The effects and mechanism of estrogen on rats with Parkinson's disease in different age groups.

OBJECTIVE: In order to investigate the effect and mechanism of estrogen in rotenone-induced Parkinson's disease (PD) rats in different age groups. METHODS: we established rat models of PD by rotenone at different interventions. Then, behavioral tests, immunohistochemistry, western blot, high-performance liquid chromatography-electrochemical detector (HPLC-ECD) and electron microscopy were performed. RESULTS: Results revealed the following: (1) Rotenone significantly reduced rotarod latencies in senile rats, prolonged their climbing pole time, and decreased TH positive cells, DA and its metabolite, DOPAC. Estrogen ameliorated this effect, in which weaker effects were observed in younger rats compared with older rats. (2) Rotenone increased the expression of LC3-II in older rats, but estrogen and tamoxifen did not show the same effect. (3) Rotenone increased the number of autophagosomes, but estrogen increased the proportion of autolysosomes/autophagosomes in the rotenone-treated group. (4) U0126 could reduce the number of autophagosomes in the rotenone-treated group, but this did not change the proportion of autolysosome/autophagosome in combining rotenone with the estrogen group. Rapamycin did not increase the number of autophagosomes in the rotenone-treated group, but combining rapamycin with estrogen and rotenone was able to further increase the proportion of autolysome/autophagosomes. Therefore, we speculate that the senile rat model of PD was more reliable than that in young rats. CONCLUSIONS: In addition, estrogen could promote autophagy maturation through the ERK pathway, and had an obvious therapeutic effect on the rat model of PD.

Upregulation of cell surface estrogen receptor alpha is associated with the mitogen-activated protein kinase/extracellular signal-regulated kinase activity and promotes autophagy maturation.

Recently, accumulating evidence has implicated the dysregulation of autophagy as underlying the pathophysiology of several neurodegenerative diseases. The human neuronal cell line SH-SY5Y was exposed to 1-Methyl-4-phenylpyridinium (MPP(+)). The mechanism is that the sustained activation of the MAPK/ERK pathway by MPP(+) alters autophagy selectively at the maturation step, significant increasing in autophagy formation and delaying in autophagy degradation in SHSY5Y cells. In this study, we provided evidences that estrogen was capable of promoting SHSY5Y cells survival in MPP(+)-treated group. In particular, the up-regulation of mERα, but not mERß, was associated with a rapid and transient activation of ERK phosphorylation compatible with promoting autophagy maturation. The up-regulation of mERα changed the sustained activation of ERK phosphorylation in MPP(+)-treated group into a temporary activation. Taken together, these findings strongly support that the expression of mERα promotes the maturation of autophagosomes into functional autolysosomes by regulating ERK, determining SHSY5Y cells survival.

Promotion of autophagy at the maturation step by IL-6 is associated with the sustained mitogen-activated protein kinase/extracellular signal-regulated kinase activity.

Increased autophagic vacuoles (AVs) occur in injured or degenerating neurons, under both developmental and pathological situations. Although an induced autophagy has been shown in inflammation response to cell factors, the underlying mechanism(s) remain(s) unknown. Here, we show that both cell factor IL-6 and environmental toxin MPP(+) promote the formation of vacuolation in SHSY5Y cells. By electron and immunofluorescent microscopy analyses, we showed that these structures are acid autolysosomes, containing cellular debris, and labeled by LC3 or LAMP1, markers of autophagosomes or lysosomes, respectively. Combining MPP(+) and IL-6 do not further increase vacuolation of SHSY5Y cells, and the vacuolation is less than that in the MPP(+)-treated group. MPP(+)-induced vacuolation results from significant increase in autophagy formation and delay in autophagy degradation, in relation to a decline of the lysosomal activity of arylsulfatase A. At molecular level, we show that this defect in autolysosomal maturation is independent of mammalian target of rapamycin and p38 inhibitions. Most importantly, we provide the first evidence that activation of ERK pathway is sufficient to commit cell to autophagic vacuolation. The sustained activation is required for MPP(+) to disrupt the autophagic pathway. IL-6 also induces a temporary and significant activation of ERK, but not sustained activation, and change sustained activation in MPP(+)-treated group into temporary activation. Taken together, these findings strongly support that IL-6 promotes the maturation of autophagosomes into functional autolysosomes by regulating ERK.