Heme oxygenase-1 protects rat kidney from ureteral obstruction via an antiapoptotic pathway

This study examined the functional significance of heme oxygenase-1 (HO-1) expression on renal injury induced by ureteral obstruction in the rat kidney. Male Sprague-Dawley rats were divided into three groups, after which unilateral ureteral obstruction (UUO) was performed: untreated (group 1), treated with 30 mg/kg body wt hemin (group 2), and treated with 50 microg/kg body wt zinc (alpha) protoporphyrin eta (ZnPP) and 30 mg/kg hemin (group 3). After 7 and 14 d, histologic changes and the expression of HO-1, Bcl-2, Bad, TGF-beta, and cleaved caspase-3 were examined. Tubular lumens were dilated and epithelial cells were flattened on day 7 after UUO. Interstitial fibrosis and separation of the tubules were markedly increased on day 14. In contrast, the kidneys that were treated with hemin exhibited minimal interstitial fibrosis and flattening of epithelial cells on day 7 and fewer changes on day 14 than in the controls. However, treatment with ZnPP, an inhibitor of HO enzyme activity, eliminated the beneficial effect of hemin on interstitial fibrosis and tubular dilation. Increased HO-1 expression was associated with increased Bcl-2. In the ZnPP-treated rats, Bcl-2 signals were decreased compared with the hemin group. The level of proapoptotic Bad was not changed in any group. The positive cells for cleaved caspase-3 were significantly increased in renal tubular epithelial cells and tubulointerstitial cells in the obstructed rats, and hemin treatment decreased the caspase-3 activation. This study demonstrates that upregulation of HO-1 provides protection against renal injury that follows UUO. This effect is dependent on modulation of the antiapoptotic pathway by HO-1 expression.     

Antibody to transforming growth factor-beta ameliorates tubular apoptosis in unilateral ureteral obstruction

BACKGROUND: Unilateral ureteral obstruction (UUO) is characterized by progressive renal atrophy, renal interstitial fibrosis, an increase in renal transforming growth factor-beta (TGF-beta), and renal tubular apoptosis. The present study was undertaken to determine the effect of a monoclonal antibody to TGF-beta (1D11) in UUO. METHODS: Mechanical stretch was applied to tubular epithelial cells (NRK-52E) by a computer-assisted system. Three doses of 1D11 (either 0.5, 2, or 4 mg/rat) were administered to rats one day prior to UUO and every two days thereafter, and kidneys were harvested at day 13. Fibrosis was assessed by measuring tissue hydroxyproline and mRNA for collagen and fibronectin. Apoptosis was assessed with the terminal deoxy transferase uridine triphosphate nick end-labeling assay. TGF-beta levels were determined by bioassay. Western blot and immunostaining were used to identify proliferating cell nuclear antigen (PCNA), p53, bcl-2, and inducible nitric oxide synthase (iNOS). RESULTS: Stretch significantly induced apoptosis in NRK-52E cells, which was accompanied by an increased release of TGF-beta; 1D11 (10 microg/mL) totally inhibited stretch-induced apoptosis. Control obstructed kidney contained 20-fold higher TGF-beta as compared with its unobstructed kidney; 1D11 neutralized tissue TGF-beta of the obstructed kidney. Control obstructed kidney exhibited significantly more fibrosis and tubular apoptosis than its unobstructed counterpart, which was blunted by 1D11. In contrast, 1D11 significantly increased tubular proliferation. p53 immunostaining was localized to renal tubular nuclei of control obstructed kidney and was diminished by 1D11. In contrast, bcl-2 was up-regulated in the 1D11-treated obstructed kidney. Total NOS activity and iNOS activity of the obstructed kidney were increased by 1D11 treatment. CONCLUSION: The present study strongly suggests that an antibody to TGF-beta is a promising agent to prevent renal tubular fibrosis and apoptosis in UUO.     

Does cyclooxygenase-2 inhibitor prevent renal tissue damage in unilateral ureteral obstruction?

