Liquiritigenin inhibits Abeta(25-35)-induced neurotoxicity and secretion of Abeta(1-40) in rat hippocampal neurons

Interpreting the Mechanism of Active Ingredients in Polygonati Rhizoma in Treating Depression by Combining Systemic Pharmacology and In Vitro Experiments

Polygonati Rhizoma (PR) has certain neuroprotective effects as a homology of medicine and food. In this study, systematic pharmacology, molecular docking, and in vitro experiments were integrated to verify the antidepressant active ingredients in PR and their mechanisms. A total of seven compounds in PR were found to be associated with 45 targets of depression. Preliminarily, DFV docking with cyclooxygenase 2 (COX2) showed good affinity. In vitro, DFV inhibited lipopolysaccharide (LPS)-induced inflammation of BV-2 cells, reversed amoeba-like morphological changes, and increased mitochondrial membrane potential. DFV reversed the malondialdehyde (MDA) overexpression and superoxide dismutase (SOD) expression inhibition in LPS-induced BV-2 cells and decreased interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6 mRNA expression levels in a dose-dependent manner. DFV inhibited both mRNA and protein expression levels of COX2 induced by LPS, and the activation of NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) and caspase1 was suppressed, thus exerting an antidepressant effect. This study proves that DFV may be an important component basis for PR to play an antidepressant role.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Protective Effects of Cirsium japonicum var. maackii Flower on Amyloid Beta25-35-Treated C6 Glial Cells

Amyloid beta (Aβ) is a neurotoxic peptide and a key factor causing Alzheimer's disease. Cirsium japonicum var. maackii (CJM) has neuroprotective effects, but the protective effects of the flower from CJM (FCJM) on the neural system remain unclear. This study aimed to identify the fraction of FCJM with the highest neuroprotective potential and investigate its protective mechanisms against Aβ_25-35-induced inflammation in C6 glial cells. The cell viability and generation of reactive oxygen species (ROS) were measured to investigate the positive effect of FCJM on oxidative stress. Treatment with the FCJM extract or fractions increased the cell viability to 60-70% compared with 52% in the Aβ_25-35-treated control group and decreased ROS production to 84% compared with 100% in the control group. The ethyl acetate fraction of FCJM (EFCJM) was the most effective among all the extracts and fractions. We analyzed the protective mechanisms of EFCJM on Aβ_25-35-induced inflammation in C6 glial cells using Western blot. EFCJM downregulated amyloidogenic pathway-related proteins, such as Aβ precursor protein, β-secretase, presenilin 1, and presenilin 2. Moreover, EFCJM attenuated the Bax/Bcl-2 ratio, an index of apoptosis, and upregulated the oxidative stress-related protein, heme oxygenase-1. Therefore, this study demonstrated that FCJM improves cell viability and inhibits ROS in Aβ_25-35-treated C6 glial cells. Furthermore, EFCJM exhibits neuroprotective effects in Aβ_25-35-induced inflammation in C6 glial cells by modulating oxidative stress and amyloidogenic and apoptosis signaling pathways. FCJM, especially EFCJM, can be a promising agent for neurodegenerative disease prevention.

Modulation of the Dipole Potential of Model Lipid Membranes with Phytochemicals: Molecular Mechanisms, Structure-Activity Relationships, and Implications in Reconstituted Ion Channels

Phytochemicals, such as flavonoids, stilbenoids, alkaloids, terpenoids, and related compounds, have a wide range of useful pharmacological properties which cannot be ascribed to binding to a single peptide or protein target alone. Due to the relatively high lipophilicity of phytochemicals, the lipid membrane is thought to mediate their effects via changes in the properties of the lipid matrix, in particular, by modulating the transmembrane distribution of the electrical potential and, consequently, the formation and functioning of the ion channels reconstituted in the lipid bilayers. Therefore, biophysical studies on the interactions between plant metabolites and model lipid membranes are still of interest. This review represents an attempt to provide a critical analysis of a variety of studies on altering membranes and ion channels with phytochemicals via disturbing the potential drop at the membrane-aqueous solution interface. Critical structural motifs and functioning groups in the molecules of plant polyphenols (alkaloids and saponins are identified) and the possible mechanisms of dipole potential modulation with phytochemicals are discussed.

Preventing Dementia Using Saffron, The Kampo Medicine, Kamiuntanto, and Their Combination, Kamiuntantokabankoka

The objective of this review is to evaluate the anti-dementia activities of saffron and its combination with Kampo medicine. The Kampo formula Kamiuntanto composed of 13 crude drugs is well known for its anti-dementia activity. A significant increase in choline acetyltransferase activity and mRNA levels were observed. Polygala radix was identified as the most essential component drug in Kamiuntanto, probably due to the saponins, tenuifolin, and sinapinic acid. Ginseng was also identified as an essential Kamiuntanto component in terms of its synergistic functions with Polygala radix. Saffron, which was recommended in the Bencao Gangmu for memory and dementia, and is used as an anti-spasmodic, anti-catarrhal, and sedative herbal drug. Saffron and its major constituent, crocin were shown to enhance learning-memory, non-rapid eye movement (rem) sleep, and inhibit depression and neuronal cell death due to strong anti-oxidant and anti-inflammation activities. In addition based on the epidemiological studies such as the treatment of sleeping disorders and the clinical trials of saffron for Alzheimer patients, we demonstrated the indirect and direct anti-dementia activities of crocin and saffron.

Protective effects of Populus tomentiglandulosa against cognitive impairment by regulating oxidative stress in an amyloid beta25–35-induced Alzheimer's disease mouse model

BACKGROUND/OBJECTIVES

Alzheimer's disease (AD) is one of the most representative neurodegenerative disease mainly caused by the excessive production of amyloid beta (Aβ). Several studies on the antioxidant activity and protective effects of Populus tomentiglandulosa (PT) against cerebral ischemia-induced neuronal damage have been reported. Based on this background, the present study investigated the protective effects of PT against cognitive impairment in AD.

MATERIALS/METHODS

We orally administered PT (50 and 100 mg/kg/day) for 14 days in an Aβ_25-35-induced mouse model and conducted behavioral experiments to test cognitive ability. In addition, we evaluated the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum and measured the production of lipid peroxide, nitric oxide (NO), and reactive oxygen species (ROS) in tissues.

RESULTS

PT treatment improved the space perceptive ability in the T-maze test, object cognitive ability in the novel object recognition test, and spatial learning/long-term memory in the Morris water-maze test. Moreover, the levels of AST and ALT were not significantly different among the groups, indicating that PT did not show liver toxicity. Furthermore, administration of PT significantly inhibited the production of lipid peroxide, NO, and ROS in the brain, liver, and kidney, suggesting that PT protected against oxidative stress.

