Autoantibody against one of the antioxidant repair enzymes, methionine sulfoxide reductase A, in systemic sclerosis: association with pulmonary fibrosis and vascular damage

Biomarkers in the Pathogenesis, Diagnosis, and Treatment of Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by vascular damage, vasoinstability, and decreased perfusion with ischemia, inflammation, and exuberant fibrosis of the skin and internal organs. Biomarkers are analytic indicators of the biological and disease processes within an individual that can be accurately and reproducibly measured. The field of biomarkers in SSc is complex as recent studies have implicated at least 240 pathways and dysregulated proteins in SSc pathogenesis. Anti-nuclear antibodies (ANA) are classical biomarkers with well-described clinical classifications and are present in more than 90% of SSc patients and include anti-centromere, anti-Th/To, anti-RNA polymerase III, and anti-topoisomerase I antibodies. Transforming growth factor-β (TGF-β) is central to the fibrotic process of SSc and is intimately intertwined with other biomarkers. Tyrosine kinases, interferon-1 signaling, IL-6 signaling, endogenous thrombin, peroxisome proliferator-activated receptors (PPARs), lysophosphatidic acid receptors, and amino acid metabolites are new biomarkers with the potential for developing new therapeutic agents. Other biomarkers implicated in SSc-ILD include signal transducer and activator of transcription 4 (STAT4), CD226 (DNAX accessory molecule 1), interferon regulatory factor 5 (IRF5), interleukin-1 receptor-associated kinase-1 (IRAK1), connective tissue growth factor (CTGF), pyrin domain containing 1 (NLRP1), T-cell surface glycoprotein zeta chain (CD3ζ) or CD247, the NLR family, SP-D (surfactant protein), KL-6, leucine-rich α2-glycoprotein-1 (LRG1), CCL19, genetic factors including DRB1 alleles, the interleukins (IL-1, IL-4, IL-6, IL-8, IL-10 IL-13, IL-16, IL-17, IL-18, IL-22, IL-32, and IL-35), the chemokines CCL (2,3,5,13,20,21,23), CXC (8,9,10,11,16), CX3CL1 (fractalkine), and GDF15. Adiponectin (an indicator of PPAR activation) and maresin 1 are reduced in SSc patients. A new trend has been the use of biomarker panels with combined complex multifactor analysis, machine learning, and artificial intelligence to determine disease activity and response to therapy. The present review is an update of the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.

Oxidative Stress and Epigenetics: miRNA Involvement in Rare Autoimmune Diseases

Autoimmune diseases (ADs) such as Sjögren’s syndrome, Kawasaki disease, and systemic sclerosis are characterized by chronic inflammation, oxidative stress, and autoantibodies, which cause joint tissue damage, vascular injury, fibrosis, and debilitation. Epigenetics participate in immune cell proliferation and differentiation, which regulates the development and function of the immune system, and ultimately interacts with other tissues. Indeed, overlapping of certain clinical features between ADs indicate that numerous immunologic-related mechanisms may directly participate in the onset and progression of these diseases. Despite the increasing number of studies that have attempted to elucidate the relationship between miRNAs and oxidative stress, autoimmune disorders and oxidative stress, and inflammation and miRNAs, an overall picture of the complex regulation of these three actors in the pathogenesis of ADs has yet to be formed. This review aims to shed light from a critical perspective on the key AD-related mechanisms by explaining the intricate regulatory ROS/miRNA/inflammation axis and the phenotypic features of these rare autoimmune diseases. The inflamma-miRs miR-155 and miR-146, and the redox-sensitive miR miR-223 have relevant roles in the inflammatory response and antioxidant system regulation of these diseases. ADs are characterized by clinical heterogeneity, which impedes early diagnosis and effective personalized treatment. Redox-sensitive miRNAs and inflamma-miRs can help improve personalized medicine in these complex and heterogeneous diseases.

