Chlorogenic acid delays the progression of Parkinson's disease via autophagy induction in Caenorhabditis elegans

OBJECTIVES

Parkinson's disease (PD) is the second most common neurodegenerative disease. Chlorogenic acid (CGA) is a polyphenolic substance derived from various medicinal plants. Although CGA is reported to have potential anti-PD effect, the beneficial effect and the underlying mechanism remain unclear. In this study, we aimed to further investigate the protective effect and clarify the mechanism of action of CGA in Caenorhabditis elegans (C. elegans) models of PD.

METHODS

Measurements of a-synuclein aggregation, movement disorders, and lipid, ROS and malondialdehyde (MDA) contents were observed in NL5901 nematodes. Determinations of dopamine (DA) neuron degeneration, food perception, and ROS content were performed in 6-OHDA-exposed BZ555 nematodes. The autophagy activation of CGA was monitored using DA2123 and BC12921 nematodes. Meanwhile, RNAi technology was employed to knockdown the autophagy-related genes and investigate whether the anti-PD effect of CGA was associated with autophagy induction in C. elegans.

RESULTS

CGA significantly reduced α-synuclein aggregation, improved motor disorders, restored lipid content, and decreased ROS and MDA contents in NL5901 nematodes. Meanwhile, CGA inhibited DA neuron-degeneration and improved food-sensing behavior in 6-OHDA-exposed BZ555 nematodes. In addition, CGA increased the number of GFP::LGG-1 foci in DA2123 nematodes and degraded p62 protein in BC12921 nematodes. Meanwhile, CGA up-regulated the expression of autophagy-related genes in NL5901 nematodes. Moreover, the anti-PD effect of CGA was closely related to autophagy induction via increasing the expression of autophagy-related genes, including unc-51, bec-1, vps-34, and lgg-1.

CONCLUSIONS

The present study indicates that CGA exerts neuroprotective effect in C. elegans via autophagy induction.

Targeting microglial autophagic degradation of the NLRP3 inflammasome for identification of thonningianin A in Alzheimer’s disease

Background

NLRP3 inflammasome-mediated neuroinflammation plays a critical role in the pathogenesis and development of Alzheimer’s disease (AD). Microglial autophagic degradation not only decreases the deposits of extracellular Aβ fibrils but also inhibits the activation of NRLP3 inflammasome. Here, we aimed to identify the potent autophagy enhancers from Penthorum chinense Pursh (PCP) that alleviate the pathology of AD via inhibiting the NLRP3 inflammasome.

Methods

At first, autophagic activity-guided isolation was performed to identify the autophagy enhancers in PCP. Secondly, the autophagy effect was monitored by detecting LC3 protein expression using Western blotting and the average number of GFP-LC3 puncta per microglial cell using confocal microscopy. Then, the activation of NLRP3 inflammasome was measured by detecting the protein expression and transfected fluorescence intensity of NLRP3, ASC, and caspase-1, as well as the secretion of proinflammatory cytokines. Finally, the behavioral performance was evaluated by measuring the paralysis in C. elegans, and the cognitive function was tested by Morris water maze (MWM) in APP/PS1 mice.

Results

Four ellagitannin flavonoids, including pinocembrin-7-O-[4″,6″-hexahydroxydiphenoyl]-glucoside (PHG), pinocembrin-7-O-[3″-O-galloyl-4″,6″-hexahydroxydiphenoyl]-glucoside (PGHG), thonningianin A (TA), and thonningianin B (TB), were identified to be autophagy enhancers in PCP. Among these, TA exhibited the strongest autophagy induction effect, and the mechanistic study demonstrated that TA activated autophagy via the AMPK/ULK1 and Raf/MEK/ERK signaling pathways. In addition, TA effectively promoted the autophagic degradation of NLRP3 inflammasome in Aβ(1–42)-induced microglial cells and ameliorated neuronal damage via autophagy induction. In vivo, TA activated autophagy and improved behavioral symptoms in C. elegans. Furthermore, TA might penetrate the blood-brain barrier and could improve cognitive function and ameliorate the Aβ pathology and the NLRP3 inflammasome-mediated neuroinflammation via the AMPK/ULK1 and Raf/MEK/ERK signaling pathways in APP/PS1 mice.

Conclusion

We identified TA as a potent microglial autophagy enhancer in PCP that promotes the autophagic degradation of the NLRP3 inflammasome to alleviate the pathology of AD via the AMPK/ULK1 and Raf/MEK/ERK signaling pathways, which provides novel insights for TA in the treatment of AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-022-00209-7.

