By Pat Anson, Editor
Injections of botulinum toxin -- more widely known as the brand name Botox -- have long been used as a cosmetic treatment that reduces wrinkles by causing muscles under the skin to relax. British researchers say a modified version of that same neurotoxin could someday be used to treat chronic pain.
In a study published in the journal Science Translational Medicine, scientists reported that they had deconstructed the botulinum molecule and reassembled it with a strong opioid called dermorphin to make "Derm-BOT" – a compound that blocks pain signals from neurons in the spinal cords of mice.
“Injected into the spine, Derm-BOT relieves chronic pain – such as that caused by nerve damage – and avoids the adverse events of tolerance and addiction often associated with repeated opioid drug use,” said co-author Steve Hunt, PhD, a professor in cell and developmental biology at University College London (UCL).
“It doesn’t affect muscles like the botulinum toxin used to reduce wrinkles but it does block nerve pain for up to four months without affecting normal pain responses. It really could revolutionize how chronic pain is treated if we can translate it into clinic."
So far, Derm-BOT has only been used on laboratory mice, so don't expect it to be available for humans anytime soon. Over a five year period, 200 mice were treated with a single injection of either Derm-BOT, SP-BOT (another modified botulinum molecule) or morphine. The behavior of the mice was observed to track their response to pain.
“Both SP-BOT and Derm-BOT have a long-lasting effect in both inflammatory and neuropathic pain model, successfully silencing neurons without cell death. We were impressed to see that one tiny injection was enough to stop chronic pain caused by inflammation and nerve damage for at least a month," said lead author Maria Maiarù, PhD, a research associate at UCL. “A single injection of Derm-BOT reduced mechanical hypersensitivity to the same extent as morphine."
Previous studies in rats and dogs show that injections of tiny amounts of toxic substances into the spine kill neurons responsible for chronic pain. In contrast, scientists say Derm-BOT does not kill neurons, is safe to manufacture and non-toxic. And although it is partially made with an opioid, it is not addictive and doesn't cause respiratory depression.
"Injected into the spine, Derm-BOT relieves chronic pain -- such as that caused by nerve damage -- and avoids the adverse events of tolerance and addiction often associated with repeated opioid drug use," Hunt said.
Botox injections are already used to treat conditions such as migraines, neuropathic pain, and some allergies. But those injection are made into the skin and muscles, not directly into the spinal cord.