New Zealand Tree Evolved "New Way" to Deliver Pain
New Zealand's ongaonga, a stinging nettle tree that can deliver a fatal dose of toxin via piercing hairs on its leaves and stems, evolved its defense mechanism in a way that causes pain differently from other plants, according to researchers at the University of Queensland.
The scientists who discovered this have said this difference could lead to greater understanding about these toxins and even lead to the development of new analgesics.
Research published in the Journal of Biological Chemistry (JBC), conducted by a team from the university's Institute for Molecular Bioscience (IMB), indicates that although the ongaonga targets the same pain receptors as that of Australia's gympie-gympie stinging tree, the plant's venom activates those receptors in a new way.
The institute's Centre for Pain Research said the discovery may lead to new understanding of how these toxins work, and, in turn, prompt the development of new pain medications.
"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," said Irina Vetter, PhD, professor of pharmacology at the University of Queensland and director of the Centre for Pain Research. "Our goal is to tackle pain more effectively without side effects and addiction."
According to the JBC article, the researchers identified 2 types of toxins they think are behind ongaonga's potency: one toxin that strikes cell membranes and a second toxin that represents a new class of neurotoxin that affects voltage-gated sodium cells.
"Both toxins represent new ways to attack the body's pain pathways-and therefore new ways to understand, and potentially treat, pain," according to the journal Freethink, in its synopsis of the JBC study.
University of Queensland researchers say the ongaonga likely developed its powerful toxin as a defense against the moa, a massive flightless bird that is now extinct but whose 9 species were once endemic to New Zealand. Moas were the dominant herbivore of this large island grouping, but were hunted to extinction once humans settled there beginning in the 14th Century.
"The Australian stinging tree and New Zealand tree nettle are both members of the nettle family, but separated millions of years ago and have evolved differently," said Sam Robinson, PhD, of the IMB. Robinson's expertise is in plant and animal toxins and investigating their use in biomedical applications.
The nettle tree is covered with spines that pierce the skin and deliver painful stings that can last for days. Hundreds of species of nettle are found around the world. Known by its binomial Urtica ferox, ongaonga is a woody shrub that can reach a height of more than 9 ft. Its spines contain triffydin, a toxin that contains histamine, serotonin, and acetylcholine.
Exposure to triffydin can cause inflammation, itching, and a rash; multiple stings can lead to loss of motor movement, blood pressure drop, convulsions, blurred vision, and paralysis.
Acute polyneuropathy can be caused by U. ferox stings, according to the New Zealand Plant Conservation Network. In 1961, a young man died of paralysis and respiratory failure several hours after walking through a patch of the plants. [See Neurotoxic and cytotoxic peptides underlie the painful stings of the tree nettle Urtica ferox-Journal of Biological Chemistry (jbc.org). This neurotoxic tree could be the key to a new kind of painkiller (freethink.com). Native New Zealand tree puts the sting on pain-YouTube. Native New Zealand tree puts the sting on pain (phys.org). https://en.wikipedia.org/wiki/Urtica_ferox. https://www.nzpcn.org.nz/flora/species/urtica-ferox/]