An abnormal Ca(2+) response in mutant sarcomere protein-mediated familial hypertrophic cardiomyopathy

Area of Science:

• Cardiology
• Molecular Biology
• Genetics

Background:

• Familial hypertrophic cardiomyopathy (FHC) results from dominant-negative sarcomere protein gene mutations.
• FHC is characterized by left-ventricular hypertrophy, angina, dyspnea, and risk of sudden death.

Purpose of the Study:

• To investigate the role of calcium (Ca2+) dysregulation in FHC pathogenesis.
• To explore the impact of pharmacologic agents on FHC progression in a murine model.

Main Methods:

• Utilized a murine model of FHC with a cardiac myosin heavy-chain gene missense mutation (alphaMHC(403/+)).
• Administered calcineurin inhibitors or a K(+)-channel agonist to FHC mice and wild-type controls.
• Assessed cardiac myocyte Ca2+ concentrations and hypertrophic responses.
• Investigated the effect of Ca2+-channel antagonists.

Main Results:

• Pharmacologic treatment exacerbated hypertrophy and worsened histopathology in FHC mice.
• Both agents increased diastolic Ca2+ in wild-type myocytes but not in FHC myocytes.
• Ca2+-channel antagonist pretreatment normalized Ca2+ levels and prevented exaggerated hypertrophy in FHC mice.

Conclusions:

• Sarcomere protein gene mutations in FHC lead to abnormal Ca2+ handling, initiating hypertrophic responses.
• Environmental factors influence FHC progression, highlighting a Ca2+-dependent pathway.
• These findings suggest potential therapeutic strategies targeting Ca2+ regulation in FHC.