Prevalence of rheumatoid arthritis in relation to serum cadmium concentrations: cross-sectional study using Korean National Health and Nutrition Examination Survey (KNHANES) data

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.

Maternal seafood intake, dietary contaminant exposure, and risk of juvenile idiopathic arthritis: exploring gene-environment interactions

Objectives

Juvenile idiopathic arthritis (JIA) originates from a complex interplay between genetic and environmental factors. We investigated the association between seafood intake and dietary contaminant exposure during pregnancy and JIA risk, to identify sex differences and gene-environment interactions.

Methods

We used the Norwegian Mother, Father, and Child Cohort Study (MoBa), a population-based prospective pregnancy cohort (1999-2008). JIA patients were identified through the Norwegian Patient Registry, with remaining mother-child pairs serving as controls. We assessed maternal seafood intake and dietary contaminants typically found in seafood using a food frequency questionnaire completed during pregnancy, mainly comparing high (≥90th percentile, P90) vs low (

Results

We identified 217 JIA patients and 71,884 controls. High vs low maternal intake of lean/semi-oily fish was associated with JIA (aOR 1.51, 95% CI 1.02-2.22), especially among boys (aOR 2.13, 95% CI 1.21-3.75). A significant gene-environment interaction was observed between total fish intake and PRS, with high fish intake associated with JIA primarily in those with low PRS (p<0.03). We found no associations between high vs low exposure to other types of seafood or environmental contaminants and JIA.

Conclusions

We found a modestly increased risk of JIA associated with high intake of lean/semi-oily fish during pregnancy, not explained by estimated exposure to dietary contaminants. Our data suggest a more pronounced association in children with a lower genetic predisposition for JIA.

Collapse

Key Words

• MoBa
• contaminants
• fish
• gene-environment interaction
• heavy metals
• juvenile idiopathic arthritis (JIA)
• polygenic risk score
• sex differences

Collapse

MESH Headings

• Humans
• Seafood/adverse effects
• Female
• Arthritis, Juvenile/genetics
• Arthritis, Juvenile/epidemiology
• Arthritis, Juvenile/etiology
• Gene-Environment Interaction
• Male
• Pregnancy
• Adult
• Norway/epidemiology
• Prenatal Exposure Delayed Effects/genetics
• Prenatal Exposure Delayed Effects/epidemiology
• Risk Factors
• Prospective Studies
• Child
• Maternal Exposure/adverse effects
• Food Contamination
• Dietary Exposure/adverse effects

Collapse

Grants Collapse

Affiliation(s)

Vilde Øverlien Dåstøl Department of Rheumatology, Oslo University Hospital, Oslo, Norway Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
Kristine Løkås Haftorn Department of Rheumatology, Oslo University Hospital, Oslo, Norway
Hamid Khoshfekr Rudsari Department of Rheumatology, Oslo University Hospital, Oslo, Norway
Piotr Pawel Jaholkowski Center for Precision Psychiatry, Division of Mental Health and Addiction, Oslo University Hospital, and Institute of Clinical Medicine, University of Oslo, Oslo, Norway KG Jebsen Centre for Neurodevelopmental Disorders, University of Oslo and Oslo University Hospital, Oslo, Norway
Ketil Størdal Department of Pediatric Research, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway Department of Pediatric and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
Siri Eldevik Håberg Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway
Clarice R Weinberg Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC, United States
Lisa G Rider Environmental Autoimmunity Group, Clinical Research Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Bethesda, MD, United States
Ole A Andreassen Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway KG Jebsen Centre for Neurodevelopmental Disorders, University of Oslo and Oslo University Hospital, Oslo, Norway Center for Precision Psychiatry, Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
Anne Lise Brantsæter Department of Food Safety and Centre for Sustainable Diets, Norwegian Institute of Public Health, Oslo, Norway
Ida Henriette Caspersen Department of Rheumatology, Oslo University Hospital, Oslo, Norway Centre for Fertility and Health, Norwegian Institute of Public Health, Oslo, Norway
Helga Sanner Department of Rheumatology, Oslo University Hospital, Oslo, Norway Oslo New University College, Oslo, Norway

