Summary: A new study identifies a possible candidate to help alleviate pain and itch sensations.
Source: Scripps Research Institute.
In a new study, scientists from the Florida campus of The Scripps Research Institute (TSRI) have identified a possible drug candidate that suppresses pain and itch in animal models. Their new approach also reduces the potential for drug abuse and avoids the most common side effects–sedation and anxiety–of drugs designed to target the nervous system’s kappa opioid receptors (KORs).
“The most significant aspect of the study is that we can preserve itch and pain treatment qualities in a KOR agonist that we developed–triazole 1.1–while avoiding the euphoria associated with narcotic opioids and the dysphoria associated with some other selective KOR agonists,” said TSRI Professor Laura Bohn, senior author of the new study.
The research was published this week online ahead of print in the journal Science Signaling.
Circumventing Side Effects
KORs help regulate the release of the neurotransmitter dopamine. Drugs that target KORs have shown promise as therapeutic candidates because of their efficacy for treating chronic itch and relieving pain. Unlike opioid narcotics that target other opioid receptors, these compounds do not produce a “high” or increased risk of overdose; however, they can deplete the body’s supply of dopamine and produce dysphoria and sedation, side effects that have limited their clinical development.
Bohn’s laboratory has pioneered the concept that KOR signaling can be fine-tuned to preferentially activate certain pathways over others so that the receptor signals through G proteins rather than through a protein called β-arrestin2.
In the new study, the researchers used rodent models to compare this kind of “biased” KOR agonist, called triazole 1.1, and a conventional KOR agonist.
They found that triazole 1.1 could indeed circumvent the two side effects of previously developed KOR compounds without decreasing dopamine levels, a property associated with dysphoria and sedation.
“This adds to the mounting evidence that shows analgesic effects can be separated from the sedative and dysphoric effects by altering how the agonist engages the receptor,” said TSRI Research Associate Tarsis Brust, first author of the study.
Bohn said the new findings clearly demonstrate that the strategy of developing biased KOR agonists offers a promising new way to treat pain and intractable itch without the potential for abuse.
In addition to Bohn, other authors of the study, “Biased Agonists of the Kappa Opioid Receptor Suppress Pain and Itch without Causing Sedation and Dysphoria,” include TSRI’s Tarsis Brust, Jenny Morgenweck, Lei Zhou, Edward L. Stahl, Cullen L. Schmid and Michael D. Cameron; Susy A. Kim, Jamie H. Rose, Jason Locke, Sara L. Jones, and Thomas J. Martin of Wake Forrest University; and Sarah M. Scarry and Jeffrey Aubé of the University of North Carolina at Chapel Hill.
Funding: This research was supported by the National Institutes of Health (grants P01GM113852, P50DA006634, R01DA014030, U01AA014091 and R01DA031297).
Source: Eric Sauter – Scripps Research Institute
Image Source: NeuroscienceNews.com image is credited to Stevens et al./Nature and is licensed CC BY-SA 3.0.
Original Research: Abstract for “Biased agonists of the kappa opioid receptor suppress pain and itch without causing sedation or dysphoria” by Tarsis F. Brust, Jenny Morgenweck, Susy A. Kim, Jamie H. Rose, Jason L. Locke, Cullen L. Schmid, Lei Zhou, Edward L. Stahl1, Michael D. Cameron1, Sarah M. Scarry4, Jeffrey Aubé, Sara R. Jones, Thomas J. Martin, and Laura M. Bohn in Science Signaling. Publishe online November 29 2016 doi:10.1126/scisignal.aai8441
[cbtabs][cbtab title=”MLA”]Scripps Research Institute. “Novel Compound to Alleviate Pain and Itch Identified.” NeuroscienceNews. NeuroscienceNews, 4 December 2016.
<https://neurosciencenews.com/pain-itch-compound-5674/>.[/cbtab][cbtab title=”APA”]Scripps Research Institute. (2016, December 4). Novel Compound to Alleviate Pain and Itch Identified. NeuroscienceNews. Retrieved December 4, 2016 from https://neurosciencenews.com/pain-itch-compound-5674/[/cbtab][cbtab title=”Chicago”]Scripps Research Institute. “Novel Compound to Alleviate Pain and Itch Identified.” https://neurosciencenews.com/pain-itch-compound-5674/ (accessed December 4, 2016).[/cbtab][/cbtabs]
Abstract
Biased agonists of the kappa opioid receptor suppress pain and itch without causing sedation or dysphoria
Agonists targeting the kappa opioid receptor (KOR) have been promising therapeutic candidates because of their efficacy for treating intractable itch and relieving pain. Unlike typical opioid narcotics, KOR agonists do not produce euphoria or lead to respiratory suppression or overdose. However, they do produce dysphoria and sedation, side effects that have precluded their clinical development as therapeutics. KOR signaling can be fine-tuned to preferentially activate certain pathways over others, such that agonists can bias signaling so that the receptor signals through G proteins rather than other effectors such as βarrestin2. We evaluated a newly developed G protein signaling–biased KOR agonist in preclinical models of pain, pruritis, sedation, dopamine regulation, and dysphoria. We found that triazole 1.1 retained the antinociceptive and antipruritic efficacies of a conventional KOR agonist, yet it did not induce sedation or reductions in dopamine release in mice, nor did it produce dysphoria as determined by intracranial self-stimulation in rats. These data demonstrated that biased agonists may be used to segregate physiological responses downstream of the receptor. Moreover, the findings suggest that biased KOR agonists may present a means to treat pain and intractable itch without the side effects of dysphoria and sedation and with reduced abuse potential.
“Biased agonists of the kappa opioid receptor suppress pain and itch without causing sedation or dysphoria” by Tarsis F. Brust, Jenny Morgenweck, Susy A. Kim, Jamie H. Rose, Jason L. Locke, Cullen L. Schmid, Lei Zhou, Edward L. Stahl1, Michael D. Cameron1, Sarah M. Scarry4, Jeffrey Aubé, Sara R. Jones, Thomas J. Martin, and Laura M. Bohn in Science Signaling. Publishe online November 29 2016 doi:10.1126/scisignal.aai8441
