ABSTRACT
1. Pramipexole (PPX), a dopamine D2 and D3 receptor agonist, exerts neuroprotective effects via both dopamine receptor-mediated and non-dopaminergic mechanisms. In the present study, we demonstrate that PPX reduces the toxicity of tunicamycin, a typical endoplasmic reticulum (ER) stressor, in PC12h cells, a subline of PC12 cells. 2. The PC12h cells were treated with 300 micromol / L PPX in the presence of 0.5 micromol / L tunicamycin for 24 h. The neuroprotective effects of PPX against tunicamycin-induced cell death were evaluated using 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release assays, Hoechst 33258 staining and western blot analysis. 3. Tunicamycin (0.2, 0.3 and 0.5 microg / mL) dose-dependently decreased MTT activity and increased LDH release from PC12h cells. Treatment with 300 micromol / L PPX rescued the tunicamycin-induced decrease in cell viability. 4. Spiperone (10 micromol / L), a dopamine D2 and D4 receptor antagonist, had no effect on PPX neuroprotection against tunicamycin in these cells. Marker proteins of ER stress and apoptosis are known to be upregulated by tunicamycin, but we detected no significant effects of PPX on these factors. 5. In conclusion, we speculate that a combination of several mechanisms may be involved in PPX-induced neuroprotection.