Early critical cortical infarction by anti-angiotensin II type 1 receptor antibody: A case report and literature review

RATIONALE

Anti-angiotensin II type 1 receptor antibodies (AT1R-Abs) have been demonstrated to increase the risk of antibody-mediated rejection. We report a case of AT1R-Ab mediated rejection which caused early critical cortical infarction.

PATIENT CONCERNS

A 52-year-old man with end-stage kidney disease underwent preemptive kidney transplantation (KT) from his wife. He had no immunologic risk except ABO incompatibility. Proper desensitization treatment were applied prior to KT. On postoperative day 1, he showed stable clinical course with adequate urine output, but there was no decrease in serum creatinine level and imaging studies showed hypoperfusion in the transplanted kidney.

DIAGNOSES

Allograft biopsy revealed total cortical infarction with severe necrotizing vasculitis, but the medullary area was preserved. Serum AT1R-Ab concentration was elevated from 10.9 U/mL before KT to 19.1 U/mL on 7 days after KT.

INTERVENTIONS

He was treated with plasmapheresis, intravenous immunoglobulin, rituximab, high-dose methylprednisolone, and bortezomib.

OUTCOMES

The treatment showed a partial response, and he was discharged with 7.3 mg/dL creatinine level. At 4 months, his creatinine plateaued at 5.5 mg/dL and AT1R-Ab decreased to 3.6 U/mL.

LESSONS

This case highlights the risk of early active antibody-mediated rejection by preformed AT1R-Ab, suggesting its ability to exhibit atypical histopathologic findings, such as total cortical infarction.

The appearance of renal cells cytoplasmic degeneration and nuclear destruction might be an indication of GNPs toxicity

BACKGROUND

Advances in nanotechnology have identified promising candidates for many biological and biomedical applications. Since the properties of nanoparticles (NPs) differ from that of their bulk materials, they are being increasingly exploited for medical uses and other industrial applications. The histological and the histochemical alterations in the renal tissues due to gold nanoparticles (GNPs) have not well documented and have not yet been identified. The aim of the present study was to investigate the particle-size effect of GNPs on the renal tissue in an attempt to address their potential toxicity.

METHODS

A total of 70 healthy male Wistar-Kyoto rats were exposed to GNPs received 50 or 100 μl of GNPs infusion of size (10, 20 and 50 nm for 3 or 7 days) to investigate particle-size effect of GNPs on the renal tissue. Animals were randomly divided into groups, 6 GNPs-treated rats groups and one control group. Groups 1, 2 and 3 received infusion of 50 μl GNPs of size 10 nm (3 or 7 days), size 20 nm (3 or 7 days) and 50 nm (3 or 7 days), respectively; while groups 4, 5 and 6 received infusion of 100 μl GNPs of size 10 nm, size 20 nm and 50 nm, respectively.

RESULTS

The histological alterations were mainly seen in the cortex and the proximal renal convoluted tubules were more affected than the distal ones. In comparison with respective control rats, exposure to GNPs doses has produced the following renal tubular alterations: cloudy swelling and renal tubular necrosis. Interstitial alterations included: intertubular blood capillaries dilatation, intertubular hemorrhage and inflammatory cell infiltrations. The glomeruli showed moderate congestion with no hypercelluraity and mesangial proliferation or basement membrane thickening.

CONCLUSIONS

The induced histological alterations might be an indication of injured renal tubules due to GNPs toxicity that become unable to deal with the accumulated residues resulting from metabolic and structural disturbances caused by these NPs. These alterations were size-dependent with smaller ones induced more effects and related with time exposure of GNPs. The produced histological alterations may suggest that GNPs interact with proteins and enzymes of the renal tissue interfering with the antioxidant defense mechanism and leading to reactive oxygen species (ROS) generation which in turn may induce stress in the renal cells to undergo atrophy and necrosis. More histomorphologcal investigations are needed to address the potential threat of GNPs as a therapeutic and diagnostic tool.

Induction of passive Heymann nephritis in complement component 6-deficient PVG rats

Passive Heymann nephritis (PHN), a model of human membranous nephritis, is induced in susceptible rat strains by injection of heterologous antisera to rat renal tubular Ag extract. PHN is currently considered the archetypal complement-dependent form of nephritis, with the proteinuria resulting from sublytic glomerular epithelial cell injury induced by the complement membrane attack complex (MAC) of C5b-9. This study examined whether C6 and MAC are essential to the development of proteinuria in PHN by comparing the effect of injection of anti-Fx1A antisera into PVG rats deficient in C6 (PVG/C6(-)) and normal PVG rats (PVG/c). PVG/c and PVG/C6(-) rats developed similar levels of proteinuria at 3, 7, 14, and 28 days following injection of antisera. Isolated whole glomeruli showed similar deposition of rat Ig and C3 staining in PVG/c and PVG/C6(-) rats. C9 deposition was abundant in PVG/c but was not detected in PVG/C6(-) glomeruli, indicating C5b-9/MAC had not formed in PVG/C6(-) rats. There was also no difference in the glomerular cellular infiltrate of T cells and macrophages nor the size of glomerular basement membrane deposits measured on electron micrographs. To examine whether T cells effect injury, rats were depleted of CD8+ T cells which did not affect proteinuria in the early heterologous phase but prevented the increase in proteinuria associated with the later autologous phase. These studies showed proteinuria in PHN occurs without MAC and that other mechanisms, such as immune complex size, early complement components, CD4+ and CD8+ T cells, disrupt glomerular integrity and lead to proteinuria.

TNF-alpha neutralization ameliorates obstruction-induced renal fibrosis and dysfunction

Upper urinary tract obstruction results in tubulointerstitial fibrosis and a progressive decline in renal function. Although several inflammatory mediators have been implicated in the pathophysiology of renal obstruction, the contribution of TNF-alpha to obstruction-induced fibrosis and renal dysfunction has not been thoroughly evaluated. To study this, male Sprague-Dawley rats were subjected to left unilateral ureteral obstruction vs. sham operation. Rats received either vehicle or a pegylated form of soluble TNF receptor type 1 (PEG-sTNFR1) every 84 h. The kidneys were harvested 1, 3, or 7 days postoperatively, and tissue samples were analyzed for TNF-alpha expression (ELISA), macrophage infiltration (ED-1 staining), transforming growth factor-beta(1) expression (ELISA, RT-PCR), collagen I and IV activity (Western Blot, immunohistochemistry), alpha-smooth muscle actin accumulation (immunohistochemistry, Western blot analysis), and angiotensinogen expression (Western blot). In a separate arm, the glomerular filtration rate (inulin clearance) of rats subjected to unilateral ureteral obstruction in the presence of either vehicle or PEG-sTNFR1 was determined. Renal obstruction induced increased tissue TNF-alpha and transforming growth factor-beta(1) levels, collagen I and IV activity, interstitial volume, alpha-smooth muscle actin accumulation, angiotensinogen expression, and renal dysfunction, whereas treatment with PEG-sTNFR1 significantly reduced each of these markers of renal fibrosis. These results demonstrate that TNF-alpha mediates obstruction-induced renal fibrosis and identify TNF-alpha neutralization as a potential therapeutic option for the amelioration of obstruction-induced renal injury.

Structural and functional properties of proteasomes purified from the human kidney

BACKGROUND

Proteasomes are 'proteolytic machineries' implicated in many cellular functions, including protein turnover, inflammatory response and immunosurveillance. They exist in various forms sharing the same catalytic core - the 20S proteasome. This core consists of 28 subunits codified by 14 different genes, 3 of which - beta 1, beta 2 and beta 5 - are catalytically active and show peptidyl-glutamyl peptide hydrolyzing (PGPH), trypsin-like and chymo-trypsin-like activities, respectively. Under IFN- delta and TNF- alfa stimuli, the 3 active constitutive subunits are replaced by the corresponding ones - i.e., LMP2, MECL-1, LMP7 - known as inducible subunits, thus resulting in the constitution of the 'immunoproteasome' that is specifically implicated in MHC class I-presented peptide generation. This process is enhanced when the proteasome is associated with the polymeric protein 11S regulator/PA28 made up of 4 alfa and 3 beta subunits.

