Poison for Patients?
Lethal gas might save lives
Carbon monoxide is a gas with a split personality. Every winter, people die
in their sleep after breathing carbon monoxide from faulty space heaters or
furnaces. It kills by binding to hemoglobin in red blood cells — preventing
them from carrying oxygen to cells and tissues in the body.
Front: David J. Pinsky, Yasushi
Yoshikawa (at microscope), Sunitha Yanamadala
Back: Maksim Fedarau, Koichiro
Iwanaga, Hiroaki Hirada, and Elena Filippova
Photo: Martin Vloet |
But scientists have discovered that carbon monoxide also has a life-giving
side, according to David Pinsky. In recent research, Pinsky found that inhaling
carbon monoxide protected laboratory mice from lethal lung injuries produced
when blood flow to one lung was temporarily shut off.
Pinsky doesn't know exactly how breathing carbon monoxide saved his mice from
certain death, but he intends to continue his research until he finds out.
He believes carbon monoxide inhibits a genetic "master switch," which is activated
by lack of oxygen. When this switch is turned on, it triggers a series of pathological
changes in blood vessels in the oxygen-deprived organ. The result is inflammation,
swelling, excess fluid and the formation of blood clots.
"When blood flow is interrupted, the blood vessels first try to dilate and
do other things to promote the flow of blood," Pinsky explains. "But if there's
a major obstruction, such as during a heart attack or stroke, and blood doesn't
resume flowing quickly, then this master switch is activated. Now the blood
vessels change their approach. Instead of trying to get more blood into the
affected organ, blood vessels try to isolate it by forming blood clots and
calling in immune system scavenger cells. Normally this helps heal injuries,
but in this case, it just makes things worse. So you get this spiral — this
out-of-control spiral of inflammation and blood coagulation that can kill you."
The body makes proteins and enzymes to dissolve blood clots, but once the
cellular death spiral begins, it suppresses production of these healing proteins.
When Pinsky's mice inhaled carbon monoxide, it somehow prevented the suppression
of clot- dissolving enzymes. With less lung damage, the mice were able to recover,
once blood started flowing through both lungs again.
If Cardiovascular Center scientists can discover exactly how carbon monoxide
protects against organ damage caused by lack of oxygen, it could lead to new
treatments for patients with heart attacks or stroke. Pinsky warns, however,
that any clinical use of carbon monoxide would require clinical testing, close
medical supervision and careful monitoring, since the difference between a
therapeutic dose and a lethal dose could be very small.
Pinsky points out that carbon monoxide would not be the first poisonous gas
with life-saving therapeutic benefits. Consider the case of nitric oxide -
a corrosive gas and industrial pollutant, which is not the same as nitrous
oxide or "laughing gas" used as an anesthetic.
"Just a few years ago, no one would have dreamed of giving nitric oxide to
patients," Pinsky says. "But in 1998, three scientists received a Nobel Prize
for their discovery that this so-called poison is produced by cells in the
body and has important biological functions, including the dilation of blood
vessels. Now there are tanks of nitric oxide in virtually every intensive care
unit in the country."
-SFP
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