Air pollution and Alzheimer disease phenotype deplete esterified proresolving lipid mediator reserves in the brain

BACKGROUNDTraffic-related air pollution (TRAP) is a risk factor for Alzheimer disease (AD), where unresolved brain inflammation has been linked to deficits in the levels of free lipid mediators that enable the resolution of inflammation. It is unknown whether these deficits are due to reductions in esterified lipid pools, the main source of free bioactive proresolving lipids in the brain, and whether they are related AD pathophysiology.METHODSThis unknown was tested by measuring brain esterified lipid mediators and pathogenic markers of AD in TgF344-AD and WT male and female rats exposed to filtered air or TRAP for 14 months; it was also tested in human postmortem prefrontal cortex of individuals with or without AD.RESULTSSignificant reductions in proresolving lipid mediators esterified to neutral lipids and/or phospholipids were seen in AD and TRAP-exposed female rats, where levels were associated with inflammation, synaptic loss, and impaired glucose metabolism. Lower esterified proresolving lipid mediator concentrations were associated with older age in prefrontal cortex of humans with AD compared with controls.CONCLUSIONImpaired resolution in AD is due to depletion of esterified proresolving lipid pools that supply the brain with free bioactive mediators involved in inflammation resolution. TRAP exposure alters the same esterified resolution pathways, reflecting convergent mechanisms underlying AD.