Mitochondrial dysfunction induces Sarm1-dependent cell death in sensory neurons

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Mitochondrial dysfunction is implicated in neurological disorders and neuronal death.
• Mitochondria generate ATP via a proton gradient; disruptions cause reactive oxygen species (ROS) accumulation.
• Axon degeneration, like Wallerian degeneration, involves loss of mitochondrial potential.

Purpose of the Study:

• To investigate the role of mitochondrial depolarization in primary mouse sensory neuron degeneration.
• To identify the molecular mechanisms underlying depolarization-induced axon degeneration and cell death.
• To explore the relationship between Sarm1, ROS, and neuronal cell death.

Main Methods:

• Primary mouse sensory neuron culture.
• Induction of mitochondrial depolarization using CCCP.
• Assessment of cell death, axon degeneration, ROS levels, and ATP depletion.
• Genetic deletion of Sarm1 to evaluate its necessity.

Main Results:

• Mitochondrial depolarization directly triggers axon degeneration and cell death in sensory neurons.
• Inhibitors of apoptosis, necroptosis, and parthanatos do not prevent this degeneration.
• Sarm1 is essential for depolarization-induced axon degeneration and cell death.
• Neurons lacking Sarm1 survive depolarization, despite ROS accumulation, indicating Sarm1 acts downstream of ROS.
• Loss of Sarm1 protects neurons from oxidative stress-induced degeneration.

Conclusions:

• Sarm1 mediates a novel form of programmed cell death, termed sarmoptosis, triggered by mitochondrial depolarization.
• Sarm1 functions downstream of ROS generation in the pathway leading to neuronal cell death.
• Targeting Sarm1 may offer a therapeutic strategy for neurological disorders involving mitochondrial dysfunction and oxidative stress.