Exercise capacity correlating to exercise hemodynamics in coronary artery disease

RyR1-targeted drug discovery pipeline integrating FRET-based high-throughput screening and human myofiber dynamic Ca2+ assays

Elevated cytoplasmic [Ca²⁺] is characteristic in severe skeletal and cardiac myopathies, diabetes, and neurodegeneration, and partly results from increased Ca²⁺ leak from sarcoplasmic reticulum stores via dysregulated ryanodine receptor (RyR) channels. Consequently, RyR is recognized as a high-value target for drug discovery to treat such pathologies. Using a FRET-based high-throughput screening assay that we previously reported, we identified small-molecule compounds that modulate the skeletal muscle channel isoform (RyR1) interaction with calmodulin and FK506 binding protein 12.6. Two such compounds, chloroxine and myricetin, increase FRET and inhibit [³H]ryanodine binding to RyR1 at nanomolar Ca²⁺. Both compounds also decrease RyR1 Ca²⁺ leak in human skinned skeletal muscle fibers. Furthermore, we identified compound concentrations that reduced leak by > 50% but only slightly affected Ca²⁺ release in excitation-contraction coupling, which is essential for normal muscle contraction. This report demonstrates a pipeline that effectively filters small-molecule RyR1 modulators towards clinical relevance.

The effect of atenolol on the left ventricular performance in patients with angina pectoris measured with isotope technique

Working capacity, left ventricular ejection fraction (EF), stroke volume and the phase of the left ventricular contraction were tested before and after 3 weeks of atenolol treatment in 14 patients with angina pectoris and coronary insufficiency diagnosed by thallium tomography. Eight patients (group A) increased their EF during exercise and six patients (group B) showed a decrease in EF when tested with placebo. When treated with atenolol the changes in EF during exercise were reversed in the two groups. Group B increased and group A decreased their EF. Atenolol caused an increase in working capacity in group B, but not in group A. In both groups atenolol caused an increased stroke volume and a decreased phase deviation at rest, while no significant volume changes or phase changes occurred during exercise. These results indicate that atenolol treatment had the most marked effect in patients with the most pronounced disease.