CONCLUSIONS

Our study demonstrated that administration of PT improved Aβ_25–35-induced cognitive impairment by regulating oxidative stress. Therefore, we propose that PT could be used as a natural agent for AD improvement.

Network Pharmacology-Based Strategy for Elucidating the Molecular Basis Forthe Pharmacologic Effects of Licorice (Glycyrrhiza spp.)

Licorice (Glycyrrhiza spp.) is used widely in traditional Chinese medicine (TCM) due to its numerous pharmacologic effects. However, the mechanisms of action of the chemical constituents of licorice and their structure–function relationships are not fully understood. To address these points, we analyzed the chemical compounds in licorice listed in the TCM Systems Pharmacology database and TCM Integrated database. Target proteins of the compounds were predicted using Integrative Pharmacology-based Research Platform of TCM v2.0. Information on the pharmacologic effects of licorice was obtained from the 2020 Chinese Pharmacopoeia, and disease-related genes that have been linked to these effects were identified from the Encyclopedia of TCM database. Pathway analyses using the Kyoto Encyclopedia of Genes and Genomes database were carried out for target proteins, and pharmacologic networks were constructed based on drug target–disease-related gene and protein–protein interactions. A total of 451 compounds were analyzed, of which 211 were from the medicinal parts of the licorice plant. The 241 putative targets of 106 bioactive compounds in licorice comprised 52 flavonoids, 47 triterpenoids, and seven coumarins. Four distinct pharmacologic effects of licorice were defined: 61 major hubs were the putative targets of 23 compounds in heat-clearing and detoxifying effects; 68 were targets of six compounds in spleen-invigorating and qi-replenishing effects; 28 were targets of six compounds in phlegm-expulsion and cough-suppressant effects; 25 compounds were targets of six compounds in spasm-relieving and analgesic effects. The major bioactive compounds of licorice were identified by ultra-high-performance liquid chromatography–quadrupole time-of-flight–tandem mass spectrometry. The anti-inflammatory properties of liquiritin apioside, liquiritigenin, glycyrrhizic acid and isoliquiritin apioside were demonstrated by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. Liquiritin apioside, liquiritigenin, isoliquiritin, isoliquiritin apioside, kaempferol, and kumatakenin were the main active flavonoids, and 18α- and 18β-glycyrrhetinic acid were the main active triterpenoids of licorice. The former were associated with heat-clearing and detoxifying effects, whereas the latter were implicated in the other three pharmacologic effects. Thus, the compounds in licorice have distinct pharmacologic effects according to their chemical structure. These results provide a reference for investigating the potential of licorice in treatment of various diseases.

Bioactive Compounds and Traditional Herbal Medicine: Promising Approaches for the Treatment of Dementia

Dementia is a term that encompasses a group of clinical symptoms affecting memory, thinking and social abilities, characterized by progressive impairment of memory performance and cognitive functions. There are several factors involved in the pathogenesis and progression of dementia, such as old age, brain ischemia, toxin exposure, and oxidative stress. There are extensive similarities between dementia and Alzheimer's disease (AD) either in clinical manifestations or experimental animal models. AD is the most dominant form of dementia, characterized by the accumulation of beta-amyloid protein and cholinergic neurotransmission deficits in the brain. Currently available medications for the treatment of dementia, such as choline esterase inhibitors, N-methyl-D-aspartate (NMDA) antagonists (memantine), have short-term efficacy and only relieve symptoms rather than targeting the main underlying pathogenesis. Several animal studies and clinical trials are being conducted to provide a rational approach to these medicinal plants in the prevention or treatment of memory deficits. This review highlights the potential effects of medicinal plants and their derived lead molecules, and explains the related mechanisms and effects reviewed from published literature as major thrust aspects and hopeful strategies in the prevention or treatment of dementia.

Natural products as pharmacological modulators of mitochondrial dysfunctions for the treatments of Alzheimer's disease: A comprehensive review

Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder characterized by neuronal loss and cognitive impairment that harshly affect the elderly individuals. Currently, the available anti-AD pharmacological approaches are purely symptomatic to alleviate AD symptoms, and the curative effects of novel anti-AD drugs focused on Aβ target are disappointing. Hence, there is a tremendous need to adjust AD therapeutic targets and discover novel anti-AD agents. In AD, mitochondrial dysfunction gradually triggers neuronal death from different aspects and worsens the occurrence and progress of AD. Consequently, it has been proposed that the intervention of impaired mitochondria represents an attractive breakthrough point for AD treatments. Due to chemical diversity, poly-pharmacological activities, few adverse effects and multiple targeting, natural products (NPs) have been identified as a valuable treasure for drug discovery and development. Multiple lines of studies have scientifically proven that NPs display ameliorative benefits in AD treatment in relation to mitochondrial dysfunction. This review surveys the complicated implications for mitochondrial dysregulation and AD, and then summarizes the potentials of NPs and their underlying molecular mechanisms against AD via reducing or improving mitochondrial dysfunction. It is expected that this work may open the window to speed up the development of innovative anti-AD drugs originated from NPs and improve upcoming AD therapeutics.

Alkaloids extracted from Uncaria rhynchophylla demonstrate neuroprotective effects in MPTP-induced experimental parkinsonism by regulating the PI3K/Akt/mTOR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Alkaloids isolated from Uncaria rhynchophylla (Miq.) Miq. ex Havil. (Rubiaceae), alkaloids (URA) have been used to treat diseases related to the central nervous system, such as Parkinson's disease. Nevertheless, the potential mechanisms underlying their neuroprotective effects are not well-understood.

AIM OF THE STUDY

We investigated the neuroprotective effects of URAs in a mouse model of 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) and the possible involvement of a molecular signaling pathway.

MATERIALS AND METHODS

Two typical experiments for animal behavior despair, the spontaneous motor activity and the rotarod experiments, were employed to evaluate the efficacy of URAs in mice with PD symptoms. Dopamine (DA) neurons and their metabolism were evaluated using high-performance liquid chromatography-tandem mass spectrometry. The mechanism of action of the alkaloids was investigated by analyzing their effects on the phosphoinositide 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway using western blotting.

RESULTS

URA treatment effectively improved the behaviors of the mice during the "spontaneous motor activity and latency to fall off the rotarod test". Moreover, URAs demonstrated a protective role in dopaminergic neurons by increasing the expression of the dopamine transporter and tyrosine hydroxylase, which were supposed to be reduced by MPTP, inhibiting dopamine turnover, and changing dopamine and relevant metabolites. In addition to its association with the increase in the Bcl-2/Bad ratio, URA treatment also attenuated the cleaved caspase-3 level and enhanced the phosphorylation of Akt and mTOR.

