Administration of IgG Fc fragments prevents glomerular injury in experimental immune complex nephritis

Sialylated Immunoglobulins for the Treatment of Immuno-Inflammatory Diseases

Immunoglobulins are the potent effector proteins of the humoral immune response. In the course of evolution, immunoglobulins have formed extremely diverse types of molecular structures with antigen-recognizing, antigen-binding, and effector functions embedded in a single molecule. Polysaccharide moiety of immunoglobulins plays the essential role in immunoglobulin functioning. There is growing evidence that the carbohydrate composition of immunoglobulin-linked glycans, and especially their terminal sialic acid residues, provide a key effect on the effector functions of immunoglobulins. Possibly, sialylation of Fc glycan is a common mechanism of IgG anti-inflammatory action in vivo. Thus, the post-translational modification (glycosylation) of immunoglobulins opens up significant possibilities in the diagnosis of both immunological and inflammatory disorders and in their therapies. This review is focused on the analysis of glycosylation of immunoglobulins, which can be a promising addition to improve existing strategies for the diagnosis and treatment of various immuno-inflammatory diseases.

Application of microphysiological systems in biopharmaceutical research and development

Within the last 10 years, several tissue microphysiological systems (MPS) have been developed and characterized for retention of morphologic characteristics and specific gene/protein expression profiles from their natural in vivo state. Once developed, their utility is typically further tested by comparing responses to known toxic small-molecule pharmaceuticals in efforts to develop strategies for further toxicity testing of compounds under development. More recently, application of this technology in biopharmaceutical (large molecules) development is beginning to be more appreciated. In this review, we describe some of the advances made for tissue-specific MPS and outline the advantages and challenges of applying and further developing MPS technology in preclinical biopharmaceutical research.

The effects of Salvia przewalskii total phenolic acid extract on immune complex glomerulonephritis

CONTEXT

Salvia przewalskii Maxim. (Lamiaceae) is a Chinese herbal medicine that has long been used for the treatment of cardiovascular disease.

OBJECTIVE

The study investigated the therapeutic efficacy of S. przewalskii total phenolic acid extract (SPE) on immune complex glomerulonephritis (ICG) in rats.

MATERIALS AND METHODS

Sixty-two Wistar rats were randomized into six groups. ICG was induced in all groups except normal control group. SPE was administered intragastrically at 24 h intervals for 40 consecutive days. Urine protein (UP), total serum protein (TSP), serum albumin (SA), serum cholesterol (SC) and serum urea nitrogen (SUN) were measured one day before, on day 20 and 40 after SPE administration. On day 40 after SPE administration, the kidneys were removed and prepared into pathologic sections. In addition, kidney wet mass was measured for calculating the kidney wet mass coefficient (KWMC).

RESULTS

UP excretion was reduced significantly on day 20 after SPE administration in all three SPE groups as compared with that in medium group, and this effect was observable continuously until 40 days after SPE administration. Compared with medium group, TSP and SA were increased in all three SPE groups after 40 days treatment, while SC and SUN were decreased. KWMC was decreased significantly in 100 mg/kg SPE group after 40 days treatment compared with that in medium group. Histopathologic analyses showed that renal inflammatory infiltration and kidney intumesce were alleviated in all three SPE groups.

CONCLUSIONS

SPE may be a potential therapeutic drug for glomerulonephritis.

Fc-gamma receptors: Attractive targets for autoimmune drug discovery searching for intelligent therapeutic designs

Autoantibody immune complexes (ICs) mediate pathogenesis in multiple autoimmune diseases via direct interference with target function, complement fixation, and interaction with Fc-gamma receptors (FcγRs). Through high avidity interactions, ICs are able to crosslink low affinity FcγRs expressed on a wide variety of effector cells, leading to secretion of pro-inflammatory mediators and inducing cytotoxicity, ultimately resulting in tissue injury. Given their relevance in numerous autoimmune diseases, FcγRs have been considered as attractive therapeutic targets for the last three decades. However, a limited number of investigational drug candidates have been developed targeting FcγRs and only a few approved therapeutics have been associated with impacting FcγRs. This review provides a historical overview of the different therapeutic approaches used to target FcγRs for the treatment of autoimmune and inflammatory diseases.

