Mycophenolate Mofetil Pharmacokinetic Monitoring in Pediatric Kidney Transplant Recipients

This open-label, longitudinal, long-term study of de novo pediatric renal transplant recipients was designed to investigate the pharmacokinetics (PK) of mycophenolic acid (MPA) and its possible interaction with cyclosporine (CsA). Thirty-four children on an immunosuppressive regimen of CsA, prednisone, and mycophenolate mofetil (MMF, 300-400 mg/m2 twice daily) were investigated at 6, 30, 180, and 360 days after transplantation. Considerable interindividual variability in the areas under the concentration curve (AUC(0-12)) of MPA was observed during the follow-up, although the dose of MMF remained the same over the same time. Predose levels (C0) increased significantly during the first 6 months after transplantation: C0 at 6 and 180 days after transplantation was 0.8 +/- 0.6 and 1.9 +/- 1.1 microg/mL (P < .0001). A significant time-dependent increase in the AUC of MPA was also observed during the first 6 posttransplant months: AUC(0-12) at 6 and 180 days after transplantation was 23.3 +/- 10.8 and 40 +/- 11.6 mg*h/L (P = .003). MPA concentrations 3 and 4 hours after MMF intake were the individual time points that best correlated with the full MPA AUC (r = 0.8 and 0.79; P < .001). The abbreviated MPA AUC (0-4 hours) correlated reasonably with the full AUC (r = 0.87; P < .001). Finally, a significant reduction in CsA dose during the first 6 posttransplant months (P < .001) matched the significant increases in both MPA C0 and full MPA AUC, thus demonstrating the interaction of the 2 immunosuppressive drugs. These observations suggest the need for therapeutic drug monitoring when adjusting the dose of MMF in children.

A multicenter survey on automated peritoneal dialysis prescription in children

Automated peritoneal dialysis (APD) is considered the first-choice chronic peritoneal dialysis modality for pediatric patients. Nighttime APD courses reduce the impact of PD treatment on a patient's and family's way of life, and the wide range of prescription options permit the dialysis schedule to be tailored to the needs of children of varying age and body size. We registered data concerning the dialytic regimens adopted in 12 pediatric dialysis centers for the treatment of 110 children on APD. Of the 110 children, 64 (aged 7.6 +/- 5.1 years) were on nightly intermittent peritoneal dialysis (NIPD); 29 (aged 9.2 +/- 4.3 years) were on tidal peritoneal dialysis (TPD); and 17 (aged 8.2 +/- 4.9 years) were on continuous cycling peritoneal dialysis (CCPD). The main prescription parameters for the various regimens (mean +/- standard deviation) were these: NIPD--exchanges: 13.0 +/- 5.8; duration: 10.0 +/- 1.1 hours; dwell volume: 36.5 +/- 6.2 mL/kg body weight (BW); glucose concentration: 1.69% +/- 0.41%. TPD--exchanges: 23.3 +/- 8.1; duration: 10.0 +/- 1.0 hours; dwell volume: 36.1 +/- 5.9 mL/kg BW; glucose concentration: 1.63% +/- 0.37%. CCPD--exchanges: 13.0 +/- 4.7; duration: 10.1 +/- 1.3 hours; dwell volume: 37.7 +/- 5.2 mL/kg BW; glucose concentration: 1.65% +/- 0.28%. Tidal volume was 52.2% +/- 9.0% of initial fill volume. Daytime dwell volume was 54.8% +/- 17.3% of night volume in CCPD patients, and 56.6% +/- 13.3% in 9 patients on continuous TPD. Because the patient population in this report varied in age, body size, and metabolic needs, the resulting range in prescription parameters was quite wide. Nevertheless, the duration of nightly PD sessions averaged 10 hours, fill volume averaged 36 mL per kilogram body weight, and daytime volume averaged 50% of nighttime fill volume.

[Neonatal chronic kidney failure associated with cyclo-oxygenase-2 inhibitors administered during pregnancy]

Non-steroidal anti-inflammatory drugs (NSAID) are used since years as tocolytic due to their capacity to inhibit cyclo-oxygenase (COX) expressed in uterus and fetal membranes, fundamental for labour initiation and maintenance. The use of nimesulide, a COX-2 selective NSAID, has been recently proposed due to its capacity to selectively inhibit the enzyme expressed in the myometrium and endometrium. A case of neonatal irreversible end stage renal failure after maternal assumption of nimesulide as tocolytic for 6 week is reported. Cesarean section at the 32nd week due to oligohydramnios gave birth to a baby girl of 2090 g, in good general conditions, without signs of respiratory distress and of visible abnormalities. From birth she displayed oligo-anuria which required dialytic substitutive therapy from the second day of life. At US scan both kidneys had normal diameters for gestational age slightly increased echogenicity and a reduced cortico-medullary differentiation. On the 20th day of life she had a surgical renal biopsy for the persistence of oligo-anuria, showing fetal glomeruli, without lymphocytic interstitial infiltrate, and normal tubuli without evidence of necrosis. She is now 16 months old and under automated peritoneal dialysis on a home dialysis program. The occurrence of chronic renal failure in strict relationship with maternal nimesulide assumption in this case is strongly suggestive for a pharmacological damage, either direct or mediated by renin angiotensin inhibition, and possibly modulated by genetic factors, likely to account for the different outcome of similarly treated patients. A cautious use of this drug as long term tocolytic should be recommended while waiting for ad hoc experimental and clinical evidences of safeness.

[Treatment of fluid overload and kidney failure with periotoneal dialysis after heart surgery]

BACKGROUND

Infants undergoing cardiac surgery with prolonged cardio-pulmonary bypass are particularly exposed to the risk of acute renal failure for renal hypoxia due to low cardiac output.

