Experimental IgA Nephropathy Research Articles

Immunoglobulin A nephropathy is characterized by anticommensal humoral immune responses.

IgA nephropathy (IgAN) is a leading cause of kidney failure, yet little is known about the immunopathogenesis of this disease. IgAN is characterized by deposition of IgA in the kidney glomeruli, but the source and stimulus for IgA production are not known. Clinical and experimental data suggest a role for aberrant immune responses to mucosal microbiota in IgAN, and in some countries with high disease prevalence, tonsillectomy is regarded as standard-of-care therapy. To evaluate the relationship between microbiota and mucosal immune responses, we characterized the tonsil microbiota in patients with IgAN versus nonrelated household-matched control group participants and identified increased carriage of the genus Neisseria and elevated Neisseria-targeted serum IgA in IgAN patients. We reverse-translated these findings in experimental IgAN driven by BAFF overexpression in BAFF-transgenic mice rendered susceptible to Neisseria infection by introduction of a humanized CEACAM-1 transgene (B × hC-Tg). Colonization of B × hC-Tg mice with Neisseria yielded augmented levels of systemic Neisseria-specific IgA. Using a custom ELISPOT assay, we discovered anti-Neisseria–specific IgA-secreting cells within the kidneys of these mice. These findings suggest a role for cytokine-driven aberrant mucosal immune responses to oropharyngeal pathobionts, such as Neisseria, in the immunopathogenesis of IgAN. Furthermore, in the presence of excess BAFF, pathobiont-specific IgA can be produced in situ within the kidney.

FC 037NEUTROPHILS PLAY A KEY ROLE IN THE INITIATION OF GLOMERULAR HEMATURIA IN A POSTINFECTIOUS IGAN EXPERIMENTAL MODEL

Abstract Background and Aims Hematuria is a common finding in patients with IgA nephropathy (IgAN), occurring mainly after upper respiratory tract infections. Hematuria can lead to acute kidney injury and chronic loss of renal function in IgAN. However, the mechanisms involved in egression of erythrocytes from the glomerular capillaries into the urinary space are unknown. To answer this question, we developed an infection with Streptococcus pneumoniae (SP) in a humanized experimental IgAN model (α1KICD89tg mice) that resembles the pathological and clinical findings of disease (IgA1 and soluble CD89 mesangial deposits, complement activation, proteinuria and hematuria). Method α1KICD89tg mice (12 weeks old) received an intranasal instillation of SP (107 bacteria). Blood, urine and renal samples were obtained during 1 month after induction of respiratory infection. The presence of SP in lungs from these mice was confirmed by microbiological analysis. Hematuria was quantified in the urinary sediment and renal function was determined by biochemical analysis. Renal histological characteristics were evaluated by hematoxylin/eosin, masson's trichrome and PAS staining. IgA glomerular deposits, activation of complement system and infiltration of proinflammatory cells was examined by immunohistochemistry or immunofluorescence. Circulating leukocyte populations were studied on a hemocytometer. Renal inflammatory cytokines, metalloproteases, as well as markers of tubular and glomerular damage were determined in kidneys by RT-PCR and western-blot. To further validate the role of neutrophils in this pathological setting, we selective depleted these cells through a single injection of anti-Ly6G mAb (200 µg/kg i.p). Results SP-intranasal instillation in α1KICD89tg mice increased hematuria, microalbuminuria and proteinuria, peaking at 48h after induction of the respiratory infection. SP instillation caused disruption of the glomerular basement membrane, with decreased expression of the slit diaphragm proteins nephrin and synaptopodin, as well as higher glomerular accumulation of IgA and proteins of complement system (C3, MBL). Hematuria intensity was positively correlated with the presence of interstitial F4/80+ macrophages, matrix metalloproteinase 9 (MMP-9), inflammatory cytokines and chemokines (IL-1β, IL-6, TNF-α, CCL-2, CCL5 and CX3CL1/CX3CR1) as well as p65 NF-κB activation. Hematuria was negatively correlated with anti-inflammatory IL-10 mRNA expression, Factor H levels and collagen IV content. Notably, SP infection induced expression of the tubular injury markers N-GAL and KIM-1. Increased peripheral neutrophils levels were observed in the SP-infected α1KICD89tg mice. Mechanistically, anti-Ly6G-mediated neutrophil depletion reduced SP-mediated hematuria, proteinuria and albuminuria, prevented loss of synaptopodin and nephrin, decreased renal inflammation and MMP-9 expression in α1KICD89tg mice Conclusion In a humanized mouse model of IgAN, hematuria bouts following respiratory tract infections are caused by a neutrophil-mediated alteration of the glomerular filtration barrier (podocyte damage, complement deposits and loss of Collagen IV). These findings may help to unveil novel potential therapeutic approaches to combat one of the key elements in the progression of IgAN and related conditions.

