Occupational silica and solvent exposures and risk of systemic lupus erythematosus in urban women

Environmental exposure to polycyclic aromatic hydrocarbons: An underestimated risk factor for systemic lupus erythematosus onset and progression

OBJECTIVE

To investigate the link between systemic lupus erythematosus (SLE) incidence and exposure to environmental polycyclic aromatic hydrocarbons (PAH).

METHODS

A case-control study (ChiCTR2000038187) involving 316 SLE patients and 851 healthy controls (HCs) was executed. Environmental exposure was assessed via a questionnaire, stratified by gender and age (females <35 and ≥35 years, males). Blood samples collected from 89 HCs, 85 inactive, and 95 active SLE patients were used to measure serum benzo[a]pyrene diol epoxide -albumin (BPDE-Alb) adducts and PAH concentrations, indicating long-term and short-term exposure respectively. Intergroup comparisons and statistical analyses were conducted using R version 4.3.1.

RESULTS

Diverse patterns were found in how environmental factors affect SLE onset across different demographics. Lifestyle exposure factors were found to be a stronger determinant of SLE onset than occupational exposure factors in women under 35. Indoor air pollution had a significant impact on SLE incidence, potentially comparable to outdoor air pollution. Lifestyle-related PAH exposure had a greater impact on SLE than occupational PAH exposure. PAH exposure levels progressively increase from HCs to inactive and active SLE patients. Active SLE patients show markedly higher BPDE-Alb levels than HCs.

CONCLUSIONS

Environmental PAH, particularly lifestyle-related, are significant, yet under-recognized, risk factors for SLE.

STATEMENT OF ENVIRONMENTAL IMPLICATION

We examined the relationship between exposure to environmental polycyclic aromatic hydrocarbons (PAH) and the incidence of systemic lupus erythematosus (SLE). PAH, prevalent in sources such as cigarette smoke, air pollution, and charred food, pose significant health hazards. This study is the first to investigate specific PAH exposure levels in SLE patients. We determined actual PAH exposure levels in both SLE patients and healthy individuals and indicated that long-term PAH exposure biomarker is more reliable for evaluating exposure in non-occupationally exposed groups like SLE, compared to short-term markers. These findings provide valuable insights for future research on similar non-occupationally exposed populations.

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.

Crystalline silica-induced pulmonary inflammation and autoimmunity in mature adult NZBW/f1 mice: age-related sensitivity and impact of omega-3 fatty acid intervention

OBJECTIVE

Occupational exposure to respirable crystalline silica (cSiO2) has been linked to lupus development. Previous studies in young lupus-prone mice revealed that intranasal cSiO2 exposure triggered autoimmunity, preventable with docosahexaenoic acid (DHA). This study explores cSiO2 and DHA effects in mature lupus-prone adult mice, more representative of cSiO2-exposed worker age.

METHODS

Female NZBWF1 mice (14-week old) were fed control (CON) or DHA-supplemented diets. After two weeks, mice were intranasally instilled saline (VEH) or 1 mg cSiO2 weekly for four weeks. Cohorts were then analyzed 1- and 5-weeks postinstillation for lung inflammation, cell counts, chemokines, histopathology, B- and T-cell infiltration, autoantibodies, and gene signatures, with results correlated to autoimmune glomerulonephritis onset.

RESULTS

VEH/CON mice showed no pathology. cSiO2/CON mice displayed significant ectopic lymphoid tissue formation in lungs at 1 week, increasing by 5 weeks. cSiO2/CON lungs exhibited elevated cellularity, chemokines, CD3+ T-cells, CD45R + B-cells, IgG + plasma cells, gene expression, IgG autoantibodies, and glomerular hypertrophy. DHA supplementation mitigated all these effects.

DISCUSSION

The mature adult NZBWF1 mouse used here represents a life-stage coincident with immunological tolerance breach and one that more appropriately represents the age (20-30 yr) of cSiO2-exposed workers. cSiO2-induced robust pulmonary inflammation, autoantibody responses, and glomerulonephritis in mature adult mice, surpassing effects observed previously in young adults. DHA at a human-equivalent dosage effectively countered cSiO2-induced inflammation/autoimmunity in mature mice, mirroring protective effects in young mice.

CONCLUSION

These results highlight life-stage significance in this preclinical lupus model and underscore omega-3 fatty acids' therapeutic potential against toxicant-triggered autoimmune responses.

Crystalline silica-induced proinflammatory eicosanoid storm in novel alveolar macrophage model quelled by docosahexaenoic acid supplementation

Introduction

Phagocytosis of inhaled crystalline silica (cSiO2) particles by tissue-resident alveolar macrophages (AMs) initiates generation of proinflammatory eicosanoids derived from the ω-6 polyunsaturated fatty acid (PUFA) arachidonic acid (ARA) that contribute to chronic inflammatory disease in the lung. While supplementation with the ω-3 PUFA docosahexaenoic acid (DHA) may influence injurious cSiO2-triggered oxylipin responses, in vitro investigation of this hypothesis in physiologically relevant AMs is challenging due to their short-lived nature and low recovery numbers from mouse lungs. To overcome these challenges, we employed fetal liver-derived alveolar-like macrophages (FLAMs), a self-renewing surrogate that is phenotypically representative of primary lung AMs, to discern how DHA influences cSiO2-induced eicosanoids.

Methods

We first compared how delivery of 25 µM DHA as ethanolic suspensions or as bovine serum albumin (BSA) complexes to C57BL/6 FLAMs impacts phospholipid fatty acid content. We subsequently treated FLAMs with 25 µM ethanolic DHA or ethanol vehicle (VEH) for 24 h, with or without LPS priming for 2 h, and with or without cSiO2 for 1.5 or 4 h and then measured oxylipin production by LC-MS lipidomics targeting for 156 oxylipins. Results were further related to concurrent proinflammatory cytokine production and cell death induction.

Results

DHA delivery as ethanolic suspensions or BSA complexes were similarly effective at increasing ω-3 PUFA content of phospholipids while decreasing the ω-6 PUFA arachidonic acid (ARA) and the ω-9 monounsaturated fatty acid oleic acid. cSiO2 time-dependently elicited myriad ARA-derived eicosanoids consisting of prostaglandins, leukotrienes, thromboxanes, and hydroxyeicosatetraenoic acids in unprimed and LPS-primed FLAMs. This cSiO2-induced eicosanoid storm was dramatically suppressed in DHA-supplemented FLAMs which instead produced potentially pro-resolving DHA-derived docosanoids. cSiO2 elicited marked IL-1α, IL-1β, and TNF-α release after 1.5 and 4 h of cSiO2 exposure in LPS-primed FLAMs which was significantly inhibited by DHA. DHA did not affect cSiO2-triggered death induction in unprimed FLAMs but modestly enhanced it in LPS-primed FLAMs.

Discussion

FLAMs are amenable to lipidome modulation by DHA which suppresses cSiO2-triggered production of ARA-derived eicosanoids and proinflammatory cytokines. FLAMs are a potential in vitro alternative to primary AMs for investigating interventions against early toxicant-triggered inflammation in the lung.

Histopathological, biochemical and molecular studies on a model of systemic autoimmune disease induced by sodium silicate in non-genetically prone rats

Sodium silicate (Na2SiO₃) is an inorganic silica salt used in many products. Few studies reported autoimmune diseases (AIDs) due to Na2SiO₃ exposure. This study investigates the role of Na2SiO₃ exposure by different routes and doses in AID development in rats. We assigned 40 female rats to four groups: G1 control group, G2 rats were subcutaneously injected with 5 mg Na2SiO₃ suspension, and G3 and G4 rats were orally administered 5 mg and 7 mg Na2SiO₃ suspension, respectively. Na2SiO₃ was administered weekly for 20 weeks. Serum anti-nuclear antibodies (ANA) detection, histopathology of kidney, brain, lung, liver, and heart, oxidative stress biomarkers (MDA and GSH) in tissues, Matrix metalloproteinase activity in serum, TNF-α, and Bcl-2 expression in tissues were performed. ANA was significantly increased in silicate groups, especially G2. Creatinine was significantly increased in silicate groups. Histopathology revealed vasculitis and fibrinoid degeneration of blood vessels, a picture of immune-mediated glomerulonephritis in the kidneys, and chronic interstitial pneumonia with medial hypertrophy of pulmonary blood vessels. The activity of gelatinases (MMP-2 and MMP-9) and collagenase (MMP-13), which play role in inflammation, remodeling, and immune complex degradation, were significantly increased in the silicate-exposed groups. Bcl-2 was significantly decreased, indicating apoptosis. Therefore, oral administration and subcutaneous injection of Na2SiO₃ induced immune-mediated glomerulonephritis with elevated ANA levels and overexpression of TNF-α in rats.

