X-Message-Number: 32612
Date: Fri, 11 Jun 2010 19:09:45 -0700 (PDT)
From:
Subject: Freezing 'to Death' and Living to Tell About It
[I'd prefer to see some work done with human cells first, before putting too
much faith in this. Is there a nitric oxide connection here?]
Freezing 'to Death' and Living to Tell About It: Study Reveals How Suspended
Animation Protects Against Lethal Hypothermia
ScienceDaily (June 10, 2010) - How is it that some people who apparently freeze
to death, with no heart rate or respiration for extended periods, can be brought
back to life with no long-term negative health consequences? New findings from
the laboratory of cell biologist Mark B. Roth, Ph.D., of Fred Hutchinson Cancer
Research Center, may help explain the mechanics behind this widely documented
phenomenon.
Reporting online ahead of the July 1 print issue of Molecular Biology of the
Cell, Roth, a member of the Hutchinson Center's Basic Sciences Division, and
colleagues show that two widely divergent model organisms -- yeast and
nematodes, or garden worms -- can survive hypothermia, or potentially lethal
cold, if they are first put into a state of suspended animation by means of
anoxia, or extreme oxygen deprivation.
Roth and colleagues found that under normal conditions, yeast and nematode
embryos cannot survive extreme cold. After 24 hours of exposure to temperatures
just above freezing, 99 percent of the creatures expire. In contrast, if the
organisms are first deprived of oxygen and thus enter a state of anoxia-induced
suspended animation, 66 percent of the yeast and 97 percent of the nematode
embryos will survive the cold. Once normal growth conditions are resumed -- upon
rewarming and reintroduction of oxygen -- the organisms will reanimate and go
on to live a normal lifespan.
A better understanding of the potentially beneficial, symbiotic relationship
between low oxygen and low temperatures may one day lead to the development of
improved techniques for extending the shelf life of human organs for
transplantation, Roth said.
"We have found that extension of survival limits in the cold is possible if
oxygen consumption is first diminished," he said. "Our experiments in yeast and
nematodes suggest that organs may last longer outside the body if their oxygen
consumption is first reduced before they are made cold."
Roth's laboratory studies the potential clinical benefits of metabolic
flexibility -- from anoxia-induced reversible suspended animation to metabolic
hibernation brought on by exposure to agents such as hydrogen sulfide. The
ultimate goal of this work is to find ways to temporarily lower metabolism --
like dialing down a dimmer switch on a lamp -- as a means to "buy time" for
patients in trauma situations, such as victims of heart attack or blood-loss
injury, by reducing their need for oxygen until definitive medical care can be
given.
Roth first got the idea to study the link between anoxia-induced suspended
animation and hypothermia from documented cases in which humans have managed to
make complete recoveries after apparently freezing to death. Widely publicized
cases include Canadian toddler Erica Nordby, who in the winter of 2001 wandered
outside clad only in a diaper. Her heart had stopped beating for two hours and
her body temperature had plummeted to 61 degrees Fahreneit before she was
discovered, rewarmed and resuscitated. Another incident that made headlines was
that of a Japanese man, Mitsutaka Uchikoshi, who in 2006 fell asleep on a snowy
mountain and was found by rescuers 23 days later with a core body temperature of
71 degrees Fahrenheit. He, too, was resuscitated and made a full recovery.
"There are many examples in the scientific literature of humans who appear
frozen to death. They have no heartbeat and are clinically dead. But they can be
reanimated. Similarly, the organisms in my lab can be put into a state of
reversible suspended animation through oxygen deprivation and other means. They
appear dead but are not. We wondered if what was happening with the organisms in
my laboratory was also happening in people like the toddler and the Japanese
mountain climber. Before they got cold did they somehow manage to decrease their
oxygen consumption? Is that what protected them? Our work in nematodes and
yeast suggests that this may be the case, and it may bring us a step closer to
understanding what happens to people who appear to freeze to death but can be
reanimated," Roth said.
The mechanism by which anoxia-induced suspended animation protects against
extreme cold has to do with preventing the cascade of events that lead to
biological instability and, ultimately, death. For example, suspended animation
preserves the integrity of cell-cycle control by preventing an organism's cells
from dividing in an error-prone fashion. During suspended animation, the cell
cycle is reversibly halted. Upon reanimation, the cycle resumes as normal.
"When an organism is suspended its biological processes cannot do anything
wrong," Roth said. "Under conditions of extreme cold, sometimes that is the
correct thing to be doing; when you can't do it right, don't do it at all."
The first author of the paper, Kin Chan, Ph.D., formerly a postdoctoral research
associate in the Roth lab, is now with the Laboratory of Molecular Genetics in
the National Institute of Environmental Health Sciences at the National
Institutes of Health. The NIH and the National Science Foundation funded this
research.
Note: a video showing anoxia-induced suspended animation in a nematode embryo
can be found on YouTube at: http://www.youtube.com/watch?v=6okurk9O1ow
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff)
from materials provided by Fred Hutchinson Cancer Research Center.
Journal Reference:
Mol Biol Cell. 2010 May 12. [Epub ahead of print]
Suspended Animation Extends Survival Limits of Caenorhabditis elegans and
Saccharomyces cerevisiae at Low Temperature.
Chan K, Goldmark JP, Roth MB. Division of Basic Sciences, Fred Hutchinson Cancer
Research Center, Seattle, WA 98109.
