Baicalein ameliorated the upregulation of striatal glutamatergic transmission in the mice model of Parkinson's disease

Oxidative Stress and Dopaminergic Metabolism: A Major PD Pathogenic Mechanism and Basis of Potential Antioxidant Therapies

Reactive oxygen species (ROS)-induced oxidative stress triggers the vicious cycle leading to the degeneration of dopaminergic neurons in the nigra pars compacta. ROS produced during the metabolism of dopamine is immediately neutralized by the endogenous antioxidant defense system (EADS) under physiological conditions. Aging decreases the vigilance of EADS and makes the dopaminergic neurons more vulnerable to oxidative stress. As a result, ROS left over by EADS oxidize the dopamine-derived catechols and produces a number of reactive dopamine quinones, which are precursors to endogenous neurotoxins. In addition, ROS causes lipid peroxidation, uncoupling of the electron transport chain, and DNA damage, which lead to mitochondrial dysfunction, lysosomal dysfunction, and synaptic dysfunction. The mutations in genes such as DNAJC6, SYNJ1, SH3GL2, LRRK2, PRKN, and VPS35 caused by ROS have been associated with synaptic dysfunction and the pathogenesis of Parkinson's disease (PD). The available drugs that are used against PD can only delay the progression of the disease, but they produce various side effects. Through their antioxidant activity, flavonoids can substantiate the EADS of dopaminergic neurons and disrupt the vicious cycle incepted by oxidative stress. In this review, we show how the oxidative metabolism of dopamine generates ROS and dopamine-quinones, which then exert unrestrained OS, causing mutations in several genes involved in the proper functioning of mitochondrion, synapse, and lysosome. Besides, we also present some examples of approved drugs used for the treatment of PD, therapies in the clinical trial phase, and an update on the flavonoids that have been tested to boost the EADS of dopaminergic neurons.

Baicalein Attenuates Brain Iron Accumulation through Protecting Aconitase 1 from Oxidative Stress in Rotenone-Induced Parkinson's Disease in Rats

Aconitase 1 (ACO1) links oxidative stress and iron accumulation in Parkinson's disease (PD). ACO1 loses its aconitase activity and turns into iron regulatory protein 1 (IRP1) upon oxidative stress. IRP1 plays an important role in the accumulation of intracellular iron. Baicalein is a flavonoid isolated from the roots of Scutellaria baicalensis. The present results show that baicalein could bind to ACO1 and protect its isoform from the oxidative stress induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Furthermore, baicalein promoted aconitase activity and inhibited IRP1 activation in rotenone-induced PD models. Additionally, baicalein decreased the hydroxyl radicals generated by iron. In conclusion, baicalein attenuated iron accumulation and iron-induced oxidative stress in the brain of PD rats by protecting ACO1.

Momordica Charantia Polysaccharides Attenuates MPP+-Induced Injury in Parkinson’s Disease Mice and Cell Models by Regulating TLR4/MyD88/NF-κB Pathway

Objective. To investigate the potential role of Momordica charantia polysaccharides (MCPs) in Parkinson’s disease (PD) and reveal the molecular mechanism of its function. Method. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium (1-methyl-4-phenylpyridinium, MPP+) were used to establish PD mice and cell models. The mice and cells were divided into 4 groups: Control group, Control+MCPs group, PD group, and PD+MCPs group. Pole climbing experiment and Rotarod experiment were used to observe the coordination ability of mice. High-performance liquid chromatography and enzyme-linked immunosorbent assay (ELISA) were used to determine neurotransmitters and metabolites, inflammatory factors TNF-α and IL-1β, oxidative stress-related markers SOD, MDA, and GSH in striatum tissues. Western blot was used to determine the protein levels of tyrosine hydroxylase (TH), oxidative stress-related protein Cytochrome C (Cytochrome C), and apoptosis-related proteins Bcl-2, Bax, and cleaved Caspase-3 in tissues and cells. Moreover, flow cytometry, PI staining, and fluorescence were used to observe cell apoptosis. Finally, the activation effect of MCPs on TLR4/MyD88/NF-κB signaling pathway was observed and verified. Results. Compared with the Control group, MPTP treatment can induce brain damage in mice (all $P<0.05$ ), change the metabolic state of neurotransmitters (all $P<0.05$ ), induce inflammation (all $P<0.05$ ), and induce apoptosis and the occurrence of oxidation reaction (all $P<0.05$ ); however, MCPs treatment can significantly reverse the above changes (all $P<0.05$ ). In cell models, studies have found that MCPs can play a protective role by regulating the activation state of TLR4/MyD88/NF-κB pathway. Conclusion. This study found that the application of MCPs therapy can play anti-inflammatory, antioxidative stress, and antiapoptotic effects in PD by regulating the activation of the TLR4/MyD88/NF-κB pathway.

