MAPT and Alzheimer disease: However, some potential mechanisms have been suggested for HHcy-induced brain damage and explain the connections between HHcy and AD, such as increasing cellular oxidative stress and hypo-methylation of DNA and proteins [38,39,40,41] ER stress [42], cerebrovascular damage [43], neuroinflammation [44], Aβ elevation [45,46], and tau protein phosphorylation [47].