ROBERT F. BUKATY / AP
Another anti-HIV drug called maravirok can be used unexpectedly.
This drug seems to restore a kind of memory, which allows us to connect an event like a wedding with the people who saw it there, writes this week’s issue of the magazine. Nature.
The ability of maraviroc to improve this type of memory has been shown in mice, but the drug also affects the brain system in humans and plays a role in a number of problems with the brain and nervous system.
“You can be affected by Alzheimer’s disease, stroke, Parkinson’s and also spinal cord injuries,” says the doctor. S. Thomas Carmichael, Department of Neurology, University of California, Los Angeles, did not participate in the study.
From mice to maravirok
The ability to connect simultaneous memories is called relational memory. It usually decreases with age and can be severely debilitating in people with Alzheimer’s disease.
Relational memory problems can occur in people who have no difficulty forming new memories, says Alsino Silva, author of the new study and director of the Integrated Learning and Memory Center at UCLA.
“You know about something, but you can’t remember where you heard it from. You can’t remember who told you about it,” Silva said. “These stories will be repeated more and more as we move from middle age to old age.”
Scientists have long known that people have relational memory, says Silva. “We don’t know how the brain does it.”
This changed when Silva’s laboratory began studying a molecule called CCR5.
CCR5 in the body is a key part of the immune system. However, in the brain, CCR5 controls the process that helps to separate the last memories from the old ones. Were it not for this separation, we would not have known that we met someone at a wedding we attended last week or at a conference held decades ago.
Silva wondered why the CCR5 molecule could explain the memory problems associated with aging in humans and mice.
“But we checked, and voila,” he says.
It appears that CCR5 levels increase with age and seem to “disable” the ability to link memories.
Silva’s laboratory tested the idea in mice with a disabled form of CCR5.
These mice can link memories made within a week, while normal mice can only link memories made within a few hours.
The team then took typical, middle-aged mice and injected maraviroc into the hippocampal region of the brain, which is important for memory.
“This medicine has given you the same thing,” Silva says. “It restores memory connectivity.”
Possible treatment for stroke
According to Carmichael, the results are promising for the elderly, even those who have had a stroke.
In 2019, Silva and Carmichael were among the authors of the paper, which showed that CCR5 levels would rise sharply after a stroke.
In the short term, this CCR5 explosion activates systems that help brain cells survive, Carmichael said. “The problem is that these systems remain active and they limit the ability of brain cells to regenerate.”
In order to repair the long-term damage caused by a stroke, brain cells must make new connections – a process similar to the process used to connect specific memories. CCR5 does not allow this.
So Silva and Carmichael tried to give maravirok to mice that had suffered a stroke or brain injury. Of course, they healed faster than other mice.
They then studied a group of stroke patients with genes that produced naturally low levels of CCR5. Once again, this means a faster recovery.
Carmichael is currently involved in a study to see if maraviroc can help people who have had a stroke.