Nucleosomes contribute to increase mesangial cell chemokine expression during the development of lupus nephritis

Genetically predicted associations between circulating cytokines and autoimmune diseases: a bidirectional two-sample Mendelian randomization

Objectives

Previous studies have indicated a correlation between cytokines and autoimmune diseases. yet the causality remains uncertain. Through Mendelian Randomization (MR) analysis, we aimed to investigate the causal relationships between genetically predicted levels of 91 cytokines and three autoimmune diseases: Multiple Sclerosis (MS), Systemic Lupus Erythematosus (SLE), and Hashimoto's Thyroiditis (HT).

Methods

A bidirectional two-sample MR approach was utilized to assess the causal relationships between cytokines and MS, SLE, and HT. The datasets included 47,429 MS cases and 68,374 controls, 5,201 SLE cases and 9,066 controls, and 16,191 HT cases with 210,612 controls. Data on 91 cytokines comprised 14,824 participants. Causal analyses primarily employed inverse variance weighted, weighted median, and MR-Egger methods, with sensitivity analyses including heterogeneity and pleiotropy assessment.

Results

Genetically predicted levels of IL-18 (OR = 0.706; 95% C.I. 0.538-0.925), ADA (OR = 0.808; 95% C.I. 0.673-0.970), and SCF (OR = 0.898; 95% C.I. 0.816-0.987) were associated with a decreased risk of MS. IL-4 (OR = 1.384; 95% C.I. 1.081-1.771), IL-7 (OR = 1.401; 95% C.I. 1.010-1.943), IL-10RA (OR = 1.266; 95% C.I. 1.004-1.596), CXCL5 (OR = 1.170; 95% C.I. 1.021-1.341), NTN (OR = 1.225; 95% C.I. 1.004-1.496), FGF23 (OR = 0.644; 95% C.I. 0.460-0.902), and MCP4 (OR = 0.665; 95% C.I. 0.476-0.929) were associated with SLE risk. CDCP1 (OR = 1.127; 95% C.I. 1.008-1.261), IL-33 (OR = 0.852; 95% C.I. 0.727-0.999), and TRAIL (OR = 0.884; 95% C.I. 0.799-0.979) were associated with HT risk. Bidirectional MR results suggest the involvement of CCL19, IL-13, SLAM, ARTN, Eotaxin, IL-22RA1, ADA, and MMP10 in the downstream development of these diseases.

Conclusions

Our findings support causal relationships between certain cytokines and the risks of MS, SLE, and HT, identifying potential biomarkers for diagnosis and prevention. Additionally, several cytokines previously unexplored in these autoimmune disease contexts were discovered, laying new groundwork for the study of disease mechanisms and therapeutic potentials.

The immunoregulatory roles of non-haematopoietic cells in the kidney

The deposition of immune complexes, activation of complement and infiltration of the kidney by cells of the adaptive and innate immune systems have long been considered responsible for the induction of kidney damage in autoimmune, alloimmune and other inflammatory kidney diseases. However, emerging findings have highlighted the contribution of resident immune cells and of immune molecules expressed by kidney-resident parenchymal cells to disease processes. Several types of kidney parenchymal cells seem to express a variety of immune molecules with a distinct topographic distribution, which may reflect the exposure of these cells to different pathogenic threats or microenvironments. A growing body of literature suggests that these cells can stimulate the infiltration of immune cells that provide protection against infections or contribute to inflammation - a process that is also regulated by draining kidney lymph nodes. Moreover, components of the immune system, such as autoantibodies, cytokines and immune cells, can influence the metabolic profile of kidney parenchymal cells in the kidney, highlighting the importance of crosstalk in pathogenic processes. The development of targeted nanomedicine approaches that modulate the immune response or control inflammation and damage directly within the kidney has the potential to eliminate the need for systemically acting drugs.

Three Diseases Mediated by Different Immunopathologic Mechanisms-ANCA-Associated Vasculitis, Anti-Glomerular Basement Membrane Disease, and Immune Complex-Mediated Glomerulonephritis-A Common Clinical and Histopathologic Picture: Rapidly Progressive Crescentic Glomerulonephritis

