I-REFF diagrams: enhancing transparency in systematic review through interactive reference flow diagrams.

Systematic review methods are recognized for their rigor and transparency and are widely adapted to frameworks that cover review types such as systematic reviews, scoping reviews, and systematic evidence maps. Reporting guidelines help promote better systematic review practices and detailed documentation of the review process for different types of health research (e.g., PRISMA-Preferred Reporting Items for Systematic Reviews and Meta-Analyses; CONSORT-Consolidated Standards of Reporting Trials; and STROBE-Strengthening the Reporting of Observational Studies in Epidemiology). Transparency in the systematic review process and reporting of results is one of the key advantages of the methods and particularly important for hazard and risk assessments due to the high level of scrutiny these reviews face from scientific, political, and public communities. Data visualizations are important to clearly convey information from a review by helping readers perceive, understand, and assess the displayed information easily and quickly. The study flow diagram is a required element of a systematic review and maps out the number of included and excluded records identified, and the reasons for exclusion. Static literature flow diagrams help viewers readily understand the general review methodology and summarize the number of records included or excluded at each stage of the review. However, such diagrams can be time-consuming to develop and maintain during a systematic review or scoping review, and they provide limited summary-level information. We explored how the use of online systematic review tools such as DistillerSR coupled with visualization software such as Tableau can efficiently generate an Interactive REFerence Flow (I-REFF) diagram that is linked to the literature screening data, thus requiring minimal preparation, and resulting in a simplified process for updating the diagram. Furthermore, I-REFF diagrams enhance transparency and traceability by not only summarizing the records in the review but also allowing viewers to follow specific records throughout the review process. We present an example I-REFF diagram and discuss recommendations for key interactive elements to include in these diagrams and how this workflow can improve efficiency and result in an accessible and transparent interactive literature flow diagram without advanced programming.

Systematic evidence mapping informs a class-based approach to assessing personal care products and pubertal timing.

BACKGROUND: Personal care products (PCPs) contain many different compounds and are a source of exposure to endocrine disrupting chemicals (EDCs), including phthalates and phenols. Early-life exposure to EDCs commonly found in PCPs has been linked to earlier onset of puberty. OBJECTIVE: To characterize the human and animal evidence on the association between puberty-related outcomes and exposure to PCPs and their chemical constituents and, if there is sufficient evidence, identify groups of chemicals and outcomes to support a systematic review for a class-based hazard or risk assessment. METHODS: We followed the OHAT systematic review framework to characterize the human and animal evidence on the association between puberty-related health outcomes and exposure to PCPs and their chemical constituents. RESULTS: Ninety-eight human and 299 animal studies that evaluated a total of 96 different chemicals were identified and mapped by key concepts including chemical class, data stream, and puberty-related health outcome. Among these studies, phthalates and phenols were the most well-studied chemical classes. Most of the phthalate and phenol studies examined secondary sex characteristics and changes in estradiol and testosterone levels. Studies evaluating PCP use and other chemical classes (e.g., parabens) had less data. CONCLUSIONS: This systematic evidence map identified and mapped the published research evaluating the association between exposure to PCPs and their chemical constituents and puberty-related health outcomes. The resulting interactive visualization allows researchers to make evidence-based decisions on the available research by enabling them to search, sort, and filter the literature base of puberty-related studies by key concepts. This map can be used by researchers and regulators to prioritize and target future research and funding to reduce uncertainties and address data gaps. It also provides information to inform a class-based hazard or risk assessment on the association between phthalate and phenol exposures and puberty-related health outcomes.

Becoming aWARE: The Development of a Web-Based Tool for Autism Research and the Environment.

A sharp rise in autism spectrum disorder (ASD) prevalence estimates, beginning in the 1990s, suggested factors additional to genetics were at play. This stimulated increased research investment in nongenetic factors, including the study of environmental chemical exposures, diet, nutrition, lifestyle, social factors, and maternal medical conditions. Consequently, both peer- and non-peer-reviewed bodies of evidence investigating environmental contributors to ASD etiology have grown significantly. The heterogeneity in the design and conduct of this research results in an inconclusive and unwieldy 'virtual stack' of publications. We propose to develop a Web-based tool for Autism Research and the Environment (aWARE) to comprehensively aggregate and assess these highly variable and often conflicting data. The interactive aWARE tool will use an approach for the development of systematic evidence maps (SEMs) to identify and display all available relevant published evidence, enabling users to explore multiple research questions within the scope of the SEM. Throughout tool development, listening sessions and workshops will be used to seek perspectives from the broader autism community. New evidence will be indexed in the tool annually, which will serve as a living resource to investigate the association between environmental factors and ASD.

