Inter-individual differences in anti-proteinuric response to ACEi in established adriamycin nephrotic rats are predicted by pretreatment renal damage

ACE inhibition (ACEi) reduces proteinuria and provides reno-protection, but not all subjects benefit from ACEi. Individual differences in the reduction in proteinuria at the onset of treatment and in residual proteinuria during therapy predict differences in renal outcome. The present study investigated whether individual differences in the anti-proteinuric efficacy of ACEi are explained by differences in the severity of pretreatment renal structural damage and whether differences in the level of residual proteinuria during therapy are explained by the severity of renal structural damage at that time, in adriamycin nephrosis in the rat. Pretreatment renal structural damage was assessed in biopsies 6 weeks after exposure to adriamycin (2 mg/kg iv). Then ACEi (75 mg/l lisinopril, n = 23) or vehicle (n = 10) was administered; renal biopsies were repeated after stabilization of the anti-proteinuric response (week 8). Early renal damage (interstitial alpha-smooth muscle actin expression and macrophage accumulation) and established lesions [focal glomerulosclerosis (FGS) and interstitial fibrosis] were scored. During ACEi, proteinuria fell from 834 (487-851) mg/24 h pretreatment to 153 (66-265) mg/24 h at week 8 (p < 0.05); FGS stabilized from 27 (4-70) arbitrar units (AU) pretreatment to 26 (4-84) at week 12, whereas the vehicle did not affect proteinuria, resulting in progressive FGS: 18 (10-26) AU pretreatment versus 88 (46-130) at week 12 (p < 0.05). All parameters of pretreatment damage significantly predicted the anti-proteinuric response. Residual proteinuria during ACEi correlated significantly with renal structural damage parameters at that time. Pretreatment renal damage also predicted renal outcome during extended treatment. Thus, in this experimental setting, in rats with the same renal disorder and the same duration of disease, individual differences in pretreatment renal damage, albeit relatively modest, explain individual differences in renal responsiveness to ACEi. This implies that the limits of the efficacy of ACEi are set by prevalent renal damage. Further studies into the mechanisms of individual resistance to the anti-proteinuric action of ACEi are needed to develop additive intervention strategies.     

ACE inhibition has adverse renal effects during dietary sodium restriction in proteinuric and healthy rats

Angiotensin-converting enzyme inhibitors (ACEi) provide renoprotection. A low sodium diet enhances their efficacy. However, the added effect of sodium restriction on proteinuria and blood pressure is not invariably associated with better preservation of renal morphology, suggesting that the combination of ACEi with a low sodium diet can elicit renal structural abnormalities. To test this hypothesis, the effects of ACEi in combination with a control (CS) or a low sodium (LS) diet were investigated in healthy rats and in adriamycin nephrotic rats. After 3 weeks of treatment, rats were sacrificed and kidneys examined for renal structural abnormalities. In healthy rats, ACEi reduced blood pressure: the fall in blood pressure was significantly greater in the ACEi/LS group. Renal morphology was normal in the ACEi/CS group but severe interstitial damage was found in the ACEi/LS group. This was associated with increased interstitial macrophage influx and up-regulation of osteopontin, alpha-smooth muscle actin, and collagen III expression. In addition, ACEi/LS induced an increase in the total medial area of afferent arterioles. In nephrotic rats, ACEi/LS reduced both blood pressure and proteinuria, whereas only blood pressure was reduced in the ACEi/CS group. Mild interstitial damage was present in the ACEi/CS group but, strikingly, pronounced tubulo-interstitial abnormalities occurred in the ACEi/LS group, similar to those seen in ACEi/LS healthy rats, with similar changes in afferent arteriolar walls. In conclusion, the combination of ACEi/LS elicits pronounced renal interstitial abnormalities in healthy and nephrotic rats, despite a significant reduction of proteinuria in the latter. Considering their occurrence in healthy rats, these renal adverse effects cannot be due to specific characteristics of adriamycin nephrosis. Further studies should elucidate the mechanisms underlying these observations and their impact on long-term renoprotection.     

