High prevalence of occupational exposure to solvents or silica in male systemic sclerosis patients: a Belgian cohort analysis

Dynamic biodistribution of inhaled silica particles to extrapulmonary sites: Early and late translocation mechanisms with implication for particle biomonitoring

An innovative method based on inductively coupled plasma mass spectrometry (ICP-MS) was developed to quantify the time-dependent systemic redistribution pattern of pulmonary-deposited crystalline silica particles by measuring silicon (Si) levels in the lungs, distal organs, and biological fluids. The method was applied in a murine model and validated in blood and urine samples from two occupationally exposed cohorts (miners and porcelain industry workers). In mice, 30 % of silica particles deposited in the lungs via oropharyngeal administration accumulated in extrapulmonary sites in less than 4 months. An early translocation (within 3 days) resulted in silica distribution to liver and kidneys (13 %), followed by a delayed migration (up to 60 days) in mediastinal lymph nodes (12 %), spleen (1.7 %), and abdominal skin (1.7 %). The long-term increase of Si in urine suggested silica renal clearance. Our data also indicated that the toxic potential of particles is a key determinant of extrapulmonary redistribution. The interest of Si as biomarker of exposure has been confirmed in workers exposed to crystalline silica dust. In these individuals, elevated Si levels in blood and urine paralleled silica exposure. Our findings quantify the dynamics of silica biodistribution in extrapulmonary organs, offering new insights on the biomonitoring of silica exposure in different scenarios.

Environmental factors and rheumatic diseases

The pathogenesis and pathophysiology of rheumatic diseases is complex and relies on the interaction of different factors. The common view is that the pathological autoimmunity develops in genetically predisposed individuals upon exposure to an environmental trigger. This highlights the importance of recognizing and deconstructing the effects of environmental agents in rheumatic diseases. Several factors have been identified in the last decades, with detrimental or protective effects, impacting not only on disease onset, but also on its natural history. Cigarette smoking has been identified as one of the strongest environmental risk factors, being associated with disease development and severity for several rheumatic diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and spondyloarthropathies. Moreover, other airborne pollutants, such as silica, solvents, asbestos and metals are recognized risk factors for rheumatic diseases. The effect of some other agents is however not straightforward, of which a remarkable example is alcohol consumption. Alcohol has been associated with both pro- and anti-inflammatory effects, exerting a variable effect on rheumatic diseases depending on quantity and frequency of consumption, as well as sex and ethnicity. Similarly, ultraviolet light exposure has been associated with a higher risk of SLE but lower risk of RA. The relationship between microbial exposure and autoimmunity is also complex: while some infectious agents increase the risk of rheumatic diseases, it is widely accepted that less exposure to microbial agents, particularly during immune system development, increases the risk of autoimmunity. Furthermore, in recent years the spotlight has switched to the human microbiome, as alterations in organ-specific microbiome composition are anticipated to be early participants in the onset of immune-mediated illnesses. The aim of this review is to highlight the most relevant environmental factors and their role in Rheumatology, with a specific focus on proposed pathophysiological effect and correlation with clinical outcomes.

Occupational dust and chemical exposures and the development of autoimmune rheumatic diseases

Although the association between certain occupational exposures and the development of autoimmune rheumatic disease was first described over a century ago, this association has only become more widely recognized in the past 10 years because of the use of high-silica-content engineered stone in construction and home renovation. There is now a substantial and growing body of evidence that occupational dust and chemical exposure, be it through mining, stonemasonry, building or other trades, increases the risk of various systemic autoimmune rheumatic diseases (SARDs) including rheumatoid arthritis and systemic sclerosis. Although the pathogenic mechanisms of silica-induced autoimmunity are not fully elucidated, it is thought that alveolar macrophage ingestion of silica and the ensuing phagosomal damage is an initiating event that ultimately leads to production of autoantibodies and immune-mediated tissue injury. The purportedly causal association between occupational exposure to chemicals, such as organic solvents, and an increased risk of SARDs is less frequently recognized compared with silica dust, and its immunopathogenesis is less well understood. An appreciation of the importance of occupational dust and chemical exposures in the development of SARDs has implications for workplace health and safety regulations and offers a unique opportunity to better understand autoimmune disease pathogenesis and implement preventative strategies.

External and internal exposome as triggers of biological signalling in systemic sclerosis - A narrative synthesis

Systemic sclerosis (SSc) is an autoimmune chronic connective tissue disorder with a complex pathogenesis and a strong gene-environment interaction. Despite the low prevalence of SSc, with around 100-250 cases per million, the morbidity and mortality are high and disproportionately affecting women. In this context, we review the influence of the external and internal exposome on the "immunome" in SSc. While several studies have addressed aspects of exposure-induced autoimmunity in general, very few have focused on SSc-specific phenotypes. In epidemiological studies, targeted characterization of the external exposome component in relation to SSc has often been limited to a single exposure. Despite the selective characterization of exposure, such studies play an important role in providing evidence that can be used towards reduction of exposure of modifiable factors, and can lead to proper management and prevention of SSc. Additionally, there is an effort towards integration of external exposome data with health data (health records, medical imaging, diagnostic results, etc.), to significantly improve our understanding of the environmental and occupational causes of SSc. A limited number of studies have identified biological processes related to the vascular homeostasis, fibrotic processes and the immune system. The key findings of the current review show advances in our understanding of the SSc disease phenotype and associated biomarkers in relation to specific pathophysiological features, however most often such studies are not supplemented with external exposome data.