PURPOSE: We determined whether the cyclooxygenase-2 inhibitor etodolac affects renal tubular damage and interstitial fibrosis in unilateral ureteral obstruction. MATERIALS AND METHODS: Etodolac (10 mg./kg.) was administered to rats 1 day before unilateral ureteral obstruction and every day thereafter. Kidneys were harvested at day 14 after unilateral ureteral obstruction. Tissue transforming growth factor-beta and prostaglandin E2 were measured by bioassay using mink lung epithelial cells and enzyme linked immunosorbent-sandwich assay. Renal tubular proliferation and apoptosis were detected by immunostaining with proliferating cellular nuclear antigen and by terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling, respectively. Cyclooxygenase-2 expression was detected by immunohistochemistry. Fibrosis was assessed by measuring collagen deposition in trichrome stained slides. RESULTS: Bioassay showed that in the control group obstructed kidneys contained significantly higher mean transforming growth factor-beta1 than unobstructed kidneys (79.1 +/- 8.3 versus 33.6 +/- 4.2 ng./gm. tissue) and etodolac significantly decrease the mean value in obstructed kidneys (46.2 +/- 10.0 ng./gm. tissue). Assay demonstrated that obstructed control kidneys had significantly more mean tubular apoptosis than their unobstructed counterparts (26.6 +/- 5.4 versus 2.2 +/- 1.4 nuclei per high power field) and etodolac significantly decreased mean renal tubular apoptosis in the obstructed kidneys (16.2 +/- 1.9 nuclei per high power field). In addition, immunostaining with proliferating cellular nuclear antigen showed that obstructed kidneys in the control group had significantly more mean renal tubular proliferation than unobstructed kidneys (9.8 +/- 3.4 versus 3.9 +/- 0.1 per high power field) and etodolac significantly increased mean proliferating renal tubule in the obstructed kidneys (24.9 +/- 4.3 per high power field). Control obstructed kidneys had significantly more fibrosis and prostaglandin E2 production, which were also significantly blunted by etodolac. CONCLUSIONS: The cyclooxygenase-2 inhibitor etodolac significantly reduces tissue transforming growth factor-beta, resulting in decreased tubular damage and interstitial fibrosis. This finding suggests that etodolac is a promising agent for preventing renal tissue damage in unilateral ureteral obstruction.     

Fluvastatin suppresses oxidative stress and fibrosis in the interstitium of mouse kidneys with unilateral ureteral obstruction

BACKGROUND: Recently, we demonstrated increased oxidative stress in the interstitium of ureteral obstructed kidneys based on the increased expression of heme oxygenase-1 and immunohistochemical detection of advanced glycation end products (AGE) in the interstitium. Antioxidant therapy may have a therapeutic potential toward interstitial fibrosis of unilateral ureteral obstruction (UUO) kidneys. Fluvastatin is an HMG-CoA reductase inhibitor and has been demonstrated to have an antioxidant activity in vitro. METHODS: The effects of fluvastatin on UUO kidneys from the viewpoints of antioxidant action in vivo and antifibrosis action were studied. To investigate the antioxidant action and its therapeutic efficacy of fluvastatin in UUO kidneys, AGE accumulation and fibrosis in the obstructed kidneys was compared among vehicle-, pravastatin-, or fluvastatin-treated (10 or 40 mg/kg/day) groups. RESULTS: Tubulointerstitial fibrosis was significantly attenuated in fluvastatin-treated animals. Fluvastatin significantly suppressed the degree of immunostaining of AGE in UUO kidneys. CONCLUSIONS: These results provide evidence for the antioxidant action of fluvastatin in vivo. The decreased interstitial fibrosis along with a decreased oxidative stress marker in the interstitial lesion strongly suggests the existence of a causal relationship between them. Fluvastatin may have therapeutic value in slowing or preventing interstitial fibrosis in progressive renal disease.     

Obstructive uropathy in the mouse: role of osteopontin in interstitial fibrosis and apoptosis.

