Apoptosis in systemic lupus erythematosus

Programmed Cell Death Pathways in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease characterized by excessive inflammatory and immune responses and tissue damage. Increasing evidence has demonstrated the important role of programmed cell death in SLE pathogenesis. When apoptosis encounters with defective clearance, accumulated apoptotic cells lead to secondary necrosis. Different forms of lytic cell death, including secondary necrosis after apoptosis, NETosis, necroptosis, and pyroptosis, contribute to the release of damage-associated molecular patterns (DAMPs) and autoantigens, resulting in triggering immunity and tissue damage in SLE. However, the role of autophagy in SLE pathogenesis is in dispute. This review briefly discusses different forms of programmed cell death pathways and lay particular emphasis on inflammatory cell death pathways such as NETosis, pyroptosis, and necroptosis and their roles in the inflammatory and immune responses in SLE.

Systemic Lupus Erythematosus: Pathogenesis at the Functional Limit of Redox Homeostasis

Systemic lupus erythematosus (SLE) is a disease characterized by the production of autoreactive antibodies and cytokines, which are thought to have a major role in disease activity and progression. Immune system exposure to excessive amounts of autoantigens that are not efficiently removed is reported to play a significant role in the generation of autoantibodies and the pathogenesis of SLE. While several mechanisms of cell death-based autoantigenic exposure and compromised autoantigen removal have been described in relation to disease onset, a significant association with the development of SLE can be attributed to increased apoptosis and impaired phagocytosis of apoptotic cells. Both apoptosis and impaired phagocytosis can be caused by hydrogen peroxide whose cellular production is enhanced by exposure to endogenous hormones or environmental chemicals, which have been implicated in the pathogenesis of SLE. Hydrogen peroxide can cause lymphocyte apoptosis and glutathione depletion, both of which are associated with the severity of SLE. The cellular accumulation of hydrogen peroxide is facilitated by the myriad of stimuli causing increased cellular bioenergetic activity that enhances metabolic production of this toxic oxidizing agent such as emotional stress and infection, which are recognized SLE exacerbating factors. When combined with impaired cellular hydrogen peroxide removal caused by xenobiotics and genetically compromised hydrogen peroxide elimination due to enzymatic polymorphic variation, a mechanism for cellular accumulation of hydrogen peroxide emerges, leading to hydrogen peroxide-induced apoptosis and impaired phagocytosis, enhanced autoantigen exposure, formation of autoantibodies, and development of SLE.

Dysregulation of PTEN caused by the underexpression of microRNA‑130b is associated with the severity of lupus nephritis

There are several reports in the literature regarding microRNA (miR)‑130b. It has been reported that miR‑130b is involved in several diseases. The present study aimed to understand the association between the levels of miR‑130b and lupus nephritis in patients. A total of 61 blood samples were collected and the expression level of miR‑130b was determined. The online miRNA database was then searched using the 'seed sequence' located within the 3'‑untranslated region of the target gene. Linear analysis and a luciferase assay were performed to understand the regulatory association between miR‑130b and phosphatase and tensin homolog (PTEN). In addition, reverse transcription‑polymerase chain reaction and western blot analyses were performed to examine the mRNA and protein expression levels of PTEN among individuals with lupus nephritis (n=28) and those without lupus nephritis (n=31), and in mesangial cells treated with scramble control, miR‑130b mimics, PTEN small interfering (si)RNA and miR‑130b inhibitors. In addition mesangial cells were treated with scramble control, miR‑130b mimics, PTEN siRNA and miR‑130b inhibitors to investigate the affect of miR‑130b and PTEN on the viability and apoptosis of mesangial cells. The results demonstrated that miR‑130b was downregulated in the hormone‑resistant group of lupus nephritis patients. PTEN was a virtual target of miR‑130b. There was a negative regulatory association between miR‑130b and PTEN. The mRNA and protein expression levels of PTEN were increased in the hormone‑resistant group. miR‑130b decreased the expression of PTEN. miR‑130b negatively interfered with the viability of mesangial cells and PTEN positively interfered with the viability of mesangial cells. miR‑130b accelerated apoptosis and PTEN inhibited apoptosis. Taken together, the results showed that miR‑130b was upregulated in the lupus nephritis group. PTEN was a virtual target of miR‑130b, and there was a negative regulatory association between miR‑130b and PTEN. miR‑130b and PTEN interfered with the viability and apoptosis of the mesangial cells.

Evaluation of polymorphic variants in apoptotic genes and their role in susceptibility and clinical progression to systemic lupus erythematosus

Background Systemic lupus erythematosus (SLE) is an autoimmune disease marked by the disruption of the immune homeostasis. Patients exhibit a wide range of clinical manifestations, and environmental and genetic factors are involved in SLE pathogenesis. Evidence suggests that abnormalities in the cellular and molecular events that coordinate apoptosis may favour the generation of autoantigens involved in autoimmunity. In this way, the apoptotic deregulation may be affected by polymorphic variants in apoptotic-related genes. Methods We analyzed FAS, FASL, BCL-2 and BAX polymorphisms in order to correlate to SLE susceptibility and clinical features. A total of 427 SLE patients from the Hospital de Clínicas de Porto Alegre and 543 controls from southern Brazil were evaluated. Results We observed higher frequencies of the FASL -844CC genotype and -844C allele, as well as of the FASL-844C/IVS2nt-124A haplotype in African-derived SLE patients when compared to controls ( P < 0.001). FASL -844C, which is related to high FasL expression, could contribute to increased apoptosis and to the breakdown of immunological tolerance, favouring autoantibody production and inflammation. On the other hand, the BAX -248GA genotype and the -248A allele , related to low protein expression, were observed as a protective factor against SLE in this same population. The rate of apoptosis and cell death was evaluated in peripheral lymphocytes, and SLE patients presented a higher percentage of dead lymphocytes (CD3⁺Annexin V⁺ 7-AAD⁺) compared to the control group. Conclusion Our data support a role for apoptosis in SLE susceptibility.

Molecular effects of autoimmune-risk promoter polymorphisms on expression, exon choice, and translational efficiency of interferon regulatory factor 5

The rs2004640 single nucleotide polymorphism and the CGGGG copy-number variant (rs77571059) are promoter polymorphisms within interferon regulatory factor 5 (IRF5). They have been implicated as susceptibility factors for several autoimmune diseases. IRF5 uses alternative promoter splicing, where any of 4 first exons begin the mRNA. The CGGGG indel is in exon 1A's promoter; the rs2004640 allele creates a splicing recognition site, enabling usage of exon 1B. This study aimed at characterizing alterations in IRF5 mRNA due to these polymorphisms. Cells with risk polymorphisms exhibited ~2-fold higher levels of IRF5 mRNA and protein, but demonstrated no change in mRNA stability. Quantitative PCR demonstrated decreased usage of exons 1C and 1D in cell lines with the risk polymorphisms. RNA folding analysis revealed a hairpin in exon 1B; mutational analysis showed that the hairpin shape decreased translation 5-fold. Although translation of mRNA that uses exon 1B is low due to a hairpin, increased IRF5 mRNA levels in individuals with the rs2004640 risk allele lead to higher overall protein expression. In addition, several new splice variants of IRF5 were sequenced. IRF5's promoter polymorphisms alter first exon usage and increase transcription levels. High levels of IRF5 may bias the immune system toward autoimmunity.