Risk prediction models for incident systemic lupus erythematosus among women in the Nurses' health study cohorts using genetics, family history, and lifestyle and environmental factors

OBJECTIVE

Systemic lupus erythematosus (SLE) is a severe multisystem autoimmune disease that predominantly affects women. Its etiology is complex and multifactorial, with several known genetic and environmental risk factors, but accurate risk prediction models are still lacking. We developed SLE risk prediction models, incorporating known genetic, lifestyle and environmental risk factors, and family history.

METHODS

We performed a nested case-control study within the Nurses' Health Study cohorts (NHS). NHS began in 1976 and enrolled 121,700 registered female nurses ages 30-55 from 11 U.S. states; NHSII began in 1989 and enrolled 116,430 registered female nurses ages 25-42 from 14 U.S. states. Participants were asked about lifestyle, reproductive and environmental exposures, as well as medical information, on biennial questionnaires. Incident SLE cases were self-reported and validated by medical record review (Updated 1997 American College of Rheumatology classification criteria). Those with banked blood samples for genotyping (∼25% of each cohort), were selected and matched by age (± 4 years) and race/ethnicity to women who had donated a blood sample but did not develop SLE. Lifestyle and reproductive variables, including smoking, alcohol use, body mass index, sleep, socioeconomic status, U.S. region, menarche age, oral contraceptive use, menopausal status/postmenopausal hormone use, and family history of SLE or rheumatoid arthritis (RA) were assessed through the questionnaire prior to SLE diagnosis questionnaire cycle (or matched index date). Genome-wide genotyping results were used to calculate a SLE weighted genetic risk score (wGRS) using 86 published single nucleotide polymorphisms (SNPs) and 10 classical HLA alleles associated with SLE. We compared four sequential multivariable logistic regression models of SLE risk prediction, each calculating the area under the receiver operating characteristic curve (AUC): 1) SLE wGRS, 2) SLE/RA family history, 3) lifestyle, environmental and reproductive factors and 4) combining model 1-3 factors. Models were internally validated using a bootstrapped estimate of optimism of the AUC. We also examined similar sequential models to predict anti-dsDNA positive SLE risk.

RESULTS

We identified and matched 138 women who developed incident SLE to 1136 women who did not. Models 1-4 yielded AUCs 0.63 (95%CI 0.58-0.68), 0.64 (95%CI 0.59-0.68), 0.71(95% CI 0.66-0.75), and 0.76 (95% CI 0.72-0.81). Model 4 based on genetics, family history and eight lifestyle and environmental factors had best discrimination, with an optimism-corrected AUC 0.75. AUCs for similar models predicting anti-dsDNA positive SLE risk, were 0.60, 0.63, 0.81 and 0.82, with optimism corrected AUC of 0.79 for model 4.

CONCLUSION

A final model including SLE weighted genetic risk score, family history and eight lifestyle and environmental SLE risk factors accurately classified future SLE risk with optimism corrected AUC of 0.75. To our knowledge, this is the first SLE prediction model based on known risk factors. It might be feasibly employed in at-risk populations as genetic data are increasingly available and the risk factors easily assessed. The NHS cohorts include few non-White women and mean age at incident SLE was early 50s, calling for further research in younger and more diverse cohorts.

Systemic Lupus Erythematosus Risk: The Role of Environmental Factors

Systemic lupus erythematosus (SLE) is a complex, chronic autoimmune disease. The etiology of SLE is multifactorial and includes potential environmental triggers, which may occur sequentially (the "multi-hit" hypothesis). This review focuses on SLE risk potentially associated with environmental factors including infections, the microbiome, diet, respirable exposures (eg, crystalline silica, smoking, air pollution), organic pollutants, heavy metals, and ultraviolet radiation.

Understanding the Concept of Pre-Clinical Autoimmunity: Prediction and Prevention of Systemic Lupus Erythematosus: Identifying Risk Factors and Developing Strategies Against Disease Development

There is growing evidence that preceding the diagnosis or classification of systemic lupus erythematosus (SLE), patients undergo a preclinical phase of disease where markers of inflammation and autoimmunity are already present. Not surprisingly then, even though SLE management has improved over the years, many patients will already have irreversible disease-related organ damage by time they have been diagnosed with SLE. By gaining a greater understanding of the pathogenesis of preclinical SLE, we can potentially identify patients earlier in the disease course who are at-risk of transitioning to full-blown SLE and implement preventative strategies. In this review, we discuss the current state of knowledge of SLE preclinical pathogenesis and propose a screening and preventative strategy that involves the use of promising biomarkers of early disease, modification of lifestyle and environmental risk factors, and initiation of preventative therapies, as examined in other autoimmune diseases such as rheumatoid arthritis and type 1 diabetes.

The role of environmental exposures and gene-environment interactions in the etiology of systemic lupus erythematous

Systemic lupus erythematosus (SLE) is a complex, chronic autoimmune disease, whose etiology includes both genetic and environmental factors. Individual genetic risk factors likely only account for about one-third of observed heritability among individuals with a family history of SLE. A large portion of the remaining risk may be attributable to environmental exposures and gene-environment interactions. This review focuses on SLE risk associated with environmental factors, ranging from chemical and physical environmental exposures to lifestyle behaviors, with the weight of evidence supporting positive associations between SLE and occupational exposure to crystalline silica, current smoking, and exogenous estrogens (e.g., oral contraceptives and postmenopausal hormones). Other risk factors may include lifestyle behaviors (e.g., dietary intake and sleep) and other exposures (e.g., ultraviolet [UV] radiation, air pollution, solvents, pesticides, vaccines and medications, and infections). Alcohol use may be associated with decreased SLE risk. We also describe the more limited body of knowledge on gene-environment interactions and SLE risk, including IL-10, ESR1, IL-33, ITGAM, and NAT2 and observed interactions with smoking, UV exposure, and alcohol. Understanding genetic and environmental risk factors for SLE, and how they may interact, can help to elucidate SLE pathogenesis and its clinical heterogeneity. Ultimately, this knowledge may facilitate the development of preventive interventions that address modifiable risk factors in susceptible individuals and vulnerable populations.

The Relationship between 9/11 Exposure, Systemic Autoimmune Disease, and Post-Traumatic Stress Disorder: A Mediational Analysis

The relationship between 9/11 exposure, systemic autoimmune disease (SAD) and mental health remains poorly understood. This report builds on a prior analysis of World Trade Center Health Registry data to determine whether 9/11 exposure is associated with higher risk of SAD, and if so, whether post-traumatic stress disorder (PTSD) is a mediating factor and whether the association varies by responder/community member status. The final analytic sample comprised 41,656 enrollees with 123 cases of SAD diagnosed post 9/11 through November 2017. SAD diagnosis was ascertained from survey responses and confirmed by medical record review or physician survey. Logistic regression models were constructed to determine the relationship between 9/11 exposure and PTSD and SAD. Causal mediation analysis was used to determine the mediational effect of PTSD. Each analysis was stratified by 9/11 responder/community member status. Rheumatoid arthritis (n = 75) was the most frequent SAD, followed by Sjögren’s syndrome (n = 23), systemic lupus erythematosus (n = 20), myositis (n = 9), mixed connective tissue disease (n = 7), and scleroderma (n = 4). In the pooled cohort, those with 9/11-related PTSD had 1.85 times the odds (95% CI: 1.21–2.78) of SAD. Among responders, those with dust cloud exposure had almost twice the odds of SAD, while among community members, those with 9/11-related PTSD had 2.5 times the odds of SAD (95% CI: 1.39, 4.39). PTSD was not a significant mediator. Although emerging evidence suggests 9/11 exposure may be associated with SAD, more research is needed, particularly using pooled data sources from other 9/11-exposed cohorts, to fully characterize this relationship.

