Honokiol, a Neuroprotectant against Mouse Cerebral Ischaemia, Mediated by Preserving Na+, K+-ATPase Activity and Mitochondrial Functions

Role of Network Pharmacology in Prediction of Mechanism of Neuroprotective Compounds

Network pharmacology is an emerging pioneering approach in the drug discovery process, which is used to predict the therapeutic mechanism of compounds using various bioinformatic tools and databases. Emerging studies have indicated the use of network pharmacological approaches in various research fields, particularly in the identification of possible mechanisms of herbal compounds/ayurvedic formulations in the management of various diseases. These techniques could also play an important role in the prediction of the possible mechanisms of neuroprotective compounds. The first part of the chapter includes an introduction on neuroprotective compounds based on literature. Further, network pharmacological approaches are briefly discussed. The use of network pharmacology in the prediction of the neuroprotective mechanism of compounds is discussed in detail with suitable examples. Finally, the chapter concludes with the current challenges and future prospectives.

Pharmacological features, health benefits and clinical implications of honokiol

Honokiol (HNK) is a natural polyphenolic compound extracted from the bark and leaves of Magnolia grandiflora. It has been traditionally used as a medicinal compound to treat inflammatory diseases. HNK possesses numerous health benefits with a minimal level of toxicity. It can cross the blood-brain barrier and blood-cerebrospinal fluid, thus having significant bioavailability in the neurological tissues. HNK is a promising bioactive compound possesses neuroprotective, antimicrobial, anti-tumorigenic, anti-spasmodic, antidepressant, analgesic, and antithrombotic features . HNK can prevent the growth of several cancer types and haematological malignancies. Recent studies suggested its role in COVID-19 therapy. It binds effectively with several molecular targets, including apoptotic factors, chemokines, transcription factors, cell surface adhesion molecules, and kinases. HNK has excellent pharmacological features and a wide range of chemotherapeutic effects, and thus, researchers have increased interest in improving the therapeutic implications of HNK to the clinic as a novel agent. This review focused on the therapeutic implications of HNK, highlighting clinical and pharmacological features and the underlying mechanism of action.Communicated by Ramaswamy H. Sarma.

Inhibitory Effects of Honokiol on Substantia Gelatinosa Neurons of the Trigeminal Subnucleus Caudalis in Juvenile Mice

Inhibitory neurotransmitters such as gamma-aminobutyric acid (GABA) and glycine are known to be abundant in the substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc). Thus, it has been recognized as an initial synaptic site for regulating orofacial nociceptive stimuli. Honokiol, a principal active ingredient derived from the bark of Magnolia officinalis, has been exploited in traditional remedies with multiple biological effects, including anti-nociception on humans. However, the anti-nociceptive mechanism of honokiol on SG neurons of the Vc remains fully elusive. In this study, effects of honokiol on SG neurons of the Vc in mice were investigated using the whole-cell patch-clamp method. In a concentration-dependent manner, honokiol significantly enhanced frequencies of spontaneous postsynaptic currents (sPSCs) that were independent of action potential generation. Notably, honokiol-induced increase in the frequency of sPSCs was attributed to the release of inhibitory neurotransmitters through both glycinergic and GABAergic pre-synaptic terminals. Furthermore, higher concentration of honokiol induced inward currents that were noticeably attenuated in the presence of picrotoxin (a GABAA receptor antagonist) or strychnine (a glycine receptor antagonist). Honokiol also exhibited potentiation effect on glycine- and GABAA receptor-mediated responses. In inflammatory pain model, the increase in frequency of spontaneous firing on SG neurons induced by formalin was significantly inhibited by the application of honokiol. Altogether, these findings indicate that honokiol might directly affect SG neurons of the Vc to facilitate glycinergic and GABAergic neurotransmissions and modulate nociceptive synaptic transmission against pain. Consequently, the inhibitory effect of honokiol in the central nociceptive system contributes to orofacial pain management.

Honokiol attenuates mitochondrial fission and cell apoptosis by activating Sirt3 in intracerebral hemorrhage

BACKGROUND

Sirtuin-3 (Sirt3) has been documented to protect against mitochondrial dysfunction and apoptosis. Honokiol (HKL) is a Sirt3 pharmacological activator with reported neuroprotective effects in multiple neurological disorders. The present study aimed to explore the neuroprotective effects of HKL and the role of Sirt3 following intracerebral hemorrhage (ICH).

METHODS

An in vivo ICH model in rats was established by injecting autologous blood into the right basal ganglia. PC12 cells were stimulated with hemin. For the in vivo investigation, the modified Neurological Severity Scores and the Morris water maze test were performed to assess neurological deficits. Hematoxylin-Eosin and Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining were employed to evaluate the histopathology and apoptosis. Immunohistochemical staining was used to investigate the expression of Sirt3. Adenosine triphosphate (ATP) levels were quantified to assess mitochondrial dysfunction. Cell counting kit-8, lactate dehydrogenase assay, and flow cytometry were used to analyze cell vitality and apoptosis in vitro. Immunofluorescence staining was performed to observe mitochondrial morphology and dynamin-related protein 1 (Drp1) localization to mitochondria. Western blot was applied to quantify the expression of Sirt3, Bax, Bcl-2, cleaved-caspase-3, Drp1, phosphorylation of Drp1 at serine-616, and phosphorylation of Drp1 at serine-637 in vivo and in vitro.

RESULTS

HKL treatment alleviated neurological deficits, attenuated the histopathological damage and cell apoptosis, and restored the decreased ATP levels in ICH rats. HKL improved cell survival rate, reduced cell apoptosis, and inhibited mitochondrial fission in PC12 cells. Moreover, both in vivo and in vitro models showed increased phosphorylation of Drp1 at Ser616, and reduced phosphorylation of Drp1 at Ser637. Meanwhile, immunofluorescence co-localization analysis revealed that hemin increased the overlap of Drp1 and mitochondria in PC12 cells. The phosphorylation and mitochondrial translocation of Drp1 were effectively reversed by HKL treatment. Importantly, the selective Sirt3 inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine suppressed these effects.

CONCLUSION

Our findings demonstrated that HKL ameliorated ICH-induced apoptosis and mitochondrial fission by Sirt3, suggesting that HKL has immense prospects for the treatment of ICH.

