CCL2 and Parkinson disease: Meanwhile, in the pathological state, the CCL2/CCR2 signaling pathway formed by the combination of CCL2 synthesized by glial cells and CCR2 on neurons is involved in the formation of neuroinflammation, which may lead to nervous system diseases, such as Alzheimer’s disease (AD), multiple sclerosis (MS), Parkinson’s disease (PD), and so on [17,18].