Occupational quantitative exposure to crystalline silica, solvents and pesticides and risk of clinical forms of systemic sclerosis

OBJECTIVES

To estimate the association between SSc clinical phenotypes and quantitative occupational exposure to crystalline silica, chlorinated solvents, trichloroethylene and pesticides using job-exposure matrices.

METHODS

In the VISS-EXPOSITION transversal study, data on declarative occupational exposure to crystalline silica, solvents and pesticides were retrieved. In parallel, the lifetime occupational history was evaluated using a questionnaire and cursus laboris for SSc patients followed at Bordeaux University Hospital (France). Using job-exposure matrices, we assessed patients' occupational exposure in relation to relevant clinical phenotypic forms of the disease.

RESULTS

Toxic exposure to crystalline silica and pesticides is underestimated by patients. Non-biased job-exposure matrices retrieved more exposed patients than the declarative assessment (10.1% of patients by job-exposure matrices vs 6.3% by declaration for crystalline silica and 25.9% vs 12.2% for pesticides). Patients overestimate their solvent exposure (7.9% for chlorinated solvents and 4.8% for trichlorethylene assessed by job-exposure matrices and 24.4% declarative exposure to solvents at large). Clinical form evaluation revealed a non-significant trend toward an increased risk of crystalline silica occupational exposure in the pulmonary fibrotic group of SSc patients [odds ratio (OR) 3.12 (95% CI 0.80, 12.15)]. We also observed a non-significant trend toward an elevated OR ([2.89 (95% CI 0.93, 8.95)] for chlorinated solvent occupational exposure and the vascular phenotype of SSc. Of note, pesticide occupational exposure evaluation represents one of the largest to date in SSc patients.

CONCLUSION

This study emphasizes that many exposed SSc patients are unaware of their occupational exposure. Job-exposure matrices allow better exposure screening for SSc secondary prevention and occupational exposure compensation.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov (https://www.clinicaltrials.gov), NCT03543956.

Interstitial Lung Disease Associated with Systemic Sclerosis

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by a tripod combining vasculopathy, fibrosis, and immune-mediated inflammatory processes. The prevalence of interstitial lung disease (ILD) in SSc varies according to the methods used to detect it, ranging from 25 to 95%. The fibrotic and vascular pulmonary manifestations of SSc, particularly ILD, are the main causes of morbidity and mortality, contributing to 35% of deaths. Although early trials were conducted with cyclophosphamide, more recent randomized controlled trials have been performed to assess the efficacy and tolerability of several medications, mostly mycophenolate, rituximab, tocilizumab, and nintedanib. Although many uncertainties remain, expert consensus is emerging to optimize the therapeutic management and to provide clinicians with evidence-based clinical practice guidelines for patients with SSc-ILD. This article provides an overview, in the light of the latest advances, of the available evidence for the diagnosis and management of SSc-ILD.

Contributions of Synthetic Chemicals to Autoimmune Disease Development and Occurrence

PURPOSE OF REVIEW

Exposure to many synthetic chemicals has been linked to a variety of adverse human health effects, including autoimmune diseases. In this scoping review, we summarize recent evidence detailing the effects of synthetic environmental chemicals on autoimmune diseases and highlight current research gaps and recommendations for future studies.

RECENT FINDINGS

We identified 68 recent publications related to environmental chemical exposures and autoimmune diseases. Most studies evaluated exposure to persistent environmental chemicals and autoimmune conditions including rheumatoid arthritis (RA), systemic lupus (SLE), systemic sclerosis (SSc), and ulcerative colitis (UC) and Crohn's disease. Results of recent original research studies were mixed, and available data for some exposure-outcome associations were particularly limited. PFAS and autoimmune inflammatory bowel diseases (UC and CD) and pesticides and RA appeared to be the most frequently studied exposure-outcome associations among recent publications, despite a historical research focus on solvents. Recent studies have provided additional evidence for the associations of exposure to synthetic chemicals with certain autoimmune conditions. However, impacts on other autoimmune outcomes, particularly less prevalent conditions, remain unclear. Owing to the ubiquitous nature of many of these exposures and their potential impacts on autoimmune risk, additional studies are needed to better evaluate these relationships, particularly for understudied autoimmune conditions. Future research should include larger longitudinal studies and studies among more diverse populations to elucidate the temporal relationships between exposure-outcome pairs and to identify potential population subgroups that may be more adversely impacted by immune modulation caused by exposure to these chemicals.

