PTGS2 and Alzheimer disease: However, these reasons are still controversial as the elevated expressions of COX-2 occur before the activation of microglia and astrocytes as shown by neuropathological studies (Hoozemans et al., 2002), whereas the expression has been found to reduce later on as the disease progresses and the number of neurons expressing COX-2 in severe cases of AD is very few (Hoozemans et al., 2004), which might be due to selective degeneration of neurons at these stages and a loss in the synaptic activity (Hoozemans et al., 2008).