Olea europaea Linn (Oleaceae) fruit pulp extract exhibits potent antioxidant activity and attenuates neuroinflammatory responses in lipopolysaccharide- stimulated microglial cells

Abstract

Purpose: To investigate the antioxidant and anti-neuroinflammatory potentials of Olea europaea Linn. fruit pulp (OFP-EA) extract in LPS-stimulated BV-2 microglial cells. Methods: Cell viabilities were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyl-tetrazolium bromide (MTT) assay. Antioxidant properties were evaluated using 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity. Lipopolysaccharide (LPS) was used to stimulate BV-2 microglia. Nitric oxide (NO) production was measured using Griess assay. Inducible NO synthase (iNOS) expression and tumor necrosis factor-alpha (TNF-α) production were measured using enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. Results: OFP-EA extract significantly (p<0.001 at 20-200 μg/ml, respectively) scavenged the free radicals in a dose-dependent fashion. The increased levels of No stimulated by LPS (34±2.41) were also inhibited by OFP-EA extract significantly and concentration dependently (27±2.32, 21±2.54, 17±1.92 and 11±1.94 at 10, 20, 40 and 80 μg/ml, respectively). Further, OFP-EA suppressed the elevated levels iNOS expression and TNF-α production (p<0.001 at 20, 40 and 80 μg/ml) in LPSstimulated BV-2 cells. Conclusion: Results indicate that OFP-EA extract exhibited strong antioxidant properties and inhibited the excessive production of pro-inflammatory mediators such as NO, iNOS and TNF-α in LPSstimulated BV-2 cells. The antioxidant activity exhibited by OFP-EA extract might play a critical role in ameliorating the inflammatory processes in LPS-stimulated BV-2 microglial cells. © Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria. All rights reserved.