Abstract
Monitoring Editor: David G. Drubin The orderly progression through the cell
division cycle is of paramount importance to all organisms, as improper
progression through the cycle could result in defects with grave
consequences. Previously, our lab has shown that model eukaryotes such as
Saccharomyces cerevisiae, Caenorhabditis elegans, and Danio rerio all retain
high viability after prolonged arrest in a state of anoxia-induced
suspended animation, implying that in such a state, progression through the
cell division cycle is reversibly arrested in an orderly manner. Here, we
show that S. cerevisiae (both wild-type and several cold-sensitive strains)
and C. elegans embryos exhibit a dramatic decrease in viability that is
associated with dysregulation of the cell cycle when exposed to low
temperatures. Further, we find that when the yeast or worms are first
transitioned into a state of anoxia-induced suspended animation before cold
exposure, the associated cold-induced viability defects are largely
abrogated. We present evidence that by imposing an anoxia-induced reversible
arrest of the cell cycle, the cells are prevented from engaging in aberrant
cell cycle events in the cold, thus allowing the organisms to avoid the
lethality that would have occurred in a cold, oxygenated environment.
PMID: 20462960
Free text>
http://www.molbiolcell.org/cgi/reprint/E09-07-0614v1
EMBO J. 2003 Feb 3;22(3):580-7.
Nitric oxide-induced suspended animation promotes survival during hypoxia.
Teodoro RO, O'Farrell PH. Department of Biochemistry and Biophysics, University
of California, San Francisco, CA 94143-0448, USA.
Abstract
Oxygen plays a key role in energy metabolism. However, there are organisms
that survive severe shortfalls in oxygen. Drosophila embryos rapidly arrest
development upon severe hypoxia and recover upon restoration of oxygen, even
days later. Stabilization of the normally unstable engrailed RNA and
protein preserved the localized striped pattern of this embryonic patterning
gene during 3 days in hypoxia. Severe hypoxia blocked expression of a
heat-shock-inducible lacZ transgene. Cyanide, a metabolic poison, did not
immediately block gene expression or turnover, arguing against a passive
response to energy limitation. In contrast, nitric oxide, a putative hypoxia
signal, induced a reversible arrest of development, gene expression and
turnover. Reciprocally, a nitric oxide scavenger allowed continued gene
expression and turnover during hypoxia, but it reduced hypoxia tolerance. We
suggest that hypoxia-induced stasis preserves the status quo of embryonic
processes and promotes survival. Our data implicate nitric oxide as a
mediator of this response and provide a system in which to investigate its
action.
PMID: 12554658
Free text>
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC140754/pdf/cdg070.pdf
[Interesting.]
J Neurochem. 2007 Jan;100(2):382-94. Epub 2006 Nov 20.
Nitric oxide regulates cell survival in purified cultures of avian retinal
neurons: involvement of multiple transduction pathways.
Mejia-Garcia TA, Paes-de-Carvalho R. Department of Neurobiology and Program of
Neuroimmunology, Institute of Biology, Federal Fluminense University, Niteroi,
Brazil.
Abstract
Nitric oxide (NO) is an important signaling molecule in the CNS, regulating
neuronal survival, proliferation and differentiation. Here, we explored the
mechanism by which NO, produced from the NO donor
S-nitroso-acetyl-d-l-penicillamine (SNAP), exerts its neuroprotective effect
in purified cultures of chick retinal neurons. Cultures prepared from
8-day-old chick embryo retinas and incubated for 24 h (1 day in culture, C1)
were treated or not with SNAP, incubated for a further 72 h (up to 4 days
in culture, C4), fixed, and the number of cells estimated, or processed for
cell death estimation, by measuring the reduction of the metabolic dye
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT).
Experimental cultures were run in parallel but were re-fed with fresh medium
in the absence or presence of SNAP at culture day 3 (C3), incubated for a
further 24 h up to C4, then fixed or processed for the MTT assay. Previous
studies showed that the re-feeding procedure promotes extensive cell death.
SNAP prevented this death in a concentration- and time-dependent manner
through the activation of soluble guanylate cyclase; this protection was
significantly reversed by the enzyme inhibitors
1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ) or LY83583, and mimicked
by 8-bromo cyclic guanosine 5'-phosphate (8Br-cGMP) (GMP) or
3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), guanylate cyclase
activators. The effect was blocked by the NO scavenger
2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). The effect of
NO was also suppressed by LY294002, Wortmannin, PD98059, KN93 or H89,
indicating the involvement, respectively, of phosphatidylinositol-3 kinase,
extracellular-regulated kinases, calmodulin-dependent kinases and protein
kinase A signaling pathways. NO also induced a significant increase of
neurite outgrowth, indicative of neuronal differentiation, and blocked cell
death induced by hydrogen peroxide. Cyclosporin A, an inhibitor of the
mitochondrial permeability transition pore considered an important mediator
of apoptosis and necrosis, as well as boc-aspartyl (OMe) fluoromethylketone
(BAF), a caspase inhibitor, also blocked cell death induced by re-feeding
the cultures. These findings demonstrate that NO inhibits apoptosis of
retinal neurons in a cGMP/protein kinase G (PKG)-dependent way, and
strengthens the notion that NO plays an important role during CNS
development.
PMID: 17116229
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