The cytoplasmic domain of tissue factor restricts physiological albuminuria and pathological proteinuria associated with glomerulonephritis in mice

BACKGROUND/AIMS

Tissue factor (TF) is a transmembrane protein that is essential for coagulation. TF is expressed on podocytes and its cytoplasmic domain has cell signalling functions in epithelial cells.

METHODS

Mice lacking the cytoplasmic domain of TF (TF(CT-/-) mice) were used to study its role in physiological albuminuria and pathological proteinuria following induction of glomerulonephritis (GN).

RESULTS

Absence of the cytoplasmic domain of TF was associated with increased albuminuria, podocyte effacement, reduced podocyte numbers and increased spontaneous glomerular tumour necrosis factor α(TNFα) production under physiological conditions. In mice developing GN, absence of the cytoplasmic domain of TF resulted in increased proteinuria and enhanced renal TNFα production without altering other parameters of renal inflammation and injury. Studies in TF(CT-/-) chimeric mice (created by bone marrow transplantation) showed increased proteinuria and renal TNFα mRNA in GN was associated with absence of the cytoplasmic domain of TF in the kidney and was independent of the leucocyte phenotype.

CONCLUSION

These studies demonstrate that the cytoplasmic domain of TF contributes to renal albumin retention and its renal expression protects against proteinuria in leucocyte-mediated renal inflammation. Increased glomerular production of TNFα in the absence of cytoplasmic domain of TF may contribute to podocyte injury resulting in albuminuria and proteinuria.

The cytoplasmic domain of tissue factor in macrophages augments cutaneous delayed-type hypersensitivity

In addition to its procoagulant role, tissue factor (TF) has important coagulation-independent roles, including in inflammation. The cytoplasmic domain of TF has been implicated in some of these coagulation-independent roles, particularly cell signaling. To assess the contribution of the cytoplasmic domain of TF to cell-mediated adaptive immunity, the development of cutaneous delayed-type hypersensitivity (DTH) was studied in mice lacking the cytoplasmic domain of TF (TF(deltaCT/deltaCT) mice). DTH responses in sensitized mice were significantly attenuated in TF(deltaCT/deltaCT) mice, and leukocyte-endothelial cell interactions, assessed by intravital microscopy, were impaired significantly. Studies in chimeric mice, created by bone marrow transplantation, showed that the absence of the cytoplasmic domain of TF in leukocytes rather than endothelial cells was responsible for reduced DTH and leukocyte recruitment. DTH responses to OVA could be induced in wild-type mice but not in TF(deltaCT/deltaCT) mice by transfer of activated CD4(+) OVA-specific TCR transgenic T cells, demonstrating that the defective DTH response in TF(deltaCT/deltaCT) mice was independent of any defect in T cell activation. Macrophage and neutrophil accumulation and expression of TNF-alpha mRNA and phospho-p38-MAPK were reduced significantly in TF(deltaCT/deltaCT) mice, and their macrophages had reduced P-selectin-binding capacity and reduced in vivo emigration in response to MCP-1. These results indicate that leukocyte expression of the cytoplasmic domain of TF contributes to antigen-specific cellular adaptive immune responses via effects on leukocyte recruitment and activation.

Protease-activated receptor-2 augments experimental crescentic glomerulonephritis

Protease-activated receptor-2 (PAR-2) is a cellular receptor expressed prominently on epithelial, mesangial, and endothelial cells in the kidney and on macrophages. PAR-2 is activated by serine proteases such as trypsin, tryptase, and coagulation factors VIIa and Xa. It induces pleiotropic effects including vasodilatation, increasing plasminogen activator inhibitor (PAI-1) expression, mesangial cell proliferation, and cytokine production by macrophages. The role of PAR-2 in renal inflammation was studied in antiglomerular basement membrane antibody-induced crescentic glomerulonephritis (CGN) using PAR-2-deficient (PAR-2(-/-)) mice and wild-type littermate controls. PAR-2(-/-) mice had reduced crescent formation, proteinuria, and serum creatinine compared with wild-type mice 21 days after initiation of CGN. Glomerular accumulation of CD4(+) T cells and macrophages and the number of proliferating cells in glomeruli were similar in both groups. Glomerular fibrin deposition was significantly reduced in PAR-2(-/-) mice, and this was associated with reduced renal plasminogen activator inhibitor expression and increased renal matrix-metalloprotinase-9 activity. These results demonstrate a proinflammatory role for PAR-2 in CGN that is independent of effects on glomerular leukocyte recruitment and mesangial cell proliferation. PAR-2-mediated augmentation of renal plasminogen activator inhibitor expression and inhibition of matrix-metalloprotinase-9 activity may contribute to increased glomerular fibrin accumulation and glomerular injury in CGN.

Cytokines in Glomerulonephritis

Cytokines play central roles in both innate and adaptive immune responses that lead to renal inflammation. They are involved systemically in cross-talk between antigen-presenting cells, leukocytes, and regulatory cells to initiate and modulate nephritogenic immunity. Within the kidney, cytokines play a central role in signaling between infiltrating leukocytes and intrinsic renal cells and orchestrate the effector responses that lead to renal damage. Glomerulonephritis (GN) is an important cause of renal inflammation leading to renal failure that results from adaptive responses targeted at the kidney. Animal models of GN have shown that cytokines play critical roles in initiation and modulation of renal inflammatory responses through their ability to modulate the T helper 1/T helper 2 balance of nephritogenic immune responses. Evidence from clinical studies is now confirming the importance of this paradigm in directing the inflammatory mechanisms, histologic patterns, and clinical consequences of human GN. Cytokines also have critical intrarenal effector roles in the development, perpetuation, and resolution of GN. The proinflammatory role of intrarenal cytokine production by leukocytes in GN is well recognized, but, more recently, the role of intrinsic renal cell cytokine production in amplifying renal inflammation has been shown in animal models of GN. Studies showing benefits of specific anticytokine therapies directed at tumor necrosis factor in human GN are now appearing.

T cells in crescentic glomerulonephritis

Crescent formation in glomerulonephritis (GN) is a manifestation of severe glomerular injury that usually results in a poor clinical outcome. In humans, crescentic GN is frequently associated with evidence of either systemic or organ-specific autoimmunity. T cells play a major role in initiation of adaptive immune responses that lead to crescentic injury. In experimental models of crescentic GN, Th1 predominant immune responses have been shown to promote crescent formation. Perturbation of regulatory T cell function may contribute to development of autoimmune crescentic GN. The presence of T cells and macrophages in crescentic glomeruli, frequently in the absence of humoral mediators of immunity, suggest a dominant effector role for T cells in crescentic GN. The association of cellular immune mediators with local fibrin deposition implicates cell-mediated "delayed-type hypersensitivity-like" mechanisms in crescent formation. Intrinsic renal cells also contribute to T cell-driven effector mechanisms in crescentic GN, via expression of MHC II and co-stimulatory molecules and by production of chemokines and cytokines that amplify leukocyte recruitment and injury.

Conditional ablation of macrophages halts progression of crescentic glomerulonephritis

The presence of macrophages in inflamed glomeruli of rat kidney correlates with proliferation and apoptosis of resident glomerular mesangial cells. We assessed the contribution of inflammatory macrophages to progressive renal injury in murine crescentic glomerulonephritis (GN). Using a novel transgenic mouse (CD11b-DTR) in which tissue macrophages can be specifically and selectively ablated by minute injections of diphtheria toxin, we depleted renal inflammatory macrophages through days 15 and 20 of progressive crescentic GN. Macrophage depletion reduced the number of glomerular crescents, improved renal function, and reduced proteinuria. Morphometric analysis of renal tubules and interstitium revealed a marked attenuation of tubular injury that was associated with reduced proliferation and apoptosis of tubular cells. The population of interstitial myofibroblasts decreased after macrophage depletion and interstitial fibrosis also decreased. In the presence of macrophages, interstitial myofibroblasts exhibited increased levels of both proliferation and apoptosis, suggesting that macrophages act to support a population of renal myofibroblasts in a high turnover state and in matrix deposition. Finally, deletion of macrophages reduced CD4 T cells in the diseased kidney. This study demonstrates that macrophages are key effectors of disease progression in crescentic GN, acting to regulate parenchymal cell populations by modulating both cell proliferation and apoptosis.