Identifying environmental factors that influence immune response to SARS-CoV-2: Systematic evidence map protocol.

BACKGROUND: Widespread environmental contamination can directly interact with human immune system functions. Environmental effects on the immune system may influence human susceptibility to respiratory infections as well as the severity of infectious diseases, such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Furthermore, the efficacy of vaccines to respiratory diseases may be impacted by environmental exposures through immune perturbations. Given the quick pace of research about COVID-19 and associated risk factors, it is critical to identify and curate the streams of evidence quickly and effectively. OBJECTIVE: We developed this systematic evidence map protocol to identify and organize existing human and animal literature on high-priority environmental chemical classes (Per- and polyfluoroalkyl substances, pesticides, phthalates, quaternary ammonium compounds, and air pollutants) and their potential to influence three key outcomes: (1) susceptibility to respiratory infection, including SARS-CoV-2 (2) severity of the resultant disease progression, and (3) impact on vaccine efficacy. The result of this project will be an online, interactive database which will show what evidence is currently available between involuntary exposures to select environmental chemicals and immune health effects, data gaps that require further research, and data rich areas that may support further analysis. SEARCH AND STUDY ELIGIBILITY: We will search PubMed for epidemiological or toxicological literature on select toxicants from each of the chemical classes and each of the three outcomes listed above. STUDY APPRAISAL AND SYNTHESIS OF METHODS: For each study, two independent reviewers will conduct title and abstract screening as well as full text review for data extraction of study characteristics. Study quality will not be evaluated in this evidence mapping. The main findings from the systematic evidence map will be visualized using a publicly available and interactive database hosted on Tableau Public.

Evaluation of a semi-automated data extraction tool for public health literature-based reviews: Dextr.

INTRODUCTION: There has been limited development and uptake of machine-learning methods to automate data extraction for literature-based assessments. Although advanced extraction approaches have been applied to some clinical research reviews, existing methods are not well suited for addressing toxicology or environmental health questions due to unique data needs to support reviews in these fields. OBJECTIVES: To develop and evaluate a flexible, web-based tool for semi-automated data extraction that: 1) makes data extraction predictions with user verification, 2) integrates token-level annotations, and 3) connects extracted entities to support hierarchical data extraction. METHODS: Dextr was developed with Agile software methodology using a two-team approach. The development team outlined proposed features and coded the software. The advisory team guided developers and evaluated Dextr's performance on precision, recall, and extraction time by comparing a manual extraction workflow to a semi-automated extraction workflow using a dataset of 51 environmental health animal studies. RESULTS: The semi-automated workflow did not appear to affect precision rate (96.0% vs. 95.4% manual, p = 0.38), resulted in a small reduction in recall rate (91.8% vs. 97.0% manual, p < 0.01), and substantially reduced the median extraction time (436 s vs. 933 s per study manual, p < 0.01) compared to a manual workflow. DISCUSSION: Dextr provides similar performance to manual extraction in terms of recall and precision and greatly reduces data extraction time. Unlike other tools, Dextr provides the ability to extract complex concepts (e.g., multiple experiments with various exposures and doses within a single study), properly connect the extracted elements within a study, and effectively limit the work required by researchers to generate machine-readable, annotated exports. The Dextr tool addresses data-extraction challenges associated with environmental health sciences literature with a simple user interface, incorporates the key capabilities of user verification and entity connecting, provides a platform for further automation developments, and has the potential to improve data extraction for literature reviews in this and other fields.

Developing a database of systematic reviews of animal studies.