Recombinant human hepatocyte growth factor (HGF), but not rat HGF, elicits glomerular injury and albuminuria in normal rats via an immune complex-dependent mechanism

1. Hepatocyte growth factor (HGF) has the therapeutic potential to improve renal fibrosis and proteinuria in rodents with chronic kidney disease. In contrast, long-term administration of human HGF to normal rats reportedly elicits proteinuria. Thus, the role of HGF during proteinuria remains contentious. The aim of the present study was to demonstrate that human HGF is antigenic to rodents and that immune complex formation causes proteinuria. 2. We administered either human or rat HGF to normal rats for 28 days. Albuminuria was evaluated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The renal phenotypes of the two HGF treatments were examined using histological techniques. 3. Administration of human HGF (1 mg/kg per day, i.v.) to rats led to severe albuminuria and glomerular hypertrophy in association with increased blood levels of anti-human HGF IgG and IgG deposition in mesangial areas. Furthermore, an immune complex between human HGF and anti-human HGF IgG stimulated the production of proteinuric cytokines (including transforming growth factor-β) in rat cultured mesangial cells. In contrast, treatment of healthy rats with rat HGF for 4 weeks caused neither mesangial IgG deposition nor elevated anti-HGF IgG in the blood. Overall, rat HGF did not provoke albuminuria. 4. We conclude that human HGF produces pseudotoxic effects in normal rat kidneys via an immune complex-mediated pathway, whereas syngenic HGF is safe due to less deposition of glomerular IgG. Our results affirm the safety of the repeated use of syngenic HGF for the treatment of chronic organ diseases, such as renal fibrosis and liver cirrhosis.

Experimental poststreptococcal glomerulonephritis elicited by IgG Fc-binding M family proteins and blocked by IgG Fc fragment

The pathogenesis of acute poststreptococcal glomerulonephritis (APSGN), a major nonsuppurative complication of group A streptococcal (GAS) throat or skin disease, remains unclear. During the years, various theories based on certain streptococcal extracellular factors, as well as immunological mimicry between streptococci and renal tissue, have been forwarded. We earlier reported that many clinical GAS isolates with documented nephritogenic capacity show non-immune binding of monomeric or aggregated IgG. Moreover, in a rabbit model of APSGN we obtained evidence for an important role of streptococcal IgG Fc binding proteins (IgGFcBPs) belonging to the M family surface proteins; thus, hyperimmunization by whole IgGFcBP-positive streptococci was shown to induce renal glomerular changes with deposition of IgG and complement C3, resembling the picture recorded in human APSGN. These typical renal changes were always preceded by the appearance of circulating anti-IgG antibodies. In the present work, using the same rabbit model, each of two purified IgGFcBPs, isolated from type M22 GAS, were found to elicit glomerular degenerative damage comparable to that caused by whole bacteria, as well as formation of anti-IgG. In addition, the induction by whole streptococci (type M1) of experimental APSGN was inhibited by the i.v. administration of purified human or rabbit IgG Fc, but not Fab, fragment, supporting the importance of Fc-mediated mechanisms in causation of glomerulonephritis. We propose that anti-IgG antibody, induced by streptococcal IgGFcBP, facilitated renal accumulation of IgG-containing complexes, which in turn triggered complement deposition and proinflammatory cascades. Further studies on the possible beneficial effect of IgG Fc fragment in APSGN should be of interest.

Fcgamma receptor deficiency confers protection against atherosclerosis in apolipoprotein E knockout mice

IgG Fc receptors (FcgammaRs) play a role in activating the immune system and in maintaining peripheral tolerance, but their role in atherosclerosis is unknown. We generated double-knockout (DKO) mice by crossing apolipoprotein E-deficient mice (apoE(-/-)) with FcgammaR gamma chain-deficient mice (gamma(-/-)). The size of atherosclerotic lesions along the aorta was approximately 50% lower in DKO compared with apoE(-/-) control mice, without differences in serum lipid levels. The macrophage and T-cell content of lesions in the DKO were reduced by 49+/-6% and 56+/-8%, respectively, compared with the content in apoE(-/-) lesions. Furthermore, the expression of monocyte chemoattractant protein-1 (MCP-1), RANTES (Regulated on Activated Normal T-cell Expressed and Secreted), and intercellular adhesion molecule-1 (ICAM-1) and the activation of nuclear factor-kappaB (NF-kappaB) were significantly reduced in aortic lesions from DKO mice. In vitro, vascular smooth muscle cells (VSMCs) from both gamma(-/-) and DKO mice failed to respond to immune complexes, as shown by impaired chemokine expression and NF-kappaB activation. ApoE(-/-) mice have higher levels of activating FcgammaRI and FcgammaRIIIA, and inhibitory FcgammaRIIB, compared with wild-type mice. The DKO mice express only the inhibitory FcgammaRIIB receptor. We conclude that FcgammaR deficiency limits development and progression of atherosclerosis. In addition to leukocytes, FcgammaR activation in VSMCs contributes to the inflammatory process, in part, by regulating chemokine expression and leukocyte invasion of the vessel wall. These results underscore the critical role of FcgammaRs in atherogenesis and support the use of immunotherapy in the treatment of this disease.

