronic Unilateral Ureteral Obstruction on Glomerular Processes.

Applying novel microscopy methods to suitable animal disease models to explore the dynamic physiology of the kidney remains a challenge. Rats with surface glomeruli provide a unique opportunity to investigate physiological and pathophysiological processes using intravital 2-photon microscopy. Quantification of glomerular capillary blood flow and vasoconstriction and dilatation in response to drugs, permeability, and inflammation are just some of the processes that can be studied. In addition, transgenic rats, i.e., podocytes labeled with fluorescent dyes and other molecular biomarker approaches, provide increased resolution to directly monitor and quantify protein-protein interactions and the effects of specific molecular alterations. In mice, which lack surface glomeruli after four weeks of age, unilateral ureteral obstruction (UUO) for several weeks has been used to induce surface glomeruli. As this induction model does not allow for baseline studies, we quantified the effects of UUO on glomerular processes in the UUO model in Munich Wistar Frömter (MWF) rats, which have surface glomeruli under physiologic conditions. The UUO model for five weeks or more induced significant alterations to gross renal morphology, the peritubular and glomerular microvasculature, as well as the structure and function of tubular epithelia. Glomerular and peritubular red blood cell (RBC) flow decreased significantly (p < 0.01), probably due to the significant increase in the adherence of white blood cells (WBCs) within glomerular and peritubular capillaries. The glomerular sieving coefficient of albumin increased from 0.015 ± 0.002 in untreated MWFs to 0.045 ± 0.05 in 5-week-old UUO MWF rats. Twelve weeks of UUO resulted in further increases in surface glomerular density and glomerular sieving coefficient (GSC) for albumin. Fluorescent albumin filtered across the glomeruli was not reabsorbed by the proximal tubules. These data suggest that using UUO to induce surface glomeruli limits the ability to study and interpret normal glomerular processes and disease alterations.

Using 2-Photon Microscopy to Quantify the Effects of Chronic Unilateral Ureteral Obstruction on Glomerular Processes

Applying novel microscopy methods to suitable animal disease models to explore the dynamic physiology of the kidney remains a challenge. Rats with surface glomeruli provide a unique opportunity to investigate physiological and pathophysiological processes using intravital 2-photon microscopy. Quantification of glomerular capillary blood flow and vasoconstriction and dilatation in response to drugs, permeability, and inflammation are just some of the processes that can be studied. In addition, transgenic rats, i.e., podocytes labeled with fluorescent dyes and other molecular biomarker approaches, provide increased resolution to directly monitor and quantify protein-protein interactions and the effects of specific molecular alterations. In mice, which lack surface glomeruli after four weeks of age, unilateral ureteral obstruction (UUO) for several weeks has been used to induce surface glomeruli. As this induction model does not allow for baseline studies, we quantified the effects of UUO on glomerular processes in the UUO model in Munich Wistar Frömter (MWF) rats, which have surface glomeruli under physiologic conditions. The UUO model for five weeks or more induced significant alterations to gross renal morphology, the peritubular and glomerular microvasculature, as well as the structure and function of tubular epithelia. Glomerular and peritubular red blood cell (RBC) flow decreased significantly (p < 0.01), probably due to the significant increase in the adherence of white blood cells (WBCs) within glomerular and peritubular capillaries. The glomerular sieving coefficient of albumin increased from 0.015 ± 0.002 in untreated MWFs to 0.045 ± 0.05 in 5-week-old UUO MWF rats. Twelve weeks of UUO resulted in further increases in surface glomerular density and glomerular sieving coefficient (GSC) for albumin. Fluorescent albumin filtered across the glomeruli was not reabsorbed by the proximal tubules. These data suggest that using UUO to induce surface glomeruli limits the ability to study and interpret normal glomerular processes and disease alterations.

