Attenuation of neonatal ischemic brain damage using a 20‐HETE synthesis inhibitor

Abstract

20-hydroxyeicosatetraenoic acid (20-HETE) is a cytochrome P450 (CYP) metabolite of arachidonic acid that that contributes to infarct size following focal cerebral ischemia. However, little is known about the role of 20-HETE in global cerebral ischemia or neonatal hypoxia-ischemia (H-I). The present study examined the effects of blockade of the synthesis of 20-HETE with HET0016 in neonatal piglets after H-I to determine if it protects highly vulnerable striatal neurons. Administration of HET0016 after H-I improved early neurological recovery and protected neurons in putamen after 4 days of recovery. HET0016 had no significant effect on cerebral blood flow. CYP 4A immunoreactivity was detected in putamen neurons, and direct infusion of 20-HETE in the putamen increased phosphorylation of Na+,K+-ATPase and NMDA receptor NR1 subunit selectively at PKC-sensitive sites but not at PKA-sensitive sites. HET0016 selectively inhibited the H-I–induced phosphorylation at these same sites at 3 h of recovery and improved Na+,K+-ATPase activity.At 3 h, HET0016 also suppressed H-I–induced Erk1/2 activation and protein markers of nitrosative and oxidative stress. Thus, 20-HETE can exert direct effects on key proteins involved in neuronal excitotoxicity in vivo and contributes to neurodegeneration after global cerebral ischemia in immature brain.

Increase of 20-HETE Synthase after Brain Ischemia in Rats Revealed by PET Study with 11C-Labeled 20-HETE Synthase-Specific Inhibitor

“…ND, not detected. Recent studies reported that CYP4A immunoreactivity was detected in neurons in hippocampus and putamen (Renic et al, 2012;Yang et al, 2012). In this study, CYP4A immunoreactivity was also detected in neurons in contralateral cortex and striatum.…”

20-Hydroxyeicosatetraenoic Acid Inhibition by HET0016 Offers Neuroprotection, Decreases Edema, and Increases Cortical Cerebral Blood Flow in a Pediatric Asphyxial Cardiac Arrest Model in Rats

“…26,31 In other studies, 20-HETE inhibition reduced lesion volume and neurodegeneration independent of CBF, suggesting a direct neuroprotective effect of 20-HETE inhibition. 17,18,32 In a global cerebral ischemia model in immature piglets similar in some ways to our model, Yang et al 17 showed direct neuroprotection after CA in piglets treated with HET0016. In that report, focal cortical CBF measured by laser Doppler was not affected by treatment with HET0016 at 5 minutes after resuscitation.…”

“…In our model, HET0016 was administered at resuscitation (versus 5 minutes after resuscitation in the other study), suggesting that inhibition of 20-HETE immediately on reperfusion might be necessary to inhibit the cascade of events that occurs at reperfusion. The dose of HET0016 was 10-fold lower in our study, 17 and it is possible that a higher dose of HET0016 may lose selectivity for inhibition of CYP4A/4 F enzymes and thus inhibit CYP2C/2 J enzymes responsible for synthesis of vasodilatory EETs. Nevertheless, these two studies in global ischemia suggest neuroprotective effects of HET0016 inhibition.…”

“…15 Eicosanoids are also suggested to have direct neuronal effects: inhibition of 20-HETE formation may be neuroprotective, whereas increasing EETs by inhibiting their degradation to dihydroxyeicosatrienoic acids (DHETEs) may be neuroprotective. [16][17][18] Based on the potent vascular effects of CYP eicosanoids, our primary objective was to determine if imbalances of vasoconstrictor and vasodilator CYP eicosanoids are associated with decreased cortical blood flow in a model of pediatric asphyxial CA in 16-to 18-day-old rats. Our secondary objective was to determine whether inhibiting the synthesis of vasoconstrictor 20-HETE improves cortical perfusion, functional outcome, and neurodegeneration, and decreases brain edema after pediatric asphyxial CA.…”

Additive Neuroprotection of a 20-HETE Inhibitor with Delayed Therapeutic Hypothermia after Hypoxia-Ischemia in Neonatal Piglets

“…Such inhibitors have been shown to directly protect hippocampal slice cultures from oxygen-glucose deprivation [18]. CYP 4A is also expressed in striatal neurons of neonatal piglets, and early administration of the 20-HETE synthesis inhibitor N -hydroxy- N ′-(4-n-butyl-2-methylphenyl)formamidine (HET0016) [22] after reoxygenation in a piglet model of hypoxia followed by complete asphyxia partially protected striatal neurons without affecting the recovery of cerebral blood flow [23]. Direct effects of 20-HETE on neuronal signaling are supported by the observed increases in phosphorylation of N-methyl-D-aspartate receptors and Na,K-ATPase during infusion of 20-HETE into piglet putamen and by attenuation of phosphorylation at these same sites by HET0016 administration after HI [23].…”