Licochalcone E activates Nrf2/antioxidant response element signaling pathway in both neuronal and microglial cells: therapeutic relevance to neurodegenerative disease

JE-133 Suppresses LPS-Induced Neuroinflammation Associated with the Regulation of JAK/STAT and Nrf2 Signaling Pathways

Neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases, and interrupting the microglial-mediated neuroinflammation has been suggested as a promising strategy to delay or prevent the progression of neurodegeneration. In this study, we investigated the effects of JE-133, an optically active isochroman-2H-chromene conjugate containing a 1,3-disubstituted isochroman unit, on lipopolysaccharide (LPS)-induced microglial neuroinflammation and underlying mechanisms both in vitro and in vivo. First, JE-133 treatment decreased LPS-induced overproduction of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nitrite, and nitric oxide synthase (iNOS) in BV2 microglial cells. Further study revealed that JE-133 downregulated the phosphorylation level of JAK/STAT and upregulated the protein level of Nrf2/HO-1 in LPS-stimulated BV2 microglial cells and verified that JE-133 directly bound to Keap1 by a pull-down assay. Next, JE-133 administration also inhibited neuroinflammation in vivo, as indicated by a reduced CD11b protein level and an overexpressed mRNA level of the pro-inflammatory cytokine TNF-α in the hippocampus of LPS-injected mice. Moreover, the regulative effects of JE-133 on the JAK/STAT and Nrf2/HO-1 pathways were also verified in the hippocampus of LPS-injected mice. Taken together, our study for the first time reports that JE-133 exhibits inhibitory effects against LPS-stimulated neuroinflammation both in vitro and in vivo, which might be associated with the simultaneous regulation of the JAK/STAT and Nrf2 pathways. Our findings may provide important clues for the discovery of effective drug leads/candidates against neuroinflammation-associated neurodegeneration.

Scutellarin attenuates oxidative stress and neuroinflammation in cerebral ischemia/reperfusion injury through PI3K/Akt-mediated Nrf2 signaling pathways

Cerebral ischemia/reperfusion injury (CIRI) seriously threatens human life and health. Scutellarin (Scu) exhibits neuroprotective effects, but little is known about its underlying mechanism. Therefore, we explored its protective effect on CIRI and the underlying mechanism. Our results demonstrated that Scu rescued HT22 cells from cytotoxicity induced by oxygen and glucose deprivation/reoxygenation (OGD/R). Scu also showed antioxidant activity by promoting nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation, upregulating heme oxygenase-1 (HO-1) expression, increasing superoxide dismutase (SOD) activity, and inhibiting reactive oxygen species (ROS) generation in vitro. Additionally, Scu reduced nuclear factor-kappa B (NF-κB) activity and the levels of pro-inflammatory factors. Interestingly, these effects were abolished by Nrf2 inhibition. Furthermore, Scu reduced infarct volume and blood-brain barrier (BBB) permeability, improved sensorimotor functions and depressive behaviors, and alleviated oxidative stress and neuroinflammation in rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). Mechanistically, Scu-induced Nrf2 nuclear accumulation and inactivation of NF-κB were accompanied by an enhanced level of phosphorylated protein kinase B (p-AKT) both in vitro and in vivo. Pharmacologically inhibiting the phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathway blocked Scu-induced Nrf2 nuclear translocation and inactivation of NF-κB, as well as its antioxidant and anti-inflammatory activities. In summary, these results suggest that Scu exhibits antioxidant, anti-inflammatory, and neuroprotective effects in CIRI through Nrf2 activation mediated by the PI3K/Akt pathway.

The key roles of reactive oxygen species in microglial inflammatory activation: Regulation by endogenous antioxidant system and exogenous sulfur-containing compounds

Aberrant innate immunity in the brain has been implicated in the pathogenesis of several central nervous system (CNS) disorders, including Alzheimer's disease, Huntington's disease, Parkinson's disease, stroke, amyotrophic lateral sclerosis, and depression. Except for extraparenchymal CNS-associated macrophages, which predominantly afford protection against peripheral invading pathogens, it has been reported that microglia, a population of macrophage-like cells governing CNS immune defense in nearly all neurological diseases, are the main CNS resident immune cells. Although microglia have been recognized as the most important source of reactive oxygen species (ROS) in the CNS, ROS also may underlie microglial functions, especially M1 polarization, by modulating redox-sensitive signaling pathways. Recently, endogenous antioxidant systems, including glutathione, hydrogen sulfide, superoxide dismutase, and methionine sulfoxide reductase A, were found to be involved in regulating microglia-mediated neuroinflammation. A series of natural sulfur-containing compounds, including S-adenosyl methionine, S-methyl-L-cysteine, sulforaphane, DMS, and S-alk(enyl)-l-cysteine sulfoxide, modulating endogenous antioxidant systems have been discovered. We have summarized the current knowledge on the involvement of endogenous antioxidant systems in regulating microglial inflammatory activation and the effects of sulfur-containing compounds on endogenous antioxidant systems. Finally, we discuss the possibilities associated with compounds targeting the endogenous antioxidant system to treat neuroinflammation-associated diseases.

Analysis of phenolic compounds in Parkinson's disease: a bibliometric assessment of the 100 most cited papers

Objective

The aim of this study was to identify and characterize the 100 most cited articles on Parkinson's disease (PD) and phenolic compounds (PCs).

Methods

Articles were selected in the Web of Science Core Collection up to June 2022 based on predetermined inclusion criteria, and the following bibliometric parameters were extracted: the number of citations, title, keywords, authors, year, study design, tested PC and therapeutic target. MapChart was used to create worldwide networks, and VOSviewer software was used to create bibliometric networks. Descriptive statistical analysis was used to identify the most researched PCs and therapeutic targets in PD.

Results

The most cited article was also the oldest. The most recent article was published in 2020. Asia and China were the continent and the country with the most articles in the list (55 and 29%, respectively). In vitro studies were the most common experimental designs among the 100 most cited articles (46%). The most evaluated PC was epigallocatechin. Oxidative stress was the most studied therapeutic target.

Conclusion

Despite the demonstrations in laboratorial studies, the results obtained point to the need for clinical studies to better elucidate this association.

Michael acceptor molecules in natural products and their mechanism of action

Purpose: Michael receptor molecules derived from plants are biologically active due to electrophilic groups in their structure. They can target nucleophilic residues on disease-related proteins, with significant therapeutic effects and low toxicity for many diseases. They provide a good option for relevant disease treatment. The aim of this study is to summarize the existing MAMs and their applications, and lay a foundation for the application of Michael receptor molecules in life science in the future. Methods: This review summarizes the published studies on Michael receptor molecules isolated from plants in literature databases such as CNKI, Wanfang Data, PubMed, Web of Science, ScienceDirect, and Wiley. Latin names of plants were verified through https://www.iplant.cn/. All relevant compound structures were verified through PubChem and literature, and illustrated with ChemDraw 20.0. Result: A total of 50 Michael receptor molecules derived from various plants were discussed. It was found that these compounds have similar pharmacological potential, most of them play a role through the Keap1-Nrf2-ARE pathway and the NF-κB pathway, and have biological activities such as antioxidant and anti-inflammatory. They can be used to treat inflammatory diseases and tumors. Conclusion: The Michael receptor molecule has electrophilicity due to its unsaturated aldehyde ketone structure, which can combine with nucleophilic residues on the protein to form complexes and activate or inhibit the protein pathway to play a physiological role. Michael receptor molecules can regulate the Keap1-Nrf2-ARE pathway and the NF-κB pathway. Michael receptor molecules can be used to treat diseases such as inflammation, cancer, oxidative stress, etc.