Collapse

Environmental pollution impact on the severity of some rheumatic diseases: a comparative analytical study on inflammatory and non-inflammatory samples

OBJECTIVE

Environmental pollution of heavy metals is increasingly a problem and has become of great concern due to the adverse effects it causes worldwide. Heavy metal exposure has been implicated in health problems, including fibromyalgia and rheumatoid arthritis. We aim to evaluate the rule of chronic heavy metals toxicity on the induction of vitamin D3 (VD) deficiency and parathyroid hormone (PTH) disturbances in an inflammatory disease like rheumatoid arthritis (RA) and non-inflammatory disease like fibromyalgia syndrome (FMS).

METHODS

This comparative analytical study was conducted on sixty adults (age ≥ 18 years). Participants were divided into three groups. Group I: twenty patients diagnosed with RA according to the specific ACR/EULAR criteria for RA. Group II: twenty patients diagnosed with FMS according to the specific 2010 (ACR) criteria for FMS. Group III: twenty healthy adults. All patients and controls were subjected to routine laboratory tests as well as the measurement of PTH, VD and estimation of serum levels of lead, cadmium, and chromium.

RESULTS

VD was significantly inversely correlated to PTH, lead, cadmium, chromium, and activity scores in the RA and FMS groups. Lead, Cadmium and Chromium had a significant independent risk on the VD level in RA patients, while lead had a significant independent risk on the VD level in FMS patients.

CONCLUSION

Heavy metals may affect VD synthesis, leading to hypovitaminosis D and secondary hyperparathyroidism in RA and FMS patients. Heavy metals play a key role in the pathogenesis of RA, FMS, and their disease activity.

Analyzing the impact of heavy metal exposure on osteoarthritis and rheumatoid arthritis: an approach based on interpretable machine learning

Introduction

This investigation leverages advanced machine learning (ML) techniques to dissect the complex relationship between heavy metal exposure and its impacts on osteoarthritis (OA) and rheumatoid arthritis (RA). Utilizing a comprehensive dataset from the National Health and Nutrition Examination Survey (NHANES) spanning from 2003 to 2020, this study aims to elucidate the roles specific heavy metals play in the incidence and differentiation of OA and RA.

Methods

Employing a phased ML strategy that encompasses a range of methodologies, including LASSO regression and SHapley Additive exPlanations (SHAP), our analytical framework integrates demographic, laboratory, and questionnaire data. Thirteen distinct ML models were applied across seven methodologies to enhance the predictability and interpretability of clinical outcomes. Each phase of model development was meticulously designed to progressively refine the algorithm's performance.

Results

The results reveal significant associations between certain heavy metals and an increased risk of arthritis. The phased ML approach enabled the precise identification of key predictors and their contributions to disease outcomes.

Discussion

These findings offer new insights into potential pathways for early detection, prevention, and management strategies for arthritis associated with environmental exposures. By improving the interpretability of ML models, this research provides a potent tool for clinicians and researchers, facilitating a deeper understanding of the environmental determinants of arthritis.

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 of blood cadmium levels and all-cause mortality among adults with rheumatoid arthritis: The NHANES cohort study

BACKGROUND

The potential impact of environmental cadmium exposure on the prognosis of patients with rheumatoid arthritis (RA) remains unclear, despite its known association with various adverse health outcomes.

METHODS

In this study, a total of 1285 RA patients were included in the National Health and Nutrition Examination Survey (NHANES) conducted between 2003 and 2016. The Cox regression model was employed to investigate the relationship between blood cadmium levels and the risk of all-cause mortality in RA patients.