METHODS

The 20S proteasome was purified from post mortem specimens of human kidney cortex by chromatographic and ultracentrifugation techniques. It was then characterized on the basis of (i) multicatalytic activity evaluated using specific fluorogenic peptides, (ii) electrophoretic mobility on non-denaturating polyacrylamide gels followed by in-gel visualization by fluorogenic peptide overlaying and Coomassie blue staining and (iii) subunit composition as ascertained by SDS-PAGE and 2-dimensional electrophoresis followed by silver staining or Western immunoblotting using specific antibodies against the proteasome subunits. The 20S proteasome was also studied for its association with the 11S regulator by Western immunoblotting using an antibody to the regulator alfa subuniT.

RESULTS

T he purified proteasome was shown to have PGPH, trypsin-like and chymotrypsin-like activities. Furthermore, it incorporated the inducible subunits and was associated with the 11S regulator.

CONCLUSIONS

The features we observed make renal cells susceptible to an over-expression of inflammatory response to immunological challenges.

Nuclear factor kappaB activity determines the sensitivity of kidney epithelial cells to apoptosis: implications for mercury-induced renal failure

Nuclear factor kappa B (NF-kappaB) is a thiol-dependent transcriptional factor that promotes cell survival and protects cells from apoptotic stimuli. Numerous studies have demonstrated increased sensitivity to apoptosis associated with inhibition of NF-kappaB activation in various cell types. We have previously demonstrated that mercuric ion (Hg(2+)), one of the strongest thiol-binding agents known, impairs NF-kappaB activation and DNA binding at low microM concentrations in kidney epithelial cells. In the present studies we investigated the hypothesis that inhibition of NF-kappaB activation by Hg(2+) and other selective NF-kappaB inhibitors would increase the sensitivity of kidney epithelial (NRK52E) cells to apoptogenic agents to which these cells are normally resistant. Fewer than 10% of untreated cells in culture were found to be apoptotic when evaluated by DNA fragmentation (TUNEL) assay. Treatment of cells with Hg(2+) in concentrations up to 5 microM or with tumor necrosis factor-alpha (TNF) (300 units/ml) did not significantly increase the proportion of apoptotic cells, compared with untreated controls. However, when TNF was given following Hg(2+) pretreatment (0.5 to 5 microM for 30 min), the proportion of cells undergoing apoptosis increased by 2- to 6-fold over that seen in untreated controls. Kidney cells pretreated with specific NF-kappaB inhibitors (Bay11-7082 or SN50) prior to TNF also showed a significant increase in apoptosis. Increased sensitivity to apoptotic cell death following these treatments was significantly attenuated in cells transfected with a p65 expression vector. In studies in vivo, rats pretreated by intraperitoneal injection with Hg(2+) (0.75 mg/kg) 18 h prior to administration of bacterial lipopolysaccharide (LPS) (10 mg/kg) displayed impaired NF-kappaB activation and an increased mitochondrial cytochrome c release in kidney cortical cells. These findings are consistent with the view that prevention of NF-kappaB activity in vitro or in vivo enhances the sensitivity of kidney cells to apoptotic stimuli to which these cells are otherwise resistant. Since apoptosis is known to play a seminal role in the pathogenesis of renal failure caused by toxicant injury to tubular cells, the present findings suggest that inhibition of NF-kappaB activity may define a molecular mechanism underlying the pathogenesis of Hg(2+) toxicity in kidney cells.

Expression of the progesterone receptor and progesterone- metabolising enzymes in the female and male human kidney

Due to high binding affinity of progesterone to the human mineralocorticoid receptor (hMR), progesterone competes with the natural ligand aldosterone. In order to analyse how homeostasis can be maintained by mineralocorticoid function of aldosterone at the MR, especially in the presence of elevated progesterone concentrations during the luteal phase and pregnancy, we investigated protective mechanisms such as the decrease of free progesterone by additional binding sites and progesterone metabolism in renal cells. As a prerequisite for sequestration of progesterone by binding to the human progesterone receptor (hPR) we demonstrated the existence of hPR expression in female and male kidney cortex and medulla at the level of transcription and translation. We identified hPR RNA by sequencing the RT-PCR product and characterised the receptor by ligand binding and scatchard plot analysis. The localisation of renal hPR was shown predominantly in individual epithelial cells of distal tubules by immunohistology, and the isoform hPR-B was detected by Western blot analysis. As a precondition for renal progesterone metabolism, we investigated the expression of steroid-metabolising enzymes for conversion of progesterone to metabolites with lower affinity to the hMR. We identified the enzyme 17alpha-hydroxylase for renal 17alpha-hydroxylation of progesterone. For 20alpha-reduction, different hydroxysteroid dehydrogenases (HSDs) such as 20alpha-HSD, 17beta-HSD type 5 (3alpha-HSD type 2) and 3alpha-HSD type 3 were found. Further, we detected the expression of 3beta-HSD type 2 for 3beta-reduction, 5alpha-reductase (Red) type 1 for 5alpha-reduction, and 5beta-Red for 5beta-reduction of progesterone in the human kidney. Therefore metabolism of progesterone and/or binding to hPR could reduce competition with aldosterone at the MR and enable the mineralocorticoid function.

Fibroblasts and antigen-presenting cells in the renal interstitium of streptozotocin-induced diabetic rats on a high cholesterol diet

The cortical peritubular interstitium of the normal kidney contains both fibroblasts and antigen-presenting dendritic cells. Characteristics of these interstitial cells were analyzed in an overnutrition model by electron microscopy after the cold-dehydration technique and immunohistochemistry for antigen-presenting cells. In control rats, fibroblasts and dendritic cells were clearly identified by electron microscopy on the basis of their distinct ultrastructures. Fibroblasts possessed slender cell processes, and contained an abundance of actin filament bundles occasionally anchoring to surrounding structures, whereas dendritic cells possessed irregularly-shaped cell processes with a clear cytoplasm and a paucity of actin filament bundles. In the experimental kidney from diabetic rats given a high cholesterol diet, the peritubular interstitium contained fibroblasts and vacuolated cells, and the extracellular matrices such as collagen bundles were distinctly increased compared with the control rat kidney. Immunohistochemical staining with OX6 and ED1 revealed that the peritubular interstitium in the control rat kidney contained dendritic cells, while that in the experimental rats was occupied by macrophages. The present study provides the first evidence indicating that overnutrition may dramatically affect the immune cells in nonlymphoid tissue.

MCP-1 and RANTES are expressed in renal cortex of rats chronically treated with nitric oxide synthase inhibitor. Involvement in macrophage and monocyte recruitment

Long-term inhibition of nitric oxide synthase (NOS) in rats is known to cause systemic hypertension and renal parenchymal injury. We have previously reported that activation of intra-renal renin-angiotensin system was a major contributing factor for renal injury in chronically NOS-inhibited rats. Massive interstitial infiltration of monocytes/macrophages (M/M) was characteristically seen in this model. The present study was performed to elucidate the role of chemokines, RANTES and MCP-1, in promoting M/M recruitment into the renal cortex. The number of infiltrating ED-1-positive cells was examined in association with the level of expression of RANTES and MCP1 mRNAs in the renal cortex of rats treated orally for 12 weeks with L-NAME. Compared to controls rats, the number of infiltrating ED-1-positive cells was significantly higher in L-NAME-treated rats. The mRNA expressions of both RANTES and MCP-1 were significantly higher in L-NAME-treated rats than the control. In L-NAME-treated rats, the high number of ED-1-positive cells and increased expression of both RANTES and MCP-1 were suppressed by ACE inhibitor, but not by hydralazine. In contrast, neither ED-1 counts nor RANTES mRNA expression were affected by angiotensin (Ang) II type 1 receptor antagonist. These results suggest the likely involvement of RANTES and MCP-1 in the recruitment of M/M into the renal cortex of rats with chronic NOS inhibition. Furthermore, it is also indicated that Ang II stimulates MCP-1 expression via Ang II type 1 receptor, whereas RANTES expression is mediated via Ang II type 2 receptor.

