Identification of Small Molecule Inhibitors of Neurite Loss Induced by Aβ peptide using High Content Screening

Multiple lines of evidence indicate a strong relationship between A beta peptide-induced neurite degeneration and the progressive loss of cognitive functions in Alzheimer disease (AD) patients and in AD animal models. This prompted us to develop a high content screening assay (HCS) and Neurite Image Quantitator (NeuriteIQ) software to quantify the loss of neuronal projections induced by A beta peptide neurons and enable us to identify new classes of neurite-protective small molecules, which may represent new leads for AD drug discovery. We identified thirty-six inhibitors of A beta-induced neurite loss in the 1,040-compound National Institute of Neurological Disorders and Stroke (NINDS) custom collection of known bioactives and FDA approved drugs. Activity clustering showed that non-steroidal anti-inflammatory drugs (NSAIDs) were significantly enriched among the hits. Notably, NSAIDs have previously attracted significant attention as potential drugs for AD; however their mechanism of action remains controversial. Our data revealed that cyclooxygenase-2 (COX-2) expression was increased following A beta treatment. Furthermore, multiple distinct classes of COX inhibitors efficiently blocked neurite loss in primary neurons, suggesting that increased COX activity contributes to A beta peptide-induced neurite loss. Finally, we discovered that the detrimental effect of COX activity on neurite integrity may be mediated through the inhibition of peroxisome proliferator-activated receptor gamma(PPAR gamma) activity. Overall, our work establishes the feasibility of identifying small molecule inhibitors of A beta-induced neurite loss using the NeuriteIQ pipeline and provides novel insights into the mechanisms of neuroprotection by NSAIDs.