Minimal change-like glomerular alterations induced by a human plasma factor

Circulating factors, including the plasma protease (100 KF) described previously, have been suspected to play a role in the pathogenesis of minimal change disease (MCD) for several decades. This factor was able to induce MCD-like alterations in kidney tissue in vitro, i.e. impairment of glomerular polyanion (GPA), as well as glomerular ecto-ATPase. We conducted permeability studies using alternate perfusion of the rat kidney ex vivo according to standard techniques. Either native 100 KF (n = 7) or control factor (n = 7) perfusion, followed by perfusion with diluted rat serum was carried out, while urine samples were collected by ureter cannulation. Total urinary protein (by spectrophotometry) as well as IgG (by ELISA) and albumin (by rocket electrophoresis) were measured. Sections of perfused kidneys were stained (immuno-) histochemically for GPA and glomerular ecto-ATPase, and the stainability was quantified using image analysis and expressed as arbitrary units. The results show significantly increased protein leakage after perfusion of 100 KF versus control factor (150.0 +/- 48.9 vs. 33.2 +/- 7.7 micrograms/min, p < or = 0.01), while the IgG/albumin ratio has decreased (12.0 +/- 9.4 vs 26.9 +/- 14.4%, p < or = 0.01). Plasma protein leakage after 100KF perfusion is associated with a significant loss of GPA (57.3 +/- 27.5 vs. 98.4 +/-12.0, p < or = 0.01) and significant decrease of glomerular ecto-ATPase expression (28.7 +/- 11.5 vs. 79.5 +/- 15.0, p < or = 0.001). The capability of 100KF to induce MCD-like glomerular lesions, in association with selectively increased permeability for plasma proteins, suggests that this human plasma constituent may be important in the pathogenesis of MCD.

Urinary tumor necrosis factor levels in primary glomerulopathies

In the present study, urinary tumor necrosis factor-alpha (TNF) levels in nonproliferative glomerulopathies [minimal change disease (n = 4), focal glomerulosclerosis (n = 4), membranous glomerulonephritis (GN) (n = 1), and in patients with chronic glomerulopathies (n = 4)] were compared to proliferative ones [a rapidly progressive GN patient and 8 patients with mesangial proliferative GN and membranoproliferative GN (MPGN) who had clinically active disease]. The mean urine TNF levels of the proliferative group were significantly higher than both the nonproliferative GN and 4 controls, whereas the mean value of the nonproliferative group was not significantly different than the controls. The urine TNF levels in 4 MPGN patients with chronic disease and in 2 who entered remission were also very low. In the patients with active renal disease and cellular proliferation there were significant correlations between the urinary TNF levels and both proteinuria and the clinical activity scores. We suggest that in human proliferative glomerulopathies TNF may be implicated in the glomerular inflammation.

The role of novel 30-kD protein in human podocytes: special relevance to proteinuria in glomerulonephritis

A new monoclonal antibody (MAb) was raised against human glomerular components to investigate the possible existence of glomerular antigens reflecting cellular adaptation in glomerulonephritis. The MAb recognized a podocyte antigen as well as those expressed on renal arterial endothelial cells and smooth muscle cells by indirect immunofluorescence. An additional, but weaker immunoreaction was found in epithelial cells of the Bowman's capsule. This MAb recognized a 30-kD protein on western blotting of glomerular extracts under non-reducing and reducing conditions. Immunoperoxidase electron microscopy revealed that this antigen is present within the cytoplasm, but not on the cell membrane of the podocytes. Moreover, the antigen was found to be reduced in the glomeruli of patients with minimal change glomerulonephritis. These results suggest that the 30-kD protein is a novel protein, which we hypothesize is involved in maintenance of the structural and functional integrity of the podocytes. In addition, reduced expression of the 30-kD protein in the podocytes may be related to the increasing proteinuria in minimal change glomerulonephritis.

