Influence of cardiotoxicity on visual function in developing zebrafish (Danio rerio) exposed to Deepwater Horizon crude oil

Area of Science:

• Environmental Toxicology
• Developmental Biology
• Neuroscience

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are toxic crude oil components affecting aquatic life.
• PAHs can cause cardiac dysfunction and vision impairment in early life stage (ELS) fish.
• The relationship between PAH-induced cardiotoxicity and visual impairment remains unclear.

Purpose of the Study:

• To investigate whether visual impairments in ELS zebrafish are independent effects or a consequence of PAH-induced cardiotoxicity.
• To determine the influence of cardiac dysfunction and direct oil exposure on visual function.
• To elucidate the mechanism linking PAH exposure to visual deficits in developing fish.

Main Methods:

• Microinjection of microRNA 133b (miR133b) to induce cardiac defects in ELS zebrafish.
• Exposure of ELS zebrafish to crude oil (54.68-60.41 µg/L tPAH50).
• Assessment of cardiac endpoints (pericardial area) and visual endpoints (eye area, optokinetic response - OKR) at 7 days post-fertilization (dpf).
• Statistical analysis including correlation and generalized linear models (GLM).

Main Results:

• Over 94% of miR133b-injected larvae and 45% of oil-exposed larvae developed pericardial edema.
• A strong negative correlation was observed between pericardial area and eye area (r=-0.839, p < 0.0001).
• Microphthalmia (reduced eye area) occurred in all miR133b larvae with edema and 18% of oil-exposed larvae with edema.
• Reduced OKR was significantly associated with both pericardial edema and microphthalmia.
• GLM analysis identified reduced eye area (p < 0.0001) as a significant predictor of reduced OKR, while pericardial edema was not (p = 0.76).

Conclusions:

• Visual impairment in PAH-exposed zebrafish is significantly predicted by reduced eye area (microphthalmia).
• While pericardial edema (cardiac dysfunction) is correlated with microphthalmia, it is not the direct predictor of visual dysfunction.
• These findings suggest that visual deficits result from a combination of cardiotoxicity and direct impacts on ocular development from PAH exposure.