Enhanced expression of C chemokine lymphotactin in IgA nephropathy

Leukocyte accumulation in the kidney is observed in patients with IgA nephropathy. Chemokines are a large family of cytokines chemotactic for leukocytes and have been shown to be upregulated in renal diseases. We previously reported that the gene expression of lymphotactin, a sole member of C chemokine subfamily, is enhanced in an animal model of crescentic glomerulonephritis, but its expression in human renal diseases is totally unknown. In the present study, we investigated the expression of mRNAs of lymphotactin and some other chemokines in IgA nephropathy. The expression of mRNAs for three chemokines, lymphotactin, MCP-1, and MIP-1beta, in renal cortex was increased and the levels of lymphotactin and MCP-1 mRNAs were statistically higher in patients with glomerular crescents than in those without crescents. These levels also correlated with tubulointerstitial changes and urinary protein excretion. Glomerular levels of mRNAs for lymphotactin and MCP-1, but not MIP-1beta, were higher in IgA nephropathy than controls. By immunohistochemical analysis, lymphotactin was detected in tryptase-positive cells (putative mast cells) in the interstitial space. These results suggest that lymphotactin, as well as MCP-1, may contribute to leukocyte infiltration and disease progression in IgA nephropathy.

Human single chain antibodies against heparin: selection, characterization, and effect on coagulation

Heparin, located in mast cells and basophilic granulocytes, is widely used as an anticoagulant. It belongs to a class of linear polysaccharides called glycosaminoglycans (GAGs). Using phage display technology, we have selected 19 unique human antiheparin antibodies. Some antibodies react almost exclusively with heparin, others also react with the structurally related heparan sulfate, and some with chondroitin sulfate. In all cases, sulfate groups are essential for binding. For activity of some antibodies, O-sulfation is more important than N-sulfation. Antibodies are reactive with heparin in mast cells. Each antibody showed a defined staining pattern on cryosections of rat kidney, pancreas, and testis. Enzymatic digestion with glycosidases on tissue sections further indicated that the antibodies are specific for GAGs. All antibodies recognize a unique epitope. The effect of the antibodies on heparin as an anticoagulant was also studied. There were 3 antibodies that were very effective inhibitors of heparin action in the activated partial thromboplastin time (APTT) clotting assay, and their effect was related to the amount of heparin bound. Some antibodies reacted strongly with the pentasaccharide, which interacts with antithrombin III. The human antibodies selected represent unique tools to study the structure, location, and function of heparin and related GAGs, and some may be used as blocking agents.

Cortical fibroblast culture from human biopsies

BACKGROUND

Tubulointerstitial fibrosis is an integral part of progressive renal disease. Human cortical fibroblasts are believed to be key effector cells in fibrogenesis. Thus, a reliable culture of these cells is necessary for studies of their pathophysiology.

METHODS

Cortical fibroblast culture from routine kidney biopsies were analyzed and the cells were characterized. Indirect immunofluorescence staining was done after the first passage for cytokeratin, vimentin, alpha-smooth muscle actin, CD 44, CD 54, CD 68, collagen types I, III, and HLA-DR. We then assessed the utility of the putative fibroblast markers CD 90, prolyl-4-hydroxylase (P4H) and F1b in simultaneous stainings of tubular epithelial cells.

RESULTS

During the study period, 49 biopsy cores were cultured and cortical fibroblasts could be successfully established in 21 cases (42.9%). There was no relation between the success rate of culture and the degree of interstitial fibrosis, but an association was seen with the time of completion of the first passage. There was a negative correlation between the extent of scarring and the percentage of cytokeratin positive cells (r = -0.66, p < 0.001). All primary fibroblasts were negative for factor VIII, HLA-DR, CD 68, and cytokeratin. They expressed alpha-smooth muscle actin and collagen types I and III to variable degrees. There was a robust correlation between the percentage of alpha-smooth muscle actin positive cells and interstitial scarring but no such association with collagen type I or type III positive cells. The three putative fibroblast markers did not prove useful in differentiating between tubular epithelial cells and fibroblasts. However, since only fibroblasts stained positive for CD 90 and negative for cytokeratin, these two markers may suffice to distinguish fibroblasts from other renal cellular elements.

CONCLUSIONS

Cortical renal fibroblasts can be easily cultured from kidney biopsy cores, though the success rate of pure cultures is below 50%. Staining for CD 90 and cytokeratin may suffice for initial characterization of these cells.

Grafting of mitomycin C-treated islet xenograft under the kidney capsule produces a clear bleb

We have previously shown that mitomycin C (MMC) treatment of donor tissue resulted in significant prolongation of graft survival in allo- and xenotransplantation models. However, the mechanisms involved in this prolongation are not clearly understood. This study aims to shed light on the immune responses to MMC-treated islet xenografting under the kidney capsule. Collagenase-digested WS (RT1k) rat islets incubated for 30 min with MMC and subsequently cultured for 20 h were transplanted into the renal subcapsular space of streptozotocin-induced diabetic C57BL/6 (B6;H-2b) mice. The grafts were harvested on postgrafting day 7 and sections were prepared and stained by hematoxylin and eosin (H&E). Histological study of the grafts in a group not treated with MMC showed marked cellular infiltration and destruction of islet clusters, whereas that of MMC-treated grafts demonstrated a bleb formation under the kidney capsule, in which islet cell clusters were reorganized, creating a layer of cells fixed to the interior of the bleb. Minimal invasion by inflammatory cells was observed only at the edge of the bleb, and most islet cells were protected from these infiltrating cells. In conclusion, MMC treatment induces remodeling of islet structure and forms a bleb under the kidney capsule, where no inflammatory cell infiltration occurs, suggesting that this site is a kind of immunologically privileged environment for xenografted islets.

Autoantibodies against the angiotensin receptor (AT1) in patients with hypertension

Sera from patients with malignant essential hypertension (n = 14), malignant secondary hypertension mainly attributable to renovascular diseases (n = 12) and renovascular diseases without malignant hypertension (n = 11) and from normotensive healthy blood donors (n = 35) were studied for the presence of autoantibodies against G-protein-coupled cardiovascular receptors. Autoantibodies against the angiotensin II receptor (AT1) were detected in 14, 33, 18 and 14% of patients with malignant essential hypertension, malignant secondary hypertension, renovascular diseases and control patients, respectively. Sensitivity of the enzyme immunoassay was assessed as 5 microg/ml IgG. Patients did not show antibodies against bradykinin (B2) or angiotensin II subtype 2 (AT2) receptors. Autoantibodies affinity-purified from positive patients localized AT receptors in Chinese hamster ovary transfected cells, and displayed a positive chronotropic effect on cultured neonatal rat cardiomyocytes. These results demonstrate the existence of autoantibodies against a functional extracellular domain of human AT1 receptors in patients with malignant hypertension, and suggest that these autoantibodies might be involved in the pathogenesis of malignant hypertension.

Interleukin-8 secretion of cortical tubular epithelial cells is directed to the basolateral environment and is not enhanced by apical exposure to Escherichia coli

In upper urinary tract infections, tubular epithelial cells (TEC) may play a pivotal role in the initiation of the renal inflammatory response. They exert crucial immunological functions such as processing and presentation of foreign antigen, secretion of proinflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha) and chemokines (IL-8, MCP-1, ENA-78, and RANTES). Since monolayer cultures are a limited model for polarized tubular epithelial cells, we studied the side-dependent IL-8 secretion of TEC by using cell culture inserts as a basement membrane imitation. Primary cultures of proximal TEC were stimulated with differently fimbriated mutants of Escherichia coli, E. coli LPS, S-fimbria isolates, and IL-1alpha. IL-8 protein was measured by enzyme-linked immunosorbent assay, and IL-8-like biological activity was tested by measuring elastase release from polymorphonuclear cells in supernatants of the upper and lower compartments. IL-8 mRNA was compared by competitive PCR. IL-8 secretion by TEC into the basolateral environment was significantly higher than secretion into the apical compartment, representing the tubular lumen. However, stimulation of IL-8 secretion by TEC was restricted to IL-1alpha and was not inducible by E. coli mutants, S fimbriae, or lipopolysaccharide. With this in vitro model of polarized TEC, we show that luminal contact of TEC with uropathogenic E. coli does not result in enhanced IL-8 secretion. The basolaterally directed production of the neutrophil chemotactic factor IL-8 by TEC after stimulation with IL-1alpha might play an important role in the initiation of inflammatory cell influx into the renal parenchyma.