The endogenous immune response modulates the course of IgA-immune complex mediated nephropathy

In animal models of IgA nephropathy, the inevitable endogenous immune response to passively administered antigens alone or in complex with specific IgA mask the exact role each might play in pathogenesis. To delineate the role the immune response might play, we have developed a passive model with exclusive IgA-immune complex-mediated nephropathy in B-cell-deficient (BCD) mice. Glomerular IgA immune deposits were induced by administration of purified IgA antiphosphorylcholine and the specific pneumococcal C-polysaccharide (PnC) antigen daily for 2 weeks into BCD and wild-type (WT) mice. In BCD mice IgA+PnC deposits induced severe glomerular injury and renal dysfunction. In contrast, WT mice developed intense glomerular IgG and IgM and C3 co-deposits of the IgA+PnC with significantly less renal injury. Cytofluorometric analysis revealed that PnC induced in BCD, but not in WT, a rapid and dramatic increase in number of activated CD3(+)/CD69(+) T-cell population. The nuclear factor-kappa B (NF-kappaB) transcription factor was activated early and progressively increased in response to glomerular IgA+PnC deposits. These results suggest that nephritogenic IgA+PnC immune deposits induce glomerular and renal dysfunction through activation of the NF-kappaB. This inflammatory pathway is modulated by the endogenous cellular and antibody response to the antigen affecting the course of IgA nephropathy progression.

Parthenolide modulates the NF-kappaB-mediated inflammatory responses in experimental atherosclerosis

OBJECTIVE

Activation of transcription factor NF-kappaB is an important step in the development of vascular damage, because it controls inducible genes, including many inflammatory mediators. The pharmacological modulation of this process is the main objective in the design of new therapies for atherosclerosis. In this work we analyzed the effects of the natural compound parthenolide (PTN), an NF-kappaB inhibitor.

METHODS AND RESULTS

In vascular smooth muscle cells (VSMCs) and monocytes stimulated with lipopolysaccharide (LPS), nontoxic doses of PTN reduced IkappaBalpha degradation, NF-kappaB activation, and MCP-1 expression, without inhibiting AP-1 and MAPK. In apoE mice, treatment with low (2 mg/kg, 20 weeks), medium (4 mg/kg, 10 weeks), and high (10 mg/kg, 10 weeks) dose of PTN reduced the size of aortic lesion, decreased macrophage, and increased VSMC content in the lesions. Treated mice showed reduced serum levels of MCP-1 and attenuated NF-kappaB activity, but not AP-1, in the lesions. Moreover, PTN affects neither apoptotic cell death nor oxidative stress in cultured cells and mice.

CONCLUSIONS

NF-kappaB inhibition by PTN retards atherosclerotic lesions in apoE mice, by reducing lesion size and changing plaque composition. This natural compound could represent a novel therapeutic approach to inflammation during vascular damage.

Accumulation of immune complexes in glomerular disease is independent of locally synthesized c3

Although complement activation can make immune complex glomerulonephritis worse, the third complement component also can solubilize immune complexes and thus reduce the severity of disease. How C3 that is produced within the kidney contributes to this balance is unknown. This study therefore investigated the relative roles of systemic and local C3 production in a model of glomerular immune complex disease. Injection of sheep anti-glomerular basement membrane antibody into preimmunized mice resulted in accumulation of immune complexes and progressive loss of function over 14 d that was much more marked in C3-deficient (C3-/-) mice. In C3-sufficient mice that received a transplant of a C3-/- mouse kidney and in C3-/- mice with C3-sufficient mouse kidney transplants, the severity and the pattern of injury went with the complement status of the recipient. That is, mice with deficient circulating C3 developed severe glomerular immune complex disease, whereas those with a high level of circulating C3 had well-preserved glomerular structure and function. It is concluded that circulating C3 is a critical factor in reducing the glomerular accumulation of immune complexes. Local synthesis of C3 did not have a major influence on this aspect of glomerular disease.

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

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

Suppressors of cytokine signaling regulate Fc receptor signaling and cell activation during immune renal injury

Suppressors of cytokine signaling (SOCS) are cytokine-inducible proteins that modulate receptor signaling via tyrosine kinase pathways. We investigate the role of SOCS in renal disease, analyzing whether SOCS regulate IgG receptor (FcgammaR) signal pathways. In experimental models of immune complex (IC) glomerulonephritis, the renal expression of SOCS family genes, mainly SOCS-3, significantly increased, in parallel with proteinuria and renal lesions, and the proteins were localized in glomeruli and tubulointerstitium. Induction of nephritis in mice with a deficiency in the FcgammaR gamma-chain (gamma(-/-) mice) resulted in a decrease in the renal expression of SOCS-3 and SOCS-1. Moreover, blockade of FcgammaR by Fc fragment administration in rats with ongoing nephritis selectively inhibited SOCS-3 and SOCS-1, without affecting cytokine-inducible Src homology 2-containing protein and SOCS-2. In cultured human mesangial cells (MC) and monocytes, IC caused a rapid and transient induction of SOCS-3 expression. Similar kinetics was observed for SOCS-1, whereas SOCS-2 expression was very low. MC from gamma(-/-) mice failed to respond to IC activation, confirming the participation of FcgammaR. Interestingly, IC induced tyrosine phosphorylation of SOCS-3 and Tec tyrosine kinase, and both proteins coprecipitated in lysates from IC-stimulated MC, suggesting intracellular association. IC also activated STAT pathway in MC, which was suppressed by SOCS overexpression, mainly SOCS-3. In SOCS-3 knockdown studies, specific antisense oligonucleotides inhibited mesangial SOCS-3 expression, leading to an increase in the IC-induced STAT activation. Our results indicate that SOCS may play a regulatory role in FcgammaR signaling, and implicate SOCS as important modulators of cell activation during renal inflammation.

