Glomerular matrix metalloproteinases and their regulators in the pathogenesis of lupus nephritis

The Inflammatory Profile Orchestrated by Inducible Nitric Oxide Synthase in Systemic Lupus Erythematosus

(1) Background: The pathogenesis of systemic lupus erythematosus (SLE) involves complicated and multifactorial interactions. Inducible nitric oxide synthase overactivation (iNOS or NOS2) could be involved in SLE pathogenesis and progression. This study explored the relationship between NOS2-associated inflammation profiles and SLE phenotypes. (2) Methods: We developed a prospective, case control study that included a group of 86 SLE subjects, a group of 73 subjects with lupus nephritis, and a control group of 60 people. Laboratory determinations included serum C reactive protein (CRP-mg/L), enzymatic activity of NOS2 (U/L), serum levels of inducible factors of hypoxia 1 and 2 (HIF1a-ng/mL, HIF2a-ng/mL), vascular endothelial growth factor VEGF (pg/mL), matrix metalloproteinases 2 and 9 (MMP-2, MMP-9-ng/mL), thrombospondin 1 (TSP-1-ng/mL), and soluble receptor of VEGF (sVEGFR-ng/mL). (3) Results: CRP, NOS2, HIF-1a, HIF-2a, VEGF, MMP-2, and MMP-9 were significantly increased, while TSP-1 and sVEGFR were decreased in the SLE and lupus nephritis groups compared with the control group. The variations in these biomarkers were strongly associated with the decrease in eGFR and increase in albuminuria. (4) Conclusions: The inflammatory phenotype of SLE patients, with or without LN, is defined by NOS2 and hypoxia over-expression, angiogenesis stimulation, and inactivation of factors that induce resolution of inflammation in relation with eGFR decline.

Dysbiosis in Peripheral Blood Mononuclear Cell Virome Associated With Systemic Lupus Erythematosus

Objective: Pathogen infection plays a role in the development and progression of systemic lupus erythematosus (SLE). Previous studies showed that peripheral blood mononuclear cells (PBMCs) harbor many viral communities. However, little is known about the viral components and the expression profiles of SLE-associated virome. We aimed to identify viral taxonomic markers of SLE that might be used in the detection of disease or in predicting its outcome.

Methods: Non-human sequence data from high-throughput transcriptome sequencing of PBMC samples from 10 SLE patients and 10 healthy individuals were used for taxonomic alignment against an integrated virome reference genome database. Based on abundance profiles of SLE-associated virome species, genera, or host, Random Forests model was used to identify the viruses associated with SLE diagnostic markers. Spearman's correlation and functional clustering was used to analyze the interaction of candidate virome dysbiosis and SLE-associated differentially expressed genes.

Results: A total of 419 viruses (38 human associated viruses, 350 phage, and 31 other viruses) was detected and the diversity of the PBMC virome was significantly increased in patients with SLE compared to the healthy controls (HCs). Viral taxa discriminated the cases from the controls, with an area under the receiver operating characteristic curve of 0.883, 0.695, and 0.540 for species, genus, and host, respectively. Clinical subgroup analysis showed that candidate PBMC viral markers were associated with stable- and active-stage SLE. Functional analyses showed that virome dysbiosis was mainly relevant to cellular and metabolic processes.

Conclusion: We identified virome signatures associated with SLE, which might help develop tools to identify SLE patients or predict the disease stage.