Urine glycosaminoglycans and heparan sulfate excretions in adult patients with glomerular diseases

We measured the concentrations of urine glycosaminoglycans (GAG) by the modified dimethylmethylene blue method and the concentration of urine heparan sulfate (HS) by enzyme-linked immunosorbent assay (ELISA) in patients with various glomerular diseases. The GAG/creatinine(Crea) ratios in patients with IgA nephropathy (mean +/- SD, 0.31 +/- 0.056) and membranous nephropathy (0.41 +/- 0.115) were significantly greater than in healthy controls (0.18 +/- 0.045). Urine GAG/Crea ratios in minimal change nephrotic patients increased during remission (0.38 +/- 0.102) and decreased to normal values during the nephrotic stage (0.25 +/- 0.088). In contrast, urine HS/Crea ratios in patients with minimal change nephrotic syndrome decreased during remission (0.0069 +/- 0.0029) and increased markedly during the nephrotic period (0.047 +/- 0.0007 versus controls 0.0158 +/- 0.0046). Serial measurement in three minimal change nephrotic patients showed the similar change for the HS/Crea ratio and urine albumin excretion in the course of steroid therapy. The loss of HS from the glomerular basement membrane (GBM) may therefore be related to the pathogenesis of increased albumin excretion and measurement of urine HS excretion may be helpful for studying metabolism in renal disease, especially in patients with minimal change lesions.

Proteinuria selectivity index--prognostic value in lipoid nephrosis and related diseases

In order to predict the steroid response in lipoid nephrosis (LN), we studied age, sex, proteinuria level, histological features and proteinuria selectivity index (SI; ratio between IgG and transferrin clearances) in 52 LN cases (minimal-change disease: n = 39; focal glomerulosclerosis+IgM nephropathy: n = 13). The multivariate analysis showed that age, sex and proteinuria level were not contributive, whereas histology and SI were. The predictive value of SI was much higher than that of histological type (McFadden's r2: 47% vs. 22%, p < 0.001). Thus, SI should be systemically assessed in idiopathic nephrotic syndrome for reviewing the pathologic classification obtained by histology. However, if its prognostic value is lower than that of selectivity, initial renal biopsy remains necessary for diagnosis in adults.

Lymphocyte release of soluble IL-2 receptors in patients with minimal change nephropathy

Minimal change nephrotic syndrome has been reported to be a lymphocyte-mediated disorder. It has been suggested that the secretion of lymphokine(s) is involved in the pathogenesis of MCN and in determining proteinuria. The presence of a soluble form of IL-2 receptor (sIL-2R) has been previously described in the sera of patients with some autoimmune disorders. In this work, we report the detection of high sIL-2R levels, both in the plasma (mean value 844 +/- 436 U/ml versus normal value 276 +/- 86 U/ml) and urine of patients with MCN during the nephrotic phase alone. Instead, when the patients achieve stable remission, sIL-2R levels decrease to within normal values (mean value 332 +/- 272 U/ml). Furthermore, during the nephrotic syndrome we observed a significant inverse relationship between sIL-2R plasma levels and the mitogenic response to PHA (p less than 0.005). Since sIL-2R exerts a down-modulation on T-proliferative expansion, sIL-2R might represent one of the inhibitory serum factors extensively reported in the serum of patients with MCN-induced nephrotic syndrome.

Raised concentrations of the carboxy terminal propeptide of type IV (basement membrane) procollagen (NC1) in serum and urine of patients with glomerulonephritis

Type IV collagen is a major component of the glomerular and tubular basement membrane. We used a specific radioimmunoassay to determine (mean +/- SD) the concentration of carboxy terminal non-collagenous fragment (NC1) of type IV procollagen in the serum (normal 6.0 +/- 1.2 ng ml-1) and urine (normal 1.5 +/- 2.0 ng ml-1) of 142 patients with various kidney diseases. The 15 patients with active glomerulonephritis displayed (ANOVA, Scheffé test) significantly elevated NCl values in their serum (14 +/- 8.2 ng ml-1) as compared with the 32 patients with chronic interstitial nephritis (7.8 +/- 3.0 ng ml-1), the 17 patients with various other chronic kidney diseases (8.1 +/- 2.4 ng ml-1) and the 23 ambulatory kidney transplant patients (9.1 +/- 1.7 ng ml-1). The highest serum NCl concentrations were found in nine patients with membranoproliferative glomerulonephritis (16 +/- 9.4 ng ml-1). Sequential serum NCl concentrations in the one patient with active Goodpasture's syndrome were marginally elevated (less than 11 ng ml-1). Serum NCl did not increase with acute interstitial rejection episodes in six kidney transplant patients. The highest urinary NCl concentrations were found in seven patients with minimal change glomerulonephritis (7.5 +/- 3.2 ng ml-1). No correlation was found between serum NCl and serum creatinine, NCl and creatinine clearance, or renal NCl clearance and creatinine clearance. There was a significant correlation between serum NCl and proteinuria. Serum and urinary NCl concentrations were elevated independently from renal function, thus indicating intrinsic renal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary platelet factor four (Pf4) levels in mesangial IgA glomerulonephritis and thin basement membrane disease

