Improved survival and amelioration of nephrotoxic nephritis in intercellular adhesion molecule-1 knockout mice

Inhibition of the chemokine signal regulator FROUNT by disulfiram ameliorates crescentic glomerulonephritis

Activated monocytes/macrophages promote glomerular injury, including crescent formation, in anti-glomerular basement membrane (GBM) glomerulonephritis. Disulfiram, an alcohol-aversion drug, inhibits monocyte/macrophage migration by inhibiting FROUNT, a cytosolic protein that enhances chemokine receptor signaling. Our study found that disulfiram at a human equivalent dose successfully blocked albuminuria and crescent formation with podocyte loss, and later stage kidney fibrotic lesions, in a rat model of anti-GBM glomerulonephritis. A disulfiram derivative, DSF-41, with more potent FROUNT inhibition activity, inhibited glomerulonephritis at a lower dose than disulfiram. Disulfiram markedly reduced the number of monocytes or macrophages at the early stage of glomerulonephritis and that of CD3⁺ and CD8⁺ lymphocytes at the established stage. Impaired pseudopodia formation was observed in the glomerular monocytes/macrophages of the disulfiram group; consistent with the in vitro observation that disulfiram blocked chemokine-dependent pseudopodia formation and chemotaxis of bone marrow-derived monocytes/macrophages. Furthermore, disulfiram suppressed macrophage activation as revealed by reduced expression of inflammatory cytokines and chemokines (TNF-α, CCL2, and CXCL9) and reduced CD86 and MHC class II expressions in monocytes/macrophages during glomerulonephritis. The dramatic reduction in monocyte/macrophage number might have resulted from disulfiram suppression of both the chemotactic response of monocytes/macrophages and their subsequent activation to produce cytokines and chemokines, which further recruit monocytes. Additionally, FROUNT was expressed in CD68⁺ monocytes/macrophages infiltrating the crescentic glomeruli in human anti-GBM glomerulonephritis. Thus, disulfiram can be a highly effective and safe drug for the treatment of glomerulonephritis by blocking the chemotactic responses of monocytes/macrophages and their activation status in the glomerulus.

A Deep Insight Into Regulatory T Cell Metabolism in Renal Disease: Facts and Perspectives

Kidney disease encompasses a complex set of diseases that can aggravate or start systemic pathophysiological processes through their complex metabolic mechanisms and effects on body homoeostasis. The prevalence of kidney disease has increased dramatically over the last two decades. CD4⁺CD25⁺ regulatory T (Treg) cells that express the transcription factor forkhead box protein 3 (Foxp3) are critical for maintaining immune homeostasis and preventing autoimmune disease and tissue damage caused by excessive or unnecessary immune activation, including autoimmune kidney diseases. Recent studies have highlighted the critical role of metabolic reprogramming in controlling the plasticity, stability, and function of Treg cells. They are also likely to play a vital role in limiting kidney transplant rejection and potentially promoting transplant tolerance. Metabolic pathways, such as mitochondrial function, glycolysis, lipid synthesis, glutaminolysis, and mammalian target of rapamycin (mTOR) activation, are involved in the development of renal diseases by modulating the function and proliferation of Treg cells. Targeting metabolic pathways to alter Treg cells can offer a promising method for renal disease therapy. In this review, we provide a new perspective on the role of Treg cell metabolism in renal diseases by presenting the renal microenvironment、relevant metabolites of Treg cell metabolism, and the role of Treg cell metabolism in various kidney diseases.

T cell plasticity in renal autoimmune disease

The presence of immune cells is a morphological hallmark of rapidly progressive glomerulonephritis, a disease group that includes anti-glomerular basement membrane glomerulonephritis, lupus nephritis, and anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis. The cellular infiltrates include cells from both the innate and the adaptive immune responses. The latter includes CD4⁺ and CD8⁺ T cells. In the past, CD4⁺ T cell subsets were viewed as terminally differentiated lineages with limited flexibility. However, it is now clear that Th17 cells can in fact have a high degree of plasticity and convert, for example, into pro-inflammatory Th1 cells or anti-inflammatory Tr1 cells. Interestingly, Th17 cells in experimental GN display limited spontaneous plasticity. Here we review the literature of CD4⁺ T cell plasticity focusing on immune-mediated kidney disease. We point out the key findings of the past decade, in particular that targeting pathogenic Th17 cells by anti-CD3 injection can be a tool to modulate the CD4⁺ T cell response. This anti-CD3 treatment can trigger a regulatory phenotype in Th17 cells and transdifferentiation of Th17 cells into immunosuppressive IL-10-expressing Tr1 cells (Tr1exTh17 cells). Thus, targeting Th17 cell plasticity could be envisaged as a new therapeutic approach in patients with glomerulonephritis.

A Novel Inflammatory Dendritic Cell That Is Abundant and Contiguous to T Cells in the Kidneys of Patients With Lupus Nephritis

The mechanisms that promote local inflammatory injury during lupus nephritis (LN) flare are largely unknown. Understanding the key immune cells that drive intrarenal inflammation will advance our knowledge of disease pathogenesis and inform the development of new therapeutics for LN management. In this study, we analyzed kidney biopsies from patients with proliferative LN and identified a novel inflammatory dendritic cell (infDC) population that is highly expressed in the LN kidney, but minimally present in healthy human kidneys. During an agnostic evaluation of immune transcript expression in the kidneys of patients with proliferative LN, the most abundantly overexpressed transcript from isolated glomeruli was FCER1G, which encodes the Fc receptor gamma chain (FcRγ). To identify the cell types expressing FcRγ that infiltrate the kidney in LN, studies were done on kidney biopsies from patients with active LN using confocal immunofluorescence (IF) microscopy. This showed that FcRγ is abundantly present in the periglomerular (PG) region of the kidney and to a lesser extent in the tubulointerstitium (TI). Further investigation of the surface markers of these cells showed that they were FcRγ+, MHC II+, CD11c+, CD163+, CD5-, DC-SIGN+, CD64+, CD14+, CD16+, SIRPα+, CD206-, CD68-, CD123-, CD3-, and CD11b-, suggesting the cells were infDCs. Quantification of the infDCs showed an average 10-fold higher level of infDCs in the LN kidney compared to the healthy kidneys. Importantly, IF identified CD3+ T cells to be adjacent to these infDCs in the PG space of the LN kidney, whereas both cell types are minimally present in the healthy kidney. Thus, we have identified a previously undescribed DC in lupus kidneys that may interact with intrarenal T cells and play a role in the pathogenesis of kidney injury during LN flare.

