Bruce M. Tune

Treatment of steroid-resistant focal segmental glomerulosclerosis with pulse methylprednisolone and alkylating agents

In children, steroid-resistant nephrotic syndrome due to focal segmental glomerulosclerosis (FSGS) is frequently a progressive condition resulting in end-stage renal disease. There have been no reports of effective treatment for this condition. For the past several years, the Pediatric Nephrology services at the University of California, San Diego and Stanford University Schools of Medicine have treated these patients with a protocol involving infusions of high doses of methylprednisolone, often in combination with oral alkylating agents. Twenty-three children have been treated in this manner with a follow-up of 46±5 months. Twelve of these children are in complete remission. Six have minimal to moderate proteinuria. Four children remain nephrotic. Each of these children has a normal glomerular filtration rate. One child developed chronic renal failure and subsequently died while on dialysis. These results appear significantly better than previous series of children with FSGS. A controlled, multi-center trial of this protocol has been proposed.

Nephrotoxicity of beta-lactam antibiotics: mechanisms and strategies for prevention

The nephrotoxic beta-lactam antibiotics cause acute proximal tubular necrosis. Significant renal toxicity, which has been rare with the penicillins and uncommon with the cephalosporins, is a greater risk with the penems. Mechanisms of injury include: (1) transport into the tubular cell, mainly through the antiluminal organic anion secretory carrier; (2) acylation of target proteins, causing respiratory toxicity by inactivation of mitochondrial anionic substrate carriers; and (3) lipid peroxidation. The most nephrotoxic beta-lactams available for study are cephaloridine, cephaloglycin, and imipenem; panipenem, which is comparably nephrotoxic, is currently available only in Japan. Cephaloridine has several unique properties, probably all caused by its pyridinium side-group: (1) its secretory transport into the tubular cell is followed by minimal cell to luminal fluid movement, resulting in extreme intracellular sequestration; (2) it is the only beta-lactam shown to cause significant oxidative injury; (3) it has a limited ability to attack the mitochondrial carriers for pyruvate and the short-chain fatty anions. Cephaloglycin and imipenem undergo less intracellular trapping than cephaloridine, but have sufficient tubular cell uptake, reactivity, and generalized toxicity to mitochondrial substrate carriers to be severely nephrotoxic. Cephaloridine and cephaloglycin are no longer used clinically. Imipenem and panipenem are marketed in combination with nephroprotective renal transport inhibitors. Strategies for avoiding renal toxicity with new cephalosporins and penems are discussed.

Serum IgE in patients with minimal-change nephrotic syndrome

Serum levels of IgE were studied in 53 children; 17 children had minimal-change nephrotic syndrome, 9 had probable MCNS, and 27 had other renal diseases. These studies showed higher levels of IgE in patients with MCNS and probable MCNS than in the renal control subjects or in the general population. Patients with MCNS who received therapy with cyclophosphamide had lower levels of IgE than those who did not.

Steroid-resistant nephrotic focal segmental glomerulosclerosis : a treatable disease

Abstract. If not aggressively treated, oral steroid-resistant (SRst) nephrotic focal segmental glomerulosclerosis (FSGS) is likely to progress to end-stage renal failure. Three observations challenge the conclusion of the International Study of Kidney Diseases in Children (ISKDC) that SRst FSGS is unresponsive to further immunosuppression: (1) The ISKDC definitions of response and relapse, which fit the patterns in minimal change disease, precluded appropriate recognition of partial or gradual responses. (2) In two ISKDC studies, a small number of children with FSGS in one case, and the use of a year of alternate-day prednisone as a control in the other, may have obscured the effects of cyclophosphamide. (3) Recent studies of more aggressive therapies have provided strong evidence of benefit. High-dose methylprednisolone infusion therapy, with alternate-day prednisone alone or with alternate-day prednisone plus an alkylating agent (the M-P/triple therapy protocol) has achieved sustained, complete remissions with stable renal function in 66% of children with SRst FSGS, and near-complete resolution of proteinuria in another 9%. Cyclosporine (CsA) plus alternate-day prednisone has produced complete or near-complete remissions in 35% of similar cases. Whether or not controlled studies will confirm the apparently greater efficacy of the M-P/triple therapy protocol, the favorable outcomes with both the M-P and the CsA regimens support the conclusion that a conservative approach to SRst FSGS is no longer appropriate.