BACKGROUND: Osteopontin is a macrophage adhesive protein that is expressed by renal tubules in tubulointerstitial disease. METHODS: To investigate the function of OPN, we induced tubulointerstitial disease in OPN null mutant (OPN-/-) and wild-type (OPN+/+) mice by unilateral ureteral ligation. Tissue was analyzed for macrophages (ED-1), types I and IV collagen deposition, TGF-beta expression, and for tubular and interstitial cell apoptosis. RESULTS: Obstructed kidneys from both OPN-/- and OPN+/+ mice developed hydronephrosis, tubular atrophy, interstitial inflammation and fibrosis. OPN was absent in OPN-/- kidneys but was increased in obstructed OPN+/+ kidneys. Macrophage influx, measured by computer-assisted quantitative immunostaining, was less in OPN-/- mice compared to OPN+/+ mice at day 4 (threefold, P < 0.02), day 7 (fivefold, P < 0.02), but not at day 14. Interstitial deposition of types I and IV collagen were also two- to fourfold less in obstructed OPN-/- kidneys (P < 0.02). There was also a reduction of TGF-beta mRNA expression in the interstitium at day 7 (by in situ hybridization) and a near significant 34% reduction in cortical TGF-beta activity (P = 0.06) compared to obstructed OPN+/+ kidneys at day 14. Obstructed kidneys from OPN-/- mice also had more interstitial and tubular apoptotic cells (TUNEL assay) compared to obstructed OPN+/+ mice at all time points. The ability of OPN to act as a cell survival factor was also documented by showing that the apoptosis of serum-starved NRK52E renal epithelial cells was markedly enhanced in the presence of neutralizing anti-OPN antibody. CONCLUSION: OPN mediates early interstitial macrophage influx and interstitial fibrosis in unilateral ureteral obstruction. OPN may also function as a survival factor for renal tubulointerstitial cells.     

Reduction in connective tissue growth factor by antisense treatment ameliorates renal tubulointerstitial fibrosis

Connective tissue growth factor (CTGF/CCN2) is one of the candidate factors mediating fibrogenic activity of TGF-beta. It was shown previously that the blockade of CTGF by antisense oligonucleotide (ODN) inhibits TGF-beta-induced production of fibronectin and type I collagen in cultured renal fibroblasts. The in vivo contribution of CTGF in renal interstitial fibrosis, however, remains to be clarified. With the use of a hydrodynamics-based gene transfer technique, the effects of CTGF antisense ODN are investigated in rat kidneys with unilateral ureteral obstruction (UUO). FITC-labeled ODN injection via the renal vein showed that the ODN was specifically introduced into the interstitium. At day 7 after UUO, the gene expression of CTGF, fibronectin, fibronectin ED-A, and alpha1(I) collagen in untreated or control ODN-treated obstructed kidneys was prominently upregulated. CTGF antisense ODN treatment, by contrast, markedly attenuated the induction of CTGF, fibronectin, fibronectin ED-A, and alpha1(I) collagen genes, whereas TGF-beta gene upregulation was not affected. The antisense treatment also reduced interstitial deposition of CTGF, fibronectin ED-A, and type I collagen and the interstitial fibrotic areas. The number of myofibroblasts determined by the expression of alpha-smooth muscle actin was significantly decreased as well. Proliferation of tubular and interstitial cells was not altered with the treatment. These findings indicate that CTGF expression in the interstitium plays a crucial role in the progression of interstitial fibrosis but not in the proliferation of tubular and interstitial cells during UUO. CTGF may become a potential therapeutic target against tubulointerstitial fibrosis.     

mTOR通路调控肾间质成纤维细胞活化的机制

目的 探讨mTOR信号通路在肾间质成纤维细胞增生活化过程中的调控作用,并研究其抑制剂在抗肾纤维化治疗中的可行性.方法 用8周龄雌性C57BL/6小鼠构建单侧输尿管结扎(UUO)肾间质纤维化动物模型(n=30),按数字随机法分为雷帕霉素组(n=15)及UUO组(n=15).雷帕霉素组术前1d开始腹腔注射雷帕霉素(2 mg·kg-1·d-1)至实验结束;UUO组注射生理盐水.分别于术后1、3、7、14 d处死小鼠(n=3),留肾组织进行相关检测.同时,体外实验评估雷帕霉素对TGF-β诱导鼠成纤维细胞株(NIH3T3细胞)活化的干预作用.结果 UUO小鼠肾组织中活化的肌成纤维细胞[α肌动蛋白(α-SMA)阳性]高表达mTOR通路下游效应因子pS6K.雷帕霉素显著抑制pS6K表达及肾间质中肌成纤维细胞的活化,改善肾小管间质损伤及纤维化程度.实时荧光定量PCR结果提示雷帕霉素组小鼠肾皮质组织中成纤维细胞特异蛋白1 (FSP1)、转化生长因子β(TGF-β)、结缔组织因子(CTGF)及Ⅳ型胶原蛋白基因α1 (Col 4A1)的mRNA水平显著下降.体外实验结果示TGF-β诱导小鼠成纤维细胞株( NIH3T3)的mTOR通路显著活化,并大量合成α-SMA.雷帕霉素能够明显抑制mTOR通路活性,降低细胞的纤维化活性.结论 肾间质纤维化过程中成纤维细胞内的mTOR信号通路高度活化.抑制mTOR通路能够显著降低成纤维细胞的活性,改善肾间质纤维化程度.     

