Popular HIV drug may cause memory declines
Johns Hopkins study
suggests the commonly prescribed anti-retroviral drug efavirenz attacks brain
cells
The way the body metabolizes a commonly prescribed anti-retroviral
drug that is used long term by patients infected with HIV may contribute to
cognitive impairment by damaging nerve cells, a new Johns Hopkins research
suggests.
Nearly 50 percent of people infected with HIV will eventually
develop some form of brain damage that, while mild, can affect the ability to
drive, work or participate in many daily activities. It has long been assumed
that the disease was causing the damage, but Hopkins researchers say the drug
efavirenz may play a key role.
People infected with HIV typically take a cocktail of medications
to suppress the virus, and many will take the drugs for decades. Efavirenz is
known to be very good at controlling the virus and is one of the few that
crosses the blood-brain barrier and can target potential reservoirs of virus in
the brain. Doctors have long believed that it might be possible to alleviate
cognitive impairment associated with HIV by getting more drugs into the brain,
but researchers say more caution is needed because there may be long-term
effects of these drugs on the brain.
"People with HIV infections can't stop taking anti-retroviral
drugs. We know what happens then and it's not good," says Norman J.
Haughey, Ph.D., an associate professor of neurology at the Johns Hopkins
University School of Medicine. "But we need to be very careful about the
types of anti-retrovirals we prescribe, and take a closer look at their
long-term effects. Drug toxicities could be a major contributing factor to
cognitive impairment in patients with HIV."
For the study led by Haughey and described online in the Journal of Pharmacology and Experimental Therapeutics,
researchers obtained samples of blood and cerebrospinal fluid from HIV-infected
subjects enrolled in the NorthEastern AIDS Dementia study who were taking
efavirenz. Researchers looked for levels of the drug and its various
metabolites, which are substances created when efavirenz is broken down by the
liver. Performing experiments on neurons cultured in the lab, the investigators
examined the effects of 8-hydroxyefavirenz and other metabolites and found
major structural changes when using low levels of 8-hydroxyefavirenz, including
the loss of the important spines of the cells.
Haughey and his colleagues found that 8-hydroxyefavirenz is 10
times more toxic to brain cells than the drug itself and, even in low
concentrations, causes damage to the dendritic spines of neurons. The dendritic
spine is the information processing point of a neuron, where synapses — the
structures that allow communication among brain cells — are located.
In the case of efavirenz, a minor modification in the drug's
structure may be able block its toxic effects but not alter its ability to
suppress the virus. Namandje N. Bumpus, Ph.D., one of the study's other
authors, has found a way to mod
ify the drug to prevent it from metabolizing
into 8-hydroxyefavirenz while maintaining its effectiveness as a tool to
suppress the HIV virus.
"Finding and stating a problem is one thing, but it's another
to be able to say we have found this problem and here is an easy fix,"
Haughey says.
Haughey says studies like his serve as a reminder that while
people infected with HIV are living longer than they were 20 years ago, there
are significant problems associated with the drugs used to treat the infection.
"Some people do seem to have this attitude that HIV is no
longer a death sentence," he says. "But even with anti-retroviral
treatments, people infected with HIV have shortened lifespans and the chance of
cognitive decline is high. It's nothing you should treat lightly."
###
The study was supported by grants from the National Institute on
Alcohol Abuse and Alcoholism (AA0017408), the National Institute of Mental
Health (MH077543, MH075673 and MH71150), the National Institute on Aging
(AG034849) and the National Institute of Neurological Disorders and Stroke
(NS049465).
Other Hopkins researchers involved in the study include Luis B.
Tovar y Romo, Ph.D.; Lindsay B. Avery, Ph.D.; Ned Sacktor, M.D.; and Justin
McArthur, M.B.B.S., M.P.H.
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