The researchers showed that microglial cells that were exposed to a bacterial toxin produced inflammatory cytokines that could kill neurons. When the microglia were exposed to luteolin before they encountered the toxin, however, the neurons lived.
"The neurons survived because the luteolin inhibited the production of neurotoxic inflammatory mediators," Johnson said.
Exposing only the neurons to luteolin before the experiment had no effect on their survival, the researchers found.
"This demonstrated that luteolin isn't protecting the neurons directly," he said. "It's doing it by affecting the microglial cells."
The researchers next turned their attention to the effects of luteolin on the brains and behavior of adult (3- to 6-month-old) and aged (2-year-old) mice. The mice were fed a control diet or a luteolin-supplemented diet for four weeks. The researchers assessed their spatial memory and measured levels of inflammatory markers in the hippocampus, a brain region that is important to memory and spatial awareness.
Normally, aged mice have higher levels of inflammatory molecules in the hippocampus and are more impaired on memory tests than younger adult mice. Aged mice on the luteolin-supplemented diet, however, did better on the learning and memory task than their peers, and the levels of inflammatory cytokines in their brains were more like those of the younger adult mice.
"When we provided the old mice luteolin in the diet it reduced inflammation in the brain and at the same time restored working memory to what was seen in young cohorts," Johnson said.
Studies have shown that plant compounds such as luteolin can get into the brain, Johnson said.
"We believe dietary luteolin accesses the brain and inhibits or reduces activation of microglial ce
|Contact: Diana Yates|
University of Illinois at Urbana-Champaign