The Network of Inflammatory Mechanisms in Lupus Nephritis

Several signaling pathways are involved in the progression of kidney disease in humans and in animal models, and kidney disease is usually due to the sustained activation of these pathways. Some of the best understood pathways are specific proinflammatory cytokine and protein kinase pathways (e.g., protein kinase C and mitogen-activated kinase pathways, which cause cell proliferation and fibrosis and are associated with angiotensin II) and transforming growth factor-beta (TGF-β) signaling pathways (e.g., the TGF-β signaling pathway, which leads to increased fibrosis and kidney scarring. It is thus necessary to continue to advance our knowledge of the pathogenesis and molecular biology of kidney disease and to develop new treatments. This review provides an update of important findings about kidney diseases (including diabetic nephropathy, lupus nephritis, and vasculitis, i.e., vasculitis with antineutrophilic cytoplasmic antibodies). New disease targets, potential pathological pathways, and promising therapeutic approaches from basic science to clinical practice are presented, and the blocking of JAK/STAT and TIM-1/TIM-4 signaling pathways as potential novel therapeutic agents in lupus nephritis is discussed.

Recombinant human soluble thrombomodulin attenuates anti-glomerular basement membrane glomerulonephritis in Wistar-Kyoto rats through anti-inflammatory effects

BACKGROUND

Since recombinant human soluble thrombomodulin (RH-TM) has anti-inflammatory properties through neutralizing high-mobility group box 1 protein (HMGB1), the protective effects of RH-TM were examined in anti-glomerular basement membrane (GBM) glomerulonephritis (GN) in Wistar-Kyoto rats.

METHODS

Rats were injected with nephrotoxic serum (NTS) to induce anti-GBM GN on Day 0, and were given either RH-TM or vehicle from Day 0 to Day 6. Rats were sacrificed 7 days after NTS injection.

RESULTS

RH-TM-treated rats had decreased proteinuria and serum creatinine level. RH-TM significantly reduced the percentage of glomeruli with crescentic features and fibrinoid necrosis. In addition, RH-TM-treated rats had significantly reduced glomerular ED1+ macrophage accumulation as well as reduced renal cortical proinflammatory cytokine expression. Furthermore, RH-TM had a potent effect in reducing intercellular adhesion molecule-1 (ICAM-1) expression in kidneys and urine. RH-TM significantly reduced renal cortical mRNA levels for toll-like receptor -2 and -4, known as receptors for HMGB1, and their downstream adopter protein, myeloid differentiation primary respond protein 88 (MyD88).

CONCLUSIONS

We showed for the first time that anti-inflammatory effects, which were characterized by reduced glomerular macrophage influx concomitant with a marked reduction in proinflammatory cytokines, were involved in the mechanism of attenuating experimental anti-GBM GN by RH-TM. The observed effects might be attributable to the downregulation of ICAM-1 by reducing the HMGB1/TLR/MyD88 signaling pathway.

Organ-Specific Mechanisms of Transendothelial Neutrophil Migration in the Lung, Liver, Kidney, and Aorta

Immune responses are dependent on the recruitment of leukocytes to the site of inflammation. The classical leukocyte recruitment cascade, consisting of capture, rolling, arrest, adhesion, crawling, and transendothelial migration, is thoroughly studied but mostly in model systems, such as the cremasteric microcirculation. This cascade paradigm, which is widely accepted, might be applicable to many tissues, however recruitment mechanisms might substantially vary in different organs. Over the last decade, several studies shed light on organ-specific mechanisms of leukocyte recruitment. An improved awareness of this matter opens new therapeutic windows and allows targeting inflammation in a tissue-specific manner. The aim of this review is to summarize the current understanding of the leukocyte recruitment in general and how this varies in different organs. In particular we focus on neutrophils, as these are the first circulating leukocytes to reach the site of inflammation. Specifically, the recruitment mechanism in large arteries, as well as vessels in the lungs, liver, and kidney will be addressed.

Murine glomerular transcriptome links endothelial cell-specific molecule-1 deficiency with susceptibility to diabetic nephropathy

Diabetic nephropathy (DN) is the leading cause of kidney disease; however, there are no early biomarkers and no cure. Thus, there is a large unmet need to predict which individuals will develop nephropathy and to understand the molecular mechanisms that govern this susceptibility. We compared the glomerular transcriptome from mice with distinct susceptibilities to DN at four weeks after induction of diabetes, but before histologic injury, and identified differential regulation of genes that modulate inflammation. From these genes, we identified endothelial cell specific molecule-1 (Esm-1), as a glomerular-enriched determinant of resistance to DN. Glomerular Esm-1 mRNA and protein were lower in DN-susceptible, DBA/2, compared to DN-resistant, C57BL/6, mice. We demonstrated higher Esm-1 secretion from primary glomerular cultures of diabetic mice, and high glucose was sufficient to increase Esm-1 mRNA and protein secretion in both strains of mice. However, induction was significantly attenuated in DN-susceptible mice. Urine Esm-1 was also significantly higher only in DN-resistant mice. Moreover, using intravital microscopy and a biomimetic microfluidic assay, we showed that Esm-1 inhibited rolling and transmigration in a dose-dependent manner. For the first time we have uncovered glomerular-derived Esm-1 as a potential non-invasive biomarker of DN. Esm-1 inversely correlates with disease susceptibility and inhibits leukocyte infiltration, a critical factor in protecting the kidney from DN.

Pentraxin-2 suppresses c-Jun/AP-1 signaling to inhibit progressive fibrotic disease

Pentraxin-2 (PTX-2), also known as serum amyloid P component (SAP/APCS), is a constitutive, antiinflammatory, innate immune plasma protein whose circulating level is decreased in chronic human fibrotic diseases. Here we show that recombinant human PTX-2 (rhPTX-2) retards progression of chronic kidney disease in Col4a3 mutant mice with Alport syndrome, reducing blood markers of kidney failure, enhancing lifespan by 20%, and improving histological signs of disease. Exogenously delivered rhPTX-2 was detected in macrophages but also in tubular epithelial cells, where it counteracted macrophage activation and was cytoprotective for the epithelium. Computational analysis of genes regulated by rhPTX-2 identified the transcriptional regulator c-Jun along with its activator protein-1 (AP-1) binding partners as a central target for the function of rhPTX-2. Accordingly, PTX-2 attenuates c-Jun and AP-1 activity, and reduces expression of AP-1-dependent inflammatory genes in both monocytes and epithelium. Our studies therefore identify rhPTX-2 as a potential therapy for chronic fibrotic disease of the kidney and an important inhibitor of pathological c-Jun signaling in this setting.