Transcriptomics analysis of sirolimus treatment in lupus nephritis

Lupus nephritis (LN) is one of the principal causes of mortality and disability in patients with systemic lupus erythematosus. Sirolimus has been used to treat patients with LN; however, the effects and mechanism of sirolimus in these patients remains unclear. The present study aimed to elucidate the therapeutic effects and mechanisms of sirolimus in LN mice using low, medium and high doses of sirolimus (0.1, 0.3 and 1 mg/kg, respectively). The survival probability and kidney index were calculated, and renal fibrosis was determined using Masson's Trichrome staining. The expression levels of E-cadherin, α-smooth muscle actin (α-SMA) and vimentin were assessed via immunofluorescence analysis. Transcriptome analysis of control and sirolimus-treated LN mice was performed using RNA-sequencing, differentially expressed gene (DEG) identification and annotation, and Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. The results suggested that a medium dose of sirolimus alleviated renal fibrosis and increased the survival rates of mice with LN (P<0.05). Furthermore, transcriptome analysis revealed 334 DEGs associated with LN, 176 of which were upregulated and 158 were downregulated. Following GO functional enrichment, ‘biological process’, ‘molecular function’ and ‘cellular component’ terms were identified. A total of 10 KEGG pathways were enriched, with ‘cytokine-cytokine receptor interaction’ and ‘interleukin-17 signaling pathway’ being significantly enriched (P<0.05). To the best of our knowledge, the present study is the first to conduct transcriptome analysis of LN mice treated with sirolimus, and demonstrated that a dose of 0.3 mg/kg exerted the greatest therapeutic effects.

[Upcoming value of gene expression analysis in rheumatology]

Rheumatoid arthritis (RA) is a chronic inflammatory disease of unknown etiology, which involves disturbance in immune system signaling pathway functions, damage of other tissues, pain and joint destruction. Modern treatment attempts to improve pathophysiological and biochemical mechanisms damaged by the disease. However, due to the RA patient heterogeneity personalized approach to treatment is required; the choice of personalized treatment is complicated by the variability of patient's response to treatment. Gene expression analysis might serve a tool for the disease control and therapy personification for inhibition of inflammation and pain as well as for prevention of joint destruction.

Urinary metalloproteinases and tissue inhibitors of metalloproteinases as potential early biomarkers for renal fibrosis in children with nephrotic syndrome

In chronic glomerulopathies, renal fibrosis (RF) results from extracellular matrix remodeling processes regulated by matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP). We assessed urinary (u-) and serum (s-) MMP-1, -2, -9, TIMP-1, -2 concentrations and MMP-1, -2, -9/TIMP-1, -2 ratios in children with nephrotic syndrome. Steroid-dependent and steroid-resistant nephrotic patients (SDNS-Ps and SRNS-Ps, respectively) were compared with respect to measured parameters. The correlations of measured parameters with magnitude of proteinuria and histopathological diagnosis were determined.The study comprised of 39 children with nephrotic syndrome and 20 healthy controls. Twenty-three patients had SDNS and 16 ones-SRNS. The concentrations MMPs and TIMPs were measured using enzyme-linked immunosorbent assay.In nephrotic patients, higher u-MMP-1, -2, -9/creatinine ratios and u-TIMP-1, -2/creatinine ratios were observed as compared with controls. Nephrotic children were also characterized by lower MMP-1, -2, -9/TIMP-1 ratios. In SRNS-Ps, u-MMP-2/creatinine ratio and u-TIMP-1/creatinine ratio were higher as compared with SDNS-Ps. Magnitude of proteinuria correlated positively with u-MMP-2/creatinine ratio and negatively with u-MMP-2/TIMP-1. In minimal change disease (MCD) patients as compared with those with other glomerulopathies, there was higher u-MMP-2/TIMP-1 ratio. No significant differences in s-MMPs, s-TIMPs, and s-MMPs/TIMPs ratios between nephrotic patients and controls were observed.Children with nephrotic syndrome are characterized by increased u-fibrotic biomarkers excretions. U-MMP-1, -2, -9 excretions and u-MMP-2/TIMP-1 ratio may become potential early biomarkers for RF. SRNS-Ps, those with heavier proteinuria and other than MCD glomerulopathies, seem to be more susceptible to early RF.

The clinical utility of gene expression examination in rheumatology

Rheumatoid arthritis (RA) is a chronic inflammatory disease with unknown etiology that affects various pathways within the immune system, involves many other tissues and is associated with pain and joint destruction. Current treatments fail to address pathophysiological and biochemical mechanisms involved in joint degeneration and the induction of pain. Moreover, RA patients are extremely heterogeneous and require specific treatments, the choice of which is complicated by the fact that not all patients equally respond to therapy. Gene expression analysis offer tools for patient management and personalization of patient’s care to meet individual needs in controlling inflammation and pain and delaying joint destruction.