CONCLUSION

These findings provide evidence that URA can effectively protect neurons from the neurotoxicity caused by MPTP in mouse models of PD by up-regulating the PI3K/Akt/mTOR signaling pathway.

Liquiritigenin Decreases Aβ Levels and Ameliorates Cognitive Decline by Regulating Microglia M1/M2 Transformation in AD Mice

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases and is currently incurable. Amyloid β protein (Aβ) deposition is the main pathogenesis of AD, and many studies have shown that Aβ accumulation is toxic to neurons, leading to the inflammatory reaction, neuronal apoptosis, and neurofibrillary tangles. Thus, reducing Aβ levels might be a potential therapeutic strategy for AD. Liquiritigenin (LG), a dihydroflavone monomer compound extracted from natural plant licorice, has a variety of biological activities such as antioxidant, anti-tumor, anti-inflammatory and anti-virus. However, the exact function of LG in the pathogenesis of AD is elusive. Here, we reported that LG could significantly attenuate neuronal apoptosis in Aβ-induced N2A cells and APP/PS1 transgenic mice. Our in vivo and in vitro studies revealed that LG could alleviate the inflammation response, reflected by the reduction of NLRP3 and cleaved caspase-1. Meanwhile, we also found that LG was able to shift M1 type microglia towards M2 type microglia in Aβ-induced BV2 cells and AD mice. Furthermore, LG could reduce the Aβ levels by decreasing APP processing and accelerating Aβ clearance in AD mice. More importantly, daily treatment of LG (30 mg/kg day) for 90 days dramatically ameliorated the spatial learning and memory of AD mice. Taken together, these results suggest that LG can reduce the Aβ levels by regulating the M1/M2 transformation of microglia, thereby reversing memory decline during AD development, suggesting that LG may be a potential therapeutic agent for treating AD.

Identification of novel class I and class IIb histone deacetylase inhibitor for Alzheimer's disease therapeutics

Histone deacetylase enzymes were prominent chromatin remodeling drug that targets in the pathophysiology of Alzheimer's disease associated with transcriptional dysregulation. In vitro and in vivo models of AD have demonstrated overexpression of HDAC activity. Non-specificity and non-selectivity of HDAC are the major problems of existing HDAC inhibitors. Hence, we aim to set up a methodology describing the rational development of isoform-selective HDAC inhibitor targeting class, I and class IIb. A convenient multistage virtual screening followed by machine learning and IC₅₀ screenings were used to classify the 5064 compounds into inhibitors and non-inhibitors classes retrieved from the ChEMBL database. ADMET analysis identified the pharmacokinetics and pharmacodynamics properties of selected compounds. Molecular docking, along with mutational analysis of eleven compounds, characterized the inhibiting potency. Herein, for the first time, we reported ChEMBL1834473 (2-[[5-(4-chlorophenyl)-1,3,4-thiadiazol-2-yl]amino]-N-hydroxypyrimidine-5-carboxamide) as the isoform-selective HDAC inhibitor, which interact central Zn²⁺ atom. The negative energy and interacting residue of the ChEMBL1834473 with six HDAC isoform has also been tabulated and mapped. Moreover, our findings concluded histidine, glycine, phenylalanine, and aspartic acid as key residues in protein-ligand interaction and classify 2347 compounds as HDAC inhibitors. Later, a protein-protein interaction network of six HDAC with the key proteins involved in the progression of an AD and signaling pathway, which describes the relationship between ChEMBL1834473 and AD, has been demonstrated using PPI network where the chosen inhibitor will work. Altogether, we conclude that the compound ChEMBL1834473 may be capable of inhibiting all isoforms of class I and class IIb HDAC based on computational analysis for AD therapeutics.

Effect of Glycyrrhizic Acid on Scopolamine-Induced Cognitive Impairment in Mice

Purpose

Cognitive impairment is one of the main symptoms of Alzheimer disease and other dementias. Glycyrrhiza uralensis is a natural product that has a protective effect against cognitive impairment. In this study, we investigated whether glycyrrhizic acid, among the main bioactive components of Glycyrrhiza uralensis, has a neuroprotective effect on scopolamine-induced cognitive impairment.

Methods

Twenty-week-old male Institute of Cancer Research mice were used in this study. The scopolamine-induced cognitive impairment mice model was used. Glycyrrhizic acid was orally administered to mice once daily for 21 days, while scopolamine (1 mg/kg) treatment was delivered 30 minutes before behavioral tests. Donepezil (2 mg/kg) was used as a positive drug control. To evaluate the effect of glycyrrhizic acid, the following assessments were performed on hippocampal tissue: Y-maze test, acetylcholinesterase activity, antioxidant enzymes’ activity (superoxide dismutase, catalase). Western blotting for phosphor-extracellular signal-regulated kinase, P38, and c-Jun NH2-terminal kinase was conducted.

Results

We found that glycyrrhizic acid administration significantly improved scopolamine-induced cognitive impairment in the Y-maze test. The acetylcholinesterase activity, superoxide dismutase, and catalase activity in the glycyrrhizic acid-treated group showed a significant reversal of cognitive impairment compared with the scopolamine-treated group.

Conclusions

Our results suggest that glycyrrhizic acid has a neuroprotective effect on cognitive function in scopolamine-induced cognitive impairment.

Betanin Attenuates Oxidative Stress Induced by 6-OHDA in PC12 Cells via SAPK/JNK and PI3 K Pathways

Parkinson's disease is a neurodegenerative disorder which accompanied with cognitive decline, chorei form moves and behavioral difficulties. Oxidative stress which promote the apoptotic cell death are responsible for neurodegeneration in Parkinson. The purpose of this study is to evaluate the protective effects of betanin against toxicity and oxidative damage induced by 6-hydroxydopamine (6-OHDA) and hydrogen peroxide (H₂O₂) in PC12 cells as an appropriate model of Parkinson's cell damage. PC12 cells pretreated with betanin (1-200 µM) for 24 h, and exposed to either 6-OHDA (100 µM) or H₂O₂ (150 µM) for 24 h. Cell survival and intracellular reactive oxygen species (ROS) production analyzed by resazurin and DCF-DA assay. The anti-apoptotic effects of betanin in PC12 cells were studied using flow cytometry of PI stained cells. Also, western blot analysis of survivin, Cyt c, Phospho SAPK/JNK, SAPK/JNK, Phospho-PI3 kinase P85, PI3 kinase P85 was performed for detection of apoptosis. Betanin (1-200 µM) significantly decreased the 6-OHDA and H₂O₂ cytotoxicity also attenuated the ROS level. Cell apoptosis significantly increased after 6-OHDA (100 µM) treatment, compared to the control. However, pretreatment with betanin (20 and 50 µM), protected against apoptosis. Western blot analysis of PC12 cells showed that 100 µM 6-OHDA could increase the proteins involved in apoptosis signaling and betanin (20 and 50 µM), could decrease the apoptosis. The results show that betanin has antioxidant and anti-apoptotic effects and may have the ability to prevent or delay the progress of neural death in Parkinson's disease.

