Walnut oil and blueberry treatments have beneficial individual but not synergistic effects on neuroinflammation in vitro

Authors: Fisher, Derek; CAHOON, DANIELLE - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; Shukitt-Hale, Barbara

Submitted to: Current Developments in Nutrition
Publication Type: Abstract Only
Publication Acceptance Date: 3/8/2021
Publication Date: 6/7/2021
Citation: Fisher, D.R., Cahoon, D., Shukitt Hale, B. 2021. Walnut oil and blueberry treatments have beneficial individual but not synergistic effects on neuroinflammation in vitro. Current Developments in Nutrition. 5(Suppl 2):904. https://doi.org/10.1093/cdn/nzab049_017.
DOI: https://doi.org/10.1093/cdn/nzab049_017

Interpretive Summary:

Technical Abstract: Objectives: Neuroinflammation has been associated with cognitive decline and neurodegenerative disease. Walnuts and blueberries (BB) each provide neuroprotective anti-inflammatory components. However, it is unknown whether they act synergistically to enhance the effects seen with individual supplementation. This study aimed to examine the individual and potentially synergistic beneficial effects of walnut oil (WO) and BB on lipopolysaccharide (LPS)-induced neuroinflammation in rat microglial cells. The effects of pre-treatment time and concentration were also explored. Methods: Rat microglial cells were pre-treated for 48 hours, 1, 2 or 4 weeks with control media or freeze-dried BB extract, WO or WO/BB diluted in media at 0.05, 0.1, 0.2, 0.5 and 1.0 mg/mL. At the end of each treatment time point, cells were stressed with LPS (100 ng/mL) overnight. Standard immunochemical techniques were used to measure biomarkers of inflammation: nitrite, inducible nitrous oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Data were analyzed using three-way ANOVAs with treatment, concentration, and time as experimental factors, and Tukey’s post-hoc test to determine differences among groups. Results: Results showed that BB, WO, and WO/BB reduced LPS-induced nitrite, COX2 and iNOS relative to control (P < 0.05). BB had a stronger effect on reducing nitrite production than WO/BB, and both BB and WO/BB were more effective than WO (P < 0.05). However, there were no significant differences between treatments for COX2 and iNOS expression. All three treatments attenuated LPS-induced nitrite, COX2, and iNOS in a concentration- and time-dependent manner (P < 0.05), with higher doses and longer treatment durations being most beneficial. Conclusions: Although BB, WO and WO/BB reduced LPS-induced neuroinflammation, WO/BB was not more effective than either individual treatment. This result suggests that BB and WO do not act synergistically to attenuate inflammation in microglia. Additionally, the intermediate effect of WO/BB relative to BB and WO on nitrite suggests that BB is primarily responsible for the beneficial effects of WO/BB. Overall, the reduction in neuroinflammation following all treatments shows that the addition of blueberries and/or walnuts to the diet may attenuate the neurodegenerative effects of inflammation.