Cytoprotective effect of chlorogenic acid against α-synuclein-related toxicity in catecholaminergic PC12 cells

Chlorogenic Acid: A Systematic Review on the Biological Functions, Mechanistic Actions, and Therapeutic Potentials

Chlorogenic acid (CGA) is a type of polyphenol compound found in rich concentrations in many plants such as green coffee beans. As an active natural substance, CGA exerts diverse therapeutic effects in response to a variety of pathological challenges, particularly conditions associated with chronic metabolic diseases and age-related disorders. It shows multidimensional functions, including neuroprotection for neurodegenerative disorders and diabetic peripheral neuropathy, anti-inflammation, anti-oxidation, anti-pathogens, mitigation of cardiovascular disorders, skin diseases, diabetes mellitus, liver and kidney injuries, and anti-tumor activities. Mechanistically, its integrative functions act through the modulation of anti-inflammation/oxidation and metabolic homeostasis. It can thwart inflammatory constituents at multiple levels such as curtailing NF-kB pathways to neutralize primitive inflammatory factors, hindering inflammatory propagation, and alleviating inflammation-related tissue injury. It concurrently raises pivotal antioxidants by activating the Nrf2 pathway, thus scavenging excessive cellular free radicals. It elevates AMPK pathways for the maintenance and restoration of metabolic homeostasis of glucose and lipids. Additionally, CGA shows functions of neuromodulation by targeting neuroreceptors and ion channels. In this review, we systematically recapitulate CGA's pharmacological activities, medicinal properties, and mechanistic actions as a potential therapeutic agent. Further studies for defining its specific targeting molecules, improving its bioavailability, and validating its clinical efficacy are required to corroborate the therapeutic effects of CGA.

Molecular mechanism of caloric restriction mimetics-mediated neuroprotection of age-related neurodegenerative diseases: an emerging therapeutic approach

Aging-induced neurodegenerative diseases (NDs) are significantly increasing health problem worldwide. It has been well documented that oxidative stress is one of the potential causes of aging and age-related NDs. There are no drugs for the treatment of NDs, therefore there is an immediate necessity for the development of strategies/treatments either to prevent or cure age-related NDs. Caloric restriction (CR) and intermittent fasting have been considered as effective strategies in increasing the healthspan and lifespan, but it is difficult to adhere to these routines strictly, which has led to the development of calorie restriction mimetics (CRMs). CRMs are natural compounds that provide similar molecular and biochemical effects of CR, and activate autophagy process. CRMs have been reported to regulate redox signaling by enhancing the antioxidant defense systems through activation of the Nrf2 pathway, and inhibiting ROS generation through attenuation of mitochondrial dysfunction. Moreover, CRMs also regulate redox-sensitive signaling pathways such as the PI3K/Akt and MAPK pathways to promote neuronal cell survival. Here, we discuss the neuroprotective effects of various CRMs at molecular and cellular levels during aging of the brain. The CRMs are envisaged to become a cornerstone of the pharmaceutical arsenal against aging and age-related pathologies.

Chlorogenic acid delays the progression of Parkinson's disease via autophagy induction in Caenorhabditis elegans

OBJECTIVES

Parkinson's disease (PD) is the second most common neurodegenerative disease. Chlorogenic acid (CGA) is a polyphenolic substance derived from various medicinal plants. Although CGA is reported to have potential anti-PD effect, the beneficial effect and the underlying mechanism remain unclear. In this study, we aimed to further investigate the protective effect and clarify the mechanism of action of CGA in Caenorhabditis elegans (C. elegans) models of PD.

METHODS

Measurements of a-synuclein aggregation, movement disorders, and lipid, ROS and malondialdehyde (MDA) contents were observed in NL5901 nematodes. Determinations of dopamine (DA) neuron degeneration, food perception, and ROS content were performed in 6-OHDA-exposed BZ555 nematodes. The autophagy activation of CGA was monitored using DA2123 and BC12921 nematodes. Meanwhile, RNAi technology was employed to knockdown the autophagy-related genes and investigate whether the anti-PD effect of CGA was associated with autophagy induction in C. elegans.

RESULTS

CGA significantly reduced α-synuclein aggregation, improved motor disorders, restored lipid content, and decreased ROS and MDA contents in NL5901 nematodes. Meanwhile, CGA inhibited DA neuron-degeneration and improved food-sensing behavior in 6-OHDA-exposed BZ555 nematodes. In addition, CGA increased the number of GFP::LGG-1 foci in DA2123 nematodes and degraded p62 protein in BC12921 nematodes. Meanwhile, CGA up-regulated the expression of autophagy-related genes in NL5901 nematodes. Moreover, the anti-PD effect of CGA was closely related to autophagy induction via increasing the expression of autophagy-related genes, including unc-51, bec-1, vps-34, and lgg-1.

CONCLUSIONS

The present study indicates that CGA exerts neuroprotective effect in C. elegans via autophagy induction.