Diphenyl diselenide modulate antioxidant status, inflammatory and redox-sensitive genes in diesel exhaust particle-induced neurotoxicity

This study seeks to determine the influence of diphenyl diselenide (DPDSe) on redox status, inflammatory and redox-sensitive genes in diesel exhaust particle (DEP)-induced neurotoxicity in male albino rats. Male Wistar albino rats were administered nasally with DEP (30 and 60 μg/kg) and treated with intraperitoneal administration of 10 mg/kg DPDSe. Non-enzymatic (lipid peroxidation and conjugated diene concentrations) and enzymatic (catalase, superoxide dismutase, glutathione peroxidase) antioxidant indices and activity of acetylcholinesterase enzyme were evaluated in brain tissues of the rats. Furthermore, the expression of genes linked to oxidative stress (HO-1, Nrf2), pro-inflammatory (NF-KB, IL-8, TNF-α) anti-inflammatory (IL-10) and brain-specific (GFAP, ENO-2) genes were also determined. The results indicated that DPDSe caused a notable reduction in the high levels of thiobarbituric acid reactive substances and conjugated diene observed in the brain of DEP-administered rats. DPDSe also reversed the observed reduction in catalase, superoxide dismutase and glutathione peroxidase enzyme activities in the brain of DEP-administered rats. Lastly, the downregulation of genes associated with redox homeostasis, anti-inflammatory and brain-specific genes and upregulation of pro-inflammatory genes observed in the DEP-treated groups were ameliorated by DPDSe. The immediate restoration of altered biochemical conditions and molecular expression in the brain of DEP-treated rats by DPDSe further validates its use as a promising therapeutic candidate for restoring neurotoxicity linked with DEP-induced oxidative stress.

Licochalcone B, a Natural Autophagic Agent for Alleviating Oxidative Stress-Induced Cell Death in Neuronal Cells and Caenorhabditis elegans Models

Autophagy has been implicated in the regulation of neuroinflammation and neurodegenerative disorders. Licochalcone B (LCB), a chalcone from Glycyrrhiza inflata, has been reported to have anti-cancer, anti-oxidation and anti-β–amyloid fibrillation effects; however, its effect in autophagy remain un-investigated. In the current study, the potential neuro-protective role of LCB in terms of its anti-oxidative, anti-apoptotic, and autophagic properties upon oxidative stress-induced damage in neuronal cells was investigated. With the production of reactive oxygen species (ROS) as a hallmark of neuroinflammation and neurodegeneration, hydrogen peroxide (H2O2) was adopted to stimulate ROS-induced cell apoptosis in PC-12 cells. Our findings revealed that LCB reduced cell cytotoxicity and apoptosis of PC-12 cells upon H2O2-stimulation. Furthermore, LCB increased the level of the apoptosis-associated proteins caspase-3 and cleaved caspase-3 in H2O2-induced cells. LCB effectively attenuated the level of oxidative stress markers such as MDA, SOD, and ROS in H2O2-induced cells. Most importantly, LCB was confirmed to possess its anti-apoptotic effects in H2O2-induced cells through the induction of ATG7-dependent autophagy and the SIRT1/AMPK signaling pathway. As a novel autophagic inducer, LCB increased the level of autophagy-related proteins LC3–II and decreased p62 in both neuronal cells and Caenorhabditis elegans (C. elegans) models. These results suggested that LCB has potential neuroprotective effects on oxidative damage models via multiple protective pharmacological mechanisms.

Microglia-mediated neuroinflammation and neuroplasticity after stroke

Stroke remains a major cause of long-term disability and mortality worldwide. The immune system plays an important role in determining the condition of the brain following stroke. As the resident innate immune cells of the central nervous system, microglia are the primary responders in a defense network covering the entire brain parenchyma, and exert various functions depending on dynamic communications with neurons, astrocytes, and other neighboring cells under both physiological or pathological conditions. Microglia activation and polarization is crucial for brain damage and repair following ischemic stroke, and is considered a double-edged sword for neurological recovery. Microglia can exist in pro-inflammatory states and promote secondary brain damage, but they can also secrete anti-inflammatory cytokines and neurotrophic factors and facilitate recovery following stroke. In this review, we focus on the role and mechanisms of microglia-mediated neuroinflammation and neuroplasticity after ischemia and relevant potential microglia-based interventions for stroke therapy.

Dl-3-n-Butylphthalide Improves Neuroinflammation in Mice with Repeated Cerebral Ischemia-Reperfusion Injury through the Nrf2-Mediated Antioxidant Response and TLR4/MyD88/NF-κB Signaling Pathway

Increasing evidence shows that oxidative stress and neuroinflammation play a crucial role in the pathology of vascular dementia (VD). Previously, we have found that Dl-3-n-butylphthalide (NBP) has antioxidant and anti-inflammatory activities in VD, whereas little is known about its mechanism. Therefore, the objective of our study was to explore the contribution of nuclear factor erythroid-2 related factor 2 (Nrf2) to NBP and its effects on anti-inflammatory activity in a mouse model of VD. Our studies revealed that NBP could effectively mitigate cognitive deficits, neuron cell loss, and apoptosis in mice subjected to repeated cerebral ischemia-reperfusion (RCIR). Additionally, NBP promoted both the expression of brain-derived neurotrophic factor (BDNF) and tyrosine receptor kinase B (TrkB) in hippocampus tissue. NBP exhibited antioxidant activity by enhancing Nrf2 nuclear accumulation, increasing HO-1 and NQO1 expression, enhancing SOD activity, and inhibiting RCIR-induced MDA and 8-iso PGF2α generation in the hippocampus. NBP also significantly inhibited TLR4/MyD88/NF-κB signaling and suppressed microglial proliferation and the production of proinflammatory mediators in RCIR mice. Importantly, the antioxidant, antineuroinflammatory, and neuroprotective effects of NBP above were abolished by Nrf2 knockout. Collectively, these results indicated the effects of NBP on neuroinflammation were strongly associated with the Nrf2 pathway. Modulation of TLR4/MyD88/NF-κB pathway by Nrf2 is involved in the neuroprotective effect of NBP against VD induced by RCIR injury. With antioxidant and anti-neuroinflammatory properties, NBP could be a promising drug candidate for the prevention and/or treatment of VD and other neuroinflammatory disorders.

Licochalcone E inhibits trxR1 expression, alters Nrf2/STAT6 signal, and induces antitumor effects in vitro against human SH-SY5Y and SK-N-BE(2) neuroblastoma cells

Neuroblastoma (NB) is the most common solid tumor of the sympathetic nervous system (SNS) arising in childhood less than 15 years age. Licochalcone (Lic) is known to show inhibitory effects in cancer growth, and there has evidence suggested that Lic A inhibits hypoxic induced NB SK-N-SH cell proliferation. However, it is unclear whether LicE exerts similar effects in NB and the associated molecular mechanism of Lic in neuroblastoma is still unclear. In the current study, we found that LicE at the concentration 2, 4 and 6 μM all induced a profound reduction in cell viability, colony formation and cell proliferation. Next, LicE treatment effectively promoted cell apoptosis, inhibited cell migration and invasion. LicE significantly suppressed trxR1 expression, activated Nrf2 expression and inhibited STAT6 expression in SH-SY5Y and SK-N-BE(2) NB cells. We further identified that trxR1, STAT6 overexpression or Nrf2 silence reversed the antitumor effects of LicE in human SH-SY5Y and SK-N-BE(2) NB cells. Finally, LicE treatment significantly inhibited tumor growth in nude mice carrying a SK-N-SH cell xenograft. These results provide new insights into the effects and highlighting a novel mechanism of LicE through regulating trxR1/Nrf2/STAT6 signal pathway in NB.