Role of MMP-7 in the pathogenesis of systemic lupus erythematosus (SLE)

Systemic lupus erythematosus (SLE) is a clinically heterogeneous chronic, inflammatory autoimmune disorder. The association of MMP-7 and disease severity is still unclear. A total of 150 SLE patients and matched healthy controls were recruited for this study. Disease activity was scored according to SLEDAI (98 active and 52 inactive disease). Mean serum MMP-7 levels were significantly higher in SLE patients than controls ( p < 0.001). Patients with active disease showed higher levels (16.24 ± 6.2 ng/ml) as against inactive disease (10.50 ± 3.97 ng/ml) ( p ≤ 0.0001). Mean MMP-7 mRNA expression was significantly higher in patients (RQ = 3.16 ± 0.93) as compared to controls (RQ = 2.21 ± 0.89, p = 0.006). A positive correlation between MMP-7 levels, mRNA expression and SLEDAI score was observed ( r = 0.563, r = 0.427). The MMP-7 -181 G allele was found to be significantly higher among SLE patients ( p < 0.0001). A significant association was noted between MMP-7 -181 A/G +G/G genotypes with renal ( p = 0.0027) and CNS ( p = 0.0031) manifestations and anti-dsDNA autoantibodies ( p = 0.0312). Serum MMP-7 levels and mRNA expression were elevated in advanced stages of SLE, indicating that MMP-7 is associated with disease activity in SLE.

Murine and Human Lupus Nephritis: Pathogenic Mechanisms and Theoretical Strategies for Therapy

Lupus nephritis is one of the most serious manifestations of systemic lupus erythematosus, and represents one of the criteria implemented to classify systemic lupus erythematosus. Although studied for decades, no consensus has been reached related to the basic cellular, molecular, and immunologic mechanism(s) responsible for lupus nephritis. No causal treatments have been developed; therapy is approached mainly with nonspecific immunosuppressive medications. More detailed insight into disease mechanisms therefore is indispensable to develop new therapeutic strategies. In this review, contemporary knowledge on the pathogenic mechanisms of lupus nephritis is discussed based on recent data in murine and human lupus nephritis. Specific focus is given to the effect of anti-double-stranded DNA/antinucleosome antibodies in the kidneys and whether they bind exposed chromatin fragments in glomeruli or whether they bind inherent glomerular structures by cross-recognition. Overall, the data presented here favor the exposed chromatin model because we did not find any indication to substantiate the anti-double-stranded DNA antibody cross-reacting model. At the end of this review we present data on why chromatin fragments are expressed in the glomeruli of patients with lupus nephritis, and discuss how this knowledge can be used to direct the development of future therapies.

The Role of Anti-DNA Antibodies in the Development of Lupus Nephritis: A Complementary, or Alternative, Viewpoint?

Kidney disease, or lupus nephritis, is the organ involvement that is most closely associated with specific autoantibodies in patients with SLE. The concept of anti-DNA antibodies being instrumental in the pathogenesis of lupus nephritis emerged ~50 years ago, and has been a topic of debate ever since. This article focuses on the description of the renal sub-cellular targets of nephritogenic autoantibodies and offers a counter-point opinion to the article by Pedersen et al. In addition, we provide an overview of some of the mechanisms by which anti-DNA antibodies bind to their renal targets and the pathogenic relevance to clinical nephritis.

Potential of Serum and Urinary Matrix Metalloproteinase-9 Levels for the Early Detection of Renal Involvement in Children With Henoch-Schönlein Purpura

Background

Matrix metalloproteinase-9 (MMP-9) is an enzyme implicated in the pathogenesis of renal diseases. Renal involvement is the principal cause of morbidity and mortality in children with Henoch-Schönlein purpura (HSP).