Nephroprotective effect of losartan in IgA model rat.

ObjectiveThis study was performed to investigate the possible nephroprotective effects of losartan in a rat model of experimental IgA nephropathy (IgAN).MethodsThirty male Sprague–Dawley rats were randomly divided into three groups. The rats in the model group were treated with bovine serum albumin (oral gavage), lipopolysaccharide (tail vein injection), and carbon tetrachloride (subcutaneous injection); rats in the losartan group received treatments similar to those of the model group, and were orally gavaged with losartan; and rats in the control group received phosphate-buffered saline alone (both orally and intravenously).ResultsLosartan treatment lowered the 24-hour urinary protein, serum blood urea nitrogen, and serum creatinine levels. Proliferating mesangial cells with a variable increase in the mesangial matrix were detected in the model group, whereas injury in the losartan group was significantly attenuated. Immunohistochemistry revealed that the expression levels of transforming growth factor (TGF)-β1 and α-smooth muscle actin were significantly elevated in the model group but reduced in the losartan group. The expression levels of TGF-β1 and monocyte chemoattractant protein-1 were minimal in the control group, significantly increased in the model group, and reduced in the losartan group.ConclusionLosartan has a protective effect against tubulointerstitial injury in IgAN.

Critical Role of Kupffer Cell CD89 Expression in Experimental IgA Nephropathy.

Although IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide, its etiology remains only partly understood. It is clear that the pathogenesis of IgAN involves the formation of macromolecular IgA1 complexes and increased levels of serum IgA1 and IgA1-immune complexes(IC), due to defective IgA1 clearance. Previous studies suggest that the blood and tissue myeloid cell-expressed IgA Fc receptor (FcαR/CD89) mediates IgA-IC clearance and its dysfunction, via decreased activity or excessive levels of soluble FcαR/sCD89 induces IgAN. Such a mechanism requires robust stimulation of IgAN levels via forced expression of CD89. In the absence of unequivocal evidence supporting such a mechanism to date, we attempted to test the extent of CD89-evoked IgAN by generating a transgenic mouse strain expressing human CD89 under the control of murine CD14 promotor. No deposition of IgA-CD89 complexes or glomerulonephritis was detected, however. Further studies showed that elimination of murine IgA was mediated by Kupffer cells. In patients, however, CD89/IgA complexes were detected, and injection of patient IgA induced IgAN-like features in CD89 Tg mice. In transgenic mice, IgAN pathogenesis involves impaired clearance of abnormal IgA via CD89, primarily by the Kupffer cells. Conditional IgAN progression in CD89 transgenic mice thus reveals important aspects of IgAN pathogenesis.

Tonsillar CD4+CD25+ Regulatory T Cells from IgA Nephropathy Patients Have Decreased Immunosuppressive Activity in Experimental IgA Nephropathy Rats

