Cellular proliferation and macrophage influx precede interstitial fibrosis in cyclosporine nephrotoxicity

A comparison of pathomolecular markers of fibrosis and morphology in kidney from autopsies of African Americans and whites

African Americans have an increased incidence of chronic kidney disease (CKD) due to hypertension and arteriosclerosis and increased death due to coronary artery disease, compared with whites. The pathogenesis of CKD involves the increased presence and activation of myofibroblasts and macrophages, promotion of tubulointerstitial fibrosis, and effects of tubulointerstitial cell mitosis and apoptosis. We hypothesized that increased risk of hypertensive vascular disease may be identified by renal pathomolecular markers that are associated with progressive CKD. Renal sections were available from 50 autopsies of 33 African Americans (55% males) and 17 whites (76% males) undergoing forensic autopsy for unexpected death. Sclerotic glomeruli, severity of cortical fibrosis, and renal arteriolosclerosis, total glomerular number (N (glom)), average glomerular volume (V (glom)), birth weights, and blood pressure were known. Presence and locality of markers for myofibroblasts (alpha-SMA), macrophages (CD68), collagen, pro-fibrotic transforming growth factor-beta1 were scored in renal autopsies, and tubulointerstitial apoptosis was recorded. The results demonstrated a strong positive correlation between age, cortical fibrosis and alpha-SMA (p<0.05), and between CD68 and hypertension and coronary artery disease (p<0.05). The findings confirm the role of myofibroblasts and macrophages in pathogenesis of human CKD. However, the markers showed no significant relationships to V (glom), N (glom), birth weight, or race.

FTY720 in combination with cyclosporine--an analysis of skin allograft survival and renal function

Acute and chronic nephrotoxicity caused by CsA continuous administration impair kidney allograft survival. Several clinical and experimental protocols have shown benefits to the kidney after decreasing CsA dose, withdrawing the drug or delaying its introduction after transplantation. FTY720 is a new compound that has immunosuppressive characteristics and increase allograft survival in animal models without causing the side effects of calcineurin inhibitors (CNIs). FTY720 described mechanism of action that consists to alter the lymphocyte migration pattern without impairment of the immune system response against pathogens. In our mice model, FTY720 administered alone or in combination with CsA during 21 days increased skin allograft survival in a fully mismatched strain combination and did not cause significant changes in renal function. Moreover, renal structure was normal in all groups suggesting that at low doses (10 mg/kg/day) CsA can be associated during short-term period to other immunosuppressive drugs, i.e. FTY720 without affecting the kidney. Combination of immunosuppressive compounds with FTY720 and/or delayed introduction of low cyclosporine dose could prevent graft rejection and avoid nephrotoxicity.

Effect of cyclosporine a on glucose interstitial concentration in renal cortex and medulla from rats

AIM

To standardize microdialysis in rat kidneys and address cyclosporine A (CsA) effects on renal cortex and medulla interstitial glucose.

METHODS

Munich-Wistar rats were treated with vehicle or CsA (15 mg/kg/day) for 3 weeks. Glucose was assessed by spectrophotometry in dialysate samples from cortex, medulla and arterial plasma. Plasma insulin was measured by radioimmunoassay. Renal blood flow (RBF) was measured by Doppler ultrasound. Creatinine and urea were measured by spectrophotometry.

RESULTS

CsA significantly increased the plasma levels of urea and creatinine (1.5 +/- 0.20 vs. 0.73 +/- 0.03 mg/dl in controls, p < 0.05). Medullary glucose in control was 44% lower than arterial glucose (56 +/- 6 vs. 101 +/- 8 mg/dl, p < 0.05). At the same time, CsA increased arterial (163 +/- 35 vs. 101 +/- 8 mg/dl in controls, p < 0.05) and medullary interstitial glucose (100 +/- 18 vs. 56 +/- 6 mg/dl in controls, p < 0.05), but did not affect cortical glucose (114 +/- 21 vs. 90 +/- 11 mg/dl in controls). These changes occurred in the presence of a decreased plasma insulin level (2.7 +/- 0.2 vs. 9.3 +/- 0.4 microU/ml in controls, p < 0.05). The increment in medullary glucose in CsA group occurred despite a reduction in RBF (4.6 +/- 0.8 vs. 6.5 +/- 1.0 ml/min/kidney in controls, p < 0.05).

CONCLUSIONS

Microdialysis was an adequate tool to investigate in vivo regulation of renal glucose metabolism. Renal glucose uptake was dependent on medullary cells and CsA treatment induced diabetogenic effects on renal medulla in situ.

Lipoic acid supplementation prevents cyclosporine-induced hypertension and nephrotoxicity in spontaneously hypertensive rats

BACKGROUND

Cyclosporine (CsA) has significantly improved long-term survival after organ transplantations. Hypertension and nephrotoxicity are common side effects during CsA treatment and are aggravated by high salt intake.

OBJECTIVE

To examine whether lipoic acid (LA), a natural antioxidant that scavenges reactive oxygen species and regenerates/recycles endogenous antioxidants, could prevent CsA-induced hypertension and nephrotoxicity.

METHODS

Six-week-old spontaneously hypertensive rats (SHR) on a high-sodium diet (NaCl 6%) received CsA [5 mg/kg subcutaneously (s.c.)] alone or in combination with LA (0.5% w/w) for 6 weeks. Blood pressure, arterial functions, and tissue morphology were determined. Immunohistochemistry, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and high-pressure liquid chromatography were used for kidney and heart samples.

RESULTS

CsA induced severe hypertension, cardiac hypertrophy, endothelial dysfunction, and pronounced albuminuria. Histologically, the kidneys showed severe thickening of the media of the afferent arteries with fibrinoid necrosis, perivascular monocyte/macrophage infiltration and nitrotyrosine overexpression. CsA induced the expression of fibrogenic connective tissue growth factor both in the heart and kidneys. The detrimental effects of CsA were associated with upregulation of myocardial atrial natriuretic peptide (ANP) mRNA expression, paradoxical activation of the renin-angiotensin system (RAS), induction of renal reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and overexpression of oxidative stress-induced transcription factor NRF2. LA lowered blood pressure, ameliorated cardiac hypertrophy and endothelial dysfunction, and totally normalized albuminuria. In LA-treated rats, renal and cardiac morphologies were indistinguishable from those of SHR controls. CsA-induced myocardial ANP and connective tissue growth factor (CTGF) mRNA overexpression, RAS activation, NADPH oxidase induction, and NRF2 overexpression were prevented by LA. LA induced the mRNA expression of gamma-glutamylcysteine ligase, the rate-limiting enzyme in glutathione synthesis, and markedly increased hepatic cysteine and glutathione concentrations.

CONCLUSIONS

Our findings suggest a salutary role for lipoic acid supplementation in the prevention of CsA-induced hypertension and nephrotoxicity, and underscore the importance of increased oxidative stress in the pathogenesis of CsA toxicity.

Effect of FTY720 on chronic cyclosporine nephropathy in rats

BACKGROUND

Long-term treatment with cyclosporine A (CsA) causes tubulointerstitial inflammation and fibrosis in the kidney. To define the role of lymphocytes in this process, the novel lymphocyte-specific inhibitor FTY720 was administered to rats with experimental model of chronic CsA nephropathy.

METHODS

Sprague-Dawley rats were treated daily for 4 weeks with CsA (7.5 mg/kg), or both CsA and FTY720 (0.125 mg/kg). The effects of FTY720 on CsA-induced renal injury were evaluated using renal function tests and histopathology, and the expression of mediators of CsA-induced renal injury (osteopontin, transforming growth factor-beta1 [TGF-beta1], betaig-h3, and angiotensin II).

RESULTS

FTY720 treatment significantly decreased T-lymphocyte accumulation in kidneys compared with CsA treatment alone. FTY720 treatment improved not only CsA-induced renal dysfunction but also renal histopathology, demonstrated by decreased macrophage infiltration and interstitial fibrosis. Increased osteopontin, TGF-beta1, betaig-h3, and angiotensin II expression in CsA-treated rat kidneys were decreased with FTY720 treatment.

CONCLUSIONS

FTY720 treatment prevents CsA-induced renal injury.

Distinct immunohistochemical expression of osteopontin in the adult rat major salivary glands

Osteopontin is a multifunctional protein secreted by epithelial cells of various tissues. Its expression in the adult rat major salivary glands has not yet been studied. We examined osteopontin expression by immunohistochemistry using a well characterized monoclonal antibody. Submandibular glands of young adult male rats (70-100 days old) showed specific expression in secretion granules of granular duct cells but also in cells of the striated ducts and excretory duct. In the major sublingual as well as the parotid gland expression was found solely in the duct system. In addition, a few interstitial-like cells exhibiting very strong immunostaining for osteopontin could be found in either organ. Expression could neither be seen in acinar cells nor in cells of the intercalated ducts. Moreover, in submandibular glands of more aged rats (6- to 7-month old) which show well developed granular convoluted tubules, there was almost exclusive expression of osteopontin in granular duct cells as well as in some interstitial-like cells, but barely in the striated/excretory duct system. Western blot analysis of the submandibular gland showed a specific band migrating at approximately 74 kDa, detectable at both age stages. Osteopontin secreted fom granular duct cells may influence the composition of the saliva, e.g. thereby modulating pathways affecting sialolithiasis. Its expression in striated duct cells may also hint to roles such as cell-cell attachment or cell differentiation. The cell-specific expression detected in the rat major salivary glands differs in part from that reported in mice, human and monkey.