Free radical biology in neurological manifestations: mechanisms to therapeutics interventions

Recent advancements and growing attention about free radicals (ROS) and redox signaling enable the scientific fraternity to consider their involvement in the pathophysiology of inflammatory diseases, metabolic disorders, and neurological defects. Free radicals increase the concentration of reactive oxygen and nitrogen species in the biological system through different endogenous sources and thus increased the overall oxidative stress. An increase in oxidative stress causes cell death through different signaling mechanisms such as mitochondrial impairment, cell-cycle arrest, DNA damage response, inflammation, negative regulation of protein, and lipid peroxidation. Thus, an appropriate balance between free radicals and antioxidants becomes crucial to maintain physiological function. Since the 1brain requires high oxygen for its functioning, it is highly vulnerable to free radical generation and enhanced ROS in the brain adversely affects axonal regeneration and synaptic plasticity, which results in neuronal cell death. In addition, increased ROS in the brain alters various signaling pathways such as apoptosis, autophagy, inflammation and microglial activation, DNA damage response, and cell-cycle arrest, leading to memory and learning defects. Mounting evidence suggests the potential involvement of micro-RNAs, circular-RNAs, natural and dietary compounds, synthetic inhibitors, and heat-shock proteins as therapeutic agents to combat neurological diseases. Herein, we explain the mechanism of free radical generation and its role in mitochondrial, protein, and lipid peroxidation biology. Further, we discuss the negative role of free radicals in synaptic plasticity and axonal regeneration through the modulation of various signaling molecules and also in the involvement of free radicals in various neurological diseases and their potential therapeutic approaches. The primary cause of free radical generation is drug overdosing, industrial air pollution, toxic heavy metals, ionizing radiation, smoking, alcohol, pesticides, and ultraviolet radiation. Excessive generation of free radicals inside the cell R1Q1 increases reactive oxygen and nitrogen species, which causes oxidative damage. An increase in oxidative damage alters different cellular pathways and processes such as mitochondrial impairment, DNA damage response, cell cycle arrest, and inflammatory response, leading to pathogenesis and progression of neurodegenerative disease other neurological defects.

Chlorogenic Acid: a Polyphenol from Coffee Rendered Neuroprotection Against Rotenone-Induced Parkinson's Disease by GLP-1 Secretion

Parkinson's disease (PD) is a chronic motor disorder, characterized by progressive loss of dopaminergic neurons. Numerous studies suggest that glucagon-like peptide-1 (GLP-1) secretagogue has a neuroprotective role in PD models. The present study evaluated potential of coffee bioactive compounds in terms of their ability to bind GPR-40/43 and tested the neuroprotective effect of best candidate on rotenone-induced PD mice acting via GLP-1 release. In silico molecular docking followed by binding free energy calculation revealed that chlorogenic acid (CGA) has a strong binding affinity for GPR-40/43 in comparison to other bioactive polyphenols. Molecular dynamics simulation studies revealed stable nature of GPR40-CGA and GPR43-CGA interaction and also provided information about the amino acid residues involved in binding. Subsequently, in vitro studies demonstrated that CGA-induced secretion of GLP-1 via enhancing cAMP levels in GLUTag cells. Furthermore, in vivo experiments utilizing rotenone-induced mouse model of PD revealed a significant rise in plasma GLP-1 after CGA administration (50 mg/kg, orally for 13 weeks) with concomitant increase in colonic GPR-40 and GPR-43 mRNA expression. CGA treatment also prevented rotenone-induced motor and cognitive impairments and significantly restored the rotenone-induced oxidative stress. Meanwhile, western blot results confirmed that CGA treatment downregulated rotenone-induced phosphorylated alpha-synuclein levels by upregulating PI3K/AKT signaling and inactivating GSK-3β through the release of GLP-1. CGA treatment ameliorated rotenone-induced dopaminergic nerve degeneration and alpha-synuclein accumulation in substantia nigra and augmented mean density of dopaminergic nerve fibers in striatum. These findings demonstrated novel biological function of CGA as a GLP-1 secretagogue. An increase in endogenous GLP-1 may render neuroprotection against a rotenone mouse model of PD and has the potential to be used as a neuroprotective agent in management of PD.

The Regulatory effect of chlorogenic acid on gut-brain function and its mechanism: A systematic review

Chlorogenic acid (CGA) is a phenolic compound that is widely distributed in honeysuckle, Eucommia, fruits and vegetables. It has various biological functions, including cardiovascular, nerve, kidney, and liver protection, and it exerts a protective effect on human health, according to clinical research and basic research. The intestine and brain are two important organs that are closely related in the human body. The intestine is even called the "second brain" in humans. However, among the many reports in the literature, an article systematically reporting the regulatory effects and specific mechanisms of CGA on the intestines and brain has not been published. In this context, this review uses the regulatory role and mechanism of CGA in the intestine and brain as the starting point and comprehensively reviews CGA metabolism in the body and the regulatory role and mechanism of CGA in the intestine and brain described in recent years. Additionally, the review speculates on the potential biological actions of CGA in the gut-brain axis. This study provides a scientific theory for CGA research in the brain and intestines and promotes the transformation of basic research and the application of CGA in food nutrition and health care.