Immune mechanisms play an important role in the pathogenesis of glomerulonephritis (GN), with autoimmunity being the main underlying pathogenetic process of both primary and secondary GN. We present three autoimmune diseases mediated by different autoimmune mechanisms: glomerulonephritis in vasculitis mediated by anti-neutrophil cytoplasmic antibodies (ANCAs), glomerulonephritis mediated by anti-glomerular basement membrane antibodies (anti-GBM antibodies), and immune complex-mediated glomerulonephritis. Some of these diseases represent a common clinical and histopathologic scenario, namely rapidly progressive crescentic glomerulonephritis. This is a severe illness requiring complex therapy, with the main role being played by therapy aimed at targeting immune mechanisms. In the absence of immune therapy, the crescents, the characteristic histopathologic lesions of this common presentation, progress toward fibrosis, which is accompanied by end-stage renal disease (ESRD). The fact that three diseases mediated by different immunopathologic mechanisms have a common clinical and histopathologic picture reveals the complexity of the relationship between immunopathologic mechanisms and their clinical expression. Whereas most glomerular diseases progress by a slow process of sclerosis and fibrosis, the glomerular diseases accompanied by glomerular crescent formation can progress, if untreated, in a couple of months into whole-nephron glomerulosclerosis and fibrosis. The outcome of different immune processes in a common clinical and histopathologic phenotype reveals the complexity of the relationship of the kidney with the immune system. The aim of this review is to present different immune processes that lead to a common clinical and histopathologic phenotype, such as rapidly progressive crescentic glomerulonephritis.

Immune-dysregulated neutrophils characterized by upregulation of CXCL1 may be a potential factor in the pathogenesis of abdominal aortic aneurysm and systemic lupus erythematosus

Background

The abdominal aortic aneurysm (AAA) incidence is closely related to systemic lupus erythematosus (SLE). However, the common mechanisms between AAA and SLE are still unknown. The purpose of this research was to examine the main molecules and pathways involved in the immunization process that lead to the co-occurrence of AAA and SLE through the utilization of quantitative bioinformatics analysis of publicly available RNA sequencing databases. Moreover, routine blood test information was gathered from 460 patients to validate the findings.

Materials and methods

Datasets of both AAA (GSE57691 and GSE205071) and SLE (GSE50772 and GSE154851) were downloaded from the Gene Expression Omnibus (GEO) database, and differentially expressed genes (DEGs) were analyzed using bioinformatic tools. To determine the functions of the common differentially expressed genes (DEGs), Gene Ontology (GO) and Kyoto Encyclopedia analyses were conducted. Subsequently, the hub gene was identified through cytoHubba, and its validation was carried out in GSE47472 for AAA and GSE81622 for SLE. Immune cell infiltration analysis was performed to identify the key immune cells correlated with AAA and SLE, and to evaluate the correlation between key immune cells and the hub gene. Subsequently, the routine blood test data of 460 patients were collected, and the result of the immune cell infiltration analysis was further validated by univariate and multivariate logistic regression analysis.

Results

A total of 25 common DEGs were obtained, and three genes were screened by cytoHubba algorithms. Upon validation of the datasets, CXCL1 emerged as the hub gene with strong predictive capabilities, as evidenced by an area under the curve (AUC) > 0.7 for both AAA and SLE. The infiltration of immune cells was also validated, revealing a significant upregulation of neutrophils in the AAA and SLE datasets, along with a correlation between neutrophil infiltration and CXCL1 upregulation. Clinical data analysis revealed a significant increase in neutrophils in both AAA and SLE patients (p < 0.05). Neutrophils were found to be an independent factor in the diagnosis of AAA and SLE, exhibiting good diagnostic accuracy with AUC >0.7.

Conclusion

This study elucidates CXCL1 as a hub gene for the co-occurrence of AAA and SLE. Neutrophil infiltration plays a central role in the development of AAA and SLE and may serve to be a potential diagnostic and therapeutic target.

Dampened Inflammation and Improved Survival After CXCL5 Administration in Murine Lupus via Myeloid and Neutrophil Pathways

OBJECTIVE

To determine the efficacy of CXCL5 administration in lupus-prone MRL/lpr (Fas^lpr ) mice and elucidate its working mechanisms.

METHODS

CXCL5 expression in blood (obtained from SLE patients and Fas^lpr mice) and major internal organs (obtained from Fas^lpr mice) was examined by Luminex, real-time polymerase chain reaction, and immunofluorescent staining analyses. Pharmacokinetic studies were performed in Fas^lpr mice and healthy Institute of Cancer Research mice. Efficacy of CXCL5 administration was demonstrated in Fas^lpr mice, and the working mechanism of CXCL5 treatment was elucidated by flow cytometry, Luminex, and RNA sequencing.