IL-1 up-regulates osteopontin expression in experimental crescentic glomerulonephritis in the rat

Osteopontin (OPN) is a macrophage chemotactic and adhesion molecule that acts to promote macrophage infiltration in rat anti-glomerular basement membrane (GBM) glomerulonephritis. The present study investigated the role of interleukin-1 (IL-1) in the up-regulation of renal OPN expression in this disease model. Accelerated anti-GBM glomerulonephritis was induced in groups of six rats. Animals were treated by a constant infusion of the IL-1 receptor antagonist or saline (control) over days -1 to 14 (induction phase) or days 7 to 21 (established disease). In normal rat kidney, OPN was expressed in a few tubules (<5%) and absent from glomeruli. During the development of rat anti-GBM disease (days 7 to 21), there was substantial up-regulation of OPN mRNA and protein expression in glomeruli (>5 cells per glomerular cross-section) and tubular epithelial cells (50-75% OPN-positive). Up-regulation of OPN expression was associated with macrophage accumulation within the kidney, severe proteinuria, loss of renal function, and severe histological damage including glomerular crescentic formation and tubulointerstitial fibrosis. In contrast, IL-1 receptor antagonist treatment of either the induction phase of disease or established disease significantly reduced OPN mRNA and protein expression in glomeruli (/75-85%, P < 0.001) and tubules (/45-60%, P < 0.001). The reduction in OPN expression was associated with significant inhibition of macrophage accumulation and progressive renal injury. In vitro, the addition of IL-1 to the normal rat tubular epithelial cell line NRK52E up-regulated OPN mRNA and protein levels, an effect that was dose-dependent and inhibited by the addition of IL-1 receptor antagonist, thus demonstrating that IL-1 can act directly to up-regulate renal OPN expression. In conclusion, this study provides in vivo and in vitro evidence that IL-1 up-regulates OPN expression in experimental kidney disease and support for the argument that inhibition of OPN expression is one mechanism by which IL-1 receptor antagonist treatment suppresses macrophage-mediated renal injury.     

骨调素和巨噬细胞集落刺激因子在糖尿病大鼠肾组织中的表达及霉酚酸酯的干预作用

目的： 研究骨调素(OPN)和巨噬细胞集落刺激因子（M-CSF)在糖尿病大鼠肾组织中的表达及免疫抑制剂霉酚酸酯（MMF）的干预作用，旨在探讨MMF对糖尿病肾病(DN)的保护作用及机制。方法: Wistar大鼠行右肾切除术2周后,随机分为右肾切除对照组(NC)、糖尿病组(DM)、霉酚酸酯治疗组(DM+MMF)。腹腔注射链脲佐菌素(STZ,65 mg/kg ) 诱发糖尿病模型,MMF15 mg·kg^-1·d^-1灌胃。检测各组8周末的左肾重/体重比值、24 h尿蛋白（Upro）、血糖(BG) 、血肌酐( Scr)，观察肾脏形态学变化，免疫组化检测肾组织中OPN、M-CSF及CD68表达，荧光实时定量PCR测定肾组织中OPN mRNA表达。结果: 与对照组相比，DM组大鼠血糖、Upro、肾重/体重比值均显著上升(P<0.01);肾间质纤维化面积扩大(P<0.01);肾组织内OPN、M-CSF、CD68表达及OPN mRNA的表达均显著上调(P<0.01)。MMF干预后，上述指标除血糖外均被明显抑制(P<0.05或P<0.01)。结论: MMF减少糖尿病大鼠肾组织中OPN、M-CSF、CD68及OPN mRNA的表达，降低蛋白尿，预防肾损伤。MMF明显抑制DN肾小管－间质损害，可能与其抑制巨噬细胞的趋化与增殖有关。     

Focal glomerulosclerosis in proviral and c-fms transgenic mice links Vpr expression to HIV-associated nephropathy

Clinical and morphologic features of human immunodeficiency virus (HIV)-associated nephropathy (HIVAN), such as proteinuria, sclerosing glomerulopathy, tubular degeneration, and interstitial disease, have been modeled in mice bearing an HIV proviral transgene rendered noninfectious through a deletion in gag/pol. Exploring the genetic basis of HIVAN, HIV transgenic mice bearing mutations in either or both of the accessory genes nef and vpr were created. Proteinuria and focal glomerulosclerosis (FGS) only developed in mice with an intact vpr gene. Transgenic mice bearing a simplified proviral DNA (encoding only Tat and Vpr) developed renal disease characterized by FGS in which Vpr protein was localized to glomerular and tubular epithelia by immunohistochemistry. The dual transgenic progeny of HIV[Tat/Vpr] mice bred to HIV[DeltaVpr] proviral transgenic mice displayed a more severe nephropathy with no apparent increase in Vpr expression, implying that multiple viral genes contribute to HIVAN. However, the unique contribution of macrophage-specific Vpr expression in the development of glomerular disease was underscored by the induction of FGS in multiple murine lines bearing a c-fms/vpr transgene.     