RESULTS

During a mean follow-up duration of 105.9 months, 341 patient deaths were recorded. After adjusting for multiple factors, elevated blood cadmium was strongly correlated with an increased risk of all-cause mortality in patients with RA. With one unit rise in natural logarithm-transformed blood cadmium concentrations, the risk of patient death increased by 107%. The adjusted hazard ratios for each quartile of blood cadmium demonstrated a significant upward trend (P < 0.001). A linear dose-response relationship of blood cadmium concentrations with all-cause mortality was also distinctive (P < 0.001). Consistent findings were ascertained when conducting stratified analyses by age, gender, race, education level, body mass index, smoking status, and drinking status.

CONCLUSIONS

Elevated blood cadmium levels may serve as a risk factor for increased death risk in RA patients.

Environmental pollutants and phosphoinositide signaling in autoimmunity

Environmental pollution stands as one of the most critical challenges affecting human health, with an estimated mortality rate linked to pollution-induced non-communicable diseases projected to range from 20% to 25%. These pollutants not only disrupt immune responses but can also trigger immunotoxicity. Phosphoinositide signaling, a pivotal regulator of immune responses, plays a central role in the development of autoimmune diseases and exhibits high sensitivity to environmental stressors. Among these stressors, environmental pollutants have become increasingly prevalent in our society, contributing to the initiation and exacerbation of autoimmune conditions. In this review, we summarize the intricate interplay between phosphoinositide signaling and autoimmune diseases within the context of environmental pollutants and contaminants. We provide an up-to-date overview of stress-induced phosphoinositide signaling, discuss 14 selected examples categorized into three groups of environmental pollutants and their connections to immune diseases, and shed light on the associated phosphoinositide signaling pathways. Through these discussions, this review advances our understanding of how phosphoinositide signaling influences the coordinated immune response to environmental stressors at a biological level. Furthermore, it offers valuable insights into potential research directions and therapeutic targets aimed at mitigating the impact of environmental pollutants on the pathogenesis of autoimmune diseases. SYNOPSIS: Phosphoinositide signaling at the intersection of environmental pollutants and autoimmunity provides novel insights for managing autoimmune diseases aggravated by pollutants.

Endocrine-disrupting chemicals and autoimmune diseases

Endocrine-disrupting chemicals (EDCs) widely exist in people's production and life which have great potential to damage human and animal health. Over the past few decades, growing attention has been paid to the impact of EDCs on human health, as well as immune system. So far, researchers have proved that EDCs (such as bisphenol A (BPA), phthalate, tetrachlorodibenzodioxin (TCDD), etc.) affect human immune function and promotes the occurrence and development of autoimmune diseases (ADs). Therefore, in order to better understand how EDCs affect ADs, we summarized the current knowledge about the impact of EDCs on ADs, and elaborated the potential mechanism of the impact of EDCs on ADs in this review.

The combined effect of heavy metals and polycyclic aromatic hydrocarbons on arthritis, especially osteoarthritis, in the U.S. adult population

The evaluation of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) impact on arthritis is usually limited to the analysis of the arthritis subtype (rheumatoid arthritis, RA), whereas studies on osteoarthritis (OA) are relatively sparse. Furthermore, the combined effect of HMs and PAHs co-exposure on arthritis also has rarely been analyzed. Herein, we aimed to comprehensively estimate the association between HMs and PAHs (three blood HMs and six urinary PAHs metabolites) co-exposure and arthritis. Using data from the National Health and Nutrition Examination Survey (NHANES), 2003-2016, we included 9735 adults, of whom 2464 had total arthritis, 1371 had OA, and 468 had RA. The logistic regression model was conducted to estimate the single effect of HMs and PAHs on arthritis. Moreover, weighted quantile sum (WQS) regression, quantile-based g computation (qgcomp), and Bayesian kernel machine regression (BKMR) were separately performed to assess the combined effect of HMs and PAHs co-exposure on arthritis. In the single-exposure analyses, cadmium (Cd) and lead (Pb) statistically grew the risk of total arthritis, OA, and RA. Among PAHs, 1-hydroxynaphthalene (1-NAP) and 3-hydroxyfluorene (3-FLU) showed a positive association with total arthritis, OA, and RA. Meanwhile, 2-NAP also was significantly associated with total arthritis. 2-NAP, 2-FLU, and 1-hydroxyphenanthrene (1-PHE) also were significantly associated with RA. Furthermore, the three complementary models consistently demonstrated that co-exposure to high levels of HMs and PAHs was positively associated with total arthritis, OA, and RA risk. The above associations were more obvious in young and medium-aged people. Interestingly, BKMR analyses indicated that 1-NAP might interact with Cd and 3-FLU in total arthritis, while Pb might interact with Cd in OA. Therefore, this study provided novel evidence that co-exposure to HMs and PAHs positively correlated with arthritis, especially OA, and these results were worthy of further prospective studies.