Honokiol alleviated neurodegeneration by reducing oxidative stress and improving mitochondrial function in mutant SOD1 cellular and mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting both upper and lower motor neurons (MNs) with large unmet medical needs. Multiple pathological mechanisms are considered to contribute to the progression of ALS, including neuronal oxidative stress and mitochondrial dysfunction. Honokiol (HNK) has been reported to exert therapeutic effects in several neurologic disease models including ischemia stroke, Alzheimer's disease and Parkinson's disease. Here we found that honokiol also exhibited protective effects in ALS disease models both in vitro and in vivo. Honokiol improved the viability of NSC-34 motor neuron-like cells that expressed the mutant G93A SOD1 proteins (SOD1-G93A cells for short). Mechanistical studies revealed that honokiol alleviated cellular oxidative stress by enhancing glutathione (GSH) synthesis and activating the nuclear factor erythroid 2-related factor 2 (NRF2)-antioxidant response element (ARE) pathway. Also, honokiol improved both mitochondrial function and morphology via fine-tuning mitochondrial dynamics in SOD1-G93A cells. Importantly, honokiol extended the lifespan of the SOD1-G93A transgenic mice and improved the motor function. The improvement of antioxidant capacity and mitochondrial function was further confirmed in the spinal cord and gastrocnemius muscle in mice. Overall, honokiol showed promising preclinical potential as a multiple target drug for ALS treatment.

The Neuropharmacological Effects of Magnolol and Honokiol: A Review of Signal Pathways and Molecular Mechanisms

Magnolol and honokiol are natural lignans with good physiological effects. As the main active substances derived from Magnolia officinalis, their pharmacological activities have attracted extensive attention. It is reported that both of them can cross the blood-brain barrier (BBB) and exert neuroprotective effects through a variety of mechanisms. This suggests that these two ingredients can be used as effective therapeutic compounds to treat a wide range of neurological diseases. This article provides a review of the mechanisms involved in the therapeutic effects of magnolol and honokiol in combating diseases, such as cerebral ischemia, neuroinflammation, Alzheimer's disease, and brain tumors, as well as psychiatric disorders, such as anxiety and depression. Although magnolol and honokiol have the pharmacological effects described above, their clinical potential remains untapped. More research is needed to improve the bioavailability of magnolol and honokiol and perform experiments to examine the therapeutic potential of magnolol and honokiol.

SIRT3 activation promotes enteric neurons survival and differentiation

Enteric neuron degeneration has been observed during aging, and in individuals with metabolic dysfunction including obesity and diabetes. Honokiol, a naturally occurring compound, is an activator of Sirtuin-3 (SIRT3) that has antioxidant activity. Its role in modulating enteric neuron-specific neurodegeneration is unknown. We studied the effects of honokiol and its fluorinated analog, hexafluoro-honokiol, on enteric neuronal differentiation and survival. We used a previously established model of mouse primary enteric neuronal cells and an enteric neuronal cell line treated with palmitate (PA) and lipopolysaccharide (LPS) to induce mitochondrial dysfunction and enteric neuronal cell death. The effect of honokiol and hexafluoro-honokiol was assessed on neuronal phenotype, fiber density, differentiation, and pyroptosis. Honokiol and hexafluoro-honokiol significantly increased neuronal networks and fiber density in enteric neurons and increased levels of neuronal nitric oxide synthase and Choline acetyltransferase mRNA. Hexafluoro-honokiol and honokiol also significantly increased SIRT3 mRNA levels and suppressed palmitate and LPS-induced neuronal pyroptosis. SIRT3 knock-down prevented the hexafluoro-honokiol mediated suppression of mitochondrial superoxide release. Our data supports a neuroprotective effect of honokiol and its derivative and these could be used as prophylactic or therapeutic agents for treating enteric neurodegeneration and associated motility disorders.

Recent Progress in Research on Mechanisms of Action of Natural Products against Alzheimer's Disease: Dietary Plant Polyphenols

Alzheimer's disease (AD) is an incurable degenerative disease of the central nervous system and the most common type of dementia in the elderly. Despite years of extensive research efforts, our understanding of the etiology and pathogenesis of AD is still highly limited. Nevertheless, several hypotheses related to risk factors for AD have been proposed. Moreover, plant-derived dietary polyphenols were also shown to exert protective effects against neurodegenerative diseases such as AD. In this review, we summarize the regulatory effects of the most well-known plant-derived dietary polyphenols on several AD-related molecular mechanisms, such as amelioration of oxidative stress injury, inhibition of aberrant glial cell activation to alleviate neuroinflammation, inhibition of the generation and promotion of the clearance of toxic amyloid-β (Aβ) plaques, inhibition of cholinesterase enzyme activity, and increase in acetylcholine levels in the brain. We also discuss the issue of bioavailability and the potential for improvement in this regard. This review is expected to encourage further research on the role of natural dietary plant polyphenols in the treatment of AD.

Therapeutic Effect of Icaritin on Cerebral Ischemia-Reperfusion-Induced Senescence and Apoptosis in an Acute Ischemic Stroke Mouse Model

An ischemic stroke is brain damage caused by interruption of blood supply to the brain that can cause death and long-term disability. New medical strategies or therapies are urgently needed for ischemic stroke. Icaritin (ICT) is a metabolite of icariin (ICA), which are two active flavonoid components extracted from Herba epimedii and considered neuroprotective agents in animal models of Alzheimer’s disease and ischemic stroke. The therapeutic effect of ICT on ischemic still remains to be clarified. The aim of this study was to investigate the therapeutic effect of ICT on cerebral ischemia-reperfusion-associated senescence and apoptosis in a middle cerebral artery occlusion (MCAO) mouse model (ischemia for 50 min and reperfusion for 24 h). Administration of ICT after ischemia significantly reduced MCAO-induced neurological damage, infarct volume, and histopathological changes in the brain of acute ischemic stroke mice. ICT treatment could also reduce neuronal apoptosis and senescence and reversed the expression of apoptosis- and senescence-related signaling proteins. These findings suggest that ICT may have therapeutic potential to ameliorate acute ischemic stroke.

Polyphenols Targeting Oxidative Stress in Spinal Cord Injury: Current Status and Future Vision

A spinal cord injury (SCI) occurs when the spinal cord is deteriorated or traumatized, leading to motor and sensory functions lost even totally or partially. An imbalance within the generation of reactive oxygen species and antioxidant defense levels results in oxidative stress (OS) and neuroinflammation. After SCI, OS and occurring pathways of inflammations are significant strenuous drivers of cross-linked dysregulated pathways. It emphasizes the significance of multitarget therapy in combating SCI consequences. Polyphenols, which are secondary metabolites originating from plants, have the promise to be used as alternative therapeutic agents to treat SCI. Secondary metabolites have activity on neuroinflammatory, neuronal OS, and extrinsic axonal dysregulated pathways during the early stages of SCI. Experimental and clinical investigations have noted the possible importance of phenolic compounds as important phytochemicals in moderating upstream dysregulated OS/inflammatory signaling mediators and axonal regeneration's extrinsic pathways after the SCI probable significance of phenolic compounds as important phytochemicals in mediating upstream dysregulated OS/inflammatory signaling mediators. Furthermore, combining polyphenols could be a way to lessen the effects of SCI.

