Rapamycin attenuates unilateral ureteral obstruction-induced renal fibrosis

Unilateral ureteral obstruction (UUO) is a well-characterized hydronephrosis model exhibiting interstitial inflammatory-cell infiltration and tubular dilatation followed by tubulointerstitial fibrosis of the obstructed kidney. Our recent report indicates that rapamycin is effective for 50% of transplant recipients with chronic allograft nephropathy. In this study, we investigate the effect of rapamycin on UUO-induced renal fibrosis. UUO or sham-operated rats were randomly assigned to rapamycin or vehicle and were killed on days 7 and 14 after UUO or sham operation. Rapamycin decreased cross-sectional and gross-morphology changes in the obstructed kidney significantly. Rapamycin markedly blunted the increase in weight of the obstructed kidney, obstructed kidney length, and the obstructed/non-obstructed kidney weight ratio (by 74.6, 42.8, and 61.6% on day 14, respectively, all P<0.01). The scores for tubular dilatation, interstitial volume, interstitial collagen deposition, and alpha-smooth muscle actin (alpha-SMA) after UUO were significantly reduced by rapamycin. Rapamycin also decreased the number of infiltrative anti-ED1-positive cells and the gene expression of transforming growth factor (TGF)-beta1 (84.8 and 80.2% on day 7) after UUO (both P<0.01). By double immunostaining and Western analysis, rapamycin blocked the TGF-beta1-induced loss of E-cadherin expression and de novo increase of the expression of alpha-SMA in a dose-dependent manner. In conclusion, rapamycin significantly attenuated tubulointerstitial damage in a UUO-induced rat model of renal fibrosis, suggesting that rapamycin may have the potential to delay the progression of tubulointerstitial renal fibrosis.     

Characterization of G Proteins in Obstructed Kidneys

Background: Urinary tract obstruction has a marked effect on renal function. Activation of phospholipases which results in incremental production of vasoactive eicosanoids may contribute to the hemodynamic changes characteristic of an obstructed kidney. G proteins play an important role in transmembrane signal transduction, which controls phospholipase activities and eicosanoid production. The present study was designed to determine the presence of G proteins in obstructed kidneys in rats, and to characterize the differences between unilateral ureteral obstruction (UUO) and bilateral ureteral obstruction (BUO).
Methods: Several G-protein α subunits (Gas, Gαi1,2, and Gαi3) and the β subunit (Gβ) were determined by immunoblotting and immunocytochemical techniques using specific antibodies against these G proteins.
Results: lmmunoblots demonstrated a decreased Gαi3 content in the outer medullary tubules and a significantly lower Gβ level in the glomeruli of UUO. In BUO, there was an increased leeel of Gβ in the cortical tubules, and the Gαs level was markedly reduced in the inner medullary tubules.
Immunocytochemical studies revealed that these G proteins were predominantly localized in the brush border side of the cortical tubules. However, we could not demonstrate staining differences between UUO and BUO.
Conclusions: These results indicate that a modulation of G-protein-coupled transmembrane signal transduction may contribute to the renal functional changes in an obstructed kidney. A different level of expression of G-protein subunits between UUO and BUO may be a factor in the differences of hemodynamics and renal tubular damage between UUO and BUO.     

Sulfasalazine reduces inflammatory renal injury in unilateral ureteral obstruction