Systematic reviews (SRs) are common practice in clinical and public health research, but less common in non-human animal research. Systematic reviews of animal studies can be valuable to inform clinical research, to evaluate the need for further animal experiments on a given topic, and to assess the hazard of an environmental exposure in the evaluation of toxicological studies. In the last 10 years, there has been an increase in the number of SRs of animal research, as well as several publications with detailed guidance on how to perform high-quality systematic reviews of experimental animal studies. In order to evaluate current analytical approaches used in SRs of animal studies, easily identify all systematic reviews on a specific topic, and subsequently the original animal studies and their results and promote awareness and understanding of these emerging approaches, we compiled a database of SRs of animal studies. The database was developed using a rigorous, systematic approach and covers a broad range of research fields: preclinical research, toxicology, environmental health, and veterinary medicine. The database currently includes 3113 SRs of animal studies (search date June 2019). In addition to bibliographical information, data on whether or not a risk of bias assessment and meta-analysis were conducted were extracted. For future users, the search features of the database provide users with a platform to identify and select SRs with a particular characteristic for export to Microsoft Word or Microsoft Excel. From there, users may perform additional data extraction to meet their research needs. The database is freely available at www.Mendeley.com (link). The database provides methodologists a comprehensive source that can be used to explore and advance the current methodology applied to SRs of animal studies, and can help researchers to easily identify all systematic reviews on a specific topic, and subsequently the original animal studies and their results and avoid duplication and unnecessary animal research.

Systematic evidence maps as a novel tool to support evidence-based decision-making in chemicals policy and risk management.

BACKGROUND: While systematic review (SR) methods are gaining traction as a method for providing a reliable summary of existing evidence for health risks posed by exposure to chemical substances, it is becoming clear that their value is restricted to a specific range of risk management scenarios - in particular, those which can be addressed with tightly focused questions and can accommodate the time and resource requirements of a systematic evidence synthesis. METHODS: The concept of a systematic evidence map (SEM) is defined and contrasted to the function and limitations of systematic review (SR) in the context of risk management decision-making. The potential for SEMs to facilitate evidence-based decision-making are explored using a hypothetical example in risk management priority-setting. The potential role of SEMs in reference to broader risk management workflows is characterised. RESULTS: SEMs are databases of systematically gathered research which characterise broad features of the evidence base. Although not intended to substitute for the evidence synthesis element of systematic reviews, SEMs provide a comprehensive, queryable summary of a large body of policy relevant research. They provide an evidence-based approach to characterising the extent of available evidence and support forward looking predictions or trendspotting in the chemical risk sciences. In particular, SEMs facilitate the identification of related bodies of decision critical chemical risk information which could be further analysed using SR methods, and highlight gaps in the evidence which could be addressed with additional primary studies to reduce uncertainties in decision-making. CONCLUSIONS: SEMs have strong and growing potential as a high value tool in resource efficient use of existing research in chemical risk management. They can be used as a critical precursor to efficient deployment of high quality SR methods for characterising chemical health risks. Furthermore, SEMs have potential, at a large scale, to support the sort of evidence summarisation and surveillance methods which would greatly increase the resource efficiency, transparency and effectiveness of regulatory initiatives such as EU REACH and US TSCA.

Human and animal evidence of potential transgenerational inheritance of health effects: An evidence map and state-of-the-science evaluation.

BACKGROUND: An increasing number of reports suggest early life exposures result in adverse effects in offspring who were never directly exposed; this phenomenon is termed "transgenerational inheritance." Given concern for public health implications for potential effects of exposures transmitted to subsequent generations, it is critical to determine how widespread and robust this phenomenon is and to identify the range of exposures and possible outcomes. OBJECTIVES: This scoping report examines the evidence for transgenerational inheritance associated with exposure to a wide range of stressors in humans and animals to identify areas of consistency, uncertainty, data gaps, and to evaluate general risk of bias issues for the transgenerational study design. METHODS: A protocol was developed to collect and categorize the literature into a systematic evidence map for transgenerational inheritance by health effects, exposures, and evidence streams following the Office of Health Assessment and Translation (OHAT) approach for conducting literature-based health assessments. RESULTS: A PubMed search yielded 63,758 unique records from which 257 relevant studies were identified and categorized into a systematic evidence map by evidence streams (46 human and 211 animal), broad health effect categories, and exposures. Data extracted from the individual studies are available in the Health Assessment Workspace Collaborative (HAWC) program. There are relatively few bodies of evidence where multiple studies evaluated the same exposure and the same or similar outcomes. Studies evaluated for risk of bias generally had multiple issues in design or conduct. CONCLUSIONS: The evidence mapping illustrated that risk of bias, few studies, and heterogeneity in exposures and endpoints examined present serious limitations to available bodies of evidence for assessing transgenerational effects. Targeted research is suggested to addressed inconsistencies and risk of bias issues identified, and thereby establish more robust bodies of evidence to critically assess transgenerational effects - particularly by adding data on exposure-outcome pairs where there is some evidence (i.e., reproductive, metabolic, and neurological effects).

