The promising antioxidant effects of lignans: Nrf2 activation comes into view

Lignans are biologically active compounds widely distributed, recognized, and identified in seeds, fruits, and vegetables. Lignans have several intriguing bioactivities, including anti-inflammatory, antioxidant, and anticancer activities. Nrf2 controls the expression of many cytoprotective genes. Activation of Nrf2 is a promising therapeutic approach for treating and preventing diseases resulting from oxidative injury and inflammation. Lignans have been demonstrated to stimulate Nrf2 signaling in a variety of in vitro and experimental animal models. The review summarizes the findings of fourteen lignans (Schisandrin A, Schisandrin B, Schisandrian C, Magnolol, Honokiol, Sesamin, Sesamol, Sauchinone, Pinoresinol, Phyllanthin, Nectandrin B, Isoeucommin A, Arctigenin, Lariciresinol) as antioxidative and anti-inflammatory agents, affirming how Nrf2 activation affects their pharmacological effects. Therefore, lignans may offer therapeutic candidates for the treatment and prevention of various diseases and may contribute to the development of effective Nrf2 modulators.

Intramyocardial delivery of injectable hydrogel with arctigenin alleviated myocardial ischemia-reperfusion injury in rats

Arctigenin belongs to a major bioactive component of Fructus arctii and has been found with cardioprotective effects on rats with ischemia‒reperfusion (I/R) injury. The application of arctigenin is limited due to poor water solubility and low bioavailability. Hydrogel drug delivery systems can improve the efficacy and safety of drugs, increase drug utilization, and reduce side effects. We hypothesized that hydrogels containing arctigenin would facilitate the effect of arctigenin and alleviate I/R injury in the rat heart. Presently, adult Sprague-Dawley (SD) rats were subjected to 1 h of I/R injury, then hydrogels comprising arctigenin were implanted into the myocardium of rats. Triphenyl tetrazolium chloride staining, hematoxylin-eosin staining, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining and Western blot were performed for evaluating the infarct size, histopathological, and vital protein alterations of hearts. It was discovered that the hydrogel combined with arctigenin abated apoptosis and reduced infarct size. In addition, the results of echocardiography and Masson staining suggested that the hydrogel with arctigenin improved cardiac function, restrained myocardial fibrosis, and activated AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1). Collectively, the injectable hydrogel delivery system enhances the effect of arctigenin, which may play a protective role in I/R injury by activating AMPK and SIRT1.

Effect of arctigenin on neurological diseases: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Arctium lappa L. is a common specie of Asteraceae. Its main active ingredient, Arctigenin (AG), in mature seeds exerts pharmacological effects on the Central Nervous System (CNS).

AIM OF THE STUDY

To review studies on the specific effects of the AG mechanism on various CNS diseases and elucidate signal transduction mechanisms and their pharmacological actions.

MATERIALS AND METHODS

This investigation reviewed the essential role of AG in treating neurological disorders. Basic information on Arctium lappa L. was retrieved from the Pharmacopoeia of the People's Republic of China. The related articles from 1981 to 2022 on the network database (including CNKI, PubMed, and Wan Fang and so on) were reviewed using AG and CNS diseases-related terms such as Arctigenin and Epilepsy.

RESULTS

It was confirmed that AG has a therapeutic effect on Alzheimer's disease, Glioma, infectious CNS diseases (such as Toxoplasma and Japanese Encephalitis Virus), Parkinson's disease, Epilepsy, etc. In these diseases, related experiments such as a Western blot analysis revealed that AG could alter the content of some key factors (such as the reduction of Aβ in Alzheimer's disease). However, in-vivo AG's metabolic process and possible metabolites are still undetermined.

CONCLUSION

Based on this review, the existing pharmacological research has indeed made objective progress to elucidate how AG prevents and treats CNS diseases, especially senile degenerative disease such as Alzheimer's diseases. It was revealed that AG could be used as a potential nervous system drug as it has a wide range of effects in theory with markedly high application value, especially in the elder group. However, the existing studies are limited to in-vitro experiments; therefore, little is known about how AG metabolizes and functions in-vivo, limiting its clinical application and requiring further research.

Arctigenin improves neuropathy via ameliorating apoptosis and modulating autophagy in streptozotocin-induced diabetic mice

BACKGROUND

Oxidative stress mediates the pathophysiology of diabetic neuropathy (DN) with activation of apoptotic pathway and reduction of autophagy. Arctigenin (ARC) is a natural lignan isolated from some plants of the Asteraceae family that shows antioxidant property. The present study aimed to explore the mechanistic neuroprotective effect of ARC on animal model for DN.

METHODS

DN was induced using streptozotocin (STZ) at a dose of 45 mg/kg, i.p, for five consecutive days and ARC was administered orally (25 or 50 mg) for 3 weeks. The mechanical sensitivity and thermal latency were determined using von Frey and hotplate, respectively. Beclin, p62, and LC3 were detected as markers for autophagy by western blot. Levels of reduced glutathione, lipid peroxides, and activities of catalase and superoxide dismutase were detected as readout for oxidative stress. Apoptotic parameters and histopathological changes were revealed in all experimental groups.

RESULTS

The present study showed deterioration of the function and structure of neurons as a result of hyperglycemia. Oxidative stress and impaired autophagy were observed in diabetic neurons as well as the activation of apoptotic pathway. ARC improved the behavioral and histopathological changes of diabetic mice. ARC combated oxidative stress through diminishing lipid peroxidation and improving the activity of antioxidant enzymes. This was concomitant by reducing the biomarkers of apoptosis. ARC augmented the expression of Beclin and LC3 while it lessened the expression of p62 indicating the activation of autophagy. These findings suggest that ARC can ameliorate DN by combating apoptosis and oxidative stress and improving autophagy.