38 - Attenuation of partial unilateral ureteral obstruction-induced renal damage with hyperbaric oxygen therapy in a rat model

ABSTRACT Objective: The objective of the present study was to evaluate the effectiveness of HBO therapy on biochemical parameters, renal morphology and renal scintigraphy in rats undergoing chronic unilateral partial ureteral obstruction (UPUO). Material and methods: Thirty-five rats were divided into five equal groups: Control group; Sham group; HBO group; UPUO group and UPUO/HBO group. The effects of HBO therapy were examined using biochemical parameters and histopathological changes. After calculating the score for each histopathological change, the total histopathological score was obtained by adding all the scores. In addition, dynamic renal scintigraphy findings were evaluated. Results: Serum parameters indicating inflammation, serum tumor necrosis factor- alpha, ischemia modified-albumin, IMA/albumin ratio and Pentraxin-3 levels, were observed to be high in the UPUO group and low in the UPUO/HBO treatment group. Similarly, in the treatment group, the reduction in malondialdehyde, total oxidant status and oxidative stress index levels and increase in total antioxidant capacity values were observed to be statistically significant compared to the UPUO group (p<0.001, p=0.007, p<0.001, p=0.001, respectively). The total score and apoptosis index significantly decreased after administration of HBO treatment. Dynamic 99mTc-MAG3 renal scintigraphy also showed convincing evidence regarding the protective nature of HBO against kidney injury. In the UPUO/HBO therapy group, the percentage contribution of each operated kidney increased significantly compared to the UPUO group (41.73% versus 32.72%). Conclusion: The findings of this study indicate that HBO therapy had a reno-protective effect by reducing inflammation and oxidative stress, and preserving renal function after renal tissue damage due to induction of UPUO.

Attenuation of partial unilateral ureteral obstruction - induced renal damage with hyperbaric oxygen therapy in a rat model.

ABSTRACTObjective:The objective of the present study was to evaluate the effectiveness of HBO therapy on biochemical parameters, renal morphology and renal scintigraphy in rats undergoing chronic unilateral partial ureteral obstruction (UPUO).Material and methods:Thirty-five rats were divided into five equal groups: Control group; Sham group; HBO group; UPUO group and UPUO/HBO group. The effects of HBO therapy were examined using biochemical parameters and histopathological changes. After calculating the score for each histopathological change, the total histopathological score was obtained by adding all the scores. In addition, dynamic renal scintigraphy findings were evaluated.Results:Serum parameters indicating inflammation, serum tumor necrosis factor- alpha, ischemia modified-albumin, IMA/albumin ratio and Pentraxin-3 levels, were observed to be high in the UPUO group and low in the UPUO/HBO treatment group. Similarly, in the treatment group, the reduction in malondialdehyde, total oxidant status and oxidative stress index levels and increase in total antioxidant capacity values were observed to be statistically significant compared to the UPUO group (p<0.001, p=0.007, p<0.001, p=0.001, respectively). The total score and apoptosis index significantly decreased after administration of HBO treatment. Dynamic 99mTc-MAG3 renal scintigraphy also showed convincing evidence regarding the protective nature of HBO against kidney injury. In the UPUO/HBO therapy group, the percentage contribution of each operated kidney increased significantly compared to the UPUO group (41.73% versus 32.72%).Conclusion:The findings of this study indicate that HBO therapy had a reno-protective effect by reducing inflammation and oxidative stress, and preserving renal function after renal tissue damage due to induction of UPUO.

MP58-18 EXOGENOUS HYDROGEN SULFIDE TREATMENT REDUCES RENAL FIBROSIS ASSOCIATED WITH CHRONIC URETERAL OBSTRUCTION BY ATTENUATING EPITHELIAL-MESENCHYMAL TRANSITION