Evaluation of the association between maternal smoking, childhood obesity, and metabolic disorders: a national toxicology program workshop review.

BACKGROUND: An emerging literature suggests that environmental chemicals may play a role in the development of childhood obesity and metabolic disorders, especially when exposure occurs early in life. OBJECTIVE: Here we assess the association between these health outcomes and exposure to maternal smoking during pregnancy as part of a broader effort to develop a research agenda to better understand the role of environmental chemicals as potential risk factors for obesity and metabolic disorders. METHODS: PubMed was searched up to 8 March 2012 for epidemiological and experimental animal studies related to maternal smoking or nicotine exposure during pregnancy and childhood obesity or metabolic disorders at any age. A total of 101 studies-83 in humans and 18 in animals-were identified as the primary literature. DISCUSSION: Current epidemiological data support a positive association between maternal smoking and increased risk of obesity or overweight in offspring. The data strongly suggest a causal relation, although the possibility that the association is attributable to unmeasured residual confounding cannot be completely ruled out. This conclusion is supported by findings from laboratory animals exposed to nicotine during development. The existing literature on human exposures does not support an association between maternal smoking during pregnancy and type 1 diabetes in offspring. Too few human studies have assessed outcomes related to type 2 diabetes or metabolic syndrome to reach conclusions based on patterns of findings. There may be a number of mechanistic pathways important for the development of aberrant metabolic outcomes following perinatal exposure to cigarette smoke, which remain largely unexplored. CONCLUSIONS: From a toxicological perspective, the linkages between maternal smoking during pregnancy and childhood overweight/obesity provide proof-of-concept of how early-life exposure to an environmental toxicant can be a risk factor for childhood obesity.

Estrogen receptor-α mediates diethylstilbestrol-induced feminization of the seminal vesicle in male mice.

BACKGROUND: Studies have shown that perinatal exposure to the synthetic estrogen diethylstilbestrol (DES) leads to feminization of the seminal vesicle (SV) in male mice, as illustrated by tissue hyperplasia, ectopic expression of the major estrogen-inducible uterine secretory protein lactoferrin (LF), and reduced expression of SV secretory protein IV (SVS IV). OBJECTIVES: The present study was designed to evaluate the role of the estrogen receptor (ER) in this action by using ER-knockout (ERKO) mice. METHODS: Wild-type (WT), ERα-null (αERKO), and ERß-null (ßERKO) male mice were treated with either vehicle or DES (2 µg/day) on neonatal days 1-5. These mice were divided into two groups: In the first group, intact mice were sacrificed at 10 weeks of age; in the second group, mice were castrated at 10 weeks of age, allowed to recover for 10 days, treated with dihydrotestosterone (DHT) or placebo, and sacrificed 2 weeks later. Body weights and SV weights were recorded, and mRNA expression levels of Ltf (lactoferrin), Svs4, and androgen receptor (Ar) were assessed. RESULTS: In DES-treated intact mice, SV weights were reduced in WT and ßERKO mice but not in αERKO mice. DES-treated WT and ßERKO males, but not αERKO males, exhibited ectopic expression of LF in the SV. DES treatment resulted in decreased SVS IV protein and mRNA expression in WT males, but no effect was seen in αERKO mice. In addition, DES-treated ßERKO mice exhibited reduced Svs4 mRNA expression but maintained control levels of SVS IV protein. In DES-treated castrated mice, DHT implants restored SV weights to normal levels in αERKO mice but not in WT mice, suggesting full androgen responsiveness in αERKO mice. CONCLUSIONS: These data suggest that DES-induced SV toxicity and feminization are primarily mediated by ERα; however, some aspects of androgen response may require the action of ERß.