Endogenous Tim-1 promotes severe systemic autoimmunity and renal disease MRL-Faslpr mice

The T-cell immunoglobulin mucin 1, also known as kidney injury molecule-1, modulates CD4+ T-cell responses and is also expressed by damaged proximal tubules within the kidney. Both Th subset imbalance (Th1/Th2/Th17) and regulatory T-cell and B-cell alterations contribute to the pathogenesis of autoimmune disease. This study investigated the effects of an inhibitory anti-T-cell immunoglobulin mucin 1 antibody (RMT1–10) in lupus-prone MRL- Fas lpr mice. MRL- Fas lpr mice were treated with RMT1–10 or a control antibody intraperitoneally twice weekly from 3 mo of age for 16 wk. RMT1–10 treatment significantly improved survival, limited the development of lymphadenopathy and skin lesions, preserved renal function and decreased proteinuria, reduced serum anti-DNA antibody levels, and attenuated renal leukocyte accumulation. Th1 and Th17 cellular responses systemically and intrarenally were reduced, but regulatory T and B cells were increased. RMT1–10 treatment also reduced glomerular immunoglobulin and C3 deposition and suppressed cellular proliferation and apoptosis. Urinary excretion and renal expression of kidney injury molecule-1 was reduced, reflecting diminished interstitial injury. As RMT1–10 attenuated established lupus nephritis, manipulating immune system T-cell immunoglobulin mucin 1 may represent a therapeutic strategy in autoimmune diseases affecting the kidney.

Microvesicles derived from human Wharton's Jelly mesenchymal stromal cells ameliorate renal ischemia-reperfusion injury in rats by suppressing CX3CL1

Introduction

Studies have demonstrated that mesenchymal stromal cells (MSCs) could reverse acute and chronic kidney injury by a paracrine or endocrine mechanism, and microvesicles (MVs) have been regarded as a crucial means of intercellular communication. In the current study, we focused on the therapeutic effects of human Wharton-Jelly MSCs derived microvesicles (hWJMSC-MVs) in renal ischemia/reperfusion injury and its potential mechanisms.

Methods

MVs isolated from conditioned medium were injected intravenously in rats immediately after ischemia of the left kidney for 60 minutes. The animals were sacrificed at 24 hours, 48 hours and 2 weeks after reperfusion. The infiltration of inflammatory cells was identified by the immunostaining of CD68+ cells. ELISA was employed to determine the inflammatory factors in the kidney and serum von Willebrand Factor (VWF). Tubular cell proliferation and apoptosis were identified by immunostaining. Renal fibrosis was assessed by Masson’s tri-chrome straining and alpha-smooth muscle actin (α-SMA) staining. The CX3CL1 expression in the kidney was measured by immunostaining and Western blot, respectively. In vitro, human umbilical vein endothelial cells were treated with or without MVs for 24 or 48 hours under hypoxia injury to test the CX3CL1 by immunostaining and Western blot.

Results

After administration of hWJMSC-MVs in acute kidney injury (AKI) rats, renal cell apoptosis was mitigated and proliferation was enhanced, inflammation was also alleviated in the first 48 hours. MVs also could suppress the expression of CX3CL1 and decrease the number of CD68+ macrophages in the kidney. In the late period, improvement of renal function and abrogation of renal fibrosis were observed. In vitro, MVs could down-regulate the expression of CX3CL1 in human umbilical vein endothelial cells under hypoxia injury at 24 or 48 hours.

Conclusions

A single administration of MVs immediately after ischemic AKI could ameliorate renal injury in both the acute and chronic stage, and the anti-inflammatory property of MVs through suppression of CX3CL1 may be a potential mechanism. This establishes a substantial foundation for future research and treatment.

Mononuclear phagocyte system in kidney disease and repair

The mononuclear phagocyte system is comprised of circulating monocytes, tissue macrophages and dendritic cells (DCs) that play key roles in tissue homeostasis, immune surveillance, and immune and non-immune-mediated tissue injury and repair. This review summarizes the various subsets within this system that exhibit significant functional and phenotypic diversity that can adapt to their surrounding microenvironments during inflammation and in response to colony-stimulating factor (CSF)-1. The current understanding of the co-ordination of monocyte infiltration into the homeostatic and diseased kidney through adhesion molecules, chemokines and chemokine receptors, and cytokines are described. Furthermore, the significant confusion and controversy associated with monocyte differentiation into renal macrophages and DCs following infiltration into the kidney, the considerable functional and phenotypic overlap between both tissue populations and their respective roles in immune and non-immune-mediated renal is also discussed. Understanding the factors that control the activation and recruitment of cells from the mononuclear phagocyte system during renal injury may offer an avenue for the development of new cellular and growth factor-based therapies in combination with existing therapies as an alternative treatment option for patients with renal disease.

Endogenous Tim-1 (Kim-1) promotes T-cell responses and cell-mediated injury in experimental crescentic glomerulonephritis

The T-cell immunoglobulin mucin 1 (Tim-1) modulates CD4(+) T-cell responses and is also expressed by damaged proximal tubules in the kidney where it is known as kidney injury molecule-1 (Kim-1). We sought to define the role of endogenous Tim-1 in experimental T-cell-mediated glomerulonephritis induced by sheep anti-mouse glomerular basement membrane globulin acting as a planted foreign antigen. Tim-1 is expressed by infiltrating activated CD4(+) cells in this model, and we studied the effects of an inhibitory anti-Tim-1 antibody (RMT1-10) on immune responses and glomerular disease. Crescentic glomerulonephritis, proliferative injury, and leukocyte accumulation were attenuated following treatment with anti-Tim-1 antibodies, but interstitial foxp3(+) cell accumulation and interleukin-10 mRNA were increased. T-cell proliferation and apoptosis decreased in the immune system along with a selective reduction in Th1 and Th17 cellular responses both in the immune system and within the kidney. The urinary excretion and renal expression of Kim-1 was reduced by anti-Tim-1 antibodies reflecting diminished interstitial injury. The effects of anti-Tim-1 antibodies were not apparent in the early phase of renal injury, when the immune response to sheep globulin was developing. Thus, endogenous Tim-1 promotes Th1 and Th17 nephritogenic immune responses and its neutralization reduces renal injury while limiting inflammation in cell-mediated glomerulonephritis.

Fibrinogen, acting as a mitogen for tubulointerstitial fibroblasts, promotes renal fibrosis

Fibrinogen plays an important role in blood coagulation but its function extends far beyond blood clotting being involved in inflammation and repair. Besides these crucial functions it can also promote tissue fibrosis. To determine whether fibrinogen is involved in the development of renal tubulointerstitial fibrosis we utilized the profibrotic model of unilateral ureteral obstruction in fibrinogen-deficient mice. In the heterozygotes, obstruction was associated with a massive deposition of intrarenal fibrinogen. Fibrinogen deficiency provided significant protection from interstitial damage and tubular disruption, attenuated collagen accumulation, and greatly reduced de novo expression of α-smooth muscle actin in the obstructed kidney. While no differences were found in renal inflammatory cell infiltration, fibrinogen deficiency was associated with a significant reduction in interstitial cell proliferation, a hallmark of renal fibrosis. In vitro, fibrinogen directly stimulated renal fibroblast proliferation in a dose-dependent manner. This mitogenic effect of fibrinogen was mediated by at least three different cell surface receptors on renal fibroblasts: TLR2, TLR4, and ICAM-1. Thus, our study suggests that fibrinogen promotes renal fibrosis by triggering resident fibroblast proliferation.

