Role In Lupus Nephritis Research Articles

Immunoadsorbent apheresis eliminates pathogenic IgG in childhood lupus nephritis

It is suggested that the highly cation-charged fraction of the IgG and IgG3 subclasses may play a pathogenic role in lupus nephritis. In contrast, immunoadsorbent therapy using a sodium dextransulfate fixed cellulose gel column-low invasive selective immunoadsorbent apheresis therapy (SDSC-IAT) has been applied to lupus nephritis with favorable results. However, elimination using pathogenic IgG by SDSC-IAT has never been investigated. Two patients with diffuse proliferative lupus nephritis were treated using SDSC-IAT concomitant with immunosuppressive therapy. The eluates from the SDSC, and the patients' serum obtained before and just after SDSC-IAT were subjected to an IgG charge analysis using isoelectric focusing and immunoblotting, and also to laser nephelometry assay, which is used for measuring IgG subclass concentration. Indirect immunofluorescence staining was performed to detect IgG subclass deposition in the glomerulus. Both of the patients had an immediate decrease in anti-double-strand DNA antibody and in the circulating immune complex with a following clinical improvement. Repeated biopsies demonstrated improvement of glomerular lesions with a marked reduction of IgG and C3 deposition. The IgG of the SDSC eluates consisted of highly cation charged (isoelectric points: 9-10) fractions. In addition, IgG3 was specifically removed from the patients' serum using an SDSC among the IgG subclasses. The subclass of deposited IgG in the glomeruli showed IgG3 predominance. SDSC-IAT specifically removed the highly cation charged fractions of IgG and IgG3 from the patients' serum and the elimination of these fractions may have resulted in clinical improvement.

Chemokines and Chemokine Receptors as Therapeutic Targets in Lupus Nephritis

Recruitment of leukocytes is a characteristic feature of tissue injury in systemic lupus erythematosus, including lupus nephritis. Locally secreted chemokines and their receptors are important mediators of leukocyte recruitment to the specific sites of immune complex injury, and contribute to renal inflammatory disease in the initiation and progression phase. Therefore, chemokines and chemokine receptors represent potential therapeutic targets in lupus nephritis. In this review we summarize available experimental and human data supporting their functional role in lupus nephritis. Moreover, interventional studies with chemokine and chemokine receptor antagonists that show the therapeutic potential of chemokine antagonists in experimental models of lupus nephritis and potentially in human renal disease are discussed.

Role of abetimus in systemic lupus erythematosus

Anti-DNA antibodies and the B cells that produce them play a major pathogenic role in lupus nephritis. Although current immunosuppressive therapy suppresses autoantibody production and B-cell activity, it is often associated with severe side effects. Abetimus, a soluble, synthetic, double-stranded (ds)DNA tetramer, was developed to bind to circulating DNA antibodies and membrane-bound anti-DNA antibodies on B cells, with the goal of removing circulating pathogenic antibodies and inducing B-cell tolerance. Two large clinical trials with this agent have shown promising results in reducing lupus nephritis flares, especially in patients with high affinity anti-dsDNA antibodies. Nevertheless, although safe and well tolerated, the second trial did not reproduce the desired, statistically significant end point. This was probably due to the trial design and, therefore, given its potential efficacy and safety profile, it seems that once dosing is optimized and the responsive patient population is defined, abetimus...

Signaling through Up-Regulated C3a Receptor Is Key to the Development of Experimental Lupus Nephritis

Signaling of the C3a anaphylatoxin through its G protein-coupled receptor, C3aR, is relevant in a variety of inflammatory diseases, but its role in lupus nephritis is undefined. In this study, we show that expression of C3aR was significantly increased in prediseased and diseased kidneys of MRL/lpr lupus mice compared with MRL/+ controls. To investigate the role of C3aR in experimental lupus, a small molecule antagonist of C3aR (C3aRa) was administered continuously to MRL/lpr mice from 13 to 19 wk of age. All 13 C3aRa-treated mice survived during the 6-wk treatment compared with 9 of 14 (64.3%) control animals given vehicle (p = 0.019). Relative to controls, C3aRa-treated animals were protected from renal disease as measured by albuminuria (p = 0.040) and blood urea nitrogen (p = 0.021). In addition, there were fewer neutrophils, monocytes, and apoptotic cells in the kidneys of C3aRa-treated mice. C3aRa treatment also led to reduced renal IL-1beta and RANTES mRNA and phosphorylated phosphatase and tensin homologue deleted on chromosome 10 protein, whereas the mass of phosphorylated protein kinase B/Akt was increased by C3aRa. Thus, C3aR antagonism significantly reduces renal disease in MRL/lpr mice, which further translates into prolonged survival. These data illustrate that C3aR is relevant in experimental lupus nephritis and may be a target for therapeutic intervention in the human disease.