Association between silicosis and autoimmune disease

PURPOSE OF REVIEW

There is a well established association between silica inhalational exposure and autoimmune disease, particularly in the context of intense exposure. We will provide in this article an update overview of new sources of silica dust exposure, with evidences of mechanisms from human and animal studies for association between silica and autoimmune diseases, their early detection of silicosis and new options for treatment.

RECENT FINDINGS

New industries such as jewelry polishing, denim jean production, fabrication of artificial stone benchtops, glass manufacturing and glassware has led to re-emergence of silicosis around the world. Silicosis with long term exposure to dust containing crystalline silica has been examined as a possible risk factor with respect to several autoimmune diseases as scleroderma, rheumatoid arthritis, lupus erythematosus, and some types of small vessel vasculitis with renal involvement. The dust may act to promote or accelerate disease development, requiring some other factors to break immune tolerance or initiate autoimmunity. Autophagy, apoptosis, or pyroptosis-related signaling pathways have also been suggested to contribute to the formation of those pathways with coordination of environmental co-exposure that can magnify autoimmune vulnerability.

SUMMARY

Better understanding the mechanisms that involve silica -induced autoimmune diseases may contribute to early diagnosis.

Results from omic approaches in rat or mouse models exposed to inhaled crystalline silica: a systematic review

BACKGROUND

Crystalline silica (cSiO2) is a mineral found in rocks; workers from the construction or denim industries are particularly exposed to cSiO2 through inhalation. cSiO2 inhalation increases the risk of silicosis and systemic autoimmune diseases. Inhaled cSiO2 microparticles can reach the alveoli where they induce inflammation, cell death, auto-immunity and fibrosis but the specific molecular pathways involved in these cSiO2 effects remain unclear. This systematic review aims to provide a comprehensive state of the art on omic approaches and exposure models used to study the effects of inhaled cSiO2 in mice and rats and to highlight key results from omic data in rodents also validated in human.

METHODS

The protocol of systematic review follows PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Eligible articles were identified in PubMed, Embase and Web of Science. The search strategy included original articles published after 1990 and written in English which included mouse or rat models exposed to cSiO2 and utilized omic approaches to identify pathways modulated by cSiO2. Data were extracted and quality assessment was based on the SYRCLE's Risk of Bias tool for animal studies.

RESULTS

Rats and male rodents were the more used models while female rodents and autoimmune prone models were less studied. Exposure of animals were both acute and chronic and the timing of outcome measurement through omics approaches were homogeneously distributed. Transcriptomic techniques were more commonly performed while proteomic, metabolomic and single-cell omic methods were less utilized. Immunity and inflammation were the main domains modified by cSiO2 exposure in lungs of mice and rats. Less than 20% of the results obtained in rodents were finally verified in humans.

CONCLUSION

Omic technics offer new insights on the effects of cSiO2 exposure in mice and rats although the majority of data still need to be validated in humans. Autoimmune prone model should be better characterised and systemic effects of cSiO2 need to be further studied to better understand cSiO2-induced autoimmunity. Single-cell omics should be performed to inform on pathological processes induced by cSiO2 exposure.

Clinical characteristics of systemic sclerosis patients with occupational silicosis

To explore the clinical characteristics of systemic sclerosis complicated with silicosis. The systemic sclerosis patients treated in the Guangxi Workers' Hospital and the People's Hospital of Guangxi Zhuang Autonomous Region from January 2000 to December 2020 were divided into the systemic sclerosis with silicosis group and the systemic sclerosis without silicosis group. Survival analysis was performed using Kaplan-Meier estimates the Cox proportional hazards model. A propensity score matching was applied in order to avoid the selection bias.Over the past 20 years, 72 systemic sclerosis patients with silicosis and 238 systemic sclerosis patients without silicosis were treated in the two hospitals. The systemic sclerosis patients with silicosis group had more males (P < 0.000),lower mean age at onset of SSc (P < 0.000), more frequent occurrence of weight loss (P = 0.028), smoking (P < 0.000), tuberculosis (P < 0.000), cardiac involvement (P < 0.000), ILD (P = 0.017), pulmonary hypertension (P = 0.024), elevated BNP (P < 0.000). With regards to the multivariate Cox regression analysis, silicosis was related with a higher overall mortality before (HR = 3.666, 95% CI = 1.440-11.234, p = 0.025) and after the propensity score matching analysis (HR = 2.817, 95% CI = 1.196-10.764, p = 0.014). Independent risk factors for overall mortality were Gangrene (HR = 3.003, 95% CI = 1.343-9.431), Cardiac involved (HR = 5.370, 95% CI = 1.910-15.472), Scl-70 (HR = 3.569, 95% CI = 1.333-10.869), Elevated BNP (HR = 2.135, 95% CI = 1.293-9.564).Concomitant silicosis worsens systemic sclerosis patients' prognoses. Gangrene, Scl-70, elevated BNP and cardiac involvement are independent risk factors for overall mortality. Key Points •Concomitant silicosis worsens SSc patients' prognoses. •For individuals with occupational exposure, close observation of the symptoms of SSc, early diagnosis, and interruption of exposure may improve the prognosis. •Gangrene, Scl-70, elevated BNP and cardiac involvement are independent risk factors for overall mortality.

