In Vitro Evaluation of the Neuroprotective Effect of Panax notoginseng Saponins by Activating the EGFR/PI3K/AKT Pathway

Natural products for the treatment of neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are among the most common diseases in older adults worldwide. Alzheimer's disease (AD) and Parkinson's disease (PD) are two of the most common neurodegenerative diseases, and are accompanied by cerebral cortical atrophy, neuronal loss, protein accumulation, and excessive accumulation of metal ions. Natural products exhibit outstanding performance in improving cerebral circulatory disorders, promoting cerebral haematoma absorption, repairing damaged nerve tissue, and improving damaged nerve function. In recent years, studies have shown that neuroinflammatory mechanisms and signalling pathways closely related to the occurrence and development of neurological diseases include microglial activation, nuclear factor-κB (NF-κB) pathway, mitogen activated protein kinases (MAPK) pathway, reactive oxygen pathway, nucleotide binding oligomerisation domain-like receptor protein3 (NLRP3) inflammasomes, toll-like receptor4 (TLR4) pathway, nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) pathway, phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, and intestinal flora. Therefore, this study considered the mechanism of neurological diseases as the starting point to review the mechanism of action of natural products in the prevention and treatment of AD and PD in recent years to provide a theoretical basis for clinical prevention and treatment.

AIM

Natural products are a promising source of novel lead structures that have long been used to treat various nervous system diseases.

METHODOLOGY

This review collected literature on neurological diseases and natural products from 2012 to 2022, which were mainly searched through databases such as ScienceDirect, Springer, PubMed, SciFinder, China National Knowledge Infrastructure (CNKI), Wanfang, Google Scholar, and Baidu Academic. The following keywords were searched: neurological disorders, natural products, signalling pathway, mechanism of action.

RESULTS

This review summarises the pathogenesis of degenerative neurological diseases, recent findings on natural products used in neurodegenerative diseases, and the molecular mechanisms underlying these effects.

Neuronal Responses to Ischemia: Scoping Review of Insights from Human-Derived In Vitro Models

Translation of neuroprotective treatment effects from experimental animal models to patients with cerebral ischemia has been challenging. Since pathophysiological processes may vary across species, an experimental model to clarify human-specific neuronal pathomechanisms may help. We conducted a scoping review of the literature on human neuronal in vitro models that have been used to study neuronal responses to ischemia or hypoxia, the parts of the pathophysiological cascade that have been investigated in those models, and evidence on effects of interventions. We included 147 studies on four different human neuronal models. The majority of the studies (132/147) was conducted in SH-SY5Y cells, which is a cancerous cell line derived from a single neuroblastoma patient. Of these, 119/132 used undifferentiated SH-SY5Y cells, that lack many neuronal characteristics. Two studies used healthy human induced pluripotent stem cell derived neuronal networks. Most studies used microscopic measures and established hypoxia induced cell death, oxidative stress, or inflammation. Only one study investigated the effect of hypoxia on neuronal network functionality using micro-electrode arrays. Treatment targets included oxidative stress, inflammation, cell death, and neuronal network stimulation. We discuss (dis)advantages of the various model systems and propose future perspectives for research into human neuronal responses to ischemia or hypoxia.

Determination of Dencichine in Panax notoginseng in the Forest and Field Using High Performance Liquid Chromatography

Dencichine is a nonprotein amino acid, an effective ingredient in Panax notoginseng with hemostatic and anti-inflammatory effects. There are few studies on the effects of regions and cultivation models on the accumulation of dencichine. In the current study, the content of dencichine in P. notoginseng collected from its global cultivation and trading center Yunnan, China, (>640 samples) was determined using an optimized high-performance liquid chromatography method coupled with a diode array detector but without derivatization. The recovery rate of this method was 80-110%, the relative standard deviation was <10%, and the limits of detection and quantification were 0.003% (w/w) and 0.01% (w/w), respectively. The content of dencichine in each part of P. notoginseng was as follows: rootlets (39.59%) > main roots (29.91%) > leaves (16.21%) > stems (14.29%). For leaves, P. notoginseng in the forest (5.52 ± 2.26 mg/g) was significantly higher than that in the field (3.93 ± 1.72 mg/g) but opposite for main roots. The origins and altitudes made different contributions to the accumulation of dencichine in P. notoginseng. This study provides an effective analytical method to determine dencichines in various parts of P. notoginseng from different origins and altitudes and supports quality control and product development of P. notoginseng.