You have accessJournal of UrologyStone Disease: Basic Research & Pathophysiology I1 Apr 2016MP58-18 EXOGENOUS HYDROGEN SULFIDE TREATMENT REDUCES RENAL FIBROSIS ASSOCIATED WITH CHRONIC URETERAL OBSTRUCTION BY ATTENUATING EPITHELIAL-MESENCHYMAL TRANSITION Shouzhe Lin, Fazil Visram, Ian Lobb, Weihua Liu, Aaron Haig, Jifu Jiang, Amy Mok, Dameng Lian, Mark E. Wood, Matthew Whiteman, and Alp Sener Shouzhe LinShouzhe Lin More articles by this author , Fazil VisramFazil Visram More articles by this author , Ian LobbIan Lobb More articles by this author , Weihua LiuWeihua Liu More articles by this author , Aaron HaigAaron Haig More articles by this author , Jifu JiangJifu Jiang More articles by this author , Amy MokAmy Mok More articles by this author , Dameng LianDameng Lian More articles by this author , Mark E. WoodMark E. Wood More articles by this author , Matthew WhitemanMatthew Whiteman More articles by this author , and Alp SenerAlp Sener More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.816AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Prolonged ureteral obstruction can cause fibrosis, leading to irreversible renal injury and chronic kidney disease. Recent studies suggest that transforming growth factor beta 1 (TGF-β1), a cytokine released by infiltrating inflammatory cells, can initiate epithelial-mesenchymal transition (EMT), thereby causing fibrosis. Currently, there are few preemptive measures available for mitigating renal fibrosis during obstruction. Hydrogen sulfide (H2S) is an endogenous gasotransmitter that mediates physiological processes and can mitigate tissue injury via anti-oxidant and anti-inflammatory properties. The current study investigates the effects of H2S on renal fibrosis and EMT progression in chronic obstructive uropathy. METHODS Male Lewis rats underwent unilateral ureteral obstruction (UUO) via ligation of left ureter. Following UUO, male Lewis rats were given daily injections of either phosphate buffered saline (PBS) or 200 μM/kg GYY 4137 (slow-releasing H2S donor)+PBS for 30 days. Kidneys were removed on day 30 and stained with Masson′s trichrome for histological analysis of renal fibrosis. qRT-PCR and Western blot analysis were completed on renal tissue to assess expression of EMT markers. EMT progression was also analyzed via an in vitro scratch wound assay, whereby a scratch wound was created with a 200μL pipette in a confluent monolayer of pig kidney epithelial cells (LLC-PK1). Cells were serum-starved for 24 hours. Cells were then treated with 10ng/mL TGF-β1 to induce EMT, as well as various doses of GYY 4137. Scratch wound was imaged every half hour for 72 hours. EMT progression was determined as a function of wound closure. RESULTS Histological analysis showed significantly reduced fibrosis (P<0.01) in H2S-treated rats following chronic obstruction when compared to PBS treatment. H2S-treated rats also demonstrated significantly decreased (P<0.05) expression of EMT markers following chronic UUO. TGF-β1-induced progression of EMT in renal epithelial cells was significantly reduced (P<0.05) upon H2S treatment. CONCLUSIONS Our findings suggest that supplemental H2S can mitigate renal fibrosis associated with chronic ureteral obstruction. H2S may represent a preemptive therapy against renal damage associated with obstructive uropathy, potentially improving long-term renal function following resolution of renal obstruction. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e783 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Shouzhe Lin More articles by this author Fazil Visram More articles by this author Ian Lobb More articles by this author Weihua Liu More articles by this author Aaron Haig More articles by this author Jifu Jiang More articles by this author Amy Mok More articles by this author Dameng Lian More articles by this author Mark E. Wood More articles by this author Matthew Whiteman More articles by this author Alp Sener More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Unilateral ureteral obstruction induces DNA repair by APE1.