Nutraceuticals as Modulators of Autophagy: Relevance in Parkinson’s Disease

Dietary supplements and nutraceuticals have entered the mainstream. Especially in the media, they are strongly advertised as safe and even recommended for certain diseases. Although they may support conventional therapy, sometimes these substances can have unexpected side effects. This review is particularly focused on the modulation of autophagy by selected vitamins and nutraceuticals, and their relevance in the treatment of neurodegenerative diseases, especially Parkinson’s disease (PD). Autophagy is crucial in PD; thus, the induction of autophagy may alleviate the course of the disease by reducing the so-called Lewy bodies. Hence, we believe that those substances could be used in prevention and support of conventional therapy of neurodegenerative diseases. This review will shed some light on their ability to modulate the autophagy.

Dietary Plant Polyphenols as the Potential Drugs in Neurodegenerative Diseases: Current Evidence, Advances, and Opportunities

Neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), are characterized by the progressive degeneration of neurons. Although the etiology and pathogenesis of neurodegenerative diseases have been studied intensively, the mechanism is still in its infancy. In general, most neurodegenerative diseases share common molecular mechanisms, and multiple risks interact and promote the pathologic process of neurogenerative diseases. At present, most of the approved drugs only alleviate the clinical symptoms but fail to cure neurodegenerative diseases. Numerous studies indicate that dietary plant polyphenols are safe and exhibit potent neuroprotective effects in various neurodegenerative diseases. However, low bioavailability is the biggest obstacle for polyphenol that largely limits its adoption from evidence into clinical practice. In this review, we summarized the widely recognized mechanisms associated with neurodegenerative diseases, such as misfolded proteins, mitochondrial dysfunction, oxidative damage, and neuroinflammatory responses. In addition, we summarized the research advances about the neuroprotective effect of the most widely reported dietary plant polyphenols. Moreover, we discussed the current clinical study and application of polyphenols and the factors that result in low bioavailability, such as poor stability and low permeability across the blood-brain barrier (BBB). In the future, the improvement of absorption and stability, modification of structure and formulation, and the combination therapy will provide more opportunities from the laboratory into the clinic for polyphenols. Lastly, we hope that the present review will encourage further researches on natural dietary polyphenols in the treatment of neurodegenerative diseases.

Green coffee extract attenuates Parkinson's-related behaviors in animal models

Epidemiological studies have shown an inverse association between coffee consumption and the development of Parkinson's disease (PD). The effects of the oral treatment with green (non-roasted) coffee extracts (CE, 100 or 400 mg/kg) and caffeine (31.2 mg/kg) were evaluated on catalepsy induced by haloperidol in mice, and unilateral 6-OHDA lesion of medial forebrain bundle (MFB) or striatum in rats. Also, the in vitro antioxidant activity and the monoamine levels in the striatum were investigated. CE presented a mild antioxidant activity in vitro and its administration decreased the catalepsy index. CE at the dose of 400 mg/kg induced ipsilateral rotations 14 days after lesion; however, chronic 30-day CE and caffeine treatments did not interfere with the animals' rotation after apomorphine or methamphetamine challenges in animals with MFB lesion, nor on monoamines levels. Furthermore, CE and caffeine were effective in inhibiting the asymmetry between ipsilateral and contralateral rotations induced by methamphetamine and apomorphine in animals with lesion in the striatum but did not avoid the monoamines depletion. These results indicate that CE components indirectly modulate dopaminergic transmission, suggesting a pro-dopaminergic action of CE, and further investigation must be conducted to elucidate the mechanisms of action and the possible neuroprotective role in PD.

Beneficial effects of chlorogenic acid treatment on neuroinflammation after deep hypothermic circulatory arrest may be mediated through CYLD/NF-κB signaling

Deep hypothermic circulatory arrest (DHCA) during heart surgery may induce neuroinflammation leading to neurocognitive dysfunction. Chlorogenic acid (CA) is a common phytochemical, which can attenuate neuroinflammation. Nevertheless, the underlying mechanism involved in the anti-inflammatory effect of CA after DHCA is unknown. The present study therefore characterized the anti-inflammatory functions of CA after DHCA using in vivo and in vitro DHCA models. The activation of microglia, inflammatory cytokine levels, and the NF-κB pathway were measured. The results showed that CA treatment ameliorated neurocognitive function and reduced the inflammatory cytokine levels in the brain and circulation. Furthermore, the microglial and NF-κB activations were suppressed after DHCA. CA exerted the same anti-inflammatory effect in hypothermia OGD microglial cells as the in vivo study. Additional studies indicated that the regulation of ubiquitin ligase activity of TRAF6 and RIP1 by CYLD was related to the mechanism involving inhibition of CA in the NF-κB pathway. Together, the results showed that CA may attenuate neuroinflammation after DHCA by modulating the signaling of CYLD/NF-κB.

Beneficial Effects of Epigallocatechin-3-O-Gallate, Chlorogenic Acid, Resveratrol, and Curcumin on Neurodegenerative Diseases

Many observational and clinical studies have shown that consumption of diets rich in plant polyphenols have beneficial effects on various diseases such as cancer, obesity, diabetes, cardiovascular diseases, and neurodegenerative diseases (NDDs). Animal and cellular studies have indicated that these polyphenolic compounds contribute to such effects. The representative polyphenols are epigallocatechin-3-O-gallate in tea, chlorogenic acids in coffee, resveratrol in wine, and curcumin in curry. The results of human studies have suggested the beneficial effects of consumption of these foods on NDDs including Alzheimer's and Parkinson's diseases, and cellular animal experiments have provided molecular basis to indicate contribution of these representative polyphenols to these effects. This article provides updated information on the effects of these foods and their polyphenols on NDDs with discussions on mechanistic aspects of their actions mainly based on the findings derived from basic experiments.

