Abstract TP233: Activation Of Alpha 7 Nicotinic Acetylcholine Receptor Protects The Ischemic Brain Via Reductions In Jak2/stat3 Signaling In Mice.

Abstract

Introduction: The alpha7 nicotinic acetylcholine receptor (α7nAChR) is the principal mediator of the cholinergic anti-inflammatory pathway (CAP). CAP is mediated through several signaling pathways, including the JAK2/ STAT3 pathway. Studies have shown decrease in brain α7nAChR and increase in phosphorylation (p) of JAK2 and STAT3 expression after stroke. Increase JAK2/STAT3 signaling induces expression of high mobility group box 1 (HMGB1) and receptor for advanced glycation end products (RAGE), which promotes release of cytokines. Pharmacological activation of α7nAChR reduced microglial activation and inflammatory cytokines and improved functional outcomes after experimental stroke. However, little is known about how the activation of α7nAChR modulates JAK2/STAT3 signaling after stroke. Hypothesis: We hypothesized α7nAChR activation by PNU120596 (PNU), an allosteric modulator will decrease JAK2/STAT3 signaling and improve neurological deficits (ND) after stroke. Methods: Young (8-12 weeks, n=5-6) male mice underwent 60-minute middle cerebral artery occlusion (MCAo) or sham surgery and euthanized at 24 hours. In second cohort (n=5-6), PNU or vehicle was administered for 3 consecutive days. One hour after the last injection, MCAo or sham surgery was done. Twenty-four hours after MCAo, body weight, ND scores were recorded and brains harvested for western blotting. Brain α7nAChR, pSTAT3, HMGB1 and RAGE expression was determined. Results: At 24 hours after MCAo, the brain expression of α7nAChR decreased (p=0.006) while pSTAT3 expression increased (p=0.001) as compared to sham. PNU treatment prevented a decrease in α7nAChR expression in the brain (p=0.017) and decreased pSTAT3 expression (p=0.005) compared to the vehicle group after MCAo. No difference in the HMGB1 expression was seen between groups. An increase in RAGE expression was observed in vehicle MCAo (p=0.006) compared to sham. A decline (p=0.08) in RAGE expression in PNU MCAo compared to vehicle MCAo was observed. NDS and percent body weight loss were lower in the PNU MCAo compared to vehicle MCAo. Conclusions: Activation of α7nAChR downregulated inflammatory JAK2/STAT3-HMGB1/RAGE signaling and may be a druggable target to improve recovery after stroke.