12-hydroxy-5-8-10-14-eicosatetraenoic-acid and Brain-Ischemia

The enzyme 12/15-lipoxygenase (LOX) oxidizes various free fatty acids, including arachidonic acid (AA). In the brain, the principal 12/15-LOX metabolites of AA are 12(S)-HETE and 15(S)-HETE. PPARγ is a nuclear receptor whose activation is neuroprotective through its anti-inflammatory properties. In this study, we investigate the involvement of 12(S)- and 15(S)-HETE in the regulation of PPARγ following cerebral ischemia and their effects on ischemia-induced inflammatory response. We show here the increased expression of 12/15-LOX, predominantly in neurons, and elevated production of 12(S)-HETE and 15(S)-HETE in ischemic brain. The exogenous 12(S)- and 15(S)-HETE increase PPARγ protein level, nuclear translocation, and DNA-binding activity in ischemic rats, suggesting the activation of PPARγ. This effect was further confirmed by showing the increased PPARγ transcriptional activity in primary cortical neurons when incubated with 12(S)- or 15(S)-HETE. Moreover, both 12(S)- and 15(S)-HETE potently inhibited the induction of nuclear factor-κB, inducible NO synthase, and cyclooxygenase-2 in ischemic rats, and elicited neuroprotection. The reversal of the effects of 12(S)- and 15(S)-HETE on pro-inflammatory factors by PPARγ antagonist GW9662 indicated their actions were mediated via PPARγ. Thus, the induction of 12(S)- and 15(S)-HETE during brain ischemia suggests that endogenous signals of neuroprotection may be generated.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Active Transport, Cell Nucleus; Anilides; Animals; Arachidonate 12-Lipoxygenase; Arachidonate 15-Lipoxygenase; Arachidonic Acid; Brain Ischemia; Cell Nucleus; Enzyme Activation; Hydroxyeicosatetraenoic Acids; Male; Neurons; PPAR gamma; Rats; Rats, Sprague-Dawley

The monohydroxylated metabolite of arachidonic acid, 20-hydroxyeicosatetraenoic acid (20-HETE), is a potent vasoconstrictor of cerebral microvessels. 20-HETE formation is substantially elevated in the cerebral spinal fluid (CSF) in the rat subarachnoid hemorrhage (SAH) model. The presence of 20-HETE in human CSF has not been demonstrated. Therefore, it was the purpose of this study to determine if HETE metabolites are present in human CSF after SAH.. CSF samples were collected daily from four SAH patients over 15 days. HETE metabolites were separated by HPLC with identification by ion-trap MS/MS and quantification via single quadrupole MS operating in negative single ion monitoring mode.. Two major metabolites were identified as 12-HETE and 20-HETE. 20-HETE maximal concentrations were 2.9 and 0.7 ng/ml at approximately 70 h in the two patients with symptomatic cerebral vasospasm (SV) after SAH. Concentrations of 12-HETE in these patients peaked at 21.9 ng/ml and 2.8 ng/ml. Concentrations of 20-HETE and 12-HETE were non-detectible in the majority of the samples obtained from two matched SAH patients without SV.. This study is the first to demonstrate that 20-HETE and 12-HETE are present in the CSF of SAH patients at physiologically relevant concentrations. Based on this information future prospective studies will allow for the delineation of the role of these metabolites in the pathogenesis of SAH.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Adult; Aged; Arachidonic Acid; Brain Ischemia; Cerebral Arteries; Cerebrospinal Fluid; Chromatography, High Pressure Liquid; Humans; Hydroxyeicosatetraenoic Acids; Mass Spectrometry; Middle Aged; Neurochemistry; Subarachnoid Hemorrhage; Time Factors; Vasospasm, Intracranial