Cortical benign fibromatous tumor (fibroma) of the kidney

Benign fibromatous tumor (BFT), also named 'fibroma', is a distinctive clinico-pathologic entity occurring in epididymis, spermatic cord, paratesticular structures, testis, renal peripelvis and rarely in renal parenchyma. We report the first case of a BFT (fibroma) located in the cortex of the kidney, and a critical review on the topic is provided. Tumor was found incidentally at autopsy as a small cortical nodule. With the increasing use of radiological imaging of the abdomen, it is likely that an increased number of incidental and asymptomatic benign renal tumors will be diagnosed. We underline that BFT (fibroma) should be considered in the preoperative differential diagnosis of renal cortical nodules.

Glomerular overexpression and increased tyrosine phosphorylation of focal adhesion kinase p125FAK in lupus-prone MRL/MP-lpr/lpr mice

Much progress has been made in understanding how mammalian cells receive a diverse array of external stimuli and convert them into intracellular biochemical signals. Such efforts have identified a large number of signalling molecules. However, our knowledge is limited as to their pathophysiological role in particular diseases. We demonstrate herein that an integrin-linked signalling molecule, focal adhesion kinase p125FAK (FAK), is overexpressed in glomeruli of lupus-prone MRL/MP-lpr/lpr (MRL-lpr) mouse as compared to its congeneic MRL-+/+ strain. Increased expression was specifically demonstrated in glomeruli but not in other tissues examined. The overexpression was observed in 16-week-old MRL-lpr mice with active nephritis, as well as in younger animals at 4 weeks of age. Thus, the upregulation of FAK clearly preceded the clinical onset of nephritis. FAK in MRL-lpr glomeruli is highly tyrosine phosphorylated and is associated with adapter protein Grb2. Previous in vitro studies have shown that the association of FAK/Grb2 links cell adhesion to the Ras pathway, which ultimately stimulates mitogen-activated protein (MAP) kinase, an important regulator of cell proliferation. In accordance, we observed constitutive MAP kinase activation in MRL-lpr glomeruli. Our findings suggest that signalling pathways involving FAK are activated in MRL-lpr glomeruli, and are likely to play a role in the development and progression of autoimmune-mediated murine nephritis.

ICAM-1 interactions in the renal interstitium: a novel activator of fibroblasts during nephritis

Chronic renal diseases often degenerate towards end-stage failure, requiring replacement renal therapy. The progressive decline of such diseases is a highly complex, multi-factorial process, which is poorly understood. Indeed, not all chronic conditions take on a progressive course, some may recover to regain normal function, while others may remain functionally impaired yet stable. The structural features of progressive decline, however, show common histological features, despite the diverse nature of the primary injury. These aberrant structural alterations are characterised essentially by a dramatic expansion of the tubulointerstitium, with accompanying tubular atrophy, resulting from interstitial fibrosis. These changes are thought to be a uniform response to prolonged inflammation which may originate in the glomerulus, the vasculature or the interstitial space (Strutz et al., 1995). A histomorphometric analysis of renal diseases, initially performed by Risdon et al. (1968), and supported by Bohle et al. (1987) and others (Eknoyan et al., 1990), revealed that the severity of abnormal glomerular pathology did not always correlate directly with impaired renal function. The extent of interstitial inflammation and the degree of interstitial fibrosis, however, were both shown to be more accurate predictors of renal function (Bohle et al., 1992). Furthermore there was a high probability of irreversible functional decline, in the presence of interstitial fibrotic lesions and tubular atrophy. Interstitial fibrosis is therefore considered an important histological marker for end stage renal failure, and is believed to be functionally more significant than primary changes within the glomerulus. In most tissues, resident fibroblasts are believed to be the cells principally responsible for the synthesis and breakdown of extracellular matrix (ECM) within connective tissues. Indeed in fibrotic diseases of lung and skin, the resident fibroblast has been identified as the most important cell responsible for the abnormal deposition of ECM components during the disease process (Phan et al., 1985). In the kidney, there are probably several sources of matrix components during fibrosis including tubular epithelial cells, inflammatory macrophages (Vaage and Linbland, 1990) as well as interstitial fibroblasts. Although the precise cellular source of the bulk of this matrix requires clarification, there is mounting evidence supporting a significant contribution from resident or infiltrating fibroblasts (Rodemann and Muller, 1990, 1991a,b; Strutz and Muller, 1995).

Mycophenolate mofetil prevents the induction of active Heymann nephritis: association with Th2 cytokine inhibition

The effect of mycophenolate mofetil (MMF) was examined in active Heymann nephritis (HN), an animal model of human membranous nephropathy. HN was induced in Lewis rats with Fx1A/complete Freund's adjuvant (CFA), and controls only received CFA. The induction of HN was prevented by MMF (30 mg/kg per d) from 0 to 4 wk after immunization. Proteinuria was not different in CFA controls up to 16 wk, and was significantly less than in untreated HN from 6 wk onward. Serum anti-Fx1A antibody (Ab) levels and glomerular Ig deposition were suppressed during therapy. The interstitial infiltrate of alphabetaTCR+, CD4+ and CD8+ T cells, natural killer cells, and macrophages (mphi) observed in untreated HN at 8 wk was absent from rats treated from 0 to 4 wk with MMF. Semiquantitative reverse transcription-PCR for renal mononuclear cell cytokine mRNA at 8 wk demonstrated that MMF from 0 to 4 wk prevented the increased expression of Th1 (interferon-gamma, lymphotoxin), Th2 (interleukin-4), and mphi (tumor necrosis factor-alpha) cytokines identified in untreated HN. In lymph node draining sites of immunization, MMF limited both enlargement and the increased proportion of CD3+, CD4+, and CD8+ T cells observed in untreated HN and CFA controls. MMF suppressed Th2 (interleukin-4) but not Th1 (interferon-gamma, lymphotoxin) cytokine mRNA expression in lymph nodes. MMF from 4 to 8, 6 to 12, or 10 to 14 wk did not prevent proteinuria, serum anti-Fx1A Ab, or glomerular IgG deposition when compared with untreated HN. This study showed that MMF from 0 to 4 wk prevented the induction of HN and was associated with preferential suppression of Th2 cytokines. This therapy may prove useful in human idiopathic membranous nephropathy.

Cytokine production in primary histoculture by human normal kidney, renal cell carcinoma and benign renal angiomyolipoma tissues

In order to understand the ability of normal human kidney, benign renal angiomyolipoma and malignant renal cell carcinoma (RCC) cells to produce cytokines, we determined the IL-1-beta, IL-6, IL-10, IL-11, TNF-alpha and TGF-beta-1 concentration in the supernatant of histoculture specimens according to thymidine labelling indices. From these studies, we conclude that normal, benign and malignant renal tissues are one of the main sources of IL-6 production and patterns of IL-6 production are inversely proportional to thymidine labelling index in normal kidney(r = -0.9). However, IL-6 production is increased in proportion to the increasing thymidine labelling index in benign or malignant tissues (r = 0.94, r = 0.76). There is no production of IL-1-beta, IL-10, IL-11, TNF-alpha or TGF-beta-1. These findings allows many important studies of cytokines in normal, benign and malignant renal disease. Patterns of IL-6 production are different in normal and benign or malignant changed renal disease. There is no overlapping biologic effects among IL-6, IL-1-beta and TNF-alpha. Histoculture supports future studies of these cytokines.

Attenuation of renomedullary phospholipase C isozyme, PLC-delta 1, in spontaneously hypertensive rats

The distributional patterns of PLC isozymes within the kidney were investigated using spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats at 4 and 12 weeks of age. PLC-beta 1, PLC-beta 3 and PLC-delta 1 quantified by Western blot analysis, were present in the highest concentrations in the inner medulla of rats at both 4 and 12 weeks of age. On the other hand, PLC-beta 4, PLC-gamma 1 and PLC-gamma 2 were distributed almost equally among the regions for the rats of both ages. When compared with WKY rats at 12 weeks of age, the amounts of PLC-beta 1, PLC-beta 3, PLC-gamma 1, PLC-gamma 2, and PLC-delta 1 in the inner medulla of SHRs were significantly lower, and the amount of PLC-delta 1 in the inner stripe of the outer medulla was also significantly lower. Even at the prehypertensive stage at 4 weeks of age, the inner medullary concentration of PLC-delta 1 was significantly lower in SHRs than WKY rats. These results suggest that PLC-delta 1 would play an important role in the development of hypertension.

