Mitochondrial MMP activation, dysfunction and arrhythmogenesis in hyperhomocysteinemia

Area of Science:

• Cardiology
• Mitochondrial Biology
• Neurocardiology

Background:

• Chronic heart failure involves oxidative stress and matrix metalloproteinase activation, leading to endothelial-myocyte uncoupling and impaired cardiac function.
• Elevated homocysteine (Hcy) levels, or hyperhomocysteinemia (HHcy), are linked to reduced cardiac performance, ventricular hypertrophy, cardiac stiffness, and diastolic heart failure.
• While N-methyl-D-aspartate receptors (NMDA-R) are implicated in Hcy-induced neurological defects and are present in the heart, their role in cardiac function during HHcy is not well understood.

Purpose of the Study:

• To elucidate the mitochondrial mechanisms by which Hcy contributes to the decline in cardiac mechano-electrical function and arrhythmogenesis through NMDA-R activation.
• To discuss the role of mitochondrial membrane potential (MMP) activation, protease stress, and mitochondrial permeability transition in cardiac conduction during HHcy.
• To investigate the potentiation between NMDA-R activation and mitochondrial defects in causing cardiac dysfunction during HHcy.

Main Methods:

• Review of existing literature on hyperhomocysteinemia, oxidative stress, NMDA receptor activation, and mitochondrial function in the context of heart failure.
• Analysis of the molecular pathways linking Hcy, NMDA-R, intracellular calcium handling, and mitochondrial dysfunction.
• Discussion of the role of cyclophilin D and the mitochondrial permeability transition pore in HHcy-induced cardiac pathology.

Main Results:

• Hcy increases intracellular calcium levels, activates calpain, and leads to mitochondrial abnormalities.
• Mitochondrial permeabilization and uncoupling in HHcy are driven by redox stress and calcium mishandling.
• Hcy amplifies mitochondrial membrane potential (mtMMP) activation via increased mitochondrial calcium overload and oxidative stress, leading to opening of the mitochondrial permeability transition pore.

Conclusions:

• Hcy-induced NMDA-R activation contributes to cardiac dysfunction and arrhythmogenesis through mitochondrial pathways.
• Mitochondrial dysfunction, including mtMMP activation and pore opening, plays a critical role in the mechano-electrical dysfunction observed in HHcy.
• Targeting NMDA-R and mitochondrial pathways may offer therapeutic strategies for managing HHcy-related cardiac complications.