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Mouse Research Bolsters Controversial Theory of Aging


May 6, 2005   Scientific American


Aging is a process we humans tend to fight every step of the way. The results of a mouse study underscore the potential of antioxidants as a tool in that battle: animals genetically modified to produce more antioxidant enzymes lived longer than control animals did. They also exhibited fewer age-related health problems overall.


The free radical theory of aging posits that substances with unpaired electrons attack the body's molecules and cause the functional decline of organs over time. Thus, antioxidants, which neutralize free radicals, should slow this deterioration. But animal models of aging designed to test the hypothesis have so far shown contradictory results.

In the new work, Peter S. Rabinovitch of the University of Washington and his colleagues engineered mice to produce higher-than-normal amounts of the enzyme catalase. Within cells, catalase removes hydrogen peroxide, a waste product of metabolism that could otherwise lead to damaging oxygen free radicals. In a paper published online yesterday by Science, the team reports that animals with higher levels of catalase in their mitochondria--the cell's energy-producing organelles--lived 20 percent longer on average than control animals did. What is more, mice in this so-called MCAT group had healthier heart tissue than normal mice and showed fewer mutations in their mitochondrial DNA. "This study is very supportive of the free-radical theory of aging," Rabinovitch says. "It shows the significance of free radicals, and of reactive oxygen species in particular, in the aging process."


Animals that overexpressed catalase in other parts of the cell, such as the nucleus, also exhibited longer lifespans than their normal counterparts did, but the gains were more modest. As such, the scientists note, the results reinforce the importance of mitochondria as a supplier of free radicals. The researchers have no plans to modify humans to increase protein expression, but they point out that future drug development could focus on protecting the body from free radicals. --Sarah Graham


(jk) The term controversial is inappropriate.  For it has been long believed that free radicals in the mitochondria are more signficant than elsewhere, based on both decline in numbers of mitochondria in cells with age and their output.  Most of the antioxidants, however, do not penetrate the mitochondria cell wall.  Which is whyh some medical practitioners, who aren't aware of this distinction, rely upon studies which use oxidants that do not penetrate. 







Aging is mainly the result of oxidative damage, which slowly alters the functioning of all process.  While some of this effect is environmental, oxidative damage results from the production of energy through the Kreb’s cycle and other synthesis.

At bio.com http://www.bio.com/newsfeatures/newsfeatures_research.jhtml?cid=22100011


09/26/06 -- Scientists in the Linus Pauling Institute at Oregon State University have discovered a new technique to let them watch, visualize and precisely measure a key oxidant in animal cells, an important breakthrough that could dramatically speed research on everything from Lou Gehrig's Disease to heart disease, hypertension, diabetes and aging.


The findings are being published online this week in Proceedings of the National Academy of Sciences, a professional journal. They could open the door to major advances on some of the world's most significant degenerative diseases, researchers say.

The OSU scientists, in collaboration with Molecular Probes-Invitrogen of Eugene, Ore., found a chemical process to directly see and visualize "superoxide" in actual cells. This oxidant, which was first discovered 80 years ago, plays a key role in both normal biological processes and - when it accumulates to excess - the destruction or death of cells and various disease processes.

"In the past, our techniques for measuring or understanding superoxide were like blindly hitting a box with a hammer and waiting for a reaction," said Joseph Beckman, a professor of biochemistry and director of the OSU Environmental Health Sciences Center. "Now we can really see and measure, in real time, what's going on in a cell as we perform various experiments."

In research on amyotrophic lateral sclerosis, or Lou Gehrig's Disease, which is one of his lab's areas of emphasis, Beckman said they have used the new technique to learn as much in the past three months about the basic cell processes as they did in the previous 15 years. Hundreds of experiments can now rapidly be done that previously would have taken much longer or been impossible.

"This will enable labs all over the world to significantly speed up their work on the basic causes and processes of many diseases, including ALS, arthritis, diabetes, Parkinson's disease, Alzheimer's disease, heart disease and others," Beckman said. "And it should be especially useful in studying aging, particularly the theory that one cause of aging is mitochondrial decay."

The process of oxidation in the body, researchers say, is one that's fundamental to life but also prone to problems. Oxygen in the cells can be reduced to a molecule called superoxide, which is part of normal immune system processes and may also have other functions - it was first named by OSU alumnus Linus Pauling in 1934.

"Oxygen is actually one of the more toxic molecules in the environment," Beckman said. "Breathing 100 percent pure oxygen will destroy your lungs in about three days because it increases the formation of superoxide."

Superoxide is efficiently removed by an enzyme, superoxide dismutase. Antioxidants in food, such as vitamin C and E, are also part of this process.  [Studies of these vitamins and their effect upon superoxide, however, have failed to show an effect upon aging—jk.] And in healthy animals, including humans, this delicate balancing act can work well and cause few problems. But sometimes the process breaks down and excess levels of superoxide begin to accumulate and lead to a wide variety of degenerative diseases.

Prior to this, there was no direct and accurate way to measure superoxide or its origin from the two places that produce it, the cell's cytosol or mitochondria. Now there is.

With the new system developed at OSU, researchers can use a fluorescent microscope, a fairly standard laboratory tool, to actually see levels of superoxide and observe changes as experiments are performed with living cells.

"If we poison the mitochondria, using something like the pesticides that have been implicated in Parkinson's disease, we can actually see superoxide levels begin to rapidly rise," Beckman said. "You get a similar reaction if a growth factor is added that's implicated in the development of Lou Gehrig's Disease."

The data available from this new technology, Beckman said, are so profound that for some time many in the science community didn't believe it was possible.

"This will become a critical tool in learning how superoxide works in a cell," he said. "I've been studying this for more than 10 years and never thought we would have such a clear and accurate picture of what's going on inside a living cell."

In their research on ALS, for instance, OSU scientists have used the new system to actually see cells eating themselves alive and dying from excess superoxide production. A new compound is in phase one clinical trials that appears to inhibit this process and may ultimately provide a therapy for the disease.

Oxidative stress resulting from mitochondrial dysfunction has already been implicated in neurodegeneration, aging, diabetes and cancer, the researchers said in their report. The new findings could rapidly speed research in all of those fields, they said.

Source: Oregon State University