Gastrointestinal Involvement in Systemic Sclerosis: Overview, Neglected Aspects, Malnutrition, Body Composition and Management

Gastrointestinal tract (GIT) involvement is the most common internal organ manifestation and is present in up to 90% of patients with systemic sclerosis (SSc). Clinical manifestations can differ according to the part of the GIT affected, disease course and symptoms. A majority of the symptoms are caused by GIT dysmotility. Up to 8% of SSc patients develop several GIT symptoms, which increase the mortality. Although GIT involvement is rarely the direct cause of death, it can lead to several comorbidities including malnutrition and negative alterations of body composition. These factors have a negative impact on quality of life and increase the mortality. To date, the treatment is rather symptomatic. The pathogenesis of GIT involvement in SSc still remains to be clarified to improve the treatment approaches including intravenous immunoglobulins and microRNA interventions

Atherosclerosis and Cardiovascular Risk in Systemic Sclerosis

Atherosclerosis (ATS) has been considered to be a degenerative disease affecting large and medium-sized arteries, resulting in a passive build-up of cholesterol in the artery wall. In the last decade, immune system was proved to play the key role in the pathogenesis of ATS, suggesting ATS to be more progressive and accelerated in chronic inflammatory conditions. Studies in patients with autoimmune diseases, particularly in the most prevalent ones such as rheumatoid arthritis and systemic lupus erythematosus, confirmed the significantly more serious atherosclerotic disease and increased cardiovascular (CV) risk compared to the general population, suggesting these diseases as an independent risk factor for CV diseases. There are only few studies evaluating ATS and CV risk in systemic sclerosis (SSc). Moreover, these studies present contradictory results. Furthermore, it is complicated to differentiate primary vascular affection related to the pathogenesis of SSc from the secondary vascular infliction due to ATS. Nevertheless, most of the studies to date suggest ATS and its clinical manifestations to be more prevalent in SSc. Future studies evaluating larger cohorts of patients are required to determine the relevance of ATS and CV disease and management of these comorbidities in SSc

Animal Models of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare, chronic connective tissue disease affecting the skin, vessels, musculoskeletal system, and internal organs. Despite advances in pharmacotherapy of organ manifestations and new knowledge about the pathogenesis of SSc, there is still no effective universal treatment of this serious disease. The aim of this chapter is to introduce traditional, most commonly used experimental animal models of SSc, clarify their basic pathological mechanism, describe their advantages and limitations, and outline their use in preclinical tests of potential therapeutic agents with subsequent clinical trials in patients with SSc. The existing models have already contributed significantly to preclinical testing of several available biological agents and small molecules, some of which achieved promising results in early clinical studies, and could provide better prospects for patients with this incurable disease

Atherosclerosis in Rheumatology: Old and New Insights

Cardiovascular diseases are the leading cause of morbidity and mortality in general population worldwide. There is an increasing significance of cardiovascular risk in the field of rheumatology, and accordingly, the evidence on the relation between immune system disorders and atherosclerosis has been substantially growing especially in last decades. Since novel immune and metabolic factors are considered to participate in pathogenesis of atherosclerosis and increased cardiovascular risk in rheumatic patients, they are getting to the forefront of the research. Since novel therapeutic approaches have improved survival of rheumatic patients, and decreased morbidity caused by rheumatic disease activity and damage, the significance of other comorbidities leading to premature mortality has arisen. Nevertheless, appropriate recommendations for the management of cardiovascular risk are still lacking. Recently, European League Against Rheumatism (EULAR) recommendations for management of the cardiovascular risk and comorbidities in patients with inflammatory arthropathies have been published. However, the cardiovascular management of these patients is still suboptimal. In addition, the situation in other orphan diseases such as idiopathic inflammatory myopathies, systemic sclerosis and others is even more uncertain and strongly requires further research. This chapter provides an overview of epidemiology, pathogenesis, clinical manifestations, screening and management of atherosclerosis in patients with rheumatic diseases

New Insights into Systemic Sclerosis

Systemic sclerosis (scleroderma) is an incurable connective tissue disease of unknown etiology. Three key processes play a pivotal role in the pathogenesis: immune dysregulation and inflammation, endothelial injury and vasculopathy, and fibrosis. Tissue fibrosis is the dominant and characteristic feature that affects the skin and visceral organs. Life expectancy of scleroderma patients has improved over recent years, mainly because of better treatment of organ involvement and complications; however, no curative disease-modifying therapies exist to date. This book aims to provide students, trainees, rheumatologists, and other specialists interested in this disease with a comprehensive overview of novel pathogenetic mechanisms, management approaches, and therapeutic targets of several major vascular and fibrotic manifestations, and is useful insight into a number of usually neglected aspects of scleroderma

Sirt1 regulates canonical TGF-β signalling to control fibroblast activation and tissue fibrosis

