Peppery Plant Heat and the Future of Painkillers

Peppery Plant Heat and the Future of Painkillers

pepper plant that may provide pain relief

Welcome to February! Right about now is the point in the winter when I start dreaming of warmer climes — if only for a vacation. One of my personal life goals is to visit some of my favourite hot-weather plants, cacti, in their natural habitats. Saguaro cacti  in particular look so friendly  that I’d be tempted to give them a high five. (Though with their significant spines), only tempted…!)
Another plant I’d like to get to know from a distance is Euphorbia resinifera, which is native to Morocco. Also known as the resin spurge, this cactus-like plant has an incredibly powerful defense mechanism: it’s hot. Like, 16 billion Scovilles hot. To get an idea, imagine pepper spray, then multiply its effect three (!) thousand (!) times.
The heat has long prevented predators from chowing down on the spiny leaves; now it’s also being studied as a possible painkiller. Dubbed resiniferatoxin, or RTX, the spicy chemical derived from the resin spurge can be injected into a pain site, like a bad knee or injured back, while the patient is anesthetized. There it basically burns away the nerve endings that transmit the feeling of pain to the brain. Though it seems counterintuitive for something that causes violent pain to block out violent pain, the science is there. From Wired:
“[RTX] binds to a major molecule in specifically pain-sensing nerve endings, called TRPV1 (pronounced TRIP-vee one). […]

RTX is a capsaicin analog, only it’s between 500 and 1,000 times more potent. When RTX binds to TRPV1, it props open the nerve cell’s ion channel, letting a whole lot of calcium in. That’s toxic, leading to the inactivation of the pain-sensing nerve endings.

This leaves other varieties of sensory neurons unaffected because RTX is highly specific to TRPV1. ‘So you gain selectivity because it only acts on TRPV1, which is only on a certain class offibers, which only transmit pain,’ says [UC San Diego anesthesiology professor Tony] Yaksh. ‘Therefore you can selectively knock out pain without knocking out, say, light touch or your ability to walk.’”
Researchers all over are looking at this naturally inspired pain solution, partly in response to the opioid epidemic that is gripping the US in particular. It’s also being tried as an alternative to morphine for end-of-life pain management. Localized injection treatments have already been attempted — and proven very effective — in dogs, with researchers reporting cessation of joint pain lasting up to five months (which feels like years to a pup)!
I’m very interested in further research into RTX, both for the immensely practical applications and for the coolness factor. Joint pain or no, at this point in the year we all need some heat!