Unique toxin in poisonous Australian tree may lead to better painkillers

Scientists have decoded the unique process by which toxins from a notorious Australian stinging tree cause intense pain, an advance that could lead to new painkillers.

Researchers, including Irina Vetter from the University of Queensland in Australia, studied how toxins in the venom of the Gympie-Gympie tree cause intense pain that can last for weeks.

“This toxin causes pain in a way we’ve never seen before,” Dr Vetter says.

In previous studies, scientists found that the toxin – named gympietides – interacts with nerves in the body after it is injected by fine needle-like hairs on the leaves.

“The gympietide toxin in the stinging tree has a similar structure to toxins produced by cone snails and spiders, but the similarity ends there,” Dr Vetter explained in a statement.

While many toxins can cause pain by binding directly to sodium channels in sensory nerve cells, researchers have made an “unexpected finding” that the gympietide toxin needs assistance to bind.

“It requires a partner protein called TMEM233 to function and in the absence of TMEM233 the toxin has no effect,” Dr Vetter explained.

“This was an unexpected finding and the first time we’ve seen a toxin that requires a partner to impact sodium channels,” she added.

Researchers believe the new understanding may lead to the development of new non-opioid painkillers.

They hope to determine from future studies whether switching off the toxin’s pain mechanism might lead to the development of such painkillers.

Compared to opioid painkillers, whose long-term use to treat severe pain is linked to increasing addiction-like symptoms, non-opioid analgesics may not lead to physical dependence on the medicine.

“The persistent pain the stinging tree toxins cause gives us hope that we can convert these compounds into new painkillers or anaesthetics which have long-lasting effects,” Dr Vetter said.

“We are excited to uncover a new pain pathway that has the potential for us to develop new pain treatments without the side effects or dependency issues associated with conventional pain relief,” she added.