Thousands
of contaminants are used worldwide and eventually released
into the environment, presenting a challenge of health risk assessment.
The identification of key toxic pathways and characterization of interactions
with target biomacromolecules are essential for health risk assessments.
The adverse outcome pathway (AOP) incorporates toxic mechanisms into
health risk assessment by emphasizing the relationship among molecular
initiating events (MIEs), key events (KEs), and adverse outcome (AO).
Herein, we attempted the use of AOP to decipher the toxic effects
of 2,6-di-tert-butylphenol (2,6-DTBP) and its para-quinone
metabolite 2,6-di-tert-butyl-1,4-benzoquinone (2,6-DTBQ)
based on integrated transcriptomics, molecular modeling, and cell-based
assays. Through transcriptomics and quantitative real-time PCR validation,
we identified retinoic acid receptor β (RARβ) as the key
target biomacromolecule. The epigenetic analysis and molecular modeling
revealed RARβ interference as one MIE, including DNA methylation
and conformational changes. In vitro assays extended
subsequent KEs, including altered protein expression of p-Erk1/2 and
COX-2, and promoted cancer cell H4IIE proliferation and metastasis.
These toxic effects altogether led to carcinogenic risk as the AO
of 2,6-DTBP and 2,6-DTBQ, in line with chemical carcinogenesis identified
from transcriptome profiling. Overall, our simplified AOP network
of 2,6-DTBP and 2,6-DTBQ facilitates relevant health risk assessment.