Bioactivity of the ubiquitous tire preservative 6PPD and degradant, 6PPD-quinone in fish and mammalian-based assays.

6PPD-quinone (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone), a transformation product of the antiozonant 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) is a likely causative agent of coho salmon (Oncorhynchus kisutch) pre-spawn mortality. Stormwater runoff transports 6PPD-quinone into freshwater streams, rapidly leading to neurobehavioral, respiratory distress, and rapid mortality in laboratory exposed coho salmon, but causing no mortality in many laboratory-tested species. Given this identified hazard, and potential for environmental exposure, we evaluated a set of U.

Mapping out strategies to further develop human-relevant, new approach methodology (NAM)-based developmental neurotoxicity (DNT) testing.

On occasion of the DNT5 meeting in Konstanz, Germany (April-2024), participants brainstormed on future challenges concerning a regulatory implementation of the developmental neurotoxicity (DNT) in vitro test battery (DNT-IVB). The five discussion topics below outline some of the key issues, opportunities and research directions for the next several years: (1) How to contextualize DNT hazard with information on potential maternal toxicity or other toxicity domains (non-DNT)? Several approaches on how to use cytotoxicity data from NAMs were discussed. (2) What opportunities exist for an immediate or near-future application of the DNT-IVB, e.

State of the science on assessing developmental neurotoxicity using new approach methods.

The workshop titled State of the Science on Assessing Developmental Neurotoxicity Using New Approach Methods was co-organized by University of Maryland’s Joint Institute for Food Safety and Applied Nutrition (JIFSAN) and the U.S. Food and Drug Administration’s (FDA) Center for Food Safety and Applied Nutrition (CFSAN; now called the Human Foods Program), and was hosted by FDA in College Park, MD on November 14-15, 2023.

Organoid intelligence for developmental neurotoxicity testing.

The increasing prevalence of neurodevelopmental disorders has highlighted the need for improved testing methods to determine developmental neurotoxicity (DNT) hazard for thousands of chemicals. This paper proposes the integration of organoid intelligence (OI); leveraging brain organoids to study neuroplasticity into the DNT testing paradigm. OI brings a new approach to measure the impacts of xenobiotics on plasticity mechanisms - a critical biological process that is not adequately covered in current DNT assays.

Identification of neural-relevant toxcast high-throughput assay intended gene targets: Applicability to neurotoxicity and neurotoxicant putative molecular initiating events.

The US EPA's Toxicity Forecaster (ToxCast) is a suite of high-throughput in vitro assays to screen environmental toxicants and predict potential toxicity of uncharacterized chemicals. This work examines the relevance of ToxCast assay intended gene targets to putative molecular initiating events (MIEs) of neurotoxicants. This effort is needed as there is growing interest in the regulatory and scientific communities about developing new approach methodologies (NAMs) to screen large numbers of chemicals for neurotoxicity and developmental neurotoxicity.

Liver Transplant Costs and Activity After United Network for Organ Sharing Allocation Policy Changes.

Importance: A new liver allocation policy was implemented by United Network for Organ Sharing (UNOS) in February 2020 with the stated intent of improving access to liver transplant (LT). There are growing concerns nationally regarding the implications this new system may have on LT costs, as well as access to a chance for LT, which have not been captured at a multicenter level.

Objective: To characterize LT volume and cost changes across the US and within specific center groups and demographics after the policy implementation.

Chemical effects on neural network activity: Comparison of acute versus network formation exposure in microelectrode array assays.

New approach methodologies (NAMs) can address information gaps on potential neurotoxicity or developmental neurotoxicity hazard for data-poor chemicals. Two assays have been previously developed using microelectrode arrays (MEA), a technology which measures neural activity. The MEA acute network function assay (AcN) uses dissociated rat cortical cells cultured at postnatal day 0 and evaluates network activity during a 40-minute chemical exposure on day in vitro (DIV)13 or 15.

Why do users continue to contribute to darknet Child Sexual Abuse Material forums? Examining social exchange, social capital, and social learning explanations using digital forensic artifacts.

