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Better proteine than morphine

Staff writer |
More people suffer from pain, but many of the drugs used to relieve suffering are not completely effective or have harmful side effects.

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Now researchers at the University of North Carolina at Chapel Hill School of Medicine and the University of Helsinki have discovered a new therapeutic target for pain control, one that appears to be eight times more effective at suppressing pain than morphine.

The scientists pinpointed the identity and role of a particular protein that acts in pain-sensing neurons, or nerve cells, to convert the chemical messengers that cause pain into ones that suppress it.

The biological basis of pain is complex. To study the transmission of painful signals throughout the body, many researchers use "marker" proteins that label pain-sensing neurons. One such marker, FRAP (fluoride-resistant acid phosphatase), has been employed for this purpose for nearly 50 years, but the gene that codes for its production was never identified. That is, until researchers at UNC found that FRAP is identical to PAP (prostatic acid phosphatase), a protein routinely used to diagnose prostate cancer whose levels increase in the blood of patients with metastatic prostate cancer.

Previous research hinted that FRAP and PAP may have a shared identity. To determine whether or not this was the case, Zylka teamed up with Dr. Pirkko Vihko, a professor from the University of Helsinki who had genetically engineered mice that were missing the gene for PAP. When Zylka and his colleagues studied tissues from these mutant mice, they were happy to see that FRAP activity was missing. This revealed that the two proteins were in fact identical.

Further, the mutant mice proved more sensitive than normal mice to inflammatory pain and neuropathic pain, two common forms of chronic pain in humans. These increased sensitivities diminished when researchers injected excess amounts of PAP into the spinal cords of the mutant mice.

"We were really blown away that a simple injection could have such a potent effect on pain," Zylka said. "Not only that, but it appeared to work much better than the commonly used drug morphine." The new protein suppressed pain as effectively as morphine but for substantially longer. One dose of PAP lasted for up to three days, much longer than the five hours gained with a single dose of morphine.