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The venom of the Chilean Rose tarantula
(shown at the San Francisco Zoo) contains a protein that can help stop heart attacks. |
Why
would you take poison as medicine?
BY JOSH CLARK
Humans have
used poison to dispatch their enemies and rivals for a very long time.
Some of
history’s greatest figures met their ends through poisoning.
For publicly
criticizing the ruling class, the Greek philosopher Socrates was executed in
399 B.C. by being made to drink a cup filled with poison hemlock [source: Linder].
Hemlock
depresses the central nervous system, leading to slowed respiration and pulse
before the body shuts down [source: Perdue].
Around 3,000
B.C., the Kemite pharaoh Menes was documented as
the first person to conduct research into poisons.
Menes gave
rise to a sophisticated knowledge of poisons among the Egyptians culminating
1,500 years later.
A papyrus (ancient
Egyptian document) dated circa 1553 B.C. found in Luxor, Egypt, in 1872 lists
700 different drugs (including poisons) of animal, mineral or plant origin [source: Hayes].
The Luxor
papyrus also includes another significant source of ancient knowledge:
antidotes to the poisons it listed.
It’s a safe
bet that about the same time humans came to understand poisons, they set about
looking for antidotes to them.
Some of these
antidotes proved more effective than others. For example, whiskey was a
standard treatment for snakebites in the 19th century.
Experiments
conducted by Brazilian researchers in the 1920s proved the method was
worthless. Even worse, it actually hastened death by improving blood
circulation and thus speeding delivery of the venom to the organs [source: New York Times].
These same
Brazilian doctors also came up with a clever method of fighting the effects of
venom on humans by employing the same venom as an antidote -- using poison to
fight poison.
Researchers
realized that by introducing gradually increased doses of snake venom into
large animals like horses, the animal’s immune system would produce antibodies
called antivenin that fight off the venom.
Antivenin was
extracted from the hemoglobin of an immunized horse’s blood, and, when
introduced into the bloodstream of a snakebite victim, it attached to the venom
and prevented it from interfering with normal body processes.
Other poisons
have been shown to counteract the effects of poisons, and some are still being
used in labs today. Find out more on the next page.
Poison as an
Antidote
A
pretty full understanding of how the body works is required before one can
confidently introduce poison into a human being as a means to cure illness.
After
all, just trying different poisons willy-nilly as antidotes ostensibly results in
extensive deaths among a test subject population.
Trial
and error, in other words, isn't a good means of identifying which poisons can
also serve as a cure.
This is why the use of poisons
as antidotes didn't gain much traction until the 19th and 20th centuries.
As
physiological knowledge converged with scientific understanding of the
poisonous properties of plants, the two were married to combat illness.
One of the
first effective uses of a known poison as an antitoxin in modern medicine came
in 1870, when Scottish physician Thomas Frasier used atropine as
an acetylcholinesterase inhibitor [source: Heath].
Acetylcholinesterase
is an enzyme that's naturally produced in the brain;
it tells neurons to fire, which sends electrical impulses throughout the
central nervous system.
If it's not
broken down, however, neurons will fire continually, leading to a nervous
system overload and painful death [source: New Scientist].
Nerve toxins
like sarin and anthrax inhibit the breakdown of this enzyme. The alkaloids
found in atropine, which is derived from the poisonous plant known as deadly nightshade or belladonna,
turns off the nerve receptors, counteracting the effects of these toxins.
It may sound
like pretty dangerous toxicology (and it can be -- the alkaloid is deadly in
high doses), but atropine is still used today as an antidote to nerve agents.
And the line
of reasoning behind using toxins as cures can be found in laboratories around
the world in some radical treatments for disease.
Instead of
plants, however, a few researchers are looking to some of the most feared
insects on Earth for cures.
Biophysicists
from the University at Buffalo are using a protein from the venom of the Chilean
Rose tarantula to combat death from heart attacks.
The walls of
your cells have tiny channels that open when
the cell stretches. Among other body functions, these channels are responsible
for the contraction of heart muscles.
When these
channels open too wide (which can happen from stretching the heart muscles over
time), they allow a flood of positive ions into the cell.
These extra
ions disrupt the electrical signals in the heart, causing the organ to fibrillate (beat
wildly and irregularly) [source: University at Buffalo].
The protein
from the Chilean tarantula venom binds to these channels, which can block the
positive ions from passing through. This could ostensibly prevent fibrillation
-- and hopefully death -- if delivered during a heart attack [source: BBC].
The venom from
another menacing arachnid is being used to help treat cancer. Researchers at the Transmolecular
Corporation in Cambridge, Mass., have isolated a protein that occurs in the
venom of the Israeli yellow scorpion.
This protein
has been shown to seek out and bind itself to the types of cancerous cells
found in gliomas, a type of brain cancer that's particularly
difficult to treat.
The
researchers created a synthetic version of the protein and attached radioactive
iodine solution to it.
When
introduced into the bloodstream, the protein seeks out glioma cells and binds to
them, carrying the radioactive solution along for the ride. The solution then
destroys the cells -- and with enough treatments, the cancer [source: Health Physics Society].
With
treatments like these emerging, perhaps the cure being worse than the disease
isn't so bad after all.
Josh
Clark
has wanted to be a professional writer since his third-grade teacher told him a
short story he wrote was kind of good. He's written ever since. At
HowStuffWorks.com, he's a senior writer and co-host of the Stuff You Should
Know podcast. Josh lives with his wife, Umi. The pair really, really enjoys
traveling, solving mysteries, having pizza parties and visiting museums (both
renowned and obscure). Josh has been to the real-life house that served as the
Robin's Nest on "Magnum, P.I." and is on an indefinite hiatus from
being a jerk.
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