Dietary Postbiotics Reduce Cytotoxicity and Inflammation Induced by Crystalline Silica in an In Vitro RAW 264.7 Macrophage Model

Crystalline silica (cSiO₂) particles are naturally existing environmental toxicants. Exposure to cSiO₂ could cause local or systemic inflammation and aggregate inflammation-associated diseases. Dietary postbiotics are reported to possess anti-inflammatory activities; however, their effects on cSiO₂-triggered inflammation are unknown. Here, we investigate the impact of postbiotics from Lacticaseibacillus rhamnosus (LGG), Limosilactobacillus reuteri (L.reu), and Bifidobacterium animalis subsp. lactis Bb12 (BB12) on cSiO₂-induced cytotoxicity and IL-1 cytokines in vitro using macrophages. The postbiotics used in this study were cell-free fractions of a probiotic growth medium collected at different time points. The in vitro model used was the wild-type murine macrophage RAW 264.7 cell line stably transfected with the inflammasome adapter protein, ASC. Our results indicate that all the postbiotics could reduce cSiO₂-induced cytotoxicity in the wild-type and ASC macrophages and the effects were OD-dependent. Following priming with a lipopolysaccharide, cSiO₂ treatment resulted in robust inflammasome activation in ASC, as reflected by the IL-1β release. These responses were minimal or absent in the wild-type RAW cells. All the postbiotics decreased the release of IL-1β from ASC; however, only LGG and BB12 reduced the IL-1β secretion from wild-type cells. Only the L.reu postbiotics reduced the IL-1α release from ASC. We conclude that the postbiotics from LGG, BB12, and L.reu can protect macrophages against cSiO₂-induced cytotoxicity and suppress IL-1β activation.

Centrality of Myeloid-Lineage Phagocytes in Particle-Triggered Inflammation and Autoimmunity

Exposure to exogenous particles found as airborne contaminants or endogenous particles that form by crystallization of certain nutrients can activate inflammatory pathways and potentially accelerate autoimmunity onset and progression in genetically predisposed individuals. The first line of innate immunological defense against particles are myeloid-lineage phagocytes, namely macrophages and neutrophils, which recognize/internalize the particles, release inflammatory mediators, undergo programmed/unprogrammed death, and recruit/activate other leukocytes to clear the particles and resolve inflammation. However, immunogenic cell death and release of damage-associated molecules, collectively referred to as "danger signals," coupled with failure to efficiently clear dead/dying cells, can elicit unresolved inflammation, accumulation of self-antigens, and adaptive leukocyte recruitment/activation. Collectively, these events can promote loss of immunological self-tolerance and onset/progression of autoimmunity. This review discusses critical molecular mechanisms by which exogenous particles (i.e., silica, asbestos, carbon nanotubes, titanium dioxide, aluminum-containing salts) and endogenous particles (i.e., monosodium urate, cholesterol crystals, calcium-containing salts) may promote unresolved inflammation and autoimmunity by inducing toxic responses in myeloid-lineage phagocytes with emphases on inflammasome activation and necrotic and programmed cell death pathways. A prototypical example is occupational exposure to respirable crystalline silica, which is etiologically linked to systemic lupus erythematosus (SLE) and other human autoimmune diseases. Importantly, airway instillation of SLE-prone mice with crystalline silica elicits severe pulmonary pathology involving accumulation of particle-laden alveolar macrophages, dying and dead cells, nuclear and cytoplasmic debris, and neutrophilic inflammation that drive cytokine, chemokine, and interferon-regulated gene expression. Silica-induced immunogenic cell death and danger signal release triggers accumulation of T and B cells, along with IgG-secreting plasma cells, indicative of ectopic lymphoid tissue neogenesis, and broad-spectrum autoantibody production in the lung. These events drive early autoimmunity onset and accelerate end-stage autoimmune glomerulonephritis. Intriguingly, dietary supplementation with ω-3 fatty acids have been demonstrated to be an intervention against silica-triggered murine autoimmunity. Taken together, further insight into how particles drive immunogenic cell death and danger signaling in myeloid-lineage phagocytes and how these responses are influenced by the genome will be essential for identification of novel interventions for preventing and treating inflammatory and autoimmune diseases associated with these agents.

Occupational exposure to respirable crystalline silica and risk of autoimmune rheumatic diseases: a nationwide cohort study

Background

Exposure to respirable crystalline silica is suggested to increase the risk of autoimmune rheumatic diseases. We examined the association between respirable crystalline silica exposure and systemic sclerosis, rheumatoid arthritis, systemic lupus erythematosus and small vessel vasculitis.

Methods

In a cohort study of the total Danish working population, we included 1 541 505 male and 1 470 769 female workers followed since entering the labour market 1979–2015. Each worker was annually assigned a level of respirable crystalline silica exposure estimated with a quantitative job exposure matrix. We identified cases of autoimmune rheumatic diseases in a national patient register and examined sex-specific exposure-response relations by cumulative exposure and other exposure metrics.

Results

We identified 4673 male and 12 268 female cases. Adjusted for age and calendar year, men exposed to high levels of respirable crystalline silica compared with non-exposed showed increased incidence rate ratio (IRR) for the four diseases combined of 1.53 [95% confidence interval (CI): 1.39–1.69], for systemic sclerosis of 1.62 (1.08–2.44) and rheumatoid arthritis of 1.57 (1.41–1.75). The overall risk increased with increasing cumulative exposure attained since entering the workforce [IRR: 1.07 (1.05–1.09) per 50 µg/m³-years]. Female workers were less exposed to respirable crystalline silica, but showed comparable risk patterns with overall increased risk with increasing cumulative exposure [IRR: 1.04 (0.99–1.10) per 50 µg/m³-years].

Conclusions

This study shows an exposure-dependent association between occupational exposure to respirable crystalline silica and autoimmune rheumatic diseases and thus suggests causal effects, most evident for systemic sclerosis and rheumatoid arthritis.

Systematic review and meta-analysis of epidemiological studies on the association of occupational exposure to free crystalline silica and systemic lupus erythematosus

Objectives

Some evidence suggests that exposure to free crystalline silica may contribute to the risk of developing SLE. A systematic search was carried out for all published epidemiological studies concerning this association. A meta-analysis was conducted on relevant studies.

Methods

We searched PubMed and EMBASE databases for original articles published from 1960 to November 2019 in any language. In addition, we also searched the reference lists of included studies manually for additional relevant articles. Finally, seven studies were included in the systematic review and six studies in the meta-analysis (four case–control and two cohort studies). The odds ratio and 95% CI were calculated using a random effect meta-analysis.

Results

The meta-analysis of the studies, applying a random effect model, yielded an overall odds ratio of 3.49 (95% CI, 1.24, 9.83), with I2 = 92.36% (pronounced heterogeneity). We also stratified the meta-analysis by study design; case–control studies: odds ratio 1.85 (95% CI, 0.96, 3.59) with I2 = 75.92%; and cohort studies (cases with silicosis): odds ratio 9.71 (95% CI, 1.13, 83.58) with I2 = 72.65%.

Conclusions

The obtained results support the hypothesis of a possible association between occupational exposure to free crystalline silica and SLE, in particular at higher exposure levels, known to induce silicosis. The studies that have investigated this association are still scarce and the heterogeneity between the studies remains high. New studies are deemed necessary to confirm the association.

