Microbiota-derived TMAO links PM2.5 exposure to cognitive impairment: A gut liver brain axis

Although fine particulate matter (PM2.5) is linked to cognitive impairment, the mechanistic links between pulmonary exposure and neurodegeneration remain poorly understood. This study investigates the role of the gut-liver-brain axis in mediating PM2.5-induced neurotoxicity. We demonstrate that three weeks of intratracheal PM2.5 instillation in mice causes significant memory deficits, impaired hippocampal adult neurogenesis, and reduced synaptic plasticity in both sexes. Metagenomic analysis revealed that PM2.5 alters gut microbiota composition, specifically by upregulating pathways involved in trimethylamine (TMA) synthesis. This microbial shift led to a systemic increase in the metabolite trimethylamine N-oxide (TMAO) and its accumulation in the hippocampus. Mechanistic experiments revealed that TMAO drives neurotoxicity by activating the hippocampal PERK-mediated endoplasmic reticulum (ER) stress pathway. Critically, these deficits were reversed by suppressing hepatic TMAO production via either pharmacological inhibitors or genetic knockdown. Additionally, hippocampal-specific PERK silencing or dietary resveratrol intervention attenuated hippocampal ER stress, thereby protecting against PM2.5-induced cognitive and hippocampal impairments. These results identify the microbial metabolite TMAO as a key mediator of air pollution-related neurotoxicity and highlight the gut-liver-brain axis as a promising therapeutic strategy to counteract the neurological impacts of air pollution.