Effects of Senegenin against hypoxia/reoxygenation-induced injury in PC12 cells

Genome assembly of Polygala tenuifolia provides insights into its karyotype evolution and triterpenoid saponin biosynthesis

Polygala tenuifolia is a perennial medicinal plant that has been widely used in traditional Chinese medicine for treating mental diseases. However, the lack of genomic resources limits the insight into its evolutionary and biological characterization. In the present work, we reported the P. tenuifolia genome, the first genome assembly of the Polygalaceae family. We sequenced and assembled this genome by a combination of Illumnina, PacBio HiFi, and Hi-C mapping. The assembly includes 19 pseudochromosomes covering ~92.68% of the assembled genome (~769.62 Mb). There are 36 463 protein-coding genes annotated in this genome. Detailed comparative genome analysis revealed that P. tenuifolia experienced two rounds of whole genome duplication that occurred ~39-44 and ~18-20 million years ago, respectively. Accordingly, we systematically reconstructed ancestral chromosomes of P. tenuifolia and inferred its chromosome evolution trajectories from the common ancestor of core eudicots to the present species. Based on the transcriptomics data, enzyme genes and transcription factors involved in the synthesis of triterpenoid saponin in P. tenuifolia were identified. Further analysis demonstrated that whole-genome duplications and tandem duplications play critical roles in the expansion of P450 and UGT gene families, which contributed to the synthesis of triterpenoid saponins. The genome and transcriptome data will not only provide valuable resources for comparative and functional genomic researches on Polygalaceae, but also shed light on the synthesis of triterpenoid saponin.

A direct interaction between RhoGDIα/Tau alleviates hyperphosphorylation of Tau in Alzheimer's disease and vascular dementia

RhoGDIα is an inhibitor of RhoGDP dissociation that involves in Aβ metabolism and NFTs production in Alzheimer's disease (AD) by regulating of RhoGTP enzyme activity. Our previous research revealed that RhoGDIα, as the target of Polygala saponin (Sen), might alleviate apoptosis of the nerve cells caused by hypoxia/reoxygenation (H/R). To further clarify the role of RhoGDIα in the generation of NFTs, we explored the relationship between RhoGDIα and Tau. We found out that RhoGDIα and Tau can bind with each other and interact by using coimmunoprecipitation (Co-IP) and GST pulldown methods in vitro. This RhoGDIα-Tau partnership was further verified by using immunofluorescence colocalization and fluorescence resonance energy transfer (FRET) approaches in PC12 cells. Using the RNA interference (RNAi) technique, we found that the RhoGDIα may be involved in an upstream signaling pathway for Tau. Subsequently, in Aβ25-35- and H/R-induced PC12 cells, forced expression of RhoGDIα via cDNA plasmid transfection was found to reduce the hyperphosphorylation of Tau, augment the expression of bcl-2 protein, and inhibit the expression of Bax protein (reducing the Bax/bcl-2 ratio) and the activity of caspase-3. In mouse AD and VaD models, forced expression of RhoGDIα via injection of a viral vector (pAAV-EGFP-RhoGDIα) into the lateral ventricle of the brain alleviated the pathological symptoms of AD and VaD. Finally, GST pulldown confirmed that the binding sites on RhoGDIα for Tau were located in the range of the ΔC33 fragment (aa 1-33). These results indicate that RhoGDIα is involved in the phosphorylation of Tau and apoptosis in AD and VaD. Overexpression of RhoGDIα can inhibit the generation of NFTs and delay the progress of these two types of dementia.

Mechanisms of ferroptosis in Alzheimer's disease and therapeutic effects of natural plant products: A review

Neurodegenerative diseases, such as Alzheimer's disease (AD), are characterized by massive loss of specific neurons. It is a progressive disabling, severe and fatal complex disease. Due to its complex pathogenesis and limitations of clinical treatment strategies, it poses a serious medical challenge and medical burden worldwide. The pathogenesis of AD is not clear, and its potential biological mechanisms include aggregation of soluble amyloid to form insoluble amyloid plaques, abnormal phosphorylation of tau protein and formation of intracellular neurofibrillary tangles (NFT), neuroinflammation, ferroptosis, oxidative stress and metal ion disorders. Among them, ferroptosis is a newly discovered programmed cell death induced by iron-dependent lipid peroxidation and reactive oxygen species. Recent studies have shown that ferroptosis is closely related to AD, but the mechanism remains unclear. It may be induced by iron metabolism, amino acid metabolism and lipid metabolism affecting the accumulation of iron ions. Some iron chelating agents (deferoxamine, deferiprone), chloroiodohydroxyquine and its derivatives, antioxidants (vitamin E, lipoic acid, selenium), chloroiodohydroxyquine and its derivatives Fer-1, tet, etc. have been shown in animal studies to be effective in AD and exert neuroprotective effects. This review summarizes the mechanism of ferroptosis in AD and the regulation of natural plant products on ferroptosis in AD, in order to provide reference information for future research on the development of ferroptosis inhibitors.