RESULTS

In SLE patients, serum CXCL5 levels were significantly lower than in healthy individuals (P < 0.0001) and negatively correlated with disease activity (P = 0.004). In Fas^lpr mice, disease severity progressed with age and was negatively associated with plasma CXCL5 levels. Intravenous administration of CXCL5 to Fas^lpr mice restored endogenous circulatory CXCL5, improved mice survival, and reduced anti-double-stranded DNA antibodies, proteinuria, lupus nephritis activity and chronicity indices, renal complements, and neutrophil extracellular traps over short-term (10 weeks) and long-term (2 years) time periods. In vitro and in vivo assays demonstrated that CXCL5 dictated neutrophil trafficking and suppressed neutrophil activation, degranulation, proliferation, and renal infiltration. Renal and splenic RNA sequencing further showed that CXCL5-mediated immunomodulation occurred by promoting energy production in renal-infiltrated immune cells, activating certain T cells, and reducing tissue fibrosis, granulocyte extravasation, complement components, and interferons. Further factorial design results indicated that CXCL5 appears to enhance host tolerability to cyclophosphamide in vulnerable individuals.

CONCLUSION

We found that serum CXCL5 levels were significantly lower in SLE patients than in healthy individuals and were negatively correlated with disease activity. By administering CXCL5 intravenously in a mouse model of lupus, mouse survival improved, and indices of disease activity reduced significantly. Taken together, these findings indicate CXCL5 administration may represent a novel myeloid/neutrophil-targeting therapy for SLE.

CCL7 as a novel inflammatory mediator in cardiovascular disease, diabetes mellitus, and kidney disease

Chemokines are key components in the pathology of chronic diseases. Chemokine CC motif ligand 7 (CCL7) is believed to be associated with cardiovascular disease, diabetes mellitus, and kidney disease. CCL7 may play a role in inflammatory events by attracting macrophages and monocytes to further amplify inflammatory processes and contribute to disease progression. However, CCL7-specific pathological signaling pathways need to be further confirmed in these chronic diseases. Given the multiple redundancy system among chemokines and their receptors, further experimental and clinical studies are needed to clarify whether direct CCL7 inhibition mechanisms could be a promising therapeutic approach to attenuating the development of cardiovascular disease, diabetes mellitus, and kidney disease.

Chemokine CXCL1 as a potential marker of disease activity in systemic lupus erythematosus

Objectives

The chemokine CXCL1, known as growth-related oncogene α (GRO-α), is a potent chemoattractant and regulator of neutrophils. The purpose of our study was to evaluate the regulatory response of CXCL1 in the serum of patients with systemic lupus erythematosus (SLE) in the active stage of disease and to assess whether it was implicated in the pathogenesis/inflammatory process in lupus.

Methods

CXCL1 serum concentrations were examined in 90 SLE patients, 56 other autoimmune diseases (OADs) patients and 100 healthy controls using enzyme-linked immunosorbent methodology.

Results

SLE patients exhibited significant increases in serum CXCL1 concentrations [1492.86 (735.47–2887.34) pg/ml] compared with OADs patients [155.88 (10.77–366.78) pg/ml] and healthy controls [13.58 (8.46–37.22) pg/ml] (p < 0.001). Moreover, the level of CXCL1 decreased as the level of anti-dsDNA IgG decreased after treatment between the anti-dsDNA-positive SLE patients and the anti-dsDNA-negative SLE patients. Additionly, serum CXCL1 concentrations were related to different disease activity levels in SLE and lupus nephritis (LN) and high avidity of IgG ANAs (HA IgG ANAs) (p < 0.05). Furthermore, CXCL1 serum concentrations were significantly correlated with the SLE Disease Activity Index(SLEDAI) score, relative avidity index (RAI) of HA IgG ANAs and the levels of anti-dsDNA IgG, CRP, ESR, albumin, C3 and C4.Additionally, Statistical analysis revealed that positivity for IgG ANA (p < 0.001), the presence of HA IgG ANAs (p = 0.001) and the logarithmic level of anti-dsDNA IgG (p = 0.021) were significantly associated with the logarithmic level of CXCL1 with standard partial regression coefficients (95% CI) of 2.371 (1.734–3.009), 1.231 (0.52–1.937) and 0.409 (0.062–0.755), respectively. Finally, using cutoff points of 1182.17 pg/mL and 1500.31 pg/mL, serum CXCL1 levels had a similar sensitivity of 76% and specificity of 100% and 75% for the diagnosis of active SLE and LN, respectively.

Conclusions

Serum CXCL13 concentrations might represent a potential marker of disease activity in systemic lupus erythematosus.