Intercellular adhesion molecule-1 plays a critical role in glomerulosclerosis after subtotal nephrectomy

BACKGROUND

Hyperfiltration in the glomeruli have been considered to be an important cause of glomerular injury; however, the role of intercellular adhesion molecule (ICAM)-1 in the pathogenesis of glomerulosclerosis is not known.

METHODS

To elucidate the effects of ICAM-1 depletion on hyperfiltration-induced glomerular disorder, we used subtotally nephrectomized ICAM-1(+/+) and ICAM-1(-/-) mice. We evaluated macrophage infiltration, mesangial matrix expansion, transforming growth factor (TGF)-β and type IV collagen accumulation in glomeruli.

RESULTS

Macrophage infiltration into the glomeruli and mesangial matrix expansion coincident with increased expression of both ICAM-1 and TGF-β, and accumulation of type IV collagen were ameliorated in subtotally nephrectomized ICAM-1(-/-) mice compared to ICAM-1(+/+) mice. ICAM-1 depletion significantly reduced hyperfiltration-induced glomerular injury after renal ablation.

CONCLUSIONS

Our present findings suggest that glomerular hyperfiltration is the leading cause of glomerulosclerosis, and it is mediated, at least in part, by ICAM-1 expression and macrophage infiltration.

Targeting the recruitment of monocytes and macrophages in renal disease

Macrophages convert proinflammatory or anti-inflammatory signals of tissue microenvironments into response mechanisms. These response mechanisms largely derive from evolutionary conserved defense programs of innate host defense, wound healing, and tissue homeostasis. Hence, in many settings these programs lead to renal inflammation and tissue remodeling (ie, glomerulonephritis and sclerosis or interstitial nephritis and fibrosis). There is abundant experimental evidence that blocking macrophage recruitment or macrophage activation can ameliorate renal inflammation and fibrosis. In this review we discuss experimental tools to target renal macrophage recruitment by using antagonists against selectins, chemokines, integrins, or other important cytokines that mediate renal injury via macrophage recruitment, some of these already having been used in clinical trials.

Kidney dendritic cells in acute and chronic renal disease

Dendritic cells are not only the master regulators of adaptive immunity, but also participate profoundly in innate immune responses. Much has been learned about their basic immunological functions and their roles in various diseases. Comparatively little is still known about their role in renal disease, despite their obvious potential to affect immune responses in the kidney, and immune responses that are directed against renal components. Kidney dendritic cells form an abundant network in the renal tubulointerstitium and constantly survey the environment for signs of injury or infection, in order to alert the immune system to the need to initiate defensive action. Recent studies have identified a role for dendritic cells in several murine models of acute renal injury and chronic nephritis. Here we summarize the current knowledge on the role of kidney dendritic cells that has been obtained from the study of murine models of renal disease.

EMT and proteinuria as progression factors

Tubulointerstitial fibrosis is an integral part of the structural changes of the kidney in chronic progressive renal failure. The accumulation of the extracellular matrix in the tubulointerstitial space is mediated mainly by myofibroblasts. These are derived from resident interstitial fibroblasts, tubular epithelial cells, periadventitial cells, and possibly also mesenchymal stem cells and endothelial cells. Fibrosis is usually preceded by tubulointerstitial infiltration of mononuclear inflammatory cells. Proteinuria is one of several mechanisms of primary glomerular or vascular disease to transmit the disease process to the interstitial space. Increased protein filtration may have direct toxic effects on tubular epithelial cells, induce chemokine and cytokine secretion and result in increased expression of adhesion molecules, all contributing to the influx of mononuclear cells. Inflammatory cells in return secrete cytokines, which stimulate resident fibroblasts and tubular epithelial cells to differentiate into matrix-producing cells. The phenotypic conversion of primary epithelial cells into mesenchymal cells, termed epithelial-mesenchymal transition (EMT), has been studied in great detail in recent years. Several signal transduction pathways of this process have been clarified and may eventually result in novel therapeutic approaches. The severity of proteinuria and the extent of EMT have both been associated with the decline in renal function in clinical studies. Limiting proteinuria results in a slower decline of renal function deterioration, whereas reducing EMT has had beneficial effects in a number of animal studies, including those indicating reversal of fibrotic lesions. However, the association between proteinuria and EMT and vice versa is far from clear and has not been carefully studied.

Experimental anti-GBM disease as a tool for studying spontaneous lupus nephritis

Lupus nephritis is an immune-mediated disease, where antibodies and T cells both play pathogenic roles. Since spontaneous lupus nephritis in mouse models takes 6-12 months to manifest, there is an urgent need for a mouse model that can be used to delineate the pathogenic processes that lead to immune nephritis, over a quicker time frame. We propose that the experimental anti-glomerular basement membrane (GBM) disease model might be a suitable tool for uncovering some of the molecular steps underlying lupus nephritis. This article reviews the current evidence that supports the use of the experimental anti-GBM nephritis model for studying spontaneous lupus nephritis. Importantly, out of about 25 different molecules that have been specifically examined in the experimental anti-GBM model and also spontaneous lupus nephritis, all influence both diseases concordantly, suggesting that the experimental model might be a useful tool for unraveling the molecular basis of spontaneous lupus nephritis. This has important clinical implications, both from the perspective of genetic susceptibility as well as clinical therapeutics.

Enhanced susceptibility to immune nephritis in DBA/1 mice is contingent upon IL-1 expression

The DBA/1 mouse strain is particularly sensitive to experimental immune-mediated nephritis. Previous studies have indicated that various chemokines/cytokines are elevated in strains of mice susceptible to immune-mediated glomerulonephritis. One of the many elevated cytokines is IL-1. This study was designed to determine if IL-1 is essential for the development of immune-mediated nephritis in the DBA/1 mouse strain that is particularly sensitive to this disease. Both male and female DBA/1 mice and DBA/1.IL-1R1(-/-) mice were challenged with anti-GBM sera. We then compared DBA/1 mice to DBA/1.IL-1R1(-/-) mice to determine the influence of IL-1 on immune-mediated nephritis. Compared to DBA/1 mice, DBA/1.IL-1R1(-/-) mice excreted significantly less protein post anti-GBM serum challenge. None of the DBA/1.IL-1R1(-/-) mice, male or female, had a BUN higher than 22 mg/dl post-challenge whereas wild-type DBA/1 mice had significantly elevated BUN. Wild-type DBA/1 mice exhibited pronounced glomerulonephritis, with crescent formation, as well as tubulo-interstitial disease compared to DBA/1.IL1R1(-/-) mice. These findings indicate that IL-1 is necessary for the development of nephritis in DBA/1 mice and suggest that the elevated IL-1 levels in these mice may be one reason why the DBA/1 strain is particularly sensitive to multiple end organ diseases.