Neuroprotective Effects of Coffee Bioactive Compounds: A Review

Coffee is one of the most widely consumed beverages worldwide. It is usually identified as a stimulant because of a high content of caffeine. However, caffeine is not the only coffee bioactive component. The coffee beverage is in fact a mixture of a number of bioactive compounds such as polyphenols, especially chlorogenic acids (in green beans) and caffeic acid (in roasted coffee beans), alkaloids (caffeine and trigonelline), and the diterpenes (cafestol and kahweol). Extensive research shows that coffee consumption appears to have beneficial effects on human health. Regular coffee intake may protect from many chronic disorders, including cardiovascular disease, type 2 diabetes, obesity, and some types of cancer. Importantly, coffee consumption seems to be also correlated with a decreased risk of developing some neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, and dementia. Regular coffee intake may also reduce the risk of stroke. The mechanism underlying these effects is, however, still poorly understood. This review summarizes the current knowledge on the neuroprotective potential of the main bioactive coffee components, i.e., caffeine, chlorogenic acid, caffeic acid, trigonelline, kahweol, and cafestol. Data from both in vitro and in vivo preclinical experiments, including their potential therapeutic applications, are reviewed and discussed. Epidemiological studies and clinical reports on this matter are also described. Moreover, potential molecular mechanism(s) by which coffee bioactive components may provide neuroprotection are reviewed.

Dietary Antioxidants and the Mitochondrial Quality Control: Their Potential Roles in Parkinson's Disease Treatment

Advances in medicine and dietary standards over recent decades have remarkably increased human life expectancy. Unfortunately, the chance of developing age-related diseases, including neurodegenerative diseases (NDDs), increases with increased life expectancy. High metabolic demands of neurons are met by mitochondria, damage of which is thought to contribute to the development of many NDDs including Parkinson’s disease (PD). Mitochondrial damage is closely associated with the abnormal production of reactive oxygen species (ROS), which are widely known to be toxic in various cellular environments, including NDD contexts. Thus, ways to prevent or slow mitochondrial dysfunction are needed for the treatment of these NDDs. In this review, we first detail how ROS are associated with mitochondrial dysfunction and review the cellular mechanisms, such as the mitochondrial quality control (MQC) system, by which neurons defend against both abnormal production of ROS and the subsequent accumulation of damaged mitochondria. We next highlight previous studies that link mitochondrial dysfunction with PD and how dietary antioxidants might provide reinforcement of the MQC system. Finally, we discuss how aging plays a role in mitochondrial dysfunction and PD before considering how healthy aging through proper diet and exercise may be salutary.

The Antiaggregative and Antiamyloidogenic Properties of Nanoparticles: A Promising Tool for the Treatment and Diagnostics of Neurodegenerative Diseases

Due to the progressive aging of the society, the prevalence and socioeconomic burden of neurodegenerative diseases are predicted to rise. The most common neurodegenerative disorders nowadays, such as Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis, can be classified as proteinopathies. They can be either synucleinopathies, amyloidopathies, tauopathies, or TDP-43-related proteinopathies; thus, nanoparticles with a potential ability to inhibit pathological protein aggregation and/or degrade already existing aggregates can be a promising approach in the treatment of neurodegenerative diseases. As it turns out, nanoparticles can be a double-edged sword; they can either promote or inhibit protein aggregation, depending on coating, shape, size, surface charge, and concentration. In this review, we aim to emphasize the need of a breakthrough in the treatment of neurodegenerative disorders and draw attention to nanomaterials, as they can also serve as a diagnostic tool for protein aggregates or can be used in a high-throughput screening for novel antiaggregative compounds.

Chlorogenic acid: A comprehensive review of the dietary sources, processing effects, bioavailability, beneficial properties, mechanisms of action, and future directions

Chlorogenic acids (CGAs), a group of hydroxycinnamates, are generally abundant in everyday foods and beverages, most prominently in certain coffee drinks. Among them, the chlorogenic acid (CGA), also termed as 5-O-caffeoylquinic acid (5-CQA), is one of the most abundant, highly functional polyphenolic compounds in the human diet. The evidence of its health benefits obtained from clinical studies, as well as basic research, indicates an inverse correlation between 5-CQA consumption and a lower risk of metabolic syndromes and chronic diseases. This review focuses on the beneficial properties for health and mechanisms of action of 5-CQA, starting with its history, isomers, dietary sources, processing effects, preparation methods, pharmacological safety evaluation, and bioavailability. It also provides the possible molecular mechanistic bases to explain the health beneficial effects of 5-CQA including neuroprotective, cardiovascular protective, gastrointestinal protective, renoprotective, hepatoprotective, glucose and lipid metabolism regulatory, and anticarcinogenic effects. The information summarized here could aid in the basic and clinical research on 5-CQA as a natural dietary additive, potential drug candidate, as well as a natural health promoter.

