Small molecules as therapeutic drugs for Alzheimer's disease

Mitochondrial dysfunction is a central protagonist of Alzheimer's disease (AD) pathogenesis. Mitochondrial dysfunction stems from various factors including mitochondrial DNA damage and oxidative stress from reactive oxygen species, membrane and ionic gradient destabilization, and interaction with toxic proteins such as amyloid beta (Aβ). Therapeutic drugs such as cholinesterase and glutamate inhibitors have proven to improve synaptic neurotransmitters, but do not address mitochondrial dysfunction. Researchers have demonstrated that oxidative damage may be reduced by increasing endogenous antioxidants, and/or increasing exogenous antioxidants such as vitamin C & E, beta-carotene and glutathione. Nonetheless, as AD pathology intensifies, endogenous antioxidants are overwhelmed, and exogenous antioxidants are unable to reach neuronal mitochondria as they are blocked by the blood brain barrier. Current therapeutic methods however include novel usage of lipophilic phosphonium cation bound to antioxidants, to effect neuronal mitochondria targeted activity. Mitochondria targeted MitoQ, MitoVitE, MitoTempo, MitoPBN and MCAT concentrate within mitochondria where they scavenge free-radicals, and augment mitochondrial dysfunction. Additional molecules include Szeto-Schiller (SS) peptides which target stability of the inner mitochondrial membrane, and DDQ molecule capable of improving bioenergetics and reduce mitochondrial fragmentation. This article discusses advantages and disadvantages of small molecules, their ability to mitigate Aβ induced damage, and ability to ameliorate synaptic dysfunction and cognitive loss.