Genetic basis of murine lupus nephritis

Systemic lupus erythematosus is a generalized autoimmune disease affecting multiple end-organs including the kidneys. Glomerulonephritis is a leading cause of death in lupus, both in patients and murine models that develop disease spontaneously. Genetic mapping studies have uncovered several genetic intervals that confer susceptibility to nephritis both in human beings and in mice. This review surveys the genomic positions of these nephritis susceptibility loci in murine lupus. Currently we know very little about the molecular identities of the culprit genes within these mapped loci and whether these genetic elements contribute to nephritis directly in a renal-intrinsic fashion or indirectly by augmenting the formation of pathogenic autoantibodies. The next decade is likely to witness a significant broadening of our understanding of how different genes and molecules might facilitate end-organ damage in lupus.

TIMP-1 promotes age-related renal fibrosis through upregulating ICAM-1 in human TIMP-1 transgenic mice

Imbalance of matrix metalloproteinases and tissue inhibitors of metalloproteinases (MMPs/TIMPs) takes part in age-related renal fibrosis; so does molecular inflammation. As several inflammatory mediators including intercellular adhesion molecule-1 (ICAM-1) are substrates of MMPs, we speculated that TIMP-1 might affect ICAM-1 through MMPs and subsequently promote age-related renal fibrosis. Then, we observed changes of kidney in human TIMP-1 transgenic mice and wild-type mice of different ages. It was found that the expressions and activities of gelatinases were downregulated; the expressions of ICAM-1, collagen III, collagen IV, and transforming growth factor (TGF)-beta1 were upregulated; and the number of infiltrating macrophages was increased in kidneys of 24-month-old TIMP-1 transgenic mice with high expressions of TIMP-1, compared with wild-type mice. Our results indicated that TIMP-1 could promote age-related renal fibrosis, which was partly attributed to enhancing inflammation through upregulation of ICAM-1.

Excreted urinary mediators in an animal model of experimental immune nephritis with potential pathogenic significance

OBJECTIVE

Currently, proteinuria is viewed as the earliest indicator of renal disease in immune-mediated nephritis. The objective of this study was to determine whether additional mediators may be excreted in the urine during immune-mediated nephritis, using an experimental model with a well-defined disease course.

METHODS

Urine samples from mice with anti-glomerular basement membrane (anti-GBM) antibody-induced experimental nephritis were screened using a focused immunoproteome array bearing 62 cytokines/chemokines/soluble receptors. Molecules identified through this screening assay were validated using an enzyme-linked immunosorbent assay. One of these molecules was further evaluated for its pathogenic role in disease, using antibody-blocking studies.

RESULTS

Compared with B6 and BALB/c mice, in which moderately severe immune-mediated nephritis develops, the highly nephritis-susceptible 129/Sv and DBA/1 mice exhibited significantly increased urinary levels of vascular cell adhesion molecule 1 (VCAM-1), P-selectin, tumor necrosis factor receptor I (TNFRI), and CXCL16, particularly at the peak of disease. Whereas some of the mediators appeared to be serum derived early in the disease course, local production in the kidneys appeared to be an important source of these mediators later in the course of disease. Both intrinsic renal cells and infiltrating leukocytes appeared to be capable of producing these mediators. Finally, antibody-mediated blocking of CXCL16 ameliorated experimental immune nephritis.

CONCLUSION

These studies identified VCAM-1, P-selectin, TNFRI, and CXCL16 as a quartet of molecules that have potential pathogenic significance; the levels of these molecules are significantly elevated during experimental immune nephritis. The relevance of these molecules in spontaneous immune nephritis warrants investigation.

Leukocyte recruitment to the inflamed glomerulus: a critical role for platelet-derived P-selectin in the absence of rolling

The renal glomerulus is one of the few sites within the microvasculature in which leukocyte recruitment occurs in capillaries. However, due to the difficulty of directly visualizing the glomerulus, the mechanisms of leukocyte recruitment to glomerular capillaries are poorly understood. To overcome this, we rendered murine kidneys hydronephrotic to allow the visualization of the functional glomerular microvasculature during an inflammatory response. These experiments demonstrated that following infusion of anti-glomerular basement membrane (GBM) Ab, leukocytes became adherent in glomerular capillaries via a process of immediate arrest, without undergoing prior detectable rolling. However, despite the absence of rolling, this recruitment involved nonredundant roles for the P-selectin/P-selectin glycoprotein ligand-1 and beta2 integrin/ICAM-1 pathways, suggesting that a novel form of the multistep leukocyte adhesion cascade occurs in these vessels. Anti-GBM Ab also increased glomerular P-selectin expression and induced a P-selectin-independent increase in platelet accumulation. Moreover, platelet depletion prevented both the increase in glomerular P-selectin, and the leukocyte recruitment induced by anti-GBM Ab. Furthermore, depletion of neutrophils and platelets also prevented the increase in urinary protein excretion induced by anti-GBM Ab, indicating that their accumulation in glomeruli contributed to the development of renal injury. Finally, infusion of wild-type platelets into P-selectin-deficient mice restored the ability of glomeruli in these mice to support leukocyte adhesion. Together, these data indicate that anti-GBM Ab-induced leukocyte adhesion in glomeruli occurs via a novel pathway involving a nonrolling interaction mediated by platelet-derived P-selectin.

Inducible co-stimulatory molecule ligand is protective during the induction and effector phases of crescentic glomerulonephritis

The inducible co-stimulatory molecule (ICOS)/ICOS ligand (ICOSL) co-stimulatory pathway is critical in T cell activation, differentiation, and effector function. Its role was investigated in a model of Th1-driven crescentic glomerulonephritis (GN). GN was induced by sensitizing mice to sheep globulin (day 0) and challenging them with sheep anti-mouse glomerular basement membrane antibody (Ab; day 10). Disease and immune responses were assessed on day 20. For testing the role of ICOSL in the induction of GN, control or anti-ICOSL mAb were administered from days 0 to 8. For examining the role of ICOSL in the effector phase of GN, treatment lasted from days 10 to 18. Blockade of ICOSL during the induction of GN increased glomerular accumulation of CD4+ T cells and macrophages and augmented renal injury. These results correlated with attenuated splenocyte production of protective Th2 cytokines IL-4 and IL-10 and decreased apoptosis of splenic CD4+ T cells. ICOSL was upregulated within glomeruli of mice with GN. Inhibition of ICOSL during the effector phase of GN enhanced glomerular T cell and macrophage accumulation and augmented disease, without affecting the systemic immune response (cytokine production, T cell apoptosis/proliferation, Ab levels). Increased presence of leukocytes in glomeruli of mice that received anti-ICOSL mAb was associated with enhanced cellular proliferation and upregulation of P-selectin and intercellular adhesion molecule-1 within glomeruli. These studies demonstrate that ICOSL is protective during the induction of GN by augmenting Th2 responses and CD4+ T cell apoptosis. They also show that ICOSL is upregulated in nephritic glomeruli, where it locally reduces accumulation of T cells and macrophages and attenuates renal injury.

