Elevated interleukin-18 levels in the urine of nephrotic patients

BACKGROUND/AIM: The etiology of minimal-change nephritic syndrome (MCNS) is obscure. It has been speculated that T cells play a role in the pathogenesis of MCNS. Interleukin (IL)-18, a novel immunoregulatory cytokine with potent inferon-gamma-inducing activities, may play an important role in T-helper type 1-mediated immune responses. To examine further the possible role of IL-18 in nephrotic syndrome (NS), in the present study we measured IL-18 levels in the urine in different clinical stages of MCNS. The aim of this study was to investigate the involvement of IL-18 in MCNS. METHODS: Urine samples were obtained from 20 MCNS patients. The disease controls included 20 patients with IgA nephropathy. The samples were assayed for IL-18 protein by a sandwich enzyme-linked immunosorbent assay. RESULTS: Compared with normal controls, significantly increased urinary levels of IL-18 were detected in MCNS patients with the NS. The urinary IL-18 (uIL-18) levels correlated with the degree of proteinuria in MCNS patients. Moreover, when individual MCNS patients were followed through their clinical illness, uIL-18 levels were increased during the active phase and decreased as the patients went into remission. CONCLUSIONS: These results indicate that uIL- 18 is detectable in a subgroup of patients with active NS and correlates to their disease activity in patients with MCNS. Our findings support the notion that IL-18 may play a role in the pathophysiology of NS.     

Elevated vascular endothelial growth factor levels in the urine of patients with minimal-change nephrotic syndrome

BACKGROUND: Vascular endothelial growth factor (VEGF) is a selective endothelial mitogen and vascular permeability factor (VPF), that is mainly produced by activated monocytes/macrophages and T cells. To our knowledge, very little is known about the involvement of VEGF in minimal-change nephrotic syndrome (MCNS). The aim here was to define further the involvement of VEGF in MCNS. PATIENTS AND METHODS: Urine samples were obtained from 20 MCNS patients. The disease controls included 20 patients with IgA nephropathy (IgAN). The samples were assayed for VEGF protein by a sandwich enzyme-linked immunosorbent assay (ELISA). RESULTS: Compared with normal controls, markedly increased urinary levels of VEGF were detected in both MCNS and IgAN patients with the nephrotic syndrome (NS). The urinary VEGF (uVEGF) levels correlated with the degree ofproteinuria in MCNS and IgAN patients. Moreover, when individual MCNS patients were followed through their clinical illness, uVEGF levels were increased during the active phase and decreased as the patients went into remission. Our main concern is to distinguish between two possibilities: Increases in uVEGF excretion might indeed relate to specific glomerular pathology and thus have a pathophysiological role. Alternatively, uVEGF may be derived from the circulation and as such may be nothing more than an assay for proteinuria. In fact, given the strict correlation between uVEGF excretion and the amount of proteinuria, the second possibility appears quite conceivable. CONCLUSION: Therefore, this may be a coincidental finding which has no bearing on the pathophysiology of MCNS.     

Augmented interleukin-18 production by peripheral blood monocytes in patients with minimal-change nephrotic syndrome

BACKGROUND/AIM: The etiology of minimal-change nephrotic syndrome (MCNS) is poorly understood. It has been proposed that cell-mediated immunity and T-cell activation are key features of this glomerular disease. Interleukin (IL)-18, a novel interferon-gamma-stimulating factor, may act as an important effector molecule involved in various immune responses. To our knowledge, very little is known about the involvement of IL-18 in NCNS. The aim here was to define further the involvement of IL-18 in MCNS. METHODS: To understand the role of this cytokine, in vitro IL-18 levels were analyzed by a sensitive enzyme-linked immunosorbent assay (ELISA) method in 16 patients with MCNS who were either in a stable or active condition. The disease controls included 16 patients with IgA nephropathy (IgAN). The IL-18 levels were compared with values in healthy controls. RESULTS: Significantly increased spontaneous and lipopolysaccharide (LPS)-stimulated production of IL-18 was detected in peripheral blood monocyte (PBM) cultures of MCNS patients with the nephrotic syndrome (NS) as compared with those of normal controls. Moreover, when individual MCNS patients were followed through their clinical illness, IL-18 levels were increased during the active phase and normalized as the patients went into remission. The amounts of IL-18 are significantly correlated with the levels of vascular permeability factor (VPF) in MCNS patients. CONCLUSIONS: Thus, in MCNS patients, the level of IL-18 was increased and this increase was related to the activity of this disease. The data provide circumstantial evidence for a role of IL-18 in MCNS.     

