Extracellular lactate as an alternative energy source for retinal bipolar cells

Area of Science:

• Neuroscience
• Retinal Biology
• Cellular Metabolism

Background:

• Retinal neurons process visual information through complex metabolic pathways.
• Aerobic glycolysis and lactate shuttle systems are implicated in retinal energy metabolism.
• The specific role of bipolar cells in these metabolic circuits remains largely unknown.

Purpose of the Study:

• To investigate the expression and function of monocarboxylate transporter 2 (MCT2) in inner retinal neurons.
• To determine if inner retinal neurons can utilize extracellular lactate as an energy source.
• To elucidate the functional consequences of lactate metabolism in rod bipolar cells.

Main Methods:

• Immunohistochemistry to detect MCT2 expression.
• Genetically encoded Förster Resonance Energy Transfer (FRET) nanosensors to measure intracellular lactate.
• Electrophysiological recordings to assess neuronal function.
• Cell viability assays to evaluate cell death rates.

Main Results:

• Monocarboxylate transporter 2 is expressed and functional in inner retinal neurons.
• Inner retinal neurons demonstrate the capacity to consume extracellular lactate.
• Lactate consumption by rod bipolar cells supports ion homeostasis and electrical responses.
• Inhibition of lactate synthesis or transport leads to functional deficits and increased cell death.

Conclusions:

• Inner retinal neurons, particularly rod bipolar cells, actively participate in retinal metabolic circuits by consuming lactate.
• Lactate serves as a viable alternative fuel source for these neurons, crucial for maintaining retinal function and survival.
• Targeting lactate metabolism pathways may offer new therapeutic strategies for retinal diseases.