Bcl-2 expression and apoptosis in nephrotoxic nephritis

The product of the Bcl-2 proto-oncogene has been shown to prolong cell survival by preventing apoptosis in several cell lineages. To investigate the regulatory mechanisms of apoptosis in glomerulonephritis, we examined the expression pattern of the Bcl-2 protein together with cellular events in rat nephrotoxic nephritis. Bcl-2 protein and proliferating cell nuclear antigen were detected in glomeruli by immunohistochemistry. Morphologic changes of apoptosis were identified by electron and light microscopy and an in situ DNA nick end labeling method. The first (heterologous) phase began with significant neutrophil infiltration shortly after the injection of nephrotoxic serum. Both Bcl-2 expression and the number of proliferating cells in the glomeruli were at maximum at 24 h in the heterologous phase. Glomerular hypercellularity with an influx of macrophages and the number of apoptotic glomerular cells peaked on day 14 in the second (autologous) phase. Glomerulonephritis resolved after that. These results suggest that overexpression of the Bcl-2 protein may play a role in glomerular cell survival and exacerbation of glomerulonephritis. Apoptosis may occur as an active mechanism in the resolution of the autologous phase in nephrotoxic nephritis.

Alpha-enolase is a renal-specific antigen associated with kidney involvement in mixed cryoglobulinemia

OBJECTIVE

To study the specificity of antibodies reactive with renal antigens in mixed cryoglobulinemia.

METHODS

Sera from mixed cryoglobulinemia (MC) patients were tested on human kidney extracts by immunoblot. A partially purified renal antigen was subjected to N-terminal sequencing.

RESULTS

Antibodies reactive with a renal antigen of 48 kD were detected in 7 out of 11 patients with MC and renal involvement. N-terminal sequencing of this antigen showed that it was identical with alpha-enolase. This result was confirmed by the reactivity of the renal antigen with a rabbit anti-serum specific for alpha-enolase.

CONCLUSIONS

The results indicate that antibodies specific for alpha-enolase are frequently produced by mixed cryoglobulinemia patients with renal involvement.

Chemokine expression in experimental tubulointerstitial nephritis

Chemokines may be important in the pathogenesis of leukocyte infiltration in tubulointerstitial nephritis associated with glomerular disease. We studied the renal cortical expression of the C-C (macrophage inflammatory protein-1alpha (MIP-1alpha)), monocyte chemotactic protein-1 (MCP-1), and RANTES) and C-X-C (interferon-inducible protein-10 (IP-10), MIP-2, and cytokine-induced neutrophil chemoattractant (CINC)) chemokines 4, 6, 8, 10, 14, and 21 days after the induction of puromycin aminonucleoside (PAN) nephrosis. There was a 7- to 10-fold increase in the steady state mRNA expression of IP-10 and MCP-1 in the renal cortex of rats 6 to 8 days after the administration of PAN that declines thereafter reaching control values by day 21. The site of IP-10 and MCP-1 mRNA production was localized to intrinsic tubulointerstitial cells and not to infiltrating monocytes or macrophages. By comparison, there was a low basal expression of RANTES mRNA in the renal cortex of nephrotic rats that did not differ from those of control rats. In contrast, CINC, MIP-2, and MIP-1alpha mRNAs were not detected. Translation of MCP-1 mRNA into protein was confirmed with an ELISA. These changes in chemokine gene expression were associated with a tubulointerstitial T lymphocyte and macrophage infiltration beginning on day 6 that peaked on day 10. Administration of a neutralizing Ab to rat MCP-1 (n = 5) beginning on day 4 resulted in a 45% decline in tubulointerstitial macrophage infiltration from 8.4 +/- 1.3% to 4.6 +/- 0.4% (p < 0.001) on day 6. These data provide evidence that MCP-1, and possibly IP-10, are important in the pathogenesis of monocyte/macrophage infiltration in the tubulointerstitial nephritis associated with PAN nephrosis.

Lipopolysaccharide-induced glomerulonephritis develops in the absence of interferon-gamma signaling

IFN gamma is a costimulator of macrophage activation and it plays an important role as a proinflammatory cytokine by upregulation of adhesion molecules and MHC antigens. In this study we tested the role of IFN gamma in a model of endotoxin-induced glomerulonephritis. A systemic lupus-like disease was induced by injection of 50 micrograms bacterial LPS twice a week for 4 weeks in wild-type and in IFN gamma receptor-deficient (IFN gamma R-/-) mice. The renal cortex was examined by immunofluorescence and by light microscopy. LPS treatment induced an increase in serum levels of IgG and anti-dsDNA antibodies. A mild glomerulonephritis was characterized morphologically, but proteinuria was not observed. The main histological features of glomerulonephritis were an increase in ICAM-1 expression, deposition of immune complexes and of complement in the glomeruli, increased mesangial matrix and mesangial hypercellularity. The number of intraglomerular leukocytes, detected by MHC class-II and LFA-1 expression increased roughly 4-fold. All those alterations took place in a similar manner in wild-type and in IFN gamma R-/-mice. Therefore it is concluded that IFN gamma does not play an important role in the development of endotoxic glomerulonephritis.

In vivo treatment of Heymann's Nephritis using a cytotoxic protein-toxin conjugate

In this study we investigated the possibility of treating Heymann's Nephritis (HN) by destroying antibody producing cells by targetting a toxin, gelonin--conjugated to gp330, the renal brush border antigen. HN was induced in rats by immunizing them with purified gp330. The gelonin-gp330 conjugate was administered 12 days after the antigenic challenge. Serum was screened for circulating antibodies. Proteinurea was estimated. The gp330-gelonin conjugate-treated animals had a circulating antibody titre in the serum much lower than that of diseased (untreated) animals. Proteinurea seen in diseased animals was not observed in treated animals. This work suggests the possibility of using a toxin-antigen conjugate for immunomodulating antibody mediated autoimmune renal disease.

Enhancement of renal disease in BXSB lupus prone mice after prior exposure to bacterial lipopolysaccharide

The mechanism, or mechanisms, responsible for enhancement of renal disease after episodes of infection are poorly understood. We used the BXSB mouse as a lupus model of autoimmune disease and we used bacterial lipopolysaccharide (LPS) as a surrogate infectious agent to gain some insight into the mechanism by which infections promote enhancement of autoimmune disease to chronicity. BXSB mice were exposed to LPS for 5 weeks, LPS was withdrawn and various tests and measurements were performed 6 weeks thereafter. Matched BXSB mice exposed to vehicle injections for 5 weeks served as controls. We verified that previous exposure to LPS enhances polyclonal B cell activation, impairs carrier function of blood cells for immune complexes, increases deposition of immune complexes in the microcirculation and promotes glomerular inflammation and sclerosis. These changes occurred at 6 weeks after withdrawal of LPS in the presence of unimpaired function of mononuclear phagocytes. Some of the effects of LPS are reversible, others are partially so and others are irreversible. Altered immune functions elicited by prior exposure to LPS can result in enhanced involvement of various renal compartments and can result in renal insufficiency.

Crescentic glomerulonephritis in interferon-gamma receptor deficient mice

Activation of macrophages by T cells is considered an initiating event in glomerular crescent formation. Since interferon-gamma (INF gamma) is a key mediator in T-cell-mediated activation of macrophages, we decided to test its role in a model of crescentic glomerulonephritis. An anti-glomerular basement membrane (GBM) serum was injected intravenously in presensitized wild-type or IFN gamma receptor deficient (IFN gamma(R)-/-) mice. Glomerulonephritis with glomerular crescents and tubulointerstitial inflammation developed in both strains, even though most evaluated morphological parameters and proteinuria indicated a less severe pathology in the mutant mice compared to the wild type. Thus, IFN gamma is not essential either for glomerular crescent formation or for tubulointerstitial involvement in anti-GBM glomerulonephritis in mice. In conclusion, the role of macrophages in this model might have been overestimated, or other cytokines may compensate for deficient IFN gamma signaling in the activation of macrophages.