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.     

Molecular and cellular pathophysiology of obstructive nephropathy

Congenital obstructive nephropathy remains one of the most-important causes of renal insufficiency in children. This review focuses on the unique interactions that result from urinary tract obstruction during the period of renal development in the neonatal rodent. Following unilateral ureteral obstruction (UUO), growth of the obstructed kidney is impaired and compensatory growth by the intact opposite kidney is related directly to the duration of obstruction. Development of the renal vasculature is delayed by UUO, and the activity of the intrarenal renin-angiotensin system is enhanced throughout the period of obstruction. Glomerular maturation is also delayed by UUO, and nephrogenesis is permanently impaired. The effects of UUO on the developing tubule are also profound, with a suppression of proliferation, stimulation of apoptosis, and the maintenance of an immature phenotype by tubular epithelial cells. Expression of tubular epidermal growth factor is suppressed and transforming growth factor-β1 and clusterin are increased. Maturation of interstitial fibroblasts is delayed, with progression of tubular atrophy and interstitial fibrosis resulting in part from continued activation of the renin-angiotensin system and oxygen radicals. Future efforts to prevent the consequences of congenital urinary tract obstruction must account for the dual effects of obstruction: interference with normal renal development and progression of irreversible tubulointerstitial injury. Received: 9 September 1998 / Revised: 9 November 1998 / Accepted: 13 November 1998     

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.     

Hepatocyte growth factor gene therapy retards the progression of chronic obstructive nephropathy

BACKGROUND: Unilateral ureteral obstruction (UUO) is characterized by progressive tubular atrophy and interstitial fibrosis. Rupture of the balance between cell proliferation and apoptosis plays a critical role in renal atrophy. Hepatocyte growth factor (HGF) is a cytokine function on cell survival and tissue regeneration. We studied the effects and possible mechanisms of HGF gene therapy on tubular cell survival and anti-fibrosis in chronic obstructed nephropathy. METHODS: An in vivo transfection procedure of repeatedly transducing skeletal muscles with the HGF gene using liposomes containing the hemagglutinating virus of Japan (HVJ liposome) was tested on UUO rats. Expression of HGF and c-Met were examined by in situ hybridization, ELISA, or immunohistochemical staining. Interstitial fibrosis and macrophage infiltration were evaluated by Masson's Trichrome staining, alpha-smooth muscle actin and ED-1 immunostaining. Cell survival indices including proliferating cell nuclear antigen (PCNA), Bcl-2, Bcl-xL and Bax were measured by immunohistochemistry and Western blots. Apoptosis was determined by the TUNEL method. RESULTS: After HVJ-HGF gene transfer, endogenous HGF and c-Met were up-regulated in UUO kidneys. Renal fibrosis, macrophage infiltration and tubular atrophy were suppressed both at day 14 and 28 after UUO (P < 0.05 or 0.01). Tubular cell proliferation was activated while apoptosis was inhibited, especially at the late stage of UUO. Bcl-2 was enhanced in the HGF-transfected UUO rats, while no changes of Bcl-xL and Bax were found. CONCLUSIONS: In vivo HGF gene transfection retards the progression of chronic obstructed nephropathy and protects tubular cell survival in the long-term UUO model. Bcl-2 rather than Bcl-xL or Bax may contribute to the anti-apoptotic function of HGF.     