Enrichment of anti-glomerular antigen antibody-producing cells in the kidneys of MRL/MpJ-Fas(lpr) mice.

Lupus nephritis is characterized by immune complex deposition and infiltration of inflammatory cells into the kidney including Ab-producing cells (AbPCs). Although AbPCs play a central role in the pathogenesis of immune complex glomerulonephritis in lupus, the specificity and pathogenic role of AbPCs infiltrating into the kidneys in lupus are poorly understood. To characterize AbPCs present in lupus kidneys, we isolated AbPCs from diseased MRL/MpJ-Faslpr (MRL/lpr) mouse kidneys. ELISPOT assays, using glomerular Ag (GA) extracts as Ag, demonstrated significant enhancement of anti-GA AbPCs in the kidneys as compared in peripheral blood or spleen of the same mouse. We isolated hybridomas with anti-GA specificity from MRL/lpr mouse kidneys. All the anti-GA mAbs had polyreactive binding to ssDNA, dsDNA, and IgG (i.e., rheumatoid factor), but not to histones or Sm. Sequence analysis of anti-GA Abs suggested the occurrence of somatic mutations and amino acid replacement in complementarity-determining regions with a high replacement to silent ratio resulting in charged amino acids. Intravenous administration of the monoclonal anti-GA Abs into BALB/c mice resulted in graded deposition in glomeruli paralleling their ELISA anti-GA reactivity. These results suggest that AbPCs infiltrating the kidneys in MRL/lpr mice accumulate as a result of Ag selection and likely play a pathologic role in lupus nephritis.

Alpha-actinin is a cross-reactive renal target for pathogenic anti-DNA antibodies.

Anti-DNA Abs commonly found in patients with systemic lupus erythematosus are thought to play an important pathogenic role in lupus nephritis. Anti-DNA Abs may contribute to renal disease by cross-reactivity with renal Ags, the identity of which remain elusive. To identify a target Ag for pathogenic anti-DNA Abs, we performed Western blotting and immunoprecipitations of mesangial cell lysates from the lupus-prone MRL-lpr/lpr mouse and a nonautoimmune BALB/c mouse with the pathogenic anti-DNA Ab R4A. We found that R4A (but not a nonpathogenic Ab mutant of R4A) binds to and immunoprecipitates a 100-kDa protein expressed on the cell surface and in lysates of MRL-lpr/lpr mesangial cells. DNase treatment of the lysate and of the R4A Ab did not effect binding, indicating that the binding of R4A to the 100-kDa protein was direct and not mediated by an antigenic bridge containing DNA. Binding was greatly diminished in BALB/c lysates, suggesting that Ag expression or availability at the level of the target organ may be a factor in determining susceptibility to lupus nephritis. Following identification of this 100-kDa protein as nonmuscle alpha-actinin, binding of R4A to alpha-actinin was confirmed by Western blot, ELISA, inhibition studies, and immunofluorescence. High titers of anti-alpha-actinin Abs were present in sera and kidney eluates of lupus mice with active nephritis. These results indicate that the nephritogenicity of some anti-DNA Abs may be mediated via cross-reactivity with alpha-actinin. Furthermore, variations in target Ag display between individuals may underlie differential susceptibility to anti-DNA Ab-induced renal disease.

Mycophenolic acid inhibits inosine 5 ′-monophosphate dehydrogenase and suppresses production of pro-inflammatory cytokines, nitric oxide, and LDH in macrophages

Mycophenolic acid (MPA) inhibits reversibly inosine 5 ′-monophosphate dehydrogenase, an enzyme involved in the de novo synthesis of guanine nucleotides. Previously, mycophenolate mofetil (MMF), the pro-drug of MPA, was shown to exert beneficial effects on the systemic lupus erythematosus (SLE)-like disease in MRL lpr/ lpr mice. In this study MPA’s immunomodulating effects in vitro on the murine macrophage cell line IC-21 were investigated. The cells were exposed to MPA together with lipopolysaccharide and IFN-γ. Cytokine, NO 2 −, and lactate dehydrogenase levels in supernatants and cell lysates were analysed as well as the proliferation of IC-21 cells. MPA exposure reduced the total levels of all molecules investigated and suppressed the proliferation. All MPA-induced effects were reversed by the addition of guanosine to the cultures. Since macrophages play a role in lupus nephritis, our results indicate that modulation of macrophages may be involved in the ameliorating effects of MMF in SLE.

