Manganese flux across the blood-brain barrier

Area of Science:

• Neuroscience
• Toxicology
• Biochemistry

Background:

• Manganese (Mn) is vital for brain development and function.
• Excessive manganese exposure poses a neurotoxic risk.
• The chemical form of manganese influences its brain uptake and toxicity.

Purpose of the Study:

• To elucidate the mechanisms of manganese transport into and out of the brain.
• To investigate the role of specific transporters, like DMT-1, in brain manganese uptake.
• To understand how manganese kinetics influence its neurotoxic potential.

Main Methods:

• Investigated brain manganese influx in normal and DMT-1 deficient rats (Belgrade rats).
• Assessed the dependence of manganese uptake on sodium, ATP, and mitochondrial inhibitors.
• Examined manganese efflux rates using impermeable reference compounds.
• Identified potential calcium-mediated transport mechanisms.

Main Results:

• Brain manganese influx was not dependent on DMT-1, sodium, or ATP hydrolysis.
• Mitochondrial energy inhibitors reduced brain manganese uptake.
• Manganese and iron did not compete for brain uptake.
• Brain manganese efflux was slower than diffusion-controlled processes, suggesting diffusion mediation.
• Evidence suggests a store-operated calcium channel mediates manganese uptake, not a p-type ATPase.

Conclusions:

• Brain manganese uptake is primarily carrier-mediated, potentially via store-operated calcium channels.
• Brain manganese efflux is diffusion-mediated and slow.
• The kinetics of manganese transport lead to accumulation with repeated exposure, increasing neurotoxicity risk.