The toxicity of guaiacol on craniofacial cartilage development through ROS-induced oxidative stress in zebrafish embryos.

The combustion of biomass (e.g., wood, agricultural residues) and coal releases significant amounts of guaiacol (GUA) and its derivatives, major constituents of PM2.5 that threaten human health and ecosystems. GUA can rapidly enter the Earth's water circulation system through atmospheric deposition. However, its potential threat to aquatic organism and humans remains poorly understood. Using zebrafish-a model organism with high genetic homology to humans, transparent embryos, and rapid development-we investigated GUA's ecological effects. Zebrafish embryos were exposed to 0.08-0.24 mM GUA from 12 to 120 h post-fertilization (hpf). GUA induced craniofacial malformations, behavioral abnormalities (reduced locomotion, impaired stimuli response), and oxidative stress via reactive oxygen species (ROS) accumulation. Disrupted migration, proliferation, and differentiation of cranial neural crest cells (NCCs) were observed, alongside altered Wnt signaling pathway gene expression. Both astaxanthin (AST, an ROS scavenger) and C59 (a Wnt inhibitor) could mitigate craniofacial defects. These findings demonstrate that GUA reduces antioxidant capacity, impairs NCCs function, and disrupts Wnt signaling, leading to craniofacial deformities. This study highlights GUA's ecological and health risks, providing insights into its toxic mechanisms.