Background/Aim: CD4+CD25+ regulatory T (Treg) cells are of critical importance for maintenance of tolerance. We showed that the number of CD4+CD25+ Treg cells was significantly lower in tonsils of patients with IgA nephropathy (IgAN); however, the function of tonsillar CD4+CD25+ Treg cells in IgAN has not been reported. The aim of this study was to investigate the effect of tonsillar CD4+CD25+ Treg cells of IgAN patients on experimental IgAN in rats. Methods: Tonsillar CD4+CD25+ Treg cells were isolated by magnetic beads. A total of 2 × 10⁶ CD4+CD25+ Treg cells were transferred into rats that were previously orally immunized over a period of 14 weeks and subsequently received an injection of BSA into the tail vein on 3 consecutive days. Urine protein and erythrocytes were measured. Glomerular injury was assessed by histopathology. Plasminogen activator inhibitor type 1 (PAI-1), interleukin (IL)-6 and transforming growth factor (TGF)-β1 in mesangial cells of rats were examined by reverse transcription PCR. Serum IgA and C3 and supernatants of IL-2, IL-4 and IL-6 in splenic cells were analysed by ELISA. Transferred tonsillar CD4+CD25+ Treg cells were tracked by reverse transcription PCR and flow cytometry. Results: IgA deposition in the mesangial region and the glomerular planar area and the number of cells, levels of serum IgA and supernatant IL-2, IL-4 and IL-6 in splenic cells and PAI-1, IL-6 and TGF-β1 expression in renal mesangial cells of rats that received CD4+CD25+ Treg cells from IgAN patients were significantly higher than in rats that received CD4+CD25+ Treg cells from the control group, although they were dramatically lower compared with rats treated without CD4+CD25+ Treg cells. Transferred tonsillar CD4+CD25+ Treg cells migrated predominantly to secondary lymphoid organs but not to the kidneys. Conclusion: Dysfunction of tonsillar CD4+CD25+ Treg cells may be an important cause of IgAN progression.

Additive effect of PPAR-γ agonist and ARB in treatment of experimental IgA nephropathy

Our recent in vitro study demonstrated peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist potentiated the anti-inflammatory effect of angiotensin receptor blocker (ARB) in tubular epithelial cell under milieu mimicking IgA nephropathy (IgAN). Here we studied the therapeutic effect of combining a PPAR-γ agonist, rosiglitazone (Ros), with an ARB, losartan (Los), in experimental IgAN induced in Lewis rats by oral and intravenous immunization with bovine gamma-globulin (BGG). The rats were randomly divided into six groups: control, IgAN, IgAN with unilateral nephrectomy (IgAN/1K), and IgAN/1K receiving Ros, Los, or Ros + Los. Medication was given 1 week after nephrectomy until killing. Rats developing IgAN had hematuria, mesangial hypercellularity with IgA deposition, glomerular damage, and tubulointerstitial infiltration of CD25+ leukocytes accompanied by increased renal expression of TGF-β, AngII receptor subtype-1 (ATR1) and ICAM-1. The renal histopathology, albuminuria, and renal expression of TGF-β, ATR1 and ICAM-1 worsened with unilateral nephrectomy. Ros or Los reduced the renal expression of PCNA, TGF-β, ATR1, and ICAM-1 in IgAN rats with nephrectomy. Despite no difference between rats treated with monotherapy, combined therapy offered additive effect with decreased renal expression of TGF-β, ATR1 and ICAM-1 and attenuation of renal injury. Our animal study suggests combined PPAR-γ agonist and ARB holds promise for future therapy for IgAN.

(E)-N-[(3,4-dimethoxyphenethyl)]-N-methyl-3-(3-pyridyl)-2-propenamide (TJN-331) inhibits mesangial expansion in experimental IgA nephropathy in ddY mice

TJN-331 is an inhibitor of transforming growth factor β1 (TGF-β1) production that has similar structural features to the natural product acteoside. This study was performed to examine the antinephritic effects of TJN-331 in a mouse model of experimental IgA nephropathy. IgA nephropathy was induced in ddY mice by oral administration of bovine γ globulin, followed by reticuloendothelial blocking by colloidal carbon injection and heminephrectomy. Effects of TJN-331 were examined over oral administration periods from 10 to 15 weeks after the third colloidal carbon injection. Intravenous administration of a TGF-β1-neutralizing antibody was used to investigate the role of TGF-β1 in IgA nephropathy. Administration of TJN-331 or captopril prevented elevation of serum creatinine. Histopathological examination after both experimental periods showed that TJN-331 inhibited increases in the mesangial matrix index and the number of nuclei per glomerular cross-section, compared with in untreated ddY mice with IgA nephropathy. TJN-331 prevented increase in glomerular TGF-β1 staining without affecting IgA. In the in vitro study, TJN-331 prevented total TGF-β1 production from splenocytes stimulated with concanavalin A. A neutralizing antibody against TGF-β1 prevented increase in the mesangial matrix index and the number of glomerular cells per cross-sectional area. These results suggest that TJN-331 is effective against IgA nephropathy in ddY mice and acts via suppression of TGF-β1 production in glomeruli.