Lychee seed polyphenol protects the blood-brain barrier through inhibiting Aβ(25-35)-induced NLRP3 inflammasome activation via the AMPK/mTOR/ULK1-mediated autophagy in bEnd.3 cells and APP/PS1 mice

Blood-brain barrier (BBB) dysfunction has been implicated in Alzheimer's disease (AD) and is closely linked to the release of proinflammatory cytokines in brain capillary endothelial cells. We have previously reported that lychee seed polyphenols (LSP) exerted anti-neuroinflammatory effect. In this study, we aimed to explore the protective effect of LSP on BBB integrity. The monolayer permeability of bEnd.3 cells, and the mRNA level and protein expression of tight junction proteins (TJs), including Claudin 5, Occludin, and ZO-1, were examined. In addition, the inhibition of Aβ(25-35)-induced NLRP3 inflammasome activation, and the autophagy induced by LSP were investigated by detecting the expression of NLRP3, caspase-1, ASC, LC3, AMPK, mTOR, and ULK1. Furthermore, the cognitive function and the expression of TJs, NLRP3, caspase-1, IL-1β, and p62 were determined in APP/PS1 mice. The results showed that LSP significantly decreased the monolayer permeability and inhibited the NLRP3 inflammasome in Aβ(25-35)-induced bEnd3 cells. In addition, LSP induced autophagy via the AMPK/mTOR/ULK1 pathway in bEnd.3 cells, and improved the spatial learning and memory function, increased the TJs expression, and inhibited the expression of NLRP3, caspase-1, IL-1β, and p62 in APP/PS1 mice. Therefore, LSP protects BBB integrity in AD through inhibiting Aβ(25-35)-induced NLRP3 inflammasome activation via the AMPK/mTOR/ULK1-mediated autophagy.

Polyphenols isolated from lychee seed inhibit Alzheimer's disease-associated Tau through improving insulin resistance via the IRS-1/PI3K/Akt/GSK-3β pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Lychee seed, the seed of Litchi chinensis Sonn. is one of the commonly used in traditional Chinese medicine (TCM). It possesses many pharmacological effects such as blood glucose and lipid-lowering effects, liver protection, and antioxidation. Our preliminary studies have proven that an active fraction derived from lychee seed (LSF) can significantly decrease the blood glucose level, inhibit amyloid-β (Aβ) fibril formation and Tau hyperphosphorylation, and improve the cognitive function and behavior of Alzheimer's disease (AD) model rats.

AIM OF THE STUDY

The aim of this study was to identify the main active components in LSF that can inhibit the hyperphosphorylation of Tau through improving insulin resistance (IR) in dexamethasone (DXM)-induced HepG2 and HT22 cells.

MATERIALS AND METHODS

The isolation was guided by the bioactivity evaluation of the improvement effect of IR in HepG2 and HT22 cells. The mRNA and protein expressions of IRS-1, PI3K, Akt, GSK-3β, and Tau were measured by RT-PCR, Western blotting, and immunofluorescence methods, respectively.

RESULTS

After extraction, isolation, and elucidation using chromatography and spectrum technologies, three polyphenols including catechin, procyanidin A1 and procyanidin A2 were identified from fractions 3, 5, and 9 derived from LSF. These polyphenols inhibit hyperphosphorylated Tau via the up-regulation of IRS-1/PI3K/Akt and down-regulation of GSK-3β. Molecular docking result further demonstrate that these polyphenols exhibit good binding property with insulin receptor.

CONCLUSIONS

catechin, procyanidin A1, and procyanidin A2 are the main components in LSF that inhibit Tau hyperphosphorylation through improving IR via the IRS-1/PI3K/Akt/GSK-3β pathway. Therefore, the findings in the current study provide novel insight into the anti-AD mechanism of the components in LSF derived from lychee seed, which is valuable for the further development of a novel drug or nutrient supplement for the prevention and treatment of AD.

Novel steroidal saponin isolated from Trillium tschonoskii maxim. exhibits anti-oxidative effect via autophagy induction in cellular and Caenorhabditis elegans models

BACKGROUND

Emerging evidences indicate the important roles of autophagy in anti-oxidative stress, which is closely associated with cancer, aging and neurodegeneration.

OBJECTIVE

In the current study, we aimed to identify autophagy inducers with potent anti-oxidative effect from traditional Chinese medicines (TCMs) in PC-12 cells and C. elegans.