Role of B-Cell in the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare multisystem autoimmune disease, characterized by fibrosis, vasculopathy, and autoimmunity. Recent advances have highlighted the significant implications of B-cells in SSc. B-cells are present in affected organs, their subpopulations are disrupted, and they display an activated phenotype, and the regulatory capacities of B-cells are impaired, as illustrated by the decrease in the IL-10+ producing B-cell subpopulation or the inhibitory membrane co-receptor density. Recent multi-omics evidence highlights the role of B-cells mainly in the early stage of SSc and preferentially during severe organ involvement. This dysregulated homeostasis partly explains the synthesis of anti-endothelial cell autoantibodies (AECAs) or anti-fibroblast autoantibodies (AFAs), proinflammatory or profibrotic cytokines (interleukin-6 and transforming growth factor-β) produced by B and plasma cells. That is associated with cell-to-cell interactions with endothelial cells, fibroblasts, vascular smooth muscle cells, and other immune cells, altogether leading to cell activation and proliferation, cell resistance to apoptosis, the impairment of regulatory mechanisms, and causing fibrosis of several organs encountered in the SSc. Finally, alongside these exploratory data, treatments targeting B-cells, through their depletion by cytotoxicity (anti-CD20 monoclonal antibody), or the cytokines produced by the B-cell, or their costimulation molecules, seem interesting, probably in certain profiles of early patients with severe organic damage.

Role of Alarmins in the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare chronic autoimmune disease associated with significant morbidity and mortality. Two main subsets of SSc are recognized: (i) diffuse cutaneous SSc with rapidly progressive fibrosis of the skin, lungs, and other internal organs; and (ii) limited cutaneous SSc, which is dominated by vascular manifestations, with skin and organ fibrosis generally limited and slowly progressing. In spite of intense investigation, both etiology and pathogenesis of SSc are still unknown. Genetic and environmental factors, as well as abnormalities of immune functions, are strongly suggested for etiology, while microvascular abnormalities, immune system activation, and oxidative stress are suggested for the pathogenesis. Recently, it has been found that a multitude of mediators and cytokines are implicated in the fibrotic processes observed in SSc. Among these, a central role could be exerted by “alarmins”, endogenous and constitutively expressed proteins/peptides that function as an intercellular signal defense. This review describes, in a detailed manner, the role of alarmins in the pathogenesis of scleroderma.

Plasma Glycosaminoglycan Profiles in Systemic Sclerosis: Associations with MMP-3, MMP-10, TIMP-1, TIMP-2, and TGF-Beta

The aim of the study was to determine whether plasma levels of total glycosaminoglycans (GAGs), matrix metalloproteinases (MMPs) (MMP-3, MMP-10), and their tissue inhibitors (TIMPs) (TIMP-1, TIMP-2) as well as transforming growth factor β (TGF-β) differ in the patients with systemic sclerosis (SSc) in relation to the healthy subjects. Plasma samples were obtained from 106 people (64 patients with SSc and 42 healthy individuals) and measured for MMP-3, MMP-10, TIMP-1, TIMP-2, and TGF-β levels using ELISA methods. GAGs isolated from plasma samples were quantified using a hexuronic acid assay. The plasma levels of total GAGs, TIMP-1, TIMP-2, and TGF-β were significantly higher, while MMP-3 was significantly decreased in SSc patients compared to the controls. We have revealed a significant correlation between plasma GAGs and TGF-β (r = -0.47) and TIMP-2 (r = 0.38), respectively. The results of this study revealed that remodeling of the extracellular matrix, reflected by quantitative changes in plasma glycosaminoglycans, occurs during systemic sclerosis. Thus, the alterations in GAG metabolism connected with SSc may lead to systemic changes in the properties of the connective tissue extracellular matrix.

Identification of Ocular Autoantigens Associated With Juvenile Idiopathic Arthritis-Associated Uveitis

