Houttuyniae Herba protects rat primary cortical cells from Aβ(25-35)-induced neurotoxicity via regulation of calcium influx and mitochondria-mediated apoptosis

Linderae Radix Ameliorates Cognitive Dysfunction by Inhibiting Neuroinflammation and Synaptic Damage in Alzheimer's Disease Models

Neuroinflammation and synaptic damage are important etiologies associated with the progression of Alzheimer's disease (AD). Linderae Radix (LR) has antioxidant and anti-inflammatory properties. This study investigated whether LR attenuates microglia activation-mediated neuroinflammation and synaptic degeneration and improves AD pathological phenotypes induced by amyloid beta oligomers (AβO) or lipopolysaccharide (LPS) toxicity. For in vitro studies, we treated LR to AβO-stimulated HT22 cells or LR LPS-stimulated BV2 cells. For in vivo studies, we administered LR to mice and AβO was injected by stereotaxic to induce cognitive impairment, neuroinflammation, and synaptic loss. We found that LR increased the cell viability reduced by AβO. Moreover, LR inhibited pro-inflammatory mediators such as nitric oxide (NO), inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2), and downregulated p38 mitogen-activated protein kinase (MAPK) signaling in BV2 cells. Behavioral assessments demonstrated that LR administration significantly improved cognitive decline induced by AβO-injection. Furthermore, we found that microglia activation increased, and the expression of synaptic proteins decreased in the hippocampus of the AβO-injected group, which was alleviated in the LR-treated group. These findings suggest that LR may be a potential candidate for protection against neuroinflammation and synaptic loss, and may prevent or delay AD progression.

Aerial part of Houttuynia cordata reverses memory impairment by regulating amyloid beta accumulation and neuroinflammation in Alzheimer's disease model

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by amyloid-β (Aβ) deposition, accompanied by neuroinflammation and memory dysfunction. Houttuyniae Herba (aerial parts of Houttuynia cordata, also known as fish mint; HH), an herbal medicine traditionally used to treat fever, urinary disorders, and pus, is revealed to protect neurons from Aβ toxicity and regulate cholinergic dysfunction in AD models. In this study, we aimed to investigate the effects of HH on excessive accumulation of Aβ followed by neuroinflammation, synaptic degeneration, and memory impairment. Two-month-old 5xFAD transgenic mice were administered HH at 100 mg/kg for 4 months. We observed that HH treatment ameliorated memory impairment and reduced Aβ deposits in the brains of the mice. HH directly inhibited Aβ aggregation in vitro using the Thioflavin T assay and indirectly suppressed the amyloidogenic pathway by increasing alpha-secretase expression in the mice brain. In addition, HH exerted antineuroinflammatory effects by reducing of glial activation and p38 phosphorylation. Moreover, HH treatment increased the expression of synaptophysin, a presynaptic marker protein. Overall, HH alleviates memory impairment in AD by facilitating nonamyloidogenic pathway and inhibiting neuroinflammation. Therefore, we suggest that HH can be a promising herbal drug for patients with AD requiring multifaceted improvement.

2-undecanone protects against fine particles-induced heart inflammation via modulating Nrf2/HO-1 and NF-κB pathways

Exposure to air pollution has been closely associated with some cardiovascular disease. One of the mechanisms of PM_2.5 -mediated heart injury may be to promote inflammation. We aim to investigate whether the main extract of Houttuynia cordata, 2-undecanone, can prevent the inflammation caused by PM_2.5 , and to reveal the underlying mechanisms. The results showed that PM_2.5 increased the expression of certain inflammatory cytokines, and caused oxidative damage in BALB/c mice and H9C2 cells. Supplementation with 2-undecanone attenuated this PM_2.5 -induced inflammatory injury and oxidative damage. Further, we elucidated that the protective effect of 2-undecanone may be associated with NF-κB and Nrf2/HO-1 pathways. The NF-κB pathway was distinctly activated after treated by PM_2.5 , which can be blocked by 2-undecanone, accompanied by increasing Nrf2 and HO-1 levels. To figure out the relationship between NF-κB and Nrf2/HO-1 pathways, we knocked down Nrf2 gene. NF-κB pathway proteins and downstream inflammatory cytokines were significantly increased after treatment with PM_2.5 , while 2-undecanone could decrease expression of these proteins. In conclusion, it is possible that 2-undecanone can induce the expression of the antioxidant enzyme HO-1 by activating Nrf2, thereby reducing NF-κB pathway and inflammatory damage of mouse myocardium caused by PM_2.5 exposure.