Renocortical mRNA expression of vasoactive factors during spironolactone protective effect in chronic cyclosporine nephrotoxicity

We showed that spironolactone reduced structural damage and prevented renal dysfunction in chronic cyclosporine (CsA) nephrotoxicity. These findings evidenced an aldosterone renal vascular effect under this condition. To investigate aldosterone’s role in modulating renal vascular tone, renocortical vasoactive pathways mRNA levels in chronic CsA nephrotoxicity as well as spironolactone’s effect on renal function in acute CsA nephrotoxicity were evaluated. Two experimental sets were designed. For chronic nephrotoxicity, rats fed with low-sodium diet were divided into groups receiving vehicle, spironolactone (Sp), CsA, and CsA+Sp, for 21 days. Creatinine clearance, survival percentage, and renocortical mRNA levels of pro-renin, angiotensinogen (Ang), angiotensin receptors (AT1A, AT1B, and AT2), preproendothelin, endothelin receptors (ETA, ETB), cyclooxygenase-2 (COX-2), and adenosine receptors (Ad1, Ad2A, Ad2B, and Ad3) were analyzed. For acute nephrotoxicity, similar groups fed with a standard chow diet for 7 days were included. Serum potassium and sodium, glomerular filtration rate (GFR), and renal blood flow (RBF) were determined. In chronic model, CsA produced pro-renin and ET upregulation, altered adenosine receptors expression, and reduced Ang, AT1A, AT1B, ETB, and COX-2 mRNA levels. Spironolactone protective effect in chronic nephrotoxicity was associated with prevention of pro-renin upregulation and increased AT2, together with ETBreduction. In acute nephrotoxicity, spironolactone completely prevented GFR and RBF reduction induced by CsA. Our results suggest that aldosterone contributes to renal vasoconstriction observed in CsA nephrotoxicity and that renoprotection conferred by spironolactone was related to modification of renocortical vasoactive pathways expression, in which pro-renin normalization was the most evident change in chronic nephropathy. Finally, our data point to spironolactone as a potential treatment to reduce CsA nephrotoxicity in transplant patients.

Protective Effect of Oral L-arginine Supplementation on Cyclosporine Induced Nephropathy in Rats

BACKGROUND

One of the major adverse effects of long term cyclosporine A (CyA) administration is chronic nephrotoxicity. Several studies have suggested that alterations of the L-arginine (L-Arg) nitric oxide (NO) pathway may be involved in the pathogenesis of CyA-induced kidney damage.

AIM

We postulated that in vivo activation of L-Arg-NO pathway might have a beneficial effect on CyA-induced renal damage. Conditions of chronic NO enhancement was established with L-Arg supplementation and chronic NO blockade with N-nitro-L-Arg methyl ester (L-NAME). We tested the hypothesis that, if CyA administration alters intrarenal NO synthesis, then exogenous L-Arg supplementation could limit renal injury, on the contrary, L-NAME, a potent competitive inhibitor of NO synthesis, could enhance CyA nephrotoxicity. Harmful effect of NO blockade indirectly supports the beneficial effect of NO in a model of CyA nephrotoxicity.

METHODS

Rats were administered vehicle (VH), CyA (7.5 mg/kg/day), CyA + L-Arg (2g/kg/day), CyA + L-NAME (5 mg/100 ml/day), CyA + L-Arg + L-NAME, VH + L-Arg, VH + L-NAME and were sacrificed at the end of the experiment. Body weight, serum creatinine, blood urea nitrogen (BUN) and NO levels were determined. Tubular injury and interstitial fibrosis were evaluated semiquantitatively using scoring systems on paraffin sections stained with hematoxylin/eosin (H/E), Masson's trichromic and periodic acid-Schiff (PAS).

RESULTS

The CyA group developed marked renal injury, characterized by a significant increase in serum creatinine and BUN, and histopathological alterations including tubular dilatation, vacuolization, necrosis, interstitial cell infiltration and tubulointerstitial fibrosis. CyA reduced serum NO level. L-Arg treatment significantly enhanced NO biosynthesis and protected animals from CyA-induced kidney damage. In contrast L-NAME strikingly reduced serum NO level, and worsened biochemical and histopathological alterations.

CONCLUSION

Chronic CyA nephrotoxicity can be aggravated by NO blockade and ameliorated by NO enhancement suggesting that L-Arg supplementation may be protective in CyA nephrotoxicity.

Tacrolimus and Cyclosporinein vitro and in vivo Induce Osteopontin mRNA and Protein Expression in Renal Tissues

The mechanism of immunosuppression-linked nephrotoxicity in organ transplantation remains to be solved. Expression of osteopontin (OPN), a multifunctional secreted glycoprotein, has been associated with various forms of renal injuries. In this study, using in vitro and in vivo models, we examined the effects of cyclosporine (CsA) and tacrolimus (TAC) on OPN mRNA and protein expression. We also examined if CsA- and TAC-induced OPN expression is dependent on transforming growth factor (TGF)-beta expression. For in vivo experiments mice and rats were injected with CsA (25 mg/kg) and TAC (0.2 mg/kg). For in vitro experiments, human proximal tubular epithelial (PTE) cells were treated with CsA and TAC for 4 h. To study the in vivo effect of TGF-beta on OPN mRNA, mice were injected with recombinant TGF-beta protein (3 mg/kg). The expression of OPN was also studied in CsA-treated PTE cells with and without anti-TGF-beta antibody. At the end of in vitro and in vivo treatments, RNA was isolated from kidney tissue and renal cells reverse transcribed to cDNA and amplified for OPN mRNA. Using immunochemistry and Western blot analysis OPN protein expression was also studied in vivo and in vitro, respectively. Both in vitro and in vivo treatment with CsA and TAC resulted in significantly increased OPN mRNA and protein expression. TGF-beta treatment in vivo also resulted in a significantly increased OPN mRNA expression and anti-TGF-beta antibody but not the control antibody in vivo in CsA-treated mice, and in vitro in CsA-treated PTE cells inhibited OPN mRNA expression. OPN may contribute to the CsA- and TAC-induced nephrotoxicity in organ transplant recipients and the increased OPN expression might be mediated by TGF-beta.

Renal expression of SIBLING proteins and their partner matrix metalloproteinases (MMPs)

BACKGROUND

Three members of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family of proteins have recently been shown to bind and activate specific promatrix metalloproteinases (MMPs) and to overcome the inhibition of tissue inhibitors of MMPs (TIMPs). Although usually associated with mineralized tissues, we have shown that the SIBLINGs and their MMP partners, when known, are coexpressed in salivary gland ductal cells. The present study examined the expression patterns of both the SIBLINGs and their MMP partners in adult kidney.

METHODS

The expression patterns of all five SIBLINGs known to date, and their MMP partners were determined in monkey kidney using immunohistochemistry and in situ hybridization techniques.

RESULTS

Bone sialoprotein (BSP) and its partner, MMP-2, were coexpressed in both the proximal and distal tubules. Osteopontin, as previously shown, was expressed in the distal tubules while its partner MMP-3 was expressed in both the proximal tubule and distal tubles. Dentin matrix protein-1 (DMP1) and MMP-9 were coexpressed throughout the nephron, including both parietal cells of Bowman's capsule and the thin limb of the loop of Henle. Dentin sialophosphoprotein (DSPP) and matrix extracellular phosphoglycoprotein (MEPE) were expressed in the proximal tubule and distal tubule, and proximal tubule, respectively.

CONCLUSION

In contrast to salivary gland in which all SIBLINGs and their MMP partners were coexpressed throughout the length of the ducts, these proteins were differentially expressed within the normal adult nephron. We hypothesize that the cells use the SIBLING/MMP pairs in the normal turnover of cell surface proteins and/or pericellular matrix proteins such as those in basement membranes.

Cisplatin-induced renal interstitial fibrosis in neonatal rats, developing as solitary nephron unit lesions

Cisplatin (CDDP)-induced renal lesions in rats prove a useful model for analysis of the pathogenesis of post-tubular injury-renal interstitial fibrosis. This study investigated the histopathological changes in 10-day-old neonatal rats induced by a single injection of CDDP (4.5 mg/kg). Compared with age-matched controls, on postinjection (PI) days 1 to 6, the number of apoptotic cells, demonstrable with TUNEL method, was significantly increased in CDDP-treated neonates, and there was no marked epithelial necrosis nor fibrotic lesions. Fibrotic lesions began to be developed solitarily around some nephrons with dilated ducts in the corticomedullary junction on PI day 10 and the lesions became more prominent until PI day 20. The alpha-SMA-positive myofibroblastic cells were seen exclusively in the fibrotic lesions. Additionally, the numbers of macrophages reacting with EDI (specific for exudate macrophages), ED2 (for resident macrophages), and OX6 (recognizing MHC class II antigens expressed in antigen-presenting macrophages/dendritic cells) were significantly increased around the affected renal tubules. A greater immunoreaction for TGF-beta1 was seen mostly in the renal epithelial cells of CDDP-treated neonates. These findings indicated that macrophage populations and myofibrolastic cells as well as TGF-beta1 may be responsible for the production of neonatal renal interstitial fibrosis. Compared with CDDP-injected adult rats that develop extensive interstitial fibrosis (Yamate et al., J Comp Pathol, 1995), the formation of fibrotic lesions was delayed, and the lesions were limited to the area around the affected nephrons; this could be attributable to differences in renal morphology between neonates and mature kidney of adult rats.

CCR1 blockade reduces interstitial inflammation and fibrosis in mice with glomerulosclerosis and nephrotic syndrome

BACKGROUND

CC chemokines mediate leukocyte infiltration into inflamed tissue. We have recently shown that blockade of the CC chemokine receptor CCR1 reduces interstitial inflammation and fibrosis in murine obstructive nephropathy. However, it is not known whether CCR 1 blockade is protective in progressive renal injury associated with severe proteinuria. We therefore studied the effect of the small-molecule CCR1 antagonist BX471 in a murine model of adriamycin-induced focal segmental glomerulosclerosis (FSGS) with nephrotic syndrome and progressive interstitial inflammation and fibrosis.

METHODS

Adriamycin nephropathy with persistent proteinuria was induced in male BALB/c mice by two intravenous injections of adriamycin (13 mg/kg) at day 0 and 14. BX471 treatment was started at day 14 when proteinuria and interstitial inflammation had developed. At 6 weeks, renal histology was studied by morphometry and immunohistochemistry.

RESULTS

At week 6, adriamycin-treated mice showed FSGS, associated with tubulointerstitial injury consisting of tubular dilation and atrophy, interstitial leukocyte infiltration, and fibrosis. The mRNA expression of CCR1 and CC chemokines, including the CCR1 ligands CCL3 (MIP-1alpha) and CCL5 (RANTES), was up-regulated in diseased kidneys, with a prominent interstitial expression of CCL5. Compared to vehicle-treated controls BX471 significantly reduced the amount of macrophages and T lymphocytes in interstitial lesions by 51% and 22%, respectively. Markers of renal fibrosis such as interstitial fibroblasts (48%) and interstitial volume (23%) were significantly reduced by BX471 treatment. In contrast, the extent of proteinuria and glomerular sclerosis was not affected by BX471 treatment.