A case report: a patient with IgA nephropathy and coeliac disease. Complete clinical remission following gluten-free diet.

IgA nephropathy (IgAN) presents usually as a primary disease. However, secondary forms of IgAN have been described, most commonly associated with liver disease [1]. The presence of high levels of IgA against food antigens including gliadin and IgG and IgA antiendomysial antibodies in some patients with IgAN has raised the possibility of a pathophysiological link between IgAN and coeliac disease (CD) [2]. Experimental IgAN can be induced by dietary gluten or gliadin [3]. Furthermore, a favourable outcome of gluten-free diet on IgAN has been described [4].

T cell cytokines determine the severity of experimental IgA nephropathy by regulating IgA glycosylation.

Hyperfunction of Th2 cells and aberrant glycosylation of IgA have been proposed independently as factors in the pathogenesis of IgA nephropathy (IgAN), the most common form of glomerulonephritis. To investigate the relationship between Th2 cytokines and IgA glycosylation in the genesis of IgAN, we induced IgAN in C3HeB and BALB/c mice by oral immunization and intranasal challenge with Sendai virus. Although both strains of mice developed microhaematuria and glomerular IgA immune deposits to similar degrees, only BALB/c mice developed significant renal insufficiency. More profound reductions of terminal galactosylation and sialylation occurred in Sendai virus-specific IgA from BALB/c versus C3HeB mice, and splenocytes from immunized BALB/c mice produced more Th2 and less Th1 cytokines compared to C3HeB mice when stimulated with antigen in vitro. Furthermore, the decreased glycosylation of IgA elicited by Th2 cytokines in vitro was blunted by the addition of IFN-gamma. We conclude that increased production of Th2 cytokines can lead to abnormalities in IgA glycosylation, which in turn promote heightened phlogistic responses to IgA immune complexes lodging in the glomerulus. We suggest that a relative or absolute increase in Th2 cytokine production in response to mucosal infection is a significant pathogenic factor in human IgAN.

Effect of PA-MSHA vaccine on plasma phospholipids metabolic profiling and the ratio of Th2/Th1 cells within immune organ of mouse IgA nephropathy

Phospholipids as a class of important constituents in the biomembranes have been paid increasing attention in many fields. IgA nephropathy is now generally known to be the most common form of primary glomerulonephritis in the world. However, phospholipids metabolism in IgA nephropathy was not clear. Until recently, there was no effective treatment available for patients with IgA nephropathy. In this paper, effect of PA-MSHA vaccine on plasma phospholipid metabolic profile of mouse IgA nephropathy was investigated using high performance liquid chromatography/mass spectrometry (HPLC/MS) and principal components analysis (PCA). Female Balb/c mice were divided into four groups: model group, control group, PA-MSHA treatment group and medicine control group (dipyridamole + common threewingnut root). The experimental IgA nephropathy model was established by the immunity combination method of oral BSA and injection of SEB. It was found that combination of LC/MS technology with PCA can be successfully applied to phospholipids profile analysis, clearly classify the model group and normal group, and PA-MSHA treatment group is closer to the normal control group than medicine control group. The result showed that Th 2/Th 1 (=CD 4 +CD 30 +/CD 4 +CD 30 −) of the model group is 20.70 ± 3.57, which is significantly higher than that of the control group (1.34 ± 0.14) ( P < 0.001). The Th 2/Th 1 ratio of the PA-MSHA treatment group and the medicine control group are lower than that of the model group ( P < 0.01). It is suggested that mouse IgA nephropathy has the phospholipids metabolic abnormality, PA-MSHA vaccine cannot only regulate the abnormal phospholipids metabolism mouse with the IgA nephropathy, but also correct the over unbalance of Th 2/Th 1 proportion.