The purpose of the current study was to analyze the binding patterns of serum autoantibodies from juvenile idiopathic arthritis (JIA) and JIA-associated uveitis (JIAU) patients to proteomes from different ocular tissues and to identify potential ocular autoantigens in JIAU. Proteomes from porcine iris, ciliary body, or retina tissue were isolated, separated using 2D-gel electrophoresis, and transferred to a blotting membrane. The binding pattern of serum antibodies from JIA or JIAU patients or healthy controls to ocular proteins was visualized by using anti-human IgG secondary antibodies and chemiluminescence reaction. Selected protein spots were excised from silver-stained 2D gels and subjected to mass spectrometry. Serum antibodies binding to ocular proteins were detected in all patient groups and healthy controls. Irrespective of the patient groups, serum antibodies bound to 49 different protein spots of the retina proteome, to 53 of the ciliary body proteome, and to 44 of the iris proteome. The relative binding frequency of sera to these iris protein spots was significantly higher in JIAU than in JIA patients or healthy controls. Particularly in JIAU patients, cluster analyses indicated a broad range of serum antibodies directed against ocular antigens, mostly in the iris proteome. Iris proteins frequently bound by serum antibodies in all groups were identified as tubulin beta chain, vimentin, ATP synthase subunit beta, actin, and L-lactate dehydrogenase B chain. Iris proteins exclusively bound by JIAU serum antibodies were heat shock cognate 71 kDa protein and keratin. Although serum autoantibody binding to ocular antigens was not disease-specific, a significant diversity of autoantibodies against a broad range of antigens, particularly from the iris tissue, was detected in JIAU patients. As the iris is a major site of inflammation in JIAU, the present data give further evidence that autoantibodies may be involved in JIAU immunopathology.

Rapid free thiol rebound is a physiological response following cold-induced vasoconstriction in healthy humans, primary Raynaud and systemic sclerosis

Raynaud's phenomenon (RP) is often the first sign of systemic sclerosis (SSc). Molecular mechanisms involved are incompletely understood, but reactive oxygen, nitrogen, and sulfur species are thought to play an important role in the pathogenesis of SSc. Free thiol groups play a protective role against oxidative stress and may represent an attractive therapeutic target. We aimed to investigate the effects of hypothermia-induced vasoconstriction on the responsiveness of redox-related markers. Thirty participants (n = 10/group [SSc, primary Raynaud's phenomenon (PRP), healthy controls (HC)]) were included in this study. Fingertip photoelectric plethysmography was performed during a standardized cooling and recovery experiment. Venous blood was collected at four predetermined time points. Free thiols, NO-derived species (nitros(yl)ated species, nitrite, nitrate), sulfate and endothelin-1 were measured. Lower baseline concentrations of free thiols were observed in PRP and SSc patients (HC: 5.87 [5.41-5.99] μmol/g; PRP: 5.17 [4.74-5.61]; SSc 5.28 [4.75-5.80], P = 0.04). Redox-related markers remained unchanged during cooling. However, an unexpected increase in systemic free thiol concentrations was observed in all groups during the recovery phase. The response of this marker differed between groups, with a higher increase found in SSc patients (HC Δ = 1.30 [1.48-1.17]; PRP Δ = 1.04 [1.06-1.03]; SSc Δ = 1.72 [1.13-1.49], P = 0.04). NO-derived species, sulfate and endothelin-1 levels remained unchanged throughout the recovery phase. This exploratory study sheds light on the rapid responsiveness of systemic free thiol concentrations following reperfusion, which may reflect overall redox balance. The robust response to reperfusion in SSc patients suggests that reductive systems involved in this response are functionally intact in these patients.

Implication of oxidative stress in the pathogenesis of systemic sclerosis via inflammation, autoimmunity and fibrosis

Systemic sclerosis is an autoimmune disorder characterized by inflammation and a progressive fibrosis affecting the skin and visceral organs. Over the last two decades, it became clear that oxidative stress plays a key role in its pathogenesis. In this review, we highlighted the role of ROS in the various pathological components of systemic sclerosis, namely the inflammatory, the autoimmune and the fibrotic processes. We also discussed how these pathological processes can induce ROS overproduction, thus maintaining a vicious circle. Finally, we summarized the therapeutic approaches targeting oxidative stress tested in systemic sclerosis, in cells, animal models and patients.

The Role of Oxidative Stress in the Development of Systemic Sclerosis Related Vasculopathy

