Blueberry Treatment Administered Before and/or After Lipopolysaccharide Attenuates Neuroinflammation and Oxidative Stress in Rat Microglial Cells

Abstract

ObjectivesNeuroinflammation and oxidative stress (OS) are implicated as mediators of cognitive decline and neurodegenerative diseases. Microglia, the primary immune cells of the central nervous system (CNS), are key regulators of inflammation and OS in the CNS. Blueberries (BB) are rich in anti-inflammatory and antioxidant polyphenols and reduce inflammation and OS when administered to microglia before pathogenic stimuli such as lipopolysaccharide (LPS). However, the therapeutic value of BBs administered to microglial cells after activation by LPS on inflammation and OS has not been examined. This study investigated the potential differential effects of pre-, post-, and pre-/post-BB on LPS-induced inflammation and OS in rat microglia. MethodsRat microglia were pre-treated with freeze-dried BB diluted in media (0.5 mg/mL) or control media (C) for 24 h, incubated overnight with LPS (0 or 100 ng/mL), and post-treated with BB or C for 24 h. Standard immunochemical techniques were used to measure biomarkers of inflammation and OS, including nitrite, tumor necrosis factor alpha (TNFɑ), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Data were analyzed using two-way ANOVAs with treatment group (pre-/post-BB) and LPS exposure as experimental factors. Post-hoc testing was performed using Tukey’s test to determine differences among groups. ResultsPreliminary results showed that all BB treatments (pre-, post- and pre-/post-BB) reduced LPS-induced nitrite and TNFɑ relative to no BB (P < 0.01). Pre-BB was more effective at reducing nitrite than post-BB (P < 0.01), although neither was significantly different than pre-/post-BB. In contrast, the attenuating effects of pre-BB and post-BB on TNFɑ were not different from each other, although both treatments were more beneficial than pre-/post-BB (P < 0.001). Compared to no BB, both pre-BB and post-BB, although not pre-/post-BB reduced LPS-induced iNOS expression (P < 0.05), and only pre-BB attenuated COX2 expression (P < 0.01). ConclusionsResults suggest that BBs can target the downstream effects of microglial activation in addition to preventing stressor-induced neuroinflammation and OS. Therefore, although potentially more effective, BBs may not need to be present prior to microglial activation for beneficial effects. Funding SourcesSupported by USDA intramural funding.