An Overview of Crucial Dietary Substances and Their Modes of Action for Prevention of Neurodegenerative Diseases

Neurodegenerative diseases, namely Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis are becoming one of the main health concerns due to the increasing aging of the world's population. These diseases often share the same biological mechanisms, including neuroinflammation, oxidative stress, and/or protein fibrillation. Recently, there have been many studies published pointing out the possibilities to reduce and postpone the clinical manifestation of these deadly diseases through lifelong consumption of some crucial dietary substances, among which phytochemicals (e.g., polyphenols) and endogenous substances (e.g., acetyl-L-carnitine, coenzyme Q10, n-3 poysaturated fatty acids) showed the most promising results. Another important issue that has been pointed out recently is the availability of these substances to the central nervous system, where they have to be present in high enough concentrations in order to exhibit their neuroprotective properties. As so, such the aim of this review is to summarize the recent findings regarding neuroprotective substances, their mechanisms of action, as well as to point out therapeutic considerations, including their bioavailability and safety for humans.

Amelioration of Mitochondrial Quality Control and Proteostasis by Natural Compounds in Parkinson's Disease Models

Parkinson’s disease (PD) is a well-known age-related neurodegenerative disorder associated with longer lifespans and rapidly aging populations. The pathophysiological mechanism is a complex progress involving cellular damage such as mitochondrial dysfunction and protein homeostasis. Age-mediated degenerative neurological disorders can reduce the quality of life and also impose economic burdens. Currently, the common treatment is replacement with levodopa to address low dopamine levels; however, this does not halt the progression of PD and is associated with adverse effects, including dyskinesis. In addition, elderly patients can react negatively to treatment with synthetic neuroprotection agents. Recently, natural compounds such as phytochemicals with fewer side effects have been reported as candidate treatments of age-related neurodegenerative diseases. This review focuses on mitochondrial dysfunction, oxidative stress, hormesis, proteostasis, the ubiquitin‒proteasome system, and autophagy (mitophagy) to explain the neuroprotective effects of using natural products as a therapeutic strategy. We also summarize the efforts to use natural extracts to develop novel pharmacological candidates for treatment of age-related PD.

Plant Extracts and Phytochemicals Targeting α-Synuclein Aggregation in Parkinson's Disease Models

α-Synuclein (α-syn) is a presynaptic protein that regulates the release of neurotransmitters from synaptic vesicles in the brain. α-Syn aggregates, including Lewy bodies, are features of both sporadic and familial forms of Parkinson's disease (PD). These aggregates undergo several key stages of fibrillation, oligomerization, and aggregation. Therapeutic benefits of drugs decline with disease progression and offer only symptomatic treatment. Novel therapeutic strategies are required which can either prevent or delay the progression of the disease. The link between α-syn and the etiopathogenesis and progression of PD are well-established in the literature. Studies indicate that α-syn is an important therapeutic target and inhibition of α-syn aggregation, oligomerization, and fibrillation are an important disease modification strategy. However, recent studies have shown that plant extracts and phytochemicals have neuroprotective effects on α-syn oligomerization and fibrillation by targeting different key stages of its formation. Although many reviews on the antioxidant-mediated, neuroprotective effect of plant extracts and phytochemicals on PD symptoms have been well-highlighted, the antioxidant mechanisms show limited success for translation to clinical studies. The identification of specific plant extracts and phytochemicals that target α-syn aggregation will provide selective molecules to develop new drugs for PD. The present review provides an overview of plant extracts and phytochemicals that target α-syn in PD and summarizes the observed effects and the underlying mechanisms. Furthermore, we provide a synopsis of current experimental models and techniques used to evaluate plant extracts and phytochemicals. Plant extracts and phytochemicals were found to inhibit the aggregation or fibril formation of oligomers. These also appear to direct α-syn oligomer formation into its unstructured form or promote non-toxic pathways and suggested to be valuable drug candidates for PD and related synucleinopathy. Current evidences from in vitro studies require confirmation in the in vivo studies. Further studies are needed to ascertain their potential effects and safety in preclinical studies for pharmaceutical/nutritional development of these phytochemicals or dietary inclusion of the plant extracts in PD treatment.

Effects of Enteric Environmental Modification by Coffee Components on Neurodegeneration in Rotenone-Treated Mice

Epidemiological studies have shown that coffee consumption decreases the risk of Parkinson's disease (PD). Caffeic acid (CA) and chlorogenic acid (CGA) are coffee components that have antioxidative properties. Rotenone, a mitochondrial complex I inhibitor, has been used to develop parkinsonian models, because the toxin induces PD-like pathology. Here, we examined the neuroprotective effects of CA and CGA against the rotenone-induced degeneration of central dopaminergic and peripheral enteric neurons. Male C57BL/6J mice were chronically administered rotenone (2.5 mg/kg/day), subcutaneously for four weeks. The animals were orally administered CA or CGA daily for 1 week before rotenone exposure and during the four weeks of rotenone treatment. Administrations of CA or CGA prevented rotenone-induced neurodegeneration of both nigral dopaminergic and intestinal enteric neurons. CA and CGA upregulated the antioxidative molecules, metallothionein (MT)-1,2, in striatal astrocytes of rotenone-injected mice. Primary cultured mesencephalic or enteric cells were pretreated with CA or CGA for 24 h, and then further co-treated with a low dose of rotenone (1⁻5 nM) for 48 h. The neuroprotective effects and MT upregulation induced by CA and CGA in vivo were reproduced in cultured cells. Our data indicated that intake of coffee components, CA and CGA, enhanced the antioxidative properties of glial cells and prevents rotenone-induced neurodegeneration in both the brain and myenteric plexus.