Spontaneous airway hyperresponsiveness in estrogen receptor-alpha-deficient mice.

RATIONALE: Airway hyperresponsiveness is a critical feature of asthma. Substantial epidemiologic evidence supports a role for female sex hormones in modulating lung function and airway hyperresponsiveness in humans. OBJECTIVES: To examine the role of estrogen receptors in modulating lung function and airway responsiveness using estrogen receptor-deficient mice. METHODS: Lung function was assessed by a combination of whole-body barometric plethysmography, invasive measurement of airway resistance, and isometric force measurements in isolated bronchial rings. M2 muscarinic receptor expression was assessed by Western blotting, and function was assessed by electrical field stimulation of tracheas in the presence/absence of gallamine. Allergic airway disease was examined after ovalbumin sensitization and exposure. MEASUREMENTS AND MAIN RESULTS: Estrogen receptor-alpha knockout mice exhibit a variety of lung function abnormalities and have enhanced airway responsiveness to inhaled methacholine and serotonin under basal conditions. This is associated with reduced M2 muscarinic receptor expression and function in the lungs. Absence of estrogen receptor-alpha also leads to increased airway responsiveness without increased inflammation after allergen sensitization and challenge. CONCLUSIONS: These data suggest that estrogen receptor-alpha is a critical regulator of airway hyperresponsiveness in mice.

Estrogen receptor beta mediates gender differences in ischemia/reperfusion injury.

Under hypercontractile conditions associated with increased intracellular calcium, male hearts show enhanced ischemia/reperfusion injury compared to female hearts. Our aim in this study was to identify the specific estrogen receptor involved in this gender difference. Following brief treatment with isoproterenol, isolated mouse hearts were subjected to ischemia and reperfusion. Postischemic contractile function and infarct size were measured in wild-type (WT) male and female hearts, and female hearts lacking functional alpha estrogen receptor (alpha ERKO), or the beta estrogen receptor (beta ERKO). WT male hearts exhibited significantly less functional recovery and more necrosis than WT females. alpha ERKO female hearts exhibited ischemia/reperfusion injury similar to that observed in WT females, whereas beta ERKO females exhibited significantly less functional recovery than WT females and were similar to WT males. These data suggest that estrogen, through the beta-estrogen receptor, plays a role in the protection observed in the female heart. Furthermore, we identified genes that were differentially expressed in beta ERKO female hearts compared to alpha ERKO and WT female hearts, and found altered expression of a number of metabolism genes, which may be important in ischemic injury. We further showed that WT female hearts have increased ratio of carbohydrate to fatty acid metabolism relative to WT males.

Estrogen receptor knockout mice as a model for endocrine research.

The biological effects of estrogen in mammalian target tissues are important for multiple organ systems including the male and female reproductive tract and the neuroendocrine, skeletal, and cardiovascular systems. Numerous physiological effects of estradiol are modulated by the estrogen receptor (ER), a Class I member of the nuclear receptor superfamily. However, more recent studies have also implicated nongenomic effects of estrogen, which may involve a membrane-binding site. The two forms of the ER are the classical estrogen receptor-alpha (ERalpha) and the more recently discovered estrogen receptor-beta (ERbeta). Gene-targeting techniques were used to generate mice lacking either functional ERalpha (alphaERKO), ERbeta (betaERKO), or both ERs (alphabetaERKO) to provide a model for evaluating estrogen receptor action. These knockout models provide a unique tool to study the effects of estrogen in the context of the whole animal and to discern the role of each ER in various tissues. The reproductive phenotypes as well as some of the nonreproductive phenotypes of the different ERKO models are summarized.

Update on animal models developed for analyses of estrogen receptor biological activity.

Targeted disruption of the different ER genes has generated experimental animal models that are very useful in evaluating the distinct and cooperative roles of the two estrogen receptors, ERalpha and ERbeta, in reproductive but also non-reproductive tissues of both sexes. Phenotypic analysis has provided definitive experimental findings for estrogen receptor mediated physiological actions, involving ERalpha in uterine, mammary gland and neuroendocrine sites. ERbeta is involved most dramatically in the ovary as is ERalpha. More detailed studies in combination with tissue specific or inducible ER knock outs will be important for future research.