Neuroprotective Potency of Neolignans in Magnolia officinalis Cortex Against Brain Disorders

In recent years, neurological diseases including Alzheimer’s disease, Parkinson’s disease and stroke are one of the main causes of death in the world. At the same time, the incidence of psychiatric disorders including depression and anxiety has been increasing. Accumulating elderly and stressed people suffer from these brain disorders, which is undoubtedly a huge burden on the modern aging society. Neolignans, the main active ingredients in Magnolia officinalis cortex, were reported to have neuroprotective effects. In addition, the key bioactive ingredients of neolignans, magnolol (1) and honokiol (2), were proved to prevent and treat neurological diseases and psychiatric disorders by protecting nerve cells and brain microvascular endothelial cells (BMECs). Furthermore, neolignans played a role in protecting nerve cells via regulation of neuronal function, suppression of neurotoxicity, etc. This review summarizes the neuroprotective effect, primary mechanisms of the leading neolignans and provides new prospects for the treatment of brain disorders in the future.

Promising Therapeutic Candidate for Myocardial Ischemia/Reperfusion Injury: What Are the Possible Mechanisms and Roles of Phytochemicals?

Percutaneous coronary intervention (PCI) is one of the most effective reperfusion strategies for acute myocardial infarction (AMI) despite myocardial ischemia/reperfusion (I/R) injury, causing one of the causes of most cardiomyocyte injuries and deaths. The pathological processes of myocardial I/R injury include apoptosis, autophagy, and irreversible cell death caused by calcium overload, oxidative stress, and inflammation. Eventually, myocardial I/R injury causes a spike of further cardiomyocyte injury that contributes to final infarct size (IS) and bound with hospitalization of heart failure as well as all-cause mortality within the following 12 months. Therefore, the addition of adjuvant intervention to improve myocardial salvage and cardiac function calls for further investigation. Phytochemicals are non-nutritive bioactive secondary compounds abundantly found in Chinese herbal medicine. Great effort has been put into phytochemicals because they are often in line with the expectations to improve myocardial I/R injury without compromising the clinical efficacy or to even produce synergy. We summarized the previous efforts, briefly outlined the mechanism of myocardial I/R injury, and focused on exploring the cardioprotective effects and potential mechanisms of all phytochemical types that have been investigated under myocardial I/R injury. Phytochemicals deserve to be utilized as promising therapeutic candidates for further development and research on combating myocardial I/R injury. Nevertheless, more studies are needed to provide a better understanding of the mechanism of myocardial I/R injury treatment using phytochemicals and possible side effects associated with this approach.

Effects of Polyphenols on Oxidative Stress, Inflammation, and Interconnected Pathways during Spinal Cord Injury

Despite the progression in targeting the complex pathophysiological mechanisms of neurodegenerative diseases (NDDs) and spinal cord injury (SCI), there is a lack of effective treatments. Moreover, conventional therapies suffer from associated side effects and low efficacy, raising the need for finding potential alternative therapies. In this regard, a comprehensive review was done regarding revealing the main neurological dysregulated pathways and providing alternative therapeutic agents following SCI. From the mechanistic point, oxidative stress and inflammatory pathways are major upstream orchestras of cross-linked dysregulated pathways (e.g., apoptosis, autophagy, and extrinsic mechanisms) following SCI. It urges the need for developing multitarget therapies against SCI complications. Polyphenols, as plant-derived secondary metabolites, have the potential of being introduced as alternative therapeutic agents to pave the way for treating SCI. Such secondary metabolites presented modulatory effects on neuronal oxidative stress, neuroinflammatory, and extrinsic axonal dysregulated pathways in the onset and progression of SCI. In the present review, the potential role of phenolic compounds as critical phytochemicals has also been revealed in regulating upstream dysregulated oxidative stress/inflammatory signaling mediators and extrinsic mechanisms of axonal regeneration after SCI in preclinical and clinical studies. Additionally, the coadministration of polyphenols and stem cells has shown a promising strategy for improving post-SCI complications.

The rich pharmacological activities of Magnolia officinalis and secondary effects based on significant intestinal contributions

ETHNOPHARMACOLOGICAL RELEVANCE

Magnolia officinalis Cortex (M. officinalis) is a traditional herbal drug widely used in Asian countries. Depending on its multiple biological activities, M. officinalis is used to regulate gastrointestinal (GI) motility, relieve cough and asthma, prevent cardiovascular and cerebrovascular diseases, and treat depression and anxiety.

AIM OF THE REVIEW

We aimed to review the abundant form of pharmacodynamics activity and potential mechanisms of action of M. officinalis and the characteristics of the internal processes of the main components. The potential mechanisms of local and distance actions of M. officinalis based on GI tract was provided, and it was used to reveal the interconnections between traditional use, phytochemistry, and pharmacology.

MATERIALS AND METHODS

Published literatures about M. officinalis and its main components were collected from several scientific databases, including PubMed, Elsevier, ScienceDirect, Google Scholar and Web of Science etc. RESULTS: M. officinalis was shown multiple effects including effects on digestive system, respiratory system, central system, which is consistent with traditional applications, as well as some other activities such as cardiovascular system, anticancer, anti-inflammatory and antioxidant effects and so on. The mechanisms of these activities are abundant. Its chief ingredients such as magnolol and honokiol can be metabolized into active metabolites in vivo, which can increase water solubility and bioavailability and exert pharmacological activity in the whole body. In the GI tract, M. officinalis and its main ingredient can regulate GI hormones and substance metabolism, protect the intestinal barrier and affect the gut microbiota (GM). These actions are effective to improve local discomfort and some distal symptoms such as depression, asthma, or metabolic disorders.

CONCLUSIONS

Although M. officinalis has rich pharmacological effects, the GI tract makes great contributions to it. The GI tract is not only an important place for absorption and metabolism but also a key site to help M. officinalis exert local and distal efficacy. Pharmacodynamical studies on the efficacies of distal tissues based on the contributions of the GI tract hold great potential for understanding the benefits of M. officinalis and providing new ideas for the treatment of important diseases.

Bioactive Flavonoids Icaritin and Icariin Protect against Cerebral Ischemia-Reperfusion-Associated Apoptosis and Extracellular Matrix Accumulation in an Ischemic Stroke Mouse Model

Stroke, which is the second leading cause of mortality in the world, is urgently needed to explore the medical strategies for ischemic stroke treatment. Both icariin (ICA) and icaritin (ICT) are the major active flavonoids extracted from Herba epimedii that have been regarded as the neuroprotective agents in disease models. In this study, we aimed to investigate and compare the neuroprotective effects of ICA and ICT in a middle cerebral artery occlusion (MCAO) mouse model. Male ICR mice were pretreated with both ICA and ICT, which ameliorated body weight loss, neurological injury, infarct volume, and pathological change in acute ischemic stroke mice. Furthermore, administration of both ICA and ICT could also protect against neuronal cell apoptotic death, oxidative and nitrosative stress, lipid peroxidation, and extracellular matrix (ECM) accumulation in the brains. The neuroprotective effects of ICT are slightly better than that of ICA in acute cerebral ischemic stroke mice. These results suggest that pretreatment with both ICA and ICT improves the neuronal cell apoptosis and responses of oxidative/nitrosative stress and counteracts the ECM accumulation in the brains of acute cerebral ischemic stroke mice. Both ICA and ICT treatment may serve as a useful therapeutic strategy for acute ischemic stroke.