The aim of this study was to assess the significance of platelet factor four (Pf4) excretion in the urine of patients with mesangial IgA glomerulonephritis (IgAGN) and thin basement membrane disease (TBMD), and ascertain if Pf4 is a useful parameter to distinguish these diseases. The concentration of Pf4 in urine (Pf4) was determined by an enzyme linked immunoabsorbent assay (ELISA) in patients with IgAGN (n = 80), TBMD (n = 37), membranous nephropathy (MN) (n = 12), minimal change nephrotic syndrome (MCNS) (n = 3), crescentic glomerulonephritis (CGN) (n = 6) and in healthy controls (n = 20), and then compared with urinalysis and renal function. An immunoperoxidase method was used to examine urine sediments for the presence of platelets. Urinary Pf4 was detected in 35 out of 80 patients with IgAGN (median 0.15, range 0.07-2.5 ng/ml, n = 35), in only 2 out of 37 patients with TBMD (p less than 0.005), in all patients with CGN and in no patients from MN, MCNS or control groups. A positive correlation between urinary Pf4 levels and red blood cell counts was observed in patients with IgAGN (r = 0.876, p less than 0.001), but not in TBMD. Pf4 did not correlate with proteinuria or plasma creatinine in either group. Platelets were detected in urine in 10 out of 15 patients with IgAGN but in only 1 out of 9 patients with TBMD. Urinary red blood cell counts in all of these 24 patients were over 100,000/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Urine glycosaminoglycans in congenital and acquired nephrotic syndrome

To evaluate the specificity of a raised heparan sulphate (HS) excretion previously reported in four children with congenital nephrotic syndrome (CNS), we measured the urinary excretion of HS and chondroitin sulphate (CS) in seven children with Finnish-type congenital nephrotic syndrome (CNSF), seven with diffuse mesangial sclerosis (DMS), nine with focal segmental glomerulosclerosis (FSGS), 14 with steroid-sensitive nephrotic syndrome of whom eight had a biopsy confirming minimal change histology (SSNS), and 17 controls. The urine HS/CS ratio in normal children had a median of 0.36 (observed range 0.21 to 0.68) and was independent of age. HS/CS ratio was significantly greater than controls in CNSF (median 0.80, range 0.43 to 1.28), DMS (median 0.81, range 0.49 to 1.13) and FSGS children (median 0.66, range 0.38 to 1.6), but was not in SSNS (median 0.44, range 0.28 to 0.70). There was a positive correlation between the HS/CS ratio and urine albumin excretion. High HS/CS ratios are not diagnostic of a particular histological variety of CNS.

Preliminary report: renal thromboxane A2 synthesis in children with frequent relapsing nephrotic syndrome

An evaluation was made of the possible relation between renal thromboxane (Tx)A2 synthesis (measured as urinary excretion of TxB2) and the loss of glomerular permeability to proteins, in 5 children with seven episodes of minimal change nephrotic syndrome. Urinary TxB2 excretion was significantly higher in children with minimal change nephrotic syndrome than in 14 healthy controls, and reached its maximum at the time of peak proteinuria. During remission of nephrotic syndrome urinary excretion of TxB2 was still significantly higher than in healthy controls. A significant positive correlation between urinary excretion of TxB2 and proteinuria was observed in 3 patients. The results suggest that renal TxA2 could be regarded as one of the possible mediators of the altered glomerular permeability to proteins in minimal change nephrotic syndrome.

[Manifestations of adaptive processes in the epithelium of the renal glomerular filter]

Fifteen kidney biopsy samples+, obtained from children suffering from the primary nephrotic syndrome, characterized with a high selective proteinuria and non-inflammatory character of changes in the renal corpuscles have been investigated after hormonotherapy (11 cases before and 4 cases 2-3 weeks after it). In podocytes certain disturbances in the lysosomal-vascular apparatus develop with a successive appearance of degeneration, desquamation and even necrosis of these cells. After prednisolone++ treatment edema of cytoplasm of the cells and their processes disappears, amount and size of the filtration slits are partly restored.

