From gut leakage to memory loss: environmental 2,4-DTBP triggers neuroinflammation through the gut-brain axis in zebrafish.

Despite widespread environmental detection of 2,4-di-tert-butylphenol (2,4-DTBP), its neurotoxic impacts on cognitive behavior remain largely unexplored. In this study, adult zebrafish were exposed to 0.01, 0.1, and 1 μM 2,4-DTBP for 28 days. T-maze testing revealed dose-dependently longer path lengths to the food-baited target zone, indicative of impaired spatial memory. Evans blue extravasation demonstrated that 2,4-DTBP increased blood-brain barrier permeability and bioaccumulated in the zebrafish brain. Ultrastructural analysis confirmed impaired synaptic plasticity and neuron injury. Targeted metabolomics identified six significantly alterated neurotransmitter-related metabolites (threonine, glycine, arginine, aspartic acid, histidine, and tyramine) implicated in neuroinflammation. 2,4-DTBP disrupted intestinal barrier integrity (reduced ZO-1 and occludin) and elevated nitric oxide (NO) levels and expressions of pro-inflammatory cytokines gene (il1b and il6). These gut-derived inflammatory mediators (NO, IL-1β, IL-6, and TNF-α) entered systemic circulation and subsequently translocated into the brain. Decreased brain NF-κB and iNOS expression indicated that neuroinflammation was driven by a gut-to-brain inflammatory cascade rather than de novo cerebral synthesis. Although bdnf and mmp9 transcripts were up-regulated, the mature brain-derived neurotrophic factor (mBDNF) levels were not proportionally increased, indicating impaired neurorepair. Our findings provide novel mechanistic insights into the potential contribution of environmental SPA contaminants to the pathogenesis of neurodegenerative disorders.