Role of the terminal complement pathway in experimental membranous nephropathy in the rabbit.

Our recent observations of a complement-mediated, cell-independent mechanism of altered glomerular permeability in rat membranous nephropathy suggested a possible role for the terminal complement pathway in the mediation of proteinuria in certain forms of glomerular disease. To directly determine whether the membranolytic terminal complement components (C5b-C9) are involved in glomerular injury, we studied the development of proteinuria in normal and C6-deficient (C6D) rabbits, in both of which a membranous nephropathy-like lesion develops early in the course of immunization with cationized bovine serum albumin (cBSA) (pI 8.9-9.2). C6 hemolytic activity of C6D was 0.01% that of control rabbits. After 1 wk of daily intravenous injections of cBSA, proteinuria developed in 71% of controls (median 154, range 1-3,010 mg/24 h, n = 24), whereas none of C6D were proteinuric (median 6, range 2-12 mg/24 h, n = 12, P less than 0.01). After 1 wk of cBSA, both groups had qualitatively identical glomerular deposits of BSA, rabbit IgG, and C3 on immunofluorescence microscopy, predominantly subepithelial electron-dense deposits on electron microscopy, and minimal glomerular inflammatory cell infiltration of glomeruli. Glomeruli were isolated from individual animals after 1 wk of cBSA and deposits of rabbit IgG antibody were quantitated by a standardized in vitro assay using anti-rabbit IgG-125I. Rabbit IgG deposits were found to be similar in control (29.8 +/- 13.2, range 12.7-48.6 micrograms anti-IgG/2,000 glomeruli, n = 6) and C6D rabbits (32.6 +/- 13.8, range 16.8-48.8 micrograms anti-IgG/2,000 glomeruli, n = 5, P greater than 0.05). After 2 wk, coincident with a prominent influx of mononuclear cells and neutrophils, proteinuria developed in C6D rabbits. These results document, for the first time, a requirement for a terminal complement component in the development of immunologic glomerular injury. Since the only known action of C6 is in the assembly of the membrane attack complex, these observations suggest that the membranolytic properties of complement may contribute to glomerular damage.

Acute thrombosis of the renal transplant artery: a case report and review of the literature.

Acute thrombosis of the renal transplant artery is a known but unusual complication of renal transplantation usually occurring in the first month. Reported here is a case of acute renal artery thrombosis in a well functioning long-term renal allograft in which there was clear angiographic evidence of a normal renal artery two years earlier.

Insulin-like growth factor-1 stimulates production of mesangial cell matrix components.

Diabetic nephropathy is characterized by mesangial cell proliferation and expansion of the mesangial matrix. Insulin-like growth factor-1 (IGF-1) increases in the kidney early in experimental diabetes. The effect of IGF-1 on mesangial cell proliferation and synthesis of extracellular matrix (ECM) proteins was examined to test the hypothesis that IGF-1 stimulates mesangial cells to synthesize ECM proteins. ECM proteins were measured by immunoprecipitation after metabolic labeling of rat mesangial cells in culture. IGF-1 caused a 2.4-fold increase in mesangial cell proliferation as measured by 3H-thymidine incorporation. IGF-1 caused an increase in cellular laminin, fibronectin and type IV collagen, 46.8 +/- 15.4%, 31.3 +/- 11.4%, and 27.7 +/- 12.6% increase respectively compared to control cells. IGF-1 did not effect cellular type 1 collagen, decrease of 8.2 +/- 8.7%. There was a trend toward increased total protein synthesis by IGF-1, 36.5 +/- 2.5%. In summary, IGF-1 stimulates ECM component production by mesangial cells. Thus, IGF-1 has the capacity to mediate the histologic changes characteristic of diabetic nephropathy.

Update on diabetic nephropathy in NIDDM.

Diabetic nephropathy is an important clinical entity in the geriatric population. One half of newly enrolled patients in dialysis programs have non-insulin-dependent diabetes mellitus (NIDDM), and the number of NIDDM patients with chronic renal insufficiency is estimated to be eight times greater than those with insulin-dependent diabetes mellitus. In view of this growth potential, this paper is intended to briefly review the epidemiology and pathogenesis of diabetic nephropathy, and to highlight some important considerations in the clinical evaluation and treatment of patients with NIDDM.

Diabetic nephropathy.

Diabetic nephropathy is an important microvascular complication of both insulin-dependent and non-insulin-dependent diabetes mellitus. It is the leading cause of end-stage renal disease. The natural course, pathogenesis, clinical evaluation, and treatment of diabetic nephropathy were reviewed, with special emphasis on recent important studies of glucose control and use of the angiotensin-converting enzyme inhibitors in the treatment of diabetic nephropathy.

