Glomerular deposition of mannose-binding lectin in human glomerulonephritis.

BACKGROUND: Mannose-binding lectin (MBL), a member of the collectin family, binds to various oligosaccharides and activates the classical pathway of complement independent from C1q. At present it is unknown whether this so-called lectin pathway of complement activation plays a role in the pathogenesis of human glomerulonephritis. METHODS: Direct immunofluorescence of 84 renal biopsies using an MBL-specific monoclonal antibody and antibodies directed against IgG, IgA, IgM, C1q, C3, and terminal complement complex (TCC) was performed. Serum MBL levels of 50 patients were determined by enzyme-linked immunosorbent assay. RESULTS: MBL was detected in the glomeruli of patients with lupus nephropathy (15 of 16), membranous nephropathy (10/15), membranoproliferative glomerulonephritis type I (5/6) and anti-GBM nephritis (2/4). MBL deposition paralleled that of immunoglobulins, C1q, C3, and TCC but was less intense as compared to C1q. Focal segmental deposits of MBL were present in focal segmental glomerulosclerosis (4/6), IgA nephropathy (3/11), amyloidosis AL (1/4), and advanced renal fibrosis (2/2). Here MBL staining was identical to IgM and C3 and considered an unspecific entrapment of MBL in sclerotic lesions in these cases. No significant difference in MBL serum levels was observed between normal controls and patients with lupus nephritis, membranous nephropathy, membranoproliferative glomerulonephritis, focal segmental sclerosis, minimal change disease or IgA nephropathy. In patients suffering from membranous nephropathy with (n=10) or without (n=5) glomerular MBL deposits serum creatinine, C3, C4, serum protein, and proteinuria were not statistically different. CONCLUSION: MBL is present in the glomeruli of patients with glomerulonephritis involving deposition of IgG and activation of the classical pathway of complement. We propose that MBL binds to agalactosyl oligosaccharides of IgG that terminate in N-acetylglucosamine. The extent to which the lectin pathway of complement contributes to overall complement activation in the glomeruli remains unknown, but is likely to be marginal.     

Glomerular deposits and hypoalbuminemia in acute post-streptococcal glomerulonephritis

In a search for correlations between glomerular morphology and clinical manifestations in acute post-streptococcal glomerulonephritis, data for 40 biopsied patients were reviewed. A major correlation was observed between severe hypoalbuminemia and the absence of deposits on the paramesangial portion of the glomerular basement membrane. Subepithelial deposits were present on both the capillary loop and paramesangial segments of the basement membrane in 29 patients, whereas in 11 the deposits were present only on the capillary loop. Patients with paramesangial segments devoid of deposits had a mean (±1 SD) nadir serum albumin level of 1.90 (±0.40) g/dl, whereas the mean nadir level in those with deposits in both locations was 2.83 (±0.64) g/dl (P<0.001). Also significant was the difference in paramesangial deposit scores in patients with nadir serum albumin levels ≤2.5 g/dl versus those with levels >2.5 g/dl. The amount of subepithelial deposit on the capillary loop was not significantly different in the two groups, and no correlation was found between loop deposits and serum albumin levels. Except for greater edema and significantly less-frequent gross hematuria in those with absent paramesangial deposits, clinical and laboratory findings for the two groups did not differ. Received September 18, 1997; received in revised form December 8, 1997; accepted January 27, 1998     

Glomerular lesions and final outcome in children with glomerulonephritis of acute onset.

131 children with nephritic syndrome of acute onset were studied by renal biopsy and were followed clinically from 2 to 13 years. 87 patients (66%) with proliferative endocapillary glomerulonephritis all recovered. 21 (16%) had focal extracapillary and diffuse endocapillary glomerulonephritis. Eleven (52%) of these recovered. Six patients (5%) had diffuse extra and endocapillary glomerulonephritis, 13 (10%) had membrano-proliferative glomerulonephritis and four had diffuse glomerular fibrosis. All 23 patients of the latter groups progressed to renal insufficiency. A correlation between morphology and prognosis was apparent in this study.     

