Effect of Chronic Stress in the Onset of Parkinson’s Disease: Possible Role of Microglial Cells in Neuroinflammation

For many years, several studies have been conducted to investigate the effect of stress on the onset of Parkinson’s disease (PD), which is characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). de Pablos et al. reported that stressed animals were associated with a higher rate of death of dopaminergic neurons in the substantia nigra, and that this effect was dependent on glucocorticoids [1]. In addition, Smith et al. reported that stress accelerates neural degeneration in the SNpc, further demonstrating that elevated corticosterone levels can exaggerate nigral neuronal loss and motor symptoms in a rate of rat analogue of PD [2]. These studies demonstrated the progression of nigral DA neuronal loss which is primarily triggered by extrinsic neurotoxins, such as Lipopolysaccharide (LPS) and 6-hydroxydopamine (OHDA). In this regard, it was not fully understood whether solely exposure to stress could induce DA neuronal loss in the SNpc.