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

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are toxic constituents of crude oil that can induce cardiac dysfunction and vision impairment in early life stage (ELS) fishes. However, it is currently unknown whether visual impairments are independent effects or if they result from underlying PAH cardiotoxicity. To better understand this mechanism, microinjection of microRNA 133b (miR133b) was used to impair cardiac development in ELS zebrafish (injected at <1.25 hpf). Vision and cardiac endpoints were compared between miR133b-injected and oil-exposed zebrafish (4-72 hpf, 54.68-60.41 µg/L tPAH₅₀) to determine the influence of cardiac dysfunction and oil exposure on visual function. At 7 dpf, pericardial area and eye area were measured, and visual function was assessed by optokinetic response (OKR). Over 94 % of miR133b larvae and 45 % of oil-exposed larvae exhibited pericardial edema. Across treatments, there was a strong negative linear correlation between pericardial area and eye area (r=-0.839, p < 0.0001). All miR133b larvae that exhibited pericardial edema and 18 % of the oil-exposed larvae that exhibited pericardial edema also exhibited reduced eye area (microphthalmia). In both the miR133b and oil groups, OKR was significantly reduced in larvae exhibiting pericardial edema (p < 0.0001) and in larvae exhibiting reduced eye area (p < 0.0001). A negative binomial generalized linear model (GLM) indicated that reduced eye area (p < 0.0001), rather than pericardial edema (p = 0.76), was a significant predictor of OKR. However, pericardial edema was strongly correlated with reduced eye area across treatments. These results suggest that visual effects may result from an interaction of cardiotoxicity as well as direct impacts to the visual system.

Keywords: Crude oil; Early life stage (ELS) fish; Microphthalmia; Optokinetic response (OKR); Pericardial edema; Polycyclic aromatic hydrocarbon (PAH); microRNA.