Urinary levels of macrophage migration inhibitory factor in patients with IgA nephropathy

BACKGROUND/AIM: The processes involved in development of IgA nephropathy (IgAN) are not yet well understood. Macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine and is an essential component of immune and inflammatory responses. To examine further the possible role of MIF in IgAN, we measured MIF levels in the urine. The purpose of the present study was to evaluate the involvement of MIF in IgAN. METHODS: Urine samples were obtained from 20 IgAN patients. The disease controls included 20 patients with minimal-change nephrotic syndrome (MCNS). A group of healthy subjects served as control. The samples were assayed for MIF protein by a sandwich enzyme-linked immunosorbent assay (ELISA). RESULTS: The MIF levels in the urine of patients with IgAN examined were significantly higher than those of the healthy control subjects. In contrast, the levels of urinary MIF (uMIF) in patients with MCNS did not differ significantly from normal values. In IgAN patients, uMIF significantly correlated with the magnitude of proteinuria, but not with the grade of hematuria. We also investigated the relationship between uMIF levels and pathological features. Among patients with IgAN, uMIF levels were significantly correlated with the grade of glomerular crescent formation and that of mesangial cell proliferation. There was also a significant correlation between uMIF levels and the number of both intraglomerular and interstitial macrophages. CONCLUSION: Although the underlying mechanisms remain to be determined, these data provide evidence that urinary excretion of MIF is increased in IgAN patients with active renal lesions.     

Renal dopaminergic system in nephrotic syndrome and after remission

Background. Although intrarenal dopamine is known to behave as an endogenous natriuretic hormone the role of the renal dopaminergic system in the sodium handling of nephrotic oedema remains unknown. Study design. We monitored the daily urinary excretion of free dopamine, L-DOPA - its precursor, and its metabolites, DOPAC and HVA, during sodium retention accompanying the nephrotic state and natriuresis leading to oedema mobilization in eight patients (mean age 8.0±2.4 years) with drug-induced remission of minimal-change nephrotic syndrome (MCNS). Results. During natriuresis the urinary levels of dopamine did not increase in any of the eight patients studied. Moreover, after remission of the nephrotic syndrome the urinary levels of dopamine were significantly lower than during the nephrotic state (1565.3±361.7 vs 2416.1±558.4, P=0.02). In contrast, the urinary excretion of L-DOPA increased markedly during natriuresis resulting from remission of proteinuria (from 87.0±40.5 up to 296.9±86.3 nmol/24 h; P<0.01). Conclusion. We conclude that the natriuretic response resulting from drug-induced remission of proteinuria in MCNS is accompanied by a decrease in the renal uptake/decarboxylation of L-DOPA to dopamine.     

Lower urinary-interleukin-1 receptor-antagonist excretion in IgA nephropathy than in Henoch-Sch?nlein nephritis.

BACKGROUND: IgA nephropathy (IgAN) and Henoch-Sch?nlein nephritis (HSN) share many clinical, histological and immunological features. It has been postulated that these two conditions have a common pathogenesis and that HSN might be a systemic form of IgAN. Activity of interleukin-1beta (IL-1beta) in urine has been found to be higher in IgAN and HSN patients than in healthy controls. Interaction between IL-1beta and interleukin-1 receptor antagonist (IL-1ra) plays a significant role in the regulation of inflammatory responses. We studied levels of urinary excretion of IL-1beta and IL-1ra in patients with IgAN and HSN. METHODS: Amounts of IL-1beta and IL-1ra excreted in 24-h urine samples collected from 241 IgAN, 26 HSN patients and from 33 healthy controls were determined. Results were expressed as cytokine/creatinine (ng/mmol) ratios. RESULTS: Urinary IL-1beta excretion by the IgAN and HSN patients was no greater than urinary IL-1beta excretion by healthy controls. Urinary IL-1ra excretion by the IgAN patients was lower than urinary IL-1ra excretion by healthy controls (P < 0.05) and by the HSN patients (P < 0.01). In both patients and controls women had significantly higher IL-1ra, IL-1beta excretion levels and IL-1ra/IL-1beta ratios. The differences in urinary excretions of IL-1ra by the healthy controls and by the IgAN and HSN patients were significant in both sexes. Excretion of IL-1beta or IL-1ra did not correlate with excretion of urinary protein, duration of the disease or any histopathological variable. However, histopathological changes in renal biopsy specimens from patients with IL-1ra/IL-1beta ratios above normal were significantly milder than in renal biopsy specimens from patients with low or normal IL-1ra/IL-1beta ratios. CONCLUSION: Urinary IL-1ra levels in IgAN patients were lower than urinary IL-1ra levels in healthy controls or HSN patients, a finding which may indicate that the two diseases have a different pathogenesis. Whether the male predominance in IgAN and HSN and the worse outcomes in males that have been reported previously in IgAN and HSN are connected with the lower excretion of IL-1ra and consequently lower IL-1ra/IL-1beta ratios in male patients than in female patients needs more thorough investigation.     

