α7 nicotinic acetylcholine receptor agonism confers neuroprotection through GSK-3β inhibition in a mouse model of intracerebral hemorrhage.

BACKGROUND AND PURPOSE Perihematomal edema formation and consequent cell death contribute to the delayed brain injury evoked by intracerebral hemorrhage (ICH). We aimed to evaluate the effect of α7 nicotinic acetylcholine receptor (α7nAChR) stimulation on behavior, brain edema, and neuronal apoptosis. Furthermore, we aimed to determine the role of the proapoptotic glycogen synthase kinase-3β (GSK-3β) after experimental ICH. METHODS Male CD-1 mice (n=109) were subjected to intracerebral infusion of autologous blood (n=88) or sham surgery (n=21). ICH animals received vehicle administration, 4 or 12 mg/kg of α7nAChR agonist PHA-543613, 12 mg/kg of α7nAChR agonist PNU-282987, 6 mg/kg of α7nAChR antagonist methyllycaconitine (MLA), 15 μg/kg of phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, or PHA-543613 combined with MLA or wortmannin. Behavioral deficits and brain water content were evaluated at 24 and 72 hours after surgery. Western blotting and immunofluorescence staining were used for the quantification and localization of activated Akt (p-Akt), GSK-3β (p-GSK-3β), and cleaved caspase-3 (CC3). Neuronal cell death was quantified through terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). RESULTS α7nAChR stimulation improved neurological outcome and reduced brain edema at 24 and 72 hours after surgery (P<0.05 compared with vehicle). Furthermore, PHA-543613 treatment increased p-Akt and decreased p-GSK-3β and CC3 expressions in the ipsilateral hemisphere (P<0.05, respectively), which was reversed by MLA and wortmannin. P-Akt, p-GSK-3β, and CC3 were generally localized in neurons. PHA-543613 reduced neuronal cell death in the perihematomal area (P<0.05). CONCLUSIONS α7nAChR stimulation improved functional and morphological outcomes after experimental ICH in mice. PHA-543613 reduced the expression of proapoptotic GSK-3β through the PI3K-Akt signaling pathway.