Terpenoid natural products exert neuroprotection via the PI3K/Akt pathway

PI3K/Akt, an essential signaling pathway widely present in cells, has been shown to be relevant to neurological disorders. As an important class of natural products, terpenoids exist in large numbers and have diverse backbones, so they have a great chance to be identified as neuroprotective agents. In this review, we described and summarized recent research for a range of terpenoid natural products associated with the PI3K/Akt pathway by classifying their basic chemical structures of the terpenes, identified by electronic searches on PubMed, Web of Science for research, and Google Scholar websites. Only articles published in English were included. Our discussion here concerned 16 natural terpenoids and their mechanisms of action, the associated diseases, and the methods of experimentation used. We also reviewed the discovery of their chemical structures and their derivatives, and some compounds have been concluded for their structure–activity relationships (SAR). As a result, terpenoids are excellent candidates for research as natural neuroprotective agents, and our content will provide a stepping stone for further research into these natural products. It may be possible for more terpenoids to serve as neuroprotective agents in the future.

Panax notoginseng saponins improves healing of high glucose-induced wound through the GSK-3β/β-catenin pathway

Chronic non-healing wounds are one of the most common complications of diabetes mellitus and results in a huge physical and mental burden for patients. Panax notoginseng saponins (PNS) have a wide range of applications in anti-apoptosis, anti-oxidation, and promoting blood circulation. Our study aimed to explore whether PNS could improve diabetic wound healing. High-glucose (HG, 30 Mm) were used to incubated human umbilical vein endothelial cells (HUVECs) to simulate the hyperglycemia environment in vivo, and 200 μg/ml (optimum harmless concentration screened) PNS was added into HG-incubated HUVECs to investigate the protective effect of PNS on the cells. Compared with control, high glucose treatment significantly suppressed HUVEC proliferation, invasion, migration, angiogenesis, malondialdehyde (MDA) production and nitric oxide (NO) release, promoted cell apoptosis, and deactivated the GSK-3β/β-catenin/VEGF pathway. PNS treatment could largely rescue the effects of HG on cell dysfunction and improve the deactivation of GSK-3β/β-catenin/VEGF pathway. ICG-001, a small molecular β-catenin inhibitor that can selectively antagonize β-catenin mediated transcriptional activity, could eliminate the protective effects of PNS on cell dysfunction and activation of GSK-3β/β-catenin/VEGF pathway. Moreover, Furthermore, a diabetic model (50 mg/kg streptozotocin induced) with back skin wound was established in rats, and the wounds were administrated with petrolatum, gelatin/Bletilla striata gelatin (GT/BSGT), or GT/BSGT plus PNS. We found that PNS signally facilitated wound healing and matrix remodeling in vivo. In conclusion, our study verified that PNS improved wound healing in hyperglycemic rats via promoting endothelial cell proliferation, invasion, migration, angiogenesis, suppressing cell apoptosis and oxidative damage, and activating the GSK-3β/β-catenin pathway.