Honokiol: A naturally occurring lignan with pleiotropic bioactivities

Honokiol is the dominant biphenolic compound isolated from the Magnolia tree, and has long been considered as the active constituent of the traditional Chinese herb, 'Houpo', which is widely used to treat symptoms due to 'stagnation of qi'. Pharmacological studies have shown that honokiol possesses a wide range of bioactivities without obvious toxicity. Honokiol protects the liver, kidneys, nervous system, and cardiovascular system through reducing oxidative stress and relieving inflammation. Moreover, honokiol shows anti-diabetic property through enhancing insulin sensitivity, and anti-obese property through promoting browning of adipocytes. In vivo and in vitro studies indicated that honokiol functions as an anti-cancer agent through multiple mechanisms: inhibiting angiogenesis, promoting cell apoptosis, and regulating cell cycle. A variety of therapeutic effects of honokiol may be associated with its physiochemical properties, which make honokiol readily cross the blood brain barrier and the blood-cerebrospinal fluid barrier, with high bioavailability. In the future, more clinical researches on honokiol are needed to fully authenticate its therapeutic values.

Melatonin protects against focal cerebral ischemia-reperfusion injury in diabetic mice by ameliorating mitochondrial impairments: involvement of the Akt-SIRT3-SOD2 signaling pathway

Diabetic patients are more vulnerable to cerebral ischemia-reperfusion (CIR) injury and have a worse prognosis and higher mortality after ischemic stroke than non-diabetic counterparts. Melatonin can exert neuroprotective effects against CIR injury in nondiabetic animal models. However, its effects on diabetic CIR injury and the underlying mechanisms remain unclarified. Herein, we found that melatonin administration improved neurological deficit, cerebral infarct volume, brain edema, and cell viability, reduced mitochondrial swelling, reactive oxygen species generation, and cytoplasmic cytochrome C release, and increased mitochondrial antioxidant enzymes activities, adenosine triphosphate production, and mitochondrial membrane potential in both streptozotocin-induced diabetic mice and high glucose-treated HT22 cells. Importantly, melatonin also activated protein kinase B (Akt) and sirtuin 3 (SIRT3)/superoxide dismutase 2 (SOD2) signaling and upregulated mitochondrial biogenesis-related transcription factors. However, these effects were largely attenuated by LY294002 (a specific Akt signaling blocker) administration. Additionally, 3-TYP (a selective SIRT3 inhibitor) and SIRT3 siRNA inhibited the above protective effects of melatonin as well as the upregulation of SIRT3 and the decrease of SOD2 acetylation but did not affect the p-Akt/Akt ratio. Overall, we demonstrate that melatonin can alleviate CIR injury in diabetic mice by activating Akt-SIRT3-SOD2 signaling and subsequently improving mitochondrial damage.

Nutraceutical based SIRT3 activators as therapeutic targets in Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, and its incidence is increasing worldwide with increased lifespan. Currently, there is no effective treatment to cure or prevent the progression of AD, which indicates the need to develop novel therapeutic targets and agents. Sirtuins, especially SIRT3, a mitochondrial deacetylase, are NAD-dependent histone deacetylases involved in aging and longevity. Accumulating evidence indicates that SIRT3 dysfunction is strongly associated with pathologies of AD, hence, therapeutic modulation of SIRT3 activity may be a novel application to ameliorate the pathologies of AD. Natural products commonly used in traditional medicine have wide utility and appear to have therapeutic benefits for the treatment of neurodegenerative diseases such as AD. The present review summarizes the currently available natural SIRT3 activators and their potentially neuroprotective molecular mechanisms of action that make them a promising agent in the treatment and management of neurodegenerative diseases such as AD.

A review of the phytochemistry and pharmacological activities of Magnoliae officinalis cortex

ETHNOPHARMACOLOGICAL RELEVANCE

Magnoliae Officinalis Cortex (the dried bark of Magnolia officinalis), a widely used traditional Chinese medicine, is also known as 'Houpo' (Chinese: ). Magnoliae Officinalis Cortex has a wide range of pharmacological effects and has been used to treat conditions such as abdominal distention, vomiting, diarrhea, food accumulation, Qi stagnation, constipation, phlegm and fluid retention and cough resulting from asthma.

AIMS OF THE REVIEW

The present paper reviews advances in research relating to the botany, ethnopharmacology, phytochemistry, pharmacology and toxicology of Magnoliae Officinalis Cortex. Prospects for future investigation and application of this herb are also discussed.

MATERIALS AND METHODS

Information on Magnoliae Officinalis Cortex was obtained from published materials, including ancient and modern books; PhD and MSc dissertations; monographs on medicinal plants; the pharmacopoeia of different countries and electronic databases, such as SCI finder, PubMed, Web of Science, ACS, Science Direct, Wiley, Springer, Taylor, AGRIS, Europe PMC, EBSCO host, CNKI, WanFang DATA, J-STAGE and Google Scholar.

RESULTS

More than 200 chemical compounds have been isolated from Magnoliae Officinalis Cortex, including lignans, phenylethanoid glycosides, phenolic glycosides, alkaloids, steroids and essential oils. The plant has been reported to have pharmacological effects on the digestive system, nervous system and cardiovascular and cerebrovascular systems, as well as antibacterial, anti-tumour, analgesic, anti-inflammatory and anti-oxidative effects.

CONCLUSIONS

Magnoliae Officinalis Cortex is an essential traditional Chinese medicine with pharmacological activities that mainly affect the digestive system, nervous system and cardiovascular and cerebrovascular systems. This review summarises its botany, ethnopharmacology, phytochemistry, pharmacology and toxicology. These information suggest that we should focus on the development of new drugs related to Magnoliae Officinalis Cortex, including specific constituents, so that Magnoliae Officinalis Cortex can exert greater therapeutic potential. Meanwhile, it is important to pay attention to the rational use of Magnolia resources, avoiding over-harvesting which could lead to lack of resources. We should also pursue research on Magnolia substitutes and develop resources such as Magnoliae Officinalis Flos and Magnolia Leaf.