Safranal protects against beta-amyloid peptide-induced cell toxicity in PC12 cells via MAPK and PI3 K pathways

Alzheimer's disease is a type of cerebrovascular problem with progressive mental disabilities for the patient. This study aimed to investigate the protective effect of safranal on toxicity and oxidative damage induced by beta-amyloid (Aβ) and hydrogen peroxide (H₂O₂) in PC12 cells as an appropriate model of Alzheimer's cell damage. PC12 cells pretreated with saffron extract (2.5-40 μg/ml), essential oil (2.5-40 μg/ml), safranal (2.5-5-40 μM) and donepezil (5, 10 and 20 μM) for 120 min. Then exposed to either Aβ (25 μM) for 48 h or H₂O₂ (150 μM) for 24 h. In the end, the cell survival and intracellular reactive oxygen species (ROS) production analyzed. The anti-apoptotic effects of safranal in PC12 cells were studied using flow cytometry after PI staining. Also, western blot analysis of Cyt c, survivin, p44/42 MAPK (ERK1/2), Phospho-p44/42 MAPK (ERK1/2), PI3 Kinase P85, Phospho-PI3 Kinase P85, phospho SAPK/JNK, SAPK/JNK and caspase 3 performed for detection of apoptosis. Safranal (2.5 and 5 μM) and donepezil (10 and 20 μM) significantly decreased the Aβ toxicity. The ROS significantly attenuated when cells pretreated with essential oil, saffron extract, safranal, and donepezil. Cell apoptosis significantly increased after treatment with Aβ _(25-35) (25 μM) compared to control. However, after pretreatment with safranal (2.5 μM) apoptosis was significantly reduced. Western blot analysis of PC12 cells showed that 25 μM Aβ _(25-35) could increase proteins involved in apoptosis signaling and pretreatment with safranal (2.5 μM) could decrease the apoptosis. According to the results, safranal showed anti-apoptotic and antioxidant effects and may exert promising potential for the prevention of Alzheimer's disease.

Phytochemical and Pharmacological Role of Liquiritigenin and Isoliquiritigenin From Radix Glycyrrhizae in Human Health and Disease Models

The increasing lifespan in developed countries results in age-associated chronic diseases. Biological aging is a complex process associated with accumulated cellular damage by environmental or genetic factors with increasing age. Aging results in marked changes in brain structure and function. Age-related neurodegenerative diseases and disorders (NDDs) represent an ever-growing socioeconomic challenge and lead to an overall reduction in quality of life around the world. Alzheimer’s disease (AD) and Parkinson’s disease (PD) are most common degenerative neurological disorders of the central nervous system (CNS) in aging process. The low levels of acetylcholine and dopamine are major neuropathological feature of NDDs in addition to oxidative stress, intracellular calcium ion imbalance, mitochondrial dysfunction, ubiquitin-proteasome system impairment and endoplasmic reticulum stress. Current treatments minimally influence these diseases and are ineffective in curing the multifunctional pathological mechanisms. Synthetic neuroprotective agents sometimes have negative reactions as an adverse effect in humans. Recently, numerous ethnobotanical studies have reported that herbal medicines for the treatment or prevention of NDDs are significantly better than synthetic drug treatment. Medicinal herbs have traditionally been used around the world for centuries. Radix Glycyrrhizae (RG) is the dried roots and rhizomes of Glycyrrhiza uralensis or G. glabra or G. inflata from the Leguminosae/Fabaceae family. It has been used for centuries in traditional medicine as a life enhancer, for the treatment of coughs and influenza, and for detoxification. Diverse chemical constituents from RG have reported including flavanones, chalcones, triterpenoid saponins, coumarines, and other glycosides. Among them, flavanone liquiritigenin (LG) and its precursor and isomer chalcone isoliquiritigenin (ILG) are the main bioactive constituents of RG. In the present review, we summarize evidence in the literature on the structure and phytochemical properties and pharmacological applications of LG and ILG in age-related diseases to establish new therapeutics to improve human health and lifespan.

Chinese Herbal Medicine Glycyrrhiza inflataReduces Aβ Aggregation and Exerts Neuroprotection through Anti-Oxidation and Anti-Inflammation

Amyloid [Formula: see text] (A[Formula: see text]) plays a major role in the pathogenesis of Alzheimer's disease (AD). The accumulation of misfolded A[Formula: see text] causes oxidative and inflammatory damage leading to apoptotic cell death. Chinese herbal medicine (CHM) has been widely used in clinical practice to treat neurodegenerative diseases associated with oxidative stress and neuroinflammation. This study examined the neuroprotection effects of CHM extract Glycyrrhiza inflata (G. inflata) and its active constituents, licochalcone A and liquiritigenin in AD. We examined A[Formula: see text] aggregation inhibition, anti-oxidation and neuroprotection in Tet-On A[Formula: see text]-GFP 293/SH-SY5Y cells and anti-inflammatory potential in lipopolysaccharide (LPS)-stimulated RAW 264.7 and LPS and interferon (IFN)-[Formula: see text] (LPS/IFN-[Formula: see text])-activated BV-2 cells. In addition, we applied conditioned media (CM) of BV-2 cells primed with LPS/IFN-[Formula: see text] to A[Formula: see text]-GFP SH-SY5Y cells to uncover the neuroprotective mechanisms. Our results showed that G. inflata extract and its two constituents displayed potentials of A[Formula: see text] aggregation inhibition and radical-scavenging in biochemical assays, A[Formula: see text] misfolding inhibition and reactive oxygen species (ROS) reduction in A[Formula: see text]-GFP 293 cells, as well as neurite outgrowth promotion, acetylcholinesterase inhibition and SOD2 up-regulation in A[Formula: see text]-GFP SH-SY5Y cells. Meanwhile, both G. inflata extract and its constituents suppressed NO, TNF-[Formula: see text], IL-1[Formula: see text], PGE2 and/or Iba1 productions in inflammation-stimulated RAW 264.7 or BV-2 cells. G. inflata extract and its constituents further protected A[Formula: see text]-GFP SH-SY5Y cells from BV-2 CM-induced cell death by ameliorating reduced BCL2 and attenuating increased IGFBP2, cleaved CASP3, BAD and BAX. Collectively, G. inflata extract, licochalcone A and liquiritigenin display neuroprotection through exerting anti-oxidative and anti-inflammatory activities to suppress neuronal apoptosis.