Evaluation of some trace elements and antioxidants in sera of patients with rheumatoid arthritis: a case-control study

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease that destroys joints. The concentrations of elements (Zn, Cu, Mg, Mn, Fe, Ni, Cr, K, Na, Ca, Pb, and Cd), as well as antioxidant glutathione GSH and lipid peroxidation marker malondialdehyde MDA, will be determined in this study.

METHOD

The study involves 120 female RA patients and 60 healthy females in the control group, all of whom are between the ages of 20 and 60. Patients having diabetes, hypertension, hyperthyroidism, or psoriasis, in addition to RA, were excluded.

RESULTS

When RA patients were compared to healthy individuals, the levels of Cu, Ni, Na, Pb, and Cd were significantly higher (p < 0.01), whereas the levels of Zn, Mg, Mn, Cr, Ca, K, and Fe were significantly lower (p < 0.01). The Cu/Zn (2.21 and 1.16) and Na/k (38.67 and 34.87) ratios were also found to be significantly higher in RA patients compared to controls. Furthermore, the data indicated that GSH concentrations in RA patients were significantly lower (p < 0.01) than those in controls (655.90 and 1345.17 mol/l, respectively). MDA levels in RA patients were significantly higher (p < 0.01) than those in controls (2.739 and 1.673 mol/l, respectively).

CONCLUSIONS

The data indicate that Cu/Zn and Na/k ratios can be of great value in the diagnosis and evaluation of RA patients. On this basis, we conclude that these elements can be relied upon to provide indications of RA risk and the measurement of oxidative stress can serve as a biomarker to monitor disease activity and severity in RA patients. Key Points • Trace elements may be of value and may have an expected significance in the early diagnosis, prognosis, and treatment evaluation of rheumatoid arthritis. • The distortion in the levels of trace elements may reflect their possible role in the pathogenesis of rheumatoid arthritis. • Oxidative stress can act as a biomarker to monitor disease activity and severity in patients with rheumatoid arthritis. • The trace elements can contribute to the manifestation of inflammatory diseases due to their role in the synthesis of some antioxidants or due to their effect on the immune system.

Impact of Cadmium Mediated by Tobacco Use in Musculoskeletal Diseases

Tobacco use has a negative impact on health due to its relationship with the development of high-mortality diseases, such as pulmonary cancer. However, the effect of cadmium (Cd), present in tobacco smoke, on the development of joint diseases has been scarcely studied. The objective of this review is to discuss the evidence regarding the mechanisms by which Cd exposure, through tobacco smoke, may lead to the development of osteoarthritis (OA), osteoporosis (OP), and rheumatoid arthritis (RA). There's evidence suggesting a string association between moderate to severe OA development and tobacco use, and that a higher blood concentration of Cd can trigger oxidative stress (OS) and inflammation, favoring cartilage loss. At the bone level, the Cd that is inhaled through tobacco smoke affects bone mineral density, resulting in OP mediated by a decrease in the antioxidant enzymes, which favors the bone resorption process. In RA, tobacco use promotes the citrullination process through Cd exposure and increases OS and inflammation. Understanding how tobacco use can increase the damage at the articular level mediated by a toxic metal, i.e., Cd, is important. Finally, we propose prevention, control, and treatment strategies for frequently disabling diseases, such as OA, OP, and RA to reduce its prevalence in the population.