The Age-Related Macular Degeneration (AMD)-Preventing Mechanism of Natural Products

Age-related macular degeneration (AMD) is related to central visual loss in elderly people and, based on the increment in the percentage of the aging population, the number of people suffering from AMD could increase. AMD is initiated by retinal pigment epithelium (RPE) cell death, finally leading to neovascularization in the macula lutea. AMD is an uncurable disease, but the symptom can be suppressed. The current therapy of AMD can be classified into four types: device-based treatment, anti-inflammatory drug treatment, anti-vascular endothelial growth factor treatment, and natural product treatment. All these therapies have adverse effects, however early AMD therapy used with products has several advantages, as it can prevent RPE cell apoptosis in safe doses. Cell death (apoptosis) is caused by various factors, such as oxidative stress, inflammation, carbonyl stress, and a deficiency in essential components for cells, and RPE cell death is related to oxidative stress, inflammation, and carbonyl stress. Some natural products have anti-oxidative effects, anti-inflammation effects, and/or anti-carbonylation effects. The AMD preventive mechanism of natural products varies, with some natural products activating one or more anti-apoptotic pathways, such as the Nrf2/HO-1 anti-oxidative pathway, the anti-inflammasome pathway, and the anti-carbonyl pathway. As AMD drug candidates from natural products effectively inhibit RPE cell death, they have the potential to be developed as drugs for preventing early (dry) AMD.

Natural Products as Novel Neuroprotective Agents; Computational Predictions of the Molecular Targets, ADME Properties, and Safety Profile

Neurodegenerative diseases (NDs) are one of the most challenging public health issues. Despite tremendous advances in our understanding of NDs, little progress has been made in establishing effective treatments. Natural products may have enormous potential in preventing and treating NDs by targeting microglia; yet, there have been several clinical concerns about their usage, primarily due to a lack of scientific evidence for their efficacy, molecular targets, physicochemical properties, and safety. To solve this problem, the secondary bioactive metabolites derived from neuroprotective medicinal plants were identified and selected for computational predictions for anti-inflammatory activity, possible molecular targets, physicochemical properties, and safety evaluation using PASS online, Molinspiration, SwissADME, and ProTox-II, respectively. Most of the phytochemicals were active as anti-inflammatory agents as predicted using the PASS online webserver. Moreover, the molecular target predictions for some phytochemicals were similar to the reported experimental targets. Moreover, the phytochemicals that did not violate important physicochemical properties, including blood-brain barrier penetration, GI absorption, molecular weight, and lipophilicity, were selected for further safety evaluation. After screening 54 neuroprotective phytochemicals, our findings suggest that Aromatic-turmerone, Apocynin, and Matrine are the most promising compounds that could be considered when designing novel neuroprotective agents to treat neurodegenerative diseases via modulating microglial polarization.

Quercetin-biapigenin nanoparticles are effective to penetrate the blood-brain barrier

Search for efficient therapeutic agents for central nervous system (CNS) disorders has been extensive. Nevertheless, blood-brain barrier (BBB) is an obstacle that prevents the majority of compounds to act in these diseases. It is, thus, of extreme relevance the BBB overcome, in order to deliver a drugs therapeutically active concentration to the action site, with the least losses and interaction with other organs, tissues, or cells. The present study aimed to investigate the potential protective effect of quercetin-biapigenin encapsulated into poly(Ɛ-polycaprolactone) (PCL) nanoparticles against t-BOOH-induced oxidative stress in several brain cell lines, as well as evaluate the permeability of those active molecules through an in vitro BBB model. The three cell lines under study (BV-2, hcmec/D3, and U87) presented different reactions to t-BOOH. In general, quercetin-biapigenin PCL-loaded nanoparticles were able to minimize compound toxicity they convey, regardless the cell line. Quercetin-biapigenin PCL-loaded nanoparticles (Papp of approximately 80 × 10-6 cm/s) revealed to be more permeable than free compounds (Papp of approximately 50 × 10-6 cm/s). As of our knowledge, this is the first report of quercetin-biapigenin PCL-loaded nanoparticle activity in brain cells. It is also the first determining its permeability through BBB, as an effective nanocarrier for brain delivery.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Activated Phosphoinositide 3-Kinase/Akt/Mammalian Target of Rapamycin Signal and Suppressed Autophagy Participate in Protection Offered by Licochalcone A Against Amyloid-β Peptide Fragment 25-35-Induced Injury in SH-SY5Y Cells

OBJECTIVE

To assess effect of licochalcone A (LicA) on amyloid-β (Aβ) peptide fragment 25-35-induced nerve injury and reveal the potential molecular mechanisms involved.

METHODS

Viability of SH-SY5Y cells was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay after treatment with Aβ25-35 and/or LicA, following which apoptosis was detected by flow cytometry and Hoechst staining. Then, reactive oxygen species, glutathione, and superoxide dismutase were measured with flow cytometry and spectrophotometry. The ultrastructure of mitochondria was examined by transmission electron microscopy, and the biomarker proteins of autophagy, apoptosis, and phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway were measured with Western blotting.

RESULTS

LicA improved cell viability and decreased lactate dehydrogenase leakage remarkably in Aβ25-35-induced injury in SH-SY5Y cells. After treatment with LicA, reactive oxygen species, glutathione, and superoxide dismutase levels in cells all were significantly decreased, which indicated that LicA has an antioxidative effect on Aβ25-35-induced oxidative injury. LicA could also significantly reduce Aβ25-35-induced autophagy in SH-SY5Y cells. In the cells injured by Aβ25-35, LicA prevented the transformation from light chain protein 3-I to light chain protein 3-II and reduced the levels of proteins GRP78, GRP94, CHOP, and Bax, but increased the levels of antiapoptotic protein and phosphorylation of PI3K, Akt, and mTOR. These effects of LicA were restored or suppressed by mTOR inhibitor rapamycin or PI3K inhibitor LY294002.

CONCLUSIONS

LicA protects SH-SY5Y cells against Aβ25-35-induced injury, wherein suppressed autophagy and activated PI3K/Akt/mTOR signaling pathway are involved, and mTOR-dependent autophagy at least plays some role.

Licochalcone B attenuates neuronal injury through anti-oxidant effect and enhancement of Nrf2 pathway in MCAO rat model of stroke

BACKGROUND

Investigating anti-oxidant therapies that lead to the diminution of oxidative injury is priority in clinical. We herein aimed to explore whether and how Licochalcone B (Lico B) act as an anti-oxidant in the stroke model.

METHODS

Middle cerebral artery occlusion (MCAO) was constructed as stroke model and exposed to various doses of Lico B. Behavioral tests and neurological behavior status were detected for neurological function examination. Histological staining was used for evaluating cerebral injury, and neuronal apoptosis or damage. Levels of oxidative stress and inflammation were also assessed by biochemical analysis and expression analysis. Nrf2 knockdown induced by lentiviral vector was used for the research on mechanism.

RESULTS

Lico B had improvement effects on cerebral infarction size, memory impairments, and neurological deficits after MCAO. Histological evaluation also revealed the amelioration of neuronal injury and apoptosis by Lico B, along with down-regulation of apoptosis-related proteins. Additionally, Lico B rescued the down-regulation of BDNF and NGF after MCAO. Moreover, Lico B suppressed the oxidative stress and inflammation, manifesting as the enhancement of SOD, GSH and IL-4, but the decline of MDA, iNOS, and TNF-α. Finally, Nrf2 knockdown reversed the Lico B-caused improvement in neuronal injury, apoptosis and oxidative stress levels.

CONCLUSIONS

The present study revealed the neuroprotective effects of Lico B in MCAO rats. Importantly, we proposed a potential mechanism that Lico B activated the Nrf2 pathway, thereby acting as anti-oxidant to attenuate neuronal injury and apoptosis after stroke. The proposed mechanism provided an encouraging possibility for anti-oxidant therapy of stroke.