Ureteral obstruction is associated with oxidative stress and the development of fibrosis of the kidney parenchyma. Apurinic/apyrimidinic endonuclease (APE1) is an essential DNA repair enzyme for repair of oxidative DNA lesions and regulates several transcription factors. The aim of the present study was to investigate whether APE1 is regulated by acute (24 h) and chronic (7 days) unilateral ureteral obstruction (UUO). APE1 was expressed in essentially all kidney cells with the strongest expression in proximal tubuli. After 24 h of UUO, APE1 mRNA was induced in the cortex, inner stripe of the outer medulla (ISOM), and inner medulla (IM). In contrast, the APE1 protein level was not regulated in the IM and ISOM and only slightly increased in the cortex. APE1 DNA repair activity was not significantly changed. A different pattern of regulation was observed after 7 days of UUO, with an increase of the APE1 mRNA level in the cortex but not in the ISOM and IM. The APE1 protein level in the cortex, ISOM, and IM increased significantly. Importantly, we observed a significant increase in APE1 DNA repair activity in the cortex and IM. To confirm our model, we investigated heme oxygenase-1, collagen type I, fibronectin I, and α-smooth muscle actin levels. In vitro, we found the transcriptional regulatory activity of APE1 to be involved in the upregulation of the profibrotic factor connective tissue growth factor. In summary, APE1 is regulated at different levels after acute and chronic UUO. Thus, our results suggest that DNA repair activity is regulated in response to progressive (7 days) obstruction and that APE1 potentially could play a role in the development of fibrosis in kidney disease.

Estrogen preserves split renal function in a chronic complete unilateral ureteral obstruction animal model.

Estrogen may help to preserve renal function in chronic kidney disease. This study examined whether estrogen administration or deprivation affected the split renal function in rats subjected to chronic unilateral ureteral obstruction (UUO). Fifteen adult female Sprague-Dawley rats were randomly divided into three groups. Low- and high-estrogen groups were modeled by female castration or estrogen intraperitoneal injection, respectively, and the rats in the normal-estrogen group were untreated. Intermittent split renal function [glomerular filtration rate (GFR)] examination was performed on rats on days 2, 6 and 16 after UUO surgery via single-photon emission computed tomography (SPECT/CT). Routine hematoxylin and eosin (H&E) staining, immunohistochemistry, pathology examination and electron microscopy were performed to compare the histological differences. Low-, normal- and high-estrogen groups were successfully established (P<0.001). In the acute stage, the GFR of the contralateral healthy kidney showed a greater compensatory rise in the normal- and high-estrogen groups than in the low-estrogen group (P<0.05). In the chronic stage, the GFR of the obstructed kidney continued to decrease with the GFR of the high-estrogen group being significantly better preserved than that of the low-estrogen group (P<0.05). The GFR of the contralateral kidney compensated to the greatest extent in the high-estrogen group (P=0.01), and the total GFR was significantly superior (P<0.05). Routine H&E examination showed significant histological changes following surgery. The low-estrogen group had significant renal interstitial fibrosis compared with the normal- and high-estrogen groups (P<0.05), as observed by immunohistochemical (IHC) examination of transforming growth factor-β (TGF-β) and α-smooth muscle actin (α-SMA). Electron-microscopic (EM) examination also differentiated between groups. In conclusion, estrogen administration and deprivation significantly affected renal function. Estrogen may preserve the split renal function (GFR) in rats with chronic UUO.

Chronic unilateral ureteral obstruction in the neonatal mouse delays maturation of both kidneys and leads to late formation of atubular glomeruli

Unilateral ureteral obstruction (UUO) in the adult mouse is the most widely used model of progressive renal disease: the proximal tubule is the nephron segment most severely affected and atubular glomeruli are formed after only 7 days of UUO. To determine the proximal nephron response to UUO in the maturing kidney, neonatal mice were examined 7 to 28 days following complete UUO under general anesthesia. Proximal tubular mass and maturation were determined by staining with Lotus tetragolonobus lectin. Superoxide was localized by nitroblue tetrazolium and collagen by Sirius red. Cell proliferation, cell death, PAX-2, megalin, α-smooth muscle actin (α-SMA), renin, and fibronectin were identified by immunohistochemistry. During the first 14 days of ipsilateral UUO, despite oxidative stress (4-hydroxynonenal staining), glomerulotubular continuity was maintained and mitochondrial superoxide production persisted. However, from 14 to 28 days, papillary growth was impaired and proximal tubules collapsed with increased apoptosis, autophagy, mitochondrial loss, and formation of atubular glomeruli. Fibronectin, α-SMA, and collagen increased in the obstructed kidney. Oxidative stress was present also in the contralateral kidney: renin was decreased, glomerulotubular maturation and papillary growth were delayed, followed by increased cortical and medullary growth. We conclude that neonatal UUO initially delays renal maturation and results in oxidative stress in both kidneys. In contrast to the adult, proximal tubular injury in the neonatal obstructed kidney is delayed at 14 days, followed only later by the formation of atubular glomeruli. Antioxidant therapies directed at proximal tubular mitochondria during early renal maturation may slow progression of congenital obstructive nephropathy.