Systemic Autoimmune Disease Among Adults Exposed to the September 11, 2001 Terrorist Attack

Objective

Autoimmune disease is an emerging condition among persons exposed to the September 11, 2001 attack on the World Trade Center (WTC). Components of the dust cloud resulting from the collapse of the WTC have been associated with development of a systemic autoimmune disease, as has posttraumatic stress disorder (PTSD). We undertook this study to determine whether dust exposure and PTSD were associated with an increased risk of systemic autoimmune disease in a 9/11‐exposed cohort.

Methods

Among 43,133 WTC Health Registry enrollees, 2,786 self‐reported having a post‐9/11 systemic autoimmune disease. We obtained informed consent to review medical records to validate systemic autoimmune disease diagnoses for 1,041 enrollees. Diagnoses of systemic autoimmune diseases were confirmed by classification criteria, rheumatologist diagnosis, or having been prescribed systemic autoimmune disease medication. Controls were enrollees who denied having an autoimmune disease diagnosis (n = 37,017). We used multivariable log‐binomial regression to examine the association between multiple 9/11 exposures and risk of post‐9/11 systemic autoimmune disease, stratifying by responders (rescue, recovery, and clean‐up workers) and community members (e.g., residents, area workers).

Results

We identified 118 persons with systemic autoimmune disease. Rheumatoid arthritis was most frequent (n = 71), followed by Sjӧgren's syndrome (n = 22), systemic lupus erythematosus (n = 20), myositis (n = 9), mixed connective tissue disease (n = 7), and scleroderma (n = 4). Among 9/11 responders, those with intense dust cloud exposure had almost twice the risk of systemic autoimmune disease (adjusted risk ratio 1.86 [95% confidence interval 1.02–3.40]). Community members with PTSD had a nearly 3‐fold increased risk of systemic autoimmune disease.

Conclusion

Intense dust cloud exposure among responders and PTSD among community members were associated with a statistically significant increased risk of new‐onset systemic autoimmune disease. Clinicians treating 9/11 survivors should be aware of the potential increased risk of systemic autoimmune disease in this population.

Contribution of mouse models in our understanding of lupus

Laboratory animal models are beneficial when they recapitulate all or just some of the clinical and immunological manifestations of the disease. Various animals such as cats, rats, dogs, hamsters, guinea pigs, rabbits, horses, minks, pigs, and primates have been described lupus-like phenotype. However, a mouse has remained the preferable animal for scientific investigations as a result of their reduced lifespan, easy reproduction, markedly low costs, public acceptance, ease of genetic management, and the probability to stay under standardized conditions. It is highly challenging to establish a mouse model with all features of lupus because of the difficulty and the heterogeneity of the clinical features in systemic lupus erythematous (SLE). Additionally, due to the multiple differences between the mouse and human immune system, the direct translation usually fails. Each mouse model has specific characteristics and shares many subsets of aspects with the disease observed in humans, which gives researchers a tool to select their particular needs. Over 50 years, many mice models have been developed and used to dissect the pathogenesis of lupus, also to test novel drugs and therapies. In general, mice models that contribute considerably in SLE understanding can be divided into four groups: Spontaneous models, induced models, genetically modified models, along with humanizing mouse models that are the link between the mouse and human immune system. In this updated review, we will present what has been learned from different lupus mice models and how these models have contributed to a better understanding of lupus pathogenesis and treatment.

A follow-up study of occupational styrene exposure and risk of autoimmune rheumatic diseases

Objectives

Increased risk has been suggested for autoimmune rheumatic diseases following solvent exposure. The evidence for specific solvents is limited, and little is known about exposure–response relations. Styrene is an aromatic, organic solvent and the objective of this study was to analyse the association between occupational styrene exposure and autoimmune rheumatic diseases in men and women.

Methods

We followed 72 212 styrene-exposed workers of the Danish reinforced plastics industry from 1979 to 2012. We modelled full work history of styrene exposure from employment history, survey data and historical styrene exposure measurements. We identified cases in the national patient registry and investigated gender-specific exposure–response relations by cumulative styrene exposure for different exposure time windows adjusting for age, calendar year and educational level.

Results

During 1 515 126 person-years of follow-up, we identified 718 cases of an autoimmune rheumatic disease, of which 73% were rheumatoid arthritis. When adjusting for potential confounders and comparing the highest with the lowest styrene exposure tertile, we observed a statistically non-significantly increased risk of systemic sclerosis among women (incidence rate ratio (IRR)=2.50; 95% CI 0.50 to 12.50) and men (IRR=1.86; 95 % CI 0.50 to 7.00), based on 9 and 22 cases, respectively. Results were inconsistent for the other autoimmune rheumatic diseases examined.

Conclusion

This study suggests an association between occupational styrene exposure and systemic sclerosis in men as well as in women but based on few cases. This is a new finding and has to be replicated before conclusions can be drawn.

The study of interactions between genome and exposome in the development of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic inflammatory autoimmune disease characterized by a broad spectrum of clinical and serological manifestations. This may reflect a complex and multifactorial etiology involving several identified genetic and environmental factors, though not explaining the full risk of SLE. Established SLE risk genotypes are either very rare or with modest effect sizes and twin studies indicate that other factors besides genetics must be operative in SLE etiology. The exposome comprises the cumulative environmental influences on an individual and associated biological responses through the lifespan. It has been demonstrated that exposure to silica, smoking and exogenous hormones candidate as environmental risk factors in SLE, while alcohol consumption seems to be protective. Very few studies have investigated potential gene-environment interactions to determine if some of the unexplained SLE risk is attributable hereto. Even less have focused on interactions between specific risk genotypes and environmental exposures relevant to SLE pathogenesis. Cohort and case-control studies may provide data to suggest such biological interactions and various statistical measures of interaction can indicate the magnitude of such. However, such studies do often have very large sample-size requirements and we suggest that the rarity of SLE to some extent can be compensated by increasing the ratio of controls. This review summarizes the current body of knowledge on gene-environment interactions in SLE. We argue for the prioritization of studies that comprise the increasing details available of the genome and exposome relevant to SLE as they have the potential to disclose new aspects of SLE pathogenesis including phenotype heterogeneity.

Pesticide exposure and risk of systemic lupus erythematosus in an urban population of predominantly African-American women

OBJECTIVE

Past studies have reported associations between pesticide exposure and the risk of systemic lupus erythematosus (SLE). Residential pesticide exposure has been less well studied than agricultural exposure. The purpose of this study was to assess SLE risk associated with residential pesticide exposure in an urban population of predominantly African-American women.

METHODS

Adult women with SLE were identified from six hospital databases and community screening in three neighborhoods in Boston, Massachusetts, USA. Controls were adult women volunteers from the same neighborhoods who were screened for the absence of connective tissue disease and anti-nuclear antibodies. Subjects were considered exposed to pesticides if they had ever had an exterminator for an ant, cockroach, or termite problem prior to SLE diagnosis or corresponding reference age in controls. Risks associated with pesticide exposure were analyzed using multivariable logistic regression models, adjusted for sociodemographic factors.

RESULTS

We identified 93 SLE subjects and 170 controls with similar baseline characteristics. Eighty-three per cent were African-American. Pesticide exposure was associated with SLE, after controlling for potential confounders (odds ratio 2.24, 95% confidence interval 1.28-3.93).

CONCLUSION

Residential exposure to pesticides in an urban population of predominantly African-American women was associated with increased SLE risk. Additional studies are needed to corroborate these findings.

Mouse models of lupus: what they tell us and what they don't

Lupus is a complex heterogeneous disease characterised by autoantibody production and immune complex deposition followed by damage to target tissues. Animal models of human diseases are an invaluable tool for defining pathogenic mechanisms and testing of novel therapeutic agents. There are perhaps more applicable murine models of lupus than any other human disease. There are spontaneous models of lupus, inducible models of lupus, transgenic-induced lupus, gene knockout induced lupus and humanised mouse models of lupus. These mouse models of lupus have contributed significantly to our knowledge of the pathogenesis of lupus and served as valuable preclinical models for proof of concept for new therapies. Despite their utility, mouse models of lupus have their distinct limitations. Although similar, mouse and human immune systems are different and thus one cannot assume a mechanism for disease in one is translatable to the other. Efficacy and toxicity of compounds can vary significantly between humans and mice, also limiting direct translation. Finally, the heterogeneous aspects of human lupus, both in clinical presentation, underlying pathogenesis and genetics, are not completely represented in current mouse models. Thus, proving a therapy or mechanism of disease in one mouse model is similar to proving a mechanism/therapy in a limited subset of human lupus. These limitations, however, do not marginalise the importance of animal models nor the significant contributions they have made to our understanding of lupus.

