Tower and his team had noticed that overexpression of the enzyme, known as superoxide dismutase (SOD), boosted the activity level of fruit flies and even increased the life span of certain genetically engineered strains.
Tower suspected that hydrogen peroxide was the key ingredient in SOD's action.
"Hydrogen peroxide is a great candidate for a signaling molecule that would be involved in rhythms and behaviors. It's the most stable and diffusible of the reactive oxygen species (by-products of combustion), but no one had demonstrated a role for it."
As a test, Tower's group administered hydrogen peroxide directly to fruit flies through feeding and injection.
The researchers observed similar effects from the direct administration of hydrogen peroxide and the over-expression of the SOD enzyme.
Both strategies increased the activity levels of adult flies. Long-term direct treatment with hydrogen peroxide suppressed daily rhythms, while SOD over-expression altered those rhythms.
Tower explained that he had not expected identical results from direct treatment versus genetic over-expression.
"I think it's just a little too crude of an intervention, to feed them or inject them with the drug," he said, because those effects will not be rhythmic, whereas production of hydrogen peroxide by the mitochondria and by SOD is expected to be rhythmic and to correspond to the rhythm of metabolism.
Still, the similarities in the flies' reactions to direct treatment and to SOD over-expression suggested to the researchers that hydrogen peroxide is the crucial chemical.
"It's a very exciting result for us that our data now start to point to hydrogen
|Contact: Carl Marziali|
University of Southern California