怡肾丸对单侧输尿管结扎模型大鼠肾脏TGF-β1及P38MAPK表达的影响

目的:观察不同时相单侧输尿管结扎(UUO)模型大鼠肾脏组织,通过测定肾脏组织TGF-β1及丝裂原活化蛋白激酶p38(P38MAPK)的含量,探讨怡肾丸是否是通过阻断P38MAPK信号传导通路来延缓肾间质纤维化的发展从而达到保护肾脏的目的。方法:采用UUO诱导的肾间质纤维化模型,分别于造模后3、7、14d三个时间点处死该时间点大鼠,并用免疫组化法检测大鼠肾脏TGF-β1及P38MAPK的表达。结果:(1)怡肾丸组对改善大鼠活动等均优于其余各组;(2)通过采用HE及Masson染色观察UUO大鼠肾小管间质组织形态学的改变;(3)免疫组化结果提示怡肾丸组及依那普利组肾小管上皮细胞TGF-β1及P38MAPK的表达低于模型组。结论:(1)P38MAPK的活性在大鼠梗阻性肾病组织中随时间增加明显增高,提示P38MAPK的活化与肾间质纤维化有正相关。(2)怡肾丸可能通过抑制TGF-β1及P38MAPK的表达,减轻炎症反应和纤维化程度,从而达到保护肾脏、延缓肾间质纤维化的作用。     

Macrophage infiltration and renal damage are independent of matrix metalloproteinase 12 in the obstructed kidney

Aim: To determine whether matrix metalloproteinase‐12 (MMP‐12) plays a functional role in renal interstitial macrophage accumulation, interstitial fibrosis or tubular apoptosis in the unilateral ureteric obstruction (UUO) model. Background: MMP‐12 is an enzyme that can cleave a number of extracellular matrix proteins and plays a role in macrophage‐mediated injury in experimental models of emphysema and antibody‐dependent glomerular disease. Macrophages are thought to promote renal fibrosis and tubular damage in the obstructed kidney. Furthermore, upregulation of MMP‐12 expression by infiltrating macrophages in the obstructed kidney has been described, but the potential role of MMP‐12 in renal injury induced by this non‐immune insult is unknown. Methods: Groups of eight MMP‐12 gene deficient (MMP‐12^?/?) and wild type (WT) C57BL/6J mice were killed 3, 7 or 14 days after UUO. Results: Analysis of three different lineage markers found no difference in the degree of interstitial macrophage accumulation between MMP‐12^?/? and WT UUO groups at any time point. Examination of renal fibrosis by total collagen staining, α‐SMA + myofibroblast accumulation, and TGF‐β1, PAI‐1 and collagen IV mRNA levels showed no difference between MMP‐12^?/? and WT UUO groups. Finally, tubular damage (KIM‐1 levels) and tubular apoptosis (cleaved caspase‐3) in the obstructed kidney was not affected by MMP‐12 gene deletion. Conclusion: In contrast to lung injury and antibody‐dependent glomerular injury, MMP‐12 is not required for renal interstitial macrophage accumulation, interstitial fibrosis or tubular damage in the obstructed kidney.     

Effect and mechanism of soluble epoxide hydrolase inhibitor in renal fibrosis mice model

Objective To investigate the effect and mechanism of soluble epoxide hydrolase inhibitor (sEHI) for NF-κB pathway and cell circle arrest of tubular epithelial cell in unilateral ureteral obstruction (UUO) mice model. Methods Thirty-two healthy C57BL/6 male mice performed UUO surgery to induce renal interstitial fibrosis. Animals were randomly divided into 4 groups: sham group (n=8), sEHI (1 mg?kg-1?d-1) group (n=8), UUO group (n=8) and UUO+sEHI (1 mg?kg-1?d-1) group (n=8). Daily sEHI [1-(1-methylsulfonyl-piperidin-4-yl)-3-(4-trifluoromethoxy-phenyl)-urea, TUPS] or 2% DMSO was applied to mice by oral gavage from day 1 to day 14 after surgery. All mice were sacrificed at day 14 and kidneys were harvested for further analysis. The changes of renal tissue morphology and pathology were observed by Hematoxylin and eosin (HE) and sirius red staining. The expressions of sEH, nuclear factor κB p65 (NF-κB p65) and IκB were measured by Western blotting. The expressions of TNF-α, IL-1β, MCP-1, IL-6, TGF-β, CTGF, collagen-IV and α-SMA were analyzed by real-time PCR. Immunofluorescence staining of phospho-histone H3 (p-HH3) and Ki67 was performed to determine the stage of cell cycle G2/M arrest. Results The expression and activity of sEH increased in UUO group (P﹤0.05). Administration of sEHI inhibited activity of sEH and infiltration of inflammatory cell in tubular interstitial, as well as attenuated tubular damage and tubular interstitial fibrosis. Western blotting analysis revealed administration of sEHI inhibited up-regulated NF-κB p65 and down-regulated IκB in UUO group (P﹤0.05). Real-time PCR demonstrated that administration of sEHI obviously decreased the mRNA expression of cytokines and fibrosis markers, including of TNF-α, IL-1β, MCP-1, IL-6, TGF-β, CTGF, Collagen-IV, α-SMA (P﹤0.05). Immunofluorescence staining showed that there were much more p-HH3 and Ki67 double positive nuclear tubular epithelial cells and interstitial cells in UUO group, compared with Sham group (P﹤0.05). Administration of sEHI reduced the number of double positive nuclear cell only in tubular epithelial cells (P﹤0.05), but not in interstitial cells. Conclusions In UUO tubular interstitial fibrosis model, sEHI inhibits the activation of NF-κB pathway by down-regulating p65 and up-regulating IκB and ameliorates the infiltration of inflammatory cells. In addition, sEHI plays anti-fibrosis effect by moderating cell cycle G2/M arrest and reducing the excrete of pro-fibrosis factors of tubular epithelial cells.     