Role of the terminal complement pathway in accelerated autologous anti-glomerular basement membrane nephritis.

The terminal complement pathway (C5b to C9) has been demonstrated to have an important role in the mediation of glomerular immune injury in various models of experimental glomerulonephritis. In the present studies, the role of the terminal complement pathway in the accelerated autologous phase of anti-glomerular basement membrane (GBM) nephritis in the rabbit was investigated. Normocomplementemic rabbits and rabbits deficient in C6 (C6D) who are therefore unable to form the terminal complement pathway were immunized with sheep immunoglobulin G (IgG) before being injected with a subnephrotoxic dose of the gamma 2 fraction of sheep anti-rabbit GBM. C6D animals had a delay in the onset of the glomerular injury, as manifested by proteinuria. At 72 hours, controls had a greater degree of proteinuria (15.2 +/- 8.8 mg protein/mg creatinine vs. 2.6 +/- 2.1, P = 0.197), but at 120 hours there were no differences in proteinuria between C6D and control animals (11.1 +/- 3.6 mg protein/mg creatinine vs. 12.2 +/- 6.2, P = 0.89). Light microscopy demonstrated more severe glomerular injury in C6D animals with marked cellular proliferation and large areas of glomerular necrosis. Interestingly, C6D animals had significantly higher levels of sheep IgG remaining in their glomeruli at 120 hours (0.95 +/- 0.12 micrograms sheep IgG/1 x 10(4) glomeruli, N = 11, vs. 0.57 +/- 0.07, N = 11, P = 0.014) and 72 hours (1.22 +/- 0.25 micrograms, N = 3, vs. 0.60 +/- 0.15, N = 3, P = 0.104) compared with 24 hours when there was no difference (1.25 +/- 0.22 micrograms, N = 7, vs. 1.08 +/- 0.14, N = 7, P = 0.53). C6D rabbits had a greater rise in serum creatinine at 120 hours (2.3 +/- 0.5 mg/dl vs. 1.3 +/- 6.4, P = 0.132). We conclude that in C6D animals, the persistence of glomerular immune deposits is responsible for more severe renal injury and renal failure.

Production of an inhibitor of rat mesangial cell growth by the glomerulus and its alteration in puromycin nephrosis.

Mesangial cell proliferation is found in many forms of progressive renal disease. This proliferation may be due to dysregulation of mesangial cell growth. The studies presented here test the hypothesis that the normal glomerulus produces a regulator of mesangial cell growth. Conditioned media (CM) from primary glomerular cultures were able to inhibit rat mesangial cell growth in a dose- and time-dependent fashion, from 30.0 +/- 3.8 to 86.6 +/- 3.9% growth inhibition. The growth inhibitor in glomerular CM appears to have a molecular weight of less than 3,000. Glomerular CM caused significantly more growth inhibition than did 3T3 fibroblast CM, 77.9 +/- 2.8% growth inhibition by 10% glomerular CM versus 21.2 +/- 5.4% by 10% 3T3 CM (P < 0.001). The growth inhibition was completely reversible. Glomerular CM had no effect on the growth of 3T3 fibroblasts. Treatment of the glomerular CM with either trypsin or neutral protease had no effect on its growth inhibitory activity. Glomerular CM obtained from rats with puromycin aminonucleoside nephrosis caused significantly less growth inhibition than did control glomerular CM; at a concentration of 10% CM, control glomerular CM had 65.1 +/- 1.9% growth inhibition and puromycin had 45.4 +/- 2.1% (P < 0.001). Thus, the rat glomerulus produces a small, nonprotein inhibitor of rat mesangial cell growth and the activity of this inhibitor is reduced in puromycin nephrosis. Impairment of mesangial cell growth regulation may be important in the pathogenesis of progressive renal disease.

Anterior ischemic optic neuropathy as a complication of hemodialysis.

Hypotension is a common and sometimes difficult to manage occurrence during hemodialysis. The consequences of dialysis-induced hypotension are unpredictable. Anterior ischemic optic neuropathy is an entity associated with many systemic processes, including shock. Anterior ischemic optic neuropathy presents as sudden painless loss of vision. This is the first report of anterior ischemic optic neuropathy as a result of hemodialysis-associated hypotension.

Heparan sulfate stimulates extracellular matrix protein synthesis by mesangial cells in culture.

