PDCD4 and Alzheimer disease: Indeed, the miR-21 negatively regulated PDCD4 expression, whichled to activated PI3K/AKT/GSK-3β signaling.Conclusion: Our study demonstratedthat miR-21 cloud inhibits cell apoptosis in AD through the activation ofPI3K/AKT/GSK-3β signaling pathway using inhibition of PDCD4 expression.