Antioxidant activity and inhibitory effect on nitric oxide production of rang chuet (Thunbergia laurifolia Lindl.) leaf extracts in lipopolysaccharide-stimulated BV2 microglial cells

Background: Oxidative stress and neuroinflammation mediated by microglial activation play a significant role in the pathogenesis of neurodegenerative diseases. Therefore, negative regulators of microglial activation have been identified as potential therapeutic candidates for the treatment of such diseases. Objectives: The aim of this study was to investigate the effects of Thunbergia laurifolia Lindl. or Rang Chuet (RC) extracts on reactive oxygen species (ROS) and nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV2 microglia cells. Materials and Methods: BV2 cells were treated with LPS in the presence or absence of RC extract, and the levels of ROS and NO were measured using CM-H2DCFDA and Griess reagent assay, respectively. The nuclear levels of nuclear factor kappa B (NF-kB) p65 and the activation of Akt and the extracellular signal-regulated kinase 1/2 (ERK1/2) were detected using immunofluorescence and western blotting assay, respectively. Results: The treatment of BV2 cells with RC concentration-dependently suppressed the LPS-induced ROS production compared to the control group. RC treatment also significantly decreased LPS-induced NO production in a concentration-dependent manner. In addition, RC treatment also suppressed NF-kB p65 translocation and the activation of Akt and the ERK1/2 pathway in LPS-stimulated BV2 cells. Conclusion: Taken together, these results demonstrate that RC exerts anti-oxidative activity by suppressing ROS production and that it exerts antioxidative activity by suppressing NO in LPS-stimulated BV2 cells. The mechanisms by which RC suppresses NO and ROS production may occur through inhibition of Akt and the ERK1/2-mediated NF-κB pathway. The results suggest that RC may be useful in treating neurodegenerative diseases mediated by microglial cells.