Regulatory mechanisms of natural compounds from traditional Chinese herbal medicines on the microglial response in ischemic stroke

BACKGROUND

Development of clinically effective neuroprotective agents for stroke therapy is still a challenging task. Microglia play a critical role in brain injury and recovery after ischemic stroke. Traditional Chinese herbal medicines (TCHMs) are based on a unique therapeutic principle, have various formulas, and have long been widely used to treat stroke. Therefore, the active compounds in TCHMs and their underlying mechanisms of action are attracting increasing attention in the field of stroke drug development.

PURPOSE

To summarize the regulatory mechanisms of TCHM-derived natural compounds on the microglial response in animal models of ischemic stroke.

METHODS

We searched studies published until 10 April 2023 in the Web of Science, PubMed, and ScienceDirect using the following keywords: natural compounds, natural products or phytochemicals, traditional Chinese Medicine or Chinese herbal medicine, microglia, and ischemic stroke. This review was prepared according to PRISMA (Preferred Reporting Item for Systematic Reviews and Meta-Analysis) guidelines.

RESULTS

Natural compounds derived from TCHMs can attenuate the M1 phenotype of microglia, which is involved in the detrimental inflammatory response, via inhibition of NF-κB, MAPKs, JAK/STAT, Notch, TLR4, P2X7R, CX3CR1, IL-17RA, the NLRP3 inflammasome, and pro-oxidant enzymes. Additionally, the neuroprotective response of microglia with the M2 phenotype can be enhanced by activating Nrf2/HO-1, PI3K/AKT, AMPK, PPARγ, SIRT1, CB2R, TREM2, nAChR, and IL-33/ST2. Several clinical trials showed that TCHM-derived natural compounds that regulate microglial responses have significant and safe therapeutic effects, but further well-designed clinical studies are needed.

CONCLUSIONS

Further research regarding the direct targets and potential pleiotropic or synergistic effects of natural compounds would provide a more reasonable approach for regulation of the microglial response with the possibility of successful stroke drug development.

Arctigenin: pharmacology, total synthesis, and progress in structure modification

Arctium lappa L. is a prevalent medicinal herb and a health supplement that is commonly used in Asia. Over the last few decades, the bioactive component arctigenin has attracted the attention of researchers because of its anti-inflammatory, antioxidant, immunomodulatory, multiple sclerosis fighting, antitumor, and anti-leukemia properties. After summarising the research and literature on arctigenin, this study outlines the current status of research on pharmacological activity, total synthesis, and structural modification of arctigenin. The purpose of this study is to assist academics in obtaining a more comprehensive understanding of the research progress on arctigenin and to provide constructive suggestions for further investigation of this useful molecule.

The mechanism of microglia-mediated immune inflammation in ischemic stroke and the role of natural botanical components in regulating microglia: A review

Ischemic stroke (IS) is one of the most fatal diseases. Neuroimmunity, inflammation, and oxidative stress play important roles in various complex mechanisms of IS. In particular, the early proinflammatory response resulting from the overactivation of resident microglia and the infiltration of circulating monocytes and macrophages in the brain after cerebral ischemia leads to secondary brain injury. Microglia are innate immune cells in the brain that constantly monitor the brain microenvironment under normal conditions. Once ischemia occurs, microglia are activated to produce dual effects of neurotoxicity and neuroprotection, and the balance of the two effects determines the fate of damaged neurons. The activation of microglia is defined as the classical activation (M1 type) or alternative activation (M2 type). M1 type microglia secrete pro-inflammatory cytokines and neurotoxic mediators to exacerbate neuronal damage, while M2 type microglia promote a repairing anti-inflammatory response. Fine regulation of M1/M2 microglial activation to minimize damage and maximize protection has important therapeutic value. This review focuses on the interaction between M1/M2 microglia and other immune cells involved in the regulation of IS phenotypic characteristics, and the mechanism of natural plant components regulating microglia after IS, providing novel candidate drugs for regulating microglial balance and IS drug development.

Synthesis and pharmacological characterisation of arctigenin analogues as antagonists of AMPA and kainate receptors

(-)-Arctigenin and a series of new analogues have been synthesised and then tested for their potential as AMPA and kainate receptor antagonists of human homomeric GluA1 and GluK2 receptors expressed in HEK293 cells using a Ca2+ influx assay. In general, these compounds showed antagonist activity at both receptors with greater activity evident at AMPARs. Schild analysis indicates that a spirocyclic analogue 6c acts as a non-competitive antagonist. Molecular docking studies in which 6c was docked into the X-ray crystal structure of the GluA2 tetramer suggest that (-)-arctigenin and its analogues bind in the transmembrane domain in a similar manner to the known AMPA receptor non-competitive antagonists GYKI53655 and the antiepileptic drug perampanel. The arctigenin derivatives described herein may serve as novel leads for the development of drugs for the treatment of epilepsy.