The purpose of this study was to test whether sulfasalazine has a protective action against interstitial inflammation and the development of renal fibrosis in obstructive nephropathy. Female rats were subjected to a sham (n = 10) or unilateral ureteral obstruction (UUO, n = 30). UUO was induced in rats by ligating the left ureter. Three days after operation, rats subjected to UUO were randomized to receive tretment with either sulfasalazine (100 mg/kg) or vehicle every day for the last 7 days of the experiment. At 10 days following UUO, the obstructed kidney exhibited tubulointerstitial injury and leukocyte infiltration (mainly monocytes) that were associated with high levels of reactive oxygen species, cytokines, transforming growth factor (TGF)-β1, myeloperoxidase (MPO), and lipid peroxidation. Ten days after UUO, the obstructed kidney was also associated with increased nuclear factor kappa beta (NF-κβ) expression in saline-treated rats. Compared with sham-operated rats, UUO rat kidneys showed lower concentrations of antioxidant enzymes in the obstructed kidney tissue. All of these changes were significantly attenuated by treatment with sulfasalazine in the obstructed kidney. Sulfasalazine protected against the renal interstitial inflammation and tissue damage elicited by ureteral occlusion. Inhibition of the NF-κβ-dependent pathway and inflammatory response and oxidative stress inhibition is likely to be involved in the beneficial effects of sulfasalazine.     

The role of autophagy in unilateral ureteral obstruction rat model

Aim: Autophagy is a cellular process of degradation of damaged cytoplasmic components and regulates cell death or proliferation. Unilateral ureteral obstruction (UUO) is a model of progressive renal fibrosis in the obstructed kidney. And UUO is followed by compensatory cellular proliferation in the contralateral kidney. We investigate the role of autophagy in the obstructed kidney and contralateral kidney after UUO. Methods: To obtain the evidence and the patterns of autophagy during UUO, the rats were sacrificed 3, 7 and 14 days after UUO. To examine the efficacy of the autophagy inhibitors, 3‐methyladenine (3‐MA), the rats were treated daily with intraperitoneal injection of 3‐MA (30 mg/kg per day) for 7 days. Results: After UUO, autophagy was induced in the obstructed kidney in a time‐dependent manner. Inhibition of autophagy by 3‐MA enhanced tubular cell apoptosis and tubulointerstitial fibrosis in the obstructed kidney after UUO. In the contralateral kidney, autophagy was also induced and prolonged during UUO. Inhibition of autophagy by 3‐MA increased the protein expression of proliferating cell nuclear antigen significantly in the contralateral kidney after UUO. The Akt‐mammalian target of rapamycin (mTOR) signalling pathway was involved in the induction of autophagy after UUO in both kidneys. Conclusion: Our present results support that autophagy induced by UUO has a renoprotective role in the obstructed kidney and regulatory role of compensatory cellular proliferation in the contralateral kidney through Akt‐mTOR signalling pathway.     

Adenosine receptors are up-regulated in unilateral ureteral obstructed rat kidneys

Despite recent improvements in immunosuppressive regimens, chronic renal allograft rejection remains a major problem. Tubulointerstitial fibrosis is one of the major histological features of chronic renal allograft rejection, but its exact pathogenic mechanisms are not fully understood. Adenosine present in the normal kidney is significantly elevated in response to cellular damage. The cellular effect of adenosine occurs through 4 known adenosine receptor (AR) subtypes; A₁AR, A_2AAR, A_2BAR, and A₃AR. All AR subtypes are expressed in the kidney, but the expression of each AR subtype has not been defined under fibrotic conditions. In the present study, we examined AR subtype expression in kidneys that underwent unilateral ureteral obstruction (UUO), a well-characterized model for tubulointerstitial fibrosis. At 5 days after the induction of UUO, we observed α-smooth muscle actin (α-SMA), fibronectin, and collagen I messenger RNA (mRNA) and protein expressions to be significantly up-regulated in the obstructed compared with the sham kidneys, confirming that fibrosis had occurred in the former organs. A₁AR mRNA expression in the obstructed kidney cortex was 3.2-fold higher than an the sham kidney cortex. Relative to the sham kidney A_2AAR and A_2BAR mRNA expressions were also 2.6- and 2.0-fold increased, respectively. A₃AR mRNA expression in the obstructed kidney cortex was also up-regulated by 3.3-fold. These data demonstrated that all 4 subtypes of AR were increased in the obstructed kidney, which was accompanied by tubulointerstitial fibrosis. Further studies are needed to determine which subtypes of AR play a protective or pathogenic role in tubulointerstitial fibrosis.     

