Corporate Banner
Satellite Banner
Proteomics
Scientific Community
 
Become a Member | Sign in
Home>News>This Article
  News
Return

NIH-Funded Research Provides New Clues on How ApoE4 Affects Alzheimer's Risk

Published: Tuesday, October 30, 2012
Last Updated: Tuesday, October 30, 2012
Bookmark and Share
Researchers found that ApoE4 triggers an inflammatory reaction that weakens the blood-brain barrier.

Common variants of the ApoE gene are strongly associated with the risk of developing late-onset Alzheimer's disease, but the gene's role in the disease has been unclear.

Now, researchers funded by the National Institutes of Health have found that in mice, having the most risky variant of ApoE damages the blood vessels that feed the brain.

The researchers found that the high-risk variant, ApoE4, triggers an inflammatory reaction that weakens the blood-brain barrier, a network of cells and other components that lines brain's brain vessels.

Normally, this barrier allows nutrients into the brain and keeps harmful substances out.

The study appears in Nature, and was led by Berislav Zlokovic, M.D., Ph.D., director of the Center for Neurodegeneration and Regeneration at the Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles.

"Understanding the role of ApoE4 in Alzheimer's disease may be one of the most important avenues to a new therapy," Dr. Zlokovic said. "Our study shows that ApoE4 triggers a cascade of events that damages the brain's vascular system," he said, referring to the system of blood vessels that supply the brain.

The ApoE gene encodes a protein that helps regulate the levels and distribution of cholesterol and other lipids in the body. The gene exists in three varieties.

ApoE2 is thought to play a protective role against both Alzheimer's and heart disease, ApoE3 is believed to be neutral, and ApoE4 confers a higher risk for both conditions.

Outside the brain, the ApoE4 protein appears to be less effective than other versions at clearing away cholesterol; however, inside the brain, exactly how ApoE4 contributes to Alzheimer's disease has been a mystery.

Dr. Zlokovic and his team studied several lines of genetically engineered mice, including one that lacks the ApoE gene and three other lines that produce only human ApoE2, ApoE3 or ApoE4. Mice normally have only a single version of ApoE.

The researchers found that mice whose bodies made only ApoE4, or made no ApoE at all, had a leaky blood-brain barrier. With the barrier compromised, harmful proteins in the blood made their way into the mice's brains, and after several weeks, the researchers were able to detect loss of small blood vessels, changes in brain function, and a loss of connections between brain cells.

"The study demonstrates that damage to the brain's vascular system may play a key role in Alzheimer's disease, and highlights growing recognition of potential links between stroke and Alzheimer's-type dementia," said Roderick Corriveau, Ph.D., a program director at NIH's National Institute of Neurological Disorders and Stroke (NINDS), which helped fund the research. "It also suggests that we might be able to decrease the risk of Alzheimer's disease among ApoE4 carriers by improving their vascular health."

The researchers also found that ApoE2 and ApoE3 help control the levels of an inflammatory molecule called cyclophilin A (CypA), but ApoE4 does not. Levels of CypA were raised about five-fold in blood vessels of mice that produce only ApoE4.

The excess CypA then activated an enzyme, called MMP-9, which destroys protein components of the blood-brain barrier. Treatment with the immunosuppressant drug cyclosporine A, which inhibits CypA, preserved the integrity of the blood-brain barrier and lessened damage to the brain.

An inhibitor of the MMP-9 enzyme had similar beneficial effects. In prior studies, inhibitors of this enzyme have been shown to reduce brain damage after stroke in animal models.

"These findings point to cyclophilin A as a potential new drug target for Alzheimer's disease," said Suzana Petanceska, Ph.D., a program director at NIH's National Institute on Aging (NIA), which also funded Dr. Zlokovic's study.

"Many population studies have shown an association between vascular risk factors in mid-life, such as high blood pressure and diabetes, and the risk for Alzheimer's in late-life. We need more research aimed at deepening our understanding of the mechanisms involved and to test whether treatments that reduce vascular risk factors may be helpful against Alzheimer's."

Alzheimer's disease is the most common cause of dementia in older adults, and affects more than 5 million Americans. A hallmark of the disease is a toxic protein fragment called beta-amyloid that accumulates in clumps, or plaques, within the brain.

Gene variations that cause higher levels of beta-amyloid are associated with a rare type of Alzheimer's that appears early in life, between age 30 and 60.

However, it is the ApoE4 gene variant that is most strongly tied to the more common, late-onset type of Alzheimer's disease. Inheriting a single copy of ApoE4 from a parent increases the risk of Alzheimer's disease by about three-fold. Inheriting two copies, one from each parent, increases the risk by about 12-fold.

Dr. Zlokovic's study and others point to a complex interplay between beta-amyloid and ApoE4. On the one hand, beta-amyloid is known to build up in and damage blood vessels and cause bleeding into the brain.

On the other hand, Dr. Zlokovic's data suggest that ApoE4 can damage the vascular system independently of beta-amyloid. He theorizes that this damage makes it harder to clear beta-amyloid from the brain.

Some therapies under investigation for Alzheimer's focus on destroying amyloid plaques, but therapies designed to compensate for ApoE4 might help prevent the plaques from forming, he said.


Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,500+ scientific posters on ePosters
  • More than 3,700+ scientific videos on LabTube
  • 35 community eNewsletters


Sign In



Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into TechnologyNetworks.com you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Crystal Clear Images Uncover Secrets of Hormone Receptors
NIH researchers gain better understanding of how neuropeptide hormones trigger chemical reactions in cells.
Monday, August 03, 2015
Vital Protein in Healthy Fertilization Process Identified
Researchers at the National Institutes of Health have discovered a protein that plays a vital role in healthy egg-sperm union in mice.
Monday, July 27, 2015
NIH Joins Public-Private Partnership to Fund Research on Autism Biomarkers
Biomarkers Consortium project to improve tools for measuring and treating social impairment in children with autism.
Tuesday, July 21, 2015
Mystery of the Tubulin Code Unravelled
NIH study provides a glimpse into the code that controls variety of cell functions.
Wednesday, May 13, 2015
Mouse Study Reveals Potential Clue to Extra Fingers or Toes
NIH-funded study finds that gene appears to regulate protein signals inside the cell.
Tuesday, December 02, 2014
NIH Grant for Texas Biomed to Perform Mass Spec-Based Studies into Heart Disease
Institute awarded $2.7M grant from the NIH to fund innovative approaches to genetics research for the development of new therapies for heart disease and other conditions.
Wednesday, August 20, 2014
GTEx Project to Expand Functional Studies of Genomic Variation
Larger set of human tissues to be analyzed to contribute to a database and tissue bank that researchers can use to study how genomic variants influence gene activity.
Wednesday, August 06, 2014
Subcellular Imaging Visualizes Structures of Brain Receptors
The advance opens a new window to study protein interactions in cell membranes in exquisite detail.
Tuesday, August 05, 2014
NIH Funds $24M into Alzheimer’s Disease Genome Research
Scientists will analyze genome sequence data to identify gene risk, protective factors.
Tuesday, July 08, 2014
Muscle Weakness Seen in Alcoholism Linked to Mitochondrial Repair Issues
Scientists found evidence that chronic heavy alcohol use affects a gene involved in mitochondrial repair and muscle regeneration.
Tuesday, April 22, 2014
Gene Linked to Excess Male Hormones in Female Infertility Disorder
Discovery by NIH-supported researchers may lead to diagnostic test, treatment.
Thursday, April 17, 2014
Unexpected Protein Partnership has Implications for Cancer Treatment
Scientists have identified a macrophage that works together in response to cancer drugs to increase inflammation in a way that may alter tumor growth.
Tuesday, April 15, 2014
Too Much Protein May Kill Brain Cells As Parkinson’s Progresses
NIH-funded study on key Parkinson’s gene finds a possible new target for monitoring the disease.
Friday, April 11, 2014
Underlying Genetics and Marker For Stroke Discovered
NIH-funded findings point to new potential strategies for disease prevention, treatment.
Friday, March 21, 2014
Speeding Validation of Disease Targets
NIH, industry and non-profits join forces to develop new treatments earlier, beginning with Alzheimer’s, type 2 diabetes, and autoimmune disorders.
Tuesday, February 04, 2014
Scientific News
Liquid Biopsies: Utilization of Circulating Biomarkers for Minimally Invasive Diagnostics Development
Market Trends in Biofluid-based Liquid Biopsies: Deploying Circulating Biomarkers in the Clinic. Enal Razvi, Ph.D., Managing Director, Select Biosciences, Inc.
Self-Assembling, Biomimetic Membranes May Aid Water Filtration
A synthetic membrane that self assembles and is easily produced may lead to better gas separation, water purification, drug delivery and DNA recognition, according to an international team of researchers.
Crystal Clear Images Uncover Secrets of Hormone Receptors
NIH researchers gain better understanding of how neuropeptide hormones trigger chemical reactions in cells.
Error Correction Mechanism in Cell Division
Cell biologists have reported an advance in understanding the workings of an error correction mechanism that helps cells detect and correct mistakes in cell division early enough to prevent chromosome mis-segregation and aneuploidy, that is, having too many or too few chromosomes.
Crucial for Stem Cell Survival Protein Identified Using Editing Tool CRISPR
A team of University of Wisconsin-Madison engineers has identified a protein that is integral to the survival and self-renewal processes of human pluripotent stem cells (hPSC).
Sorting Through Cellular Statistics
Aaron Dinner, professor in chemistry, and his graduate student Herman Gudjonson are trying to read the manual of life, DNA, as part of the Dinner group’s research into bioinformatics—the application of statistics to biological research.
First Artificial Ribosome Designed
Researchers at the University of Illinois at Chicago and Northwestern University have engineered a tethered ribosome that works nearly as well as the authentic cellular component, or organelle, that produces all the proteins and enzymes within the cell.
The Genetic Roots of Adolescent Scoliosis
Scientists at the RIKEN Center for Integrative Medical Sciences in collaboration with Keio University in Japan have discovered a gene that is linked to susceptibility of Scoliosis.
HIV Susceptibility Linked to Little-Understood Immune Cell Class
High levels of diversity among immune cells called natural killer cells may strongly predispose people to infection by HIV, and may be driven by prior viral exposures, according to a new study.
New Tech Enables Epigenomic Analysis with a Mere 100 Cells
A new technology that will dramatically enhance investigations of epigenomes, the machinery that turns on and off genes and a very prominent field of study in diseases such as stem cell differentiation, inflammation and cancer has been developed by researchers at Virginia Tech.
Scroll Up
Scroll Down
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
 
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,500+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
3,700+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FREE!