Effect of lipoid nephrosis cytokine on glomerular sulfated compounds and albuminuria

"Idiopathic" minimal change nephrotic syndrome: a podocyte mystery nears the end

The discovery of zinc fingers and homeoboxes (ZHX) transcriptional factors and the upregulation of hyposialylated angiopoietin-like 4 (ANGPTL4) in podocytes have been crucial in explaining the cardinal manifestations of human minimal change nephrotic syndrome (MCNS). Recently, uncovered genomic defects upstream of ZHX2 induce a ZHX2 hypomorph state that makes podocytes inherently susceptible to mild cytokine storms resulting from a common cold. In ZHX2 hypomorph podocytes, ZHX proteins are redistributed away from normal transmembrane partners like aminopeptidase A (APA) toward alternative binding partners like IL-4Rα. During disease relapse, high plasma soluble IL-4Rα (sIL-4Rα) associated with chronic atopy complements the cytokine milieu of a common cold to displace ZHX1 from podocyte transmembrane IL-4Rα toward the podocyte nucleus. Nuclear ZHX1 induces severe upregulation of ANGPTL4, resulting in incomplete sialylation of part of the ANGPTL4 protein, secretion of hyposialylated ANGPTL4, and hyposialylation-related injury in the glomerulus. This pattern of injury induces many of the classic manifestations of human minimal change disease (MCD), including massive and selective proteinuria, podocyte foot process effacement, and loss of glomerular basement membrane charge. Administration of glucocorticoids reduces ANGPTL4 upregulation, which reduces hyposialylation injury to improve the clinical phenotype. Improving sialylation of podocyte-secreted ANGPTL4 also reduces proteinuria and improves experimental MCD. Neutralizing circulating TNF-α, IL-6, or sIL-4Rα after the induction of the cytokine storm in Zhx2 hypomorph mice reduces albuminuria, suggesting potential new therapeutic targets for clinical trials to prevent MCD relapse. These studies collectively lay to rest prior suggestions of a role of single cytokines or soluble proteins in triggering MCD relapse.

Effect of tumor necrosis factor alpha and vascular permeability growth factor on albuminuria in rats

The purposes of this study were to measure the serum levels of vascular permeability growth factor (VPGF) and tumor necrosis factor alpha (TNFalpha) in minimal lesion nephrotic syndrome (MLNS) patients and to assess their effect on albuminuria in rats. Serum for VPGF and TNFalpha was obtained during relapse and remission from 18 MLNS patients. Tumor necrosis factor alpha was infused at the rate of 10 and 20 ng/h and VPGF at the rate of 20 and 40 ng/h for 5 days into the left renal artery of rats. Urinary albumin (24-h collection) was measured prior to infusion and on days 2, 4 and 5. Rats infused with 1% bovine serum albumin served as controls. Serum VPGF and TNFalpha levels in MLNS patients in relapse were not different from those seen during remission. A significant increase in albuminuria was observed on day 4 and 5 only when rats were infused with TNFalpha at the rate of 20 ng/h as compared to the excretion seen in same animals prior to the infusion of cytokine and on days 4 and 5 of normal controls. Neither VPGF nor TNFalpha seems to be the circulating pathogenic cytokine for proteinuria in MLNS. However, TNFalpha may contribute to the increased albuminuria via a paracrine effect at the glomerulus.

Proteinuria and Fusion of Podocyte Foot Processes in Rats after Infusion of Cytokine from Patients with Idiopathic Minimal Lesion Nephrotic Syndrome

BACKGROUND/AIMS

We report on the isolation of a factor secreted by peripheral blood mononuclear cells from patients with idiopathic minimal lesion nephrotic syndrome (IMLNS) in relapse and its effect on proteinuria and podocyte morphology in the rat.

METHODS

Peripheral blood mononuclear cells from patients with IMLNS (in relapse and in remission) and patients with focal segmental glomerulosclerosis were cultured for 72 h. Supernatants from 20 x 10(6) cultured cells were separated by liquid chromatography into three fractions according to markers (bovine serum albumin, beta-amylase, and apoferritin). Each supernatant fraction was infused into rats for 5 days using an osmotic pump. Proteinuria, 24-hour albumin excretion or albumin/creatinine ratio in a 24-hour urine collection, was measured daily starting 3 days prior to fraction infusion. Renal tissue was obtained for electron microscopy studies. The beta-amylase fraction underwent electrophoresis using isoelectric focusing gel.

RESULTS

When protein excretion was compared prior to and during supernatant fraction infusion, a significant increase in proteinuria was observed only when beta-amylase fraction from IMLNS patients in relapse was infused (p < 0.05). Protein electrophoresis of the beta-amylase fraction showed a single band at pH 6.0 only in samples from IMLNS patients in relapse. The band was composed of two proteins, beta-amylase and a 100-kDa glycoprotein. Fusion of foot processes was observed only when the beta-amylase fraction from IMLNS patients in relapse was infused.

CONCLUSIONS

The infusion of the beta-amylase fraction containing a 100-kDa glycoprotein from IMLNS patients in relapse induced proteinuria and effacement of foot processes in the rat. This protein may play a role in the pathogenesis of IMLNS.