CONCLUSION

Blockade of CCR1 substantially reduced interstitial leukocyte accumulation and the subsequent renal fibrosis in a murine model of nephrotic syndrome and FSGS. These findings support a role for CCR1 in interstitial leukocyte recruitment and suggest that CCR1 blockade might be a new therapeutic strategy in progressive nephropathies such as FSGS.

Attenuation of interstitial inflammation and fibrosis by recombinant human erythropoietin in chronic cyclosporine nephropathy

BACKGROUND

Evidence suggests that recombinant human erythropoietin (rHuEPO) protects neurons and cardiomyocytes from acute insults. We investigated the protective effect of rHuEPO on cyclosporine (CsA)-induced renal injury.

METHODS

CsA (15 mg/kg/day) was given to rats for 1 or 4 weeks, and rHuEPO was concurrently administered at a dose of 100 units/kg (thrice weekly). Effects of rHuEPO on CsA-induced renal injury were evaluated with tubulointerstitial fibrosis (TIF) score, macrophage infiltration, expression of proinflammatory and profibrotic cytokines, and apoptotic cell death.

RESULTS

Administration of rHuEPO decreased TIF score and the number of macrophages, which increased significantly in CsA-treated rat kidneys. At the molecular level, rHuEPO treatment decreased proinflammatory mediators (osteopontin and C-reactive protein) and profibrotic mediators (transforming growth factor-beta1 and transforming growth factor-beta1-inducible gene-h3). Increased apoptotic cell death in CsA-treated rat kidneys was significantly decreased with rHuEPO cotreatment, and apoptosis-related genes were regulated in favor of cell survival (increased Bcl-2 and suppressed caspase-3).

CONCLUSION

rHuEPO has a renoprotective effect against chronic CsA-induced renal injury.

Cyclosporine-A induced nephrotoxicity is associated with decreased renal bone morphogenetic protein-7 expression in rats

The aim of our study was to investigate bone morphogenetic protein-7 (BMP-7) expression in a rat model of chronic cyclosporine (CsA) toxicity compare with healthy controls, as well as the influence of treatment with the angiotensin-converting enzyme inhibitor (ACEI) quinapril. Twenty-four male Wistar rats were divided into groups of eight animals treated with CsA (15 mg/kg intraperitoneally) for 8 weeks (CsA group) without or with quinapril (10 mg/kg per day in the drinking water: CsA group + Q) for comparison with healthy controls (H group). The renal tissues were examined by light microscopy for CsA toxicity; specifically, tubulointerstitial damage and afferent arteriolopathy as well as BMP-7 expression were semiquantitatively scored by immunohistochemical staining. Mean CsA levels were 1982 ng/mL and 1968 ng/mL for the CsA and CsA + Q groups, respectively. At the end of the study period, the mean serum creatinine levels were 0.8 +/- 0.2 mg/dL, 1.6 +/- 0.8 mg/dL, and 1.4 +/- 0.8 mg/dL for the H, CsA, and CsA + Q groups, respectively. Interstitial fibrosis, tubular atrophy, and afferent arteriolar hyalinization were present in the CsA group and, to a lesser degree, in the CsA + Q group, compared with the H group. CsA-treated rats displayed significantly decreased BMP-7 expression compared with healthy controls (P <.0005). BMP-7 expression was higher among the CsA + Q group than the the group CsA group. In a rat model histologic changes characteristic of CsA-induced nephrotoxicity are associated with decreased expression of BMP-7, which seems to be at least partially restored by ACE inhibition.

Long-term treatment with cyclosporine decreases aquaporins and urea transporters in the rat kidney

The aim of this study was to evaluate the long-term effects of cyclosporine (CsA) treatment on urinary concentration ability. Rats were treated daily for 4 wk with vehicle (VH; olive oil, 1 ml/kg sc) or CsA (15 mg/kg sc). The influence of CsA on the kidney's ability to concentrate urine was evaluated using functional parameters and expression of aquaporins (AQP1-4) and of urea transporters (UT-A-1-3, and UT-B). Plasma vasopressin levels and the associated signal pathway were evaluated, and the effect of vasopressin infusion on urine concentration was observed in VH- and CsA-treated rats. Toxic effects of CsA on tubular cells in the medulla as well as the cortex were evaluated with aldose reductase (AR), Na-K-ATPase-alpha(1) expression, and by determining the number of terminal transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells. Long-term CsA treatment increased urine volume and fractional excretion of sodium and decreased urine osmolality and free-water reabsorption compared with VH-treated rats. These functional changes were accompanied by decreases in the expression of AQP (1-4) and UT (UT-A2, -A3, and UT-B), although there was no change in AQP2 in the cortex and outer medulla and UT-A1 in the inner medulla (IM). Plasma vasopressin levels were not significantly different between two groups, but infusion of vasopressin restored CsA-induced impairment of urine concentration. cAMP levels and Gsalpha protein expression were significantly reduced in CsA-treated rat kidneys compared with VH-treated rat kidneys. CsA treatment decreased the expression of AR and Na-K-ATPase-alpha(1) and increased the number of TUNEL-positive renal tubular cells in both the cortex and medulla. Moreover, the number of TUNEL-positive cells correlated with AQP2 or UT-A3) expression within the IM. In conclusion, CsA treatment impairs urine-concentrating ability by decreasing AQP and UT expression. Apoptotic cell death within the IM at least partially accounts for the CsA-induced urinary concentration defect.

Late calcineurin inhibitor withdrawal as a strategy to prevent graft loss in patients with suboptimal kidney transplant function

Chronic allograft nephropathy is a major cause of progressive renal failure in renal transplant recipients. Its etiology is multifactorial and may include both immunologic and nonimmunologic causes. In this observational cohort study we set out to see if calcineurin inhibitor withdrawal would reduce the likelihood of graft loss.

METHODS

One hundred and five renal transplant recipients with impaired kidney function (mean serum creatinine 3.0 +/- 0.1 mg/dl) and biopsy-proven chronic allograft nephropathy had the dose of their calcineurin inhibitors, cyclosporine (CSA), or tacrolimus (FK), reduced or discontinued with either the addition of, or continuation of mycophenolate mofetil and low-dose corticosteroids. This intervention occurred at a mean of 29.0 +/- 2.7 months after transplantation. Follow-up after intervention was 54.3 +/- 4.1 months in the reduced CSA group (n = 64), 41.6 +/- 3.2 months in the reduced FK group (n = 28), and 75.5 +/- 6.7 months in the calcineurin inhibitor withdrawal group (n = 13).

RESULTS

There were 24 graft failures in the reduced CSA group, 9 graft failures in the reduced FK group, and 1 graft lost in the calcineurin inhibitor withdrawal group. The unadjusted relative risk for graft failure in the CSA and FK groups combined (confidence interval 1.05-31.6), was 4.07 using the calcineurin inhibitor withdrawal group as the reference, p = 0.05. A Cox proportional hazards model adjusting for baseline covariates including age, gender, race, type of transplant, delayed graft function, baseline blood pressure and random serum glucose and cholesterol demonstrated that only calcineurin inhibitor dose reduction but not withdrawal, older age, delayed graft function, higher serum creatinine at the time of intervention, and higher diastolic blood pressure and serum glucose, correlated with graft loss. Only 6 of the 105 patients developed Banff grade acute rejection. All responded to steroid therapy. We conclude that although this observational cohort study may have a selection bias, late calcineurin inhibitor withdrawal in patients with chronic allograft nephropathy and impaired kidney function appears safe and durable as a treatment strategy to reduce the likelihood of graft failure.

SUPPRESSION OF CYCLOSPORINE A NEPHROTOXICITY IN VIVO BY TRANSFORMING GROWTH FACTOR β RECEPTOR-IMMUNOGLOBULIN G CHIMERIC PROTEIN

BACKGROUND

Transforming growth factor (TGF)beta is implicated in the pathogenesis of cyclosporine A (CsA) nephrotoxicity. We examined the efficacy of TGF beta receptor (R)II/immunoglobulin (Ig)G Fc, a soluble chimeric protein consisting of the extracellular domain of human TGF beta RII and IgG1 Fc, on CsA nephrotoxicity in mice.

METHODS

Subcutaneous injection of CsA (25 mg/kg/d) was given daily to mice maintained on a low-sodium diet. On days 1 and 7, an expression vector carrying cDNA for either TGF beta RII/IgG Fc or beta-galactosidase was transfected into the skeletal muscles by electroporation. At 2 or 3 weeks of CsA administration, plasma and renal TGF beta 1 levels, and tubulointerstitial injury and fibrosis were evaluated.

RESULTS

After 2 weeks of CsA administration, plasma and renal TGF beta 1 levels increased to the maximum and then declined toward the baseline levels. Renal TGF beta 1 mRNA remained elevated until 3 weeks. Tubulointerstitial alterations became appreciable in 2 weeks and intensified by 3 weeks. At 2 weeks, the TGF beta RII/IgG Fc intervention abolished the increase in plasma TGF beta 1, attenuated the increase in renal TGF beta 1 by 50%, and markedly suppressed the histologic alterations. At 3 weeks, the histologic alterations remained markedly suppressed by the intervention, with no appreciable effects on the renal TGF beta 1 mRNA and protein.

CONCLUSION

The introduction of TGF beta RII/IgG Fc by gene transfer effectively abrogated CsA-induced tubulointerstitial alterations. Suppression of tubulointerstitial changes was evident at 3 weeks when renal TGF beta 1 mRNA and protein were comparable to those with CsA alone, indicating that early anti-TGF beta intervention is effective in suppressing the progression of CsA nephrotoxicity despite persistent increases in renal TGF beta 1 expression.

Cyclosporine A sensitizes the kidney to tubulointerstitial fibrosis induced by renal warm ischemia

BACKGROUND

Renal warm ischemic injury and immunosuppression with cyclosporin A (CsA) may contribute to chronic allograft nephropathy after cadaveric transplantation. This study establishes whether CsA can sensitize the kidney to injury and fibrosis induced by renal warm ischemia (RWI).