冬虫夏草通过诱导血色素加氧酶-1表达抑制肾小管间质纤维化

目的：观察冬虫夏草对单侧输尿管梗阻（unilateral ureteral obstruction,UUO）模型大鼠肾小管间质纤维化进展的保护作用。方法：72只雄性清洁级SD大鼠随机分为4组：假手术组,UUO模型组,UUO加冬虫夏草治疗组,UUO加冬虫夏草和血色素加氧酶抑制剂卟啉锌[（zinc（a）protoporphyrinη,znpp）]治疗组。各组大鼠分别于术后（建模后）第3、7、14天分批处死,留取手术侧（模型组梗阻侧）肾脏组织。采用HE、Masson染色、荧光定量PCR、免疫组织化学染色评价肾小管间质纤维化损伤程度并检测肾脏组织血色素加氧酶-1（hemoglobin oxygenase-1,HO-1）,α平滑肌肌动蛋白（α-smooth muscle ac-tin,α-SMA）mRNA及蛋白表达变化情况。结果：冬虫夏草治疗组相对于UUO模型组,肾脏病理损伤及进展程度明显减轻且HO-1的表达上调,α-SMA的表达下调（P〈0.05）,而冬虫夏草加HO-1抑制剂znpp后,以上作用明显减弱。结论：冬虫夏草可以通过诱导血色素加氧酶的表达减轻肾小管间质纤维化程度。     

Progression after release of obstructive nephropathy

Progressive glomerular and tubulointerstitial fibrosis develop in 1-year-old rats even after relief (R) of unilateral ureteral obstruction (UUO) at 5 days of age. The present study investigated whether a progressive renal injury model of UUO could be achieved after reversal of UUO (RUUO) in adult instead of neonatal rats. The potential for α-tocopherol modulation of mRNA for the fibrogenic cytokine, transforming growth factor-β1 (TGFβ1), apoptosis (TUNEL assay), and the presence of the stress protein, heat shock protein-70 (HSP-70), was also studied in this post-obstructive model. Male Sprague-Dawley rats weighing 125–150 g were randomly assigned to groups of 4 animals each for durations of 7 or 14 days of α-tocopherol supplementation after RUUO. The groups included: (i) sham, regular chow; (ii) RUUO, regular chow; (iii) RUUO, contralateral nephrectomy (NX); and (iv) RUUO, NX plus α-tocopherol supplementation. We found a significant increase in the ratio of kidney weight/body weight in the RUUO+NX group at 14 days compared with the sham and RUUO groups. This rise in the RUUO+NX group was significantly reduced after 14 days of α-tocopherol administration. The elevated level of kidney TGFβ1 mRNA in the RUUO+NX group was only partially reduced at 7 days. But at 14 days this became significantly reduced with the continued α-tocopherol treatment. The HSP-70 staining and the apoptosis of the kidney showed results parallel to those of TGFβ mRNA at 14 days. To separate the effects of hypertrophy after unilateral NX from the RUUO studies, we carried out a second experiment in control animals subjected to NX, with and without α-tocopherol supplementation. Fourteen days after NX, the apoptosis and TGFβ1 mRNA showed no significant differences from the control animals. Our data suggest that a model of progressive renal injury in RUUO can be established in adult rats. After contralateral NX, the progressive injury is evidenced by the increase in the ratio of kidney weight/total body weight, the apoptotic counts, as well as fibrogenic cytokine TGFβ1 mRNA in the post- obstructed kidney. Finally, our data also support the concept that α-tocopherol is renal protective, as judged by TGFβ1 mRNA, apoptosis, and HSP-70 staining, even in the progressive disease process of the post-obstructed model. Received: 17 February 2000 / Revised: 21 September 2000 / Accepted: 21 September 2000     

