Pioglitazone Enhances the Beneficial Effects of Glucocorticoids in Experimental Nephrotic Syndrome

Glucocorticoids are the primary therapy for nephrotic syndrome (NS), but have serious side effects and are ineffective in ~20-50% of patients. Thiazolidinediones have recently been suggested to be renoprotective, and to modulate podocyte glucocorticoid-mediated nuclear receptor signaling. We hypothesized that thiazolidinediones could enhance glucocorticoid efficacy in NS. We found that puromycin aminonucleoside-induced proteinuria in rats was significantly reduced by both high-dose glucocorticoids (79%) and pioglitazone (61%), but not low-dose glucocorticoids (25%). Remarkably, pioglitazone + low-dose glucocorticoids also reduced proteinuria (63%) comparably to high-dose glucocorticoids, whereas pioglitazone + high-dose glucocorticoids reduced proteinuria to almost control levels (97%). Molecular analysis revealed that both glucocorticoids and pioglitazone enhanced glomerular synaptopodin and nephrin expression, and reduced COX-2 expression, after injury. Furthermore, the glomerular phosphorylation of glucocorticoid receptor and Akt, but not PPARγ, correlated with treatment-induced reductions in proteinuria. Notably, clinical translation of these findings to a child with refractory NS by the addition of pioglitazone to the treatment correlated with marked reductions in both proteinuria (80%) and overall immunosuppression (64%). These findings together suggest that repurposing pioglitazone could potentially enhance the proteinuria-reducing effects of glucocorticoids during NS treatment.

Identification and characterization of hic-5/ARA55 as an hsp27 binding protein

hsp27 has been reported to participate in a wide variety of activities, including resistance to thermal and metabolic stress, regulation of growth and differentiation, and acting as a molecular chaperone or a regulator of actin polymerization. We hypothesized that these diverse functions are regulated in a cell- or tissue-specific manner via interaction with various binding proteins. To investigate this hypothesis, we used hsp27 as a "bait" to screen a yeast two-hybrid cDNA library from rat kidney glomeruli and identified a novel hsp27 binding protein, hic-5 (also known as ARA55), a focal adhesion protein and steroid receptor co-activator. Biochemical interaction between hsp27 and hic-5 was confirmed by co-immunoprecipitation, and critical protein.protein interaction regions were mapped to the hic-5 LIM domains and the hsp27 C-terminal domain. Initial analysis of the functional role of hsp27.hic-5 interaction revealed that hic-5 significantly inhibited the protection against heat-induced cell death conferred by hsp27 overexpression in co-transfected 293T cells. In contrast, when a non-hsp27-interacting hic-5 truncation mutant (hic-5/DeltaLIM4) was co-expressed with hsp27, the hic-5 inhibition of hsp27 protection was absent. We conclude that hic-5 is a true hsp27 binding protein and inhibits the ability of hsp27 to provide protection against heat shock in an interaction-dependent manner.

Intravenous nicardipine for treatment of severe hypertension in children

OBJECTIVE

To examine the effect of intravenous nicardipine in the treatment of children with severe hypertension.

METHODS

The medical records of 29 children (mean age 94 months) treated with intravenous nicardipine were retrospectively reviewed. The mean duration of severe hypertension before nicardipine use was 12.5 hours. Most (74%) patients were receiving other antihypertensive agents before nicardipine.

RESULTS

The initial nicardipine dose was 0.8 +/- 0.3 microg/kg/min (mean +/- SD). The mean effective dose was 1.8 +/- 1.0 microg/kg/min (range, 0.3 to 4.0). Blood pressure control was achieved within 2.7 +/- 2.1 hours after nicardipine was started. Nicardipine treatment produced a 16% reduction in systolic blood pressure, a 23% reduction in diastolic blood pressure, and a 7% increase in heart rate. Nicardipine was effective as a single agent on 26 (84%) of 31 occasions. Adverse effects included tachycardia, flushing, palpitations, and hypotension.

CONCLUSIONS

When administered in the intensive care unit setting with close patient monitoring, intravenous nicardipine effectively lowered blood pressure in children with severe hypertension. Larger prospective studies should be conducted to confirm these findings.

Peritoneal dialysis for management of pediatric acute renal failure

BACKGROUND

While the use of continuous renal replacement therapies in the management of children with acute renal failure (ARF) has increased, the role of peritoneal dialysis (PD) in the treatment of pediatric ARF has received less attention.

DESIGN

Retrospective database review of children requiring PD for ARF over a 10-year period.

SETTING

Pediatric intensive care unit at a tertiary-care referral center.

PATIENTS

Sixty-three children without previously known underlying renal disease who required PD for treatment of ARF.

RESULTS

Causes of ARF were congestive heart failure (27), hemolytic-uremic syndrome (13), sepsis (10), nonrenal organ transplant (7), malignancy (3), and other (3). Mean duration of PD was 11 +/- 13 days. Children with ARF were younger (30 +/- 48 months vs 88 +/- 68 months old, p < 0.0001) and smaller (11.9 +/- 15.9 kg vs 28 +/- 22 kg, p < 0.0001) than children with known underlying renal disease who began PD during the same time period. Percutaneously placed PD catheters were used in 62% of children with ARF, compared to 4% of children with known renal disease (p < 0.0001). Hypotension was common in patients with ARF (46%), which correlated with a high frequency of vasopressor use (78%) at the time of initiation of PD. Complications of PD occurred in 25% of patients, the most common being catheter malfunction. Recovery of renal function occurred in 38% of patients; patient survival was 51%.