Beyond very early systemic sclerosis: deciphering pre‑scleroderma and its trajectories to open new avenues for preventive medicine

The identification of individuals with systemic sclerosis in an oligosymptomatic phase preceding the very early manifestations of the disease represents a challenge in the search for a new window of opportunity in systemic sclerosis. This phase could be identified in a clinical scenario as the pre-scleroderma phase, in which the disease would still be far from systemic sclerosis-related fibrotic or irreversible manifestations in skin or organs. In this Personal View, we discuss parameters and candidate definitions for a conceptual framework of pre-scleroderma, from the identification of populations at risk to autoantibodies and their potential functional activities. We discuss how this new paradigm of pre-scleroderma could represent a game-changing approach in the management of systemic sclerosis, allowing the treatment of patients at high risk of organ involvement or skin fibrosis before such events occur.

B-1 cells in immunotoxicology: Mechanisms underlying their response to chemicals and particles

Since their discovery nearly 40 years ago, B-1 cells have continued to challenge the boundaries between innate and adaptive immunity, as well as myeloid and lymphoid functions. This B-cell subset ensures early immunity in neonates before the development of conventional B (B-2) cells and respond to immune injuries throughout life. B-1 cells are multifaceted and serve as natural- and induced-antibody-producing cells, phagocytic cells, antigen-presenting cells, and anti-/pro-inflammatory cytokine-releasing cells. This review retraces the origin of B-1 cells and their different roles in homeostatic and infectious conditions before focusing on pollutants comprising contact-sensitivity-inducing chemicals, endocrine disruptors, aryl hydrocarbon receptor (AHR) ligands, and reactive particles.

Geographical heterogeneity of clinical and serological phenotypes of systemic sclerosis observed at tertiary referral centres. The experience of the Italian SIR-SPRING registry and review of the world literature

INTRODUCTION

Systemic sclerosis (SSc) is characterized by a complex etiopathogenesis encompassing both host genetic and environmental -infectious/toxic- factors responsible for altered fibrogenesis and diffuse microangiopathy. A wide spectrum of clinical phenotypes may be observed in patients' populations from different geographical areas. We investigated the prevalence of specific clinical and serological phenotypes in patients with definite SSc enrolled at tertiary referral centres in different Italian geographical macro-areas. The observed findings were compared with those reported in the world literature.

MATERIALS AND METHODS

The clinical features of 1538 patients (161 M, 10.5%; mean age 59.8 ± 26.9 yrs.; mean disease duration 8.9 ± 7.7 yrs) with definite SSc recruited in 38 tertiary referral centres of the SPRING (Systemic sclerosis Progression INvestiGation Group) registry promoted by Italian Society of Rheumatology (SIR) were obtained and clustered according to Italian geographical macroareas.

RESULTS

Patients living in Southern Italy were characterized by more severe clinical and/or serological SSc phenotypes compared to those in Northern and Central Italy; namely, they show increased percentages of diffuse cutaneous SSc, digital ulcers, sicca syndrome, muscle involvement, arthritis, cardiopulmonary symptoms, interstitial lung involvement at HRCT, as well increased prevalence of serum anti-Scl70 autoantibodies. In the same SSc population immunusppressive drugs were frequently employed. The review of the literature underlined the geographical heterogeneity of SSc phenotypes, even if the observed findings are scarcely comparable due to the variability of methodological approaches.

CONCLUSION

The phenotypical differences among SSc patients' subgroups from Italian macro-areas might be correlated to genetic/environmental co-factors, and possibly to a not equally distributed national network of information and healthcare facilities.

Exposure to silica and systemic sclerosis: A retrospective cohort study based on the Canadian Scleroderma Research Group

Introduction

Systemic sclerosis (SSc) is thought to be induced by an environmental trigger in genetically predisposed individuals. This study assessed the demographic and clinical characteristics and disease severity of silica exposed SSc patients.

Methods

Data was obtained from the Canadian Scleroderma Research Group (CSRG) cohort, containing 1,439 patients (2004–2019). Univariate and multivariate logistic regression analyses were performed, to determine the phenotype and severity of silica-exposed SSc patients. Mortality was assessed using Cox Survival Regression and Kaplan-Meier analyses.

Results

Among 1,439 patients (86.7% females), 95 patients reported exposure to silica. Those exposed were younger, of male sex and with more severe disease. Sex differences were observed where male patients exposed to silica were more likely to be Caucasian and smokers whereas female patients were younger at SSc diagnosis compared to unexposed. Multivariate regression, controlled for multiple confounders, showed that silica exposure was associated with a younger age at diagnosis and worse disease severity and mortality.

