The Early Activation of PI3K Strongly Enhances the Resistance of Cortical Neurons to Hypoxic Injury via the Activation of Downstream Targets of the PI3K Pathway and the Normalization of the Levels of PARP Activity, ATP, and NAD+

Abstract

Phosphatidylinositol 3-kinase (PI3K) plays several important roles in neuronal survival. Activation of the pathway is essential for the neuroprotective mechanisms of materials that shield neuronal cells from many stressful conditions. However, there have been no reports to date about the effect of the direct activation of the pathway in hypoxic injury of neuronal cells. We investigated whether the direct activation of the PI3K pathway inhibits neuronal cell death induced by hypoxia. Primary cultured cortical neurons (PCCNs) were exposed to hypoxic conditions (less than 1 mol% O2) and/or treated with PI3K activator. Hypoxia reduced the viability of PCCNs in a time-dependent manner, but treatment with PI3K significantly restored viability in a concentration-dependent manner. Among the signaling proteins involved in the PI3K pathway, those associated with survival, including Akt and glycogen synthase kinase-3β, were decreased shortly after exposure to hypoxia and those associated with cell death, including BAX, apoptosis-induced factor, cytochrome c, caspase-9, caspase-3, and poly(ADP-ribose) polymerase (PARP), were increased. However, treatment with PI3K activator normalized the expression levels of those signaling proteins. PARP activity and levels of ATP and NAD(+) altered by hypoxia were also normalized with direct PI3K activation. All these findings suggest that direct and early activation is important for protecting neuronal cells from hypoxic injury.

Neuroprotective effects of a novel poly (ADP‐ribose) polymerase‐1 inhibitor, JPI‐289, in hypoxic rat cortical neurons

“…Primary cultured cortical neurons (PCCNs) were obtained from the cerebral cortex of fetal Sprague‐Dawley rats (16 days of gestation) as previously described . To induce hypoxia, we used an anaerobic chamber (Anaerobic System Model 1025, Thermo Forma, Marietta, OH, USA).…”

“…as previously described. 23 To induce hypoxia, we used an anaerobic chamber (Anaerobic System Model 1025, Thermo Forma, Marietta, OH, USA). To determine the best hypoxic conditions for our experiments, PCCNs were exposed to hypoxia in the anaerobic chamber in a humidified, temperature controlled incubator.…”

Acetylcholine‐dependent upregulation of TASK‐1 channels in thalamic interneurons by a smooth muscle‐like signalling pathway

“…5A). The use of IRS-1-Y608P (10 μM), which activates PI3K by association with the SH2 domains of the p85 subunit Noh et al 2013), confirmed the effect of insulin receptor activation. With IRS-1-Y608P included in the internal solution, the OxoM effect was strongly increased (28.1 ± 2.1%, n = 7; P ANOVA < 0.01, with respect to the OxoM effect in cocktail 1) and the I-V relationship of the OxoM-sensitive current was typical for outwardly rectifying K + channels ( Fig.…”

The role of PI3K/AKT pathway and its therapeutic possibility in Alzheimer's disease

“…In many stressful conditions, the pathway is inhibited and then it is involved in cell death. Describing in detail, ischemia in the brain and oxidative stress inhibit the PI3K/AKT pathway in neurons and neural stem cells and then induce cell death, so there have been a lot of studies to develop the way to protect neurons and neural stem cells by activating the pathway [10][11][12][13]. This phenomenon also happens in amyloid-induced cell death [14,15].…”