CONCLUSIONS

Peritoneal dialysis remains an appropriate therapy for pediatric ARF from many causes, even in severely ill children requiring vasopressor support. Such children can be cared for without the use of more expensive and technology-dependent forms of renal replacement therapies.

Hemodialysis followed by continuous hemofiltration for treatment of lithium intoxication in children

Hemodialysis is the usual recommended treatment for severe lithium intoxication; however, rebound of lithium levels may require repeated hemodialysis treatments. We proposed that the addition of continuous hemofiltration after hemodialysis would prevent rebound by providing ongoing clearance of lithium. We report two pediatric patients with lithium intoxication treated by hemodialysis followed by continuous venovenous hemofiltration with dialysis (CVVHD). Both patients were symptomatic at presentation and had initial lithium levels more than three times the usual therapeutic range. Hemodialysis followed by CVVHD resulted in rapid resolution of symptoms, followed by continuous clearance of lithium without requiring repeated hemodialysis sessions. Both patients had return of normal mental status during CVVHD treatment, and neither patient experienced complications of hemodialysis or CVVHD. Total duration of treatment with hemodialysis followed by CVVHD was 34.5 hours for the first patient and 26 hours for the second patient. We conclude that hemodialysis followed by CVVHD is a safe and effective approach to the management of lithium intoxication in children.

Treatment of Henoch-Schönlein Purpura glomerulonephritis in children with high-dose corticosteroids plus oral cyclophosphamide

BACKGROUND

Henoch-Schönlein Purpura (HSP) is a common childhood vasculitis with manifestations in numerous organ systems, including glomerulonephritis. Patients with more severe HSP-associated glomerulonephritis may develop chronic renal failure. Currently, no widely accepted treatment protocols exist for patients with significant renal involvement.

METHODS

We retrospectively reviewed the clinical courses of 12 children (mean age 9 years) with HSP glomerulonephritis treated with high-dose corticosteroids plus oral cyclophosphamide. All patients had nephrotic-range proteinuria, and all had significant histopathologic changes on biopsy, including crescentic nephritis in 10 patients. Treatment consisted of either intravenous pulse methylprednisolone or oral prednisone followed by oral cyclophosphamide (2 mg/kg/day) for 12 weeks, along with either daily or alternate-day oral prednisone. Prednisone was tapered following completion of cyclophsophamide.

RESULTS

Serum albumin rose significantly after treatment from 2.8 +/- (SD) 0.5 to 3.7 +/- 0.4 g/dl (p < 0.001), and there was a concurrent reduction in proteinuria, as reflected by decreasing serial protein-to-creatinine ratios: from 6.3 +/- 4.4 to 0.8 +/- 0.8 (p = 0.002). Renal function remained normal in all patients. Hypertension developed during treatment in 10 patients, all but 1 of whom were normotensive at last follow-up, 35 +/- 17 months following biopsy.

CONCLUSIONS

We conclude that treatment of children with HSP nephritis with high-dose corticosteroids plus oral cyclophosphamide is safe and, as in nephrotic syndrome, appears to significantly reduce proteinuria which is a known risk factor for the development of renal insufficiency in HSP. Further studies with larger numbers of patients should be conducted to confirm this finding.

Treatment of hypertensive children with amlodipine

Amlodipine, a long-acting dihydropyridine calcium channel blocking agent, was administered to 55 children (age: 11.5 +/- 5.4 years) with hypertension, 49 of whom (89%) had secondary hypertension. Efficacy was assessed by comparing pretreatment blood pressure (BP) to follow-up BP obtained in our outpatient Pediatric Nephrology clinic. Thirty-two (58%) patients achieved BP control with amlodipine alone, and 31 (55%) patients received amlodipine twice daily. Eleven patients received amlodipine as a suspension. Mean amlodipine dose was 0.16 +/- 0.12 mg/kg/day; there was an inverse relationship between patient age and amlodipine dose. Follow-up BP were significantly lower than pretreatment BP: systolic BP fell from 129 +/- 12 to 122 +/- 12 mm Hg (P = .004), and diastolic BP fell from 78 +/- 13 to 70 +/- 19 mm Hg (P = .003). A small, clinically insignificant increase in heart rate (from 91 +/- 19 beats/min to 99 +/- 26 beats/min; P = .02) occurred during amlodipine treatment. Adverse effects reported included dizziness (three patients), fatigue (two patients), flushing (two patients), and leg edema (one patient). All improved with dose reduction. We conclude that amlodipine provides effective BP control without significant adverse effects in children with hypertension, and can be used as monotherapy in most children. Young children appear to require significantly higher doses per kilogram of body weight than older children. Twice-daily dosing may be required in many children to achieve BP control. Detailed pharmacokinetic studies are needed to confirm these observations.

