Brain Selective Estrogen Treatment Protects Dopaminergic Neurons and Preserves Behavioral Function in MPTP-induced Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic neurons in the substantia nigra and loss of both motor and non-motor features. Several clinical and preclinical studies have provided evidence that estrogen therapy reduces the risk of PD but have limitations in terms of adverse peripheral effects. Therefore, we examined the potential beneficial effects of the brain-selective estrogen prodrug, 10 beta, 17 beta-dihydroxyestra-1,4-dien-3-one (DHED) on nigrostriatal dopaminergic neurodegeneration and behavioral abnormalities in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Wild-type mice were treated with daily subcutaneous injections of DHED (50 and 100 mu g/kg) or vehicle for four weeks. To produce PD-like symptoms, mice were injected with MPTP (18 mg/kg in saline; intraperitoneally) four times at 2-hr intervals for one day. After behavioral examination, mice were sacrificed, and the brains were isolated for neurochemical and morphological examinations. MPTP injected mice exhibited loss of dopaminergic neurons and fibers in substantia nigra and striatum respectively, along with impaired motor function at day 7 post MPTP injection. These phenotypes were associated with significantly increased oxidative stress and inflammatory responses in the striatum regions. DHED treatments significantly mitigated behavioral impairments and dopaminergic neurodegeneration induced by MPTP. We further observed that DHED treatment suppressed oxidative stress and inflammation in the striatum of MPTP treated mice when compared to vehicle treated mice. In conclusions, our findings suggest that DHED protects dopaminergic neurons from MPTP toxicity in mouse model of PD and support a beneficial effect of brain-selective estrogen in attenuating neurodegeneration and motor symptoms in PD-related neurological disorders.