Nephrotoxic serum nephritis in nude rats: the role of cell-mediated immunity

SM22α: The Novel Phenotype Marker of Injured Glomerular Epithelial Cells in Anti-Glomerular Basement Membrane Nephritis

BACKGROUND/AIMS

Our previous comprehensive analysis of the genes expressed in kidneys with anti-glomerular basement membrane (GBM) nephritis using DNA microarrays showed that SM22alpha was one of the highly expressed genes. SM22alpha is a 22-kDa cytoskeletal protein that is exclusively expressed in smooth muscle cells. We investigated the localization of SM22alpha at mRNA and protein levels, and its pathological significance in anti-GBM nephritis kidneys.

METHODS

Northern blot analysis, in situ hybridization, immunohistochemistry and double immunofluorescence studies were performed. The specific antibody (Ab) against SM22alpha was obtained by immunization of rabbits with recombinant rat SM22alpha protein.

RESULTS

SM22alpha mRNA expression was upregulated in kidneys and inducibly expressed in the parietal and visceral glomerular epithelial cells in anti-GBM nephritis kidneys. Immunohistochemistry with anti-SM22alpha Ab showed that SM22alpha protein was localized in the same series of cells. Double immunofluorescence with anti-SM22alpha and anti-glomerular cell markers demonstrated that SM22alpha might be expressed in epithelial cells of injured glomeruli. In visceral epithelial cells, SM22alpha might be expressed in cells in which podocyte specific markers, podocalyxin and nephrin were lost.

CONCLUSION

The injured glomerular epithelial cells in anti-GBM nephritis might undergo structural and functional alterations, including the expression of a smooth muscle marker, SM22alpha.

Expression of allograft inflammatory factor-1 in kidneys: A novel molecular component of podocyte

Our comprehensive gene expression profiles of the kidneys in an anti-glomerular basement membrane (GBM) nephritis model using DNA arrays revealed that allograft inflammatory factor-1 (AIF-1) was one of the highly expressed genes. Here, we explored the pathological significance of AIF-1 expression in the kidneys. The expression pattern of AIF-1 mRNA and protein in the kidneys of normal and diseased rats, such as anti-GBM nephritis and puromycin aminonucleoside nephrosis, was investigated by in situ hybridization, immunohistochemistry, and immunoelectron microscopy. Furthermore, the expression of AIF-1 in human kidneys and urinary sediments was examined. AIF-1 was expressed at both mRNA and protein levels in podocytes of normal and diseased rats, and in infiltrating cells in anti-GBM nephritis kidneys. The expression of AIF-1 in podocytes was constitutive; positive in podocytes of both normal and diseased rats. In humans, AIF-1 was expressed in podocytes and infiltrating inflammatory cells, similarly. Moreover, it was detected in urinary podocytes from patients with immunoglobulin A nephropathy. These data document for the first time that AIF-1, a constitutively expressed protein in rat and human podocytes, is a novel molecular component of podocytes, and that the upregulation of AIF-1 in an anti-GBM nephritis model may mainly be a consequence of its expression in infiltrating cells.

Bezafibrate suppresses rat antiglomerular basement membrane crescentic glomerulonephritis

BACKGROUND

The immunoregulatory activity of ligands for peroxisome proliferator-activated receptors (PPARs) has been recently paid attention. The regulatory effect of bezafibrate (BZF), a ligand for PPARalpha on glomerulonephritis was investigated using a rat anti-glomerular basement membrane (GBM) glomerulonephritis model.

METHODS

The effect on development of anti-GBM glomerulonephritis was examined by treatment with BZF from day -7 to day 7 after intravenous injection of rabbit anti-GBM serum into Wistar Kyoto (WKY) rats. The therapeutic efficacy after onset of the glomerulonephritis was also checked by treatment with BZF from day 3 to 7. On day 7, the condition was evaluated histologically. The expression of a tissue injury molecule, macrophage metalloesterase (MME), was measured by Northern blot analysis. The suppressive effect on immune cells was assessed by proliferation assay with mitogen-stimulated rat spleen cells.

RESULTS

Histopathologic changes induced by anti-GBM in rats treated with BZF (day -7 to day 7) were markedly suppressed in a dose-dependent fashion. Infiltration of ED-1+ macrophages in glomeruli, proteinuria, and mRNA expression of MME in kidneys were diminished in parallel with histologic improvement. Moreover, the disease activity was also attenuated even by the treatment after onset of the glomerulonephritis (day 3 to 7). The mitogen-induced proliferation of spleen cells was down-regulated at concentrations of BZF, which were equivalent to those in sera of BZF-treated rats.

CONCLUSION

BZF markedly suppresses the activity of rat anti-GBM crescentic glomerulonephritis. Fibrates might serve as a therapeutic option for crescentic glomerulonephritis.

Cell-type-specific activation of mitogen-activated protein kinases in PAN-induced progressive renal disease in rats

We examined the time-course activation and the cell-type specific role of MAP kinases in puromycin aminonucleoside (PAN)-induced renal disease. The maximal activation of c-Jun-NH2-terminal kinase (JNK), extracellular signal regulated kinase (ERK), and p38 MAP kinase was detected on Days 52, 38, and 38 after PAN-treatment, respectively. p-JNK was localized in mesangial and proximal tubular cells at the early renal injury. It was expressed, therefore, in the inflammatory cells of tubulointerstitial lesions. While, p-ERK was markedly increased in the glomerular regions and macrophages p-p38 was observed in glomerular endothelial cells, tubular cells, and some inflammatory cells. The results show that the activation of MAP kinases in the early renal injury by PAN-treatment involves cellular changes such as cell proliferation or apoptosis in renal native cells. The activation of MAP kinases in infiltrated inflammatory cells and fibrotic cells plays an important role in destructive events such as glomerulosclerosis and tubulointerstitial fibrosis.

