Neuroprotective effect of Raphanus sativus var. hortensis f. raphanistroides, in SH-SY5Y cells via regulation of microglial activation

The activation of microglial by external stimuli plays an important role in cell growth and survival; however, overactivated microglia destroy neurons [1,2]. Raphanus sativus var. hortensis f. raphanistroides (a root vegetable from the Brassicaceae family) has been traditionally used as a medicinal food to treat hepatotoxicity or indigestion [3 – 5] it belongs to the Brassicaceae family and is a popular in Asia. Many studies have shown that phenolic compound extracted from radish have anti-inflammatory and anti-cancer effects. However, no study has reported a protective effect on central nervous system. In the current study, we investigated the ability of Methanol extracts (80%) of Korean wild radish (WR), Raphanus sativus var. hortensis f. raphanistroides (a root vegetable from the Brassicaceae family), to control microglial overactivation induced by LPS (2 µg/ml). Microglia cells were treated with WR extract (1, 10, and 50 µg/mL), which produced concentration-dependent decreases in nitric oxide (NO) production and inducible NO synthase expression. The NO level of LPS treated microglia decreased from 23.0µM to 18.2µM by 1 µg/ml of WR extracts. WR extract inhibited inflammatory cytokines, such as interlukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α). Moreover, WR extract inhibited LPS-induced phosphorylation of the p38 kinase. We further found that the conditioned media from cells treated with WR extract +LPS or LPS alone in microglia cells were harvested and used to treat SH-SY5Y human neuroblastoma cells. We confirmed that the conditioned media regulated microglial activation, inhibiting neuronal apoptosis. LPS conditioned media reduced the cell viability to 58% whereas WR+LPS conditioned media treatment produced 86% cell viability in SH-SY5Y cells. These results suggest that WR extract could act as a potential neuroprotective agent through its inhibitory effect on overactivated microglia.

Acknowledgements: This work was supported by Korea Food Research Institute.

Keywords: microglia, Korean wild radish (Raphanus sativus var. hortensis f. raphanistroides), lipopolysaccharide, neuroinflammation, nitric oxide, neuroprotection.

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