Interplay of immune and kidney resident cells in the formation of tertiary lymphoid structures in lupus nephritis

Kidney involvement confers significant morbidity and mortality in patients with systemic lupus erythematosus (SLE). The pathogenesis of lupus nephritis (LN) involves diverse mechanisms instigated by elements of the autoimmune response which alter the biology of kidney resident cells. Processes in the glomeruli and in the interstitium may proceed independently albeit crosstalk between the two is inevitable. Podocytes, mesangial cells, tubular epithelial cells, kidney resident macrophages and stromal cells with input from cytokines and autoantibodies present in the circulation alter the expression of enzymes, produce cytokines and chemokines which lead to their injury and damage of the kidney. Several of these molecules can be targeted independently to prevent and reverse kidney failure. Tertiary lymphoid structures with true germinal centers are present in the kidneys of patients with lupus nephritis and have been increasingly recognized to associate with poorer renal outcomes. Stromal cells, tubular epithelial cells, high endothelial vessel and lymphatic venule cells produce chemokines which enable the formation of structures composed of a T-cell-rich zone with mature dendritic cells next to a B-cell follicle with the characteristics of a germinal center surrounded by plasma cells. Following an overview on the interaction of the immune cells with kidney resident cells, we discuss the cellular and molecular events which lead to the formation of tertiary lymphoid structures in the interstitium of the kidneys of mice and patients with lupus nephritis. In parallel, molecules and processes that can be targeted therapeutically are presented.

The Th17/IL-17 Axis and Kidney Diseases, With Focus on Lupus Nephritis

Systemic lupus erythematosus (SLE) is a disease characterized by dysregulation and hyperreactivity of the immune response at various levels, including hyperactivation of effector cell subtypes, autoantibodies production, immune complex formation, and deposition in tissues. The consequences of hyperreactivity to the self are systemic and local inflammation and tissue damage in multiple organs. Lupus nephritis (LN) is one of the most worrying manifestations of SLE, and most patients have this involvement at some point in the course of the disease. Among the effector cells involved, the Th17, a subtype of T helper cells (CD4+), has shown significant hyperactivation and participates in kidney damage and many other organs. Th17 cells have IL-17A and IL-17F as main cytokines with receptors expressed in most renal cells, being involved in the activation of many proinflammatory and profibrotic pathways. The Th17/IL-17 axis promotes and maintains repetitive tissue damage and maladaptive repair; leading to fibrosis, loss of organ architecture and function. In the podocytes, the Th17/IL-17 axis effects include changes of the cytoskeleton with increased motility, decreased expression of health proteins, increased oxidative stress, and activation of the inflammasome and caspases resulting in podocytes apoptosis. In renal tubular epithelial cells, the Th17/IL-17 axis promotes the activation of profibrotic pathways such as increased TGF-β expression and epithelial-mesenchymal transition (EMT) with consequent increase of extracellular matrix proteins. In addition, the IL-17 promotes a proinflammatory environment by stimulating the synthesis of inflammatory cytokines by intrinsic renal cells and immune cells, and the synthesis of growth factors and chemokines, which together result in granulopoiesis/myelopoiesis, and further recruitment of immune cells to the kidney. The purpose of this work is to present the prognostic and immunopathologic role of the Th17/IL-17 axis in Kidney diseases, with a special focus on LN, including its exploration as a potential immunotherapeutic target in this complication.

Positron emission tomography and single photon emission computed tomography imaging of tertiary lymphoid structures during the development of lupus nephritis

Lymphoid neogenesis occurs in tissues targeted by chronic inflammatory processes, such as infection and autoimmunity. In systemic lupus erythematosus (SLE), such structures develop within the kidneys of lupus-prone mice ((NZBXNZW)F1) and are observed in kidney biopsies taken from SLE patients with lupus nephritis (LN). The purpose of this prospective longitudinal animal study was to detect early kidney changes and tertiary lymphoid structures (TLS) using in vivo imaging. Positron emission tomography (PET) by tail vein injection of 18-F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG)(PET/FDG) combined with computed tomography (CT) for anatomical localization and single photon emission computed tomography (SPECT) by intraperitoneal injection of ^99mTC labeled Albumin Nanocoll (^99mTC-Nanocoll) were performed on different disease stages of NZB/W mice (n = 40) and on aged matched control mice (BALB/c) (n = 20). By using one-way ANOVA analyses, we compared two different compartmental models for the quantitative measure of ¹⁸F-FDG uptake within the kidneys. Using a new five-compartment model, we observed that glomerular filtration of ^18FFDG in lupus-prone mice decreased significantly by disease progression measured by anti-dsDNA Ab production and before onset of proteinuria. We could not visualize TLS within the kidneys, but we were able to visualize pancreatic TLS using ^99mTC Nanocoll SPECT. Based on our findings, we conclude that the five-compartment model can be used to measure changes of FDG uptake within the kidney. However, new optimal PET/SPECT tracer administration sites together with more specific tracers in combination with magnetic resonance imaging (MRI) may make it possible to detect formation of TLS and LN before clinical manifestations.

