Traditional Chinese medicine compounds regulate autophagy for treating neurodegenerative disease: A mechanism review

Repurposing small-molecule drugs for modulating toxic protein aggregates in neurodegenerative diseases

Neurodegenerative diseases (NDs) are often age-related disorders that can cause dementia in people, usually over 65 years old, are still lacking effective therapies. Some NDs have recently been linked to toxic protein aggregates, for example Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington disease; therefore, mulating toxic protein aggregates would be a promising therapeutic strategy. Moreover, drug repurposing, in other words exploiting drugs that are already in use for another indication, has been attracting mounting attention for potential therapeutic purposes in NDs. Thus, in this review, we focus on summarizing a series of repurposed small-molecule drugs for eliminating or inhibiting toxic protein aggregates and further discuss their intricate molecular mechanisms to improve the current ND treatment. Taken together, these findings will shed new light on exploiting more repurposed small-molecule drugs targeting different types of toxic proteins to fight NDs in the future. Teaser: Drug repurposing has been gaining attention to yield therapeutic potential in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington disease.

Klotho an Autophagy Stimulator as a Potential Therapeutic Target for Alzheimer’s Disease: A Review

Alzheimer’s disease (AD) is an age-associated neurodegenerative disease; it is the most common cause of senile dementia. Klotho, a single-pass transmembrane protein primarily generated in the brain and kidney, is active in a variety of metabolic pathways involved in controlling neurodegeneration and ageing. Recently, many studies have found that the upregulation of Klotho can improve pathological cognitive deficits in an AD mice model and have demonstrated that Klotho plays a role in the induction of autophagy, a major contributing factor for AD. Despite the close association between Klotho and neurodegenerative diseases, such as AD, the underlying mechanism by which Klotho contributes to AD remains poorly understood. In this paper, we will introduce the expression, location and structure of Klotho and its biological functions. Specifically, this review is devoted to the correlation of Klotho protein and the AD phenotype, such as the effect of Klotho in upregulating the amyloid-beta clearance and in inducing autophagy for the clearance of toxic proteins, by regulating the autophagy lysosomal pathway (ALP). In summary, the results of multiple studies point out that targeting Klotho would be a potential therapeutic strategy in AD treatment.

Neuroprotective effects of naturally sourced bioactive polysaccharides: an update

Polysaccharides are macromolecular complexes that have various biological activities. In vivo and in vitro studies have shown that polysaccharides play neuroprotective roles through multiple mechanisms; consequently, they have potential in the prevention and treatment of neurodegenerative diseases. This paper summarizes related research published during 2015-2020 and reviews advances in the understanding of the neuroprotective effects of bioactive polysaccharides. This review focuses on 15 bioactive polysaccharides from plants and fungi that have neuroprotective properties against oxidative stress, apoptosis, neuroinflammation, and excitatory amino acid toxicity mainly through the regulation of nuclear factor kappa-B, phosphatidylinositol-3-kinase/protein kinase B, mitogen-activated protein kinase, nuclear factor-E2-related factor 2/ hemeoxygenase-1, c-jun N-terminal kinase, protein kinase B-mammalian target of rapamycin, and reactive oxygen species-nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 signaling pathways. Natural bioactive polysaccharides have potential in the prevention and treatment of neurodegenerative diseases because of their advantageous characteristics, including multi-targeting, low toxicity, and synergistic effects. However, most of the recent related research has focused on cell and animal models. Future randomized clinical trials involving large sample sizes are needed to validate the therapeutic benefits of these neuroprotective polysaccharides in patients having neurodegenerative diseases.

Panax ginseng and aging related disorders: A systematic review

The aging process predisposes numerous homeostatic disorders, metabolic disorders, cardiovascular diseases, neurodegenerative diseases, and cancer. Changes in diet and lifestyle and therapeutic adjuvants are essential to minimize the effects of comorbidities associated with aging. Natural products such as Panax ginseng have been used to treat and prevent diseases related to aging. This review aims to investigate the effects of Panax ginseng in various conditions associated with aging, such as inflammation, oxidative stress, mitochondrial dysfunction, apoptosis, neurodegenerative and metabolic disorders, cardiovascular diseases, and cancer. The ginsenosides, chemical constituents found in Panax ginseng, can inhibit the effects of inflammatory cytokines, inhibit signaling pathways that induce inflammation, and inhibit cells that participate in inflammatory processes. Besides, ginsenosides are involved in neuroprotective effects on the central nervous system due to anti-apoptotic, antioxidant, and anti-inflammatory effects. The use of ginseng extract showed actions on lipid homeostasis, positively regulating high-density lipoprotein, down-regulating low-density lipoprotein and triglyceride levels, and producing beneficial effects on vascular endothelial function. The use of this plant in cancer resulted in improved quality of life and mood. It decreased symptoms of fatigue, nausea, vomiting, and dyspnea, reducing anxiety. Panax ginseng has been shown to exert potent therapeutic benefits that can act as a complementary treatment in managing patients with chronic diseases related to aging.