Heparan sulfate, a glycosaminoglycan which is a component of the glomerular basement membrane and the mesangial matrix, has been demonstrated to inhibit mesangial cell growth. The present studies investigated the effects of heparan sulfate on extracellular matrix protein synthesis by cultured rat mesangial cells. Mesangial cells were metabolically labeled with 35S-methionine and specific extracellular matrix proteins were immunoprecipitated from supernatant and cellular fractions. The following extracellular proteins were assayed: type I collagen, type IV collagen, type V collagen, laminin and fibronectin. Western blotting was performed to demonstrate the specificity of the immunoprecipitates. Heparan sulfate decreased cell number by 23.5%, p < 0.05, while chondroitin sulfate, another glycosaminoglycan, increased cell number by 11.5%, p < 0.05. Heparan sulfate significantly increased type V collagen and laminin in the cellular material and significantly increased laminin and fibronectin in the supernatant material. Chondroitin sulfate had no effect on matrix protein synthesis. Thus, heparan sulfate has effects on both mesangial cell growth and synthesis of matrix proteins and alterations in heparan sulfate may play a role in the development of glomerulosclerosis.

The kidney in hypergammaglobulinemic purpura.

A 25-year-old woman with long-standing hypergammaglobulinemic purpura developed distal renal tubular acidosis and a urine-concentrating defect. The acidification defect was characterized as suggestive of impaired distal proton secretion by infusion of neutral phosphate. The concentrating defect was a form of acquired nephrogenic diabetes insipidus. On renal biopsy, IgM mesangial nephropathy was found along with multiple large hyaline tubular casts. The renal findings in hypergammaglobulinemic purpura are reviewed.

Proteoglycan and glycosaminoglycan synthesis by cultured rat mesangial cells.

The synthesis of metabolically labeled proteoglycans and glycosaminoglycans from medium, cell layer and substrate attached material by rat glomerular mesangial cells in culture was characterized. The cellular localization of the labeled proteoglycans and glycosaminoglycans was determined by treating the cells with Flavobacterial heparinase. Of the total sulfated glycosaminoglycans, 33% were heparan sulfate; 55% of the cell layer material was heparan sulfate; 80% of sulfated proteins in the medium were chondroitin sulfate/dermatan sulfate. Putative glycosaminoglycan free chains of heparan sulfate and chondroitin sulfate were found in both the medium and cell layer; 95% of total proteoglycans and most (90%) of the putative heparan sulfate free chains were removed from the cell layer by the heparinase, whereas only 50% of the chondroitin sulfate and 25% of dermatan sulfate were removed. Large amounts of hyaluronic acid labeled with 3H glucosamine were found in the cell layer. In summary, approximately 60% of total sulfated glycoproteins was in the form of putative glycosaminoglycan free chains. Thus rat mesangial cells may synthesize large amounts of putative glycosaminoglycan free chains, which may have biological functions in the glomerulus independent of proteoglycans.

Glomerulonephritis with associated hypocomplementemia and crescents: an unusual case of fibrillary glomerulonephritis.

Fibrillary glomerulonephritis is an unusual, but not rare cause of glomerulonephritis. Hypocomplementemia in association with fibrillary glomerulonephritis has been reported only once previously. A patient with hypocomplementemia and fibrillary deposits as demonstrated by electronmicroscopy is reported. The clinical and pathologic features of fibrillary glomerulonephritis and immunotactoid glomerulopathy are reviewed.

Changes in heparan sulfate correlate with increased glomerular permeability.

The glomerular capillary wall functions as both a size-selective and charge-selective barrier. Heparan sulfate is known to be an important component of the charge-selective barrier to filtration of polyanions. We studied the alterations in both the charge and size selectivity barriers in a model of experimental membranous nephropathy in the rabbit. The fractional clearance of both charged and uncharged dextrans compared to inulin was measured. Sulfate incorporation into glycosaminoglycans was measured and the glomerular heparan sulfate was isolated and biochemically characterized. Membranous nephropathy in the rabbit was induced with daily injections of cationic bovine serum albumin. After three weeks of injection animals had 735 +/- 196 mg/24 hours of protein excretion. There was no change in [35S] incorporation in 24 hours by experimental animals, 440 +/- 91 DPM/mg dry weight of glomeruli, N = 9 versus 410 +/- 98, N = 11 in controls. The percentage of [35S] incorporated into heparan sulfate versus chondroitin sulfate was decreased, 60% +/- 3 versus 79% +/- 2, P less than 0.001. Heparan sulfate from membranous nephropathy eluted from ion exchange chromatography in a lower molarity salt, indicating a lower effective charge. Fractional clearance of neutral dextrans was significantly increased in membranous nephropathy for dextrans greater than 48 A, while fractional clearance of dextran sulfates was significantly increased compared to controls for dextrans greater than 32 A. Thus, in membranous nephropathy there is loss of both charge selectivity and size selectivity. The loss of charge selectivity correlated with a change in the structure of the glomerular heparan sulfate.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of terminal complement pathway in the heterologous phase of antiglomerular basement membrane nephritis.