Objectives

The aim of this study was to evaluate whether serum and urinary MMP-9 levels are associated with renal involvement in HSP

Patients and Methods

We evaluated 40 children with HSP (patient group) and 27 healthy volunteer children (control group). The patient group was divided into two subgroups based on the presence or absence of nephritis. Nephritis was defined as the existence of hematuria and/or proteinuria. All anthropometric data, physical examination findings, blood pressure, and laboratory parameters were recorded. The serum and urine samples were analyzed to determine the MMP-9 levels three days after the initial phase of the disease.

Results

The mean age was 7.65 ± 3.41 (range 2 - 16) years in the patient group and 9.52 ± 3.91 (range 2 - 16) years in the control group. Henoch-Schonlein purpura nephritis (HSPN) was identified in eight patients. There was no significant difference in the serum MMP-9 levels between the HSPN subgroup and the controls (P > 0.05). However, there were significant differences in the urinary MMP-9 levels between the HSP subgroup and the control group (P < 0.05), with the urinary MMP-9 levels being significantly higher in patients in the HSP subgroup (P = 0.001). Further, the urinary MMP-9 levels were significantly higher in the patients with nephritis than in the patients without nephritis (P = 0.001) and the controls (P = 0.001). The optimal cut-off point (sensitivity; specificity) of the urinary MMP-9 level for the diagnosis of HSPN was 94.7 pg/mL.

Conclusions

The levels of MMP-9 in the urine were remarkably high in patients with HSPN. This non-invasive marker may therefore be an important indicator for the early diagnosis of nephritis in children with HSP.

Soluble fas and the -670 polymorphism of fas in lupus nephritis

This study was performed to clarify the role of soluble Fas (sFas) in lupus nephritis (LN) and establish a potential relationship between LN and the −670 polymorphism of Fas in 67 patients with systemic lupus erythematosus (SLE), including a subset of 24 LN patients with proteinuria. Additionally, a group of 54 healthy subjects (HS) was included. The allelic frequency of the −670 polymorphism of Fas was determined using PCR-RFLP analysis, and sFas levels were assessed by ELISA. Additionally, the WT-1 protein level in urine was measured. The Fas receptor was determined in biopsies by immunohistochemistry (IHC) and in situ hybridization (FISH) and apoptotic features by TUNEL. Results. The −670 Fas polymorphism showed that the G allele was associated with increased SLE susceptibility, with an odds ratio (OR) of 1.86. The sFas was significantly higher in LN patients with the G/G genotype, and this subgroup exhibited correlations between the sFas level and proteinuria and increased urinary WT-1 levels. LN group shows increased expression of Fas and apoptotic features. In conclusion, our results indicate that the G allele of the −670 polymorphism of Fas is associated with genetic susceptibility in SLE patients with elevated levels of sFas in LN with proteinuria.

Neutrophil extracellular traps induce endothelial dysfunction in systemic lupus erythematosus through the activation of matrix metalloproteinase-2

RATIONALE

The structural and functional integrity of the endothelium is crucial in maintaining vascular homeostasis and preventing atherosclerosis. Patients with systemic lupus erythematosus (SLE) have an increased risk of developing endothelial dysfunction and premature cardiovascular disease. Neutrophil extracellular trap (NET) formation is increased in SLE and has been proposed to contribute to endothelial damage, but the mechanism remains unclear.

OBJECTIVE

To determine the mechanism by which enhanced NET formation by low-density granulocytes (LDGs) in SLE contributes to endothelial damage and disrupts the endothelium.

RESULTS

The putative role of NET-externalised matrix metalloproteinases (MMPs) in altering the functional integrity of the endothelium was examined. MMP-9 externalised by lupus LDGs during NET formation specifically impaired murine aortic endothelium-dependent vasorelaxation and induced endothelial cell apoptosis. Endothelial dysfunction correlated with the activation of endothelial MMP-2 by MMP-9 present in NETs, while inhibition of MMP-2 activation restored endothelium-dependent function and decreased NET-induced vascular cytotoxicity. Moreover, immunogenic complexes composed of MMP-9 and anti-MMP-9 were identified in SLE sera. These complexes, as well as anti-MMP-9 autoantibodies, induced NETosis and enhanced MMP-9 activity.