METHODS

To limit fluid overload deriving from oligo-anuria and low cardiac output we have recently adopted an early peritoneal dialysis protocol, positioning the peritoneal catheter during the intervention and performing early exchanges at first signs of inadequate diuretic response and/or "leaky capillary syndrome" with diffuse edema. From 1-1 to 31-12-1997 12 patients (8 males), of median age of 65.5 days (range 1-350 days) and median weight of 3463 g (range 2380-6550 g) were treated with peritoneal dialysis (automated exchanges of 10 ml/kg body weight of 1.5% glucose, dwell time 20 minutes). Cardiac pathologies included complex hearth malformations. Cardiopulmonary bypass lasted a mean of 202 minutes (range 102-372 minutes). The children were treated for a minimum of 1 to 42 peritoneal dialysis sessions. The infusional therapy included human albumin and fresh frozen plasma to substitute losses and furosemide at the dose of 4 mg/kg/day to reduce the "leaky capillary syndrome".

RESULTS

The results were very satisfactory: only 3 children died in the first 30 days after surgery. Renal function was normal at the end of the observation in 8/12 cases, and 2 cases presented chronic renal failure.

CONCLUSIONS

Since similar series report a mortality rate of 33-79%, it is suggested that early peritoneal dialysis may have positively influenced the final survival rate.

Neonatal end-stage renal failure associated with maternal ingestion of cyclo-oxygenase-type-1 selective inhibitor nimesulide as tocolytic

Cyclo-oxygenase-type-2 (COX-2) enzyme is fundamental for nephrogenesis, upregulated on fetal membranes and myometrium at parturition. Fetal COX-2 inhibition, due to maternal nimesulide assumption, can be responsible for neonatal chronic renal failure.

Clinical features of Henoch-Schönlein purpura. Italian Group of Renal Immunopathology

Henoch-Schönlein purpura (HSP) is a vasculitis that often involves the kidneys with a IgA nephropathy indistinguishable from Berger's disease. It can affect patients of any age, even though an uneven distribution of prevalence and severity of renal disease is commonly observed as the renal involvement with transient hematuria without renal functional impairment is much more frequent in children than in adults. The Italian Group of Renal Immunopathology analyzed a cohort of HSP patients with the homogeneous criterium of a renal disease severe enough to indicate renal biopsy both in adults and in children. We report the clinical features of 219 HSP patients (136 adults and 83 children) enrolled from 43 Italian Centers of Nephrology. The diagnosis was based on the detection of IgA nephropathy in a clinical setting of palpable purpura and/or bowel angina. The peak age was in second decade (28% of the patients). In 37% of the cases a potential eliciting factor was identified, mostly infectious (41% in children vs 23% in adults, p < 0.05). A seasoned incidence was found in June (20% of the cases). Most patients had palpable purpura (96.3%), while bowel angina was reported in 54.1% and arthritis in 50.2% at onset. The full extrarenal syndrome was more frequent in children (59%) than in adults (47%, p < 0.05). The extrarenal signs were often not coincident with urinary manifestations. The clinical onset with nephrotic syndrome was more common in children than in adults (35% vs 24.3% respectively, p < 0.02) who more often presented with minimal or moderate proteinuria. The frequency of impaired renal function at onset was similar in both adults and children (24.2% and 31.2% respectively).

Polymorphisms in angiotensin-converting enzyme gene and severity of renal disease in Henoch-Schoenlein patients. Italian Group of Renal Immunopathology

BACKGROUND

The influence of angiotensin converting enzyme (ACE) gene polymorphism on the progression of primary IgA nephropathy (pIgAN) is still debated. Even though the allele frequency was reported to be similar to controls, in some studies D/D patients had a faster decline of renal function and need of dialysis. Since Henoch-Schoenlein purpura (HSP) nephritis is considered a systemic vasculitis with renal lesions indistinguishable from pIgAN, we investigated the effect of the ACE polymorphism on presentation and progression of HSP IgAN.

METHODS

We examined the insertion (I) and deletion (D) polymorphism in intron 16 of ACE gene by PCR amplification of genomic DNA of 82 patients (37 children), with biopsy-proven IgAN associated with HSP enrolled in a collaborative study.

RESULTS

No significant association with clinical presentation at onset or with final outcome was found (functional impairment at outcome in 31.8%, D/D, 27.4%, I/D and 44% I/I, heavy proteinuria in 36.3% D/D, 21.6% I/D, and 11.1% I/I). Patients homozygous for the D allele had a greater number of extrarenal relapses (P=0.0028). No association was found between the ACE genotype and the presence of hypertension at onset and at the end of the follow-up. No difference was found between adults and children.

CONCLUSIONS

In this cohort of HSP IgAN, no ACE I/D polymorphisms were found to be associated with progressive deterioration of renal function. Different genes possibly involved in vasculitis might more strictly modulate expression and evolution of HSP IgAN.

Frequency of renal diseases and clinical indications for renal biopsy in children (report of the Italian National Registry of Renal Biopsies in Children). Group of Renal Immunopathology of the Italian Society of Pediatric Nephrology and Group of Renal Immunopathology of the Italian Society of Nephrology

BACKGROUND

Children's renal biopsy data were gathered for 3 consecutive years (1992-1994) by the Group of Renal Immunopathology of the Italian Society of Pediatric Nephrology, which opened a paediatric section of the Italian Registry of Renal Biopsies.

MATERIALS

The Registry recorded the histological diagnosis and the clinical data at renal biopsy of 432 children < or = 15 years old (mean age 8.96 +/- 3.7 years).

RESULTS

The most common glomerulonephritis (GN) at renal biopsy was idiopathic IgAGN (18.8%) and the most frequent secondary GN was Henoch-Schönlein purpura (HSP) nephritis (11.6%). Minimal-change disease (MCD) accounted for 11.6%, focal and segmental sclerosis (FSG) 8.5%, mesangial proliferative GN (MPGN) 9.5%, membranoproliferative GN 5.5%, and thin-membrane disease 5%. Lupus nephritis was diagnosed in 5% and Alport's GN in 3.9% of the cases. The annual incidence of primary GN in Italian children was 11.1 cases per million children population (p.m.c.p.), IgAN accounting for 3.1 cases, MCD 2.3, and HSP nephritis 1.9 cases p.m.c.p. respectively. Italian children underwent renal biopsy because of isolated microscopic haematuria in 19.3% of the cases, non-nephrotic proteinuria with or without microscopic haematuria in 31.2%, and nephrotic-range proteinuria in 34.2%, less frequently (15.3%) because of acute or chronic renal failure. Children with persistent isolated microscopic haematuria had most frequently IgAN (34.9%) or thin-membrane disease (25.3%), while those with non-nephrotic proteinuria had IgAN (30.4%) and HSP nephritis (23%). In cases with nephrotic proteinuria renal biopsy showed MCD in 34.5% of the cases, FSG in 16.9%, and MPGN in 12.2%. When renal biopsy was performed in chronic renal failure, chronic interstitial renal disease was detected in 62.5% of the cases.

