Investigating Endogenous Opioids Unravels the Mechanisms Behind Opioid-Induced Constipation, a Mathematical Modeling...

Area of Science:

• Gastroenterology
• Pharmacology
• Computational Biology

Background:

• Opioid-induced constipation (OIC) is a common side effect of pharmaceutical opioids, stemming from μ-opioid receptor activation in the gut.
• Endogenous opioids like Endomorphin-2 are not typically linked to severe constipation, suggesting differing mechanisms.

Purpose of the Study:

• To mathematically model the interplay between serotonin and opioid signaling in the enteric nervous system (ENS).
• To investigate the mechanisms of OIC, focusing on adenylyl cyclase (AC) activity, cAMP levels, and differences between pharmaceutical and endogenous opioids.
• To evaluate the impact of serotonin on OIC and identify key factors differentiating opioid effects.

Main Methods:

• Developed a mathematical model integrating serotonergic and opioid pathways within the ENS.
• Simulated the effects of pharmaceutical opioids (Morphine, Fentanyl, Methadone) and Endomorphin-2 on AC activity and cAMP.
• Analyzed the influence of serotonin signaling and opioid degradation rates on OIC mechanisms.

Main Results:

• Opioids primarily affect AC activity, not serotonin signaling, indicating serotonin levels do not alleviate OIC.
• A key difference between endogenous and pharmaceutical opioids lies in their degradation rates.
• Modulating opioid degradation rates significantly enhances cAMP recovery, suggesting a therapeutic avenue.

Conclusions:

• Serotonin does not influence OIC; targeting AC activity is crucial.
• Opioid degradation rate is a critical factor differentiating endogenous and pharmaceutical opioid effects.
• Developing gut-localized opioid-degrading enzymes presents a promising strategy for mitigating OIC.