Toxicity assessment and behavioral effects of parabens in zebrafish early-life stages

Parabens are esters of p-hydroxybenzoic acid used as preservatives in personal care products, food and pharmaceuticals due to their antimicrobial activity. Recently, data on human exposure and ecotoxicological studies raised concerns regarding their safety. Thus, this study aimed to enrich the knowledge about the neurotoxicological effects of parabens using zebrafish (Danio rerio) as animal model. Fish embryo acute toxicity tests (FET tests) were performed on zebrafish fertilized eggs according to OECD guideline n. 236. And methylparaben (MeP), ethyl-paraben (EtP) and butylparaben (BuP) were tested. The toxicity of parabens was found in the order of BuP > EtP > MeP. Moreover, parabens exposure led to developmental abnormalities and teratological effects including misshaped yolk sac, reduction in blood circulation, reduced heartbeat, blood stasis, pericardial edema and deformed notochord as well as delay in hatching rate. To study behavior, circadian photic entrainment, average locomotor activity, and thigmotaxis were recorded automatically using DanioVision equipment. Zebrafish larvae exposed to sublethal concentrations of parabens showed able to synchronize their behavior to photic conditions with a typical diurnal pattern, i.e., higher activity during light phases compared to dark phases. However, high sublethal concentrations of parabens led to alternation in the average locomotor activity, namely activity suppression for BuP and hyperactivity for EtP and MeP. In addition, exposure to higher concentrations of BuP and EtP caused increased thigmotaxis response in larvae. The present study detected sublethal effects and behavioral changes in zebrafish early-life stages exposed to parabens, then further surveys are needed to understand new potential modes of action of these endocrine-disrupting chemicals on central nervous system.