Neuroprotective Strategies for Neurological Disorders by Natural Products: An update

Nature has bestowed mankind with surplus resources (natural products) on land and water. Natural products have a significant role in the prevention of disease and boosting of health in humans and animals. These natural products have been experimentally documented to possess various biological properties such as antioxidant, anti-inflammatory and anti-apoptotic activities. In vitro and in vivo studies have further established the usefulness of natural products in various preclinical models of neurodegenerative disorders. Natural products include phytoconstituents, like polyphenolic antioxidants, found in herbs, fruits, nuts, vegetables and also in marine and freshwater flora. These phytoconstituents may potentially suppress neurodegeneration and improve memory as well as cognitive functions of the brain. Also, they are known to play a pivotal role in the prevention and cure of different neurodegenerative diseases, such as Alzheimer's disease, epilepsy, Parkinson's disease and other neuronal disorders. The large-scale neuro-pharmacological activities of natural products have been documented due to the result of either the inhibition of inflammatory processes, or the up-regulation of various cell survival proteins or a combination of both. Due to the scarcity of human studies on neuroprotective effects of natural products, this review focuses on the various established activities of natural products in in vitro and in vivo preclinical models, and their potential neuro-therapeutic applications using the available knowledge in the literature.

SIRT3 activator honokiol ameliorates surgery/anesthesia-induced cognitive decline in mice through anti-oxidative stress and anti-inflammatory in hippocampus

AIMS

Increasing evidence indicates that neuroinflammatory and oxidative stress play two pivotal roles in cognitive impairment after surgery. Honokiol (HNK), as an activator of Sirtuin3 (SIRT3), has potential multiple biological functions. The aim of these experiments is to evaluate the effects of HNK on surgery/anesthesia-induced cognitive decline in mice.

METHODS

Adult C57BL/6 mice received a laparotomy under sevoflurane anesthesia and HNK or SIRT3 inhibitor (3-TYP) treatment. Cognitive function and locomotor activity of mice were evaluated using fear conditioning test and open field test on postoperative 1 and 3 days. Neuronal apoptosis in CA1 and CA3 area of hippocampus was examined using TUNEL assay. And Western blot was applied to measure the expression of pro-inflammatory cytokines and SIRT3/SOD2 signaling-associated proteins in hippocampus. Meanwhile, SIRT3 positive cells were calculated by immunohistochemistry. The mitochondrial membrane potential, malondialdehyde (MDA), and mitochondrial radical oxygen species (mtROS) were detected using standard methods.

RESULTS

Honokiol attenuated surgery-induced memory loss and neuronal apoptosis, decreased neuroinflammatory response, and ameliorated oxidative damage in hippocampus. Notably, surgery/anesthesia induced an obviously decrease in hippocampal SIRT3 expression, whereas the HNK increased SIRT3 expression and thus decreased the acetylation of superoxide dismutase 2 (SOD2). However, 3-TYP treatment inhibited the HNK's rescuing effects.

CONCLUSIONS

These results suggested that activation of SIRT3 by honokiol may attenuate surgery/anesthesia-induced cognitive impairment in mice through regulation of oxidative stress and neuroinflammatory in hippocampus.

Preventive Effect of Low Intensity Pulsed Ultrasound against Experimental Cerebral Ischemia/Reperfusion Injury via Apoptosis Reduction and Brain-derived Neurotrophic Factor Induction

Stroke is known as the top 10 causes of death worldwide. Development of effectively neuroprotective or preventive strategies for ischemia stroke is imperative. For the purpose of stroke prevention, we tested the neuroprotective effects of low-intensity pulsed ultrasound (LIPUS) on ischemic stroke. Adult C57BL/6 mice were used to daily treatment with LIPUS for 5 days on left hemisphere before middle cerebral artery occlusion (MCAO)-induced cerebral ischemia/reperfusion injury. Western blotting and immunohistochemistry were performed to assess the protein expressions of signaling molecules. Pretreatment with LIPUS significantly ameliorated the brain ischemic damage, including the reduction of neurological deficit score, infarct area, histopathological score, and showed a better performance in neurological and behavior functions. LIPUS pretreatment could also significantly decrease the neuronal cell apoptosis and upregulation of apoptosis-related signaling molecules and downregulation of brain-derived neurotrophic factor (BDNF) in brain tissues of MCAO-treated mice. Furthermore, LIPUS significantly prevented the decreased cell viability, the increased caspase-3 cleavage, and the decreased BDNF expression in ischemia/reperfusion-treated microglial cells. These results demonstrate that LIPUS effectively prevented the cerebral ischemia/reperfusion injury through apoptosis reduction and BDNF induction in a MCAO mouse model. The neuroprotective potential of LIPUS may provide a novel preventive strategy for ischemic stroke in high-risk patients.

NOX Inhibitors - A Promising Avenue for Ischemic Stroke

NADPH-oxidase (NOX) mediated superoxide originally found on leukocytes, but now recognized in several types of cells in the brain. It has been shown to play an important role in the progression of stroke and related cerebrovascular disease. NOX is a multisubunit complex consisting of 2 membrane-associated and 4 cytosolic subunits. NOX activation occurs when cytosolic subunits translocate to the membrane, leading to transport electrons to oxygen, thus producing superoxide. Superoxide produced by NOX is thought to function in long-term potentiation and intercellular signaling, but excessive production is damaging and has been implicated to play an important role in the progression of ischemic brain. Thus, inhibition of NOX activity may prove to be a promising treatment for ischemic brain as well as an adjunctive agent to prevent its secondary complications. There is mounting evidence that NOX inhibition in the ischemic brain is neuroprotective, and targeting NOX in circulating immune cells will also improve outcome. This review will focus on therapeutic effects of NOX assembly inhibitors in brain ischemia and stroke. However, the lack of specificity and toxicities of existing inhibitors are clear hurdles that will need to be overcome before this class of compounds could be translated clinically.

One-Compound-Multi-Target: Combination Prospect of Natural Compounds with Thrombolytic Therapy in Acute Ischemic Stroke

Tissue plasminogen activator (t-PA) is the only FDA-approved drug for acute ischemic stroke treatment, but its clinical use is limited due to the narrow therapeutic time window and severe adverse effects, including hemorrhagic transformation (HT) and neurotoxicity. One of the potential resolutions is to use adjunct therapies to reduce the side effects and extend t-PA's therapeutic time window. However, therapies modulating single target seem not to be satisfied, and a multitarget strategy is warranted to resolve such complex disease. Recently, large amount of efforts have been made to explore the active compounds from herbal supplements to treat ischemic stroke. Some natural compounds revealed both neuro- and bloodbrain- barrier (BBB)-protective effects by concurrently targeting multiple cellular signaling pathways in cerebral ischemia-reperfusion injury. Thus, those compounds are potential to be one-drug-multi-target agents as combined therapy with t-PA for ischemic stroke. In this review article, we summarize current progress about molecular targets involving in t-PA-mediated HT and neurotoxicity in ischemic brain injury. Based on these targets, we select 23 promising compounds from currently available literature with the bioactivities simultaneously targeting several important molecular targets. We propose that those compounds merit further investigation as combined therapy with t-PA. Finally, we discuss the potential drawbacks of the natural compounds' studies and raise several important issues to be addressed in the future for the development of natural compound as an adjunct therapy.

