A type of antioxidant may not be as safe as once thought

Sep 04, 2007

Certain preparations taken to enhance athletic performance or stave off disease contain an anti-oxidant that could cause harm. According to new research at the University of Virginia Health System, N-acetylcysteine (NAC), an anti-oxidant commonly used in nutritional and body-building supplements, can form a red blood cell-derived molecule that makes blood vessels think they are not getting enough oxygen.

This leads to pulmonary arterial hypertension (PAH), a serious condition characterized by high blood pressure in the arteries that carry blood to the lungs. The results appear in the September issue of the Journal of Clinical Investigation.

“NAC fools the body into thinking that it has an oxygen shortage,” said Dr. Ben Gaston, UVa Children’s Hospital pediatrician and researcher who led the study. “We found that an NAC product formed by red blood cells, know as a nitrosothiol, bypasses the normal regulation of oxygen sensing. It tells the arteries in the lung to ‘remodel’; they become narrow, increasing the blood pressure in the lungs and causing the right side of the heart to swell.”

Gaston notes that this is an entirely new understanding of the way oxygen is sensed by the body. The body responds to nitrosothiols, which are made when a decreased amount of oxygen is being carried by red blood cells; the response is not to the amount of oxygen dissolved in blood. He says that this pathway was designed much more elegantly than anyone had previously imagined. “We were really surprised”, he said.

The research team administered both NAC and nitrosothiols to mice for three weeks. The NAC was converted by red blood cells into the nitrosothiol, S-nitroso-N-acetylcysteine (SNOAC). The normal mice that received NAC and SNOAC developed PAH. Mice missing an enzyme known as endothelial nitric oxide synthase did not convert NAC to SNOAC, and were protected from the adverse effects of NAC, but not SNOAC. This suggests that NAC must be converted to SNOAC to cause PAH.

Could regular use of NAC produce the same effects in humans" The next step is to determine a threshold past which antioxidant use becomes detrimental to heart or lung function, according to Dr. Lisa Palmer, co-researcher of the study.

“The more we understand about complexities in humans, the more we need to be aware of chemical reactions in the body,” said Palmer.

According to Gaston and Palmer, NAC is being tested in clinical trials for patients with cystic fibrosis as well as other conditions; and clinical trials with nitrosothiols are being planned. These results, Palmer says, should motivate researchers to check their patients for PAH.

The results also open up a range of possibilities in treating PAH. Palmer added that the signaling process could be restorative and healing if they figured out how to keep NAC from fooling the body.

“From here we could devise new ways for sensing hypoxia or we could in theory modify signaling to treat PAH,” Palmer said.

Source: University of Virginia Health System

Explore further: Chile government rejects 14 year-old's plea for euthanasia

add to favorites email to friend print save as pdf

Related Stories

Trial nears in high-profile Silicon Valley sex bias case

4 hours ago

(AP)—A jury was picked Monday to determine whether a venerable Silicon Valley venture capital firm is liable in a sexual discrimination lawsuit or is the victim of a former employee forced out because of ...

UN report urges drones for peace missions

4 hours ago

A UN report is calling for drones to be deployed in most peacekeeping missions as part of a major technological leap needed to help the United Nations confront world crises, the lead expert of the study said Monday.

Recommended for you

Many transplant surgeons suffer burnout

Feb 25, 2015

Despite saving thousands of lives yearly, nearly half of organ transplant surgeons report a low sense of personal accomplishment and 40% feel emotionally exhausted, according to a national study on transplant surgeon burnout

5 tips for handling early-year medical expenses

Feb 25, 2015

The clock on insurance deductibles reset on Jan. 1, and that means big medical bills are in store for some. Patients may be required to pay thousands of dollars before their health care coverage kicks in.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.