Planet Earth

Treating Disease With Nature’s Deadliest Toxins

Drug companies and scientists are turning nature’s weapons into life-saving treatments.

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Photo Credits: All text by Jeremy Jacquot; Credit: prilfish/Flickr

The idea of using lethal toxins to make life-saving medicines may seem unconventional, but humans have been doing it for centuries. Here, we take a look at eight species whose venoms and stingers have inspired a slew of treatments.

Anyone who has had the misfortune of stepping on a sea anemone can attest to the jolt of pain its tentacles deliver. Sea anemones are part of the same group of invertebrates as jellyfish and possess the same potent stinging cells, known as cnidocytes. Each cnidocyte contains a cnidocyst, an organelle which resembles a miniature coiled harpoon.

Toxins contained within the cells, typically neurotoxins, help immobilize small prey. The cnidocysts' brutal efficiency served as inspiration for the Israel-based drug company NanoCyte, which hopes to harness the anemone's stinging cells to create a unique drug for diabetics.

NanoCyte envisages mixing cnidocysts into a special skin cream that could be used to dispense insulin. The insulin would be added to a cream containing the stinging cells; the harpoon-like cells would then inject the insulin directly into the skin.

Photo Credits: Credit: don_macauley/Flickr

One of the most toxic plants in the world, the deadly nightshade (Atropa belladonna) is filled with tropane alkaloids, which can kill an adult in large enough doses. Its primary active agent, atropine, attacks the parasympathetic nervous system and disrupts its ability to regulate subconscious activities like breathing.

Considering its lethality, it may come as a surprise that scientists have found beneficial uses for atropine in medicine. When used as an acetylcholine receptor blocker to curb the activity of overactive neurons, it helps to negate the deadly effects of nerve agents like sarin and anthrax, which cause victims to lose control of their bodily functions. Atropine is also used to treat glaucoma and to resuscitate patients suffering from cardiac arrest.

Photo Credits: Credit: Furryscaly/Flickr

The Chilean Rose Tarantula is the source of an important protein used in drugs to stop atrial fibrillation, an abnormal heart rhythm, or cardiac arrhythmia, which can result in death. Atrial fibrillation prevents the heart's atria from efficiently pumping blood by disrupting their beating rhythm, causing the blood to clot within the chambers. A piece of clot that breaks off and enters the brain can become lodged in an artery, triggering a stroke.

A team of researchers at the University of Buffalo discovered a peptide (a protein building block), GSMtx-4, in the tarantula's venom that prevents fibrillation by blocking the activity of certain gate-like structures of neurons in the heart. These "channels" can become overstimulated when an individual suffers from a heart disease like congestive heart failure.

Other experiments have since shown that the peptide could be used as an analgesic to reduce pain. No drug that uses GSMtx-4 is yet available, but the scientists hope to begin development on one in the near future.

Photo Credits: Credit: CIT/SC

Getting bitten by a snake hardly sounds like a relaxing experience, but a peptide found in one species' venom could help relieve hypertension and some forms of congestive heart failure. A bite from the South American pit viper in question, Bothrops jararaca, causes swelling, bleeding of the gums, hemorrhage, and, in some cases, death.

During the early 1970s, a group of researchers in Brazil led by Sergio Henrique Ferreira discovered a family of peptides in the pit viper's venom that increased the activity of bradykinin, a peptide that lowers blood pressure by causing blood vessels to dilate. This peptide family, which became known collectively as the bradykinin potentiating factor (BPF), was also found to block the conversion of angiotensin I to angiotensin II, a process that causes blood pressure to rise.

The peptides were later used by researchers at Bristol-Myers Squibb to develop the first group of angiotensin-converting enzyme (ACE) inhibitors. The resulting drug, named captopril, is now commonly used to treat hypertension and certain cardiac diseases.

Photo Credits: Credit: geoftheref/Flickr

Sure, adding chili peppers to your cooking is a great way to spice up dishes, but did you know that they may help to relieve neuropathic pain? It turns out that the chemical that gives chili peppers their kick, capsaicin, is also responsible for soothing several forms of pain from aching muscles or damaged nerves.