Flavonoids: Potential Candidates for the Treatment of Neurodegenerative Disorders

Neurodegenerative disorders, such as Parkinson's disease (PD), Alzheimer's disease (AD), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD), are the most concerning disorders due to the lack of effective therapy and dramatic rise in affected cases. Although these disorders have diverse clinical manifestations, they all share a common cellular stress response. These cellular stress responses including neuroinflammation, oxidative stress, proteotoxicity, and endoplasmic reticulum (ER)-stress, which combats with stress conditions. Environmental stress/toxicity weakened the cellular stress response which results in cell damage. Small molecules, such as flavonoids, could reduce cellular stress and have gained much attention in recent years. Evidence has shown the potential use of flavonoids in several ways, such as antioxidants, anti-inflammatory, and anti-apoptotic, yet their mechanism is still elusive. This review provides an insight into the potential role of flavonoids against cellular stress response that prevent the pathogenesis of neurodegenerative disorders.

Potential therapeutic effects of polyphenols in Parkinson's disease: in vivo and in vitro pre-clinical studies

Parkinson’s disease is a neurodegenerative disorder characterized by a combination of severe motor and non-motor symptoms. Over the years, several factors have been discovered to play a role in the pathogenesis of this disease, in particular, neuroinflammation and oxidative stress. To date, the pharmacological treatments used in Parkinson’s disease are exclusively symptomatic. For this reason, in recent years, the research has been directed towards the discovery and study of new natural molecules to develop potential neuroprotective therapies against Parkinson’s disease. In this context, natural polyphenols have raised much attention for their important anti-inflammatory and antioxidant properties, but also for their ability to modulate protein misfolding. In this review, we propose to summarize the relevant in vivo and in vitro studies concerning the potential therapeutic role of natural polyphenols in Parkinson’s disease.

Preclinical Evidence and Possible Mechanisms of Baicalein for Rats and Mice With Parkinson's Disease: A Systematic Review and Meta-Analysis

Baicalein, a major bioactive flavone of Scutellaria baicalensis Georgi, has neuroprotective properties in several animal models of Parkinson's disease (PD). Here, we conducted a systematic review and meta-analysis to assess the available preclinical evidence and possible mechanisms of baicalein for animal models of PD. Ultimately, 20 studies were identified by searching 7 databases from inception to December 2019. Review Manager 5.3 was applied for data analysis. Meta-analyses showed baicalein can significantly improve neurobehavioral function in animal models with PD, including spontaneous motor activity test (n = 5), pole test (n = 2), rotarod test (n = 9), apomorphine-induced rotations test (n = 4), grid test (n = 2), and tremor test (n = 2). Compared with controls, the results of the meta-analysis showed baicalein exerted a significant effect in increasing the frequency of spontaneous activity, prolongating the total time for climbing down the pole, decreasing the number of rotations, prolongating the descent latency, reducing the amplitude, and the frequency in animal models with PD. The possible mechanisms of baicalein for PD are regulating neurotransmitters, adjusting enzyme activity, antioxidation, anti-inflammatory, inhibiting protein aggregation, restorating mitochondrial dysfunction, inhibiting apoptosis, and autophagy. In conclusion, these findings preliminarily demonstrated that baicalein exerts potential neuroprotective effects through multiple signaling pathways in animal models of PD.

Baicalein enhances the effect of low dose Levodopa on the gait deficits and protects dopaminergic neurons in experimental Parkinsonism

Parkinson's Disease (PD) is the second most common neurodegenerative disease with the clinical characteristics of gait deficits. The classical symptomatic treatment for PD is Levodopa (L-DOPA) which brings a plethora of side effects and dosage problems in a prolonged drug regimen. Baicalein is a flavonoid extracted from Scutellaria baicalensis Georgi with the properties of neuroprotection. In this study, we investigated the ameliorative effect of baicalein with low dose L-DOPA (25 mg/kg) on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced Parkinsonism. The gait variability was assessed by a computer-assisted gait analysis system Catwalk. The results showed that MPTP challenged mice had significant gait deficits on dynamic paw function and posture stability. L-DOPA reversed the MPTP induced gait deficits and the effect was positively dose-dependent. The combined treatment of baicalein and under threshold dose of L-DOPA significantly improved gait functions, compared with exclusive low dose L-DOPA treatment, and the effect was comparable with high dose L-DOPA treatment. The histological assessment demonstrated that the Tyrosine hydroxylase expression increased in all the baicalein stratified groups, which suggest baicalein might have the neuroprotective effect to retain the dopaminergic neurons or enhance the dopaminergic neuron regeneration after MPTP injection. This neuroprotection probably depended on altering the inflammatory response and resisting the apoptosis through the underlying mechanism investigation. Our study provides experimental evidence that the combination of L-DOPA and baicalein might be a potential treatment for Parkinson's disease. The synergistic interaction of baicalein and L-dopa treatment might reduce the side-effect of the normal to high dose L-DOPA used today.