Regulation of mouse podocyte process dynamics by protein tyrosine phosphatases rapid communication

BACKGROUND

Effacement of podocyte foot processes occurs early in many glomerular diseases associated with proteinuria and is accompanied by a reorganization of the actin cytoskeleton. The molecular mechanisms regulating these structural changes are poorly understood.

METHODS

To address these questions, we analyzed the effect of the polycation, protamine sulfate (PS), and puromycin aminonucleoside (PA) on the morphology, cytoskeleton, and tyrosine phosphorylation of differentiated process-bearing cultured podocytes.

RESULTS

PS and PA induced similar profound morphological alterations, including retraction and detachment of podocyte processes from the extracellular matrix (ECM). The effects of PS occurred within six hours, whereas PA showed its most severe effects after 72 hours. Structural changes included reorganization of the actin cytoskeleton and focal contacts and were accompanied by an increase in tyrosine phosphorylation. The same effects were induced by application of vanadate, an inhibitor of protein tyrosine phosphatases (PTPs), suggesting that PTPs regulate podocyte process structure. Since disruption of the actin cytoskeleton with cytochalasin B protected the cells from PS-induced effacement and detachment, cytoplasmic PTPs were implicated in these events. Using reverse transcription-polymerase chain reaction (RT-PCR), we demonstrated the expression of four cytoplasmic PTPs in podocytes: SHP-2, PTP-PEST, PTP-1B, and PTP-36.

CONCLUSIONS

These studies indicate an important role for cytoplasmic PTPs as regulators of podocyte process dynamics. Future studies will aim at restoring the normal foot process architecture of podocytes in glomerular diseases associated with proteinuria by modulating the activity of cytoplasmic PTPs.

Childhood diethylene glycol poisoning treated with alcohol dehydrogenase inhibitor fomepizole and hemodialysis

Diethylene glycol (DEG), a commonly used solvent, has been implicated in multiple poisoning deaths, the most recent being the Haitian acetaminophen tragedy. Unlike the more commonly seen ethylene glycol ingestion, little is understood of DEG metabolism or kinetics in humans. This has made the clinical presentation, biochemical correlates, and treatment options unclear. Patients presenting less than 12 hours after DEG ingestion may not show metabolic acidosis, whereas those presenting later may show florid metabolic acidosis. Kinetic data lend support to these observations. We report a case of DEG ingestion in a 17-month-old girl who was managed with activated charcoal, fomepizole (a recently available alcohol dehydrogenase inhibitor), and hemodialysis (HD). Pre-HD and post-HD DEG levels support clearance of DEG with HD.

Amino acid loss and nitrogen balance in critically ill children with acute renal failure: a prospective comparison between classic hemofiltration and hemofiltration with dialysis

HYPOTHESIS

Amino acid (AA) loss is not equivalent on continuous venovenous hemofiltration (CVVH) compared with continuous venovenous hemodiafiltration (CVVHD). Amino acid supplementation may be necessary to adjust for a greater clearance on CVVH to maintain nitrogen balance similar to that of CVVHD.

OBJECTIVE

To compare AA losses and nitrogen balance between CVVH and CVVHD in children with acute renal failure.

SETTING

Pediatric patients in the pediatric intensive care unit of a tertiary referral center.

DESIGN

Prospective randomized crossover study in consecutive children who required hemofiltration.

PATIENTS

A total of 12 plasma clearance studies for AA and urea, consisting of 24-hr collections of ultrafiltrate and urine for nitrogen balance, was performed on six patients during CVVH and CVVHD. Patients received total parenteral nutrition (TPN) with caloric intake 20% to 30% above their resting energy expenditure measured by indirect calorimetry and 1.5 g/kg/day protein of TPN. Study conditions were comprised of 2 L/hr/1.73 m2 of dialysate or prefiltered replacement fluid and hemofilter flow rates of 4 mL/kg/min were maintained for all patients.

METHODS AND MAIN RESULTS

Amino acid clearances were greater on CVVH than CWHD, except for glutamic acid, where clearance was 6.73+/-2.31 (SEM) mL/min/1.73 m2 on CVVH and 7.59+/-2.79 mL/min/1.73 m2 for CVVHD (NS). The clearance difference between the two modalities was 30%. Urea clearance was equivalent (30.1+/-1.74 mL/min/1.73 m2 and 29.0+/-.97 mL/min/1.73 m2) for CVVH and CVVHD, respectively. Amino acid loss on CVVH and CVVHD was similar (12.50+/-1.29 g/day/1.73 m2 vs. 11.61+/-1.86 g/day/1.73 m2, respectively), representing 12% and 11%, respectively, of the daily protein intake. The catabolic state, as measured by urea nitrogen appearance, was high for all patients during the 48-hr study period with a mean of 291 mg/kg/day during CVVH, and 245 mg/kg/day for CVVHD. Nitrogen balance varied from a negative 12.95 g/day/1.73 m2 to a positive 4.93 g/day/1.73 m2 on CVVH and a negative 7.69 g/day/1.73 m2 to a positive 5.50 g/day/1.73 m2 on CVVHD.