The urinary podocyte as a marker for the differential diagnosis of idiopathic focal glomerulosclerosis and minimal-change nephrotic syndrome

BACKGROUND/AIMS: Detection of podocytes in the urine sediment of children indicates that severe podocyte injury occurred in the glomerulus. Focal glomerulosclerosis (FGS) and minimal-change nephrotic syndrome (MCNS) are kidney diseases characterized by massive proteinuria. The aim of the present study was to determine whether urinary podocytes can be detected in patients with idiopathic FGS or MCNS and whether immunosuppression therapy alters these cells. METHODS: Twenty patients with MCNS (nephrotic stage, n = 12; remission stage, n = 8), 15 patients with FGS and 20 healthy controls were included in the present study. Urinary podocytes were stained by immunofluorescence. All patients with MCNS at the nephrotic stage received prednisolone for 6 months, and all patients with FGS received some form of immunosuppression therapy including prednisolone, cyclophosphamide or mizoribine for 12 months. RESULTS: The 12 nephrotic-stage MCNS patients achieved remission after treatment. Seven of the 15 FGS patients also achieved remission, but the other 8 remained in the nephrotic stage. Urinary podocytes were not detected in any patient with MCNS nor were they detected in healthy controls. Urinary podocytes were detected in all FGS patients (mean, 4.2 cells/ml) before treatment and the number of cells decreased in the 7 patients who achieved remission. The number of podocytes was unchanged in the other 8 patients even after treatment. CONCLUSION: Urinary podocytes may be a useful diagnostic indicator for differentiation between FGS and MCNS. These cells may also mark disease progression in cases of FGS.     

Elevated urinary neopterin: A clue of activated macrophage and cellular immune response in the pathogenesis of idiopathic nephrotic syndrome

Summary: A study of cell mediated immunity (CMI) activation in patients with idiopathic nephrotic syndrome (INS) in the tropics was undertaken. Cell mediated immunity activation was investigated by measuring urinary neopterin excretion. All 31 patients with idiopathic nephrotic syndrome due to either minimal change nephrotic syndrome (MCNS), and focal and segmental glomerulosclerosis (FSGS) had significant elevation of neopterin excretion (mean values 451, 544 μmol neopterin/mol creatinine) when compared with 222 normal subjects (mean value 130, P < 0.001). However, in 25 patients with non-nephrotic IgA nephropathy and eight nephrotic membranous nephropathy the urinary neopterin was not raised (mean value 131 and 129). A further 10 patients with MCNS were restudied when in complete remission and their urinary neopterin was found to have decreased significantly (mean value 186); however, this level was still above the normal range. Our study suggests that CMI and macrophage activation takes place in the pathogenesis of idiopathic nephrosis.     