Honokiol suppresses TNF-α-induced neutrophil adhesion on cerebral endothelial cells by disrupting polyubiquitination and degradation of IκBα

Adhesion molecules expressed on cerebral endothelial cells (ECs) mediate leukocyte recruitment and play a significant role in cerebral inflammation. Increased levels of adhesion molecules on the EC surface induce leukocyte infiltration into inflammatory areas and are thus hallmarkers of inflammation. Honokiol, isolated from the Chinese medicinal herb Magnolia officinalis, has various pharmacological activities, including anti-inflammatory effects, yet the nature of honokiol targeting molecules remains to be revealed. Here, we investigated the inhibitory effect of honokiol on neutrophil adhesion and vascular cell adhesion molecule-1 (VCAM-1) expression, which underlie its molecular target, and mechanisms for inactivating nuclear factor κ enhancer binding protein (NF-κB) in mouse cerebral ECs. Honokiol inhibited tumour necrosis factor-α (TNF-α)-induced neutrophil adhesion and VCAM-1 gene expression in cerebral ECs. The inflammatory transcription factor NF-κB was downregulated by honokiol. Honokiol significantly blocked TNF-α-induced NF-κB p65 nuclear translocation and degradation of the proteasome-dependent inhibitor of NF-κB α (IκBα). From docking model prediction, honokiol directly targeted the ubiquitin-ubiquitin interface of Lys48-linked polychains. Moreover, honokiol prevented the TNF-α-induced Lys48-linked polyubiquitination, including IκBα-polyubiquitin interaction. Honokiol has protective anti-inflammatory effects on TNF-α-induced neutrophil adhesion and VCAM-1 gene expression in cerebral ECs, at least in part by directly inhibiting ubiquitination-mediated IκBα degradation and then preventing NF-κB nuclear translocation.

Embryo-fetal development toxicity of honokiol microemulsion intravenously administered to pregnant rats

The aim of this study was to evaluate the embryo-fetal development toxicity of honokiol microemulsion. The drug was intravenously injected to pregnant SD rats at dose levels of 0, 200, 600 and 2000 μg/kg/day from day 6-15 of gestation. All the pregnant animals were observed for body weights and any abnormal changes and subjected to caesarean-section on gestation day (GD) 20; all fetuses obtained from caesarean-section were assessed by external inspection, visceral and skeletal examinations. No treatment-related external alterations as well as visceral and skeletal malformations were observed in honokiol microemulsion groups. There was no significant difference in the body weight gain of the pregnant rats, average number of corpora lutea, and the gravid uterus weight in the honokiol microemulsion groups compared with the vehicle control group. However, at a dose level of 2000 μg/kg/day, there was embryo-fetal developmental toxicity observed, including a decrease in the body length and tail length of fetuses. In conclusion, the no-observed-adverse-effect level (NOAEL) of honokiol microemulsion is 600 μg/kg/day, 75 times above the therapeutic dosage and it has embryo-fetal toxicity at a dose level of 2000 μg/kg/day, which is approximately 250 times above the therapeutic dosage.

Honokiol downregulates Kruppel-like factor 4 expression, attenuates inflammation, and reduces histopathology after spinal cord injury in rats

STUDY DESIGN

Randomized experimental study.

OBJECTIVE

To investigate the neuroprotective effect of honokiol (HNK) on rats subjected to traumatic spinal cord injury (SCI) and the molecular mechanisms.

SUMMARY OF BACKGROUND DATA

Inflammation contributes to the secondary injury to the spinal cord. Honokiol has been used as a neuroprotective agent because of its strong antioxidant and anti-inflammatory properties. Kruppel-like factor 4 (Klf4) is a newly identified critical target for the anti-inflammatory effect of HNK. Whether HNK can inhibit inflammatory response in rat model of SCI through mediating the expression of Klf4 has yet to be elucidated.

METHODS

Eighty-four adult female Sprague-Dawley rats were randomly divided into 4 groups as sham, SCI, SCI + Vehicle (0.1% propylene glycol in saline, intraperitoneally), and SCI + HNK (20 mg/kg, intraperitoneally) groups. The influences of HNK on the proinflammatory cytokines, microglial activation, neutrophil infiltration, histological changes, and improvement in motor function were assessed.

RESULTS

In the SCI group, proinflammatory cytokines, microglial activation, neutrophil infiltration, and Klf4 expression levels were increased compared with the sham group (P < 0.001). HNK intervention downregulated the expression of Klf4, reduced the production of proinflammatory cytokines, inhibited microglial activation, and neutrophil infiltration (P < 0.05). Furthermore, HNK also reduced histopathology and improved functional outcome after traumatic SCI.

CONCLUSION

HNK reduces secondary tissue damage and improves locomotor function recovery after SCI through suppressing inflammatory response, and can be used as a potential therapeutic agent for SCI.

LEVEL OF EVIDENCE

NA.

Mechanisms and potential therapeutic applications of microglial activation after brain injury

As the resident immune cells of the central nervous system, microglia rapidly respond to brain insults, including stroke and traumatic brain injury. Microglial activation plays a major role in neuronal cell damage and death by releasing a variety of inflammatory and neurotoxic mediators. Their activation is an early response that may exacerbate brain injury and many other stressors, especially in the acute stages, but are also essential to brain recovery and repair. The full range of microglial activities is still not completely understood, but there is accumulating knowledge about their role following brain injury. We review recent progress related to the deleterious and beneficial effects of microglia in the setting of acute neurological insults and the current literature surrounding pharmacological interventions for intervention.

Honokiol abrogates lipopolysaccharide-induced depressive like behavior by impeding neuroinflammation and oxido-nitrosative stress in mice

Depression is an inflammatory, commonly occurring and lethal psychiatric disorder having high lifetime prevalence. Preclinical and clinical studies suggest that activation of immuno-inflammatory and oxido-nitrosative stress pathways play major role in the pathophysiology of depression. Honokiol (HNK) is a biphenolic neolignan possessing multiple biological activities including antioxidant, anti-inflammatory, anxiolytic, antidepressant and neuroprotective. The present study investigated the effect of HNK (2.5 and 5 mg/kg, i.p.) pretreatment (30 min prior to LPS) on lipopolysaccharide (LPS) (0.83 mg/kg, i.p.) induced depressive like behavior, neuroinflammation, and oxido-nitrosative stress in mice. HNK pretreatment at both the doses significantly attenuated LPS induced depressive-like behavior by reducing the immobility time in forced swim and tail suspension test, and by improving the anhedonic behavior observed in sucrose preference test. HNK pretreatment ameliorated LPS induced neuroinflammation by reducing IL-1β, IL-6 and TNF-α level in hippocampus (HC) and prefrontal cortex (PFC). HNK pretreatment prevented LPS evoked oxidative/nitrosative stress via improving reduced glutathione level along with reduction in the lipid peroxidation and nitrite level in HC and PFC. Pretreatment with HNK also prevented the increase in plasma corticosterone (CORT) and decrease in hippocampal BDNF level in LPS challenged mice. In conclusion, current investigation suggested that HNK pretreatment provided protection against LPS-induced depressive like behavior which may be mediated by repression of pro-inflammatory cytokines as well as oxido-nitrosative stress in HC and PFC. Our results strongly speculated that HNK could be a therapeutic approach for the treatment of depression and other pathophysiological conditions which are closely associated with neuroinflammation and oxido-nitrosative stress.