Glomerulonephritis, Th1 and Th2: what's new?

Glomerulonephritis (GN), the major worldwide cause of chronic renal disease and renal failure, shows a wide spectrum of histological patterns, severity of injury and clinical outcomes that may be related to the nature of the nephritogenic immune response. In the majority of cases, there is evidence of a central role for cognate immunity in the initiation of human GN and contributions of both humoral and cellular effector mechanisms have been demonstrated in both humans and in animal models. T helper cell subsets are known to activate different immune effector mechanisms which influence disease outcomes in infectious and autoimmune diseases and evidence is now accumulating that Th1 and Th2 subsets direct diverging effector pathways that lead to different patterns and severity of glomerular injury in GN. Th1-predominant responses appear to be associated strongly with proliferative and crescentic forms of GN that result in severe renal injury, while Th2 responses are associated with membranous patterns of injury. The challenge remains to understand fully the relevance of T helper cell subset responses to the spectrum of human GN and to apply this new knowledge to the development of more potent and selective therapeutic strategies.

A pathogenetic role for mast cells in experimental crescentic glomerulonephritis

Mast cells infiltrate kidneys of humans with crescentic glomerulonephritis (GN), and the degree of infiltrate correlates with outcome. However, a functional role for mast cells in the pathogenesis of GN remains speculative. GN was induced by intravenous administration of sheep anti-mouse glomerular basement membrane globulin. After 21 d, systemic immune responses and disease severity were analyzed in wild-type, mast cell-deficient (W/Wv), and bone marrow-derived mast cell-reconstituted W/Wv mice (BMMC-->W/Wv). There were no significant differences in the humoral response toward the nephritogenic antigen or in memory T cell number among the three groups; however, antigen-stimulated T cell IFN-gamma production was significantly elevated in BMMC-->W/Wv mice. Dermal delayed-type hypersensitivity in W/Wv mice was reduced compared with wild-type and BMMC-->W/Wv mice. No mast cells were detected in kidneys of W/Wv mice with GN, whereas in BMMC-->W/Wv mice, the numbers of renal mast cells were similar to wild-type mice with GN. W/Wv mice were protected from the development of crescentic GN, exhibiting reduced crescent formation (10 +/- 1% c.f. 36 +/- 2% in wild type), glomerular influx of T cells/macrophages, and interstitial infiltrate compared with wild-type mice. In contrast, BMMC-->W/Wv demonstrated a similar severity of GN as wild-type mice (35 +/- 2% crescentic glomeruli), accompanied by a prominent inflammatory cell infiltrate into glomeruli and interstitial areas. Glomerular expression of intercellular adhesion molecule-1 and P-selectin were reduced in W/Wv mice but restored to wild-type levels in BMMC-->W/Wv mice. These findings suggest that renal mast cells mediate crescentic GN by facilitating effector cell recruitment into glomeruli via augmentation of adhesion molecule expression.

CD80 and CD86 costimulatory molecules regulate crescentic glomerulonephritis by different mechanisms

BACKGROUND

CD80 and CD86 costimulatory molecules have been shown to affect the induction of Th1-mediated crescentic antiglomerular basement membrane (GBM) antibody-initiated glomerulonephritis (GN). The aim of the current studies was to define the mechanisms by which CD80 and CD86 regulate the development of this disease.

METHODS

Anti-GBM GN was induced in CD80-/-, CD86-/-, and CD80/86-/- mice, as well as in C57BL/6 controls. Renal injury and immune responses were assessed after 21 days. To examine whether costimulation by OX40-ligand compensates for the absence of CD80 and CD86 in inducing GN, OX40-ligand was blocked in wild-type and CD80/86-/- mice.

RESULTS

Crescentic GN and glomerular accumulation of CD4+ T cells and macrophages were attenuated in CD80-/- mice, correlating with significantly enhanced apoptosis and decreased proliferation of spleen CD4+ T cells. GN was exacerbated in CD86-/- mice, which was associated with attenuated IL-4 and enhanced IFN-gamma levels. In contrast, CD80/86-/- mice developed crescentic GN similar to that in controls. Inhibition of OX40-ligand exacerbated GN in wild-type mice by enhancing IFN-gamma production, and attenuated disease in CD80/86-/- mice by reducing glomerular CD4+ T-cell and macrophage accumulation.

CONCLUSION

CD80 is pathogenic in crescentic GN by enhancing survival and proliferation of CD4+ T cells, whereas CD86 is protective by enhancing Th2 and attenuating Th1 responses. Furthermore, in the presence of CD80 and CD86, OX40-ligand attenuates, whereas in their absence it enhances GN, suggesting that, in the absence of CD80 and CD86, the OX40/OX40-ligand pathway is an alternative costimulatory pathway in inducing crescentic GN.

Contributions of intrinsic renal cells to crescentic glomerulonephritis

The pro-inflammatory contributions of leukocytes, particularly macrophages and T cells, to the immunopathogenesis of proliferative forms of glomerulonephritis (GN) have been clearly established by various techniques, including in vivo depletion studies in experimental models. The evidence for an active pro-inflammatory role for intrinsic renal cells in GN has relied on studies demonstrating their production of pro-inflammatory mediators in vitro and during the development of GN. Until recently,the specific in vivo contributions of mediators from intrinsic renal cells to inflammatory injury in GN have proven difficult to define. Utilising 'chimeric' mice as a tool, several studies have explored the involvement of intrinsic renal cells via their production of cytokines and other key pro-inflammatory molecules. These studies provide evidence of important functional contributions of intrinsic renal cells to inflammatory injury in GN via their expression of cytokines, cytokine receptors, MHC-II and co-stimulatory molecules. They suggest a sequence of interactions between cytokines from leukocytes and intrinsic renal cells and important contributions of glomerular epithelial cell proliferation to crescent formation.

Granulocyte Macrophage Colony-Stimulating Factor Expression by Both Renal Parenchymal and Immune Cells Mediates Murine Crescentic Glomerulonephritis

GM-CSF has previously been demonstrated to be important in crescentic glomerulonephritis (GN). As both renal parenchymal cells and infiltrating inflammatory cells produce GM-CSF, their separate contributions to inflammatory renal injury were investigated by creation of two different types of GM-CSF chimeric mice: (1) GM-CSF-deficient (GM-CSF-/-)-->wild-type (WT) chimeras with leukocytes that are unable to produce GM-CSF and (2) WT-->GM-CSF-/- chimeras with deficient renal cell GM-CSF expression. Crescentic anti-glomerular basement membrane GN was induced in WT, GM-CSF(-/-)-->WT chimeras, WT-->GM-CSF-/- chimeras, and GM-CSF-/- mice by planting an antigen (sheep globulin) in their glomeruli. WT mice developed severe crescentic GN, whereas GM-CSF-/- were protected from development of disease. Glomerular T cell recruitment, CD40+ glomerular cells, and renal IFN-gamma and TNF expression were similar in both chimeras and WT mice but significantly reduced in GM-CSF-/- mice, indicating that either leukocyte or renal sources of GM-CSF are sufficient to drive these aspects of the inflammatory response. Restricted expression of GM-CSF revealed a major role for renal cell-derived GM-CSF but a minor role for leukocyte-derived GM-CSF in the formation of cellular crescents; glomerular MHC II expression; serum creatinine; and monocyte chemoattractant protein-1, vascular cellular adhesion molecule, and IL-1beta expression. Glomerular macrophage accumulation, proteinuria, and interstitial infiltrate were equivalent in both chimeric groups but intermediate between WT and GM-CSF-/-, indicating that both sources are required for the full development of glomerular injury in crescentic GN.

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.

