JUN 08, 2016 4:52 AM PDT

Infections and Alzheimer's: Is There a Link?

It’s been known for a while that plaques of the protein amyloid beta are part of the pathology of Alzheimer’s disease. Multiple studies show that a build up of this protein in the brain is associated with the destruction of brain tissue and the devastating cascade of memory loss and cognitive decline that defines Alzheimer’s. A new study out of Massachusetts General Hospital (MGH) shows that there is more to it. Amyloid-beta protein now seems to be part of the body’s defense system against infection.
 Are infections the start of Alzheimer's pathology?
Neurologists Rudolph Tanzi and Robert Moir, working at Harvard Medical School and MGH have published a study in the journal Science Translational Medicine that suggests another protein, LL37, which they studied in 2010, is similar to amyloid-beta. LL37 is known as an immune system soldier, fighting off infections, but the same was not known then about the plaques of A-beta.  The 2010 study compared synthetic forms of A-beta with LL37, which is an antimicrobial peptide (AMP), and found that A-beta inhibited the growth of several important toxins as well as, or in  a few instances, better than, LL-37.  Their new research is the first time human A-beta was investigated in living models and their results showed that initially A-beta does have infection fighting properties.
 
Robert Moir, MD, of the Genetics and Aging Research Unit in the MassGeneral Institute for Neurodegenerative Disease (MGH-MIND), co-corresponding author of the paper, said in a press release,“Neurodegeneration in Alzheimer’s disease has been thought to be caused by the abnormal behavior of A-beta molecules, which are known to gather into tough fibril-like structures called amyloid plaques within patients’ brains. This widely held view has guided therapeutic strategies and drug development for more than 30 years, but our findings suggest that this view is incomplete.” In other words, while A-beta plaques do accumulate and cause tissue degeneration, there is more to it. Before they went rogue, they appear to have been helpful.
 
When the team injected bacteria into the brains of mice that had been genetically altered to have Alzheimer’s, plaques of A-beta surrounded the bacteria, essentially trapping it.  They used salmonella bacterium, but other research teams have experimented with herpes and influenza and seen similar reactions. While initially, it’s a good thing, Tanzi and Moir believe that the process goes awry when A-beta is overexpressed, perhaps in reaction to repeated infections or larger amounts of bacteria. Once the scale is tipped and there is too much A-beta the process goes from therapeutic to toxic and Alzheimer’s can be the result.
 
While the AMP LL37 is good at fighting off infection, it’s also been implicated in causing the inflammation seen in several diseases where the onset is in later years like rheumatoid arthritis, lupus and atherosclerosis. That inflammation could be responsible for the A-betas to grow larger and more invasive, thus setting off the Alzheimer’s disease process.
 
Tanzi, who is the Kennedy Professor of Neurology (Neuroscience) at Harvard Medical School and vice-chair of Neurology at MGH, stated, “While our data all involve experimental models, the important next step is to search for microbes in the brains of Alzheimer’s patients that may have triggered amyloid deposition as a protective response, later leading to nerve cell death and dementia. If we can identify the culprits – be they bacteria, viruses, or yeast –  we may be able to therapeutically target them for primary prevention of the disease.” The video below explains the balance of A-beta and how too much of a good thing can have consequences in the development of Alzheimer’s.

Sources: Mass General, Scientific American
About the Author
  • I'm a writer living in the Boston area. My interests include cancer research, cardiology and neuroscience. I want to be part of using the Internet and social media to educate professionals and patients in a collaborative environment.
You May Also Like
DEC 20, 2019
Neuroscience
DEC 20, 2019
Hand-Motion Center of the Brain Involved in Speech
During a long-term study focused on improving computer-assistant interfaces for quadriplegia patients, researchers at Stanford University were able to use...
DEC 27, 2019
Drug Discovery & Development
DEC 27, 2019
Acne Drug Linked to 10 Suicides
UK regulators claim to have found a link between at least ten suicides and a powerful acne drug, manufactured under the names Roaccutane and Accutane. Alth...
FEB 24, 2020
Genetics & Genomics
FEB 24, 2020
Circular RNAs May Play a Role in Psychiatric Disorders
The genome contains the sequences for many genes that code for proteins. There are also regions and chemical tags that help control the activation of genes....
MAR 01, 2020
Genetics & Genomics
MAR 01, 2020
Treating Huntington's Disease With a Gene Therapy That Targets Brain Cells
A new therapeutic approach for Huntington's disease may aid patients with other neurodegenerative disorders....
MAR 03, 2020
Neuroscience
MAR 03, 2020
How Brain is Wired Caused Learning Difficulties, Not Specific Brain Regions
For quite some time, science has attributed learning difficulties such as dyslexia and language processing disorder to malfunctions in specific areas of th...
MAR 07, 2020
Drug Discovery & Development
MAR 07, 2020
Single Trip on Magic Mushrooms Boosts Mindfulness
According to new research, a single trip from magic mushrooms is enough for people to experience long-term increases in mindfulness and openness. Mindfulne...
Loading Comments...