Levodopa Impairs Lysosomal Function in Sensory Neurons In Vitro.

Area of Science:

• Neuroscience
• Cell Biology
• Pharmacology

Background:

• Parkinson's disease (PD) is a prevalent neurodegenerative disorder characterized by motor symptoms.
• Non-motor symptoms and peripheral neuropathy are increasingly recognized in PD patients.
• High-dose levodopa, a primary PD treatment, is suspected to induce or worsen neuropathy, potentially via homocysteine.

Purpose of the Study:

• To investigate the direct effects of levodopa on sensory neurons.
• To examine levodopa's impact on neuronal morphology, mitochondrial function, and lysosomal activity.
• To determine if levodopa's effects on sensory neurons are mediated by homocysteine.

Main Methods:

• Primary cultures of dorsal root ganglia and a sensory neuronal cell line were treated with levodopa.
• Assessed cell morphology, mitochondrial membrane potential, and lysosomal content and acidity.
• Investigated the role of homocysteine in levodopa's effects.

Main Results:

• High-dose levodopa reduced mitochondrial membrane potential in sensory neurons.
• Levodopa exposure increased beta III tubulin immunoreactivity at patient-relevant concentrations.
• Levodopa impaired lysosomal function by reducing lysosome content and acidity, independent of homocysteine.

Conclusions:

• Levodopa, while crucial for Parkinson's disease treatment, exhibits detrimental effects on sensory neurons at therapeutic concentrations.
• These adverse effects on neuronal function, particularly lysosomal activity, are not attributable to homocysteine.
• Findings highlight potential mechanisms for levodopa-induced neuropathy in PD patients.