Autoantigens: novel forms and presentation to the immune system

It is clear that lupus autoimmunity is marked by a variety of abnormalities, including those found at a macroscopic scale, cells and tissues, as well as more microenvironmental influences, originating at the individual cell surface through to the nucleus. The convergence of genetic, epigenetic, and perhaps environmental influences all lead to the overt clinical expression of disease, reflected by the presences of autoantibodies and tissue pathology. This review will address several specific areas that fall among the non-genetic factors that contribute to lupus autoimmunity and related syndromes. In particular, we will discuss the importance of understanding various protein post-translational modifications (PTMs), mechanisms that mediate the ability of "modified self" to trigger autoimmunity, and how these PTMs influence lupus diagnosis. Finally, we will discuss altered pathways of autoantigen presentation that may contribute to the perpetuation of chronic autoimmune disease.

Leptin promotes lupus T-cell autoimmunity

In systemic lupus erythematosus (SLE), the impairment in apoptosis can facilitate the initiation and maintenance of autoimmune responses to self antigens. Here we show that the adipocytokine leptin, which is abnormally elevated in SLE, promotes the survival and proliferation of autoreactive T-cells in mice with an autoreactive T-cell repertoire, including (NZB x NZW)F1 lupus-prone mice. This ability of leptin to promote lupus T-cell autoimmunity suggests the possibility of a therapeutic targeting of leptin in SLE.

Lupus nephritis: enigmas, conflicting models and an emerging concept

Autoantibodies to components of chromatin, which include double-stranded DNA (dsDNA), histones and nucleosomes, are central in the pathogenesis of lupus nephritis. How anti-chromatin autoantibodies exert their nephritogenic activity, however, is controversial. One model assumes that autoantibodies initiate inflammation when they cross-react with intrinsic glomerular structures such as components of membranes, matrices or exposed nonchromatin ligands released from cells. Another model suggests glomerular deposition of autoantibodies in complex with chromatin, thereby inducing classic immune complex-mediated tissue damage. Recent data suggest acquired error of renal chromatin degradation due to the loss of renal DNaseI enzyme activity is an important contributing factor to the development of lupus nephritis in lupus-prone (NZBxNZW)F1 mice and in patients with lupus nephritis. Down-regulation of DNaseI expression results in reduced chromatin fragmentation and in deposition of extracellular chromatin-IgG complexes in glomerular basement membranes in individuals who produce IgG anti-chromatin autoantibodies. The main focus of the present review is to discuss whether exposed chromatin fragments in glomeruli are targeted by potentially nephritogenic anti-dsDNA autoantibodies or if the nephritogenic activity of these autoantibodies is explained by cross-reaction with intrinsic glomerular constituents or if both models coexist in diseased kidneys. In addition, the role of silencing of the renal DNaseI gene and the biological consequences of reduced chromatin fragmentation in nephritic kidneys are discussed.

TRAIL mRNA expression in peripheral blood mononuclear cells of Egyptian SLE patients

Although the definite etiopathogenesis of systemic lupus erythematosus (SLE) remains unclear, many different mechanisms may contribute to its pathogenesis. Tumor-necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor (TNF) family with pro-apoptotic activity. The accumulation of apoptotic cell debris has been hypothesized to induce the autoimmune inflammation in SLE, and TRAIL may trigger this programmed cell death. We investigated TRAIL mRNA expression levels in peripheral blood mononuclear cells (PBMCs) from 60 SLE patients and 40 controls using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), and we studied the association between the results and clinical and laboratory parameters of the patients. Expression levels of TRAIL mRNAs in SLE patients were significantly higher than in controls (p<0.001). A statistically significant association was detected between TRAIL mRNA expression and SLE activity (p=0.001).

Polymorphisms of Toll-like receptor-4 and CD14 in systemic lupus erythematosus and rheumatoid arthritis

Background

Toll-like receptor 4 (TLR4) and its co-receptor CD14 play a major role in innate immunity by recognizing PAMPs and signal the activation of adaptive responses. These receptors can recognize endogenous ligands mainly auto-antigens. In addition, TLR4 (Asp299Gly) and CD14 (C/T -159) polymorphisms (SNPs) may modify qualitatively and/or quantitatively their expression. Therefore, they could be implied in autoimmune diseases and can influence both susceptibility and severity of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).

Patients and methods

TLR4 (Asp299Gly) and CD14 (C/T -159) SNPs were genotyped using polymerase chain reaction (PCR)-RFLP in 127 SLE patients, 100 RA patients, and 114 healthy controls matched in age and gender.

Results

CD14*T allele was significantly more frequent in SLE patients (0.456) comparatively to controls (0.355), p = 0.02 OR (95% CI) = 1.53 [1.04-2.24]. In RA patients, the higher frequency of CD14*T allele (0.405) failed to reach significance, p = 0.28. Investigation of the TLR4 (Asp299Gly) SNP showed no significant association neither with SLE nor with RA.

Analysis of these SNPs according to clinical and biological features showed a significant higher frequency of arthritis in SLE patients carrying CD14*T/T genotype (92%) comparatively to those with C/C and C/T genotypes (72.5%), p = 0.04. Moreover, SLE patients carrying CD14*T/T/TLR4*A/A haplotype had significantly more arthritis (91.3%) than the rest of SLE group (73%), p = 0,044 and confirmed by multivariable analysis after adjustment according to age and gender, p = 0.01.

Conclusion

The CD14 (-159)*T allele seems to be associated with susceptibility to SLE and arthritis occurrence.

Structural requirements for the procoagulant activity of nucleic acids

Nucleic acids, especially extracellular RNA, are exposed following tissue- or vessel damage and have previously been shown to activate the intrinsic blood coagulation pathway in vitro and in vivo. Yet, no information on structural requirements for the procoagulant activity of nucleic acids is available. A comparison of linear and hairpin-forming RNA- and DNA-oligomers revealed that all tested oligomers forming a stable hairpin structure were protected from degradation in human plasma. In contrast to linear nucleic acids, hairpin forming compounds demonstrated highest procoagulant activities based on the analysis of clotting time in human plasma and in a prekallikrein activation assay. Moreover, the procoagulant activities of the DNA-oligomers correlated well with their binding affinity to high molecular weight kininogen, whereas the binding affinity of all tested oligomers to prekallikrein was low. Furthermore, four DNA-aptamers directed against thrombin, activated protein C, vascular endothelial growth factor and nucleolin as well as the naturally occurring small nucleolar RNA U6snRNA were identified as effective cofactors for prekallikrein auto-activation. Together, we conclude that hairpin-forming nucleic acids are most effective in promoting procoagulant activities, largely mediated by their specific binding to kininogen. Thus, in vivo application of therapeutic nucleic acids like aptamers might have undesired prothrombotic or proinflammatory side effects.