Medicinal plants and bioactive natural products as inhibitors of NLRP3 inflammasome

The NLR family, pyrin domain-containing 3 (NLRP3) inflammasome is a multiprotein complex that induces caspase-1 activation and the downstream substrates involved with the processing and secretion of the pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-18 and tumor necrosis factor-α (TNF- α). The NLRP3 inflammasome is activated by a wide range of danger signals that derive from metabolic dysregulation. Activation of this complex often involves the adaptor ASC and upstream sensors including NLRP1, NLRP3, NLRC4, AIM2, and pyrin, which are activated by different stimuli including infectious agents and changes in cell homeostasis. It has been shown that nutraceuticals and medicinal plants have antiinflammatory properties and could be used as complementary therapy in the treatment of several chronic diseases that are related to inflammation, for example, cardiovascular diseases and diabetes mellitus. Herb-based medicine has demonstrated protective effects against NLRP3 inflammasome activation. Therefore, this review focuses on the effects of nutraceuticals and bioactive compounds derived from medicinal plants on NLRP3 inflammasome activation and the possible mechanisms of action of these natural products. Thus, herb-based, natural products/compounds can be considered novel, practical, and accessible agents in chronic inflammatory diseases by inhibiting NLRP3 inflammasome activation.

Arctigenin protects mice from thioglycollate-induced acute peritonitis

Acute peritonitis is an acute inflammatory response of the peritoneal cavity to physical injury and chemical stimulation. Timely resolution of this response is critical to prevent further damage to the body, which can eventually lead to more severe chronic inflammation. Arctigenin (ATG) is the main active ingredient of the Chinese medicine Arctium lappa. In recent years, there have been an increasing number of studies on the anti-inflammatory effect of ATG, but there have been few studies on the effect of ATG on acute inflammation, especially in acute peritonitis, which has not been reported. In this study, a mouse model of experimental acute peritonitis induced by thioglycolate (TG) solution was used to study the protective anti-inflammatory effect of ATG against acute peritonitis and the relevant mechanism. Our results showed that, after 12 hours of TG treatment, ATG significantly reduced inflammatory cell infiltration in mouse tissues and inhibited the secretion and expression of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in mice. ATG significantly reduced the percentage of CD11b+ Ly6G+ neutrophils and F4/80+ macrophages in the spleen and peritoneal exudate. In addition, ATG significantly inhibited the expression of the chemokines CCL3 and CCL4 and the adhesion molecule CD62L on the surface of CD11b-positive monocytes. ATG was observed to inhibit the phosphorylation of p65 and p38 in LPS-stimulated RAW264.7 cells. In conclusion, ATG can improve the symptoms of TG-induced acute peritonitis through immune regulation. ATG can reduce the inflammatory response in TG-induced acute peritonitis in mice.

Arctigenin alleviates myocardial infarction injury through inhibition of the NFAT5-related inflammatory phenotype of cardiac macrophages/monocytes in mice

In this study, we screened potential natural compounds for the treatment of myocardial infarction (MI) and explored the underlying mechanisms. We built three machine learning models to screen the potential compounds. qPCR, flow cytometry, immunohistochemistry, and immunofluorescence analyses were applied to analyze the pharmacological effects of the compounds on macrophages/monocytes in vivo and in vitro. Arctigenin (AG) was selected as a candidate, and echocardiography, Masson's trichrome staining, and TUNEL staining were utilized to detect the effect of AG on MI in vivo. Transcriptome analysis and subsequent bioinformatics analyses were performed to predict the target of the selected compound. Western blot and luciferase reporter assays were used to confirm the target and mechanism of AG. The reversibility of the effects of AG were verified through overexpression of NFAT5. The results showed that AG can improve cardiac injury after MI by reducing infarct size, improving heart function, and inhibiting cardiac death. In addition, AG suppresses inflammatory macrophages/monocytes and proinflammatory cytokines in vivo and in vitro. Transcriptomic and biological experiments revealed that AG modulates macrophage polarization via the NFAT5-induced signaling pathway. Therefore, our data suggest that AG can improve MI by inhibiting the inflammatory phenotype of macrophages/monocytes through targeting of NFAT5.

Arctigenin prevents monocrotaline-induced pulmonary arterial hypertension in rats

The hallmark features of the development of pulmonary arterial hypertension (PAH) include the proliferation of pulmonary vascular smooth muscle cells, oxidative stress, inflammation, and pulmonary artery remodeling. Arctigenin is a bioactive component of Arctium lappa that exerts anti-inflammatory and antiproliferative effects in several diseases; however, its effects on pulmonary arteries are still unclear. This study aimed to investigate the efficacy of arctigenin to prevent PAH. Rats injected with monocrotaline (MCT) progressively developed PAH. Arctigenin treatment (50 mg per kg per day, intra-peritoneally) ameliorated right ventricular systolic pressure and pulmonary arterial remodeling, decreased the expression of inflammatory cytokines, and limited the proliferation of pulmonary vascular smooth muscle cells in lungs. Mechanistically, arctigenin effectively inhibited the MCT-induced elevation of NLRP3, caspase-1, and interleukin 1-beta expression in the lungs. These results indicate that arctigenin ameliorates MCT-induced PAH, at least in part, through exerting its anti-inflammatory, antioxidant, and antiproliferative effects, which inhibit the NLRP3 inflammasome signal pathway in rats.

Arctigenin ameliorates monocrotaline-induced pulmonary arterial hypertension, at least in part, through exerting its anti-inflammatory, antioxidant, and antiproliferative effects, which inhibit the NLRP3 inflammasome signal pathway in rats.