Prospectively Estimating the Recoverability of Renal Function after Relief of Unilateral Urinary Obstruction by Measurement of Renal Parenchymal Volume

Renal parenchymal volume (RPV) has been suggested as an indicator of the potential functional residual capacity for a given kidney. The goal of this study was to determine whether the recoverability of renal function could be predicted by RPV as estimated by computed tomography (CT) before an operation. Eighty-two adult patients diagnosed with long-term chronic unilateral ureteral obstruction and a normal contralateral kidney were recruited for evaluation. RPV was measured by nonenhanced CT. Glomerular filtration rate (GFR) was measured by radioisotope renal scan. Animal models were used to validate use of the CT method to measure RPV. RPV and GFR values for all patients were obtained before surgical relief of the urinary obstruction and compared with those values obtained at 12 months postsurgery. There was no statistically significant difference found between RPV measured by CT or by the water displacement method. Among patient age, sex, and pre-RPV and pre-GFR of obstructed and contralateral kidney, pre-RPV and pre-GFR of obstructed kidney were the independent factors that best indicated recoverability of renal function. Pre-RPV correlated well with post-GFR (r = 0.68, P < .01). The cut-off point of pre-RPV to predict recoverability of renal function after the relief operation was 58.2 mL, as determined by receiver operating characteristic curve analysis. Pre-RPV was the independent factor that determines recoverability of renal function. Renal function may stabilize or improve after relief of urinary obstruction when the pre-RPV value is ≥58.2 mL.

Urine and kidney cytokine profiles in experimental unilateral acute and chronic hydronephrosis

In search of potential urinary biomarkers of obstructive nephropathy, this study examined whether a potential change in the concentration of urinary cytokines [interferon-γ(IFN-γ), interleukin-1β (IL-1β), IL-2, IL-6, IL-10 and tumour necrosis factor-α (TNF-α)] reliably reflects changes in renal parenchymal levels of the same cytokines following the release of acute and chronic unilateral ureteral obstruction, respectively. Acute obstruction was performed in 12 adult rats. After 48 h, six rats were used for selective urine collection and six rats had their kidneys removed and dissected into inner medulla and cortex. Chronic obstruction was performed in newborn rats. After 10 weeks, a similar set-up to that of the acute study was implemented. Sham-operated rats were prepared in parallel. Urine and tissue cytokines were measured with a bead-based multiplex sandwich immunoassay and analysed on a Luminex 100 IS instrument. In the acute study, there were significantly increased concentrations of IL-1β and IL-6 in inner medulla and in urine from the obstructed kidney, significantly increased concentrations of TNF-α in urine from the obstructed kidney and, importantly, significantly increased levels of IL-10 in cortex and in urine from the non-obstructed kidney. In the chronic study, there were similar changes in IL-1β and IL-6 (not significant) but no changes in TNF-α and IL-10. This study showed that inflammatory cytokines can be detected both in renal parenchyma and in urine from rats with experimental unilateral ureteral obstruction. Further studies are needed to confirm the diagnostic accuracy of IL-1β, IL-6, IL-10 and TNF-α in urine.