Systemic sclerosis (SSc) is a rare connective tissue disease characterized by autoimmunity, vasculopathy, and progressive fibrosis typically affecting multiple organs including the skin. SSc often is a lethal disorder, because effective disease-modifying treatment still remains unavailable. Vasculopathy with endothelial dysfunction, perivascular infiltration of mononuclear cells, vascular wall remodeling and rarefaction of capillaries is the hallmark of the disease. Most patients present with vasospastic attacks of the digital arteries referred to as 'Raynaud's phenomenon,' which is often an indication of an underlying widespread vasculopathy. Although autoimmune responses and inflammation are both found to play an important role in the pathogenesis of this vasculopathy, no definite initiating factors have been identified. Recently, several studies have underlined the potential role of oxidative stress in the pathogenesis of SSc vasculopathy thereby proposing a new aspect in the pathogenesis of this disease. For instance, circulating levels of reactive oxygen species (ROS) related markers have been found to correlate with SSc vasculopathy, the formation of fibrosis and the production of autoantibodies. Excess ROS formation is well-known to lead to endothelial cell (EC) injury and vascular complications. Collectively, these findings suggest a potential role of ROS in the initiation and progression of SSc vasculopathy. In this review, we present the background of oxidative stress related processes (e.g., EC injury, autoimmunity, inflammation, and vascular wall remodeling) that may contribute to SSc vasculopathy. Finally, we describe the use of oxidative stress related read-outs as clinical biomarkers of disease activity and evaluate potential anti-oxidative strategies in SSc.

Oxidative stress in the pathogenesis of systemic scleroderma: An overview

Systemic sclerosis (SSc) is a rare disorder of the connective tissue characterized by fibrosis of the skin, skeletal muscles and visceral organs. Additional manifestations include activation of the immune system and vascular injury. SSc causes disability and death as the result of end‐stage organ failure. Two clinical subsets of the SSc are accepted: limited cutaneous SSc (lc‐SSc) and diffuse cutaneous SSc (dc‐SSc). At present, the aetiology and pathogenesis of SSc remain obscure, and consequently, disease outcome is unpredictable. Numerous studies suggest that reactive oxidizing species (ROS) play an important role in the pathogenesis of scleroderma. Over the years, several reports have supported this hypothesis for both lc‐SSc and dc‐SSc, although the specific role of oxidative stress in the pathogenesis of vascular injury and fibrosis remains to be clarified. The aim of the present review was to report and comment the recent findings regarding the involvement and role of oxidative stress in SSc pathogenesis. Biomarkers proving the link between ROS and the main pathological features of SSc have been summarized.

Role of anti-receptor autoantibodies in pathophysiology of scleroderma

The pathophysiology of SSc-mediated organ damage is complex and not well understood. Hallmarks of the disease include skin thickening, vasculopathy and gastrointestinal dysmotility. Diverse anti-nuclear antibodies can be used as biomarkers for classification and prognosis, but their role in producing tissue pathology/organ dysfunction is not established. In contrast, antibodies against cell surface receptors for platelet derived growth factor, angiotensin II, endothelin A, ICAM-1, and type 3 muscarinic acetyl choline receptors may play a major role in skin thickening, vasoconstriction/pulmonary and renal hypertension, ischemia and gastrointestinal dysmotility, respectively. In addition, antibodies to an inhibitory B-lymphocyte surface molecule, CD 22, may allow increased production of other autoantibodies. Each of these types of antibodies have been reported in some SSc patients, and laboratory studies suggest signaling pathways and mechanisms by which they may contribute to disease activity. However, we are far from a consensus on their importance. Additional epidemiologic, mechanistic and physiologic studies are needed. Confirmation of the roles of anti-receptor antibodies and identification of the signaling pathways by which they alter cellular functions would have major implications for treatment of SSc, both in terms of targeting autoantibodies and the cells that produce them, and in the use of small molecules which inhibit their pernicious effects.

Pathogenesis of systemic sclerosis: recent insights of molecular and cellular mechanisms and therapeutic opportunities

Systemic sclerosis (SSc) is a complex disease characterized by early microvascular abnormalities, immune dysregulation and chronic inflammation, and subsequent fibrosis of the skin and internal organs. Excessive fibrosis, distinguishing hallmark of SSc, is the end result of a complex series of interlinked vascular injury and immune activation, and represents a maladaptive repair process. Activated vascular, epithelial, and immune cells generate pro-fibrotic cytokines, chemokines, growth factors, lipid mediators, autoantibodies, and reactive oxygen species. These paracrine and autocrine cues in turn induce activation, differentiation, and survival of mesenchymal cells, ensuing tissue fibrosis through increased collagen synthesis, matrix deposition, tissue rigidity and remodeling, and vascular rarefaction. This review features recent insights of the pathogenic process of SSc, highlighting three major characteristics of SSc, microvasculopathy, excessive fibrosis, and immune dysregulation, and sheds new light on the understanding of molecular and cellular mechanisms contributing to the pathogenesis of SSc and providing novel avenues for targeted therapies.

