PTEN and Alzheimer disease: To investigate the molecular mechanism(s) underlying PTEN loss in the brains of AD patients, we examined these oxidative events with a special focus on H2O2 and NO-mediated S-nitrosylation; the later, a process of reversible addition of NO to Cys-sulfur in proteins, has emerged as a major regulatory mechanism in fine-tuning many critical molecules in the neuronal death pathway and neurodegeneration [24].