Behavioral Studies of Zebrafish Reveal a New Perspective on the Reproductive Toxicity of Micro- and Nanoplastics

Abstract

The escalating prevalence of microplastics and nanoplastics in aquatic environments is a major challenge affecting the behavior and reproductive health of aquatic organisms while posing potential risks to human health and ecosystems. This review focuses on the neurobehavioral changes and reproductive toxicity of MNPs in zebrafish and their relationships. At the same time, the neurobehavioral changes caused by MNPs were studied, and the synergistic effects of the interaction of these pollutants with other environmental contaminants were explored. In addition, zebrafish, as a model organism, provide valuable insights into the subtle but important effects of MNPs on reproductive behavior, which is critical for understanding reproductive success, suggesting that behavioral changes can serve as an early biomarker of reproductive toxicity. In addition, based on classical endocrine disruptor models and behavioral research methods, the current status of the research on the reproductive toxicity of MNPs in zebrafish was reviewed, which further indicated that the behavioral parameters of zebrafish can be used as an effective and rapid tool to evaluate the reproductive toxicity of MNPs. However, behavioral methods for rapidly assessing the toxicity of MNPs are still an area of exploration. To address limitations and challenges in the current scope of research, this review outlines future research directions with the aim of improving our understanding of the environmental and health impacts of MNPs. This work aims to inform targeted environmental policies and advance public health strategies to address the growing challenge of MNPs pollution.

Neurotoxicity of Some Environmental Pollutants to Zebrafish

“…As plastics enter the aquatic environment, they undergo photodegradation and alteration, fragmenting into smaller particles ranging in size from nanometers to micrometers [47]. This fragmentation leads to the formation of microplastics and nanoplastics in aquatic ecosystems, which pose a significant ecological threat [48], affecting the behavior and reproductive health of aquatic organisms and endangering human health [49].…”

“…Bioaccumulation of nanoplastics has also been identified in the brain, gills, blood, liver, and digestive tract of zebrafish immediately after hatching and has been shown to cause oxidative DNA damage and developmental malformations, among other problems [79]. Fluorescence spectroscopic analysis of tissues treated with polystyrene nanoplastics showed strong green fluorescence, observed predominantly in the gonads, intestine, liver, and brain, but with a significant proportion in the gonads (about five times more than in the brain) [49].…”

“…The primary abnormalities that fish exhibit after being exposed to nanoplastics are neurobehavioral in nature [49], and in most experimental studies, zebrafish have been exposed to polystyrene nanoplastics (PS-NPs) to assess the toxic effects. Exposure to PS-NPs was found to alter behavioral parameters, decreasing the fishes' interest in exploration; they exhibited stay-at-the-bottom behavior in the aquarium they were introduced to, with no improvement in anxiety as they adapted to the new environment, and at the highest concentration of exposure, they exhibited hyperreactivity-like behavior, highlighted by increased mean velocity [80].…”

“…Microplastics usually accumulate in adult zebrafish and less frequently in embryos and larvae. Short-or long-term exposure to microplastics has negative effects on their nervous system and can lead to behavioral abnormalities, which can manifest as significant changes in swimming, social interaction, and reproductive behaviors, including impaired fertility [49,80]. Current studies suggest the existence of several mechanisms responsible for microplastic toxicity in zebrafish, but the most relevant is considered to be oxidative stress, which can interfere with normal nervous system function and energy metabolism [50,141].…”

“…Current studies suggest the existence of several mechanisms responsible for microplastic toxicity in zebrafish, but the most relevant is considered to be oxidative stress, which can interfere with normal nervous system function and energy metabolism [50,141]. Microplastics have been shown to cause oxidative damage in specific regions of the brain, posing a risk to development, including neurodevelopment [8,142], which can lead to an imbalance between ROS production and the antioxidant capacity to scavenge them [49], thus maintaining ongoing oxidative stress. For example, zebrafish exposed to polystyrene microplastics had significantly increased ROS levels and altered CAT, SOD and GPx expression [5].…”