Conclusion

Exposure to silica was reported in ∼7% of CSRG cohort and ∼20% of male patients and was associated with a worse prognosis in terms of age of diagnosis, organ involvement and mortality. Hence, screening for silica exposure among higher risk individuals may be beneficial and these patients may require closer monitoring for systemic disease.

Independent association between occupational exposure and decline of forced vital capacity in systemic sclerosis (SSc): a multicenter recruitment retrospective cohort study

BACKGROUND

Although male sex is associated with poor prognosis in Systemic Sclerosis (SSc), it is unclear whether this association is independent of confounding factors such as occupational exposure to toxicants.

RESEARCH QUESTION

What is the respective impact of sex and occupational exposure on SSc patients' characteristics with a focus on lung function decline?

STUDY DESIGN AND METHODS

Patients with SSc (n=210, 55 males) underwent standardized quantitative assessment of occupational exposure through a cumulative exposure score (CES) in a multicenter recruitment retrospective cohort. Association of the CES with patients' characteristics was assessed. Mixed linear, logistic and Cox regression models were used to identify predictors of time variation of forced vital capacity (FVC) and the hemoglobin-corrected transfer coefficient for carbon monoxide in the lung (DLCOc).

RESULTS

Male sex was strongly associated with occupational exposure (OR=10.3, p<.0001). The CES was inversely correlated (r= -.20) and independently associated with decline in FVC over time and with occurrence of FVC decline ≥10% from baseline (p<.05). By contrast, the CES was not associated with decline in DLCOc or DLCOc decline ≥15%. There was no independent association between sex and decline in FVC or DLCOc. The prevalence of interstitial lung disease was similar across sex or occupational exposure.

INTERPRETATION

Occupational exposure to toxicants appears to independently predict decline of FVC in SSc patients, regardless of sex. Assessment of occupational exposure may be useful for SSc prognostication.

Airborne pollutants as potential triggers of systemic autoimmune rheumatic diseases: a narrative review

The pathogenesis of systemic autoimmune rheumatic diseases (SARDs) is complex and remains insufficiently understood. It is commonly accepted that both intrinsic and extrinsic environmental factors interact to induce a self-reactive immune response. Case reports and observational studies have revealed an association between SARDs and specific airborne environmental factors, but the heterogeneity of the published studies hampers clear conclusions. The aim of this review is to provide an overview of the available epidemiological evidence on the relationship between airborne pollutants and SARDs. We performed a narrative review using the PubMed database. Observational studies have shown significant associations between airborne pollutants and SARDs. Cigarette smoking is strongly associated with the development of rheumatoid arthritis (RA) while the association between cigarette smoke and the development of other SARDs remains controversial. For decades, silica exposure has been linked to systemic sclerosis (SSc), RA and systemic lupus erythematosus (SLE). There is also strong evidence for a link between solvents and SSc. Recent observations even suggest that ambient air pollution is associated with the development of SARDs. Some studies have shown associations between asbestos, organic dust, metals and pesticides and SARDs, but more studies are needed to confirm these findings. Increasing evidence has linked airborne pollutants to SARDs. Although more studies are needed to understand the potential mechanisms by which these environmental agents contribute to disease pathogenesis, awareness of the link between environmental agents and SARDs is important to recognize and prevent work-related and environmentally induced diseases.

Novel classifications for systemic sclerosis: challenging historical subsets to unlock new doors

PURPOSE OF REVIEW

Systemic sclerosis (SSc) is a severe rheumatic disease characterized by a considerable heterogeneity in clinical presentations and pathophysiological mechanisms. This variability has a substantial impact on morbidity and mortality and limits the generalizability of clinical trial results. This review aims to highlight recent studies that have proposed new innovative approaches to decipher this heterogeneity, in particular, by attempting to optimize disease classification.

RECENT FINDINGS

The historical dichotomy limited/diffuse subsets based on cutaneous involvement has been challenged by studies highlighting an underestimated heterogeneity between these two subtypes and showing that presence of organ damage and autoantibody profiles markedly influenced survival beyond skin extension. Advanced computational methods using unsupervised machine learning analyses of clinical variables and/or high-throughput omics technologies, clinical variables trajectories modelling overtime or radiomics have provided significant insights on key pathogenic processes that could help defining new subgroups beyond the diffuse/limited subsets.

SUMMARY

We can anticipate that a future classification of SSc patients will integrate innovative approaches encompassing clinical phenotypes, variables trajectories, serological features and innovative omics molecular signatures. It nevertheless seems crucial to also pursue the implementation and standardization of readily available and easy to use tools that can be used in clinical practice.

Toward Understanding of Environmental Risk Factors in Systemic Sclerosis

IMPORTANCE

Systemic sclerosis (SSc) is a severe, chronic, and incurable autoimmune fibrotic skin disease with significant extracutaneous involvement. Low concordance rate in twin studies and unequal geographic distribution of SSc argues for importance of environment in disease initiation and progression.