Resident Kidney Cells and Their Involvement in Glomerulonephritis

Each year, worldwide, there is an increasing number of patients with chronic kidney disease that progress to end-stage renal disease. Glomerulonephritis (GN) is the commonest single cause of end-stage renal failure in the world. GN can be a manifestation of primary renal injury or may be a secondary feature of a systemic disease process, for example Systemic Lupus Erythematosus (SLE) and Anti-Neutrophilic Cytoplasmic Antibody (ANCA) associated vasculitis. Understanding of the immunopathogenesis of GN has advanced considerably over the last 25 years, particularly the immune system's role. The injurious role of infiltrating leukocytes and humoral mediators has been emphasised, however, the contribution of intrinsic renal cells has proved difficult to define. Most evidence for the pro-inflammatory capacity of intrinsic renal cells has been derived from in vitro studies. Although cytokine production by intrinsic renal cells has been demonstrated by immunohistochemistry and in situ hybridisation studies in renal tissue during the development of GN, the functional contribution of this cytokine production to renal injury was unknown. Little was known about direct and specific interactions between different glomerular cell types and infiltrating leukocytes in the pathogenesis of GN. The development of mice with genetic deficiencies of pro-inflammatory mediators and cytokines, and the technique of bone marrow transplantation into irradiated recipients to produce chimeric mice with restricted cytokine expression has allowed in vivo assessment of the functional contribution made by intrinsic renal cells. Studies have demonstrated the significant contribution of intrinsic renal cell derived cytokines (e.g. TNF) in mediating GN, whereas others (IL-1beta) have a relatively minor role.

IL-12p40 and IL-18 in crescentic glomerulonephritis: IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 promotes local inflammation and leukocyte recruitment

Experimental crescentic glomerulonephritis (GN) is characterized by T helper 1 (Th1) directed nephritogenic immune responses and cell-mediated glomerular injury. IL-12p40, the common cytokine chain for both IL-12 and IL-23, is important in the generation and potentially the maintenance of Th1 responses, whereas IL-18 is a co-factor for Th1 responses that may have systemic and local proinflammatory effects. For testing the hypothesis that both endogenous IL-12p40 and endogenous IL-18 play pathogenetic roles in crescentic GN, accelerated anti-glomerular basement membrane GN was induced in mice genetically deficient in IL-12p40 (IL-12p40-/-), IL-18 (IL-18-/-), or both IL-12p40 and IL-18 (IL-12p40-/-IL-18-/-). Compared with wild-type C57BL/6 mice, IL-12p40-/- mice failed to make a nephritogenic Th1 response and developed markedly reduced crescent formation and renal leukocytic infiltration, despite renal production of chemoattractants and adhesion molecules. IL-18-/- mice developed an intact antigen-specific systemic Th1 response, a similar degree of crescent formation, but fewer glomeruli affected by other severe histologic changes and fewer leukocytes in glomeruli and interstitium. IL-18 was expressed within diseased kidneys. Local production of TNF, IL-1beta, IFN-gamma, CCL3 (MIP-1alpha), and CCL4 (MIP-1beta) was reduced in IL-18-/- mice, demonstrating a local proinflammatory role for IL-18. Combined deletion of IL-12p40 and IL-18 did not result in synergistic effects. Consistent with the hypothesis that inflammation leads to fibrosis, all three groups of deficient mice expressed lower levels of intrarenal TGF-beta1 and/or alpha1(I) procollagen mRNA. These studies demonstrate that in severe experimental crescentic GN, IL-12p40 is the key Th1-defining cytokine chain, whereas IL-18 has local proinflammatory roles.

Fibrin independent proinflammatory effects of tissue factor in experimental crescentic glomerulonephritis

BACKGROUND

Tissue factor initiated glomerular fibrin deposition is an important mediator of injury in crescentic glomerulonephritis. Recent data have suggested noncoagulant roles for tissue factor in inflammation.

METHODS

To test the hypothesis that in addition to its effects in initiating coagulation, tissue factor has proinflammatory effects in glomerulonephritis, rabbits given crescentic anti-glomerular basement membrane (GBM) antibody-induced glomerulonephritis were defibrinogenated with ancrod. One group of defibrinogenated rabbits was also given anti-tissue factor antibodies. Comparisons were made between these groups, as well as a third group that was neither defibrinogenated with ancrod nor given anti-tissue factor antibodies.

RESULTS

Defibrinogenation alone abolished glomerular fibrin deposition, reduced crescent formation, and limited renal impairment (ancrod-treated, serum creatinine 274 +/- 37 micromol/L; untreated 415 +/- 51 micromol/L; P < 0.01). Tissue factor inhibition in defibrinogenated rabbits resulted in further protection of renal function (creatinine 140 +/- 19 micromol/L, P < 0.01) and reduced proteinuria (0.4 +/- 0.2g/day, untreated 2.6 +/- 0.4 g/day, P <0.01), which was significantly increased by defibrinogenation alone (ancrod-treated, 5.6 +/- 1.2 g/day). Anti-tissue factor antibodies (but not defibrinogenation alone) attenuated glomerular T-cell and macrophage recruitment, and major histocompatibility complex (MHC) class II expression.

CONCLUSION

These results demonstrate important proinflammatory effects of tissue factor in crescentic glomerulonephritis that are fibrin independent and provide in vivo evidence for tissue factor's proinflammatory effects on MHC class II expression and leukocyte accumulation.

The cytoplasmic domain of tissue factor contributes to leukocyte recruitment and death in endotoxemia

Tissue factor (TF) is an integral membrane protein that binds factor VIIa and initiates coagulation. The extracellular domain of TF is responsible for its hemostatic function and by implication in the dysregulation of coagulation, which contributes to death in endotoxemia. The role of the cytoplasmic domain of tissue factor in endotoxemia was studied in mice, which lack the cytoplasmic domain of TF (TF(deltaCT/deltaCT)). These mice develop normally and have normal coagulant function. Following i.p injection with 0.5 mg of lipopolysaccharide (LPS), TF(deltaCT/deltaCT) mice showed significantly greater survival at 24 hours compared to the wt mice (TF(+/+)). The serum levels of TNF-alpha and IL-1beta were significantly lower at 1 hour after LPS injection and IL-6 levels were significantly lower at 24 hours in TF(deltaCT/deltaCT) mice compared to TF(+/+)mice. Neutrophil recruitment into the lung was also significantly reduced in TF(deltaCT/deltaCT) mice. Nuclear extracts from tissues of endotoxemic TF(deltaCT/deltaCT) mice also showed reduced NFkappaB activation. LPS induced leukocyte rolling, adhesion, and transmigration in post-capillary venules assessed by intravital microscopy was also significantly reduced in TF(deltaCT/deltaCT) mice. These results indicate that deletion of the cytoplasmic domain of TF impairs the recruitment and activation of leukocytes and increases survival following endotoxin challenge.

Endogenous IL-13 Limits Humoral Responses and Injury in Experimental Glomerulonephritis but Does Not Regulate Th1 Cell-Mediated Crescentic Glomerulonephritis

IL-13 is produced by T helper 2 (Th2) cells, has a role in stimulating Th2-mediated injury, alters humoral responses, and may directly suppress macrophage and neutrophil function. In immune renal disease, the engagement of different effector mediator systems, including humoral and cell-mediated effectors, can result in glomerular injury. Experimental crescentic glomerulonephritis (known as autologous anti-glomerular basement membrane glomerulonephritis) induced by planting an antigen in glomeruli of mice is Th1 directed, delayed-type hypersensitivity (DTH)-like, and antibody independent. To test the hypothesis that, like the counterregulatory Th2 cytokines IL-4 and IL-10, endogenous IL-13 limits effector Th1 responses in glomerulonephritis, crescentic glomerulonephritis was induced in IL-13+/+ and IL-13-/- mice. Although IL-13-/- mice developed increased serum antigen-specific antibody levels, increased glomerular antibody deposition and enhanced switching to the Th1-associated IgG2a subclass, they developed a similar degree of crescentic glomerulonephritis, with similar glomerular T cell/macrophage numbers, renal impairment, and proteinuria. Antigen-specific dermal DTH and IFN-gamma production by antigen-stimulated splenocytes was unaltered. In immune complex (apoferritin-induced) glomerulonephritis, where renal injury is humorally mediated, IL-13-/- mice developed enhanced humoral immune responses and increased proteinuria, with increased IgG2a responses, a more peripheral distribution of immune complexes, but no alterations in leukocyte recruitment. These results demonstrate dissociation of IL-13's effects in antigen induced renal disease with little effect on cellular responses but suppressive effects on humoral effectors and switching to IgG2a. They indicate a role for IL-13 in limiting antibody-mediated renal injury, but not in regulating DTH-like cell-mediated responses in the kidney.