Aberrant expression of cell-free nucleosomes in dermatomyositis/polymyositis

Nucleosomes are typically located intracellularly, and extracellular levels of nucleosomes indicated the degree of cell death. We postulated aberrant nucleosomes expression in dermatomyositis (DM) and polymyositis (PM). To assess the aberrant expression of circulating nucleosomes in DM and polymyositis. 76 consecutive DM and PM patients from 1 September 2017 to 31 October 2018 were enrolled in this study, in addition to 20 healthy controls. The levels of circulating nucleosomes, with 16 kinds of detectable myositis-specific antibodies (MSAs) were detected in IIMs patients using enzyme-linked immunosorbent assay kit (ELISA). Receiver operating characteristic (ROC) curve analysis was performed for evaluating the ability of this candidate marker for detecting DM/PM. The results showed that the levels of circulating nucleosomes in DM/PM patients were significantly higher than that in normal individuals. Specifically, elevated levels of nucleosomes were associated with MDA5 Ab, ARS, and TIF1γAb. In addition, elevated levels of circulating nucleosomes correlated with skin eruption. This study has evidenced nucleosomes as a potential new biomarker of DM/PM. Aberrant nucleosomes expression occurs in myositis patients and the difference in nucleosomes expression between patients with and without skin eruption is statistically significant. A unique expression profile of elevated serum nucleosomes was detected in DM/PM-MDA5 Ab(+), ASS, and TIF1γAb(+).

Kidney Tertiary Lymphoid Structures in Lupus Nephritis Develop into Large Interconnected Networks and Resemble Lymph Nodes in Gene Signature

Immune aggregates organized as tertiary lymphoid structures (TLS) are observed within the kidneys of patients with systemic lupus erythematosus and lupus nephritis (LN). Renal TLS was characterized in lupus-prone New Zealand black × New Zealand white F1 mice analyzing cell composition and vessel formation. RNA sequencing was performed on transcriptomes isolated from lymph nodes, macrodissected TLS from kidneys, and total kidneys of mice at different disease stages by using a personal genome machine and RNA sequencing. Formation of TLS was found in anti-double-stranded DNA antibody-positive mice, and the structures were organized as interconnected large networks with distinct T/B cell zones with adjacent dendritic cells, macrophages, plasma cells, high endothelial venules, supporting follicular dendritic cells network, and functional germinal centers. Comparison of gene profiles of whole kidney, renal TLS, and lymph nodes revealed a similar gene signature of TLS and lymph nodes. The up-regulated genes within the kidneys of lupus-prone mice during LN development reflected TLS formation, whereas the down-regulated genes were involved in metabolic processes of the kidney cells. A comparison with human LN gene expression revealed similar up-regulated genes as observed during the development of murine LN and TLS. In conclusion, kidney TLS have a similar cell composition, structure, and gene signature as lymph nodes and therefore may function as a kidney-specific type of lymph node.

Anti-double Stranded DNA Antibodies: Origin, Pathogenicity, and Targeted Therapies

Systemic lupus erythematosus (SLE) is characterized by high-titer serological autoantibodies, including antibodies that bind to double-stranded DNA (dsDNA). The origin, specificity, and pathogenicity of anti-dsDNA antibodies have been studied from a wider perspective. These autoantibodies have been suggested to contribute to multiple end-organ injuries, especially to lupus nephritis, in patients with SLE. Moreover, serum levels of anti-DNA antibodies fluctuate with disease activity in patients with SLE. By directly binding to self-antigens or indirectly forming immune complexes, anti-dsDNA antibodies can accumulate in the glomerular and tubular basement membrane. These autoantibodies can also trigger the complement cascade, penetrate into living cells, modulate gene expression, and even induce profibrotic phenotypes of renal cells. In addition, the expression of suppressor of cytokine signaling 1 is reduced by anti-DNA antibodies simultaneously with upregulation of profibrotic genes. Anti-dsDNA antibodies may even participate in the pathogenesis of SLE by catalyzing hydrolysis of certain DNA molecules or peptides in cells. Recently, anti-dsDNA antibodies have been explored in greater depth as a therapeutic target in the management of SLE. A substantial amount of data indicates that blockade of pathogenic anti-dsDNA antibodies can prevent or even reverse organ damage in murine models of SLE. This review focuses on the recent research advances regarding the origin, specificity, classification, and pathogenicity of anti-dsDNA antibodies and highlights the emerging therapies associated with them.