CONCLUSIONS

These observations implicate activation of endothelial MMP-2 by MMP-9 contained in NETs as an important player in endothelial dysfunction, and MMP-9 as a novel self-antigen in SLE. These results further support that aberrant NET formation plays pathogenic roles in SLE.

Aberrant activation of the WNT/β-catenin signaling pathway in lupus nephritis

Objective

The canonical WNT pathway has been implicated as playing important roles in the pathogenesis of a variety of kidney diseases. Recently, WNT pathway activity was reported to be elevated in the renal tissue of a lupus mouse model. This study aimed to evaluate the potential role of the WNT pathway in the pathogenesis of human lupus nephritis.

Methods

The expression of β-catenin was evaluated in renal biopsy specimens from lupus nephritis patients and control kidney tissues by immunohistochemistry and western blotting. Real-time polymerase chain reaction (RT-PCR) was used to detect RNA expression of β-catenin, Dkk-1 and Axin2. Plasma concentrations of Dkk-1 were measured by ELISA.

Results

Immunohistochemistry and western blotting revealed increased expression of β-catenin in the kidneys of patients with lupus nephritis compared with control kidney tissues (p<0.05), accompanied by an increase in mRNA expression of β-catenin (p<0.01) and axin2 (p<0.05).

β-catenin was significantly greater in LN patients without renal interstitial fibrosis compared with those with renal interstitial fibrosis (p<0.01) at the mRNA expression level; the increase in β-catenin mRNA positively correlated with the creatinine clearance rate (Ccr) and negatively correlated with chronicity indices of renal tissue injury. Greater plasma Dkk-1 concentrations were found in LN patients compared with controls (p<0.05). Plasma Dkk-1 concentrations also correlated negatively with anti-dsDNA antibody levels and positively with serum C3 levels.

Conclusions

The canonical WNT/β-catenin signaling pathway was activated in lupus nephritis patients, accompanied by an increase in plasma levels of Dkk-1. Altered WNT/β-catenin signaling was related to the pathogenesis of lupus nephritis and might play a role in renal fibrosis.

Systemic effects of Wnt signaling

Wnt signaling plays a key role in several physiological and pathological aspects. Even if Wnt signal was first described more than 20 years ago, its role in systemic effects, such as angiogenesis and vascular disorders, bone biology, autoimmune diseases, neurological diseases, and neoplastic disorders, was only recently emerged through the use of animal and in vitro models. Moreover, Wnt signaling inhibitors, such as DKK-1, may be advantageously considered targets for the treatment of several diseases, including osteoporosis, vascular diseases, inflammatory diseases, neurological diseases, and cancer. Nevertheless, further studies are required to provide a complete understanding of this complex signaling pathway, and especially of its role in human diseases, considering the possible advantageous effects of Wnt signaling inhibitors on the progression of disease conditions.

Refractory Proliferative Lupus Nephritis

Objective: To review the literature available regarding treatment of lupus nephritis (LN) refractory to cyclophosphamide, mycophenolate mofetil, azathioprine, and glucocorticoids. Data Sources: PubMed-MEDLINE and SCOPUS databases were searched through June 2013 using the terms lupus nephritis, refractory, induction, systemic lupus erythematosus, diffuse proliferative glomerulonephritis, rituximab, cyclosporine, tacrolimus, leflunomide, mizoribine, intravenous immunoglobulin, and belimumab. Study Selection and Data Extraction: Included studies were limited to human studies that evaluated clinical efficacy and English language articles. Articles assessing treatment with first-line agents such as glucocorticoids, cyclophosphamide, mycophenolate, and azathioprine were excluded from this review. Data Synthesis: There are an increasing number of medications being used in refractory LN, making the selection of an appropriate agent more difficult. Thirty studies evaluating the treatment of LN with alternative agents were identified. Although rituximab and calcineurin inhibitors have demonstrated the ability to induce remission in approximately 60% of patients with LN, large randomized trials have not confirmed these results. Leflunomide, mizoribine, and intravenous immunoglobulin have revealed potential benefits in some patient populations; however, there is not enough data to support the regular use of these agents for refractory LN. Conclusions: Rituximab and calcineurin inhibitors have the most evidence to support their use and should be the preferred agents in the treatment of refractory LN at this time. Further studies may elucidate the efficacy of other agents for refractory LN.