Lumbee traditional medicine: Neuroprotective activities of medicinal plants used to treat Parkinson's disease-related symptoms

ETHNOPHARMACOLOGICAL RELEVANCE

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a loss of dopaminergic neurons in the substantia nigra pars compacta and the presence in surviving neurons of Lewy body inclusions enriched with aggregated forms of the presynaptic protein α-synuclein (aSyn). Although current therapies provide temporary symptomatic relief, they do not slow the underlying neurodegeneration in the midbrain. In this study, we analyzed contemporary herbal medicinal practices used by members of the Lumbee tribe to treat PD-related symptoms, in an effort to identify safe and effective herbal medicines to treat PD.

AIM OF THE STUDY

The aims of this study were to (i) document medicinal plants used by Lumbee Indians to treat PD and PD-related symptoms, and (ii) characterize a subset of plant candidates in terms of their ability to alleviate neurotoxicity elicited by PD-related insults and their potential mechanisms of neuroprotection.

MATERIALS AND METHODS

Interviews of Lumbee healers and local people were carried out in Pembroke, North Carolina, and in surrounding towns. Plant samples were collected and prepared as water extracts for subsequent analysis. Extracts were characterized in terms of their ability to induce activation of the nuclear factor E2-related factor 2 (Nrf2) antioxidant response in cortical astrocytes. An extract prepared from Sambucus caerulea flowers (elderflower extract) was further examined for the ability to induce Nrf2-mediated transcription in induced pluripotent stem cell (iPSC)-derived astrocytes and primary midbrain cultures, to ameliorate mitochondrial dysfunction, and to alleviate rotenone- or aSyn-mediated neurotoxicity.

RESULTS

The ethnopharmacological interviews resulted in the documentation of 32 medicinal plants used to treat PD-related symptoms and 40 plants used to treat other disorders. A polyphenol-rich extract prepared from elderflower activated the Nrf2-mediated antioxidant response in cortical astrocytes, iPSC-derived astrocytes, and primary midbrain cultures, apparently via the inhibition of Nrf2 degradation mediated by the ubiquitin proteasome system. Furthermore, the elderflower extract rescued mitochondrial functional deficits in a neuronal cell line and alleviated neurotoxicity elicited by rotenone and aSyn in primary midbrain cultures.

CONCLUSIONS

These results highlight potential therapeutic benefits of botanical extracts used in traditional Lumbee medicine, and they provide insight into mechanisms by which an elderflower extract could suppress neurotoxicity elicited by environmental and genetic PD-related insults.

Sphingosine Kinase-1 Involves the Inhibitory Action of HIF-1α by Chlorogenic Acid in Hypoxic DU145 Cells

Hypoxia enhances cancer development in a solid tumor. Hypoxia-inducible factor-1 α (HIF-1α) is a transcription factor that is dominantly expressed under hypoxia in solid tumor cells and is a key factor that regulates tumor. HIF-1α regulates several target genes involved in many aspects of cancer progression, including angiogenesis, metastasis, anti-apoptosis and cell proliferation as well as imparts resistance to cancer treatment. In this study, we assessed Crataegus Pinnatifida Bunge var. typical Schneider ethanol extract (CPE) for its anti-cancer effects in hypoxia-induced DU145 human prostate cancer cell line. CPE decreased the abundance of HIF-1α and sphingosine kinase-1 (SPHK-1) in hypoxia-induced prostate cancer DU145 cells. CPE decreased HIF-1α and SPHK-1 as well as SPHK-1 activity. Chlorogenic acid (CA) is one of four major compounds of CPE. Compared to CPE, CA significantly decreased the expression of HIF-1α and SPHK-1 as well as SPHK-1 activity in hypoxia-induced DU145 cells. Furthermore, CA decreased phosphorylation AKT and GSK-3β, which are associated with HIF-1α stabilization and affected SPHK-1 in a concentration-dependent manner. We confirmed the mechanism of CA-induced inhibition of HIF-1α by SPHK-1 signaling pathway using SPHK-1 siRNA and SPHK inhibitor (SKI). CA decreased the secretion and cellular expression of VEGF, thus inhibiting hypoxia-induced angiogenesis. Treatment of DU145cells with SPHK1 siRNA and CA for 48 h decreased cancer cell growth, and the inhibitory action of SPHK siRNA and CA on cell growth was confirmed by decrease in the abundance of Proliferating cell nuclear antigen (PCNA).

Chlorogenic Acid and Mental Diseases: From Chemistry to Medicine

BACKGROUND

At present, much attention has been focused on the beneficial effects of natural products on the human health due to their high efficacy and low adverse effects. Among them, polyphenolic compounds are known as one of the most important and common classes of natural products, which possess multiple range of health-promotion effects including anti-inflammatory and antioxidant activities. A plethora of scientific evidence has shown that polyphenolic compounds possess beneficial effects on the central nervous system.