Background: The darknet hosts an increasing number of hidden services dedicated to the distribution of child sexual abuse material (CSAM). Given that by contributing CSAM to the forum members subject themselves to criminal prosecution, questions regarding the motivation for members contributing to darknet CSAM forums arise.

Objective: Building on insights gained from research into clearnet communities, here we examine the extent to which social incentives generated by the online CSAM community may explain members' posting behavior on darknet CSAM forums.

A Comparison of In Vitro Points of Departure with Human Blood Levels for Per- and Polyfluoroalkyl Substances (PFAS).

Per- and polyfluoroalkyl substances (PFAS) are widely used, and their fluorinated state contributes to unique uses and stability but also long half-lives in the environment and humans. PFAS have been shown to be toxic, leading to immunosuppression, cancer, and other adverse health outcomes. Only a small fraction of the PFAS in commerce have been evaluated for toxicity using in vivo tests, which leads to a need to prioritize which compounds to examine further.

Pervasive environmental chemicals impair oligodendrocyte development.

Exposure to environmental chemicals can impair neurodevelopment, and oligodendrocytes may be particularly vulnerable, as their development extends from gestation into adulthood. However, few environmental chemicals have been assessed for potential risks to oligodendrocytes. Here, using a high-throughput developmental screen in cultured cells, we identified environmental chemicals in two classes that disrupt oligodendrocyte development through distinct mechanisms.

HESI workshop summary: Interpretation of developmental and reproductive toxicity endpoints and the impact on data interpretation of adverse events.

The Health and Environmental Sciences Institute Developmental and Reproductive Toxicology (HESI-DART) group held a hybrid in-person and virtual workshop in Washington, DC, in 2022. The workshop was entitled, "Interpretation of DART in Regulatory Contexts and Frameworks." There were 154 participants (37 in person and 117 virtual) across 9 countries.

Identification of neurotoxicology (NT)/developmental neurotoxicology (DNT) adverse outcome pathways and key event linkages with in vitro DNT screening assays.

There is a need to assess compounds reliably and quickly for neurotoxicity (NT) and developmental neurotoxicity (DNT). Adverse outcome pathways (AOPs) enable the mapping of molecular events to an apical endpoint in a chemical agnostic manner and have begun to be applied in NT and DNT testing frameworks. We assessed the status of NT/DNT AOPs in the AOP-Wiki (ca.

Assaying Spontaneous Network Activity and Cellular Viability Using Multi-Well Microelectrode Arrays.

Microelectrode array (MEA) technology is a neurophysiological method that allows for the measurement of spontaneous or evoked neural activity to determine chemical effects thereon. Following assessment of compound effects on multiple endpoints that evaluate network function, a cell viability endpoint in the same well is determined using a multiplexed approach. Recently, it has become possible to measure electrical impedance of cells attached to the electrodes, where greater impedance indicates greater number of cells attached.

Evaluation of Per- and Polyfluoroalkyl Substances (PFAS) Toxicity Testing for Developmental Neurotoxicity.

Per- and polyfluoroalkyl substances (PFAS) are a diverse set of commercial chemicals widely detected in humans and the environment. However, only a limited number of PFAS are associated with epidemiological or experimental data for hazard identification. To provide developmental neurotoxicity (DNT) hazard information, the work herein employed DNT new approach methods (NAMs) to generate screening data for a set of 160 PFAS.

Pervasive environmental chemicals impair oligodendrocyte development.

Exposure to environmental chemicals can impair neurodevelopment. Oligodendrocytes that wrap around axons to boost neurotransmission may be particularly vulnerable to chemical toxicity as they develop throughout fetal development and into adulthood. However, few environmental chemicals have been assessed for potential risks to oligodendrocyte development.

An expert-driven literature review of "negative" chemicals for developmental neurotoxicity (DNT) in vitro assay evaluation.

