For over a century, Alzheimer's disease has confounded all attempts to treat it. But in recent years, perplexing experiments using flickering light have shown promise.
Now, researchers have tapped into how the flicker may work. They discovered in the lab that the exposure to light pulsing at 40 hertz – 40 beats per second – causes brains to release a surge of signaling chemicals that may help fight the disease.
Though conducted on healthy mice, this new study is directly connected to human trials, in which Alzheimer's patients are exposed to 40 Hz light and sound. Insights gained in mice at the Georgia Institute of Technology are informing the human trials in collaboration with Emory University.
I'll be running samples from mice in the lab, and around the same time, a colleague will be doing a strikingly similar analysis on patient fluid samples." Kristie Garza, the study's first author
Garza is a graduate research assistant in the lab of Annabelle Singer at Georgia Tech and also a member of Emory's neuroscience program.
One of the surging signaling molecules, in particular, is associated with the activation of brain immune cells called microglia, which purge an Alzheimer's hallmark – amyloid beta plaque, junk protein that accumulates between brain cells. Immune signaling
In 2016, researchers discovered that light flickering at 40 Hz mobilized microglia in mice afflicted with Alzheimer's to clean up that junk. The new study looked for brain chemistry that connects the flicker with microglial and other immune activation in mice and exposed a surge of 20 cytokines – small proteins secreted externally by cells and which signal to other cells. Accompanying the cytokine release, internal cell chemistry – the activation of proteins by phosphate groups – left behind a strong calling card.
"The phosphoproteins showed up first. It looked as though they were leading, and our hypothesis is that they triggered the release of the cytokines," said Singer, who co-led the new study and is an assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory.
"Beyond cytokines that may be signaling to microglia, a number of factors that we identified have the potential to support neural health," said Levi Wood, who co-led the study with Singer and is an assistant professor in Georgia Tech's George W. Woodruff School of Mechanical Engineering.
The team publishes its findings in the Journal of Neuroscience on February 5, 2020. (There is no embargo. Pre-publication appeared in December but did not yet contain all edits and elements.) The research was funded by the National Institute of Neurological Disorders and Stroke at the National Institutes of Health, and by the Packard Foundation.
Singer was co-first author on the original 2016 study at the Massachusetts Institute of Technology, in which the therapeutic effects of 40 Hz were first discovered in mice. Sci-fi surrealness
Alzheimer's strikes, with few exceptions, late in life. It destroys up to 30% of a brain's mass, carving out ravines and depositing piles of amyloid plaque, which builds up outside of neurons. Inside neurons, phosphorylated tau protein forms similar junk known as neurofibrillary tangles suspected of destroying mental functions and neurons. Related Stories
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