Corporate Banner
Satellite Banner
Genomics
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

Join For Free

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 3,000+ scientific posters on ePosters
  • More than 4,500+ 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

Drug Might Help Treat Sepsis
A DNA enzyme called Top1 plays a key role in turning on genes that cause inflammation in mouse and human cells in response to pathogens. A drug blocking this enzyme rescued mice from lethal inflammatory responses, suggesting a potential treatment for sepsis.
Wednesday, May 18, 2016
NIH Funds New Studies on Ethical, Legal and Social Impact of Genomic Information
Four new grants from the National Institutes of Health will support research on the ethical, legal and social questions raised by advances in genomics research and the increasing availability of genomic information.
Wednesday, May 18, 2016
Researchers Identify Genetic Links to Educational Attainment
Researchers at NIH have suggested that the large genetics analyses may be able to help discover biological pathways as well.
Thursday, May 12, 2016
Submissions Open for the Cancer Moonshot Program
NCI opens online platform to submit ideas about research for Cancer Moonshot.
Tuesday, April 19, 2016
NIH Sequences Genome of a Fungus
Researchers at the Institute have sequenced genome of human, mouse and rat Pneumocystis that cause life-threatening Pneumonia in immunosuppressed hosts.
Tuesday, April 12, 2016
Decoding Ties Between Vascular Disease, Alzheimer’s
NIH consortium uses big data, team science to uncover complex interplay of factors.
Tuesday, March 15, 2016
Researchers Find Link Between Death of Tumor-Support Cells and Cancer Metastasis
Researchers at NIH have found that the lifespan of supportive cells in a tumor may control the spread of cancer.
Tuesday, February 23, 2016
Tick Genome Reveals Secrets of a Successful Bloodsucker
NIH-funded study could lead to new tick control methods.
Tuesday, February 09, 2016
Genomic Signature Shared by Five Types of Cancer
National Institutes of Health researchers have identified a striking signature in tumor DNA that occurs in five different types of cancer.
Monday, February 08, 2016
Cancer Drug Target Visualized at Atomic Resolution
New study using cryo-electron microscopy shows how potential drugs could inhibit cancer.
Thursday, February 04, 2016
Genome-Wide Study Yields Markers of Lithium Response
An international consortium of scientists has identified a stretch of chromosome that is associated with responsiveness to the mood-stabilizing medication lithium among patients with bipolar disorder.
Monday, February 01, 2016
Schizophrenia’s Strongest Known Genetic Risk Deconstructed
Suspect gene may trigger runaway synaptic pruning during adolescence – NIH-funded study.
Thursday, January 28, 2016
NIH Genome Sequencing Program Targets the Genomic Bases of Common, Rare Disease
The National Institutes of Health will fund a set of genome sequencing and analysis centers whose research will focus on understanding the genomic bases of common and rare human diseases.
Friday, January 15, 2016
Three Glaucoma-Related Genes Discovered
NIH-funded genetics analysis of glaucoma is largest to date.
Tuesday, January 12, 2016
International Study Reveals New Genetic Clues to AMD
NIH-funded research provides framework for future studies of AMD biology, therapy.
Tuesday, December 22, 2015
Scientific News
Scientists Find Evidence That Cancer Can Arise Changes
Researchers at Rockefeller University have found a mutation that affects the proteins that package DNA without changing the DNA itself can cause a rare form of cancer.
Modified Microalgae Converts Sunlight into Valuable Medicine
A special type of microalgae can soon produce valuable chemicals such as cancer treatment drugs and much more just by harnessing energy from the sun.
Breakthrough Approach to Breast Cancer Treatment
Scripps scientists have designed a drug candidate that decreases growth of breast cancer cells.
Loss Of Y Chromosome Increases Risk Of Alzheimer’s
Men with blood cells that do not carry the Y chromosome are at greater risk of being diagnosed with Alzheimer’s disease. This is in addition to an increased risk of death from other causes, including many cancers. These new findings by researchers at Uppsala University could lead to a simple test to identify those at risk of developing Alzheimer’s disease.
A Guide to CRISPR Gene Activation
A comparison of synthetic gene-activating Cas9 proteins can help guide research and development of therapeutic approaches.
Gene That Lowers Heart Attack Risk Identified
Individuals with a rare twelve-letter deletion from a gene on chromosome 17 have significantly reduced non-HDL cholesterol levels and a 35% lower than average risk of heart disease.
Testing Non-Breast/Ovarian Cancer Genes
Researchers have found that expanding gene panel beyond breast/ovarian cancer genes in these patients does not add any clinical benefit. Instead, testing has produced more questions than answers.
Myeloid-Derived Suppressor Cells Play Role in Tumor Growth
Researchers at Baylor College of Medicine have reported a new mechanism that helps cancer cells engage myeloid-derived suppressor cells.
Cancer Cells Coordinate to Form Roving Clusters
Rice University scientists identify ‘smoking gun’ in metastasis of hybrid cells.
Genes For Nose Shape Found
Genes that drive the shape of human noses have been identified by a UCL-led study.
Skyscraper Banner

SELECTBIO Market Reports
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
3,000+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
4,500+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FOR FREE!