This hypothesis proposes that CYP2J2-derived DHA epoxides primarily function by promoting microglial M2 polarization rather than directly protecting synaptic membranes from Aβ-induced rigidification. Microglia are the primary phagocytic cells responsible for Aβ clearance, and their dysfunction contributes significantly to Alzheimer's disease pathogenesis. Evidence suggests that DHA epoxides, particularly 19,20-EpDPE, activate PPAR-γ signaling pathways that promote anti-inflammatory M2 microglial phenotypes (pmid:28483571). M2-polarized microglia exhibit enhanced phagocytic capacity and produce anti-inflammatory cytokines like IL-10 and TGF-β, facilitating more efficient Aβ clearance compared to pro-inflammatory M1 microglia. Supporting this mechanism, 5xFAD mice supplemented with DHA show increased microglial IL-10 expression and reduced TNF-α levels alongside improved Aβ clearance (pmid:29982765). The microglial target explains why sEH inhibition proves beneficial: stabilizing CYP2J2-derived epoxide levels maintains sustained microglial M2 polarization signals.

This hypothesis proposes that CYP2J2-derived DHA epoxides primarily function by promoting microglial M2 polarization rather than directly protecting synaptic membranes from Aβ-induced rigidification. Microglia are the primary phagocytic cells responsible for Aβ clearance, and their dysfunction contributes significantly to Alzheimer's disease pathogenesis. Evidence suggests that DHA epoxides, particularly 19,20-EpDPE, activate PPAR-γ signaling pathways that promote anti-inflammatory M2 microglial phenotypes (pmid:28483571). M2-polarized microglia exhibit enhanced phagocytic capacity and produce anti-inflammatory cytokines like IL-10 and TGF-β, facilitating more efficient Aβ clearance compared to pro-inflammatory M1 microglia. Supporting this mechanism, 5xFAD mice supplemented with DHA show increased microglial IL-10 expression and reduced TNF-α levels alongside improved Aβ clearance (pmid:29982765). The microglial target explains why sEH inhibition proves beneficial: stabilizing CYP2J2-derived epoxide levels maintains sustained microglial M2 polarization signals. However, critical gaps remain: the specific epoxide species responsible for microglial modulation are poorly characterized, and the temporal dynamics of M2 polarization relative to Aβ burden reduction remain unclear. Additionally, chronic M2 activation might impair other microglial functions, such as synaptic pruning, potentially causing unintended neurological consequences. The rapid sEH-mediated metabolism of epoxides (2-4 hour half-lives) still presents pharmacokinetic challenges, requiring sustained sEH inhibition with compounds like EC-5026 or GSK225629 for therapeutic efficacy. This microglial-centered mechanism provides a distinct therapeutic angle focusing on neuroinflammation resolution rather than membrane biophysics.