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Neurotoxin modified to treat chronic pain

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    Neurotoxin modified to treat chronic pain

    Monday September 10, 01:30 PM

    Neurotoxin modified to treat chronic pain

    The deadly botulinum neurotoxin could be harnessed to treat pain, says a British team. Researchers at the Centre for Applied Microbiology and Research (CAMR) in Salisbury have chemically altered the toxin so that instead of acting on motor neurones and causing paralysis, it targets nerve cells that transmit pain signals.
    "We are developing molecules that will specifically target pain neurones," says researcher Keith Foster.

    The team hopes their work will lead to effective treatments for a wide range of pain disorders including chronic back pain, neck pain, headaches, post-surgical pain and chronic cancer pain.

    The advantage of engineered neurotoxins is that they can be made very specific to the target cell of choice, so minimising side effects, Foster says. They are also long-lasting, with one "dose" acting for two to three months.

    The researchers have already shown that the engineered toxin can relieve pain in rats, but Foster says clinical trials on humans are still a few years away.

    Ironically, the research is founded on expertise gained in biological weapons studies involving the toxin during the 1950s and 1960s. CAMR itself looks only at the clinical potential of the toxin, however.

    Respiratory failure

    Botulinum toxin is produced by Clostridium botulinum , the bacterium that causes botulism. It achieves its toxic effects by preventing the transmission of signals between motor neurones.

    The toxin binds to receptors on the surface of the cell membrane, enters the cell and prevents neurotransmitter release. This can cause paralysis and respiratory failure as the body loses control over all muscle movement.

    In its naturally occurring form, botulinum toxin has been used to treat some 180 disorders - including writer's cramp and squint. Doctors inject the toxin into specific muscles to relax them.

    But the new work involves changing the structure of botulinum so that instead of targeting motor neurones, it homes in on pain neurones. The toxin is made up of three protein "modules", each with separate jobs. One module allows the toxin to bind to the target cell. The team have been able to alter just this part, so that the toxin can be delivered to the cells of choice.

    The idea is that doctors could inject the modified toxin into the painful area. The toxin acts locally, so should not block the pain response in the rest of the body.

    The new research was presented the British Association Festival of Science in Glasgow.

    I've heard of botulinum being given in botox injections for at least awhile now. It's reasonably common in plastic surgery to "relax" some parts of the face and offer some cosmetic benefits.

    I've also heard of botox being used for pain management, but usually only for small areas. One fellow said that his doctor at a pain clinic was going to, at his suggestion, try using botox injections for his whole leg for neuropathic pain, but this took many injections. I haven't heard back on his results. I understand that botox injections have to be repeated every few months for at least awhile, and I think the effect may eventually become more-or-less permanent. Anyone feel free to correct me on this, but this is the way I recall it.

    I'm not sure why this is coming out as news now, unless it's some news twist on the specific form of botulinum. If it works, I'll be glad to see the research advance.

    David Berg