N3rvousSystem: A 3R systems biology strategy for human neurotoxicity hazard, risk and safety assessment

Humans are exposed to numerous chemicals via the environment. To prevent adverse health effects, risk and safety assessment are obligatory before chemicals are allowed on the market. Regulation regarding chemical legislation and exposure has been based on animal research for many years. Currently, there is societal and scientific incentive to (partly) replace animal research by human cellular assays. The aim of the InnoSysTox call is the development and/or application of (new and existing) innovative systems-biology-based 3R (animal research reduction, refinement and replacement) methods in toxicology. This proposed research contributes to these objectives by combining the application of a number of innovative in vitro methods with information from the intact animal in a testing strategy for neurotoxicity hazard. The innovative in vitro methods include the use of human and mouse embryonic stem cell derived neurons grown on multi-electrode arrays to study the effects of chemical exposure on neuronal activity, which is the basis for brain function and human cognition. Underlying mechanisms of effects on neuronal activity will be assessed using pathway analysis based on kinase activity profiling. These innovative in vitro data will be combined with information on kinetics and the effects of chemical exposure on neurobehavior of the intact organism. Systems biology is the computational and mathematical modeling of complex biological systems. In the field of chemical risk and safety assessment, based on exposure and toxicity information, this is mostly applied in integrated toxicological testing strategies. In this proposed research, systems biology (mathematical modelling) will be also be applied to integrate all obtained information. The information on chemical-induced effects obtain in in vitro and in vivo studies will be combined with kinetic information (obtained from the in vivo studies and from literature) and fed into chemical-specific physiology-based pharmacokinetic (PBPK) models. The different constituents (e.g. human and rodent data from different levels of biological organization) in this systems-biology approach will be evaluated for their contribution to the predictivity of the model for human neurotoxicity hazard assessment. To establish this holistic innovative testing strategy for human neurotoxicity hazard and risk assessment, its applicability domain will be evaluated, with specific focus on potential differences with regards to nano- and non-nanochemicals. In this manner, this proposed research will contribute to an improved risk and safety assessment framework for environmental chemicals including engineered nano-particles. The main research question ‘Can human neurotoxicity hazard be predicted using a systems-biology- based 3R testing strategy?’ is thus addressed by answering the following research sub-questions: 1) Does exposure to (known) neurotoxicants affect neurophysiology similarly in human and mouse stem cell derived neurons?; 2) Does exposure to (known) neurotoxicants alter similar or different signalling pathways in human and mouse stem cell derived neurons?; 3) Can chemical-induced effects on neurophysiology in vitro predict effects on neurophysiology and/or neurobehavior in rodents?; 4) Which component(s) in the pharmacokinetic model is/are critical for prediction of human neurotoxicity hazard?; and 5) Can the neurotoxicity hazard of engineered nanomaterials be assessed with a general chemical testing strategy or are specific adaptations required? To answer these questions, input is required from a multitude of disciplines. Therefore, expertise from the fields of toxicology, neurophysiology, neurobehavioral toxicology, biology, mathematical/kinetic modelling is included in this proposed research to reach the transdisciplinary goal of the creation of a holistic and innovative testing strategy for human neurotoxicity hazard, risk and safety assessment. To achieve this goal there will be given specific attention to open discussion and dialogue within the consortium. The ultimate aim of this proposed research is to contribute to the prevention of adverse health effects from chemical exposure via the environmental and food. To optimize the impact of this proposed research to all parties within the value creation chain of N3rvousSystem, there will be active outreach to stakeholders (academic, societal, regulatory and governmental parties). During the project this will include newsletters, updates at a N3rvousSystem LinkedIn Group, and dedicated presentations at international scientific meetings. At the end of the project a international workshop will be organized for all stakeholders to actively disseminate the final results of the project to the stakeholders and to define the final steps needed for actual implementation.