More than 1.5 billion people suffer from chronic pain around the world. For many of these people, finding pain relief can be nearly impossible, despite the number of painkillers available over the counter and by prescription. Considering this, it’s no surprise that pain is the focus of a lot of scientific research.
There have been quite a few big breakthroughs in pain relief and painkiller research this year. Here are seven of the biggest.
1. TRPV1 receptor
The TRPV1 receptor is involved in both pain and heat. It’s also the receptor that capsaicin binds to, which has led to it also being called the “capsaicin receptor.” Capsaicin is what makes chili peppers taste hot, but it can be used for pain relief, too.
It was already known that capsaicin binds to the capsaicin receptor, but there were some missing details about the interaction. Recently, researchers used computer models to look more closely at this interaction, and they were able to identify details about the molecular architecture and structural details involved. These same researchers also found that a compound called capsiate (from sweet peppers) is different from capsaicin (from hot peppers) at one key interaction site, but this difference is enough to cause capsiate to bind poorly to TRPV1. This is likely why capsiate doesn’t taste hot, and it also helps shed more light on how capsaicin does what it does.
The more that’s understood about how and why capsaicin can relieve pain, the more likely it is that scientists can develop specialized drug treatments for pain in the future.
This receptor, informally called the “wasabi receptor,” detects specific chemical irritants found in substances like wasabi and tear gas, but it’s also involved in pain signals that originate from inflammation and tissue damage. As with the capsaicin receptor TRPV1, scientists knew some information about the wasabi receptor TRPA1, but several important details about its molecular structure were missing. Now, though, researchers have used a computer imaging technique called cryo-microscopy to get an idea of what this receptor looks like.
As with the research into the capsaicin receptor, new information about the wasabi receptor could help with future targeted drug development. An article from the University of California San Francisco (UCSF) explains why these insights are important, noting:
“But without knowing enough about the receptor’s overall structure to see where a given compound might connect, designing a drug to alleviate pain by controlling the action of the ion channel is something of a shot in the dark.”
Cordycepin is a compound found in cordyceps mushrooms, which are a parasitic mushroom that grow on caterpillars. These mushrooms have been widely used in traditional Chinese medicine, but researchers from the University of Nottingham didn’t expect the compound to work too well as a painkiller when subjected to clinical testing. However, they were surprised to find in a pilot study that the compound cordycepin worked just as well as traditional over-the-counter painkillers.
Testing on cordycepin as a potential painkiller is still in its very early phases. It could be years before researchers even begin testing with humans. However, if it continues to perform as well as it did in the pilot test with rat subjects, it could lead to the development of an entirely new class of painkillers.
Lidocaine is one of the most commonly used painkillers. It can be used topically for stings, bites, or similar painful conditions, or it can be injected to prevent pain from dental procedures or minor surgeries. However, lidocaine wears off quickly. This can sometimes necessitate another dose, which increases the risk of negative side effects.
Researchers at the University of Missouri, though, have altered aspects of lidocaine’s chemical structure to produce a new compound called boronicaine. In pre-clinical trials so far, boronicaine has provided pain relief comparable to lidocaine, but it lasts a lot longer. Lidocaine was effective for about five minutes, while boronicaine provided pain relief for 25 minutes. If it continues to do well in testing, boronicaine could provide a viable alternative to lidocaine in instances when a longer-lasting painkiller is needed.
Implanted devices to control pain typically use either medication or electric stimulation to interrupt pain signals, but both of these methods have potential drawbacks. Medications can have side effects, while electric stimulation doesn’t eliminate pain completely. Within the next few years, though, there might be an entirely new type of implanted device to control pain.
Researchers from Sweden have created a device that delivers a naturally-produced neurotransmitter. When implanted next to the area where an injured nerve meets the spinal cord, the neurotransmitters completely block pain signals. Testing has only been done in rats so far, but this new implanted device seems to be capable of controlling pain extremely effectively with no visible side effects.
Most people have probably heard of dopamine. It’s involved in cognition, movement, and reward-motivation behavior. Researchers at the University of Texas Dallas have found that dopamine is also involved in pain.
The researchers discovered that when they removed a collection of neurons that contained dopamine, chronic pain in mice was diminished. This collection of neurons, called A11, didn’t have an effect on acute pain (the type of pain you experience immediately after an injury). Rather, the A11 neurons only impacted chronic pain (pain that lasts long after an injury has healed). The effect of A11 on chronic pain was so profound that by targeting A11, researchers were able to permanently reverse a chronic pain state in mice.
It’s hoped that further research into A11 and dopamine could yield better understanding of the processes around chronic pain, which could eventually lead to more effective, targeted drug therapies.
Just as chronic pain can have a huge impact on a person’s life, the inability to feel any pain can have a huge impact, too. This condition, called congenital insensitivity to pain (CIP), is quite rare and tends to run in families.
Researchers analyzed the genetic makeup of 11 families with CIP throughout the UK and Europe and were able to identify variants of the gene PRDM12 as a cause of CIP. Family members who’d inherited two copies of the gene variant had CIP, while family members who’d inherited just one copy of the gene variant were unaffected. In previous research, the gene PRDM12 had been implicated in the modification of a molecule called chromatin. Chromatin is involved in the development of specialized cells like neurons, so if the variant PRDM12 gene affects chromatin, which affects neuron development, this could explain the lack of pain response in people with CIP.
Five other genes have already been identified as involved with the development of CIP. Of these, two genes have led to the development of new painkillers. Therefore, researchers are hopeful that the identification of PRDM12 and its effect on chromatin production could lead to more specialized painkillers in the future.
Have you heard of any recent breakthroughs in chronic pain or painkiller research?
Image by Idaho National Laboratory via Flickr