Distinct contributions of TNF receptor 1 and 2 to TNF-induced glomerular inflammation in mice

TNF is an important mediator of glomerulonephritis. The two TNF-receptors TNFR1 and TNFR2 contribute differently to glomerular inflammation in vivo, but specific mechanisms of TNFR-mediated inflammatory responses in glomeruli are unknown. We investigated their expression and function in murine kidneys, isolated glomeruli ex vivo, and glomerular cells in vitro. In normal kidney TNFR1 and TNFR2 were preferentially expressed in glomeruli. Expression of both TNFRs and TNF-induced upregulation of TNFR2 mRNA was confirmed in murine glomerular endothelial and mesangial cell lines. In vivo, TNF exposure rapidly induced glomerular accumulation of leukocytes. To examine TNFR-specific inflammatory responses in intrinsic glomerular cells but not infiltrating leukocytes we performed microarray gene expression profiling on intact glomeruli isolated from wildtype and Tnfr-deficient mice following exposure to soluble TNF ex vivo. Most TNF-induced effects were exclusively mediated by TNFR1, including induced glomerular expression of adhesion molecules, chemokines, complement factors and pro-apoptotic molecules. However, TNFR2 contributed to TNFR1-dependent mRNA expression of inflammatory mediators in glomeruli when exposed to low TNF concentrations. Chemokine secretion was absent in TNF-stimulated Tnfr1-deficient glomeruli, but also significantly decreased in glomeruli lacking TNFR2. In vivo, TNF-induced glomerular leukocyte infiltration was abrogated in Tnfr1-deficient mice, whereas Tnfr2-deficiency decreased mononuclear phagocytes infiltrates, but not neutrophils. These data demonstrate that activation of intrinsic glomerular cells by soluble TNF requires TNFR1, whereas TNFR2 is not essential, but augments TNFR1-dependent effects. Previously described TNFR2-dependent glomerular inflammation may therefore require TNFR2 activation by membrane-bound, but not soluble TNF.

TNFα enhances TLR3-dependent effects on MMP-9 expression in human mesangial cells

The role of MMPs (matrix metalloproteinases) in kidney diseases has been widely accepted, where they can regulate inflammatory response because of their effects on both recruitment and survival of inflammatory cells. TNFα (tumour necrosis factor α) has also been implicated in the pathogenesis of inflammatory kidney diseases, including forms of glomerulonephritis associated with viral diseases. Previously, we established the functional linkage between viral receptors of the innate immune system, the TLRs (Toll-like receptors) and control of MMP activity in human MC (mesangial cells). Expression levels of MMP-2, MMP-7, MMP-9, TIMP-1 (tissue inhibitor of metalloproteinase 1) and TIMP-2 in human MC in culture were analysed by RT-PCR (reverse transcription-PCR). TNFα significantly enhanced the TLR3-dependent induction of MMP-9 in human MC. Expression levels of MMP-2, TIMP-1 and TIMP-2 were not significantly affected by the activation of TLR3 or TNFα stimulation. No significant MMP-7 expression was found. We conclude that the role of MMP-9 in chemotaxis, activation and proliferation of inflammatory cells is amplified by TNFα originating from infiltrating cells, especially monocytes, producing a regulatory loop that potentially leads to a self-propagating inflammation.

Matrix metalloproteinases in kidney homeostasis and diseases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that have been increasingly linked to both normal physiology and abnormal pathology in the kidney. Collectively able to degrade all components of the extracellular matrix, MMPs were originally thought to antagonize the development of fibrotic diseases solely through digestion of excessive matrix. However, increasing evidence has shown that MMPs play a wide variety of roles in regulating inflammation, epithelial-mesenchymal transition, cell proliferation, angiogenesis, and apoptosis. We now have robust evidence for MMP dysregulation in a multitude of renal diseases including acute kidney injury, diabetic nephropathy, glomerulonephritis, inherited kidney disease, and chronic allograft nephropathy. The goal of this review is to summarize current findings regarding the role of MMPs in kidney diseases as well as the mechanisms of action of this family of proteases.

