Rapid lupus autoantigen relocalization and reactive oxygen species accumulation following ultraviolet irradiation of human keratinocytes

Recent advances in cutaneous lupus

Cutaneous lupus erythematosus (CLE) is an inflammatory and autoimmune skin condition that affects patients with systemic lupus erythematosus (SLE) and exists as an isolated entity without associated SLE. Flares of CLE, often triggered by exposure to ultraviolet (UV) light result in lost productivity and poor quality of life for patients and can be associated with trigger of systemic inflammation. In the past 10 years, the knowledge of CLE etiopathogenesis has grown, leading to promising targets for better therapies. Development of lesions likely begins in a pro-inflammatory epidermis, conditioned by excess type I interferon (IFN) production to undergo increased cell death and inflammatory cytokine production after UV light exposure. The reasons for this inflammatory predisposition are not well-understood, but may be an early event, as ANA + patients without criteria for autoimmune disease exhibit similar (although less robust) findings. Non-lesional skin of SLE patients also exhibits increased innate immune cell infiltration, conditioned by excess IFNs to release pro-inflammatory cytokines, and potentially increase activation of the adaptive immune system. Plasmacytoid dendritic cells are also found in non-lesional skin and may contribute to type I IFN production, although this finding is now being questioned by new data. Once the inflammatory cycle begins, lesional infiltration by numerous other cell populations ensues, including IFN-educated T cells. The heterogeneity amongst lesional CLE subtypes isn't fully understood, but B cells appear to discriminate discoid lupus erythematosus from other subtypes. Continued discovery will provide novel targets for additional therapeutic pursuits. This review will comprehensively discuss the contributions of tissue-specific and immune cell populations to the initiation and propagation of disease.

Anti-Ro52 Autoantibody Is Common in Systemic Autoimmune Rheumatic Diseases and Correlating with Worse Outcome when Associated with interstitial lung disease in Systemic Sclerosis and Autoimmune Myositis

This review highlights the 30 plus years research progress since the discovery of autoantibody to Ro52/TRIM21 in patients with systemic lupus erythematosus (SLE) and Sjögren's syndrome (SjS). After the initial expression cloning of the Ro52 cDNA, it has taken many years to the current understanding in the interesting biological function of Ro52 as an E3 ubiquitin ligase and its role in innate immune clearance of intracellular IgG-bound complex. Early observations show that anti-Ro52, mostly associated with anti-SS-A/Ro60 and/or anti-SS-B/La, is commonly found in SLE (40-70%), SjS (70-90%), neonatal lupus erythematosus (NLE, 75-90%), and subacute cutaneous lupus erythematosus (50-60%). Anti-Ro52 has long been postulated to play a direct pathogenic role in congenital heart block in NLE as well as in the QT interval prolongation in some adults. The widespread availability of the anti-Ro52 assay has led to the detection of anti-Ro52 in other diseases including autoimmune hepatitis (20-40%), systemic sclerosis (10-30%), and autoimmune myositis (20-40%). More than ten studies have pointed to an association of anti-Ro52 with interstitial lung disease and, more importantly, correlating with poor outcome and worse survival. Other studies are implicating an interesting role for anti-Ro52 in the diagnosis of certain cancers. Future studies are needed to examine the mechanism in the pathogenesis of anti-Ro52 and carefully documenting its causal relationships in different disease conditions.

TRIM21/Ro52 - Roles in Innate Immunity and Autoimmune Disease

TRIM21 (Ro52/SSA1) is an E3 ubiquitin ligase with key roles in immune host defence, signal transduction, and possibly cell cycle regulation. It is also an autoantibody target in Sjögren's syndrome, systemic lupus erythematosus, and other rheumatic autoimmune diseases. Here, we summarise the structure and function of this enzyme, its roles in innate immunity, adaptive immunity and cellular homeostasis, the pathogenesis of autoimmunity against TRIM21, and the potential impacts of autoantibodies to this intracellular protein.

Mechanisms of Photosensitivity in Autoimmunity

Aberrant responses to UV light frequently lead to the formation of skin lesions and the activation of systemic inflammation in some autoimmune diseases, especially systemic lupus erythematosus. Whereas the effects of UV light on the skin have been studied for decades, only recently have some of the mechanisms that contribute to abnormal responses to UV light in patients with autoimmune diseases been uncovered. This review will discuss the biology of UV in the epidermis and discuss the abnormal epidermal and inflammatory mechanisms that contribute to photosensitivity. Further research is required to fully understand how to normalize UV-mediated inflammation in patients with autoimmune diseases.

Immunopathogenesis of skin injury in systemic lupus erythematosus

PURPOSE OF REVIEW

Skin injury is the most common clinical manifestation of SLE and is disfiguring, difficult to treat, and incompletely understood. We provide an overview of recently published articles covering the immunopathogenesis of skin injury in SLE.

RECENT FINDINGS

Skin of SLE has an inherent susceptibility to apoptosis, the cause of which may be multifactorial. Chronic IFN overexpression leads to barrier disruption, infiltration of inflammatory cells, cytokine production, and release of autoantigens and autoantibody production that result in skin injury. Ultraviolet light is the most important CLE trigger and amplifies this process leading to skin inflammation and potentially systemic disease flares.

SUMMARY

The pathogenesis of skin injury in CLE is complex but recent studies highlight the importance of mechanisms driving dysregulated epidermal cell death likely influenced by genetic risk factors, environmental triggers (UV light), and cytotoxic cells and cellular signaling.

Current Insights in Cutaneous Lupus Erythematosus Immunopathogenesis

Cutaneous Lupus Erythematosus (CLE) is a clinically diverse group of autoimmune skin diseases with shared histological features of interface dermatitis and autoantibodies deposited at the dermal-epidermal junction. Various genetic and environmental triggers of CLE promote infiltration of T cells, B cells, neutrophils, antigen presenting cells, and NK cells into lesional skin. In this mini-review, we will discuss the clinical features of CLE, insights into CLE immunopathogenesis, and novel treatment approaches.