Differential activation of NF-kappa B, AP-1, and C/EBP in endotoxin-tolerant rats: mechanisms for in vivo regulation of glomerular RANTES/CCL5 expression

Chemokines play a pivotal role in the regulation of inflammatory cell infiltration in glomerular immune injury. To characterize mechanisms relevant for the regulation of chemokine expression in vivo, the LPS-mediated model of renal inflammation in rats was used in which we have previously demonstrated that the chemokine RANTES/CCL5 is expressed and secreted in glomeruli. Glomerular RANTES/CCL5 expression in this model correlated with an increased glomerular binding activity of the transcription factors AP-1, C/EBP, and NF-kappaB. To gain further insight into the functional roles of these transcription factors in the regulation of glomerular RANTES/CCL5 expression, we cloned the rat RANTES/CCL5 promoter and established the model of in vivo LPS tolerance. In tolerant rats, LPS-induced glomerular RANTES/CCL5 expression and activation of the transcription factors AP-1 and C/EBP were significantly reduced using both consensus and rat RANTES/CCL5-specific oligonucleotides. Reduced glomerular NF-kappaB binding activity after LPS injection could be demonstrated in tolerant rats only when using rat RANTES/CCL5-specific oligonucleotides. Reduced binding activity to this RANTES/CCL5-specific NF-kappaB binding site in the context of broad NF-kappaB activation might be due to changes in transcription factor interactions or chromatin remodeling processes.

IgG Fc receptor polymorphisms in human disease: implications for intravenous immunoglobulin therapy

Polymorphisms of human Fc receptors (FcRs) have been described that are associated with the development or progression of autoimmune diseases. The FcR polymorphisms affect the affinity with which FcRs interact with immunoglobulin molecules. Intravenous immunoglobulin is administered as therapy for many autoimmune diseases and might exert its effects by interacting with FcRs. Thus, FcR polymorphisms might influence the efficacy of intravenous immunoglobulin therapy for patients with certain autoimmune diseases. In this article we review FcR polymorphisms in relation to autoimmune diseases for which intravenous immunoglobulin is used therapeutically.

Pre-existing glomerular immune complexes induce polymorphonuclear cell recruitment through an Fc receptor-dependent respiratory burst: potential role in the perpetuation of immune nephritis

In immune complex (IC) diseases, FcR are essential molecules facilitating polymorphonuclear cell (PMN) recruitment and effector functions at the IC site. Although FcR-dependent initial tethering and FcR/integrin-dependent PMN accumulation were postulated, their underlying mechanisms remain unclear. We here addressed potential mechanisms involved in PMN recruitment in acute IC glomerulonephritis (nephrotoxic nephritis). Since some renal cells may be recruited from bone marrow (BM) lineages, reconstitution studies with BM chimeras and PMN transfer between wild-type (WT) and FcR-deficient mice (gamma(-/-)) were performed. Severe glomerular damage was induced in WT and W gamma chimeras (BM from WT to irradiated gamma(-/-)), while it was absent in gamma(-/-) and gamma W chimeras (gamma(-/-) BM to WT). Moreover, WT PMN transfer, but not gamma(-/-) PMN, reconstituted the disease in gamma(-/-), indicating that FcR on resident cells is not a prerequisite for PMN recruitment in this disease. Surprisingly, transferred WT PMN were recruited coincidentally with NF-kappa B activation and TNF-alpha overexpression even in glomeruli with preformed IC (nephrotoxic Ab administered 3 days previously), suggesting that PMN can initially be recruited via its own FcR without previous chemoattractant release. Furthermore, H(2)O(2) inhibition by catalase attenuated the acute WT PMN recruitment and the induction of NF-kappa B and TNF-alpha much more than integrin (CD18) blockade, indicating a role for the respiratory burst before integrin-dependent accumulation. In coculture experiments with IC-stimulated PMN and glomeruli, PMN caused acute glomerular TNF-alpha expression predominantly via FcR-mediated H(2)O(2) production. In conclusion, glomerular IC, even preformed, can cause PMN recruitment and injury through PMN FcR-mediated respiratory burst during initial PMN tethering to IC.

