Davies and his team worked with a line of human lung cells. They exposed the cells to hydrogen peroxide, a powerful oxidant that is a byproduct of energy production and that also can result from metabolism of some drugs, toxins, pesticides and herbicides.
To fight the oxidant, young cells doubled the size of their Lon army within five hours and maintained it for a day. In some experiments, young cells increased their Lon army as much as seven-fold.
Middle-aged cells took a full day to double their Lon army, during which time the cells were exposed to harmful levels of oxidized proteins.
Older cells started with a standing Lon army only half as large and showed no statistically significant increase in Lon levels over 24 hours.
The Davies group, which discovered Lon in 2002, previously had shown that Lon's standing army gets smaller with age and that the anti-oxidant power of Lon depends more on its reserves than on enzymes present when stress first hits the body.
The latest study completes the picture of Lon's sluggish response as senescent cells a technical term for cells that mimic several key features of the aging process try to cope with stress.
"In the senescent cells, the Lon levels are drastically low to begin with, and they don't increase" in response to stress, Davies said.
Scientists have known for decades that mitochondria become less efficient with age, contributing to the body's loss of energy.
"It may well be that our ability to induce Lon synthesis and our loss of adaptability to stress may be an even more significant factor in the aging process," Davies said.
Davies and others are investigating potential treatments to boost the function of Lon. Costly enzyme supplements are useless, Davies noted, since the digestive system breaks down the enzyme to amino acids before it can rea
|Contact: Carl Marziali|
University of Southern California