Understanding the role of environmental factors in the development of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem disease with a complex etiology. Its risk is higher among women, racial and ethnic minorities, and individuals with a family history of SLE or related autoimmune diseases. It is believed that genetic factors interact with environmental exposures throughout the lifespan to influence susceptibility to developing SLE. The strongest epidemiologic evidence exists for increased risk of SLE associated with exposure to crystalline silica, current cigarette smoking, use of oral contraceptives, and postmenopausal hormone replacement therapy, while there is an inverse association with alcohol use. Emerging research results suggest possible associations of SLE risk with exposure to solvents, residential and agricultural pesticides, heavy metals, and air pollution. Ultraviolet light, certain infections, and vaccinations have also been hypothesized to be related to SLE risk. Mechanisms linking environmental exposures and SLE include epigenetic modifications resulting from exposures, increased oxidative stress, systemic inflammation and inflammatory cytokine upregulation, and hormonal effects. Research needs to include new studies of environmental risk factors for SLE in general, with a focus on lifetime exposure assessment. In addition, studies in susceptible subgroups, such as family members, studies based on genetic risk profiles, and studies in individuals with evidence of pre-clinical autoimmunity based on the detection of specific auto-antibodies are also required. Understanding the role of environmental exposures in the development of SLE may help identify modifiable risk factors and potential etiological mechanisms.

Environmental triggers in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect almost any organ in the human body. Despite significant advancements in our understanding of SLE over the recent years, its exact mode of onset and disease progression remains elusive. Low concordance rates among monozygotic twins with SLE (as low as 24%), clustering of disease prevalence around polluted regions and an urban-rural difference in prevalence all highlight the importance of environmental influences in SLE. Experimental data strongly suggests a complex interaction between the exposome (or environmental influences) and genome (genetic material) to produce epigenetic changes (epigenome) that can alter the expression of genetic material and lead to development of disease in the susceptible individual. In this review, we focus on the available literature to explore the role of environmental factors in SLE disease onset and progression and to better understand the role of exposome-epigenome-genome interactions in this dreaded disease.

Favorable effects of hydroxychloroquine on serum low density lipid in patients with systemic lupus erythematosus: A systematic review and meta-analysis

AIMS

Hydroxychloroquine (HCQ) has shown to have significant immunomodulatory effects in the treatment of systemic lupus erythematosus (SLE). Current studies show favorable effects of HCQ on traditional cardiac risk factors in patients with SLE. This review examined the effects of HCQ on serum low-density lipoprotein (LDL) level in patients with SLE.

METHODS

A systematic search of seven major literature search databases from their inception until 3 April, 2017 identified nine studies. Random-effects pooled mean difference with corresponding 95% confidence intervals (CI) were estimated. Heterogeneity was measured by I² . Publication bias was assessed by visual inspection of funnel plots. Sensitivity analysis examined whether HCQ effect on serum total cholesterol level was similar to the main analysis. The Grading of Recommendations Assessment, Development, and Evaluation system was used to assess the overall quality of evidence.

RESULTS

Pooled study participants were 559 patients from eight observation studies (two before-after studies; six case-control studies) examining the effects of HCQ on serum LDL. Pooled study participants' characteristics were as follows: mean age 45.719, female 95.262%, and prednisone use 58.366%. HCQ reduced mean LDL levels by 24.397 mg/dL (95% CI 8.921-39.872; P = 0.002). The number of studies identifying statin use was too few to perform meta-regression analysis of statin use. Heterogeneity was extensive (I² = 94.739%). Symmetrical funnel plot visualized no evidence of publication bias.

CONCLUSION

HCQ was associated with serum LDL level reduction by mean 24.397 mg/dL in patients with SLE. Future prospective studies are need to fully characterize the treatment effect.

Development of autoantibodies precedes clinical manifestations of autoimmune diseases: A comprehensive review

The etiology of autoimmune diseases is due to a combination of genetic predisposition and environmental factors that alter the expression of immune regulatory genes through various mechanisms including epigenetics. Both humoral and cellular elements of the adaptive immune system play a role in the pathogenesis of autoimmune diseases and the presence of autoantibodies have been detected in most but not all autoimmune diseases before the appearance of clinical symptoms. In some cases, the presence or levels of these autoantibodies portends not only the risk of developing a corresponding autoimmune disease, but occasionally the severity as well. This observation is intriguing because it suggests that we can, to some degree, predict who may or may not develop autoimmune diseases. However, the role of autoantibodies in the pathogenesis of autoimmune diseases, whether they actually affect disease progression or are merely an epiphenomenon is still not completely clear in many autoimmune diseases. Because of these gaps in our knowledge, the ability to accurately predict a future autoimmune disease can only be considered a relative risk factor. Importantly, it raises the critical question of defining other events that may drive a patient from a preclinical to a clinical phase of disease.

Obesity and the risk of systemic lupus erythematosus among women in the Nurses' Health Studies

BACKGROUND

Obesity is increasingly prevalent and related to increased risk of several autoimmune diseases, likely via generation of inflammatory adipokines. Prior studies have not evaluated obesity in relation to systemic lupus erythematosus (SLE) risk. We prospectively evaluated whether obesity was associated with increased SLE risk among women in the U.S. Nurses' Health Study cohorts.

METHODS

We conducted a prospective cohort study among 238,130 women in the Nurses' Health Studies (NHS, 1976-2012; NHSII, 1989-2013). Incident SLE was confirmed by American College of Rheumatology 1997 criteria and validated through medical record review. Body mass index (BMI, kg/m²) was calculated at baseline and on biennial questionnaires. Cox proportional hazards models estimated HRs (95% CIs) for SLE by cumulative average BMI category {18.5 to <25 [normal (reference)], 25 to <30 (overweight), ≥30 (obese)}, adjusting for potential time-varying confounders. Models were performed separately in each cohort; results were meta-analyzed. Sensitivity analyses used simple time-varying BMI, a 4-year lag between exposure and SLE risk window to address potential reverse causation, and evaluated BMI at age 18 and weight change since age 18. A secondary analysis started follow-up in both cohorts at similar calendar years when the prevalence of obesity in the U.S. increased most dramatically [1988 (NHS)/1989 (NHSII)].

RESULTS

We identified 153 NHS incident SLE cases and 115 incident NHSII cases during 5,602,653 person-years of follow-up. At baseline, 8.4% of women in NHS and 11.8% in NHSII were obese. Mean age at enrollment was 42.5 (SD 7.2) years in NHS and 34.4 (SD 4.7) years in NHSII. Cumulative average obesity was significantly associated with SLE risk in NHSII [HR = 1.85 (1.17-2.91)], but not in NHS [HR = 1.11 (0.65-1.87)] compared to normal BMI. In the meta-analysis of both cohorts, obesity was not significantly associated with increased risk of SLE [HR = 1.46 (0.88-2.40)]. Simple time-varying BMI and lagging the exposure window by 4 years produced similar findings to the primary analysis. In NHSII, a 4.54 kg gain between age 18 and enrollment slightly increased SLE risk [HR = 1.09 (1.02-1.18)]. In the secondary analysis starting follow-up of both cohorts at similar calendar years, the point estimate for obesity in NHS was higher than the primary analysis [HR = 1.67 (0.81-3.45)].

CONCLUSION

We observed an 85% significantly increased risk of SLE among obese compared to normal BMI women in the more recent NHSII cohort, but no association was observed in the earlier NHS cohort. Secular trends in obesity may account for the differences between the two birth cohorts.

