The Putative Use of Lithium in Alzheimer's Disease

Alzheimer's disease is a progressive neurodegenerative illness characterized by the invariant existence of beta-amyloid plaques and neurofibrillary tangles. Presently approved pharmaceutical approaches offer only marginal efficacy and as yet there is no effective treatment which reverses or arrests the disease. Thus far, drugs targeting any single aspect of disease pathology have proved to be a failure or at best provided very slight clinical benefit. The consistent failure of drugs targeting aspects of the A beta cascade has questioned the causal role of this pathway. There is a growing appreciation that the pathogenesis of the illness is multifactorial with Amyloid Beta, Phosphorylated Tau (ptau), inflammation, mitochondrial dysfunction, calcium dyshomeostasis, heavy metal imbalances, and GSK-3 interact in a highly complex manner to provoke a self-sustaining spiraling cascade of pathology, driving disease progression. In the light of such complex pathology, the failure of drugs aimed a targeting single molecules is not surprising as such approaches are usually ineffective against other complex diseases with a multifactorial pathogenesis. Combination therapies or multi target drugs might be more effective in controlling such illnesses. The putative neuroprotective effects of Lithium are achieved via the positive modulation of numerous homeostatic mechanisms regulating autophagy, oxidative stress, inflammation, and mitochondrial dysfunction likely achieved by inhibiting GSK-3 and inositol-145 triphosphate. Data regarding efficacy in human trials and animal models of AD are mixed, but recent data using "microdose" lithium in mild cognitive impairment is encouraging, hence lithium could be a putative multi target treatment in these patients. However, additional well designed long-term trials are needed to confirm its efficacy and safety, given that long term use is necessary to achieve reasonable therapeutic benefit.