ABSTRACTMicroglia are key regulators of inflammation and oxidative stress (OS) in the CNS. Microglia activation can lead to chronic inflammation, OS, and neurodegeneration. Blueberries (BB) reduce inflammation and OS when administered to microglia before stressors such as lipopolysaccharide (LPS), but the therapeutic value of BBs administered after activation by stressors has not been examined. Therefore, this study investigated the differential effects of pre-, post-, and pre-/post-BB on inflammation and OS in LPS-activated microglia. Rat microglia were pretreated with BB (0.5 mg/mL) or control media (C) for 24 hours, incubated overnight with LPS (0 or 200 ng/mL), and post-treated with BB or C for 24 hours. Biomarkers of inflammation (e.g. nitrite [NO2-], tumor necrosis factor-ɑ [TNFɑ], inducible nitric oxide synthase [iNOS], cyclooxygenase-2 [COX-2], phosphorylated IκB-α [pIκB-ɑ]) and OS (e.g. NADPH oxidase [NOX2]) were assessed. LPS increased NO2-, TNFɑ, COX-2, iNOS, pIκB-ɑ, and NOX2 compared to non-stressed conditions (P < 0.05), however BB before and/or after LPS significantly reduced these markers compared to no BB (P < 0.05). Pre-BB was more effective than post-BB at reducing LPS-induced NO2-, TNFɑ, and COX-2 (P < 0.05). Pre-BB was also more effective than pre-/post-BB at attenuating LPS-induced NO2- and TNFɑ (P < 0.05). All BB treatments were equally effective in reducing LPS-induced iNOS, pIκB-ɑ, and NOX2. Results suggest that BBs can target the downstream events of LPS-induced microglial activation and prevent stressor-induced neuroinflammation and OS. Furthermore, BBs may not need to be present prior to microglial activation for beneficial effects, suggesting that dietary interventions may be effective even after initiation of disease processes.Graphical Abstract. Cascade of inflammatory and OS-inducing events associated with self-propelling microglial activation by LPS and the effects of blueberry (0.5 mg/mL) administered before and/or after LPS on these processes (blue arrows). BB, blueberry; COX2, cyclooxygenase-2; IκB-ɑ, inhibitor kappa-B-ɑ; iNOS, inducible nitric oxide synthase; LPS, lipopolysaccharide; NF-κB, nuclear factor kappa-B; NO, nitric oxide; NOX2, NADPH oxidase; OS, oxidative stress; ROS, reactive oxygen species; TNFɑ, tumor necrosis factor-ɑ.
Keywords: blueberry; cyclooxygenase-2; cytokines; inducible nitric oxide synthase; inflammation; lipopolysaccharide; microglia; neuroinflammation; oxidative stress; polyphenolics.