Counterbalance in functional adaptation to ureteral obstruction during development

Renal counterbalance, as described by Hinman in 1923, is the phenomenon of increased function of the intact kidney in proportion to the loss of function resulting from unilateral ureteral obstruction (UUO). In the neonatal guinea pig, chronic partial UUO results in severe vasoconstriction and growth arrest of the ipsilateral kidney. Angiotensin II appears to contribute significantly to the vasoconstriction, and the renin-angiotensin system is also involved in the hemodynamic response of the intact opposite kidney to UUO and to relief of UUO. Immunolocalization of renin following complete UUO in the neonatal rat revealed extension of renin-containing cells along the length of the afferent arteriole in both the obstructed and the intact opposite kidney. The proportion of juxtaglomerular apparatuses with detectable renin and renin messenger ribonucleic acid (mRNA) (identified by in situ hybridization), as well as renal renin content (a measure of active renin), were increased in the obstructed kidney compared with the intact opposite kidney. Chemical sympathectomy by chronic guanethidine administration reduced the total renin mRNA in the obstructed kidney (determined by Northern blot analysis) and prevented the increased renin immunostaining in both kidneys. Thus, renal counterbalance in the developing kidney subjected to UUO is mediated or modulated by the renal nerves and involves marked alterations in gene expression and cellular processing of renin.     

上调肾组织intermedin表达抑制单侧输尿管梗阻大鼠肾间质纤维化

目的观察上调肾组织intermedin(IMD)表达对单侧输尿管梗阻(UUO)大鼠肾间质纤维化的影响。 方法健康雄性Wistar大鼠随机分为假手术组、UUO组、IMD＋UUO组、空质粒＋UUO组。IMD＋UUO组和空质粒＋UUO组在输尿管结扎前分别将IMD-pcDNA3.1真核表达质粒和空质粒转入肾组织,real-time RT-PCR及免疫组化法检测转染效率。各组分别于术后7 d、14 d留取梗阻侧肾组织。HE、Masson染色观察肾组织病理变化;real-time RT-PCR检测肾组织中转化生长因子-β1(TGF-β1)、纤连蛋白(Fn1)的mRNA表达;Western印迹法检测Fn1的蛋白表达;免疫组化法检测TGF-β1的蛋白表达。 结果与假手术组相比,UUO组肾脏出现明显的病理改变,肾间质纤维化程度随梗阻时间延长加重(与假手术组比较,7 d, t＝11.927,P＝0.0003;14 d, t＝8.891,P＝0.0009);IMD＋UUO组肾脏病理改变及肾间质纤维化程度较同时间点UUO组明显减轻(7 d, t＝3.892,P＝0.018;14 d, t＝4.047,P＝0.016),而空质粒＋UUO组与UUO组无显著差别(7 d, t＝0.562,P＝0.604;14 d, t＝0.035,P＝0.974)。与同时间点假手术组相比,UUO组TGF-β1、Fn1的表达明显升高(TGF-β1 mRNA水平7 d, t＝4.432,P＝0.011;14 d, t＝4.873,P＝0.006;蛋白质水平7 d, t＝5.312,P＝0.006;14 d, t＝4.482,P＝0.011;Fn1 mRNA水平7 d, t＝6.053,P＝0.004;14 d, t＝7.345,P＝0.002;蛋白质水平7 d, t＝8.791,P＝0.009;14 d t＝8.027,P＝0.001);转染IMD质粒后Fn1的表达较同时间点UUO组明显下降(mRNA水平7 d, t＝3.103,P＝0.036;14 d, t＝2.913,P＝0.044;蛋白质水平7 d, t＝2.955,P＝0.042;14 d, t＝2.991,P＝0.040);而转染空质粒后Fn1的表达无明显变化(mRNA水平7 d, t＝0.095,P＝0.929;14 d, t＝0.158,P＝0.882;蛋白质水平7 d, t＝0.159,P＝0.881;14 d, t＝0.170,P＝0.874)。转染IMD和空质粒对TGF-β1的表达均无明显影响(转染IMD质粒mRNA水平7 d, t＝0.176,P＝0.869;14 d, t＝0.126,P＝0.906;蛋白质水平7 d, t＝0.198,P＝0.853;14 d, t＝0.196,P＝0.854;转染空质粒mRNA水平7 d, t＝0.100,P＝0.925;14 d, t＝0.097,P＝0.928;蛋白质水平7 d, t＝0.042,P＝0.968; 14 d, t＝0.060,P＝0.955)。 结论上调肾组织IMD的表达能明显减轻肾间质纤维化,但其作用不是通过直接抑制TGF-β1的表达实现的。     