METHODS

The left kidney of Sprague-Dawley rats was subjected to 30 min of warm ischemia and/or intraperitoneal CsA (15 mg/kg/d) for 30 days (n=6 per group). Renal injury and fibrosis were assessed histologically together with immunohistochemistry for collagen III, transforming growth factor (TGF)-beta1, ED1 (macrophage marker), and alpha-smooth muscle actin. Renal mRNAs for collagen III, TGF-beta 1, matrix metalloproteinase (MMP)-2, and tissue inhibitor of metalloproteinase-1 together with MMP enzyme activity were also determined.

RESULTS

RWI or CsA alone produced only minor effects on renal injury and fibrosis. However, in CsA-treated rats, RWI produced a marked increase in tubulointerstitial fibrosis, as shown by the potentiation of collagen III and TGF-beta1 determined by immunochemistry and mRNA analysis. The up-regulation of tissue inhibitor of metalloproteinase-1 mRNA was associated with a decrease in MMP enzyme activity. In CsA-treated rats, RWI was also associated with an increase in inflammatory infiltrates, elevated immunostain for ED1 (indicating extensive macrophage influx), and elevated immunostain for alpha-smooth muscle actin (indicating myofibroblast activation).

CONCLUSIONS

In the rat, CsA can sensitize the kidney to fibrosis induced by renal warm ischemia. In renal transplantation, when cadaveric donor kidneys have been subjected to a period of warm ischemia, CsA may be an inappropriate choice for immunosuppressive therapy.

Pravastatin treatment attenuates interstitial inflammation and fibrosis in a rat model of chronic cyclosporine-induced nephropathy

We investigated the effects of pravastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, on interstitial inflammation and fibrosis, using an animal model of chronic cyclosporine A (CsA)-induced nephropathy. Sprague-Dawley rats were maintained on a low-salt diet (0.05% sodium) and treated daily for 1 or 4 wk with vehicle (olive oil; 1 ml/kg sc), CsA (15 mg/kg sc), or both CsA and pravastatin (5 or 20 mg/kg in the drinking water). Anti-inflammatory and antifibrotic effects of pravastatin were studied by evaluating the concentrations of the inflammatory mediators osteopontin (OPN) and C-reactive protein (CRP), of fibrotic cytokine-transforming growth factor (TGF)-β1, and the presence of ED-1-positive cells (macrophages). In addition, renal function, serum lipid levels, histopathology (arteriolopathy and tubulointerstitial fibrosis), and the expression of the vasoactive factors endothelial nitric oxide synthase (eNOS) and renin protein were also compared for different treatment groups. Pravastatin induced dose-dependent decreases in the expression of OPN, intrarenal CRP, and TGF-β1, and in the numbers of ED-1-positive cells at 1 and 4 wk. These were accompanied by a significant attenuation of tubulointerstitial fibrosis at 4 wk. The downregulation of eNOS protein expression in CsA-treated rat kidney was markedly upregulated by pravastatin treatment, although intrarenal renin expression was unaffected. Renal dysfunction induced by CsA significantly improved with administration of pravastatin at a dose of 20 mg/kg. Neither CsA nor pravastatin influenced serum lipid or high-sensitivity CRP levels in the treatment groups. Thus in chronic CsA nephropathy, pravastatin effectively abrogates the progression of tubulointerstitial inflammation and fibrosis. This may support the clinical use of pravastatin.

Mycophenolate mofetil ameliorates arteriolopathy and decreases transforming growth factor-beta1 in chronic cyclosporine nephrotoxicity

Afferent arteriolopathy is the most characteristic lesion of chronic cyclosporine (CsA) nephrotoxicity. We investigated the effect of therapeutic doses of mycophenolate mofetil (MMF) in a model of chronic CsA nephrotoxicity where transforming growth factor-beta (TGF-beta) was shown to play a central role. Rats treated with vehicle, MMF 10 mg/kg/day, CsA 10 mg/kg/day or CsA + MMF were sacrificed at 7 or 28 days. Physiologic and histologic changes were studied in addition to TGF-beta1 mRNA and protein expressions, and mRNA expression of plasminogen activator inhibitor-1 (PAI-1) and the extracellular matrix (ECM) proteins biglycan and types I and IV collagen. While MMF markedly ameliorated afferent arteriolopathy, it had no significant effect on interstitial fibrosis and tubular atrophy. In addition, MMF treatment reduced both TGF-beta1 mRNA and protein levels by 39% and 32%, respectively (p < 0.05 vs. CsA only). The expression of the ECM proteins followed that of TGF-beta1 and was significantly decreased with MMF; a similar effect was observed with PAI-1, suggesting an increase in ECM degradation. These results suggest that MMF exerts a beneficial effect on CsA arteriolopathy and that it decreases TGF-beta1. While this drug combination may be useful clinically, long-term studies are needed to determine if MMF has a lasting benefit.

Cyclosporine nephrotoxicity

After more than 20 years of cyclosporine use its nephrotoxicity remains a significant clinical problem. Cyclosporine-induced renal injury has been described in solid organs recipients and in patients treated for autoimmune diseases. It is manifested in 2 distinct and well characterized forms, acute nephrotoxicity and chronic nephrotoxicity. This communication reviews the current literature analyzing the available data about the pathogenesis and mechanisms of acute and chronic cyclosporine-induced nephrotoxicity. A working hypothesis for the possible mechanisms of chronic cyclosporine nephrotoxicity will be provided.

Early interstitial accumulation of collagen type I discriminates chronic rejection from chronic cyclosporine nephrotoxicity

Little is known regarding the composition of the interstitial extracellular matrix of kidney allografts with deteriorating function. Collagen I, III, and IV, the collagen IV alpha3 chain, and the laminin beta2 chain were investigated in biopsies of allografted kidneys with chronic cyclosporine A nephrotoxicity (CsAT) (n = 17), chronic rejection (CR) (n = 12), or chronic allograft nephropathy (CAN) (n = 19). alpha-Smooth muscle actin expression was also examined. Normal native kidneys were used as control samples (n = 11). Biopsy samples were studied with routine light microscopy and immunostaining. The mean interstitial fibrosis scores were significantly higher for the CR and CAN groups, compared with the chronic CsAT group. The cortical tubulointerstitial areas of the CR and CAN groups, but not the chronic CsAT group, contained more collagen I than did normal control samples. Differences were noted even in biopsies with mild fibrosis. Accumulation of collagen III, IV, and IV alpha3 was increased in all patient groups. Collagen III accumulation was greater in the CR and CAN groups than in the chronic CsAT group. Receiver-operating characteristic curve analysis demonstrated that collagen I staining had the best discriminatory value in differentiating CR from chronic CsAT, with a sensitivity of 63% and a specificity of 94% at a cutoff value of 19%. Laminin beta2 staining did not differentiate CR from CsAT. Increased alpha-smooth muscle actin staining did not differ among the three groups. It was concluded that, during chronic CsAT, collagen III and IV were preferentially accumulated in the tubulointerstitium. Early increases in the deposition of collagen I, with collagen III and IV, were more specific for CR. CR seems to elicit a more pronounced fibrotic response than does chronic CsAT.

Role of renal NO production in the regulation of medullary blood flow

The unique role of nitric oxide (NO) in the regulation of renal medullary function is supported by the evidence summarized in this review. The impact of reduced production of NO within the renal medulla on the delivery of blood to the medulla and on the long-term regulation of sodium excretion and blood pressure is described. It is evident that medullary NO production serves as an important counterregulatory factor to buffer vasoconstrictor hormone-induced reduction of medullary blood flow and tissue oxygen levels. When NO synthase (NOS) activity is reduced within the renal medulla, either pharmacologically or genetically [Dahl salt-sensitive (S) rats], a super sensitivity to vasoconstrictors develops with ensuing hypertension. Reduced NO production may also result from reduced cellular uptake of l-arginine in the medullary tissue, resulting in hypertension. It is concluded that NO production in the renal medulla plays a very important role in sodium and water homeostasis and the long-term control of arterial pressure.

Synergistic effects of mycophenolate mofetil and losartan in a model of chronic cyclosporine nephropathy

BACKGROUND

Combined treatments of mycophenolate mofetil (MMF) and losartan (LSRT) have synergistic effects on various renal diseases through their hemodynamic and anti-inflammatory effects. This study investigated whether MMF treatment is effective in inhibiting inflammatory processes in chronic cyclosporine A (CsA) nephrotoxicity, and whether combined treatment using MMF and LSRT affords superior protection compared with the respective monotherapies.

METHODS

Rats on a low-salt diet were given vehicle (VH group, olive oil, 1 mg/kg per day), CsA (15 mg/kg per day), CsA and LSRT (CsA+LSRT group, 100 mg/L per day), CsA and MMF (CsA+MMF group; 40 mg/kg per day), or CsA, LSRT and MMF (CsA+LSRT MMF group). Control groups received each drug without CsA treatment. Renal function, histologic parameters (arteriolopathy, tubulointerstitial fibrosis, and inflammatory cell infiltration), and mediators of CsA-induced nephrotoxicity (angiotensin-II, osteopontin, and transforming growth factor [TGF]-beta1) were studied.

RESULTS

The CsA-treated rats showed decreased renal function and increased histologic parameters compared with the VH-treated rats. The CsA+MMF treatment significantly improved renal function and histopathologic parameters compared with the CsA group, and combined treatment with MMF and LSRT further improved those parameters compared with the CsA+LSRT and CsA+MMF groups. At a molecular level, increased expression of angiotensin II protein, osteopontin, and TGF-beta1 mRNAs in the CsA group were significantly decreased with MMF, and further decrease was observed with the combined treatment using MMF and LSRT.

CONCLUSIONS

MMF treatment decreases CsA-induced nephrotoxicity, and combined treatment with LSRT has a synergistic effect in preventing chronic CsA nephrotoxicity.