Nitric oxide production in renal cells by immune complexes: Role of kinases and nuclear factor-kappaB

BACKGROUND

Interaction of deposited immune complexes (IC) with Fc receptors (FcR) on tissue cells elicits the release of inflammatory mediators leading to tissue damage. Nitric oxide (NO) radicals generated by inducible NO synthase (iNOS) are important mediators in inflammatory processes. To analyze the role of NO in IC-mediated glomerular inflammation, we studied the in vitro and in vivo expression of iNOS in renal cells [resident mesangial cells (MC), and infiltrating monocytes] induced by IC, and the possible intermediate steps between FcR occupancy and iNOS induction.

METHODS

MC and monocytes were stimulated with IgG- and IgA-containing IC, and NO production (nitrite accumulation), iNOS transcription (luciferase assay) and their expression was measured by RT-PCR and Western blot. The involvement of FcR, transcription factor nuclear factor-kappaB (NF-kappaB), and protein kinases was assessed by using Fc fragments and specific inhibitors. Immune glomerulonephritis was induced in rats, and iNOS expression and NF-kappaB activation were analyzed.

RESULTS

In MC and monocytes, IC enhanced iNOS transcription/expression and NO generation, which were attenuated by specific inhibitors of NF-kappaB. In addition, mitogen-activated protein kinase (MAPK) inhibitors decreased NO production, but did not interfere with NF-kappaB activity, suggesting that both pathways may converge downstream in the induction of iNOS. In experimental immune glomerulonephritis, increased iNOS expression correlated with proteinuria levels, and appeared colocalized with NF-kappaB in glomerular and infiltrating cells. Treatment of animals and cells with Fc fragments prevented iNOS induction and NF-kappaB activation by IC.

CONCLUSIONS

These results indicate that IC, through activation of FcR, induce iNOS expression in renal resident and recruited cells by mechanisms involving MAPK and NF-kappaB, and support the idea of the important role of local NO generation in IC-mediated glomerular injury.

Susceptibility to T cell-mediated injury in immune complex disease is linked to local activation of renin-angiotensin system: the role of NF-AT pathway

FcR provides a critical link between ligands and effector cells in immune complex diseases. Emerging evidence reveals that angiotensin (Ang)II exerts a wide variety of cellular effects and contributes to the pathogenesis of inflammatory diseases. In anti-glomerular basement membrane Ab-induced glomerulonephritis (GN), we have previously noted that FcR-deficient mice (gamma(-/-)) surviving from lethal initial damage still developed mesangial proliferative GN, which was drastically prevented by an AngII type 1 receptor (AT1) blocker. We further examined the mechanisms by which renin-Ang system (RAS) participates in this immune disease. Using bone marrow chimeras between gamma(-/-) and AT1(-/-) mice, we found that glomerular injury in gamma(-/-) mice was associated with CD4(+) T cell infiltration depending on renal AT1-stimulation. Based on findings in cutaneous delayed-type hypersensitivity, we showed that AngII-activated renal resident cells are responsible for the recruitment of effector T cells. We next examined the chemotactic activity of AngII-stimulated mesangial cells, as potential mechanisms coupling RAS and cellular immunity. Chemotactic activity for T cells and Th1-associated chemokine (IFN-gamma-inducible protein-10 and macrophage-inflammatory protein 1alpha) expression was markedly reduced in mesangial cells from AT1(-/-) mice. Moreover, this activity was mainly through calcineurin-dependent NF-AT. Although IFN-gamma-inducible protein-10 was NF-kappaB-dependent, macrophage-inflammatory protein 1alpha was dominantly regulated by NF-AT. Furthermore, AT1-dependent NF-AT activation was observed in injured glomeruli by Southwestern histochemistry. In conclusion, our data indicate that local RAS activation, partly via the local NF-AT pathway, enhances the susceptibility to T cell-mediated injury in anti-glomerular basement membrane Ab-induced GN. This novel mechanism affords a rationale for the use of drugs interfering with RAS in immune renal diseases.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Nuclear factor-kappa B inhibitors as potential novel anti-inflammatory agents for the treatment of immune glomerulonephritis

