High frequency light stimulation can reduce beta amyloid plaques in mice
Alzheimer's disease is commonly defined by characteristic beta amyloid plaques that gradually build upon onset of the disease. While some individuals appear to have these without neurological decline, it's clear they play a large role in the disease in some form. Getting rid of these plaques, whether they're a cause or consequence, is therefore an important medical target.
Could LED therapy be a new treatment option?
The problem with Alzheimer's is that we are yet to see an effective drug be marketed to halt or reverse decline. Developing new pharmaceuticals is also extremely expensive. Research on Alzheimer's brains has shown that patients typically are deficient in something called gamma oscillations. These are unique brain waves (markers of brain activity) that operate at 25 to 80 hertz. They are believed to aid memory, perception and attention. Alzheimer's model mice tasked with remembering a maze's layout show reduced gamma oscillations in contrast to their healthy companions.
In an effort to target this gamma oscillation issue, researchers designed a light stimulation therapy. They firstly targeted the hippocampus alone, and found that stimulation at 40 hertz was able to reduce plaque in the region by up to 50%. Stimulation at below or above 40 hertz surprisingly has little to no effect.
Moving to a less invasive technique
Hippocampus targeting requires invasive insertion of lights into the brain, so researchers designed a new LED strip programmed to flicker at 40 hertz. In mice with early stage Alzheimer's these strips were able to halve the number of plaques in the visual cortex, but unfortunately the proteins returned to normal after 24 hours. Treating the mice for an hour every day for 7 days however was able to significantly reduce plaques, suggesting that long term repetitive treatment may have some therapeutic value.
"The bottom line is, enhancing gamma oscillations in the brain can do at least two things to reduced amyloid load. One is to reduce beta amyloid production from neurons. And second is to enhance the clearance of amyloids by microglia"
How does it work?
These flickering lights appear to alter the behaviour of microglia - cells which clear out toxic materials from the brain. In Alzheimer's patients these cells typically secrete damaging molecules and adopt an inflammatory stance which is associated with neuron death. Increasing gamma oscillations appeared to reduce this in mice, inducing noticeable changes in these cells and improving beta amyloid removal.
"It's a big 'if,' because so many things have been shown to work in mice, only to fail in humans. But if humans behave similarly to mice in response to this treatment, I would say the potential is just enormous, because it's so noninvasive, and it's so accessible"
While the therapy is a promising and low cost alternative to traditional treatment models, it's yet to be tested on people. It's also not clear whether it would help later stage patients in addition to early stage ones, if human results follow the mouse data.
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