Anti-Inflammatory Effects of alpha-Galactosylceramide Analogs in Activated Microglia: Involvement of the p38 MAPK Signaling Pathway

Abstract

Microglial activation plays a pivotal role in the development and progression of neurodegenerative diseases. Thus, anti-inflammatory agents that control microglial activation can serve as potential therapeutic agents for neurodegenerative diseases. Here, we designed and synthesized alpha-galactosylceramide (alpha-GalCer) analogs to exert anti-inflammatory effects in activated microglia. We performed biological evaluations of 25 alpha-GalCer analogs and observed an interesting preliminary structure-activity relationship in their inhibitory influence on NO release and TNF-alpha production in LPS-stimulated BV2 microglial cells. After identification of 4d and 4e as hit compounds, we further investigated the underlying mechanism of their anti-inflammatory effects using RT-PCR analysis. We confirmed that 4d and 4e regulate the expression of iNOS, COX-2, IL-1 beta, and IL-6 at the mRNA level and the expression of TNF-alpha at the post-transcriptional level. In addition, both 4d and 4e inhibited LPS-induced DNA binding activities of NF-kappa B and AP-1 and phosphorylation of p38 MAPK without affecting other MAP kinases. When we examined the anti-inflammatory effect of a p38 MAPK-specific inhibitor, SB203580, on microglial activation, we observed an identical inhibitory pattern as that o