CONCLUSIONS

This National Registry provides data on the indications for performing renal biopsy in Italian children and on the frequency and annual incidence of histological lesions detected. IgAN, primary or related to HSP, was the most common nephritis in Italian children undergoing renal biopsy.

The Italian Registry of Pediatric Chronic Peritoneal Dialysis: a ten-year experience with chronic peritoneal dialysis catheters

OBJECTIVE

To analyze the data from 347 peritoneal catheters implanted in 249 pediatric patients aged < or = 15 years at start of chronic peritoneal dialysis (CPD).

DESIGN

Restrospective study of the data collected between 1986 and 1995, in 20 dialysis centers, from the Italian Registry of Pediatric Chronic Peritoneal Dialysis. Data collection for each pediatric catheter included: catheter type, site and technique of insertion, complications, duration, and reason for removal or replacement.

RESULTS

Fifty catheters were inserted in patients under 2 years of age, 50 in patients aged 2 - 5 years and 247 in patients over 5 years of age. Catheter types included 307 (88.5%) Tenckhoff (286 double cuff, 21 single cuff) and 40 (11.5%), double-cuff, Valli-type catheters. All catheters were surgically implanted and omentectomy was performed in 83.5% of cases; the entry-site was in the midline in 136 cases (39.2%) and paramedian in 211 (60.8%). During 6076 CPD months we observed 274 catheter-related complications: 182 catheter infections (exit-site and/or tunnel infection), 23 leakages, 19 obstructions, 19 cuff-extrusions, 14 dislocations, 6 hemoperitoneum, 10 other (incidence of one complication every 21.8 dialysis-months). A significant reduction of catheter-related complications occurred in the last five years, compared with the first 5 years. One hundred and six catheters were removed due to catheter-related causes: infection (83 cases), obstruction (11), dislocation (4), outer-cuff extrusion (3), leakage (2), bowel incarceration (2), and bowel infarction (1). Catheter survival was 72.2% at 12 months, 52.3% at 24 months, 32.8% at 36 months, and 25.7% at 48 months. Significantly lower catheter survival was found in younger children (0 - 2 years) compared with two other age groups (2 - 5 years, and > 5 years). No significant correlation was found between catheter survival and catheter entry-site (midline vs paramedian).

CONCLUSIONS

Catheter-related infections were confirmed to be the most common complication and most frequent cause of peritoneal catheter removal. In addition, catheter survival rate was worse in younger children, indicating that more effort should be made to improve peritoneal catheter survival particularly in this age group.

Acetate intolerance is mediated by enhanced synthesis of nitric oxide by endothelial cells

The clinical picture of acetate intolerance strictly mimics the nitric oxide (NO) effect, including smooth muscle relaxation and extreme vasodilation. Because acetate induces production of cAMP, which is a powerful stimulus of NO synthase (NOS), we evaluated the effect of different dialysate solutions with and without acetate on NOS activity in endothelial cells (EC). NOS activity of EC, evaluated as H3-citrulline produced from H3-arginine, was modulated by the dialysate composition (e.g., 38 mmol/L acetate produced an increase of 3.2 +/- 0.39-fold compared with basal values (P < 0.0005), and the small amount of acetate (4 mmol/L) in 35 mmol/L bicarbonate solution increased the NOS activity by 2 +/- 0.49-fold (P < 0.05). Conversely, the acetate-free solution produced no effect on NOS activity. The mRNA encoding for inducible NOS was highly expressed in EC incubated with acetate buffer and also with acetate in bicarbonate dialysis buffer. The EC proliferative index was depressed by acetate (P < 0.0005), and tumor necrosis factor synthesis was increased (P < 0.0005) compared with acetate-free buffer. This study suggests that dialytic "acetate intolerance" can be induced by the activation, through cAMP and tumor necrosis factor release, of NOS. The small amount of acetate in bicarbonate dialysate, although capable of inducing in vitro NOS activation, is likely to be rapidly metabolized, whereas the large amounts of this anion in acetate fluids overwhelm metabolism by the liver. Acetate-free dialysate is the only solution that provides an acceptable level of biocompatibility both in vivo and in vitro.

Processing of IgA aggregates in a rat model of chronic liver disease

Heavy alcohol intake and/or lipotrope-deficient diet induced hepatocellular injury and mesangial deposition of IgA and often IgG in Lewis rats. The experimental animals showing more severe urinary abnormalities and histologic damage in the glomeruli had increased levels of IgA antibodies to dietary antigens and altered intestinal permeability. Based on human studies, the prolonged circulation of IgA-containing complexes associated with the liver disease could be envisaged as important for the development of mesangial IgA deposits. In order to verify this hypothesis, four groups (G) of Lewis rats were studied: G1 received thrice a weak an intragastric infusion of 1.5 ml/100 g body wt of whiskey; G2 rats were nourished with lipotrope-deficient diet; G3 rats were given both whiskey and LD diet; G4 rats were nourished with regular chow. After 12 weeks, heat-aggregated rat monomeric IgA was labeled with 133I and intravenously injected. Three control subgroups of rats, one given whiskey, one nourished with LD diet, and one with regular chow, were injected with radiolabeled heat-aggregated rat IgG. A large field-of-view digital gamma camera, equipped with an ultra-high-resolution collimator and interfaced to a dedicated computer, was used to analyze tracer kinetics and fate. The liver was the main organ involved in clearance of both test probes. The hepatic mean transit (MTT) was 11.4 +/- 11 min in G1 (proteinuria of 6.9 +/- 1.41 mg/day and hematuria +/+2), 221 +/- 19 min in G2 (proteinuria 9.1 +/- 0.64 mg/day and hematuria +2/+3), and 230 +/- 15 min in G3 (proteinuria 9.5 +/- 0.58 mg/day and hematuria +2/+3). In each case MTT value was found to be significantly prolonged compared to G4 (85 +/- 4 min). The multiple regression analysis showed that MTT values, proteinuria, and hematuria were significantly correlated (P < 0.01). Controls had trace amount proteinuria (0.82 +/- 0.17 mg/day, significantly lower than for each study group, P < 0.08) and undetectable hematuria. Similar results were obtained in control rats injected with aggregated IgG; i.e., MTT values were more prolonged in rats given whiskey or LD diet than normally nourished rats (P < 0.01). The lipotrope-deficient diet and the chronic alcohol abuse per se seem to lead to critical changes in hepatic uptake and catabolism of both an IgA and an IgG aggregate, which could account in turn for the reported appearance of renal immunoglobulin deposits in this experimental model. Due to the comparable delay in removal of IgA and IgG probes in equally nourished animals, additional factors are likely to be involved in the prominent deposition of IgA.