Ion Channels Induced by Antimicrobial Agents in Model Lipid Membranes are Modulated by Plant Polyphenols Through Surrounding Lipid Media

The potential therapeutic applications of plant polyphenols in various neurological, cardiovascular, metabolic and malignant disorders determine the relevance of studying the molecular mechanisms of their action on the cell membranes. Here, the quantitative changes in the physical parameters of model bilayer lipid membranes upon the adsorption of plant polyphenols were evaluated. It was shown that butein and naringenin significantly decreased the intrinsic dipole potential of cholesterol-free and cholesterol-enriched membranes. Cardamonin, 4'-hydroxychalcone, licochalcone A and liquiritigenin demonstrated the average efficiency, while resveratrol did not characterized by the ability to modulate the bilayer electrostatics. At the same time, the tested polyphenols affected melting of phospholipids with saturated acyl chains. The effects were attributed to the lipid disordering and a promotion of the positive curvature stress. According to DSC data and results of measurements of the threshold voltages that cause bilayer breakdown licochalcone A is the most effective agent. Furthermore, the role of the polyphenol induced changes in the electric and elastic properties of lipid host in the regulation of reconstituted ion channels was examined. The ability of the tested polyphenols to decrease the conductance of single ion channels produced by the antifungal cyclic lipopeptide syringomycin E was in agreement with their effects on the dipole potential of the lipid bilayers. The greatest effect of licochalcone A on the steady-state membrane conductance induced by the antifungal polyene macrolide antibiotic nystatin correlated with its greatest efficacy to induce the positive curvature stress. We also found that butein and naringenin bind specifically to a single pore formed by α-hemolysin from Staphylococcus aureus.

The Memory-Enhancing Effects of Liquiritigenin by Activation of NMDA Receptors and the CREB Signaling Pathway in Mice

Liquiritigenin (LQ) is a flavonoid that can be isolated from Glycyrrhiza radix. It is frequently used as a tranditional oriental medicine herbal treatment for swelling and injury and for detoxification. However, the effects of LQ on cognitive function have not been fully explored. In this study, we evaluated the memory-enhancing effects of LQ and the underlying mechanisms with a focus on the N-methyl-D-aspartic acid receptor (NMDAR) in mice. Learning and memory ability were evaluated with the Y-maze and passive avoidance tests following administration of LQ. In addition, the expression of NMDAR subunits 1, 2A, and 2B; postsynaptic density-95 (PSD-95); phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII); phosphorylation of extracellular signal-regulated kinase 1/2 (ERK 1/2); and phosphorylation of cAMP response element binding (CREB) proteins were examined by Western blot. In vivo, we found that treatment with LQ significantly improved memory performance in both behavioral tests. In vitro, LQ significantly increased NMDARs in the hippocampus. Furthermore, LQ significantly increased PSD-95 expression as well as CaMKII, ERK, and CREB phosphorylation in the hippocampus. Taken together, our results suggest that LQ has cognition enhancing activities and that these effects are mediated, in part, by activation of the NMDAR and CREB signaling pathways.

The development prospection of HDAC inhibitors as a potential therapeutic direction in Alzheimer's disease

Alzheimer’s disease (AD) is a chronic neurodegenerative disease, which is associated with learning and memory impairment in the elderly. Recent studies have found that treating AD in the way of chromatin remodeling via histone acetylation is a promising therapeutic regimen. In a number of recent studies, inhibitors of histone deacetylase (HDACs) have been found to be a novel promising therapeutic agents for neurological disorders, particularly for AD and other neurodegenerative diseases. Although HDAC inhibitors have the ability to ameliorate cognitive impairment, successful treatments in the classic AD animal model are rarely translated into clinical trials. As for the reduction of unwanted side effects, the development of HDAC inhibitors with increased isoform selectivity or seeking other directions is a key issue that needs to be addressed. The review focused on literatures on epigenetic mechanisms in recent years, especially on histone acetylation in terms of the enhancement of specificity, efficacy and avoiding side effects for treating AD.

Pharmacological Activities and Phytochemical Constituents

Glycyrrhiza glabra is one of the most popular medicinal plants and it has been used in traditional herbal remedy since ancient times (Blumenthal et al. in Herbal medicine: expanded commission E monographs. Integrative Medicine Communications, Newton, 2000; Parvaiz et al. in Global J Pharmocol 8(1):8–13, 2014; Altay et al. in J Plant Res 129(6):1021–1032, 2016). Many experimental, pharmacological and clinical studies show that liquorice has antimicrobial, antibacterial, antiviral, antifungal, antihepatotoxic, antioxidant, antiulcer, anti-hemorrhoid antihyperglycemic, antidiuretic, antinephritic, anticarcinogenic, antimutagenic, anticytotoxic, anti-inflammatory, and blood stopper activity.

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.

Expression Profiles of SIRT1 and APP Genes in Human Neuroblastoma SK-N-SH Cells Treated with Two Epigenetic Agents

In our previous studies, significant hypermethylation of the sirtuin 1 (SIRT1) gene and demethylation of the β-amyloid precursor protein (APP) gene were found in patients with Alzheimer's disease (AD) compared with the normal population. Moreover, the expression of SIRT1 was significantly decreased while that of APP was increased in AD patients. These results indicated a correlation of DNA methylation with gene expression levels in AD patients. To further investigate the epigenetic mechanism of gene modulation in AD, we used two epigenetic drugs, the DNA methylation inhibitor 5-aza-2'-deoxycytidine (DAC) and the histone deacetylase inhibitor trichostatin A (TSA), to treat human neuroblastoma SK-N-SH cells in the presence of amyloid β-peptide Aβ25-35(Aβ25-35). We found that DAC and TSA had different effects on the expression trends of SIRT1 and APP in the cell model of amyloid toxicity. Although other genes, such as microtubule-associated protein τ, presenilin 1, presenilin 2, and apolipoprotein E, were up-regulated after Aβ25-35 treatment, no significant differences were found after DAC and/or TSA treatment. These results support the evidence in AD patients and reveal a strong correlation of SIRT1/APP expression with DNA methylation and/or histone modification, which may help understand the pathogenesis of AD.