METHODS

The autophagy inducers were extensively screened in our herbal extracts library by using the stable RFP-GFP-LC3 U87 cells. The components with autophagic induction effect in Trillium tschonoskii Maxim. (TTM) was isolated and identified by using the autophagic activity-guided column chromatography and Pre-HPLC technologies, and MS and NMR spectroscopic analysis, respectively. The anti-oxidative effect of the isolated autophagy inducers was evaluated in H₂O₂-induced PC-12 cells and C. elegans models by measuring the viability of PC-12 cells and C. elegans, with quantitation on the ROS level in vitro and in vivo using H₂DCFDA probe.

RESULTS

The total ethanol extract of TTM was found to significantly increase the formation of GFP-LC3 puncta in stable RFP-GFP-LC3 U87 cells. One novel steroidal saponin 1-O-[2,3,4-tri-O-acetyl-α-L-rhamnopyranosyl-(1→2)-4-O-acetyl-α-L-arabinopyranosyl]-21-Deoxytrillenogenin, (Deoxytrillenoside CA, DTCA) and one known steroidal saponin 1-O-[2,3,4-tri-O-acetyl-α-L-rhamnopyranosyl-(1→2)-4-O-acetyl-α-L-arabinopyranosyl]-21-O-acetyl-epitrillenogenin (Epitrillenoside CA, ETCA) were isolated, identified and found to have novel autophagic effect. Both DTCA and ETCA could activate autophagy in PC-12 cells via the AMPK/mTOR/p70S6K signaling pathway in an Atg7-dependent. In addition, DTCA and ETCA could increase the cell viability and decrease the intracellular ROS level in H₂O₂-treated PC-12 cells and C. elegans, and the further study demonstrated that the induced autophagy contributes to their anti-oxidative effect.

CONCLUSION

Our current findings not only provide information on the discovery of novel autophagy activators from TTM, but also confirmed the anti-oxidative effect of the components from TTM both in vitro and in vivo.

Polyphyllin VI, a saponin from Trillium tschonoskii Maxim. induces apoptotic and autophagic cell death via the ROS triggered mTOR signaling pathway in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancers. Our previous studies have proven that Trillium tschonoskii Maxim. (TTM), a traditional Chinese medicine, possesses potent anti-tumor effect. However, the detailed components and molecular mechanism of TTM in anti-NSCLC are still unknown. In the present experiment, polyphyllin VI (PPVI) was successfully isolated from TTM with guidance of the anti-proliferative effect in A549 cells, and the cell death of PPVI treated A549 and H1299 cells was closely linked with the increased intracellular ROS levels. In addition, PPVI induced apoptosis by promoting the protein expression of Bax/Bcl2, caspase-3 and caspase-9, and activated autophagy by improving LC3 II conversion and GFP-LC3 puncta formation in A549 and H1299 cells. The mechanism study found that the activity of mTOR which regulates cell growth, proliferation and autophagy was significantly suppressed by PPVI. Accordingly, the PI3K/AKT and MEK/ERK pathways positively regulating mTOR were inhibited, and AMPK negatively regulating mTOR was activated. In addition, the downstream of mTOR, ULK1 at Ser 757 which downregulates autophagy was inhibited by PPVI. The apoptotic cell death induced by PPVI was confirmed, and it was significantly suppressed by the overexpression of AKT, ERK and mTOR, and the induced autophagic cell death which was depended on the Atg7 was decreased by the inhibitors, such as LY294002 (LY), Bafilomycin A1 (Baf), Compound C (CC) and SBI-0206965 (SBI). Furthermore, the mTOR signaling pathway was regulated by the increased ROS as the initial signal in A549 and H1299 cells. Finally, the anti-tumor growth activity of PPVI in vivo was validated in A549 bearing athymic nude mice. Taken together, our data have firstly demonstrated that PPVI is the main component in TTM that exerts the anti-proliferative effect by inducing apoptotic and autophagic cell death in NSCLC via the ROS-triggered mTOR signaling pathway, and PPVI may be a promising candidate for the treatment of NSCLC in future.

Direct sequencing of mutations in the copper-transporting P-type adenosine triphosphate (ATP7B) gene for diagnosis and pathogenesis of Wilson's disease