Induction of apoptosis by VB1 in breast cancer cells: the role of reactive oxygen species and Bcl-2 family proteins

We have previously reported that the EVn-50 mixture of vitexins (lignan compounds) containing the purified vitexin (neolignan) compound, 6-hydroxy-4(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl‑7-methoxy-3,4-dihydro-2-naphthaldehyde, termed VB1, exhibits potent anticancer activity through the induction of apoptosis in several types of cancer cells, including MDA-MB‑231 cells. However, the exact molecular mechanisms by which VB1 induces apoptosis in MDA-MB‑231 cells have not yet been fully elucidated. In this study, to our knowledge, we provide for the first time mechanistic evidence that VB1-induced apoptosis in the human breast cancer line, MDA-MB-231, is associated with the generation of reactive oxygen species (ROS), the activation of caspases and the modulation of the expression of myeloid leukemia cell differentiation protein 1 (Mcl‑1), B cell lymphoma‑2 (Bcl-2) and Bcl-2-associated X (Bax) proteins. The silencing of Mcl-1 by RNA interference enhanced VB1-induced apoptosis. In addition, VB1 did not induce ROS generation or apoptosis in the immortalized non‑cancerous breast cell line, MCF-10A. Our findings reveal a novel mechanism underlying VB1-induced apoptosis, and highlight VB1 as a promising candidate for the therapy of human breast cancer.

Neuro-modulating effects of honokiol: a review

Honokiol is a poly-phenolic compound that exerts neuroprotective properties through a variety of mechanisms. It has therapeutic potential in anxiety, pain, cerebrovascular injury, epilepsy, and cognitive disorders including Alzheimer’s disease. It has been traditionally used in medical practices throughout much of Southeast Asia, but has now become more widely studied due to its pleiotropic effects. Most current research regarding this compound has focused on its chemotherapeutic properties. However, it has the potential to be an effective neuroprotective agent as well. This review summarizes what is currently known regarding the mechanisms involved in the neuroprotective and anesthetic effects of this compound and identifies potential areas for further research.

Modulation of crucial adenosinetriphosphatase activities due to U-74389G administration in a porcine model of intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) represents a partially-understood cerebrovascular disease of high incidence, morbidity and mortality. We, herein, report the findings of our study concerning the role of two important adenosinetriphosphatases (ATPases) in a porcine model of spontaneous ICH that we have recently developed (by following recent references as well as previously-established models and techniques), with a focus on the first 4 and 24 h following the lesion's induction, in combination with a study of the effectiveness of the lazaroid antioxidant U-74389G administration. Our study demonstrates that the examined ICH model does not cause a decrease in Na(+),K(+)-ATPase activity (the levels of which are responsible for a very large part of neuronal energy expenditure) in the perihematomal basal ganglia territory, nor a change in the activity of Mg(2+)-ATPase. This is the first report focusing on these crucial ATPases in the experimental setting of ICH and differs from the majority of the findings concerning the behavior of these (crucial for central nervous system cell survival) enzymes under stroke-related ischemic conditions. The administration of U-74389G (an established antioxidant) in this ICH model revealed an injury specific type of behavior, that could be considered as neuroprotective provided that one considers that Na(+),K(+)- and Mg(2+)-ATPase inhibition might in this case diminish the local ATP consumption.

Honokiol protects rat hearts against myocardial ischemia reperfusion injury by reducing oxidative stress and inflammation

Honokiol, a potent radical scavenger, has been demonstrated to ameliorate cerebral infarction following ischemia/reperfusion (I/R) injury. However, its effects on myocardial I/R injury remain unclear. The present study aimed to examine the effects of honokiol on myocardial I/R injury and to investigate its potential cardioprotective mechanisms. Sprague-Dawley rats were pretreated with honokiol and exposed to a 30-min myocardial ischemia followed by 2-h coronary reperfusion. Myocardial I/R-induced infarct size and biochemical and histological changes were compared. The expression of nuclear factor κB(NF-κB; p65) was assessed by western blotting. Pretreatment with honokiol significantly reduced infarct size, and serum creatine kinase (CK) and lactate dehydrogenase (LDH) release compared with those in the I/R group following a 2-h reperfusion. The malondialdehyde (MDA) level, myeloperoxidase (MPO) activity, concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-6 and expression level of NF-κB were all reduced by honokiol pretreatment, while honokiol inhibited the decreases in superoxide dismutase (SOD) and catalase (CAT) activities. In addition, less neutrophil infiltration and histopathological damage in the myocardium were observed in the honokiol-pretreated group. These findings indicate that honokiol pretreatment diminished myocardial I/R injury through attenuation of oxidative stress and inflammation.

NADPH oxidase in stroke and cerebrovascular disease

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) was originally identified in immune cells as playing an important microbicidal role. In stroke and cerebrovascular disease, inflammation is increasingly being recognized as contributing negatively to neurological outcome, with NOX as an important source of superoxide. Several labs have now shown that blocking or deleting NOX in the experimental stroke models protects from brain ischemia. Recent work has implicated glucose as an important NOX substrate leading to reperfusion injury, and that NOX inhibition can improve the detrimental effects of hyperglycemia on stroke. NOX inhibition also appears to ameliorate complications of thrombolytic therapy by reducing blood-brain barrier disruption, edema formation, and hemorrhage. Further, NOX from circulating inflammatory cells seems to contribute more to ischemic injury more than NOX generated from endogenous brain residential cells. Several pharmacological inhibitors of NOX are now available. Thus, blocking NOX activation may prove to be a promising treatment for stroke as well as an adjunctive agent to prevent its secondary complications.

Magnolol Protects against MPTP/MPP(+)-Induced Toxicity via Inhibition of Oxidative Stress in In Vivo and In Vitro Models of Parkinson's Disease

The aim of this study is to investigate the role of magnolol in preventing 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP-) induced neurodegeneration in mice and 1-methyl-4-phenylpyridinium ion-(MPP(+)-) induced cytotoxicity to human neuroblastoma SH-SY5Y cells and to examine the possible mechanisms. Magnolol (30 mg/kg) was orally administered to C57BL/6N mice once a day for 4 or 5 days either before or after MPTP treatment. Western blot analysis revealed that MPTP injections substantially decreased protein levels of dopamine transporter (DAT) and tyrosine hydroxylase (TH) and increased glial fibrillary acidic protein (GFAP) levels in the striatum. Both treatments with magnolol significantly attenuated MPTP-induced decrease in DAT and TH protein levels in the striatum. However, these treatments did not affect MPTP-induced increase in GFAP levels. Moreover, oral administration of magnolol almost completely prevented MPTP-induced lipid peroxidation in the striatum. In human neuroblastoma SH-SY5Y cells, magnolol significantly attenuated MPP(+)-induced cytotoxicity and the production of reactive oxygen species. These results suggest that magnolol has protective effects via an antioxidative mechanism in both in vivo and in vitro models of Parkinson's disease.