Activation of Nrf2 signaling pathway by natural and synthetic chalcones: a therapeutic road map for oxidative stress

Introduction:Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway plays a key role in diverse gene expressions responsible for protection against oxidative stress and xenobiotics. Chalcones with a common chemical scaffold of 1,3-diaryl-2- propen-1-one, are abundantly present in nature with a wide variety of pharmacological properties. This review will discuss the interactions of natural and synthetic chalcones with Nrf2 signaling.Areas covered:Chalcones are reportedly found to activate Nrf2 signaling pathway, expression of Nrf2-regulated antioxidant genes, induce cytoprotective proteins and upregulate multidrug resistance-associated proteins. Chalcones being soft electrophiles are less prone to hostile off-target effects and unlikely to induce carcinogenicity and mutagenicity. Furthermore, their low toxicity, structural diversity, feasibility in structural reorganization and the presence of α,β-unsaturated carbonyl group which makes them suitable drug candidates targeting Nrf2-dependent diseases.Expert opinion:Nrf2-Keap1 signaling pathway plays a central role in redox signaling. However, available therapeutic agents for Nrf2 activation have limited practical applications due to their associated risks, relatively low efficacy and bioavailability. The designing and fabrication of new chemical entities with chalcone scaffold-based Michael acceptor mechanism should be aimed as potential therapeutic Nrf2 activators to target oxidative stress and inflammation-mediated diseases such as atherosclerosis, Parkinson's disease and many more.

The Nrf2 pathway in psychiatric disorders: pathophysiological role and potential targeting

Introduction: All psychiatric disorders exhibit excitotoxicity, mitochondrial dysfunction, inflammation, oxidative stress, and neural damage as their common characteristic. The endogenous nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway is implicated in the defense mechanism against oxidative stress and has a significant role in psychiatric disorders.Areas covered: We explore the role of Nrf2 pathway and its modulators in psychiatric disorders. The literature was searched utilizing various databases such as Embase, Medline, Web of Science, Pub-Med, and Google Scholar from 2010 to 2020. The search included research articles, clinical reports, systematic reviews, and meta-analyses.Expert opinion: Environmental factors and genetic predisposition can be a trigger for the development of psychiatric disorders. Nrf2 downregulates certain inflammatory pathways and upregulates various antioxidant enzymes to maintain a balance. However, its intricate balance with NF-Kβ (Nuclear factor kappa light chain enhancer of activated B cells) and its crosstalk with the transcription factor Nrf2 is critical in severe oxidative stress. Several Nrf2 modulators are now in clinical trials and can help reduce oxidative stress and neuroinflammation. There are immense potential opportunities for these modulators to become a novel therapeutic option.

The anti-diabetic activity of licorice, a widely used Chinese herb

ETHNOPHARMACOLOGICAL RELEVANCE

A great deal of valuable experience has been accumulated in the traditional Chinese medicine (TCM) system for the treatment of "Xiaoke" disease which is known as diabetes mellitus now. As the most-commonly used Chinese herb, licorice has been used in TCM for more than two thousand years. It is often used in combination with other herbs to treat metabolic disorders, especially diabetes mellitus.

AIM OF THE STUDY

To summarize the characteristics, mechanisms, and clinical use of licorice and its active components for treating diabetes mellitus.

METHODS

PubMed, Web of Science, Research Gate, Science Direct, Google Scholar, and Academic Journals were used as information sources by the inclusion of the search terms 'diabetes', 'licorice', 'licorice extracts', 'flavonoids', 'triterpenoids', and their combinations, mainly from 2005 to 2019.

RESULTS

Licorice extracts, five flavonoids and three triterpenoids isolated from licorice possess great antidiabetic activities in vivo and in vitro. This was done by several mechanisms such as increasing the appetency and sensitivity of insulin receptor site to insulin, enhancing the use of glucose in different tissues and organs, clearing away the free radicals and resist peroxidation, correcting the metabolic disorder of lipid and protein, and improving microcirculation in the body. Multiple signaling pathways, including the PI3K/Akt, AMPK, AGE-RAGE, MAPK, NF-кB, and NLRP3 signaling pathways, are targets of the licorice compounds.

CONCLUSION

Licorice and its metabolites have a great therapeutic potential for the treatment of diabetes mellitus. However, a better understanding of their pharmacological mechanisms is needed for evaluating its efficacy and safety.

Design and development of innovative microparticulate/nanoparticulate inhalable dry powders of a novel synthetic trifluorinated chalcone derivative and Nrf2 agonist

Chalcone derivatives are shown to possess excellent anti-inflammatory and anti-oxidant properties which are of great interest in treating respiratory diseases such as acute lung injury (ALI), acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis (PF). This study successfully designed and developed dry powder inhaler (DPI) formulations of TMC (2-trifluoromethyl-2'-methoxychalone), a new synthetic trifluorinated chalcone and Nrf2 agonist, for targeted pulmonary inhalation aerosol drug delivery. An advanced co-spray drying particle engineering technique was used to design and produce microparticulate/nanoparticulate formulations of TMC with a suitable excipient (mannitol) as inhalable particles with tailored particle properties for inhalation. Raw TMC and co-spray dried TMC formulations were comprehensively characterized for the first time using scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy, thermal analysis, X-ray powder diffraction (XRPD), and molecular fingerprinting as dry powders by ATR-FTIR spectroscopy and Raman spectroscopy. Further, biocompatibility and suitability of formulations were tested with in vitro cellular transepithelial electrical resistance (TEER) in air-interface culture (AIC) using a human pulmonary airway cell line. The ability of these TMC formulations to perform as aerosolized dry powders was systematically evaluated by design of experiments (DOEs) using three different FDA-approved human inhaler devices followed by interaction parameter analyses. Multiple spray drying pump rates (25%, 75%, and 100%) successfully produced co-spray dried TMC:mannitol powders. Raw TMC exhibited a first-order phase transition temperature at 58.15 ± 0.38 °C. Furthermore, the results demonstrate that these innovative TMC dry powder particles are suitable for targeted delivery to the airways by inhalation.

Neurotrophic, anti-neuroinflammatory, and redox balance mechanisms of chalcones

The passage of time that evoke aging; the tilted redox balance that contribute oxidative entropy; the polarization of microglia cells that produce inflammatory phenotype; all represent the intricacies of CNS-dependent disease progression. Neurological diseases that result from CNS injury raise social concerns and the available therapeutic strategies are frustrated by low efficacy, high toxicity, and multiple side effects. However, emergent studies have shown the neuroprotective role of natural compounds - including chalcones - with high efficacy in the protection of CNS structures. These compounds reportedly demonstrate neurotrophic mechanism through the upregulation of neurotrophic factors, anti-apoptotic Bcl-2, and downregulation of Bax protein; anti-neuroinflammatory mechanism via the inhibition of neuroinflammatory pathways, attenuated secretion of pro-inflammatory cytokines, prevention of blood brain barrier (BBB) disruption, and protection against nerve senescence; antioxidant mechanism through the upregulation of Nrf2 activities, inhibition of Keap1, synthesis of antioxidant enzymes, and maintenance of high antioxidant/oxidant ratio. All these mechanisms represent chalcones' neuroprotective mechanisms. In this review, we highlight different pathways involved in CNS-related diseases and elucidate various mechanisms by which chalcones can perturb these shunts as a potential therapeutic modality.