OBJECTIVE

In this manuscript we provide a summary of all investigated potential external risk factors for SSc.

DATA SOURCES

A literature search in PubMed and EMBASE database was performed for studies published until January 1, 2020 by 2 reviewers (EN and LO) independently.

FINDINGS

Occupational and/or environmental exposures to silica and organic solvents are associated with increased incidence and severity of SSc. Exposure to epoxy resins, asbestos, and particulate air pollution favors increased risk of SSc, but data are based on limited number of observational studies. There is insufficient evidence to conclude an association between SSc development and other occupational (eg, welding fumes) or personal exposures (eg, smoking, vitamin D deficiency). Association of SSc with silicone breast implants has been disproven. Infectious pathogens (eg, Helicobacter pylori and angiotropic viruses) and dysbiosis seem to play a role in SSc development and severity, but their role remains to be clarified.

CONCLUSIONS AND RELEVANCE

It may be prudent to counsel our patients with SSc (or those at risk of SSc) to avoid occupations with exposure to silica, organic solvents, asbestos and epoxy resins; restraint from smoking, using cocaine or drugs with pro-fibrotic potential. While the association between low vitamin D and SSc remains to be confirmed, we believe that SSc patients should be encouraged to maintain healthy vitamin D levels as benefits outweigh the risks.

Omega-3 fatty acid intake suppresses induction of diverse autoantibody repertoire by crystalline silica in lupus-prone mice

Inhalation of crystalline silica (cSiO2) in the workplace is etiologically linked to lupus and other autoimmune diseases. Exposing lupus-prone NZBWF1 mice to respirable cSiO2 unleashes a vicious cycle of inflammation and cell death in the lung that triggers interferon-regulated gene expression, ectopic lymphoid structure (ELS) development, elevation of local and systemic autoantibodies (AAbs), and glomerulonephritis. However, cSiO2-induced inflammation and onset of autoimmunity can be prevented by inclusion of the ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) into the diet of these mice. Since cSiO2 both causes cell death and interferes with efferocytosis, secondary necrosis of residual cell corpses might provide a rich and varied autoantigen (AAg) source in the lung. While it is known that the particle induces anti-nuclear and anti-dsDNA AAbs in NZBWF1 mice, the full extent of the cSiO2-induced AAb response relative to specificity and isotype is not yet understood. The purpose of this study was to test the hypotheses that cSiO2 exposure induces a wide spectrum of AAbs in the pulmonary and systemic compartments, and that dietary DHA intervention prevents these changes. Archived tissue fluid samples were obtained from a prior study in which NZBWF1 mice were fed purified isocaloric diets containing no DHA (control) or DHA corresponding calorically to human doses of 2 and 5 g/day. Mice were intranasally instilled with 1 mg cSiO2 or saline vehicle weekly for 4 weeks, then groups euthanized 1, 5, 9, or 13 weeks post-instillation (PI) of the last cSiO2 dose. Bronchoalveolar lavage fluid (BALF) and plasma from each time point were subjected to AAb profiling using a microarray containing 122 AAgs. cSiO2 triggered robust IgG and IgM AAb responses against lupus-associated AAgs, including DNA, histones, ribonucleoprotein, Smith antigen, Ro/SSA, La/SSB, and complement as early as 1 week PI in BALF and 5 weeks PI in plasma, peaking at 9 and 13 weeks PI, respectively. Importantly, cSiO2 also induced AAbs to AAgs associated with rheumatoid arthritis (collagen II, fibrinogen IV, fibrinogen S, fibronectin, and vimentin), Sjögren's syndrome (α-fodrin), systemic sclerosis (topoisomerase I), vasculitis (MPO and PR3), myositis (Mi-2, TIF1-γ, MDA5), autoimmune hepatitis (LC-1), and celiac disease (TTG). cSiO2 elicited comparable but more modest IgA AAb responses in BALF and plasma. cSiO2-induced AAb production was strongly associated with time dependent inflammatory/autoimmune gene expression, ELS development, and glomerulonephritis. AAb responses were dose-dependently suppressed by DHA supplementation and negatively correlated with the ω-3 index, an erythrocyte biomarker of ω-3 content in tissue phospholipids. Taken together, these findings suggest that cSiO2 exposure elicits a diverse multi-isotype repertoire of AAbs, many of which have been reported in individuals with lupus and other autoimmune diseases. Furthermore, induction of this broad AAb spectrum could be impeded by increasing ω-3 tissue content via dietary DHA supplementation.

Occupational silica exposure in an Australian systemic sclerosis cohort

Objective

To determine the frequency of self-reported occupational exposure to silica in SSc patients enrolled in the Australian Scleroderma Cohort Study, and to compare the disease characteristics of the silica-exposed patients with those of the non-exposed patients.