Attenuation of Aβ toxicity by promotion of mitochondrial fusion in neuroblastoma cells by liquiritigenin

Mitochondrial dynamics control mitochondrial morphology and function, and aberrations in these are associated with various neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. To identify novel regulators of mitochondrial dynamics, we screened a phytochemical library and identified liquiritigenin as a potent inducer of mitochondrial fusion. Treatment with liquiritigenin induced an elongated mitochondrial morphology in SK-N-MC cells. In addition, liquiritigenin rescued mitochondrial fragmentation induced by knockout of mitochondrial fusion mediators such as Mfn1, Mfn2, and Opa1. Furthermore, we found that treatment with liquiritigenin notably inhibited mitochondrial fragmentation and cytotoxicity induced by Aβ in SK-N-MC cells.

Vitamin D2 suppresses amyloid-β 25-35 induced microglial activation in BV2 cells by blocking the NF-κB inflammatory signaling pathway

AIMS

Present emerging world is emphasizing the implication of vitamin D deficiency associated with development of inflammation and neurodegenerative disorder like Alzheimer's disease (AD). The chief neuropathological hallmark of AD is aggregation of amyloid-beta (Aβ) peptides surrounding microglial cells in human brain. Microglial activation plays a key role in inflammatory response and neuronal injury. Naturally abundant vitamin D2 (VD2) exhibiting anti-inflammatory activities are yet to explore more. This study has investigated the inhibitory effect of VD2 on inflammatory activities of BV2 microglial cells.

MAIN METHODS

Cellular compatibility of VD2 and Aβ25-35 protein in treated BV2 microglial cells were measured by CCK-8 assay. Induction of iNOS, COX-2 and NF-κB signaling cascade were measured by western blotting, whereas pro-inflammatory cytokines were measured by ELISA. In addition, generation of ROS was detected by fluorescence intensity.

KEY FINDINGS

Morphological observations showed that Aβ25-35 induced BV2 cells stimulation noticeably got reduced in VD2 pre-treated group at 24h time period. Anti-inflammatory activities of VD2 was observed demonstrating the inhibition of up-regulated iNOS and COX-2 protein expression further confirmed by attenuating the activated microglia released pro-inflammatory cytokines IL-1β, IL-6, TNF- α and ROS, while blocking the phosphorylation of NF-κB p65 in nucleus by preventing IκB-α degradation and phosphorylation in cytosol.

SIGNIFICANCE

The present study revealed that VD2 blocked the phosphorylation of NF-κB inflammatory signaling pathway in Aβ25-35 induced activated BV2 microglial cells by suppressing ROS generation and inflammatory cytokines. Our finding suggests that vitamin D2 has therapeutic potential against inflammation and Alzheimer's disease.

Protective effect of liquiritigenin on depressive-like behavior in mice after lipopolysaccharide administration

Liquiritigenin (Liq), the main active ingredient of traditional Chinese medicine licorice, possesses anti-inflammatory and neuroprotective properties. The current investigation was designed to explore whether liquiritigenin could relieve lipopolysaccharide (LPS)-induced depression-like behavior in mice and the underlying mechanism. Liquiritigenin (7.5mg/kg, 15mg/kg) and fluoxetine (20mg/kg) were pretreated intragastrically once daily for 7 consecutive days. LPS (0.5mg/kg) was injected subcutaneously to establish the depression model 30min after pretreatment on day 7. Interleukin (IL)-6 and tumor necrosis factor (TNF)-α levels in serum and hippocampus were detected by enzyme-linked immunosorbent assay (ELISA). Behavioral assessment was conduct 24h post LPS injection. The expressions of p65NF-κB, IκBα, brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) in hippocampus were determined by western blot. The obtained results showed that liquiritigenin effectively reduced the levels of pro-inflammatory cytokines and the expressions of p-p65NF-κB and p-IκBα. Furthermore, liquiritigenin preconditioning could down-regulate the immobility time in tail suspension test (TST), forced swimming test (FST) and up-regulate BDNF and TrkB contents in hippocampus. Thus, it is assumed that the antidepressant activity of liquiritigenin might be attributed to its anti-inflammatory property and BDNF/TrkB signaling pathway.

Isoliquiritigenin and liquiritin from Glycyrrhiza uralensis inhibit α-synuclein amyloid formation

Bioactive isoliquiritigenin and liquiritin inhibit α-synuclein aggregation and extend the life span of theC. elegansmodel of Parkinson's disease.

Protective effects of low molecular weight chondroitin sulfate on amyloid beta (Aβ)-induced damage in vitro and in vivo

In the present study, we investigated the effects of low molecular weight chondroitin sulfate (LMWCS) on amyloid beta (Aβ)-induced neurotoxicity in vitro and in vivo. The in vitro results showed that LMWCS blocked Aβ25-35-induced cell viability loss and apoptosis, decreased intracellular calcium concentration, reactive oxygen species (ROS) levels, the mitochondrial membrane potential (MMP) depolarization, and the protein expression of Caspase-3. During in vivo experiments, LMWCS improved the cognitive impairment induced by Aβ1-40, increased the level of choline acetyltransferase (ChAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and decreased the level of malondialdehyde (MDA) and acetylcholinesterase (AChE) in the mouse brain. Moreover, LMWCS decreased the density of pyramidal cells of CA1 regions, and suppressed the protein expression of Bax/Bcl-2 and Caspase-3, -9 in the hippocampus of mice. In conclusion, LMWCS possessed neuroprotective properties against toxic effects induced by Aβ peptides both in vitro and in vivo, which might be related to anti-apoptotic activity. LMWCS might be a useful preventive and therapeutic compound for Alzheimer's disease.

Protective effects of glycycoumarin and procyanidin B1, active components of traditional Japanese medicine yokukansan, on amyloid β oligomer-induced neuronal death

ETHNOPHARMACOLOGICAL RELEVANCE

Yokukansan, a traditional Japanese (Kampo) medicine, is composed of seven medicinal herbs, and has been traditionally used to treat neurosis, insomnia, and night crying and irritability in children. Yokukansan and its constituent herbs, Glycyrrhiza and Uncaria Hook, have recently been shown to have protective effects against amyloid β (Aβ) oligomer-induced apoptosis by suppressing the activation of caspase-3 in primary cultured neurons. The aim of the present study was to identify the effective components of Glycyrrhiza and Uncaria Hook against Aβ oligomer-induced neurotoxicity. We also attempted to clarify the mechanisms by which yokukansan and these herbs, as well as their components, suppressed the activation of caspase-3 in Aβ oligomer-treated neurons.

