Excessive microglial activation-mediated neurotoxicity has been implicated in playing a crucial role in the pathogenesis of
stroke and
neurodegenerative diseases. Therefore, much attention has been paid to therapeutic strategies aimed at suppressing neurotoxic microglial activation. The microglial regulatory mechanism of methyl
lucidone, a cyclopentenedione isolated from the stem bark of Lindera erythrocarpa Makino, was investigated in the present study. Methyl
lucidone treatment (0.1-10 μM) significantly inhibited
lipopolysaccharide (LPS, 100 ng/ml, 24 h)-stimulated
nitric oxide (NO) production in a dose-dependent manner in both primary cortical microglia and BV-2 cell line. Moreover, it strongly inhibited LPS-stimulated secretion of pro-inflammatory
cytokines, such as
interleukin 6 (IL-6) and
tumor necrosis factor α (TNF-α). Methyl
lucidone treatment markedly induced down-regulation of LPS-induced nuclear translocation of nuclear factor κB (NF-κB) through preventing the degradation of the inhibitory
protein IκBα. In addition, phosphorylation of Akt and
mitogen-activated protein kinases (MAPKs) such as
extracellular signal-regulated kinase (ERK) and p38
kinases were also suppressed by methyl
lucidone. The cell viabilities of HT-22 neurons were significantly attenuated by treatment of the
conditioned media containing neurotoxic secretary molecules from LPS-stimulated microglia. However, methyl
lucidone significantly blocked neuronal cell death induced by microglial
conditioned media. These
neuroprotective effects of methyl
lucidone were also confirmed in a neuron-microglia co-culture system using EGFP-transfected B35
neuroblastoma cell line. Taken together, these results suggest that methyl
lucidone may have a neuroprotective potential via inhibition of neurotoxic microglial activation implicated in neurodegeneration.