Pharmacological activation of GPR55 improved cognitive impairment, neuroinflammation, oxidative stress and apoptosis induced by lipopolysaccharide in mice

Abstract

BackgroundNeuroinflammation, oxidative stress and apoptosis are implicated in the pathogenesis of Alzheimer’s disease (AD). The purpose of the present study was to investigate the neuroprotective effects and possible mechanism of G-protein coupled receptor 55 (GPR55) agonist, O-1602, on lipopolysaccharide (LPS)-induced cognitive deficits in mice. MethodsICR mice were treated with intracerebroventricular (i.c.v.) injection of LPS. Cognitive tests were performed, including the open field, Morris water maze, novel object recognition, and passive avoidance tests. The expression of GPR55, NF-κB p65, caspase-3, Bax and Bcl-2 were examined in the hippocampus by western blotting. Pro-inflammatory cytokines and microglia were detected by ELISA kit and immunohistochemical analyses, respectively. The malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity were examined by assay kits. Furthermore, TUNEL-staining was used to detect neuronal apoptosis.ResultsI.c.v. injection of LPS exhibited impaired performance in the behavior tests, which were ameliorated by O-1602 treatment(2.0 or 4.0 μg/mouse, i.c.v.). Importantly, O-1602 reversed GPR55 down-regulation, decreased the expression of NF-κB p65, and suppressed the accumulation of pro-inflammatory cytokines and microglia activation, decreased malondialdehyde (MDA) level, and increased superoxide dismutase (SOD) activity. In addition, O-1602 also significantly decreased Bax and increased Bcl-2 expression as well as decreased caspase-3 activity and TUNEL-positive cells, suppressed neuronal apoptosis in the hippocampus of LPS-treated mice.Conclusionswe conclude that O-1602 may ameliorate LPS-induced cognition deficits via inhibiting neuroinflammation, oxidative stress and apoptosis mediated by NF-κB signaling in mice.