Nonenzymatically glycated albumin (Amadori adducts) enhances nitric oxide synthase activity and gene expression in endothelial cells

Hyperglycemia is considered to induce diabetic nephropathy through nonenzymatic glycation of proteins. Since hyperfiltration is likely to be the mechanism initiating the glomerular lesions, we investigated the effects of Amadori glucose adducts in serum albumin on the production of vasoactive mediators, including nitric oxide (NO) and eicosanoids, by endothelial cells (EC). Amadori adducts of glycated albumin induced a dose-response increase in NO synthase activity of murine endothelioma cells, up to 16.4 +/- 2.1-fold increase of basal values (P < 0.0001) at concentrations of 35 mg/ml mimicking physiological serum albumin concentration, and 4.6 +/- 0.8-fold increase at 17 mg/ml (P < 0.001). The effect was still detectable with glycated albumin 1.7 mg/ml, which approaches its estimated concentration in diabetic serum (1.6 +/- 0.3-fold increase, P < 0.05) The phenomenon was reproducible in human umbilical vein endothelial cells, though to a lesser extent, and further studies on murine EC were employed. The mRNA encoding for inducible NO synthase was overexpressed in EC incubated with Amadori adducts of glycated albumin in comparison to native albumin. Glycated albumin induced increased mRNA expression and synthesis of TNF-alpha. The stimulatory effect induced by glycated albumin on NO synthase activity was almost completely inhibited by anti TNF alpha antibodies. 3H-thymidine incorporation by EC was significantly inhibited when cells were grown in presence of glycated albumin (P < 0.001), and the phenomenon was abolished by the coincubation of the NO competitive inhibitor L-NAME. The early glycosylation products increased thromboxane production (P < 0.001), while prostaglandin E2 synthesis was unaffected. These data indicate that Amadori products of glycated albumin modulate NO synthase activity and eicosanoid balance in EC. These effects may be relevant to the hemodynamic changes in the early phases of diabetic nephropathy and in the lasting progression to sclerosis.

Tubulointerstitial responses in the progression of glomerular diseases: albuminuria modulates alpha v beta 5 integrin

Proteinuria represents one of the most unfavorable prognostic factors in the progression of nephropathies. Several lines of evidence support a role for proteinuria per se in the development of interstitial fibrosis, albeit the molecular mechanisms are still unknown. We investigated the potential role of integrins expressed on tubular cells in regulating the synthesis and organization of interstitial matrix or as mediators of tubulointerstitial damage in conditions mimicking the nephrotic milieu. Under basal conditions, cultured tubular cells highly expressed alpha 3 beta 1 and, at focal contacts, alpha v beta 3. In contrast, alpha v beta 5 was weakly and diffusely distributed all over the plasma membrane. Cultures on a variety of matrix substrates (fibronectin, laminin, collagen types I and IV, vitronectin, von Willebrand factor, fibrinogen) did not induce any phenotypic change in integrin expression by tubular cells. Conversely, the addition of albumin resulted in a highly increased membrane expression of beta 5, which was organized in typical focal contacts and was related to the dose of albumin added. Immunofluorescence, flow cytometry, immunoprecipitation and RT-PCR experiments argue for a complex mechanism that includes increased post-transcriptionally regulated protein synthesis, accelerated conversion of precursors to mature forms, and increased surface delivery to discrete adhesive structures. Up-regulation of the beta 5 chain in tubular cells was confirmed in 9 out of 11 kidney biopsies from proteinuric glomerulonephritides including membranous and focal sclerosing glomerulonephritis, while it was not expressed in nonproteinuric kidneys including five biopsy specimens. This is the first report indicating that proteinuria up-regulates the surface expression and distribution of a specific integrin chain on tubular cells. These observations suggest the participation of integrins in a hitherto unexplored mechanism of tubulo-interstitial responses to glomerular injury.

Adriamycin-induced proteinuria in nude mice: an immune-system-mediated toxic effect

BACKGROUND

The renal minimal lesion disease induced in rats by adriamycin (ADR) is generally thought to be consequent to a direct cytotoxic effect of this drug on glomerular epithelial cells. Only recently an altered synthesis of mediators, including reactive oxygen species and monocyte-macrophage cytokines, has been hypothesized.

METHODS

A mouse strain (nude) bearing a congenital thymic aplasia is a suitable experimental animal to evaluate the role of immune reactions in the development of the ADR nephropathy, provided mouse susceptibility to its toxic effect. Therefore, experimental mice were divided into three groups (G) each receiving adriamycin 7.5 mg/kg b.w.: GA (15 heterozygous nu/O mice with normal immune system); GB (15 homozygous nu/nu athymic mice); GC (15 homozygous nu/nu mice which were also splenectomized, irradiated, and treated with anti-asialo Gm1 antibody to abolish NK and decrease macrophage activity). All animals were maintained under pathogen-free conditions. Urinary proteins, albumin and TNF-alpha excretion were measured.