Environmental Basis of Autoimmunity

The three common themes that underlie the induction and perpetuation of autoimmunity are genetic predisposition, environmental factors, and immune regulation. Environmental factors have gained much attention for their role in triggering autoimmunity, with increasing evidence of their influence as demonstrated by epidemiological studies, laboratory research, and animal studies. Environmental factors known to trigger and perpetuate autoimmunity include infections, gut microbiota, as well as physical and environmental agents. To address these issues, we will review major potential mechanisms that underlie autoimmunity including molecular mimicry, epitope spreading, bystander activation, polyclonal activation of B and T cells, infections, and autoinflammatory activation of innate immunity. The association of the gut microbiota on autoimmunity will be particularly highlighted by their interaction with pharmaceutical agents that may lead to organ-specific autoimmunity. Nonetheless, and we will emphasize this point, the precise mechanism of environmental influence on disease pathogenesis remains elusive.

The global burden of SLE: prevalence, health disparities and socioeconomic impact

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease that can potentially lead to serious organ complications and even death. Its global burden - in terms of incidence and prevalence, differential impact on populations, economic costs and capacity to compromise health-related quality of life - remains incompletely understood. The reported worldwide incidence and prevalence of SLE vary considerably; this variation is probably attributable to a variety of factors, including ethnic and geographic differences in the populations being studied, the definition of SLE applied, and the methods of case identification. Despite the heterogeneous nature of the disease, distinct patterns of disease presentation, severity and course can often be related to differences in ethnicity, income level, education, health insurance status, level of social support and medication compliance, as well as environmental and occupational factors. Given the potential for the disease to cause such severe and widespread organ damage, not only are the attendant direct costs high, but these costs are sometimes exceeded by indirect costs owing to loss of economic productivity. As an intangible cost, patients with SLE are, not surprisingly, likely to endure considerably reduced health-related quality of life.

Silica-Triggered Autoimmunity in Lupus-Prone Mice Blocked by Docosahexaenoic Acid Consumption

Occupational exposure to respirable crystalline silica (cSiO2, quartz) is etiologically linked to systemic lupus erythematosus (lupus) and other human autoimmune diseases (ADs). In the female NZBWF1 mouse, a widely used animal model that is genetically prone to lupus, short-term repeated intranasal exposure to cSiO2 triggers premature initiation of autoimmune responses in the lungs and kidneys. In contrast to cSiO2's triggering action, consumption of the ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) prevents spontaneous onset of autoimmunity in this mouse strain. The aim of this study was to test the hypothesis that consumption of DHA will prevent cSiO2-triggered autoimmunity in the female NZBWF1 mouse. Mice (6 wk old) were fed isocaloric AIN-93G diets containing 0.0, 0.4, 1.2 or 2.4% DHA. Two wk after initiating feeding, mice were intranasally instilled with 1 mg cSiO2 once per wk for 4 wk and maintained on experimental diets for an additional 12 wk. Mice were then sacrificed and the lung, blood and kidney assessed for markers of inflammation and autoimmunity. DHA was incorporated into lung, red blood cells and kidney from diet in a concentration-dependent fashion. Dietary DHA dose-dependently suppressed cSiO2-triggered perivascular leukocyte infiltration and ectopic lymphoid tissue neogenesis in the lung. DHA consumption concurrently inhibited cSiO2-driven elevation of proinflammatory cytokines, B-cell proliferation factors, IgG and anti-dsDNA Ig in both bronchoalveolar lavage fluid and plasma. DHA's prophylactic effects were further mirrored in reduced proteinuria and glomerulonephritis in cSiO2-treated mice. Taken together, these results reveal that DHA consumption suppresses cSiO2 triggering of autoimmunity in female NZBWF1 mice as manifested in the lung, blood and kidney. Our findings provide novel insight into how dietary modulation of the lipidome might be used to prevent or delay triggering of AD by cSiO2. Such knowledge opens the possibility of developing practical, low-cost preventative strategies to reduce the risk of initiating AD and subsequent flaring in cSiO2-exposed individuals. Additional research in this model is required to establish the mechanisms by which DHA suppresses cSiO2-induced autoimmunity and to ascertain unique lipidome signatures predictive of susceptibility to cSiO2-triggered AD.

Systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect many organs, including the skin, joints, the central nervous system and the kidneys. Women of childbearing age and certain racial groups are typically predisposed to developing the condition. Rare, inherited, single-gene complement deficiencies are strongly associated with SLE, but the disease is inherited in a polygenic manner in most patients. Genetic interactions with environmental factors, particularly UV light exposure, Epstein-Barr virus infection and hormonal factors, might initiate the disease, resulting in immune dysregulation at the level of cytokines, T cells, B cells and macrophages. Diagnosis is primarily clinical and remains challenging because of the heterogeneity of SLE. Classification criteria have aided clinical trials, but, despite this, only one drug (that is, belimumab) has been approved for use in SLE in the past 60 years. The 10-year mortality has improved and toxic adverse effects of older medications such as cyclophosphamide and glucocorticoids have been partially offset by newer drugs such as mycophenolate mofetil and glucocorticoid-sparing regimes. However, further improvements have been hampered by the adverse effects of renal and neuropsychiatric involvement and late diagnosis. Adding to this burden is the increased risk of premature cardiovascular disease in SLE together with the risk of infection made worse by immunosuppressive therapy. Challenges remain with treatment-resistant disease and symptoms such as fatigue. Newer therapies may bring hope of better outcomes, and the refinement to stem cell and genetic techniques might offer a cure in the future.

Silica Triggers Inflammation and Ectopic Lymphoid Neogenesis in the Lungs in Parallel with Accelerated Onset of Systemic Autoimmunity and Glomerulonephritis in the Lupus-Prone NZBWF1 Mouse

Genetic predisposition and environmental factors influence the development of human autoimmune disease. Occupational exposure to crystalline silica (cSiO₂) has been etiologically linked to increased incidence of autoimmunity, including systemic lupus erythematosus (SLE), but the underlying mechanisms are poorly understood. The purpose of this study was to test the hypothesis that early repeated short-term cSiO₂ exposure will modulate both latency and severity of autoimmunity in the lupus-prone female NZBWF1 mouse. Weekly intranasal exposure to cSiO₂ (0.25 and 1.0 mg) for 4 wk beginning at 9 wk of age both reduced latency and increased intensity of glomerulonephritis. cSiO₂ elicited robust inflammatory responses in the lungs as evidenced by extensive perivascular and peribronchial lymphoplasmacytic infiltration consisting of IgG-producing plasma cells, and CD45R+ and CD3+ lymphocytes that were highly suggestive of ectopic lymphoid tissue (ELT). In addition, there were elevated concentrations of immunoglobulins and the cytokines MCP-1, TNF-α and IL-6 in bronchoalveolar lavage fluid. cSiO₂-associated kidney and lung effects paralleled dose-dependent elevations of autoantibodies and proinflammatory cytokines in plasma. Taken together, cSiO₂-induced pulmonary inflammation and ectopic lymphoid neogenesis in the NZBWF1 mouse corresponded closely to systemic inflammatory and autoimmune responses as well as the early initiation of pathological outcomes in the kidney. These findings suggest that following airway exposure to crystalline silica, in mice genetically prone to SLE, the lung serves as a platform for triggering systemic autoimmunity and glomerulonephritis.

Environmental influences on systemic lupus erythematosus expression

The etiology of systemic lupus erythematosus (SLE) is unknown, but multiple genetic, epigenetic, and environmental risk factors have been implicated. The inheritance of genes alone is not sufficient for developing SLE, suggesting the influence of environmental triggers on disease expression. Despite the tremendous amount of progress in elucidating potential environmental risk factors for SLE, much more needs to be done. An interdisciplinary approach to studies of the causes and, ultimately, prevention of SLE is needed. This article reviews what is understood about the epidemiology of the relationship between environmental exposures and SLE, in addition to emerging areas of study.

