Nrf2-mediated neuroprotection by MANF against 6-OHDA-induced cell damage via PI3K/AKT/GSK3β pathway.

Oxidative stress and apoptosis are thought to be broadly involved in the pathogenesis of Parkinson's disease. We previously reported that Mesencephalic astrocyte-derived neurotrophic factor (MANF) possesses anti-oxidation and anti-apoptotic effects against 6-OHDA-induced neurotoxicity, but the specific molecular mechanism remains unclear. In this study, we showed that MANF up-regulates the expression of nuclear factor erythroid 2-related factor (Nrf2) and promotes its translocation into the nucleus. The anti-oxidation and anti-apoptotic effects of MANF could be partially blocked by inhibitor or shRNA-mediated knockdown of Nrf2. Furthermore, MANF activated phospoinositide-3-kinase (PI3K)/Akt signaling and suppressed glycogen synthase kinase (GSK3β) activation. PI3K inhibitor (LY49002) abolished effects of MANF on AKT phosphorylation, GSK3β inactivation, Nrf2 nuclear translocation and subsequently abrogated MANF-mediates cytoprotection. Collectively, our findings indicated that MANF-mediated protection against 6-OHDA-induced cytotoxicity by potentiating the Nrf2-related survival mechanism through the PI3K/Akt/GSK3β pathway.

Zhang J ，Tong W ，Sun H ，Jiang M ，Shen Y ，Liu Y ，Gu H ，Guo J ，Fang J ，Jin L ... -  《-》

DJ-1 regulating PI3K-Nrf2 signaling plays a significant role in bibenzyl compound 20C-mediated neuroprotection against rotenone-induced oxidative insult.

Oxidative stress is thought to be involved in the development of Parkinson's disease (PD). We previously reported that 20C, a bibenzyl compound isolated from Gastrodia elata, possesses antioxidative properties, but its in-depth molecular mechanisms against rotenone-induced neurotoxicity remains unknown. Recent studies indicate that without intact DJ-1, nuclear factor erythroid 2-related factor (Nrf2) protein becomes unstable, and the activity of Nrf2-mediated downstream antioxidant enzymes are thereby suppressed. In this study, we showed that 20C clearly protected PC12 and SH-SY5Y cells against rotenone-induced oxidative injury. Furthermore, 20C markedly up-regulated the levels of DJ-1, which in turn activated phosphoinositide-3-kinase (PI3K)/Akt signaling and inhibited glycogen synthase kinase 3β (GSK3β) activation, eventually promoted the nuclear translocation of Nrf2 and induced the expression of hemeoxygenase-1 (HO-1). The antioxidant effects of 20C could be partially blocked by ShRNA-mediated knockdown of DJ-1 and inhibition of the PI3K/Akt pathways with Akt1/2 kinase inhibitor, respectively. Conclusively, our findings confirm that DJ-1 is necessary for 20C-mediated protection against rotenone-induced oxidative damage, at least in part, by activating PI3K/Akt signaling, and subsequently enhancing the nuclear accumulation of Nrf2. The findings from our investigation suggest that 20C should be developed as a novel candidate for alleviating the consequences of PD in the future.

Zhang XL ，Yuan YH ，Shao QH ，Wang ZZ ，Zhu CG ，Shi JG ，Ma KL ，Yan X ，Chen NH ... -  《-》

Neuroprotective effects of astaxanthin against oxygen and glucose deprivation damage via the PI3K/Akt/GSK3β/Nrf2 signalling pathway in vitro.

Astaxanthin (ATX), which is the most abundant flavonoid in propolis, has previously shown neuroprotective properties against cerebral ischaemia-induced apoptosis. However, the mechanisms by which ATX mediates its therapeutic effects are unclear. At present, we explored the underlying mechanisms involved in the protective effects of ATX via the phosphoinositide 3-kinase (PI3K)/Akt/glycogen synthase kinase 3 beta (GSK3β)/nuclear factor erythroid 2-related factor 2 (Nrf2) signalling pathway in SH-SY5Y cells. The PI3K/Akt inhibitor LY294002 and GSK3β inhibitor LiCl were employed in this study. Pre-treatment with ATX for 24 hours significantly decreased the oxygen and glucose deprivation (OGD)-induced viability loss, reduced the proportion of apoptosis and regulated OGD-mediated reactive oxygen species (ROS) production. Furthermore, ATX suppressed OGD-caused mitochondrial membrane potential and decomposition of caspase-3 to cleaved caspase-3, and heightened the B-cell lymphoma 2 (Bcl-2)/Bax ratio. PI3K/Akt/GSK3β/Nrf2 signalling pathway activation in SH-SY5Y cells was verified by Western blot. ATX and LiCl treatment raised the protein levels of p-Akt, p-GSK3β, nucleus Nrf2 and haeme oxygenase 1 (HO-1). However, these protein expression levels decreased by treatment of LY294002. The above in vitro data indicate that ATX can confer neuroprotection against OGD-induced apoptosis via the PI3K/Akt/GSK3β/Nrf2 signalling pathway.

Zhang J ，Ding C ，Zhang S ，Xu Y ... -  《-》

Isoorientin exerts a protective effect against 6-OHDA-induced neurotoxicity by activating the AMPK/AKT/Nrf2 signalling pathway.

Ma L ，Zhang B ，Liu J ，Qiao C ，Liu Y ，Li S ，Lv H ... -  《-》

Mesencephalic astrocyte-derived neurotrophic factor alleviated 6-OHDA-induced cell damage via ROS-AMPK/mTOR mediated autophagic inhibition.

Autophagy and apoptosis are commonly involved in the dopaminergic neuron damage in the pathogenesis of Parkinson's disease. Recently, the autophagy pathway is thought to be critical to the process of PD. Therefore, the regulation of autophagy may be a potential strategy for PD treatment. Mesencephalic astrocyte-derived neurotrophic factor (MANF) has been reported to have neuroprotective effects through anti-apoptosis, anti-oxidative, and anti-inflammatory mechanisms in PD. In this study, we investigated the role of autophagy system in MANF-mediated neuroprotection against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity. Our results showed that MANF protected SH-SY5Y cells against 6-OHDA-induced cell viability decrease and apoptosis by inhibiting autophagy. Mitochondrion damage and energetic dysfunction triggered by reactive oxidative stress (ROS) accumulation were also alleviated by MANF treatment. Furthermore, MANF downregulated phosphorylation of AMP-activated protein kinase (AMPK), a cellular energy sensor and regulator, but upregulated phosphorylation of Mammalian target of rapamycin (mTOR) under energy depletion conditions, indicating AMPK/mTOR signaling pathway is involved in the autophagic inhibition of MANF. These results suggest that autophagic inhibition provides protective mechanism of MANF in 6-OHDA-induced SH-SY5Y cell death and this inhibition is associated with AMPK/mTOR pathway.

Zhang J ，Cai Q ，Jiang M ，Liu Y ，Gu H ，Guo J ，Sun H ，Fang J ，Jin L ... -  《-》