Method

Data collected over a 12-year period from 1670 SSc patients were analysed. We compared the demographic and clinical characteristics of those who reported occupational silica exposure with those who did not. A subgroup analysis of male patients was performed, as well as a multivariable analysis of correlates of silica exposure.

Results

Overall, 126 (7.5%) of the cohort reported occupational silica exposure. These individuals were more likely to be male (73 of 231, i.e. 31.6% males exposed) and to have worked in mining and construction industries. Those who reported silica exposure were younger at the onset of SSc skin involvement [odds ratio (OR) 0.9, P = 0.02], of male gender (OR 14.9, P &lt; 0.001), have joint contractures (OR 1.8, P = 0.05) and have higher physical disability as defined by scleroderma HAQ (OR 1.4, P = 0.01).

Conclusion

The highest percentage of silica exposure was found in males. These patients were more likely to have the presence of certain clinical manifestations and Scl-70 antibody, which is known to confer a poor prognosis. These findings support the association between occupational silica exposure and the subsequent development of SSc. Further investigation is required to describe the range of clinical manifestations and disease course, including prognosis and treatment response, in those diagnosed with occupationally induced SSc compared with idiopathic SSc.

Mechanisms of Environment-Induced Autoimmunity

Although numerous environmental exposures have been suggested as triggers for preclinical autoimmunity, only a few have been confidently linked to autoimmune diseases. For disease-associated exposures, the lung is a common site where chronic exposure results in cellular toxicity, tissue damage, inflammation, and fibrosis. These features are exacerbated by exposures to particulate material, which hampers clearance and degradation, thus facilitating persistent inflammation. Coincident with exposure and resulting pathological processes is the posttranslational modification of self-antigens, which, in concert with the formation of tertiary lymphoid structures containing abundant B cells, is thought to promote the generation of autoantibodies that in some instances demonstrate major histocompatibility complex restriction. Under appropriate gene-environment interactions, these responses can have diagnostic specificity. Greater insight into the molecular and cellular requirements governing this process, especially those that distinguish preclinical autoimmunity from clinical autoimmunedisease, may facilitate determination of the significance of environmental exposures in human autoimmune disease.

Was Paul Klee's scleroderma an occupational disease? A series of historical and clinical vignettes, part III

Paul Klee (1879-1940), one of the most influential artists of the 20th century, died at 60 years of age from complications of systemic sclerosis (scleroderma). The precipitating event(s) of Klee's scleroderma, as in most cases, will never be known. Among various potential factors, exposure to heavy metals, crystalline silica, and organic solvents-acting alone or in combination-can now be considered potential factors in the onset of Klee's disease. By altering and modulating epigenetic determinants in a genetically susceptible host, these and other environmental factors may have led to perturbations of self-tolerance and inflammation culminating in Klee's scleroderma.

Crystalline Silica Impairs Efferocytosis Abilities of Human and Mouse Macrophages: Implication for Silica-Associated Systemic Sclerosis

Inhalation of crystalline silica (SiO2) is a risk factor of systemic autoimmune diseases such as systemic sclerosis (SSc) and fibrotic pulmonary disorders such as silicosis. A defect of apoptotic cell clearance (i.e., efferocytosis, a key process in the resolution of inflammation) is reported in macrophages from patients with fibrotic or autoimmune diseases. However, the precise links between SiO2 exposure and efferocytosis impairment remain to be determined. Answering to this question may help to better link innate immunity and fibrosis. In this study, we first aim to determine whether SiO2 might alter efferocytosis capacities of human and mouse macrophages. We secondly explore possible mechanisms explaining efferocytosis impairment, with a specific focus on macrophage polarization and on the RhoA/ROCK pathway, a key regulator of cytoskeleton remodeling and phagocytosis. Human monocyte-derived macrophages (MDM) and C57BL/6J mice exposed to SiO2 and to CFSE-positive apoptotic Jurkat cells were analyzed by flow cytometry to determine their efferocytosis index (EI). The effects of ROCK inhibitors (Y27632 and Fasudil) on EI of SiO2-exposed MDM and MDM from SSc patients were evaluated in vitro. Our results demonstrated that SiO2 significantly decreased EI of human MDM in vitro and mouse alveolar macrophages in vivo. In human MDM, this SiO2-associated impairment of efferocytosis, required the expression of the membrane receptor SR-B1 and was associated with a decreased expression of M2 polarization markers (CD206, CD204, and CD163). F-actin staining, RhoA activation and impairment of efferocytosis, all induced by SiO2, were reversed by ROCK inhibitors. Moreover, the EI of MDM from SSc patients was similar to the EI of in vitro- SiO2-exposed MDM and Y27632 significantly increased SSc MDM efferocytosis capacities, suggesting a likewise activation of the RhoA/ROCK pathway in SSc. Altogether, our results demonstrate that SiO2 exposure may contribute to the impairment of efferocytosis capacities of mouse and human macrophages but also of MDM in SiO2-associated autoimmune diseases and fibrotic disorders such as SSc; in this context, the silica/RhoA/ROCK pathway may constitute a relevant therapeutic target.