CONCLUSIONS

Clearance of AA is greater on CVVH than on CVVHD, but no significant difference in AA loss was present between the two therapies. Nitrogen balance often is not met on either therapy when a standard 1.5 g/kg/day protein and a resting energy expenditure of 120% to 130% of calories is delivered by TPN.

Improvement of glycemic control by CAPD with intraperitoneal insulin in a child with IDDM and ESRD

Use of intraperitoneal insulin in diabetic end-stage renal disease (ESRD) patients receiving continuous ambulatory peritoneal dialysis (CAPD) is known to result in improved glycemic control. This route of insulin administration, although standard in adult diabetic CAPD patients, has not previously been reported in children. A 12-year old boy with ESRD from renal dysplasia who also had insulin-dependent diabetes mellitus (IDDM) was treated with CAPD and intraperitoneal insulin prior to renal transplantation. Diabetes and renal dysplasia were both diagnosed at 11 weeks of age. When he reached end-stage he was initially started on hemodialysis via a central line but was switched to CAPD because of recurrent line sepsis. His IDDM had been poorly controlled up to that time. CAPD was performed using 4 exchanges per day of 1.5% dialysate with a fixed dose of insulin added to each bag and with adjustments made based on blood glucose. His glycemic control markedly improved, with a fall in his glycosylated hemoglobin from 13.6% to 6%. CAPD was continued for 7 months until a living-related renal transplant was performed. Two episodes of peritonitis occurred while the patient received CAPD (1 episode/3.5 patient-months). We conclude that the use of intraperitoneal insulin in children with IDDM and ESRD leads to improved glycemic control. The rate of peritonitis, however, may be increased in these children.

Quantitative morphometry of renal biopsies prior to cyclosporine in nephrotic syndrome

Use of cyclosporine (CsA) in the management of children with steroid-resistant (SRNS) and steroid-dependent (SDNS) nephrotic syndrome has become increasingly popular in recent years. Although most children receive a renal biopsy prior to initiation of CsA, the relationship between initial renal histology and the subsequent clinical response to CsA is not known. We analyzed the correlation between pre-CsA segmental and global glomerular scarring and interstitial fibrosis and the subsequent response to CsA in 23 children (5.6+/-1.0 years, Mean+/-SEM) with SDNS (n=8) and SRNS (n=15) treated with CsA for 24.2+/-3.8 months and followed for 28.0+/-4.1 months. Complete remission was obtained in 78% of patients within 67.6+/-16 days, while 18% had a partial response and 4% no response. Quantitative histological analysis revealed a trend toward partial rather than complete response with increasing segmental glomerular (P=0.13), global glomerular (P=0.05), and interstitial (P=0.08) scarring, and among patients with minimal change nephrotic syndrome versus IgM nephropathy versus focal segmental glomerulosclerosis. Among complete responders, linear regression analyses revealed no correlation between time to response and pre-CsA glomerular or interstitial scarring. We conclude that increased glomerular or interstitial scarring on a pre-CsA renal biopsy tends to correlate with a partial, rather than complete, response to CsA in childhood nephrotic syndrome.

Regulation of podocyte structure during the development of nephrotic syndrome

Nephrotic syndrome is a common kidney disease seen in both children and adults. The clinical syndrome includes massive proteinuria, hypoalbuminemia, edema, and usually hypercholesterolemia. Development of these clinical changes is closely correlated with profound structural changes in glomerular epithelial cells, or podocytes, which together with the glomerular basement membrane and endothelium comprise the kidney's blood filtration barrier. Although relatively little is known about the cellular or molecular changes which occur within podocytes during the development of nephrotic syndrome, cytoskeletal proteins very likely play a central role in these changes since they are primarily responsible for the maintenance of cell structure in almost all cells. This review focuses on: (a) the structure and function of podocytes in both the normal state and during nephrotic syndrome and (b) the potential roles of several cytoskeleton-associated proteins identified in podocytes in the development of and/or recovery from the pathophysiological cytoskeletal changes which occur in podocytes during nephrotic syndrome.

Outcome of antineutrophil cytoplasmic autoantibodies-positive glomerulonephritis and vasculitis in children: a single-center experience

Vasculitis associated with antineutrophil cytoplasmic autoantibodies (ANCA) can be accompanied by a focal and necrotizing glomerulonephritis that carries a high morbidity. As many as 60% of reported children with ANCA-associated glomerulonephritis progress to end-stage renal disease. Seven children (13.0+/-0.89 years, mean age +/- SEM) with both a focal and necrotizing glomerulonephritis and a positive ANCA titer are described. Presenting symptoms were constitutional (100%) and sinopulmonary (71%); additional renal features included microscopic hematuria (100%), proteinuria (71%), and renal insufficiency (71%). Acute therapy (0 to 2 weeks from diagnosis) included intravenous corticosteroids and intravenous cyclophosphamide for all patients. Induction therapy (2 weeks to 6 months from diagnosis) consisted of cyclophosphamide (100%) and daily corticosteroids (86%) for a minimum of 6 months. Maintenance therapy that followed 6 months of induction therapy consisted of alternate day steroids (100%) combined with either oral azathioprine (50%) or oral cyclophosphamide (50%). Long-term follow-up for 48+/-12 months in all seven patients revealed that only one (14%) patient had end-stage renal disease, whereas the remaining patients had microscopic hematuria (100%), proteinuria (50%), and renal insufficiency (33%). These findings suggest that early recognition and aggressive treatment of children with ANCA-associated glomerulonephritis and vasculitis may result in an improved renal outcome compared with previous reports.