Repeated arctigenin treatment produces antidepressant- and anxiolytic-like effects in mice

Depression is the root of various diseases. It is one of the most debilitating conditions globally. Antidepressant drugs are usually the first-line of depression treatment. Arctigenin (ARC), one of active ingredient of Arctium lappa L, has been found to exert neuroprotective, anti-decrepitude, and anti-inflammatory activities. Thus, the aim of this study was to investigate the potential antidepressant- and anxiolytic-like effects of ARC using acute and chronic mild stress (CMS) mice model. ICR mice model received acute stress or chronic mild stress assessed by open field test (OFT), novelty suppressed feeding (NSF), sucrose preference test (SPT), forced-swimming test (FST), and tail suspension test (TST). After the final test, blood was collected to detect the serum levels of angiogenin (ANG), thrombopoietin (TPO), and vascular endothelial growth factor (VEGF) by enzyme-linked immunosorbent assay (ELISA). The behavioral results showed that repeated ARC (10, 30 mg/kg) administration significantly relieved the antidepressant- and anxiolytic-like effects. And repeated ARC administration at the dose of 10 and 30 mg/kg could significantly block depressive- and anxiety-like behaviors caused by CMS. Finally, ELISA results showed that ARC administration increased the serum levels of angiogenin (ANG), thrombopoietin (TPO), and vascular endothelial growth factor (VEGF). Results showed that chronic ARC administration produces antidepressant- and anxiolytic-like effects, which provides direct evidence for the first time that ARC may be a novel strategy for the treatment of depression and even stress-related disorders. The present data supports further exploration for developing ARC administration as a novel therapeutic strategy for depression and even stress-related disorders.

Overview of the anti-inflammatory effects, pharmacokinetic properties and clinical efficacies of arctigenin and arctiin from Arctium lappa L

Arctigenin (AR) and its glycoside, arctiin, are two major active ingredients of Arctium lappa L (A lappa), a popular medicinal herb and health supplement frequently used in Asia. In the past several decades, bioactive components from A lappa have attracted the attention of researchers due to their promising therapeutic effects. In the current article, we aimed to provide an overview of the pharmacology of AR and arctiin, focusing on their anti-inflammatory effects, pharmacokinetics properties and clinical efficacies. Compared to acrtiin, AR was reported as the most potent bioactive component of A lappa in the majority of studies. AR exhibits potent anti-inflammatory activities by inhibiting inducible nitric oxide synthase (iNOS) via modulation of several cytokines. Due to its potent anti-inflammatory effects, AR may serve as a potential therapeutic compound against both acute inflammation and various chronic diseases. However, pharmacokinetic studies demonstrated the extensive glucuronidation and hydrolysis of AR in liver, intestine and plasma, which might hinder its in vivo and clinical efficacy after oral administration. Based on the reviewed pharmacological and pharmacokinetic characteristics of AR, further pharmacokinetic and pharmacodynamic studies of AR via alternative administration routes are suggested to promote its ability to serve as a therapeutic agent as well as an ideal bioactive marker for A lappa.

Arctigenin exerts protective effects against myocardial infarction via regulation of iNOS, COX‑2, ERK1/2 and HO‑1 in rats

The present study aimed to determine the protective effects of arctigenin against myocardial infarction (MI), and its effects on oxidative stress and inflammation in rats. Left anterior coronary arteries of Sprague‑Dawley rats were ligated, in order to generate an acute MI (AMI) model. Arctigenin was administered to AMI rats at 0, 50, 100 or 200 µmol/kg. Western blotting and ELISAs were performed to analyze protein expression and enzyme activity. Arctigenin was demonstrated to effectively inhibit the levels of alanine transaminase, creatine kinase‑MB and lactate dehydrogenase, and to reduce infarct size in AMI rats. In addition, the activity levels of malondialdehyde, interleukin (IL)‑1β and IL‑6 were significantly suppressed, and the levels of glutathione peroxidase, catalase and superoxide dismutase were significantly increased by arctigenin treatment. Arctigenin treatment also suppressed the protein expression levels of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX‑2) and heme oxygenase 1 (HO‑1), and increased the protein expression levels of phosphorylated‑extracellular signal‑regulated kinase 1/2 (p‑ERK1/2) in AMI rats. Overall, the results of the present study suggest that arctigenin may inhibit MI, and exhibits antioxidative and anti‑inflammatory effects through regulation of the iNOS, COX‑2, ERK1/2 and HO‑1 pathways in a rat model of AMI.

Arctigenin improves vascular tone and decreases inflammation in human saphenous vein

The goal of this study was to test the effects of bioactive phenylpropanoid dibenzylbutyrolactone lignan arctigenin (ATG) in vascular tone. Human bypass graft vessel, from a saphenous vein (SV), were set up in organ bath system and contracted with potassium chloride (KCl, 40mM). Two concentration-response curves of noradrenaline (NE) (10nM-100μM) separated with an incubation period of 30min without (Control) or with ATG (3-100μM) were established. Inhibitors of nitric oxide, prostaglandins, K⁺ related channels or calcium influx were used to delineate the molecular mechanisms beyond ATG effects. To investigate anti-inflammatory actions, SV were treated with 10μM or 100μM ATG and incubated for 18h in the absence or presence of both interleukin-1beta (IL-1β) and lipopolysaccharide (LPS) to mimic the physiological or inflamed tissue conditions. Proatherogenic and inflammatory mediators İnterleukine-1 beta (IL-1β), Monocyte Chemoattractant Proteine-1 (MCP-1), Tumor Necrosis Factor- α (TNF-α), İnterleukine-6 (IL-6), Prostaglandin E₂ (PGE₂) and İnterleukine-8 (IL-8) in the supernatant were measured. ATG significantly decreased vascular contractile response to NE. Moreover, it reduced contractions induced by KCl and cumulative addition of CaCl_2. The mediators were significantly increased in inflammatory conditions compared to normal conditions, an effect which was inhibited by ATG (10 and 100µM). ATG reduces contractions in SV and decreases the production of proinflammatory-proatherogenic mediators, setting the stage for further evaluating the effect of ATG in cardiovascular diseases.