The Study of Chinese Medicinal Herbal Formula Shen San Fang in the Treatment of Experimental IgA Nephropathy

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide, yet there is no effective or specific therapy. Shen San Fang (S3F) is a traditional Chinese herbal medicinal formula that has been used in China for many years to treat patients with hematuria. The aim of this study is to test the therapeutic value of S3F in an experimental model of IgAN. IgAN was induced in Lewis rats by continuous oral immunization with bovine gamma-globulin (BGG) in the drinking water for 8 weeks, followed by intravenous injection of 1 mg BGG daily for 3 successive days. The rats were randomly divided into four groups (five rats/group): control, control receiving S3F, induction of IgAN, and IgAN receiving S3E S3F decoction was fed to rats beginning week 4 from the first day of oral sensitization with BGG. The S3F treatment was continued until the rats were sacrificed or for a 4-week period. Hematuria, renal immunohistochemistry for IgA and transforming growth factor-beta 1 (TGF-beta1), renal histopathology, and renal content of TGF-beta1 were measured. Rats developing IgAN had marked hematuria, profound mesangial proliferation and mesangial expansion, intense and diffuse glomerular IgA deposition, increased glomerular TGF-beta1 expression, and raised renal TGF-beta1 levels. S3F treatment resulted in a significant reduction of hematuria, decreased mesangial IgA deposition, weaker immunostaining of TGF-beta1 in glomerulus, and a lower renal TGF-beta1 concentration. Our animal data suggests a therapeutic value for the Chinese medicinal formula S3F in experimental IgAN. This beneficial effect was due to reduced glomerular IgA deposition and TGF-beta1 expression. Our preliminary findings hold promise for future human therapy.

Anti-macrophage migration inhibitory factor reduces transforming growth factor-beta 1 expression in experimental IgA nephropathy.

In human glomerulonephritis, including immunoglobulin-A nephropathy (IgAN), glomerular expression of macrophage migration inhibitory factor (MIF) is found to correlate with progressive renal injury. We have shown previously that polymeric IgA is capable of inducing MIF production in cultured human mesangial cells, suggesting a role in inducing inflammatory injury in IgAN. Herein, we examined whether IgA deposition and the subsequent renal injury can be ameliorated with anti-MIF treatment in an experimental murine model of IgAN. Glomerular IgA deposition was induced in 4-week-old BALB/c mice by intravenous injection of immune complexes consisting of dinitrophenyl-conjugated bovine serum albumin (DNP-BSA) and IgA MOPC-315 myeloma anti-DNP antibodies. To determine the therapeutic effect of anti-MIF, mice were given anti-MIF (5 mg/kg) or isotypic control antibody intravenously 2 h before the immune complexes administration. The mice were sacrificed 48 h after injection of DNP-IgA. Proteinuria and haematuria were determined and the kidneys were removed for histopathology, immunostaining and immunoblotting. The effect of exogenous MIF on production of TGF-beta 1 by cultured mesangial cells was also examined. IgA deposits were detected in glomeruli of all mice receiving the immune complexes while no glomerular deposit was detected in the control mice. Microscopic haematuria and mesangial hypercellularity were present in mice of the three experimental groups and were absent in the control group. Proteinuria was absent in all groups. Anti-MIF treatment also resulted in decreased renal expression of TGF-beta 1. Moreover, the reduction in TGF-beta 1 expression was confined mainly to glomerular mesangium. An in vitro culture experiment demonstrated that MIF increased TGF-beta 1 production in a time- and dose-dependent fashion. MIF-induced TGF-beta 1 synthesis was abolished by incubating cells with neutralizing antibody against MIF. Our finding shows that anti-MIF treatment can ameliorate kidney injury and reduce glomerular TGF-beta 1 expression in an experimental model of IgAN.