An IL-12-independent role for CD40-CD154 in mediating effector responses: studies in cell-mediated glomerulonephritis and dermal delayed-type hypersensitivity

Crescentic glomerulonephritis (GN) results from IL-12-driven Th1-directed cell-mediated responses (akin to delayed-type hypersensitivity (DTH)) directed against glomerular Ags. CD40-CD154 interactions are critical for IL-12 production and Th1 polarization of immune responses. Crescentic anti-glomerular basement membrane GN was induced in C57BL/6 (wild-type (WT)) mice (sensitized to sheep globulin) by planting this Ag (as sheep anti-mouse glomerular basement membrane globulin) in their glomeruli. Crescentic GN did not develop in CD40(-/-) mice due to significantly reduced nephritogenic Th1 responses. IL-12 was administered to CD40(-/-) mice with GN to dissect interactions between IL-12 and CD40 in inducing nephritogenic immunity and injury. Administration of IL-12 to CD40(-/-) mice restored Th cell IFN-gamma production, and up-regulated intrarenal chemokines and glomerular T cell and macrophage accumulation compared with WT control mice. Despite this, renal macrophages were not activated and renal injury and dermal DTH were not restored. Thus, CD40-directed IL-12 drives Th1 generation and effector cell recruitment but CD40 is required for activation. To test this hypothesis, activated OT-II OVA-specific CD4(+) cells and OVA(323-339)-loaded nonresponsive APCs were transferred into footpads of WT, CD40(-/-), and macrophage-depleted WT mice. WT mice developed significant DTH compared with CD40(-/-) and macrophage-depleted WT mice. This study demonstrated that CD40-induced IL-12 is required for generation of systemic Th1 immunity to nephritogenic Ags, and that IL-12 enhances Th1 effector cell recruitment to peripheral sites of Ag presentation via generation of local chemokines. Effector cell activation, renal DTH-like injury, and dermal DTH require direct Th1 CD154/macrophage CD40 interactions.

Leukocyte-derived interleukin-1beta interacts with renal interleukin-1 receptor I to promote renal tumor necrosis factor and glomerular injury in murine crescentic glomerulonephritis

The involvement of proinflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF) in crescentic glomerulonephritis (GN) is well established. Recently the requirement of intrinsic renal cell participation via their production of TNF in crescentic GN was demonstrated. The current studies address the relative contributions of leukocyte and intrinsic renal cell-derived IL-1beta in the induction of TNF production and glomerular injury by studying bone marrow chimeric mice. Leukocyte-derived IL-1beta was critical in the development of crescentic renal injury because IL-1beta(-/-)-->WT (absent leukocyte IL-1beta) chimeric mice had significantly attenuated TNF expression and were protected from the development of crescentic GN. In contrast, WT-->IL-1beta(-/-) chimeric mice (intact leukocyte but absent renal IL-1beta) developed similar TNF expression and crescentic GN to wild-type mice. To determine the cellular target for IL-1 in this model, IL-RI chimeric mice were studied. IL-1RI(-/-)-->WT chimeric (absent leukocyte IL-1RI expression) mice showed no attenuation of crescentic GN, whereas in the absence of renal IL-1RI (WT-->IL-1RI(-/-) chimeras), glomerular TNF expression and the development of crescentic GN were significantly decreased. These studies demonstrate that leukocytes are the major cellular source of IL-1beta, and that IL-1beta acts principally via the IL-1RI on intrinsic renal cells to induce TNF expression and crescentic glomerular injury.

Intrinsic renal cell expression of CD40 directs Th1 effectors inducing experimental crescentic glomerulonephritis

Evidence suggests that human and experimental crescentic GN results from Th1-predominant immunity to glomerular antigens. CD40/CD154 signaling plays a key role in initiating Th1 responses and may direct Th1 effector responses. The role of CD40 in the development of GN was assessed in murine experimental anti-glomerular basement membrane GN. In this model, C57BL/6 wild-type (WT) mice sensitized to sheep globulin develop crescentic GN resulting from Th1 effector responses when challenged with sheep globulin planted in glomeruli. CD40-/- mice do not develop immunity in response to sheep globulin and thus fail to develop effector responses or significant GN. CD40 is expressed in nephritic glomeruli, suggesting a potential role for intrarenal CD40-CD154 interactions in injurious effector responses. Immune neutralization of the CD40 ligand (CD154) at the time of challenge significantly reduced accumulation of Th1 effectors and injury. The role of CD40 expression by renal cells was assessed by comparing GN in WT-->CD40-/- chimeras (absent renal but intact bone marrow CD40) and sham chimeric mice (WT-->WT). Both groups developed strong antigen-specific immune responses (antibody and IFN-gamma production). However, WT-->CD40-/- chimeras demonstrated reduced renal monocyte chemotactic protein 1 and IFN-inducible protein 10 mRNA levels and minimal T cell and macrophage influx and were protected from renal injury. Sham chimeric mice developed reduced GFR, with prominent renal expression of monocyte chemotactic protein 1 and IFN-inducible protein 10 mRNA and effector cell accumulation. In conclusion, the expression of CD40 by nonimmune renal cells plays a major role in Th1 effector responses by inducing Th1 chemokine production. Therefore, CD40-CD154 interactions are a potential therapeutic target in GN.

Contributions of IL-1beta and IL-1alpha to crescentic glomerulonephritis in mice

ABSTRACT. Interleukin-1 (IL-1) is a pleiotropic proinflammatory cytokine with two distinct isoforms (IL-1alpha and IL-1beta) that signal through the same IL-1 type I receptor (IL-1RI). Contributions of IL-1beta have been demonstrated in human and experimental proliferative glomerulonephritis (GN), but the involvement of IL-1alpha has received little attention. To determine the combined contribution of IL-1alpha and IL-1beta and to dissect the specific contribution of IL-1beta, the development of anti-glomerular basement membrane globulin-induced crescentic GN was studied in mice genetically deficient in either the IL-1 receptor type I (IL-1RI-/-), which are unresponsive to both IL-1alpha and IL-1beta, or IL-1beta alone (IL-1beta-/-). IL-1beta-/- mice showed significant reductions in crescent formation and glomerular T cell and macrophage recruitment compared with strain matched controls (WT). No additional reductions of these indices of injury were observed in IL-1RI-/- mice. However, IL-1RI-/- mice showed greater functional renal protection with significantly less proteinuria and reduced serum creatinine compared with IL-1beta-/- mice, suggesting a significant contribution of IL-1alpha to these parameters of injury. IL-1RI-/- mice had lower serum titers of antibody to the nephritogenic antigen (sheep globulin) and reduced glomerular deposition of complement compared with either IL-1beta-/- or WT mice. This suggests that in the absence of responses to both IL-1alpha and IL-1beta, attenuation of humoral mediators provides additional functional protection from renal injury that is not seen in the absence of IL-1beta alone. These studies indicate that IL-1beta but not IL-1alpha contributes to crescent formation and inflammatory cell recruitment, whereas IL-1alpha but not IL-1beta contributes to humoral mechanisms of glomerular injury.

The role of interleukin-4 and interleukin-12 in the progression of atherosclerosis in apolipoprotein E-deficient mice

Accumulation of T cells and macrophages in atherosclerotic plaques and the formation of antibodies directed against plaque proteins suggests that adaptive immunity contributes to the development of atherosclerosis. The contribution of Th1 and Th2 helper cell subsets to atherogenesis was studied in a murine model by interbreeding apolipoprotein E-deficient (apoE(-/-)) mice with mice deficient in key cytokines that drive either Th1 responses [interleukin (IL)-12] or Th2 responses (IL-4). Compared to apoE(-/-) mice, apoE(-/-)/IL-12(-/-) mice had a 52% reduction in plaque area in the aortic root at 30 weeks of age (P < 0.001). ApoE(-/-)/IL-4(-/-) mice had a 27% reduction in plaque area compared to apoE(-/-) mice (P < 0.05) at 30 weeks of age, but their plaques were significantly larger than in apoE(-/-)/IL-12(-/-) mice at this stage (P < 0.05). By 45 weeks of age, there were no significant differences in lesion sizes in the aortic root between the strains, however apoE(-/-)/IL-4(-/-) mice showed a 58% and 64% decrease in disease in their aortic arch compared to apoE(-/-) (P < 0.05) and apoE(-/-)/IL-12(-/-) (P < 0.05) mice, respectively, and a 78% decrease in thoracic lesions compared to apoE(-/-)/IL-12(-/-) (P < 0.05). This suggests that both Th1 and Th2 cytokines play roles throughout the development of atherosclerosis in various vascular sites in apoE(-/-) mice.