Glomerular binding sites for peanut agglutinin in acute poststreptococcal glomerulonephritis

Streptococcal neuraminidase may be responsible for the development of auto-immune reactivity in acute poststreptococcal glomerulonephritis (APSGN). Neuraminidase may react with immunoglobulins in the circulation and with sialic acid-rich sites in the endothelial and epithelial glomerular capillary, therefore, extrinsic or intrinsic sialic acid-depleted substrate may be localized in the glomeruli. We studied renal biopsies from 17 patients with APSGN, 48 patients with other renal pathologies and 2 normal kidneys for the capacity to bind fluorescein-labelled peanut agglutinin (PNA) lectin. PNA has specificity for galactosyl radicals which are exposed after sialic acid removal. We similarly studied the kidneys of rats at intervals ranging from hours to 32 days after an intravenous injection of 0.02 units of neuraminidase per g of body weight. Five biopsies of APSGN patients and 2 biopsies from patients with renal pathologies different from APSGN showed glomerular PNA binding. Of APSGN patients, 4 corresponded to the 5 patients biopsied within 30 days of the beginning of the disease and only 1 biopsy was positive in the 12 patients who were biopsied later. The PNA binding predominated in the mesangium and the pattern was irregular and speckled. These findings suggest that sialic-acid depleted material is present in the glomeruli, early in the course of APSGN.     

Glomerular podocyte vacuolation in idiopathic membranous glomerulonephritis.

Vacuoles in glomerular visceral epithelial cells were found in 149 of 254 patients with idiopathic membranous glomerulonephritis (IMGN). In the whole population studied, 115 patients were nephrotic, 88 (76.5%) of which were found to have intraepithelial vacuoles. Fifty (35.9%) of 139 non-nephrotic patients had vacuolated podocytes (p less than 0.01). Vacuolation occurred most frequently in stages II and III of IMGN. A few intraepithelial vacuoles were observed in stage IV. Increase in vacuolation tended to correlate with subepithelial deposits which were larger in size. From these results, we concluded that the appearance of epithelial vacuolation coincides with an increased filtration of protein in IMGN and that it is an important histological marker when diagnosing the level of severity of glomerular lesions. It was not, however, prognostic.     

Glomerular epithelial-mesenchymal transdifferentiation in pauci-immune crescentic glomerulonephritis.

BACKGROUND: Among the cellular changes occurring in renal fibrosis, epithelial-mesenchymal cell transdifferentiation or transition (EMT) is a phenomenon characterized in epithelial cells by loss of epithelial markers and acquisition of mesenchymal phenotype and of fibrosing properties. METHODS: To test the hypothesis that EMT is involved in human pauci-immune crescentic glomerulonephritis (PICGN), we studied 17 renal biopsies from 11 PICGN patients for: (i) proliferating cell nuclear antigen (PCNA) and cell cycle inhibitors (cyclin-dependent kinase inhibitors) p27 and p57; (ii) cell lineage phenotype markers: podocalyxin, synaptopodin and GLEPP-1 for podocytes; CD68 for macrophagic epitope; CD3 for T lymphocytes; alpha-smooth muscle actin (alpha-SMA) for myofibroblasts; vimentin for mesenchymal cells; and cytokeratins (CKs) for parietal epithelial cells (PECs); (iii) glomerular fibrosis by labelling collagens I, III and IV, and heat-shock protein 47 (HSP47), a marker of collagen-synthesizing cells; and (iv) co-localization of alpha-SMA, CK and HSP47 using confocal laser microscopy. RESULTS: The crescent cells proliferated greatly. They did not express p27 and p57. Different cell lineage markers could be identified in crescents: the major component was made of 'dysregulated' PECs negative for CK, followed by PECs positive for CK, macrophagic cells and myofibroblasts. Furthermore, some cells co-expressed CK and alpha-SMA. This latter co-expression suggests a transitional phase in the dynamic phenomenon of EMT. Therefore, proliferative and dysregulated glomerular epithelial cells could be a possible cellular source of myofibroblasts via EMT. In addition, HSP47 labelled many crescent cells and frequently co-localized in CK-positive epithelial cells and in alpha-SMA-positive myofibroblasts, indicating that these cells were involved in glomerular accumulation of collagens. CONCLUSION: EMT is a transient cellular phenomenon present in glomeruli in human PICGN contributing to the formation of myofibroblasts from epithelial cells and to glomerular fibrosis.     