Terminal complement components, including the membrane attack complex, have been demonstrated in glomeruli of patients with immune complex and anti-GBM nephritis. We recently demonstrated the functional significance of C6 in the mediation of experimental membranous nephropathy in rabbits. In the present study, the role of C6 was examined in the heterologous phase of rabbit anti-GBM nephritis by studying normal and C6-deficient (C6D) rabbits. In C6D rabbits, C6 hemolytic activity was less than 0.01% of control. All control rabbits became heavily proteinuric in the first 24 hr following injection of a standard dose of sheep anti-rabbit GBM antibody (mean, 42.0 +/- 26.3; range, 18.4 to 83.5 mg protein/mg creatinine, N = 5). In contrast, C6D rabbits excreted a mean of only 5.1 +/- 5.5 mg/mg creatinine (range, 0.06 to 14.4, N = 6, P = 0.002). Protein excretion in normal rabbits was less than 0.06 mg/mg creatinine. Both control and C6D rabbits had similar deposits of sheep anti-rabbit GBM IgG in glomeruli when measured by radiolabeling techniques (control 15.8 +/- 2.71, N = 5; C6D 18.7 +/- 1.99 micrograms of sheep IgG/10(4) glomeruli, N = 6, P greater than 0.05). Control rabbits had a greater rise in serum creatinine in the first 24 hr (1.74 +/- 1.15 vs. 0.53 +/- 0.44 mg/dl, P less than 0.05). Both groups had similar deposits of sheep IgG and rabbit C3 by IF. By light microscopy at 4 and 24 hr, both groups had qualitatively similar proliferative changes and similar numbers of neutrophils infiltrating glomeruli.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloidosis and Reiter's syndrome: report of a case and review of the literature.

Reiter's syndrome is classically described as the triad of urethritis, conjunctivitis, and arthritis, It has many manifestations and has rarely been reported to occur in association with amyloidosis. Four cases of systemic amyloidosis have previously been reported. This case describes a patient who developed progressive renal amyloidosis after a 17-year history of severe Reiter's syndrome. Immunofluorescent staining of the renal biopsy was strongly positive for AA protein, the type of protein found in secondary amyloidosis. This is the first case in which amyloidosis has been proven to be secondary to Reiter's syndrome and not merely the coincidental occurrence of two rare diseases.

Inhibition of rat mesangial cell growth by heparan sulfate.

The ability of heparan sulfate, an endogenous component of the glomerulus, to regulate the growth of cultured rat mesangial cells was investigated. Heparan sulfate caused a dose-dependent inhibition of rat mesangial cell growth, 85% inhibition compared with controls at the highest dose (1,000 micrograms/ml). Chondroitin sulfate produced no inhibition. The low-sulfated fraction of heparan sulfate (9%) produced more inhibition than the high-sulfated fraction (13%), 90 +/- 1 vs. 71 +/- 2% (P = 0.002). The effects of the heparan sulfate were completely reversible. Treatment of heparan sulfate with heparitinase increased the degree of inhibition, 71 +/- 1 vs. 84 +/- 1% (P less than 0.001). Four different oligosaccharides derived from heparan sulfate and heparin were tested for their ability to inhibit growth. One of the oligosaccharides, low-sulfated (10%), caused significant inhibition, 76 +/- 2%. Heparan sulfate was also able to inhibit the growth of Swiss 3T3 fibroblasts (63 +/- 5%). This inhibition was less marked than that seen with mesangial cells. Thus heparan sulfate was able to significantly inhibit rat mesangial cell growth in culture. Alterations in glomerular heparan sulfate may play an important role in alterations in mesangial cell growth.

Enalapril and low protein reverse chronic puromycin aminonucleoside nephropathy.