Network Pharmacology Study of Heat-Clearing and Detoxifying Traditional Chinese Medicine for Alzheimer's Disease

This study aims to explore the possible homologous mechanism of 7 frequently-used herbs for heat-clearing and detoxification in traditional Chinese medicine (HDTCM) for treating Alzheimer's disease (AD), one of the most common types of dementia, based on network pharmacology. Herbs that satisfied the criteria of containing chlorogenic acid, relating to AD and aligning with HDTCM, were simultaneously collected to determine whether they have anti-AD effect based on a survey of the literature. Herb-ingredient-target-disease networks were constructed by collecting information from the TCMSP and GeneCards public databases. The common targets of the herbs and AD were identified for conducting a Gene Ontology (GO) analyses and a Reactome pathway enrichment analysis. The results showed that PTGS1, IL-6, CASP3, and VEGFA were the predicted key gene targets. The IL-4 and IL-13 signaling pathway, the ESR-mediated signaling pathway, and the extranuclear estrogen signaling pathway were the significant pathways associated with the 7 herbs. This study revealed that the analogous anti-AD mechanism of the 7 herbs of HDTCM may be associated with anti-inflammation, which is a common effect of the chlorogenic acid and quercetin components.

Therapeutic Effects of Natural Drugs on Alzheimer's Disease

Alzheimer disease (AD) is characterized as a chronic neurodegenerative disease associated with aging. The clinical manifestations of AD include latent episodes of memory and cognitive impairment, psychiatric symptoms and behavioral disorders, as well as limited activities in daily life. In developed countries, AD is now acknowledged as the third leading cause of death, following cardiovascular disease and cancer. The pathogenesis and mechanism of AD remain unclear, although some theories have been proposed to explain AD, such as the theory of β-amyloid, the theory of the abnormal metabolism of tau protein, the theory of free radical damage, the theory of the inflammatory response, the theory of cholinergic damage, etc. Effective methods to predict, prevent or reverse AD are unavailable, and thus the development of new, efficient therapeutic drugs has become a current research hot spot worldwide. The isolation and extraction of active components from natural drugs have great potential in treating AD. These drugs possess the advantages of multiple targets in multiple pathways, fewer side effects and a long duration of curative effects. This article summaries the latest research progress regarding the mechanisms of natural drugs in the treatment of AD, providing a review of the literature and a theoretical basis for improving the clinical treatment of AD.

Oleanolic Acid Exerts a Neuroprotective Effect Against Microglial Cell Activation by Modulating Cytokine Release and Antioxidant Defense Systems

Microglia respond to adverse stimuli in order to restore brain homeostasis and, upon activation, they release a number of inflammatory mediators. Chronic microglial overactivation is related to neuroinflammation in Alzheimer's disease. In this work, we show that oleanolic acid (OA), a natural triterpene present in food and medicinal plants, attenuates the activation of BV2 microglial cells induced by lipopolysaccharide (LPS). Cell pretreatment with OA inhibited the release of IL-1β, IL-6, TNF-α, and NO, which was associated with the downregulation of the expression of genes encoding for these cytokines and inducible nitric oxide synthase (iNOS), and the reinforcement of the endogenous antioxidant cell defense. These findings advocate considering OA as a novel neuroprotective agent to inhibit oxidative stress and inflammatory response in activated microglia associated with Alzheimer's disease.

