APP is a target of caspase-3 (137), and APP cleavage by caspase-3 or caspase-6 may promote As formation (138,139). Thus, increased production of As may be a consequence of neuronal apoptosis. As can induce apoptosis (140) and necrosis (141) in neuronal cell culture. Caspase-12 has been implicated in cortical neuron apoptosis in vitro induced by As (142). Presenilin proteins are also substrates for caspase-3 (143). Presenilin proteins have a widespread distribution throughout the CNS (144) and can influence mitochondrial regulation of apoptosis, such as Bax activation and cytochrome c release, through interactions with Bcl-XL (145). However, the real contribution of apoptosis to the neurodegeneration in AD still remains to be definitively ascertained.