Inhibitory Effects of T/L-type Calcium Channel Blockers on Tubulointerstitial Fibrosis in Obstructed Kidneys in Rats

To examine the effect of L- and T/L-type calcium channel blockers on interstitial fibrosis in chronic unilateral ureteral obstruction (UUO). Tubulointerstitial fibrosis is a common outcome of several progressive renal diseases. Calcium channel blockers are widely used for the treatment of hypertension with renal diseases; however, the direct effect of calcium channel blockers on renal diseases independent of lowering blood pressure has not been fully elucidated. Sprague-Dawley rats were divided into 3 treatment groups: (1) vehicle control; (2) nifedipine, an L-type calcium channel blockers; and (3) efonidipine, a T/L-type calcium channel blockers. Treatment was initiated 1 day before and continued until 6 days after creation of the UUO. Tubulointerstitial fibrosis in the obstructed kidney was significantly increased compared with that in the contralateral unobstructed kidney. Furthermore, the increased fibrosis was accompanied by increased fibrogenic signaling expressed by transforming growth factor β1 and connective tissue growth factor mRNA levels, increased oxidative stress expressed by p22phox, p47phox and gp91phox mRNA level. Moreover, treatment with a nonhypotensive dose of efonidipine but not nifedipine in the obstructed kidney significantly suppressed the fibrogenic signaling and the oxidative stress, resulting in reduced tubulointerstitial fibrosis. The plasma aldosterone level in efonidipine-treated animals was increased compared with vehicle-treated animals, although not significantly. The increased plasma aldosterone level did not increase sgk-1 mRNA level in efonidipine but not in nifedipine treated animals. Treatment with efonidipine improved tubulointerstitial fibrosis more effectively than treatment with nifedipine in UUO. The antifibrogenic effect by efonidipine was obtained through suppression of fibrogenic signaling.

Atorvastatin Protects Renal Function in the Rat With Acute Unilateral Ureteral Obstruction

To examine the effects of atorvastatin on renal hemodynamics and urinary microalbumin levels in rats with acute unilateral ureteral obstruction (UUO). Previous studies have demonstrated that treatment with statins attenuated renal structural damages in rodents with chronic UUO. However, it is not known whether statins afford protection of renal function. UUO was created by ligation of the left ureter in rats maintained on a regular diet or the same diet but supplemented with atorvastatin (50 mg/kg/d) for 2 weeks. Renal clearance experiments were performed after release of UUO at 1 hour, 6 hours, or 12 hours. Atorvastatin treatment lowered plasma triglyceride but not cholesterol levels. Both glomerular filtration rate and effective renal plasma flow were significantly greater in atorvastatintreated rats after release of UUO at 1 hour, 6 hours, and 12 hours. Significant reduction of urinary microalbumin to creatinine ratios occurred in the atorvastatin-treated group at 12 hours but not earlier. Atorvastatin treatment affords protection of renal function in acute UUO and reduces urinary microalbumin levels without lowering cholesterol levels. This pleiotropic action of atorvastatin on preservation of renal hemodynamics may be important in attenuating subsequent renal structural injury in chronic UUO.

Activation of Erk1/2 and Akt following unilateral ureteral obstruction

Chronic unilateral ureteral obstruction is a well characterized model of renal injury leading to tubulointerstitial fibrosis and distinct patterns of cell proliferation and apoptosis in the obstructed kidney. In this study we assessed the contribution of the mitogen activated protein kinase (MAPK)-ERK1/2 and the phosphatidylinositol 3 kinase (PI3K)-Akt pathways to early renal changes following unilateral obstruction. Increased activation of small Ras GTPase and its downstream effectors ERK1/2 and Akt was detected in ligated kidneys. The use of specific pharmacological inhibitors to either ERK1/2 or Akt activation led to decreased levels of fibroblast-myofibroblast markers in the interstitium while inhibition of PI3K reduced the number of proliferating cells and the amount of interstitial extracellular matrix deposition. Treatment with an ERK1/2 inhibitor diminished the number of apoptotic tubule and interstitial cells. Our results suggest a role for the MAPK-ERK1/2 and PI3K-Akt systems in early changes induced by ureteral obstruction and that inhibition of these signaling pathways may provide a novel approach to prevent progression of renal fibrosis.