Norcepharadione B attenuates H2O2-induced neuronal injury by upregulating cellular antioxidants and inhibiting volume-sensitive Cl- channel

Oxidative stress acts as an essential culprit factor in the development of stroke and Alzheimer’s disease. Norcepharadione B possesses various pharmacologic features as an extract obtained from Houttuynia cordata. Nevertheless, the anti-apoptotic and neuroprotective characteristics of norcepharadione B remain unclear. In this study, the neuronal protection effect provided by norcepharadione B against injury caused by hydrogen peroxide (H2O2) in HT22 cell as well as the fundamental mechanism was systematically explored. The neurotoxicity assays of hippocampal cells, which were co-cultured with H2O2, showed that norcepharadione B had the ability to insulate the toxicity induced by H2O2 with significant reduced cell apoptosis. Besides, norcepharadione B potentiated the activity of superoxide dismutase (SOD), increased the level of glutathione (GSH), and decreased malondialdehyde content. The H2O2-induced apoptotic protein Bax was suppressed, and the anti-apoptotic protein Bcl-2 was boosted by norcepharadione B. Norcepharadione B promoted Akt phosphorylation and further upregulated heme oxygenase (HO-1) in cells exposed to oxidative stress. However, the inductive effect of HO-1 by norcepharadione B was shut off via the PI3K/Akt inhibitor LY294002. Furthermore, 2-h incubation with H2O2 substantially increased cell volume in HT22 cells, while norcepharadione B effectively alleviated such effect by interrupting the activation of VSOR Cl− channel. Collectively, our data revealed protective properties of norcepharadione B in resisting oxidative stress induced by H2O2 through elevation of HO-1 in the dependence of PI3K/Akt and in inhibiting H2O2-induced cell swelling by VSOR Cl− channel obstruction in HT22 cells.

Impact statement

Norcepharadione B is an aporphine alkaloid compound extracted from Chinese herb Houttuynia cordata. It was well known for its anti-inflammatory, anti-cancer, and anti-platelet aggregation outcomes. Our study demonstrated that Norcepharadione B protected hippocampal neurons against oxidative stress and the resultant cell apoptosis upon H2O2 exposure. Meanwhile, Norcepharadione B also substantially reduced cell swelling induced by H2O2 via inhibiting VSOR Cl− channel in neurons. These findings uncovered the potential mechanisms of Norcepharadione B in protecting neuron apoptosis under oxidative stress and propose that Norcepharadione B may serve as a favorable herb medicine for restoring neuronal injury in the pathogenesis of stroke together with other neurodegenerative diseases.

Houttuynia cordata Thunb. and its bioactive compound 2-undecanone significantly suppress benzo(a)pyrene-induced lung tumorigenesis by activating the Nrf2-HO-1/NQO-1 signaling pathway

Background

Lung cancer remains the most common cause of cancer-related deaths, with a high incidence and mortality in both sexes worldwide. Chemoprevention has been the most effective strategy for lung cancer prevention. Thus, exploring novel and effective candidate agents with low toxicity for chemoprevention is essential and urgent. Houttuynia cordata Thunb. (Saururaceae) (H. cordata), which is a widely used herbal medicine and is also popularly consumed as a healthy vegetable, exhibits anti-inflammatory, antioxidant and antitumor activity. However, the chemopreventive effect of H. cordata against benzo(a)pyrene (B[a]P)-initiated lung tumorigenesis and the underlying mechanism remain unclear.

Methods

A B[a]P-stimulated lung adenocarcinoma animal model in A/J mice in vivo and a normal lung cell model (BEAS.2B) in vitro were established to investigate the chemopreventive effects of H. cordata and its bioactive compound 2-undecanone against lung tumorigenesis and to clarify the underlying mechanisms.

Results

H. cordata and 2-undecanone significantly suppressed B[a]P-induced lung tumorigenesis without causing obvious systemic toxicity in mice in vivo. Moreover, H. cordata and 2-undecanone effectively decreased B[a]P-induced intracellular reactive oxygen species (ROS) overproduction and further notably protected BEAS.2B cells from B[a]P-induced DNA damage and inflammation by significantly inhibiting phosphorylated H2A.X overexpression and interleukin-1β secretion. In addition, H. cordata and 2-undecanone markedly activated the Nrf2 pathway to induce the expression of the antioxidative enzymes heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO-1). Nrf2 silencing by transfection with Nrf2 siRNA markedly decreased the expression of HO-1 and NQO-1 to diminish the reductions in B[a]P-induced ROS overproduction, DNA damage and inflammation mediated by H. cordata and 2-undecanone.