Neuroprotective effects of baicalein in animal models of Parkinson's disease: A systematic review of experimental studies

BACKGROUND

There is an increasing of reports describing the efficacy of neuroprotective small molecule in Parkinson's disease (PD) models. Ideally, the choice of pushing drug candidates to clinical trial should be based on an unbiased assessment of all available data. Systematic review uses a methodical approach to minimize the bias in the selection of studies for inclusion, providing a comprehensive understanding of the drug's effects on multiple animal models with different mechanism. To our knowledge, such assessments of baicalein, which is a candidate neuroprotective drug with efficacy in PD, have not been fully conducted.

PURPOSE

To provide a comprehensive understanding of baicalein's effects on different animal models with different mechanism by using a methodical approach to minimize the bias in the selection of studies.

METHODS

In this study, we used a systematic review method to comprehensively assess the efficacy of baicalein in animal PD models. By using electronic and manual search for the literatures, we identified studies describing the efficacy of baicalein in animal models of PD.

RESULTS

We identified 16 studies describing the efficacy of baicalein in animal models of PD. The methodological quality of all preclinical trials is ranged from 2 to 5. 16 studies involved 4 main kinds of PD animal models. They are MPP+-induced, rotenone-induced, 6-OHDA-induced and acrolein-induced PD models, respectively. The protective effects of baicalein were studied mainly focusing on the anti-oxidative, anti-apoptotic, and anti-inflammatory action. Beyond that, there are 2 articles describing the effects of baicalein on neurotransmitter balance in the basal ganglia, and 2 articles reporting the effects in decreasing synuclein aggregation.

CONCLUSIONS

The results demonstrated the neuroprotective effects of baicalein in PD experimental animals and analyzed the pharmacological mechanism. The information will be useful for the further development of baicalein into anti-PD agent and provide unbiased evidence for the conduct of clinical trials. In addition, such evaluation based on animal experiments can give us a general introduction to different animal models of PD, either guiding the further model tests, or avoiding the unnecessary replication.

Baicalein improves cognitive deficits and hippocampus impairments in temporal lobe epilepsy rats

Temporal lobe epilepsy (TLE) is a chronic neurological disorder that is a refractory disease. Baicalein possesses various pharmacological activities, including neuroprotection in neurodegenerative disease. However, whether baicalein is protective in the treatment of TLE is not determined. Therefore, the present study investigated the role of baicalein in the treatment of TLE. Baicalein was injected intraperitoneally to TLE rats for two weeks after the onset of spontaneous recurrent seizures (SRS). Rats were observed for the occurrence of SRS, and cognitive and hippocampus injuries were evaluated. Oxidative stress and inflammatory cytokines were measured. Corticosterone and its receptor, actin-associated protein F-actin and cofilin-1 were investigated in the brains of epileptic rats. Baicalein significantly improved cognition and reduced hippocampus damage and mossy fibre sprouting in TLE rats without obvious SRS suppression. Baicalein produced excellent anti-oxidative and anti-inflammatory effects in TLE rats. Baicalein restored the disruption of the glucocorticoid signal pathway and actin-associated protein in TLE rats. These results suggest that the neuroprotective effects of baicalein on cognition and the hippocampus are associated with the suppression of oxidative stress and inflammation and the regulation of the glucocorticoid pathway and actin-associated protein in TLE rats. This evidence supports the use of baicalein as an adjuvant agent for epilepsy treatment.

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.

