7-(4-Hydroxy-3-methoxyphenyl)-1-phenyl-4E-hepten-3-one alleviates Aß1-42 induced cytotoxicity through PI3K-mTOR pathways.

Alzheimer's disease (AD) is the most common neurodegenerative disease in the elderly. Increasing evidence has shown that ß-amyloid protein (Aß) production is the key pathological cause of AD. 7-(4-Hydroxy-3-methoxyphenyl)-1-phenyl-4E-hepten-3-one (AO-2), a natural diarylheptanoid, is previously found to have activities in neuronal differentiation and neurite outgrowth, and its analogue shows protective effects against Aß. In this study, we further investigated the function of AO-2 toward Aß-induced injuries in PC12 cells and hippocampal neurons. Pretreatment of PC12 cells with AO-2 restored cell viability in a concentration-dependent manner against Aß-induced neurotoxicity. Moreover, the Aß stimulated apoptosis and caspase-3 activation were markedly inhibited by AO-2. We found that AO-2 prevented the downregulation of PI3K-Akt-mTOR signaling after Aß damage, and blockade of either PI3K or mTOR activity led to the failure of AO-2 on caspase-3 inhibition. We further showed that AO-2 was protective against two devastating effects of Aß, increased reactive oxygen species (ROS) production and dendrite injury, and this protection was also dependent on PI3K and mTOR activities. Taken together, this study showed that AO-2 acts against Aß-induced damages in PC12 cells and hippocampal neurons through PI3K-mTOR pathways, thus providing a new neuroprotective compound which may shed light on drug development of AD.

7-(4-Hydroxyphenyl)-1-phenyl-4E-hepten-3-one, a Diarylheptanoid from Alpinia officinarum, Protects Neurons against Amyloid-ß Induced Toxicity.

Amyloid-ß (Aß) is one of the major causative agents of Alzheimer's disease (AD), the most common neurodegenerative disorder characterized by progressive cognitive impairment. While effective drugs for AD are currently limited, identifying anti-Aß compounds from natural products has been shown as a promising strategy which may lead to breakthroughs for new drug candidate discovery. We have previously reported that 7-(4-hydroxyphenyl)-1-phenyl-4E-hepten-3-one (AO-1), a diarylheptanoid extracted from the plant Alpinia officinarum, has strong effects on neuronal differentiation and neurite outgrowth in vitro and in vivo. The present study further uncovers that AO-1 exerts neuroprotective effects against the neurotoxicity caused by Aß. Under the damage of Aß oligomers, the major pathological forms of Aß, dendrites of neurons become atrophic and simplified, but such impairments were substantially alleviated by AO-1 treatment. Moreover, AO-1 reduced apoptotic levels and oxidative stress triggered by Aß. Further analysis showed that the anti-caspase and dendrite protective effects of AO-1 were dependent on activation of phosphatidylinositol 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathways. These findings collectively identify AO-1 as a beneficial compound to ameliorate the deleterious effects of Aß on dendrite integrity and cell survival, and may provide new insights on drug discovery of AD.

A natural product, resveratrol, protects against high-glucose-induced developmental damage in chicken embryo.

Resveratrol, a famous plant-derived polyphenolic phytoalexin, has been considered to play physiological roles such as antioxidative, neuroprotective, and anticancer effects in adults. However, its antioxidative activity and neuroprotective effect were seldom discussed in the embryonic system. In this study, the effect of resveratrol on chicken embryo development under high glucose and its underlying mechanism of resveratrol were investigated. High glucose administrated to chicken embryo at embryonic Day 1 induced stillbirth, growth retardation, and impaired blood vessel development on yolk sac. However, resveratrol supplementation before glucose exposure showed significant effect on decreasing the death rate, developmental damage, and vessel injury. In addition, oxidative stress was caused by high-glucose exposure, and resveratrol could rescue this high-glucose-induced oxidative stress. Moreover, the neural developmental marker paired box 3 was significantly decreased by high glucose and recovered by resveratrol. Cell cycle-regulated gene expression was also intervened by resveratrol. This study had found an association between resveratrol and hyperglycemia-induced embryonic damage, which suggested a potential protective effect of resveratrol on gestational diabetes.

A Bivalent Securinine Compound SN3-L6 Induces Neuronal Differentiation via Translational Upregulation of Neurogenic Transcription Factors.

Developing therapeutic approaches that target neuronal differentiation will be greatly beneficial for the regeneration of neurons and synaptic networks in neurological diseases. Protein synthesis (mRNA translation) has recently been shown to regulate neurogenesis of neural stem/progenitor cells (NSPCs). However, it has remained unknown whether engineering translational machinery is a valid approach for manipulating neuronal differentiation. The present study identifies that a bivalent securinine compound SN3-L6, previously designed and synthesized by our group, induces potent neuronal differentiation through a novel translation-dependent mechanism. An isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic analysis in Neuro-2a progenitor cells revealed that SN3-L6 upregulated a group of neurogenic transcription regulators, and also upregulated proteins involved in RNA processing, translation, and protein metabolism. Notably, puromycylation and metabolic labeling of newly synthesized proteins demonstrated that SN3-L6 induced rapid and robust activation of general mRNA translation. Importantly, mRNAs of the proneural transcription factors Foxp1, Foxp4, Hsf1, and Erf were among the targets that were translationally upregulated by SN3-L6. Either inhibition of translation or knockdown of these transcription factors blocked SN3-L6 activity. We finally confirmed that protein synthesis of a same set of transcription factors was upregulated in primary cortical NPCs. These findings together identify a new compound for translational activation and neuronal differentiation, and provide compelling evidence that reprogramming transcriptional regulation network at translational levels is a promising strategy for engineering NSPCs.

Arhgef1 is expressed in cortical neural progenitor cells and regulates neurite outgrowth of newly differentiated neurons.

Neurite outgrowth is crucial for the maturation of neurons and the establishment of anatomical connections during development of the nervous system. We report here that Arhgef1, a RhoA guanine nucleotide exchange factor previously found expressed in the early stages of neuronal development to regulate neurite outgrowth, is also highly expressed in cortical neural progenitor cells (NPCs). To better dissect its role in NPCs, we knocked down Arhgef1 expression in these cells and induced differentiated of them into neurons. Notably, silencing of Arhgef1 markedly enhanced neurite outgrowth in neurons derived from NPCs. Furthermore, we showed that Arhgef1 silencing inhibited the activity of RhoA, and pharmacological blockade of RhoA activity promoted neurite outgrowth in NPC-derived neurons. These findings reveal that Arhgef1 controls the process of neurite formation in newborn cortical neurons derived from NPCs.

Arhgef1 negatively regulates neurite outgrowth through activation of RhoA signaling pathways.

Neurite outgrowth is essential for the establishment of functional neuronal connections during brain development. This study identifies that Arhgef1 is predominantly expressed in early neuronal developmental stages and negatively regulates neurite outgrowth. Knockdown of Arhgef1 in either Neuro-2a cells or primary cortical neurons leads to excess growth of neurites, whereas overexpression of Arhgef1 prominently restricts neurite formation. Arhgef1 strongly activates RhoA activity while concomitantly inhibits Rac1 and Cdc42 activities. Pharmacological blockade of RhoA activity restores normal neurite outgrowth in Arhgef1-overexpressed neurons. Importantly, Arhgef1 promotes F-actin polymerization in neurons, probably through inhibiting the activity of the actin-depolymerizing factor cofilin. Collectively, these findings reveal that Arhgef1 functions as a negative regulator of neurite outgrowth through regulating RhoA-cofilin pathway and actin dynamics.