Innate Stimuli Accentuate End-Organ Damage by Nephrotoxic Antibodies via Fc Receptor and TLR Stimulation and IL-1/TNF-α Production

Innate stimuli are well recognized as adjuvants of the systemic immune response. However, their role in driving end-organ disease is less well understood. Whereas the passive transfer of glomerular-targeting Abs alone elicited minimal renal disease, the concomitant delivery of innate stimuli triggered severe nephritis, characterized by proliferative glomerulonephritis with crescent formation, and tubulointerstitial disease. Specifically, stimulating TLR2, TLR3, TLR4, and TLR5 by using peptidoglycan, poly(I:C), LPS, and flagellin, respectively, all could facilitate anti-glomerular Ab-elicited nephritis. In this model, innate and immune triggers synergistically activated several cytokines and chemokines, including IL-1, IL-6, TNF-alpha, and MCP-1, some of which were demonstrated to be absolutely essential for the development of renal disease. Genetic studies revealed that, whereas the innate trigger is dependent on TLR/IL-1R-associated kinase-mediated signaling, the immune component was contingent on FcR-mediated signals. Importantly, infiltrating leukocytes as well as intrinsic glomerular cells may both serve to integrate these diverse signals. Extrapolating to spontaneous immune-mediated nephritis, although the adaptive immune system may be important in generating end-organ targeting Abs, the extent of damage inflicted by these Abs may be heavily dependent on cues from the innate immune system.

Progression in chronic kidney disease

The pathogenic mechanisms that lead to chronic kidney disease (CKD) converge on a common pathway that results in progressive interstitial fibrosis, peritubular capillary loss with hypoxia, and destruction of functioning nephrons because of tubular atrophy. Interstitial recruitment of inflammatory leukocytes and myofibroblasts occurs early in kidneys destined to develop fibrosis. Circulating monocytes are recruited by locally secreted chemoattractant molecules, facilitated by leukocyte adhesion molecules. Functionally heterogeneous macrophages secrete many fibrosis-promoting molecules, but under some circumstances they may also serve a protective scavenging role. Excessive extracellular matrix production occurs primarily within interstitial myofibroblasts, a population of cells that appears to have more than 1 origin, including the resident interstitial fibroblasts, trans-differentiated tubular epithelial cells, and bone marrow-derived cells. Impaired activity of the endogenous renal matrix-degrading proteases may enhance interstitial matrix accumulation, but the specific pathways that are involved remain unclear. Tubules, inflammatory cells, and myofibroblasts synthesize the molecules that activate the fibrogenic cascades, the most important of which is transforming growth factor beta (TGF-beta). TGF-beta may direct cells to assume a pro-fibrotic phenotype or it may do so indirectly after stimulating synthesis of other fibrogenic molecules such as connective tissue growth factor and plasminogen activator inhibitor-1. Reduced levels of antifibrotic factors that are normally produced in the kidney such as hepatocyte growth factor and bone morphogenic protein-7 may accelerate fibrosis and its destructive consequences. Development of new therapeutic agents for CKD looks promising, but several agents that target different components of the fibrogenic cascade will almost certainly be necessary.

Glomerular expression of CD80 and CD86 is required for leukocyte accumulation and injury in crescentic glomerulonephritis

The participation of renal expression of CD80 and CD86 in the immunopathogenesis of crescentic Th1-mediated anti-glomerular basement membrane (anti-GBM) glomerulonephritis (GN) has not been assessed. Immunohistochemical staining demonstrated prominent upregulation of both molecules in glomeruli of mice with anti-GBM GN, suggesting a potential role for the local expression of CD80 and CD86 in nephritogenic effector T cell responses. For testing this hypothesis, control or inhibitory anti-CD80 and/or anti-CD86 mAb were administered to mice during the effector phase of the disease but after the establishment of a systemic immune response. Anti-CD80 or anti-CD86 mAb treatment had no effect on the development of GN or infiltration of leukocytes into glomeruli; however, administration of anti-CD80/86 mAb attenuated glomerular accumulation of CD4+ T cells and macrophages, crescent formation, and proteinuria, correlating with reduced antigen-specific skin delayed-type hypersensitivity. Attenuated glomerular infiltration of leukocytes in mice that were treated with anti-CD80/86 mAb was associated with decreased intraglomerular expression of adhesion molecules P-selectin and intercellular adhesion molecule-1, as well as attenuated renal mRNA levels of proinflammatory cytokines IFN-gamma and migration inhibitory factor, without reducing chemokine and chemokine receptor expression in the kidney or intraglomerular apoptosis and proliferation. The systemic Th1/Th2 balance (assessed by splenocyte production of IFN-gamma and IL-4 and circulating levels of IgG1 and IgG2a) was not affected by the inhibition of CD80 and CD86. These studies show that CD80 and CD86 are expressed in glomeruli of mice with crescentic anti-GBM GN, in which they play a critical role in facilitating accumulation of Th1 effectors and macrophages, thus exacerbating renal injury.

Heat shock protein 60 is released in immune-mediated glomerulonephritis and aggravates disease: in vivo evidence for an immunologic danger signal

Heat shock proteins (Hsp) are ubiquitous intracellular proteins that can be released in various forms of cellular stress. Some Hsp, such as Hsp60, have been shown to stimulate directly T cell-mediated immune responses in vitro. Here, it is demonstrated that Hsp60 is released from the kidneys and excreted into the urine of mice with nephrotoxic nephritis (NTN), a model of rapidly progressive glomerulonephritis. For examining the functional relevance of Hsp60 release, this protein was injected into mice with subnephritogenic NTN, in which only transient proteinuria and minimal organ damage occur that do not progress to terminal kidney failure. Injection of Hsp60 strikingly aggravated disease, as evidenced by global glomerular necrosis, tubulointerstitial damage, and complete anuria after 10 to 12 d. This effect was mediated neither by endotoxin contaminations of Hsp60 nor by autologous antibodies. It was strictly T cell dependent but not associated with a systemic Th1/Th2 shift. Thus, Hsp60 is an endogenous mediator stimulating immune effector mechanisms that contribute to the progression of NTN. These findings demonstrate in vivo that Hsp60 fulfills criteria of immunologic danger signals and suggest that such signals may be involved in immune-mediated kidney disease.