骨调素和单核细胞趋化蛋白在大鼠梗阻性肾病中的表达及可能作用

目的:探讨骨调素(OPN)和单核细胞趋化蛋白(MCP-1)在大鼠梗阻性模型中的表达及其在肾脏纤维化发病机制中的作用.方法:采用-单侧输尿管结扎制造梗阻性肾病模型,分别于造模后7 d、14 d取肾组织,应用HE染色观察肾脏病理改变,免疫组化方法检测肾组织畔OPN和MCP-1蛋白的表达,应用逆转录-聚合酶链式反应(RT-PCR)法观察肾组织中OPN mRNA和MCP-1 mRNA的变化.结果:OPN、MCP-1表达主要位于肾小管上皮细胞,随着梗阻时间的延长,肾组织中OPN、MCP-1蛋白和mRNA表达明显增加.结论:OPN、MCP-1蛋白和mRNA在梗阻性肾病大鼠肾组织表达明显增加介导炎症过程,参与肾间质纤维化.     

染料木黄酮在减轻肾间质纤维化中的作用

目的 探讨染料木黄酮(Genistein)在减轻单侧输尿管结扎模型(UUO)诱导肾间质纤维化中的作用及可能机制.方法 将30只SD大鼠随机分为5组,A组:假手术+DMSO 1 ml/d×14 d;B组:假手术+Genistein每日20 mg/ks体重×14 d;C组:UUO+DMSO 1 ml/d×14 d;D组:UUO+Genistein 5mg/kg体重每日×14d;E组:UUO+Genistein 20mg/kg体重每日×14d.术后14d比较各组大鼠左/右肾重量和长度的比值;酶联免疫吸附实验(ELISA)法检测血清INF-y和TGFa1表达;病理观察肾小管扩张和肾间质增生的程度,免疫组织化学观察肾脏á-SMA和ED-1表达.结果 C、D、E组左/右肾重量及长度比值均明显高于A、B组,但E组左/右肾重量及长度比值、血清TGF-a1及INF-y浓度、肾小管扩张分数和肾小管容量分数、á-SMA和ED-1的表达均低于C组.结论 染料木黄酮可明显降低由单侧输尿管结扎模型所导致的肾间质纤维化的病理改变,其可能机制是染料木黄酮抑制TGF-a1及INF-y的表达,从而抑制肾小管上皮细胞向成纤维细胞转化.     

Expression of renin and its mRNA in the adult rat kidney with chronic ureteral obstruction