Methionine sulfoxide reductase A deficiency exacerbates progression of kidney fibrosis induced by unilateral ureteral obstruction

Methionine sulfoxide reductase A (MsrA), which stereospecifically catalyzes the reduction of methionine-S-sulfoxide, is an important reactive oxygen species (ROS) scavenger. Tissue fibrosis is a maladaptive repair process following injury, associated with oxidative stress. In this study, we investigated the role of MsrA in unilateral ureteral obstruction (UUO)-induced kidney fibrosis and its underlying mechanisms by using MsrA gene-deleted mice (MsrA(-/-)). MsrA deletion increased collagen deposition in the interstitium and the expression of collagen III and α-smooth muscle actin in the UUO kidneys, indicating that MsrA deficiency exacerbated the progression of UUO-induced kidney fibrosis. UUO reduced the kidney expression of MsrA, MsrB1, and MsrB2, thereby decreasing MsrA and MsrB activity. UUO increased hydrogen peroxide and lipid peroxidation levels and the ratio of oxidized glutathione (GSSG) to total glutathione (GSH) in the kidneys. The UUO-induced elevations in the levels of these oxidative stress markers and leukocyte markers were much higher in the MsrA(-/-) than in the MsrA(+/+) kidneys, the latter suggesting that the exacerbated kidney fibrosis in MsrA(-/-) mice was associated with enhanced inflammatory responses. Collectively, our data suggest that MsrA plays a protective role in the progression of UUO-induced kidney fibrosis via suppression of fibrotic responses caused by oxidative stress and inflammation.

High reactive oxygen species in fibrotic and nonfibrotic skin of patients with diffuse cutaneous systemic sclerosis

Systemic sclerosis (SSc) is a chronic multisystemic connective tissue disease characterized by progressive fibrosis affecting skin and internal organs. Despite serious efforts to unveil the pathogenic mechanisms of SSc, they are still unclear. High levels of reactive oxygen species (ROS) in affected patients have been shown, and ROS are suggested to play a role in fibrosis pathogenesis. In this study we evaluate ROS levels in nonfibrotic and fibrotic skin of patients with SSc and we compare them with those obtained from healthy controls. We enrolled nine SSc patients fulfilling the EULAR/ACR classification criteria and seven healthy controls. Patients included four men and five women with mean age of 46 ± 10 years. Controls were matched by sex and age. All patients were affected by the diffuse cutaneous form of SSc and the ANA pattern anti-Scl70. Mean disease duration was 7.5 ± 5 years. Skin involvement was evaluated by modified Rodnan skin score. Skin samples (4-mm punch biopsy) were taken from fibrotic skin and nonfibrotic skin of patients and from healthy controls as well. To detect ROS, specimens were analyzed immediately after sampling by electron paramagnetic resonance spectroscopy. Blood samples were drawn from all patients and controls to assess oxidative stress biomarkers. ROS levels (expressed as median and range, in nmol/L/min/mg of dry weight) were 24.7 (10.9-47.0) in fibrotic skin, 18.7 (7.3-34.0) in nonfibrotic skin, and 7.7 (3.5-13.6) in healthy control skin. ROS levels in fibrotic and nonfibrotic skin of SSc patients were significantly higher than in healthy controls (p = 0.002 and p = 0.009, respectively). ROS levels in fibrotic skin were raised in comparison to nonfibrotic skin, when samples related to each patient were compared (p = 0.01). ROS levels in fibrotic skin were correlated with forced vital capacity (r = -0.75, p = 0.02) and erythrocyte sedimentation rate (r = 0.70, p = 0.04). All other clinical and lab parameters showed no significant correlation. Compared to controls, blood from SSc patients showed lower ascorbate (vitamin C) levels (8 (3.8-9.8) vs 10.5 (9-19.1) mg/L, p = 0.004) and higher lipid peroxides (873.5 (342-1973) vs 422 (105-576) μmol/L, p = 0.004). Our results indicate the presence of high oxidative stress in both nonfibrotic skin and fibrotic skin of SSc patients, but with higher tendency in the latter. Raised ROS levels in nonfibrotic skin of SSc patients might be a hint of early involvement in skin fibrogenesis. However, a longitudinal prospective study is necessary for such proof.