Association of FAS gene polymorphisms with systemic lupus erythematosus: A case-control study and meta-analysis

The association of functional polymorphisms in the promoter of the apoptosis gene FAS with systemic lupus erythematosus (SLE) susceptibility has been a controversial subject. We conducted a case-control study to investigate this association in a Chinese population and performed a meta-analysis in different populations. The single nucleotide polymorphisms (SNPs) rs2234767 (-1377G>A) and rs1800682 (-670A>G) were genotyped by TaqMan allelic discrimination assays in 552 Chinese SLE patients and 718 healthy controls. In our case-control study, we observed allelic association between the promoter SNP rs2234767 [P=0.033, odds ratio (OR)=0.836, 95% confidence interval (CI), 0.709-0.986] and SLE but not the SNP rs1800682. Haplotype analysis revealed that one haplotype of GA was significantly associated with the disease (P=0.039, OR=1.184, 95% CI, 1.009-1.391). In the meta-analysis available studies, including our data, were combined using the STATA software package v.7.0. The meta-analysis revealed a significant association between FAS polymorphisms and SLE (rs2234767 A vs. G allele; P=0.004, OR=0.819, 95% CI, 0.715-0.938, rs1800682 G vs. A allele: P=0.034, OR=0.791, 95% CI, 0.637-0.983). In conclusion, FAS gene polymorphisms may contribute to SLE susceptibility in the Chinese population, and the meta-analysis shows that FAS polymorphisms may be associated with SLE susceptibility in different populations.

Expression of Toll-like receptors and their detection of nuclear self-antigen leading to immune activation in JSLE

OBJECTIVES

Toll-like receptors (TLRs) essential in the functioning of the immune system have been implicated in the development of autoimmunity. TLR3, 7, 8 and 9 are capable of recognizing nucleic autoantigens typical of SLE. Their expression correlates positively with disease activity in adult-onset SLE. This study aimed to determine the role of TLRs in JSLE and whether apoptotic neutrophils are a source of nuclear autoantigen being detected through TLR3, 7, 8 and 9, leading to an inflammatory response.

METHODS

TLR3, 7, 8 and 9 mRNA and protein expression were measured in peripheral blood mononuclear cells (PBMCs) in JSLE patients compared with JIA and non-inflammatory controls. Activation of the TLRs by JSLE serum-induced apoptotic neutrophils was detected by measuring IFN-α mRNA and protein expression, and confirmed using myeloid differentiation factor 88 (MyD88) and TIR domain-containing adapter-inducing IFN-β (TRIF) inhibitors.

RESULTS

JSLE patients have increased TLR3, 8 and 9 mRNA and protein expression compared with controls (P < 0.05). Incubation of PBMCs with apoptotic neutrophils demonstrated a dose-response relationship for IFN-α mRNA expression. Inhibition of TLR signalling by blocking MyD88 and TRIF signalling decreased IFN-α mRNA expression in PBMCs incubated with apoptotic neutrophils (P < 0.05).

CONCLUSIONS

This study demonstrated significantly increased TLR expression in JSLE compared with controls. Our data indicate that apoptotic neutrophils trigger TLR activation through their presentation of autoantigens. The role of TLRs in this inflammatory response was demonstrated by a dose-response relationship to apoptotic neutrophil concentration and confirmed by a decrease in IFN-α production after inhibition of TLR signalling.

Neutrophils in the pathogenesis and manifestations of SLE

Systemic lupus erythematosus (SLE) is an autoimmune disease of unclear etiology that affects mostly women of childbearing age. Profound abnormalities in both innate and adaptive immunity triggered by genetic and environmental factors are well documented to play an important part in the pathogenesis of SLE. Nonetheless, the role of neutrophils--the most abundant immune cell type--in the pathology of this disease has been unclear. Over the past decade, compelling evidence has emerged that implicates neutrophils in the initiation and perpetuation of SLE and also in the resultant organ damage frequently observed in patients with this disease. SLE-derived low-density granulocytes (LDGs) induce vascular damage and synthesize increased amounts of type I interferons and, as such, could play a prominent part in the pathogenesis of SLE. Furthermore, increased cell death and enhanced extracellular trap formation observed in SLE-derived neutrophils might have key roles in the induction of autoimmunity and the development of organ damage in patients with SLE. Together, these events could have significant deleterious effects and promote aberrant immune responses in this disease. This Review highlights the role of neutrophils in the pathogenesis of SLE, with a particular focus on the putative deleterious effects of LDGs and neutrophil extracellular trap formation.

C-reactive protein functions as a negative regulator of macrophage activation induced by apoptotic DNA

C-reactive protein (CRP), an acute-phase protein with an ability to bind to nuclear antigen, has been reported to regulate cytokine secretion and modulate immune responses. We previously reported that activated syngeneic lymphocyte-derived apoptotic DNA (apopDNA) could induce macrophage activation and contribute to the initiation and progression of lupus nephritis. It is reasonable to hypothesize that CRP might regulate apopDNA-induced macrophage activation. Herein, CRP was shown to promote macrophage-mediated apopDNA uptake by binding to apopDNA (CRP/apopDNA complex). Notably, CRP/apopDNA treatment inhibited the production of inflammatory cytokines and chemokines by macrophages which could be induced by apopDNA alone. Further coculture and transwell studies revealed that CRP/apopDNA-induced macrophages prohibited apopDNA-induced macrophage activation in an IL-10 dependent manner. These results provide insight into the potential mechanism of CRP regulatory activity in macrophage activation induced by apopDNA in the context of lupus nephritis and other autoimmune diseases.

The pathway of estradiol-induced apoptosis in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a disease with unknown etiology. The pathologic role of sex hormones and apoptosis in SLE has often been discussed. We studied the effects of estradiol in the pathway of induced apoptosis in Iranian SLE patients. T lymphocytes from 35 SLE patients and 20 age-matched controls were isolated and cultured in the presence of 10(-8) M 17-β estradiol. The expression levels of Fas, Fas ligand (FasL), Bcl-2, caspase-8, and caspase-9 mRNAs were determined semiquantitatively in comparison to the expression level of beta actin RNA. Estradiol exposure did not have any significant effects on the expression levels of Fas, Bcl-2, and caspase-9 in SLE patients and controls. However, the expression levels of FasL and caspase-8 were significantly increased in SLE patients, but not in controls. This suggests the probable involvement of extrinsic apoptosis pathway in estradiol-induced apoptosis in SLE.

Cellular localization of nuclear antigen during neutrophil apoptosis: mechanism for autoantigen exposure?