Intrinsic renal cells are the major source of tumor necrosis factor contributing to renal injury in murine crescentic glomerulonephritis

Macrophages are prominent participants in crescentic glomerulonephritis (GN) and have been suggested to be the major source of TNF in this cell-mediated form of glomerular inflammation. Intrinsic renal cells also have the capacity to produce TNF. For dissecting the contribution of local versus bone marrow (BM)-derived TNF in inflammatory renal injury, TNF chimeric mice were created by transplanting normal wild-type (WT) BM into irradiated TNF-deficient recipients (WT-->TNF-/- chimeras) and vice versa (TNF-/- -->WT chimeras). A model of crescentic GN induced by an intravenous injection of sheep anti-murine glomerular basement membrane antibody was studied in WT mice, mice with complete TNF deficiency (TNF-/-), and chimeric mice. Crescentic GN was attenuated in TNF-/- mice with fewer crescents (crescents, 13.7 +/- 1.7% of glomeruli) and reduced functional indices of renal injury (serum creatinine, 15.2 +/- 0.8 micromol/L). Similar protection (crescents, 14.3 +/- 1.9% of glomeruli; serum creatinine, 18.9 +/- 1.1 micromol/L) was observed in chimeric mice with intact BM but absent renal-derived TNF (WT-->TNF-/- chimeras), suggesting a minor contribution of infiltrating leukocytes to TNF-mediated renal injury. Chimeric mice with TNF-deficient leukocytes but intact intrinsic renal cell-derived TNF (crescents, 20.5 +/- 2.0% of glomeruli; serum creatinine, 21.6 +/- 1.4 micromol/L) developed similar crescentic GN to WT mice (crescents, 22.3 +/- 1.4% of glomeruli; serum creatinine, 24.8 +/- 1.9 micromol/L). Cutaneous delayed-type hypersensitivity after subdermal challenge with the nephritogenic antigen was attenuated in the absence of BM cell-derived TNF but unaffected in WT-->TNF-/- chimeric mice. These studies suggest that intrinsic renal cells are the major cellular source of TNF contributing to inflammatory injury in crescentic GN.

Plasminogen activator inhibitor-1 is a significant determinant of renal injury in experimental crescentic glomerulonephritis

Crescentic glomerulonephritis is characterized by glomerular fibrin deposition, and experimental crescentic glomerulonephritis has been shown to be fibrin-dependent. Net fibrin deposition is a balance between activation of the coagulation system causing glomerular fibrin deposition and fibrin removal by the plasminogen-plasmin (fibrinolytic) system. Plasminogen activator inhibitor-1 (PAI-1) inhibits fibrinolysis by inhibiting plasminogen activators and has effects on leukocyte recruitment and matrix deposition. To test the hypothesis that the presence of PAI-1 and its levels were a determinant of injury in crescentic glomerulonephritis, accelerated anti-glomerular basement membrane glomerulonephritis was induced in mice genetically deficient in PAI-1 (PAI-1 -/-), PAI-1 heterozygotes (PAI-1 +/-), and mice engineered to overexpress PAI-1 (PAI-1 tg). Compared with strain-matched genetically normal animals, PAI-1 -/- mice with glomerulonephritis developed fewer glomerular crescents, less glomerular fibrin deposition, fewer infiltrating leukocytes, and less renal collagen accumulation at day 14 of disease. The reduction in disease persisted at day 28, when injury had become more established. In contrast, mice overexpressing the PAI-1 gene (PAI-1 tg), that have basal plasma and renal PAI-1 levels several times, normal developed increased glomerular crescent formation, more glomerular fibrin deposition, increased numbers of infiltrating leukocytes, and more renal collagen at both time points. These studies demonstrate that PAI-1 is a determinant of glomerular fibrin deposition and renal injury in crescentic glomerulonephritis.

T cells in glomerulonephritis

The involvement of immunoglobulin and complement in glomerulonephritis has been recognized for many decades, but the involvement of sensitized T cells and the contributions of cellular immunity have only recently been appreciated. The relative contributions of humoral and cellular immunity in the immunopathogenesis may be an important determinant of the various histological patterns and clinical features of human glomerulonephritis. Subsets of T helper cells, Th1 and Th2, induce immune activation with distinct patterns of involvement of immunoglobulin isotypes and cellular immune effectors. The relative activation of Th subsets is determined by a variety of factors including the nature, dose and mode of presentation of antigens and the cytokine milieu. The balance of Thl/Th2 activation may be important in directing effector pathways and patterns of injury in glomerulonephritis. In the effector phase, T cells are most prominent in proliferative and crescentic glomerulonephritis, where they are usually associated with other mediators of delayed-type hypersensitivity including macrophages and fibrin. In anti-neutrophil cytoplasmic antibody-associated crescentic glomerulonephritis, T cells are invariable participants, frequently in the absence of glomerular antibody deposition. In these forms of glomerulonephritis, which characteristically have a rapid course and poor outcome, T cells are likely to play a pivotal effector role.

Angiopoietin correlates with glomerular capillary loss in anti-glomerular basement membrane glomerulonephritis

BACKGROUND

Emerging evidence suggests that endothelial turnover occurs in several glomerular diseases and correlates with resolution or progression of glomerular lesions. We hypothesized that the growth factors modulating embryonic kidney endothelial cell survival and capillary morphogenesis may be implicated in capillary loss that occurs in immune-mediated glomerulonephritis (GN).

METHODS

GN was induced in C57BL/6 mice by intravenous administration of sheep anti-mouse glomerular basement membrane (GBM) globulin and assessed with markers of vascularity in glomerular lesions, correlating these with expression of specific vascular growth factors.

RESULTS

As assessed by periodic acid Schiff staining, 14 +/- 4% (mean +/- SD) glomeruli were affected by sclerosis at 14 days after globulin administration, and 33 +/- 5% were affected at 21 days. By 21 days, a significant increase of plasma creatinine and urinary protein occurred. P-selectin expression was increased in glomerular capillaries 14 days after disease induction, and capillary loss, as assessed by immunohistochemistry for platelet-endothelial cell adhesion molecule, vascular endothelial growth factor (VEGF) receptor 2 and the angiopoietin (Ang) receptor Tie-2, was recorded at 14 and 21 days in glomeruli affected by proliferative crescents and/or sclerosis. VEGF-A immunostaining, evident in control glomeruli, was qualitatively diminished in glomeruli with lesions. Ang-1 immunostaining was detected in control glomeruli and was diminished at 14 days after administration of anti-mouse GBM globulin; instead, Ang-1 was immunolocalized to distal tubules. In contrast, Ang-2 immunostaining was barely detectable in control glomeruli but was prominent in disease glomeruli. In GN mice, rare apoptotic glomerular endothelia were detected by electron microscopy and in situ end-labeling, but such cells were not seen in controls.

CONCLUSIONS

Loss of glomerular capillaries during the course of anti-GBM GN in mice was temporally associated with decreases in endothelial survival molecules VEGF-A and Ang-1, and with up-regulation of Ang-2, an antagonist of Ang-1. A changing balance of these growth factors may contribute to decreased glomerular vascularity in crescentic GN.

Effects of CTLA4-Fc on glomerular injury in humorally-mediated glomerulonephritis in BALB/c mice

The effect of cytotoxic T-lymphocyte-associated molecule 4-immunoglobulin fusion protein (CTLA4-Fc) on humorally-mediated glomerulonephritis was studied in accelerated anti-glomerular basement membrane (anti-GBM) glomerulonephritis induced in BALB/c mice. This strain of mice develops antibody and complement dependent glomerulonephritis under this protocol. Sensitized BALB/c mice developed high levels of circulating autologous antibody titres, intense glomerular deposition of mouse immunoglobulin and complement, significant proteinuria, renal impairment, significant glomerular necrosis and a minor component of crescent formation 10 days after challenge with a nephritogenic antigen (sheep anti-GBM globulin). Early treatment during the primary immune response, or continuous treatment throughout the disease with CTLA4-Fc, significantly suppressed mouse anti-sheep globulin antibody titres in serum, and immunoglobulin and complement deposition in glomeruli. The degree of glomerular necrosis was improved and proteinuria was reduced, particularly in the earlier stages of disease. Late treatment by CTLA4-Fc starting one day after challenge with sheep anti-mouse GBM did not affect antibody production and did not attenuate glomerulonephritis. The low level of crescent formation found in BALB/c mice developing glomerulonephritis was not prevented by the administration of CTLA4-Fc. These results demonstrate that CTLA4-Fc is of benefit in this model of glomerulonephritis by its capacity to attenuate antibody production, without affecting the minor degree of cell-mediated glomerular injury.

