Astrocytes play pivotal roles in regulating
glutamate homeostasis at tripartite synapses. Inhibition of soluble
epoxide hydrolase (sEHi) provides neuroprotection by blocking the degradation of
14,15-epoxyeicosatrienoic acid (14,15-EET), a
lipid mediator whose synthesis can be activated downstream from group 1
metabotropic glutamate receptor (mGluR) signaling in astrocytes. However, it is unclear how sEHi regulates
glutamate excitotoxicity. Here, we used three primary rat cortical culture systems, neuron-enriched (NE), astrocyte-enriched glia-neuron mix (GN), and purified astrocytes, to delineate the underlying mechanism by which sEHi and
14,15-EET attenuate excitotoxicity. We found that sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic
acid (AUDA) and
14,15-EET both attenuated
N-methyl-D-aspartate (
NMDA)-induced neurite damage and cell death in GN, not NE, cortical cultures. The anti-excitotoxic effects of
14,15-EET and AUDA were both blocked by the group 1 mGluR5 antagonist
2-methyl-6-(phenylethynyl)pyridine (MPEP), as were their protective effects against
NMDA-disrupted perineuronal astrocyte processes expressing
glutamate transporter-1 (GLT-1) and subsequent
glutamate uptake. Knockdown of sEH expression also attenuated
NMDA neurotoxicity in mGluR5- and GLT-1-dependent manners. The 14,15-EET/AUDA-preserved astroglial integrity was confirmed in
glutamate-stimulated primary astrocytes along with the reduction of the
c-Jun N-terminal kinase 1 phosphorylation, in which the
14,15-EET effect is mGluR5-dependent. In vivo studies validated that sEHi and genetic deletion of sEH (Ephx2-KO) ameliorated excitotoxic
kainic acid-induced seizure, memory impairment, and neuronal loss while preserving GLT-1-expressing perineuronal astrocytes in hippocampal CA3 subregions. These results suggest that
14,15-EET mediates mGluR5-dependent anti-excitotoxicity by protecting astrocytes to maintain
glutamate homeostasis, which may account for the beneficial effect of sEH inhibition in excitotoxic
brain injury and diseases.