Juvenile-onset systemic lupus erythematosus (JSLE) is a multisystem autoimmune disease characterized by hyperactive B-cells producing auto-antibodies directed against nuclear antigens. A potential source of these antigenic components is apoptotic cells. We have previously demonstrated increased dysregulated neutrophil apoptosis in JSLE patients. Here we investigate autoantigen expression on JSLE neutrophils during apoptosis. Neutrophils from non-inflammatory controls and JSLE patients were incubated with JSLE and control serum. Apoptosis and dsDNA expression was measured using flow cytometry and confocal microscopy. Increased neutrophil apoptosis and dsDNA expression was observed in JSLE and control neutrophils incubated with JSLE serum. During neutrophil apoptosis nuclear material was exposed on the cell surface rather than within the cell as seen with viable neutrophils. The increased neutrophil apoptosis induced by JSLE compared with control serum resulted in increased surface expression of nuclear antigens. This may provide an additional mechanism leading to the generation of autoantibodies in JSLE.

Proteomic analysis for the anti-apoptotic effects of cystamine on apoptosis-prone macrophage

Increased macrophage vulnerability is associated with progression of systemic lupus erythematosus. Our previous studies have shown that cystamine, an inhibitor of transglutaminase 2 (TG2), alleviated the apoptosis of hepatocyte and brain cell in lupus-prone mice NZB/W-F1. In present study, we further investigated the effects of cystamine on apoptosis-prone macrophages (APMs) in the lupus mice. Using two-dimensional gel electrophoresis (2-DE) analysis, we found that cystamine induced a differential protein expression pattern of APM as comparing to the PBS control. The protein spots presenting differential level between cystamine and PBS treatment were then identified by peptide-mass fingerprinting (PMF). After bioinformatic analysis, these identified proteins were found involved in mitochondrial apoptotic pathway, oxidative stress, and mitogen-activated protein (MAP) kinase-mediated pathway. Further investigation revealed that cystamine significantly decreased the levels of apoptotic Bax and Apaf-1 and the activity of caspase-3, and increased the levels of anti-apoptotic Bcl-2 in APM. We also found that these apoptotic mediators were up-regulated in a correlation with the progression of lupus severity in NZB/W-F1, which were little affected in BALB/c mice. We also found that the reduced serum glutathione was restored by cystamine in NZB/W-F1. Interestingly, the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in APM and the phagocytic ability was diminished in presence of cystamine. In conclusion, our findings indicate that cystamine significantly inhibited mitochondrial pathway, induced antioxidant proteins, and diminished phosphorylation of extracellular ERK1/2, which may alleviate the apoptosis and the phagocytic ability of APM.

Dendritic cell function in lupus: Independent contributors or victims of aberrant immune regulation

Dendritic cells (DCs) represent an important component of the immune system connecting the innate and adaptive immune responses. They are able to trigger strong immunity as well as tolerance against certain antigens, and therefore it is obvious that they have a central role in the expression of immunological diseases. However, because DCs are sparse, heterogeneous and plastic, their exact role in complex autoimmune diseases, such as systemic lupus erythematosus (SLE) remains not well defined. In this review, we make an attempt to summarize critically recent knowledge on the role of conventional DCs in the expression of autoimmunity and pathology in SLE.

Advances in lupus stemming from the parent-into-F1 model

The parent-into-F1 model has led to important advances in our understanding of lupus. Here, we review the work in murine lupus that elucidated the role of T cells and supported the conclusion that the parent-into-F1 model of induced lupus compares favorably with de facto gold standard spontaneous models of lupus. Then we focus on recent work in parent-into-F1 mice, which has yielded novel insights into unresolved controversies, such as the role of apoptosis in the pathogenesis of lupus and lupus in patients receiving TNF blockade. Finally, the review considers the evidence that supports a potential role for CD8 T cells, both cytotoxic and memory cells, in mediating disease remission.

A distinct subset of proinflammatory neutrophils isolated from patients with systemic lupus erythematosus induces vascular damage and synthesizes type I IFNs

Neutrophil-specific genes are abundant in PBMC microarrays from lupus patients because of the presence of low-density granulocytes (LDGs) in mononuclear cell fractions. The functionality and pathogenicity of these LDGs have not been characterized. We developed a technique to purify LDGs from lupus PBMCs and assessed their phenotype, function, and potential role in disease pathogenesis. LDGs, their autologous lupus neutrophils, and healthy control neutrophils were compared with regard to their microbicidal and phagocytic capacities, generation of reactive oxygen species, activation status, inflammatory cytokine profile, and type I IFN expression and signatures. The capacity of LDGs to kill endothelial cells and their antiangiogenic potential were also assessed. LDGs display an activated phenotype, secrete increased levels of type I IFNs, TNF-alpha, and IFN-gamma, but show impaired phagocytic potential. LDGs induce significant endothelial cell cytotoxicity and synthesize sufficient levels of type I IFNs to disrupt the capacity of endothelial progenitor cells to differentiate into mature endothelial cells. LDG depletion restores the functional capacity of endothelial progenitor cells. We conclude that lupus LDGs are proinflammatory and display pathogenic features, including the capacity to synthesize type I IFNs. They may play an important dual role in premature cardiovascular disease development in systemic lupus erythematosus by simultaneously mediating enhanced vascular damage and inhibiting vascular repair.

Pathogenesis of human systemic lupus erythematosus: recent advances

Systemic lupus erythematosus (SLE) is an autoimmune disease with manifestations derived from the involvement of multiple organs including the kidneys, joints, nervous system and hematopoietic organs. Immune system aberrations, as well as heritable, hormonal and environmental factors interplay in the expression of organ damage. Recent contributions from different fields have developed our understanding of SLE and reshaped current pathogenic models. Here, we review recent findings that deal with (i) genes associated with disease expression; (ii) immune cell molecular abnormalities that lead to autoimmune pathology; (iii) the role of hormones and sex chromosomes in the development of disease; and (iv) environmental and epigenetic factors thought to contribute to the expression of SLE. Finally, we highlight molecular defects intimately associated with the disease process of SLE that might represent ideal therapeutic targets and disease biomarkers.

The U1-snRNP complex: structural properties relating to autoimmune pathogenesis in rheumatic diseases

The U1 small nuclear ribonucleoprotein particle (snRNP) is a target of autoreactive B cells and T cells in several rheumatic diseases including systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD). We propose that inherent structural properties of this autoantigen complex, including common RNA-binding motifs, B and T-cell epitopes, and a unique stimulatory RNA molecule, underlie its susceptibility as a target of the autoimmune response. Immune mechanisms that may contribute to overall U1-snRNP immunogenicity include epitope spreading through B and T-cell interactions, apoptosis-induced modifications, and toll-like receptor (TLR) activation through stimulation by U1-snRNA. We conclude that understanding the interactions between U1-snRNP and the immune system will provide insights into why certain patients develop anti-U1-snRNP autoimmunity, and more importantly how to effectively target therapies against this autoimmune response.