Strain Distribution Pattern of Susceptibility to Immune-Mediated Nephritis

The genetic basis of immune-mediated nephritis is poorly understood. Recent studies have demonstrated that the NZW mouse strain is more prone to immune-mediated nephritis compared with C57BL/6 and BALB/c strains. The present study extends these findings by challenging 12 additional inbred strains of mice with rabbit anti-mouse glomerular basement membrane (GBM) reactive sera. Compared with control sera-injected mice and anti-GBM-injected A/J, AKR/J, C3H/HeJ, DBA/2J, MRL/MpJ, NOD/LtJ, P/J, SJL/J, and SWR/J mice, the anti-GBM-injected BUB/BnJ, DBA/1J, and 129/svJ mice developed severe proteinuria and azotemia. Their kidneys exhibited pronounced glomerulonephritis, with crescent formation, as well as tubulointerstitial disease, with these phenotypes being particularly profound in 129/svJ mice. However, these strains did not appear to differ in the nature of their xenogeneic immune response to the administered rabbit sera, either quantitatively or qualitatively. Collectively, these findings allude to the presence of genetic elements in the BUB/BnJ, DBA/1J, and 129/svJ genomes that may potentially confer susceptibility to immune-mediated nephritis. Detailed studies to dissect out the immunological and genetic basis of renal disease in these three strains are clearly warranted.

Intercellular adhesion molecule-1-deficient mice are resistant against renal injury after induction of diabetes

Diabetic nephropathy is a leading cause of end-stage renal failure. Several mechanisms, including activation of protein kinase C, advanced glycation end products, and overexpression of transforming growth factor (TGF)-beta, are believed to be involved in the pathogenesis of diabetic nephropathy. However, the significance of inflammatory processes in the pathogenesis of diabetic microvascular complications is poorly understood. Accumulation of macrophages and overexpression of leukocyte adhesion molecules and chemokines are prominent in diabetic human kidney tissues. We previously demonstrated that intercellular adhesion molecule (ICAM)-1 mediates macrophage infiltration into the diabetic kidney. In the present study, to investigate the role of ICAM-1 in diabetic nephropathy, we induced diabetes in ICAM-1-deficient (ICAM-1(-/-)) mice and ICAM-1(+/+) mice with streptozotocin and examined the renal pathology over a period of 6 months. The infiltration of macrophages was markedly suppressed in diabetic ICAM-1(-/-) mice compared with that of ICAM-1(+/+) mice. Urinary albumin excretion, glomerular hypertrophy, and mesangial matrix expansion were significantly lower in diabetic ICAM-1(-/-) mice than in diabetic ICAM-1(+/+) mice. Moreover, expressions of TGF-beta and type IV collagen in glomeruli were also suppressed in diabetic ICAM-1(-/-) mice. These results suggest that ICAM-1 is critically involved in the pathogenesis of diabetic nephropathy.

Expression of the chemokines MCP-1/CCL2 and RANTES/CCL5 is differentially regulated by infiltrating inflammatory cells

BACKGROUND

Chemokines are involved in the regulation of the cellular renal infiltrate in glomerulonephritis; however, it is unclear to which degree resident glomerular cells or infiltrating leukocytes contribute to the formation of chemokines in glomerular inflammatory lesions. We therefore examined whether monocytes/macrophages play a role in the expression of the C-C chemokines MCP-1/CCL2 and RANTES/CCL5 in renal tissue in a lipopolysaccharide (LPS)-induced model of inflammation, where previously we have shown increased glomerular RANTES expression and glomerular infiltration of ED-1-positive cells.

METHODS

Inflammatory lesions were induced by an intraperitoneal injection of LPS. The infiltration of monocytes into the glomerulus was reduced by two experimental approaches. First, rats were depleted of monocytes by the use of specific monocyte-antisera or by cytotoxic drugs. Second, the infiltration of monocytes into the kidney was reduced by using intercellular adhesion molecule-1 (ICAM-1) knockout mice.

RESULTS

Both experimental approaches demonstrated a significant reduction in the number of infiltrating monocytes/macrophages after lipopolysaccharide injection. This reduction in the infiltration of inflammatory cells was associated with significantly reduced RANTES/CCL5 mRNA expression. However, MCP-1/CCL2 mRNA expression was not inhibited after the LPS injection by monocyte/macrophage depletion. Also, the increase in nuclear factor-kappaB (NF-kappaB) binding activity after the LPS injection was not reduced in pretreated animals. The experiments therefore demonstrate that infiltrating monocytes/macrophages contribute to increased RANTES/CCL5 mRNA expression in inflammatory renal lesions, whereas MCP-1/CCL2 mRNA expression and NF-kappaB activation were not reduced by monocyte/macrophage depletion.

CONCLUSION

MCP-1/CCL2 released from renal tissue upon stimulation plays a major role in the regulation of monocyte/macrophage infiltration, which contributes significantly to increased renal RANTES/CCL5 expression. This cross-talk between resident renal cells and monocytes/macrophages is therefore likely to boost the number of infiltrating inflammatory cells.

Murine lupus genetics: lessons learned

Recent reverse genetic studies in murine lupus have taught us the following lessons: (1) Lupus is extremely polygenic; (2) A single locus may be associated with many different phenotypes; (3) What appears to be a single locus may turn out to be a cluster of loci; (4) Different loci facilitate different immunologic steps leading to lupus; (5) Epistatic interactions between loci may engender novel autoimmune phenotypes; (6) Whereas some loci may be pathogenic, others may confer disease resistance; (7) Whereas the expression of some loci is sex-dependent, the expression of others clearly is not; (8) Two or more loci may have an impact on the same phenotype; (9) Lupus susceptibility loci appear to co-cluster with other autoimmunity susceptibility loci; (10) Lupus genes are likely to be polymorphic alleles with subtle impacts, rather than outright mutations with extreme functions. In contrast, forward genetic studies have revealed that molecules that impact apoptosis, the clearance of apoptotic cells, B-cell or T-cell function, and end-organ pathology can all potentially contribute to lupus. Collectively, the loci and genes identified by these two different approaches factorize into a few distinct pathways leading to lupus. Delineating the molecular mediators of these distinct checkpoints is the challenge that lies ahead.

Combinatorial model of chemokine involvement in glomerular monocyte recruitment: role of CXC chemokine receptor 2 in infiltration during nephrotoxic nephritis

A sequential model involving chemokines has been proposed for leukocyte extravasation into areas of inflammation; however, site-specific aspects remain to be elucidated. Hence, we studied the role of chemokines produced by mesangial (MC) or glomerular endothelial cells (GEC) and their receptors in glomerular recruitment of monocytes. Stimulation of MC with TNF-alpha up-regulated mRNA and protein of CC and CXC chemokines but not constitutive expression of the CX(3)C chemokine fractalkine. While growth-related activity (GRO)-alpha was immobilized to MC proteoglycans, monocyte chemotactic protein (MCP)-1 was secreted into the soluble phase. Firm adhesion and sequestration of monocytes on activated MC was supported by the GRO-alpha receptor CXCR2 and to a lesser extent by CX(3)CR, whereas the MCP-1 receptor CCR2 contributed to their transendothelial chemotaxis toward activated MC. In contrast, fractalkine mRNA and protein was induced by TNF-alpha in transformed rat GEC, and both CXCR2 and CX(3)CR mediated monocyte arrest on GEC in shear flow. The relevance of these mechanisms was confirmed in a rat nephrotoxic nephritis model where acute glomerular macrophage recruitment was profoundly inhibited by blocking CXCR2 or CCR2. In conclusion, our results epitomize a combinatorial model in which chemokines play specialized roles in driving glomerular monocyte recruitment and emphasize an important role for CXCR2 in macrophage infiltration during early phases of nephrotoxic nephritis.