Conclusions

H. cordata and 2-undecanone could effectively activate the Nrf2-HO-1/NQO-1 signaling pathway to counteract intracellular ROS generation, thereby attenuating DNA damage and inflammation induced by B[a]P stimulation and playing a role in the chemoprevention of B[a]P-induced lung tumorigenesis. These findings provide new insight into the pharmacological action of H. cordata and indicate that H. cordata is a novel candidate agent for the chemoprevention of lung cancer.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1255-3) contains supplementary material, which is available to authorized users.

DL0410, a novel dual cholinesterase inhibitor, protects mouse brains against Aβ-induced neuronal damage via the Akt/JNK signaling pathway

AIM

1,1'-([1,1'-Biphenyl]-4,4'-diyl)bis(3-(piperidin-1-yl)propan-1-one)dihydrochloride (DL0410) is a novel synthetic dual acetylcholinesterase (AChE)/butyrocholinesterase (BuChE) inhibitor, which has shown a potential therapeutic effect on Alzheimer's disease (AD). In this study we examined whether DL0410 produced neuroprotective effects in an AD cellular model and an Aβ1-42-induced amnesia mouse model.

METHODS

The in vitro inhibitory activities against AChE and BuChE were estimated using Ellman's assay. Copper-induced toxicity in APPsw-SY5Y cells was used as AD cellular model, the cell viability was assessed using MTS assay, and cell apoptosis was evaluated based on mitochondrial membrane potential detection. Aβ1-42-induced amnesia mouse model was made in male mice by injecting aggregated Aβ1-42 (2 μg in 2 μL 0.1% DMSO) into the right cerebral ventricle. Before and after Aβ1-42 injection, the mice were orally administered DL0410 (1, 3, 9 mg·kg-1·d-1) or rivastigmine (2 mg·kg-1·d-1) for 3 and 11 d, respectively. Memory impairments were examined using Morris water maze (MWM) test and passive avoidance test. The expression levels of APP, CREB, BDNF, JNK and Akt in the mouse brains were measured with either immunohistochemistry or Western blotting.

RESULTS

DL0410 exhibited in vitro inhibitory abilities against AChE and BuChE with IC50 values of 0.286±0.004 and 3.962±0.099 μmol/L, respectively, which were comparable to those of donepezil and rivastigmine. In APPsw-SY5Y cells, pretreatment with DL0410 (1, 3, and 10 μmol/L) decreased the phosphorylation of JNK and increased the phosphorylation of Akt, markedly decreased copper-stimulated Aβ1-42 production, reversed the loss of mitochondrial membrane potential, and dose-dependently increased the cell viability. In Aβ1-42-treated mice, DL0410 administration significantly ameliorated learning and memory deficits in MWM test and passive avoidance test. Furthermore, DL0410 administration markedly decreased Aβ1-40/42 deposits in mouse cerebral cortices, and significantly up-regulated neurotrophic CREB/BDNF. Meanwhile, Akt/JNK signaling pathway may play a key role in the neuroprotective effect of DL0410.

CONCLUSION

DL0410 ameliorates cognitive deficit and exerts neuronal protection in AD models, implicating this compound as a candidate drug for the prevention and therapy of AD.

Mori Fructus improves cognitive and neuronal dysfunction induced by beta-amyloid toxicity through the GSK-3β pathway in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

A growing body of literature supports the concept that antiaging herbs may be potential candidates for use in treating age-related neurodegeneration, including Alzheimer׳s disease (AD). Mori Fructus is a well-known traditional herbal medicine, food, and dietary supplement. This study employed models of amyloid beta (Aβ)-induced AD to investigate the protective effects of Mori Fructus ethanol extract (ME) against age-related disease and cognitive deficits.