Influence of nephrotic state on the infectious profile in childhood idiopathic nephrotic syndrome

Patients with idiopathic nephrotic syndrome present alterations in their cellular and humoral immune reactions that predispose them to the development of infectious processes. PURPOSE: To characterize the infectious processes in patients with idiopathic nephrotic syndrome. PATIENTS AND METHODS: Ninety-two children and adolescents with idiopathic nephrotic syndrome were assessed retrospectively. The types of infection were grouped as follows: upper respiratory tract infections; pneumonia; skin infections; peritonitis; diarrhea; urinary tract infection ; herpes virus; and others. The patients were divided into 2 groups: Group I (steroid-responsive) n = 75, with 4 subgroups-IA (single episode) n = 10, IB (infrequent relapsers) n = 5, IC (frequent relapsers) n = 14, and ID (steroid-dependent) n = 46; and Group II (steroid-resistant) n = 17. The incidence-density of infection among the patients was assessed throughout the follow-up period. Comparisons for each group and subgroup were done during the periods of negative and nephrotic proteinuria. RESULTS: The analysis revealed a greater incidence-density of infections during the period of nephrotic proteinuria in all the groups and subgroups, with the exception of subgroup IA. During the period of nephrotic proteinuria, subgroups IC, ID, and Group II presented a greater incidence-density of infections as compared to subgroup IA. For the period of negative proteinuria, there was no difference in the incidence-density of infections between the groups and subgroups. Upper respiratory tract infections were the most frequent infectious processes. CONCLUSION: The nephrotic condition, whether as part of a course of frequent relapses, steroid dependence, or steroid resistance, conferred greater susceptibility to infection among the patients with idiopathic nephrotic syndrome. The results of this study suggest that the best preventive action against infection in this disease is to control the nephrotic state.

Induction of experimental proteinuria in vivo following infusion of human plasma hemopexin

BACKGROUND

The human plasma constituent hemopexin (Hx), following incubation with renal tissue, is able to induce glomerular alterations in vitro that are similar to those seen in minimal change disease (MCD). Whether this acute phase reactant is also able to induce proteinuria and minimal change-like alterations in vivo is questioned.

METHODS

In the first set of experiments, Hx (4.0 mg in 5.0 mL saline) or equal amounts of control fraction, that is, heat-inactivated Hx (HI-Hx), were infused into conscious rats (N = 6) that had been surgically equipped with a cannula inserted into the suprarenal artery (SRA), enabling direct contact of the infusate and the renal microvasculature. Each animal received HI-Hx at day 1 for 15 minutes (flow rate 20.0 mL/h), subsequently followed by saline for seven hours (Flow rate 5.0 mL/h), after which the cannula was disconnected. At day 2, identical infusions in the same rat were carried out, using native Hx. Urine samples collected every 30 minutes during the experiments were monitored for protein content using standard methods. In the second set of experiments, unilateral perfusion was done ex vivo in anesthetized rats with Hx (N = 5) or HI-Hx (N = 3; 1.5 mg/mL; 4.0 mL during 6 min). After reconnection of the circulation, urine samples of both kidneys were collected every 30 minutes during five hours via ureter cannulation. Urinary protein (expressed as the difference in excretion between perfused and nonperfused kidney) was calculated in mg/24 h. In additional experiments, rats were sacrificed two hours after perfusion of Hx or heat-inactivated (control) Hx (first set of experiments) or after five hours (second set of experiments), and kidneys were processed for immunohistochemical and ultrastructural examination.

RESULTS

The results of experiment 1 show a significant increase of proteinuria after Hx infusion versus HI-Hx (means +/- SD, 41.91 +/- 16.01 mg/24 h vs. control, 21.22 +/- 5.69 mg/24 h; P </= 0.03). Histochemical and electron microscopical examination of kidney tissue fragments taken at the time of proteinuria showed diminished expression of glomerular ecto-ATPase and enhanced effacement of epithelial foot processes at the ultrastructural level. In the second set of experiments, the results show significant urinary protein excretion peaking one hour after perfusion (6.63 +/- 7.06 mg/24 h), exclusively in Hx-perfused animals (analysis of variance, P < or = 0.001).

CONCLUSION

It is concluded that Hx is able to induce proteinuria associated with MCD-like alterations in rat kidney in vivo.

Dominant T cells in idiopathic nephrotic syndrome of childhood

BACKGROUND

Because of several studies, idiopathic nephrotic syndrome (INS) of childhood is suspected to have an immunologic pathogenesis with T cells playing a major role. To investigate this hypothesis further, we studied the diversity of the CDR3 region of the T-cell receptor (TCR) beta-chain from peripheral T cells isolated from patients with INS.

METHODS

The study was performed over a three-year period to obtain longitudinal data on the repertoire of peripheral T cells. mRNA from peripheral mononuclear cells (PBMCs) of seven INS patients and two healthy controls (NHD) was prepared and analyzed for CDR3 length polymorphism of TCR beta-chain by spectratyping.

RESULTS

All INS patients presented individually skewed spectratype histograms in at least one Vbeta-family. Patients suffering from a frequent relapsing course of INS or a focal global sclerosis showed some alterations to persist in all samples isolated in the observation period (up to 3 years). In addition, sequence analyses of the beta-chain of the TCR CDR3 region confirmed clonal expansion of peripheral T cells in those patients who had displayed spectratype alterations.

CONCLUSIONS

The data give strong evidence for an direct involvement of CD8+ T cells in the complicated course of INS.