Chemokine and chemokine receptor expression during initiation and resolution of immune complex glomerulonephritis

Chemokines participate in leukocyte infiltration, which plays a major role in glomerular injury during immune complex glomerulonephritis (IC-GN). Because target cell expression of chemokine receptors (CCR) is thought to mediate leukocyte migration, the expression pattern of chemokines and CCR in a model of IC-GN was examined. The transient course and predominant glomerular pathology of this model allows the examination of both the induction and resolution phases of IC-GN. GN was induced in mice by daily apoferritin injection for 2 wk. Urine samples and kidneys were obtained at 1, 2, and 4 wk. Albuminuria was noted at 2 wk, but resolved after 4 wk. This was associated with glomerular IC deposits and mesangial proliferation. Glomerular macrophage infiltration was prominent at 1 and 2 wk, which resolved at 4 wk. Expression of monocyte chemoattractant protein-1 (MCP-1) and RANTES mRNA was upregulated at week 1 and decreased to control levels at weeks 2 and 4. The expression was localized to glomeruli by in situ hybridization and immunohistochemistry. The mRNA of CCR1, CCR2, and CCR5 but not CCR3 or CCR4 were upregulated at week 1 and decreased at weeks 2 and 4. Expression of CCR5 was located to the glomerulus by in situ hybridization and quantitative reverse transcription-PCR of isolated glomeruli. In summary, in a model of transient IC-GN, MCP-1 and RANTES and their receptors CCR1, CCR2, and CCR5 are expressed early and are already downregulated at the peak of proteinuria and leukocyte infiltration. Resolution of glomerulonephritis is associated with a return to baseline of chemokine and CCR expression. Therefore, it is concluded that glomerular MCP-1 and RANTES production directs circulating leukocytes that express CCR1, CCR2, and CCR5 into the glomerulus. After initiating GN, MCP-1 and RANTES and their receptors are readily downregulated.

IL-18 has IL-12-independent effects in delayed-type hypersensitivity: studies in cell-mediated crescentic glomerulonephritis

IL-18 (formerly known as IFN-gamma-inducing factor) enhances Th1 responses via effects that are thought to be dependent on and synergistic with IL-12. The potential for IL-18 to exert IL-12-independent effects in delayed-type hypersensitivity (DTH) responses was studied in a model of Th1-directed, DTH-mediated crescentic glomerulonephritis induced by planting an Ag in glomeruli of sensitized mice as well as in cutaneous DTH. Sensitized genetically normal (IL-12(+/+)) mice developed proteinuria and crescentic glomerulonephritis with a glomerular influx of DTH effectors (CD4(+) T cells, macrophages, and fibrin deposition) in response to the planted glomerular Ag. IL-12p40-deficient (IL-12(-/-)) mice showed significant reductions in crescent formation, proteinuria, and glomerular DTH effectors. Administration of IL-18 to IL-12(-/-) mice restored the development of histological (including effectors of DTH) and functional glomerular injury in IL-12(-/-) mice to levels equivalent to those in IL-12(+/+) mice. IL-18 administration to IL-12(-/-) mice increased glomerular ICAM-1 protein expression, but did not restore Ag-stimulated splenocyte IFN-gamma, GM-CSF, IL-2, or TNF-alpha production. Sensitized IL-12(+/+) mice also developed cutaneous DTH following intradermal challenge with the nephritogenic Ag. Cutaneous DTH was inhibited in IL-12(-/-) mice, but was restored by administration of IL-18. IL-12(+/+) mice given IL-18 developed augmented injury, with enhanced glomerular and cutaneous DTH, demonstrating the synergistic effects of IL-18 and IL-12 in DTH responses. These studies demonstrate that even in the absence of IL-12, IL-18 can induce in vivo DTH responses and up-regulate ICAM-1 without inducing IFN-gamma, GM-CSF, or TNF-alpha production.

Expression of LFA-1 (CD11a/CD18) and ICAM-1 (CD54) in an animal model of renal interstitial fibrosis induced by unilateral ureteral obstruction

Unilateral ureteral obstruction (UUO) has been used as an experimental model to induce tubulointerstitial damage and interstitial fibrosis. UUO is characterized by cellular proliferation, accumulation of inflammatory cells, and subsequent replacement of renal parenchyma by fibrous tissue. The influx of inflammatory cells into the renal interstitium is mediated by adhesion molecules. In this study, the development of fibrosis in the UUO model of the rat was examined and its relation to the time course of LFA-1 and ICAM-1 expression was assessed by immunohistochemistry. An increase in interstitial connective tissue was detected on day 10 after UUO, with a maximum on day 35. After unilateral ureteral obstruction, LFA-1 was prominently expressed in interstitial infiltrates, and to a lesser degree in glomerular areas. An initial increase in LFA-1-positive cells was noted already on day 10, with a maximum on day 20 and a decline on day 25. During the time course of 35 days after UUO, we observed an increase in ICAM-1 expression in the vascular endothelium, in tubular epithelium and in interstitial areas. This study shows that LFA-1 expression and ICAM-1 expression are concordant and that this process is associated with increasing interstitial fibrosis. ICAM-1 interstitial tissue may facilitate the homing and persistence of an interstitial infiltrate by ICAM-1/LFA-1 interactions, thereby preceding the development of renal interstitial fibrosis.

Immunopathogenesis of crescentic glomerulonephritis

Crescentic glomerulonephritis provides an important therapeutic challenge because of its rapidly progressive course and poor outcome. Studies in animal models have elucidated some of the pivotal pathogenetic mechanisms, and human studies increasingly support the clinical relevance of these animal data. Accumulating evidence suggests that crescentic glomerulonephritis results from a complex cell-mediated nephritogenic immune response. Interruption of a number of immune and inflammatory mediators can improve the outcome of this disease.

Glomerular inflammation: use of genetically deficient mice to elucidate the roles of leukocyte adhesion molecules and Fc-gamma receptors in vivo

Single gene knock-outs in mice have been used to define the biological role of leukocyte adhesion receptors, Fc-gamma receptors and complement in animal models of immune complex glomerulonephritis. These studies have shown important differences in the role of P-selectin in glomerular inflammation and inflammation at other sites, and have given a new appreciation of the dominant role played by Fc-gamma receptors in immune complex-induced glomerular injury.