The suppressive effects of gx-50 on Aβ-induced chemotactic migration of microglia.

Microglia, the main immune cells of the central nervous system (CNS), play a vital role in the development of AD. Once microglia are activated, they migrate to neuritic plaques and persistently release pro-inflammatory mediators that lead to neuroinflammation and neuronal degeneration, accelerating the progression of AD. In this study, we analyzed whether an AD candidate drug, N-[2-(3,4-dimethoxyphenyl)ethyl]-3-phenyl-acrylamide (gx-50), a compound extracted from Sichuan pepper (Zanthoxylum bungeanum), exhibited suppressive effects on the chemotactic migration of microglia induced by Aβ. At first, the effects of gx-50 on the migration of primary cultured microglia to Aβ were detected by transwell assay, and the secretion of chemokine CCL5 was measured by ELISA assay. Then, the release of TGF-β1 was detected by ELISA and quantitative real-time PCR, and the activation of the TGF-β1-Smad2 pathway was analyzed by Western blotting. The LDH assay revealed that cell viability was not affected by gx-50 at concentrations from 0.01 to 100 μM; thus, combined with our previous studies, 1 μM was chosen as the treatment concentration. The cell transwell measurement demonstrated that gx-50 suppressed the chemotactic migration of microglia by nearly 50% and inhibited the increase in CCL5 triggered by Aβ. Moreover, the analysis of the TGF-β1-Smad2 pathway revealed that gx-50 can antagonize Aβ-induced down-regulation of TGF-β1 at both the mRNA and protein levels and stimulate the signal pathway activation. Simultaneously, gx-50 pretreatment also significantly enhanced the phosphorylation of glycogen synthase kinase-3β (GSK-3β), which correlated closely with the migration of microglia. In conclusion, in the presence of Aβ, gx-50 pretreatment inhibited the excessive chemotactic migration of microglia.