Glomerular plasmin-like activity in relation to nephritis-associated plasmin receptor in acute poststreptococcal glomerulonephritis

A nephritogenic antigen for acute poststreptococcal glomerulonephritis (APSGN) was isolated recently from group A streptococcus and termed nephritis-associated plasmin receptor (NAPlr). In vitro experimental data indicate that the pathogenic role of NAPlr occurs through its ability to bind to plasmin and maintain its proteolytic activity. However, the mechanism whereby this antigen induces glomerular damage in vivo has not been fully elucidated. Renal biopsy tissues from 17 patients with APSGN, 8 patients with rapidly progressive glomerulonephritis, and 10 normal kidneys were analyzed in this study. Plasmin-like activity was assessed on cryostat sections by in situ zymography with a plasmin-sensitive synthetic substrate. Serial sections were simultaneously assessed for NAPlr deposition by immunofluorescence staining. Glomerular plasmin-like activity was absent or weak in normal controls and in patients with rapidly progressive glomerulonephritis, although tubulointerstitial activity was occasionally detected. Prominent glomerular plasmin-like activity was found in patients who had APSGN and in whom glomerular NAPlr was positive, whereas it was absent or weak in patients who had APSGN and in whom glomerular NAPlr was negative. The distribution of glomerular plasmin-like activity was identical to that of NAPlr deposition but was generally different from that of fibrin(ogen) deposition as assessed by double staining. The activity was abolished by the addition of aprotinin to the reaction mixture but was not altered by the addition of a matrix metalloprotease inhibitor, a cysteine protease inhibitor, or inhibitors of plasminogen activators. Thus, upregulated glomerular plasmin-like activity in relation to NAPlr deposition in APSGN was identified. This result supports the nephritogenic character of NAPlr and offers insight into the mechanism whereby this antigen induces nephritis.     

Extracellular matrix deposition and cell proliferation in a model of chronic glomerulonephritis in the rat.

BACKGROUND: Resident glomerular cell proliferation, matrix deposition and secretion of matrix metalloproteinases play a major role in the progression of chronic glomerular disease. These features were studied in a novel approach in a rat model of chronic glomerulonephritis induced by four injections of an anti-Thy 1.1 antiserum at weekly intervals. METHODS: Chronic immune mediated mesangial injury was induced in male Sprague-Dawley rats by repeated intravenous injection of an anti-Thy 1.1 antiserum. One week after the first and fourth injection of the antiserum proteinuria was evaluated and the kidneys were removed. Immunohistology was performed for proliferating cells, monocytes and collagen type IV. Furthermore, mRNA expression of collagen type IV, TGF-beta and the matrix degrading enzyme MMP-2 as well as MMP-2 protein expression were studied. RESULTS: Urinary protein excretion was dramatically increased after one antiserum injection and stayed elevated at a lower level after the fourth antiserum injection. After the initial induction of nephritis, 7 days following antiserum, resident glomerular cell proliferation was increased whereas with repeated injections of the antiserum cell numbers were not different from controls, as measured 1 week after the fourth injection. In contrast, extracellular matrix accumulation (collagen type IV) increased after the first antiserum injection and further increased after the fourth antiserum injection. The mRNA expression for collagen type IV increased after the first antiserum injection and showed further increase after the fourth antiserum injection. Induction of nephritis also stimulated glomerular mRNA expression of MMP-2 and TGF-beta, both of which remained at a high level after the fourth antiserum injection. Glomerular protein levels of MMP-2 also increased after the first antiserum injection and showed a further slight increase after the fourth injection. CONCLUSION: Increased cellular proliferation is involved in an early stage of this disease, while enhanced expression of glomerular matrix and augmented mRNA and protein expression of the matrix degrading enzyme MMP-2 continue into the chronic phase, and contribute to the extensive structural remodeling process that accompanies this form of glomerular injury.     