Involvement of neutrophil gelatinase-associated lipocalin and osteopontin in renal tubular regeneration and interstitial fibrosis after cisplatin-induced renal failure

The kidney has a capacity to recover from ischemic or toxic insults that result in cell death, and timely tissue repair of affected renal tubules may arrest progression of injury, leading to regression of injury and paving the way for recovery. To investigate the roles of neutrophil gelatinase-associated lipocalin (NGAL/lcn2) and osteopontin (OPN/spp1) during renal regeneration, the expression patterns of NGAL and OPN in the cisplatin-induced rat renal failure model were examined. NGAL expression was increased from day 1 after injection; it was seen mainly in the completely regenerating proximal tubules of the cortico-medullary junction on days 3–35; however, the expression was not seen in abnormally dilated or atrophied renal tubules surrounded by fibrotic lesions. On the other hand, OPN expression was increased from day 5 and the increased expression developed exclusively in the abnormal renal tubules. NGAL expression level well correlated with the proliferating activity in the regenerating renal epithelial cells, whereas OPN significantly correlated with the α-smooth muscle actin-positive myofibroblast appearance, expression of transforming growth factor (TGF)-β1, and the number of CD68-positive macrophages. Interestingly, rat renal epithelial cell line (NRK-52E) treated with TGF-β1 decreased NGAL expression, but increased OPN expression in a dose-dependent manner. Because increases of TGF-β1, myofibroblasts and macrophages contribute to progressive interstitial renal fibrosis, OPN may be involved in the pathogenesis of fibrosis; on the contrary, NGAL may play a role in tubular regeneration after injury. Expression analysis of NGAL and OPN would be useful to investigate the tubule damage in renal-toxicity.     

Morphometric analysis of the glomerular capillary area--a comparison of minimal change nephrotic syndrome, focal glomerular sclerosis, and pre-eclampsia.

A morphometric analysis was performed to compare the capillary area in non-sclerotic glomeruli in focal glomerular sclerosis (FGS), pre-eclampsia with focal sclerotic change of the glomeruli, and minimal change nephrotic syndrome (MCNS). The mean and standard deviation of the capillary area was greater in FGS than in pre-eclampsia and MCNS. Tubulo-interstitial lesions, such as tubular atrophy, interstitial fibrosis, and lymphocytic infiltration, were more severe in FGS than in pre-eclampsia. The presence of tubulo-interstitial changes including tubular atrophy and interstitial fibrosis with lymphocytic infiltration is thought to be an important prognostic factor in pre-eclampsia as well as in FGS. Unequal dilatation of the glomerular capillaries in non-sclerotic glomeruli may be harmful to the glomeruli and may lead to the development of glomerular sclerosis.     

The membrane attack complex, C5b-9, up regulates collagen gene expression in renal tubular epithelial cells

Evidence suggesting a direct role for proteinuria in the pathogenesis of renal tubulointerstitial fibrosis is accumulating. However the mechanism by which proteinuria leads to injury is unknown. In proteinuric states complement proteins are filtered through the glomerulus and could contribute to the tubular damage. The aim of this study was to investigate the role of complement activation in the progression of interstitial fibrosis. To determine whether complement activation may be responsible for the pro-fibrotic response that occurs in the tubulointerstitial compartment we stimulated primary cultures of proximal tubular epithelial cells with membrane attack complex, C5b-9. This led to increased mRNA concentrations of both collagen type IV and its intracellular chaperone, Heat Shock Protein 47 (HSP47). To determine whether this occurred in vivo Adriamycin was used to induce proteinuria in female Balb/c mice. The expression of collagen type IV and HSP47 was increased in proteinuric mice compared to control mice. In proteinuric mouse kidney, C3 was deposited at sites of tubulointerstitial injury and there was a relationship between C3 deposition and immunochemical staining for collagen type IV and HSP47. In situ hybridization suggested that the renal tubular epithelium was actively expressing HSP47 mRNA and, by implication, excess collagen. These observations support the hypothesis that complement activation on tubular epithelial cells can directly increase the pro-fibrotic process associated with tubulointerstitial damage.     

