CASP9 and Parkinson disease: It has been reported that mitochondrial production of reactive oxygen species (ROS) was increased in Parkinson's disease (PD), and pro-apoptotic pathways were also activated with following activation of caspase-9, caspase-3 and Bax, which were crucial factors in mitochondria-mediated apoptosis pathway (Bose and Beal, 2016).