Interleukin-17 stimulates the release of pro-inflammatory cytokines by blood monocytes in patients with IgA nephropathy

OBJECTIVE: Interleukin-17 (IL-17) is a newly discovered cytokine implicated in the regulation of inflammation. The present study was designed to explore whether IL-17 is involved in the immunoregulatory response in IgA nephropathy (IgAN). MATERIAL AND METHODS: We examined the in vitro effect of recombinant human IL-17 (rhIL-17) on pro-inflammatory cytokine release by peripheral blood monocytes (PBM) from patients with IgAN. Measurement of IL-1beta and tumor necrosis factor-alpha (TNF-alpha) was performed by means of a sandwich enzyme-linked immunosorbent assay. RESULTS: IL-1beta and TNF-alpha release were upregulated by rhIL-17 in a dose- and time-dependent fashion. Treatment of PBM from patients with IgAN with lipopolysaccharide and rhIL-17 resulted in significant activation and release of IL-1beta and TNF-alpha protein. Levels of IL-1beta and TNF-alpha were significantly higher in IgAN patients with the nephrotic syndrome (NS) than in patients without NS or in healthy subjects. We also provide information indicating that there is excessive production of IL-17 in IgAN patients. When IL-17-activated PBM were incubated in the presence of IL-10, IL-10 exerted a significant suppressive effect on IL-1beta and TNF-alpha release in vitro. CONCLUSION: IL-17 can stimulate the release of pro-inflammatory cytokines from PBM in patients with IgAN.     

Effects of interleukin-15 on vascular permeability factor release by peripheral blood mononuclear cells in normal subjects and in patients with minimal-change nephrotic syndrome

The characteristic function of interleukin (IL)-15 appears to be its ability to mimic the stimulatory action of IL-2 on lymphocytes by utilizing part of the IL-2 receptor complex. To gain insight into the immunoregulatory properties of this cytokine in patients with minimal-change nephrotic syndrome (MCNS), we analyzed effects of IL-15 on vascular permeability factor (VPF) release in vitro. Peripheral blood mononuclear cells (PBMC) were isolated from 16 patients with MCNS, 16 patients with IgA nephropathy (IgAN) and 16 healthy controls. Cells were stimulated with concanavalin A (Con A) and the VPF was assessed using the method of Lagrue with minor modifications. PBMC secreted significantly increased amounts of VPF under stimulation with Con A in patients with MCNS and IgAN patients with the nephrotic syndrome as compared with normal controls. Here we have demonstrated, for the first time, that addition of IL-15 to PBMC obtained from nephrotic patients as well as from normal controls increased Con A-induced release of VPF by 250%. This stimulatory effect was found highly significant and was dose-dependent. The effect of IL-15 on the secretion of VPF was specific, since a complete reversion was obtained with a neutralizing antibody to human IL-15. Our findings reveal that IL-15 has the potential to function as an immunoregulatory molecule of PBMC VPF release. In addition, IL-15 had similar effects to IL-2 in terms of its capacity to upregulate VPF release. Taken together, our data emphasize a positive regulatory role for IL-15 in inducing the release of VPF when present at optimal levels. Therefore, IL-15 antagonists may provide a basis for immune intervention in the pathophysiology of VPF.     

Interleukin-15 and interleukin-12 have an additive effect on the release of vascular permeability factor by peripheral blood mononuclear cells in normals and in patients with nephrotic syndrome.

BACKGROUND: The vascular permeability factor (VPF) is a lymphokine that has been shown to play a role in minimal-change nephrotic syndrome (MCNS). A better understanding of the mechanisms that upregulate VPF release is of basic importance to control the immune system in nephrotic syndrome (NS). Interleukin (IL)-15 is a key inducer of differentiation of uncommitted T helper cells, which regulates cellular immunity. The cytokine IL-15 appears to mimic the stimulatory activity of IL-2 on T cells. PATIENTS AND METHODS: In the present report, we studied the ability of IL-15, alone or in combination with IL-12, to influence the release of VPF by peripheral blood mononuclear cells (PBMC) from nephrotic patients. We have analyzed the release of VPF by concanavalin-A- (Con A) stimulated PBMC in normals, 16 patients with MCNS and 16 patients with IgA nephropathy (IgAN). RESULTS: In both patient groups 50% had a proteinuria below 0.8 g/day. We demonstrate that nephrotic, but not non-nephrotic patients (both MCNS and IgAN), exhibit a high VPF release, which can be stimulated further by IL-15 + IL-12. To determine the specificity of the stimulatory effect, neutralizing anti-IL-15 and anti-IL-12 antibodies were preincubated with IL- 15 and IL-12 prior to the addition of responder cells, respectively. The antibodies completely inhibited the effects of IL-15 and IL-12. CONCLUSION: These results indicate that IL-15 plus IL-12 acted additively to augment VPF release. These biological interactions between IL-15 and IL-12 may be important in the pathophysiology of VPF in vitro.     