Elevated macrophage migration inhibitory factor (MIF) levels in the urine of patients with focal glomerular sclerosis

The pathogenesis of focal glomerular sclerosis (FGS) is poorly understood. Macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine released from T cells and macrophages, and is a key molecule in inflammation. To examine further the possible role of MIF in FGS, we measured MIF levels in the urine. The purpose of the present study was to evaluate the involvement of MIF in FGS. Urine samples were obtained from 20 FGS patients. The disease controls included 40 patients with minimal-change nephrotic syndrome (MCNS) and membranous nephropathy (MN). A group of healthy subjects also served as controls. Biopsies were performed in all patients prior to entry to the study. The samples were assayed for MIF protein by a sandwich enzyme-linked immunosorbent assay (ELISA). The levels of MIF in the urine of FGS patients were significantly higher than those of the normal controls and patients with MCNS and MN. In contrast, the levels of urinary MIF (uMIF) in patients with MCNS and MN did not differ significantly from normal values. In the present study, attention also focused on the relationship between uMIF levels and pathological features. Among the patients with FGS, uMIF levels were significantly correlated with the grade of mesangial matrix increase and that of interstitial fibrosis. There was also a significant correlation between uMIF levels and the number of both intraglomerular and interstitial macrophages. Although the underlying mechanisms remain to be determined, our study presents evidence that urinary excretion of MIF is increased in FGS patients with active renal lesions.     

Correlations between relative interstitial volume of the renal cortex and serum creatinine concentration in minimal changes with nephrotic syndrome and in focal sclerosing glomerulonephritis

Summary Morphometric investigations were performed in 33 biopsies with minimal proliferative intercapillary glomerulonephritis with nephrotic syndrome (MPI with NS, minimal changes with nephrotic syndrome) and in 65 biopsies with focal sclerosing glomerulonephritis (FGS). Both diseases are, in our opinion, variants of a single entity. Positive significant correlations (corresponding to linear and parabolic functions) between the relative interstitial volume of the renal cortex and serum creatinine concentration at the time of biopsy could be found. No correlations were observed between percentage of glomeruli affected by segmental and focal sclerosis in FGS and relative interstitial volume, or the percentage of involved glomeruli and serum creatinine concentration. The enlargement of the cortical interstitium by fibrosis may lead to a narrowing of the postglomerular vessels, to an elevation of the postglomerular flow resistance and to a slowing of the glomerular blood flow. In this way the filtrate of the glomerulus could be reduced and lead to a elevation of the serum creatinine concentration. Alternatively the observed tubular atrophy in fibrotic areas — caused by malnutrition or inactivity — could impair the tubular capacity of resorption. This may lead to a reduction of the glomerular filtrate by the so called Thurau mechanism in the case of interstitial fibrosis.Supported by the Deutsche Forschungsgemeinschaft     

促红细胞生成素对大鼠肾间质纤维化发动蛋白-1表达影响

目的探讨促红细胞生成素（EPO）对大鼠肾间质纤维化发动蛋白．1（Drp-1）表达的影响。方法81只sD大鼠,分为假手术组、对照组和EPO组,每组各27只。EPO组、对照组采用单侧输尿管结扎并剪断建立肾间质纤维化模型,假手术组仅游离输尿管而不结扎和剪断;EPO组予EPO皮下注射;假手术组和对照组给予等量生理盐水皮下注射。各组于术后7、14和21d取动脉血分离血清检测血肌酐和尿素氮水平。取梗阻侧肾组织行苏木精．伊红和Masson染色,观察肾脏病理学变化。用免疫组化方法检测肾组织Drp一1的表达。结果@EPO组各时点血清肌酐和尿素氮水平显著低于对照组（P〈0．01）,但高于假手术组（P〈0．05）。②EPO组各时点肾组织病理改变较对照组明显减轻,肾小管间质损伤评分和肾间质纤维化相对面积均低于对照组（P均〈0．05）,但高于假手术组（P〈0．05）。③EPO组肾组织的Drp．1表达显著低于对照组（P〈0．05）,但高于假手术组（P〈0．05）。结论Drp-1在大鼠肾间质纤维化肾组织中表达增加,参与。肾脏纤维化过程;EPO可以通过抑制Drp一1表达,从而延缓肾间质纤维化的进展。     