Patients who suffer from neuropathy ; these sensations and feelings of pain are called allodynias and dyesthesias, respectively.

Capsaicin is already found in a range of topical pain-relief creams for arthritis and sore joints. Zostrix, an over-the-counter cream that contains .075 percent capsaicin, has shown to be effective in calming arthritis pain. A new review conducted by a team of researchers from Oxford University concluded that capsaicin provides relief to 4 in 10 patients who suffer from neuropathy and often feel itchy, tingly, numb, or alternatively hot and cold. The pepper-derived compound creates a sensation of heat in patients who apply the cream by binding to TRPV1s, heat-activated calcium channels that are located on the surface of pain- and heat-sensing neurons.

Photo Credits: Credit: Deepinon/Flickr

Tribes in the Amazon discovered long ago that these small, intensely colorful frogs produced potent toxins in their skins. Hunters would coat the tips of their arrows in these deadly cocktails before going on a hunt. When scientists first encountered these tribes, they were intrigued by their use of the toxins and wondered what unusual compounds they might contain.

During the early 1990's, scientists isolated an unusual alkaloid from a poison-dart frog in Ecuador. The compound produced by Epipedobates tricolor, or the phantasmal poison frog, as it was nicknamed, was found to be 200 times more effective than morphine in relieving pain, at least in mice. Though an effective painkiller, epibatidine, as it is now known, was too toxic to be used as a drug (perhaps unsurprising considering its use in the Amazon).

To overcome this obstacle, researchers have been trying to tweak epibatidine's chemical structure in order to eliminate its toxicity. They succeeded in producing hundreds of new compounds, one of which, ABT-594, has looked promising in trials.

Photo Credits: Credit: Jeff Servoss/US FWS

A lizard's saliva may not seem like the most obvious place to look for a new weight loss drug, but, in the case of the Gila monster, it proved to be the right strategy. The only venomous lizard that is endemic to the United States, the Gila monster is found in the Southwest and Mexico. Despite its intimidating appearance, it presents little real threat, mainly because it is so sluggish.

Unlike some of its fellow reptiles, the Gila monster does not directly inject venom into its prey. Instead, salivary glands in its lower jaw slowly release venom as it begins to chew. A neurotoxin, the venom causes edema (collection of fluid) and sudden drop in blood pressure.

Over the past decade, researchers have isolated over a dozen proteins and individual toxins from the lizard's saliva. One of these, exendin-4, was found to be almost 50 percent identical to a hormone found in the human digestive tract that boosts the production of insulin when blood sugar levels spike.

A synthetic version of exendin-4, called exenatide, was approved for use by the FDA in 2005 after a three-year study showed that it helped patients with type 2 diabetes maintain healthy blood sugar levels and lose weight. According to a more recent study, the drug could also help nondiabetic individuals lose weight as well: Subjects who received the drug reported losing three times more weight over a six-month period than those who received a placebo.

Photo Credits: Credit: Kerry Matz/University of Utah (NAS)

A favorite among shell collectors, the diminutive cone snail--larger specimens grow to be about 23 centimeters in length--is as renowned for its beautiful shell as it is for its potent venom. The majority of cone snails are found in warm, tropical waters.

Their appearance notwithstanding, cone snails are fearsome predators that immobilize their prey with a poison-tipped radula, a tooth-like ribbon made out of hard chitin that can be launched with the force of a spear. Their venom, which paralyzes their prey almost instantly, contains neurotoxins that target specific nerve receptors, or channels.

Though these toxins can be lethal when injected, scientists have been extracting the compounds to create pain-relieving drugs. In 2004, the first painkiller derived from the toxin of the species Conus magus, called Prialt, was approved for use in the United States and Europe. The drug helps relieve chronic pain in patients who no longer respond to morphine. Applied directly to the spine, Prialt (generic name: ziconotide) acts by selectively blocking calcium channels in the brain, preventing the release of neurotransmitters that cause the sensation of pain.

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