Photoperiod perturbations impact perfluorohexane sulfonate (PFHxS) induced developmental toxicity

Area of Science:

• Environmental Toxicology
• Chronobiology
• Developmental Neurotoxicity

Background:

• Perfluorohexane sulfonate (PFHxS) is a persistent environmental contaminant with potential developmental neurotoxicity.
• Circadian rhythms, regulated by photoperiod, influence physiological processes and can modulate chemical toxicity.
• Disruption of natural light-dark cycles is increasingly common due to artificial lighting and modern lifestyles.

Purpose of the Study:

• To investigate the influence of photoperiod on the toxicity of perfluorohexane sulfonate (PFHxS) in zebrafish embryos.
• To determine if environmental lighting conditions alter PFHxS uptake, endocrine disruption, and developmental outcomes.
• To assess the role of photoperiod in PFHxS-induced neurobehavioral and ocular effects.

Main Methods:

• Zebrafish embryos were exposed to PFHxS across a concentration range under different photoperiods: 14-hour light:10-hour dark (14L:10D) and constant darkness (24D).
• PFHxS uptake was measured using LC-MS, and toxicity was assessed through photomotor behavioral assays, melatonin level analysis, and transcriptomic profiling.
• Gene expression analysis focused on DNA replication, cell cycle, oxidative stress pathways, and eye-specific developmental markers.

Main Results:

• PFHxS uptake was comparable between 14L:10D and 24D photoperiods.
• Constant darkness (24D) exacerbated PFHxS toxicity, leading to hyperactivity, elevated oxidative stress, DNA damage, and suppressed cell proliferation compared to the 14L:10D cycle.
• PFHxS disrupted melatonin levels differently across photoperiods and caused photoperiod-specific ocular developmental aberrations, including reduced retinal proliferating cells under 24D.

Conclusions:

• Photoperiod is a critical factor modulating the toxicological outcomes of PFHxS exposure.
• Constant darkness amplifies PFHxS-induced developmental neurotoxicity and endocrine disruption in zebrafish embryos.
• Risk assessments for persistent chemicals like PFHxS must consider environmental lighting conditions and circadian disruption.