A tolerogenic peptide down-regulates mature B cells in bone marrow of lupus-afflicted mice by inhibition of interleukin-7, leading to apoptosis

Systemic lupus erythematosus (SLE) is an autoimmune disease mediated by T and B cells. It is characterized by a variety of autoantibodies and systemic clinical manifestations. A tolerogenic peptide, designated hCDR1, ameliorated the serological and clinical manifestations of SLE in both spontaneous and induced models of lupus. In the present study, we evaluated the status of mature B cells in the bone marrow (BM) of SLE-afflicted mice, and determined the effect of treatment with the tolerogenic peptide hCDR1 on these cells. We demonstrate herein that mature B cells of the BM of SLE-afflicted (New Zealand Black x New Zealand White)F(1) mice were largely expanded, and that treatment with hCDR1 down-regulated this population. Moreover, treatment with hCDR1 inhibited the expression of the pathogenic cytokines [interferon-gamma and interleukin (IL)-10], whereas it up-regulated the expression of transforming growth factor-beta in the BM. Treatment with hCDR1 up-regulated the rates of apoptosis of mature B cells. The latter was associated with inhibited expression of the survival Bcl-xL gene and of IL-7 by BM cells. Furthermore, the addition of recombinant IL-7 abrogated the suppressive effects of hCDR1 on Bcl-xL in the BM cells and resulted in elevated levels of apoptosis. Hence, the down-regulated production of IL-7 contributes to the hCDR1-mediated apoptosis of mature B cells in the BM of SLE-afflicted mice.

A new model of induced experimental systemic lupus erythematosus (SLE) in pigs and its amelioration by treatment with a tolerogenic peptide

INTRODUCTION

Systemic lupus erythematosus (SLE) is characterized by a variety of autoantibodies and systemic clinical manifestations. A tolerogenic peptide, hCDR1, ameliorated lupus manifestations in mice models. The objectives of this study were to induce experimental SLE in pigs and to determine the ability of hCDR1 to immunomodulate the disease manifestations.

RESULTS AND DISCUSSION

We report here the successful induction, by a monoclonal anti-DNA antibody, of an SLE-like disease in pigs, manifested by autoantibody production and glomerular immune complex deposits. Treatment of pigs with hCDR1 ameliorated the lupus-related manifestations. Furthermore, the treatment downregulated the gene expression of the pathogenic cytokines, interleukin (IL)-1beta, tumor necrosis factor alpha, interferon gamma, and IL-10, and upregulated the expression of the immunosuppressive cytokine transforming growth factor beta, the antiapoptotic molecule Bcl-xL, and the suppressive master gene, Foxp3, hence restoring the expression of the latter to normal levels. Thus, hCDR1 is capable of ameliorating lupus in large animals and is a potential candidate for the treatment of SLE patients.

Progression of murine lupus nephritis is linked to acquired renal Dnase1 deficiency and not to up-regulated apoptosis

The accumulation of apoptotic cells has been suggested as a possible mechanism of nucleosome conversion into self-antigens that may both initiate autoimmune responses and participate in immune complex deposition in lupus nephritis. In this study, we analyzed both the rate of transcription of apoptosis-related genes and the presence of activated apoptotic factors within kidneys of lupus-prone (NZBxNZW) F1 mice during disease progression. The results of this study demonstrated no activation of apoptotic pathways in kidneys of these lupus-prone mice at the time of appearance of anti-double standard DNA antibodies in serum, as well as the formation of mesangial immune deposits in glomeruli. In contrast, the transition of mesangial into membranoproliferative lupus nephritis coincided with an accumulation of activated caspase 3-positive cells in kidneys, in addition to a dramatic decrease in Dnase1 gene transcription. Highly reduced expression levels of the Dnase1 gene may be responsible for the accumulation of large chromatin-containing immune complexes in glomerular capillary membranes. Thus, the initiation of lupus nephritis is not linked to increased apoptotic activity in kidneys. The combined down-regulation of Dnase1 and the increased number of apoptotic cells, which is possibly due to their reduced clearance in affected kidneys, may together be responsible for the transformation of mild mesangial lupus nephritis into severe membranoproliferative, end-stage organ disease.

Upregulated BclG(L) expression enhances apoptosis of peripheral blood CD4+ T lymphocytes in patients with systemic lupus erythematosus

Increased lymphocyte apoptosis has been suggested to contribute to the development of systemic lupus erythematosus (SLE), but the critical factors involved in the apoptotic pathways are still unknown. By long serial analysis of gene expression (LongSAGE) profiles and microarray analyses, a novel apoptosis-related gene BclG(L) expression was found significantly increased in peripheral blood CD4+ T cells of SLE patients, which was correlated with the enhanced CD4+ T cells apoptosis, anti-nuclear antibody (ANA) titer and proteinuria. In vitro, BclG(L) expression could be specially upregulated by SLE serum stimulation and positively correlated with induced CD4+ T cell apoptosis. Enforcing BclG(L) overexpression by lentivirus could directly enhance CD4+ T cell apoptosis, but these apoptosis-inducing effects could be partially inhibited by knockdown of BclG(L) expression. Collectively, these results indicate that increased BclG(L) expression may contribute to the aberrant CD4+ T cell apoptosis which causes an inappropriate immune response and impaired homeostasis in SLE.

Multidimensional degradomics identifies systemic autoantigens and intracellular matrix proteins as novel gelatinase B/MMP-9 substrates

The action radius of matrix metalloproteinases or MMPs is not restricted to massive extracellular matrix (ECM) degradation, it extends to the proteolysis of numerous secreted and membrane-bound proteins. Although many instances exist in which cells disintegrate, often in conjunction with induction of MMPs, the intracellular MMP substrate repertoire or degradome remains relatively unexplored. We started an unbiased exploration of the proteolytic modification of intracellular proteins by MMPs, using gelatinase B/MMP-9 as a model enzyme. To this end, multidimensional degradomics technology was developed by the integration of broadly available biotechniques. In this way, 100-200 MMP-9 candidate substrates were isolated, of which 69 were identified. Integration of these results with the known biological functions of the substrates revealed many novel MMP-9 substrates from the intracellular matrix (ICM), such as actin, tubulin, gelsolin, moesin, ezrin, Arp2/3 complex subunits, filamin B and stathmin. About 2/3 of the identified candidates were autoantigens described in multiple autoimmune conditions and in cancer (e.g. annexin I, nucleolin, citrate synthase, HMGB1, alpha-enolase, histidyl-tRNA synthetase, HSP27, HSC70, HSP90, snRNP D3). These findings led to the insight that MMPs and other proteases may have novel (immuno)regulatory properties by the clearance of toxic and immunogenic burdens of abundant ICM proteins released after extensive necrosis. In line with the extracellular processing of organ-specific autoantigens, proteolysis might also assist in the generation of immunodominant 'neo-epitopes' from systemic autoantigens. The study of proteolysis of ICM molecules, autoantigens, alarmins and other crucial intracellular molecules may result in the discovery of novel roles for proteolytic modification.