Copper-transporting P-type adenosine triphosphatase (ATP7B) has been identified as the pathogenic gene in hepatolenticular degeneration, or Wilson's disease (WD). The aim of this study was to explore the correlation between genetic mutations and the clinical profile of WD, and to discuss the value of mutation examination in its diagnosis for providing a scientific basis for the development of a method to examine genetic mutations. Sixty-eight Chinese Han patients with WD and 20 controls were included in this study. The ATP7B gene in DNA extracted from patient blood samples was amplified by PCR and sequenced. These sequences were compared against corresponding gene sequences obtained from healthy controls to statistically analyze the genetic mutations. Five of the nineteen mutations in ATP7B were newly detected mutations; moreover, 8 of these mutations were polymorphic (2 were newly identified). The Arg778Leu and Pro992Leu mutations in exons 8 and 13 were detected at the highest mutation frequencies of 25.74 and 16.91%, respectively. The frequencies of all other mutations were below 5%. However, the clinical manifestations of WD did not differ significantly in patients with the Arg778Leu and Pro992Leu mutations. Therefore, these mutations were considered as hotspot mutations in Chinese WD patients. However, we observed no significant correlation between these genetic types and the clinical symptoms of WD. The correlation between the mutation genotype and disease phenotype remains to be elucidated. In conclusion, the highly sensitive and specific direct DNA sequencing method can be used to screen for the causative genes of WD.

Effect of integrin combined laminin on peripheral blood vessel of cerebral infarction and endogenous nerve regeneration

The third Chinese nationwide survey on causes of death states that cerebrovascular disease, accounting for 22.45% of total deaths, ranks as the first cause of death among rural and urban residents. It has become a serious public health problem since it has the highest disability and fatality rate among single diseases. Cerebral infarction is the most common cerebrovascular disease. In order to enhance the treatment response of cerebral infarction, this paper established male Sprague Dawley (SD) rat reperfusion model with 2 h of cerebral artery embolism by suture method. Neurological function deficit was scored according to rat improvement 24 h after model establishment, and 50 rats with scores between 10 and 13 were included in an ultimate experiment and were randomly divided into 5 groups: undisturbed control group, vascular endothelial growth factor (VEGF) up-regulated vessel group, endostatin down-regulated vessel group, ventricle injected Cxc Chemokin Receptor 4 (CXCR4) antibody group, ventricle injected α6β1 antagonist (GoH3 antibody) group, respectively. The experiment was initiated after grouping and measurement of the relative data. The obtained results showed that the behavioral recovery of the VEGF group was more obvious compared with the control group, and the differences were statistically significant. The research was carried out using decreased modified neurological severity scores (mNSS), and the time a rat took to remove a pasted object. However, the behavioral recovery in the endostatin group, anti-CXCR4 group and GoH3 group was slow, and the difference was statistically significant, which showed as slowly decreased mNSS scoring and inconspicuous improved time of a rat removing a sticker. Compared with the control group, the number of peripheral BrdU+/ vWF+ cells of rat cerebral infarction in the VEGF group increased, and the peripheral VEGF expression quantity of cerebral infarction increased, thus the difference was statistically significant. However, cells in the endostatin group, anti-CXCR4 group, and GoH3 group were fewer and VEGF expression was reduced, and the difference was statistically significant. All these findings suggest that the promotion of angiogenesis after cerebral infarction can better provide the vascular niche for the proliferation, migration and differentiation of neural stem/progenitor cells (NSPCs), thereby further promoting endogenous nerve regeneration. NSPCs can always closely connect with vessels through the interaction of integrin α6β1 and laminin; furthermore, under the support provided by the vascular niche and the chemotaxis of stromal cellderived factor (SDF-1), NSPCs can migrate from the subventricular zone (SVZ) to the periphery of infarction.

Association between adiponectin receptor 2 gene polymorphisms and cerebral infarction

We examined the association between the adiponectin receptor 2 gene and the risk of ischemic stroke. Polymerase chain reaction-restriction fragment length polymorphism was used to detect rs12342 genotypes of the adiponectin receptor 2 gene in 300 ischemic stroke patients and 320 age- and gender-matched healthy controls. In the patient group, the AA, GA, and GG genotype frequencies were 39.3, 42.7, and 18.0%, respectively. The A and G allele frequencies were 0.607 and 0.393, respectively. In the control group, the AA, GA, and GG genotype frequencies were 29.0, 51.7, and 19.3%, respectively. The A and G allele frequencies were 0.548 and 0.452, respectively. The AA genotype and A allele frequencies in the patient group were significantly higher than those in the control group (both P < 0.01). The risk of ischemic stroke in AA genotype carriers was 1.786-fold greater than that in GG genotype carriers (odds ratio = 1.786, 95% confidence interval: 1.432-2.775; P = 0.013). After adjusting for various confounding factors, the difference remained significant (odds ratio = 1.874, 95% confidence interval: 1.221-2.765; P = 0.012). The AA genotype and A allele of rs12342 in the adiponectin receptor 2 gene may increase the risk of ischemic stroke, particularly the risk of atherosclerosis cerebral infarction.