Glomerular deposition and serum levels of complement control proteins in patients with IgA nephropathy

We examined complement control proteins focusing on the role of modulating the complement activation in IgA nephropathy. Glomerular C4-binding protein (C4-bp) deposits were found in 60% of patients with IgA nephropathy, while C4 deposits were found in 30%. Glomerular deposits of beta 1H globulin (beta 1H) were found in 85% of patients with IgA nephropathy. The frequency of glomerular deposits of C4-bp tended to be higher in the group with deposits of various immunoglobulin types than in the group with deposits of IgA alone, and it increased parallel with the progression of glomerular histologic changes. The serum C4-bp level was higher in IgA nephropathy patients. No significant correlation was found between the serum level of C4-bp or beta 1H and the extent or distribution of tissue deposits of these complement control proteins. These results suggest that glomerular immune deposits in IgA nephropathy may be attributable to the activation not only of the alternative pathway but also of the classical pathway, the latter of which may take place locally in glomeruli with advanced histologic change or various immunoglobulin deposits in IgA nephropathy.     

Glomerular distribution and gelatinolytic activity of matrix metalloproteinases in human glomerulonephritis.

BACKGROUND: Matrix metalloproteinases (MMPs) have been implicated in the development of glomerular injury in rat experimental glomerulonephritis (GN). However, the significance of MMPs in human GN remains obscure. In order to evaluate the role of MMPs in human GN, we examined the glomerular distribution and gelatinolytic activities of MMP-2 and MMP-9 in human GN. METHODS: We performed immunohistochemistry with polyclonal anti-MMP-2 and MMP-9 antibodies, and analysed gelatin zymograms of five isolated glomeruli from various types of human renal disease. The renal specimens investigated were from normal kidneys (n=5), IgA nephritis (n=20), Henoch-Sch?nlein nephritis (n=4), non-IgA mesangial proliferative GN (n=9), lupus nephritis (n=6), acute poststreptococcal GN (APSGN) (n=4) and diabetic nephropathy (DN) (n=4). RESULTS: MMP-2 immunoreactivity was not detected in normal controls or in any type of GN. MMP-9 staining, which was almost negative in normal glomeruli, was increased mainly in the mesangial region and corresponded to the level of glomerular cell proliferative changes in mesangial proliferative GN (IgA nephritis, Henoch-Sch?nlein nephritis, non-IgA mesangial proliferative GN and lupus nephritis). Positive but weak staining for MMP-9 was observed in mesangial areas in DN. In addition, double immunostaining showed that MMP-9 is colocalized in scattered neutrophils within diseased glomeruli in APSGN. MMP-9 gelatinolytic activity in five normal glomeruli was weakly detected. Consistent with the levels of immunostaining, MMP-9 glomerular activity was dramatically increased in nephritic glomeruli with IgA nephritis, lupus nephritis and DN. The gelatinolytic activity of MMP-2 was occasionally detectable in nephritic glomeruli. CONCLUSION: These results strongly suggest that MMP-9 plays an important role in abnormal mesangial proliferative changes in human GN.     

Glomerular fibrin deposition and removal

Glomerular fibrin deposits may occur within vessels or in extracapillary crescents. Studies suggest that intravascular thrombosis is promoted by endothelial cell activation/injury, resulting in the release of endothelial-cell-derived tissue factor procoagulant, fibrinolytic inhibitors, platelet activating factor, and large multimers of von Willebrand factor. Fibrin in crescents may arise from coagulation of plasma in Bowman's space mediated by the release of tissue factor from infiltrating macrophages. Glomerular fibrin may be removed by fibrinolytic or phagocytic mechanisms or persist and lead to glomerular obsolescence. Suppression or elimination of factors that promote glomerular fibrin deposition and enhancement of mechanisms that remove glomerular fibrin may be important in the recovery from several forms of human kidney disease.     

Glomerular platelet-activating factor levels and origin in experimental glomerulonephritis

The content of platelet activating factor (PAF) in glomeruli isolated from rats with nephrotoxic serum glomerulonephritis (NSGN) was quantified at various stages of the disease and the role of complement, platelets and neutrophils in mediating changes in glomerular PAF levels was evaluated. PAF content was assessed following extraction, isolation and quantification of this alkyl ether lipid using a bioassay based on [3H]-serotonin release from labelled rabbit platelets. Following induction of NSGN using proteinuric doses of rabbit immune serum raised against rat glomerular basement membrane, enhanced glomerular PAF levels were observed at 3 hours, 24 hours and on day 15 following induction of the disease. In complement depleted rats and at three hours following induction of NSGN, glomerular PAF levels were significantly lower than in complement replete controls studied in parallel. At the same time point of the disease, platelet depleted rats with NSGN demonstrated significantly lower glomerular PAF levels than parallel controls, whereas in neutrophil depleted rats glomerular PAF levels were no different than controls. These observations indicate that in infiltrative and complement dependent forms of glomerular immune injury, glomerular PAF levels are increased via a complement mediated mechanism. Infiltrating platelets, but not neutrophils, partially account for the enhanced glomerular PAF levels. The observations are of potential importance in the pathophysiology of glomerulonephritis.     

