Economics, pharmacoeconomics and drug discovery for dementias

Selective estrogen receptor modulators (SERMs) for the brain: current status and remaining challenges for developing NeuroSERMs

Multiple issues regarding the efficacy of estrogen action in the brain remain unresolved. These include the timing, formulation and duration of the therapy intervention. Moreover, issues of thrombotic and neoplastic risks must be factored into the design of estrogen alternatives developed to prevent age-associated neurodegenerative disorders, as well as other climacteric symptoms such as hot flush and sleep dysfunction. One strategy to address these issues is to develop molecules that selectively target and activate estrogen mechanisms of action in the brain while avoiding activation of estrogen receptors peripheral to the brain, particularly in reproductive organs. An overview of recent advances in our understanding of the molecular mechanisms of estrogen action is discussed in the context of designing an efficacious NeuroSERM that will activate cellular, biochemical and genomic events required for the promotion of memory function and neuronal survival. Pharmacological analyses of estrogen receptor subtypes and the case for a membrane-associated estrogen receptor splice variant in mediating these mechanisms are provided along with a summary of the activation profiles of existing clinically relevant estrogen alternatives or SERMs in neurons. Results of these endeavors have yielded insights into strategies for developing novel molecules with NeuroSERM potential in order to prevent brain related climacteric symptoms and neurodegenerative diseases.

Progress toward identification of protease activity involved in proteolysis of apolipoprotein e in human brain

Apolipoprotein E (apoE) genotype is the single most important genetic risk factor for the most common (sporadic) form of Alzheimer's disease (AD). Increasing evidence supports the hypothesis that the presence of the E4 isoform of this cholesterol-binding protein contributes directly to disease risk, age of onset, and severity of the neuropathology. For example, studies in transgenic mice demonstrate that apoE is necessary for the formation of plaques with neuritic pathology. The precise mechanism by which apoE contributes to the disease remains unknown. However, several lines of investigation from a number of laboratories now point to a role for proteolytic fragments of apoE in the formation of both plaques and tangles, the two pathological hallmarks of the disease. In particular, the C-terminal portion of apoE has been implicated in binding to amyloid and is localized to plaques. The N-terminal domain, on the other hand, is neurotoxic in culture and has been localized to, and implicated in the formation of, neurofibrillary tangles. These results suggest that inhibition of apoE proteolysis is a potential therapeutic strategy for AD. Using human brain homogenates, we have determined that proteolysis of apoE is greatest at acidic pH and can be inhibited by compounds targeting aspartic proteases. The feasibility of screening candidate inhibitors is supported by both ELISA and immunoblotting methods. Future studies will use a combination of in vitro and in vivo assays to test the efficacy of the most effective compounds for their ability to inhibit apoE proteolysis in human brain and apoE transgenic mouse brain tissue.