Salvianolic Acids for Injection (SAFI) suppresses inflammatory responses in activated microglia to attenuate brain damage in focal cerebral ischemia

BACKGROUND

Inflammatory reactions induced by microglia in the brain play crucial roles in ischemia/reperfusion (I/R) cerebral injuries. Microglia activation has been shown to be closely related to TLR4/NF-κB signal pathways. Salvianolic acids for injection (SAFI) have been used in clinical practice to treat ischemic stroke with reported neuroprotective effects; however, the underlying mechanisms are still uncertain.

OBJECTIVE AND METHODS

First, we studied the effect of SAFI on inflammatory responses in LPS-stimulated BV-2 microglia. Then, to discover whether the beneficial in vitro effects of SAFI lead to in vivo therapeutic effects, an MCAO (Middle cerebral artery occlusion) rat model was further employed to elucidate the probable mechanism of SAFI in treating ischemic stroke. Rats in the SAFI group were given SAFI (23 or 46mg/kg) before I/R injury.

RESULTS

The results showed that SAFI treatment significantly decreased neuroinflammation and the infarction volume compared with the vehicle group. Activation of microglia cells was reduced, and TLR4/NF-κB signals, which were markedly inhibited by SAFI treatment in ischemic hemisphere, were accompanied by reduced expression and release of cytokines IL-1β and IL-6.

CONCLUSION

This study provides evidence that SAFI effectively protects the brain after cerebral ischemia, which may be caused by attenuating inflammation in microglia.

Effect of L-pGlu-(1-benzyl)-l-His-l-Pro-NH2 against in-vitro and in-vivo models of cerebral ischemia and associated neurological disorders

Central nervous system plays a vital role in regulation of most of biological functions which are abnormally affected in various disorders including cerebral ischemia, Alzheimer's and Parkinson's (AD and PD) worldwide. Cerebral stroke is an extremely fatal and one of the least comprehensible neurological disorders due to limited availability of prospective clinical approaches and therapeutics. Since, some endogenous peptides like thyrotropin-releasing hormone have shown substantial neuroprotective potential, hence present study evaluates the newer thyrotropin-releasing hormone (TRH) analogue L-pGlu-(1-benzyl)-l-His-l-Pro-NH₂ for its neuroprotective effects against oxygen glucose deprivation (OGD), glutamate and H₂O₂ induced injury in pheochromocytoma cell lines (PC-12 cells) and in-vivo ischemic injury in mice. Additionally, the treatment was further analyzed with respect to models of AD and PD in mice. Cerebral ischemia was induced by clamping both bilateral common carotid arteries for ten minutes. Treatment was administered to the mice five minute after restoration of blood supply to brain. Consequential changes in neurobehavioural, biochemical and histological parameters were assessed after a week. L-pGlu-(1-benzyl)-l-His-l-Pro-NH₂ showed significant reduction in glutamate, H₂O₂ and OGD -induced cell death in concentration and time dependent manner. Moreover, L-pGlu-(1-benzyl)-l-His-l-Pro-NH₂ resulted in a substantial reduction in CA1 (Cornus Ammonis 1) hippocampal neuronal cell death, inflammatory cytokines, TNF-α, IL-6 and oxidative stress in hippocampus. In addition, L-pGlu-(1-benzyl)-l-His-l-Pro-NH₂ was found to be protective in two acute models of AD and PD as well these findings demonstrate the neuroprotective potential of L-pGlu-(1-benzyl)-l-His-l-Pro-NH₂ in cerebral ischemia and other diseases, which may be mediated through reduction of excitotoxicity, oxidative stress and inflammation.

Anti-Inflammatory Effects of Traditional Chinese Medicines against Ischemic Injury in In Vivo Models of Cerebral Ischemia

Inflammation plays a crucial role in the pathophysiology of acute ischemic stroke. In the ischemic cascade, resident microglia are rapidly activated in the brain parenchyma and subsequently trigger inflammatory mediator release, which facilitates leukocyte-endothelial cell interactions in inflammation. Activated leukocytes invade the endothelial cell junctions and destroy the blood-brain barrier integrity, leading to brain edema. Toll-like receptors (TLRs) stimulation in microglia/macrophages through the activation of intercellular signaling pathways secretes various proinflammatory cytokines and enzymes and then aggravates cerebral ischemic injury. The secreted cytokines activate the proinflammatory transcription factors, which subsequently regulate cytokine expression, leading to the amplification of the inflammatory response and exacerbation of the secondary brain injury. Traditional Chinese medicines (TCMs), including TCM-derived active compounds, Chinese herbs, and TCM formulations, exert neuroprotective effects against inflammatory responses by downregulating the following: ischemia-induced microglial activation, microglia/macrophage-mediated cytokine production, proinflammatory enzyme production, intercellular adhesion molecule-1, matrix metalloproteinases, TLR expression, and deleterious transcription factor activation. TCMs also aid in upregulating anti-inflammatory cytokine expression and neuroprotective transcription factor activation in the ischemic lesion in the inflammatory cascade during the acute phase of cerebral ischemia. Thus, TCMs exert potent anti-inflammatory properties in ischemic stroke and warrant further investigation.

