TLR4 and Alzheimer disease: Because LPS and Aβ both act as agonists for the TLR4/CD14 receptor [14, 43, 44], they may establish a vicious circle in which LPS acts on the TLR4/CD14 receptor, thereby increasing Aβ, which in turn provides positive feedback to the TLR4/CD14 receptor, thus producing progressive damage in the brain, hippocampus, and cortical neurons, which are the most severely affected cells in AD [45].