Microplastics and the gut-brain axis: Unraveling neurotoxic mechanisms and health implications

Microplastics (MPs) are emerging environmental contaminants with increasing global prevalence, leading to inevitable human exposure through ingestion, inhalation, and dermal absorption. Despite the protective role of the blood-brain barrier (BBB), MPs can translocate and accumulate in the brain, raising concerns about their potential neurotoxicity. This review systematically evaluates the neurotoxic mechanisms of MPs, emphasizing their occurrence in the gastrointestinal tract and interaction with the gut-brain axis. MPs can disrupt intestinal barrier integrity, alter gut microbiota composition, and induce systemic inflammation, ultimately affecting neurotransmitter homeostasis. These disturbances may propagate to the central nervous system through neuroinflammatory pathways, oxidative stress, and dysregulated neurotransmission. Additionally, we discuss potential mechanisms of BBB penetration by MPs and their implications for neurodegenerative and neurodevelopmental disorders. It also highlights environmental exposure risks, technological challenges in assessing MPs’ toxicity in real-world conditions, and current research gaps. We emphasize the urgent need for human-based studies to elucidate the long-term health risks associated with MPs exposure, and implementing comprehensive strategies and policies to reduce reliance on conventional plastics and promote sustainable material alternatives can serve as an effective approach to mitigating MPs consumption.