A novel compound DBZ ameliorates neuroinflammation in LPS-stimulated microglia and ischemic stroke rats: Role of Akt(Ser473)/GSK3β(Ser9)-mediated Nrf2 activation

Microglia-mediated neuroinflammation plays a crucial role in the pathophysiological process of multiple neurological disorders such as ischemic stroke, yet lacks effective therapeutic agents. Previously, we discovered one novel synthetic compound, tanshinol borneol ester (DBZ), possesses anti-inflammatory and anti-atherosclerotic activities, whereas little is known about its effects in CNS. Therefore, the present study aims to explore the effects and potential mechanism of DBZ on neuroinflammation and microglial function. Our studies revealed that DBZ significantly inhibited NF-κB activity, suppressed the production of pro-inflammatory mediators meanwhile promoted M2 mediators expression in LPS-stimulated BV2 cells and mouse primary microglia cells. DBZ also exhibited antioxidant activity by enhancing Nrf2 nuclear accumulation and transcriptional activity, increasing HO-1 and NQO1 expression, and inhibiting LPS-induced ROS generation in BV2 cells. Importantly, the anti-neuroinflammatory and antioxidant effects of DBZ above were reversed by Nrf2 knockdown. Additionally, DBZ ameliorated sickness behaviors of neuroinflammatory mice induced by systemic LPS administration, and significantly reduced infract volume, improved sensorimotor and cognitive function in rats subjected to transient middle cerebral artery occlusion (tMCAO); besides, DBZ restored microglia morphological alterations and shifted the M1/M2 polarization in both murine models. Mechanistically, DBZ-induced Nrf2 nuclear accumulation and antioxidant enzymes expression were accompanied by increased level of p-Akt(Ser473) (activation) and p-GSK3β(Ser9) (inactivation), and decreased nuclear level of Fyn both in vitro and in vivo. Pharmacologically inhibiting PI3K or activating GSK3β markedly increased nuclear density of Fyn in microglia cells, which blocked the promoting effect of DBZ on Nrf2 nuclear accumulation and its antioxidant and anti-neuroinflammatory activities. Collectively, these results indicated the effects of DBZ on microglia-mediated neuroinflammation were strongly associated with the nuclear accumulation and stabilization of Nrf2 via the Akt(Ser473)/GSK3β(Ser9)/Fyn pathway. With anti-neuroinflammatory and antioxidant properties, DBZ could be a promising new drug candidate for prevention and/or treatment of cerebral ischemia and other neuroinflammatory disorders.

A Comprehensive Review for Phytochemical, Pharmacological, and Biosynthesis Studies on Glycyrrhiza spp

Licorice is extensively applied in food as well as herbal medicine across the world, possessing a substantial share in the global market. It has made great progress in chemical and pharmacological research in recent years. Currently, Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat., and Glycyrrhiza glabra L. were officially used as Gan-Cao according to the Chinese Pharmacopoeia. Accumulating evidence demonstrated three varieties of licorice have their own special compounds except for two quality markers set by Pharmacopoeia, providing great possibility for better understanding their characteristics, evaluating quality of each species and studying biosynthesis mechanisms of species-specific compounds. As a special "guide drug" in clinic, licorice plays an important role in Chinese herbal formulas. The interaction between licorice with other ingredients and their metabolism in vivo should also be taken into consideration. In addition, draft genome annotation, and success of the final step of glycyrrhizin biosynthesis have paved the way for biosynthesis of other active constituents in licorice, a promising beginning of solving source shortage. Accordingly, we comprehensively explored the nearly 400 chemical compounds found in the three varieties of licorice so far, systematically excavated various pharmacological activities, including metabolism via CYP450 system in vivo, and introduced the complete biosynthesis pathway of glycyrrhizin in licorice. The review will facilitate the further research toward this herbal medicine.

7-methoxyflavanone alleviates neuroinflammation in lipopolysaccharide-stimulated microglial cells by inhibiting TLR4/MyD88/MAPK signalling and activating the Nrf2/NQO-1 pathway

OBJECTIVES

Neuroprotective potential of 7-methoxyflavanone (7MF) and its underlying mechanism was investigated.

METHODS

Inhibitory effects of 7MF on microglial activation and neuroinflammation were evaluated by employment of lipopolysaccharide (LPS)-induced BV2 microglial cells. Changes in expression of genes and proteins of interest were investigated by RT-qPCR analysis and Western blot analysis. Inhibitory effects of 7MF on microglial overactivation were verified in LPS-treated C57BL/6J mice using ionized calcium-binding adaptor molecule-1 (Iba1) in the brain and interleukin-6 (IL-6) in serum as indicators.

KEY FINDINGS

In BV2 cells, pretreatment with 7MF antagonized LPS-induced production of inflammatory factors IL-6, tumour necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1). Mechanistic studies revealed reduced expression of Toll-like receptor 4 (TLR4), myeloid differentiation factor-88 (MyD88), phosphorylated forms of c-Jun N-terminal kinase (p-JNK) and extracellular signal-regulated kinases 1/2 (p-ERK) but increased nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and cellular expression of NAD(P)H quinone dehydrogenase-1 (NQO-1) by 7MF. In LPS-treated mice, pretreatment with 7MF reduced the brain level of Iba1 and serum level of IL-6.

CONCLUSIONS

7-methoxyflavanone inhibited LPS-stimulated TLR4/MyD88/MAPK signalling and activated Nrf2-mediated transcription of antioxidant protein NQO-1, showing antineuroinflammatory effect, so it is a potential neuroprotective agent.

Reasonably activating Nrf2: A long-term, effective and controllable strategy for neurodegenerative diseases

Neurodegenerative diseases are a variety of debilitating and fatal disorder in central nervous system (CNS). Besides targeting neuronal activity by influencing neurotransmitters or their corresponding receptors, modulating the underlying processes that lead to cell death, such as oxidative stress and mitochondrial dysfunction, should also be emphasized as an assistant strategy for neurodegeneration therapy. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) has been closely verified to be related to anti-inflammation and oxidative stress, rationally regulating its belonging pathway and activating Nrf2 is emphasized to be a potential treatment approach. There have existed multiple Nrf2 activators with different mechanisms and diverse structures, but those applied for neuro-disorders are still limited. On the basis of research arrangement and compound summary, we put forward the limitations of existing Nrf2 activators for neurodegenerative diseases and their future developing directions in enhancing the blood-brain barrier permeability to make Nrf2 activators function in CNS and designing Nrf2-based multi-target-directed ligands to affect multiple nodes in pathology of neurodegenerative diseases.

Antioxidant, Anti-inflammatory, and Neuroprotective Effects of Novel Vinyl Sulfonate Compounds as Nrf2 Activator

The main pathway responsible for cellular regulation against oxidative stress is nuclear factor E2-related factor-2 (Nrf2) signaling. We previously synthesized and reported a novel vinyl sulfone (1) as an Nrf2 activator with therapeutic potential for Parkinson's disease (PD). In this study, we changed the vinyl sulfone to vinyl sulfonamide or vinyl sulfonate to improve Nrf2 activating efficacy. We observed that the introduction of vinyl sulfonamide led to a reduction of the effects on Nrf2 activation, whereas vinyl sulfonate compounds exhibited superior activity compared to the vinyl sulfone compounds. Among the vinyl sulfonates, 3c exhibited 6.9- and 83.5-fold higher effects on Nrf2 activation than the corresponding vinyl sulfone (1) and vinyl sulfonamide (2c), respectively. Compound 3c was confirmed to induce expression of the Nrf2-dependent antioxidant enzymes at the protein level in cells. In addition, 3c mitigated PD-associated behavioral deficits by protecting DAergic neurons in the MPTP-induced mouse model of PD.

A metabolic perspective of late onset Alzheimer's disease

After decades of research, the molecular neuropathology of Alzheimer's disease (AD) is still one of the hot topics in biomedical sciences. Some studies suggest that soluble amyloid β (Aβ) oligomers act as causative agents in the development of AD and could be initiators of its complex neurodegenerative cascade. On the other hand, there is also evidence pointing to Aβ oligomers as mere aggravators, with an arguable role in the origin of the disease. In this line of research, the relative contribution of soluble Aβ oligomers to neuronal damage associated with metabolic disorders such as Type 2 Diabetes Mellitus (T2DM) and obesity is being actively investigated. Some authors have proposed the endoplasmic reticulum (ER) stress and the induction of the unfolded protein response (UPR) as important mechanisms leading to an increase in Aβ production and the activation of neuroinflammatory processes. Following this line of thought, these mechanisms could also cause cognitive impairment. The present review summarizes the current understanding on the neuropathological role of Aβ associated with metabolic alterations induced by an obesogenic high fat diet (HFD) intake. It is believed that the combination of these two elements has a synergic effect, leading to the impairement of ER and mitochondrial functions, glial reactivity status alteration and inhibition of insulin receptor (IR) signalling. All these metabolic alterations would favour neuronal malfunction and, eventually, neuronal death by apoptosis, hence causing cognitive impairment and laying the foundations for late-onset AD (LOAD). Moreover, since drugs enhancing the activation of cerebral insulin pathway can constitute a suitable strategy for the prevention of AD, we also discuss the scope of therapeutic approaches such as intranasal administration of insulin in clinical trials with AD patients.

