Researchers Find How Alzheimer’s Kills Nerve Cells, Develop New Drugs

Gerontologists at the University of Southern California have discovered how the chief molecular villain of Alzheimer's disease kills nerve cells – and have identified two drugs that appear to cancel its toxicity.

The finding, reported in the May 1 issue of the Journal of Neuroscience, is apparently a solid advance in the quest to cure the degenerative brain disease that afflicts roughly 4 million Americans and kills about 100,000 each year.

The harmful molecule – called the beta-amyloid peptide – has long been associated with the progressive, mind-eroding cell die-offs that AD patients suffer. But the causal chain has been indirect and the list of suspects long.

Instead of directly affecting neurons, the brain's computing cells, the beta-amyloid stimulates a different kind of brain cell called microglia to release peroxynitrite – a brain toxin.

Microglia act like janitors, mopping up substances that don't belong in the brain. However, when the microglia come into contact with beta-amyloid, their response is to release a neurotoxin, which is disastrous for the system they are designed to maintain.

Valter Longo, an assistant professor of gerontology at USC's Leonard Davis School of Gerontology, led the research team that finally identified beta-amyloid's modus operandi and its accomplices.

"It was a tricky experiment to perform," said Longo, who holds the Paul F. Glenn Foundation Chair in Cellular and Molecular Biology, "because peroxynitrite is a very short-lived molecule and is very difficult to measure. (But) peroxynitrite appears by far to be the most toxic molecule that is produced in response to beta-amyloid."

But there is a silver lining: The researchers also identified two drugs that may effectively block peroxynitrite's toxicity. The next stage of research will be to test these drugs on mice that have been bred to acquire a rodent version of AD, said Longo. If either of the drugs proves safe and effective for the mice, human clinical trials may follow.

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