[Inhibitory effects of vina-ginsenoside R7 on activation of rat C6 astrocytes induced by LPS and TNF-α combination]

Abstract

To investigate the inhibitory effect and mechanism of vina-ginsenoside R7 (R7) on the activation of rat C6 astrocytes cells induced by LPS/TNF-α, cells in logarithmic growth phase were cultured in DMEM medium without FBS for 24 h. After dissociated using 0.25% EDTA-trypsin, the cells were seeded into respective plates at the density of 1.5×10⁶ cells per mL and cultured overnight. The cells were divided into the following groups： control group (no treatment), model group (treated with LPS 1 μg•mL⁻¹ and TNF-α 10 μg•L⁻¹ treated for 24 h), R7 groups (pre-treated with 6.25, 12.5, 25, 50, and 75 μmol•L⁻¹ R7, 4 μmol•L⁻¹ L-NMMA for 2 h and then stimulated with LPS 1 mg•L⁻¹ and TNF-α 10 μg•L⁻¹ for 24 h). Cell viability was analyzed by CCK-8 kit. Secretion of nitric oxide (NO) in the medium was measured by Greiss method. Concentrations of interleukin-6 (IL-6) and tumor necrosis factor (TNF-α) were assayed by ELISA kits. Gene expressions of inflammatory factors were examined by quantitative-PCR analysis. Activation of NF-κB was detected by dual luciferase reporter gene assay kit. The results showed that R7 could significantly inhibit the secretion of NO from C6 cells in a dose-effect manner, with an IC₅₀ of 34 μmol•L⁻¹. And it could reduce cell proliferation induced by LPS/TNF-α stimulation. Furthermore, R7 at 50 μmol•L⁻¹ significantly down-regulated gene expressions of iNOS (P<0.001), TNF-α (P<0.001), IL-1β(P<0.05), and COX-2 (P<0.001), but could not change gene expression of IL-6. However, R7 reduced the secretion of TNF-α (P<0.001) and IL-6 (P<0.001). Further studies disclosed that, different concentrations of R7 (25, 50, 100 μmol•L⁻¹) could significantly inhibit the transcription activity of NF-κB(P<0.05, P<0.01, and P<0.001). In conclusion, R7 could inhibit inflammatory responses in C6 cells induced by LPS/TNF-α probably by inhibiting the transcription activity of NF-κB, which indicates its possible therapeutic effect in neurological diseases related to neuroinflammation.

Keywords: LPS; NF-κB; astrocyte; inflammatory factor; neuroinflammtion; vina-ginsenoside R7.