Add-On Effects of Chinese Herbal Medicine for Post-Stroke Spasticity: A Systematic Review and Meta-Analysis

Background: Treatment for post-stroke spasticity (PSS) remains a major challenge in clinical practice. Chinese herbal medicine (CHM) is often administered to assist in routine care (RC) in the treatment of PSS, with increasing numbers of clinical research and preclinical studies suggesting that it has potential benefits. Therefore, we conducted a systematic review and meta-analysis to evaluate the add-on effects and safety of CHM for PSS. Methods: Five English and four Chinese databases were searched from their respective inception to 28 February 2018. We included randomized controlled trials that evaluated the add-on effects of CHM for PSS, based on changes in the scores of the (Modified) Ashworth Scale (AS or MAS), Fugl-Meyer Assessment of Sensorimotor Recovery (FMA), and Barthel Index (BI). Results: Thirty-five trials involving 2,457 patients were included. For upper-limb AS or MAS, the estimated add-on effects of CHM to RC were significantly better when using oral (SMD -1.79, 95% CI: -3.00 to -0.57) or topical CHM (SMD -1.06, 95% CI: -1.40 to -0.72). For lower-limb AS or MAS, significant add-on benefits to RC were also detected (SMD -1.01, 95% CI: -1.43 to -0.59 and SMD -1.16, 95% CI: -1.83 to -0.49) using oral and topical CHM, respectively. For FMA and BI, better results were detected when adding CHM to RC, except for the subgroup of oral CHM for upper-limb FMA. Ten of the 35 included studies reported safety information, with two of them mentioning two mild adverse events. Conclusions: Noting the quality concerns of the included trials, this review suggests that CHM appears to be a well-tolerated therapy for patients with PSS, and the potential add-on effects of CHM in reducing spasticity and improving the daily activities of patients with PSS require further rigorous assessment.

Biological Effects of Licochalcones

Medicinal plants and their natural bioactive molecules, are evaluated as the foundation for health preservation and care of humanity. The licorice root, known as "Radix Glycyrrhizae", is a perennial plant that comes from Mediterranean countries, central to southern Russia, Asia, Turkey, Iraq and Iran. The licorice root has been used in traditional Chinese medicines for centuries and has been defined as "the progenitor of herbs". The name 'Licorice' is derived from the ancient Greek word Glukurrhiza, meaning 'sweet root'. It consists of approximately 30 species, however, the most common ones consist of Glycyrrhiza glabra L., Glycyrrhiza uralensis Fisch and Glycyrrhiza Inflata. In addition, the licorice root contains chalcones, which are a part of an important class of natural products and are precursors of flavonoids. Chemically, chalcones are composed of two aromatic rings associated with α, β-unsaturated α-carbon ketone, representing the prima nucleus of the structure. They have been classified, according to chemical structures, in Licochalcone A, B, C, D, E, F and G. This review aims to highlight all the in vitro and in vivo studies that have been conducted on the licochalcones, extracted from Glycyrrhiza species. The main effects are as follows: anti-inflammatory, antioxidant, anticancer, antimicrobial, antiviral, antiallergic, antidiabetic, hepatotoxic and osteogenic. It is important to implement the introduction of biologically active natural molecules from the bench (research) to the bedside (clinical practice). However, in the future, it is required to conduct additional studies to validate these biological effects.

Natural products as a potential modulator of microglial polarization in neurodegenerative diseases

Neurodegenerative diseases (NDs) are characterized by the progressive loss of structure and function of neurons most common in elderly population, mainly including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). Neuroinflammation caused by microglia as the resident macrophages of the central nervous system (CNS) plays a contributory role in the onset and progression of NDs. Activated microglia, as in macrophages, to be heterogeneous, can polarize into M1 (pro-inflammatory) and M2 (anti-inflammatory) functional phenotypes. The former elaborate pro-inflammatory mediators promoting neuroinflammation and neuronal damage. In contrast, the latter generate anti-inflammatory mediators and neurotrophins that inhibit neuroinflammation and promote neuronal healing. Consistently, the regulation of microglial polarization from M1 to M2 phenotype appears as an outstanding therapeutic and preventive approach for NDs treatment. Although non-steroidal anti-inflammatory drugs (NSAIDs) currently used to alleviate M1 microglia-associated neuroinflammation responsible for the development of NDs, these drugs have different degrees of adverse effects and limited efficacy. As the advantages of novel structure, multi-target, high efficiency and low toxicity, natural products as the modulators of microglial polarization have attracted considerable concerns in the therapeutic areas of NDs. In this review, we mainly summarized the therapeutic potential of natural products and their various molecular mechanisms for NDs treatment through modulating microglial polarization. The aim of the current review is expected to be useful to develop innovative modulators of microglial polarization from natural products for the amelioration and treatment of NDs.

Sitagliptin improves renal function in diabetic nephropathy in male Sprague Dawley rats through upregulating heme oxygenase-1 expression

PURPOSE

Oxidative stress is an important mechanism for diabetic nephropathy. Studies showed that hemo oxygenase-1 (HO-1) expression in renal tissue of patients with diabetic nephropathy has upregulated, while the HO-1 can protect the body through anti-oxidative stress. The study aimed to preliminarily explore the molecular mechanism by observing the effect of Sitagliptin on HO-1 expression in renal tissue of rats with diabetic nephropathy.

METHODS

The diabetic nephropathy rat model was established by STZ injection followed by intraperitoneal injection of sitagliptin with different concentrations. The mRNA expressions of HO-1 were detected by real-time PCR and Western blot and HO-1 enzyme activity change was detected by colorimetry. Human renal mesangial cell (HRMC) were cultured in vitro with high glucose concentration (30 μmol/L), phosphatidylinositol-3-kinase (PI3K) level and nuclear factor erythroid-2-related factor (Nrf2) content in cytoplasm and cell nucleus were observed before and after treatment with sitagliptin, as well as the action of in meditating HO-1 expression.

RESULTS

HO-1 mRNA, protein level, and HO-1 enzyme activity in renal tissue of rats with diabetic nephropathy were significantly increased after treatment with sitagliptin (P < 0.05). As comparison, the 24 h urinary microalbumin, creatinine, and boold urea nitrogen were all decreased after treatment of sitagliptin (P < 0.05). Similar results were observed after CoPP (an agonist of HO-1) treatment (P < 0.05). In contrast, ZnPP, an inhibitor of HO-1, significantly abrogated the inhibitory effect of sitagliptin (P < 0.05). Phosphorylation of PI3K and Nrf2 nuclear translocation under high-glucose concentration condition was induced by sitagliptin in HRMC. HO-1 expression was suppressed by pretreating HRMC with PI3K inhibitor or RNA interference.

CONCLUSIONS

Sitagliptin may induce HO-1 expression via activation of PI3K and Nrf2 in rats with diabetic nephropathy; HO-1 can improve the oxidative stress of diabetic nephropathy, eventually protect from diabetic nephropathy.

