Eduardo H. Garin

Clinical Significance of Primary Vesicoureteral Reflux and Urinary Antibiotic Prophylaxis After Acute Pyelonephritis: A Multicenter, Randomized, Controlled Study

OBJECTIVES. To evaluate the role of primary vesicoureteral reflux (VUR) in increasing the frequency and severity of urinary tract infections (UTIs) and renal parenchymal damage among patients with acute pyelonephritis and to determine whether urinary antibiotic prophylaxis reduces the frequency and/or severity of UTIs and/or prevents renal parenchymal damage among patients with mild/moderate VUR. METHODS. Patients 3 months to 18 years of age with acute pyelonephritis, with or without VUR, were assigned randomly to receive urinary antibiotic prophylaxis or not. Patients were monitored every 3 months for 1 year. Dimercaptosuccinic acid renal scans were repeated at 6 months or if there was a recurrence of febrile UTI. Urinalysis and urine culture were performed at each clinic visit. Renal ultrasound scans and voiding cystourethrograms were repeated at the end of 1 year of follow-up monitoring. RESULTS. Of the 236 patients enrolled in the study, 218 completed the 1-year follow-up monitoring. Groups were similar with respect to age, gender, and reflux grade distribution for those with VUR. No statistically significant differences were found among the groups with respect to rate of recurrent UTI, type of recurrence, rate of subsequent pyelonephritis, and development of renal parenchymal scars. CONCLUSIONS. After 1 year of follow-up monitoring, mild/moderate VUR does not increase the incidence of UTI, pyelonephritis, or renal scarring after acute pyelonephritis. Moreover, a role for urinary antibiotic prophylaxis in preventing the recurrence of infection and the development of renal scars is not supported by this study.

Urinary CD80 Excretion Increases in Idiopathic Minimal-Change Disease

CD80 is expressed on all antigen-presenting cells and is present on podocytes in a number of experimental models of nephrotic syndrome. We tested whether urinary soluble CD80 increased with idiopathic minimal-change disease (MCD). We collected urine and serum samples from patients with MCD in relapse and in remission, patients with nephrotic syndrome resulting from other glomerular diseases (FSGS, membranoproliferative glomerulonephritis, IgA nephropathy, and membranous nephropathy), patients with systemic lupus erythematosus, and normal control subjects. Urinary concentrations of soluble CD80 in patients with relapsed MCD were significantly higher compared with those observed in patients with MCD in remission, other glomerular diseases, and systemic lupus erythematosus with and without proteinuria and healthy control subjects. Urinary concentrations of soluble CTLA-4, which is a negative regulator of CD80, were not statistically different in patients with relapsed MCD compared with those in remission. The urinary soluble CD80/CTLA-4 ratio was >100-fold higher in patients with relapsed MCD compared with those in remission (P < 0.008). In contrast, serum concentrations of soluble CD80 and CTLA-4 did not distinguish patients with MCD in relapse and in remission. In conclusion, urinary soluble CD80 is elevated in idiopathic MCD, which could be relevant to both diagnosis and pathogenesis.

Urinary CD80 is elevated in minimal change disease but not in focal segmental glomerulosclerosis.

Controversy exists as to whether minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) represent different diseases or are manifestations within the same disease spectrum. Urinary excretion of CD80 (also known as B7.1) is elevated in patients with MCD and hence we tested whether urinary CD80 excretion might distinguish between patients with MCD from those with FSGS. Urinary CD80 was measured in 17 patients with biopsy-proven MCD and 22 with proven FSGS using a commercially available enzyme-linked immunosorbent assay and its molecular size determined by western blot analysis. A significant increase in urinary CD80, normalized to urinary creatinine, was found in patients with MCD in relapse compared to those in remission or those with FSGS. No significant differences were seen when CD80 urinary excretion from MCD patients in remission were compared to those with FSGS. In seven of eight MCD patients in relapse, CD80 was found in glomeruli by immunohistochemical analysis of their biopsy specimen. No CD80 was found in glomeruli of two patients with FSGS and another MCD patient in remission. Thus, our study supports the hypothesis that MCD and FSGS represent two different diseases rather than a continuum of one disease. Urinary CD80 excretion may be a useful marker to differentiate between MCD and FSGS.

