SACHA PFEIFFER, HOST:
A drug used to treat HIV aids may have another unexpected use. It appears to reverse a form of memory loss, at least in mice. NPR's Jon Hamilton reports that the finding suggests a new approach to treating brain changes associated with aging or even disease.
JON HAMILTON, BYLINE: As a brain gets older, it can still form new memories, but it has trouble linking them together. Alcino Silva, a neuroscientist at the University of California, Los Angeles, explains the problem this way.
ALCINO SILVA: You learn about something, but you can't remember where you heard it. You can't remember who told you about. These incidents happen more and more often as we go from middle age into older age.
HAMILTON: Silva says scientists have known that for a long time.
SILVA: What we haven't known is how we do this, how the brain does this.
HAMILTON: Silva's lab was studying a molecule called CCR5 that helps the brain separate recent memories from older ones. Silva doubted that this same molecule could play a role in memory problems associated with aging.
SILVA: But we checked (laughter) and voila.
HAMILTON: It turned out that levels of CCR5 increase with age and start to interfere with the process that helps us do things like link a name and a face.
SILVA: Then you no longer link memories after that because that molecule turns off memory mechanisms.
HAMILTON: Silva's lab showed that in mice, memory linking could be restored by blocking CCR5, but they wanted to do that in people as well as mice.
SILVA: The unbelievable luck of all of this is that there is an FDA-approved drug.
HAMILTON: A drug called maraviroc. It blocks CCR5 to prevent HIV from entering immune cells.
SILVA: So we took this drug, we gave to middle age animals, and this drug gave you the same thing. It restored memory linking.
HAMILTON: The results, which appear in the journal Nature, are limited to mice, but they hold promise for aging people and even for stroke patients. Several years ago, Silva and Dr. S. Thomas Carmichael, the chair of neurology at UCLA, did a study that showed levels of CCR5 rise sharply after a stroke. Carmichael says in the short term, this activates systems that help brain cells survive.
S THOMAS CARMICHAEL: The problem is those systems stay active, and then they limit in weeks and months the ability of those brain cells to recover.
HAMILTON: Because the cells can't form the new links needed to carry out tasks like moving an arm or a leg. Mice who got maraviroc didn't have this problem and recovered faster. And the team found that stroke patients with naturally low levels of CCR5 also recovered faster. Carmichael says the findings together suggest a drug like maraviroc could help people with a wide range of brain problems.
CARMICHAEL: You might have an effect in Alzheimer's disease and stroke and Parkinson's and also in spinal cord injury.
HAMILTON: Carmichael is part of a team that is now studying maraviroc in people who've had a stroke. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.
