Ongaonga: Research shows tree nettle could help treat pain

Ongaonga, despite its danger, could help researchers develop treatments for pain. Photo / Supplied

A native New Zealand stinging tree could hold clues for future pain medication, University of Queensland researchers say.

Dr Thomas Durek, Dr Sam Robinson and a team from the university's Institute for Molecular Bioscience (IMB) studied toxins from the tree nettle known as ongaonga, in a bid to find new molecules that affect pain pathways.

Ongaonga is one of New Zealand's most poisonous plants and can cause painful stings that last for days. In severe cases, it can even be fatal.

Robinson had previously investigated toxins found in an Australian gympie-gympie stinging tree but discovered the New Zealand tree nettle toxins activated pain receptors in a new way.

"The New Zealand nettle tree toxins target the same receptor as their Australian counterparts but they cause pain in a different way."

While the Australian stinging tree and New Zealand tree nettle were both members of the nettle family, they were separated millions of years ago and had evolved differently, Robinson said.

"The New Zealand tree nettle can grow up to four metres tall and its leaves and stems are covered with stinging hairs that pierce the skin and deliver venom which causes long-lasting pain."

Ongaonga leaves and stems are covered with stinging hairs. Photo / Supplied

Fossil remains show that Moa had a liking for eating the tree nettle and it's likely the strong toxins evolved to fend off the now-extinct bird.

Robinson said the team faced challenges during the study due to international Covid travel restrictions.

"Covid made it difficult to source nettles but to keep our research going through the pandemic, we managed to source seeds from the New Zealand tree nettle and grow the plant under quarantine in the lab."

Professor Irina Vetter, director of IMB's Centre for Pain Research, said understanding pain pathways was key to finding new ways to treat chronic pain.

"Animal venoms have been studied for decades but plants have evolved toxins differently, and this gives us a chance to find molecules that work in a unique way."

Vetter said the goal was to tackle pain more effectively without side effects and addiction.

The research team also included IMB's Dr Edward Gilding and Jing Xie.

With travel bans lifting, Gilding planned to go to Vietnam later this year to experience "anything that stings" and was applying for funding to also visit Madagascar and South America to widen the net.

There were several hundred nettles in the Urticaceae family with stinging hairs around the world, Gilding said.

"We're keen to compare how they have evolved and whether they all use the same toxins."

The research is published in the Journal of Biological Chemistry and was funded by organisations including the Australian Research Council and the National Health and Medical Research Council.