Nuclear factor (NF)-kappa B regulates several genes implicated in the inflammatory response and represents an interesting therapeutic target. We examined the effects of gliotoxin (a fungal metabolite) and parthenolide (a plant extract), which possess anti-inflammatory activities in vitro, on the progression of experimental glomerulonephritis. In the anti-Thy 1.1 rat model, gliotoxin (75 micro g/rat/day, 10 days, n = 18 rats) markedly reduced proteinuria, glomerular lesions, and monocyte infiltration. In anti-mesangial cell nephritis in mice, parthenolide (70 micro g/mouse/day, 7 days, n = 17 mice) significantly decreased proteinuria, hematuria, and glomerular proliferation. NF-kappa B activity, localized in glomerular and tubular cells, was attenuated by either gliotoxin or parthenolide, in association with diminished renal expression of monocyte chemoattractant protein-1 and inducible nitric oxide synthase. In cultured mesangial cells and monocytes, gliotoxin and parthenolide inhibited NF-kappa B activation and expression of inflammatory genes induced by lipopolysaccharide and cytokines, by blocking the phosphorylation/degradation of the I kappa B(alpha) subunit. In summary, gliotoxin and parthenolide prevent proteinuria and renal lesions by inhibiting NF-kappa B activation and expression of regulated genes. This may represent a novel approach for the treatment of immune and inflammatory renal diseases.

Antibody-mediated immune enhancement in coxsackievirus B3 myocarditis

The aim of the present study was to explore the contribution of antibody-mediated immune enhancement in coxsackievirus B3(CB3) infection. Murine macrophage-like P388D1 cells were exposed to various concentrations of anti-CB3 immunoglobulin G (anti-CB3 IgG) or the Fab fragment of anti-CB3 IgG, and were infected with CB3 in Experiment I. High concentrations of anti-CB3 IgG showed a virus-neutralizing activity; however, a subneutralizing antibody concentration of IgG significantly enhanced virus replication. This infectious enhancement was blocked not only by the pretreatment of heat-aggregated gamma-globulin but by a specific Fc receptor (Fc gamma III/II receptor) antibody treatment. In contrast, the Fab fragment of anti-CB3 IgG did not enhance CB3 infection, but showed a rational neutralizing activity to CB3. These findings suggest the presence of Fc receptor mediated enhancement of CB3 infection in vitro. In Experiment II, C(3)H/He mice were inoculated with various amounts of an amyocarditic variant of CB3 followed 15 days later by myocarditic CB3. By this rechallenge, myocarditis was not induced in the mice with high neutralizing antibody titers. There was an inverse relationship between preexisting neutralizing antibody titers and the severity of myocarditis. The severity of myocarditis and myocardial CB3 titers, however, were markedly enhanced in the mice with a subneutralizing level of immunity compared to those with no immunity. The distribution of myocardial Fc receptor-bearing cells and serum macrophage inflammatory protein-2 levels paralleled the severity of myocarditis. By another virus rechallenge in Experiment III, enhanced infection of CB3 was not observed in vivo. These findings suggest that antibody-mediated immune enhancement might be involved in the pathogenesis of CB3 myocarditis.

Apolipoprotein J/clusterin prevents a progressive glomerulopathy of aging

Apoliprotein J (apoJ)/clusterin has attracted considerable interest based on its inducibility in multiple injury processes and accumulation at sites of remodeling, regression, and degeneration. We therefore sought to investigate apoJ/clusterin's role in kidney aging, as this may reveal the accumulated effects of diminished protection. Aging mice deficient in apoJ/clusterin developed a progressive glomerulopathy characterized by the deposition of immune complexes in the mesangium. Up to 75% of glomeruli in apoJ/clusterin-deficient mice exhibited moderate to severe mesangial lesions by 21 months of age. Wild-type and hemizygous mice exhibited little or no glomerular pathology. In the apoJ/clusterin-deficient mice, immune complexes of immunoglobulin G (IgG), IgM, IgA, and in some cases C1q, C3, and C9 were detectable as early as 4 weeks of age. Electron microscopy revealed the accumulation of electron-dense material in the mesangial matrix and age-dependent formation of intramesangial tubulo-fibrillary structures. Even the most extensively damaged glomeruli showed no evidence of inflammation or necrosis. In young apoJ/clusterin-deficient animals, the development of immune complex lesions was accelerated by unilateral nephrectomy-induced hyperfiltration. Injected immune complexes localized to the mesangium of apoJ/clusterin-deficient but not wild-type mice. These results establish a protective role of apoJ/clusterin against chronic glomerular kidney disease and support the hypothesis that apoJ/clusterin modifies immune complex metabolism and disposal.

Atorvastatin reduces the expression of cyclooxygenase-2 in a rabbit model of atherosclerosis and in cultured vascular smooth muscle cells

