Brighter prospects for chronic pain sufferers

Posted on Thursday, April 21, 2016
It is estimated that 1.5 million Canadians suffer from chronic pain.

It is estimated that 1.5 million Canadians suffer from chronic pain.

Researchers use optogenetics to produce pain relief by shutting off neurons with light

By Shawn Hayward

The potential of light as a non-invasive, highly-focused alternative to pain medication was made more apparent thanks to research conducted by scientists at the Montreal Neurological Institute and Hospital of McGill University and the McGill University Health Centre.

Researchers bred mice with a light-sensitive trait in peripheral neurons that were known to be responsible for pain transmission. The mice were genetically modified so that these neurons, called Nav 1.8+ nociceptors, express proteins called opsins, which react to light, a process known as optogenetics.

When these sensory neurons are exposed to yellow light, the opsins move ions across the membrane, reducing the level of bioelectric activity of the cells. This effectively shuts off the neurons, decreasing the mouse’s sensitivity to touch and heat.

“The opsins we added to these neurons were initially isolated from archaebacteria and sense yellow light,” explains Professor Philippe Séguéla, a researcher at the Montreal Neurological Institute and Hospital and the article’s senior author. “When we transfer these to neurons, we can control their responses simply by illuminating the skin with innocuous yellow light.”

Optogenetics is a growing field of research with a wide variety of applications. In this case the activity of pain-signaling neurons was reduced in a localized part of the mouse’s body, the hind paw, and the duration of the effect could easily be controlled by the amount of time the light was applied. The precision of this technique underlines potential advantages for use in humans.

Light therapy based on optogenetics would have the advantage of providing “on-demand” analgesia (pain relief) to patients who could control their pain by shining light on the sensitive part of the body.

Opiates are the most commonly used treatment for chronic pain today, but they are often used systemically and not directed to the specific region of the body affected by the pain. The duration of the opiate effects can be estimated, but without the same precision as a beam of light.

Further advances in neuroscience are necessary to apply this method of pain relief to humans. Séguéla says one possible way to make human neurons photosensitive would be through the use of a harmless virus that could temporarily deliver opsins to certain neurons without causing side effects.

According to a report in the Community Health Survey, 1 in 10 Canadians between the ages of 12 and 44, about 1.5 million in total, experienced chronic pain — pain lasting over a period of months or years. Chronic pain is associated with a number of different medical conditions including diabetes, arthritis, cancer, shingles, and sciatica, among others. Chronic pain reduces the sufferer’s ability to perform daily tasks and may lead to other health issues such as sleep disorders and depression.

“Chronic pain is an increasingly big problem clinically and for many years we’ve relied only on opiates,” says Séguéla. “It’s hard to treat because of tolerance, making it necessary to increase dosages, which leads to serious side effects. Optogenetic therapy could be a highly effective way to relieve chronic pain while avoiding the side effects of traditional pain medication.”

 

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One Response to Brighter prospects for chronic pain sufferers

  1. Witch-doctoring at it’s very finest.

    Prof Séguéla proposes to create Genetically Modified Organisms (GMO’s), to wit, a GMO virus. And supposedly, this GMO virus will be “harmless”. But patients will be intentionally infected with this allegedly harmless GMO virus, and the infection will allegedly be contained in one specific part of the body. Allegedly, harmlessly. And after all that’s been done, a yellow light shining through the skin, will cause pain relief. Allegedly, with no risks or side-effects whatsoever.

    This is precisely the trouble with overuse of the human imagination. We become fixated over imaginary. possibilities, because we imagine them to be possible, and having once done that, we imagine them to have no drawbacks or adverse consequences.

    It is important for voters and policy-makers to comprehend, that these wonderful properties only exist, for imaginary inventions.

    Real technologies happen in reality and are limited by the unknown problems, that we will only discover, after the technology is invented. The aspects of reality that contradict our imaginary wishes, are not discovered until we get there.

    Suppose the late artist known as Prince, had been able to get one of these imaginary viral injections for each of his failing hip joints. Suppose every time he gave a performance, he mounted a yellow light to each hip and danced, pain-free. Staying “hooked” on brighter and brighter yellow lights, would have enabled him to ignore the pain of hip bones that were repeatedly cracking. Until one fine day, he gave a performance, the hip shattered, and he bled internally from the jagged pieces of bone thrusting through his muscles, collapsing on stage and bleeding to death in the hospital.

    Would anyone consider this outcome, to be safer than using Percocet, according to directions, to relieve pain?

    Now suppose that the allegedly-harmless virus, turned out not to be harmless at all. Suppose it induced an allergy to a nutritious food, that infected people could no longer eat, because they caught a GMO virus that wasn’t understood to be harmful, until the harm was discovered. (In my lifetime, I witnessed this to happen with wheat gluten. An experiment to make a food by boiling gluten in lye, yielded a chemically-modified food that caused celiac disease. Millions of people are now allergic, to what used to be a nutritious source of protein, and used to be Canada’s largest export. Could we afford do that again, with some other crop? Would we want to take that risk?)

    Viewed as purely a research tool, optogenetics could yield useful information about how DNA is interpreted. Arguing that optogenetics will make a safer alternative to pain medicine, is irresponsible. That’s because it’s entirely possible that there will be adverse consequences we don’t understand as yet, to making a GMO virus to exploit the possibility.

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