Ascorbate availability and neurodegeneration in amyotrophic lateral sclerosis

Area of Science:

• Neuroscience
• Biochemistry
• Pathology

Background:

• Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease causing progressive motor neuron death.
• Current ALS mechanisms (e.g., superoxide dismutase, neurofilaments, autoimmunity, hyperglutamatergic activity) don't explain disease onset timing, male predisposition, or differential neuronal vulnerability.
• Specific physiological characteristics of alpha-motoneurons, including high metabolic activity and calcium dynamics, may contribute to their vulnerability.

Purpose of the Study:

• To propose and investigate the hypothesis that age-dependent decline in ascorbate (vitamin C) availability triggers ALS.
• To explore the role of ascorbate in relation to existing defects, such as altered superoxide dismutase (SOD1).
• To explain inconsistencies in ALS pathogenesis, including late onset, male predilection, and neuronal vulnerability patterns.

Main Methods:

• Review and synthesis of existing literature and evidence.
• Analysis of consistencies linking ascorbate levels and function to ALS pathogenesis.
• Consideration of the scorbutic guinea pig as a potential ALS model.

Main Results:

• Ascorbate shares substrates with superoxide dismutase and is linked to CNS injury tolerance.
• Ascorbate levels decline with age and are lower in males; its release is associated with motor activity and glutamate uptake.
• Ascorbate may modulate NMDA receptor activity and prevent peroxynitrite formation, crucial in oxidative stress.

Conclusions:

• Age-dependent decrease in ascorbate availability, coupled with primary defects (e.g., in SOD1), likely triggers ALS.
• Competition between superoxide dismutase and ascorbate in high-concentration proteins may be a key factor.
• The findings suggest a novel therapeutic avenue targeting ascorbate levels in ALS patients.