Involvement of renal progenitor tubular cells in epithelial-to-mesenchymal transition in fibrotic rat kidneys

Renal progenitor tubular cells (label-retaining cells [LRC]) were recently identified in normal kidneys by in vivo bromodeoxyuridine (BrdU) labeling. This study was conducted to examine the behavior of LRC in renal fibrosis. BrdU was injected intraperitoneally into normal rats daily for 7 d. After a 2-wk chase period, unilateral ureteral obstruction (UUO) was induced in these rats. In normal and contralateral kidneys, LRC were observed scattering among tubular epithelial cells. After UUO, the number of the LRC significantly increased, and most of them were positive for proliferating cell nuclear antigen (PCNA). In contrast, PCNA+ cells lacking BrdU label were rarely observed. It is interesting that LRC were detected not only in tubules but also in the interstitium after UUO. Laminin staining showed that a number of the LRC were adjacent to the destroyed tubular basement membrane. Some tubules, including LRC, lost the expression of E-cadherin after UUO. A large number of cell populations expressed vimentin, heat shock protein 47, or alpha-smooth muscle actin in the UUO kidneys, and each population contained LRC. None of the LRC was positive for these fibroblastic markers in contralateral kidneys. When renal tubules from BrdU-treated rats were cultured in the gel, some cells protruded from the periphery of the tubules and migrated into the gel. Most of these cells were BrdU+. Neither the total content of BrdU in the kidneys nor the number of LRC in bone marrow significantly changed after UUO. Collectively, these results suggest that LRC is a cell population that proliferates, migrates, and transdifferentiates into fibroblast-like cells during renal fibrosis.     

补体C5α受体和转化生长因子-β1在大鼠肾间质纤维化不同阶段肾组织的表达

目的：动态观测补体C5α受体（C5αR）和转化生长因子β1（TGF-β1）在单侧输尿管梗阻（UUO）大鼠肾组织的表达变化,从而探讨C5αR在。肾小管间质纤维化发生中的作用机制。方法：将36只雄性SPF级SD大鼠随机分为模型组及假手术组。模型组行UUO术,假手术组仅游离输尿管,不结扎。术后第5、10、15天分别处死每组中的6只大鼠,取梗阻侧肾行苏木精-伊红（H—E）和Masson染色,并用免疫组织化学ELiVision^TMplus法检测肾小管间质中C5αR和TGF-β1的表达。结果：模型组第5天肾小管扩张,小管间质细胞部分变性,第10天小管间质细胞可见坏死,间质纤维增多,第15天可见弥漫的肾小管基底膜增厚皱缩,纤维化明显（P〈0．05）。免疫组织化学结果显示：假手术组大鼠肾小管间质中仅有少量TGF-β1和C5αR表达,随时间延长未见明显变化;模型组大鼠梗阻侧肾组织中C5αR和TGF-β1的表达随时间进展而明显增加（P〈0．05）,其中C5αR在梗阻早期（第5～10天）表达明显增多,而晚期（第11～15天）仅轻微增多。结论：模型组实验大鼠梗阻侧。肾组织中C5αR和TGF-β1表达随着梗阻时间延长而上调,提示C5αR可能在。肾间质纤维化早期通过介导TGF-β1的上调发挥作用。     