Angiotensin II has been implicated in mediating renal vasoconstriction resulting from chronic unilateral ureteral obstruction (UUO) in both mature and developing animals. We have previously shown that chronic neonatal UUO results in increased distribution of renin and its mRNA in the obstructed kidney, as well as of immunoreactive renin in the intact opposite kidney. The present study was designed to evaluate the effects of 24 hours versus 4 weeks of UUO on the distribution of renin mRNA and its protein in the adult rat kidney. Renin was detected by immunocytochemistry using a polyclonal anti-rat renin antibody. Renin mRNA was localized by in situ hybridization to an oligonucleotide complementary to renin mRNA. UUO of 24 hours' or 4 weeks' duration did not alter the distribution of renin and its mRNA in the obstructed kidneys as compared with sham-operated kidneys, although kidneys obstructed for 4 weeks had a significant increase in the percent of renin-containing juxtaglomerular apparatuses (JCA) when compared with the intact opposite kidneys (P less than 0.05). Compensatory hypertrophy was not present in the intact opposite kidneys after 24 hours of UUO and distribution of renin gene expression was not altered at that time. However, 4 weeks following contralateral UUO, the intact kidneys were hypertrophied and showed a decrease in renin gene expression relative to the obstructed and sham-operated kidneys. We conclude that unlike UUO during early development, chronic UUO in the mature animal does not activate renin gene expression nor alter renin distribution in the obstructed kidneys. Renin gene expression is suppressed in the hypertrophied kidney with prolonged contralateral UUO.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reimplantation of the ureter after unilateral ureteral obstruction provides a model that allows functional evaluation

Experimental unilateral ureteral obstruction (UUO) is widely used to study renal fibrosis; however, renal injury can only be scored semiobjectively by histology. We sought to improve the UUO model by reimplanting the obstructed ureter followed by removal of the contralateral kidney, thus allowing longitudinal measurements of renal function. Mice underwent UUO for different lengths of time before ureteral reimplantation and contralateral nephrectomy. Measurement of blood urea nitrogen (BUN) allows objective evaluation of residual renal function. Seven weeks after reimplantation and contralateral nephrectomy, mean BUN levels were increased with longer duration of UUO. Interstitial expansion, fibrosis, and T-cell and macrophage infiltration were similar in kidneys harvested after 10 days of UUO or following 10 weeks of ureter reimplantation, suggesting that the inflammatory process persisted despite relief of obstruction. Urinary protein excretion after reimplantation was significantly increased compared to control animals. Our study shows that functional assessment of the formerly obstructed kidney can be made after reimplantation and may provide a useful model to test therapeutic strategies for reversing renal fibrosis and preserving or restoring renal function.     

Epidermal growth factor suppresses renal tubular apoptosis following ureteral obstruction

Objectives. Acute unilateral ureteral obstruction (UUO) results in ipsilateral hydronephrosis characterized by a decrease in epidermal growth factor (EGF) mRNA expression and EGF protein levels in the distal renal tubules. UUO results in programmed cell death with increases in the characteristic markers of apoptosis. To suppress the apoptotic response during UUO, recombinant EGF was administered during renal obstruction and the ensuing molecular and histologic changes were studied.Methods. Mature Sprague-Dawley rats underwent left ureteral obstruction and the kidneys were harvested at 24, 48, and 72 hours. Markers of apoptosis included DNA laddering pattern on agarose gel electrophoresis, in situ gap labeling of fragmented DNA for quantitative apoptotic body determination, polyadenylated mRNA expression of SGP-2, and in situ hybridization for sulfated glycoprotein-2 (SGP-2) mRNA. Studies were repeated in rats following administration of 10, 20, and 40 μg of subcutaneous recombinant EGF on a daily basis after UUO.Results. Subcutaneous injection of EGF into unilaterally obstructed rats promotes renal tubular epithelial cell regeneration, as demonstrated by increased cortical mitotic activity. Systemic EGF supplementation in these unilaterally obstructed rats also resulted in a decrease in the intensity of the DNA laddering pattern associated with renal tubular apoptosis. An in situ labeling procedure to identify apoptotic nuclei in the ureterally obstructed kidneys revealed a 50% reduction in apoptosis after EGF administration. Northern blot analysis and in situ hybridization for SGP-2 mRNA or clusterin gene product also revealed a decreased expression in the obstructed and EGF-treated renal parenchyma.Conclusions. These data suggest that EGF, apart from its known role as a mitogenic substance for renal tubular epithelial cells, is also a critical in vivo renal cell survival factor for the developmentally mature kidney.     