Human and Murine Evidence for Mechanisms Driving Autoimmune Photosensitivity

Ultraviolet (UV) light is an important environmental trigger for systemic lupus erythematosus (SLE) patients, yet the mechanisms by which UV light impacts disease are not fully known. This review covers evidence in both human and murine systems for the impacts of UV light on DNA damage, apoptosis, autoantigen exposure, cytokine production, inflammatory cell recruitment, and systemic flare induction. In addition, the role of the circadian clock is discussed. Evidence is compared in healthy individuals and SLE patients as well as in wild-type and lupus-prone mice. Further research is needed into the effects of UV light on cutaneous and systemic immune responses to understand how to prevent UV-light mediated lupus flares.

DNA Damage and Deficiencies in the Mechanisms of Its Repair: Implications in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a perplexing and potentially severe disease, the pathogenesis of which is yet to be understood. SLE is considered to be a multifactorial disease, in which genetic factors, immune dysregulation, and environmental factors, such as ultraviolet radiation, are involved. Recently, the description of novel genes conferring susceptibility to develop SLE even in their own (monogenic lupus) has raised the interest in DNA dynamics since many of these genes are linked to DNA repair. Damage to DNA induces an inflammatory response and eventually triggers an immune response, including those targeting self-antigens. We review the evidence that indicates that patients with SLE present higher levels of DNA damage than normal subjects do and that several proteins involved in the preservation of the genomic stability show polymorphisms, some of which increase the risk for SLE development. Also, the experience from animal models reinforces the connection between DNA damage and defective repair in the development of SLE-like disease including characteristic features such as anti-DNA antibodies and nephritis. Defining the role of DNA damage response in SLE pathogenesis might be strategic in the quest for novel therapies.

Acetylated Histones in Apoptotic Microparticles Drive the Formation of Neutrophil Extracellular Traps in Active Lupus Nephritis

Objective

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of autoantibodies against nuclear components. Lupus nephritis (LN) is the major cause of morbidity and mortality in patients with SLE. Central to the pathogenesis of SLE is the accumulation of cellular waste, especially apoptotic microparticles (MPs), which stimulates diverse immune reactions including the formation of neutrophil extracellular traps (NETs). In this study, we investigated the content of MPs from SLE patients with and without (active) LN, their capacity to stimulate NET release, and assessed the molecular mechanisms underlying MP-induced NETosis.

Methods

MPs from SLE patients with biopsy-proven active LN, remissive LN, without LN, and healthy controls were characterized by flow cytometry. Isolated neutrophils were exposed to MPs derived from either patient plasma or apoptotic human umbilical vein endothelial cells, and NET release was quantified by immunofluorescence imaging, spectrofluorometry or an in-house developed NET ELISA.

Results

MPs from SLE patients with active LN contain higher levels of acetylated chromatin compared to MPs from those with remissive LN, without LN, or healthy controls. MPs enriched in hyperacetylated chromatin are more potent in inducing NETosis when compared to MPs containing moderate acetylated chromatin. The release of NETs in response to MPs occurs rapidly in a concentration-dependent manner and proceeds independent from the formation of reactive oxygen species (ROS).

Conclusion

Our data suggest that MPs containing acetylated chromatin drive ROS-independent NET release in SLE patients with active LN, which may lead to the glomerular deposition of NETs and subsequent NET-driven LN.

TWEAK/Fn14 Activation Participates in Ro52-Mediated Photosensitization in Cutaneous Lupus Erythematosus

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) binds to its sole receptor fibroblast growth factor-inducible 14 (Fn14), participating in various inflammatory responses. Recently, TWEAK/Fn14 activation was found prominent in the lesions of cutaneous lupus erythematosus (CLE). This study was designed to further reveal the potential role of this pathway in Ro52-mediated photosensitization. TWEAK, Fn14, and Ro52 were determined in the skin lesions of patients with CLE. Murine keratinocytes received ultraviolet B (UVB) irradiation or plus TWEAK stimulation and underwent detection for Ro52 and proinflammatory cytokines. The chemotaxis of J774.2 macrophages was evaluated on TWEAK stimulation of cocultured keratinocytes. We found that TWEAK, Fn14, and downstream cytokines were highly expressed in CLE lesions that overexpressed Ro52. Moreover, TWEAK enhanced the UVB-induced Ro52 upregulation in murine keratinocytes. Meanwhile, TWEAK stimulation of keratinocytes favored the migration of macrophages through promoting the production of chemokine C–C motif ligands 17 and 22. Furthermore, Fn14 siRNA transfection or nuclear factor-kappa B (NF-κB) inhibitor abrogated the TWEAK enhancement of Ro52 expression in keratinocytes. Similarly, TNF receptor associated factor 2 (TRAF2) siRNA reduced the protein level of Ro52 in these cells upon TWEAK stimulation. Interestingly, UVB irradiation increased the expression of TNF receptor type 1 (TNFR1) but not affecting TNFR2 expression in keratinocytes. In conclusion, the TWEAK/Fn14 signaling participates in Ro52-mediated photosensitization and involves the activation of NF-κB pathway as well as the function of the TRAF2/TNFR partners.

What Causes Lupus Flares?

Systemic lupus erythematosus (SLE), the prototypic systemic autoimmune disease, follows a chronic disease course, punctuated by flares. Disease flares often occur without apparent cause, perhaps from progressive inherent buildup of autoimmunity. However, there is evidence that certain environmental factors may trigger the disease. These include exposure to UV light, infections, certain hormones, and drugs which may activate the innate and adaptive immune system, resulting in inflammation, cytotoxic effects, and clinical symptoms. Uncontrolled disease flares, as well as their treatment, especially with glucocorticoids, can cause significant organ damage. Tight surveillance and timely control of lupus flares with judicial use of effective treatments to adequately suppress the excessive immune system activation are required to bring about long term remission of the disease. We hope that new clinical trials will soon offer additional effective and target-specific biologic treatments for SLE.

