De Novo Development of a Quantitative Adverse Outcome Pathway (qAOP) Network for Ultraviolet B (UVB) Radiation Using Targeted Laboratory Tests and Automated Data Mining

Ultraviolet B (UVB) radiation
is a natural nonchemical stressor posing potential hazards to organisms
such as planktonic crustaceans. The present study was conducted to
revisit the lethal effects of UVB on crustaceans, generate new experimental
evidence to fill in knowledge gaps, and develop novel quantitative
adverse outcome pathways (qAOPs) for UVB. A combination of laboratory
and computational approaches was deployed to achieve the goals. For
targeted laboratory tests, Daphnia magna was used as a prototype and exposed to a gradient of artificial
UVB. Targeted bioassays were used to quantify the effects of UVB at
multiple levels of biological organization. A toxicity pathway network
was assembled based on the new experimental evidence and previously
published data extracted using a novel computational tool, the NIVA
Risk Assessment Database (NIVA RAdb). A network of AOPs was developed,
and weight of evidence was assessed based on a combination of the
current and existing data. In addition, quantitative key event relationships
in the AOPs were developed by fitting the D. magna data to predefined models. A complete workflow for assembly and
evaluation of qAOPs has been presented, which may serve as a good
example for future de novo qAOP development for chemical and nonchemical
stressors.