Blueberry treatment administered before and/or after lipopolysaccharide stimulation and oxidative stress in rat microglial cells

Authors: CAHOON, DANIELLE - Tufts University; Fisher, Derek; LAMON-FAVA, STEFANIA - Tufts University; Wu, Dayong; ZHENG, TONG - Tufts University; Shukitt-Hale, Barbara

Submitted to: Nutritional Neuroscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2021
Publication Date: 1/4/2022
Citation: Cahoon, D.S., Fisher, D.R., Lamon-Fava, S., Wu, D., Zheng, T., Shukitt Hale, B. 2022. Blueberry treatment administered before and/or after lipopolysaccharide stimulation and oxidative stress in rat microglial cells. Nutritional Neuroscience. 26:127-137. https://doi.org/10.1080/1028415X.2021.2020404.
DOI: https://doi.org/10.1080/1028415X.2021.2020404

Interpretive Summary: Microglia are brain cells that help keep inflammation in check. However, when overwhelmed by too much stress, they become overactivated, which can lead to chronic inflammation, oxidative stress (OS), and brain degeneration. Blueberries (BB) have been shown to reduce inflammation and OS when administered to cells before application of stressors, but it is unknown if BBs will help if they are administered after stressor activation. Therefore, this study investigated the differential effects of pre-, post-, and pre-/post-BB on inflammation and OS in stressor-activated brain cells. Brain cells were treated with BB for either 24 hour prior to stressor, 24 hours following stressor, or both. Results showed that stressor application increased markers of inflammation and OS, however BB before and/or after stressor significantly reduced these markers compared to no BB. For some markers, pre-BB was more effective than post-BB or pre-/post-BB. These results show that BBs may not need to be present prior to stressor-induced activation for beneficial effects. These findings provide evidence suggesting that dietary interventions may be effective, even after initiation of disease processes.

Technical Abstract: Microglia, the primary immune cells of the central nervous system (CNS), are key regulators of inflammation and oxidative stress (OS) in the CNS. Microglia activation can lead to chronic inflammation, OS, and neurodegeneration. Blueberries (BB) have been shown to reduce inflammation and OS when administered to microglia before stressors such as lipopolysaccharide (LPS), but the therapeutic value of BBs administered to microglia after activation by stressors has not been examined. Post-stressor treatments may be important to target chronic and progressive inflammation/OS following microglia activation. 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 pre-treated with freeze-dried BB diluted in media (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-' [TNF'], inducible nitric oxide synthase [iNOS], cyclooxygenase-2 [COX-2], phosphorylated I'B-a [pI'B-']) and OS (e.g., NADPH oxidase [NOX2], nuclear factor erythroid 2-related factor 2 [Nrf2], superoxide dismutase [SOD]) were assessed. Results showed that LPS increased NO2-, TNF', COX-2, iNOS, pI'B-', and NOX2 compared to non-stressed control 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-, TNF', and COX-2 (P < 0.05). Pre-BB was also more effective than pre-/post-BB at attenuating LPS-induced NO2- and TNF' (P < 0.05). All BB treatments were equally effective in reducing LPS-induced iNOS, pI'B-', 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. These findings provide evidence suggesting that dietary interventions may be effective even after initiation of disease processes such as microglial-induced neuroinflammation and OS.