Relationship between redox status and cell fate in immunity and autoimmunity

SIGNIFICANCE

The signaling function of redox molecules is essential for an efficient and proper execution of a large number of cellular processes, contributing to the maintenance of cell homeostasis. Excessive oxidative stress is considered as playing an important role in the pathogenesis of autoimmune diseases by enhancing inflammation and breaking down the immunological tolerance through protein structural modifications that induce the appearance of neo/cryptic epitopes.

RECENT ADVANCES

There is a complex reciprocal relationship between oxidative stress and both apoptosis and autophagy, which is essential to determine cell fate. This is especially relevant in the context of autoimmune disorders in which apoptosis and autophagy play a crucial pathogenic role.

CRITICAL ISSUES

In this review, we describe the latest developments with regard to the involvement of redox molecules in the initiation and progression of autoimmune disorders, focusing on their role in cell fate regulation. We also discuss new therapeutic approaches that target oxidative stress in the treatment of these disorders. The administration of antioxidants is scarcely studied in autoimmunity, and future analyses are needed to assess its beneficial effects in preventing or ameliorating these diseases.

FUTURE DIRECTIONS

Deciphering the intricate relationships between oxidative stress and both apoptosis and autophagy in the context of autoimmunity could be critical in elucidating key pathogenic mechanisms and could lead to novel interventions for the clinical management of autoimmune diseases.

Prevalence of anti-RNA polymerase III antibodies in systemic sclerosis: New data from a French cohort and a systematic review and meta-analysis

OBJECTIVE

Studies assessing the prevalence of anti-RNA polymerase III (anti-RNAP III) antibodies in systemic sclerosis (SSc) have yielded a wide range of results. The aim of the present study was to describe a new SSc cohort tested for presence of anti-RNAP III and perform a systematic review and meta-analysis to assess the prevalence of anti-RNAP III in patients worldwide and the potential factors of variability.

METHODS

Seropositivity for anti-RNAP III was evaluated in a French cohort of SSc patients. A systematic review of the literature was carried out in PubMed and EMBase. Meta-analysis was performed using available data on prevalence, clinical characteristics of SSc patients, and the types of assays used for anti-RNAP III testing.

RESULTS

One hundred thirty-three French SSc patients were tested for anti-RNAP III, and a prevalence of 6-9% was found in these patients. Thirty studies representing a total population of 8,437 SSc patients were included in the meta-analysis. Prevalence of anti-RNAP III in this population was highly variable (range 0-41%). The overall pooled prevalence of anti-RNAP III was 11% (95% confidence interval 8-14), but heterogeneity was high among studies (I(2) = 93%, P < 0.0001). Geographic factors such as continent or country of study origin partially explained this heterogeneity and correlated with the prevalence. No other baseline SSc characteristics were significantly correlated with the prevalence of anti-RNAP III.

CONCLUSION

Data on our new cohort and our meta-analysis of the literature confirmed that anti-RNAP III prevalence in SSc varies among centers. Geographic factors were significantly associated with prevalence, which underscores the probable implication that genetic background and environmental factors play a role. Heterogeneity among studies remained largely unexplained.

Interleukin-33 potentiates bleomycin-induced lung injury

The mechanisms of interstitial lung disease (ILD) remain incompletely understood, although recent observations have suggested an important contribution by IL-33. Substantial elevations in IL-33 expression were found in the lungs of patients with idiopathic pulmonary fibrosis and scleroderma lung disease, as well as in the bleomycin injury mouse model. Most of the observed IL-33 expression was intracellular and intranuclear, suggesting involvement of the full-length (fl) protein, but not of the proteolytically processed mature IL-33 cytokine. The effects of flIL-33 on mouse lungs were assessed independently and in combination with bleomycin injury, using recombinant adenovirus-mediated gene delivery. Bleomycin-induced changes were not affected by gene deficiency of the IL-33 receptor T1/ST2. Combined flIL-33 expression and bleomycin injury exerted a synergistic effect on pulmonary lymphocyte and collagen accumulation, which could be explained by synergistic regulation of the cytokines transforming growth factor-β, IL-6, monocyte chemotactic protein-1, macrophage inflammatory protein\x{2013}1α, and tumor necrosis factor-α. By contrast, no increase in the levels of the Th2 cytokines IL-4, IL-5, or IL-13 was evident. Moreover, flIL-33 was found to increase the expression of several heat shock proteins (HSPs) significantly, and in particular HSP70, which is known to be associated with ILD. Thus, flIL-33 is a synergistic proinflammatory and profibrotic regulator that acts by stimulating the expression of several non-Th2 cytokines, and activates the expression of HSP70.

