Individual and combined walnut oil and blueberry attenuate lipopolysaccharide-induced neuroinflammation in rat microglia.

Objectives: Chronic microglial activation drives neuroinflammation, contributing to neurodegenerative diseases and cognitive decline. Walnuts and blueberries (BB) have been demonstrated to reduce neuroinflammation, but it is unknown whether they act synergistically to enhance the effects seen with individual treatment. This study examined the individual and synergistic effects of walnut oil (WO) and BB on lipopolysaccharide (LPS)-induced neuroinflammation in rat microglial cells. The effects of pretreatment duration and concentration were also explored.

Methods: Rat microglial cells were pretreated for 48 hours, one, two, or four weeks with 0.05, 0.1, 0.2, 0.5 and 1.0 mg/mL BB extract, WO or WOBB, followed by exposure to LPS (100 ng/mL). Cell viability was assessed and standard immunochemical techniques were used to measure levels of the inflammatory biomarkers: nitrite, inducible nitrous oxide synthase (iNOS), and cyclooxygenase-2 (COX-2).

Results: BB, WO, and WOBB reduced LPS-induced nitrite, COX-2 and iNOS relative to control, with higher concentrations and longer treatment durations typically being most beneficial. All treatments showed similar ability to reduce iNOS expression, while BB had a stronger effect on reducing nitrite production than WO and WOBB. There were no significant differences between treatment effects on COX-2 expression.

Conclusion: BB and WO each reduced LPS-induced inflammation in microglia, but their combination was not more effective, suggesting no synergistic effect. This result suggests that they may work through similar mechanisms to attenuate inflammation in microglia. Overall, the reduction in neuroinflammation shows that the addition of BBs or walnuts to the diet may attenuate neuroinflammation linked to neurodegeneration.