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.