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The Virtues of Venom

By Kurt Loft
of The Tampa Tribune

TAMPA - Most of us fear stepping near a poisonous snake, much less fangs sinking into our flesh. But scientists are studying new ways that snake venom might prevent heart attacks and some forms of cancer.

Venom found in certain vipers in Afghanistan and Pakistan contains a protein that blocks the spread - or metastasis - of tumors in mice injected with cancer cells, say researchers at the University of Delaware's Department of Medical Technology.

Although preliminary, the study could help pharmaceutical companies create cancer-fighting drugs for market and aid in blood control during heart surgery, says Mary Ann McLane, a clinical lab scientist working on the project.

"This venom is a biological cocktail," McLane says. "There's a group of chemicals in snake venom that can keep blood from clotting. This can be very useful."

The study revolves around snake proteins called "disintegrins" a key to how vipers kill. The venom features a loop of amino acids that latches onto cells and inhibits a "sticky" protein from binding with platelets, which make blood clot. If platelets don't bond together, clots can't form.

When a snake bites its prey, the blood doesn't clot and the animal bleeds to death and dies when it flees. The snake follows the scent trail and feasts on its dead or dying meal.

Scientists for years have been aware of biomedical uses of snake venom, but new technologies are allowing them to synthesize the raw proteins to make them safe for people.

The venom could be helpful during bypass heart surgery, because the body reacts by creating clots or "plugs" at the site of the opening, and these can break off into the bloodstream and create problems. Although drugs can thin blood during surgery, the body's defense mechanism still sends clogging platelets into battle.

"Any surgical procedure is invasive, and the body responds by trying to plug the blood vessels at the wound," McLane adds. "If the clot that forms stays at the site, it's fine. But small pieces can travel through the body into the brain, which can cause a stroke or heart attack. It's important to find out how to prevent the problem, and we think these disintegrins work perfectly."

Scientists also are working on a synthetic form of the venom to keep cancer cells from spreading. Researchers at the University of Western Ontario demonstrated that the mice infected with melanoma cells had reduced cancer growth when exposed to the venom protein. Stefan Niewiarowski of Temple University Medical School in Philadelphia is developing a molecular portrait of the protein to better examine how it works. The process involves creating 3-D structures and computer-assisted drug design.

Injecting the venom proteins into people presents problems because our bodies reject them as foreign. The trick is to synthesize the material in artificial form so it isn't toxic. If found to be safe, the proteins could be in high demand - and costly.

Laboratories buy venom from serpentariums that raise and milk vipers, which make up about 8 percent of all snake species. Snake handlers extract the venom from the reptile's hollow fangs in the upper jaw. The venom is dried, and sold for $300 to $1,000 a gram. The valuable protein makes up a fraction of 1 percent of each gram.

Dozens of pharmaceutical companies are looking into synthetic versions of viper venom for its healing qualities. Much of this research is being funded by the National Institutes for Health and the American Heart Association.

If perfected, McLane says, such research could turn the deadly viper into one of nature's more beneficial beasts.

"It's awesome to think these venom proteins have been evolving for millions of years in snakes," she says. "All of the vipers have a version of this kind of protein and if we can unlock this capability, hopefully we can use it to our benefit. What people see as a scary snake could one day save their lives."

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