HeLa Cells Containing a Truncated Form of DNA Polymerase Beta are More Sensitized to Alkylating Agents than to Agents Inducing Oxidative Stress

The present study was aimed at determining the effects of alkylating and oxidative stress inducing agents on a newly identified variant of DNA polymerase beta (polβ Δ208-304) specific for ovarian cancer. Pol β Δ208-304 has a deletion of exons 11-13 which lie in the catalytic part of enzyme. We compared the effect of these chemicals on HeLa cells and HeLa cells stably transfected with this variant cloned into in pcDNAI/neo vector by MTT, colony forming and apoptosis assays. Polβ Δ208-304 cells exhibited greater sensitivity to an alkylating agent and less sensitivity towards H2O2 and UV when compared with HeLa cells alone. It has been shown that cell death in Pol β Δ208-304 transfected HeLa cells is mediated by the caspase 9 cascade. Exon 11 has nucleotidyl selection activity, while exons 12 and 13 have dNTP selection activity. Hence deletion of this part may affect polymerizing activity although single strand binding and double strand binding activity may remain same. The lack of this part may adversely affect catalytic activity of DNA polymerase beta so that the variant may act as a dominant negative mutant. This would represent clinical significance if translated into a clinical setting because resistance to radiation or chemotherapy during the relapse of the disease could be potentially overcome by this approach.

Pathophysiology of cutaneous lupus erythematosus

The pathophysiology of cutaneous lupus erythematosus (CLE) encompasses the complex interactions between genetics, the environment, and cells and their products. Recent data have provided enhanced understanding of these interactions and the mechanism by which they cause disease. A number of candidate genes have been identified which increase the risk of developing CLE. Ultraviolet radiation, the predominant environmental exposure associated with CLE, appears to initiate CLE lesion formation by inducing apoptosis, precipitating autoantigen presentation, and promoting cellular production of specific cytokines. Autoantibodies are a well-known entity in CLE, but their exact role remains unclear. Finally, cells ranging from native skin cells to innate and adaptive immune cells produce cytokines and other molecules and play specific roles in lesion formation and perpetuation. Native skin cells implicated in CLE include keratinocytes and endothelial cells. Innate immune cells crucial to CLE pathophysiology include dendritic cells and neutrophils. The primary adaptive immune cells thought to be involved include Th1 cells, Th17 cells, cytotoxic T cells, and invariant natural killer T cells. Though the pathophysiology of CLE has yet to be fully characterized, current research provides direction for future research and therapies.

Laser vaccine adjuvants. History, progress, and potential

Immunologic adjuvants are essential for current vaccines to maximize their efficacy. Unfortunately, few have been found to be sufficiently effective and safe for regulatory authorities to permit their use in vaccines for humans and none have been approved for use with intradermal vaccines. The development of new adjuvants with the potential to be both efficacious and safe constitutes a significant need in modern vaccine practice. The use of non-damaging laser light represents a markedly different approach to enhancing immune responses to a vaccine antigen, particularly with intradermal vaccination. This approach, which was initially explored in Russia and further developed in the US, appears to significantly improve responses to both prophylactic and therapeutic vaccines administered to the laser-exposed tissue, particularly the skin. Although different types of lasers have been used for this purpose and the precise molecular mechanism(s) of action remain unknown, several approaches appear to modulate dendritic cell trafficking and/or activation at the irradiation site via the release of specific signaling molecules from epithelial cells. The most recent study, performed by the authors of this review, utilized a continuous wave near-infrared laser that may open the path for the development of a safe, effective, low-cost, simple-to-use laser vaccine adjuvant that could be used in lieu of conventional adjuvants, particularly with intradermal vaccines. In this review, we summarize the initial Russian studies that have given rise to this approach and comment upon recent advances in the use of non-tissue damaging lasers as novel physical adjuvants for vaccines.

Cutaneous lupus erythematosus: clinical aspects and molecular pathogenesis

Lupus erythematosus (LE) is an autoimmune disease with diverse clinical manifestations ranging from limited cutaneous (CLE) to potentially life-threatening systemic disease (SLE). Susceptibility to LE arises from genetic variation in multiple loci, and disease activity is provoked by exogenous or endogenous trigger(s), the best characterized of which is exposure to ultraviolet radiation (UVR). Amongst patients with LE, a cluster of photosensitive subjects with cutaneous lesions and positivity for anti-Ro/SSA autoantibodies have been described. The Ro52 antigen belongs to the tripartite motif protein family and has E3 ligase activity. New data reveal that Ro52 ubiquitinates interferon regulatory factors and modulates their transcriptional activity, indicating an important role for Ro52 in inflammation as a negative feedback regulator. Our findings indicate that UVR exposure induces upregulation of Ro52 in the CLE target cell, the keratinocyte, and that Ro52 is upregulated in spontaneous and UVR-induced CLE lesions. Recently described functional analysis of Ro52-deficient mice revealed that loss of Ro52 results in uncontrolled inflammation in response to minor skin injury leading to an LE-like condition. In summary, emerging data suggest that abnormal function or regulation of Ro52 contributes to the pathogenesis of UVR-induced CLE in genetically susceptible individuals. Ro52 may thus be an interesting therapeutic target, as its activation could contribute to downregulation of the chronic inflammatory process in LE. Here, we review the available data on the pathogenesis of CLE and, in particular, the role of the Ro52 autoantigen.