Natural Compounds for the Management of Parkinson's Disease and Attention-Deficit/Hyperactivity Disorder

Parkinson's disease (PD) is the second most common neurodegenerative disorder with an unknown aetiology. The pathogenic mechanisms include oxidative stress, mitochondrial dysfunction, protein dysfunction, inflammation, autophagy, apoptosis, and abnormal deposition of α-synuclein. Currently, the existing pharmacological treatments for PD cannot improve fundamentally the degenerative process of dopaminergic neurons and have numerous side effects. On the other hand, attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder of childhood and is characterised by hyperactivity, impulsivity, and inattention. The aetiology of ADHD remains unknown, although it has been suggested that its pathophysiology involves abnormalities in several brain regions, disturbances of the catecholaminergic pathway, and oxidative stress. Psychostimulants and nonpsychostimulants are the drugs prescribed for the treatment of ADHD; however, they have been associated with increased risk of substance use and have several side effects. Today, there are very few tools available to prevent or to counteract the progression of such neurological disorders. Thus, therapeutic approaches with high efficiency and fewer side effects are needed. This review presents a brief overview of the two neurological disorders and their current treatments, followed by a discussion of the natural compounds which have been studied as therapeutic agents and the mechanisms underlying the beneficial effects, in particular, the decrease in oxidative stress.

Enhanced AMPA receptor-mediated excitatory transmission in the rodent rostromedial tegmental nucleus following lesion of the nigrostriatal pathway

The GABAergic rostromedial tegmental nucleus (RMTg) has reciprocal connections with the dopaminergic ventral tegmental area and substantia nigra pars compacta (SNc), and is involved in inhibitory control of monoaminergic nuclei. At present, it is not clear whether unilateral 6-hydroxydopamine lesions of the SNc in rats affect AMPA receptor-mediated excitatory transmission in the RMTg. Here we found that lesions of the SNc in rats increased the firing rate of GABAergic neurons and the level of glutamate in the RMTg compared to sham-operated rats. Intra-RMTg injection of AMPA receptor agonist (S)-AMPA increased the firing rate of the GABAergic neurons in both sham-operated and the lesioned rats, while AMPA receptor antagonist NBQX decreased the firing rate of the neurons. Further, intra-RMTg injection of (S)-AMPA decreased the levels of dopamine and serotonin in the medial prefrontal cortex (mPFC) in the two groups of rats; conversely, NBQX increased the levels of dopamine and serotonin. Compared to sham-operated rats, the duration of (S)-AMPA and NBQX action on the firing rate of GABAergic neurons in the RMTg and release of doapmine and serotonin in the mPFC was prolonged in the lesioned rats. In addition, lesions of the SNc in rats increased protein expression of t-GluR1 and p-GluR1-S831 subunits compared to sham-operated rats. Therefore, these changes in the lesioned rats are associated with increased release of glutamate and up-regulated expression of GluR1 subunit-containing AMPA receptors in the RMTg, which suggest that degeneration of the nigrostriatal pathway enhances AMPA receptor-mediated excitatory transmission in the RMTg.

Astragalus Polysaccharide Protects Neurons and Stabilizes Mitochondrial in a Mouse Model of Parkinson Disease

BACKGROUND Astragalus polysaccharides (APS) have a very good therapeutic effect in the treatment of neurodegenerative diseases and nerve injury disease. However, research on Parkinson disease (PD) treatment with APS is lacking. MATERIAL AND METHODS The present study was designed to explore the effects of APS on the protection of neurons and mitochondrial in a mouse model of PD using behavioral experiments, and observations of mitochondrial structure and transmembrane potential. RESULTS It was shown that APS could attenuate 1-methyl-4-pheyl-1,2,3,6-tetrahydropyridine (MPTP)-induced motor dysfunction (P<0.01), increase the proportion of TH-positive cells (P<0.01), reverse MPTP-induced mitochondrial structural damage, and reduce MPTP-induced high levels of reactive oxygen species (ROS) and increase MPTP-induced decrease in mitochondrial membrane potential. In addition, APS also decreased the bax/bcl2 ratio, and cytochrome-c and caspase-3 protein content (P<0.01) in substantia nigra in our mouse PD model. CONCLUSIONS APS provided a protective effect on neurons and mitochondrial in a mouse PD model.