Octamethylcyclotetrasiloxane exhibits estrogenic activity in mice via ERalpha.

Octamethylcyclotetrasiloxane (D4) is a low molecular weight cyclic silicone used in the synthesis of larger silicone polymers and in the formulation of a variety of personal care products. The effects of oral D4 exposure in mice on serum estradiol levels, uterine wet weight, and uterine peroxidase activity were investigated. Additionally, in vitro estrogen receptor binding activity was evaluated. Serum estradiol levels decreased in a dose-dependent manner after exposure to 100 mg/kg to 1000 mg/kg D4. Studies with adrenalectomized animals demonstrated that the decreased serum estradiol levels were not due to elevated serum corticosterone levels. Uterine wet weights in ovariectomized mice were significantly increased in a dose-dependent manner by exposure to 250-1000 mg of D4/kg, but not by exposure to other silicone compounds tested (hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, decamethyltetrasiloxane, and octaphenylcyclotetrasiloxane). Uterine peroxidase activity, a marker for estrogenic activity, was also significantly increased in D4-exposed mice, but not in mice exposed to the other siloxanes. Pretreating mice with the estrogen receptor antagonist ICI 182,780 completely blocked the D4-induced increase in uterine weight, and ovariectomized estrogen receptor-alpha knockout mice showed no increases in uterine weights when orally exposed to D4 or estradiol. In an in vitro estrogen receptor binding assay, D4 showed significant competition with (3)H-estradiol for binding to estrogen receptor-alpha, but not estrogen receptor-beta. The data presented here indicate that D4 has weak estrogenic activity, and that these effects are mediated through estrogen receptor-alpha.

Characterization of the hypothalamic-pituitary-gonadal axis in estrogen receptor (ER) Null mice reveals hypergonadism and endocrine sex reversal in females lacking ERalpha but not ERbeta.

To determine the role of each estrogen receptor (ER) form (ERalpha, ERbeta) in mediating the estrogen actions necessary to maintain proper function of the hypothalamic-pituitary-gonadal axis, we have characterized the hypothalamic-pituitary-gonadal axis in female ER knockout (ERKO) mice. Evaluation of pituitary function included gene expression assays for Gnrhr, Cga, Lhb, Fshb, and Prl. Evaluation of ovarian steroidogenic capacity included gene expression assays for the components necessary for estradiol synthesis: i.e. Star, Cyp11a, Cyp17, Cyp19, Hsd3b1, and Hsd17b1. These data were corroborated by assessing plasma levels of the respective peptide and steroid hormones. alphaERKO and alphabetaERKO females exhibited increased pituitary Cga and Lhb expression and increased plasma LH levels, whereas both were normal in betaERKO. Pituitary Fshb expression and plasma FSH were normal in all three ERKOs. In the ovary, all three ERKOs exhibited normal expression of Star, Cyp11a, and Hsd3b1. In contrast, Cyp17 and Cyp19 expression were elevated in alphaERKO but normal in betaERKO and alphabetaERKO. Plasma steroid levels in each ERKO mirrored the steroidogenic enzyme expression, with only the alphaERKO exhibiting elevated androstenedione and estradiol. Elevated plasma testosterone in alphaERKO and alphabetaERKO females was attributable to aberrant expression of Hsd17b3 in the ovary, representing a form of endocrine sex reversal, as this enzyme is unique to the testes. Enhanced steroidogenic capacity in alphaERKO ovaries was erased by treatment with a GnRH antagonist, indicating these phenotypes to be the indirect result of excess LH stimulation that follows the loss of ERalpha in the hypothalamic-pituitary axis. Overall, these findings indicate that ERalpha, but not ERbeta, is indispensable to the negative-feedback effects of estradiol that maintain proper LH secretion from the pituitary. The subsequent hypergonadism is illustrated as increased Cyp17, Cyp19, Hsd17b1, and ectopic Hsd17b3 expression in the ovary.