Docosahexaenoic Acid and Eicosapentaenoic Acid, but Not α-Linolenic Acid, Suppress Deoxynivalenol-Induced Experimental IgA Nephropathy in Mice

Diets enriched in the (n-3) PUFAs, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and their precursor alpha-linolenic acid (ALA), were evaluated for efficacy in ameliorating the development of IgA nephropathy (IgAN) induced in mice by the mycotoxin deoxynivalenol (DON). The effects of DON were compared in mice that were fed for 18 wk with AIN-93G diets containing 1) 10 g/kg corn oil plus 60 g/kg oleic acid (control); 2) 10 g/kg corn oil plus 35 g/kg oleic acid and 25 g/kg DHA-enriched fish oil (DHA); 3) 10 g/kg corn oil plus 33 g/kg oleic acid and 27 g/kg EPA-enriched fish oil (EPA); and 4) 10 g/kg corn oil plus 37 g/kg oleic acid and 23 g/kg DHA + EPA (1:1) enriched fish oil (DHA + EPA). The DHA, EPA and DHA + EPA diets attenuated induction by dietary DON (10 mg/kg) of serum IgA and IgA immune complexes, kidney mesangial IgA deposition, and ex vivo IgA secretion by spleen cells. Consumption of the DHA + EPA diet for 8 wk significantly abrogated the DON-induced gene expression of interleukin (IL)-6, a requisite cytokine for DON-induced IgA nephropathy, in spleen and Peyer's patches. Finally, incorporation of ALA-containing flaxseed oil up to 60 g/kg in the AIN-93G diet did not affect DON-induced IgA dysregulation in mice. Taken together, both DHA and EPA, but not ALA, ameliorated the early stages of IgAN, and these effects might be related to a reduced capacity for IL-6 production.

Indices of progression of IgA nephropathy are modulated by α-tocopherol in rats

Background. We have previously shown that α-tocopherol prevents oxidative stress in experimental IgA nephropathy (IgAN) when administered before or concurrent with the induction of IgAN. We now seek to determine whether α-tocopherol can ameliorate the disease after IgAN is established. Methods. Using the classic IgAN model, 25 male Lewis rats were sorted into five groups of five animals each: 4-week control, 4-week bovine gamma globulin (BGG) treatment, 6-week control, 6-week BGG treatment, and 6-week BGG treatment with α-tocopherol administration started after 4 weeks. Serum α-tocopherol concentrations, kidney and plasma malondialdehyde concentrations, and kidney transforming growth factor beta-1 (TGFβ1) mRNA were analyzed. Results.α-Tocopherol modulated IgAN after the disease was established in the 4-week BGG model, as indicated by the reduction in tissue oxidative stress, dampening of fibrogenic cytokine (TGFβ1), and abatement of proteinuria in α-tocopherol-treated animals compared with untreated rats. Conclusions. These results substantiate the anti-oxidant role of α-tocopherol in diminishing the indices associated with progression of experimental IgAN. The ability of α-tocopherol to reduce the progression of injury after establishment of the disease reflects the clinical situation, and thus holds promise for human therapy.

Influence of alpha-tocopherol over the time course of experimental IgA nephropathy.

The present study investigated the pathogenesis and the time course of kidney injury in experimental IgA nephropathy. In order to determine an appropriate period in the course of experimental IgA nephropathy to study renal injury and repair, we examined proteinuria and IgA deposition in the renal mesangium after 4, 8, and 16 weeks of mucosal challenge by bovine gamma globulins (BGG) provided in the drinking water. The hallmark of IgA deposition in the mesangium was present after 4 weeks and 8 weeks of BGG inoculation, but by 16 weeks, the mesangial IgA deposition had resolved. In addition, we confirmed our previous report on the beneficial effects of alpha-tocopherol in reducing proteinuria in IgA nephropathy at 8 weeks, and extended this observation to investigate the effects of dietary supplementation of alpha-tocopherol at both 4 weeks and 16 weeks. Proteinuria resolved spontaneously at 16 weeks. There is oxidative stress, as suggested by the elevation in plasma and renal malondialdehyde content, and increased fibrogenic cytokine message, as suggested by elevated transforming growth factor beta1 mRNA. These increases were clearly blunted by alpha-tocopherol at both 4 weeks and 8 weeks. Treatment with alpha-tocopherol was associated with a significant reduction in the severity of proteinuria. Thus, our data suggest that the period between 4 and 8 weeks of BGG vaccination could be relevant in designing an appropriate model to study the molecular biology of the pathogenesis of renal injury and the effects of treatment. The 16-week model may be useful in exploring gene expression involved with spontaneous resolution.