Neoral induction in pediatric renal transplantation

Neoral was instituted in pediatric renal transplant patients with the hypothesis it would have more predictable kinetics than Sandimmun. However, significant questions have arisen concerning potential toxicity and dosing interval related to its rapid absorption with subsequent high initial peak. This is compounded by the fact that children appear to metabolize cyclosporine at a greater rate than adults. This combination of a rapid peak and rapid absorption may then result in lower trough levels at 12 h. We compared the trough cyclosporine levels of nine children who received Neoral with nine who received Sandimmun at the time of initial transplantation. More frequent dosing (every 8 h) was required in the Neoral population compared with the Sandimmun population for the 1st month in order to obtain comparable trough levels. Beyond the initial 4-6 weeks, trough levels were similar for Neoral and Sandimmun. Whereas 1-month creatinine levels and blood pressures were similar, the number of blood pressure medications was significantly higher in the Neoral group. At 5.5 +/- 1.1 months' followup, a single patient in the current Neoral group and in the retrospective Sandimmun group each experienced a single OKT3 allograft-treated rejection. We suggest that the area under the curve is different in Neoral than Sandimmun, and the initial dosing frequency may need to be adjusted accordingly.

Beneficial effect of Sandoglobulin upon allograft survival in the pediatric renal transplant recipient

The use of pooled immunoglobulin (IgG) has been shown to decrease panel reactive antibodies (PRA) in highly sensitized patients awaiting transplantation. IgG infusions have also been found effective for CMV prophylaxis. Analysis of 52 non-highly sensitized children (ages 1-18) who received kidney transplants from May 1991 through January 1995 was undertaken to determine if the immunoglobulin administered for CMV prophylaxis effected allograft survival. Comparison of the "Sando Pos" group (those who received Sandoglobulin for CMV prophylaxis) to the "Sando Neg" group demonstrates a significantly improved allograft survival at 1, 2, and 3 yr post-transplantation. Despite the Sando Pos group being younger [7.3 +/- 1.3 yr vs. 10.7 +/- 0.9 yr; (mean +/- SEM) p < 0.05] allograft survival was 95%, 95% and 88% in the Sando Pos group vs. 88%, 79% and 79% in the Sando Neg group at 1, 2 and 3 yr, respectively (p < 0.01 at all three time points). It is concluded that the potential mechanism of the immunosuppressive benefit of Sandoglobulin is speculative but presumed to be upon inhibition of anti-HLA class I antibodies. We conclude that Sandoglobulin may not only be useful for CMV prophylaxis but also as an adjunct to routine immunosuppression.

Management of acute renal failure in the pediatric patient: hemofiltration versus hemodialysis

Although outcome data for acute renal failure (ARF) in the adult population (analyzed by etiology of ARF, severity of illness, and modality of treatment) are readily available, few similar data exist for the pediatric population. Pediatric survival rate data vary widely, based upon era of analysis, age and size of child, and cause of ARF. Few comparative data are available that address impact by modality chosen to treat ARF. Comparison of 122 children who were treated by hemodialysis (HD; n = 58) versus hemofiltration (HF; n = 64) reveals a combined survival rate of 65%. Survival by modality was higher for HD (83%) than for HF (48%). The major diagnosis treated with HF was sepsis (29/64; 45%), with a survival rate of 31%, whereas the major diagnosis treated with HD (27/58; 46%) was primary renal failure, with a survival rate of 96%. Seventy-one percent of children undergoing HF required pressor support for hypotension, whereas only 24% of those receiving HD needed pressor support (P < 0.01). We conclude that the choice of renal replacement therapy (RRT) modality needs to be determined by the best treatment available. To adequately evaluate therapy measures, further analyses of outcome need to consider those factors that determine choice of RRT and those that affect survival independent of ARF.

Oral feeding of renal tubular antigen abrogates interstitial nephritis and renal failure in Brown Norway rats

We have examined whether oral feeding of antigen can regulate the expression of autoimmune interstitial nephritis induced by antigen-in-adjuvant (RTA/CFA) immunization of Brown Norway rats. Male rats were divided into six experimental groups: Group I, RTA/CFA immunization alone; Groups II, III, and IV were pretreated with 1 mg (Group II), 5 mg (Group III), and 25 mg (Group IV) of oral tubular antigen every other day for ten days, followed by RTA/CFA immunization; Group V was pretreated with a control antigen, followed by RTA/CFA immunization; and Group VI was immunized with CFA alone. Renal histology, inulin clearance, DTH responses to RTA, and IgG antibody responses to RTA were monitored as endpoints of the study. Our results demonstrated that Group III and IV animals had significantly less severe renal injury, as assessed by inulin clearance and extent of renal cortical involvement by mononuclear cells. Group II and IV animals had suppressed DTH responses, and only Group IV animals had significantly depressed antigen-specific IgG serum titers. Group III animals had neither suppressed DTH responses or IgG titers. We conclude that oral administration of tubular antigen can modulate the intensity of interstitial nephritis produced by immunization, but that the regulatory mechanism is not dependent (at all doses of fed antigen) on suppressed DTH reactivity to RTA or suppressed antigen-specific IgG.