Silencing of renal DNaseI in murine lupus nephritis imposes exposure of large chromatin fragments and activation of Toll like receptors and the Clec4e

Recent studies demonstrate that transformation of mild lupus nephritis into end-stage disease is imposed by silencing of renal DNaseI gene expression in (NZBxNZW)F1 mice. Down-regulation of DNaseI results in reduced chromatin fragmentation, and in deposition of extracellular chromatin-IgG complexes in glomerular basement membranes in individuals that produce IgG anti-chromatin antibodies. The main focus of the present study is to describe the biological consequences of renal DNaseI shut-down and reduced chromatin fragmentation with a particular focus on whether exposed large chromatin fragments activate Toll like receptors and the necrosis-related Clec4e receptor in murine and human lupus nephritis. Furthermore, analyses where performed to determine if matrix metalloproteases are up-regulated as a consequence of chromatin-mediated Toll like receptors/Clec4e stimulation. Mouse and human mRNA expression levels of DNaseI, Toll like receptors 7–9, Clec4e, pro-inflammatory cytokines and MMP2/MMP9 were determined and compared with in situ protein expression profiles and clinical data. We demonstrate that exposure of chromatin significantly up-regulate Toll like receptors and Clec4e in mice, and also but less pronounced in patients with lupus nephritis treated with immunosuppresants. In conclusion, silencing of renal DNaseI gene expression initiates a cascade of inflammatory signals leading to progression of both murine and human lupus nephritis. Principal component analyses biplot of data from murine and human lupus nephrits demonstrate the importance of DNaseI gene shut down for progression of the organ disease.

The role of matrix metalloproteinases and their inhibitors in the development of renal fibrosis in the patients with diabetes mellitus

The accumulation of components of extracellular matrix in the glomerular and interstitial compartments of the kidneys is a characteristic feature of diabetic nephropathy. The leading role in the extracellular matrix catabolism is played by matrix metalloproteinases (MMP). The activity of these enzymes is regulated by a group of inhibitors including tissue metalloproteinase inhibitors, plasminogen activator inhibitor-1, etc. Both in vivo and in vitro studies have demonstrated that a reduction of MMP activities and/or an increase of expression of MMP tissue inhibitors in the glomerular and tubular cells result in the suppression of catabolism of the components of extracellular matrix under the hyperglycemic conditions. Both circulating and urinary MMP as well as their inhibitors are considered to be new potential markers of renal fibrosis associated with diabetes mellitus. It is concluded that the directed activation of MMP and neutralization of their inhibitors provide a promising tool for the treatment of diabetic nephropathy.

Chromatin as a target antigen in human and murine lupus nephritis

The present review focuses on pathogenic molecular and transcriptional events in patients with lupus nephritis. These factors are renal DNaseI, exposed chromatin fragments and the corresponding chromatin-reactive autoantibodies. Lupus nephritis is the most serious complication in human systemic lupus erythematosus, and is characterised by deposition of chromatin fragment-IgG complexes in the mesangial matrix and glomerular basement membranes. The latter deposition defines end-stage disease. This event is stringently linked to a renal-restricted shutdown of expression of the DNaseI gene, as determined by loss of DNaseI mRNA level and DNaseI enzyme activity. The major aim of the present review is to generate new therapeutic strategies based on new insight into the disease pathogenesis.

Alterations in Wnt pathway activity in mouse serum and kidneys during lupus development

OBJECTIVE

The canonical Wnt/β-catenin pathway was recently identified as a factor in the pathogenesis of several renal diseases. The aim of this study was to evaluate Wnt signaling activity during disease development in a murine model of lupus nephritis.