An ethanol extract derived from Bonnemaisonia hamifera scavenges ultraviolet B (UVB) radiation-induced reactive oxygen species and attenuates UVB-induced cell damage in human keratinocytes

The present study investigated the photoprotective properties of an ethanol extract derived from the red alga Bonnemaisonia hamifera against ultraviolet B (UVB)-induced cell damage in human HaCaT keratinocytes. The Bonnemaisonia hamifera ethanol extract (BHE) scavenged the superoxide anion generated by the xanthine/xanthine oxidase system and the hydroxyl radical generated by the Fenton reaction (FeSO₄ + H₂O₂), both of which were detected by using electron spin resonance spectrometry. In addition, BHE exhibited scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical and intracellular reactive oxygen species (ROS) that were induced by either hydrogen peroxide or UVB radiation. BHE reduced UVB-induced apoptosis, as shown by decreased apoptotic body formation and DNA fragmentation. BHE also attenuated DNA damage and the elevated levels of 8-isoprostane and protein carbonyls resulting from UVB-mediated oxidative stress. Furthermore, BHE absorbed electromagnetic radiation in the UVB range (280–320 nm). These results suggest that BHE protects human HaCaT keratinocytes against UVB-induced oxidative damage by scavenging ROS and absorbing UVB photons, thereby reducing injury to cellular components.

Pathogenicity and proteomic signatures of autoantibodies to Ro and La

Ro/SSA and La/SSB comprise a linked set of autoantigens that are clinically important members of the extractable nuclear antigen family and key translational biomarkers for lupus and primary Sjögren's syndrome. Autoantibodies directed against the Ro60 and La polypeptide components of the Ro/La ribonucleoprotein complex, and the structurally unrelated Ro52 protein, mediate tissue damage in the neonatal lupus syndrome, a model of passively acquired autoimmunity in humans in which the most serious manifestation is congenital heart block (CHB). Recent studies have concentrated on two distinct pathogenic mechanisms by which maternal anti-Ro/La autoantibodies can cause CHB: by forming immune complexes with apoptotic cells in developing fetal heart; and/or by acting as functional autoantibodies that cross-react with and inhibit calcium channels. Although the precise role of the individual autoantibodies is yet to be settled, maternal anti-Ro60 and anti-Ro52 remain the most likely culprits. This article will discuss the molecular pathways that culminate in the development of CHB, including the recent discovery of β2 glycoprotein I as a protective factor, and present a proteomic approach based on direct mass spectrometric sequencing, which may give a more representative snapshot of the idiotype repertoire of these autoantibodies than genomic-based technologies.

Toll-like receptor 3: involvement with exogenous and endogenous RNA

The recognition of pathogens is assigned to an evolutionarily conserved family of receptors, the Toll-like receptors (TLRs). The investigation of RNA-based immunology has been reinvigorated with the observation that TLR3s interact with RNA (dsRNA of viral origin, poly (I:C) and endogenous RNA). Many RNAs, therefore, join the list of endogenous ligands for TLRs. The further finding that nucleoside modification alters RNA-mediated TLR signaling presents a mechanism for the long-observed differences in immunogenicity. The involvement of RNA modification in the pathogenesis of diseases, and its implications in the therapeutics, are still being studied, and will have important implications in the future.

The danger model in deciphering autoimmunity

Autoimmunity has been a topic of intensive research for several decades, yet amazingly, no uniform hypothesis exists to explain the basis for the spectrum of autoantibody specificities seen in autoimmune diseases. It therefore seems appropriate to consider whether our current framework for understanding tolerance, and thus the mechanisms controlling the initiation and perpetuation of autoimmunity, may be faulty. Adapting the paradigm of Matzinger-the 'danger model', a case can be made for a perspective that appreciates the fundamental role of the tissues in controlling immune response, favouring a shift of focus in studies on the initiation of autoimmunity. Applying the elements of this model, I set forth a number of scenarios for how autoreactivity could emerge, with emphasis on the likely sources of the involved autoantigens and the functional basis of their appearance. The emerging picture is one in which disruption of tissue homeostasis takes centre stage, with the antigen-presenting cells as the key players.

Nucleic acid-associated autoantigens: pathogenic involvement and therapeutic potential

Autoimmunity to ubiquitously expressed macromolecular nucleic acid-protein complexes such as the nucleosome or the spliceosome is a characteristic feature of systemic autoimmune diseases. Disease-specificity and/or association with clinical features of some of these autoimmune responses suggest pathogenic involvement which, however, has been proven in only a few cases so far. Although the mechanisms leading to autoimmunity against nucleic acid-containing complexes are still far from being fully understood, there is increasing experimental evidence that the nucleic acid component may act as a co-stimulator or adjuvans via activation of nucleic acid-binding receptor systems such as Toll-like receptors in antigen-presenting cells. Dysregulated apoptosis and inappropriate stimulation of nucleic acid-sensing receptors may lead to loss of tolerance against the protein components of such complexes, activation of autoreactive T cells and formation of autoantibodies. This has been demonstrated to occur in systemic lupus erythematosus and seems to represent a general mechanism that may be crucial for the development of systemic autoimmune diseases. This review provides a comprehensive overview of the most thoroughly-characterized nucleic acid-associated autoantigens, describing their structure and biological function, as well as the nature and pathogenic importance of the reactivities directed against them. Furthermore, recent advances in immunotherapy such as antigen-specific approaches targeted at nucleic acid-binding antigens are discussed.

Ro-associated Y RNAs in metazoans: evolution and diversification

The Y genes encode small noncoding RNAs whose functions remain elusive, whose numbers vary between species, and whose major property is to be bound by the Ro60 protein (or its ortholog in other species). To better understand the evolution of the Y gene family, we performed a homology search in 27 different genomes along with a structural search using Y RNA specific motifs. These searches confirmed that Y RNAs are well conserved in the animal kingdom and resulted in the detection of several new Y RNA genes, including the first Y RNAs in insects and a second Y RNA detected in Caenorhabditis elegans. Unexpectedly, Y5 genes were retrieved almost as frequently as Y1 and Y3 genes, and, consequently are not the result of a relatively recent apparition as is generally believed. Investigation of the organization of the Y genes demonstrated that the synteny was conserved among species. Interestingly, it revealed the presence of six putative "fossil" Y genes, all of which were Y4 and Y5 related. Sequence analysis led to inference of the ancestral sequences for all Y RNAs. In addition, the evolution of existing Y RNAs was deduced for many families, orders and classes. Moreover, a consensus sequence and secondary structure for each Y species was determined. Further evolutionary insight was obtained from the analysis of several thousand Y retropseudogenes among various species. Taken together, these results confirm the rich and diversified evolution history of Y RNAs.