Polyphenols in Parkinson's Disease: A Systematic Review of In Vivo Studies

Parkinson’s disease (PD) is the second most common neurodegenerative disorder. However, therapeutic options treating only its symptoms are very disappointing. Therefore there is an ongoing search for compounds capable of tackling the multi-dimensional features of PD. Recently natural polyphenols have gained great interest as potential therapeutic agents. Herein, we have attempted to summarize results obtained in different animal models demonstrating their neuroprotective effects. The in vivo findings presented below are supported by human subject data and reports regarding the ability of polyphenols to cross the blood-brain barrier. The beneficial effects of polyphenols are demonstrated by the results of behavioral examinations, mainly related to motor and cognitive capabilities, histopathological and immunohistochemical examination concerning the protection of dopaminergic neurons, analyses of dopamine and the concentration of its metabolites, as well as mechanistic studies regarding the modulation of oxidative stress, neuroinflammation, cellular iron management, proteinopathy, and additionally the regulation of signaling pathways. Importantly, data about brain distribution of the metabolic derivatives of the reviewed polyphenols are crucial for the justification of their nutritional intake in neuroprotective intervention, as well as for the identification of potential targets for a novel therapeutic approach to Parkinson’s disease.

Andrographolide suppresses the migratory ability of human glioblastoma multiforme cells by targeting ERK1/2-mediated matrix metalloproteinase-2 expression

Glioblastoma multiforme (GBM) can be a fatal tumor because of difficulties in treating the related metastasis. Andrographolide is the bioactive component of the Andrographis paniculata. Andrographolide possesses the anti-inflammatory activity and inhibits the growth of various cancers; however, its effect on GBM cancer motility remains largely unknown. In this study, we examined the antimetastatic properties of andrographolide in human GBM cells. Our results revealed that andrographolide inhibited the invasion and migration abilities of GBM8401 and U251 cells. Furthermore, andrographolide inhibited matrix metalloproteinase (MMP)-2 activity and expression. Real-time PCR and promoter activity assays indicated that andrographolide inhibited MMP-2 expression at the transcriptional level. Such inhibitory effects were associated with the suppression of CREB DNA-binding activity and CREB expression. Mechanistically, andrographolide inhibited the cell motility of GBM8401 cells through the extracellular-regulated kinase (ERK) 1/2 pathway, and the blocking of the ERK 1/2 pathway could reverse MMP-2-mediated cell motility. In conclusion, CREB is a crucial target of andrographolide for suppressing MMP-2-mediated cell motility in GBM cells. Therefore, a combination of andrographolide and an ERK inhibitor might be a good strategy for preventing GBM metastasis.

Baicalein Exerts Beneficial Effects in d-Galactose-Induced Aging Rats Through Attenuation of Inflammation and Metabolic Dysfunction

Baicalein is a flavonoid isolated from the roots of Scutellaria baicalensis Georgi. This study aimed to ascertain the effects and potential underlying mechanisms of baicalein in d-galactose (d-gal)-induced aging rat model by integration of behavior examination, biochemical detection, and ¹H nuclear magnetic resonance (NMR)-based metabolomic approach. Our findings suggest that baicalein significantly attenuated memory decline in d-gal-induced aging model, as manifested by increasing recognition index in novel object recognition test, shortening latency time, and increasing platform crossings in Morris water maze test. Baicalein significantly inhibited the releases of inflammatory mediators such as nitric oxide, interleukin-6, interleukin-1 beta, and tumor necrosis factor-α in d-gal-induced aging model. Metabolomic study revealed that 10 endogenous metabolites in cerebral cortex were considered as potential biomarkers of baicalein for its protective effect. Further metabolic pathway analysis showed that the metabolic alterations were associated with alanine, aspartate and glutamate metabolism, glycine, serine and threonine metabolism, inositol phosphate metabolism, and energy metabolism. These data indicate that baicalein improves learning and memory dysfunction in d-gal-induced aging rats. This might be achieved through attenuation of inflammation and metabolic dysfunction.

Flavonoids as detoxifying and pro-survival agents: What's new?

The role of flavonoids in the survival machinery of cells has come in the spotlight due to the recent evidence of their effect on the relationship mitochondria-ER stress-proteasome, including the intracellular mechanisms of autophagy and apoptosis. Numerous experimental animal investigations and even human clinical studies have highlighted the major role of these natural compounds in the economy of life and their deep relationship with autotrophic organisms in the evolutionary space. Their role as anti-oxidant and oxidative stress preventive molecules has to date been investigated extensively in the literature. Despite this great amount of promising evidence, many concerns, however, remain, most of which dealing with biochemistry, bioavailability, pharmacokinetics, and interaction of flavonoids with gut microbiome, issues that make difficult any good attempt to introduce these molecules in the human healthcare systems as possible, encouraging therapeutic substances. This review tries to address and elucidate these items.