METHODS

Data were collected from Web of Science (ISI Web of Knowledge), Medline, Pubmed, Scopus, Embase, and BIOSIS Previews (from 1950 to 2015), through searching of these keywords: "chlorogenic acid and mental diseases" and "chlorogenic acid and neuroprotection".

RESULTS

Chlorogenic acid is known as one of the most common polyphenolic compounds, and is found in different types of fruits and vegetables, spices, wine, olive oil, as well as coffee. The potential neuroprotective effects of chlorogenic acid have been highlighted in several in vitro and in vivo studies. This review critically analyses the available scientific evidence regarding the neuroprotective effects of chlorogenic acid, and its neuropharmacological mechanisms of action. In addition, we also discuss its biosynthesis, sources, bioavailability and metabolism, to provide a broad perspective of the therapeutic implications of this compound in brain health and disease.

CONCLUSION

The present review showed that chlorogenic acid possesses neuroprotective effects under the both in vitro and in vivo models.

Beneficial Role of Coffee and Caffeine in Neurodegenerative Diseases: A Minireview

Coffee is among the most widespread and healthiest beverages in the world. Coffee typically contains more caffeine than most other beverages, and is widely and frequently consumed. Thus, it contributes significantly to the overall caffeine consumption within the general population, particularly in adults. Controversies regarding its benefits and risks still exist as reliable evidence is becoming available supporting its health-promoting potential. Several lines of evidence have highlighted the beneficial effects towards several disease conditions including Type II diabetes, hepatitis C virus, hepatocellular carcinoma, nonalcoholic fatty liver disease and neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD) and Amyotrophic Lateral Sclerosis (ALS). The health-promoting properties of coffee are largely attributed to its rich phytochemistry, including caffeine, chlorogenic acid, caffeic acid, and hydroxy hydroquinone. In this minireview, an attempt has been made to discuss the various evidences which are mainly derived from animal and cell models. Various mechanisms chiefly responsible for the beneficial effects of caffeine have also been briefly outlined. A short note on the undesirable effects of excessive coffee intakes is also presented.

Cognitive and neuroprotective effects of chlorogenic acid

OBJECTIVES

The aim of this review was to provide an overview of studies conducted to determine the effects of chlorogenic acid (CGA) on cognition and neurological health.

METHODS

A literature search was conducted using PubMed and various search terms including chlorogenic acid, CGA, memory, neuroscience, cognition, nutrition, antioxidant, pharmacokinetics, neuroprotection, and neurodegeneration.

RESULTS

Many studies have linked CGA consumption to a wide range of health benefits, including neuroprotection, cardioprotection, weight loss, chemopreventive properties, anti-inflammatory activity, decreased blood pressure, decreased diet-induced insulin resistance, decreased blood pressure, anxiolytic effects, and antihyperalgesic effects. Pre-clinical and clinical studies both provide evidence that CGA supplementation could protect against neurological degeneration and the resulting diseases associated with oxidative stress in the brain; however, no formal, well-controlled studies have been performed to date.

DISCUSSION

Recent research suggests that dietary consumption of CGA could produce a wide range of health benefits and physiological effects. There is also mounting evidence that the consumption of polyphenols, including CGA, in the diet could reduce the risk of developing neurodegenerative conditions. Further studies should be conducted with a focus on the effects of CGA on cognition and the nervous system and employing well-designed clinical studies.

Chlorogenic acid inhibits hypoxia-induced angiogenesis via down-regulation of the HIF-1α/AKT pathway

BACKGROUND

The hypoxia-inducible factor-1 (HIF-1) is known to play an important role in cellular responses to hypoxia, including the transcriptional activation of a number of genes involved in tumor angiogenesis. Chlorogenic acid (CGA), one of the most abundant polyphenols in the human diet, has been reported to inhibit cancer cell growth. The effect of CGA on tumor angiogenesis and its underlying mechanisms are, as yet, unknown.

METHODS

The effect of CGA on HIF-1α expression was assessed by Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR) assays in A549 lung cancer cells. The transcriptional activity of the HIF-1 complex was confirmed using a luciferase assay. To assess whether angiogenic factors are increased under hypoxic conditions in these cells, vascular endothelial growth factor (VEGF) expression levels were measured by RT-PCR and Western blotting. The direct effect of CGA on human vascular endothelial cells (HUVEC) under hypoxic conditions was analyzed using in vitro assays, including tube-formation, wound healing and Transwell invasion assays. To investigate the effect of CGA on angiogenesis in vivo, we performed a Matrigel plug assay in a mouse model. Finally, the effect of CGA on AKT and ERK activation (phosphorylation) as a putative mechanism underlying the effect of CGA on VEGF-mediated angiogenesis inhibition was assessed using Western blotting.