Cadmium Body Burden and Inflammatory Arthritis: A Pilot Study in Patients from Lower Silesia, Poland

The purpose of this study was to determine the relationship between cadmium exposure and the likelihood of developing or exacerbating symptoms of inflammatory arthritis (IA). The study included 51 IA patients and 46 control subjects. Demographic and lifestyle data were collected. Haematological and biochemical parameters and blood cadmium levels (Cd-B) were determined. Cd-B correlated positively with age, smoking, living in a high-traffic area, and serum levels of inflammatory markers and negatively with mean corpuscular haemoglobin concentration (MCHC). The binary logistic regression model implied that high Cd-B (≥0.65 μg/L) is linked with an increased risk of IA in the studied population (odds ratio: 4.4). High levels of DNA oxidative damage marker (8-hydroxy-2'-deoxyguanosine) (≥7.66 ng/mL) and cyclooxygenase-2 (≥22.9 ng/mL) and frequent consumption of offal was also associated with increased risk of IA. High Cd-B was related to increased risk of disease symptoms onset in the group of IA patients, decreased the level of interleukin 10, and positively correlated with the disease activity. Increased Cd-B is associated with intensified inflammatory processes and decreased haemoglobin levels; in IA patients with decreased anti-inflammatory interleukin 10. These changes partly explain why cadmium exposure and a high cadmium body burden may raise the risk of IA and of disease symptoms exacerbation.

Highlights of Strategies Targeting Fibroblasts for Novel Therapies for Rheumatoid Arthritis

Synovial fibroblasts of rheumatoid arthritis (RA) play a critical role in perpetuation of chronic inflammation by interaction with immune and inflammatory cells and in cartilage and bone invasion, but current therapies for RA are not directly targeted fibroblasts. Selectively fibroblast targeted therapy has been hampered because of lack of fibroblast specific molecular signature. Recent advancement in technology enabled us to gain insightful information concerning RA synovial fibroblast subpopulations and functions. Exploring fibroblast targeted therapies have been focused on inducing cell death via fibroblast associated proteins; interrupting fibroblast binding to matrix protein; blocking intercellular signaling between fibroblasts and endothelial cells; inhibiting fibroblast proliferation and invasion; promoting cell apoptosis and inducing cellular senescence, and modulating fibroblast glucose metabolism. Translation into clinical studies of these fibroblast targeted strategies is required for evaluation for their clinical application, in particular for combination therapy with current immune component targeted therapies. Here, several strategies of fibroblast targeted therapy are highlighted.

Associations of blood and urinary heavy metals with rheumatoid arthritis risk among adults in NHANES, 1999-2018

Heavy metals exposure has been widely recognized as a risk factor for human health. However, limited information is available about the impacts of heavy metals on rheumatoid arthritis (RA). Herein, we estimated the associations of 3 blood and 11 urinary metals with the risk of RA among 49830 U.S. adults from the National Health and Nutrition Examination Survey (NHANES), 1999-2018. In the single-exposure model, blood cadmium (Cd) and lead (Pb), urinary Cd, Pb, antimony (Sb), tungsten (Tu), and uranium (Ur) were identified to be positively associated with RA risk. Furthermore, weighted quantile sum (WQS) regression, quantile-based g computation (qgcomp), and Bayesian kernel machine regression (BKMR) analyses consistently showed that both blood and urinary metals-mixed exposure were positively correlated with the risk of RA, and highlighted that Cd and Pb were responsible for the outcomes. Such associations were more evident in the young and middle-aged population. These findings indicated that exposure to heavy metals increased RA risk, and advanced the identification of risk factors for RA.

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.

