19 July 2007

Snail venom: Yay

A bit old and a topic I've posted on before, but relevant:

Dr Jon-Paul Bingham, of Clarkson University, has an unusual note on his file at the local hospital in New York State.

If he is admitted unconscious, they are to check to see whether he has been harpooned by a deadly snail.

Every week, he milks lethal marine molluscs called cone shells for their venom, using a condom, barbecue tongs and a fish. If anything goes wrong, though, it is no laughing matter.

Cone shells look like a seaside souvenir from the tropics. You find them in places like the Great Barrier Reef or Hawaii. The shells themselves are sometimes two to three inches long, often with striking patterns which make them collectable.

These snails will produce millions of changes in their toxins that they use to kill their prey
Dr Jon-Paul Bingham, Clarkson University
The snails inside are not all poisonous but the fish-eating ones are right up there with snakes and scorpions in the danger stakes. If you get stung by one of them, there will be enough venom in your system to kill up to 15 people; but it is not entirely hopeless.

"Get on a life support system. There have been cases where people have survived," Jon-Paul says helpfully.

Biological 'kit bag'

It is quite an overkill for a little marine animal whose usual dinner is no bigger than a goldfish, but what grips scientists is not the potency of its venom but the complexity.

Cone snail (Clarkson)
On a par with snakes and scorpions
"These snails will produce millions of changes in their toxins that they use to kill their prey," Jon-Paul tells the BBC Radio 4 programme Danger! Venomous Snails.

"If they don't make these changes, they can be at an evolutionary disadvantage, so the snails have become good pharmaceutical chemists. It is these compounds that we are trying to harness to use as specific medicines."

One of these compounds is already at work. Just over a year ago, the US Federal Drug Agency approved the first of a new type of painkiller - Prialt® - which can work in cases where ordinary drugs fail. The drug has also been approved for use in Europe.

It blocks a particular channel in nerves which communicates pain signals to the brain. The original toxin behind the drug was discovered in the lab of Professor Baldomero Olivera, at the University of Utah, and he's excited about the future.

In close-up: The cone snail's harpoon
"There's an explosion of data about neuroscience and what can go wrong," he says.

"We'd like to understand and affect many different molecules in the normal brain. Using very specific toxins that wipe out the function of just one thing in the nervous system, lets us do that.

"We see applications in epilepsy, stroke and cardiovascular conditions. Some are in development and one has reached clinical trials."

Just the beginning

Another way of stopping strokes and heart attacks is to cut down on smoking. Snail toxins might help here, too.

Professor Bruce Livett, of the University of Melbourne, Australia, is looking at how they affect the nicotinic receptor - the very thing that gets a hit when you puff on a cigarette.

A drug to inhibit that might help you stop smoking, but this research is already tackling severe pain in diabetic patients.

Some species are threatened because of the actions of collectors
There could even be applications in Alzheimer's or Parkinson's disease, says Bruce, but one thing bothers him: we should take time to get to know the snail, not just its venom.

"There's a whole world of invertebrate biology out there far more advanced than our own mammalian biology," he says.

That is where Jon-Paul Bingham's work has been important. By developing his way of milking the snails, Jon-Paul keeps the animals alive in his lab and learns more about them.

He does not need to dissect the "goose that lays the golden egg" to study its venom. He analyses their venoms and then synthesises the compounds he finds for further work.

His hope is to set up a library of venoms to help other researchers get access to this field. He sees potential for snail toxins to be used in everything from agriculture to anti-fouling paints against marine worms.

Cone shells research appears to be advancing much more quickly than your average snail.

Danger! Venomous Snails was broadcast on BBC Radio 4 on Monday 27 March. It can still be heard at the Listen again page.