The combination of vitamins and omega-3 fatty acids has an enhanced anti-inflammatory effect on microglia

Neuroinflammation is a common phenomenon in the pathology of many brain diseases. In this paper we explore whether selected vitamins and fatty acids known to modulate inflammation exert an effect on microglia, the key cell type involved in neuroinflammation. Previously these nutrients have been shown to exert anti-inflammatory properties acting on specific inflammatory pathways. We hypothesized that combining nutrients acting on converging anti-inflammatory pathways may lead to enhanced anti-inflammatory properties as compared to the action of a single nutrient. In this study, we investigated the anti-inflammatory effect of combinations of nutrients based on the ability to inhibit the LPS-induced release of nitric oxide and interleukin-6 from BV-2 cells. Results show that omega-3 fatty acids, vitamins A and D can individually reduce the LPS-induced secretion of the pro-inflammatory cytokines by BV-2 cells. Moreover, we show that vitamins A, D and omega-3 fatty acids (docosahexaenoic and eicosapentaenoic) at concentrations where they individually had little effect, significantly reduced the secretion of the inflammatory mediator, nitric oxide, when they were combined. The conclusion of this study is that combining different nutrients acting on convergent anti-inflammatory pathways may result in an increased anti-inflammatory efficacy.

Arctigenin Treatment Protects against Brain Damage through an Anti-Inflammatory and Anti-Apoptotic Mechanism after Needle Insertion

Convection enhanced delivery (CED) infuses drugs directly into brain tissue. Needle insertion is required and results in a stab wound injury (SWI). Subsequent secondary injury involves the release of inflammatory and apoptotic cytokines, which have dramatic consequences on the integrity of damaged tissue, leading to the evolution of a pericontusional-damaged area minutes to days after in the initial injury. The present study investigated the capacity for arctigenin (ARC) to prevent secondary brain injury and the determination of the underlying mechanism of action in a mouse model of SWI that mimics the process of CED. After CED, mice received a gavage of ARC from 30 min to 14 days. Neurological severity scores (NSS) and wound closure degree were assessed after the injury. Histological analysis and immunocytochemistry were used to evaluated the extent of brain damage and neuroinflammation. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was used to detect universal apoptosis. Enzyme-linked immunosorbent assays (ELISA) was used to test the inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10) and lactate dehydrogenase (LDH) content. Gene levels of inflammation (TNF-α, IL-6, and IL-10) and apoptosis (Caspase-3, Bax and Bcl-2) were detected by reverse transcription-polymerase chain reaction (RT-PCR). Using these, we analyzed ARC’s efficacy and mechanism of action. Results: ARC treatment improved neurological function by reducing brain water content and hematoma and accelerating wound closure relative to untreated mice. ARC treatment reduced the levels of TNF-α and IL-6 and the number of allograft inflammatory factor (IBA)- and myeloperoxidase (MPO)-positive cells and increased the levels of IL-10. ARC-treated mice had fewer TUNEL+ apoptotic neurons and activated caspase-3-positive neurons surrounding the lesion than controls, indicating increased neuronal survival. Conclusions: ARC treatment confers neuroprotection of brain tissue through anti-inflammatory and anti-apoptotic effects in a mouse model of SWI. These results suggest a new strategy for promoting neuronal survival and function after CED to improve long-term patient outcome.

Anti-inflammatory properties of lipoxin A4 protect against diabetes mellitus complicated by focal cerebral ischemia/reperfusion injury

Lipoxin A4 can alleviate cerebral ischemia/reperfusion injury by reducing the inflammatory reaction, but it is currently unclear whether it has a protective effect on diabetes mellitus complicated by focal cerebral ischemia/reperfusion injury. In this study, we established rat models of diabetes mellitus using an intraperitoneal injection of streptozotocin. We then induced focal cerebral ischemia/reperfusion injury by occlusion of the middle cerebral artery for 2 hours and reperfusion for 24 hours. After administration of lipoxin A4 via the lateral ventricle, infarction volume was reduced, the expression levels of pro-inflammatory factors tumor necrosis factor alpha and nuclear factor-kappa B in the cerebral cortex were decreased, and neurological functioning was improved. These findings suggest that lipoxin A4 has strong neuroprotective effects in diabetes mellitus complicated by focal cerebral ischemia/reperfusion injury and that the underlying mechanism is related to the anti-inflammatory action of lipoxin A4.

Neuroprotective effect of Cerebralcare Granule after cerebral ischemia/reperfusion injury

Cerebralcare Granule (CG) improves cerebral microcirculation and relieves vasospasm, but studies investigating its therapeutic effect on cerebral ischemia/reperfusion injury are lacking. In the present study, we administered CG (0.3, 0.1 and 0.03 g/mL intragastrically) to rats for 7 consecutive days. We then performed transient occlusion of the middle cerebral artery, followed by reperfusion, and administered CG daily for a further 3 or 7 days. Compared with no treatment, high-dose CG markedly improved neurological function assessed using the Bederson and Garcia scales. At 3 days, animals in the high-dose CG group had smaller infarct volumes, greater interleukin-10 expression, and fewer interleukin-1β-immunoreactive cells than those in the untreated model group. Furthermore, at 7 days, high-dose CG-treated rats had more vascular endothelial growth factor-immunoreactive cells, elevated angiopoietin-1 and vascular endothelial growth factor expression, and improved blood coagulation and flow indices compared with untreated model animals. These results suggest that CG exerts specific neuroprotective effects against cerebral ischemia/reperfusion injury.

