Assessment of antioxidant and anti-inflammatory actions of curcumin by application of novel neutrophil activity measurement system

Objective: Neutrophils not only play a critical role in host defense by migrating to the site of infection and producing reactive oxygen species (ROS), but also mediate pathological process in tissue destruction and inflammatory diseases. Therefore, it is important to assess and modulate neutrophil activities. In the present study, we examined the effects of curcumin on migratory activity of neutrophils into the hydrogel and their production of ROS by newly-developed neutrophil activity measurement system. Method: Curcumin was diluted to medium in wide-range concentrations. Each solution was added on hydrogel, and the mixture of blood and luminol was layered on it in each tube. The cell count in the hydrogel was quantified as migratory activity of neutrophils, whereas the ROS production was measured by luminol-dependent chemiluminescence. Result: The migratory activity of neutrophils was significantly inhibited at 160 μg/mL only in the subgroup with higher migratory activity, whereas no effect was observed in the subgroup with lower migratory activity. ROS production of neutrophils was significantly inhibited at 20 μg/mL of curcumin in a concentration-dependent manner. Conclusion: This new method for measuring neutrophil activities can be applied not only for assessing antioxidant activity for reducing oxidative stress, but also anti-inflammatory activity in terms of reducing neutrophil migration. Curcumin was the most effective antioxidant among the tested plant extracts in our previous studies.