The Nephrotic Syndrome is an immunoinflammatory disorder

The Nephrotic Syndrome is still a therapeutic and physiopathological challenge. The clinical response to systemic immunosuppression shows that an immunoinflammatory disorder supports the nephrotic syndrome. Experimental (in vitro and in vivo) studies show that proteinuria may induce kidney secretion of proinflammatory and profibrotic cytokines and subsequent renal inflammation mediated by leukocyte recruitment. In turn,the infiltrating leukocytes contribute to renal damage by releasing proinflammatory and profibrotic cytokines (kidney acute remodelling). Chronic proteinuria maintains continuous local cytokine secretion and leukocyte influx into the glomerulus or the interstitial space (kidney chronic remodelling). In glomerular injury (podocyte injury), proteinuria itself, as well as glomerular secreted cyotokines, stimulates downstream tubular epithelial cells to secrete cytokines,as well. The mutual stimulation between proteinuria-cytokines-podocyte dysfunction-infiltrating leukocytes supports progressive tubular damage, renal fibrosis and glomerulosclerosis. Interfering with the cytokine network by inhibition/blockade of the cytokine receptor and its synthesis (via NFkB and the JAK/STAT intracellular signalling pathway) may represent a promising therapeutic option for systemic immunosuppression. Renal cytokine escape into systemic circulation may provide to hypercytokinemia stress syndrome,which could help to explain the increase in efferent renal sympathetic nerve activity (physiopathological sympathetic overactivity) observed during experimental nephrotic edema.     

Experimental interstitial renal fibrosis in rats: nephritis induced by N-(3,5-dichlorophenyl)succinimide

The nephrotoxic properties of the chemical N-(3,5-dichlorophenyl)-succinimide were investigated in rats with a view to establishing the usefulness of this chemically-induced nephritis as a model of chronic interstitial renal fibrosis. The compound was synthesized and given daily by gastric intubation as a suspension in arachis oil B.P. to male WAG-strain rats, for periods of up to 108 days. Polydipsia and polyuria resulted rapidly in all treated animals and persisted for the duration of the experiment. There was a progressive increase in the extent of proteinuria in all treated animals and, by the end of the experiment, there was an increase in the plasma levels of urea and creatinine. Short term treatment (up to 3 days) resulted in focal areas of necrosis of some proximal convoluted tubules. Treatment for 28 days resulted in patchy but severe tubular interstitial nephritis with which was associated a moderate interstitial fibrosis. By 108 days, the nephritis was more widespread and the interstitial fibrosis was severe. The activity of proline hydroxylase, a part of the intracellular sequence of collagen synthesis, showed progressive increase in the renal cortex throughout the experiment and there was an associated increase in the cortical hydroxyproline content, a measure of the amount of collagen present. Associated with this biochemical evidence of an active, chronic fibrosis, was an increased water content of the cortical tissue. The results indicate that this chemically-induced, tubular interstitial nephritis is indeed a good and reliable model of interstitial renal fibrosis.     

Interstitial myofibroblasts: predictors of progression in membranous nephropathy.