Nonstandard and adjunctive medical therapies for systemic lupus erythematosus

Nonstandard and adjunctive medical therapies for systemic lupus erythematosus

Role of Reactive Oxygen Species and NFKB p65 in the Lupus Kidney

Abstract Reactive oxygen species (ROS) play an important role in lupus nephritis. It has been known that nuclear factor kB(NFkB) is activated by ROS, and binds to KB element in nucleus. Afterwards, inflammatory cytokines are translated and produced in lymphocytes, macrophages and glomerular cells in the kidney. In this study, we investigated the role of ROS and NFkB p65 in the pathogenesis of lupus nephritis (MRL lpr/lpr mice) by the histochemical and immuno-electron microscopic methods. A modified Brigg’s method was used to determine the generation of H2O2 in the renal tissue of lupus mice. Tissue samples were incubate in 0.1 MTris maleate buffer (pH 7.4) with 7% sucrose, 1mM CeCl3 and 10 mM aminotriazole at 37 °C for 30 min. After completion of the cytochemical reaction, tissues were fixed in 2% w/v glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) at 4 °C for 60 min.

A novel treatment for lupus nephritis: lignan precursor derived from flax.

Flaxseed has renoprotective effects in animal and human lupus nephritis. We have recently extracted the lignan precursor (secoisolariresinol diglucoside) (SDG) to determine if this more palatable derivative of flaxseed would exert renoprotection similar to the whole flaxseed in the aggressive MRL/lpr lupus mouse model. 131 MRL/lpr mice were randomly assigned to saline gavage, 600, 1,200 and 4,800 microg lignan gavage groups. At 7 weeks, 6 animals underwent platelet aggregating factor (PAF) lethal challenge and 40 were studied with urine collection to determine the levels of secoisolariresinol, enterodiol and enterolactone in the gavaged animals. A baseline study of 10 saline gavaged animals took place at 6 weeks. 25 animals in the saline gavage, 600 and 1200 microg lignan groups were studied at 14 and 22 weeks for GFR, spleen lymphocyte S-phase and organ weight studies. Metabolic studies indicated that secoisolariresinol is the major metabolite absorbed and the lowest lignan dose provides a lengthening in survival for the PAF lethal challenge. Body weight, fluid and water intake studies demonstrated that the lignan was well tolerated. Changes in proteinuria, GFR and renal size showed a time- and dose-dependent protection for the lignan precursor. Cervical lymph node size and spleen lymphocyte cells in the S-phase demonstrated modest dose-dependent reductions in the lignan gavaged groups. SDG was converted in the gut to secoisolariresinol, which was absorbed and well tolerated by the MRL/lpr mice. Renoprotection was evidenced, in a dose-dependent fashion, by a significant delay in the onset of proteinuria with preservation in GFR and renal size. This study suggests that SDG may have a therapeutic role in lupus nephritis.

Autoimmunity to histones, ubiquitin, and ubiquitinated histone H2A in NZB×NZW and MRL-lpr/lpr mice. Anti-histone antibodies are concentrated in glomerular eluates of lupus mice

In lupus diseases products of chromatin catabolism released from dead cells might be involved in the induction of autoantibody and in the development of glomerulonephritis. While the pathogenic role of anti-DNA antibodies is recognized, the role of antibodies directed against structural proteins of chromatin is still questioned. IgG antibodies to histones, ubiquitin, and ubiquitinated histone H2A (UH2A) have been investigated both in plasma and in glomerular eluates of NZB x NZW and MRL-lpr/lpr mice. In NZB x NZW mice, anti-ubiquitin and anti-UH2A antibodies were detected at 8 weeks of age, simultaneously with anti-double-stranded DNA antibodies, whereas anti-histone antibodies appeared later. In MRL-lpr/lpr mice, anti-DNA antibodies were detected at 4 weeks, whereas anti-histone, anti-ubiquitin, and anti-UH2A antibodies were not detected at that age but appeared in plasma rapidly thereafter. In both strains, increased anti-histone activity was found in IgG eluted from glomeruli. These results support the suggestion that anti-histone antibodies are likely to play a pathogenic role in lupus nephritis. They also indicate that, like human lupus, murine lupus is characterized by the production of anti-ubiquitin and anti-UH2A antibodies.