Immunity and acquired alterations in cognition and emotion: lessons from SLE

Classic immunologic teaching describes the brain as an immunologically privileged site. Studies of neuroimmunology have focused for many years almost exclusively on multiple sclerosis, a disease in which inflammatory cells actually infiltrate brain tissue, and the rodent model of this disease, experimental allergic encephalitis. Over the past decade, however, increasingly, brain-reactive antibodies have been demonstrated in the serum of patients with numerous neurological diseases. The contribution these antibodies make to neuronal dysfunction has, in general, not been determined. Here, we describe recent studies showing that serum antibodies to the N-methyl-D-aspartate receptor occur frequently in patients with systemic lupus erythematosus and can cause alterations in cognition and behavior following a breach in the blood-brain barrier.

Myeloid dendritic cells display downregulation of C-type lectin receptors and aberrant lectin uptake in systemic lupus erythematosus

Introduction

There is a growing body of evidence implicating aberrant dendritic cell function as a crucial component in the immunopathogenesis of systemic lupus erythematosus. The purpose of the present study was to characterize the phagocytic capacity and expression of receptors involved in pathogen recognition and self-nonself discrimination on myeloid dendritic cells from patients with lupus.

Methods

Unstimulated or stimulated monocyte-derived dendritic cells were obtained from lupus patients and healthy control individuals, and expression of C-type lectin receptors (mannose receptor and dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin), complement-receptor 3 and Fcγ receptors was determined by flow cytometry. Dextran uptake by lupus and control dendritic cells was also assessed by flow cytometry. Serum IFNγ was quantified by ELISA, and uptake of microbial products was measured using fluorescently labeled zymosan.

Results

When compared with dendritic cells from healthy control individuals, unstimulated and stimulated lupus dendritic cells displayed significantly decreased dextran uptake and mannose receptor and dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin expression. Decreased expression of the mannose receptor was associated with high serum IFNγ levels, but not with maturation status or medications. Diminished dextran uptake and mannose receptor expression correlated with lupus disease activity. There were no differences between control and lupus dendritic cells in the expression of other pattern recognition receptors or in the capacity to uptake zymosan particles

Conclusions

Lupus dendritic cells have diminished endocytic capacity, which correlates with decreased mannose receptor expression. While this phenomenon appears primarily intrinsic to dendritic cells, modulation by serum factors such as IFNγ could play a role. These abnormalities may be relevant to the aberrant immune homeostasis and the increased susceptibility to infections described in lupus.

Administration of M. leprae Hsp65 interferes with the murine lupus progression

The heat shock protein [Hsp] family guides several steps during protein synthesis, are abundant in prokaryotic and eukaryotic cells, and are highly conserved during evolution. The Hsp60 family is involved in assembly and transport of proteins, and is expressed at very high levels during autoimmunity or autoinflammatory phenomena. Here, the pathophysiological role of the wild type [WT] and the point mutated K⁴⁰⁹A recombinant Hsp65 of M. leprae in an animal model of Systemic Lupus Erythematosus [SLE] was evaluated in vivo using the genetically homogeneous [NZBxNZW]F₁ mice. Anti-DNA and anti-Hsp65 antibodies responsiveness was individually measured during the animal's life span, and the mean survival time [MST] was determined. The treatment with WT abbreviates the MST in 46%, when compared to non-treated mice [p<0.001]. An increase in the IgG2a/IgG1 anti-DNA antibodies ratio was also observed in animals injected with the WT Hsp65. Incubation of BALB/c macrophages with F₁ serum from WT treated mice resulted in acute cell necrosis; treatment of these cells with serum from K⁴⁰⁹A treated mice did not cause any toxic effect. Moreover, the involvement of WT correlates with age and is dose-dependent. Our data suggest that Hsp65 may be a central molecule intervening in the progression of the SLE, and that the point mutated K⁴⁰⁹A recombinant immunogenic molecule, that counteracts the deleterious effect of WT, may act mitigating and delaying the development of SLE in treated mice. This study gives new insights into the general biological role of Hsp and the significant impact of environmental factors during the pathogenesis of this autoimmune process.

Dynamic relocation of nuclear proteins during the execution phase of apoptosis

In the apoptotic program of controlled cell dismantling, the most characteristic nuclear changes involve chromatin, which condenses and often collapses against the nuclear envelope in the form of crescents. A severe reorganization also occurs in ribonucleoprotein (RNP)-containing structures which are involved in the synthesis and processing of transcripts: already during early apoptosis, the nucleoplasmic RNPs (namely, perichromatin fibrils, perichromatin granules, and interchromatin granules) coalesce in the interchromatin space where they associate with segregated nucleolar components, to ectopically form fibro-granular heterogeneous clusters. This was found to occur in cell systems in vivo and in cultured cell lines, after different apoptogenic stimuli. These RNP aggregates we have called heterogeneous ectopic RNP-derived structures (HERDS) move from the nucleus to the cytoplasm, and may be found in apoptotic bodies, in late apoptosis. Immunolabeling experiments demonstrated that several other proteins which are normally located inside the nucleus also move into the cytoplasm, during apoptosis, independently from HERDS. Apoptotic cells have been suggested to be a powerful source of nuclear auto-antigens, which are produced by the partial proteolytic or nucleolytic cleavage of a wide variety of nuclear substrates. In the presence of defective phagocytosis (or when massive apoptosis overwhelms the clearance capability of the tissue scavenger cells), the disposal of apoptotic cells becomes insufficient and unphagocytosed late apoptotic cells may accumulate in the tissue where they may be engulfed by antigen-presenting cells (such as dendritic cells); an autoimmune response may thus be elicited, by which apoptosis-derived auto-antigens are recognized and presented to the immune system.

Serum protein oxidation and apolipoprotein CIII levels in people with systemic lupus erythematosus with and without nephritis

Increased oxidative stress is a hallmark of the autoimmune disease systemic lupus erythematosus (SLE). This study compares serum protein oxidation levels in SLE patients without and with renal involvement (lupus nephritis); the latter have a significantly poorer prognosis. Similar increases in protein carbonyls and decreases in protein thiols were observed in both SLE groups compared to controls. Protein carbonyl distribution, determined by Western blotting of 2D gels, was similar in both SLE groups, suggesting factors other than oxidation also play a role in SLE complications. 2D electrophoresis examined the serum proteome further. Six proteins were significantly decreases in non-renal SLE patients compared to controls; five were identified by mass spectrometry, including one isoform of pro-atherogenic apoCIII. Total apoCIII levels (assessed by ELISA) in lupus nephritis patients were significantly elevated compared to controls or non-renal SLE patients. Thus, levels of oxidized proteins and apoCIII may be useful biomarkers in SLE studies.

