Neurotoxic Effects of Homocysteine on Cerebellar Purkinje Neurons in Vitro

Whilst a plethora of studies that describe the toxicity of homocysteine to CNS neurons have been published, the effects of homocysteine on the Purkinje neurons of the cerebellum that play a vital role in motor function remain wholly unexplored. We have therefore established cultures of embryonic cerebellar Purkinje neurons and exposed them to a range of concentrations of homocysteine and determined its effects on their survival. The experiments revealed that all concentrations of homocysteine studied, from 50 to 500microM, caused a significant decrease in cerebellar Purkinje neuron number. This loss could be counteracted by the pan-caspase inhibitor z-VAD-fmk in the first 24h following homocysteine exposure, revealing that the initial loss was apoptotic. However, z-VAD-fmk could not prevent homocysteine-mediated loss of cerebellar Purkinje neurons in the longer term, after 6 days in vitro. In addition to its effects on Purkinje neuron survival, homocysteine markedly reduced both the overall magnitude and the complexity of the neurite arbor extended by the cerebellar Purkinje neurons, following 6 days incubation with this agent in vitro. Taken together our data reveal that homocysteine is toxic to cerebellar Purkinje neurons in vitro, inhibiting both their survival and the outgrowth of neurites.