Arctigenin Protects against Lipopolysaccharide-Induced Pulmonary Oxidative Stress and Inflammation in a Mouse Model via Suppression of MAPK, HO-1, and iNOS Signaling

Arctigenin, a bioactive component of Arctium lappa (Nubang), has anti-inflammatory activity. Here, we investigated the effects of arctigenin on lipopolysaccharide (LPS)-induced acute lung injury. Mice were divided into four groups: control, LPS, LPS + DMSO, and LPS + Arctigenin. Mice in the LPS + Arctigenin group were injected intraperitoneally with 50 mg/kg of arctigenin 1 h before an intratracheal administration of LPS (5 mg/kg). Lung tissues and bronchoalveolar lavage fluids (BALFs) were collected. Histological changes of the lung were analyzed by hematoxylin and eosin staining. Arctigenin decreased LPS-induced acute lung inflammation, infiltration of inflammatory cells into BALF, and production of pro-inflammatory cytokines. Moreover, arctigenin pretreatment reduced the malondialdehyde level and increased superoxide dismutase and catalase activities and glutathione peroxidase/glutathione disulfide ratio in the lung. Mechanically, arctigenin significantly reduced the production of nitric oxygen and inducible nitric oxygen synthase (iNOS) expression, enhanced the expression of heme oxygenase-1, and decreased the phosphorylation of mitogen-activated protein kinases (MAPKs). Arctigenin has anti-inflammatory and antioxidative effects on LPS-induced acute lung injury, which are associated with modulation of MAPK, HO-1, and iNOS signaling.

Arctigenin, a Potent Ingredient of Arctium lappa L., Induces Endothelial Nitric Oxide Synthase and Attenuates Subarachnoid Hemorrhage-Induced Vasospasm through PI3K/Akt Pathway in a Rat Model

Upregulation of protein kinase B (PKB, also known as Akt) is observed within the cerebral arteries of subarachnoid hemorrhage (SAH) animals. This study is of interest to examine Arctigenin, a potent antioxidant, on endothelial nitric oxide synthase (eNOS) and Akt pathways in a SAH in vitro study. Basilar arteries (BAs) were obtained to examine phosphatidylinositol-3-kinase (PI3K), phospho-PI3K, Akt, phospho-Akt (Western blot) and morphological examination. Endothelins (ETs) and eNOS evaluation (Western blot and immunostaining) were also determined. Arctigenin treatment significantly alleviates disrupted endothelial cells and tortured internal elastic layer observed in the SAH groups (p < 0.01). The reduced eNOS protein and phospho-Akt expression in the SAH groups were relieved by the treatment of Arctigenin (p < 0.01). This result confirmed that Arctigenin might exert dural effects in preventing SAH-induced vasospasm through upregulating eNOS expression via the PI3K/Akt signaling pathway and attenuate endothelins after SAH. Arctigenin shows therapeutic promise in the treatment of cerebral vasospasm following SAH.

Comparative pharmacokinetics of arctigenin in normal and type 2 diabetic rats after oral and intravenous administration

Arctigenin is the main active ingredient of Fructus Arctii for the treatment of type 2 diabetes. In this study, the pharmacokinetics of arctigenin in normal and type 2 diabetic rats following oral and intravenous administration was investigated. As compared to normal rats, Cmax and AUC(0-10h) values of oral arctigenin in diabetic rats increased by 356.8% and 223.4%, respectively. In contrast, after intravenous injection, the Cmax and AUC(0-10h) values of arctigenin showed no significant difference between diabetic and normal rats. In order to explore how the bioavailability of oral arctigenin increased under diabetic condition, the absorption behavior of arctigenin was evaluated by in situ single-pass intestinal perfusion (SPIP). The results indicated that arctigenin was a substrate of P-glycoprotein (P-gp). The absorption difference of arctigenin in the normal and diabetic rats could be eliminated by the pretreatment of classic P-gp inhibitor verapamil, suggesting that P-gp might be the key factor causing the absorption enhancement of arctigenin in diabetic rats. Further studies revealed that the uptake of rhodamine 123 (Rho123) in diabetic rats was significantly higher, indicating that diabetes mellitus might impair P-gp function. Consistently, a lower mRNA level of P-gp in the intestine of diabetic rats was found. In conclusion, the absorption of arctigenin after oral administration was promoted in diabetic rats, which might be partially attribute to the decreased expression and impaired function of P-gp in intestines.

Arctigenin Increases Hemeoxygenase-1 Gene Expression by Modulating PI3K/AKT Signaling Pathway in Rat Primary Astrocytes

In the present study, we found that the natural compound arctigenin inhibited hydrogen peroxide-induced reactive oxygen species (ROS) production in rat primary astrocytes. Since hemeoxygenase-1 (HO-1) plays a critical role as an antioxidant defense factor in the brain, we examined the effect of arctigenin on HO-1 expression in rat primary astrocytes. We found that arctigenin increased HO-1 mRNA and protein levels. Arctigenin also increases the nuclear translocation and DNA binding of Nrf2/c-Jun to the antioxidant response element (ARE) on HO-1 promoter. In addition, arctigenin increased ARE-mediated transcriptional activities in rat primary astrocytes. Further mechanistic studies revealed that arctigenin increased the phosphorylation of AKT, a downstream substrate of phosphatidylinositol 3-kinase (PI3K). Treatment of cells with a PI3K-specific inhibitor, LY294002, suppressed the HO-1 expression, Nrf2 DNA binding and ARE-mediated transcriptional activities in arctigenin-treated astrocyte cells. The results collectively suggest that PI3K/AKT signaling pathway is at least partly involved in HO-1 expression by arctigenin via modulation of Nrf2/ARE axis in rat primary astrocytes.