Senegenin Rescues PC12 Cells with Oxidative Damage Through Inhibition of Ferroptosis

Oxidative stress is one of the pathological mechanisms of Alzheimer's disease (AD), and ferroptosis has been determined to be involved in neurodegenerative diseases such as AD. Senegenin (Sen) prevents oxidative damage in nerve cells via a mechanism that may be highly related to ferroptosis. However, the mechanism of ferroptosis pathway involvement in AD is unclear. In this study, we established a model of PC12 cytotoxic injury induced by Aβ_25-35, and we detected the level of oxidative damage, MMP, and ferroptosis-related protein expression. The results showed that, compared with control group, the level of ROS increased, GPX activities decreased, and MDA levels increased in Aβ_25-35 group. Aβ_25-35 could induce mitochondrial depolarization in PC12 cells and Fer-1 could not reverse this damage. WB revealed that Aβ_25-35 group had increased ACSL4 and PEBP1 proteins, and decreased GPX4 protein. After adding Sen in the model, the level of oxidative damage was reduced, and mitochondrial depolarization was reversed compared with Aβ_25-35 group. WB suggested that the expression of ACSL4 and PEBP1 proteins decreased, and the expression of GPX4 protein increased by Sen treatment. In conclusion, we found that Sen exhibits strong neuroprotective activity against Aβ_25-35 induced oxidative damage and lipid metabolic associated with ferroptosis. Inhibiting nerve cell ferroptosis might facilitate the future development of strategies to AD.

Neuroprotective Effects and Mechanisms of Senegenin, an Effective Compound Originated From the Roots of Polygala Tenuifolia

Senegenin is the main bioactive ingredient isolated from the dried roots of Polygala tenuifolia Willd. In recent years, senegenin has been proved to possess a variety of pharmacological activities, such as anti-oxidation, anti-inflammation, anti-apoptosis, enhancement of cognitive function. Besides, it has a good development prospect for the treatment of neurodegenerative diseases, depression, osteoporosis, cognitive dysfunction, ischemia-reperfusion injury and other diseases. However, there is no systematic literature that fully demonstrates the pharmacological effects of senegenin. In order to meet the needs of new drug research and precise medication, this review summarized the neuroprotective effects, mechanisms and gastrointestinal toxicity of senegenin based on the literatures published from the past 2 decades. In addition, an in-depth analysis of the existing problems in the current research as well as the future research directions have been conducted in order to provide a basis for the clinical application of this important plant extract.

Senegenin Inhibits Aβ1-42-Induced PC12 Cells Apoptosis and Oxidative Stress via Activation of the PI3K/Akt Signaling Pathway

BACKGROUND/AIM

Apoptosis and oxidative stress have been considered as key events in the pathogenesis of Alzheimer's disease (AD). Senegenin (Sen), the major and most effective ingredient of Radix Polygalae, which has anti-apoptotic and anti-oxidative effects. The aim of this study was to investigate the anti-apoptotic and anti-oxidant effects of Sen on Aβ_1-42-induced PC12 cells apoptosis and oxidative stress as well as its possible signaling pathway.

METHODS

Rat pheochromocytoma (PC12) cells were treated by 20 μM Aβ_1-42 and then divided into 5 different treatment groups (Control; Aβ_1-42 20 μM; Aβ_1-42 20 μM + Sen 10 μM; Aβ_1-42 20 μM + Sen 30 μM; Aβ_1-42 20μM + Sen 60 μM). PC12 cells activity was detected by MTT assay. Colony formation assay was performed to assess the clonogenic ability of cells. The cell apoptosis was detected by Annexin-V/PI staining. The pro-apoptotic protein (Bax), anti-apoptotic protein (Bcl-2), anti-oxidative stress factor (HO-1, Nuclear Nrf2, Total Nrf2) and pathway-related protein (Akt, P-Akt, PI3K, P-PI3K) were tested by Western blot. The reactive oxygen species (ROS) level was assessed with a DCFH-DA probe.

RESULTS

The results indicated that Sen dose-dependently increased cell viability and reduced the number of apoptotic cells. The ratio of P-PI3K/PI3K and P-Akt/Akt increased in a dose-dependent manner under the treatment of Sen, suggesting that Sen might activate the PI3K/Akt signaling pathway. Moreover, Sen upregulates the ratio of Bcl-2/Bax. Further study revealed that Sen can play an antioxidant role in enhancing HO-1, promoting Nrf2 nuclear translocation and reducing ROS accumulation to reduce oxidative stress.

CONCLUSION

Sen is effective in inhibiting apoptosis and oxidative stress in Aβ_1-42-induced PC12 cells, which likely contribute to the development of novel therapies for AD.

Polygala tenuifolia: a source for anti-Alzheimer's disease drugs

Context: Alzheimer's disease (AD) is a chronic neurodegenerative disease that originates from central nervous system lesions or recessions. Current estimates suggest that this disease affects over 35 million people worldwide. However, lacking effective drugs is the biggest handicap in treating AD. In traditional Chinese medicine (TCM), Polygala tenuifolia Willd. (Polygalaceae) is generally used to treat insomnia, memory dysfunction and neurasthenia.Objective: This review article explores the role of P. tenuifolia and its active components in anti-Alzheimer's disease.Methods: Literature for the last ten years was obtained through a search on PubMed, SciFinder, CNKI, Google Scholar, Web of Science, Science Direct and China Knowledge Resource Integrated with the following keywords: Polygala tenuifolia, polygalasaponin XXXII (PGS 32), tenuifolin, polygalacic acid, senegenin, tenuigenin, Alzheimer's disease.Results: Polygala tenuifolia and its active components have multiplex neuroprotective potential associated with AD, such as anti-Aβ aggregation, anti-Tau protein, anti-inflammation, antioxidant, anti-neuronal apoptosis, enhancing central cholinergic system and promote neuronal proliferation.Conclusions: Polygala tenuifolia and its active components exhibit multiple neuroprotective effects. Hence, P. tenuifolia is a potential drug against Alzheimer's disease, especially in terms of prevention.