IFN-gamma production by intrinsic renal cells and bone marrow-derived cells is required for full expression of crescentic glomerulonephritis in mice

The contribution of IFN-gamma from bone marrow (BM) and non-BM-derived cells to glomerular and cutaneous delayed-type hypersensitivity (DTH) was studied in mice. Chimeric IFN-gamma mice (IFN-gamma(+/+) BM chimera), in which IFN-gamma production was restricted to BM-derived cells, were created by transplanting normal C57BL/6 (wild-type (WT)) BM into irradiated IFN-gamma-deficient mice. BM IFN-gamma-deficient chimeric mice (IFN-gamma(-/-) BM chimera) were created by transplanting WT mice with IFN-gamma-deficient BM. WT and sham chimeric mice (WT mice transplanted with WT BM) developed crescentic glomerulonephritis (GN) with features of DTH (including glomerular T cell and macrophage infiltration) in response to an Ag planted in their glomeruli and skin DTH following subdermal Ag challenge. IFN-gamma-deficient mice showed significant protection from crescentic GN and reduced cutaneous DTH. IFN-gamma(+/+) BM chimeric and IFN-gamma(-/-) BM chimeric mice showed similar attenuation of crescentic GN as IFN-gamma-deficient mice, whereas cutaneous DTH was reduced only in IFN-gamma(-/-) BM chimeras. In crescentic GN, IFN-gamma was expressed by tubular cells and occasional glomerular cells and was colocalized with infiltrating CD8(+) T cells, but not with CD4(+) T cells or macrophages. Renal MHC class II expression was reduced in IFN-gamma(+/+) BM chimeric mice and was more severely reduced in IFN-gamma-deficient mice and IFN-gamma(-/-) BM chimeric mice. These studies show that IFN-gamma expression by both BM-derived cells and intrinsic renal cells is required for the development of crescentic GN, but IFN-gamma production by resident cells is not essential for the development of cutaneous DTH.

Interleukin-10 inhibits experimental mesangial proliferative glomerulonephritis

Conflicting reports exist regarding the effects of interleukin-10 (IL-10) on mesangial cells. There have been reports of both proliferative and antiproliferative effects, and both proinflammatory and anti-inflammatory effects of IL-10 on mesangial cells. However, the potential for IL-10 to affect glomerulonephritis characterized by mesangial proliferation is not known. To test the hypothesis that IL-10 would limit experimental mesangial proliferative glomerulonephritis, IL-10 was administered to rats in which mesangial proliferative glomerulonephritis was induced by administration of anti-Thy 1 antibody. Compared to control treated rats, IL-10 treated rats showed less proliferation, with fewer cells in glomeruli. Glomerular cellular proliferation was reduced, assessed by the numbers of cells within glomeruli expressing either proliferating cell nuclear antigen (PCNA) or bromodeoxyuridine. Glomerular macrophage influx (but not the proportion of glomerular macrophages that were PCNA positive) was reduced by IL-10 administration. There was no significant reduction in glomerular alpha-smooth muscle actin staining. IL-10 treatment resulted in reduced renal IL-1beta mRNA expression and reduced glomerular ICAM-1 expression, but renal expression of MCP-1 and osteopontin mRNA was unaltered. This study demonstrates that in experimental mesangial proliferative glomerulonephritis IL-10 diminishes inflammatory cell recruitment and mesangial cell proliferation. The effects of IL-10 in inhibiting mesangial cell proliferation are likely to be due to a combination of direct effects of IL-10 on mesangial cells and effects mediated by macrophages.

The requirement for granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor in leukocyte-mediated immune glomerular injury

Proliferative glomerulonephritis in humans is characterized by the presence of leukocytes in glomeruli. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) can potentially stimulate or affect T cell, macrophage, and neutrophil function. To define the roles of GM-CSF and G-CSF in leukocyte-mediated glomerulonephritis, glomerular injury was studied in mice genetically deficient in either GM-CSF (GM-CSF -/- mice) or G-CSF (G-CSF -/- mice). Two models of glomerulonephritis were studied: neutrophil-mediated heterologous-phase anti-glomerular basement membrane (GBM) glomerulonephritis and T cell/macrophage-mediated crescentic autologous-phase anti-GBM glomerulonephritis. Both GM-CSF -/- and G-CSF -/- mice were protected from heterologous-phase anti-GBM glomerulonephritis compared with genetically normal (CSF WT) mice, with reduced proteinuria and glomerular neutrophil numbers. However, only GM-CSF -/- mice were protected from crescentic glomerular injury in the autologous phase, whereas G-CSF -/- mice were not protected and in fact had increased numbers of T cells in glomeruli. Humoral responses to the nephritogenic antigen were unaltered by deficiency of either GM-CSF or G-CSF, but glomerular T cell and macrophage numbers, as well as dermal delayed-type hypersensitivity to the nephritogenic antigen, were reduced in GM-CSF -/- mice. These studies demonstrate that endogenous GM-CSF plays a role in experimental glomerulonephritis in both the autologous and heterologous phases of injury.

Crescentic glomerulonephritis is diminished in fibrinogen-deficient mice

First published August 21, 2001; 00.1152/ajprenal.0002.2001.— Crescentic forms of glomerulonephritis are characterized by the accumulation of fibrin and cells in Bowman's space and are associated with a rapid loss of renal function. Accumulation of fibrin in the glomerular tufts is thought to promote macrophage infiltration and glomerular injury. To directly explore the role of fibrin(ogen) in the development of crescentic glomerulonephritis, antiglomerular basement membrane nephritis was induced in fibrinogen-deficient and control mice. Glomeruli from control mice developed severe disease including fibrin deposits, inflammatory cell accumulation, and crescent formation (46.3 ± 7.3% of glomeruli). Fibrinogen-deficient mice developed significantly milder disease with fewer glomerular crescents (24.0 ± 4.7% of glomeruli; P < 0.03). Glomerular macrophage accumulation was diminished in fibrinogen-deficient mice (0.9 ± 0.4 macrophages/glomerular cross section) relative to control mice (3.9 ± 1.4 macrophages/glomerular cross section; P < 0.03). Finally, renal function as assessed by serum creatinine was better maintained in fibrinogen-deficient mice. These results indicate that although fibrin(ogen) is not essential for the development of glomerular crescents, it contributes significantly to the pathogenesis of crescentic glomerulonephritis by promoting glomerular macrophage accumulation and impairing filtration.

Crescentic glomerulonephritis is diminished in fibrinogen-deficient mice

Crescentic forms of glomerulonephritis are characterized by the accumulation of fibrin and cells in Bowman's space and are associated with a rapid loss of renal function. Accumulation of fibrin in the glomerular tufts is thought to promote macrophage infiltration and glomerular injury. To directly explore the role of fibrin(ogen) in the development of crescentic glomerulonephritis, antiglomerular basement membrane nephritis was induced in fibrinogen-deficient and control mice. Glomeruli from control mice developed severe disease including fibrin deposits, inflammatory cell accumulation, and crescent formation (46.3 +/- 7.3% of glomeruli). Fibrinogen-deficient mice developed significantly milder disease with fewer glomerular crescents (24.0 +/- 4.7% of glomeruli; P < 0.03). Glomerular macrophage accumulation was diminished in fibrinogen-deficient mice (0.9 +/- 0.4 macrophages/glomerular cross section) relative to control mice (3.9 +/- 1.4 macrophages/glomerular cross section; P < 0.03). Finally, renal function as assessed by serum creatinine was better maintained in fibrinogen-deficient mice. These results indicate that although fibrin(ogen) is not essential for the development of glomerular crescents, it contributes significantly to the pathogenesis of crescentic glomerulonephritis by promoting glomerular macrophage accumulation and impairing filtration.