Inflammation is involved in the genesis and rupture of atherosclerotic plaques. We assessed the effect of atorvastatin (ATV) on the expression of cyclooxygenase-2 (COX-2) and other proinflammatory molecules in a rabbit model of atherosclerosis. Fourteen animals underwent injury of femoral arteries and 2 weeks of atherogenic diet. Afterwards, they were randomized to receive either 5 mg/kg per day of ATV (n=8) or no treatment (NT, n=6) during 4 weeks, and were finally killed. ATV reduced lipid levels, neointimal size (0.13 (0.03-0.29) mm(2) vs 0.65 (0.14-1.81) mm(2), P=0.005) and the percentage of neointimal area positive for macrophages (1% (0-3) vs 19% (5-32), P=0.001), COX-2 (32% (23-39) vs 60% (37-81) P=0.019), interleukin-8 (IL-8) (23% (3-63) vs 63% (25-88) P=0.015), and metalloproteinase-3 (19% (12-34) vs 42% (27-93), P=0.010), without significant differences in COX-1 expression (immunohistochemistry). In situ hybridization confirmed a decreased expression of COX-2 mRNA (22% (5-40) vs 43% (34-59) P=0.038). The activity of nuclear factor-kappaB, which controls many proinflammatory genes including COX-2, was reduced in atherosclerotic lesions (3538 (2663-5094) vs 8696 (5429-11312)) positive nuclei per mm(2), P=0.001) and circulating mononuclear cells (2966 vs 17130 arbitrary units). In cultured vascular smooth muscle cells, ATV reduced the expression of COX-2 mRNA induced by IL-1beta and TNF-alpha without affecting COX-1 expression. In conclusion, ATV, besides decreasing a number of inflammatory mediators in the atherosclerotic lesion, significantly downregulates COX-2 both in vivo and in vitro. These anti-inflammatory actions could partially account for the reduction of acute coronary events achieved by statins.

Serine 132 is the C3 covalent attachment point on the CH1 domain of human IgG1

The covalent binding of C3 (complement component C3) to antigen-antibody complexes (Ag.Ab; immune complexes (ICs)) is a key event in the uptake, transport, presentation, and elimination of Ag in the form of Ag.Ab.C3b (IC.C3b). Upon interaction of C3 with IgG.IC, C3b.C3b.IgG covalent complexes are formed that are detected on SDS-polyacrylamide gel electrophoresis by two bands corresponding to C3b.C3b (band A) and C3b.IgG (band B) covalent complexes. This allows one to evaluate the covalent binding of C3b to IgG antibodies. It has been described that C3b can attach to both the Fab (on the CH1 domain) and the Fc regions of IgG. Here the covalent interaction of C3b to the CH1 domain, a region previously described spanning residues 125-147, has been studied. This region of the CH1 domain is exposed to solvent and contains a cluster of six potential acceptor sites for ester bond formation with C3b (four Ser and two Thr). A set of 10 mutant Abs were generated with the putative acceptor residues substituted by Ala, and we studied their covalent interaction with C3b. Single (Ser-131, Ser-132, Ser-134, Thr-135, Ser-136, and Thr-139), double (positions 131-132), and multiple (positions 134-135-136, 131-132-134-135-136, and 131-132-134-135-136-139) mutants were produced. None of the mutants (single, double, or multiple) abolished completely the ability of IgG to bind C3b, indicating the presence of C3b binding regions other than in the CH1 domain. However, all mutant Abs, in which serine at position 132 was replaced by Ala, showed a significant decrease in the ability to form C3b.IgG covalent complexes, whereas the remaining mutants had normal activity. In addition we examined ICs using the F(ab')2 fragment of the mutant Abs, and only those containing Ala at position 132 (instead of Ser) failed to bind C3b. Thus Ser-132 is the binding site for C3b on the CH1 domain of the heavy chain, in the Fab region of human IgG.

Chemokine expression precedes inflammatory cell infiltration and chemokine receptor and cytokine expression during the initiation of murine lupus nephritis

Lupus nephritis is characterized by immune complex deposition and inflammatory cell infiltration. Therefore, the initiation and progression of lupus nephritis in MRL/MpJ Fas(lpr/lpr) (MRL/lpr) mice were investigated, with a focus on the expression of several chemokines and chemokine receptors. Mice were monitored for proteinuria from 6 to 20 wk of age, and kidneys were examined every 2 wk by light microscopy, electron microscopy, and immunohistologic analyses. Furthermore, the expression of chemokines, chemokine receptors, and proinflammatory cytokines was analyzed in ribonuclease protection assays. MRL/lpr mice demonstrated increased expression of monocyte chemoattractant protein-1, regulated upon activation, normal T cell-expressed and -secreted protein, inducible protein of 10 kD, and macrophage inflammatory protein-1beta at week 8. At that time point, levels of circulating and glomerular immune complexes were increased, and no proteinuria or histopathologic signs of renal damage could be observed. As assessed in immunohistochemical and in situ hybridization analyses, monocyte chemoattractant protein-1 and regulated upon activation, normal T cell-expressed and -secreted protein expression was preferentially located in the glomeruli and interstitium. Mononuclear cell infiltration of the kidney was observed by weeks 10 to 12. At week 12, the renal expression of chemokine receptor 1 (CCR1), CCR2, and CCR5 was increased, mice became proteinuric, and renal damage was histologically evident. Finally, the expression of proinflammatory cytokines was detected (weeks 12 to 14). In summary, (1) chemokines are upregulated before inflammatory cell infiltration, proteinuria, and kidney damage are observed; (2) chemokine generation is restricted to sites of subsequent inflammatory cell infiltration, i.e., glomeruli and interstitium; (3) chemokine receptor expression parallels mononuclear cell infiltration; and (4) proinflammatory cytokines are upregulated later, in parallel with inflammatory cell infiltration and the onset of proteinuria. These results support the hypothesis that chemokines initiate leukocyte infiltration and precede proteinuria and renal damage in MRL/lpr mice.