Oxidative and mitochondrial toxic effects of cephalosporin antibiotics in the kidney: A comparative study of cephaloridine and cephaloglycin

Cephaloridine and cephaloglycin are the two most nephrotoxic cephalosporins released for human use. Cephaloridine has been shown to produce both oxidative and mitochondrial respiratory injury in renal cortex in patterns of dose (or concentration) and time that are consistent with pathogenicity. Cephaloglycin also produces respiratory toxicity, and recent studies have provided evidence that this injury results from an inactivation of mitochondrial anionic substrate transporters. The abilities of cephaloglycin to produce oxidative changes and cephaloridine to block mitochondrial substrate uptake have not been examined yet. We therefore compared these two cephalosporins with one another and with cephalexin, which is not nephrotoxic, in the production of the following: (1) several components of oxidative stress or damage [depletion of reduced glutathione (GSH) and production of oxidized glutathione (GSSG) in renal cortex, inhibition of glutathione reductase in vitro, and production of the lipid peroxidation products malondialdehyde (MDA) and conjugated dienes (CDs) in renal cortex]; and (2) renal cortical mitochondrial toxicity [to both respiration with, and the transport of, succinate]. Cephaloridine depleted GSH and elevated GSSG in renal cortex, inhibited glutathione reductase, and increased both MDA in whole cortex and CDs in cortical microsomes and mitochondria. While cephaloglycin depleted GSH at least as much as did cephaloridine, it produced one-fifth as much GSSG and had little or no effect on glutathione reductase activity or on cortical MDA or microsomal CDs; cephaloglycin caused a transient small increase of mitochondrial CDs. Cephalexin produced no oxidative changes except for a slight increase of mitochondrial CDs comparable to that produced by cephaloglycin. Both cephaloridine and cephaloglycin, but not cephalexin, decreased the unidirectional uptake of, and respiration with, succinate in cortical mitochondria. We conclude that cephaloridine and cephaloglycin are both toxic to mitochondrial substrate uptake and respiration, but differ significantly in their generation of products of oxidation.

The hemolytic-uremic syndrome in California: A review of 28 nonheparinized cases with long-term follow-up

During the years 1960 to 1969, 28 cases of the hemolytic-uremic syndrome were seen in 27 children at the Stanford University Hospital. Certain major differences were noted between this series and the comprehensively reviewed one in Buenos Aires: an older age, averaging 4 1/2 years at Stanford versus 1 1/12 years in Buenos Aires; a more prolonged and frequently more severe prodrome; and a shorter duration of oligoanuria, average 6.4 days (0 to 18) versus 12.2 days (3 to 48). Three patients died at Stanford in the acute phase, 2 of the 5 seen before peritoneal dialysis was used and 1 of the subsequent 22 patients (23 cases). Of the 24 survivors, 21 have been followed for 2 to 10 years (average 5 years). Nineteen patients have recovered completely, with normal blood pressures and normal creatinine clearances of 90 to 142 ml. per minute per 1.73M 2 . (average 114). Two patients were left with chronic renal insufficiency (9.5 per cent versus 30 per cent seen in Buenos Aires). None of these patients received heparin therapy. It is concluded that the hemolytic-uremic syndrome as seen in this geographic area has a different natural history and a more favorable long-term prognosis than the syndrome in Buenos Aires.

Treatment of Childhood Prednisone-Resistant Nephrotic Syndrome and Focal Segmental Glomerulosclerosis with Intravenous Methylprednisolone and Oral Alkylating Agents

Patients with prednisone-resistant nephrotic syndrome and biopsy-proven focal segmental glomerulosclerosis were treated with intravenous methylprednisone. After the first 2 weeks of therapy, the average urine protein excretion decreased from 247 to 96 mg/m2/h (p less than 0.04). Two of the 7 patients have had long-term, nearly complete remissions. The other patients relapsed. One relapsing patient was retreated with methylprednisolone and is now in remission. Four relapsing patients were treated with alkylating agents, in combination with methylprednisolone. All of these patients entered complete or partial remissions. Methylprednisolone causes a significant decrease in the proteinuria of children with focal segmental glomerulosclerosis. In addition, although the follow-up period is relatively short, it would appear that methylprednisolone, often in conjunction with an alkylating agent, has significantly improved the clinical status of these patients.