To date, approximately 200 chemicals have been tested in US Environmental Protection Agency (EPA) or Organization for Economic Co-operation and Development (OECD) developmental neurotoxicity (DNT) guideline studies, leaving thousands of chemicals without traditional animal information on DNT hazard potential. To address this data gap, a battery of in vitro DNT new approach methodologies (NAMs) has been proposed. Evaluation of the performance of this battery will increase the confidence in its use to determine DNT chemical hazards.

Current status and future directions for a neurotoxicity hazard assessment framework that integrates approaches.

Neurotoxicology is the study of adverse effects on the structure or function of the developing or mature adult nervous system following exposure to chemical, biological, or physical agents. The development of more informative alternative methods to assess developmental (DNT) and adult (NT) neurotoxicity induced by xenobiotics is critically needed. The use of such alternative methods including approaches that predict DNT or NT from chemical structure (e.

Integration of toxicodynamic and toxicokinetic new approach methods into a weight-of-evidence analysis for pesticide developmental neurotoxicity assessment: A case-study with DL- and L-glufosinate.

DL-glufosinate ammonium (DL-GLF) is a registered herbicide for which a guideline Developmental Neurotoxicity (DNT) study has been conducted. Offspring effects included altered brain morphometrics, decreased body weight, and increased motor activity. Guideline DNT studies are not available for its enriched isomers L-GLF acid and L-GLF ammonium; conducting one would be time consuming, resource-intensive, and possibly redundant given the existing DL-GLF DNT.

Integrating Data From In Vitro New Approach Methodologies for Developmental Neurotoxicity.

In vivo developmental neurotoxicity (DNT) testing is resource intensive and lacks information on cellular processes affected by chemicals. To address this, DNT new approach methodologies (NAMs) are being evaluated, including: the microelectrode array neuronal network formation assay; and high-content imaging to evaluate proliferation, apoptosis, neurite outgrowth, and synaptogenesis. This work addresses 3 hypotheses: (1) a broad screening battery provides a sensitive marker of DNT bioactivity; (2) selective bioactivity (occurring at noncytotoxic concentrations) may indicate functional processes disrupted; and, (3) a subset of endpoints may optimally classify chemicals with in vivo evidence for DNT.

Integrated Omic Analyses Identify Pathways and Transcriptomic Regulators Associated With Chemical Alterations of In Vitro Neural Network Formation.

Development of in vitro new approach methodologies has been driven by the need for developmental neurotoxicity (DNT) hazard data on thousands of chemicals. The network formation assay characterizes DNT hazard based on changes in network formation but provides no mechanistic information. This study investigated nervous system signaling pathways and upstream physiological regulators underlying chemically induced neural network dysfunction.

Comparison of Acute Effects of Neurotoxic Compounds on Network Activity in Human and Rodent Neural Cultures.

Assessment of neuroactive effects of chemicals in cell-based assays remains challenging as complex functional tissue is required for biologically relevant readouts. Recent in vitro models using rodent primary neural cultures grown on multielectrode arrays allow quantitative measurements of neural network activity suitable for neurotoxicity screening. However, robust systems for testing effects on network function in human neural models are still lacking.

Toward a Better Testing Paradigm for Developmental Neurotoxicity: OECD Efforts and Regulatory Considerations.

Characterization of potential chemical-induced developmental neurotoxicity (DNT) hazard is considered for risk assessment purposes by many regulatory sectors. However, due to test complexity, difficulty in interpreting results and need of substantial resources, the use of the in vivo DNT test guidelines has been limited and animal data on DNT are scarce. To address challenging endpoints such as DNT, the Organisation for Economic Co-Operation and Development (OECD) chemical safety program has been working lately toward the development of integrated approaches for testing and assessment (IATA) that rely on a combination of multiple layers of data (e.

A chemical structure-based approach for estimating the added levels of flavourings to foods for the purpose of assessing consumer intake.

Intake assessment and hazard profile of chemical substances are the two critical inputs in a safety assessment. Human intake assessment presents challenges that stem either from the absence of data or from numerous sources of variability and uncertainty, which have led regulators to adopt conservative approaches that inevitably overestimate intake. Refinements of intake assessments produce more realistic estimates and help prioritise areas of concern and better direct investment of resources.