Principal cell-specific antigen and hormonal regulatory network in RC.SVtsA58 cell line

We used a dual immunomorphological and physiological approach to demonstrate that the RC.SVtsA58 rabbit cortical cell line exhibits features of highly differentiated cortical collecting tubule (CCT) principal cells (PC). First, we raised monoclonal antibodies against RC.SVtsA58 cells and screened their reactivity with the rabbit kidney: three were specific for the basolateral domain of CCT PC and bound to 100% of RC.SVtsA58 cells. Second, we showed that bradykinin, atrial natriuretic peptide, and prostaglandin E2 increased intracellular Ca2+, guanosine 3',5'-cyclic monophosphate, and adenosine 3',5'-cyclic monophosphate (cAMP), respectively. In addition, 10 nM bradykinin inhibited desmopressin-elicited cAMP production by > or = 40%; this effect was suppressed by 10 microM of indomethacin and was reproduced with 1 nM of prostaglandin E2, indicating the conservation of arginine vasopressin-related regulatory loops described in microdissected CCT and freshly isolated cells. However, RC.SVtsA58 cells also express intercalated cell markers even after repeated cloning, which suggests that tsA58, a temperature-sensitive strain of simian virus-40, has transformed a multipotent type of PC in keeping with the cell interconversion hypothesis.

Endogenous complement C3 synthesis in immune complex nephritis

Human renal epithelial and mesangial cells have been shown to synthesise complement C3 in culture, but the relevance of this finding to the development of complement-mediated nephritis is uncertain. We investigated C3 gene expression in tissue biopsies that showed three main categories of renal injury. By semiquantitative polymerase chain reaction, biopsies from patients with immune-complex glomerulonephritis and those with cell-mediated interstitial nephritis showed increased C3 expression (p < 0.05), but biopsies from patients with non-immune glomerular injury did not. These findings suggest that local C3 production is enhanced in immune-mediated nephritis and are consistent with the hypothesis that locally synthesised complement components are involved in the pathogenesis of tissue injury.

Interferon-gamma regulation of human renal cortical epithelial cell-derived monocyte chemotactic peptide-1

The chemoattractant signal(s) that results in the transmigration of monocytes/macrophage into the tubulointerstitium during acute inflammation is not known. Monocyte chemotactic peptide-1 (MCP-1), a recently described chemotactic cytokine, may function as both a potent monocyte chemotaxin and activator in renal inflammation. We have studied the proinflammatory conditions in which cultured human renal cortical epithelial cells (RCEC) of tubular origin may be stimulated to produce MCP-1. RCEC were stimulated in a dose-time dependent manner with: IL-1 beta (0.01 to 1.0 ng/ml), TNF (0.1 to 10 ng/ml), LPS (0.1 to 10 micrograms/ml) or INF-gamma (10-1000 U/ml). Conditioned media from RCEC stimulated with either IL-1 beta or INF-gamma produced a monocyte chemoattractant activity which was significantly suppressed with neutralizing antibody to MCP-1. Stimulation of RCEC with either IL-1 beta or INF-gamma resulted in a significant (4- to 5-fold) increase in steady state levels of MCP-1 mRNA. MCP-1 antigenic peptide in RCEC conditioned media was significantly increased over control (2- to 2.5-fold) after stimulation with either IL-1 beta or IFN-gamma. In contrast, production of interleukin-8 (IL-8), a neutrophil chemotactic cytokine, was not stimulated by IFN-gamma in RCEC. Thus, the chemokine signaling repertoire of renal tubule cells may be selectively controlled by IFN-gamma.

Identification and epitope analysis of the renal Na+/Pi cotransport protein using monoclonal antibodies

Seven monoclonal antibodies (mAbs) were raised against a rabbit renal brush-border glycoprotein (molecular mass, 63-66 kDa), presumably involved in Na+/Pi cotransport, which we had previously purified and reconstituted in active form in proteoliposomes (Debiec, H., Lorenc, R., and Ronco, P. M. (1992) Biochem. J. 286, 97-102). Antibody specificity for the 63-66-kDa protein was analyzed by enzyme-linked immunosorbent assay and confirmed by Western blotting and immunoaffinity chromatography of solubilized brush-border membranes (BBM), which both yielded a single 63-66-kDa band. Enzyme-linked immunosorbent assay and immunoblotting of renal cortical cell subfractions localized the immunoreactive protein to the brush-border membrane. This location was confirmed by indirect immunofluorescence of kidney cortex sections. Binding of two of the seven mAbs (63A20 and 206A126) to native BBM only occurred when the related epitope was exposed in the presence or absence of Na+, respectively; the other mAbs did not react with native BBM probably because of intramembranous orientation of the epitopes. mAb 63A20 inhibited dose-dependently Na+/Pi cotransport when preincubation of BBM was carried out in the presence of Na+ but did not affect Na+/D-glucose cotransport. Proteoliposomes formed from BBM proteins depleted of the 63-66-kDa protein by affinity chromatography with mAb 63A20 showed an 85% reduction in Na+/Pi cotransport, whereas Na+/D-glucose cotransport was not modified. These results thus establish that the 63-66-kDa BBM protein is the essential component of the Na+/Pi cotransport system. The present study also provides the first immunologic tools available for immunohistochemical localization of the Na+/Pi cotransporter. Finally, the identification of a functional epitope by mAb 63A20 opens up new ways to explore the molecular aspects of Pi uptake.

Expression of a monoclonal antibody (3G5) defined ganglioside antigen in the renal cortex

The monoclonal antibody (mAb) 3G5 was found, by indirect immunofluorescence, to bind to renal cortical structures in frozen sections of human, rat and calf kidneys. Double indirect immunofluorescence studies on frozen sections of rat kidneys showed that 3G5 stained only the glomerulus and the distribution of the 3G5 antigen on the glomerulus was more extensive than the staining observed with antibodies to Factor VIII antigen. 3G5 stained the proximal convoluted tubules and collecting tubules in bovine renal sections but glomeruli did not stain with 3G5. The 3G5 mAb did not stain tissue cultured bovine glomerular endothelial cells or mesangial cells, but did stain bovine glomerular epithelial cell cultures. 3G5 did not stain MDCK cell cultures. The binding of mAb 3G5 to glomeruli was investigated by immunoelectron microscopy of rat renal tissue. In contrast to the podocyte specificity on bovine glomerular cells in vitro, it was found that the specificity of 3G5 expression on rat glomerular cells in vivo was broader. No binding of mAb 3G5 was found outside the glomerulus in the rat renal cortex. Podocytes, endothelial cells and capsular epithelial cells expressed the 3G5 antigen most strongly. A lesser amount of binding was found in the glomerular basement membrane. The mesangium showed a little binding of mAb 3G5 and no binding at all was found to other cortical structures. The 3G5 antigen in rat renal tissue was found to be a glycolipid that migrated between the ganglioside markers GM2 and GM1 by immunostaining of thin layer chromatograms.(ABSTRACT TRUNCATED AT 250 WORDS)

Equine glomerulonephritis and renal failure associated with complexes of group-C streptococcal antigen and IgG antibody

A 12-year-old thoroughbred gelding died from diffuse global glomerulonephritis, 3 months after a lower respiratory infection from which Streptococcus zooepidemicus was isolated. Immunopathological studies (immunofluorescence, immunodiffusion, immunoperoxidase testing and immunoblotting) indicated the presence of an immune reactant renal disease associated with IgG antibody and streptococcal antigens.

In vitro and in vivo interleukin-8 production in human renal cortical epithelia

The signals resulting in leukocytes infiltrating the tubulointerstitial compartment during renal inflammatory disease are not well understood. A recently described cytokine, interleukin-8 (IL-8), has been demonstrated to be chemotactic for lymphocytes and neutrophils at picomolar and nanomolar concentrations, respectively. Cytokeratin positive, renal cortical epithelial cells (RCEC) with tubular attributes were cultured from kidney tissue from six human subjects. We report that these human renal cortical epithelial cells in primary cell culture respond to either IL-1 beta, TNF or LPS in both a time- and dose-dependent manner by expressing IL-8 mRNA and secreting antigenic IL-8 peptide. In addition, RCEC were found to be strongly positive for cell-associated antigenic IL-8 peptide by immunostaining after 24 hour incubation with IL-1 beta, TNF and LPS. To ascertain whether IL-8 was present in renal disease associated with infiltrating leukocytes, we performed immunohistochemistry on renal biopsy specimens from patients with acute allograft rejection. Both proximal and distal tubular epithelial cells were found to be strongly positive for cell-associated antigenic IL-8. These findings suggest that the human renal tubule epithelial cell may actively participate in acute inflammatory processes in the kidney, including allograft rejection, by effecting and directing leukocyte chemotaxis via the production of IL-8.

