Reduction of tyrosine hydroxylase expression and increase of α-synuclein in the substantia nigra in a rat model of benign prostatic hyperplasia.

Parkinson's disease (PD) occurs when dopaminergic cells in the substantia nigra (SN) region are destroyed; however, the cause of the destruction of dopamine cells has not yet been determined. This study was performed to investigate whether changes in the hormones that cause benign prostatic hyperplasia (BPH) are related to pathological changes in PD. The pathological findings were examined by observing the lesion sites related to PD in a BPH rat model. BPH was induced in rats by subcutaneous injection of testosterone propionate for 4 weeks after castration. To investigate the changes in the SN regions, tyrosine hydroxylase (TH) and α-synuclein (α-syn) expression were analyzed by western blotting. TH expression, expressed in dopaminergic cells and used as a dopaminergic cell detection marker, decreased, whereas α-syn expression increased at the SN site. These results are quite similar to the pathological changes observed in patients with PD and Parkinsonism animal models. Our results showed an increased expression of inducible nitric oxide synthase and cyclooxygenase-2 in the SN regions in the BPH group. Additionally, a decreased expression of B-cell lymphoma protein 2 and an increased expression of B-cell lymphoma protein 2-associated X, suggesting increased apoptosis, were observed in the BPH group. These results suggest that the pathological changes associated with PD may be caused by BPH or factors related to BPH. Thus, this study has presented a new avenue for an approach related to hormonal changes as a method to determine the cause of PD, for which the exact cause is not yet known.