Effects of combined oral hormone replacement therapy on tissue factor pathway inhibitor and factor VII

Oral combined hormone replacement therapy (HRT) with oestradiol and norethisterone increases plasma levels of prothrombin fragment 1+2 (F1+2), indicating an increase in thrombin generation, but the mechanisms underlying this increase are uncertain. The aim of this randomized, placebo-controlled study was to determine whether an increase in factor VII, a factor that combines with tissue factor to activate the extrinsic pathway, or a decrease in tissue factor pathway inhibitor (TFPI), an inhibitor of extrinsic pathway activation, may contribute to increases in thrombin generation occurring with HRT. Healthy postmenopausal women aged 50-75 years received placebo (n=19) or oral combined HRT (n=18) and had blood collected for measurement of factor VII coagulation activity (VIIc), activated factor VII (VIIa) and TFPI at baseline and at 6 weeks. Baseline characteristics were similar in the two groups, including age, body mass index and cholesterol levels. As reported previously, HRT increased the F1+2 concentration by 20%. Placebo had no effect on VIIc, VIIa or TFPI, but 6 weeks of combined HRT decreased VIIc [from 1.11+/-0.06 (mean+/-S.E.M.) to 1.03+/-0.06 i.u./ml; P<0.03], VIIa [from 43.9; 10.8-198.3 (median; range) to 35.0; 6.3-66.8 m-units/ml; P<0.03] and TFPI [from 81.3+/-6.5 to 60.4+/-5.5 ng/ml; P<0.0001]. The decrease in TPFI with HRT was not correlated with the elevation in F1+2 levels. In conclusion, the increase in thrombin generation seen with HRT is not due to an effect on factor VII; in addition, while a contribution from the decrease in TFPI is possible, increased thrombin generation is not directly related to the decrease in TFPI.

Interleukin-12 from intrinsic cells is an effector of renal injury in crescentic glomerulonephritis

Interleukin-12 (IL-12) directs the cognate nephritogenic T helper type 1 responses that initiate renal injury in murine crescentic glomerulonephritis (GN). The recent demonstration of IL-12 production by intrinsic renal cells, including mesangial and proximal tubular cells, raises the possibility that IL-12 from nonimmune cells may contribute to inflammatory renal injury. To address this possibility, the development of sheep anti-mouse glomerular basement membrane globulin-induced crescentic GN was studied in C57BL/6 wild-type (WT), IL-12-deficient (IL-12 -/-), and IL-12 "chimeric" mice. IL-12 chimeric mice were produced by transplantation of WT bone marrow into IL-12 -/- mice to restore IL-12 production by immune cells, while leaving them deficient in renal IL-12 production. WT and "sham" chimeric mice (normal bone marrow transplanted into WT mice) developed crescentic GN with glomerular T-cell and macrophage recruitment and impaired renal function (elevated proteinuria and serum creatinine) 10 d after initiation of GN. IL-12 -/- mice showed significant protection from GN. Chimeric IL-12 mice showed significant attenuation of crescent formation, glomerular T-cell and macrophage accumulation, and renal impairment, compared with WT and sham chimeric mice, but were not protected to the same extent as IL-12 -/- mice. IL-12 chimeric mice showed no attenuation of their systemic cognate immune response to the nephritogenic antigen (sheep globulin), indicated by antigen-specific circulating antibody and cutaneous delayed-type hypersensitivity. These studies indicate that IL-12 produced by non-bone marrow derived intrinsic renal cells contributes to immune renal injury. They provide the first in vivo demonstration of a proinflammatory role for an intrinsic renal cell-derived cytokine in renal inflammation.

MHC class I pathway is not required for the development of crescentic glomerulonephritis in mice

MHC II and CD4+ T cells are required for anti-glomerular basement membrane (GBM) globulin-initiated crescentic glomerulonephritis (GN) in mice, but the role of MHC I and CD8+ T cells is unclear. The cytolytic function of CD8+ T cells requires recognition of peptide antigens presented on MHC I. CD8+ T cells can also perform helper functions via cytokine production. The contribution of MHC I to crescentic GN was investigated using TAP-1 gene knock out (TAP-1-/-) mice, which have deficient MHC I antigen presentation. Heterozygous TAP-1 mice have normal MHC I expression and developed GN with crescents in 42 +/- 4% of glomeruli (normal 0%), proteinuria (9.1 +/- 1.6 mg/20 h, normal 1.5 +/- 0.3 mg/20 h) and impaired renal function (creatinine clearance 110 +/- 8 microl/min, normal 193 +/- 10 microl/min) following administration of sheep anti-mouse GBM globulin. TAP-1-/- mice, which have extremely low MHC I expression and reduced CD8+ T cells, developed similar GN with 39 +/- 3% crescents, proteinuria (12.7 +/- 4.3 mg/20 h) and impaired renal function (creatinine clearance 123 +/- 20 microl/min). In vivo antibody-induced CD8 depletion did not attenuate crescent formation or protect renal function in C57Bl/6 mice developing GN, although significant reduction in proteinuria (5.3 +/- 1.2 mg/20 h, P = 0. 012) and glomerular recruitment of CD4+ T cells and macrophages were observed compared with control treated mice with GN. These data demonstrate that MHC I is not required for development of crescentic GN in mice. The MHC I-independent contribution of CD8+ T cells to proteinuria and inflammatory cell recruitment suggests that they may serve a 'helper' rather than cytolytic role in this disease.

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.

Chemokines as therapeutic targets in renal disease

Increased understanding of the fundamental importance of the role of chemokines and their receptors in inflammation, together with the demonstration of their involvement in human and experimental inflammatory renal disease, make these molecules potential therapeutic targets. A number of recent studies using genetically deficient mice and chemokine receptor antagonists in animal models have demonstrated that chemokine inhibition can attenuate experimental renal injury. Because there is simultaneous expression of multiple chemokines and receptors in disease, strategies that are aimed at antagonizing multiple chemokines receptor interactions are likely to be more effective than therapies that target a single chemokine. It is also now recognized that chemokines are involved in normal immune development and immune regulation. These observations, together with the results of studies that have demonstrated deleterious effects of chemokine receptor antagonism in experimental renal disease, highlight the need for thorough understanding of the role of individual chemokines in the pathogenesis of different types of renal disease before optimal therapeutic interventions may be achieved.

Crescentic glomerulonephritis--a manifestation of a nephritogenic Th1 response?

Crescentic glomerulonephritis (GN) is the histopathological correlate of the clinical syndrome of rapidly progressive glomerulonephritis. Glomerular crescent formation complicates proliferative forms of GN and indicates severe disease with a poor renal prognosis. In the past 10 years evidence from experimental models of GN and from human disease has accumulated suggesting that crescentic glomerulonephritis is a manifestation of a delayed type hypersensitivity (DTH)-like response to nephritogenic antigens. The elucidation of T helper 1 (Th1) and Th2 subsets in mice and in humans has led to the hypothesis that crescentic GN is a manifestation of a Th1 predominant DTH mediated immune response. Recent experiments performed mainly in a murine model of crescentic glomerulonephritis have tested this hypothesis. Crescent formation in this model is substantially interleukin (IL)-12 and interferon-gamma (IFN-gamma) dependent. Administration of IL-12, deletion of endogenous IL-4 or IL-10 results in enhanced disease, while administration of exogenous IL-4 and/or IL-10 reduces crescentic injury. These findings, together with the available evidence from human studies (examining the pattern of immune effectors in glomeruli, data on cytokine production by peripheral blood mononuclear cells and case reports of the induction of proliferative and/or crescentic GN by administration of IFN-gamma or IL-2) suggest that human crescentic GN is manifestation of a Th1 mediated DTH-like nephritogenic immune response.