Immunological recognition of sodium/D-glucose cotransporter from renal brush border membranes by polyclonal antibodies

Antisera prepared in rabbit to a D-glucose-inhibitable phlorizin binding component of the pig kidney brush border membrane precipitated more than 90 percent of the D-glucose-inhibitable phlorizin binding activity from a Triton extract. These antibodies also stimulated D-glucose uptake by native brush border membranes at low D-glucose concentrations (1 mM) and inhibited it at higher D-glucose concentrations. Immunoblotting was used to locate polypeptide subunits of the glucose transporter in polyacrylamide gels of proteins extracted from the brush border membranes. The antibodies labelled the Mr 70,000 phlorizin-binding component in both reducing and non reducing conditions. Two additional polypeptides with relative molecular mass of 120,000 and 45,000 were also recognized under the same conditions; they might correspond, respectively, to another Na+/D-glucose cotransport unit and to a post mortem degradation product.

The complement-inhibiting protein, protectin (CD59 antigen), is present and functionally active on glomerular epithelial cells

Protectin (CD59 antigen) is a 20-kD phosphatidyl-inositol-linked membrane protein that inhibits formation of the membrane attack complex (MAC) of complement on homologous cells. Although the antigen has been identified in a number of human tissues, until recently a functional role had been demonstrated only in circulating cells. Using immunofluorescence techniques we have shown the presence of protectin on human glomerular epithelial cells (GEC) in culture and on GEC, tubular epithelial cells and endothelial cells in frozen sections of normal human renal cortex. In addition, we present evidence that this protein functions in protection of GEC from homologous complement: cultured cells incubated with the Fab2 fragment of a monoclonal anti-protein antibody were markedly more susceptible to killing by homologous serum than were cells in the absence of Fab2 anti-protectin. These findings suggest that this protein may be important in the maintenance of glomerular integrity in vivo, and may be of relevance in certain renal diseases.

Tubulointerstitial nephritis during the heterologous phase of nephrotoxic serum nephritis

This study was designed to characterize the immunopathology of acute tubulointerstitial disease in nephrotoxic serum nephritis in nonsensitized rats. Groups of Lewis rats were studied at 12 time periods ranging from 10 min to 28 days after nephrotoxic serum injection. Nephritic rats developed interstitial nephritis during the acute heterologous phase of renal injury. Coincident with the focal deposition of nephrotoxic antibodies along tubular basement membranes at 24 h, an influx of polymorphonuclear cells and macrophages was evident. The most prominent infiltrate, present between days 3 and 7, was dominated by macrophages with smaller numbers of lymphocytes that were mainly cytotoxic T cells. Dual-labeling studies demonstrated the colocalization of linear tubular basement membrane deposits of the nephrotoxic antibody with focal clusters of interstitial lymphohemopoietic cells. Increased complement deposition was not evident along the tubular basement membranes; moreover, C3 depletion with cobra venom factor failed to attenuate the interstitial inflammation. During the late autologous phase of glomerulonephritis, tubular basement membrane deposits of rat IgG did not appear and the interstitial disease resolved. The results of this study demonstrate that the heterologous phase of nephrotoxic serum nephritis is an antibody-mediated disease directed against the basement membranes not only of the glomeruli but also of some tubules. Antibody deposition is followed by an acute influx of phagocytic cells to both regions of the kidney. These cells may play an important role in the genesis of acute interstitial injury and chronic interstitial fibrosis associated with antiglomerular basement membrane nephritis.

Characterization of a tubular basement membrane component reactive with autoantibodies associated with tubulointerstitial nephritis

A kidney tubular basement membrane (TBM) component that is bound by antibodies from individuals with anti-TBM antibody-associated tubulointerstitial nephritis (TIN) was purified and characterized (TIN antigen). TIN antigen was prepared from rabbit TBM by extraction with guanidine and purified by ion-exchange, gel filtration, and reversed-phase chromatography. Based upon yields of protein and antibody reactivity, TIN antigen accounts for about 9% of the mass of TBM and thus is a major component of this basement membrane. A predominant 58-kDa form comprises about 90% of purified TIN antigen, and a 50-kDa form accounts for the remainder. The two forms share the amino-terminal sequence Ser-Ile-Phe-Gln-Gly-Gln-Tyr-X-Arg-Ser-Phe-Gly- and give similar tryptic peptide maps, indicating that they are structurally related. Their amino acid compositions overall are similar to laminin and entactin/nidogen. The absence of hydroxyproline and hydroxylysine and the low levels of glycine in TIN antigen indicate that it is noncollagenous. No similarities were found between other known proteins and sequences of tryptic peptides and the amino terminus of TIN antigen, suggesting that it is distinct from other characterized basement membrane components. A goat polyclonal antibody toward rabbit TIN antigen showed the same kidney distribution as human antibodies and was completely inhibited in enzyme-linked immunosorbent assay by purified TIN antigen. These data further support the idea that TIN antigen is the primary target for anti-TBM antibodies associated with TIN. This research presents methods to prepare TIN antigen for biochemical studies and investigations of its role in anti-TBM autoimmune TIN.

Intraglomerular leukocyte recruitment during nephrotoxic serum nephritis in rats

Although circulating phagocytic cells are important mediators of glomerular injury, their recruitment mechanisms are not completely understood. In this study, the intraglomerular trafficking of leukocytes was characterized in a rat model of acute glomerular injury induced by nephrotoxic serum (NTS). Polymorphonuclear (PMN) cells infiltrated, then disappeared rapidly, reaching a peak at 2 hr. By 6 hr the PMN migration had almost reversed but small numbers persisted until Day 7. The monocyte influx began almost simultaneously but was of lesser magnitude. However, the number of ED-1+ monocytes increased progressively from 60 min to reach a plateau by Day 2 and persisted to the end of the study (Day 28). Quantitation of intraglomerular Ia+ cells suggested in situ activation of monocytes within the glomeruli. Increased Ia+ cells were first evident on Day 2. By Day 5, 80% of the intraglomerular macrophages were Ia+. Complement depletion with cobra venom factor abrogated early albuminuria, delayed the initial PMN influx, but failed to attenuate monocyte migration. T lymphocytes appeared briefly between 10 min and 2 hr. In vitro proliferation study failed to demonstrate lymphocyte sensitization to glomerular basement membrane (GBM) antigens. A unique population of cells (OX19 OX8+), possibly representing natural killer cells, was present from Day 1 to Day 14. During the secondary wave of proteinuria (autologous phase), all leukocytes had disappeared except for macrophages and a small number of OX19-, OX8+ cells. A complex intraglomerular migration of leukocytes was triggered by the binding of nephrotoxic antibodies to GBM antigens. We speculate that this cascade involves several cell-to-cell interactions necessary for the full expression of glomerular injury.

