CYCS and brain disorder: As an initiator of caspases, cytochrome c triggers series of events leading to cell apoptosis, which attack mitochondria to release more cytochrome c, a vicious cycle comes into play, and eventually, this vicious cycle causes mitochondrial dysfunction with disruption of electron transport chain.24 Jia et al. and Du et al. (2021)25 have stated that mitochondrial dysfunction is directly related to brain diseases and aging.