AIMS: To determine the role of interstitial myofibroblasts in the progression of membranous nephropathy; and to assess the predictive value of quantifying myofibroblasts in determining long term renal outcome. METHODS: All cases of membranous nephropathy, diagnosed by renal biopsy at University Hospital of South Manchester between 1984 and 1987, were studied retrospectively. The biopsy specimens (n = 26) were reviewed and analysed morphometrically to measure interstitial volume as a proportion of the total volume of renal cortex, and numbers of interstitial myofibroblasts (cells positive for alpha-smooth muscle actin within the interstitium). Clinical data, with a follow up of seven to eight years, was available for 24 patients, and renal outcome was correlated with pathological changes in the initial diagnostic biopsy specimen. RESULTS: The number of myofibroblasts and interstitial volume were inversely correlated with creatinine clearance at the initial biopsy, and at the end of follow up. Percentage sclerosed glomeruli or stage of glomerular disease, assessed by electron microscopy, did not correlate with renal function at initial biopsy or during follow up. The number of myofibroblasts, but not interstitial volume, correlated with severity of proteinuria at initial biopsy. Of 15 biopsy specimens showing no or mild interstitial fibrosis, four showed a notable increase in the number of interstitial myofibroblasts. All of these patients developed chronic renal failure, compared with three of 11 patients whose specimens showed no or a mild increase in myofibroblast numbers. CONCLUSIONS: Interstitial myofibroblasts play a role in the development of interstitial fibrosis and progressive renal failure in membranous nephropathy. Increased numbers of myofibroblasts in biopsy specimens showing only mild fibrosis may predict subsequent chronic renal failure.     

Mesangial lesions and focal glomerular sclerosis in the aging rat.

The pathogenesis of focal glomerular sclerosis (FGS) and its relation to proteinuria and idiopathic nephrotic syndrome are unknown. Urine protein excretion in Sprague-Dawley rats increased with age. Fifty per cent of 12-month and 90 per cent of 24-month-old animals were proteinuric (greater than 20 mg. per day). Heavily proteinuric old rats manifested biochemical changes characteristic of nephrotic syndrome without significant loss of renal function. Three-month, 6-month, and nonproteinuric 12-month-old animals had mesangial deposits of IgM in occasional lobules of some glomeruli and slight mesangial hyperplasia. Four proteinuric 12-month-old rats had diffuse 4+ deposits of IgM in the mesangium of most glomeruli, basement membrane thickening and epithelial cell foot process fusion without FGS. The mesangial IgM deposits eluted in acid buffer and did not fix complement. Six proteinuric 12-month-old rats had focal and segmental areas of glomerular sclerosis with adhesions to Bowman's capsule, foamy cells, intraluminal eosinophilic deposits and capillary wall wrinkling and collapse. These lesions were more advanced in 24-month-old animals. Nonproteinuric 24-month-old rats did not have detectable FGS. Mesangial uptake of colloidal carbon was normal in proteinuric and nonproteinuric animals without FGS. Mesangial uptake of colloidal carbon was normal in proteinuric and nonproteinuric animals without FGS and reduced in proteinuric animals with FGS. In the aging rat the development of proteinuria and mesangial IgM deposition apparently precede development of a focal sclerotic glomerular lesion with histologic and ultrastructural features similar to FGS in man. The generalized impairment of mesangial phagocytic function in proteinuric rats with FGS suggests that this lesion may result from mesangial overload and dysfunction consequent to the persistent increase in glomerular permeability and proteinuria.     

Experimental interstitial renal fibrosis in rats: nephritis induced by N-(3,5-dichlorophenyl)succinimide.

The nephrotoxic properties of the chemical N-(3,5-dichlorophenyl)-succinimide were investigated in rats with a view to establishing the usefulness of this chemically-induced nephritis as a model of chronic interstitial renal fibrosis. The compound was synthesized and given daily by gastric intubation as a suspension in arachis oil B.P. to male WAG-strain rats, for periods of up to 108 days. Polydipsia and polyuria resulted rapidly in all treated animals and persisted for the duration of the experiment. There was a progressive increase in the extent of proteinuria in all treated animals and, by the end of the experiment, there was an increase in the plasma levels of urea and creatinine. Short term treatment (up to 3 days) resulted in focal areas of necrosis of some proximal convoluted tubules. Treatment for 28 days resulted in patchy but severe tubular interstitial nephritis with which was associated a moderate interstitial fibrosis. By 108 days, the nephritis was more widespread and the interstitial fibrosis was severe. The activity of proline hydroxylase, a part of the intracellular sequence of collagen synthesis, showed progressive increase in the renal cortex throughout the experiment and there was an associated increase in the cortical hydroxyproline content, a measure of the amount of collagen present. Associated with this biochemical evidence of an active, chronic fibrosis, was an increased water content of the cortical tissue. The results indicate that this chemically-induced, tubular interstitial nephritis is indeed a good and reliable model of interstitial renal fibrosis.