Zinc and copper metabolism in nephrotic syndrome

The effect of proteinuria on urinary zinc and copper excretion was studied in children with nephrotic syndrome (NS). Clearance, fractional excretion, and urinary excretion of zinc and copper were significantly higher in children with relapse of NS than in the same children with remission of NS or in healthy children. A linear correlation was found between proteinuria and urinary zinc and copper excretion in relapse of NS. The results of this study suggest that zinc and copper deficiency in NS may be related also to increased urinary zinc and copper losses.     

Daily urinary interleukin-11 excretion correlated with proteinuria in IgA nephropathy and lupus nephritis

Interleukin-11 (IL-11) is a multifunctional cytokine with both thrombopoietic and anti-inflammatory effects. In an animal study IL-11 was shown to reduce proteinuria in mice with necrotizing glomerulonephritis. The purpose of this current study is to explore the role of IL-11 in human glomerulonephritis. Subjects of this study were patients with proteinuria (daily urine protein excretion >40 mg/m² per hour) and underlying pathology of IgA nephropathy (IgAN) (n=20), lupus nephritis (LN) (n=40), and idiopathic nephrotic syndrome (INS) (n=68). Daily urinary IL-11 level was measured by enzyme-linked immunosorbent assay (ELISA). Correlation between urinary IL-11 and urinary protein was determined by Pearson’s correlation coefficient. Another five patients with serial data of urinary protein, IL-11 and IL-11 messenger RNA (mRNA) expression in urine sediment are presented. The correlation between urinary IL-11 and daily urinary protein was significant for patients with IgAN (r=0.596, P=0.006) and LN (r=0.630, P<0.001), but not for patients with INS (r=0.030, P=0.812). Serial data revealed the same correlation. Furthermore, the peak of urinary IL-11 mRNA preceded that of urinary IL-11. We conclude that daily urinary IL-11 excretion is correlated with urinary protein loss in nephritis having local T helper (Th)1 predominant immune response, such as IgAN and LN. Local IL-11 production may serve as a counter cytokine against Th1-mediated inflammation.     

Increased production of macrophage migration inhibitory factor by T cells in patients with IgA nephropathy.

BACKGROUND/AIM: Several studies have demonstrated an upregulation of macrophage migration inhibitory factor (MIF) synthesis in experimental glomerulonephritis. To our best knowledge, no investigation of MIF production by T cells from patients with IgA nephropathy (IgAN) has been reported so far. MIF is one of the immunoregulatory cytokines involved in T-cell activation and delayed-type hypersensitivity. In this study, we examined MIF production of T cells from patients with IgAN to investigate the contribution of the cells to elevated serum MIF content and to its pathologic characteristics. METHODS: We measured MIF production by T cells from the peripheral blood of 20 healthy controls and 20 patients with IgAN before and approximately 10 days after the beginning of steroid therapy. The disease controls included 20 patients with minimal-change nephrotic syndrome (MCNS) before therapy. MIF concentrations in the supernatants of T-cell cultures were measured with a specific enzyme-linked immunosorbent assay (ELISA). We also investigated the relationship between MIF levels and disease activity. RESULTS: The mean level for MIF in patients with IgAN was significantly elevated compared with that of healthy controls and also higher than that of patients with MCNS. When T cells were stimulated by concanavalin A, MIF production by T cells of patients with IgAN was more enhanced than in control subjects or patients with MCNS. We also investigated the relationship between MIF levels and pathological features in IgAN patients. Our findings reveal that MIF levels correlated with the grade of glomerular crescent formation and immunofluorescent C3 deposits in the glomeruli. Moreover, MIF overproduction was significantly related to the acute exacerbation stage of IgAN patients. Elevated MIF levels during the acute phase or exacerbations were found to be decreased during spontaneous or steroid therapy-induced remission in all IgAN patients examined. CONCLUSIONS: We provide data indicating that a T-cell population isolated by negative selection from peripheral blood mononuclear cells shows increased in vitro production of MIF in IgAN, and a reduction in that production when patients are treated with corticosteroids. In this paper, we describe the hypothetical role of MIF in the pathophysiology of IgAN.     