Role of toll-like receptors in systemic sclerosis

Accumulative evidence demonstrates the crucial role of evolutionary conserved Toll-like receptors (TLRs) in identifying microbial or viral compounds. TLRs are also able to recognise endogenous molecules which are released upon cell damage or stress and have been shown to play a key role in numerous autoimmune diseases including systemic sclerosis (SSc). A classic feature of SSc, is vascular injury manifested as Raynaud's phenomenon and ischaemia of the skin, resulting in the release of endogenous TLR ligands during inflammation and local tissue damage. These locally released TLR ligands bind TLRs possibly complexed to autoantibodies, and initiate intracellular signalling pathways and may be one of the mechanisms that initiate and drive autoimmunity and subsequent fibrosis. Activation of the immune system results in interferon (IFN) sensitive gene transcription. There is also an IFN gene signature in SSc peripheral blood. TLRs may represent the link between immune activation, common in SSc, and tissue fibrosis. Therefore, a better understanding of the mechanisms of TLR-mediated pathogenesis and therapies targeting individual TLRs, may provide a more specific approach of treating multi-systemic autoimmune diseases. This review aims to integrate the current knowledge of TLR function in the autoimmune disorders with particular emphasis on SSc. We suggest the TLR system as a new therapeutic target.

Scleroderma - new aspects in pathogenesis and treatment

Systemic sclerosis (SSc) is a multisystem disease with a variable clinical course and a poor prognosis corresponding to extent of microangiopathy and skin and internal organ fibrosis. Microvascular damage provokes immune cells to produce autoantibodies, pro-inflammatory and pro-fibrotic cytokines and chemokines. The hallmark of SSc is excessive collagen production by activated fibroblasts and myofibroblasts, and its accumulation in skin and internal organs. Better understanding of SSc pathogenesis resulted in the development of drugs, such as prostanoids, endothelin-1 and phosphodiesterase inhibitors, for treatment of pulmonary arterial hypertension and digital ulcers. The use of biological therapies and anti-fibrotic agents is under investigation. Stem cell transplantation seems to be promising in restarting the immune system to diminish fibrosis and restore microvasculature. Future research will be directed at genetic factors, diagnostic and prognostic markers for fibrosis and microangiopathy, and development of drugs directed to pathogenic key cells and mediators.

New insights into the role of oxidative stress in scleroderma fibrosis

Systemic sclerosis (Scleroderma – SSc) is a connective tissue disorder of unknown aetiology characterized by extensive fibrosis of the skin and visceral organs, by vascular abnormalities and immunological manifestations.

Recent evidence suggest that the cellular redox state may play a significant role in the progression of scleroderma fibrosis. Mechanisms involved include an autoamplification circuit linking ROS, Ras and ERK 1-2 which in turn amplifies and maintains the autocrine loop made up by cytokines, growth factors and their cognate receptors.

This review summarizes the recent progress on the role of oxidative stress in the pathophysiology of scleroderma and disorders characterised by organ fibrosis

Autoimmune mechanisms of scleroderma and a role of oxidative stress

Scleroderma is a fibrotic condition characterized by immunological abnormalities, vascular injury and increased accumulation of extracellular matrix proteins in the skin. Although the etiology of scleroderma has not yet been fully elucidated, a growing body of evidence suggests that extracellular matrix overproduction by activated fibroblasts results from complex interactions among endothelial cells, lymphocytes, macrophages and fibroblasts via a number of mediators, such as cytokines, chemokines and growth factors. Recent investigations have further suggested that reactive oxygen species (ROS) are involved and play a role of autoimmunology in scleroderma. In this review, current findings on the autoimmune mechanisms in the pathophysiology of scleroderma are described.