Definition of glomerular antigens by monoclonal antibodies produced against a human glomerular membrane fraction

Experimental animal models of glomerulonephritis (GN) produced by direct antibody binding to non-basement membrane glomerular capillary wall antigens do not to date have human parallels. To examine the potential for this form of humoral glomerular injury in man, we sought to define discrete human non-GBM glomerular antigenic targets using hybridoma technology. Mice were immunised intraperitoneally with 20-100 micrograms of a human glomerular membrane fraction (HGMF). Six fusions have yielded 12 stable reagents defined by positive glomerular indirect immunofluorescence (IF) and microELISA using HGMF as the screening antigen. Subclass analysis of ascitic McAbs indicated several IgG1, one IgG2b, and three IgM reagents. Distinctive IF patterns of reactivity with epithelial, endothelial or mesangial structures have been observed, with or without peritubular capillary, tubular basement membrane and vessel wall reactivity. Seven normal non-renal human organs and the kidneys of rat, rabbit and sheep have shown patterns characteristic of each individual McAb, restricted to human or with species cross reactivity. To partially characterise McAb-reactive antigens, detergent-solubilised renal cortex and collagenase-solubilised GBM (CS-GBM) extracts have been probed by immunoblot. A unique McAb 7-5Q, reactive with glomerular and tubular epithelial structures, binds major bands of approximately 107 KD and 93 KD in detergent solubilised cortex and a single band of similar size by immunoprecipitation (110 KD). 5-3A (a human-restricted linear-reacting McAb) binds bands of 20-200 KD (major band 58 KD) in CS-GBM. In conclusion, distinct species-restricted and more broadly disposed glomerular epitopes are definable in man by McAbs and are potential targets for humoral injury. Purification of these antigens will allow assay for circulating putative nephritogenic auto-antibody and potentially, McAbs may be useful in screening urine for evidence of occult structural renal disease.

Postnatal development of the interstitial tissue of the rat kidney

To study the ontogenetic development of the interstitial tissue of the kidney, rats were investigated 1, 3, 7, 14, 21 and 28 days after birth. Kidneys perfusion-fixed with glutaraldehyde were studied with light- and electron microscopy. Cryostate sections from kidneys immediately frozen in liquid nitrogen were studied with respect to the expression of MHC class II antigen using the monoclonal antibody OX6. The interstitial space of both the renal cortex and the outer and inner medulla was prominent during the first days postnatally. The relative interstitial volume of the cortex and outer part of the medulla then decreased in conjunction with the outgrowth and maturation of the superficial nephrons while the inner medullary interstitium remained wide. During the first postnatal days, the abundant interstitial cells of the cortex were connected via cytoplasmic processes to form a loose network which later became less well defined. The lipid-laden interstitial cells of the inner medulla showed essentially the same ultrastructure in the newborn as in the adult animal. Strong expression of class II antigen first appeared on epithelial cells of the thick ascending limb of Henle's loop about 7 days postnatally, and became weak at 28 days. From 21 days, a weak staining of the proximal tubules was also observed. While interstitial cells in the inner medulla were always negative, cortical and outer medullary interstitial cells became strongly positive for class II antigen from day 21 post partum.

Chronic serum sickness glomerulonephritis: heparin enhances the removal of glomerular antigen

Chronic serum sickness glomerulonephritis was induced in rats using 125I-labelled cationic bovine serum albumin as antigen. During the recovery period the animals were given protamine or polyethyleneimine (PEI), both of which are cationic, or heparin, which is anionic. A control group received saline. The cationic molecules were not shown to influence the rate of removal of antigen from the glomeruli, but heparin increased removal. In subsequent experiments this effect of heparin was confirmed, and a similar effect was demonstrated using low molecular weight heparin. These results indicate that large doses of heparin can enhance the removal of antigen from well-established glomerular deposits. Fibrin is not detectable in the glomeruli in this model, so this effect of heparin may be independent of its anticoagulant properties.

The effect of cyclosporin A on the interstitial mononuclear cell infiltration and the induction of Heymann's nephritis

Heymann's nephritis was induced with brush-border (BB) antigen. Interstitial mononuclear cell infiltration was studied with cytological examinations of fine-needle aspiration biopsies (FNAB), and with immunoperoxidase stains of frozen sections with monoclonal antisera. The effect of cyclosporin A (CyA), 20 mg/kg when administered intraperitoneally for 8 days in association with both initial immunization, and with the booster 4 weeks later, on the interstitial leukocyte infiltration and on the development of membranous glomerulonephritis (MGN) and proteinuria were investigated. Another group of rats was immunized, but not given CyA. Experimental animals were killed in groups 3, 6 and 20 weeks after initial immunization. CyA inhibited significantly the initial interstitial lymphocyte and blast cell response at 3 weeks (FNAB), but did not inhibit the secondary response after the booster. The anti-BB titre reacted in a similar fashion. Immunoperoxidase stains indicated a clearly suppressed T suppressor/cytolytic (T s/c) cell response. Glomerular basement membrane (GBM) deposits of IgG developed more slowly and were more scarce in the CyA-treated rats, when compared with the untreated group. Only one out of 15 CyA treated rats developed C3 deposits in the GBM during the course of the study, and none developed proteinuria, when most untreated rats (10/17) had C3 deposits and were nephrotic at 20 weeks. Thus, CyA depressed the initial interstitial cellular response after immunization with BB antigen, and also inhibited the development of antibody response, C3 deposits and proteinuria of Heymann nephritis. These effects of CyA may be contributed to an inhibited amplification of the autoimmune response associated with interstitial damage and continuous release of autoantigen.

Characterization of a polyreactive monoclonal antibody to dsDNA, F x 1A, and heparan sulfate generated from BALB/c mice immunized with rat renal homogenates

Monoclonal antibodies (MoAb) were prepared by fusing spleen cells from BALB/c mice immunized with rat renal cortical homogenates to the mouse myeloma cell. One of them, designated MoAb26-3, revealed a positive antinuclear activity by screening an indirect immunofluorescence test on kidney cryostat sections. The reactivity of MoAb26-3 with double-stranded deoxyribonucleic acid (dsDNA) was confirmed by the Crithidia luciliae assay. The isotype of MoAb26-3 was determined to be IgM-kappa. To test the nephritogenicity of MoAb26-3, the hybridomas were grafted intraperitoneally into BALB/c mice. A deposition of IgM was observed along the base of the epithelial foot processes and on the luminal surface of the endothelium by immunoelectron microscopy. By direct enzyme-linked immunosorbent assay (ELISA), MoAb26-3 was shown to react not only with dsDNA but also with fraction 1A of renal cortical supernatant (F x 1A) and heparan sulfate. On the basis of inhibition ELISA, the dsDNA inhibited F x 1A and heparan sulfate binding of MoAb26-3 and F x 1A blocked the reactivity of Mo26-3 with dsDNA and heparan sulfate, while heparan sulfate showed a less inhibition on the binding of MoAb26-3 with F x 1A, dsDNA, and even with heparan sulfate. Using immunoprecipitation with radiolabeled F x 1A, MoAb26-3 was shown to react with MW 330,000, 440,000, and 700,000 bands which were the same with those which polyclonal Heymann nephritis serum could react. An intravenous injection of MoAb26-3 to rats resulted in the deposition of IgM along the glomerular capillary wall, but resulted in an only transient appearance of proteinuria.

Sequential localization of antibody to multiple regions of the glomerular capillary wall in passive Heymann nephritis

Passive Heymann nephritis was produced in rats by injection of the multispecific anti-Fx1A antibody. At time points 1 hour, 1 day, 2 days, 3 days, and 4 days groups of rats were sacrificed and their kidneys fixed by retrograde perfusion with paraformaldehyde lysine periodate. The antibody was visualized by direct immunofluorescence and by 125I-Protein-A electron microscopic autoradiography. Localization of the antibody in the lamina rara interna, lamina densa, lamina rara externa and the glomerular epithelial cell was determined by electron microscopic autoradiography according to the method of Saltpeter, Fertuck, and Saltpeter (Saltpeter MM, Fertuck MC, Saltpeter EE: J Cell Biol 72:161, 1977). At least 100 grains/kidney were analyzed. At one hour the antibody was localized in a linear, discontinuous pattern by immunofluorescent microscopy. Ultrastructurally, the antibody was present in all regions of the capillary wall although predominantly in the lamina rara interna. At later time points the immunofluorescence staining changed to the typical granular pattern with majority of the grains localizing to the lamina rara externa and the cell body of the glomerular epithelial cell. The importance of these observations is several-fold. (a) It suggests the involvement of multiple antigens in the pathogenesis of Heymann nephritis. (b) The initial reaction to the lamina rara interna may be potentiating the eventual formation of deposits in the lamina rara externa by locally permeabilizing the capillary wall and allowing passage to other antibodies. (c) The immune complexes formed at the various sites in the capillary may be getting shed and trapped in the lamina rara externa resulting in coalescence and genesis of the nephritogenic electron-dense deposits.