Advancements in Drug Discovery for Mood Disorders and Chronic Pain
Introduction to New Drug Development
In the fast-paced field of drug discovery, researchers have created a new drug derived from a naturally occurring protein that shows promise in treating mood disorders and chronic pain. Opioid receptors in the body play significant roles in functions such as breathing, pain perception, mood regulation, and reward mechanisms.
Opioid Receptors and Their Activation
These receptors can be triggered by naturally occurring opioids like endorphins, plant-based opioids such as those from opium, or synthetic drugs like fentanyl. However, synthetic opioids often come with side effects including constipation and reduced respiratory function, leading to challenges in managing chronic pain and mood disorders effectively.
Aiming for Beneficial Activation Without Side Effects
Recent studies have linked these adverse effects to the activation of the cell signaling protein beta-arrestin-2 when opioid receptors are engaged. This understanding has propelled scientists to explore drug formulations that can stimulate beneficial pathways while minimizing the activation of side-effect pathways.
Potential of Rubiscolin Peptides
Naturally occurring peptides derived from the protein rubisco, commonly found in plants like spinach, have been investigated for their ability to activate opioid receptors without engaging beta-arrestin-2. Researchers in the United States suggest that rubiscolin peptides can bind to and activate these receptors effectively while avoiding the stimulation of beta-arrestin-2 proteins. Their findings were published in the journal European Neuropsychopharmacology.
Experimental Validation of Peptide Effects
To validate their hypothesis, the scientists compared the binding and signaling characteristics of two rubiscolin peptides with two established peptides, deltorphin II and leuenkephalin, known for activating beta-arrestin-2. All four peptides demonstrated the capacity to bind and activate the opioid receptor pathway; however, the rubiscolin peptides exhibited lower potency and weaker receptor affinity.
Findings on Beta-Arrestin-2 Levels
When assessing beta-arrestin-2 levels, researchers discovered that those activated by rubiscolin peptides were either low or undetectable. This marks the first instance of naturally occurring peptides selectively activating opioid receptor pathways with minimal beta-arrestin-2 stimulation.
Implications for Treating Mood Disorders
Previous investigations have indicated the advantages of selective signaling toward the opioid receptor pathway without involving beta-arrestin-2. Potential benefits include reduced tolerance, less constipation, and diminished respiratory depression. Initial studies suggest that these peptides can be effectively absorbed when taken orally and have the ability to penetrate the brain, which is crucial for treating brain-related disorders like mood disorders.
Limitations and Future Research
Despite their promising properties, the weaker affinity of rubiscolin peptides for opioid receptors may pose a limitation to their therapeutic efficacy. The researchers conclude that their discovery of a naturally occurring peptide with these characteristics is a significant advancement for future drug development, warranting further exploration of its potential as a treatment for mood disorders and chronic pain.
References
Cassell, R. J., Mores, K. L., Zerfas, B. L., Mahmoud, A. H., Lill, M. A., Trader, D. J., & Rijn, R. M. (2018). Rubiscolins are naturally occurring G protein-biased delta opioid receptor peptides. European Neuropsychopharmacology. doi:10.1016/j.euroneuro.2018.12.013
Adam, C. (2019, January 3). Improved treatment for alcohol use disorders, chronic pain, and mood disorders. Retrieved January 22, 2019, from https://www.eurekalert.org/pub_releases/2019-01/pu-itf010319.php
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