Reversibility of chronic cyclosporine nephropathy in rats after withdrawal of cyclosporine

Renal interstitial inflammation is an important factor in the pathogenesis of chronic cyclosporin A (CsA) nephropathy. We studied the expression of the chemoattractant osteopontin (OPN) and the relationship between OPN expression and tubulointerstitial injury in a rat model of chronic CsA nephropathy. Chronic CsA nephropathy was induced in Sprague-Dawley rats by administering CsA (15 mg/kg sc) for 5 wk and then withdrawing it for 5 or 10 wk. Renal function, histopathology (arteriolopathy, ED-1-positive cells, and tubulointerstitial fibrosis), renin-angiotensin system (RAS) activity, and OPN expression were observed during the follow-up period. Renal function deteriorated in CsA-treated rats, with the development of typical histopathology and activation of RAS. After CsA withdrawal, these parameters were significantly reversed (all P < 0.05). The upregulation of OPN mRNA and protein expression seen in CsA-treated rat kidneys was decreased 5 wk after CsA withdrawal and was further decreased after 10 wk. Of note, OPN mRNA expression correlated with the number of infiltrating macrophage (r = 0.651, P < 0.01) and tubulointerstitial fibrosis (r = 0.729, P < 0.01). These findings suggest that OPN expression and macrophage infiltration decrease after long-term CsA withdrawal in rats with established chronic CsA nephropathy, and this is closely associated with recovery from renal injury.

Inhibition of nuclear factor-kappaB activation by pyrrolidine dithiocarbamate prevents chronic FK506 nephropathy

BACKGROUND

Chronic tacrolimus (FK506) nephrotoxicity is characterized by renal fibrosis with interstitial inflammation. Since nuclear factor-kappaB (NF-kappaB) plays a key role in chronic inflammatory diseases including renal disease, the present study was conducted to elucidate the role of NF-kappaB in the pathogenesis of chronic FK506-induced nephropathy.

METHODS

FK506 (1 mg/kg/day, SC) was administered daily to rats maintained on low sodium diet for 42 days. Some rats were treated with a putative NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC; 100, 200 mg/kg/day, by gavage). The renal function, renal histology, renal NF-kappaB-DNA binding activity and gene expression profile were examined.

RESULTS

FK506 caused a decline in glomerular filtration and induced characteristic renal morphologic changes including arteriolopathy, tubular atrophy and interstitial fibrosis. FK506 markedly activated renal cortical NF-kappaB-DNA binding. PDTC administration inhibited NF-kappaB-DNA binding activity in a dose dependent manner. With higher dose, NF-kappaB-DNA binding activity was decreased to a control level. PDTC had little effect on FK506-induced renal dysfunction. Renal cortical monocyte/macrophage infiltration observed in FK506-treated rats was dramatically suppressed by PDTC. FK506 up-regulated renal cortical gene expression of chemoattractant proteins, monocyte chemoattractant protein-1 (MCP-1) and osteopontin. PDTC significantly blocked MCP-1 gene expression but had no effect on osteopontin gene expression. Tubular atrophy and tubulointerstitial fibrosis, but not arteriolopathy, were significantly attenuated by PDTC. FK506 increased renal mRNA expression of fibrogenic molecules and extracellular matrices that also were attenuated by PDTC treatment.

CONCLUSIONS

NF-kappaB plays an important role in mediating cortical monocyte/macrophage infiltration and in the pathogenesis of tubular injury and interstitial fibrosis in experimental FK506-induced chronic nephropathy.

Therapeutic benefit of spironolactone in experimental chronic cyclosporine A nephrotoxicity

BACKGROUND

Cyclosporine A (CsA) is an immunosuppressive drug used to prevent tissue allograft rejection. However, its long-term utilization is limited due to chronic nephrotoxicity for which no prevention is available. This study evaluated the effect of spironolactone on renal functional and structural alterations induced by CsA, and assessed whether the protective effect was associated with a reduction of transforming growth factor-beta (TGF-beta) and the change of extracellular matrix protein mRNA level.

METHODS

Male Wistar rats fed with low sodium diet were divided in four treatment groups: vehicle, CsA (30 mg/kg), spironolactone (20 mg/kg), or CsA+spironolactone. After 21 days, creatinine clearance (CCr), blood CsA, arteriolopathy in renal tissue, and TGF-beta, collagen I, collagen IV, fibronectin, and epidermal growth factor (EGF) mRNA levels in renal cortex were determined.

RESULTS

CsA reduced the CCr and up-regulated TGF-beta, collagen I and fibronectin mRNA expression with a significant development of arteriolopathy, and reduced EGF mRNA levels. In contrast, spironolactone administration prevented the fall in renal function and TGF-beta, collagen I, and fibronectin up-regulation, together with a reduction of arteriolopathy and tubulointerstitial fibrosis.

CONCLUSION

Our data show that aldosterone plays an important role as a mediator of renal injury induced by CsA. Thus, mineralocorticoid receptor blockade may be a potential strategy to prevent CsA nephrotoxicity.

Interleukin-1beta stimulates human renal fibroblast proliferation and matrix protein production by means of a transforming growth factor-beta-dependent mechanism

One of the hallmarks of progressive renal disease is the development of tubulointerstitial fibrosis. This is frequently preceded by macrophage infiltration, raising the possibility that macrophages relay fibrogenic signals to resident tubulointerstitial cells. The aim of this study was to investigate the potentially fibrogenic role of interleukin-1beta (IL-1beta), a macrophage-derived inflammatory cytokine, on cortical fibroblasts (CFs). Primary cultures of human renal CFs were established and incubated for 24 hours in the presence or absence of IL-1beta. We found that IL-1beta significantly stimulated DNA synthesis (356.7% +/- 39% of control, P <.003), fibronectin secretion (261.8 +/- 11% of control, P <.005), collagen type 1 production, (release of procollagen type 1 C-terminal-peptide, 152.4% +/- 26% of control, P <.005), transforming growth factor-beta (TGF-beta) secretion (211% +/- 37% of control, P <.01), and nitric oxide (NO) production (342.8% +/- 69% of control, P <.002). TGF-beta (1 ng/mL) and the phorbol ester phorbol 12-myristate 13-acetate (PMA, 25 nmol/L) produced fibrogenic effects similar to those of IL-1beta. Neither a NO synthase inhibitor (N(G)-methyl-l-arginine, 1 mmol/L) nor a protein kinase C (PKC) inhibitor (bis-indolylmaleimide 1, 1 micromol/L) altered the enhanced level of fibronectin secretion or DNA synthesis seen in response to IL-1beta treatment. However, addition of a TGF-beta-neutralizing antibody significantly reduced IL-1beta-induced fibronectin secretion (IL-1beta + IgG, 262% +/- 72% vs IL-1beta + alphaTGF-beta 156% +/- 14%, P <.02), collagen type 1 production (IL-1beta + IgG, 176% +/- 28% vs IL-1beta + alphaTGF-beta, 120% +/- 14%, P <.005) and abrogated IL-1beta-induced DNA synthesis (245% +/- 49% vs 105% +/- 21%, P <.005). IL-1beta significantly stimulated CF DNA synthesis and production of fibronectin, collagen type 1, TGFbeta, and NO. The fibrogenic and proliferative action of IL-1beta on CF appears not to involve activation of PKC or production of NO but is at least partly TGFbeta-dependent.

Renal tubulointerstitial injury in weanling rats with hyperhomocysteinemia

BACKGROUND

While hyperhomocysteinemia is associated with an increased risk of atherosclerosis and the related cardiovascular diseases, the effect of hyperhomocysteinemia on the kidney has not been clearly demonstrated. The purpose of this study was to investigate whether long-term hyperhomocysteinemia develops atherosclerotic lesions in the kidney.

METHODS

The effects of various dietary combinations, including folate deficiency, choline deficiency and methionine loading, on the plasma homocysteine concentration, renal function and renal histopathology were examined for 12 weeks in male weanling Fisher rats.

RESULTS

Folate deficiency, choline deficiency and methionine loading synergistically induced hyperhomocysteinemia up to 69.7 +/- 23.1 micromol/L (control, 11.6 +/- 3.9 micromol/L, P < 0.01) without any change in blood pressure. Creatinine clearance was negatively correlated with the plasma homocysteine concentration (r = -0.55, P < 0.01). Arterial and arteriolar wall thickening, and focal tubulointerstitial fibrosis were found in the kidneys of the hyperhomocysteinemic rat. The lesions of tubulointerstitial fibrosis appeared striped or wedge-shaped at the subcapsular cortex of the kidney. In addition, the expression of vascular endothelial growth factor, an indicator of hypoxia, was increased in the adjacent more intact area of the cortex. These findings suggest that the renal tubulointerstitial lesions were likely to be mediated by severe ischemia due to regional circulatory disturbance. Folate supplementation diminished these vascular and tubulointerstitial changes.

CONCLUSION

These results indicate that diet-induced chronic hyperhomocysteinemia could induce vascular remodeling and tubulointerstitial injury in the kidney, and that these changes were ameliorated by folate supplementation.

Magnesium supplementation prevents experimental chronic cyclosporine a nephrotoxicity via renin-angiotensin system independent mechanism

BACKGROUND

We have previously shown that correction of hypomagnesemia by magnesium (Mg) supplementation ameliorates chronic cyclosporine A (CsA) nephropathy via inhibiting gene expression of fibrogenic molecules. Experiments were conducted to further elucidate upstream mechanism of the beneficial effects upon CsA nephrotoxicity.

METHODS

CsA (15 mg/kg/day, subcutaneous [SC]) was administered daily to rats maintained on low sodium diet for 7, 14, and 28 days. Because blockade of renin-angiotensin system improves chronic CsA nephropathy, the effects of Mg supplementation and those of angiotensin-converting enzyme inhibitor (ACEI) were compared on renal function, renal histology, mononuclear cell infiltration, and gene expression profile.

RESULTS

CsA induced a decline in glomerular filtration and developed characteristic striped fibrosis that were mostly evident at day 28. Mg attenuated CsA-induced impaired renal function, whereas ACEI did not. Interstitial inflammation as evidenced by monocyte/macrophage infiltration preceded the renal fibrosis and increased progressively with the CsA treatment period. Concomitantly, CsA markedly up-regulated expression of chemoattractant proteins, osteopontin, and monocyte chemoattractant protein-1. These changes were abolished by Mg but were only partially affected with ACEI. CsA promoted renal mRNA expression of fibrogenic molecules and extracellular matrices that were almost completely abolished by Mg but partially suppressed by ACEI. Similarly, CsA-induced chronic fibrotic lesion was markedly attenuated by Mg supplementation but was partially attenuated by ACEI.