Altered Regulation of Renin-Angiotensin, Endothelin and Natriuretic Peptide Systems in Rat Kidney with Chronic Unilateral Ureteral Obstruction

Background: The present study was designed to investigate the role of the local renin-angiotensin-aldosterone system (RAAS), endothelin (ET) and the natriuretic peptide system (NPS) for the development of renal fibrosis and progressive renal disease in experimental unilateral ureteral obstructed (UUO) rats. Methods: Male Sprague-Dawley rats (180–200 g) were unilaterally obstructed by ligation of the proximal ureters for 14 days. Control rats were treated in the same way, except that no ligature was made. The mRNA expressions of local renin-angiotensin system, aldosterone synthase (CYP11B2), ET-1 and NPS was determined in the cortex by real-time polymerase chain reaction. Results: Following the unilateral ureteral obstruction, the mRNA expressions of angiotensin-converting enzyme 1, ET-1 and transforming growth factor-β₁ (TGF-β₁) were increased, while angiotensin-converting enzyme 2 was decreased in the obstructed kidney compared with the controls. Angiotensin II type 1 receptor was decreased and TGF-β₁ was not changed in contralateral kidney compared with the controls. Atrial natriuretic peptide, brain natriuretic peptide, and C-type natri- uretic peptide expressions were increased in UUO kidneys compared with the controls, while natriuretic peptide receptor-A was decreased in UUO kidneys. Conclusion: The local RAAS and ET-1 was upregulated which may play a role in the progressive renal fibrosis in obstructed kidneys in rats with UUO. The enhanced activity of NPS in UUO kidney may play a role to compensate against progressive renal fibrosis in chronic obstructive uropathy.

Leukocytes Induce Epithelial to Mesenchymal Transition after Unilateral Ureteral Obstruction in Neonatal Mice

Urinary tract obstruction during renal development leads to tubular apoptosis, tubular atrophy, and interstitial fibrosis. Epithelial to mesenchymal transition (EMT) has been proposed as a key mechanism of myofibroblast accumulation in renal fibrosis. We studied the interplay of leukocyte infiltration, tubular apoptosis, and EMT in renal fibrosis induced by unilateral ureteral obstruction (UUO) in neonatal mice. We show that leukocytes mediate tubular apoptosis and EMT in the developing kidney with obstructive nephropathy. Blocking leukocyte recruitment by using the chemokine receptor-1 antagonist BX471 protected against tubular apoptosis and interstitial fibrosis, as evidenced by reduced monocyte influx, a decrease in EMT, and attenuated collagen deposition. EMT was rapidly induced within 24 hours after UUO along with up-regulation of the transcription factors Snail1 and Snail2/Slug, preceding the induction of alpha-smooth muscle actin and vimentin. In the presence of BX471, the expression of chemokines, as well as of Snail1 and Snail2/Slug, in the obstructed kidney was completely attenuated. This was associated with reduced macrophage and T-cell infiltration, tubular apoptosis, and interstitial fibrosis in the developing kidney. Our findings provide evidence that leukocytes induce EMT and renal fibrosis after UUO and suggest that chemokine receptor-1 antagonism may prove beneficial in obstructive nephropathy.

Atorvastatin Preserves Renal Function in Chronic Complete Unilateral Ureteral Obstruction

The pleiotropic effects of hMG-CoA (3-hydroxy-3-metylglutaryl coenzyme A) reductase inhibitors may provide renal protection in chronic kidney disease. We examined whether atorvastatin administration preserved renal function in rats with chronic unilateral ureteral obstruction. Renal clearance experiments were performed in sham operated rats and rats subjected to 3 or 12-day unilateral ureteral obstruction. Hemodynamics parameters and urinary microalbumin levels from the obstructed kidney were also measured. The rats were maintained on a regular diet or the same diet but supplemented with atorvastatin (50 mg/kg daily). Atorvastatin administration did not alter plasma total cholesterol but it significantly decreased triglyceride levels. In sham operated and 3-day unilateral ureteral obstruction rats atorvastatin treatment did not have effects on the glomerular filtration rate or effective renal plasma flow and it also did not affect urinary microalbumin levels. In rats with 12-day unilateral ureteral obstruction the glomerular filtration rate but not effective renal plasma flow was significantly higher and urinary microalbumin was significantly lower in atorvastatin treated rats than in those without atorvastatin treatment. Atorvastatin treatment decreased microalbuminuria and helped preserve filtration function in chronic unilateral ureteral obstruction without altering plasma cholesterol levels, suggesting that pleiotropic renal protection is offered by this statin.