Management of the difficult nephrotic patient

Most children with nephrotic syndrome do well, usually with multiple relapses and remissions. Some children require high doses of oral steroids to sustain a remission and develop significant steroid toxicity. These patients frequently can be managed with oral alkylating agents or with cyclosporine. A few nephrotic children to not respond to oral prednisone. The most common biopsy finding in steroid-resistant patients is focal segmental glomerulosclerosis. Many patients with this condition progress to chronic renal failure. Evidence suggests that the outcome is improved with either cyclosporine or with a protocol using pulse intravenous methylprednisolone and oral alkylating agents.

Thienamycin nephrotoxicity: Mitochondrial injury and oxidative effects of imipenem in the rabbit kidney

The nephrotoxic cephalosoprins cephaloridine and cephaloglycin both produce mitochondrial respiratory toxicity in renal cortex. Recent work has provided evidence that this respiratory toxicity is caused by acylation and inactivation of mitochondrial anionic substrate transporters. While cephaloridine also causes significant lipid peroxidative injury in cortical mitochondria and microsomes, cephaloglycin causes little or no oxidative damage under identical conditions. The recently released thienamycin antibiotic, imipenem, like the toxic cephalosporins, produces acute proximal tubular necrosis which can be prevented completely by prior administration of probenecid. The ability of imipenem to block mitochondrial substrate uptake and respiration and produce oxidative changes has not been examined. We therefore evaluated the effects of imipenem in rabbit renal cortex on the following: (1) mitochondrial function [respiration with and uptake of succinate, and uptake of ADP]; and (2) evidence of oxidative change [depletion of reduced glutathione (GSH), production of oxidized glutathione (GSSG), and production of lipid peroxidative injury, as reflected in microsomal conjugated dienes (CDs)]. The mitochondrial effects of 300 mg/kg body wt of imipenem, given i.v. 1 and 2 hr before killing the animals, were comparable to those of the nephrotoxic cephalosporins. There was significant reduction of respiration with, and unidirectional uptake of, succinate at both times, while mitochondrial ADP transport was comparatively unaffected. Imipenem also depleted GSH and increased GSSG and CDs at 1 hr. These effects, however, were considerably smaller than those of a comparably nephrotoxic dose of cephaloridine, and this evidence of oxidative stress had resolved by 2 hr. We conclude that imipenem and the nephrotoxic cephalosporins have similar effects on mitochondrial substrate uptake and respiration, but differ significantly in their production of oxidative injury.

Cephalosporin and carbacephem nephrotoxicity: Roles of tubular cell uptake and acylating potential

Three beta-lactams, desacetylcephaloglycin, ampicillin, and loracarbef, were studied to test a hypothesis derived from retrospective analysis of previously studied cephalosporins: that beta-lactam nephrotoxicity develops in approximate proportion to tubular cell antibiotic concentrations and lactam ring reactivities. Concentrations of each beta-lactam (and insulin) in rabbit renal cortex and serum were measured at the end of 0.5-hr infusions of 100 mg antibiotic/kg body weight and 0.5 to 0.67 hr later. Total cortical AUCs (total areas under the curve of concentration and time in renal cortex) and transported cortical AUCs (total minus insulin-space beta lactam) were calculated from these measurements. Reactivities, determined by the rate constants of lactam-ring opening at pH 10, were taken from the literature. Nephrotoxicity was quantified by grades of proximal tubular cell necrosis and by serum creatinine concentrations 2 days after infusion of 100-1500 mg/kg of the antibiotics. Desacetylcephaloglycin was slightly less nephrotoxic than cephaloglycin; the AUCs reactivities, and toxicities of these two cephalosporins fit the proposed model, particularly when allowance is made for hepatic and renal deacetylation of cephaloglycin. The very low AUCs, limited reactivity, and absence of nephrotoxicity of ampicillin also fit the model. Loracarbef had a transported AUC less than three times, and reactivity one-thirtieth, those of cefaclor, respectively. Although only at 1500 mg/kg, loracarbef was significantly more nephrotic than cefaclor. If the relativity of loracarbef with its targeted bacterial proteins, which is essentially the same as that of cefaclor, is considered instead of the base hydrolysis rate constant, than loracarbef also fits the model. By the same analysis, the comparatively high in vitro stability of other carbacephems, although pharmaceutically convenient, may not limit their nephrotoxicity.