The neurobiological pathogenesis of poststroke depression

Poststroke depression (PSD) is an important consequence after stroke, with negative impact on stroke outcome. The pathogenesis of PSD is complicated, with some special neurobiological mechanism, which mainly involves neuroanatomical, neuron, and biochemical factors and neurogenesis which interact in complex ways. Abundant studies suggested that large lesions in critical areas such as left frontal lobe and basal ganglia or accumulation of silent cerebral lesions might interrupt the pathways of monoamines or relevant pathways of mood control, thus leading to depression. Activation of immune system after stroke produces more cytokines which increase glutamate excitotoxicity, results in more cell deaths of critical areas and enlargement of infarctions, and, together with hypercortisolism induced by stress or inflammation after stroke which could decrease intracellular serotonin transporters, might be the key biochemical change of PSD. The interaction among cytokines, glucocorticoid, and neurotrophin results in the decrease of hippocampal neurogenesis which has been proved to be important for mood control and pharmaceutical effect of selective serotonin reuptake inhibitors and might be another promising pathway to understand the pathogenesis of PSD. In order to reduce the prevalence of PSD and improve the outcome of stroke, more relevant studies are still required to clarify the pathogenesis of PSD.

Herbal medicines for ischemic stroke: combating inflammation as therapeutic targets

Stroke is a debilitating disease for which limited therapeutic approaches are available currently. Thus, there is an urgent need for developing novel therapies for stroke. Astrocytes, endothelial cells and pericytes constitute a neurovascular network for metabolic requirement of neurons. During ischemic stroke, these cells contribute to post-ischemic inflammation at multiple stages of ischemic cascades. Upon ischemia onset, activated resident microglia and astrocytes, and infiltrated immune cells release multiple inflammation factors including cytokines, chemokines, enzymes, free radicals and other small molecules, not only inducing brain damage but affecting brain repair. Recent progress indicates that anti-inflammation is an important therapeutic strategy for stroke. Given a long history with direct experience in the treatment of human subjects, Traditional Chinese Medicine and its related natural compounds are recognized as important sources for drug discovery. Last decade, a great progress has been made to identify active compounds from herbal medicines with the properties of modulating post-ischemic inflammation for neuroprotection. Herein, we discuss the inflammatory pathway in early stage and secondary response to injured tissues after stroke from initial artery occlusion to brain repair, and review the active ingredients from natural products with anti-inflammation and neuroprotection effects as therapeutic agents for ischemic stroke. Further studies on the post-ischemic inflammatory mechanisms and corresponding drug candidates from herbal medicine may lead to the development of novel therapeutic strategies in stroke treatment.

Development of an LC/MS/MS method in order to determine arctigenin in rat plasma: its application to a pharmacokinetic study

In this study, a simple and sensitive LC/MS/MS method was developed and validated for the determination of arctigenin in rat plasma. The MS detection was performed using multiple reaction monitoring at the transitions of m/z 373.2 → 137.3 for arctigenin and m/z 187.1 → 131.0 for psoralen (internal standard) with a Turbo IonSpray electrospray in positive mode. The calibration curves fitted a good linear relationship over the concentration range of 0.2-500 ng/mL. It was found that arctigenin is not stable enough at both room temperature and -80 °C unless mixed with methanol before storage. The validated LC/MS/MS method was successfully applied for the pharmacokinetic study of arctigenin in rats. After intravenous injection of 0.3 mg/kg arctigenin injection to rats, the maximum concentration, half-life and area under the concentration-time curve were 323 ± 65.2 ng/mL, 0.830 ± 0.166 and 81.0 ± 22.1 h ng/mL, respectively.

Gua Lou Gui Zhi decoction suppresses LPS-induced activation of the TLR4/NF-κB pathway in BV-2 murine microglial cells

Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling-mediated neuroinflammation contributes to secondary brain damage in ischemic stroke; therefore, anti-inflammatory therapy via suppression of the TLR4/NF-κB pathway could be a promising strategy for the treatment of stroke and post-stroke disabilities. Gua Lou Gui Zhi decoction (GLGZD) has long been used in China to clinically treat dysfunction after stroke such as muscular spasticity, but the precise mechanisms are largely unknown. In the present study, we evaluated the anti-inflammatory effect of GLGZD and investigated the underlying molecular mechanisms using lipopolysaccharide (LPS)-stimulated BV-2 microglial cells as an in vitro inflammatory model of neural cells. We found that GLGZD inhibited the inflammatory response in microglial cells as it significantly reduced LPS-induced expression of pro-inflammatory nitric oxide, tumour necrosis factor-α, interleukin (IL)-6 and IL-1β in BV-2 cells, in a dose-dependent manner. In addition, GLGZD treatment significantly decreased the protein expression of TLR4 and myeloid differentiation factor 88, inhibited the phosphorylation of IκB and blocked the nuclear translocation of NF-κB in BV-2 cells, demonstrating its inhibitory effect on the activation of TLR4/NF-κB signaling. Collectively, our findings suggest that inhibition of the inflammatory response via suppression of the TLR4/NF-κB pathway may be one of the mechanisms through which GLGZD ameliorates the damage in ischemic cerebral tissues.