CONCLUSION

Mg supplementation abolished CsA-induced precedent interstitial inflammation possibly via inhibition of chemoattractants expression and consequently attenuated tubulointerstitial fibrosis. In this protective mechanism, factors independent of the renin-angiotensin system appears to be mainly involved.

Participation of different macrophage populations and myofibroblastic cells in chronically developed renal interstitial fibrosis after cisplatin-induced renal injury in rats

To shed some light on the mechanisms behind renal fibrogenesis, the present study immunohistochemically investigated the participation of different macrophage populations and myofibroblastic cells in rat renal interstitial fibrosis developed chronically after repeated injection of cisplatin (2 mg/kg body weight, once weekly for 7 weeks). During the 19-week recovery period after the final injection, fibrotic lesions progressively developed in the corticomedullary junction, with the greatest level at post-final injection (FPI) week 5, and then the lesions were gradually repaired by PFI week 19, indicative of a healing process. In conformity with the development of fibrotic lesions, the number of myofibroblastic cells reacting with an anti-alpha-smooth muscle actin antibody was increased, with a peak at PFI week 3, and collagens (types I, III, and IV), fibronection, and laminin were excessively accumulated in these areas. Interstitial cells forming the fibrotic lesions showed mitotic activity at the early stages, whereas they disappeared by apoptosis in the healing process. A large number of cells reacting with an antibody of ED1 (for exudate macrophages), ED2 (for resident macrophages), or OX6 (for major histocompatibility complex class II-presenting macrophages and interstitial dendritic cells) had already appeared at PF1 week 1, and then their numbers increased, with a peak at PFI weeks 7, 3, and 9 in ED1-, ED2-, and OX6-positive cells, respectively. Thereafter, the number of ED1- and ED2-positive cells decreased, whereas the number of OX6-positive cells persisted at a high level until PFI week 19. In the healing process, clusters of lymphocytes were present, the development of which might have been related to OX6-positive cells. The present study demonstrated that chronically developing rat renal interstitial fibrosis might be produced by the complicated mechanisms evoked by interactions between different macrophage populations and myofibroblastic cells, because macrophages show heterogeneous functions depending on microenvironmental factors.

Expression of apoptosis-related genes in chronic cyclosporine nephrotoxicity in mice

To define the mechanism of cyclosporine (CsA)-induced apoptosis, we investigated the expression of apoptosis-related genes in experimental chronic CsA nephrotoxicity. Mice on a low-salt (0.01%) diet were given vehicle (VH, olive oil, 1 mg/kg/day), or CsA (30 mg/kg/day), and sacrificed at 1 and 4 weeks. Apoptosis was detected with deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) stain, and the expressions of apoptosis-related genes were evaluated by reverse transcription-polymerase chain reaction, immunoblot or immunohistochemistry. The activity of caspase 1 and 3 was also evaluated. The CsA group showed increases in apoptotic cells compared with the VH group (54 +/- 41 vs. 3 +/- 3, p < 0.05), and the number of apoptotic cells correlated well with interstitial fibrosis scores (r = 0.83, p < 0.01). The CsA group showed a significant increase in Fas-ligand mRNA (0.20 vs. 0.02 amol/microgram total RNA, p < 0.05) and Fas protein expression (146% vs. 95%, p < 0.05), compared with the VH group. The CsA group showed significant increases in ICE mRNA (0.21 vs. 0.03 amol/microgram total RNA at 4 weeks, p < 0.05) and CPP32 mRNA (0.18 vs. 0.03 amol/microgram total RNA at 4 weeks, p < 0.05), compared with the VH group. The enzymatic activity of ICE (16.6 vs. 7.9 rho mol/microgram/h, p < 0.05) and CPP32 protease (15.6 vs. 2.7 rho mol/microgram/h, p < 0.05) proteases were increased in the CsA group, compared with the VH group. The ratio between bax and bcl-2 protein increased significantly in the CsA group (5.3-fold), compared with the VH group. Levels of p53 protein also increased in the CsA group. Immunohistochemical detection of Fas, Fas-ligand, ICE and CPP32 revealed strong immunoreactivity in renal tubular cells in areas of structural injury. These findings suggest that local activation of the apoptosis-related genes is associated with CsA-induced apoptotic cell death.

Quantitative analyses of osteopontin mRNA expression in human proximal tubules isolated from renal biopsy tissue sections of minimal change nephrotic syndrome and IgA glomerulonephropathy patients

Osteopontin (OPN), a secreted phosphoprotein and chemotactic to monocytes/macrophages, is upregulated in renal cortical tubules in a variety of rodent models of renal injury and is believed to possibly have a role in tubulointerstitial injury. We previously reported the establishment of a system for the quantification of messenger RNA (mRNA) expression in isolated rat glomeruli using laser-manipulated microdissection and real-time polymerase chain reaction. This system was applied to human renal biopsy specimens. We quantified OPN mRNA expression in proximal tubules of 5 patients with minimal change nephrotic syndrome (MCNS) and 11 patients with mild immunoglobulin A (IgA) glomerulonephritis. We also examined the correlation between OPN mRNA expression in proximal tubules and clinical data and pathological findings in glomeruli and tubulointerstitial regions. Patients with MCNS showed a positive correlation between OPN mRNA expression in proximal tubules and urinary protein excretion (r = 0.93; P < 0.05), whereas for patients with IgA glomerulonephritis, logarithmic values of OPN mRNA expression in proximal tubules positively correlated with low urinary protein levels (r = 0.72; P < 0.05). Pathological changes, ranging from nonexistent to minor, in glomeruli and tubulointerstitium of these patients with mild IgA glomerulonephritis did not significantly correlate with OPN mRNA expression in proximal tubules. In patients with mild IgA glomerulonephritis, OPN mRNA expression in proximal tubules increased exponentially in response to a small amount of urinary protein (<1.2 g/d).

Role of hypomagnesemia in chronic cyclosporine nephropathy

BACKGROUND

Hypomagnesemia is a common finding of cyclosporine (CsA)-treated patients and has been proposed as both a cause and a consequence of CsA-induced nephrotoxicity. This experiment was conducted to elucidate the role of hypomagnesemia in the pathogenesis of chronic CsA nephropathy.

METHODS

CsA (15 mg/kg/day subcutaneously) was administered to rats maintained on a low-sodium diet for 1, 2, and 4 weeks, and the effects of magnesium (Mg) supplementation on renal function, renal histology, and renal gene expression profile of fibrogenic molecules and vasoconstrictors was examined.

RESULTS

CsA elicited hypomagnesemia and induced a progressive decline in glomerular filtration. At 28 day, renal tubular atrophy and cortical striped interstitial fibrosis were evident with CsA treatment. Dietary supplementation of Mg ameliorated CsA-induced hypomagnesemia and almost completely abolished CsA-induced chronic fibrotic lesions. Neither CsA nor Mg supplementation affected blood pressure. Renal cortical mRNA of transforming growth factor beta, plasminogen activator inhibitor (PAI)-1, and extracellular matrix started to increase at 14 days and elevated further at 28 days. In contrast, the increase in mRNA of tissue inhibitor of matrix metalloproteinase-1 and renin was evident early at 7 days and reached peak at 14 days. These mRNA increases, except that of renin, were almost abolished when hypomagnesemia was corrected. Magnesium supplementation also improved glomerular dysfunction, at least in part, through inhibition of up-regulated mRNA of endothelin-1.

CONCLUSION

CsA-induced hypomagnesemia contributes to chronic renal fibrotic lesions seen during CsA treatment through up-regulation of fibrogenic molecules, most notably early activation of tissue inhibitor of matrix metalloproteinase-1 expression.

Pirfenidone treatment decreases transforming growth factor-beta1 and matrix proteins and ameliorates fibrosis in chronic cyclosporine nephrotoxicity

Chronic cyclosporine (CsA) nephrotoxicity is characterized by tubulointerstitial fibrosis. Pirfenidone (PFD) is a novel antifibrotic compound that was shown to prevent and even reverse fibrosis. The mechanism of action of PFD is unclear but involves inhibition of transforming growth factor-beta (TGF-beta). Salt-depleted rats were administered CsA, CsA + PFD, vehicle (VH) or VH + PFD and sacrificed at 28days. Physiologic and histologic changes were studied in addition to TGF-beta1, plasminogen activator inhibitor-1 (PAI-1) and biglycan mRNA expressions by Northern blot. TGF-beta1 immunohistochemistry was also performed. Treatment with PFD ameliorated CsA-induced fibrosis by about 50% (p < 0.05). CsA-induced decrease in creatinine clearance improved with PFD but the difference was not significant. TGF-beta1, PAI-1 and biglycan mRNA expressions increased with CsA (p < 0.05 vs. VH) but strikingly improved with PFD treatment (p < 0.05 vs. CsA), which brought the levels down to VH levels. PFD treatment also decreased TGF-beta1 protein expression by 80%. These results demonstrate that PFD can attenuate renal fibrosis in this model. PFD was associated with a decrease in TGF-beta1 expression, which, in turn, was associated with a decrease in matrix deposition. These experiments suggest that PFD can be clinically useful for preventing chronic CsA nephrotoxicity and may prove to be helpful in other progressive renal diseases.

Aristolochic acids induce chronic renal failure with interstitial fibrosis in salt-depleted rats

Chinese-herb nephropathy (CHN) is a rapidly progressive renal fibrosis associated with the intake of a Chinese herb (Aristolochia fangchi) containing nephrotoxic and carcinogenic aristolochic acids (AA). This study attempted to reproduce the main features of human CHN (renal failure, tubular atrophy, and interstitial fibrosis) in a rat model similar to that of cyclosporin-induced nephropathy. Salt-depleted male Wistar rats received daily subcutaneous injections of either 1 mg/kg body wt AA (low-dose AA group), 10 mg/kg body wt AA (high-dose AA group), or vehicle (control group) for 35 d. On days 10 and 35, assessment of renal function, measurements of urinary excretion of glucose, protein, and leucine aminopeptidase, and histologic analyses were performed (six rats euthanized/group). High-dose AA induced glucosuria, proteinuria, and elevated serum creatinine levels and reduced leucine aminopeptidase enzymuria on days 10 and 35, whereas low-dose AA had no significant effect. Tubular necrosis associated with lymphocytic infiltrates (day 10) and tubular atrophy surrounded by interstitial fibrosis (day 35) were the histologic findings for the high-dose AA-treated rats. In both AA groups, urothelial dysplasia was also observed, as well as fibrohistiocytic sarcoma at the injection site. A short-term model of AA-induced renal fibrosis was established in salt-depleted Wistar rats. These results support the role of AA in human CHN and provide a useful model for examination of the pathophysiologic pathways of renal fibrosis.