α-Tocopherol modulates lipoprotein cytotoxicity in obstructive nephropathy

Oxidative stress in unilateral ureteral obstruction (UUO) contributes to the development of glomerular and tubulointerstitial lesions. The present study investigated whether oxidized low-density lipoprotein (oLDL) contributes to the pathogenesis of kidney injury in UUO, and whether α-tocopherol modulates such cytotoxicity and promotes repair. Male Sprague-Dawley rats weighing 100–125 g were assigned to three groups of 6 animals each: (1) sham, regular chow; (2) UUO, regular chow; and (3) UUO, α-tocopherol supplementation. We found a significant increase in the level of oxidative stress in the UUO group as measured by malondialdehyde (MDA) content in both plasma and kidneys. The LDL isolated from this group was cytotoxic to rat mesangial cells. The level of oxidation and cytotoxicity was significantly reduced when animals were treated with α-tocopherol. Plasma cholesterol concentration, kidney MDA, and transforming growth factor β1 mRNA expression were all significantly increased in the UUO animals, and partially reduced in α-tocopherol-treated animals. Our data suggest that oxidative modification of LDL is associated with the renal injury in UUO. Taken together, our data support the concept that α-tocopherol can modulate LDL oxidation and its cytotoxic effects on rat mesangial cells in vitro. Received: 23 July 1999 / Revised: 1 November 1999 / Accepted: 1 November 1999     

Attenuation of ureteral obstruction-induced renal injury by polyenylphosphatidylcholine

BACKGROUND: The cytoprotective, antioxidant and antifibrotic effects of polyenylphosphatidylcholine (lecithin, PPC) have been demonstrated both experimentally and clinically. The present study investigated whether PPC treatment has any beneficial effect on renal injury in unilateral partial ureteral obstruction (UUO) in rats. METHODS: Forty Wistar-Albino rats were split into three groups (sham-operated controls, untreated and treated rats). Rats of the untreated and treated groups (n = 15) underwent UUO with two-thirds of the left ureter embedded in the psoas muscle. In group 3, PPC was given orally at a dose of 100 mg/day for 30 days. At the end of the 30th day of the experimental period, obstructed kidneys and blood samples were harvested. To investigate the therapeutic efficacy of PPC treatment in UUO kidneys, oxidant and antioxidant enzyme levels, lipid peroxidation, proinflammatory cytokines (interleukin-1, interleukin-6, tumor necrosis factor alpha), transforming growth factor beta-1 (TGFbeta-1), alpha smooth muscle actin (alpha-SMA) and nuclear factor kappa beta (NF-kappabeta) expression, leukocyte infiltration (ED1, ED2, CD4 and CD8 immunohistochemistry), and tubulointerstitial damage in the obstructed kidneys were studied. RESULTS: Oxidative stress, neutrophil infiltration, release of cytotoxic mediators, TGFbeta-1 levels, tubulointerstitial damage, alpha-SMA and NF-KB expressions in kidney tissue were significantly increased in the UUO rats. PPC treatment attenuated oxidative stress, leukocyte infiltration, cytotoxic mediator, and TGFbeta-1 levels and also decreased expressions of alpha-SMA and NF-kappabeta. It was associated with decreased tubulointerstitial damage, compared with UUO alone. CONCLUSIONS: These results indicate that PPC treatment protects against UUO-induced renal injury in rats possibly through its antioxidant, anti-inflammatory and antifibrotic actions.     