MATERIALS AND METHODS

To examine the protective effect of ME, we measured cell viability, cytotoxicity, and survival in rat primary hippocampal cultures. We performed behavioral tests and histological analysis in mouse models of AD induced by Aβ(25-35) toxicity. To investigate the mechanism underlying the protective effect, we performed western blotting using antibodies against apoptotic markers as well as the nonphosphorylated and phosphorylated forms of Akt, glycogen synthase kinase-3β (GSK-3β), and tau. We also measured apoptotic marker fluorescence intensity.

RESULTS

ME significantly attenuated Aβ-induced cell damage, enhanced Akt and GSK-3β phosphorylation, and reduced tau phosphorylation. ME reduced apoptotic markers that were activated by GSK-3β, and reduced reactive oxygen species production. Further, ME decreased the B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X expression ratio, mitochondria depolarization, cytochrome c release from mitochondria, and caspase-3 activation. We confirmed that ME treatment improved cognitive impairment and neuronal cell death induced by Aβ(25-35) toxicity in the mouse hippocampus via its antiapoptotic activity.

CONCLUSIONS

These results indicate that ME protects cognition and neurons in AD-like models induced by Aβ via reduction of tau phosphorylation and apoptosis through GSK-3β inactivation.

Oncostatin M-dependent Mcl-1 induction mediated by JAK1/2-STAT1/3 and CREB contributes to bioenergetic improvements and protective effects against mitochondrial dysfunction in cortical neurons

Oncostatin M (OSM), a cytokine in the interleukin-6 (IL-6) family, has been proposed to play a protective role in the central nervous system, such as attenuation of excitotoxicity induced by N-methyl-D-aspartate (NMDA) and glutamate. However, the potential neuroprotective effects of OSM against mitochondrial dysfunction have never been reported. In the present study, we tested the hypothesis that OSM may confer neuronal resistance against 3-nitropropionic acid (3-NP), a plant toxin that irreversibly inhibits the complex II of the mitochondrial electron transport chain, and characterized the underlying molecular mechanisms. We found that OSM preconditioning dose- and time-dependently protected cortical neurons against 3-NP toxicity. OSM stimulated expression of myeloid cell leukemia-1 (Mcl-1), an anti-apoptotic Bcl-2 family member expressed in differentiating myeloid cells, that required prior phosphorylation of Janus kinase-1 (JAK1), JAK2, extracellular signal-regulated kinase-1/2 (ERK1/2), signal transducer and activator of transcription-3 (STAT3), STAT1, and cAMP-response element-binding protein (CREB). Pharmacological inhibitors of JAK1, JAK2, ERK1/2, STAT3, STAT1, and CREB as well as the siRNA targeting at STAT3 and Mcl-1 all abolished OSM-dependent 3-NP resistance. Finally, OSM-dependent Mcl-1 induction contributed to the enhancements of mitochondrial bioenergetics including increases in spare respiratory capacity and ATP production. In conclusion, our findings indicated that OSM induces Mcl-1 expression via activation of ERK1/2, JAK1/2, STAT1/3, and CREB; furthermore, OSM-mediated Mcl-1 induction contributes to bioenergetic improvements and neuroprotective effects against 3-NP toxicity in cortical neurons. OSM may thus serve as a novel neuroprotective agent against mitochondrial dysfunction commonly associated with pathogenic mechanisms underlying neurodegeneration.

Chinese traditional medicine and adult neurogenesis in the hippocampus

Adult neurogenesis is an important therapeutic target in treating neurological disorders. Adult neurogenesis takes place in two regions of the brain: Subventricular zone and dentate gyrus in the hippocampus. The progressive understanding on hippocampal neurogenesis in aging and mood disorders increases the demand to explore powerful and subtle interventions on hippocampal neurogenesis. Traditional Chinese herbal medicine provides an abundant pharmaceutical platform for modulating hippocampal neurogenesis. Recent progress in exploring the effects of Chinese herbal medicine and the related mechanisms opens a new direction for regeneration therapy. The current review gives a thorough summary of the research progress made in traditional Chinese herbal formulas, and the effective compounds in Chinese herbs which are beneficial on hippocampal neurogenesis and the possible mechanisms involved.