Glomerular expression of lipocortin-1 in human glomerulonephritis

Summary: Lipocortin-1 (LC-1), a Ca⁺⁺-dependent phospholipid binding protein, is believed to be involved in anti-inflammatory actions of glucocorticoids. to prove the hypothesis that steroid-resistant glomerulonephritis would show increased expression of LC-1, we evaluated the expression of LC-1 in various types of glomerulonephritis. Frozen samples of seven normal kidneys and 30 kidney biopsy tissues were stained with indirect immunofluorescent method. In the normal tissues, minimal change disease ( n =9), lupus nephritis ( n =5) and IgA nephropathy ( n =6), glomeruli did not stain for LC-1. Positive reactions for LC-1 were observed along the peripheral capillary walls in all five patients with membranous nephropathy with out hepatitis B surface antigen (HBsAg). In the patients with membranous nephropathy (MN) who also had chronic liver disease and HBsAg ( n =3), only weak reactions for LC-1 were found along the capillary walls and mesangial area in 1 patient. Patients with membranoproliferative glomerulonephritis ( n =2) showed positive reactions for LC-1 along the capillary walls. Fourteen patients with minimal change disease or lupus nephritis were treated with prednisolone. Ten patients showed substantial reduction of proteinuria, but four patients did not; however, staining for LC-1 was not negative in the kidney tissues of both steroid-responsive and steroid-resistant patients. These findings suggest that LC-1 does not mediate the action of glucocorticoids in human glomerulonephritis.     

Glomerular oxidative and antioxidative systems in experimental mesangioproliferative glomerulonephritis

Increased mesangial cell proliferation is a hallmark of many glomerulopathies in humans. Whereas the pathogenic role of reactive oxygen species (ROS) in the development of experimental mesangioproliferative glomerulonephritis (GN) is well established, very little is known about the mechanisms leading to increased ROS concentrations in the glomerulus. This study therefore examined glomerular ROS and the activities of oxidative and antioxidative enzymes during the early course of mesangioproliferative anti-Thy 1.1 GN. Anti-Thy 1.1 GN was induced in male Wistar rats, and glomeruli were isolated 2, 24, and 120 h after disease induction to examine ROS levels as well as oxidative and antioxidative enzyme expression in comparison to non-nephritic controls. At all time points, increased glomerular ROS levels, particularly of hydrogen peroxide and superoxide anions, were observed. Activities of NADH-dependent and NADPH-dependent oxidative enzymes were also increased during the course of GN, whereas no increased activity of xanthine oxidase, another potential source of ROS, was detectable. Despite glomerular oxidative stress, no compensatory increase of antioxidative enzyme activities occurred. On the contrary, catalase, superoxide dismutase, and glutathione peroxidase activities even decreased during the course of disease. In tubulointerstitial samples, no increase in oxidative activity was observed in the course of disease, thus confirming that detected ROS were of glomerular origin. Our data document for the first time a pronounced dysregulation of pro-oxidative and antioxidative enzymes in mesangioproliferative GN, leading to a net increase in glomerular ROS levels. Detailed knowledge of such pathways may lead to new therapeutic approaches for GN in humans.     

Humoral immunity to streptococcal antigen in acute and chronic glomerulonephritis

A study was carried out to verify the clinical usefulness of the elaborated method for the measurement of antistreptococcal antibody in revealing the streptococcal etiology of glomerulonephritis.In 158 patients with glomerulonephritis antistreptococcal antibody (ASA), circulating immune complexes (CIC) and haemolytic activity of the complement were measured.On the basis of immune complex formation it has been concluded that streptococcal infection may cause glomerulonephritis. Serial determinations of ASA and CIC are helpful in establishing the streptococcal etiology of glomerulonephritis and in monitoring the course of the disease.     