Paeoniflorin is a promising natural monomer for neurodegenerative diseases via modulation of Ca2+ and ROS homeostasis

Neurodegenerative diseases (NDDs) are a range of neurological disorders featured by neuronal degeneration and apoptosis. Cellular Calcium (Ca²⁺) and reactive oxygen species (ROS) dyshomeostasis are the earliest and important events in the development of NDDs and may yield promising therapeutic targets for NDDs. Paeoniflorin, a water-soluble monoterpene glucoside, is the major bioactive monomer extracted from the root of Paeonia lactiflora pall. Increasing evidence has suggested that this natural compound might be used to treat various NDDs, and its potential molecular mechanisms are related to the modulation of Ca²⁺/ROS homeostasis in cells. In addition, paeoniflorin accounts for more than 40% of the total glucosides of herbaceous peonies with abundant herbaceous sources. Furthermore, it has also been validated as a safe extraction in clinical pharmacological research with a wide therapeutic window. Hence, it is rational to anticipate paeoniflorin being a promising candidate for the treatment of NDDs via regulating Ca²⁺/ROS dyshomeostasis.

Identification of autophagic target RAB13 with small-molecule inhibitor in low-grade glioma via integrated multi-omics approaches coupled with virtual screening of traditional Chinese medicine databases

Objectives

Autophagy, a highly conserved lysosomal degradation process in eukaryotic cells, has been widely reported closely related to the progression of many types of human cancers, including LGG; however, the intricate relationship between autophagy and LGG remains to be clarified.

Materials and methods

Multi‐omics methods were used to integrate omics data to determine potential autophagy regulators in LGG. The expression of ZFP36L2 and RAB13 in SW1088 cells was experimentally manipulated using cDNAs and small interfering RNAs (siRNA). RT‐qPCR detects RNAi gene knockout and cDNA overexpression efficiency. The expression levels of proteins in SW1088 cells were evaluated using Western blot analysis and immunofluorescence analysis. Homology modelling and molecular docking were used to identify compounds from Multi‐Traditional Chinese Medicine (TCM) Databases. The apoptosis ratios were determined by flow cytometry analysis of Annexin‐V/PI double staining. We detect the number of autophagosomes by GFP‐MRFP‐LC3 plasmid transfection to verify the process of autophagy flow.

Results

We integrated various omics data from LGG, including EXP, MET and CNA data, with the SNF method and the LASSO algorithm, and identified ZFP36L2 and RAB13 as positive regulators of autophagy, which are closely related to the core autophagy regulators. Both transcription level and protein expression level of the four autophagy regulators, including ULK1, FIP200, ATG16L1 and ATG2B, and LC3 puncta were increased by ZFP36L2 and RAB13 overexpression. In addition, RAB13 participates in autophagy through ATG2B, FIP200, ULK1, ATG16L1 and Beclin‐1. Finally, we screened multi‐TCM databases and identified gallic acid as a novel potential RAB13 inhibitor, which was confirmed to negatively regulate autophagy as well as to induce cell death in SW1088 cells.

Conclusion

Our study identified the key autophagic regulators ZFP36L2 and Rab13 in LGG progression, and demonstrated that gallic acid is a small molecular inhibitor of RAB13, which negatively regulates autophagy and provides a possible small molecular medicine for the subsequent treatment of LGG.

Qingyangshen mitigates amyloid-β and Tau aggregate defects involving PPARα-TFEB activation in transgenic mice of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common neurodegenerative disease. Deposition of amyloid β plaques (Aβ) and neurofibrillary tangles (NFTs) is the key pathological hallmark of AD. Accumulating evidence suggest that impairment of autophagy-lysosomal pathway (ALP) plays key roles in AD pathology.