MATERIALS AND METHODS

Rat primary cultured cortical neurons were treated with Aβ oligomer (3 μM). The protective effects of 16 components derived from Glycyrrhiza or Uncaria Hook against Aβ oligomer-induced neurotoxicity were determined using the MTT reduction assay 48 h after the treatment. The suppressive effects of the test substances, i.e., yokukansan, Glycyrrhiza, Uncaria Hook, and screened components, on the Aβ oligomer-induced activation of caspase-3(/7) were evaluated using the caspase-Glo assay 48 h after the Aβ oligomer treatment. The suppressive effects of the test substances on the activation of caspase-8 and -9, both of which are located upstream of caspase-3, were also examined 24h after the Aβ oligomer treatment.

RESULTS

Two of the 16 components tested, glycycoumarin derived from Glycyrrhiza and procyanidin B1 derived from Uncaria Hook, significantly inhibited Aβ oligomer-induced neuronal death in a dose-dependent manner. Glycyrrhiza, Uncaria Hook, and yokukansan significantly suppressed the Aβ oligomer-induced activation of caspase-3 as well as caspase-8 and -9. Glycycoumarin also suppressed the activation of caspase-3, but not caspase-8 and -9. Procyanidin B1 suppressed the activation of caspase-3, -8, and -9.

CONCLUSIONS

Our results demonstrated that glycycoumarin and procyanidin B1 had ameliorative effects on Aβ oligomer-induced neurotoxicity. The neuroprotective effects of glycycoumarin are thought to be due to the attenuated activation of caspase-3, but not caspase-8 or -9. Procyanidin B1, as well as yokukansan, Glycyrrhiza, and Uncaria Hook, may attenuate the activation of caspase-3 by inhibiting that of caspase-8 and -9.

Methyllycaconitine alleviates amyloid-β peptides-induced cytotoxicity in SH-SY5Y cells

Alzheimer's disease (AD) is a chronic progressive neurodegenerative disorder. As the most common form of dementia, it affects more than 35 million people worldwide and is increasing. Excessive extracellular deposition of amyloid-β peptide (Aβ) is a pathologic feature of AD. Accumulating evidence indicates that macroautophagy is involved in the pathogenesis of AD, but its exact role is still unclear. Although major findings on the molecular mechanisms have been reported, there are still no effective treatments to prevent, halt, or reverse Alzheimer's disease. In this study, we investigated whether Aβ_25–35 could trigger an autophagy process and inhibit the growth of SH-SY5Y cells. Furthermore, we examined the effect of methyllycaconitine (MLA) on the cytotoxity of Aβ_25–35. MLA had a protective effect against cytotoxity of Aβ, which may be related to its inhibition of Aβ-induced autophagy and the involvement of the mammalian target of rapamycin pathway. Moreover, MLA had a good safety profile. MLA treatment may be a promising therapeutic tool for AD.

Bioactivity and potential health benefits of licorice

Licorice is an herbal plant named for its unique sweet flavor. It is widely used in the food and tobacco industries as a sweetener. Licorice is also used in traditional Chinese medicine (TCM) and complementary medicine. Because the use of licorice has long been a part of TCM, the details of its therapeutic applications have been thoroughly established. In modern science, licorice is of interest because of its broad range of applications. Extracts of and compounds isolated from licorice have been well studied and biologically characterized. In this review, we discuss the nutraceutical and functional activities of licorice as well as those of the extracts of and the isolated compounds from licorice, including agents with anti-inflammatory activity, cell-protective abilities, and chemopreventive effects. The side effects of licorice are also enumerated. A comparison of the activities of licorice described by modern science and TCM is also presented, revealing the correspondence of certain characteristics.

Synaptodendritic recovery following HIV Tat exposure: neurorestoration by phytoestrogens

HIV-1 infects the brain and, despite antiretroviral therapy, many infected individuals suffer from HIV-1-associated neurocognitive disorders (HAND). HAND is associated with dendritic simplification and synaptic loss. Prevention of synaptodendritic damage may ameliorate or forestall neurocognitive decline in latent HIV-1 infections. The HIV-1 transactivating protein (Tat) is produced during viral latency in the brain and may cause synaptodendritic damage. This study examined the integrity of the dendritic network after exposure to HIV-1 Tat by labeling filamentous actin (F-actin)-rich structures (puncta) in primary neuronal cultures. After 24 h of treatment, HIV-1 Tat was associated with the dendritic arbor and produced a significant reduction of F-actin-labeled dendritic puncta as well as loss of dendrites. Pre-treatment with either of two plant-derived phytoestrogen compounds (daidzein and liquiritigenin), significantly reduced synaptodendritic damage following HIV-1 Tat treatment. In addition, 6 days after HIV-1 Tat treatment, treatment with either daidzein, or liquiritigenin enhanced recovery, via the estrogen receptor, from HIV-1 Tat-induced synaptodendritic damage. These results suggest that either liquiritigenin or daidzein may not only attenuate acute synaptodendritic injury in HIV-1 but may also promote recovery from synaptodendritic damage. The HIV-1 transactivating protein (Tat) is produced during viral latency in the brain. Treatment with either daidzein or liquiritigenin restored the loss of synaptic connectivity produced by HIV-1 Tat. This neurorestoration was mediated by estrogen receptors (ER). These results suggest that plant-derived phytoestrogens may promote recovery from HIV-1-induced synaptodendritic damage.

Eriodictyol protects against H(2)O(2)-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathway

Eriodictyol, a flavonoid isolated from the Chinese herb Dracocephalum rupestre has long been established as an antioxidant. The present study was designed to explore the protective effects of eriodictyol against hydrogen peroxide (H(2)O(2))-induced neurotoxicity with cultured rat pheochromocytoma cells (PC12 cells) and the possible mechanisms involved. For this purpose, differentiated PC12 cells were cultured and exposed to 200 μM H(2)O(2) in the absence or presence of eriodictyol (20, 40 and 80 μM). In addition, the potential contribution of the Nrf2/ARE neuroprotective pathway in eriodictyol-mediated protection against H(2)O(2)-induced neurotoxicity was also investigated. The results showed that H(2)O(2)-induced cell death can be inhibited in the presence of eriodictyol as measured by assays for MTT and apoptosis. Further study revealed that eriodictyol induced the nuclear translocation of Nrf2, enhanced the expression of heme oxygenase (HO-1) and γ-glutamylcysteine synthetase (γ-GCS), and increased the levels of intracellular glutathione. Treatment of PC12 cells with Nrf2 small interference RNA abolished eriodictyol-induced HO-1 and γ-GCS expression and its protective effects. In conclusion, these results suggest that eriodictyol upregulates HO-1 and γ-GCS expression through the activation of Nrf2/ARE pathway and protects PC12 cells against H(2)O(2)-induced oxidative stress.

