This article is available online at http://www.jlr.org to form a series of biologically active lipid mediators ( 1, 2 ). In the CNS, 12/15-LOX expression has been described throughout the cerebrum, basal ganglia, and hippocampus ( 3, 4 ). Arachidonic acid (AA) is an important component of membrane lipids that can activate several signaling pathways directly by itself or by its metabolites ( 5 ). In nervous tissue, the major enzymatic route for AA metabolism is the 12/15-LOX pathway, and the principal metabolites are 12(S)-HETE and 15(S)-HETE ( 3, 4, 6, 7 ). The biological signifi cance of these metabolites of AA is that they have been proposed to play roles as second messengers in synaptic transmission and they are thought to be involved in learning and memory processes ( 8 ). In addition, 12(S)-HETE is known to act as an inhibitory neuromodulator by reducing voltage-sensitive calcium channel activity ( 9 ) and attenuating glutamate release and affi nity to its receptors ( 10-12 ).Brain ischemia triggers the massive release of free fatty acids from membrane stores, such as AA and DHA, and then the accumulation of lipid peroxides. 12/15-LOX is thought to be damaging because of its lipid-oxidizing properties, and the detrimental effects of 12/15-LOX have been documented by demonstrating the protection in the ischemic brain through 12/15-LOX inhibition or gene deletion ( 13-15 ). Several metabolites of 12/15-LOX, however, have neuroprotective and anti-infl ammatory qualities during brain ischemia. For example, 12/15-LOX metabolites derived from DHA and other -3 fatty acids inhibit cerebral ischemia-induced injury (16)(17)(18). This suggests 12/15-LOX and its metabolites may differ in their effects following cerebral ischemia.PPAR ␥ is a member of the nuclear hormone receptor family of ligand-dependent transcription factors.
This work was supported by grants from the National Natural Science Foundation of China (number 81070968 to L.S. and number 81401023 to Y-W.X.) and from the Tianjin Municipal Science and Technology Commission (number 13ZCZDSY01900 to Y.C.). The authors declare no confl icts of interest.
Manuscript received 15 July 2014 and in revised form
12(S)-and 15(S)-HETE activate PPAR ␥ in ischemic brain 503animals survived the MCAO surgical procedure. Rats that did not demonstrate neurological defi cits during 90 min MCAO were excluded from further study. Animals dying prematurely during the reperfusion period or having subarachnoid hemorrhage at postmortem examination were also excluded. Measurements derived from these animals were not included in the present study.
Drug treatmentEicosanoids, 12(S)-HETE and 15(S)-HETE, were products of Cayman Chemical (Ann Arbor, MI) and given 30 min before the onset of MCAO by icv injection. 12(S)-and 15(S)-HETE, supplied in ethanol at 1 mg/ml, were air-dried under a stream of nitrogen and dissolved in a 30% DMSO and 70% isotonic saline solution ( 35 ). Animals received either vehicle (30% DMSO-0.9% saline) or a single dose of 12(S)-or 15(S)-HETE at 10, 15, or 20 g ( ...