Mesenchymal stem cells and T cells in the formation of Tertiary Lymphoid Structures in Lupus Nephritis

Tertiary lymphoid structures (TLS) develop in the kidneys of lupus-prone mice and systemic lupus erythematosus (SLE) patients with lupus nephritis (LN). Here we investigated the presence of mesenchymal stem cells (MSCs) in the development of TLS in murine LN, as well as the role of human MSCs as lymphoid tissue organizer (LTo) cells on the activation of CD4+ T cells from three groups of donors including Healthy, SLE and LN patients. Mesenchymal stem like cells were detected within the pelvic wall and TLS in kidneys of lupus-prone mice. An increase in LTβ, CXCL13, CCL19, VCAM1 and ICAM1 gene expressions were detected during the development of murine LN. Human MSCs stimulated with the pro-inflammatory cytokines TNF-α and IL-1β significantly increased the expression of CCL19, VCAM1, ICAM1, TNF-α, and IL-1β. Stimulated MSCs induced proliferation of CD4⁺ T cells, but an inhibitory effect was observed when in co-culture with non-stimulated MSCs. A contact dependent increase in Th2 and Th17 subsets were observed for T cells from the Healthy group after co-culture with stimulated MSCs. Our data suggest that tissue-specific or/and migratory MSCs could have pivotal roles as LTo cells in accelerating early inflammatory processes and initiating the formation of kidney specific TLS in chronic inflammatory conditions.

Tonsillitis exacerbates renal injury in IgA nephropathy through promoting Th22 cells chemotaxis

BACKGROUND

Tonsillitis can promote the progression of IgA nephropathy (IgAN) by aggravating immunopathologic response. Th22 cell disorder is involved in the pathogenesis of IgAN with tonsillitis. This study was determined to explore the possible mechanism of IgAN with tonsillitis underlying Th22 cell chemotaxis response to the effect of CCL20, CCL22, and CCL27.

METHODS

This research was conducted on 65 subjects including 16 healthy controls (HC group), 5 patients with  renal carcinoma (HTC group) and 44 patients with IgAN between 2015 and 2016. According to clinical symptoms and results of throat swab culture, patients with IgAN were divided into two groups: IgAN with tonsillitis (IgAN + tonsillitis, n = 14) and IgAN patients without tonsillitis (IgAN, n = 30). Distribution of Th22 cells in IgAN patients was determined. The expression of CCL20, CCL22, and CCL27 in both peripheral blood and kidneys of IgAN patients was investigated. Severity of pathological lesions in IgAN patients was analyzed. Coculture assay and transwell assay were performed to explore the impacts of human mesangial cells (HMC) on Th22 cell chemotaxis and Th22 cell local accumulation under hemolytic streptococcus (HS) infection.

RESULTS

Th22 cell percentages in IgAN patients increased compared with healthy controls. This increased Th22 cell percentage was positively correlated with the renal lesions of IgAN patients. Correspondingly, the expression of CCL20, CCL22, and CCL27 in renal tissue increased in IgAN patients. Tonsillitis exacerbated these overrepresentations of Th22 cells and chemokines. It was found that HMC could produce CCL20, CCL22, and CCL27. The supernatant of HMC was chemotactic for Th22 cells. This activity of HMC was stimulated by HS infection, whereas treatment of anti-CCL20, anti-CCL22, and anti-CCL27 antibodies partly blocked this chemoattractant effect of HMC.

CONCLUSIONS

Tonsil infection may aggravate the renal pathological lesions of IgAN by exacerbating Th22 cell accumulation. Our data suggested a collaboration between HMC and Th22 cells in IgAN with tonsillitis underlying the effects of CCL20, CCL22, and CCL27.