RESULTS

After 14 days the proteinuria was 43.8+/-1.7 microg/min in GA, 30.2+/-2.9 microg/min in GB (P<0.05) and 12.2+/-2.8 microg/min in GC (GA vs GC, P<0.0001; GB vs GC, P<0.05). Albuminuria gave a similar profile. TNG-alpha urinary excretion was significantly higher in GA (17.3+/-3.2 mU/min) than in GB (5+/-0.6 mU/min, P<0.001) and GC (3.2+/-0.9 mU/min, P<0.001). A significant correlation was found in GA between urinary TNF-alpha and protein losses (r2=0.63 P<0.0001). Kidney tissue homogenates failed to show in each experimental group any evidence of mRNA encoding for TNF-alpha, which was detectable in peripheral mononuclear cells from GA and GB, but undetectable in GC mice. Segmental effacements of glomerular epithelial cell foot process were observed by electron-microscopy in GA only, while they were minimal in GB and absent in GC. Iron colloidal staining for anionic sites on frozen sections always showed a normal pattern.

CONCLUSIONS

Nude mice bearing cellular immunity deficiency are protected from proteinuria following ADR toxicity. An impaired synthesis and release of lymphomonocyte mediators including TNF-alpha could be envisaged.

Enhanced production of nitric oxide by blood-dialysis membrane interaction

Nitric oxide (NO) is a powerful vasoactive product of endothelial origin, and one of its major effects is vasodilation, leading to hypotension. The role of NO in some complications of uremia is still debated. This study evaluated whether endothelial NO synthase activity could be modulated by the exposure of healthy blood to hemodialysis materials. In vitro hemodialysis sessions were performed with cuprophan and polymethylmethacrylate membranes. Blood samples from a healthy donor after recirculation for 0, 5, 15, 30, and 60 min were coincubated for 6 h with a murine endothelial cell line (t.End.1); mRNA for inducible NO synthase and enzyme activity, measured as (3H)citrulline produced from (3H)arginine, were detected. The release of interleukin (IL)-1 beta and tumor necrosis factor-alpha (TNF-alpha) from recirculating lymphomonocytes was measured, too. The NO synthase activity of endothelial cells was stimulated by blood dialyzed with cuprophan, peaking at 15 min (11-fold increase in comparison to the basal values), whereas polymethylmethacrylate was ineffective (P < 0.01 versus Cuprophan). Dialysis with cuprophan, but not with polymethylmethacrylate, induced in endothelial cells the expression of mRNA encoding for inducible NO synthase. The release of IL-1 beta and TNF-alpha after 6 h by recirculating lymphomonocytes paralleled the NO synthase activity profile in endothelial cells and was significantly higher after cuprophan exposure than after polymethylmethacrylate (P < 0.0001). In conclusion, the activity of endothelial NO synthase can be enhanced during the dialysis sessions by the interaction of lymphomonocytes with the membranes, possibly via TNF-alpha and IL-1 beta production.

A possible role for nitric oxide in modulating the functional cyclosporine toxicity by arginine

The renal damage consequent to cyclosporine A (CsA) administration ranges from hemodynamic alterations to irreversible chronic lesions. The initial vasoconstriction depends upon the imbalance between the various modulators of the renal vascular tone, among which the most powerful are endothelins and nitric oxide (NO). CsA could play a crucial role by inhibiting the Ca++/calmodulin-mediated activation of the constitutive NO synthase (NOS) isoform, which converts L-arginine (L-Arg) into NO and citrulline, with a 1:1 stoichiometry. To investigate the possibility of modulating CsA nephrotoxicity with L-Arg we studied six groups (G) of Lewis rats treated with daily gavage up to eight weeks: G1, CsA 40 mg/kg; G2, G1 plus L-Arg 300 mg/kg; G3, G2 plus the competitive inhibitor of NOS, NG-nitro-L-Arg (L-NNA); G4, L-Arg alone; G5, L-NNA alone; and G6, controls receiving vehicle alone. After eight weeks L-Arg treated rats were protected against the toxic effects of CsA [creatinine (Cr) values, G2, 0.62 +/- 0.05 mg/dl vs. G1, 0.99 +/- 0.16 mg/dl, P < 0.001; proteinuria (P), G2, 7.2 +/- 1.02 mg/day vs. G1, 15.1 +/- 1.9 mg/day, P < 0.01]. The administration of L-NNA abolished the protective effect of L-Arg (G3, Cr 1.23 +/- 0.16 mg/dl; P 16.9 = 2.3; P < 0.02 and P < 0.005, respectively vs. G2). The levels of Cr in G2 rats were superimposable to control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Macromolecular IgA and abnormal IgA reactivity in sera from children with IgA nephropathy. Italian Collaborative Paediatric IgA Nephropathy Study

This multicenter study investigated the characteristics of circulating IgA molecules in 77 children: 42 had primary IgA nephropathy (IgAN), 20 were non-IgA glomerulonephritides (CGN) and 15 had urological problems (U). Fifteen assays were employed including the detection of macromolecular IgA [IgA immune complexes (IgAIC) by the conglutinin (K) assay, heavy molecular weight IgA in 2.5% polyethylene glycol (PEG), mixed IgA/IgGIC (Jacalin assay), IgA-Fibronectin (IgA-F) aggregates]IgA antibodies to alimentary antigens (gliadin, glycgli, glutein, ovalbumin, bovine serum albumin) and IgA binding to mesangial antigens (fibronectin, laminin, type IV collagen) or polycations (poly-L-lysine). Total IgA and IgA reacting with jacalin, supposed to bear an altered galactosylation, were measured as well. Mean levels of each kind of macromolecular IgA were significantly increased in children with IgAN in comparison to U disease (K-IgAIC p < 0.05, PEG-IgAIC p < 0.01, IgA/IgGIC p < 0.004, IgA-F aggregates p < 0.0003). However, IgA-F were the only macromolecular IgA significantly higher in IgAN than in CGN (p < 0.0005). IgA-F aggregates did not correlate with any urinary sign of activity, while K-IgAIC data were significantly related with microscopic hematuria (p < 0.05) and past history of gross hematuria (p < 0.02). Children with IgAN had mean levels of IgA reacting with the lectinic fractions of gliadin significantly higher than CGN (p < 0.01) and U groups (p < 0.003). IgAN displayed an enhanced production of IgA reacting with mesangial matrix components vs CGN (p < 0.03) and U (p < 0.0003) groups and showed altered interactions with positively charged molecules (poly-L-Lysine, p < 0.01) and carbohydrate residues (jacalin p < 0.05). In IgAN there is an increased circulation of altered IgA favouring the formation of macromolecular IgA, including true IgAIC or IgA aggregated by carbohydrate interactions. The affinity for the mesangial matrix glycoproteins and for the mesangial area electrical charge might further enhance the trapping and deposition of the immune material containing IgA. IgA-F aggregates seem to be a marker of this event, while complement binding molecules in IgAIC correspond to the hematuric manifestation of the nephritogenic process.