Association of systemic lupus erythematosus with uranium exposure in a community living near a uranium-processing plant: a nested case-control study

OBJECTIVE

To explore the hypothesis that cases of systemic lupus erythematosus (SLE) would be found more frequently in community members with high prior uranium exposure in the Fernald Community Cohort (FCC).

METHODS

A nested case-control study was performed using data from the FCC, a volunteer population of individuals who had resided near a uranium ore-processing plant in Fernald, Ohio during the years of plant operation; uranium plant workers were excluded. Members of the FCC were monitored for 18 years. SLE cases were identified using the American College of Rheumatology 1997 revised classification criteria, laboratory testing, and medical record review. Each case was matched to 4 controls by age, race, and sex. Sera from potential cases and controls were screened for autoantibodies. Cumulative exposure to uranium particulates was calculated using a dosimetry model. Logistic regression with covariates was used to calculate the odds ratios (ORs) with 95% confidence intervals (95% CIs) for the probability of an association between uranium exposure and SLE.

RESULTS

The FCC comprised 4,187 individuals with minimal levels of uranium exposure, 1,273 with moderate exposure, and 2,756 with high exposure. The diagnosis of SLE was confirmed in 23 of 31 individuals who had been assigned International Classification of Diseases, Ninth Revision codes for lupus, and was also confirmed in 2 of 43 individuals who had been prescribed hydroxychloroquine. The female to male ratio was 5.25:1. Of the 25 confirmed SLE cases, 12 were in the high exposure group. The presence of SLE was associated with higher levels of uranium exposure (OR 3.92, 95% CI 1.13-13.59; P = 0.031).

CONCLUSION

High uranium exposure is associated with SLE, as compared to matched controls, in this sample of uranium-exposed individuals. Potential explanations for this relationship include possible autoimmune or estrogen effects of uranium, somatic mutation, epigenetic effects, or effects of some other unidentified accompanying exposure.

Pesticides, chemical and industrial exposures in relation to systemic lupus erythematosus

Growing evidence suggests exposure to chemicals and industrial pollutants may increase risk of systemic lupus erythematosus (SLE). Here we review research on SLE associations with occupational and industrial exposures, primarily drawing on studies in human populations and summarizing epidemiologic research published in the past decade. The association of occupational silica exposure with SLE is well established, but key questions remain, including the required dose and susceptibility factors, and SLE risk due to other silicate exposures. Research on SLE and other exposures is less well developed, though several potential associations merit further consideration because of the consistency of preliminary human findings, experimental animal research, and biologic plausibility. These include pesticides and solvents, for which experimental findings also support investigation of specific agents, including organochlorines and trichloroethylene. Experimental findings and biologic plausibility suggest research on SLE and occupational exposure to hydrocarbons (i.e. mineral oils) is warranted, especially given the widespread exposures in the population. Experimental and limited human findings support further investigation of SLE related to mercury exposure, especially in dental occupations. Research on environmental risk factors in risk-enriched cohorts (family-based) is recommended, as is further investigation of exposures in relation to intermediate markers of effect (e.g. antinuclear antibodies), clinical features (e.g. nephritis), and outcomes.

Environmental factors, toxicants and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an immune-complex-mediated multi-systemic autoimmune condition of multifactorial etiology, which mainly affects young women. It is currently believed that the onset of SLE and lupus flares are triggered by various environmental factors in genetically susceptible individuals. Various environmental agents and toxicants, such as cigarette smoke, alcohol, occupationally- and non-occupationally-related chemicals, ultraviolet light, infections, sex hormones and certain medications and vaccines, have been implicated to induce SLE onset or flares in a number case series, case-control and population-based cohort studies and very few randomized controlled trials. Here, we will describe some of these recognized environmental lupus triggering and perpetuating factors and explain how these factors potentially bias the immune system towards autoimmunity through their interactions with genetic and epigenetic alterations. Further in-depth exploration of how potentially important environmental factors mechanistically interact with the immune system and the genome, which trigger the onset of SLE and lupus flares, will certainly be one of the plausible steps to prevent the onset and to decelerate the progress of the disease.

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the “immunome” and “microbiome”. It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development.

The association between silica exposure and development of ANCA-associated vasculitis: systematic review and meta-analysis

BACKGROUND

Crystalline silica is among the environmental exposures associated with increased risk of autoimmune diseases, including rheumatoid arthritis, systemic sclerosis and systemic lupus erythematosus. Silica exposure has also been related to the development of ANCA-associated vasculitides (AAV), but past studies appear to conflict as to the presence and magnitude of the associated risks of disease. We aimed to conduct a systematic review of the existing studies and meta-analysis of their results.

METHODS

We searched EMBASE, MEDLINE and international scientific conference abstract databases for studies examining the association of silica exposure with AAV. Studies in English, French, or Spanish were included and those examining the association of silica with ANCA-positivity alone were excluded. We assessed study quality using the Newcastle-Ottawa Scale. We meta-analyzed the results using random effects models and tested for heterogeneity. We performed sensitivity and subgroup analyses, examining studies that adjusted for smoking and occupational risk factors as well as studies that analyzed by subtypes of AAV.

RESULTS

We identified 158 potential manuscripts and 3 abstracts related to silica exposure and risk of AAV. 147 were excluded after abstract review and 14 underwent detailed evaluation of full manuscript/abstract. After further application of exclusion criteria, 6 studies (all cases-controls) remained. The studies had moderate heterogeneity in selection of cases and controls, exposure assessment, disease definition and controlling for potential confounders. We found an overall significant summary effect estimate of silica "ever exposure" with development of AAV (summary OR 2.56, 95% CI 1.51-4.36), with moderate heterogeneity (I(2)=48.40%). ORs were similar for studies examining only MPA (OR 3.95, CI 95% 1.89-8.24), compared to those only studying GPA (OR 3.56, CI 95% 1.85-6.82).

CONCLUSION

Despite moderate heterogeneity among studies, the totality of the evidence after meta-analysis points to an association between silica exposure and risk for developing AAV.

The role of environmental factors in the pathogenesis of non-organ-specific autoimmune diseases

The immune system must be able to discriminate between self and non-self. However, mechanisms of doing so sometimes fail, causing the activation and clonal expansion of autoreactive lymphocytes and the development of autoimmune conditions. Although some autoimmune diseases have heritable components, these components are not sufficient to develop an autoimmune condition. A variety of environmental factors have been described as possible triggers of autoimmune diseases, including drugs, infectious agents, smoking, vaccination and adjuvants. The aim of this chapter is to review the most common environmental factors associated with autoimmune diseases.

Requirements for innate immune pathways in environmentally induced autoimmunity

There is substantial evidence that environmental triggers in combination with genetic and stochastic factors play an important role in spontaneous autoimmune disease. Although the specific environmental agents and how they promote autoimmunity remain largely unknown, in part because of diverse etiologies, environmentally induced autoimmune models can provide insights into potential mechanisms. Studies of idiopathic and environmentally induced systemic autoimmunity show that they are mediated by common adaptive immune response genes. By contrast, although the innate immune system is indispensable for autoimmunity, there are clear differences in the molecular and cellular innate components that mediate specific systemic autoimmune diseases, suggesting distinct autoimmune-promoting pathways. Some of these differences may be related to the bifurcation of toll-like receptor signaling that distinguishes interferon regulatory factor 7-mediated type I interferon production from nuclear factor-κB-driven proinflammatory cytokine expression. Accordingly, idiopathic and pristane-induced systemic autoimmunity require both type I interferon and proinflammatory cytokines whereas the less aggressive mercury-induced autoimmunity, although dependent on nucleic acid-binding toll-like receptors, does not require type I interferon but needs proinflammatory cytokines. Scavenger receptors and the inflammasome may contribute to silica-induced autoimmunity. Greater understanding of the innate mechanisms responsible for idiopathic and environmentally induced autoimmunity should yield new information into the processes that instigate and drive systemic autoimmunity.