Baicalein as a potent neuroprotective agent: A review

In recent times, neurodegenerative diseases are the most challenging global health problems. Neuronal cell death or damage is a key factor for many neurodegenerative disorders. Therefore, there has been a growing interest in the development of effective neuroprotective agents, especially from natural sources. In particular, phytochemicals have shown high efficacy with low side effects in various in vitro and in vivo studies. In the various phytoconstituents, flavonoids are important bioactive products and mainly found in various vegetables and fruits. Among them, baicalein is one of the important flavones, which is mainly found in the root of Scutellaria baicalensis Georgi. A number of studies have reported that baicalein has potent neuroprotective properties under in vitro as well as in vivo systems. Hence, the purpose of this paper is to provide a review of the existing literature in connection with the neuroprotective effects of baicalein and its molecular mechanisms of action. The current review highlights could be useful to identify novel therapeutic agents in relation to the treatment of neurotoxicity-mediated diseases.

Synaptoimmunology - roles in health and disease

Mounting evidence suggests that the nervous and immune systems are intricately linked. Many proteins first identified in the immune system have since been detected at synapses, playing different roles in normal and pathological situations. In addition, novel immunological functions are emerging for proteins typically expressed at synapses. Under normal conditions, release of inflammatory mediators generally represents an adaptive and regulated response of the brain to immune signals. On the other hand, when immune challenge becomes prolonged and/or uncontrolled, the consequent inflammatory response leads to maladaptive synaptic plasticity and brain disorders. In this review, we will first provide a summary of the cell signaling pathways in neurons and immune cells. We will then examine how immunological mechanisms might influence synaptic function, and in particular synaptic plasticity, in the healthy and pathological CNS. A better understanding of neuro-immune system interactions in brain circuitries relevant to neuropsychiatric and neurological disorders should provide specific biomarkers to measure the status of the neuroimmunological response and help design novel neuroimmune-targeted therapeutics.

Natural products against Alzheimer's disease: Pharmaco-therapeutics and biotechnological interventions

Alzheimer's disease (AD) is a severe, chronic and progressive neurodegenerative disease associated with memory and cognition impairment ultimately leading to death. It is the commonest reason of dementia in elderly populations mostly affecting beyond the age of 65. The pathogenesis is indicated by accumulation of the amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFT) in brain tissues and hyperphosphorylation of tau protein in neurons. The main cause is considered to be the formation of reactive oxygen species (ROS) due to oxidative stress. The current treatment provides only symptomatic relief by offering temporary palliative therapy which declines the rate of cognitive impairment associated with AD. Inhibition of the enzyme acetylcholinesterase (AChE) is considered as one of the major therapeutic strategies offering only symptomatic relief and moderate disease-modifying effect. Other non-cholinergic therapeutic approaches include antioxidant and vitamin therapy, stem cell therapy, hormonal therapy, use of antihypertensive or lipid-lowering medications and selective phosphodiesterase (PDE) inhibitors, inhibition of β-secretase and γ-secretase and Aβ aggregation, inhibition of tau hyperphosphorylation and intracellular NFT, use of nonsteroidal anti-inflammatory drugs (NSAIDs), transition metal chelators, insulin resistance drugs, etanercept, brain-derived neurotrophic factor (BDNF) etc. Medicinal plants have been reported for possible anti-AD activity in a number of preclinical and clinical trials. Ethnobotany, being popular in China and in the Far East and possibly less emphasized in Europe, plays a substantial role in the discovery of anti-AD agents from botanicals. Chinese Material Medica (CMM) involving Chinese medicinal plants has been used traditionally in China in the treatment of AD. Ayurveda has already provided numerous lead compounds in drug discovery and many of these are also undergoing clinical investigations. A number of medicinal plants either in their crude forms or as isolated compounds have exhibited to reduce the pathological features associated with AD. In this present review, an attempt has been made to elucidate the molecular mode of action of various plant extracts, phytochemicals and traditional herbal formulations investigated against AD as reported in various preclinical and clinical tests. Herbal synergism often found in polyherbal formulations were found effective to combat disease heterogeneity as found in complex pathogenesis of AD. Finally a note has been added to describe biotechnological improvement, genetic and genomic resources and mathematical and statistical techniques for empirical model building associated with anti-AD plant secondary metabolites and their source botanicals.

Baicalein attenuates α-synuclein aggregation, inflammasome activation and autophagy in the MPP+-treated nigrostriatal dopaminergic system in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Neuroinflammation, oxidative stress, and protein aggregation form a vicious cycle in the pathophysiology of Parkinson's disease (PD); activated microglia is the main location of neuroinflammation. A Chinese medicine book, "Shanghan Lun", known as the "Treatises on Cold damage Diseases" has suggested that Scutellaria baicalensis Georgi is effective in treating CNS diseases. The anti-inflammatory mechanisms of baicalein, a phenolic flavonoid in the dried root of Scutellaria baicalensis Georgi, remain to be explored.

