BCL2 and Parkinson disease: Numerous studies have delineated the neuroprotective effects of female sex hormones: the neuroprotective effects of estrogen have been well documented for Alzheimer's disease [19, 20], Parkinson's disease [21], spinal cord and brain injury [22–24], and so on, with the potential neuroprotective mechanisms including autoregulatory functions, antioxidant effects, reduction in excitotoxicity with glutamate exposure, increase in expression of the antiapoptotic factor bcl-2, and activation of mitogen-activated protein kinase pathways [25].