Gap junction remodeling and spironolactone-dependent reverse remodeling in the hypertrophied heart

Area of Science:

• Cardiology
• Molecular Biology
• Electrophysiology

Background:

• Pressure overload leads to pathological cardiac hypertrophy, a risk factor for sudden cardiac death.
• Gap junction remodeling (GJR) occurs in hypertrophied hearts, but its mechanisms and functional impact on impulse propagation are not fully understood.
• Therapeutic strategies to mitigate GJR remain limited.

Purpose of the Study:

• To investigate the effects of progressive pathological hypertrophy on connexin (Cx)43 expression, phosphorylation, gap junction assembly, and impulse propagation.
• To evaluate the therapeutic potential of spironolactone in modulating GJR during cardiac hypertrophy.

Main Methods:

• Transverse aortic banding (TAC) was performed in mice to induce pressure overload and cardiac hypertrophy.
• Connexin 43 (Cx43) expression, phosphorylation, and gap junction assembly were assessed.
• Impulse propagation was analyzed using optical mapping with voltage-sensitive dyes.
• Mice were treated with spironolactone to assess its effects on GJR.

Main Results:

• TAC induced significant reductions in total and phospho-Cx43 abundance and diminished Cx43 incorporation into gap junctional plaques within 2 weeks.
• These molecular changes correlated with progressive slowing of cardiac impulse propagation.
• Spironolactone treatment effectively blunted the development of GJR and reversed established GJR at molecular and functional levels, without affecting the degree of hypertrophy.

Conclusions:

• Pathological cardiac hypertrophy involves significant gap junction remodeling, characterized by reduced Cx43 expression and impaired gap junction function, leading to slowed impulse propagation.
• Spironolactone demonstrates potent efficacy in both preventing and reversing GJR, suggesting a key role for mineralocorticoid receptor antagonism in managing cardiac electrical dysfunction associated with hypertrophy.
• These findings provide a mechanistic basis for the beneficial electrophysiological and clinical outcomes observed with mineralocorticoid antagonists in myopathic hearts.