The Impact of Environmental Enrichment on Zebrafish Exposure to Human-relevant Mixtures of Endocrine Disrupting Chemicals

Tarzyna Niedziałkowska^*
*Correspondence: Tarzyna Niedziałkowska, Department of Industrial Microbiology and Biotechnology, University of Lodz, Łódź, Poland, Email:

Introduction

Endocrine Disrupting Chemicals (EDCs) are substances that can interfere with the hormonal systems of animals, including humans, potentially leading to adverse health effects. These chemicals, found in various industrial, agricultural and consumer products, pose a significant threat to both environmental and human health. Among the diverse range of organisms used to study EDCs, zebrafish (Danio rerio) have emerged as a prominent model due to their genetic similarity to humans, transparency during early development and well-characterized hormonal systems. Environmental enrichment refers to the enhancement of an organism's living environment to promote behavioral and physiological well-being. This concept, originally applied to captive animals to reduce stress and improve welfare, has increasingly been recognized for its potential to influence experimental outcomes in aquatic models. The interplay between environmental enrichment and EDC exposure in zebrafish is an emerging area of research, with implications for understanding how ecological and behavioral factors can modulate the effects of harmful chemicals. This article reviews current research on the effects of environmental enrichment on zebrafish exposed to human-relevant mixtures of EDCs. By examining relevant literature and discussing the findings, we aim to shed light on how environmental factors might influence the impact of EDCs on zebrafish and, by extension, on other species, including humans [1].

Description

Endocrine disrupting chemicals and zebrafish models

EDCs can mimic or interfere with hormonal signals, affecting reproductive, developmental and metabolic processes. Common EDCs include Bisphenol A (BPA), phthalates and pesticides. Zebrafish, with their genetic and physiological similarities to humans, have become a valuable model for studying these chemicals. Studies have demonstrated that zebrafish exposed to EDCs can exhibit a range of endocrine-related effects, including altered sexual development, reproductive dysfunction and behavioral changes. Research has shown that zebrafish are particularly sensitive to EDCs due to their rapid development and high fecundity. For instance, BPA has been found to cause developmental abnormalities and disrupt reproductive functions in zebrafish, leading to concerns about its impact on aquatic ecosystems and human health. Similarly, phthalates and other chemical mixtures have been shown to affect zebrafish behavior and physiology, highlighting the need for comprehensive studies to understand these effects fully [2].

Environmental enrichment and its benefits

Environmental enrichment involves modifications to an animal's habitat to enhance its sensory, social and physical experiences. In zebrafish, enrichment can include structural changes like additional hiding spaces, changes in water flow and the introduction of visual or olfactory stimuli. Enrichment is known to reduce stress and improve overall health in various species, including mammals and fish. In zebrafish, environmental enrichment has been shown to influence behavior and physiology. Enriched environments can lead to increased exploratory behavior, improved social interactions and enhanced cognitive function. For example, studies have demonstrated that zebrafish in enriched environments exhibit more natural behaviors compared to those in standard laboratory conditions, which can affect their responses to stress and environmental challenges.

Interaction between environmental enrichment and EDC exposure

The interaction between environmental enrichment and EDC exposure in zebrafish is a relatively new research area. Initial studies suggest that environmental enrichment might modulate the impact of EDCs, potentially altering the severity or nature of their effects. Enriched environments could help mitigate some of the adverse effects of EDCs by reducing stress or providing alternative coping mechanisms. For instance, research has indicated that zebrafish in enriched environments may exhibit different behavioral responses to EDCs compared to those in standard environments. Enrichment may also influence the physiological pathways affected by EDCs, potentially leading to less pronounced or different types of endocrine disruptions. This suggests that environmental factors should be considered when assessing the impacts of EDCs in experimental settings [1]. Environmental enrichment may influence the effects of EDCs through several mechanisms. One key factor is stress reduction. EDCs often exacerbate stress responses and enriched environments can help buffer these effects by providing a more stimulating and less stressful habitat. Reduced stress levels might, in turn, lead to less severe endocrine disruptions or alter the way EDCs affect hormonal systems. Another mechanism is behavioral modulation. Enriched environments can encourage natural behaviors, which might mitigate some of the behavioral changes induced by EDCs. For example, zebrafish in enriched environments may engage more in social interactions or exploratory behavior, which can help counteract some of the disruptive effects of EDCs on behavior.

Physiological responses are also crucial. Environmental enrichment may influence how zebrafish metabolize and respond to EDCs. For instance, enhanced sensory experiences or physical activity might alter the absorption, distribution, metabolism and excretion of EDCs. This could lead to differences in the internal concentrations of these chemicals and, consequently, their impact on endocrine systems [4,5].

Implications for research and environmental policy

Understanding the interaction between environmental enrichment and EDC exposure has important implications for research design and environmental policy. In experimental settings, incorporating environmental enrichment could lead to more accurate assessments of EDCs' effects, reflecting more natural and ecologically relevant conditions. This approach may improve the predictive value of animal studies for human health risks and contribute to more effective regulatory measures. From a policy perspective, recognizing the role of environmental factors in modulating EDC effects underscores the importance of considering habitat quality and environmental conditions when assessing chemical exposures. This could lead to more nuanced risk assessments and strategies to protect both wildlife and human populations from the adverse effects of EDCs.

Conclusion

Environmental enrichment represents a promising approach to understanding and potentially mitigating the effects of Endocrine Disrupting Chemicals (EDCs) in zebrafish. By enhancing the living conditions of zebrafish, researchers can gain deeper insights into how EDCs impact endocrine systems and behavior, leading to more accurate risk assessments and improved environmental policies. As research continues to unravel the complexities of how environmental enrichment interacts with EDC exposure, it is crucial to adopt a comprehensive and integrative approach. This will not only advance our knowledge of endocrine disruption but also contribute to the development of strategies to safeguard both ecological and human health. The evolving understanding of these interactions highlights the need for continued exploration and interdisciplinary collaboration to address the challenges posed by EDCs in a rapidly changing world

Acknowledgement

None.

Conflict of Interest

None.

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