TLR4 and Parkinson disease: LPS is a TLR4 agonist that activates microglia and alters the levels of MAPKs, NF-κB, iNOS, COX-2, PGE-2, proinflammatory cytokines, nitrites, and reactive oxygen species [24,30], which are involved in various neurodegenerative diseases such as AD, PD, and multiple sclerosis (MS) [31,32].