Pitx3‐transfected astrocytes secrete brain‐derived neurotrophic factor and glial cell line‐derived neurotrophic factor and protect dopamine neurons in mesencephalon cultures

The transcription factor Pitx3 is crucial for the development and differentiation of dopamine (DA) neurons. Our previous work has shown the Pitx3 can up-regulate the expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) in neuroblastoma cell line SH-SY5Y. Primary astrocytes are the major nonneuronal cells and can be easily modified genetically to deliver therapeutic molecules into the brain, so we investigated whether Pitx3 can increase the expression and secretion of BDNF and GDNF in primary astrocytes. We first transfected Pitx3 plasmid in purified rat astrocytes and collected the conditioned medium (CM) from the Pitx3-transfected cultures, and then we measured the BDNF and GDNF levels from the CM and tested the protective effect of the CM against rotenone-induced DA neuron injury in ventral mesencephalon (VM) cultures. We found that the BDNF and GDNF levels were 1.4-fold and 1.5-fold higher in the CM from Pitx3-transfected astrocytes than empty vectors-transfected controls. Incubation with the CM from Pitx3-transfected astrocytes significantly attenuated the rotenone-induced DA neuron injury, and such protection can be significantly blocked by preincubation with antibodies against either BDNF or GDNF, whereas preincubation with purified BDNF or GDNF replicated the neuroprotection against rotenone-induced injury in VM cultures. These results demonstrate that Pitx3-transfection in astrocytes can up-regulate BDNF and GDNF expression and produce protective benefit to DA neurons, which might be a potential therapeutic alternative for Parkinson's disease.