A Study On Mechanism Xanthoceraside Anti-Alzheimer Inflammation

Aim:Xanthoceraside is a novel triterpenoid saponin extracted from the shell of the fruit of Xanthoceras sorbifolia Bunge. Our previous study showed that xanthoceraside could significantly improve learning and memory impairment in several Alzheimer’s disease (AD) animal models. In this study, we further investigate the effect of xanthoceraside on AD model in vitro and in vivo according to inflammation hypothesis, which aims to explore its anti-AD effects and possible related mechanisms of action.Methods:①We investigated the effect of xanthoceraside on Aβ25-35/IFN-γ-induced microglia activation. The NO production was measured by Griess regent. The levels of IL-1β and TNF-a protein expression were measured by ELISA assay according to the manufacturer’s instructions; NF-κB P65nuclear translocation were measured with the immunofluorescence assay, the expression of iNOS、COX-2、 NF-κB and MAPKs were measured with western blot assay; iNOS、COX-2and TLR2mRNA expression were measured with RT-PCR.②We studied the effect of xanthoceraside on learning and memory impairments in mice induced by intracerebroventricular (i.c.v.) injection of the aggregated Aβ by using Y-maze and Morris water-maze test. The expression of CD11b in the hippocampus and cortex of mice were measured with immunohistochemistry assay; IL-6and IL-4protein expression were measured with ELISA assay according to the manufacturer’s instructions; The expression of iNOS、COX-2、NF-κB and MAPKs were measured with western blot assay; iNOS、COX-2and TLR2mRNA expression were measured with RT-PCR.Results:①Compared with model group, Pretreatment with xanthoceraside (0.01,0.1μM) significantly suppressed the increase of NO, TNF-α and IL-1β production inprimary microglia and N9microglia, respectively, down-regulated TNF-α and IL-1β mRNA expression, decreased Aβ25.35/IFN-γ-induced iNOS and COX-2protein and mRNA expression in a concentration-dependent manner; Xanthoceraside inhibited the AP25-35/IFN-γ-induced translocation of NF-κB p50and p65into the nucleus, blocked IκB degradation and increased IKK level. Pretreatment with xanthoceraside significantly attenuated the Aβ25-35/IFN-y-induced phosphorylation of ERK, JNK and p38, whereas their non-phosphorylated forms were not changed, and decreased TLR2gene expression. Xanthoceraside protected neuron damage by the inhibition of microglia activation.②Compared with model group, xanthoceraside (0.08～0.32mg/kg) significantly decreased the escape latency and swimming distance in Morris-water maze test, and increased the swimming time and percentage of the swimming distance in the fourth quadrant where the platform had been locatedin the probe test; Xanthoceraside increased the percentage of alternation behaviors in Y-maze test; Xanthoceraside suppressed the release of IL-6and increased the IL-4production, decrease in CD11b positive particles in both cerebral cortex and hippocampus, attenuated iNOS and COX-2protein and mRNA expression, inhibited the translocation of NF-κB p50and p65into the nucleus, attenuated the phosphorylation of ERK, JNK and p38; and decreased TLR2gene expression.Conclusion:Xanthoceraside has the effect of improving learning and memory impairment in mice induced by i.c.v. of Aβ and inhibited pro-inflammation expression in Aβ25-35/IFN-γ-stimulated microglia via TLR2/MAPKs and NF-κB pathways. The neuroprotective effects of xanthoceraside may include the inhibition of pro-inflammation and TLR2expression, and attenuated the NF-κB and MAPKs activity. Therefore, xanthoceraside may provide a useful therapeutic strategy for the treatment of AD.