[Lipoid nephrosis: changes in proteinemia and albuminemia after resolution of proteinuria]

Changes in serum protein and albumin levels following resolution of proteinuria were studied in 67 children with nephrosis. These two parameters returned to normal only after the 21st day, i.e. well after the natriuretic crisis and resolution of edema. Our results are consistent with recent studies showing that the fluid and electrolyte changes seen in the urine at resolution of the proteinuria (increased diuresis and natriuresis) are not due to a return to normal of serum protein and albumin levels. They probably reflect correction of an intrarenal abnormality whose mechanism is unclear.

Characterization of cationic albumin in minimal change nephropathy

The presence of isoalbumins with a less anionic charge than the normal protein (pI = 4.7) is the hallmark of proteinuria in minimal change nephropathy (MCN). Steroid-induced restoration of near normal levels of proteinuria is characterized by the appearance in urines of isoalbumins with a pI still more anionic than the normal. In our search for an explanation for the pI changes, we used preparative isoelectric focusing in granulated gels to split the microheterogeneous bands obtained from nine MCN-affected children into four fractions (A1, A2, A3, A4) with decreasing pI from 5.8 to 4.0 and we have determined their fatty acid content. The least anionic fraction, A1, was the most defatted, followed by A2, A3 and A4 in which fatty acid content progressively increased, A4 being the most fatted fraction. Accordingly, the mean content of fatty acids in urinary albumin in proteinuric children was lower than in both the remission phase and in normal children (2.17 +/- 0.03 vs. 20.91 +/- 0.38 and 20.94 +/- 0.39, respectively) and was lower by a factor of 4 compared to serum albumin in the same phase of the disease (2.17 +/- 0.03 vs. 8.59 +/- 1.64). Among medium and long-chain fatty acids, the ratio between serum and urinary albumin was the highest for linoleic acid (approximately 7), followed by that of oleic acid, palmitic acid and lauric acid. At variance in five other patients affected by non-MCN nephrotic syndrome this ratio was for practically all FAs about 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III metabolism in two patients with a nephrotic syndrome caused by minimal chain nephritis and primary amyloidosis

The metabolism and urinary excretion of 125I antithrombin III (AT III) was investigated in 2 patients with a nephrotic syndrome caused by minimal chain nephritis and primary amyloidosis, and acquired deficiency of AT III. Increased AT III catabolism was observed in both patients, even after correction for urinary protein loss. Increased AT III catabolism was due to increased influx from the extra- to the intravascular compartment in 1 patient, and to an increased fractional catabolic rate in the other patient who developed later a pulmonary embolism. Analysis of urine samples revealed biologically inactive whole AT III molecules and biologically as well as antigenically inactive fragments, respectively, whereas daily plasma gel filtration showed intact radioactive AT III. These observations reject the hypothesis that AT III deficiency in nephrotic patients is only due to urinary loss of AT III.

Urinary protein electrophoresis patterns in childhood idiopathic nephrotic syndrome

We investigated the utility of a standard urinary protein electrophoresis (UPEP) to distinguish among three common variants of childhood idiopathic nephrotic syndrome (NS). The UPEP was performed on 66 urine samples obtained during a disease relapse in 43 children and adolescents with idiopathic NS. There were 15 children with minimal change disease (MCD), 11 with IgM nephropathy (IGMN) and 17 with focal segmental glomerulosclerosis (FSGS). Fourteen of the 26 children (54%) with MCD or IGMN and 16/17 (94%) of the patients with FSGS manifested a frequently relapsing or steroid dependent course. The mean percent albumin and gamma globulin excretion in the UPEP in patients with MCD and IGMN were 75.5 and 2.9 versus 72.6 and 3.9, respectively (p = NS). Both patterns were significantly different from that observed in FSGS, albumin 62.2%, gamma globulin 7.1% (p less than 0.005). Although the percent gamma globulin excretion was inversely related to GFR in children with FSGS, this measurement exceeded a 4.3% cutoff in 9 of these patients while their GFR was normal (less than or equal to 80 ml/min/1.73M2). Therefore, we recommend the use of the UPEP as a marker of urinary protein selectivity and to monitor children with high-risk nephrotic syndrome i.e., those with a frequently relapsing or steroid dependent clinical course, for histological transitions.

