THC - the active compound in marijuana - was found to reduce beta-amyloid levels in nerve cells, a protein that is considered a hallmark of Alzheimer's.
Published in the journal Aging and Mechanisms of Disease, the study reveals how a compound present in marijuana triggered the removal of beta-amyloid protein from nerve cells, or neurons.
Beta-amyloid is considered a hallmark of Alzheimer's disease; the protein clumps together in the brain of people with the condition, forming plaques.
Studies have suggested these beta-amyloid plaques disrupt communication between neurons in the brain, which leads to symptoms associated with Alzheimer's, such as impaired memory.
Preventing beta-amyloid accumulation in the brain might seem like an obvious way to tackle Alzheimer's, but because researchers are still unclear of the exact role the protein plays in the disease process, achieving such a feat is easier said than done.
High beta-amyloid levels trigger inflammation, nerve cell death
To find out more about the role of beta-amyloid in Alzheimer's, senior author Prof. David Schubert, of the Salk Institute for Biological Studies in La Jolla, CA, and colleagues modified nerve cells to produce high levels of the protein.
- More than 5 million people in the U.S. are living with Alzheimer's
- Alzheimer's is the sixth leading cause of death for Americans
- This year, Alzheimer's and other dementias will cost the U.S. around $236 billion.
The team found that increased beta-amyloid production led to increased expression of pro-inflammatory proteins in nerve cells, causing inflammation and nerve cell death.
"Inflammation within the brain is a major component of the damage associated with Alzheimer's disease, but it has always been assumed that this response was coming from immune-like cells in the brain, not the nerve cells themselves," notes first author Antonio Currais, also of the Salk Institute for Biological Studies.
The researchers explain that nerve cells in the brain contain receptors that are activated by lipid molecules known as endocannabinoids. These molecules are naturally produced by nerve cells and are believed to aid nerve cell signaling.
Marijuana contains a chemical called tetrahydrocannabinol (THC), which is similar to naturally produced endocannabinoids and activates the same receptors. This got the team thinking: could THC prevent nerve cell death?
"When we were able to identify the molecular basis of the inflammatory response to amyloid beta, it became clear that THC-like compounds that the nerve cells make themselves may be involved in protecting the cells from dying," explains Currais.
Marijuana compound prevented nerve cell death
To test their theory, the researchers applied THC to nerve cells with high beta-amyloid production.
They found that the marijuana compound reduced beta-amyloid levels and eradicated the inflammatory response to the protein, which prevented nerve cell death.
While clinical trials are needed to confirm the role THC might play in protecting nerve cells against beta-amyloid, the researchers believe their findings shed more light on the role beta-amyloid plays in Alzheimer's disease, which could pave the way for new treatments.
"Although other studies have offered evidence that cannabinoids might be neuroprotective against the symptoms of Alzheimer's, we believe our study is the first to demonstrate that cannabinoids affect both inflammation and amyloid beta accumulation in nerve cells."
Prof. David Schubert