B7.1 and B7.2 co-stimulatory molecules regulate crescentic glomerulonephritis

The contribution of B7.1 and B7.2 co-stimulation to Th1-directed, cell-mediated renal injury was studied in a murine model of crescentic glomerulonephritis (GN) initiated by a "planted" antigen. Mice treated with anti-B7.2 monoclonal antibody (mAb), starting prior to disease initiation, developed more severe renal injury with increased glomerular crescent formation (p = 0.031), glomerular accumulation of T cells (p = 0.014) and proteinuria (p = 0.022) compared to mice treated with control antibodies. Mice treated with anti-B7.1 mAb had reduced crescent formation (p = 0.019) compared to control treated mice, but reductions in glomerular CD4(+) T cell accumulation and proteinuria were not statistically significant. B7. 1 mAb treatment significantly reduced all parameters of renal injury (above) compared to anti-B7.2 mAb treatment. Neither treatment altered the circulating antibody titer or cutaneous delayed type hypersensitivity to the nephritogenic antigen. Antibody subclasses and antigen-stimulated ex vivo splenocyte IL-4, IL-10 and IFN-gamma production did not indicate effects on Th subset responses. Treatment with CTLA4-Fc or combined treatment with anti-B7.1 and B7. 2 antibodies did not significantly attenuate crescentic GN. These data indicate that B7.1 and B7.2 are important co-stimulatory molecules involved in crescentic GN, which have opposing effects on disease development without altering the T helper cell subset response to the nephritogenic antigen.

Protease-activated receptor 1 mediates thrombin-dependent, cell-mediated renal inflammation in crescentic glomerulonephritis

Protease-activated receptor (PAR)-1 is a cellular receptor for thrombin that is activated after proteolytic cleavage. The contribution of PAR-1 to inflammatory cell-mediated renal injury was assessed in murine crescentic glomerulonephritis (GN). A pivotal role for thrombin in this model was demonstrated by the capacity of hirudin, a selective thrombin antagonist, to attenuate renal injury. Compared with control treatment, hirudin significantly reduced glomerular crescent formation, T cell and macrophage infiltration, fibrin deposition, and elevated serum creatinine, which are prominent features of GN. PAR-1-deficient (PAR-1(-/-)) mice, which have normal coagulation, also showed significant protection from crescentic GN compared with wild-type mice. The reductions in crescent formation, inflammatory cell infiltration, and serum creatinine were similar in PAR-1(-/-) and hirudin-treated mice, but hirudin afforded significantly greater protection from fibrin deposition. Treatment of wild-type mice with a selective PAR-1-activating peptide (TRAP) augmented histological and functional indices of GN, but TRAP treatment did not alter the severity of GN in PAR(-/-) mice. These results indicate that activation of PAR-1 by thrombin or TRAP amplifies crescentic GN. Thus, in addition to its procoagulant role, thrombin has proinflammatory, PAR-1-dependent effects that augment inflammatory renal injury.

Interleukin-10 inhibits macrophage-induced glomerular injury

The ability of interleukin-10 (IL-10) to inhibit macrophage recruitment, activation, and proliferation in vivo was studied in a macrophage-mediated, but T cell-independent, passive anti-glomerular basement membrane antibody-induced model of glomerulonephritis (GN) in rats. Treatment with recombinant murine IL-10 resulted in dose-dependent reductions in proteinuria (high dose: 16 +/- 1 mg/24 h; low dose: 30 +/- 2 mg/24 h; control treatment: 69 +/- 6 mg/24 h; normal: 7 +/- 1 mg/24 h) and glomerular macrophage recruitment (high dose: 1.8 +/- 0.1 macrophages per glomerular cross section [c/gcs]; low dose: 5.5 +/- 0.2 c/gcs; control treatment: 12.1 +/- 0.6 c/gcs). Macrophage and intrinsic glomerular cell proliferation were reduced at both doses of IL-10, as was glomerular expression of P-selectin and monocyte chemoattractant protein-1. IL-10 treatment also resulted in a dose-dependent reduction of macrophage activation as indicated by MHC class II and IL-1beta expression. Glomerular nitrite production by isolated cultured glomeruli was reduced after IL-10 treatment in vivo (high dose: 2.3 +/- 2.3 nmol/10(4) glomeruli per 72 h; low dose: 28 +/- 5 nmol/10(4) glomeruli per 72 h; control treatment: 82 +/- 11 nmol/10(4) glomeruli per 72 h). Tumor necrosis factor-alpha production was abolished by high-dose treatment and reduced by the lower dose (3.8 +/- 3.8 pg/10(4) glomeruli per 72 h; control treatment: 249 +/- 23 pg/10(4) glomeruli per 72 h). These studies demonstrate that IL-10 directly attenuates glomerular macrophage recruitment, activation, and proliferation in vivo and can significantly attenuate macrophage-mediated GN independent of any effects on T cells.

Endogenous interleukin-10 regulates Th1 responses that induce crescentic glomerulonephritis

BACKGROUND

Interleukin (IL)-10 plays a pivotal role in regulating the Th1/Th2 predominance of immune responses. Exogenously administered IL-10 suppresses nephritogenic Th1 responses, inhibits macrophage function, and attenuates crescentic glomerulonephritis (GN). To determine the role of endogenous IL-10, the development of the nephritogenic immune response and crescentic GN was compared in IL-10-deficient (IL-10-/-) and normal (IL-10+/+) C57BL/6 mice.

METHODS

GN was initiated in sensitized mice by the intravenous administration of sheep antimouse glomerular basement membrane globulin. Renal injury was evaluated 21 days later.

RESULTS

Following the administration of anti-glomerular basement membrane globulin, normal (IL-10+/+) C57BL/6 mice developed proliferative GN with occasional crescents, glomerular CD4+ T-cell and macrophage accumulation, and fibrin deposition. Using an identical induction protocol, IL-10-/-mice developed more severe GN. Crescent formation (IL-10-/-, 23 +/- 2% of glomeruli; IL-10+/+, 5 +/- 2%), glomerular CD4+ T cells [IL-10-/-, 1. 0 +/- 0.2 cells per glomerular cross-section (c/gcs); IL-10 +/+, 0.3 +/- 0.05 c/gcs], glomerular macrophages (IL-10-/-, 4.8 +/- 0.3 c/gcs; IL-10 +/+, 1.7 +/- 0.2 c/gcs), fibrin deposition [fibrin score (range 0 to 3+); IL-10-/-, 1.10 +/- 0.04; IL-10+/+, 0.6 +/- 0. 07], and serum creatinine (IL-10-/-, 30 +/- 2 micromol/L; IL-10 +/+, 23 +/- 1 micromol/L) were all significantly increased in IL-10-/- mice (P < 0.05). Circulating antibody (IL-10-/-, 1.05 +/- 0.16 OD units; IL-10+/+, 0.63 +/- 0.08 OD units) and cutaneous delayed-type hypersensitivity (skin swelling; IL-10-/-, 0.21 +/- 0.03 mm; IL-10+/+, 0.12 +/- 0.02 mm) to the nephritogenic antigen (sheep globulin) were also increased (both P < 0.05). Interferon-gamma production by cultured splenocytes was increased (IL-10-/- 7.9 +/- 2. 5 ng/4 x 106 cells, IL-10+/+ 0.28 +/- 0.09 ng/4 x 106 cells, P < 0. 05), but IL-4 production was unchanged.

CONCLUSIONS

Endogenous IL-10 counter-regulates nephritogenic Th1 responses and attenuates crescentic GN.

Tissue factor and factor VIIa receptor/ligand interactions induce proinflammatory effects in macrophages

The potential for tissue factor (TF) to enhance inflammation by factor VIIa-dependent induction of proinflammatory changes in macrophages was explored. Purified recombinant human factor VIIa enhanced reactive oxygen species production by human monocyte-derived macrophages expressing TF in vitro. This effect was dose- and time-dependent, ligand- and receptor-specific, and independent of other coagulation proteins. This receptor/ligand binding induced phospholipase C-dependent intracellular calcium fluxes. Transfection studies using a human monocyte-derived cell line (U937) demonstrated that an intact intracytoplasmic domain of TF is required for factor VIIa-induced intracellular calcium fluxes. The capacity of TF to enhance proinflammatory functions of rabbit peritoneal-elicited macrophages (production of reactive oxygen species and expression of major histocompatibility complex class II and cell adhesion molecules) was demonstrated in vivo by treatment with an anti-TF antibody. These data demonstrate that, in addition to its role in activation of coagulation, TF can directly augment macrophage activation. These effects are initiated by binding factor VIIa and are independent of other coagulation proteins. These studies provide the first demonstration of a direct proinflammatory role for TF acting as a cell-signaling receptor.