AIM OF THE STUDY

The neuroprotective mechanisms of baicalein involving α-synuclein aggregation, inflammasome activation, and programmed cell death were investigated in the nigrostriatal dopaminergic system of rat brain in vivo.

MATERIALS AND METHODS

Intranigral infusion of 1-methyl-4-phenylpyridinium (MPP⁺, a Parkinsonian neurotoxin) was performed on anesthetized Sprague-Dawley rats. Baicalein was daily administered via intraperitoneal injection. Striatal dopamine levels were measured using high performance liquid chromatography coupled with electrochemical detection. Cellular signalings were measured by Western blot assay, immunofluorescent staining assay and enzyme-linked immunosorbent assay.

RESULTS

Systemic administration of baicalein attenuated MPP⁺-induced reductions in striatal dopamine content and tyrosine hydroxylase (a biomarker of dopaminergic neurons) in the infused substantia nigra (SN). Furthermore, MPP⁺-induced elevations in α-synuclein aggregates (a pathological hallmark of PD), ED-1 (a biomarker of activated microglia), activated caspase-1 (a proinflammatory caspase), IL-1β and cathepsin B (a cysteine lysosomal protease) in the infused SN were attenuated in the baicalein-treated rats. Moreover, intense immunoreactivities of caspase 1 and cathepsin B were co-localized with that of ED-1 in the MPP⁺-infused SN. At the same time, baicalein inhibited MPP⁺-induced increases in active caspases 9 and 12 (biomarkers of apoptosis) as well as LC3-II levels (a biomarker of autophagy) in the rat nigrostriatal dopaminergic system.

CONCLUSION

Our in vivo study showed that baicalein possesses anti-inflammatory activities by inhibiting α-synuclein aggregation, inflammasome activation and cathepsin B production in the MPP⁺-infused SN. Moreover, baicalein is of therapeutic significance because it inhibits MPP⁺-induced apoptosis and autophagy in the nigrostriatal dopaminergic system of rat brain.

Impact of Plant-Derived Flavonoids on Neurodegenerative Diseases

Neurodegenerative disorders have a common characteristic that is the involvement of different cell types, typically the reactivity of astrocytes and microglia, characterizing gliosis, which in turn contributes to the neuronal dysfunction and or death. Flavonoids are secondary metabolites of plant origin widely investigated at present and represent one of the most important and diversified among natural products phenolic groups. Several biological activities are attributed to this class of polyphenols, such as antitumor activity, antioxidant, antiviral, and anti-inflammatory, among others, which give significant pharmacological importance. Our group have observed that flavonoids derived from Brazilian plants Dimorphandra mollis Bent., Croton betulaster Müll. Arg., e Poincianella pyramidalis Tul., botanical synonymous Caesalpinia pyramidalis Tul. also elicit a broad spectrum of responses in astrocytes and neurons in culture as activation of astrocytes and microglia, astrocyte associated protection of neuronal progenitor cells, neuronal differentiation and neuritogenesis. It was observed the flavonoids also induced neuronal differentiation of mouse embryonic stem cells and human pluripotent stem cells. Moreover, with the objective of seeking preclinical pharmacological evidence of these molecules, in order to assess its future use in the treatment of neurodegenerative disorders, we have evaluated the effects of flavonoids in preclinical in vitro models of neuroinflammation associated with Parkinson's disease and glutamate toxicity associated with ischemia. In particular, our efforts have been directed to identify mechanisms involved in the changes in viability, morphology, and glial cell function induced by flavonoids in cultures of glial cells and neuronal cells alone or in interactions and clarify the relation with their neuroprotective and morphogetic effects.

The Analgesic and Antineuroinflammatory Effect of Baicalein in Cancer-Induced Bone Pain

Cancer-induced bone pain (CIBP) is a severe type of chronic pain. It is imperative to explore safe and effective analgesic drugs for CIBP treatment. Baicalein (BE), isolated from the traditional Chinese herbal medicine Scutellaria baicalensis Georgi (or Huang Qin), has been demonstrated to have anti-inflammatory and neuroprotective effects. In this study, we examined the effect of BE on CIBP and the mechanism of this effect. Intrathecal and oral administration of BE at different doses could alleviate the mechanical allodynia in CIBP rats. Intrathecal 100 μg BE could inhibit the production of IL-6 and TNF-α in the spinal cord of CIBP rats. Moreover, intrathecal 100 μg BE could effectively inhibit the activation of p-p38 and p-JNK MAPK signals in CIBP rats. The analgesic effect of BE may be associated with the inhibition of the expression of the inflammatory cytokines IL-6 and TNF-α and through the activation of p-p38 and p-JNK MAPK signals in the spinal cord. These findings suggest that BE is a promising novel analgesic agent for CIBP.