PURPOSE

The present study aims to assess the neuroprotective effects of Qingyangshen (QYS), a Chinese herbal medicine, in AD cellular and animal models and to determine its underlying mechanisms involving ALP regulation.

METHODS

QYS extract was prepared and its chemical components were characterized by LC/MS. Then the pharmacokinetics and acute toxicity of QYS extract were evaluated. The neuroprotective effects of QYS extract were determined in 3XTg AD mice, by using a series of behavioral tests and biochemical assays, and the mechanisms were examined in vitro.

RESULTS

Oral administration of QYS extract improved learning and spatial memory, reduced carboxy-terminal fragments (CTFs), amyloid precursor protein (APP), Aβ and Tau aggregates, and inhibited microgliosis and astrocytosis in the brains of 3XTg mice. Mechanistically, QYS extract increased the expression of PPARα and TFEB, and promoted ALP both in vivo and in vitro.

CONCLUSION

QYS attenuates AD pathology, and improves cognitive function in 3XTg mice, which may be mediated by activation of PPARα-TFEB pathway and the subsequent ALP enhancement. Therefore, QYS may be a promising herbal material for further anti-AD drug discovery.

Xanthohumol ameliorates memory impairment and reduces the deposition of β-amyloid in APP/PS1 mice via regulating the mTOR/LC3II and Bax/Bcl-2 signalling pathways

OBJECTIVES

Xanthohumol (XAN) is a unique component of Humulus lupulus L. and is known for its diverse biological activities. In this study, we investigated whether Xanthohumol could ameliorate memory impairment of APP/PS1 mice, and explored its potential mechanism of action.

METHODS

APP/PS1 mice were used for in vivo test and were treated with N-acetylcysteine and Xanthohumol for 2 months. Learning and memory levels were evaluated by the Morris water maze. Inflammatory and oxidative markers in serum and hippocampus and the deposition of Aβ in the hippocampus were determined. Moreover, the expression of autophagy and apoptosis proteins was also evaluated by western blot.

KEY FINDINGS

Xanthohumol significantly reduced the latency and increased the residence time of mice in the target quadrant. Additionally, Xanthohumol increased superoxide dismutase level and reduced Interleukin-6 and Interleukin-1β levels both in serum and hippocampus. Xanthohumol also significantly reduced Aβ deposition in the hippocampus and activated autophagy and anti-apoptotic signals.

CONCLUSIONS

Xanthohumol effectively ameliorates memory impairment of APP/PS1 mice by activating mTOR/LC3 and Bax/Bcl-2 signalling pathways, which provides new insight into the neuroprotective effects of Xanthohumol.

Resveratrol in Rodent Models of Parkinson's Disease: A Systematic Review of Experimental Studies

Parkinson’s disease (PD) is a common neurodegenerative disease featured by progressive degeneration of nigrostriatal dopaminergic neurons (DA) accompanied with motor function impairment. Accumulating evidence has demonstrated that natural compounds from herbs have potent anti-PD efficacy in PD models. Among those compounds, resveratrol, a polyphenol found in many common plants and fruits, is more effective against PD. Resveratrol has displayed a potent neuroprotective efficacy in several PD animal models. However, there is still no systematic analysis of the quality of methodological design of these studies, nor of their results. In this review, we retrieved and analyzed 18 studies describing the therapeutic effect of resveratrol on PD animal models. There are 5 main kinds of PD rodent models involved in the 18 articles, including chemical-induced (MPTP, rotenone, 6-OHDA, paraquat, and maneb) and transgenic PD models. The neuroprotective mechanisms of resveratrol were mainly concentrated on the antioxidation, anti-inflammation, ameliorating mitochondrial dysfunction, and motor function. We discussed the disadvantages of different PD animal models, and we used meta-analysis approach to evaluate the results of the selected studies and used SYRCLE’s risk of bias tool to evaluate the methodological quality. Our analytical approach minimized the bias of different studies. We have also summarized the pharmacological mechanisms of resveratrol on PD models as reported by the researchers. The results of this study support the notion that resveratrol has significant neuroprotective effects on different PD models quantified using qualitative and quantitative methods. The collective information in our review can guide researchers to further plan their future experiments without any hassle regarding preclinical and clinical studies. In addition, this collective assessment of animal studies can provide a qualitative analysis of different PD animal models, either to guide further testing of these models or to avoid unnecessary duplication in their future research.