METHODS

Wnt activity and Dkk-1 expression were serially assayed in the serum and kidneys of (NZB × NZW)F(1) mice during progression of lupus nephritis. The effects of serum obtained from mice with lupus and serum-equivalent concentrations of Dkk-1 on mesangial cells were assessed in vitro.

RESULTS

Gene expression analyses revealed increased canonical Wnt pathway activity in kidneys during development of lupus nephritis, paralleled by an increase in renal and serum levels of the Wnt inhibitor Dkk-1. Sera obtained from proteinuric-stage (NZB × NZW)F(1) mice showed strong Wnt-inhibitory effects in vitro. Dkk-1 concentrations comparable to those observed in lupus-prone mice induced apoptosis in tubular and mesangial cells in vitro, whereas no such effect was seen for the range of concentrations observed in young prediseased mice and control BALB/c mice.

CONCLUSION

These data demonstrate that renal Wnt signaling activity is increased in lupus and is accompanied by an increase in renal and serum levels of Dkk-1. The Wnt pathway is involved in the turnover of extracellular matrix constituents and represents a potential mediator of the morphologic changes that occur within the glomerulus during the development of nephritis. Furthermore, increased levels of Dkk-1 serve as a potential proapoptotic stimulus in vitro and possibly in vivo and could be an important element in the initiation and progression of systemic and end-organ disease manifestations in systemic lupus erythematosus.

Proliferative lesions and metalloproteinase activity in murine lupus nephritis mediated by type I interferons and macrophages

Glomerulonephritis is a major cause of morbidity in patients with systemic lupus erythematosus. Although substantial progress has been made in the identification of pathogenic triggers that result in autoantibody production, little is known about the pathogenesis of aggressive proliferative processes that lead directly to irreversible glomerular damage and compromise of renal function. In this study, we describe a model of polyinosinic: polycytidylic acid-accelerated lupus nephritis in NZB/W mice that is characterized by severe glomerular proliferative lesions with de novo crescent formation, findings that are linked with decreased survival and adverse outcomes in lupus. Proliferative glomerulonephritis was associated with infiltrating kidney macrophages and renal expression of IFN-inducible genes, matrix metalloproteinases (MMPs), and growth factors. Crescent formation and renal MMP and growth factor expression were dependent on renal macrophages that expressed Il10, MMPs, osteopontin, and growth factors, including Pdgfc and Hbegf. Infiltrating macrophages and renal MMP expression were induced by type I IFN. These findings reveal a role for type I IFNs and alternatively activated macrophages in aggressive proliferative lesions of lupus nephritis.

Anti-dsDNA antibodies promote initiation, and acquired loss of renal Dnase1 promotes progression of lupus nephritis in autoimmune (NZBxNZW)F1 mice

Background

Lupus nephritis is characterized by deposition of chromatin fragment-IgG complexes in the mesangial matrix and glomerular basement membranes (GBM). The latter defines end-stage disease.

Methodology/Principals

In the present study we determined the impact of antibodies to dsDNA, renal Dnase1 and matrix metalloprotease (MMP) mRNA levels and enzyme activities on early and late events in murine lupus nephritis. The major focus was to analyse if these factors were interrelated, and if changes in their expression explain basic processes accounting for lupus nephritis.

Findings

Early phases of nephritis were associated with chromatin-IgG complex deposition in the mesangial matrix. A striking observation was that this event correlated with appearance of anti-dsDNA antibodies and mild or clinically silent nephritis. These events preceded down-regulation of renal Dnase1. Later, renal Dnase1 mRNA level and enzyme activity were reduced, while MMP2 mRNA level and enzyme activity increased. Reduced levels of renal Dnase1 were associated in time with deficient fragmentation of chromatin from dead cells. Large fragments were retained and accumulated in GBM. Also, since chromatin fragments are prone to stimulate Toll-like receptors in e.g. dendritic cells, this may in fact explain increased expression of MMPs.

Significance

These scenarios may explain the basis for deposition of chromatin-IgG complexes in glomeruli in early and late stages of nephritis, loss of glomerular integrity and finally renal failure.