Diagnosis and management of primary hyperoxaluria type 1 in infancy

We report a case of a 6-month-old infant who presented with failure to thrive due to end-stage renal disease as a result of primary hyperoxaluria type 1. The infant was managed with a combined daily hemodialysis and peritoneal dialysis prescription in order to manage the total body oxalate burden. Medical management included oral pyridoxine, aggressive hydration and nutritional supplementation via an enteral feeding tube. At one year of age the infant underwent a combined liver/kidney transplantation with intra- and daily post-operative hemodialysis to prevent oxalate deposition in the newly transplanted organs. The post-operative course was complicated by gross hematuria and increased hyperoxaluria, requiring an increase in hydration and thiazide diuretics. This infant received a combination of dialysis modalities which was designed to lower the potential oxalate burden prior to transplantation. This case illustrates the difficulty in medical management of an infant pre- and post-combined liver/kidney transplantation.

Podocyte alpha-actinin induction precedes foot process effacement in experimental nephrotic syndrome

Attachment of podocytes to the glomerular basement membrane is thought to be mediated primarily by alpha 3/beta 1-integrins and by cytoskeletal proteins including actin, talin, vinculin, and alpha-actinin. We analyzed the expression of those molecules in rat glomeruli at several time points during induction of podocyte foot process effacement and nephrotic syndrome with puromycin aminonucleoside (PAN). PAN injection resulted in marked induction of glomerular alpha-actinin (40% increase vs. paired controls, P < 0.01), which clearly preceded development of podocyte foot process effacement and proteinuria and localized almost exclusively to podocytes. Delayed induction of glomerular alpha 3-integrin (44% increase vs. paired controls, P < 0.01) following foot process effacement was also observed but was not restricted to podocytes. No significant changes in glomerular vinculin, talin, beta 1-integrin, or total actin expression occurred at any time point during disease development. We conclude that foot process effacement is preceded by induction of alpha-actinin in podocytes in experimental nephrotic syndrome. Altered expression of this actin cross-linking protein in podocytes may have a pathogenic role in foot process effacement in nephrotic syndrome.

Altered expression of glomerular heat shock protein 27 in experimental nephrotic syndrome

Although nephrotic syndrome is a very common kidney disease, little is known about the molecular changes occurring within glomerular capillary loops during development of disease. The characteristic histologic change is retraction (effacement) of the distal "foot" processes of glomerular epithelial cells (GEC) which surround the capillary loops. The GEC foot processes are an essential part of the kidney's filtration barrier, and their structure is regulated primarily by actin microfilaments, cytoskeletal proteins present in high concentrations in foot processes. Actin polymerization has been reported to be regulated via phosphorylation of the low molecular weight heat shock protein, hsp27. We localized hsp27 within normal rat GECs using immunofluorescence and immunoelectron microscopy. Induction of nephrotic syndrome and GEC foot process effacement using the puromycin aminonucleoside rat model resulted in significant increases in: (a) renal cortical hsp27 mRNA expression (826 +/- 233%, x +/- SEM, P < 0.01 vs. control); (b) glomerular hsp27 protein expression (87 +/- 2%, P < 0.001 vs. control); and (c) glomerular hsp27 phosphorylation (101 +/- 32%, P < 0.05 vs. control). These findings support the hypothesis that hsp27, by regulating GEC foot process actin polymerization, may be important in maintaining normal foot process structure, and regulating pathophysiologic GEC cytoskeletal changes during development of nephrotic syndrome.

Heterogeneous T cell receptor V beta gene repertoire in murine interstitial nephritis

Anti-tubular basement membrane disease (alpha TBM) produces T cell-mediated interstitial nephritis in SJL/J mice following immunization with heterologous renal tubular antigen. Initial mononuclear infiltrates appear in vivo after six to eight weeks, with subsequent progression to renal fibrosis and endstage kidney disease. Cultured lymph node derived nephritogenic T cells from these mice react to a small epitopic region of the 3M-1 target antigen and share a common amino acid motif in their V beta CDR3 regions. We now have used RT-PCR to further characterize the renal expression of T cell receptor (TcR) V beta gene repertoires during the course of this disease. Individual kidneys with focal mononuclear infiltrates characteristic of early alpha TBM disease express up to three different TcR V beta genes; however, the same V beta genes are not found in all kidneys at the same early stage of injury. DNA sequencing of the V beta RT-PCR products reveals a heterogeneous population of VDJ recombinations and deduced CDR3 amino acid sequences. Our studies do not support TcR V beta region gene restriction in histologically-detectable alpha TBM disease, but are more consistent with a dynamic, organ-specific autoimmune disease, directed at multiple autoantigenic epitopes.