Role of nitric oxide in renal tubular apoptosis of unilateral ureteral obstruction

BACKGROUND: The obstructed kidney in unilateral ureteral obstruction (UUO) is characterized by renal atrophy and tissue loss, which is mediated by renal tubular apoptosis. We sought to determine whether NO is involved in renal tubular apoptosis in vitro and in vivo. METHODS: Rat renal tubular epithelial cells (NRK-52E) were subjected to mechanical stretch, and apoptosis and cell size were analyzed by flow cytometry. Furthermore, we studied UUO in mice lacking the gene for inducible nitric oxide synthase (iNOS-/-) and their wild-type littermates. Tubular apoptosis and proliferation were detected by immunostaining. NOS activity and NOS expression were assessed by a citrulline assay and Western blot, respectively. RESULTS: Stretching-induced apoptosis in NRK-52E, which was reduced when NO was increased; conversely, stretch-induced apoptosis was increased when a NOS inhibitor was added to the cells. Stretched cells are larger and more apoptotic than unstretched cells. In UUO, the obstructed kidney of iNOS-/- mice exhibited more apoptotic renal tubules than the wild-type mice through 14 days of UUO. The obstructed kidney of iNOS-/- mice at day 3 showed more proliferative tubules compared with wild type. The obstructed kidney of wild-type mice exhibited higher total NOS activity until day 7 after UUO compared with iNOS-/- mice. However, the obstructed kidney of day 14 wild-type mice exhibited significantly lower iNOS activity and protein compared with the day 0 kidney. CONCLUSION: These results suggest that mechanical stretch is related to renal tubular apoptosis and that NO plays a protective role in this system in UUO.     

Ureteral obstruction in the neonatal rat: Renal nerves modulate hemodynamic effects

In the neonate, chronic unilateral ureteral obstruction (UUO) reduces renal blood flow (RBF) of the ipsilateral kidney and increases RBF of the opposite kidney. To determine whether renal nerves mediate or modulate these responses complete left UUO in the neonatal rat was used as a model of severe obstructive uropathy, and was compared with sham-operated controls. At 24–28 days of age, animals underwent left or right mechanical renal denervation or left sham renal denervation. One week after denervation, animals were anesthetized and blood pressure and heart reate were measured. Cardiac output and RBF were determined by the radioactive microsphere technique. UUO increased blood pressure and heart rate, and decreased RBF in the obstructed kidney, regardless of denervation. While left UUO increased RBF to the intact opposite kidney in rats with left renal denervation, this was attenuated by right renal denervation. Thus, in the neonatal rat, UUO modulates systemic renal hemodynamics, possibly through activation of the renin-angiotensin system. While renal nerves do not mediate the vasoconstriction of the obstructed kidney, renal nerves modulate vascular tone of the kidney contralateral to UUO.     

Renal structural and functional repair in a mouse model of reversal of ureteral obstruction

The end point of immune and nonimmune renal injury typically involves glomerular and tubulointerstitial fibrosis. Although numerous studies have focused on the events that lead to renal fibrosis, less is known about the mechanisms that promote cellular repair and tissue remodeling. Described is a model of renal injury and repair after the reversal of unilateral ureteral obstruction (UUO) in male C57bl/6J mice. Male mice (20 to 25 g) underwent 10 d of UUO with or without 1, 2, 4, or 6 wk of reversal of UUO (R-UUO). UUO resulted in cortical tubular cell atrophy and tubular dilation in conjunction with an almost complete ablation of the outer medulla. This was associated with interstitial macrophage infiltration; increased hydroxyproline content; and upregulated type I, III, IV, and V collagen expression. The volume density of kidney occupied by renal tubules that exhibited a brush border was measured as an assessment of the degree of repair after R-UUO. After 6 wk of R-UUO, there was an increase in the area of kidney occupied by repaired tubules (83.7 +/- 5.9%), compared with 10 d UUO kidneys (32.6 +/- 7.3%). This coincided with reduced macrophage numbers, decreased hydroxyproline content, and reduced collagen accumulation and interstitial matrix expansion, compared with obstructed kidneys from UUO mice. GFR in the 6-wk R-UUO kidneys was restored to 43 to 88% of the GFR in the contralateral unobstructed kidneys. This study describes the regenerative potential of the kidney after the established interstitial matrix expansion and medullary ablation associated with UUO in the adult mouse.