Neurotoxins and ischemia-hypoxia caused by blood–brain barrier (BBB) dysfunction and oligemia can directly induce neuronal injury and synaptic dysfunction and promote amyloid-β (Aβ) accumulation by elevating amyloid precursor protein (APP) expression and reducing Aβ clearance, resulting in a neuroinflammatory response and initiation of the neurodegenerative process, eventually leading to dementia (Zlokovic, 2011; Sagare et al., 2012; Nelson et al., 2016). The gene discussed is APP; the disease is dementia.