[Optimization of the treatment of idiopathic nephrotic syndrome in children]

From 1981 to 1992, 81 children affected by idiopathic nephrotic syndrome were treated in our Division. The majority were males (74%), with mean age at diagnosis of 4.8 (0-14)) years. They had a mean follow-up of 5.7 (0.5-11) years. The renal function at diagnosis was normal in all cases, proteinuria was selective in 86.4% of the cases. 28 children with somehow atypical behaviour underwent renal biopsy. In this negatively selected group the more frequent histologic forms were focal segmental glomerular sclerosis (33.5%), minimal change disease (37.4%), IgM mesangial glomerulonephritis (16.6%), membranous nephropathy (12.5%). First choice drug was in all cases prednisone. In the last years the trend for steroid therapy was to adopt long protocols (16 weeks), with a total dose of 105-133 mg/kg per therapeutic cycle. About 90% of children had a favourable response to steroids, but half of them were frequent relapser. In these cases the long term stable remission was obtained with steroids alone in 10.8% of the cases, with the association of cyclophosphamide in 62%. In a minor fraction and in the steroid resistant (13.6% of the total cases) levamisol and cyclosporin were also adopted. 2.4% of the cases progressed to end stage chronic renal failure. Most of the steroid sensitive children were in remission after 3-4 years of disease, only 6% relapsed more than 5 years after diagnosis.

[IgA serology in idiopathic IgA deposit nephropathy in children]

It is generally thought that in primary IgA nephropathy (IgAN) an altered immune response favours high levels of serum IgA directed against environmental or mesangial antigens (Ag) leading to circulating IgA containing immune complexes (IgAIC). The aim of this multicenter collaborative study was to evaluate some of the IgA immunologic abnormalities in children with IgAN. We investigated 42 children with biopsy-proved IgAN, 21 children with non-IgA glomerulonephritides (CD) and 15 with previous urologic disorders without any evidence of immunologic disease (U). The following methods were used: detection of macromolecular IgA (IgAIC by the conglutinin solid-phase assay, heavy MW IgA measured in 2.5% polyethylene glycol precipitate, IgA-fibronectin aggregates, mixed IgA-IgGIC); serum levels of IgA to alimentary Ags (gliadin, glyc-gli, ovalbumin, bovine serum albumin) and mesangial Ags (fibronectin, laminin, type IV collagen) and reactivity of IgA with the lectin jacalin. In children affected with IgAN serum levels of macromolecular IgA were significantly higher in comparison to U group (p < 0.05-p < 0.0005). IgA-fibronectin aggregates only were significantly higher also than CD group (p < 0.0005). Mean levels of antigliadin IgA were significantly higher in IgAN than in controls (CD p < 0.01 and U p < 0.03) and similar data were found for IgA to mesangial matrix (laminin and fibronectin), which were significantly greater in IgAN than in CD and U (p < 0.01-p < 0.0002). Serum IgA in children with IgAN showed a greater affinity for both polycations and glycosylated molecules. Children affected by IgAN present abnormalities in serum IgA similar to those observed in adults with the same disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional consequences of the binding of gliadin to cultured rat mesangial cells: bridging immunoglobulin A to cells and modulation of eicosanoid synthesis and altered cytokine production

Oral immunization with gliadin (GLI) can induce immunoglobulin A mesangial deposits (IgA nephropathy [IgAN]) in mice. A role for GLI in human IgAN has been inferred from an association with celiac disease, increased serum anti-GLI IgA in patients with IgAN, and benefit from a gluten-free diet observed in some IgAN patients. These effects might be due to the antigenic or lectinic properties of GLI. The aim of our study was to investigate whether GLI binding to glycosylated residues (ie, lectinic activity) favors binding of GLI to cultured rat mesangial cells, bridging IgA macromolecules. We also sought to determine whether GLI binding alters mesangial cell function. Gliadin binds to rat mesangial cells in the third and fourth passages, as determined by immunofluorescence. Gliadin binding is inhibited by co-incubation with 1 mol/L N-acetyl-D-glucosamine and 1 mol/L alpha-D-mannose, sugars competitive for this lectinic bond. Quantification by biotinylated GLI revealed a significant dose-dependent binding of GLI (P < 0.001) inhibited by N-acetyl-D-glucosamine (P < 0.05). Some saccharolytic enzymes, like invertase, modify the cell surface to decrease GLI binding (P < 0.02). In addition, GLI promoted the binding of purified mouse polymeric IgA to mesangial cells. The binding of GLI to mesangial cells modulates arachidonic acid metabolism by cultured mesangial cells, significantly inhibiting prostaglandin E2 production (P < 0.02), increasing synthesis of thromboxane B2 (P < 0.01) and tumor necrosis factor (P < 0.001), but not interleukin-1 beta. These responses were abrogated by co-incubation with N-acetyl-D-glucosamine and/or pretreatment with invertase. Non-immune binding of an environmental alimentary lectin, GLI, to mesangial cells in culture might favor the binding of IgA and IgAIC to mesangial cells, enhancing both IgA mesangial trapping and in situ IgA deposit formation. This could occur via GLI-specific antibodies or by virtue of the binding of nonspecific IgA on a lectinic basis, or both. Moreover, related changes in eicosanoid synthesis might stimulate mesangial cell growth and mesangial matrix production, together with mesangial cell contraction, contributing to the pathogenesis of IgAN.