Therapeutic targeting of Krüppel-like factor 4 abrogates microglial activation

BACKGROUND

Neuroinflammation occurs as a result of microglial activation in response to invading micro-organisms or other inflammatory stimuli within the central nervous system. According to our earlier findings, Krüppel-like factor 4 (Klf4), a zinc finger transcription factor, is involved in microglial activation and subsequent release of proinflammatory cytokines, tumor necrosis factor alpha, macrophage chemoattractant protein-1 and interleukin-6 as well as proinflammatory enzymes, inducible nitric oxide synthase and cyclooxygenase-2 in lipopolysaccharide-treated microglial cells. Our current study focuses on finding the molecular mechanism of the anti-inflammatory activities of honokiol in lipopolysaccharide-treated microglia with emphasis on the regulation of Klf4.

METHODS

For in vitro studies, mouse microglial BV-2 cell lines as well as primary microglia were treated with 500 ng/mL lipopolysaccharide as well as 1 μM and 10 μM of honokiol. We cloned full-length Klf4 cDNA in pcDNA3.1 expression vector and transfected BV-2 cells with this construct using lipofectamine for overexpression studies. For in vivo studies, brain tissues were isolated from BALB/c mice treated with 5 mg/kg body weight of lipopolysaccharide either with or without 2.5 or 5 mg/kg body weight of honokiol. Expression of Klf4, cyclooxygenase-2, inducible nitric oxide synthase and phospho-nuclear factor-kappa B was measured using immunoblotting. We also measured the levels of cytokines, reactive oxygen species and nitric oxide in different conditions.

RESULTS

Our findings suggest that honokiol can substantially downregulate the production of proinflammatory cytokines and inflammatory enzymes in lipopolysaccharide-stimulated microglia. In addition, honokiol downregulates lipopolysaccharide-induced upregulation of both Klf4 and phospho-nuclear factor-kappa B in these cells. We also found that overexpression of Klf4 in BV-2 cells suppresses the anti-inflammatory action of honokiol.

CONCLUSIONS

Honokiol potentially reduces inflammation in activated microglia in a Klf4-dependent manner.

Therapeutic applications of compounds in the Magnolia family

The bark and/or seed cones of the Magnolia tree have been used in traditional herbal medicines in Korea, China and Japan. Bioactive ingredients such as magnolol, honokiol, 4-O-methylhonokiol and obovatol have received great attention, judging by the large number of investigators who have studied their pharmacological effects for the treatment of various diseases. Recently, many investigators reported the anti-cancer, anti-stress, anti-anxiety, anti-depressant, anti-oxidant, anti-inflammatory and hepatoprotective effects as well as toxicities and pharmacokinetics data, however, the mechanisms underlying these pharmacological activities are not clear. The aim of this study was to review a variety of experimental and clinical reports and, describe the effectiveness, toxicities and pharmacokinetics, and possible mechanisms of Magnolia and/or its constituents.

Natural compounds from traditional medicinal herbs in the treatment of cerebral ischemia/reperfusion injury

More and more attention in the field of drug discovery has been focused on the neuroprotection of natural compounds from traditional medicinal herbs. Cerebral ischemia is a complex pathological process involving a series of mechanisms, and a framework for the development of neuroprotectants from traditional herb medicine is a promising treatment for cerebral ischemia. Natural compounds with the effects of anti-oxidation, anti-inflammation, calcium antagonization, anti-apoptosis, and neurofunctional regulation exhibit preventive or therapeutic effects on experimental ischemic brain injury. According to the pharmacological mechanisms underlying neuroprotection, we evaluated natural products from traditional medicinal herbs that exhibit protective effects on ischemic brain injury and characterized the promising targets.

Microglial activation in stroke: therapeutic targets

Microglial activation is an early response to brain ischemia and many other stressors. Microglia continuously monitor and respond to changes in brain homeostasis and to specific signaling molecules expressed or released by neighboring cells. These signaling molecules, including ATP, glutamate, cytokines, prostaglandins, zinc, reactive oxygen species, and HSP60, may induce microglial proliferation and migration to the sites of injury. They also induce a nonspecific innate immune response that may exacerbate acute ischemic injury. This innate immune response includes release of reactive oxygen species, cytokines, and proteases. Microglial activation requires hours to days to fully develop, and thus presents a target for therapeutic intervention with a much longer window of opportunity than acute neuroprotection. Effective agents are now available for blocking both microglial receptor activation and the microglia effector responses that drive the inflammatory response after stroke. Effective agents are also available for targeting the signal transduction mechanisms linking these events. However, the innate immune response can have beneficial as well deleterious effects on outcome after stoke, and a challenge will be to find ways to selectively suppress the deleterious effects of microglial activation after stroke without compromising neurovascular repair and remodeling.

Adenosine preconditions against ouabain but not against glutamate on CA1-evoked potentials in rat hippocampal slices

Hypoxic and ischaemic brain damage are believed to involve excessive release of glutamate, and recent work shows that glutamate-induced damage in brain slices can be reduced by preconditioning with hypoxia or glutamate itself. Because adenosine is a powerful preconditioning agent, we have investigated whether adenosine could precondition against glutamate in vitro. In rat hippocampal slices, glutamate depolarization reduced the amplitudes of antidromic- and orthodromic-evoked potentials, with only partial recovery. Applying adenosine before these insults failed to increase that recovery. Ouabain also produced depolarization with partial reversibility, but adenosine pretreatment increased the extent of recovery. The preconditioning effect of adenosine on ouabain responses was prevented by blocking receptors for N-methyl-D-aspartate (NMDA), but not receptors for kainate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and was blocked by inhibiting nitric oxide synthase. Preconditioning was also abolished by the ATP-dependent potassium channel blockers, glibenclamide (cytoplasmic) or 5-hydroxydecanoate (mitochondrial). We conclude that adenosine does not precondition against glutamate in hippocampal slices, but that it does precondition against ouabain with a pharmacology similar to studies in vivo. Ischaemic neuronal damage is a complex of many factors, and because adenosine can precondition against ischaemic neuronal damage, its failure to protect against glutamate highlights limitations of using glutamate alone as a model for ischaemia. Because damage following ischaemia, trauma or excitotoxicity also involves reduced Na(+),K(+)-ATPase activity, and adenosine can precondition against ouabain, we propose that ouabain-induced damage represents an additional or alternative model for the contribution to cell damage of Na(+),K(+)-ATPase loss, this being more relevant to the mechanisms of preconditioning.