Design and expression of polymeric immunoglobulin fusion proteins: a strategy for targeting low-affinity Fcgamma receptors

We have developed a family of cloning vectors that direct expression of fusion proteins that mimic aggregated immunoglobulin (IgG) (AIG) and immune complex function with respect to their interactions with FcgammaR and that allow for the inclusion and targeting of a second protein domain to cells expressing FcgammaR. This was accomplished by expressing multiple linear copies of the hinge and CH2 domains (HCH2) of human IgG(1) fused to the framework region of human IgG(1). Convenient restriction sites allow for the facile introduction of additional amino-terminal domains. The resulting molecule is tripartite. The carboxyl-IgG(1) framework domain provides stability and permits dimerization, and the intervening polymer provides increased effector function and targeting to FcgammaR while the amino-terminal domain can deliver an additional signal to cells expressing FcgammaR. To demonstrate the utility of the vectors, the extracellular domain of human CD8alpha was expressed as a HCH2 polymer fusion protein. The fusion proteins were secreted in useful amounts from polyclonal cell lines established in Sf9 cells following transfection and selection with G418. The biological activity of the recombinant CD8alpha-HCH2 polymers was determined and compared to those of AIG and an anti-CD16 monoclonal antibody using an in vitro assay. The activity of the fusion proteins positively correlates to the number of HCH2 units. The largest polymer tested was severalfold more potent than AIG at similar concentrations. The HCH2 polymers described here represent a new strategy in the design of recombinant proteins for the therapeutic targeting of FcgammaR in autoimmune disorders.

Tumor cells express FcgammaRI which contributes to tumor cell growth and a metastatic phenotype

High levels of circulating immune complexes containing tumor-associated antigens are associated with a poor prognosis for individuals with cancer. The ability of B cells, previously exposed to tumor-associated antigens, to promote both in vitro and in vivo tumor growth formed the rationale to evaluate the mechanism by which immune complexes may promote tumor growth. In elucidating this mechanism, FcgammaRI expression by tumor cells was characterized by flow cytometry, polymerase chain reaction, and sequence analysis. Immune complexes containing shed tumor antigen and anti-shed tumor antigen Ab cross-linked FcgammaRI-expressing tumor cells, which resulted in an induction of tumor cell proliferation and of shed tumor antigen production. Use of selective tyrosine kinase inhibitors demonstrated that tumor cell proliferation induced by immune complex cross-linking of FcgammaRI is dependent on the tyrosine kinase signal transduction pathway. A selective inhibitor of phosphatidylinositol-3 kinase also inhibited this induction of tumor cell proliferation. These findings support a role for immune complexes and FcgammaRI expression by tumor cells in augmentation of tumor growth and a metastatic phenotype.

Transcription factor-kappa B (NF-kappa B) and renal disease

Transcription factor-kappa B (NF-kappa B) and renal disease. Nuclear factor-kappa B (NF-kappa B) comprises a family of dimeric transcription factors that regulate the expression of numerous genes involved in inflammation and cell proliferation. Although NF-kappa B was initially identified in lymphocytes, it has been found to be a transcription factor present in virtually all cell types. In resting cells, NF-kappa B dimers remain in the cytoplasm in an inactive form bound to the inhibitory subunit I kappa B. Upon stimulation, I kappa B is phosphorylated, ubiquitinylated, and ultimately degraded by proteolytic cleavage by the proteasome system. As a result, NF-kappa B dimers are translocated into the nucleus and activate the transcription of target genes. Increasing data suggest a pivotal role for NF-kappa B in a variety of pathophysiological conditions in which either inflammation or cell number control are critical events. NF-kappa B has been found to be activated in experimental renal disease. Importantly, both in vivo and in vitro, NF-kappa B activation can be modulated by pharmacological maneuvers. Indeed, it is now widely acknowledged that the anti-inflammatory action of steroids is basically obtained through the inhibition of the transactivation of NF-kappa B-dependent genes. In addition, some of the beneficial effects of angiotensin-converting enzyme inhibitors and statins may, at least in part, be mediated by an inhibition of NF-kappa B activation. A better understanding of the mechanisms involved in NF-kappa B regulation and its modulation may provide new tools to improve the treatment of renal diseases with a better sound pathophysiological approach.

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.