Chotosan ameliorates cognitive impairment and hippocampus neuronal loss in experimental vascular dementia via activating the Nrf2-mediated antioxidant pathway

Recent studies suggested that Chotosan has ameliorative effects on vascular dementia through antioxidative pathways. Nevertheless, no systematic pharmacological research was conducted to evaluate the contribution of nuclear factor-E2-related factor 2 (Nrf2), a crucial regulator of antioxidative system, on Chotosan-induced neuroprotection invascular dementia. The present study aimed to investigate the neuroprotective effect of Chotosan on vascular dementia and reveal the possible molecular mechanism involving Nrf2. We found that Chotosan treatment could ameliorate memory impairment and reduce neuron cell loss induced by common carotid artery occlusion surgery. Furthermore, Chotosan could significantly reverse reactive oxygen species production, neuronal apoptosis and microglia over-activation in hippocampus. In addition, Chotosan enhanced Nrf2 expression and its nuclear translocation as well as its downstream antioxidant protein expression, NAD(P)H/quinone oxidoreductase 1 and heme oxygenase-1. These findings suggest that Chotosan exert neuroprotection in an animal model of vascular dementia via activating Nrf2-mediated antioxidant pathway. Chotosan may serve as a potential candidate and promising Nrf2 activator for treating vascular dementia.

Heme Oxygenase 1 in the Nervous System: Does It Favor Neuronal Cell Survival or Induce Neurodegeneration?

Heme oxygenase 1 (HO-1) up-regulation is recognized as a pivotal mechanism of cell adaptation to stress. Under control of different transcription factors but with a prominent role played by Nrf2, HO-1 induction is crucial also in nervous system response to damage. However, several lines of evidence have highlighted that HO-1 expression is associated to neuronal damage and neurodegeneration especially in Alzheimer’s and Parkinson’s diseases. In this review, we summarize the current literature regarding the role of HO-1 in nervous system pointing out different molecular mechanisms possibly responsible for HO-1 up-regulation in nervous system homeostasis and neurodegeneration.

The Keap1/Nrf2-ARE Pathway as a Pharmacological Target for Chalcones

Chalcones have shown a broad spectrum of biological activities with clinical potential against various diseases. The biological activities are mainly attributed to the presence in the chalcones of the α,β-unsaturated carbonyl system, perceived as a potential Michael acceptor. Chalcones could activate the Kelch-like ECH-associated protein 1 (Keap1)/Nuclear factor erythroid 2-related factor 2 (Nrf2) pathway through a Michael addition reaction with the cysteines of Keap1, which acts as a redox sensor and negative regulator of Nrf2. This modification allows the dissociation of Nrf2 from the cytoplasmic complex with Keap1 and its nuclear translocation. At this level, Nrf2 binds to the antioxidant response element (ARE) and activates the expression of several detoxification, antioxidant and anti-inflammatory genes as well as genes involved in the clearance of damaged proteins. In this regard, the Keap1/Nrf2–ARE pathway is a new potential pharmacological target for the treatment of many chronic diseases. In this review we summarize the current progress in the study of Keap1/Nrf2–ARE pathway activation by natural and synthetic chalcones and their potential pharmacological applications. Among the pharmacological activities highlighted, anti-inflammatory activity was more evident than others, suggesting a multi-target Michael acceptor mechanism for the chalcones involving key regulators of the Nrf2 and nuclear factor- κB (NF-κB) pathways.

Herbal Prescriptions and Medicinal Herbs for Parkinson-Related Rigidity in Korean Medicine: Identification of Candidates Using Text Mining

BACKGROUND

Dongeuibogam (DongYiBaoGian), one of the most important books in Korean medicine, comprises a comprehensive summary of all traditional medicines of North-East Asia before the 17th century. This medicinal literature was mined to establish a list of candidate herbs to treat Parkinson-related rigidity.

METHODS

A systematic search for terms describing Parkinson-related rigidity and candidate prescriptions for the treatment of Parkinson-related rigidity in the Dongeuibogam was performed. A high-frequency medicinal herb combination group and candidates for the treatment of Parkinson-related rigidity were also selected through an analysis of medicinal herb combination frequencies. The existing literature pertaining to the potential effects of candidate herbs for Parkinson-related rigidity was reviewed.

RESULTS AND CONCLUSIONS

Ten medicinal herb candidates for the treatment of Parkinson-related rigidity were selected, and their respective precedent studies were analyzed.

Supplementation of lycopene attenuates lipopolysaccharide-induced amyloidogenesis and cognitive impairments via mediating neuroinflammation and oxidative stress

Neuroinflammation is documented to be the major culprit of Alzheimer's disease. Lycopene (LYC), a fat soluble carotenoid, exhibits neuroprotective function in several neurodegenerative disorders. However, the effects of LYC to countering systemic inflammation-induced amyloidogenesis and memory deficiency remain to be elucidated. In current study, 3-month-old male C57BL/6J mice were treated with 0.03% LYC (w/w, mixed into normal chow) for 5 weeks. The mice were then treated by intraperitoneal injection of LPS (0.25mg/kg) for 9 days. It was found that LYC inhibited LPS-induced memory loss by behavior tests including Y-maze test and Morris water test. Meanwhile, LYC prevented LPS-induced accumulation of Aβ, levels of amyloid precursor protein (APP), and suppressed neuronal β-secretase BACE1 and elevated the expressions of α-secretase ADAM10. Furthermore, LYC down-regulated the expression of IBA-1 (a marker of microglia activation), reduced the levels of inflammatory mediators and inhibited oxidative stress in LPS-treated mice. Moreover, LYC suppressed the phosphorylation of MAPKs, NFκB, and activated Nrf2 signaling pathways in LPS-treated BV2 microglial cells. Therefore, our study indicated that LYC could ameliorate LPS-induced neuroinflammation, oxidative stress, amyloidogenesis and cognitive impairments possibly through mediating MAPKs, NFκB and Nrf2 signaling pathways, indicating that LYC might be a nutritional preventive strategy in neuroinflammation-related diseases such as AD.

Neuroprotective effect of licochalcone A against oxygen-glucose deprivation/reperfusion in rat primary cortical neurons by attenuating oxidative stress injury and inflammatory response via the SIRT1/Nrf2 pathway

Perinatal hypoxic-ischemic encephalopathy (HIE) is a leading cause of neonatal death and neurological disability. Oxidative stress and neuroinflammation are typical pathogenic factors of HIE. Licochalcone A (LCA) exerts various biological properties, including anti-inflammatory and antioxidant activities. However, no data have been reported to elucidate the role of LCA in the development of HIE. In the present study, primary cultured rat cortical neurons were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro to simulate the in vivo situation of neonatal HIE. Interestingly, LCA significantly antagonized cell injury under OGD/R by increasing cell survival, inhibiting lactate dehydrogenase (LDH) release and cell apoptosis. Furthermore, treatment with LCA suppressed oxidative stress by decreasing reactive oxygen species (ROS) production and malondialdehyde (MDA) content, and increasing superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in primary rat cortical neurons after OGD/R. LCA stimulation also restrained OGD/R-triggered increase in pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production. Importantly, LCA treatment effectively counteracts OGD/R-mediated downregulation of silent information regulator 1 (SIRT1), nuclear factor erythroid2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1), and upregulation of nuclear factor kappa B p65 (NF-κB p65). Moreover, administration with SIRT1 inhibitor EX527 partly abolished LCA-induced neuroprotective effects on rat cortical neurons exposed to OGD/R. In conclusion, our study indicates that LCA exerts a neuroprotective effect against OGD/R-induced neuronal injury in rat primary cortical neurons, suggesting that LCA might act as a candidate therapeutic target drug used for HIE and related diseases.

