A new study finds that giving mice light therapy while they are in deep sleep improves the brain's ability to clear beta-amyloid, a toxic protein linked to the onset of Alzheimer's disease. The discovery could lead to a non-drug, non-invasive treatment.
Despite researchers' efforts, a safe and effective drug treatment for Alzheimer's disease (AD) has not been developed, which means turning to non-drug approaches. A new study demonstrates the therapeutic potential of light therapy, or phototherapy, in treating Alzheimer's disease, with researchers showing promising results in mice that they hope will be equally effective in humans.
In the study, researchers used photobiomodulation (PBM), a non-drug treatment that uses red and near-infrared light to stimulate the body's own healing. There is evidence that PBM can promote brain metabolism and microcirculation in addition to reversing oxidative stress and inflammation. Recent research has found that PBM stimulates the brain's lymphatic system, which removes waste products and toxins.
The meninges are membranes that cover and protect the brain and spinal cord, and have a system of lymphatic vessels in them. These meningeal lymphatic vessels, or MLVs, have been shown to clear out beta-amyloid, a protein long associated with Alzheimer's disease. Abnormal amounts of this naturally occurring protein are thought to aggregate between neurons to form plaques, disrupting cell function.
Because the brain's lymphatic system is activated during sleep, the researchers tested the effects of PBM while awake and in non-rapid eye movement (deep) sleep. They used lasers to destroy MLV in mice and then injected beta-amyloid into the mice's hippocampus, a region of the brain associated with memory and learning. Mice were treated with PBM once a day for seven days using light-emitting diodes.
By measuring the levels of beta-amyloid in the hippocampus, the researchers found that levels of beta-amyloid in the hippocampus were lower whether PBM was used in the awake or sleeping state, but the decrease was greater when PBM was used in the sleeping state. They concluded that PBM during sleep stimulated amyloid beta excretion in the hippocampus more effectively than during wakefulness.
The researchers also observed that although MLVs were disrupted, inhibiting their ability to clear beta-amyloid, this ability was restored after treatment, and that PBM was more effective when administered during sleep than when awake.
The researchers said: "In our results, we found that PBM can promote the recovery of lymphatic function after MLV injury and is more effective if used during deep sleep than when used awake."
They say this non-drug, non-invasive treatment could be useful in people with ADHD and other conditions involving the brain's lymphatic system. Since drug treatment of AD has failed to show efficacy or safety, PBM, as a non-invasive and safe method, is promising in clinical practice for the treatment of brain diseases associated with lymphatic system diseases, such as AD, Parkinson's disease, glioma, brain trauma, intracranial hemorrhage, etc.
The research was published in the journal Frontiers in Optoelectronics.