BACKGROUND Sirt1 is a member of the sirtuin family of proteins. Sirt1 is a class III histone deacetylase with important regulatory roles in transcription, cellular differentiation, proliferation and metabolism. As aberrant epigenetic modifications have been linked to the pathogenesis of systemic sclerosis (SSc), we aimed to investigate the role of Sirt1 in fibroblast activation. METHODS Sirt1 expression was analysed by real-time PCR, western blot and immunohistochemistry. Sirt1 signalling was modulated with the Sirt1 agonist resveratrol and by fibroblast-specific knockout. The role of Sirt1 was evaluated in bleomycin-induced skin fibrosis and in mice overexpressing a constitutively active transforming growth factor-β (TGF-β) receptor I (TBRIact). RESULTS The expression of Sirt1 was decreased in patients with SSc and in experimental fibrosis in a TGF-β-dependent manner. Activation of Sirt1 potentiated the profibrotic effects of TGF-β with increased Smad reporter activity, elevated transcription of TGF-β target genes and enhanced release of collagen. In contrast, knockdown of Sirt1 inhibited TGF-β/SMAD signalling and reduced release of collagen in fibroblasts. Consistently, mice with fibroblast-specific knockdown of Sirt1 were less susceptible to bleomycin- or TBRIact-induced fibrosis. CONCLUSIONS We identified Sirt1 as a crucial regulator of TGF-β/Smad signalling in SSc. Although Sirt1 is downregulated, this decrease is not sufficient to counterbalance the excessive activation of TGF-β signalling in SSc. However, augmentation of this endogenous regulatory mechanism, for example, by knockdown of Sirt1, can effectively inhibit TGF-β signalling and exerts potent antifibrotic effects. Sirt1 may thus be a key regulator of fibroblast activation in SSc

A synthetic PPAR-γ agonist triterpenoid ameliorates experimental fibrosis: PPAR-γ-independent suppression of fibrotic responses

Background: Persistent fibroblast activation initiated by transforming growth factor β (TGF-β) is a fundamental event in the pathogenesis of systemic sclerosis, and its pharmacological inhibition represents a potential therapeutic strategy. The nuclear receptor, peroxisome proliferator-activated receptor γ (PPAR-γ), exerts potent fibrotic activity. The synthetic oleanane triterpenoid, 2-cyano-3,12-dioxo-olean-1,9-dien-28-oic acid (CDDO), is a PPAR-γ agonist with potential effects on TGF-β signalling and dermal fibrosis. Objective: To examine the modulation of fibrogenesis by CDDO in explanted fibroblasts, skin organ cultures and murine models of scleroderma. Material and methods: The effects of CDDO on experimental fibrosis induced by bleomycin injection or by overexpression of constitutively active type I TGF-β receptor (TgfbR1ca) were evaluated. Modulation of fibrotic gene expression was examined in human skin organ cultures. To delineate the mechanisms underlying the antifibrotic effects of CDDO, explanted skin fibroblasts cultured in two-dimensional monolayers or in three-dimensional full-thickness human skin equivalents were studied. Results: CDDO significantly ameliorated dermal fibrosis in two complementary mouse models of scleroderma, as well as in human skin organ cultures and in three-dimensional human skin equivalents. In two-dimensional monolayer cultures of explanted normal fibroblasts, CDDO abrogated fibrogenic responses induced by TGF-β. These CDDO effects occurred via disruption of Smad-dependent transcription and were associated with inhibition of Akt activation. In scleroderma fibroblasts, CDDO attenuated the elevated synthesis of collagen. Remarkably, the in vitro antifibrotic effects of CDDO were independent of PPAR-γ. Conclusions: The PPAR-γ agonist triterpenoid CDDO attenuates fibrogenesis by antagonistically targeting canonical TGF-β/Smad and Akt signalling in a PPAR-γ-independent manner. These findings identify this synthetic triterpenoid as a potential new therapy for the control of fibrosis

Critical role of the adhesion receptor DNAX accessory molecule-1 (DNAM-1) in the development of inflammation-driven dermal fibrosis in a mouse model of systemic sclerosis