Determination of the Authenticity and Origin of Panax Notoginseng: A Review

Panax notoginseng, a traditional medicinal and edible plant, is widely used in medicine, health care, cosmetics, and other industries. Affected by the discrepancy between market supply and demand and price, the adulteration of P. notoginseng products with other plant-derived ingredients occurs at times. With the continuous development of technologies such as spectroscopy, chromatography, and DNA barcoding, the detection techniques for rapid and sensitive determination of the authenticity identification and origin of P. notoginseng have become more diversified to meet the needs of different regulatory goals and could effectively control practices that mislead consumers and promote false labeling. This review analyzes and summarizes the existing technologies for determining the authenticity and origin of P. notoginseng from these three aspects: morphological, chemical, and molecular biology methods from the literature since 2001; on this basis, the current problems and future research directions are discussed to provide a reference for the establishment of rapid and accurate methods to verify authenticity and origin to promote the further development and improvement of quality control technology systems for P. notoginseng.

Challenges and Improvements of Novel Therapies for Ischemic Stroke

Stroke is the third most common disease all over the world, which is regarded as a hotspot in medical research because of its high mortality and morbidity. Stroke, especially ischemic stroke, causes severe neural cell death, and no effective therapy is currently available for neuroregeneration after stroke. Although many therapies have been shown to be effective in preclinical studies of ischemic stroke, almost none of them passed clinical trials, and the reasons for most failures have not been well identified. In this review, we focus on several novel methods, such as traditional Chinese medicine, stem cell therapy, and exosomes that have not been used for ischemic stroke till recent decades. We summarize the proposed basic mechanisms underlying these therapies and related clinical results, discussing advantages and current limitations for each therapy emphatically. Based on the limitations such as side effects, narrow therapeutic window, and less accumulation at the injury region, structure transformation and drug combination are subsequently applied, providing a deep understanding to develop effective treatment strategies for ischemic stroke in the near future.

Total Saponins of Panax notoginseng Activate Akt/mTOR Pathway and Exhibit Neuroprotection in vitro and in vivo against Ischemic Damage

OBJECTIVE

To reveal the neuroprotective effect and the underlying mechanisms of a mixture of the main components of Panax notoginseng saponins (TSPN) on cerebral ischemia-reperfusion injury and oxygen-glucose deprivation/reoxygenation (OGD/R) of cultured cortical neurons.

METHODS

The neuroprotective effect of TSPN was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, flow cytometry and live/dead cell assays. The morphology of dendrites was detected by immunofluorescence. Middle cerebral artery occlusion (MCAO) was developed in rats as a model of cerebral ischemia-reperfusion. The neuroprotective effect of TSPN was evaluated by neurological scoring, tail suspension test, 2,3,5-triphenyltetrazolium chloride (TTC) and Nissl stainings. Western blot analysis, immunohistochemistry and immunofluorescence were used to measure the changes in the Akt/mammalian target of rapamycin (mTOR) signaling pathway.

RESULTS

MTT showed that TSPN (50, 25 and 12.5 µ g/mL) protected cortical neurons after OGD/R treatment (P<0.01 or P<0.05). Flow cytometry and live/dead cell assays indicated that 25 µ g/mL TSPN decreased neuronal apoptosis (P<0.05), and immunofluorescence showed that 25 µ g/mL TSPN restored the dendritic morphology of damaged neurons (P<0.05). Moreover, 12.5 µ g/mL TSPN downregulated the expression of Beclin-1, Cleaved-caspase 3 and LC3B-II/LC3B-I, and upregulated the levels of phosphorylated (p)-Akt and p-mTOR (P<0.01 or P<0.05). In the MCAO model, 50 µ g/mL TSPN improved defective neurological behavior and reduced infarct volume (P<0.05). Moreover, the expression of Beclin-1 and LC3B in cerebral ischemic penumbra was downregulated after 50 µ g/mL TSPN treatment, whereas the p-mTOR level was upregulated (P<0.05 or P<0.01).

CONCLUSION

TSPN promoted neuronal survival and protected dendrite integrity after OGD/R and had a potential therapeutic effect by alleviating neurological deficits and reversing neuronal loss. TSPN promoted p-mTOR and inhibited Beclin-1 to alleviate ischemic damage, which may be the mechanism that underlies the neuroprotective activity of TSPN.