Macrophage metalloelastase as a major factor for glomerular injury in anti-glomerular basement membrane nephritis

Rat anti-glomerular basement membrane (GBM) nephritis is a model of crescentic glomerulonephritis induced by injection of anti-GBM antiserum. To elucidate the mechanism of glomerular injury, we analyzed the gene expression patterns in the kidneys of anti-GBM nephritis rats using DNA arrays, and found that macrophage metalloelastase/matrix metalloproteinase (MMP)-12 was one of the highly expressed genes in the kidneys on days 3 and 7 after the injection of anti-GBM antiserum. Enhancement of MMP-12 mRNA expression was confirmed by Northern blot analysis, and in situ hybridization revealed that MMP-12 mRNA was expressed in ED-1-positive macrophages and multinuclear giant cells in the glomeruli with crescent. Moreover, these cells were positive with anti-rat rMMP-12 Ab on the section of the kidneys of anti-GBM nephritis rats on day 7. To clarify the role of MMP-12, we conducted a neutralization experiment using anti-rat rMMP-12 Ab, which had an ability to inhibit rMMP-12 activity of degrading natural substrate such as bovine elastin or human fibronectin in vitro. Anti-rat rMMP-12 Ab or control Ig was injected in each of six rats on days 0, 2, 4, and 6 after the injection of anti-GBM antiserum. Consequently, crescent formation and macrophage infiltration in the glomeruli were significantly reduced in the rats treated with anti-rat rMMP-12 Ab, and the amount of urine protein was also decreased. These results disclosed that MMP-12 played an important role in glomerular injury in a crescentic glomerulonephritis model, and inhibition of MMP-12 may lead to a new therapeutic strategy for this disease.

Role of CD8(+) cells in the progression of murine adriamycin nephropathy

BACKGROUND

Many studies have shown that interstitial inflammation in human and experimental renal disease is characterized by T-cell infiltration, but published data on the involvement of inflammatory cell subsets in progressive tubulointerstitial lesions are often conflicting. A previous study suggested a role for cytotoxic T lymphocytes in the damaging effect of CD4(+) T-cell depletion in murine adriamycin (ADR) nephropathy, a model of focal segmental glomerulosclerosis (FSGS), and tubulointerstitial inflammation. The aim of this study was to investigate the role of CD8(+) cells in this model.

METHODS

Male BALB/c mice were treated with five intraperitoneal injections of anti-CD8 monoclonal antibody (mAb), beginning from five days after ADR treatment, when overt proteinuria was established. Seven mice in each of groups A (ADR + mAb), B (ADR only), and C (saline treated, age matched) were sacrificed at week 6. Changes in renal function and histopathological features were assessed. Tubulointerstitial inflammation and glomerular inflammation were examined immunohistochemically.

RESULTS

mAb treatment reduced CD8(+) cell levels to <2% of normal in spleen. Proteinuria in group A was no different from that in group B at week 6, but was markedly higher than in group C. Creatinine clearance was significantly ameliorated by anti-CD8 treatment (71.8 +/- 4.9 microL/min vs. 29.2 +/- 2.8 in group B and 81.9 +/- 3.7 in group C). Morphometric analysis showed less FSGS in group A compared with group B (6.5 +/- 1.9 vs. 13.0 +/- 2.8, P < 0.001), as well as less tubular atrophy (indicated by increased ratio of tubule cell height to tubular diameter, 0.25 +/- 0.24 in group A vs. 0.04 +/- 0.02 in group B, P < 0.05). CD8 depletion also reduced interstitial expansion (6.3 +/- 2.2% vs. 16.4 +/- 3.1 in group B, P < 0.001) and fibrosis (P < 0.01). Macrophage infiltration in tubulointerstitium was less in group A than in group B (P = 0.052). The number of interstitial CD4(+) cells appeared to increase after anti-CD8 treatment, but was not statistically different between groups A and B.

CONCLUSION

Anti-CD8 treatment protects against renal functional and structural injury in this murine model of chronic proteinuric renal disease.

The central and multiple roles of B cells in lupus pathogenesis

A standard view of B cells in systemic autoimmunity is that they promote lupus by producing autoantibodies (autoAb). However, this view is incomplete because recent studies have revealed that autoimmune disease can be dissociated from autoAb deposition. Furthermore, the spontaneous T-cell activation and organ infiltration in systemic lupus erythematosus patients and animal models are difficult to explain entirely via a direct autoAb-mediated mechanism. In this review, we describe work addressing the B-cell functions of autoantigen presentation and autoAb production in lupus pathogenesis. In the JHD-MRL-Faslpr strain (JHD/lpr), a B-cell-deficient version of the lupus-prone MRL-Faslpr (MRL/lpr) mouse, spontaneous nephritis and dermatitis is abrogated, demonstrating that B cells have a primary role in disease. B cells play a similar role in Fas-intact, lupus-prone MRL mice. To address the role of autoantigen presentation, we analyzed transgenic mice which have B cells that cannot secrete immunoglobulin (mIgM transgenic mice). The restoration of B cells without antibody caused substantial interstitial nephritis and vasculitis although less marked than the intact MRL/lpr controls. To address the role of autoAb, we infused serum from aged MRL/lpr mice into JHD/lpr mice. At most, mild to no nephritis was observed in the infused mice. These results indicate that B cells are promoting autoimmunity in mechanisms other than autoAb secretion, and we describe a model depicting these B-cell roles in the context of other inflammatory events in lupus.