Glomerular IgA deposition in pulmonary diseases

Glomerular changes of 70 cases of pulmonary diseases and 25 control cases among 1100 consecutive autopsy cases were studied by light, immunofluorescence, and electron microscopy. These pulmonary diseases consisted of 11 cases of chronic obstructive bronchiolitis (COB), 15 cases of bronchopneumonia, 4 cases of acute interstitial pneumonia, 22 cases of idiopathic interstitial pneumonia (IIP), and 18 cases of lung cancer free from IIP. Bacteriological examination of the lung was performed in these cases including control cases on autopsy. Mesangial IgA deposition was predominant in 25 out of the 70 study cases (36%) frequently accompanied by C3, whereas slight mesangial IgA deposition was observed in one of the control cases. Incidence of IgA deposition was 64% in IIP, 54.5% in COB, 13.3% in bronchopneumonia, 16.7% in lung cancer and 25% in acute interstitial pneumonia. The results of the present study suggest that recurrence or persistence of inflammatory processes of the lung leads to IgA-mediated immune abnormalities and to mild mesangial changes with predominant IgA deposition, which are similar to the immunopathologic features of IgA nephropathy.     

Glomerular expression of C-C chemokines in different types of human crescentic glomerulonephritis.

BACKGROUND: Crescentic glomerulonephritis (CGN) presents a rapidly progressive glomerulonephritis clinically, in which macrophages play a crucial role in the pathogenesis. However, the precise molecular mechanism of macrophage recruitment and activation has not been fully elucidated. C-C chemokines, monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1alpha and beta (MIP-1alpha and MIP-1beta), are major chemoattractants for macrophages. We attempted to study the expression of C-C chemokines and their correlation with CD68-positive macrophages in crescentic glomeruli to investigate further their possible roles in crescent formation and progression to fibrosis in different types of human CGN. METHODS: The expression of MCP-1, MIP-1alpha, MIP-1beta and CD68 was detected in glomeruli with different forms of crescents (cellular, fibrocellular and fibrous crescents) by immunohistochemistry in serial sections of renal biopsies taken from 32 patients with biopsy-proven CGN including eight patients with anti-glomerular basement membrane (GBM) disease (type I CGN), 12 patients with immune complex-mediated CGN (type II CGN) and another 12 patients with pauci-immune CGN (type III CGN) enrolled in this study. Eight normal human kidneys were obtained from cadaveric renal transplant donors whose kidneys were technically unsuitable for transplantation, serving as controls. RESULTS: MCP-1, MIP-1alpha, MIP-1beta and CD68 were undetectable in glomeruli of normal kidney. In crescentic biopsies, MCP-1, MIP-1alpha, MIP-1beta and CD68 were detected in fibrocellular crescents and were even more prominent in cellular crescents, but were undetectable in fibrous crescents. Using consecutive sections for staining, it was demonstrated that a high proportion of infiltrating CD68-positive macrophages, mainly localized to the area of the expression of chemokines, were MCP-1, MIP-1alpha and MIP-1beta positive in crescents. Chemokines were expressed mainly by CD68-positive macrophages and parietal epithelial cells in crescents. The number of MCP-1- and MIP-1alpha-positive cells in glomeruli with cellular crescents was positively correlated with the number of CD68-positive cells (r = 0.568 and 0.749, respectively, both P < 0.01). The number of MCP-1- and MIP-1alpha-positive cells and the incidence of Bowman's capsule rupture in glomeruli of patients with type I CGN were higher than those of type II and type III CGN. CONCLUSIONS: These observations suggest that the expressed C-C chemokines, MCP-1, MIP-1alpha and MIP-1beta, may mediate the inflammatory process of crescent formation and progression to fibrosis. The strong correlation of MCP-1 and MIP-1alpha with infiltrating macrophages within glomeruli with cellular crescents suggested that these chemokines might be of particular importance for macrophage recruitment to this site. MCP-1 and MIP-1alpha were correlated to type I CGN with its more severe inflammatory course and worse prognosis. The variance of glomerular expression of C-C chemokines may contribute to the difference in histopathological features and prognosis in these three types of CGN.