Long-term cyclosporine therapy for pediatric nephrotic syndrome: a clinical and histologic analysis

Cyclosporine (CsA) is effective in treating steroid-dependent (SDNS) and steroid-resistant (SRNS) nephrotic syndrome (NS) in children, but because of the potential for chronic nephrotoxicity, its long-term use is controversial. This study reports the results of long-term CsA treatment in 22 children with idiopathic NS. Indications for treatment included SDNS (N = 7) and SRNS (N = 15) children. Pre-CsA histology showed minimal change disease in three patients, immunoglobulin M nephropathy (IgM) in 14 patients, and focal segmental glomerulosclerosis (FSGS) in five patients. All patients had normal initial serum creatinine values. CsA was added to prednisone at 6.3 +/- 0.4 mg/kg per day (mean +/- SE) and adjusted to maintain whole blood trough HPLC levels of 70 to 120 ng/mL for a period of 6 to 53 months (mean, 22 months). Analysis by clinical course revealed that 13 of 15 patients with SRNS (87%) entered remission after a mean duration of CsA treatment of 58 days, whereas seven of seven patients with SDNS were able to be weaned off of daily prednisone therapy. Histologic analysis showed that all five patients with FSGS and 13 of 14 patients with IgM nephropathy either entered remission or were weaned off of daily steroids. Ten of the 22 patients (45%) with complete remission required CsA plus low-dose alternate-day prednisone to maintain remission. Hypertension was seen in eight of 22 patients (36%). No patient had a significant increase in serum creatinine concentration. Renal biopsies performed in 12 patients after 12 to 41 months (mean, 21 months) of CsA therapy showed no nephrotoxicity or disease progression in ten patients. Progression of the previous interstitial fibrosis and tubular atrophy was noted in two patients, suggesting a 17% incidence of CsA nephrotoxicity. This analysis of the long-term risks and benefits of CsA for childhood NS has identified two important findings: (1) combined CsA and alternate-day steroids can be highly effective in inducing complete remission in patients with SRNS and biopsy-proven IgM nephropathy, and (2) long-term use of CsA in moderate doses with closely monitored levels can result in a relatively low incidence of nephrotoxicity.

Determinants of survival in pediatric continuous hemofiltration

Continuous hemofiltration (CH) is being used in increasing numbers of pediatric intensive care unit patients. Experience with 114 CH treatments in 98 critically ill children from March 1988 to March 1993 is presented in this study. Ages ranged from 1 day to 23 yr (mean +/- SE = 7.1 +/- 0.7 yr), and 54% of patients were male. Seventeen percent of all treatments were performed in neonates under 1 month of age. The most common primary diagnoses were sepsis and adult respiratory distress syndrome (11 patients each), liver transplantation and hypoplastic left heart syndrome (10 patients each), and hemolytic uremic syndrome (9 patients). The most frequent indications for CH were fluid overload and acute renal failure (42% each). Choices for CH included: continuous arteriovenous hemofiltration (CAVH, 50%), continuous arteriovenous hemodiafiltration (CAVH, 23%), continuous venovenous hemofiltration (CVVH, 18%), and continuous venovenous hemodiafiltration (CVVH-D, 9%). Choices for anticoagulation included: none (47%), regional (49%), and systemic (4%). Treatment duration ranged from 1 to 25 days (mean = 5.3 +/- 0.4 days). Mean filter life span for 363 filters was 0.94 +/- 0.1 filters/patient per day. Despite an overall survival rate of 43%, survival to discharge varied greatly (0 to 100%) among the 24 diagnostic groups: tumor lysis syndrome and systemic lupus erythematosus (3/3 patients each, 100%), hemolytic uremic syndrome (8/9 patients, 89%). This compares with: bone marrow transplantation (0/6 patients, 0%), hypoplastic left heart syndrome (2/10 patients, 20%), and leukemia (1/4 patients, 25%). Survival to hospital discharge was better in patients who did not receive pressors (P < 0.005) and in patients treated with combined ultrafiltration and dialysis (CAVH-D, CVVH-D) compared with ultrafiltration alone (CAVH, CVVH) (P < 0.005), but was not notably affected by patient age, sex, use of anticoagulation, filter life span, blood pump-assisted versus spontaneous CH, or duration of therapy. Filter life span was not affected by use of anticoagulation, but was remarkably longer in patients with arteriovenous versus venovenous CH (P < 0.004). It was concluded that: (1) empirical anticoagulation of patients treated with CH is not necessary; (2) children with a minority of underlying diseases and those requiring pressor support at initiation of CH appear to have relatively poor survival rates despite the technically effective use of CH; and (3) the addition of countercurrent dialysis to routine CH may enhance patient survival to hospital discharge.

