Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists at the UA make critical end-stage liver disease discovery

28.04.2014

The discovery of an unknown cellular pathway has helped scientists and physicians better understand end-stage liver disease and offers a potential target for new therapeutics

A team of researchers in the University of Arizona's College of Pharmacy has discovered a molecular pathway that could be key to creating new therapeutics that would slow or even reverse the progression of end-stage liver disease.


Zhang's research group studies the molecular mechanisms cells use to protect themselves from damage caused by toxicants and carcinogens.

Credit: Daniel Stolte/ University of Arizona News

Although cirrhosis of the liver is most commonly associated with alcohol or drug abuse, the condition – marked by scar tissue replacing healthy liver tissue – also can result from viral hepatitis, obesity and diabetes, as well as certain inherited diseases.

According to the National Institutes of Health, cirrhosis is the 12th leading cause of death by disease in the U.S. As with many other human pathologic conditions, end-stage liver disease goes hand in hand with oxidative stress, which refers to damage inflicted to biological tissues by reactive oxygen molecules.

Such molecules, also called free radicals, occur naturally as a byproduct of metabolic processes in the body and are associated with many chronic diseases including cancer, diabetes, neurodegenerative and cardiovascular diseases.

"Cells keep oxidative stress under control through various mechanisms," said Donna Zhang, a professor in the UA Department of Pharmacology and Toxicology, explaining that most of these mechanisms involve Nrf2, a protein present in virtually every cell that acts as a molecular switch. Nrf2 activates various biochemical mechanisms inside the cell that capture reactive oxygen molecules or dispose of damaged cellular components before they can cause more trouble. The antioxidants found in many fruits and vegetables exert their healthful benefits by capturing reactive oxygen molecules.

Under normal, healthy conditions, when no oxidative stress response is needed, an enzyme called Keap1 constantly chews up Nrf2, keeping its level low.

"Then, under stress from reactive oxygen molecules, or when you eat antioxidants from certain plants like broccoli sprouts, it prevents Keap1 from eating up Nrf2, allowing it to accumulate in the cell," explained Zhang, who is also a member of the UA BIO5 Institute. "Nrf2 then activates the cellular antioxidant response. That is how antioxidants work." According to conventional wisdom, our bodies turn on their Nrf2-mediated protection pathway when subjected to high oxidative stress to limit the damage from the destructive oxygen compounds. During liver cirrhosis, Nrf2 should be induced by oxidative stress, but for reasons unclear until this study, this does not happen.

"This was a puzzle before we did our study," she said. "Somehow the protective mechanism mediated by Nrf2 is compromised by another factor, other than Keap1, in liver cirrhosis." Adding to the mystery is the fact that drugs aimed at inhibiting Keap1 from chewing up Nrf2 have proven ineffective in a cirrhotic liver.

When Zhang and her colleagues studied tissue samples from a human cirrhotic liver, they discovered the reason behind the inexplicably low Nrf2 levels in the face of rampant oxidative stress.

It turned out that another enzyme chews up Nrf2 and prevents the much-needed antioxidant response, exacerbating the disease process. That protein, Hrd1, is part of the cells' garbage disposal – it specializes in destroying misfolded proteins before they can accumulate and damage cell components.

Under normal conditions, Hrd1 levels are low, so it does not interfere much with Nrf2, explained Zhang. As liver cirrhosis progresses, excessive inflammation triggers the garbage-mediated stress response and Hrd1 becomes very abundant and begins chewing up Nrf2.

The study is published in the April 1 issue of the journal Genes and Development. The first author of the report is Tongde Wu, a graduate of the UA Department of Pharmacology and Toxicology, who developed the project as part of her dissertation research. Fei Zhao and Eli Chapman, in the same department, also contributed to the research. The work resulted from a collaboration between Zhang's research group and Deyu Fang, Beixue Gao and Can Tan at Northwestern University Feinberg School of Medicine in Chicago. Other contributors are Naoko Yagishita and Toshihiro Nakajima of St. Marianna University School of Medicine in Kawasaki, Japan, and Pak K. Wong of the UA College of Engineering.

The discovery could change the way scientists develop therapeutics, as it provides a new target for future drugs. In laboratory experiments, Zhang and her colleagues were able to restore Nrf2 levels in cirrhotic liver tissue by inactivating Hrd1, effectively reversing liver cirrhosis in mice.

"Previous efforts only focused on the Keap1 protein and tried to prevent it from breaking down Nrf2," Zhang said. "Now we know there is a second player in the game – Hrd1 – that we need to inhibit in order to restore Nrf2 levels.

"Boosting Nrf2 is good for protection in general, which is why you should always eat your broccoli," she stressed.

###

The study, "Hrd1 suppresses Nrf2-mediated cellular protection during liver cirrhosis," is published in the April 1 issue of the journal Genes and Development: http://genesdev.cshlp.org/content/28/7/708.abstract

Daniel Stolte | UA News
Further information:
http://www.arizona.edu

Further reports about: Department Development Medicine Toxicology damage death diseases drugs enzyme healthy liver pathway protein

More articles from Health and Medicine:

nachricht New antibody analysis accelerates rational vaccine design
09.08.2018 | Scripps Research Institute

nachricht Distrust of power influences choice of medical procedures
01.08.2018 | Johannes Gutenberg-Universität Mainz

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

Im Focus: World record: Fastest 3-D tomographic images at BESSY II

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...

Im Focus: A molecular switch may serve as new target point for cancer and diabetes therapies

If certain signaling cascades are misregulated, diseases like cancer, obesity and diabetes may occur. A mechanism recently discovered by scientists at the Leibniz- Forschungsinstitut für Molekulare Pharmakologie (FMP) in Berlin and at the University of Geneva has a crucial influence on such signaling cascades and may be an important key for the future development of therapies against these diseases. The results of the study have just been published in the prestigious scientific journal 'Molecular Cell'.

Cell growth and cell differentiation as well as the release and efficacy of hormones such as insulin depend on the presence of lipids. Lipids are small...

Im Focus: Touring IPP’s fusion devices per virtual-reality viewer

ASDEX Upgrade and Wendelstein 7-X – as if you were there / 360° view of fusion research

You seem to be standing in the plasma vessel looking around: Where otherwise plasmas with temperatures of several million degrees are being investigated, with...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Ph.D. student develops spinning heat shield for future spacecraft

10.08.2018 | Physics and Astronomy

Investigating global air pollution

10.08.2018 | Life Sciences

The “TRiC” to folding actin

10.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>