Oxalate ions and calcium oxalate crystals stimulate MCP-1 expression by renal epithelial cells

BACKGROUND

Crystals of calcium oxalate monohydrate (COM) and excess oxalate ions (OX) stimulate an array of responses inducing localized injury and inflammation in the kidneys. These inflammatory responses are key regulators of development of nephrolithiasis. We propose that monocyte chemoattractant protein-1 (MCP-1), a chemokine with potent chemotactic activity for monocytes/macrophages, is a mediator of local inflammatory responses to COM and OX-induced injury. To test this hypothesis, the effects of COM and OX on the expression of MCP-1 mRNA and protein by NRK52E rat renal tubular cells were investigated.

METHODS

Confluent cultures of NRK52E cells were exposed to COM (33 to 267 microg/cm2) or OX (125 to 1000 micromol/L, estimated free oxalate levels of 65.8 to 540 micromol/L) and catalase (400 or 2000 U/mL), a free radical scavenger that protects the cells against detrimental effects of COM and OX, for 1 to 48 hours under serum free conditions. The conditioned media were collected and total cellular RNA isolated from the cells and subjected to enzyme-linked immunosorbent assay (ELISA) and semiquantitative polymerase chain reaction (PCR) to determine the expression of MCP-1 protein and mRNA, respectively.

RESULTS

NRK52E cells express MCP-1 mRNA and protein, and the level of their expression significantly increases following treatments with COM and OX in a time and concentration dependent manner. MCP-1 mRNA expression and protein production increased more significantly after exposure to COM than to OX. These responses were significantly reduced following treatments with catalase (2000 U/mL).

CONCLUSIONS

NRK52E cells express MCP-1 mRNA and protein, and their levels are altered following COM and OX exposure. Since catalase treatment reduced MCP-1 expression, free radicals may be involved in the up-regulation of MCP-1 production by the epithelial cells. The results suggest that elevated expression of MCP-1, which is often associated with local inflammatory response, may mediate similar reactions including attraction of macrophages seen around the interstitial crystals during the early stages of nephrolithiasis.

Expression, roles, receptors, and regulation of osteopontin in the kidney

Osteopontin (OPN) is a secreted glycoprotein in both phosphorylated and non-phosphorylated forms. It contains an Arg-Gly-Asp cell-binding sequence and a thrombin-cleavage site. OPN is mainly present in the loop of Henle and distal nephrons in normal kidneys in animals and humans. After renal damage, OPN expression may be significantly up-regulated in all tubule segments and glomeruli. Studies utilizing OPN gene-deficient mice, antisense-treated or anti-OPN-treated animals have demonstrated that OPN promotes accumulation of macrophages, and may play a role in macrophage-mediated renal injury, but that the effect may be mild and short-lived. On the other hand, OPN has some renoprotective actions in renal injury, such as increasing tolerance to acute ischemia, inhibiting inducible nitric oxide synthase and suppressing nitric oxide synthesis, reducing cell peroxide levels and promoting the survival of cells exposed to hypoxia, decreasing cell apoptosis and participating in the regeneration of cells. In addition, OPN is associated with renal stones, but whether it acts as a promoter or inhibitor of stone formation is controversial. It has been demonstrated that OPN receptors include two families: integrin and CD44. The OPN integrin receptors include alpha(v)beta(3), alpha(v)beta(1), alpha(v)beta(5) and alpha(9)beta(1), and alpha(4)beta(1). In normal human kidneys, standard CD44 is expressed most dominantly. Different OPN functions are mediated via distinct receptors. Parathyroid hormone, vitamin D(3), calcium, phosphate and some cytokines increase OPN expression in vitro or in vivo, whereas female sex hormones and angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists decrease OPN expression in some renal damage states.

Obstructive nephropathy in the mouse: progressive fibrosis correlates with tubulointerstitial chemokine expression and accumulation of CC chemokine receptor 2- and 5-positive leukocytes

The infiltration of leukocytes plays a major role in mediating tubulointerstitial inflammation and fibrosis in chronic renal disease. CC chemokines participate in leukocyte migration and infiltration into inflamed renal tissue. Because CC chemokine-directed leukocyte migration is mediated by target cell expression of a group of CC chemokine receptors, this study examined the expression of CC chemokines and their receptors during initiation of tubulointerstitial fibrosis after unilateral ureteral obstruction in C57BL/6 mice. Obstructed kidneys developed hydronephrosis, tubular cell damage, interstitial inflammation, and fibrosis. From days 2 to 10, a progressive interstitial influx of F4/80+ macrophages and CD3+ lymphocytes occurred (macrophages, 4-fold; lymphocytes, 20-fold at day 10, compared with contralateral control kidneys). In parallel, the number of activated fibroblast-specific protein 1+ fibroblasts and interstitial collagen IV accumulation increased from days 2 to 10. The mRNA expression of CC chemokines (predominantly monocyte chemoattractant protein-1 [MCP-1]/CCL2, RANTES/CCL5) and their receptors CCR1, CCR2, CCR5 increased progressively from days 2 to 10. By in situ hybridization, a prominent interstitial mRNA expression of MCP-1 and RANTES and their receptors CCR2 and CCR5 localized to interstitial mononuclear cell infiltrates. MCP-1 and RANTES expression was also seen in tubular epithelial cells. Fluorescence-activated cell sorter analysis of single-cell suspensions from obstructed kidneys revealed a prominent expression of CCR2 and CCR5 by infiltrating macrophages, whereas most lymphocytes expressed CCR5 only. These data demonstrate an increased expression of MCP-1/CCL2 and RANTES/CCL5 at sites of tubulointerstitial damage and progressive fibrosis during unilateral ureteral obstruction that correlates with simultaneous accumulation of interstitial macrophages and T lymphocytes expressing the respective surface receptors CCR2 and CCR5. The chemokine receptor-mediated leukocyte influx into the tubulointerstitium could offer a new potential target for therapeutic intervention in progressive renal tubulointerstitial fibrosis.

Osteopontin expression in human cyclosporine toxicity

BACKGROUND

Osteopontin is a secreted phosphoprotein that has a number of diverse biological functions, including cell signaling, mediation of cell adhesion, migration, and chemoattraction of monocytes/macrophages. Up-regulation of osteopontin expression by proximal tubular epithelium has been demonstrated in both human and rodent models of renal injury in association with macrophage influx.

METHODS

We studied the expression of osteopontin protein and mRNA in renal donor biopsies (N = 7) and renal transplant biopsies with cyclosporine A toxicity (N = 23) by immunohistochemistry and in situ hybridization. Serial tissue sections were immunostained with a monocyte/macrophage marker, CD68, to demonstrate the pattern of macrophage infiltration.

RESULTS

Strong osteopontin expression was observed in the majority of pretransplant donor biopsies in the absence of any macrophage infiltration. In the biopsies with cyclosporine toxicity, osteopontin expression was widespread and demonstrated moderate immunohistochemical signal intensity that did not correlate with the number of interstitial macrophages present.

CONCLUSIONS

Strong osteopontin protein and mRNA expression by tubular epithelium was observed in pretransplant donor biopsies and in biopsies with cyclosporine toxicity without an inflammatory cell infiltration. Therefore, osteopontin expression alone is insufficient to serve as the principal mediator of intrarenal monocyte/macrophage influx in the transplant setting.

Rapid and diverse changes of gene expression in the kidneys of protein-overload proteinuria mice detected by microarray analysis

BACKGROUND

Microarray is a method that allows the analysis of a large number of genes at the same time. We applied this method to show the difference of gene expression in the kidney caused by proteinuria.

METHODS

An experimental mouse model of protein overload was prepared by bovine serum albumin injection. The mRNAs of kidneys isolated after 0, 1, 2, 3 and 4 weeks loading were analysed by Northern blotting. We analysed about 18000 genes by microarray. The expression patterns of the microarray were displayed on control, 1 and 3 weeks of protein overload using the clustering procedure. A clone showing the greatest changes of up-regulation in the kidney was cloned and analysed by in situ hybridization and immunohistochemistry.

RESULTS

Over 1600 kinds of gene expression were confirmed in control kidneys. Proteinuria caused systematic changes of gene expression demonstrated by the cluster analysis. The up-regulation of osteopontin mRNA was shown and confirmed by Northern blot analysis. One of the clones showing the largest changes, AA275245, was isolated and characterized. It revealed that AA275245 was an unreported 3' non-coding region of vinculin mRNA which was associated with cytoskeleton proteins (e.g. alpha-actinin, talin, F-actin). Immunohistochemistry and in situ hybridization showed that this clone was identified in glomeruli as a mesangial pattern. The detected signal intensity using both methods, however, was virtually identical in control and disease kidney models. All data including images and analysed signal intensities are accessible on the web site.

CONCLUSION

The microarray analysis revealed that the renal gene expression pattern was changed dynamically in mice with experimentally induced proteinuria within a few weeks.

Renal osteopontin protein and mRNA upregulation during acute nephrotoxicity in the rat

BACKGROUND

The effect of segment-specific proximal tubular injury on spatio-temporal osteopontin (OPN) distribution was determined in two different nephrotoxic rat models to evaluate its conceivability with a possible role for OPN in acute renal failure (ARF). OPN gene expression was further determined in proximal and distal tubular cells to investigate the origin of increased renal OPN.

METHODS

Renal OPN protein and mRNA expression were compared in the rat during mercuric-chloride- vs gentamicin-induced ARF using immunohistochemistry and in situ hybridization.

RESULTS

Mercuric chloride primarily induced tubular injury and subsequent cell proliferation in proximal straight tubules (PST), whereas gentamicin predominantly injured proximal convoluted tubules (PCT). In both models, the distribution of OPN protein was associated with increased OPN mRNA levels in proximal as well as distal tubular cells. However, upregulation was delayed in the proximal tubular segment suffering most from injury, i.e. PCT in gentamicin ARF vs PST in mercuric-chloride ARF. OPN immunostaining at the apical cell membrane from distal tubules was in contrast to perinuclear vesicular staining in proximal tubular cells.

