Cardio- and neuro-toxic effects of four parabens on Daphnia magna

Parabens can potentially disrupt the hormonal regulation of energy metabolism, leading to issues related to obesity, metabolic health, and the cardiovascular and nervous systems. However, the health effects of parabens have yielded conflicting research results. The impact of these substances on aquatic organisms, specifically their neuro- and cardio-toxic effects, has been insufficiently investigated. Hence, the primary goal of our research was to investigate and comprehensively assess the neuro- and cardio-toxic effects of four distinct parabens using the Daphnia magna model. After 48 h of exposure to various concentrations (0.1, 1, and 10 mg/L) of four parabens (methyl-, ethyl-, propyl-, and butyl-paraben), along with a solvent control, we conducted a series of physiological tests, behavioral observations, and gene transcription analyses, focusing on cardiomyopathy, serotonin, glutamate, dopamine, GABA, acetylcholine receptors, and ion flux. From a physiological perspective, the heart rate and thoracic limb activity of the exposed daphnids showed substantial time- and dose-dependent inhibitions. Notably, among the parabens tested, butylparaben exhibited the most potent inhibition, with significant alterations in cardiomyopathy-related gene transcription. In the context of neurotoxicity, all the parabens had a significant impact on gene expression, with methylparaben having the most pronounced effect. Additionally, significant changes were observed in parameters such as distance moved, the distance between individuals, and the extent of body contact among the daphnids. In summary, our findings indicate that each paraben has the capacity to induce neurobehavioral and cardiotoxic disorders in Daphnia magna. The effects of butylparaben on the cardiovascular and nervous systems were found to be the most pronounced. These discoveries showed the potential ecological implications of paraben exposure in aquatic ecosystems, particularly regarding the predator avoidance abilities of Daphnia magna.