An integrative approach for understanding the adverse outcome pathways in algae

Schade, Stefan (2020). An integrative approach for understanding the adverse outcome pathways in algae. University of Birmingham. Ph.D.

Schade2020PhD.pdf
Text - Accepted Version
Restricted to Repository staff only until 31 December 2025.
Available under License All rights reserved.
Download (10MB) | Request a copy

Abstract

Conventional environmental hazard assessment practices focus on determining intrinsic danger of chemicals via induction of crude apical endpoints. A novel chemical safety assessment paradigm is pioneering the understanding of molecular mechanisms fundamentally driving such endpoints to increase quality of future chemical safety assessment. To achieve stakeholder acceptance of new technologies such as omics to drive discovery of toxicological mechanisms, there is a need for evaluation of experimental approaches tailored towards this end, using environmentally relevant models such as microalgae. The research goal of this thesis was to propose the development, characterization and application of an experimental design and a suitable physical algal exposure system tailored towards hypothesis of acute chemical mode of action (MoA) and key events in adverse outcome pathways (AOPs) driven by time-resolved multi-omics profiling of algae. An experimental design aligned with the AOP framework was delineated, and a customized algal vial exposure system developed and rigorously validated. The developed system generated highly similar metabolomics profiles in a repeat-exposure study, and existing differences could be mitigated via an internal normalization strategy. Markers driving the adverse phenotype after exposure could be reproducibly identified from the study. Applying the experimental design via the developed exposure system, large-scale and highly time- resolved multi-omics (metabolomics, lipidomics and transcriptomics) exposure experiments of Chlamydomonas reinhardtii to the baseline-toxicant chlorobenzene and the herbicide norflurazon were conducted. Acute chemical MoA and draft AOPs were successfully constructed, using generated and retrieved literature data. Results emphasized discrete (primarily chloroplast-based oxidative stress for norflurazon, general metabolic inhibition and membrane-disruptive effects for chlorobenzene) however to a degree shared molecular stress signatures (inhibition of cellular motility, activation of autophagy and apoptosis). Finally, the utility and limitations of the presented discovery approach for application in hazard assessment were discussed, suggesting high utility to future prioritization of testing and to chemical read-across of hazard using omics-signatures, pending further validation of the method, including application to new model toxicants, putative biomarker identification from the omics datasets, and targeted manual validation of the latter.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):