In Utero and Early Life Exposure to the Great Chinese Famine and Risk of Rheumatoid Arthritis in Adulthood

OBJECTIVE

To investigate whether early life exposure to the Great Chinese Famine of 1959-1961 is associated with the risk of RA development in adulthood.

METHODS

This study included 101,510 participants who were enrolled in the Kailuan Study in 2006. RA cases were confirmed by medical record review. Logistic regression was used to calculate the odds ratio (OR) and 95% confidence interval (95% CI) for RA according to famine exposure status (exposed in utero or between ages 0 and 3 years, between ages 3 and 6 years, or at age 6 years or older), in comparison to participants born after 1961 who were not exposed to famine.

RESULTS

During 12 years of follow-up (2006-2018), we identified 187 RA cases. Individuals exposed to famine in utero or between ages 0 and 3 years had a higher prevalence of RA relative to other groups (0.2-0.35% versus 0.08-0.20%). After adjustment for potential confounders, the OR for RA was 2.95 (95% CI 1.55-5.59) for individuals exposed in utero, 4.53 (95% CI 2.72-7.54) for those exposed between ages 0 and 3 years, 2.55 (95% CI 1.43-4.57) for those exposed between ages 3 and 6 years, and 2.72 (95% CI 1.70-4.36) for those exposed at age 6 years or older versus individuals born after 1961. Similar associations with the risk of RA were observed for men and women when subjects were stratified by sex (P for interaction = 0.89).

CONCLUSION

Individuals exposed to famine in utero or in early childhood (between ages 0 and 3 years) were more likely to develop RA in adulthood, highlighting the importance of early life as a vulnerable developmental period.

Zinc and Cadmium in the Aetiology and Pathogenesis of Osteoarthritis and Rheumatoid Arthritis

Osteoarthritis (OA) and rheumatoid arthritis (RA) are inflammatory articular conditions with different aetiology, but both result in joint damage. The nutritionally essential metal zinc (Zn²⁺) and the non-essential metal cadmium (Cd²⁺) have roles in these arthritic diseases as effectors of the immune system, inflammation, and metabolism. Despite both metal ions being redox-inert in biology, they affect the redox balance. It has been known for decades that zinc decreases in the blood of RA patients. It is largely unknown, however, whether this change is only a manifestation of an acute phase response in inflammation or relates to altered availability of zinc in tissues and consequently requires changes of zinc in the diet. As a cofactor in over 3000 human proteins and as a signaling ion, zinc affects many pathways relevant for arthritic disease. How it affects the diseases is not just a question of zinc status, but also an issue of mutations in the many proteins that maintain cellular zinc homoeostasis, such as zinc transporters of the ZIP (Zrt-/Irt-like protein) and ZnT families and metallothioneins, and the multiple pathways that change the expression of these proteins. Cadmium interferes with zinc's functions and there is increased uptake under zinc deficiency. Remarkably, cadmium exposure through inhalation is now recognized in the activation of macrophages to a pro-inflammatory state and suggested as a trigger of a specific form of nodular RA. Here, we discuss how these metal ions participate in the genetic, metabolic, and environmental factors that lead to joint destruction. We conclude that both metal ions should be monitored routinely in arthritic disease and that there is untapped potential for prognosis and treatment.

Effect of cadmium on the viability on monolayer cultures of synoviocytes, chondrocytes, and Hoffa: A preliminary study

Osteoarthritis (OA) is the gradual loss of articular cartilage and involves several tissues, such as the synovial membrane, meniscus, ligaments, and adipose tissue known as Hoffa fat pad. There are largely unexplored factors that lead to OA development, such as the impact of exposure to heavy metals like cadmium (Cd) on the viability of cells in the knee joint tissue. The objective of this report was to identify the cell type with the highest susceptibility to Cd toxicity with respect to cell viability and death. Our findings showed that a concentration as low as 3 μM cadmium chloride for 12 h affects the viability of synovial cells, and a concentration of 10 μM affects Hoffa cells. Our results suggest that Cd can affect the viability of synovial and chondral cells primarily. In contrast, Hoffa cells were less susceptible, likely because Cd favors the production of pro-inflammatory cytokines before triggering their death as part of its damage mechanism at the articular level.

