Cardiac disease due to random mitochondrial DNA mutations is prevented by cyclosporin A

Area of Science:

• Mitochondrial biology
• Cardiovascular pathology
• Molecular genetics

Background:

• Mitochondrial DNA (mtDNA) mutations can lead to cellular dysfunction and disease.
• The mitochondrial permeability transition pore (mPTP) is implicated in cell death pathways.
• Dilated cardiomyopathy is a severe heart condition characterized by enlargement and weakening of the left ventricle.

Purpose of the Study:

• To investigate the role of the mPTP in the pathogenesis of heart disease caused by mtDNA mutations.
• To determine if inhibiting mPTP opening can prevent or ameliorate cardiac pathology.

Main Methods:

• Mice expressing an error-prone mitochondrial DNA polymerase were used to induce mtDNA mutations and cardiac disease.
• Mice were treated with cyclosporin A (CsA), an mPTP inhibitor, or FK506, a calcineurin inhibitor.
• Cardiac function, apoptosis, protein expression (Bcl-2, connexin 43), and mtDNA mutation accumulation were assessed.

Main Results:

• Expression of error-prone mtDNA polymerase led to rapid mtDNA mutation accumulation, dilated cardiomyopathy, cardiomyocyte apoptosis, and altered Bcl-2 and connexin 43 levels.
• CsA treatment prevented cardiac dilatation, apoptosis, Bcl-2 upregulation, and loss of connexin 43.
• FK506 treatment did not affect disease progression, indicating CsA's target is the mPTP, not calcineurin.

Conclusions:

• Breakdown of the mitochondrial permeability barrier, mediated by mPTP opening, is implicated in the pathogenesis of heart disease resulting from mtDNA mutations.
• Inhibiting mPTP opening offers a potential therapeutic strategy for conditions associated with mtDNA instability and cardiac dysfunction.