Different temporal expression of immunodominant Ro60/60 kDa-SSA and La/SSB apotopes

Opsonization of apoptotic cardiocytes by maternal anti-Ro/SSA and anti-La/SSB antibodies contributes to tissue injury in the neonatal lupus syndrome. The objective of the current study was to quantify the surface membrane expression of Ro/La components during different phases of apoptosis and map the Ro/La apotopes (epitopes expressed on apoptotic cells) bound by cognate antibodies. Multi-parameter flow cytometry was used to define early and late apoptotic populations and their respective binding by monospecific anti-Ro and anti-La IgGs. Anti-Ro60 bound specifically to early apoptotic Jurkat cells and remained accessible on the cell surface throughout early and late apoptosis. In contrast, anti-La bound exclusively to late apoptotic cells in experiments controlled for non-specific membrane leakage of IgG. Ro52 was not accessible for antibody binding on either apoptotic population. The immunodominant NH2-terminal and RNA recognition motif (RRM) epitopes of La were expressed as apotopes on late apoptotic cells, confirming recent in vivo findings. An immunodominant internal epitope of Ro60 that contains the RRM, and is recognized by a majority of sera from mothers of children with congenital heart block (CHB) and patients with primary Sjögren's syndrome, was also accessible as an apotope on early apoptotic cells. The distinct temporal expression of the immunodominant Ro60 and La apotopes indicates that these intracellular autoantigens translocate independently to the cell surface, and supports a model in which maternal antibody populations against both Ro60 and La apotopes act in an additive fashion to increase the risk of tissue damage in CHB.

Structural basis for PRYSPRY-mediated tripartite motif (TRIM) protein function

The human tripartite motif (TRIM) family comprises 70 members, including HIV restriction factor TRIM5alpha and disease-associated proteins TRIM20 (pyrin) and TRIM21. TRIM proteins have conserved domain architecture but diverse cellular roles. Here, we describe how the C-terminal PRYSPRY domain mediates diverse TRIM functions. The crystal structure of TRIM21 PRYSPRY in complex with its target IgG Fc reveals a canonical binding interface comprised of two discrete pockets formed by antibody-like variable loops. Alanine scanning of this interface has identified the hot-spot residues that control TRIM21 binding to Fc; the same hot-spots control HIV/murine leukemia virus restriction by TRIM5alpha and mediate severe familial Mediterranean fever in TRIM20/pyrin. Characterization of the IgG binding site for TRIM21 PRYSPRY reveals TRIM21 as a superantigen analogous to bacterial protein A and suggests that an antibody bipolar bridging mechanism may contribute to the pathogenic accumulation of anti-TRIM21 autoantibody immune complex in autoimmune disease.

Broad-band ultraviolet B phototherapy is associated with elevated serum thiobarbituric acid reactive substance and nitrite-nitrate levels in psoriatic patients

BACKGROUND

Although the local anti-inflammatory, immunosuppressive and oxidative activity of UVB is known, the systemic effect of UVB phototherapy in dermatological patients has not been investigated.

OBJECTIVE

We aimed to investigate the lipid peroxidation status (as represented by thiobarbituric acid reactive substance, TBARS) and nitrite-nitrate levels in psoriatic patients under broad-band ultraviolet B (BB-UVB) phototherapy in order to determine the systemic effects of UVB.

SUBJECTS AND METHODS

Thirty-two psoriatic patients and 20 healthy controls were included. Blood samples were obtained at the beginning, after 6-10 exposures to BB UVB phototherapy (mean 5 weeks) and at the end of the therapy period (mean 21 weeks). Serum TBARS and nitrite-nitrate levels were evaluated.

RESULTS

There was no statistically significant difference in serum TBARS and nitrite-nitrate levels between psoriatic patients (basal) and healthy volunteers. There was no statistically significant correlation between disease duration, disease severity, or the total cumulative dose of UVB and serum levels of TBARS and nitrite-nitrate in psoriatic patients. Total nitrite levels in samples obtained during and at the end of therapy were significantly higher than basal levels (P=0.033 and P=0.005, respectively). TBARS levels in samples obtained during and at the end of therapy were significantly higher than basal levels (P=0 and P=0.026, respectively). There was a negative correlation (r=-0.576, P=0.039) between the total nitrite and TBARS levels in psoriatic patients at the end of therapy.

CONCLUSION

Our study showed that chronic exposure to UV irradiation may lead to a systemic effect on lipid peroxidation and NO levels, which are shown by a significant elevation in TBARS and nitrite-nitrate levels in serum.

Presence of serum tripartite motif-containing 21 antibodies in patients with esophageal squamous cell carcinoma

SEREX has been applied to esophageal SCC, and the TRIM21 gene was identified as a novel SEREX antigen of esophageal SCC. The presence of s-TRIM21-Abs was confirmed by Western blotting using bacterially expressed TRIM21 gene product and was evaluated for clinicopathological significance in patients with esophageal SCC. s-TRIM21-Abs were detected in 18 (20%) of 91 patients with esophageal SCC but not in 42 healthy donors. The presence of s-TRIM21-Abs was partly associated with tumor size (P = 0.063) and poor survival (P = 0.067). To measure serum antibody levels, ELISA using purified recombinant TRIM21 protein was developed. The levels of s-TRIM21-Abs were significantly higher in patients with esophageal SCC than in healthy donors (P = 0.013). s-TRIM21-Abs may be a useful tumor marker to diagnose and predict disease progression in patients with esophageal SCC.

