Stress slows wound healing; oxygen helps
29 Jul 2005
Wound healing is slow when an animal is stressed, but extra oxygen almost
completely reverses the effect, according to researchers at the University of
Illinois at Chicago.
In a study of laboratory mice, Phillip Marucha, professor of periodontics at the
UIC College of Dentistry, and his colleagues found that psychological stress,
brought on by confinement, delayed the closing of wounds by more than 45
percent.
A range of cell and genetic changes accounted for the slow recovery.
"The cells that help remake tissue didn't differentiate the way they would
have in normal animals. They didn't line up the way they were supposed to. And
they didn't develop the tiny contractile fibers that help pull together the
edges of the wound," Marucha said. "Expression of the gene that codes
the protein for those fibers was impaired."
However, when the animals received hyperbaric oxygen (oxygen at a greater
pressure than atmospheric oxygen), the delay in healing was almost eliminated.
Marucha said stress launches a sequence of events that constrict blood vessels
and deprive the tissues of oxygen.
"Without sufficient oxygen, tissues can't heal," he said. "Oxygen
activates the inflammatory cells of the immune system that help healing. Also,
oxygen derivatives like bleach and peroxide are part of the arsenal of noxious
products that these cells use to kill the bacteria in wounds."
The researchers hypothesized that the hyperbaric oxygen therapy reversed the
delay in healing not because it relieved stress, but because it helped directly
in wound healing.
To test that hypothesis, they measured levels of expression of the gene for an
enzyme called inducible nitric oxide synthase, which makes nitric oxide. Nitric
oxide is critically involved in wound healing, by increasing blood flow and the
delivery of oxygen, and by attacking bacteria. If oxygen levels fall, the gene's
activity increases.
The researchers found that when animals were stressed, expression of the gene
increased, presumably to help make more nitric oxide. But when the animals
received hyperbaric oxygen, gene expression returned to normal levels,
suggesting that the nitric oxide levels necessary for healing had been restored
by the increased tissue oxygen levels.
Other researchers involved in the study were Praveen Gajendrareddy, at UIC, and
Chandan Sen, Michael Horan, Sukanya Subramanian and Arthur Strauch at Ohio State
University.
The study has been published in Brain, Behavior, and Immunity and was funded by
grants from the National Institutes of Health.
For more information about the UIC College of Dentistry, visit dentistry.uic.edu.
UIC ranks among the nation's top 50 universities in federal research funding and
is Chicago's largest university with 25,000 students, 12,000 faculty and staff,
15 colleges and the state's major public medical center. A hallmark of the
campus is the Great Cities Commitment, through which UIC faculty, students and
staff engage with community, corporate, foundation and government partners in
hundreds of programs to improve the quality of life in metropolitan areas around
the world.
Sharon Butler
sbutler@uic.edu
312-355-2522
University of Illinois at Chicago
http://www.uic.edu
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