Mechanisms of micro- and nanoplastics on blood-brain barrier crossing and neurotoxicity: Current evidence and future perspectives

Micro- and nanoplastics (MNPs), as emerging global pollutants, pose increasing threats to ecological environments and human health due to their widespread distribution and potential toxicity. Recent studies have demonstrated that MNPs not only enter the human body through multiple pathways but may also cross the blood-brain barrier (BBB), causing irreversible toxic damage to the central nervous system (CNS). This review summarizes the possible mechanisms of MNPs crossing the BBB, including the disruption of tight junctions and adherens juctions, paracellular transport, and endocytosis pathways. We focused on investigating the key roles of oxidative stress, inflammatory responses, mitochondrial dysfunction, and iron metabolism disorders in MNP-induced neurotoxicity, and discovered significant interconnections among these mechanisms. Furthermore, as carriers of pollutants, MNPs can facilitate co-exposure with other environmental contaminants such as heavy metals and persistent organic pollutants, producing synergistic toxic effects that further aggravate neurological damage. This review synthesizes the main research progress in this field, evaluates the potential toxicological impacts of MNPs on the CNS, and identifies key scientific questions that need to be addressed in future research, thereby providing theoretical foundations for in-depth studies of MNP neurotoxicity mechanisms and risk assessment.