Polyamide-66 microplastics and early-onset ischemic stroke: a systems toxicology, multi-omics, and molecular dynamics...

Rates of early-onset ischemic stroke (EOS) are rising even as incidence falls at older ages. Microplastics have recently been identified as a novel stroke risk factor, and among polymers detected in human arterial thrombi from ischemic stroke, polyamide-66 (PA66) microplastics show the highest detection frequency, with microplastic burden positively correlating with stroke severity. Here, using an integrative in silico framework, we integrate systems toxicology with multi-omics causal inference to map PA66-brain pathways in EOS. Target prediction for PA66 combined with curated stroke genes yielded 12 shared proteins enriched in platelet-endothelial and blood-brain barrier pathways. Brain protein-QTL two-sample Mendelian randomization (MR) identified 43 EOS-associated proteins (20 risk, 23 protective); intersecting with the 12 candidates prioritized a single overlap, EPHX2. Higher genetically proxied brain EPHX2 associated with lower EOS risk (odds ratio, OR 0.84; 95% CI 0.71-0.98), with the strongest signal for small-artery occlusion (OR 0.50; 0.26-0.96). Cell type-resolved sc-eQTL MR supported an astrocytic association (EPHX2 expression in astrocytes OR 0.925; 0.868-0.986; P = 0.016). Two-step MR implicated metabolites downstream of EPHX2-glycosyl-N-ceramide (d18:1/24:1) increased with brain EPHX2 (OR 1.205; P = 0.0073) and were inversely associated with EOS due to small-artery occlusion (OR 0.563; P = 0.049). Molecular docking placed PA66 in the canonical inhibitor pocket of soluble epoxide hydrolase, and 100-ns molecular dynamics supported a stable, pocket-bound pose. Mouse-model phenome queries for Ephx2 knockout highlighted Gene Ontology shifts in hydrolase activity, lipid metabolism and homeostasis, consistent with disrupted lipid-epoxide signaling relevant to neurovascular integrity. Single-cell RNA-seq in young-mouse stroke datasets localized Ephx2 to astrocytes and showed post-stroke downregulation. Together, these findings nominate an astrocytic EPHX2-sphingolipid axis as a plausible route by which PA66 microplastics may promote premature stroke, providing a mechanistic basis for hazard assessment and mitigation.