A New Approach to Managing Oral Manifestations of Sjogren's Syndrome and Skin Manifestations of Lupus

Sjogren's syndrome (SS) is an autoimmune disorder that affects the salivary glands, leading to xerostomia, and the lacrimal glands, resulting in xerophthalmia. Secondary SS is associated with other autoimmune disorders such as systemic rheumatic diseases and systemic lupus erythematosis (SLE), which can affect multiple organs, including the epidermis. Recent studies have demonstrated that green tea polyphenols (GTPs) possess both anti-inflammatory and anti-apoptotic properties in normal human cells. Epidemiological evidence has indicated that, in comparison to the United States, the incidence of SS, clinical xerostomia and lupus is considerably lower in China and Japan, the two leading green tea-consuming countries.Thus, GTPs might be responsible, in part, for geographical differences in the incidence of xerostomia by reducing the initiation or severity of SS and lupus. Consistent with this, molecular, cellular and animal studies indicate that GTPs could provide protective effects against autoimmune reactions in salivary glands and skin. Therefore, salivary tissues and epidermal keratinocytes could be primary targets for novel therapies using GTPs. This review article evaluates the currently available research data on GTPs, focusing on their potential application in the treatment of the oral manifestations of SS and skin manifestations of SLE.

A deficiency in the in vivo clearance of apoptotic cells is a feature of the NOD mouse

Deficiencies in apoptotic cell clearance have been linked to autoimmunity. Here we examined the time-course of peritoneal macrophage phagocytosis of dying cells following the direct injection of apoptotic thymocytes into the peritoneum of NOD mice and BALB/c controls. Macrophages from NOD mice demonstrated a profound defect in the phagocytosis of apoptotic thymocytes as compared to control macrophages. Nonobese diabetic mice also demonstrated a decrease in the clearance of apoptotic cell loads following an apoptotic stimulus to thymocytes (dexamethasone) when compared to BALB/c or NOR controls. Further, NOD mice demonstrated an increase in apoptotic cell load following an apoptotic stimulus to keratinocytes (ultraviolet light, UVB) when compared to control strains. Animals deficient in macrophage phagocytosis of apoptotic debris often manifest an autoimmune phenotype characterized by the production of antinuclear autoantibodies (ANA). We determined whether increased apoptotic cell loads (through repeated exposure to UVB irradiation) could accelerate such autoimmune phenomena in young NOD mice. Following repeated UVB irradiation, NOD mice, but not BALB/c or NOR controls, developed ANA. We propose that abnormalities in apoptotic cell clearance by macrophages predispose NOD mice to autoimmunity.

A soybean Kunitz trypsin inhibitor reduces tumor necrosis factor-alpha production in ultraviolet-exposed primary human keratinocytes

BACKGROUND

Cytokines are produced as a consequence of photo-damaged DNA and oxidative stress in ultraviolet (UV)-exposed keratinocytes. A soybean Kunitz trypsin inhibitor (KTI) down-regulates the expression of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) in tumor cells and inflammatory cells.

AIM

The effect of KTI on TNF-alpha production in UV-exposed primary human keratinocytes was analyzed.

RESULTS

We show (i) UV induced up-regulation of TNF-alpha mRNA and protein expression in keratinocytes; (ii) cells treated with KTI before UV irradiation showed a significantly lower accumulation of TNF-alpha protein in a dose-dependent manner and a reduced UV-induced up-regulation of TNF-alpha mRNA expression; (iii) KTI inhibited the induction of TNF-alpha target molecules interleukin-1beta (IL-1beta) and IL-6 proteins; (iv) UV irradiation transiently activated c-Jun N-terminal kinase (JNK) and Akt signaling but only weakly activated extracellular signal-regulated kinase (ERK) and p38; (v) KTI specifically inhibited UV-induced activation of ERK, JNK, and p38, but not Akt; (vi) treatment of cells with SP600125, a pharmacological inhibitor of JNK, predominantly suppressed UV-induced up-regulation of TNF-alpha expression; and (vii) KTI did not enhance suppression of UV-induced JNK phosphorylation by SP600125.

CONCLUSIONS

KTI specifically inhibited UV-induced up-regulation of cytokine expression predominantly through suppression of JNK signaling pathway.

Regulation of SNARK activity in response to cellular stresses

SNARK is a member of the AMPK subfamily of serine/threonine protein kinases. In this study, we examined the regulation of SNARK activity in kidney (BHK, HEK293), pancreatic beta-cell insulinoma (INS-1), hepatocarcinoma (H4IIE) and keratinocyte (NRKC)-derived cell lines in response to diverse cellular stresses. We show that SNARK activity is regulated by glucose- or glutamine-deprivation, induction of endoplasmic reticulum stress by homocysteine or DTT, elevation of cellular AMP and/or depletion of ATP, hyperosmotic stress, salt stress, ultraviolet B radiation and oxidative stress caused by hydrogen peroxide. Moreover, the regulation of SNARK activity in response to cellular stresses depends greatly upon cell type. Furthermore, SNARK activity is downregulated by metformin in a dose- and time-dependent manner in H4IIE cells. These observations support a role for SNARK as a molecular component of the cellular stress response.

UVB-induced leucocyte trafficking in the epidermis of photosensitive lupus erythematosus patients: Normal depletion of Langerhans cells

BACKGROUND

The pathogenic mechanisms of UV-induced skin lesions of lupus erythematosus (LE) are unknown. In a recent study of pathogenic mechanisms of polymorphic light eruption (PLE), significantly more Langerhans cells (LCs) persisted in the epidermis after UVB overexposure than in healthy individuals. Interestingly, the same phenomenon was observed in one subacute cutaneous lupus erythematosus (SCLE) patient. It could therefore be hypothesized that both photodermatoses share a common pathogenic mechanism of photosensitivity. In the present study, we tested this hypothesis by investigating leucocyte trafficking in the initial phase of cutaneous LE after intense UVB exposure.