Experimental IgA nephropathy induced by Haemophilus parainfluenzae antigens

Experimental IgA nephropathy induced by <i>Haemophilus parainfluenzae</i> antigens

Experimental Murine IgA Nephropathy following Passive Administration of Vomitoxin-induced IgA Monoclonal Antibodies

Oral exposure of mice to vomitoxin (VT) induces elevated levels of serum IgA, circulating IgA immune complexes (IgA-IC), mesangial IgA deposition and haematuria, which all mimic the clinical signs of human IgA nephropathy (IgAN). To further assess the effects of VT-induced IgA in the murine model, B6C3F 1 and BALB/C mice were injected intraperitoneally with affinity-purified monoclonal IgA derived from Peyer's patch hybridomas of VT-exposed mice. In B6C3F 1 mice, serum IgA, IgM and IgA-IC levels were increased two- to fivefold in treatment groups after 4 and 6 wk compared with controls, whereas increases in serum IgG as high as 18-fold were observed. Urinary erythrocyte counts were also significantly elevated in treatment groups after 2, 4 and 6 wk compared with controls. Concurrent increases in IgA and IgG complexes containing casein, the dietary protein source, occurred in treatment mice. Mesangial IgA, IgG, IgM and C3 deposition were significantly increased in all treatment mice after 6 wk. Electron-dense deposits occurred in the glomeruli of IgA-injected mice after 6 wk. All the above parameters were similarly affected in BALB/C mice. Injection of IgA-secreting hybridoma cells into BALB/C mice increased serum IgA, IgA-IC and IgG levels as well as elevated mesangial IgA, IgG and C3 deposition and haematuria after 2–3 weeks compared with controls. In total, these data indicate that passive administration of VT-induced IgAs can induce the hallmarks of IgA nephropathy. Casein, an antigen found in the diet used for these mice, appeared to form IC with IgA or IgG and these IC may participate in the pathogenesis of this nephropathy.

Effects of fish oil and alpha-tocopherol in immunoglobulin A nephropathy in the rat.

Alpha-tocopherol and fish oil have been reported to modulate the progression of IgA nephropathy in animals and humans. Because fish oil has been reported to exacerbate renal disease in subtotal nephrectomized rats, we investigated the effects of fish oil, with and without alpha-tocopherol, on the course of IgA nephropathy. Experimental IgA nephropathy was induced in male Sprague-Dawley rats, weighing 170-200 g, by oral and i.v. immunization with bovine gamma-globulin for 8 wk. IgA nephropathy was evidenced by hematuria, proteinuria, and IgA deposition in the mesangium. Standard rodent chow, containing 30 IU of alpha-tocopherol/kg of diet, was given to the control and IgA nephropathy rats. Fish oil (20% wt/wt), stripped of alpha-tocopherol preservative, was given to control and a second group of IgA nephropathy rats. Alternatively, corn oil or fish oil was supplemented with alpha-tocopherol at 100 IU/kg of diet and given to the third and fourth groups of IgA nephropathy rats. All animals were killed at 8 wk. Urinary protein excretion, plasma and kidney alpha-tocopherol concentrations, as well as glomerular planar area, and kidney transforming growth factor-beta1 mRNA were analyzed. As determined by reductions in proteinuria, glomerular planar area, and TGF-beta1 mRNA, fish oil with alpha-tocopherol ameliorated the renal injury induced by bovine gamma-globulin, whereas fish oil without alpha-tocopherol did not. Our findings support the importance of alpha-tocopherol, more so than fish oil, in mitigating the injury and promoting repair in experimental IgA nephropathy.