The most widespread desmosomal cadherin, desmoglein 2, is a novel target of caspase 3-mediated apoptotic machinery

Apoptotic cells are known to regulate the ordered dismantling of intercellular contacts through caspase activity. Despite the important role of desmoglein (Dsg) 2 in epithelial cell-cell adhesion, the fate of this widespread desmosomal cadherin during apoptosis is yet poorly understood. Here, by means of pharmacological approaches, we investigated whether Dsg2 was targeted by caspases in HaCaT and HT-29 cell lines undergoing staurosporine (STS)-induced apoptosis. Results showed that STS induced a caspase-dependent form of cell-death in both keratinocytes (HaCaT) and enterocytes (HT-29), that associated with progressive depletion of Dsg2 from cell lysates. The proteolytic processing of full-length Dsg2 resulted in the appearance of a 70-kDa fragment which was released into the cytosol. Consistently, immunofluorescence studies revealed that Dsg2 staining was abolished from cell surface whereas the cytoplasmic region of Dsg2 did localize intracellularly. Plakoglobin (Pg) also underwent cleavage and detached from Dsg2. Apoptotic changes paralleled with progressive loss of intercellular adhesion strength. All these biochemical, morphological, and functional changes were regulated by caspase 3. Indeed, in the presence of the caspase 3-inhibitor z-DEVD-fmk, full-length Dsg2 protein levels were preserved, whereas the amount of the 70-kDa fragment was maintained on control levels. Furthermore, cells pretreated with z-DEVD-fmk retained the membrane labeling of Dsg2. Taken together, our data demonstrate that the apoptotic processing of Dsg2 is mediated by caspase 3 in epithelial cells.

The genetics and biology of Irf5-mediated signaling in lupus

Recently much attention was attracted to the importance of the type I interferon pathway in the initiation and development of the autoimmune disease systemic lupus erythematosus (SLE). Many SLE patients have increased serum levels of IFN-alpha and display an IFN gene expression "signature" characterized by strong overexpression of IFN-responsive genes in leukocytes and target tissues. Moreover, about 20% of cancer patients treated with IFN-alpha therapy manifest symptoms resembling SLE and some later develop the disease. One of the key genes of the IFN-alpha pathway, IRF5, was found to be strongly associated with SLE. Two functional SNPs lead to alternative splicing and altered steady-state level of IRF5 gene expression. Besides, the gene has a polymorphic inserion/deletion in exon 6, which contributes to the diversity in the isoform pattern of IRF5. Interestingly, recent studies have not found association of IRF5 with the other autoimmune diseases, such as rheumatoid arthritis or psoriasis, suggesting the unique role for IRF5 in the development of lupus. Here, we present the current knowledge on IRF5 genetics and its biological function and discuss the possible ways in which IRF5 contributes to susceptibility to SLE.

Secondary necrosis in multicellular animals: an outcome of apoptosis with pathogenic implications

In metazoans apoptosis is a major physiological process of cell elimination during development and in tissue homeostasis and can be involved in pathological situations. In vitro, apoptosis proceeds through an execution phase during which cell dismantling is initiated, with or without fragmentation into apoptotic bodies, but with maintenance of a near-to-intact cytoplasmic membrane, followed by a transition to a necrotic cell elimination traditionally called “secondary necrosis”. Secondary necrosis involves activation of self-hydrolytic enzymes, and swelling of the cell or of the apoptotic bodies, generalized and irreparable damage to the cytoplasmic membrane, and culminates with cell disruption. In vivo, under normal conditions, the elimination of apoptosing cells or apoptotic bodies is by removal through engulfment by scavengers prompted by the exposure of engulfment signals during the execution phase of apoptosis; if this removal fails progression to secondary necrosis ensues as in the in vitro situation. In vivo secondary necrosis occurs when massive apoptosis overwhelms the available scavenging capacity, or when the scavenger mechanism is directly impaired, and may result in leakage of the cell contents with induction of tissue injury and inflammatory and autoimmune responses. Several disorders where secondary necrosis has been implicated as a pathogenic mechanism will be reviewed.

Dendritic cells and the immunopathogenesis of systemic lupus erythematosus

Over the last decade, the role of dendritic cells (DCs) in the immunopathogenesis of systemic lupus erythematosus (SLE) has become apparent. As unique mediators of both tolerance and immunity, aberrant myeloid and plasmacytoid DC function can promote autoimmune responses via a number of mechanisms and proinflammatory pathways. This review provides an overview of DC function, the potential role of DCs in promoting autoimmune responses in SLE, and how other abnormalities in lupus can lead to an enhanced engagement of DCs in immune responses. How medications used to treat SLE and other autoimmune conditions may exert effects on DCs is also explored.

Apoptotic splenocytes drive the autoimmune response to poly(ADP-ribose) polymerase 1 in a murine model of lupus

Although defects in apoptosis have been linked to both human and murine lupus, the exact mechanisms remain unknown. Moreover, it is not clear whether such defects are primary or secondary events in disease pathogenesis. To address these issues, we used an induced model of murine lupus, the parent-into-F(1) model of chronic graft-versus-host disease (cGVHD) in which a lupus-like phenotype highly similar to human systemic lupus erythematosus is reliably induced in normal F(1) mice. We addressed the role of nuclear Ags modified by caspases during apoptosis as potential targets of the autoantibody response and our results identify poly(ADP-ribose) polymerase 1 (PARP-1) as a frequently targeted autoantigen. Additional proteins cleaved during apoptosis were also targeted by the immune response. Importantly, female mice exhibited significantly greater numbers of apoptotic cells in germinal centers and higher serum anti-PARP-1 Ab levels compared with male cGVHD mice. Serum anti-PARP-1 levels in male cGVHD mice could be elevated to levels comparable to those of female cGVHD mice by the injection of apoptotic syngeneic F(1) splenocytes early in the disease course. These results provide a mechanism by which lupus autoantibodies target apoptotic molecules. Specifically, T cell-driven polyclonal B cell activation characteristic of systemic lupus erythematosus is sufficient to saturate otherwise normal apoptotic clearance mechanisms, permitting apoptotic material to accumulate, serve as autoantigens, and drive autoantibody production.

Treatment with rituximab affects both the cellular and the humoral arm of the immune system in patients with SLE

Herein we investigated how rituximab-induced B cell depletion affected leukocyte subpopulations and antibody titers in SLE patients. We focused our analysis on time points related to absence and return of B cells after depletion. A correlation was found between the baseline frequency and time to repopulation; the fewer B cells initially, the longer to their return. While the few B cells remaining after treatment were of memory, double-negative (IgD-CD27-), and CD5+ phenotype, the returning B cells were mainly naïve, indicating de novo production of B cells. Serum levels of IgG and antibodies against Ro52, Ro60, La44, measles and tetanus remained unchanged, while decreases in IgM, IgE, anti-dsDNA and anti-C1q antibodies were observed. Additionally, a significant increase in activated CD4+ and CD8+ T cells, as well as CD25bright FOXP3+ regulatory T cells was observed. In conclusion, both the humoral and the cellular immune systems were affected by treatment with rituximab.

