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LINK FOUND BETWEEN PAIN, IMMUNE, AND REPRODUCTIVE SYSTEMS
INDIANAPOLIS-- For the first time a link has been established
between the pain system, the immune system and the reproductive system.
These findings go far beyond the known pain relief role of pain receptors.
A team of scientists at the Indiana University School of Medicine
led by Lei Yu, Ph.D., professor of medical and molecular genetics and a
principal investigator at the Walther Oncology Center, has been studying the
mu opioid receptor, the body's most significant pain gateway. The mu
receptor, named after morphine's initial letter, is the body's biological
switch that mediates both the pain-relieving and the euphoric effects
produced by morphine and heroin. Dr. Yu's team was responsible for cracking
the genetic code for this receptor in 1993. And now, they have made new
discoveries about the mu receptor, by studying genetically modified mice in
which the function of the mu receptor has been disabled.
The new findings, published in the April 21, 1997, issue of the
Journal of Experimental Medicine, suggest a novel role for the mu opioid
receptor in both hematopoiesis (the creation and proliferation of cells in
the body's blood and immune system), and the reproductive system. "These
results indicate that the mu receptor is involved in a range of diverse
biological processes in addition to its known involvement in pain relief,"
said Dr. Yu.
The observation of increased proliferation of "mother"
(hematopoietic progenitor) cells which defend the body against infection
came as a complete surprise to Dr. Yu and his colleagues. "This is the
first time that the mu receptor has been linked to hematopoiesis," said Dr.
Yu. Understanding how the link is made may lead to the development of new
treatments, such as enhancing blood cell production in cancer patients who
receive bone marrow transplant, or modulating the immune system in fighting
HIV infection.
The observed link between the mu receptor and the sexual function
was equally surprising. I.U. researchers noticed that the mutant male mice
showed less interest in copulating with receptive females, as well as
decreases in sperm count/motility and smaller offspring litter size. Dr. Yu
and his colleagues speculate that this discovery may suggest new treatments
for impotence and reproductive dysfunction in males.
"These observations in the mouse model correlate with anecdotal
accounts about opioid consumption in humans influencing one's immune
functions and sex drive, and thus may serve as a model to further study the
underlying biology," said Dr. Yu.
In addition to Dr. Yu, other Indiana University researchers on the
study were Mingting Tian, Hal E. Broxmeyer, Yi Fan, Zhennan Lai, Shengwen
Zhang, Susan Aronica, Scott Cooper, Robert M. Bigsby, Rosemary Steinmetz,
Sandra J. Engle, Anton Mestek, Jonathan D. Pollock (now at the National
Institute on Drug Abuse), and Jay A. Tischfield, Michael N. Lehman, Heiko T.
Jansen, Moyin Ying, and Peter J. Stambrook of the University of Cincinnati
College of Medicine also participated in the study.
Yu's research was funded by the National Institute on Drug Abuse
(NIDA), part of the National Institutes of Health. NIDA is the primary
federal agency for the conduct and support of research to increase knowledge
and develop strategies to deal with health problems and issues associated
with drug abuse and addiction.
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Marie Brunsman
Media Assistant
Public & Media Relations
[email protected]
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