[Comparative study of urine immunoelectrophoresis and 4 indexes of glomerular selectivity in chronic glomerulopathies]

Glomerular selectivity has been evaluated in a group of 89 patients, using renal clearances of orosomucoid (Cl O), transferrin (cl T) and immunoglobulin G (Cl IgG). In all cases, protein excretion was found above 0,30 g/24 h and urinary immunoelectrophoresis (IEP) showed a glomerular pattern. Clearance ratios Cl IgG/Cl T and Cl T/Cl O as well as Joachim's and Sabot's indexes were correlated to IEP patterns, protein daily excretion, creatinin clearance and pathological findings. The ratio Cl T/Cl O and Joachim's and Sabot's indexes correlated significantly with IEP patterns while Cameron's ratio (Cl IgG/Cl T) did not. Criteria other than Cameron and Joachim's indexes were found to be related to protein excretion; all indexes, Cameron's excluded, were influenced by renal functional status. Progress may be expected from the simultaneous serum and urine determinations of 5 proteins in the range 40 000-1 000 000 molecular weight with more accurate techniques such as laser nephelometry.

Renal sodium handling in minimal change nephrotic syndrome

Renal sodium handling was studied in 23 children at three different stages of the minimal change nephrotic syndrome--the oedema forming state, proteinuric steady state, and remission. Clearances of inulin and para-aminohippuric acid and urinary sodium excretion were determined basally, after intravenous infusion of isotonic saline and hyperoncotic albumin, and after furosemide injection. Absolute and fractional basal sodium excretion were significantly lower in oedema forming patients than in proteinuric patients in steady state, and non-proteinuric patients. In contrast to proteinuric patients in steady state and non-proteinuric patients, the oedema forming patients failed to respond to isotonic saline infusion with increased sodium excretion. After diuretic blockade with furosemide, the fractional sodium excretion of the oedema forming patients increased to values no different from those of the non-proteinuric patients, whereas the fractional sodium excretion of the steady state patients increased to significantly higher values. The plasma aldosterone concentration was within normal limits in 11 of 14 proteinuric patients, and did not correlate with the basal sodium excretion. Thus, sodium retention in the minimal change nephrotic syndrome was found only in oedema forming patients, and since this is not related to the plasma aldosterone concentration it may be caused by an intrarenal mechanism, probably sited in distal parts of the nephron.

Minimal change nephropathy: an electrochemical disorder of the glomerular membrane

To investigate the mechanism of proteinuria in minimal change nephropathy, the renal handling of dextrans was studied in seven nephrotic patients with this disorder. Although the urinary excretion of albumin was greatly increased, the urinary excretion and fractional clearance of dextrans (Einstein-Stokes radius (ESR), range 20 to 48 A) were depressed relative to those in nonproteinuric healthy volunteers. This suggests that mean glomerular pore size or pore density was reduced. Uptake of colloidal iron by glomeruli obtained from these patients by needle biopsy was diminished, suggesting loss of glomerular polyanion. Since the fractional clearance of dextrans similar in size to albumin was depressed, not increased, it is proposed that the lack of electrostatic interaction between the glomerular capillaries and polyanionic plasma albumin (ESR = 36 A) accounts for the selective albuminuria which characterizes minimal change nephropathy.

Urinary high density lipoprotein in minimal change glomerular disease and chronic glomerulopathies

Serum lipids and lipoproteins and urinary apolipoprotein A (Apo A) were determined in two groups of patients. One group consisted of 11 children (ages ranging from 4 to 14 years) with minimal change glomerular disease. The other group consisted of 13 patients, eight less than 19 years old five adults, with different types of chronic glomerulopathy. Elimination of urinary lysozyme was a feature of chronic glomerulopathies, and creatinine clearances were also significantly lower in this group. Patients with chronic glomerulopathies had significantly lower HDL cholesterol and Apo A concentrations in their sera. In contrast, urinary Apo A concentrations were significantly higher in patients with chronic glomerulopathies, who also showed significantly lower urinary protein selectivities. Lipoprotein electrophoresis of urines containing Apo A showed distinct high-density lipoprotein (HDL) fractions, suggesting that HDL is eliminated in the urine as a result of increased glomerular permeability. This is also supported by a correlation coefficient of 0.77 between the selectivity indices and the ratio of urinary Apo A to total proteinuria. The determination of urinary Apo A appears to give valuable diagnostic information in patients with glomerular disease. According to our results the absence of urinary Apo A is very suggestive of minimal change glomerular disease.