Anti-dsDNA antibodies and resident renal cells - Their putative roles in pathogenesis of renal lesions in lupus nephritis

Lupus nephritis affects up to 70% of patients with systemic lupus erythematosus and is an important treatable cause of kidney failure. Cardinal features of lupus nephritis include loss of self-tolerance, production of autoantibodies, immune complex deposition and immune-mediated injury to the kidney, resulting in increased cell proliferation, apoptosis, and induction of inflammatory and fibrotic processes that destroy normal nephrons. The production anti-dsDNA antibodies is a cardinal feature in lupus and their level correlates with disease activity. In addition to the formation of immune complexes thereby triggering complement activation, how anti-dsDNA antibodies home to the kidney and induce pathological processes in the renal parenchyma remain to be fully elucidated. Data from our laboratory and other investigators show that the properties of anti-dsDNA antibodies vary between patients and change over time, and that anti-dsDNA antibodies could bind directly to integral cell surface molecules such as annexin II or α-actinin, or indirectly through chromatin material deposited on the cell surface. The binding of anti-dsDNA antibodies to mesangial cells and proximal renal tubular epithelial cells triggers downstream inflammatory and fibrotic pathways, which include the activation of the PKC and MAPK signaling pathways, increased secretion of pro-inflammatory cytokines and matrix protein deposition that contribute to pathological processes in the renal parenchyma.

Mechanisms of Kidney Injury in Lupus Nephritis - the Role of Anti-dsDNA Antibodies

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by a breakdown of self-tolerance, production of auto-antibodies and immune-mediated injury, resulting in damage accrual in multiple organs. Kidney involvement, termed lupus nephritis, is a major cause of morbidity and mortality that affects over half of the SLE population during the course of disease. The etiology of lupus nephritis is multifactorial and remains to be fully elucidated. Accumulating evidence suggests that in addition to forming immune complexes and triggering complement activation, anti-dsDNA antibodies contribute to the pathogenesis of lupus nephritis through binding, either directly or indirectly, to cross-reactive antigens or chromatin materials, respectively, to resident renal cells and/or extracellular matrix components, thereby triggering downstream cellular activation and proliferation as well as inflammatory and fibrotic processes. Several cross-reactive antigens that mediate anti-dsDNA antibody binding have been identified, such as annexin II and alpha-actinin. This review discusses the mechanisms through which anti-dsDNA antibodies contribute to immunopathogenesis in lupus nephritis. Corticosteroids combined with either mycophenolic acid (MPA) or cyclophosphamide is the current standard of care immunosuppressive therapy for severe lupus nephritis. This review also discusses recent data showing distinct effects of MPA and cyclophosphamide on inflammatory and fibrotic processes in resident renal cells.

The effect of cell death in the initiation of lupus nephritis

Cell death and the release of chromatin have been demonstrated to activate the immune system producing autoantibodies against nuclear antigens in patients with systemic lupus erythematosus (SLE). Apoptosis, necrosis, necroptosis, secondary necrosis, autophagy and the clearance of dying cells by phagocytosis are processes believed to have a role in tolerance avoidance, activation of autoimmune lymphocytes and tissue damage by effector cells. The released chromatin not only activates the immune system; it also acts as antigen for the autoantibodies produced, including anti-dsDNA antibodies. The subsequent immune complex formed is deposited within the basement membranes and the mesangial matrix of glomeruli. This may be considered as an initiating event in lupus nephritis. The origin of the released chromatin is still debated, and the possible mechanisms and cell sources are discussed in this study.

Toll-like receptor 3 signaling contributes to the expression of a neutrophil chemoattractant, CXCL1 in human mesangial cells

BACKGROUND

Mesangial proinflammatory chemokine/cytokine expressions via innate immunity play a pivotal role in the pathogenesis of glomerulonephritis. CXCL1/GROα is a strong neutrophil chemoattractant cytokine and reportedly plays an important role in regional inflammatory reactions. However, detailed signaling of mesangial CXCL1 expression induced by viral or "pseudoviral" immunity remains to be determined.

METHODS

We treated normal human mesangial cells (MCs) in culture with polyinosinic-polycytidylic acid (poly IC), an authentic double-stranded RNA, and analyzed the expression of CXCL1 by reverse transcription-polymerase chain reaction (RT-PCR), real-time quantitative RT-PCR and enzyme-linked immunosorbent assay. To elucidate the poly IC-induced signaling pathway for CXCL1 expression, we subjected the cells to RNA interference against Toll-like receptor (TLR) 3, retinoic acid-inducible gene-I (RIG-I), melanoma differentiation-associated gene 5 (MDA5), interferon (IFN)-β, nuclear factor (NF)-κB p65 and IFN regulatory factor (IRF) 3. We also conducted an immunofluorescence study to examine mesangial CXCL1 expression in biopsy specimens from patients with lupus nephritis (LN) and IgA nephropathy (IgAN).

RESULTS

We found that activation of TLR3 signaling could induce the expression of CXCL1 in MCs. NF-κB, IRF3 and IFN-β, but neither RIG-I nor MDA5, were found to be involved in mesangial CXCL1 expression in this setting. Induction of CXCL1 by poly IC was inhibited by pretreatment of cells with dexamethasone. Intense glomerular CXCL1 expression was observed in biopsy specimens from patients with LN, whereas only a trace staining occurred in specimens from patients with IgAN.