Liquiritigenin decreases selective molecular and behavioral effects of cocaine in rodents

Cocaine, as an indirect dopamine agonist, induces selective behavioral and physiological events such as hyperlocomotion and dopamine release. These changes are considered as consequences of cocaine-induced molecular adaptation such as CREB and c-Fos. Recently, methanolic extracts from licorice was reported to decrease cocaine-induced dopamine release and c-Fos expression in the nucleus accumbens. In the present study, we investigated the effects of liquiritigenin (LQ), a main compound of licorice, on acute cocaine-induced behavioral and molecular changes in rats. LQ attenuated acute cocaine-induced hyperlocomotion in dose-dependent manner. In addition, LQ inhibited CREB phosphorylation and c-Fos expression in the striatum and the nucleus accumbens induced by acute cocaine. Results provide strong evidence that LQ effectively attenuates the acute behavioral effects of cocaine exposure and prevents the induction of selective neuroadaptive changes in dopaminergic signaling pathways. Further investigation of LQ from licorice extract might provide a novel therapeutic strategy for the treatment of cocaine addiction.

Dexamethasone and Aβ₂₅-₃₅ accelerate learning and memory impairments due to elevate amyloid precursor protein expression and neuronal apoptosis in 12-month male rats

Alzheimer's disease (AD) is an irreversible, progressive brain disorder of the elderly characterized by learning and memory impairment. Stress level glucocorticoids (GCs) and β-amyloid (Aβ) peptides deposition are found to be correlated with dementia progression in patients with AD. However, little is known about the simultaneous effects of glucocorticoids and Aβ on learning and memory impairment and its mechanism. In this study, 12-month-old male rats were chronically treated with Aβ(25-35) (10 μg/rat, hippocampal CA1 injection) and dexamethasone (DEX, 1.5mg/kg) for 14 days to investigate the effects of DEX and Aβ(25-35) treatment on learning and memory impairments, pathological changes, neuronal ultrastructure, amyloid precursor protein (APP) processing and neuronal cell apoptosis. Our results showed that DEX or Aβ(25-35) treatment alone for 14 days had caused slight damage on learning and memory impairments and hippocampal neurons, but damages were significantly increased with DEX+Aβ(25-35) treatment. And the mRNA levels of the APP, β-secretase and caspase 3 were significantly increased after DEX+Aβ(25-35) treatment. The immunohistochemistry demonstrated that APP, Aβ(1-40), caspase 3 and cytochrome c in hippocampus CA1 were significantly increased. Furthermore, Hoechst 33258 staining and Aβ(1-40) ELISA results showed that DEX+Aβ(25-35) treatment induced hippocampus CA1 neuron apoptosis and increased the level of Aβ(1-40). The results suggest that the simultaneous effects of GCs and Aβ may have important roles in the etiopathogenesis of AD, and demonstrate that stressful life events and GC therapy may increase the toxicity of Aβ and have cumulative impacts on the course of AD development and progression.

Liquiritigenin attenuates the learning and memory deficits in an amyloid protein precursor transgenic mouse model and the underlying mechanisms

The present paper is to examine whether liquiritigenin is able to attenuate the Alzheimer's-like learning and memory deficits in a transgenic (Tg) mouse model that over-expresses amyloid protein precursor (APP), and explores the underlying mechanisms. Consistent with our previous observations, we found that treatment with liquiritigenin improved the behavioral performance of Tg mice and it attenuated the protein expression of oligomeric form of amyloid β-peptide (Aβ). Furthermore, treatment with liquiritigenin inhibited astrocytosis in the hippocampus, and it may through its inhibitory activities on Notch-2, an important molecular regulating neural proliferation and differentiation. These findings provide evidence for beneficial activity of liquiritigenin in a mouse model of Alzheimer's disease and support the continued investigation of Notch signaling pathway as a target for treatment of Alzheimer's disease.

Endogenous amyloidogenesis in long-term rat hippocampal cell cultures

BACKGROUND

Long-term primary neuronal cultures are a useful tool for the investigation of biochemical processes associated with neuronal senescence. Improvements in available technology make it possible to observe maturation of neural cells isolated from different regions of the rodent brain over a prolonged period in vitro. Existing experimental evidence suggests that cellular aging occurs in mature, long-term, primary neuronal cell cultures. However, detailed studies of neuronal development in vitro are needed to demonstrate the validity of long-term cell culture-based models for investigation of the biochemical mechanisms of in vitro neuronal development and senescence.

RESULTS

In the current study, neuron-enriched hippocampal cell cultures were used to analyze the differentiation and degeneration of hippocampal neurons over a two month time period. The expression of different neuronal and astroglial biomarkers was used to determine the cytochemical characteristics of hippocampal cells in long-term cultures of varying ages. It was observed that the expression of the intermediate filament nestin was absent from cultures older than 21 days in vitro (DIV), and the expression of neuronal or astrocytic markers appeared to replace nestin. Additionally, morphological evaluations of neuronal integrity and Hoescht staining were used to assess the cellular conditions in the process of hippocampal culture development and aging. It was found that there was an increase in endogenous production of Aβ(1-42) and an increase in the accumulation of Congo Red-binding amyloidal aggregates associated with the aging of neurons in primary culture. In vitro changes in the morphology of co-existing astrocytes and cell culture age-dependent degeneration of neurodendritic network resemble features of in vivo brain aging at the cellular level.

CONCLUSION

In conclusion, this study suggests that long-term primary CNS culture is a viable model for the study of basic mechanisms and effective methods to decelerate the process of neuronal senescence.

Effects of liquiritigenin treatment on the learning and memory deficits induced by amyloid beta-peptide (25-35) in rats

Considerable evidence has emerged supporting the neuroprotective and cognition-preserving effects of estrogen, but these benefits are complicated by the evidence that estrogen increases the risk of certain cancers. Selective estrogen receptor modulators (SERMs) that specifically target the brain while avoiding peripheral organs offer a way to allow the application of estrogen treatment to neurodegenerative diseases with fewer undesirable effects. In an attempt to find such estrogen substitutes, liquiritigenin was discovered as a relatively selective estrogen receptor beta (ERbeta) agonist. In the present study, we extend our previous findings to investigate the effects of liquiritigenin on the learning and memory deficits and related neuropathology in Abeta(25-35) hippocampal-injected rats. Our results show that liquiritigenin treatment improves the behavioral performance of the model rats and attenuates neuronal loss in the brain. More importantly, liquiritigenin treatment decreases mRNA levels and protein expression of Notch-2, an effect that could promote the generation of new neurons. These findings provide evidence for the beneficial activity of liquiritigenin in a brain-injured rat model and support the continued investigation of SERMs such as liquiritigenin as an alternative to estrogen-based hormone therapy in reducing the risk of neurodegenerative diseases such as Alzheimer's disease.