Exposure to ambient air pollution and autoantibody status in rheumatoid arthritis

OBJECTIVE

To evaluate the relationship between air pollutant (AP) exposure and rheumatoid arthritis (RA) autoantibody status METHODS: We performed a cross sectional study utilizing enrollment data from participants in the Veterans Affairs rheumatoid arthritis registry. HLA-DRB1 shared epitope (SE), smoking, rheumatoid factor (RF), and anti-cyclic citrullinated peptide antibody (ACPA) status were collected. Mean exposure levels were obtained for AP (NO₂, SO₂, particulate matter [PM_2.5, PM₁₀], and ozone) from air quality monitoring stations at patients' residential zip codes in the year prior to enrollment. Multivariable logistic and ordinary least squares regression models were used to determine independent associations of AP with RA seropositivity and autoantibody concentration.

RESULTS

The cohort included 557 veterans (90% male, 76% Caucasian), with mean age of 70 years and mean disease duration of 13 years. The majority were HLA-DRB1 SE, RF, and ACPA positive (73%, 79%, and 76%, respectively). In univariate models, PM_2.5 exposure was associated with higher ACPA concentration (p = 0.009). Similarly, in multivariable regression models, PM_2.5 exposure was independently associated with higher ACPA concentration (p = 0.037). Current smoking independently predicted RF and ACPA positivity and titers, while HLA-DRB1 SE alleles were associated with RF positivity and ACPA positivity and titers.

CONCLUSIONS

In an elderly cohort of RA patients, fine particulate matter (PM_2.5) exposure independently predicted higher ACPA concentration. Further study of fine particulate matter in the pathogenesis of RA is warranted. Key Points • A study that integrates both genetic and environmental exposure data, relative to RA autoantibody status. • Of different air pollutants measures, exposure to fine particulate matter (PM_2.5) appears to be most closely linked to ACPA titers.

Mercury Is Taken Up Selectively by Cells Involved in Joint, Bone, and Connective Tissue Disorders

Background: The causes of most arthropathies, osteoarthritis, and connective tissue disorders remain unknown, but exposure to toxic metals could play a part in their pathogenesis. Human exposure to mercury is common, so to determine whether mercury could be affecting joints, bones, and connective tissues we used a histochemical method to determine the cellular uptake of mercury in mice. Whole neonatal mice were examined since this allowed histological assessment of mercury in joint, bone, and connective tissue cells. Materials and Methods: Pregnant mice were exposed to a non-toxic dose of 0.5 mg/m3 of mercury vapor for 4 h a day on gestational days 14-18. Neonates were sacrificed at postnatal day 1, fixed in formalin, and transverse blocks of the body were processed for paraffin embedding. Seven micrometer sections were stained for inorganic mercury using silver nitrate autometallography, either alone or combined with CD44 immunostaining to detect progenitor cells. Control neonates were not exposed to mercury during gestation. Results: Uptake of mercury was marked in synovial cells, articular chondrocytes, and periosteal and tracheal cartilage cells. Mercury was seen in fibroblasts in the dermis, aorta, esophagus and striated muscle, some of which were CD44-positive progenitor cells, and in the endothelial cells of small blood vessels. Mercury was also present in renal tubules and liver periportal cells. Conclusions: Mercury is taken up selectively by cells that are predominantly affected in rheumatoid arthritis and osteoarthritis. In addition, fibroblasts in several organs often involved in multisystem connective tissue disorders take up mercury. Mercury provokes the autoimmune, inflammatory, genetic, and epigenetic changes that have been described in a range of arthropathies and bone and connective tissue disorders. These findings support the hypothesis that mercury exposure could trigger some of these disorders, particularly in people with a genetic susceptibility to autoimmunity.