α-Tocopherol Reduces Proteinuria, Oxidative Stress, and Expression of Transforming Growth Factor β1 in IgA Nephropathy in the Rat

Oxidative stress and the fibrogenic cytokine transforming growth factor β1 (TGFβ1) have been implicated in the pathogenesis and progression of IgA nephropathy. In the present study, we used α-tocopherol as a dietary supplement to test the hypothesis that the proteinuria, oxidative stress, and TGFβ mRNA can be more effectively lowered with higher doses of α-tocopherol. Hematuria, proteinuria, and mesangial IgA deposition are parameters which characterize IgA nephropathy. IgA nephropathy was induced by bovine gamma globulin oral immunization in rats during an 8-week course, and all hallmarks of IgA nephropathy were produced in this 8-week animal model. The elevation in renal malondialdehyde content and TGFβ1 mRNA, as well as the severity of proteinuria, was blunted by α-tocopherol. Our data suggested that conventional dosage of α-tocopherol at 100 IU/kg chow lowered kidney TGFβ1 to control values and increasing the dose by 212-fold or even 5-fold resulted in no further reduction in TGFβ1 mRNA. Significant reduction of proteinuria was achieved better with a dose of 250 IU/kg chow of α-tocopherol supplementation than with the 100 IU/kg chow. We conclude that α-tocopherol at this dose is efficacious in controlling proteinuria, downregulating TGFβ1, and reducing oxidative stress in experimental IgA nephropathy. Doubling this dose achieved no further benefits.

Interleukin-1 receptor antagonist modulates the progression of a spontaneously occurring IgA nephropathy in mice

Cytokines, such as interleukin-1 (IL-1), may play a key role in the pathogenesis of IgA nephropathy (IgAN). This study was conducted to evaluate the effects of IL-1 receptor antagonist (IL-1ra) in the treatment of a spontaneously occurring experimental IgAN in established phase. ddY mice (12/group) were injected twice daily with 3 mg/kg of IL-1ra, intraperitoneally, for 8 consecutive weeks. The placebo mice were injected with saline only. As normal controls, ddY mice, which were not treated with IL-1ra or saline, were killed at 6 weeks of age. Results showed a significant reduction of proteinuria in the IL-1ra-treated mice, compared with saline-treated mice (urinary albumin/creatinine, 0.24 ± 0.04 v 0.39 ± 0.03, P < 0.001). A significant improvement of renal 51Cr-EDTA (ethylenedi-aminetetra-acetic acid) clearance was observed in the IL-1ra-treated mice ( t 1 2 , 12 ± 2.7 minutes, compared with saline-treated mice 25 ± 2.0 minutes, P < 0.001). Similarly, serum levels of creatinine (1.0 ± 0.4 v 2.4 ± 0.3 mg/dL, P < 0.001) and urea nitrogen (46 ± 6 v 58 ± 2 mg/dL, P < 0.01) were significantly lower in IL-1ra-treated mice than in saline-treated mice. In renal tissue studies, the IL-1ra-treated mice exhibited significantly decreased mesangial cell proliferation, compared with saline-treated mice ( P < 0.001), as shown by light and electron microscopy. In addition, the IL-1ra-treated mice showed significantly lower glomerular expression of collagen type IV, fibronectin, laminin, and IL-6 ( P < 0.001) than saline-treated mice, although they still showed higher glomerular expression of collagen type IV ( P < 0.01), fibronectin ( P < 0.01), laminin ( P < 0.001), IL-1 ( P < 0.001), and IL-6 ( P < 0.01) than did normal control mice. Meanwhile, glomerular C3 deposition was significantly lower in IL-1ra-treated mice than in saline-treated mice ( P < 0.001). These findings indicate that IL-1ra partially prevented the progression of spontaneously occurring IgAN in this experimental model. Data from these experiments also confirm the pathogenic effects of IL-1 in the established phase of IgAN in ddY mice.