Glomerular permselectivity to macromolecules in reflux nephropathy: microalbuminuria during acute hyperfiltration due to aminoacid infusion

Reflux nephropathy is an important cause of chronic renal failure in children. After the parenchymal scar, the progression is thought to be mediated by glomerular hypertension in remnant nephrons resulting in modifications in permselectivity to macromolecules. Proteinuria correlates with a progressive course. The glomerular permselectivity to macromolecules in basal conditions and after acute hemodynamic stress was investigated in 28 children whose bilateral vesico-ureteric reflux (VUR) had been previously surgically corrected (meanly 5.6 years before) and with normal creatinine clearance (CrCl). Bilateral renal scarring (0 to 8 scale for both kidneys) was 4.3 +/- 1.6. Albuminuria (UAE) was evaluated in basal conditions and under acute hyperfiltration induced by amino acid (Aa) infusion. After isotonic saline at 310 ml/hour/1.73 m2, 6 mg/kg/min of Aa were infused for 2 hrs. UAE was significantly higher than controls in basal conditions (p < 0.01), and further increased after Aa infusion (p < 0.02). Microalbuminuria was detectable in 53.5% of the children in basal conditions and in 64.3% after Aa. Also urinary beta 2 microglobulin significantly increased at the end of the test (p < 0.001). CrCl significantly increased at the first hour (p < 0.05). Children with severe renal parenchymal scarring had greater UAE (p < 0.01) and beta 2M (p < 0.02) values after provocative test than those with mild renal damage. In 8 children GFR and ERPF were measured by means of inulin and p-hippurate clearance respectively. The variations in UAE during Aa infusion were significantly correlated with GFR dynamics (p < 0.05) while they were not influenced by ERPF modifications.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II local hyperreactivity in the progression of IgA nephropathy

Immunologic and hemodynamic factors are likely to work in synergism in the progression of immunoglobulin A nephropathy (IgAN) toward sclerosis. The local activation of the renin-angiotensin system may be one the most relevant mechanisms. We investigated the hemodynamic effects of the acute administration of angiotensin-converting enzyme inhibitor (ACEI) (captopril 50 mg). The glomerular filtration rate (GFR) and the effective renal plasma flow (ERPF) were measured by 51Cr-EDTA and 125I hippurate clearances. The correspondent filtration fractions (FFs) in basal conditions and after administration of ACEI were calculated, then the changes in FF (delta FF and % delta FF) were determined. We studied 27 IgAN patients. Eighteen patients had normal renal function (GFR, 112 +/- 19 mL/min/1.73 m2) and nine had moderate renal impairment (GFR, 54 +/- 13 mL/min/1.73 m2). Sixteen patients had proteinuria > or = 0.5 g/d. In addition, 12 glomerulonephritis control cases and eight healthy subjects were investigated. After the administration of ACEI in healthy subjects we observed slight modifications in the GFR, a significant increase in the ERPF (P < 0.005), and a significant decrease in FF (P < 0.04). Similarly, in IgAN patients with normal renal function the GFR increased slightly, the ERPF increased significantly (P < 0.01), and there was a decrease in FF (P < 0.01). The delta FF and % delta FF values were not significantly different from those found in the controls. In patients with initial renal failure GFR remained unchanged, ERPF increased significantly (P < 0.005), and FF significantly decreased (P < 0.004). However, the changes in delta FF and % delta FF were significantly greater than those found in healthy controls (P < 0.01) and in IgAN patients with normal renal function (P < 0.001). IgAN patients with proteinuria levels > or = 0.5 g/d showed greater changes in delta FF and % delta FF after the administration of ACEI than patients with proteinuria levels lower than 0.5 g/d (P < 0.003 and P < 0.04, respectively) or proteinuric control cases (P < 0.05 and P < 0.01, respectively). This different response in proteinuric and nonproteinuric patients was evident even when the analysis was limited to the subgroup of IgAN patients with normal renal function. The decrease in FF consequent to an increase in the ERPF after the administration of ACEI suggests a local hyperactivity of the renin-angiotensin system in some cases of IgAN.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytokine mRNA expression by cultured rat mesangial cells after contact with environmental lectins

We previously demonstrated that gliadin, a lectinic component of gluten, induces IgA mesangial deposits in orally immunized mice, binds in vitro polymeric IgA and cultured rat mesangial cells modulating their arachidonic acid metabolism. We investigated the effects of gliadin and other environmental lectins on some mesangial cell functions, including synthesis and release of cytokines and lipid mediators. Several lectins, particularly gliadin, affected the mRNA expression of c-myc and c-fos, two proto-oncogenes involved in the transcriptional enhancement of the gene cascade, which are markers of cell growth, differentiation and mitosis. Lectins modulated the ability of cultured rat mesangial cells to express mRNA for cytokines involved in the inflammation and in the regulation of the immune response. TNF-alpha and IL-6 mRNA transcription were enhanced by gliadin and other lectins, and TNF release was variably increased. Conversely, IL-1 production was less affected or slightly depressed. PAF production was not detectable while PGE2 was generally reduced and TXB2 enhanced. Gliadin was one of the lectins most active on the mesangial cells, and its effects were reversed by the addition of N-Acetylglucosamine, a sugar specific for some lectinic bindings, suggesting a carbohydrate interaction. The effects of the various lectins were distinct and only partially convergent, ruling out an aspecific mesangial cell activation. These data suggest that lectins might interfere with mesangial cell functions and modify the mesangial cell homeostasis.

[Role of food antigens and alcohol in idiopathic nephritis with IgA deposits]

It is generally thought that antigens inducing the formation of IgA immune complexes in primary IgA nephropathy and responsible for mesangial immune deposits are of infectious and alimentary origin. To investigate the possible role of alimentary antigens in eliciting the IgA mucosal immune response we studied the reactivity and the formation of mesangial IgA deposits in rodents following different experimental conditions: a) on gluten-free diet and oral immunization with gliadin; b) on gluten and soya free diet and oral immunization with soya; c) on chronic alcoholic intoxication. We found that oral immunization with gliadin induced the formation of mesangial deposits of IgA similar to those observed in human primary IgA nephropathy. On the contrary, oral immunization with soya failed to induce the formation of similar immune deposits even though the lectin components in soya and in gliadin are similar. Chronic ethanol intoxication induced an increase in serum IgA against alimentary antigens suggesting an increase in intestinal permeability due to alcohol. Mean times we observed significant IgA mesangial deposits. Our experimental data suggest that alimentary antigens can play a significant role in inducing primary IgA nephropathy.