Accelerated macrophage apoptosis induces autoantibody formation and organ damage in systemic lupus erythematosus

Increased monocyte/macrophage (Mphi) apoptosis occurs in patients with systemic lupus erythematosus (SLE) and is mediated, at least in part, by an autoreactive CD4(+) T cell subset. Furthermore, autoreactive murine CD4(+) T cells that kill syngeneic Mphi in vitro induce a lupus-like disease in vivo. However, it is unclear whether increased Mphi apoptosis in SLE per se is sufficient to accelerate/promote autoimmunity. We have investigated whether increased Mphi apoptosis in vivo, induced by the administration of clodronate liposomes, can exacerbate the autoimmune phenotype in NZB x SWR (SNF(1)) lupus-prone mice, and induce autoantibody production in haplotype-matched BALB/c x DBA1 (DBF(1)) non-lupus-prone mice. Lupus-prone mice SNF(1) mice that were treated with clodronate liposomes, but not mice treated with vehicle, developed significant increases in autoantibodies to dsDNA, nucleosomes, and the idiotypically related family of nephritic Abs Id(LN)F(1), when compared with untreated SNF(1) mice. Furthermore, clodronate treatment hastened the onset of proteinuria and worsened SNF(1) lupus nephritis. When compared with vehicle-treated controls, clodronate-treated non-lupus-prone DBF(1) mice developed significantly higher levels of anti-nucleosome and Id(LN)F(1) Abs but did not develop lupus nephritis. We propose that Mphi apoptosis contributes to the pathogenesis of autoantibody formation and organ damage through both an increase in the apoptotic load and impairment in the clearance of apoptotic material. This study suggests that mechanisms that induce scavenger cell apoptosis, such as death induced by autoreactive cytotoxic T cells observed in SLE, could play a pathogenic role and contribute to the severity of the disease.

IL-10-producing macrophages preferentially clear early apoptotic cells

Efficient clearance of apoptotic cells seems to be a prerequisite to prevent the development of autoimmunity. Here we identify that macrophage colony-stimulating factor (M-CSF)-driven macrophages (Mø2s) are potent phagocytes that have the unique capacity to preferentially bind and ingest early apoptotic cells. This macrophage subset has intrinsic anti-inflammatory properties, characterized by high interleukin-10 (IL-10) production in the absence of proinflammatory cytokines, such as IL-6 and tumor necrosis factor-alpha (TNF-alpha). Importantly, whereas the IL-6 and TNF-alpha production by granulocyte-macrophage (GM)-CSF-driven macrophages (Mø1s) is inhibited upon uptake of apoptotic cells, the anti-inflammatory status of Mø2 is retained during phagocytosis. Mø2s were shown to use CD14 to tether apoptotic cells, whereas recognition of phosphatidylserine (PS) contributed to uptake of early apoptotic cells. Mø2s showed more potent macropinocytosis compared with dendritic cells (DCs) and Mø1s, and uptake of apoptotic cells was inhibited by a macropinocytosis inhibitor. Our studies suggest that, under steady-state conditions, IL-10-producing Mø2s are prominently involved in the clearance of early apoptotic cells.

Precocious intima-media thickening in patients with primary Sjögren's syndrome

OBJECTIVE

Systemic lupus erythematosus and rheumatoid arthritis represent independent risk factors for atherosclerosis (ATS), although this may be confounded by continuous pharmacologic treatment. Primary Sjögren's syndrome (SS) shares several features of these diseases and may therefore represent an interesting model for verifying the presence of accelerated ATS in the absence of pharmacologic interference. The present study therefore used this model to describe the presence of accelerated ATS in a group of young women.

METHODS

Thirty-seven untreated white women with primary SS were evaluated clinically and serologically. Carotid and femoral artery intima-media thickness (IMT) was evaluated in the patients and in 35 age-matched healthy women who served as controls.

RESULTS

The patients had a higher IMT than did the controls at both the carotid (mean +/- SD 0.82 +/- 0.24 mm versus 0.63 +/- 0.20 mm; P < or = 0.001) and the femoral (0.81 +/- 0.26 mm versus 0.67 +/- 0.23 mm; P < or = 0.019) levels, and had a higher prevalence of carotid intima-media thickening (49% versus 11% of controls; P < or = 0.001). The patient subset with high carotid IMT showed an increased prevalence of leukopenia and circulating anti-SSA antibodies; interestingly, the number of leukocytes was inversely correlated with the level of arterial IMT in patients with SS. Multivariate analysis demonstrated that anti-SSA antibodies were independent predictors of carotid artery thickening, while leukopenia was a predictor of both carotid and femoral artery thickening.

CONCLUSION

Subclinical ATS was evident in about one-half of the patients with SS. Its association with some features typical of connective tissue diseases, such as the presence of anti-SSA and leukopenia, suggests that the immune dysregulation characterizing this autoimmune disorder may play a key role in inducing early ATS.

Amelioration of SLE-like manifestations in (NZBxNZW)F1 mice following treatment with a peptide based on the complementarity determining region 1 of an autoantibody is associated with a down-regulation of apoptosis and of the pro-apoptotic factor JNK kinase

Treatment with peptides based on the complementarity determining regions (CDR) of murine and human monoclonal anti-DNA antibodies that bear the common idiotype, 16/6 Id, ameliorates disease manifestations of mice with either induced or spontaneous SLE. Aberrant expression and function of the p21Ras/MAP kinase pathway are associated with active SLE. Therefore, we examined the effect of treatment with a CDR1-based peptide of a human autoantibody (hCDR1) on the p21Ras pathway and SLE manifestations of SLE-prone (NZBxNZW)F1 mice. Untreated SLE-afflicted mice demonstrated increased expression of p21Ras and the phosphorylated active form of its down-stream element JNK kinase in conjunction with reduced hSOS and unchanged p120GAP, as compared to healthy controls. Amelioration of SLE manifestations following treatment with hCDR1 was associated with a diminished expression of phosphorylated JNK kinase, mainly in the T cell population that also exhibited reduced rates of apoptosis. Thus, hCDR1 therapy ameliorates SLE, at least in part, via down-regulation of the activity of the pro-apoptotic JNK kinase.

The binding of sera of patients with SLE to bacterial and mammalian DNA

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by antibodies to DNA (anti-DNA). Although these antibodies have features of antigen drive, the source of this DNA is not defined. To assess the potential role of foreign and self-DNA as driving antigens, the specificity of SLE sera for bacterial and mammalian DNA was evaluated. Micrococcus lysodeikticus (MC) and calf thymus (CT) DNA were tested as antigens, with absorption on CT DNA columns used to identify antibodies to antigenic sites on the two DNA. Among 9 sets of longitudinal sera tested, all showed binding to both DNA, and none showed exclusive or predominant binding to CT DNA. With absorbed sera, antibodies could be distinguished in terms of cross-reactive or selective binding to the DNAs. These findings suggest that anti-DNA antibodies vary in specificity and are consistent with a role of both foreign and self-DNA in anti-DNA induction.

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.