The differential diagnostic value of urinary enzyme and amino acid excretion in children with nephrotic syndrome

Urinary enzymesN-acetyl--d-glucosaminidase (NAG) and -glutamyl transpeptidase (-GT) are sensitive markers of specific renal cell damage. Excessive urinary amino acid excretion may also be an indicator of renal tubular damage. We have evaluated urinary excretion of NAG,-GT and 37 amino acids, phospholipids and dipeptides in 30 children (aged 2.3–18.1 years) with nephrotic syndrome (NS), 23 with minimal change nephrotic syndrome (MCNS), 7 with focal segmental glomerulosclerosis (FSGS) and 16 healthy age-matched controls. Nine MCNS patients were in relapse and 14 in remission. Enzyme activity is expressed as micromoles per milligram urinary creatinine. In FSGS, NAG excretion correlated with the following: blood urea nitrogen (BUN) (r=0.8), serum protein (r=0.57), serum cholesterol (r=0.85), serum albumin (r=–0.68) and proteinuria (r=0.56). In FSGS the -GT excretion was not significantly different from MCNS in remission or in relapse. In FSGS, -GT excretion correlated with the following: BUN (r=0.48), serum creatinine (r=–0.66), serum protein (r=–0.54), serum albumin (r=–0.68) and serum cholesterol (r=0.87). Compared with controls, the urinary excretion of 5 amino acids was increased in FSGS patients as a possible indicator of tubular damage. The value for 7 amino acids was reduced in MCNS patients. Urinary amino acid excretion was not different from controls for the other amino acids in either FSGS or MCNS. These data suggest that urinary enzyme excretion, particularly NAG excretion, and amino acid excretion may be useful in the diagnosis and degree of disease in these histological forms of NS in children.Crippled Childrens Foundation Research Center     

C1q nephropathy and minimal change nephrotic syndrome

C1q nephropathy (C1qN) is an uncommon disorder seen in children and adults with nephrotic syndrome and non-specific urinary findings. It has been described with minimal change nephrotic syndrome (MCNS), focal segmental glomerulonephritis and isolated mesangial proliferative glomerulonephritis. We describe nine children with MCNS and mesangial C1q deposition. These children had a median age of 2.7 years at diagnosis (range 1.3–15 years), 56% were male and 78% were Hispanic. We compared these children to concurrent patients with nephrotic syndrome and biopsy-proven MCNS. We found that the C1qN patients were more likely than MCNS children to require chronic immunosuppression with calcineurin inhibitors or mycophenolate mofetil to maintain remission. However, all children were able to achieve and sustain clinical remission of nephrotic syndrome. Children with C1qN and minimal change histology have an increased frequency of frequently relapsing and steroid-unresponsive disease, but they can attain prolonged remission and stable renal function with calcineurin inhibitor or mycophenolate mofetil therapy.     

Complement activation products in the urine from proteinuric patients

The presence of plasma proteins in the tubular lumen has variety of adverse effects on the tubular cells. Among various plasma proteins filtered through glomerular barrier, complement has been proven as the possible candidate inducing tubulointerstitial injury. To study the role of intratubular complement activation in proteinuric patients, complement activation products (CAP) at C3 level (iC3b and Bb) and C9 level (membrane attack complex) were measured in both plasma and urine of patients with minimal change nephrotic syndrome (MCNS), focal glomerular sclerosis, IgA nephropathy, membranous nephropathy, and diabetic nephropathy. For evaluation of the effect of metabolic acidosis on the intratubular complement activation, urinary CAP were measured before and after sodium bicarbonate administration in patients with renal insufficiency. The following results were obtained: (1) Patients with focal glomerular sclerosis and diabetic nephropathy showed the highest level of urinary CAP excretion rate (unit/creatinine), while MCNS revealed no increase. (2) Patients with membranous nephropathy showed a unique finding, i.e., isolated increase of membrane attack complex excretion. (3) There was no significant correlation between urine and plasma levels of CAP. (4) Except for MCNS patients, the urinary excretion rate of CAP significantly increased when the level of proteinuria exceeded the nephrotic range, and it was significantly correlated with the serum creatinine level. (5) Urinary CAP excretion rate significantly decreased 2 wk after sodium bicarbonate administration without affecting the level of proteinuria or plasma CAP. These results suggest that the degree of intratubular complement activation correlates with the level of proteinuria, type of glomerular disease, impairment of renal function, and metabolic acidosis.     