METHODS

In 22 photosensitive LE patients (12 chronic discoid lupus erythematosus, seven systemic lupus erythematosus and three SCLE) and nine age/sex-matched controls, uninvolved buttock skin was exposed to six minimal erythemal dose (MED) UVB radiation. Subsequently, biopsies were taken after 24, 48 and 72 h, and one control biopsy was taken from unirradiated skin. Skin sections were stained for the presence of LCs, neutrophils and macrophages. Areal percentages of positively stained cells within the epidermis were quantified and compared between the patients and controls.

RESULTS

A gradual decrease of epidermal LCs and a gradual increase of epidermal neutrophils and macrophages at several timepoints after six MED irradiation was observed equally in both LE patients and controls.

CONCLUSION

Immunohistopathology of irradiated uninvolved skin of photosensitive LE patients did not reveal the same pathologic trafficking of LCs and neutrophils as described for PLE patients. We conclude that different mechanisms are operative in the pathogenesis of PLE and photosensitive LE.

U1 RNA induces innate immunity signaling

OBJECTIVE

The U1-70-kd RNP is a prominent target of autoimmunity in connective tissue diseases. In this study, we explored whether its endogenous ligand, U1 RNA, mediates a proimmune signal and may be immunogenic.

METHODS

We assayed the proliferation of control and MyD88-knockout splenocytes in response to in vitro-synthesized U1 RNA, and measured interleukin-6 (IL-6) and IL-8 secretion induced by U1 RNA in a human cell line competent for signaling through Toll-like receptor 3 (TLR-3) and TLR-5.

RESULTS

Treatment with U1 RNA or with poly(I-C), a known agonist of TLR-3, induced approximately twice as much control splenocyte proliferation as did treatment with RNase-digested U1 RNA. Proliferation in response to either poly(I-C) or U1 RNA by MyD88-knockout splenocytes was similarly attenuated. Similar to poly(I-C), U1 RNA induced significant secretion of both IL-6 and IL-8 from a TLR-3-expressing human cell line; in contrast, the TLR-5 agonist flagellin induced predominantly IL-8 secretion. Pretreatment of U1 RNA with RNase abolished IL-6 and IL-8 secretion.

CONCLUSION

U1 RNA is capable of inducing manifestations consistent with TLR-3 activation. The ability of U1 RNA (which has a substantial double-stranded secondary structure) to activate TLR-3 may contribute to the immunogenicity of the U1-70-kd autoantigen. Stimulation of innate immunity by native RNA molecules with a double-stranded secondary structure may help explain the high prevalence of autoimmunity to RNA binding proteins.

Chemical extraction and direct adsorptive purification of recombinant human antigen Ro52

The antigenic protein Ro52 was expressed in the E. coli system harboring a 6 x His tag in the form of insoluble inclusion bodies. Direct chemical extraction of the product using 6-8 M urea proved to be effective. Furthermore, the tagged protein was recovered by direct adsorption on Ni2+-loaded commercial adsorbents derivatized with iminodiacetic acid. Screening experiments in small packed columns revealed that selective binding and elution were possible using a denaturing buffer at pH 4.5. The hydrodynamic evaluation of scaled-up fluidized systems showed values for the phi (dynamic zone) parameter in the range 0.95-1.00 for fluidization in buffer and in the range 0.70-0.85 for the biomass-containing feedstock. Removal of macromolecular DNA released by the disrupted biomass was mandatory. Under optimized process conditions good recovery (60-70%) was achieved and a highly purified (95%) product obtained. The purified Ro52 retained its immunoreactivity against sera of patients with systemic lupus erythematosus (SLE) and Sjogren's syndrome-related disorders. The production and application of new recombinant antigens may contribute to increasing the sensitivity and specificity of the detection of anti-Ro antibodies in these autoimmune diseases.

Role of oxidative stress and the antioxidant network in cutaneous carcinogenesis

Melanoma and nonmelanoma skin cancers are among the most prevalent cancers in the human population. Solar ultraviolet radiation is considered a major etiological factor but the relationship between dose, timing, and nature of exposure to tumor development is still unclear. Free radicals are generated by normal physiologic processes, including aerobic metabolism and inflammatory response, but may inflict cellular damage when generation is increased and antioxidant defense mechanisms are overwhelmed. Important findings supporting the free radical hypothesis in skin carcinogenesis are: (1) Reactive oxygen species (ROS) are generated in UVA- and UVB-irradiated skin in excessive doses, (2) the natural cutaneous antioxidant defense is impaired upon UV-exposure, (3) free radicals are involved in all steps of carcinogenesis, (4) supplementation with antioxidants can inhibit skin carcinogenesis, and (5) conditions that increase ROS generation enhance photocarcinogenesis. These findings provide a promising rationale for the development of powerful new antioxidant strategies in the prevention and therapy of skin cancer.

The role of H2O2 as a mediator of UVB-induced apoptosis in keratinocytes

Apoptosis is an active form of cell death that is initiated by a variety of stimuli, including reactive oxygen species (ROS) and ultraviolet (UV) radiation. Previously, it has been reported that UVB-irradiation of keratinocytes leads to intracellular generation of hydrogen peroxide (H2O2) and that antioxidants can inhibit ROS-induced apoptosis. Although both UVB-irradiation and H2O2-incubation led to increased intracellular H2O2 levels, the antioxidants catalase and glutathione monoester (GME), inhibited apoptosis only when induced by H2O2, not by UVB. Furthermore, extracellular signal-regulated kinase (ERK), a prominent member of the mitogen-activated protein kinase (MAPK) family, was found to be activated by treatment with both UVB and H2O2. Inhibition of ERK phosphorylation by pre-treatment with PD98059 resulted in enhanced apoptosis after H2O2-exposure. However,no significant difference of apoptosis was observed between cells with and without inhibitor pre-treatment upon UVB-irradiation. DNA damage in the form of cyclobutane pyrimidine dimers was observed after exposure to UVB, but no photoproducts were found in H2O2-treated cells. These results suggest a ROS-independent pathway of UVB-induced apoptosis. Although UVB-irradiation causes moderate increase in H2O2, the generation of H2O2 does not contribute to the induction of apoptosis. Moreover, activation of ERK only blocks H2O2-dependent apoptosis but has no impact on UVB-induced apoptosis.