Molecular analysis of the helper T cell response in murine interstitial nephritis. T cells recognizing an immunodominant epitope use multiple T cell receptor V beta genes with similarities across CDR3

Anti-tubular basement membrane disease (alpha TBM disease) produces T cell-mediated interstitial nephritis in SJL mice after immunization with renal tubular antigen. Initial mononuclear infiltrates appear in vivo after several weeks, with the subsequent progression to renal fibrosis and end stage renal disease over many months. We have analyzed the fine specificity of the autoreactive helper T cell repertoire in alpha TBM disease through the isolation and characterization of a panel of CD4+ Th1 clones harvested after 1-2 wk from animals immunized to produce disease. All clones capable of mediating alpha TBM disease are directed towards a 14-residue immunodominant epitope (STMSAEVPEAASEA) contained within the target antigen, 3M-1. Evaluation of the T cell receptor (TCR) V beta repertoire used by these autoreactive T cells reveals the use of several V beta genes, but with some preference for V beta 14. Sequencing across the putative CDR3 region of the TCR beta chains suggests that common amino acids at the V beta(N)D beta junction and the D beta(N)J beta junction may contribute to the specific ability of these cells to recognize the immunodominant epitope.

Inherited interstitial nephritis in kdkd mice

kdkd mice, a mutant subline of CBA/Ca mice, develop a progressive, T cell-mediated, autoimmune interstitial nephritis which leads to renal failure and death of all mice at 20-28 weeks of age. This disease is inherited in an autosomal recessive manner, with complete penetrance, and has been linked to grizzled and waltzer on mouse chromosome 10. Immunologic evaluation of this lesion has demonstrated that histologic disease is initiated by a population of CD8+, H-2Kk-restricted T cells, which recognize an antigen in collagenase-solubilized syngeneic renal tubules. These nephritogenic effector cells can also be demonstrated in non-disease prone CBA/Ca mice. Susceptibility to autoimmune nephritis correlates with distinct expression of regulatory, rather than effector, T cells. Interstitial nephritis in kdkd mice can be inhibited by protein-calorie restriction, infusions of CBA/Ca CD8+ T cells, or monoclonal antibodies of ICAM-1. This murine model most closely resembles medullary cystic disease in humans, which has not historically been considered an autoimmune disease. Mapping of the genes for both medullary cystic disease and the defect in kdkd mice should augment our understanding of mechanisms of organ-specific autoimmunity.

Urethral stones: US for identification in boys with hematuria and dysuria

There are multiple causes for hematuria in infants and children. When hematuria is accompanied by dysuria, however, one should focus attention on the lower urinary tract. Although ultrasound (US) is a well-established method for assessing the kidneys and bladder, little attention has been focused on its use for evaluating urethral abnormalities, since voiding cystourethrography or retrograde urethrography usually is used. In the cases of two young boys, sonography aided in the identification of clinically unsuspected urethral stones. US evaluation of the urethra is now included as an integral part of urinary tract sonography in male patients with hematuria accompanied by dysuria.

Enhanced GFR response to oral versus intravenous arginine administration in normal adults

Both oral protein ingestion and intravenous amino acid infusions have been shown to increase glomerular filtration rate (GFR) and renal plasma flow (RPF) in normal subjects. Although the mechanism of this effect is not known, the renal responses to these loads have been associated with increases in peripheral glucagon concentrations. Conflicting data exist concerning the role of glucagon in the hyperfiltration response after an oral protein meal or administration of an intravenous amino acid mixture. Using a single amino acid as the stimulus for hyperfiltration, we compared the renal responses in six normal subjects to 30 gm oral arginine-HCl, intravenous arginine-HCl, and intravenous glucagon infused at the rate of 10 ng/kg/min. GFR, RPF, and glucagon concentration, as well as levels of plasma amino acids and selected gastrointestinal hormones, were measured for six 30-minute clearance periods after each load. Significant rises in mean peak GFR were noted after both oral arginine (104 +/- 5 ml/min x 1.73 m2 to 145 +/- 9 ml/min x 1.73 m2, p less than 0.02) and intravenous arginine (118 +/- 10 ml/min x 1.73 m2 to 134 +/- 11 ml/min x 1.73 m2, p = 0.02) administration. Mean peak RPF rose significantly after oral arginine (510 +/- 26 ml/min x 1.73 m2 to 710 +/- 32 ml/min x 1.73 m2, p less than 0.01) but not after intravenous arginine (616 +/- 60 ml/min x 1.73 m2 to 687 +/- 64 ml/min x 1.73 m2, p = 0.18). Intravenous glucagon infusion also increased both mean peak GFR (99 +/- 9 ml/min x 1.73 m2 to 149 +/- 10 ml/min x 1.73 m2, p less than 0.01) and RPF (514 +/- 48 ml/min x 1.73 m2 to 771 +/- 38 ml/min x 1.73 m2, p less than 0.01) significantly. We found the mean peak percent rise in GFR (43% +/- 13%) and RPF (42% +/- 12%) after oral arginine to be notably greater than that after intravenous arginine (14% +/- 5% and 13% +/- 9%, respectively). However, the mean peak percent rise in glucagon concentration after oral arginine was significantly lower than that after intravenous arginine (62% +/- 25% versus 479% +/- 176%, respectively, p = 0.04). Infusion of glucagon increased GFR (54% +/- 13%) and RPF (55% +/- 12%) to a degree similar to that seen after oral arginine, but again with a significantly higher mean peak percent rise in peripheral glucagon concentrations when compared with the rise after oral arginine (798% +/- 348% vs 62% +/- 25%, p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)