Renal vascular endothelial growth factor in neonatal obstructive nephropathy. I. Endogenous VEGF

Obstructive nephropathy constitutes a major cause of renal impairment in children. Chronic unilateral ureteral obstruction (UUO) impairs maturation of the developing kidney and leads to tubular apoptosis and interstitial inflammation. Vascular endothelial growth factor (VEGF) is involved in recovery from various forms of renal injury. We questioned whether the renal expression of endogenous VEGF and its receptor (VEGFR2/Flk-1) is modified by UUO in early development. Neonatal rats were subjected to partial or complete UUO or sham operation. The distribution of immunoreactive VEGF in each kidney was examined after 7, 14, or 28 days. Adult rats were also subjected to sham operation or complete UUO. Tubular VEGF increased between 14 and 28 days in sham-operated rats and in some partially obstructed neonatal rats but decreased with complete UUO. Parallel changes were found by Western blotting, but not by RT-PCR. Immunoreactive VEGF colocalized with mitochondria in proximal and distal tubules and also appeared in type A intercalated cells, glomerular vascular endothelium, and podocytes. While neonatal microvascular renal VEGFR2 receptor staining was strongly positive regardless of UUO, staining was weak in sham-operated adults but increased following UUO. Parallel changes in VEGFR2 expression were verified by RT-PCR and Western blotting. We conclude that endogenous renal VEGF is developmentally regulated in the neonatal rat and is differentially regulated by partial and complete UUO. Following UUO in the adult, the VEGF receptor is upregulated. Endogenous VEGF may serve an adaptive role in responding to tubular injury caused by UUO and may modulate adaptation by the contralateral kidney.

Osteopontin regulates renal apoptosis and interstitial fibrosis in neonatal chronic unilateral ureteral obstruction

Congenital obstructive nephropathy is a major cause of renal insufficiency in children. Osteopontin (OPN) is a phosphoprotein produced by the kidney that mediates cell adhesion and migration. We investigated the role of OPN in the renal response to unilateral ureteral obstruction (UUO) in neonatal mice. OPN null mutant (-/-) and wild-type (+/+) mice were subjected to sham operation or UUO within the first 2 days of life. At 7 and 21 days of age, fibroblasts (fibroblast-specific protein (FSP)-1), myofibroblasts (alpha-smooth muscle actin (SMA)), and macrophages (F4/80) were identified by immunohistochemical staining. Apoptotic cells were detected by terminal deoxy transferase uridine triphosphate nick end-labeling technique and interstitial collagen by Masson trichrome or picrosirius red stain. Compared to sham-operated or contralateral kidneys, obstructed kidneys showed increases in all parameters by 7 days, with further increases by 21 days. After 21 days UUO, there was an increase in tubular and interstitial apoptosis in OPN -/- mice as compared to +/+ animals (P<0.05). However, FSP-1- and alpha-SMA-positive cells and collagen in the obstructed kidney were decreased in OPN -/- compared to +/+ mice (P<0.05), whereas the interstitial macrophage population did not differ between groups. We conclude that OPN plays a significant role in the recruitment and activation of interstitial fibroblasts to myofibroblasts in the progression of interstitial fibrosis in the developing hydronephrotic kidney. However, OPN also suppresses apoptosis. Future approaches to limit the progression of obstructive nephropathy in the developing kidney will require targeting of specific renal compartments.

Plasminogen Activator Inhibitor-1 in Chronic Kidney Disease

In 1984, Loskutoff et al. ([1][1]) purified plasminogen activator inhibitor-1 (PAI-1) from conditioned media of cultured endothelial cells. This 50-kd glycoprotein is the primary physiologic inhibitor of the serine proteases tissue-type and urokinase-type plasminogen activators (tPA and uPA,