T regulatory cell function in idiopathic minimal lesion nephrotic syndrome

The purpose of this study was to test the hypothesis that, in idiopathic minimal lesion nephrotic syndrome (IMLNS), the T regulatory (T reg) cell suppressor mechanism is deficient, thereby enhancing cytokine release by T effector cells. Twenty-one patients with IMLNS, eight healthy controls and two patients with nephrotic syndrome and membranoproliferative glomerulonephritis were studied. The percentage of T reg cells was similar in the healthy controls and in patients with IMLNS in relapse or in remission. Thymidine incorporation in autologous T effector cells, as well as expression of the regulatory cytokine interleukin (IL)-10, was significantly reduced in patients in relapse when compared with patients in remission and healthy subjects. IL-2 expression was also reduced in patients in relapse but did not achieve statistical significance. In a different set of experiments, T cells, from subjects with IMLNS in remission, when stimulated with antiCD3-antiCD28 antibodies, secreted increased levels of cytokines. No such increase in cytokines was observed when cells from healthy controls were stimulated with same mitogen. The impaired T reg cell function observed in these patients may have pathogenic and therapeutic implications, because it could explain the persistence of the proposed pathogenic cytokines observed in the patients with IMLNS.

A case of unfulfilled expectations. Cytokines in idiopathic minimal lesion nephrotic syndrome

Idiopathic minimal lesion nephrotic syndrome (IMLNS) was proposed to be a disorder of T-cell dysfunction by Shalhoub in 1974. The mechanisms by which T-cells increase glomerular permeability have remained elusive (and unproven). There is evidence that IMLNS may be due to a circulating factor released from activated T-cells. In recent years, efforts have been made to identify this pathogenetic cytokine as well as to understand the mechanism(s) for the increased release of this factor. This review attempts to critically analyze the available published data. Using different methodologies, investigators have focused on the production of cytokines in patients with IMLNS during relapse and remission. This has resulted in a plethora of data without definitive conclusions. The pathogenetic cytokine has not been identified, and it is questionable whether there is a Th2 dominance in IMLNS. The review of the available data illustrates the difficulties encountered when one is studying the cytokine secretory pattern in patients with IMLNS. Differences in patient population, type of cells studies, sample preservation, and methodology used to measure cytokines are some of the factors that could account for the disparity of observed results.

Toll-like receptor 3 ligands induce CD80 expression in human podocytes via an NF-κB-dependent pathway

BACKGROUND Recent studies suggest that CD80 (also known as B7.1) is expressed on podocytes in minimal-change disease (MCD) and may have a role in mediating proteinuria. CD80 expression is known to be induced by Toll-like receptor (TLR) ligands in dendritic cells. We therefore evaluated the ability of TLR to induce CD80 in human cultured podocytes. METHODS Conditionally immortalized human podocytes were evaluated for TLR expression. Based on high expression of TLR3, we evaluated the effect of polyinosinic-polycytidylic acid (polyIC), a TLR3 ligand, to induce CD80 expression in vitro. RESULTS TLR1-6 and 9 messenger RNA (mRNA) were expressed in podocytes. Among TLR ligands 1-9, CD80 mRNA expression was significantly induced by polyIC and lipopolysaccharide (TLR4 ligand) with the greatest stimulation by polyIC (6.8 ± 0.7 times at 6 h, P < 0.001 versus control). PolyIC induced increased expression of Cathepsin L, decreased synaptopodin expression and resulted in actin reorganization which suggested a similar injury pattern as observed with lipopolyssaccharide. PolyIC induced type I and type II interferon signaling, nuclear factor kappa B (NF-κB) activation and the induction of CD80 expression. Knockdown of CD80 protected against actin reorganization and reduced synaptopodin expression in response to polyIC. Dexamethasone, a corticosteroid commonly used to treat MCD, also blocked both basal and polyIC-stimulated CD80 expression, as did inhibition of NF-κB. CONCLUSIONS Activation of TLR3 on cultured human podocytes induces CD80 expression and phenotypic change via an NF-κB-dependent mechanism and is partially blocked by dexamethasone. These studies provide a mechanism by which viral infections may cause proteinuria.

Idiopathic Nephrotic Syndrome and Atopy: Is There a Common Link?

