The quest to cure chronic pain

Prof. Brian Cairns studies chronic pain above the neck – migraines and temporomandibular disorders, which cause soreness in the jaw. Photo: Martin Dee.

Pharmacy professor Brian Cairns is tracking intriguing leads in his search for pain relief

One of the great unsolved mysteries of modern medicine is chronic pain. Scientists have yet to pinpoint its cause. Millions suffer daily from disorders like migraine headaches, fibromyalgia and irritable bowel syndrome — 60 to 80 per cent are women. Most are forced to rely on common pain relievers.

One UBC researcher wants to change that. By following his hunches, he has stumbled upon what is happening in our body that could open doors to new treatments.

“At the end of the day, our treatment options have been limited,” says Brian Cairns, a professor in the Faculty of Pharmaceutical Sciences. “Many of our current pain relieving drugs have been around since the 1960’s.”

Common pain relievers, such as ibuprofen, acetaminophen, Aspirin, opiates like oxycodone, and muscle relaxants come with side effects like ulcers, liver damage, difficulty concentrating and constipation. These side effects get worse with prolonged use – a major problem for people suffering day in and day out.

What’s more, current treatments are not specific to chronic pain. Part of the problem is that we just don’t know where this pain comes from. Unlike the aches we feel after twisting an ankle or breaking a bone, chronic pain isn’t always associated with tissue damage.

For his research, Cairns focuses on chronic pain above the neck – migraines and temporomandibular disorders, which cause soreness in the jaw. These jaw disorders affect about 10 per cent of all people at some point in their life and the pain can be so intense that it becomes difficult to speak or eat.

Only recently has Cairns stumbled across a clue to what might be causing this discomfort.

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The potential culprit: glutamate

Glutamate is a neurotransmitter that sends signals between nerve and brain cells. It occurs naturally in our brain and body but we also consume it in food – it’s the “G” in MSG. The average fast food meal contains 12 grams of glutamate.

Cairns heard about research showing that glutamate activates receptors in the brain. He knew these receptors are also found around the eyes and in skin and muscles, and when activated, cause pain.

His research led him to ask a simple question: could eating glutamate cause pain? He asked young, healthy people to ingest 12 grams of the amino acid and watched what happened. To his surprise, the experiment induced headaches, nausea or jaw pain about 50 to 60 per cent of the time.

To come at the question from another angle, he convinced brave patients with temporomandibular disorders to let his team stick a big needle through their cheeks to measure glutamate levels in their jaw muscles. He found higher levels of glutamate where the muscles were most painful.

Cairns now suspects that if glutamate levels spike in an area around the nerves in our head, it triggers headaches, such as migraines.

“You know that throbbing headache feeling? You could be sensing your pulse,” he says.

Nerves run like a telephone wires from the head to the brain and some come from the blood vessels in the brain. The idea is to develop a drug that reduces glutamate levels in this area.

Other possibilities: Botox and scorpions

Uncovering the role of glutamate offers chronic pain sufferers new hope, and Cairns has his eye on other possibilities.

He and former postdoctoral fellow Parisa Gazerani have found that Botox injections reduce certain types of muscle pain in healthy, young adults. Their work shows that Botox may decrease the pain sensitivity of nerves where it is injected, although how this contributes to decreased migraine headaches needs more study.

In another development, researchers in the United States have found a species of mouse that is resistant to the pain of scorpion toxins. These mice have a mutation in a sodium channel that triggers or halts neuron signals. They are now looking into what’s behind this immunity and how it could help design new drugs.

“When it comes to chronic pain, patients often go through amazingly complex diagnoses but in the end, we don’t necessarily treat their pain well,” says Cairns. “We need to better understand pain mechanisms so we can develop more specific treatment options.”