Inflammatory processes drive progression of Alzheimer's and other brain diseases

November 20, 2019

Inflammation drives the progression of neurodegenerative brain diseases and plays a major role in the accumulation of tau proteins within neurons. An international research team led by the German Center for Neurodegenerative Diseases (DZNE) and the University of Bonn comes to this conclusion in the journal Nature. The findings are based on the analyses of human brain tissue and further lab studies. In the particular case of Alzheimer's the results reveal a hitherto unknown connection between Abeta and tau pathology. Furthermore, the results indicate that inflammatory processes represent a potential target for future therapies.

Tau proteins usually stabilize a neuron's skeleton. However, in Alzheimer's disease, frontotemporal dementia (FTD), and other "tauopathies" these proteins are chemically altered, they detach from the cytoskeleton and stick together. As a consequence, the cell's mechanical stability is compromised to such an extent that it dies off. In essence, "tau pathology" gives neurons the deathblow. The current study led by Prof. Michael Heneka, director of the Department of Neurodegenerative Diseases and Gerontopsychiatry at the University of Bonn and a senior researcher at the DZNE, provides new insights into why tau proteins are transformed. As it turns out, inflammatory processes triggered by the brain's immune system are a driving force.

A Molecular Switch

A particular protein complex, the "NLRP3 inflammasome", plays a central role for these processes, the researchers report in Nature. Heneka and colleagues already studied this macromolecule, which is located inside the brain's immune cells, in previous studies. It is a molecular switch that can trigger the release of inflammatory substances. For the current study, the researchers examined tissue samples from the brains of deceased FTD patients, cultured brain cells, and mice that exhibited hallmarks of Alzheimer's and FTD.

"Our results indicate that the inflammasome and the inflammatory reactions it triggers, play an important role in the emergence of tau pathology", Heneka said. In particular, the researchers discovered that the inflammasome influences enzymes that induce a "hyperphosphorylation" of tau proteins. This chemical change ultimately causes them to separate from the scaffold of neurons and clump together. "It appears that inflammatory processes mediated by the inflammasome are of central importance for most, if not all, neurodegenerative diseases with tau pathology."

A Link between Abeta and Tau

This especially applies to Alzheimer's disease. Here another molecule comes into play: "amyloid beta" (Abeta). In Alzheimer's, this protein also accumulates in the brain. In contrast to tau proteins, this does not happen within the neurons but between them. In addition, deposition of Abeta starts in early phases of the disease, while aggregation of tau proteins occurs later.

In previous studies, Heneka and colleagues were able to show that the inflammasome can promote the aggregation of Abeta. Here is where the connection to the recent findings comes in. "Our results support the amyloid cascade hypothesis for the development of Alzheimer's. According to this hypothesis, deposits of Abeta ultimately lead to the development of tau pathology and thus to cell death," said Heneka. "Our current study shows that the inflammasome is the decisive and hitherto missing link in this chain of events, because it bridges the development from Abeta pathology to tau pathology. It passes the baton, so to speak." Thus, deposits of Abeta activate the inflammasome. As a result, formation of further deposits of Abeta is promoted. On the other hand, chemical changes occur to the tau proteins resulting into their aggregation.

A Possible Starting Point for Therapies

"Inflammatory processes promote the development of Abeta pathology, and as we have now been able to show, of tau pathology as well. Thus, the inflammasome plays a key role in Alzheimer's and other brain diseases," said Heneka, who is involved in the Bonn-based "ImmunoSensation" cluster of excellence and who also teaches at the University of Massachusetts Medical School. With these findings, the neuroscientist sees opportunities for new treatment methods. "The idea of influencing tau pathology is obvious. Future drugs could tackle exactly this aspect by modulating the immune response. With the development of tau pathology, mental abilities decline more and more. Therefore, if tau pathology could be contained, this would be an important step towards a better therapy."
-end-
Original Publication

NLRP3 inflammasome activation drives tau pathology
Christina Ising et al., Nature (2019), DOI: 10.1038/s41586-019-1769-z

DZNE - German Center for Neurodegenerative Diseases

Related Neurons Articles from Brightsurf:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.

Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.

A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.

Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.

Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.

Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.

Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.

How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.

A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.

Read More: Neurons News and Neurons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.