Numerous reports during the last 60 years have reported a strong association between idiopathic nephrotic syndrome and atopic disorders. Idiopathic nephrotic syndrome can be precipitated by allergic reactions and has been associated with both aeroallergens (pollens, mold, and dust) and food allergies. Patients with idiopathic nephrotic syndrome also may show increased serum immunoglobulin E (IgE) levels. A review of the literature suggests that although some idiopathic nephrotic syndrome cases may be associated with allergies, evidence that it is a type of allergic disorder or can be induced by a specific allergen is weak. Rather, it is likely that the proteinuria and increased IgE levels in patients with idiopathic nephrotic syndrome are caused by increased levels of interleukin 13 observed in these patients. Recent studies suggest that interleukin 13, a known stimulator of IgE response, may mediate proteinuria in patients with minimal change disease because of its ability to directly induce CD80 expression on the podocyte.

Minimal change disease: a "two-hit" podocyte immune disorder?

Minimal change disease (MCD) is the most common nephrotic syndrome in children and is commonly thought to be a T-cell disorder mediated by a circulating factor that alters podocyte function resulting in massive proteinuria. We suggest that MCD is a “two-hit” disorder. As originally hypothesized by Reiser et al. in 2004, we propose that the initial hit is the induction of CD80 (also known as B7.1) on the podocyte, and that this results in an alteration in shape with actin rearrangement that alters glomerular permeability and causes proteinuria. We propose that CD80 expression may result from either direct binding of the podocyte by cytokines from activated T cells or by activation of podocyte toll-like receptors (TLR) by viral products or allergens. We further hypothesize that under normal circumstances, CD80 expression is only transiently expressed and proteinuria is minimal due to rapid autoregulatory response by circulating T regulatory cells or by the podocyte itself, probably due to the expression of factors [cytotoxic T-lymphocyte-associated (CTLA)-4, interleukin (IL)-10, and possibly transforming growth factor (TGF)-β] that downregulate the podocyte CD80 response. In MCD, however, there is a defect in CD80 podocyte autoregulation. This results in persistent CD80 expression and persistent proteinuria. If correct, this hypothesis may lead to both new diagnostic tests and potential therapeutics for this important renal disease.

Pattern of response to prednisone in idiopathic, minimal lesion nephrotic syndrome as a criterion in selecting patients for cyclophosphamide therapy

Twenty-three children with idiopathic, relapsing minimal lesion nephrotic syndrome were divided according to their pattern of response to prednisone: (1) steroid dependent, if the relapse occurred while the dosage of prednisone was being decreased; and (2) frequent relapser, if the relapse occurred at variable periods of time (one week to two months) after discontinuing prednisone therapy. All patients received cyclophosphamide for eight weeks in a single daily dose of 2 mg/kg, in order to prolong the length of the remission. The percentage of patients who continued in remission at the end of the first year and thereafter was greater in the frequent relapser group (P = 0.05). This study suggests that the pattern of response to prednisone may be another criterion for the selection of patients who will benefit from cyclophosphamide therapy.

Toll-like receptor 3 ligand, polyIC, induces proteinuria and glomerular CD80, and increases urinary CD80 in mice

BACKGROUND We have reported that children with biopsy-proven minimal change disease (MCD) express CD80 (also known as B7.1) in their podocytes and excrete high levels of CD80 in their urine during active nephrotic syndrome. We also reported that polyIC, a Toll-like receptor 3 ligand, increases CD80 mRNA and protein expression in cultured human podocytes dose-dependently, with actin re-organization and a reduction in synaptopodin expression. METHODS To determine the effect of polyIC in the kidney, we subjected mice to systemic injection of polyIC or phosphate buffered saline. RESULTS Mice injected with polyIC developed significant proteinuria with increased urinary CD80 excretion. Glomeruli from mice injected with polyIC were normal by light microscopic examination, but showed increased CD80 production in podocytes by immunofluorescence staining. In isolated glomeruli from mice injected with polyIC, expressions of CD80 and interleukin 10 significantly increased with a mild non-significant increase in CTLA-4, and synaptopodin expression decreased significantly. CONCLUSIONS Our study demonstrates that systemically administered polyIC can induce transient proteinuria and urinary CD80 excretion with an increase in CD80 production in podocytes, increased glomerular CD80 and reduced synaptopodin expression. These findings may be relevant to the pathogenesis of proteinuria in MCD.