姜黄素对单侧输尿管梗阻大鼠肾间质纤维化的影响

目的 探讨姜黄素对单侧输尿管梗阻(UUO)大鼠模型的影响及其可能机制.方法 将30只大鼠随机分为3组,每组10只:假手术组、模型组、姜黄素组.模型组和姜黄素组行右侧输尿管接扎术,假手术组只游离不接扎.术后第14天处死各组中的大鼠,股动脉取血,检测血清肌酐、尿素氮;留取梗阻侧肾脏,Maason染色观察肾间质纤维化程度,免疫组织化学方法测定TGF-β1、CTGF的表达情况,RT-PCR技术榆测肾组织TGF-β1 mRNA、CTGF mRNA表达.结果 姜黄素降低了BUN、Scr的含量,同时姜黄素显著减少了大鼠肾间质TGF-β1、CTGF的表达,并有效改善了肾脏的病理学损伤.结论 姜黄素对单侧输尿管梗阻大鼠有较明显的保护作用,这可能与其能减少大鼠肾间质TGF-β1、CTGF的表达有关.     

Blockage of tubular epithelial to myofibroblast transition by hepatocyte growth factor prevents renal interstitial fibrosis.

Activation of alpha-smooth muscle actin-positive myofibroblast cells is a key event in the progression of chronic renal diseases that leads to end-stage renal failure. Although the origin of these myofibroblasts in the kidney remains uncertain, emerging evidence suggests that renal myofibroblasts may derive from tubular epithelial cells by a process of epithelial to mesenchymal transition. It was demonstrated that hepatocyte growth factor (HGF) exhibited a remarkable ability to block this phenotypic transition both in vitro and in vivo. HGF abrogated the alpha-smooth muscle actin expression and E-cadherin depression triggered by transforming growth factor-beta1 in tubular epithelial cells in a dose-dependent manner. HGF also blocked morphologic transformation of tubular epithelial cells and inhibited the expression and extracellular deposition of fibronectin. In a mouse model of renal fibrosis disease induced by unilateral ureteral obstruction, transforming growth factor-beta type I receptor expression was specifically increased in renal tubules, and myofibroblastically phenotypic transition of the tubules was evident in vivo. Remarkably, injections of exogenous HGF blocked myofibroblast activation and drastically prevented renal interstitial fibrosis in the obstructed kidneys. These results suggest that tubular epithelial to myofibroblast conversion may play an important role in the pathogenesis of renal fibrosis and that blocking this phenotypic transition could provide a novel therapeutic strategy for the treatment of fibrotic diseases.     

Chronic ureteral obstruction in the rat suppresses renal tubular Bcl-2 and stimulates apoptosis

Unilateral ureteral obstruction (UUO) results in widespread tubular apoptosis in obstructed kidneys of both adults and neonates. The oncoprotein bcl-2 inhibits many forms of apoptosis, whereas the related protein bax promotes apoptosis. To evaluate the interaction of bcl-2, bax, and apoptosis in the renal response to UUO, adult and neonatal rats were subjected to UUO or sham operation, and kidneys were harvested 14 days later. Apoptotic cells were identified by the Tunel technique, and the distribution of bcl-2 and bax was determined by immunochemistry. In both adults and neonates, tubular and interstitial apoptosis was present in the obstructed kidney, but not in intact kidneys. In both adults and neonates, there was diffuse tubular bcl-2 and bax staining of sham-operated and intact kidneys. While bcl-2 was increased in scattered nonapoptotic tubules of the obstructed kidney, there was minimal staining of dilated apoptotic tubules. These results are consistent with the premise that bcl-2 normally suppresses renal tubular apoptosis. The distribution of bax staining in tubules of the obstructed kidney overlapped that of bcl-2. We conclude that chronic UUO inhibits bcl-2 expression in selected tubules of the obstructed kidney which contributes to activation of apoptosis and progressive renal damage in either neonatal or adult kidneys. Dysregulation of apoptosis may be a response to renal injury similar to that underlying the development of cystic kidney disease or renal dysplasia.