IgA antibodies to dietary antigens and lectin-binding IgA in sera from Italian, Australian, and Japanese IgA nephropathy patients

We studied serum IgA as antibodies to dietary antigens (Ag), as lectin-binding molecules, and as conglutinin-binding immune complexes (IgAIC) in people from geographical areas in which IgA nephropathy (IgAGN) is particularly frequent. Sera from 63 Italian, 21 Australian, and 25 Japanese patients affected by IgAGN and 24 Italian, 20 Australian, and 40 Japanese healthy controls were studied. Increased values of IgAIC were detected in 42.8% of Italian patients, while only in 23.8% and 8% of Australian and Japanese patients, respectively. Mean values were significantly increased only in Italian patients (P less than 0.0001). Positive values of IgA antibodies against dietary Ag had variable prevalences, but again Italian patients showed the highest frequency, from 19% to 28.5% versus 0 to 38% in Australians and 0 to 16% in Japanese. Mean values of these antibodies were not significantly increased in any patient groups in comparison to the corresponding healthy populations. However, patients with elevated values of IgAIC had significantly higher serum concentrations of antibodies to alimentary components and a linear correlation was found between IgAIC and some IgA antibodies to food components. The relationship between these two series of data was particularly evident for Italian and Australian IgAGN patients. Moreover, the patients with positive data tended to have a cluster of increased levels of IgA antibodies against several alimentary Ag at the same time. A linear correlation was evident between values of IgA antibodies to gluten fractions and to heterologous albumins. None of these correlations was evident among healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of gluten-derived fractions on chemiluminescence production by human neutrophils

The effects of gliadin and glyc-gli on leukocyte chemiluminescence response were assessed in vitro. A dose-dependent increase in chemiluminescence response of neutrophils stimulated by zymosan was observed by using gliadin at concentrations ranging between 1 and 20 micrograms. By increasing glyc-gli concentration, a bimodal response was observed with an enhancement up to 50 micrograms/ml, followed by suppressive effects, which were again dose-dependent. The possible implications of these findings in human pathology are discussed.

Monoclonal gammopathy and glomerulonephritis with organized microtubular deposits

We report a case with IgG-kappa monoclonal gammopathy of unidentified significance (MGUS) and glomerulonephritis (GN) with organized microtubular deposits on electron microscopy (EM). Light microscopy (LM) examination showed exudative features and moderate extracapillary proliferation. An acute nephritic syndrome with a rapidly progressive renal failure was clinically manifest at the onset and during each relapse. The patient was treated with methylprednisolone pulses followed by oral prednisone, cyclophosphamide, plasmapheresis, and maintenance courses of chemotherapy. The response to treatment was good, with a temporary improvement of renal function and control of the downhill course over a 3-year follow-up.

Effects of a gluten-free diet in primary IgA nephropathy

In an uncontrolled study a gluten-free diet was given to 29 patients affected by primary IgA nephropathy (IgAGN). All of them followed the diet for 6 months, 23 patients for 1 year and 9 for 2 to 4 years. Mean levels of IgA containing circulating immune complexes (IgAIC), detected by a specific conglutinin assay and by measuring IgA content in 2.5% polyethylene glycol precipitates, on an unrestricted diet, significantly decreased after 6 months of gluten-free diet (p less than 0.01) and remained reduced during the follow-up. A decrease in IgAIC levels was evident in 85.7% of the cases with basal positive data, with complete normalization in 64.3% of them. IgA to gluten antigens (ethanol- or saline-soluble gliadin, glutenin and the lectin fraction termed glyc-gli) as well as to heterologous bovine and egg albumins were found to be significantly increased on an unrestricted diet in the group of 14 IgAGN patients with basal positive IgAIC. The mean levels of IgA to most dietary antigens significantly decreased after 6 months to 1 year of a gluten-free diet. A decrease in IgA to ethanol-soluble gliadin was evident in 81.8% of the cases with basal positive data, with complete normalization in 63.6%. A subgroup of 27.5% of IgAGN patients showed positive IgAIC values associated with increased IgA values to a variety of dietary antigens. A gluten-free diet induced in 75% of the cases a parallel improvement in these abnormal immunological data. Mean proteinuria values were found to be significantly decreased after 6 months of the diet and a reduction was also observed in microscopic hematuria. However, mean blood creatinine levels showed a significant increase after the gluten-free diet. The data of this study indicate that a gluten-free diet can modify some immunological abnormalities in a group of IgAGN patients, reducing levels of IgAIC and IgA to dietary antigens. The clinical course does not seem to be favorably influenced, since a relentless progression towards renal failure was observed.

Complement receptor (CR1) and IgG or IgA on erythrocytes and in circulating immune complexes in patients with glomerulonephritis

This study reports the quantitative analysis of complement receptor (CR1) molecules on erythrocyte surface, the amount of immunoglobulin-containing material (IgG-IC and IgA1-IM) on the erythrocyte surface, and the concentrations of circulating immune complexes (IgG-CIC and IgA-CIC); also reported are the HLA phenotypes of 44 patients affected by various forms of glomerulonephritis (including 20 primary IgA nephropathy, 11 membranous glomerulonephritis, 9 lupus nephritis and 4 renal vasculitis). Erythrocyte CR1 molecules were found to be decreased (P less than 0.02) and erythrocyte IgG-IC were less than in controls (P less than 0.025) in lupus nephritis patients, whereas IgG-CIC were significantly greater (P less than 0.02). In patients affected by primary IgA nephropathy, mean erythrocyte CR1 concentrations were significantly decreased (P less than 0.02). Patients with impaired renal function had mean erythrocyte CR1 values significantly greater than those with normal renal function (P less than 0.002). Immunoglobulin-containing material on the erythrocyte surface was not significantly increased, whereas the serum concentrations of both IgA-CIC and IgG-CIC were significantly increased (P less than 0.02). In membranous nephropathy erythrocyte CR1 molecules were quantitatively similar to control data and no increase in CIC was observed. Conversely, erythrocyte IgG-IC were significantly increased (P less than 0.01). No significant relationship among erythrocyte CR1 molecules, erythrocyte surface-associated immunoglobulins, CIC, and HLA phenotype was observed in any patient group.