Zingiberene attenuates hydrogen peroxide-induced toxicity in neuronal cells

In this experimental design, we explored the neuroprotective potential of zingiberene (ZGB), a monocyclic sesquiterpene, in hydrogen peroxide (H2O2)-induced toxicity in newborn rat cerebral cortex cell cultures for the first time. The rats were exposed to H2O2 for 6 h to determine the oxidative stress levels. To evaluate cell viability, both 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays were carried out. Total antioxidant capacity (TAC) and total oxidative stress (TOS) parameters were used to evaluate oxidative changes. Besides determining 8-hydroxy-2-deoxyguanosine (8-OH-dG) levels in vitro, single-cell gel electrophoresis was also performed to measure the resistance of neuronal DNA to H2O2- exposed rats. Our results showed that survival and TAC levels of the cells decreased, while TOS, 8-OH-dG levels and the mean values of the total scores of cells showing DNA damage increased in the H2O2 alone-treated cultures. But pretreatment of ZGB suppressed the cytotoxicity, genotoxicity and oxidative stress that were increased by H2O2. Based on these observations, it is suggested that the sesquiterpene ZGB can be used as a novel and natural potential therapeutic in counteracting oxidative damages in the field of neurodegenerative disorders.

Houttuynia cordata Improves Cognitive Deficits in Cholinergic Dysfunction Alzheimer's Disease-Like Models

Cognitive impairment is a result of dementia of diverse causes, such as cholinergic dysfunction and Alzheimer's disease (AD). Houttuynia cordata Thunb. (Saururaceae) has long been used as a traditional herbal medicine. It has biological activities including protective effects against amyloid beta (Aβ) toxicity, via regulation of calcium homeostasis, in rat hippocampal cells. To extend previous reports, we investigated the effects of water extracts of H. cordata herb (HCW) on tauopathies, also involving calcium influx. We then confirmed the effects of HCW in improving memory impairment and neuronal damage in mice with Aβ-induced neurotoxicity. We also investigated the effects of HCW against scopolamine-induced cholinergic dysfunction in mice. In primary neuronal cells, HCW inhibited the phosphorylation of tau by regulating p25/p35 expression in Aβ-induced neurotoxicity. In mice with Aβ-induced neurotoxicity, HCW improved cognitive impairment, as assessed with behavioral tasks, such as novel object recognition, Y-maze, and passive avoidance tasks. HCW also inhibited the degeneration of neurons in the CA3 region of the hippocampus in Aβ-induced neurotoxicity. Moreover, HCW, which had an IC50 value of 79.7 μg/ml for acetylcholinesterase inhibition, ameliorated scopolamine-induced cognitive impairment significantly in Y-maze and passive avoidance tasks. These results indicate that HCW improved cognitive impairment, due to cholinergic dysfunction, with inhibitory effects against tauopathies and cholinergic antagonists, suggesting that HCW may be an interesting candidate to investigate for the treatment of AD.

Houttuynia cordata Thunb fraction induces human leukemic Molt-4 cell apoptosis through the endoplasmic reticulum stress pathway

Houttuynia cordata Thunb (HCT) is a native herb found in Southeast Asia which features various pharmacological activities against allergy, inflammation, viral and bacterial infection, and cancer. The aims of this study were to determine the cytotoxic effect of 6 fractions obtained from silica gel column chromatography of alcoholic HCT extract on human leukemic Molt-4 cells and demonstrate mechanisms of cell death. Six HCT fractions were cytotoxic to human lymphoblastic leukemic Molt-4 cells in a dose-dependent manner by MTT assay, fraction 4 exerting the greatest effects. Treatment with IC50 of HCT fraction 4 significantly induced Molt-4 apoptosis detected by annexinV-FITC/propidium iodide for externalization of phosphatidylserine to the outer layer of cell membrane. The mitochondrial transmembrane potential was reduced in HCT fraction 4-treated Molt-4 cells. Moreover, decreased expression of Bcl-xl and increased levels of Smac/Diablo, Bax and GRP78 proteins were noted on immunoblotting. In conclusion, HCT fraction 4 induces Molt-4 apoptosis cell through an endoplasmic reticulum stress pathway.