Adrenomedullin and nitrite levels in children with minimal change nephrotic syndrome

Nitric oxide (NO) serves many functions within the kidney, and recent evidence suggests that NO contributes to glomerular injury. Adrenomedullin (AM) is a novel hypotensive peptide originally isolated from human pheochromocytoma. Recent studies showed that plasma AM concentrations correlated with the extent of proteinuria. We have examined the possible role of these two agents by studying plasma and urinary total nitrite (NO⁻ ₂ + NO⁻ ₃) and AM levels in children with minimal change nephrotic syndrome (MCNS). In comparison with healthy controls, children with MCNS had increased urinary nitrite excretion (μmol/mg urinary creatinine), irrespective of whether the disease was in relapse or remission (3.2±0.2 in relapse, n=13; 1.9±0.3 in remission, n=12; 1.0±0.2 in controls, n=10, P<0.05). Plasma nitrite levels (μmol/l) were high in relapse compared with controls (53.2±8.7 vs. 32±4.0, P<0.05). Plasma AM levels (pmol/ml) were decreased in relapse (27.6±1.4 in relapse, 43.3±1.2 in remission, 41.5±1.6 in controls, P<0.05). Urinary AM levels (pmol/mg urinary creatinine) were significantly higher in relapse than in remission and in controls (156±43 in relapse, 56±18 in remission, 36±16 in controls, P<0.05). Our data indicate that NO may play a role in mediating the clinical manifestations of MCNS in children. However, changes in AM levels may be the result of heavy proteinuria. Received: 20 December 1999 / Revised: 12 June 2000 / Accepted: 15 June 2000     

Endothelin-1 in the kidney and urine of patients with glomerular disease and proteinuria

BACKGROUND: Endothelin-1 (ET-1) is a strong vasoconstrictive peptide that is involved in the pathogenesis of arterial hypertension. There is increasing evidence, based on studies in experimental animals, that endothelin-1 is produced by tubular epithelial cells in response to activation by filtered protein and is involved in the development of renal scarring. The aim of this study is to examine the distribution of ET-1 in the renal tissue of patients with heavy proteinuria and to estimate the changes in its urinary excretion after immunosuppressive therapy. PATIENTS AND METHODS: Twenty-four patients with severe proteinuria (7.5 +/- 6.5 g/24 h) due to different types of glomerular disease and normal renal function (creatinine clearance 91 +/- 14 ml/ min) were investigated. All patients underwent a renal biopsy and commenced on immunosuppressive therapy with corticosteroids and cyclosporin A. The localization of ET-1 in the renal tissue was examined by immunohistochemistry and compared to control renal tissue from 9 patients who underwent nephrectomies because of hypernephroma. In patients with proteinuria, endothelin-1 excretion in the urine at diagnosis was determined by radioimmunoassay and compared to that of 14 healthy subjects. A second measurement of urinary ET-1 excretion was performed after remission of proteinuria or 6 months after the initiation of treatment in patients with persistent nephrotic syndrome. RESULTS: ET-1 in renal tissue of patients and controls was localized within the cytoplasm of endothelial cells. In nephrotic patients, it was also localized within the cytoplasm of tubular epithelial cells. Urinary ET-1 levels were higher in nephrotic patients compared to healthy subjects (746 +/- 180 ng/24 h vs 410 +/- 112 ng/ml, p < 0.001). In 17 of 24 patients who showed remission of proteinuria with immunosuppressive therapy, the urinary ET-1 levels decreased (from 803 +/- 168 ng/24 h to 511 +/- 80 ng/24 h, p < 0.001) whereas in 7 patients with persistent proteinuria, urinary ET-1 excretion remained elevated. CONCLUSIONS: The increased urinary excretion of ET-1 in patients with severe proteinuria followed by a significant decrease after remission ofproteinuria with immunosuppressive treatment, along with its expression within tubular epithelial cells, suggests a possible relationship between proteinuria and renal ET-1 production.