Disruption of the cytoskeleton after apoptosis induction with autoantibodies

F-actin cleavage was studied in PBMC after treatment with anti-dsDNA antibodies. Significant changes in F-actin disruption detected by decrease of FITC-phalloidin staining occurred after apoptosis induction with anti-dsDNA antibodies (p < 0.006). Despite of similar F-actin disruption, the switch of phosphatidylserine (PS) to the outer leaflet of the cell membrane as detected by annexin V binding was lower after anti-dsDNA antibody than without antibody treatment (58.4 +/- 11.0% vs. 81.9 +/- 7.7%). F-actin disruption was accompanied by activation of caspase 3 within the cytoplasm (r = -0.92599; p < 8.87446 x 10-(10)) under both conditions with and without autoantibodies. These findings indicate that anti-dsDNA antibody-induced apoptosis is more marked within the cell than upon the cell surface. The diminished externalization of PS might result in a decreased phagocytosis. Thereby, the reduced clearance of apoptotic cells could induce autoantibody production possibly against epitopes which arise due to the apoptotic disruption of cells.

Possible contribution of apoptosis-inducing factor (AIF) and reactive oxygen species (ROS) to UVB-induced caspase-independent cell death in the T cell line Jurkat

We analyzed the mechanism of UVB-induced cell death using the Jurkat T cell line. Apoptosis was assessed by measuring phosphatidylserine (PS) externalization, caspase activity, the decrease in mitochondrial membrane potential (Delta Psi m), nucleosomal DNA fragmentation, and morphological changes such as chromatin condensation. The mitochondrio-nuclear translocation of apoptosis-inducing factor (AIF) was evaluated by confocal laser microscopy. The cell death pattern of UVB-irradiated cells was similar to the Fas-induced cell death pattern. However, zVAD-fmk inhibited the nucleosomal fragmentation of DNA but not the externalization of PS, decrease in Delta Psi m, or mitochondrio-nuclear translocation of AIF. N-acetyl L-cysteine significantly inhibited the translocation of AIF induced by UVB. These results suggested that caspase-dependent and -independent pathways were involved in UVB-induced cell death in Jurkat cells, and the mitochondrio-nuclear translocation of AIF was associated with the latter pathway. In addition, reactive oxygen species generated by UVB might be involved in inducing the mitochondrio-nuclear translocation of AIF.

Intracellular trafficking and surface expression of SS-A (Ro), SS-B (La), poly(ADP-ribose) polymerase and alpha-fodrin autoantigens during apoptosis in human salivary gland cells induced by tumour necrosis factor-alpha

Autoantibodies directed against nucleic acid and protein complexes present in cell nuclei characterize autoimmune diseases and are employed in diagnosis. The mechanisms by which these autoantigens escape immunological tolerance are largely unknown, but a number of recent observations suggest that modified self-protein generated during apoptosis my play an important part in the development of autoimmunity. To investigate the possibility that autoantibodies in patients with Sjögren's syndrome are induced by apoptosis and presented on the surface of the cell, the internal distribution of autoantigens in apoptotic human salivary gland cells was studied in vitro. Salivary gland cells were treated with tumour necrosis factor-alpha, an apoptosis inducer. At increasing times after induction, cells were homogenized and cytoplasmic, cell surface membrane and nuclear compartments were fractionated using a sucrose density-gradient system. Autoantigens alpha-fodrin, SS-A (Ro), SS-B (La), and the enzyme poly(ADP-ribose) polymerase, were detected by conventional immunofluorescence and confirmed by Western immunoblotting. At increasing times after apoptosis, nuclear proteins SS-A (Ro) and SS-B (La), but not poly(ADP-ribose) polymerase were relocated from the cell nucleus to the cell surface membrane. Fodrin, a cytoplasmic protein, was also translocated to the cell membrane after cleavage of alpha-fodrin. These results show that autoantigens fodrin, SS-A (Ro) and SS-B (La) in human salivary gland cells undergo a striking redistribution during apoptosis and relocate to the cell membrane of apoptotic cells. The appearance of autoantigens on the surface of induced cells could form the basis of a mechanism for autoantigen presentation, processing and autoantibody induction.

Detection of poly(ADP-ribose) by immunocytochemistry: a sensitive new method for the early identification of UVB- and H2O2-induced apoptosis in keratinocytes

Apoptosis is an active form of cell death that is initiated by a variety of stimuli, including reactive oxygen species (ROS) and ultraviolet (UV) radiation. Poly (ADP-ribose) (PAR) is formed upon activation of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP), and therefore was suggested as a new marker of apoptosis. Since DNA of epidermal cells represents a well-known chromophore for UVB irradiation, and UVB is known to generate H2O2 in keratinocytes, we hypothesized that PAR is a very sensitive marker of UVB- and H2O2-induced apoptosis in keratinocytes. In order to test this hypothesis, human immortalized keratinocytes (HaCaT) were UVB-irradiated or treated with H2O2, and subsequently apoptosis was identified by comparing conventional parameters such as morphological analysis, DNA laddering, and TUNEL assay, with PAR formation. Both, UVB and H2O2 treatment induced PAR formation in HaCaT cells in a dose-dependent manner, and its formation was detected as early as 4 h after irradiation, and at lower UVB doses (10 mJ/cm2) than observed by DNA laddering and the TUNEL assay. In conclusion, the detection of PAR formation is a very sensitive and early method for the identification of apoptotic cells in UVB-induced apoptosis of human keratinocytes.