The effects of dietary protein and converting enzyme inhibition (CEI) on chronic puromycin aminonucleoside nephropathy (PAN) were studied. PAN was induced with seven SQ injections of puromycin aminonucleoside 20 mg/kg over 10 weeks in male Sprague-Dawley rats. The rats were divided into a 22.5% protein diet group (Gr 1), a 6% protein diet group (Gr 2), and an enalapril-treated group on 22.5% protein diet (Gr 3). Group 4 animals served as age-matched controls. Both diets were isocaloric and had the same phosphorus content. Rats from groups 1, 2, and 4 were sacrificed at 12, 18 and 24 weeks. Five rats of group 3 were sacrificed at 12 weeks, and the others were divided in subgroups 3A (diet changed to 6% protein) and 3B (no changes); half of each subgroup was sacrificed at 18 and 24 weeks, respectively. Group 2 had significantly less proteinuria than group 1 at all times. Group 3 had the same proteinuria as group 1 until 12 weeks and then began to decrease. In group 3A proteinuria decreased to group 2 levels, while in group 3B the decrease was slower but still prominent. Early lesions of focal and segmental glomerular sclerosis/hyalinosis (FSH) were present in groups 1, 2, 3 at 12 weeks (16 +/- 1.2%, 15 +/- 1.3%, 7 +/- 1.3%, respectively, versus 1.3 +/- 0.4% in controls), but by 18 weeks a reversal in FSH was seen in groups 2 and 3A/B (3 +/- 1.6%, 2 +/- 0.4%, and 3 +/- 0.9%, respectively, vs. 14 +/- 1.5% in group 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Charge selective properties of the glomerular capillary wall influence antibody binding in rat membranous nephropathy.

IgG antibodies, eluted from kidneys of rats with Heymann nephritis were separated into cationic and anionic fractions, labeled with 125I and 131I, respectively, mixed in equal amounts, and then injected in incremental doses into 10 rats. Glomerular antibody binding was highly correlated with blood concentration of antibody at 24 hr, however, significantly more cationic antibody bound to glomeruli than did anionic antibody at all blood levels studied. The differences were not due to greater antibody content and/or avidity of the cationic preparation, as measured by binding to isolated glomeruli in vitro. These studies demonstrate the influence of glomerular permselectivity and antibody charge on subepithelial antibody deposition.

Changes in glomerular heparan sulfate in puromycin aminonucleoside nephrosis.

Changes in glomerular anionic sites in puromycin aminonucleoside nephrosis (PAN) in the rat are controversial. The authors examined glomerular anionic sites in PAN by in vivo staining with polyethyleneimine (PEI). They also quantitated and characterized glomerular heparan sulfate (HS), which is known to be a major glomerular polyanion in PAN, using in vivo incorporation of 35S-sulfate. PAN rats had a mean protein excretion of 96 +/- 23 mg per 24 hours. Staining of anionic sites with PEI showed 15.3 +/- 2.8 sites per 1000-nm length of glomerular basement membrane in controls, 13.7 +/- 1.9 sites in PAN rats (P greater than 0.05), and 50% of rats with early PAN had absent staining. Total 35S-sulfate incorporation was similar in both the controls and established PAN rats (2900 +/- 150 dpm/mg dry wt of glomeruli versus 3005 +/- 260, P greater than 0.05) but decreased in early PAN rats (2025 +/- 148). The percentage of 35S-sulfate incorporated into chondroitin sulfate was similar in all three groups of animals. HS uronic acid was also similar (1.8 +/- 0.2 g/mg dry wt of glomeruli versus 1.7 +/- 0.3, P greater than 0.05) but decreased in early PAN (1.1 +/- 0.2). The distribution of 35S-sulfate activity within the HS subfractions was examined by ion-exchange chromatography and showed a shift in percent present from 1.0 M to 1.25 M fraction in established and early PAN animals (control 1.0 M 37% +/- 3.2% versus PAN 19% +/- 3.4%, P less than 0.01, and 1.25 M 36% +/- 2.9% versus 53% +/- 2.9%, P less than 0.01). These results demonstrate that glomerular heparan sulfate is unchanged in established PAN but decreased in early PAN. SO4 incorporation is unchanged in established PAN and diminished in early PAN. Thus, early in PAN HS synthesis is impaired, but in established PAN the HS is normal, and changes in glomerular HS cannot explain the increased permeability.

Hypocomplementemic urticarial vasculitis syndrome responsive to dapsone.

A 45-year-old woman with cutaneous urticaria-like lesions subsequently developed polyarthritis, glomerulonephritis, and chronic obstructive pulmonary disease. Biopsy of skin showed leukocytoclastic vasculitis of superficial capillaries. Biopsy of the kidney revealed mesangioproliferative glomerulonephritis, and lung biopsy revealed severe emphysema and thick-walled blood vessels with immunoglobulin deposition. Therapy with dapsone produced dramatic improvement of the patient's cutaneous vasculitis and arthritis. This case uniquely demonstrates the efficacy of dapsone for both the urticarial vasculitic and the arthritic components of this syndrome and reemphasizes the potentially severe pulmonary and renal complications.