Molecular Mechanism of μ-Opioid Receptor Activation

Area of Science:

• Pharmacology
• Computational Chemistry
• Molecular Biology

Background:

• Classical calcium channel blockers (CCBs) are widely used cardiovascular drugs.
• Their known mechanism involves blocking L-type calcium channels.
• Potential off-target effects and polypharmacology are increasingly recognized.

Purpose of the Study:

• To investigate the previously unrecognized Mu-opioid receptor (MOR) activation capabilities of structurally diverse CCBs.
• To elucidate the computational and experimental basis for CCB-MOR interactions.
• To explore the implications for drug repurposing and multi-target therapeutics.

Main Methods:

• Integrated computational (virtual screening, molecular dynamics) and experimental (cAMP inhibition assays) approaches.
• Screening of four distinct CCB structural classes: verapamil, cinnarizine, diltiazem, and flunarizine.
• Assessing binding stability, interaction profiles, and functional MOR activation (potency and efficacy).

Main Results:

• Virtual screening identified stable binding modes between CCBs and the MOR (7SBF target).
• Cinnarizine showed the most favorable binding interactions and highest MOR activation potency (IC50 = 21.4 ± 1.5 nM) and efficacy (Imax = 70% ± 2%).
• All tested CCBs demonstrated significant MOR activation, confirming a conserved polypharmacological mechanism.

Conclusions:

• Structurally diverse CCBs possess significant Mu-opioid receptor (MOR) activation capabilities.
• This polypharmacology represents a novel mechanism for CCBs.
• Findings open new avenues for drug repurposing and developing multi-target cardiovascular therapies.