Ethanolic extract of fructus Alpinia oxyphylla protects against 6-hydroxydopamine-induced damage of PC12 cells in vitro and dopaminergic neurons in zebrafish.

In an attempt to understand the neuroprotective effect of Fructus Alpinia oxyphylla (AOE) and to elucidate its underlying mechanism of action, the ethanolic extract of AOE was investigated using zebrafish and PC12 cell models. AOE prevented and restored 6-hydroxydopamine (6-OHDA)-induced dopaminergic (DA) neuron degeneration and attenuated a deficit of locomotor activity in a zebrafish (Danio rerio) model of Parkinson's disease (PD). Treatment with AOE increased the viability of 6-OHDA-treated PC12 cells in vitro in a dose-dependent manner by attenuating cellular apoptosis. However, protocatechuic acid (PCA) and chrysin, two known polyphenol components of AOE, could not reproduce the neuroprotective activity of AOE in the PD zebrafish or PC12 cell models. A mechanistic study found that the protective effect of AOE against 6-OHDA-induced neuronal injury involved anti-inflammatory action (down-regulation of gene expression of IL-1ß and TNF-α) and anti-oxidative action (inhibition of NO production and iNOS expression in PC12 cells). Moreover, the PI3K-AKT pathway might be part of the mechanism of neuroprotection of AOE. The results of this research are expected to provide a scientific rationale for the use of AOE in the treatment of PD. However, it is important that the active components that contribute to the neuroprotective action of AOE are identified and characterized.

Protective, antioxidative and antiapoptotic effects of 2-methoxy-6-acetyl-7-methyljuglone from Polygonum cuspidatum in PC12 cells.

Much correlative evidence indicates that the oxidative modification of protein by reactive oxygen species (ROS) is involved in normal aging as well as the pathogenesis of neurodegenerative diseases such as Alzheimer's disease. In this study, we explored the antioxidative and neuroprotective effects of a naphthoquinone, 2-methoxy-6-acetyl-7-methyljuglone (MAM), purified from the dried rhizome of POLYGONUM CUSPIDATUM (Chinese name Hu-Zhang). Pretreatments with MAM (24 h) were investigated for their protective effects against apoptosis induced by the oxidizing agent TERT-butyl hydroperoxide ( T-BHP) in PC12 cells. The results indicated that MAM pretreatments could effectively protect PC12 cells against cytotoxicity induced by T-BHP in a dose-dependent manner. Cell viability was determined by both MTT and LDH assays. Increasing concentrations of MAM enhanced cell viability significantly and completely prevented cell death induced by T-BHP at 2.5 µM. The corresponding extracellular lactate dehydrogenase (LDH) levels were also attenuated significantly by various concentrations of MAM. In addition, it was found that the antioxidative effect of MAM was stronger than those of resveratrol and lipoic acid. The antiapoptotic property of MAM was further investigated with Hoechst 33342 nuclear staining and TUNEL assay. Pretreatments of MAM were able to prevent the T-BHP-induced nucleus fragmentation and accumulation of apoptotic bodies (commonly accepted as markers of apoptosis) inside the cells in a dose-dependent manner. T-BHP induced the phosphorylation of ERK 1/2, JNK and p38 MAPK, which were all impeded by pretreatments with MAM, indicating that MAM may act as a potent antioxidant which significantly interferes with the MAPK apoptotic cascades, probably rescuing cells by inhibiting the death pathways.

Quercetin exerts a neuroprotective effect through inhibition of the iNOS/NO system and pro-inflammation gene expression in PC12 cells and in zebrafish.

Flavonoids have been reported to be potent antioxidants and beneficial in the treatment of oxidative stress-related diseases. Quercetin, a major flavonoid naturally occurring in plants, deserves attention because of its beneficial effects observed in various in vitro and in vivo neural damage models; however, the actions of quercetin are paradoxical. In an effort to confirm the neuroprotective effect of quercetin and to elucidate its mechanism of action, the neuroprotective effects of quercetin in PC12 cells and in zebrafish models were investigated. In this study, the selective dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA), was used to induce neural damage in PC12 cells and zebrafish models. Pretreatment with quercetin offered neuroprotection against 6-OHDA-induced PC12 cell death. Moreover, quercetin could prevent 6-OHDA-induced PC12 cell apoptosis and 6-OHDA-stimulated dopaminergic neuron loss in zebrafish. Interestingly, quercetin was able to protect, but not rescue the dopaminergic neuron damage when zebrafish were treated with quercetin at different maturation stages of the blood brain barrier. A mechanistic study showed that quercetin could inhibit NO over-production and iNOS over-expression in PC12 cells and could down-regulate the over-expression of pro-inflammatory genes (e.g. IL-1ß, TNF-α and COX-2) in zebrafish, suggesting that these genes play a role in the neuroprotective effect of quercetin. The objective of this study was to provide a scientific rationale for the clinical use of quercetin, leading to its development as an effective therapeutic agent for the treatment of Parkinson's disease.