[Changes of heme oxygenase-1 expression in the nigrostriatal system of MPTP-treated SAMP8 mouse]

To explore the relationship between the expression of hemeoxygenase-1 (HO-1) and the dopaminergic system impairment in MPTP-treated SAMP8 mice.

6-month-old male SAMP8 mice received MPTP (20 mg/kg) subcutaneous injection at 2-h intervals for 4 times, and the control group was treated with an equal volume of normal saline. Mice were sacrificed at 6 h, 24 h, 3 d and 8 d after the first injection for the detection of the changes of tyrosine hydroxylase (TH) and HO-1 in the nigrostriatal system by immunohistochemistry and Western blotting.

TH-positive neuronal loss was visible at 6 h (14.23%, P<0.05), 24 h (23.85%, P<0.01), 3 d (36.77%, P<0.001), and 8 d (45.90%, P<0.001), and the significant progression of dopaminergic neuronal loss occurred most prominently in the MPTP group from 24 h to 3 d (24 h vs 3 d, P<0.05). There was a significant decrease of striatal TH immunoreactive cells in the MPTP group (P<0.05). Additionally, HO-1 positive cells were detected in striatum just only at 3 d, with the increase of HO-1 protein expression in MPTP groups. Western blot analysis showed no change of HO-1 protein levels in the midbrain after MPTP treatment compared to those of the normal saline group.

MPTP caused the loss of dopaminergic neuron number and the decrease of TH protein levels in SAMP8 mice. The up-regulation of HO-1 was ephemeral, and its effects related with Parkinson's disease was limited in this study.