Screening for Novel Type 2 Ryanodine Receptor Inhibitors by Endoplasmic Reticulum Ca²⁺ Monitoring.

Area of Science:

• Cardiovascular Physiology
• Molecular Pharmacology
• Biomedical Engineering

Background:

• Type 2 ryanodine receptor (RyR2) hyperactivity is linked to cardiac arrhythmias like catecholaminergic polymorphic ventricular tachycardia and heart failure.
• Current treatments lack specific RyR2 inhibitors, necessitating the development of novel antiarrhythmic drugs.

Purpose of the Study:

• To identify novel inhibitors of the RyR2 channel using a high-throughput screening assay.
• To evaluate the efficacy of identified compounds in suppressing RyR2-mediated arrhythmogenic calcium release.

Main Methods:

• Screening of 1535 compounds using a genetically encoded endoplasmic reticulum (ER) calcium indicator (R-CEPIA1er) assay.
• Assessing compound effects on spontaneous Ca2+ oscillations and [3H]ryanodine binding in RyR2-expressing cells.
• Validating compound efficacy in cardiomyocytes from RyR2-mutant mice.

Main Results:

• Three compounds—chloroxylenol, methyl orsellinate, and riluzole—were identified as RyR2 inhibitors.
• These compounds suppressed spontaneous Ca2+ oscillations and reduced Ca2+-dependent [3H]ryanodine binding.
• In cardiomyocytes, the compounds reduced abnormal Ca2+ waves without affecting normal excitation-contraction coupling.

Conclusions:

• An ER Ca2+-based screening assay is effective for identifying modulators of ER Ca2+ release channels like RyR2.
• The identified compounds demonstrate potential as a new class of antiarrhythmic drugs for conditions involving RyR2 hyperactivity.
• Further development of these RyR2 inhibitors could lead to novel therapies for life-threatening cardiac arrhythmias.