CONCLUSION

TLR3 signaling also contributes to the CXCL1 expression in MCs. These observations further support the implication of viral and "pseudoviral" immunity in the pathogenesis of inflammatory renal diseases, especially in LN.

Chance, genetics, and the heterogeneity of disease and pathogenesis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a remarkably complex and heterogeneous systemic autoimmune disease. Disease complexity within individuals and heterogeneity among individuals, even genetically identical individuals, is driven by stochastic execution of a complex inherited program. Genome-wide association studies (GWAS) have progressively improved understanding of which genes are most critical to the potential for SLE and provided illuminating insight about the immune mechanisms that are engaged in SLE. What initiates expression of the genetic program to cause SLE within an individual and how that program is initiated remains poorly understood. If we extrapolate from all of the different experimental mouse models for SLE, we can begin to appreciate why SLE is so heterogeneous and consequently why prediction of disease outcome is so difficult. In this review, we critically evaluate extrinsic versus intrinsic cellular functions in the clearance and elimination of cellular debris and how dysfunction in that system may promote autoimmunity to nuclear antigens. We also examine several mouse models genetically prone to SLE either because of natural inheritance or inheritance of induced mutations to illustrate how different immune mechanisms may initiate autoimmunity and affect disease pathogenesis. Finally, we describe the heterogeneity of disease manifestations in SLE and discuss the mechanisms of disease pathogenesis with emphasis on glomerulonephritis. Particular attention is given to discussion of how anti-DNA autoantibody initiates experimental lupus nephritis (LN) in mice.

Serum nitrated nucleosome levels in patients with systemic lupus erythematosus: a retrospective longitudinal cohort study

Introduction

Circulating nucleosomes released from apoptotic cells are important in the pathogenesis of systemic lupus erythematosus (SLE). Both nucleosomes and anti-nucleosome antibodies are deposited in inflamed tissues in patients with SLE. Active inflammation promotes nitration of tyrosine residues on serum proteins. Our hypothesis was that levels of nitrated nucleosomes would be elevated in patients with SLE and could be associated with disease activity. We therefore carried out a retrospective longitudinal study to investigate factors affecting levels of nitrated nucleosomes (NN) in patients with SLE.

Methods

A novel serum ELISA was developed to measure serum NN and modified to measure serum nitrated albumin (NA). Levels of both NN and NA were measured in 397 samples from 49 patients with SLE followed through periods of disease flare and remission for a mean of 89 months. Anti-nucleosome antibody (anti-nuc) levels were measured in the same samples. The effects of 24 different clinical, demographic and serological variables on NN, NA and anti-nuc levels were assessed by univariable and multivariable analysis.

Results

Patients with SLE had higher mean NN than healthy controls or patients with other autoimmune rheumatic diseases (P =0.01). Serum samples from 18 out of 49 (36.7%) of SLE patients were never positive for NN. This group of 18 patients was characterized by lower anti-double stranded DNA antibodies (anti-dsDNA), disease activity and use of immunosuppressants. In the remaining 63.3%, NN levels were variable. High NN was significantly associated with anti-Sm antibodies, vasculitis, immunosuppressants, hydroxychloroquine and age at diagnosis. NN levels were raised in neuropsychiatric flares. NN levels did not completely parallel NA results, thus providing additional information over measuring nitration status alone. NN levels were not associated with anti-nuc levels.

Conclusions

NN are raised in a subset of patients with SLE, particularly those who are anti-Sm positive. Elevated NN may be a marker of vascular activation and neuropsychiatric flares in these patients.

Immunopathology of lupus nephritis

When patients with systemic lupus erythematosus (SLE) present with urinary abnormalities, a renal biopsy is usually needed to rule out or confirm lupus nephritis. Renal biopsy is also needed to define the type of renal manifestation as different entities are associated with different outcomes; hence, renal biopsy results shape lupus management. But why does lupus nephritis come in different shapes? Why do patients with SLE often show change over time in class of lupus nephritis or have mixed forms? How does autoimmunity in SLE evolve? Why does loss of tolerance against nuclear antigens preferentially affect the kidney? Why are immune complex deposits in different glomerular compartments associated with different outcomes? What determines crescent formation in lupus? In this review, we discuss these questions by linking the latest information on lupus pathogenesis into the context of the different classes of lupus nephritis. This should help the basic scientist, the pathologist, and the clinician to gain a more conceptual view on the immunopathology of lupus nephritis.