Licochalcone E protects against carbon tetrachloride‑induced liver toxicity by activating peroxisome proliferator-activated receptor gamma

The present study aimed to investigate the hepatoprotective role of Licochalcone E (LCE) and its mechanism of action in a mouse model of carbon tetrachloride (CCl₄)-induced liver toxicity. Hepatotoxicity was induced in Kunming mice via an intraperitoneal injection (IP) of CCl₄, 10 ml/kg body weight, diluted with corn oil at a 1:500 ratio. LCE was administered once a day for 7 days (IP) as pretreatment at a dose of 5 mg/kg/day. The levels of C-reactive protein (CRP) and tumor necrosis factor (TNF)-α were analyzed to determine the inflammation status. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were analyzed using ELISA assays. Liver ultrastructure was observed via optical microscopy. The mRNA and protein expression levels of peroxisome proliferator-activated receptor (PPAR)γ, and nuclear factor (NF)-κB were assayed using quantitative polymerase chain reaction and western blot analysis, respectively. Pretreatment with LCE decreased levels of ALT, AST, CRP and TNF-α, and NF-κB expression in the experimental hepatotoxicity mice model induced by CCl₄. In addition, LCE increased the expression of PPARγ and normalized the hepatic histoarchitecture. However, the effects of LCE were reversed by cotreatment with the PPARγ inhibitor GW9662. The present study suggests that LCE may be used for the treatment of hepatotoxicity, and primarily exhibits its protective role through a PPARγ/NF-κB-mediated pathway.

Chalcone: A Privileged Structure in Medicinal Chemistry

Privileged structures have been widely used as an effective template in medicinal chemistry for drug discovery. Chalcone is a common simple scaffold found in many naturally occurring compounds. Many chalcone derivatives have also been prepared due to their convenient synthesis. These natural products and synthetic compounds have shown numerous interesting biological activities with clinical potentials against various diseases. This review aims to highlight the recent evidence of chalcone as a privileged scaffold in medicinal chemistry. Multiple aspects of chalcone will be summarized herein, including the isolation of novel chalcone derivatives, the development of new synthetic methodologies, the evaluation of their biological properties, and the exploration of the mechanisms of action as well as target identification. This review is expected to be a comprehensive, authoritative, and critical review of the chalcone template to the chemistry community.

Licochalcone-E induces caspase-dependent death of human pharyngeal squamous carcinoma cells through the extrinsic and intrinsic apoptotic signaling pathways

The aim of the present study was to investigate licochalcone-E (Lico-E)-induced apoptosis and the associated apoptotic signaling pathway in FaDu cells, a human pharyngeal squamous carcinoma cell line. Treatment with Lico-E exhibited significant cytotoxicity on FaDu cells in a concentration-dependent manner. The IC50 value of Lico-E in FaDu cells was ~50 µM. Treatment with Lico-E increased the number of dead FaDu cells. Furthermore, chromatin condensation, which is associated with apoptotic cell death, was observed in FaDu cells treated with Lico-E for 24 h. By contrast, Lico-E did not produce cytotoxicity or increase the number of dead cells when applied to human normal oral keratinocytes (hNOKs). Furthermore, chromatin condensation was not observed in hNOKs treated with Lico-E. Treatment with Lico-E increased the expression of Fas ligand and the cleaved form of caspase-8 in FaDu cells. Furthermore, treatment with Lico-E increased the expression of pro-apoptotic factors, including apoptosis regulator BAX, Bcl-2-associated agonist of cell death, apoptotic protease-activating factor 1, caspase-9 and tumor suppressor p53, while decreasing the expression of anti-apoptotic factors, including apoptosis regulator Bcl-2 and Bcl-2-like protein 1 in FaDu cells. The expression of cleaved caspases-3 and poly (ADP-ribose) polymerase was significantly upregulated following treatment with Lico-E in FaDu cells, while Lico-E-induced apoptotic FaDu cell death was partially suppressed by treatment with Z-VAD-FMK, a pan caspase inhibitor. Therefore, Lico-E-induced oral cancer (OC) cell-specific apoptosis is mediated by the death receptor-dependent extrinsic and mitochondrial-dependent intrinsic apoptotic signaling pathways. In conclusion, these data suggested that Lico-E exhibits potential chemopreventive effects and warrants further developed as a chemotherapeutic agent against OC.

2,3,4',5-tetrahydroxystilbene-2-O-β-d-glucoside exerts anti-inflammatory effects on lipopolysaccharide-stimulated microglia by inhibiting NF-κB and activating AMPK/Nrf2 pathways

2,3,4',5-Tetrahydroxystilbene-2-O-β-d-glucoside (THSG) affects neuroinflammation-related neurodegenerative diseases and inhibits neuroinflammatory mediators. However, the detailed impacts and underlying mechanisms of THSG on neuroinflammatory responses are still unclear. The aim of this study was to investigate the anti-neuroinflammatory mechanism of THSG via AMPK/Nrf2 signaling pathways. This study showed that THSG attenuated LPS-induced iNOS, COX-2, TNF-α, and IL-6 activation in microglia. Furthermore, it was observed that activation of IκBα and NF-κB was significantly increased upon LPS stimulation, and suppressed by THSG treatment in a dose-dependent manner. The expression of HO-1 and NQO1, as well as Nrf2 activation, was induced by THSG in microglia. The promoter activity of ARE and HO-1 also increased in a dose-dependent manner following THSG treatment. Nrf2/HO-1/NQO1 has anti-inflammatory properties; the knock-down of Nrf2/HO-1/NQO1 by specific siRNA prevented the THSG-mediated inhibition of iNOS and COX-2 promoter activity. Consistent with this concept, the phosphorylation of LKB1, CaMKII, and AMPK were elevated after THSG treatment. The blockade of AMPK by a pharmacological inhibitor prevented THSG-induced HO-1 and NQO1 expression. The anti-inflammatory properties of THSG were also reversed by treatment with an AMPK inhibitor. In conclusion, we demonstrated that THSG attenuates the LPS-induced neuroinflammatory response mediated by AMPK/Nrf2 signaling pathways.

Novel compound from Polygonum multiflorum inhibits inflammatory response in LPS-stimulated microglia by upregulating AMPK/Nrf2 pathways

Polygonum multiflorum extracts are known to improve memory and learning ability, and have neuroprotective and anti-aging activity. However, its function and the underlying mechanisms in neuroinflammation-mediated neurodegenerative disease remain poorly understood. In the present study, we investigated the anti-neuroinflammatory effects of several compounds from P. multiflorum, and found a novel compound, CRPE55IB. The CRPE55IB-induced suppression of NO and PGE₂ production correlated with inhibition of iNOS and COX-2 protein expression and promoter activity in lipopolysaccharide (LPS)-stimulated microglia. CRPE55IB also reduced the production of pro-inflammatory cytokines (TNF-α and IL-6) induced by LPS. Furthermore, investigation of the molecular mechanism indicated that CRPE55IB inhibited LPS-induced NF-κB activation by inactivating phosphorylation of IKKα/β, and phosphorylation and degradation of IκBα. We further found that CRPE55IB inhibited the phosphorylation of ERK and JNK at a lower concentration than that for p38 MAPK. Further experiments revealed that CRPE55IB treatment considerably increased the activation of Nrf2/ARE, and the expression of its target genes, including HO-1 and NQO1. Moreover, the Knockdown of Nrf2, HO-1, and NQO1 by siRNA abrogated the inhibitory effect of CRPE55IB on iNOS and COX-2 promoter activity. CRPE55IB also induced phosphorylation of AMPK/LKB/CaMKII in microglia. Analysis using a specific inhibitor of AMPK demonstrated that AMPK activation was involved in CRPE55IB-induced HO-1 and NQO1 expression. In addition, the CRPE55IB-induced anti-neuroinflammatory effect was abrogated by a specific inhibitor of AMPK, indicating the important role of AMPK in CRPE55IB-induced anti-neuroinflammation. Collectively, these results demonstrate that CRPE55IB exerts anti-neuroinflammatory effects against LPS via the Nrf2/AMPK signaling pathways.