Luteolin as an anti-inflammatory and neuroprotective agent: A brief review

According to the World Health Organization, two billion people will be aged 60 years or older by 2050. Aging is a major risk factor for a number of neurodegenerative disorders. These age-related disorders currently represent one of the most important and challenging health problems worldwide. Therefore, much attention has been directed towards the design and development of neuroprotective agents derived from natural sources. These phytochemicals have demonstrated high efficacy and low adverse effects in multiple in vitro and in vivo studies. Among these phytochemicals, dietary flavonoids are an important and common chemical class of bioactive products, found in several fruits and vegetables. Luteolin is an important flavone, which is found in several plant products, including broccoli, pepper, thyme, and celery. Numerous studies have shown that luteolin possesses beneficial neuroprotective effects both in vitro and in vivo. Despite this, an overview of the neuroprotective effects of luteolin has not yet been accomplished. Therefore, the aim of this paper is to provide a review of the available literature regarding the neuroprotective effects of luteolin and its molecular mechanisms of action. Herein, we also review the available literature regarding the chemistry of luteolin, its herbal sources, and bioavailability as a pharmacological agent for the treatment and management of age-related neurodegenerative disorders.

Tricetin suppresses the migration/invasion of human glioblastoma multiforme cells by inhibiting matrix metalloproteinase-2 through modulation of the expression and transcriptional activity of specificity protein 1

OBJECTIVE

Glioblastoma multiforme (GBM) is a severely invasive tumor that can be fatal because it is difficult to treat. Tricetin, a natural flavonoid, was demonstrated to inhibit the growth of various cancers, but the effect of tricetin on cancer motility is largely unknown.

RESEARCH DESIGN AND METHODS

In the present study, we examined the anti-invasive properties of tricetin in huwman GBM cells.

RESULTS

Our results showed that tricetin inhibited the migration/invasion of two GBM cell lines. We found that tricetin inhibited MMP-2 expression in the GBM cells. Real-time polymerase chain reaction and promoter activity assays indicated that tricetin inhibited MMP-2 expression at the transcriptional level. Such inhibitory effects were associated with the suppression of specificity protein-1 (SP-1) DNA-binding activity. An examination of clinical samples revealed a positive correlation between SP-1 and MMP-2 in glioma specimens, and higher expression levels were correlated with a worse probability of survival. Moreover, blocking the extracellular signal-regulated kinase (ERK) pathway also inhibited MMP-2-mediated cell motility, and further enhanced the anti-invasive ability of tricetin in GBM cells.

CONCLUSIONS

SP-1 is an important target of tricetin for suppressing MMP-2-mediated cell motility in GBM cells, and a combination of tricetin and an ERK inhibitor may be a good strategy for preventing GBM invasion.

The effects of neuropeptide urocortin 2 on the spontaneous discharge and glutamatergic neurotransmission of striatum neurons

The primary cause of the neurodegenerative process that underlies Parkinson's disease (PD) is still unknown. Different mechanisms probably contribute to triggering neuronal death in the nigro-striatum pathway. The neuropeptide urocortin 2 (UCN2) plays an important role in the regulation of striatum (STR) neurons projection. We investigated the effects of UCN2 on spontaneous discharge and glutamatergic responses in STR for a better understanding of the pathogenesis of PD. The experiment used microiontophoresis method to observe the effects of UCN2 on STR neurons' firing rates in vivo. Corticotrophin releasing factor receptor 2 (CRF-R2) selective inhibitor, astressin-2B (AST-2B), was administered simultaneously with UCN2 to investigate the effects of UCN2 on CRF-R2. Moreover, we further explored the effects of UCN2 on glutamatergic responses in STR neurons. We found that UCN2 could significantly inhibit the firing rate of 84% of the tested STR neurons, and its inhibitory effect followed a concentration-dependent manner. During the microiontophoresis of GLU, the excitatory firing of glutamatergic neurons could be attenuated by the addition of UCN2, but enhanced by the application of AST-2B. The results suggest that UCN2 could regulate the effects of STR neurotransmitters (GLU) via CRF-R2 and may thereby contribute to the improvement of PD.