Spider Toxins Light Up Pain Paths
New venom compounds could one day help brain disorders.
A giant tarantula from Africa has become the latest poisonous critter that scientists believe may hold the key to possible treatments for human neurological disorders that could be controlled with compounds the spider makes to kill its prey.
This week researchers at the University of California, San Francisco, published a study where they isolated two compounds that activate one of the nine pain pathways that connect our nerve cells to our brain.
These pain pathways are really sodium channels that control the flow of ions and electrical energy.
"The thing that made this discovery interesting was the toxins that we found target a specific sodium channel which is involved in generating nerves and muscles," said Jeremiah Osteen, a postdoctoral researcher at UCSF and lead author on the paper published in the journal Nature. "It's hard finding agents like toxins or small molecule drugs that will stimulate one [channel] and not the others.
Osteen is a biochemist and doesn't actually have to handle the six-inch long animal, whose scientific name is Heteroscodra maculata, or the Togo starburst tarantula.
"Our collaborators in Australia are the tarantula wranglers," Osteen said. "What we are looking for is activators of the pain pathway."
WATCH: How Pain Works
Osteen says they occasionally do genetic work on the tarantula's venom sac to figure out what kinds of proteins are expressed. "It's pretty scary to have them around," he said.
Osteen said the new toxins can now be used as a highly selective tool for manipulating this type of sodium channel, which also has been implicated in neurological disorders unrelated to pain, from epilepsy to autism to Alzheimer's disease.
"The challenge in treating these disorders is you want to tune the function of the channels to get them back to baseline," he said. "You want drugs to boost the activity, or turn the gain down. We found a way to isolate one of nine pathways."
Still, it might be a long way to go from isolating a compound to developing a drug that can help people. Researchers have been looking at toxins from the deadly marine cone snail that uses its poison to paralyze fish in its South Pacific habitat for decades. Despite several clinical trials, only one drug has been brought to market after federal approvals - Ziconotide in 2004 – which is used to combat chronic pain.
"There's a long and challenging pathway for all these discoveries to convert them into a safe drug for patients," said Greg Bulaj, assistant research professor at University of Utah, where he studies the biochemistry of cone snail toxins.
Bulaj says the UCSF work is promising.
"Preclinical and clinical validation of this new analgesic mechanism and novel tarantula toxins could be very compelling."
SEE PHOTOS: Giant Spiders to Freak You Out
You almost feel for them, spiders. They can't help being what they are, and yet almost no one is happy to see them. Especially true when they have exceedingly long legs, thick bodies and a general mien that makes you turn quickly in some other direction. Photos don't bite, though, so let's take a look at some honking-big spiders -- with Halloween on the way, we may as well get started freaking ourselves out. Shown here is the Brazilian wandering spider (a.k.a. Phoneutria), a feisty and venomous crawler from South America. Just four years ago it took home an award from the Guinness World Record people for the title of "most venomous" spider. This spidey's legs can span nearly 6 inches, its body just shy of 2 inches. It gets its name thanks to its preference for strolling along the tropic floor at night seeking out prey, rather than building webs or hiding out someplace waiting to strike. During the day, it lays low wherever it's convenient -- even inside banana plants, which is how it get its nickname "banana spider."
Not to be outdone is a spider that's been making a big splash of late, with an entomologist's blog about his encounter with one. It's called the Goliath bird-eater (a.k.a., Theraphosa blondi). It can weigh in at almost 6 ounces and it's been known to reach nearly a foot in leg-span. The "bird eater" moniker must be there to warn birds away, though, because this spider doesn't typically eat birds as a matter of, er, course. It will regularly eat small land animals such as frogs, lizards, and snakes, however.
Meet the golden-silk orb weaver spider. Step into its parlor, if you must. Don't be fooled by its deceptively gentle-sounding name. The female golden-silk orb weaver's body alone can reach 2 inches, its legs can stretch to more than 5 inches, and it's even been observed killing and eating tree snakes. What's more, a study published earlier this year found that these spiders, when living in urban areas, are growing even bigger than usual. Interesting side-note: The golden-silk orb weaver also belongs to the oldest surviving genus of spiders, Nephila, which has a fossil in the record that dates to 165 million years ago.
The Brazilian salmon pink bird-eating tarantula has a leg-span that can reach 11 inches and weight that can tip the scales (well, for a spider) at about 3.5 ounces. Despite its name, it's not confirmed that they actually eat birds any more than do the Goliath bird-eaters. Instead, they dine on insects or the random small amphibian or reptile. Instead of making a web, it takes its prey by quick-strike ambush in the open.
The giant huntsman spider is so big it even took the trouble to have a size descriptor built into its name (given that Goliath was taken). The huntsman is neck and neck, or leg and leg, with the Goliath bird-eater for the title of biggest spider, by leg-span (in sheer body mass, though, the Goliath is more like an offensive lineman, while this spider is a lanky cornerback). A giant huntsman's legs can stretch out to 12 inches, and its speedy, crab-like gait makes it a fast hunter that excels at chasing down its meals. It hails from caves in Laos.