Sex-specific environmental influences on the development of autoimmune diseases

Sex differences in autoimmune diseases are evolutionarily tied to the fact that the female immune system is confronted with intense alterations during menstrual cycles, pregnancy and childbirth. These events may be associated with breaches in the mucosal epithelial layers that are shielding us from environmental factors. Associations between environmental agents and autoimmune diseases have been described extensively in prior studies. Little evidence, however, exists for sex-specific environmental effects on autoimmune diseases. In this review, we summarize studies involving this often-neglected aspect. We give examples of environmental factors that may influence the sex bias in autoimmunity. We conclude that most studies do not give insight into sex-specific environmental effects due to the influence of gender-selective social, occupational or other exposures. Prospective studies are needed in order to determine true sex-biased environmental influences. Finally, humanized murine models might aid in better understanding the mechanisms involved in sex-specific environmental effects on autoimmune diseases.

Infectome: a platform to trace infectious triggers of autoimmunity

The "exposome" is a term recently used to describe all environmental factors, both exogenous and endogenous, which we are exposed to in a lifetime. It represents an important tool in the study of autoimmunity, complementing classical immunological research tools and cutting-edge genome wide association studies (GWAS). Recently, environmental wide association studies (EWAS) investigated the effect of environment in the development of diseases. Environmental triggers are largely subdivided into infectious and non-infectious agents. In this review, we introduce the concept of the "infectome", which is the part of the exposome referring to the collection of an individual's exposures to infectious agents. The infectome directly relates to geoepidemiological, serological and molecular evidence of the co-occurrence of several infectious agents associated with autoimmune diseases that may provide hints for the triggering factors responsible for the pathogenesis of autoimmunity. We discuss the implications that the investigation of the infectome may have for the understanding of microbial/host interactions in autoimmune diseases with long, pre-clinical phases. It may also contribute to the concept of the human body as a superorganism where the microbiome is part of the whole organism, as can be seen with mitochondria which existed as microbes prior to becoming organelles in eukaryotic cells of multicellular organisms over time. A similar argument can now be made in regard to normal intestinal flora, living in symbiosis within the host. We also provide practical examples as to how we can characterise and measure the totality of a disease-specific infectome, based on the experimental approaches employed from the "immunome" and "microbiome" projects.

Organic solvents as risk factor for autoimmune diseases: a systematic review and meta-analysis

BACKGROUND

Genetic and epigenetic factors interacting with the environment over time are the main causes of complex diseases such as autoimmune diseases (ADs). Among the environmental factors are organic solvents (OSs), which are chemical compounds used routinely in commercial industries. Since controversy exists over whether ADs are caused by OSs, a systematic review and meta-analysis were performed to assess the association between OSs and ADs.

METHODS AND FINDINGS

The systematic search was done in the PubMed, SCOPUS, SciELO and LILACS databases up to February 2012. Any type of study that used accepted classification criteria for ADs and had information about exposure to OSs was selected. Out of a total of 103 articles retrieved, 33 were finally included in the meta-analysis. The final odds ratios (ORs) and 95% confidence intervals (CIs) were obtained by the random effect model. A sensitivity analysis confirmed results were not sensitive to restrictions on the data included. Publication bias was trivial. Exposure to OSs was associated to systemic sclerosis, primary systemic vasculitis and multiple sclerosis individually and also to all the ADs evaluated and taken together as a single trait (OR: 1.54; 95% CI: 1.25-1.92; p-value<0.001).

CONCLUSION

Exposure to OSs is a risk factor for developing ADs. As a corollary, individuals with non-modifiable risk factors (i.e., familial autoimmunity or carrying genetic factors) should avoid any exposure to OSs in order to avoid increasing their risk of ADs.

Epidemiology of environmental exposures and human autoimmune diseases: findings from a National Institute of Environmental Health Sciences Expert Panel Workshop

Autoimmune diseases (AID) are a collection of many complex disorders of unknown etiology resulting in immune responses to self-antigens and are thought to result from interactions between genetic and environmental factors. Here we review the epidemiologic evidence for the role of environmental factors in the development of human AID, the conclusions that can be drawn from the existing data, critical knowledge gaps, and research needed to fill these gaps and to resolve uncertainties. We specifically summarize the state of knowledge and our levels of confidence in the role of specific agents in the development of autoimmune diseases, and we define the areas of greatest impact for future investigations. Among our consensus findings we are confident that: 1) crystalline silica exposure can contribute to the development of several AID; 2) solvent exposure can contribute to the development of systemic sclerosis; 3) smoking can contribute to the development of seropositive rheumatoid arthritis; and 4) an inverse association exists between ultraviolet radiation exposure and the risk of development of multiple sclerosis. We suggest that more studies of phenotypes, genotypes, and multiple exposures are needed. Additional knowledge gaps needing investigation include: defining important windows in the timing of exposures and latencies relating to age, developmental state, and hormonal changes; understanding dose-response relationships; and elucidating mechanisms for disease development. Addressing these essential issues will require more resources to support research, particularly of rare AID, but knowledge of the risks conferred by environmental factors in specific genetic contexts could pave the way for prevention of AID in the future.

Cigarette Smoking, Alcohol Consumption, and Risk of Systemic Lupus Erythematosus: A Case-control Study in a Japanese Population

Objective.

Cigarette smoking may be associated with increased risk of systemic lupus erythematosus (SLE), whereas the role of alcohol consumption is unknown. We examined the association between SLE risk and smoking or drinking.

Methods.

We investigated the relationship of smoking and drinking compared to SLE risk among 171 SLE cases and 492 healthy controls in female Japanese subjects. Unconditional logistic regression was used to compute OR and 95% CI, with adjustments for several covariates.

Results.

Compared with nonsmoking, current smoking was significantly associated with increased risk of SLE (OR 3.06, 95% CI 1.86–5.03). The higher the level of exposure to cigarette smoke, the higher the risk of SLE. Inhalation was also associated with increased SLE risk (OR 3.73, 95% CI 1.46–9.94 for moderate inhalation; OR 3.06, 95% CI 1.81–5.15 for deep inhalation). In contrast, light/moderate alcohol consumption had a protective effect on SLE risk (OR 0.38, 95% CI 0.19–0.76). As for beer, the risks for non-beer drinkers and beer drinkers were similar. This also applies to alcoholic beverages other than beer.

Conclusion.

Our results suggest that smoking was positively associated with increased SLE risk whereas light/moderate alcohol consumption was inversely associated with SLE risk, irrespective of the type of alcoholic beverage. Additional studies are warranted to confirm these findings.

Occupational risk factors for systemic lupus erythematosus: a nationwide study based on hospitalizations in Sweden

OBJECTIVE

To investigate possible associations between occupation and hospitalization for systemic lupus erythematosus (SLE) in a nationwide study.

METHODS

A nationwide database was constructed in Sweden by linking the Swedish Census to the Hospital Discharge Register to obtain data on all first hospitalizations with a primary or secondary diagnosis of SLE in adults during the study period (1970 to 2008). Standardized incidence ratios (SIR) and 95% CI were calculated for different occupations. Two cohorts were defined based on occupational titles recorded in Swedish census data in 1970 and 1980.

RESULTS

A total of 8921 male and 42290 female hospitalizations for SLE were retrieved in individuals aged over 15 years. High education (> 12 yrs) was associated with a lower risk of hospitalization for SLE among both women (SIR = 0.73) and men (SIR = 0.72). Among men with the same occupation in 2 consecutive censuses, increased risks (SIR) > 2.0 were present among artistic workers (2.52); shop managers and assistants (3.63); miners and quarry workers (6.04); shoe and leather workers (6.93); plumbers (2.21); other construction workers (2.08); glass, ceramic and tile workers (4.43); chimney sweeps (4.54); and military personnel (3.01). Among women with the same occupation in 2 consecutive censuses, no occupation was associated with SIR > 2.0.

CONCLUSION

Occupation may carry significantly increased risk of hospital admission for SLE. Especially among men, several occupations were associated with increased risks for SLE.