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From: HEMI-KIDS Discussion list for parents of children with hemiplegia
[mailto:[log in to unmask]] On Behalf Of Meir Weiss
Sent: Monday, January 19, 2004 16:00
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Subject: [HK] Preconditioning the Brain May Protect against Stroke
Stroke
Preconditioning the Brain May Protect against Stroke
http://www.ninds.nih.gov/news_and_events/news_article_stroke_preconditio
ning.htm
National Institute of Neurological Disorders and Stroke
See MEDLINEplus topic: Stroke
Preconditioning the brain may protect against stroke
Tuesday, January 13, 2004
Overview A December 2003 news article on genetic changes to protect the
brain against a second larger stroke, prepared by the National Institute
of Neurological Disorders and Stroke (NINDS).
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Scientists studying an animal model of stroke have learned that the
brain reacts to the trauma caused by a mild stroke in a way that serves
to protect it from a subsequent injurious attack. The discovery may aid
in the development of medications for persons at risk of stroke.
Stroke is the nation's third largest killer. There are as many as
700,000 strokes in the U.S. per year and 150,000 deaths as a result. The
majority of strokes are ischemic, caused when a clot suddenly blocks
blood flow to a vein or artery. Disabilities that can result from stroke
include paralysis, cognitive deficits, speech problems, emotional
difficulties, daily living problems, and pain.
Researchers Mary Stenzel-Poore, Ph.D., Oregon Health & Science
University School of Medicine, and Roger Simon, M.D., Legacy Health
Systems, led colleagues in testing the hypothesis that "ischemic
preconditioning" naturally provides protection against a later,
prolonged ischemic stroke. This preconditioning is based on a model
which states that an organism, if given time to adjust to a trauma, will
become stronger and more able to resist later trauma that might
otherwise be lethal. The study was funded by the National Institute of
Neurological Disorders and Stroke (NINDS) and published in The Lancet.*
The researchers studied gene expression and cellular mechanisms in
normal mice and in a mouse model of stroke that was preconditioned
(these mice had their cerebral artery blocked for 15 minutes, resulting
in small protective strokes called transient ischemic attacks or TIA).
The preconditioned mice showed an innate reprogramming of certain gene
expression that led to a 70 percent decrease in brain damage during a
second larger stroke.
"These results show that the body is able to reprogram or change its
genetic response in anticipation of a future, larger stroke," said Dr.
Simon. "Several systems were found to adapt to TIA insult and either
increase or decrease gene expression in a way that protects the body."
The most striking changes in gene profiles were in response to ischemic
injury following preconditioning. In response to an induced stroke, the
genetic activity in preconditioned animals was found to slow metabolism,
conserve cellular energy, and prevent blood clotting. Other changes seen
in preconditioned mice included decreased blood flow and limited glucose
and oxygen intake similar to that seen in hibernation.
"The genetic changes that occur in animals preconditioned for stroke are
very similar to those that occur in hibernating animals, providing an
evolutionary basis for this neuroprotective response," noted Dr.
Stenzel-Poore. "Our findings link preconditioning in the brain with
systemic effects of longer blood clotting times, which would be an
important neuroprotective strategy against ischemic stroke."
Ischemic tolerance studies led by John Hallenbeck, M.D., NINDS
intramural stroke branch chief, are revealing a cellular mechanism in
hibernating ground squirrels that may protect the nervous system from
being damaged during the profound reduction in organ blood flow, greatly
reduced capacity to delivery oxygen, and extremely cold temperatures
(hypothermic stress) that characterize hibernation. "A better
understanding of the body's naturally-occurring neuroprotective
mechanisms may lead to new therapies and/or preventive measures for
persons at high risk of ischemia and other neurological disorders," said
Dr. Hallenbeck.
The findings may lead to preventive medicines that target certain genes
and/or a combination therapy to address the many aspects of stroke.
For more information on stroke, please refer to the NINDS Stroke
Information Page
*"Effect of ischaemic preconditioning on genomic response to cerebral
ischaemia: similarity to neuroprotective strategies in hibernation and
hypoxia-tolerant states." Stenzel-Poore, Mary P; Stevens, Susan L.;
Xiong, Zhigang; Lessov, Nikola S.; Harrington, Christina A.; Mori,
Motomi; Meller, Robert; Rosenzweig, Holly L.; Tobar, Eric; Shaw, Tatyana
E.; Chu, Xiangping; Simon, Roger P. The Lancet, Vol. 362, September 27,
2003, pp. 1028-1037.
- By Paul Girolami
Reviewed January 13, 2004
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