Objective: To investigate the contribution of the adhesion receptor DNAX accessory molecule-1 (DNAM-1) in the development of dermal fibrosis on gene inactivation and targeted molecular strategies. Methods: Human skin expression of DNAM-1 was determined by immunohistochemistry. Mice deficient for DNAM-1 (dnam1−/−) and wild-type controls (dnam1+/+) were injected with bleomycin or NaCl. Infiltrating leucocytes, T cells, B cells and monocytes were quantified and inflammatory cytokines were measured in lesional skin of dnam1−/− and dnam1+/+ mice. The anti-fibrotic potential of a DNAM-1 neutralising monoclonal antibody (mAb) was evaluated in the mouse model of bleomycin-induced dermal fibrosis. Results: Overexpression of DNAM-1 was detected in the skin of patients with SSc (systemic sclerosis). Dnam1−/− mice were protected from bleomycin-induced dermal fibrosis with reduction of dermal thickening (75±5%, p=0.03), hydroxyproline content (46±8%, p=0.04) and myofibroblast counts (39±5%, p=0.01). Moreover, the number of T cells was significantly decreased in lesional skin of dnam1−/− mice (69±15%, p=0.0007). Dnam1−/− mice also displayed decreased levels of TNF-α and IL-6 in lesional skin. Consistent with the gene inactivation strategy, treatment of mice with DNAM-1 neutralising mAb prevented dermal fibrosis induced by bleomycin with reduction of dermal thickness (64±6%, p=0.002), hydroxyproline content (61±8%, p=0.004) and myofibroblast counts (83±12%, p=0.002). Conclusions: An inactivation gene strategy showed that DNAM-1 exerts profibrotic effects by controlling T cell activation and cytokine release. A molecular targeted strategy confirmed that DNAM-1 neutralising mAb has potent antifibrotic properties, supporting the hypothesis that inhibition of DNAM-1 might be a promising new approach for the treatment of SSc and potentially other related fibrotic diseases

Tribbles homologue 3 stimulates canonical TGF-β signalling to regulate fibroblast activation and tissue fibrosis

OBJECTIVES Tribbles homologue 3 (TRB3) is a pseudokinase that modifies the activation of various intracellular signalling pathways to control fundamental processes extending from mitosis and cell activation to apoptosis and modulation of gene expression. Here, we aimed to analyse the role of TRB3 in fibroblast activation in systemic sclerosis (SSc). METHODS The expression of TRB3 was quantified by quantitative PCR, western blot and immunohistochemistry. The role of TRB3 was analysed in cultured fibroblasts and in experimental fibrosis using small interfering RNA (siRNA)-mediated knockdown and overexpression of TRB3. RESULTS TRB3 expression was increased in fibroblasts of patients with SSc and in murine models of SSc in a transforming growth factor-β (TGF-β)/Smad-dependent manner. Overexpression of TRB3 stimulated canonical TGF-β signalling and induced an activated phenotype in resting fibroblasts. In contrast, knockdown of TRB3 reduced the profibrotic effects of TGF-β and decreased the collagen synthesis. Moreover, siRNA-mediated knockdown of TRB3 exerted potent antifibrotic effects and ameliorated bleomycin as well as constitutively active TGF-β receptor I-induced fibrosis with reduced dermal thickening, decreased hydroxyproline content and impaired myofibroblast differentiation. CONCLUSIONS The present study characterises TRB3 as a novel profibrotic mediator in SSc. TGF-β induces TRB3, which in turn activates canonical TGF-β/Smad signalling and stimulates the release of collagen, thereby inducing a positive feedback loop that may contribute to aberrant TGF-β signalling in SSc

Vitamin D receptor regulates TGF-β signalling in systemic sclerosis

BACKGROUND Vitamin D receptor (VDR) is a member of the nuclear receptor superfamily. Its ligand, 1,25-(OH)2D, is a metabolically active hormone derived from vitamin D3. The levels of vitamin D3 are decreased in patients with systemic sclerosis (SSc). Here, we aimed to analyse the role of VDR signalling in fibrosis. METHODS VDR expression was analysed in SSc skin, experimental fibrosis and human fibroblasts. VDR signalling was modulated by siRNA and with the selective agonist paricalcitol. The effects of VDR on Smad signalling were analysed by reporter assays, target gene analyses and coimmunoprecipitation. The effects of paricalcitol were evaluated in the models of bleomycin-induced fibrosis and fibrosis induced by overexpression of a constitutively active transforming growth factor-β (TGF-β) receptor I (TBRI(CA)). RESULTS VDR expression was decreased in fibroblasts of SSc patients and murine models of SSc in a TGF-β-dependent manner. Knockdown of VDR enhanced the sensitivity of fibroblasts towards TGF-β. In contrast, activation of VDR by paricalcitol reduced the stimulatory effects of TGF-β on fibroblasts and inhibited collagen release and myofibroblast differentiation. Paricalcitol stimulated the formation of complexes between VDR and phosphorylated Smad3 in fibroblasts to inhibit Smad-dependent transcription. Preventive and therapeutic treatment with paricalcitol exerted potent antifibrotic effects and ameliorated bleomycin- as well as TBRI(CA)-induced fibrosis. CONCLUSIONS We characterise VDR as a negative regulator of TGF-β/Smad signalling. Impaired VDR signalling with reduced expression of VDR and decreased levels of its ligand may thus contribute to hyperactive TGF-β signalling and aberrant fibroblast activation in SSc