The Protective Effect of Epoxyeicosatrienoic Acids on Cerebral Ischemia/Reperfusion Injury is Associated with PI3K/Akt Pathway and ATP-Sensitive Potassium Channels

Abstract

Epoxyeicosatrienoic acids (EETs), the cytochrome P450 epoxygenase metabolite of arachidonic acid, have been demonstrated to have neuroprotective effect. Phosphatidylinositol 3-kinase (PI3K)/Akt and ATP-sensitive potassium (KATP) channels are thought to be important factors that mediate neuroprotection. However, little is known about the role of PI3K/Akt and KATP channels in brain after EETs administration. In vitro experiment, oxygen-glucose deprivation (OGD) was performed in cultured rat cerebral microvascular smooth muscle cells (SMCs) for 4 h. The effect of 14,15-EET on OGD induced cell apoptosis was examined after reoxygenation. Western blot and real-time PCR were used to analyze the expression of Kir6.1, SUR2B (two subunits of KATP channels) and p-Akt on cerebral microvascular SMCs. In vivo experiments, we use 12-(3-adamantan-1-yl-ureido)-dodecanoic acid [AUDA, a specific soluble epoxide hydrolase (sEH) inhibitor] to confirm the effect of EETs indirectly. Rats were injected intraperitoneally with AUDA before being subjected to middle cerebral artery occlusion (MCAO). We detected the apoptosis and the expression of p-Akt, Kir6.1 and SUR2B in ischemic penumbra. The results showed that EETs protect against cerebral ischemia/reperfusion (I/R) injury and upregulated the expression of p-Akt and Kir6.1 in both of ischemic penumbra and OGD induced cerebral microvascular SMCs. The protective effect was inhibited by Wortmannin (a specific PI3K inhibitor) and Glib (a specific KATP inhibitor) respectively in vitro experiment. In conclusion, these results suggested that the protective effect of EETs on cerebral I/R injury is associated with PI3K/Akt pathway and KATP channels. Furthermore, the PI3K pathway may contribute to mediating KATP channels on cerebral microvascular SMCs.

The importance of the excitatory amino acid transporter 3 (EAAT3)

“…For clarity, we will use the EAAT1 – 5 nomenclature for the proteins of this family from any organism in this review. While the EAATs share ~35–65% amino acid identity, the different subtypes have distinct cellular and developmental expression profiles and some unique pharmacology (Danbolt, 2001, Amara and Fontana, 2002, Jensen et al, 2015), and have different implications for various diseases (Bianchi et al, 2014, Jensen et al, 2015, Šerý et al, 2015). …”

Purinergic Mechanisms and Prostaglandin E Receptors Involved in ATP-Induced Relaxation of Porcine Retinal Arterioles in vitro

“…Although the effects of the used EP receptor antagonists may not have been specific, the conclusions are supported by the fact that two different EP 4 receptor antagonists resulted in the same effect at intermediate ATP concentrations, whereas EP 1 and EP 2 receptor antagonists had no effect at these concentrations. Future studies should also investigate the possible involvement of other eicosanoids such as epoxyeicosatrienoic acids which has been shown to affect ATP-induced changes in vascular function in the brain [32]. …”

Cytochrome P450 eicosanoids in cerebrovascular function and disease

“…14,15-EET protects cultured rat brain VSMCs exposed to OGD in a dose-dependent manner (Qu et al, 2015), with an associated increase in phosphorylation of Akt and Kir6.1 ATP-sensitive potassium channel (KATP) subunit. This protective effect is blocked by inhibiting Akt or KATP, indicating that 14,15-EET protects against cell death via activation of Akt and opening KATP channels.…”

“…Pharmacological sEH inhibition, using AUDA, AUDA-BE, or t-AUCB. is protective following MCAO, reducing apoptosis and infarct volume as well as improving neurological function (Zhang et al, 2007; Qu et al, 2015; Zuloaga et al, 2014). This protection is likely due to increased endogenous EETs levels since protection is absent upon inhibition of P450 epoxygenase.…”

“…In rats treated with AUDA, cellular apoptosis is reduced, (Qu et al, 2015) while phosphorylation of Akt and the ATP-sensitive potassium channel subunit Kir6.1 are increased in the ischemic penumbra, both of which have been implicated in mediating the anti-apoptotic effects of EETs in cerebral VSMCs and astrocytes (Qu et al, 2015; Li et al, 2012). BDNF is also increased in astrocytes of sEH null mice, with protection being lost upon inhibition of TrkB receptors, implicating the BDNF/TrkB pathway in mediating the protection observed, mirroring in vitro studies demonstrating involvement of this pathway in astrocyte and neuronal protection from OGD (Yuan et al, 2016).…”