CONCLUSIONS

OPN gene and protein expression is induced in both proximal and distal tubular cells during rat toxic ARF. The distinct subcellular localization in proximal vs distal tubular cells indicates differences in OPN processing and/or handling. The spatio-temporal distribution is consistent with a possible role in renal injury and regeneration.

Viral delivery of superoxide dismutase gene reduces cyclosporine A-induced nephrotoxicity

BACKGROUND

Cyclosporine A (CsA) increases free radical formation in the kidney. Accordingly, this study investigated whether gene delivery of superoxide dismutase (SOD) reduced radical production and nephrotoxicity caused by CsA.

METHODS

Rats were given adenovirus (Ad) carrying lacZ or Cu/Zn-SOD genes three days prior to CsA treatment. Histology, glomerular filtration rates (GFRs) and free radical adducts in urine were assessed.

RESULTS

SOD activity was increased 2.5-fold three days after viral infection and remained at 2- and 1.6-fold higher 10 and 17 days later. Treatment with CsA for seven days decreased GFR by 70% in rats infected with Ad-lacZ as expected; however, the decrease was diminished significantly in rats receiving Ad-SOD. CsA treatment for two weeks caused a loss of brush border and dilation of proximal tubules, necrosis, and increased leukocyte infiltration into the kidney; these effects were minimized by SOD. Dimethyl sulfoxide (DMSO) was attacked by the hydroxyl radical to produce a methyl radical. Indeed, administration of CsA with 12C-DMSO in rats infected with Ad-lacZ produced a radical adduct with hyperfine coupling constants similar to 4-POBN/methyl radical adduct and another unknown radical adduct. CsA given with 13C-DMSO produced a 12-line spectrum, confirming the involvement of hydroxyl radicals. Free radical adducts detected in urine were increased approximately fivefold by CsA, an effect blocked completely by SOD.

CONCLUSIONS

CsA increases free radical formation. Gene delivery of SOD blocks formation of free radicals, thereby minimizing nephrotoxicity caused by CsA.

Post-cyclosporine-mediated hypertension and nephropathy: amelioration by vascular endothelial growth factor

Recent studies have demonstrated a role for microvascular and tubulointerstitial injury in some models of salt-sensitive hypertension. We utilized a model of post-cyclosporin A (CsA) nephropathy and hypertension to test the hypothesis that treatment with an angiogenic factor aimed at ameliorating the microvascular and renal injury would prevent the development of hypertension. CsA was administered with a low-salt diet for 45 days, resulting in a renal lesion characterized by afferent arteriolopathy, focal peritubular capillary loss, and tubulointerstitial fibrosis. Rats were then placed on a high-salt diet and randomized to receive either vascular endothelial growth factor (VEGF(121)) or vehicle for 14 days. Placement of rats with established CsA nephropathy on a high-salt diet results in the rapid development of salt-sensitive hypertension. VEGF(121) treatment resulted in lower blood pressure, and this persisted on discontinuing the VEGF. VEGF(121) treatment was also associated with a decrease in osteopontin expression, macrophage infiltration, and collagen III deposition and markedly stimulated resolution of the arteriolopathy (20.9 +/- 7.8 vs. 36.9 +/- 6.1%, VEGF vs. vehicle, P < 0.05). In conclusion, CsA-associated renal microvascular and tubulointerstitial injury results in the development of salt-sensitive hypertension. Treatment of animals with established CsA nephropathy with VEGF reduces the hypertensive response and accelerates histological recovery. The vascular protective effect of VEGF may be due to the improvement of arteriolopathy. Angiogenic growth factors may represent a novel strategy for treating CsA-associated hypertension and renal disease.

Immunohistochemical analysis of renin activity in chronic cyclosporine nephropathy in childhood nephrotic syndrome

Although the pivotal role of activation of the intrarenal renin-angiotensin system (RAS) has been demonstrated in the rat model of chronic cyclosporine (CyA) nephropathy, it is still unclear whether intrarenal RAS activation is responsible for chronic CyA nephropathy in humans. Therefore, the distribution of renin in formalin-fixed, paraffin-embedded renal biopsy specimens obtained from 26 children who had idiopathic nephrotic syndrome (NS) and who were treated with long-term moderate-dose CyA was examined with the use of immunohistochemistry with rabbit polyclonal anti-human renin antibody. Nineteen patients had steroid-dependent NS, and 7 had steroid-resistant NS. However, CyA treatment led all of the latter patients into complete remission. All of the patients underwent renal biopsies at the start and the end of CyA treatment. In the pre-CyA specimens, immunoreactivity to renin was detected mainly in those parts of arterioles within the anatomically well-defined juxtaglomerular apparatus. In the post-CyA specimens, it was also detected in those parts of the vessels upstream from the juxtaglomerular apparatus. Moreover, the ratio of the number of renin-positive cells to the number of glomeruli (histologic renin index) increased significantly with long-term CyA treatment (from 1.26+/-0.24 to 4.30+/-0.40, P<0.0001). Eleven of the post-CyA specimens showed mild or moderate CyA-associated arteriolopathy (CAA), whereas 15 showed no CAA. The histologic renin index was significantly higher in specimens with CAA than in those without CAA (5.16+/-0.59 versus 3.67+/-0.48, P = 0.031). Seven CAA-positive patients underwent repeat biopsies 6 to 12 mo after discontinuing the CyA. Their specimens showed an improvement in the CAA and significantly lower histologic renin index compared with the post-CyA (from 4.18+/-0.69 to 2.10+/-0.25, P = 0.018). Eleven of the post-CyA specimens showed mild to moderate interstitial fibrosis, and 15 showed no fibrosis. There was no significant difference in immunoreactivity to renin between the specimens with interstitial fibrosis and those without. However, patients with interstitial fibrosis had significantly longer periods of heavy proteinuria during CyA therapy, because of either steroid-resistant NS or frequent relapses of NS (83+/-18 versus 35+/-12 d, P = 0.030). These findings indicate that long-term CyA treatment for idiopathic NS in children may stimulate renin production in arterioles. They also suggest that CyA-stimulated intrarenal RAS activation is responsible for the development of CAA and that CyA-induced interstitial fibrosis is potentiated by long-term heavy proteinuria and is at least partly independent of CyA-stimulated intrarenal RAS activation.

Lack of in vivo function of osteopontin in experimental anti-GBM nephritis

Osteopontin (Opn) is a potent chemoattractant for mononuclear cells that is upregulated in various inflammatory states of the kidney. Opn is believed to contribute to mononuclear cell infiltration and renal injury. The importance of Opn was examined in vivo in rapidly progressive glomerulonephritis in Opn knockout mice. Glomerulonephritis was induced by intravenous injection of rabbit anti-mouse glomerular basement membrane antiserum in mice that had been presensitized to rabbit IgG. Immunologic responsiveness to rabbit IgG (assessed by cutaneous delayed-type hypersensitivity and antibody titers) showed no significant difference between wild-type and Opn -/- mice. Proteinuria was also similar in both groups. Glomerular crescent formation was not different in Opn +/+ and -/- groups (26 +/- 6% versus 29 +/- 7%). Tubulointerstitial infiltration was assessed qualitatively and showed no significant difference between the two genotypes. Formation of thrombi in the glomerular capillaries on a scale from 0 to 3 also showed no significant difference (1.3 +/- 0.3 for Opn +/+ and 1.4 +/- 0.3 for Opn -/- mice). Northern blot analysis of total kidney RNA showed a 5.1-fold increase of Opn expression in Opn +/+ mice compared with untreated controls and the absence of expression in Opn -/- mice, as expected. Regulated upon activation, normal T cell expressed and secreted (RANTES) and monocyte chemoattractant protein-1 mRNA levels were also markedly upregulated with no significant difference between the two strains, excluding compensatory overexpression of these two chemokines in Opn -/- mice. It is concluded that the known upregulation of Opn in murine anti-glomerular basement membrane nephritis does not significantly contribute to the glomerular and tubulointerstitial mononuclear cell infiltration in this model.

Effect of nitric oxide modulation on TGF-beta1 and matrix proteins in chronic cyclosporine nephrotoxicity

BACKGROUND

Chronic cyclosporine (CsA) nephrotoxicity is characterized by interstitial fibrosis and afferent arteriolar hyalinosis. L-arginine (L-Arg), the substrate for nitric oxide (NO) synthase and N-nitro-L-arginine-methyl ester (L-NAME), the NO synthase inhibitor, were shown to modulate acute CsA nephrotoxicity. However, the mechanism of fibrosis in chronic CsA nephrotoxicity remains unclear. Thus, we examined the effect of NO modulation on fibrosis and the expression of transforming growth factor-beta1 (TGF-beta1) and matrix proteins in chronic CsA nephrotoxicity.

METHODS

Rats were administered CsA (7.5 mg/kg), CsA + L-Arg (1.7 g/kg), CsA + L-NAME (3.5 mg/kg), vehicle (VH), VH + L-Arg, and VH + L-NAME, and were sacrificed at 7 or 28 days. NO production, physiologic parameters, and histology were studied in addition to the mRNA expression of TGF-beta1, plasminogen activator inhibitor-1 (PAI-1) and the matrix proteins biglycan and collagens type I and IV by Northern and the protein expression of PAI-1 and fibronectin by enzyme-linked immunosorbent assay.

RESULTS

While L-NAME strikingly reduced NO biosynthesis and worsened the glomerular filtration rate and CsA-induced fibrosis, L-Arg had the opposite beneficial effect. In addition, the CsA-induced up-regulated expression of TGF-beta1, PAI-1, and the matrix proteins biglycan, fibronectin, and collagen I was significantly increased with L-NAME and strikingly improved with L-Arg. Collagen IV expression was not affected. Also, NO modulation did not affect VH-treated rats.

CONCLUSIONS

Chronic CsA nephrotoxicity can be aggravated by NO blockade and ameliorated by NO enhancement, suggesting that NO maintains a protective function. NO modulation was associated with a change in TGF-beta1 expression, which, in turn, was associated with alterations in matrix deposition and matrix degradation through its effect on PAI-1.