14,15-epoxyeicosatrienoic acid promotes production of brain derived neurotrophic factor from astrocytes and exerts neuroprotective effects during ischaemic injury

Aims: 14,15-Epoxyeicosatrienoic acid (14,15-EET) is abundantly expressed in brain and exerts protective effects against ischaemia. 14,15-EET is hydrolysed by soluble epoxide hydrolase (sEH). sEH(-/-) mice show a higher level of 14,15-EET in the brain. Astrocytes play a pivotal role in neuronal survival under ischaemic conditions. However, it is unclear whether the neuroprotective effect of 14,15-EET is associated with astrocytes. Methods: A mouse model of focal cerebral ischaemia was induced by middle cerebral artery occlusion. Oxygen-glucose deprivation/reoxygenation (OGD/R) was performed on cultured murine astrocytes, neurons and a human cell line. Cell viabilities were measured by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay. The mRNA expressions were quantified by real-time PCR. Brain derived neurotrophic factor (BDNF) concentration was measured by ELISA. Protein expressions were quantified by Western blotting. BDNF and peroxisome proliferators-activated receptor gamma (PPAR-gamma) expressions were analysed by confocal microscopy. Results: Decreased infarct volumes, elevated BDNF expression and increased numbers of BDNF/GFAP Glial Fibrillary Acidic Protein double-positive cells were observed in the ischaemic penumbra of sEH(-/-) mice. The decreased infarct volumes of sEH(-/-) mice were diminished by intracerebroventricular injection of a blocker of BDNF receptor. 14,15-EET increases BDNF expression and cell viability of murine astrocytes and U251 cells by BDNF-TrkB Tyrosine receptor kinase-B-extracellular signal-regulated kinase 1/2 signalling during OGD/R. 14,15-EET protects neurons from OGD/R by stimulating the production of astrocyte-derived BDNF. 14,15-EET stimulates the production of astrocyte-derived BDNF through PPAR-c/p-cAMP-response element binding protein signal pathways. Conclusions: Our study demonstrates the importance of 14,15-EET-mediated production of astrocyte-derived BDNF for enhancing viability of astrocytes and protecting neurons from the ischaemic injury and provides insights into the mechanism by which 14,15-EET is involved in neuroprotection.Major National Basic Research Grant of China [2010CB912504, 2014CB542200]; National Natural Science Foundation of China [81171081, 81471254, 81471064]SCI(E)PubMedARTICLErmzheng@pku.edu.cn; sgzhu@bjmu.edu.cn7607-6204