Epigenetic Control of Scleroderma: Current Knowledge and Future Perspectives

PURPOSE OF REVIEW

Epigenetics has been implicated in the pathogenesis of systemic sclerosis (SSc). In this review, the involvement of the three epigenetic mechanisms in SSc development and progression-DNA methylation, histone modifications, and non-coding RNAs-will be discussed.

RECENT FINDINGS

Alteration in epigenetics was observed in immune cells, dermal fibroblasts, and endothelial cells derived from SSc patients. Genes that are affected include those involved in immune cell function and differentiation, TGFβ and Wnt pathways, extracellular matrix accumulation, transcription factors, and angiogenesis. All the studies remain in the pre-clinical stage. Extensive research provides evidence that epigenetic alterations are critical for SSc pathogenesis. Future epigenomic studies will undoubtedly continue to broaden our understanding of disease pathogenesis and clinical heterogeneity. They will also provide the scientific basis for repurposing epigenetic-modifying agents for SSc patients.

KIR/HLA Gene Profile Implication in Systemic Sclerosis Patients from Mexico

Introduction

Systemic Sclerosis (SSc) is an autoimmune, inflammatory, and multisystemic disease characterized by the presence of autoantibodies and fibrosis. The pathogenesis involves the interaction between immune system cells such as macrophages, NK cells, T cells, and B cells. Killer-cell Immunoglobulin-like Receptors (KIR) are expressed in NK cells and some T cell subsets that recognize HLA class I molecules as ligands and are involved in regulating the activation and inhibition of these cells. The KIR family consists of 14 genes and two pseudogenes; according to the gene content, the genotype could be AA and Bx. The aim of this study was to evaluate the association between KIR/HLA genes and genotypes with SSc and the clinical characteristics.

Methods

We included 50 SSc patients and 90 Control Subjects (CS). Genotyping of KIR, HLA-C, -Bw4, and -A^∗03/^∗11 was made by SSP-PCR.

Results

In SSc patients, a higher frequency of KIR2DL2 (p = 0.0007, p′ = 0.011), KIR2DS4del (p = 0.001, p′ = 0.021), and HLA-C2 (p = 0.02, p′ = 0.09) was found. This is the first study to evaluate the frequency of HLA-A^∗03/^∗11 in SSc patients, of which a low frequency was found in both groups. Compound genotypes KIR2DL2+/HLA-C1+ or KIR2DL2+/HLA-C2+ have a higher frequency in SSc patients. The Bx genotype was the most frequent and was associated with risk to SSc (p = 0.007, OR = 3.1, 95% CI = 1.4–7.9, p′ = 0.014). The genotypes with a higher iKIR number than aKIR (iKIR > aKIR) were found in all individuals; genotypes with 7-8 iKIR genes were increased in SSc patients. We do not find an association between the KIR genes with the clinical characteristics.

Conclusion

The results suggest that KIR2DL2 and 2DS4del could have a risk role in the development of SSc, but not with clinical manifestations.

Treatment adherence in systemic sclerosis: A cross-sectional study

BACKGROUND

Treatment adherence is an important medical and pharmaco-economical phenomenon, influenced by multiple variables. Treatment adherence in systemic sclerosis (SSc) has been poorly studied.

OBJECTIVE

The aim of the present study was to assess treatment adherence in SSc patients and to identify factors associated with good and poor adherence.

METHODS

We conducted a monocentric, cross-sectional, observational study. Treatment adherence was evaluated by the Compliance Questionnaire of Rheumatology (CQR). The necessity of treatment and concerns about treatment were investigated using the Beliefs about Medicines Questionnaire-Specific (BMQ-S). The Illness Perception Questionnaire-Revised (IPQ-R) assessed illness perceptions. Disease-related characteristics were collected retrospectively.

RESULTS

A total of 66 patients were enrolled in this study. Of these, 47 (71.2%) had a weighted CQR score of ≤80% ("poor adherence") and 19 (28.8%) had a weighted CQR score of >80% ("good adherence"). No significant relationship between demographic, clinical or psychological factors and overall adherence could be found, except with the IPQ subscale "timeline acute/chronic" (p = 0.042). Our patient population estimated the necessity of their medication high (mean necessity score 20.5), with moderate concern beliefs (mean concern score 15.1). Subjective adherence, as self-reported by patients, was high.

CONCLUSIONS

This study demonstrated low treatment adherence rates in SSc patients. We could not identify demographic, clinical or psychological factors associated with treatment adherence, except with the IPQ subscale "timeline acute/chronic". This suggests a correlation between poor adherence and the belief that the disease will be chronic without improvement over time. Symptom relief was an important motivating factor for taking medication. The treatment necessity was scored higher than treatment concerns, but the necessity beliefs were not associated with adherence.