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Friday, December 5, 2014

Off switch' for pain discovered: Activating the adenosine A3 receptor subtype is key to powerful pain relief

Date:
November 26, 2014
Source:
Saint Louis University Medical Center
Summary:
A way to block a pain pathway in animal models of chronic neuropathic pain has been discovered by researchers, suggesting a promising new approach to pain relief.


Pain is an enormous problem. As an unmet medical need, pain causes suffering and comes with a multi-billion dollar societal cost. Current treatments are problematic because they cause intolerable side effects, diminish quality of life and do not sufficiently quell pain.
Credit: © Feng Yu / Fotolia

In research published in the medical journal Brain, Saint Louis University researcher Daniela Salvemini, Ph.D. and colleagues within SLU, the National Institutes of Health (NIH) and other academic institutions have discovered a way to block a pain pathway in animal models of chronic neuropathic pain including pain caused by chemotherapeutic agents and bone cancer pain suggesting a promising new approach to pain relief.

The scientific efforts led by Salvemini, who is professor of pharmacological and physiological

sciences at SLU, demonstrated that turning on a receptor in the brain and spinal cord counteracts

 chronic nerve pain in male and female rodents. Activating the A3 receptor -- either by its native 

chemical stimulator, the small molecule adenosine, or by powerful synthetic small molecule drugs

 invented at the NIH -- prevents or reverses pain that develops slowly from nerve damage without

causing analgesic tolerance or intrinsic reward (unlike opioids).
An Unmet Medical Need 
Pain is an enormous problem. As an unmet medical need, pain causes suffering and comes with a 

multi-billion dollar societal cost. Current treatments are problematic because they cause intolerable

 side effects, diminish quality of life and do not sufficiently quell pain.
The most successful pharmacological approaches for the treatment of chronic pain rely on certain 

"pathways": circuits involving opioid, adrenergic, and calcium channels.
For the past decade, scientists have tried to take advantage of these known pathways -- the series of

 interactions between molecular-level components that lead to pain. While adenosine had shown 

potential for pain-killing in humans, researchers had not yet successfully leveraged this particular 

pain pathway because the targeted receptors engaged many side effects.
A Key to Pain Relief 
In this research, Salvemini and colleagues have demonstrated that activation of the A3 adenosine 

receptor subtype is key in mediating the pain relieving effects of adenosine.
"It has long been appreciated that harnessing the potent pain-killing effects of adenosine could 

provide a breakthrough step towards an effective treatment for chronic pain," Salvemini said. "Our

 findings suggest that this goal may be achieved by focusing future work on the A3AR pathway, in

 particular, as its activation provides robust pain reduction across several types of pain."
Researchers are excited to note that A3AR agonists are already in advanced clinical trials as anti-

inflammatory and anticancer agents and show good safety profiles. "These studies suggest that A3AR 

activation by highly selective small molecular weight A3AR agonists such as MRS5698 activates a 

pain-reducing pathway supporting the idea that we could develop A3AR agonists as possible new 

therapeutics to treat chronic pain," Salvemini said.

Story Source:
The above story is based on materials provided by Saint Louis University Medical CenterNote: Materials may be edited for content and length.

Journal Reference:
  1. J. W. Little, A. Ford, A. M. Symons-Liguori, Z. Chen, K. Janes, T. Doyle, J. Xie, L. Luongo, D. K. Tosh, S. Maione, K. Bannister, A. H. Dickenson, T. W. Vanderah, F. Porreca, K. A. Jacobson, D. Salvemini. Endogenous adenosine A3 receptor activation selectively alleviates persistent pain statesBrain, 2014; DOI: 10.1093/brain/awu330

Cite This Page:
Saint Louis University Medical Center. "'Off switch' for pain discovered: Activating the adenosine A3 receptor subtype is key to powerful pain relief." ScienceDaily. ScienceDaily, 26 November 2014. <www.sciencedaily.com/releases/2014/11/141126132639.htm>.

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