RESULTS

We found that CGA significantly decreases the hypoxia-induced HIF-1α protein level in A549 cells, without changing its mRNA level. CGA was, however, found to suppress the transcriptional activity of HIF-1α under hypoxic conditions, leading to a decrease in the expression of its downstream target VEGF. We also found that CGA can block hypoxia-stimulated angiogenesis in vitro and VEGF-stimulated angiogenesis in vivo using HUVEC cells. In addition, we found that CGA can inhibit the HIF-1α/AKT signaling pathway, which plays an important role in VEGF activation and angiogenesis.

CONCLUSIONS

Our data indicate that CGA plays a role in the suppression of angiogenesis via inhibition of the HIF-1α/AKT pathway. CGA may represent a novel therapeutic option for the treatment of (lung) cancer.

Chlorogenic and caftaric acids in liver toxicity and oxidative stress induced by methamphetamine

Methamphetamine intoxication can cause acute hepatic failure. Chlorogenic and caftaric acids are the major dietary polyphenols present in various foods. The aim of this study was to evaluate the protective role of chlorogenic and caftaric acids in liver toxicity and oxidative stress induced by methamphetamine in rats. Thirty-two male albino rats were divided into 4 equal groups. Group 1, which was control group, was injected (i.p) with saline (1 mL/kg) twice a day over seven-day period. Groups 2, 3, and 4 were injected (i.p) with methamphetamine (10 mg/kg) twice a day over seven-day period, where groups 3 and 4 were injected (i.p) with 60 mg/kg chlorogenic acid and 40 mg/kg caftaric acid, respectively, one day before methamphetamine injections. Methamphetamine increased serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, bilirubin, cholesterol, low-density lipoprotein, and triglycerides. Also, malondialdehyde in serum, liver, and brain and plasma and liver nitric oxide levels were increased while methamphetamine induced a significant decrease in serum total protein, albumin, globulin, albumin/globulin ratio, brain serotonin, norepinephrine and dopamine, blood and liver superoxide dismutase, and glutathione peroxidase levels. Chlorogenic and caftaric acids prior to methamphetamine injections restored all the above parameters to normal values. In conclusion, chlorogenic and caftaric acids before methamphetamine injections prevented liver toxicity and oxidative stress where chlorogenic acid was more effective.

Eucommia ulmoides Oliv. bark. attenuates 6-hydroxydopamine-induced neuronal cell death through inhibition of oxidative stress in SH-SY5Y cells

ETHNOPHARMACOLOGICAL RELEVANCE

Eucommia ulmoides Oliv. Bark. (EUE) has commonly been used to fortify the muscles and lungs, lower blood pressure, prevent miscarriage, improve liver and kidney tone, and promote longevity as a traditional tonic medicine in Korea, China, and Japan.

AIM OF THE STUDY

In this study, we investigated the mechanisms by which EUE protects neuronal cells from apoptosis induced by the Parkinson's disease (PD)-related neurotoxin, 6-hydroxydopamine (6-OHDA).

MATERIALS AND METHODS

We determined the neuroprotective effects of EUE on 6-OHDA-induced neuronal cell death, cytotoxicity, reactive oxygen species (ROS) production, and mitochondrial membrane dysfunction. Moreover, we examined whether EUE suppressed phosphorylation of c-Jun N-terminal kinase (JNK), phosphatidylinositol 3-kinase (PI3K)/Akt, and glycogen synthase kinase-3 beta (GSK-3β). Furthermore, the neuroprotective effects of EUE on 6-OHDA-induced activation of nuclear factor-kappa B (NF-κB) was studied in SH-SY5Y cells.

RESULTS

Pretreatment of SH-SY5Y cells with EUE significantly reduced 6-OHDA-induced cell death and cytotoxicity. EUE inhibited 6-OHDA-induced generation of ROS, which conferred cytoprotection against 6-OHDA-induced oxidative injury. EUE treatment also strikingly inhibited 6-OHDA-induced mitochondrial dysfunction. In addition, EUE suppressed phosphorylation of JNK, PI3K/Akt, and GSK-3β. Furthermore, EUE blocked 6-OHDA-induced NF-κB nuclear translocation, an event downstream from JNK, PI3K/Akt, and GSK-3β phosphorylation. Moreover, chlorogenic acid (CGA), one of the active constituents of EUE, was also able to reduce 6-OHDA-induced toxicity in SH-SY5Y cells.

CONCLUSION

Taken together, these results suggest that EUE attenuates oxidative stress through activation of JNK, PI3K/Akt, GSK-3β, and NF-κB pathways, thereby protecting cells from neuronal cell death.

The flavonoid apigenin improves glucose tolerance through inhibition of microRNA maturation in miRNA103 transgenic mice

Polyphenols are representative bioactive substances with diverse biological effects. Here, we show that apigenin, a flavonoid, has suppressive effects on microRNA (miRNA) function. The effects were mediated by impaired maturation of a subset of miRNAs, probably through inhibition of the phosphorylation of TRBP, a component of miRNA-generating complexes via impaired mitogen-activated protein kinase (MAPK) Erk activation. While glucose intolerance was observed in miRNA103 (miR103)-overexpressing transgenic mice, administration of apigenin improved this pathogenic status likely through suppression of matured miR103 expression levels. These results suggest that apigenin may have favorable effects on the pathogenic status induced by overexpression of miRNA103, whose maturation is mediated by phosphorylated TRBP.

Dopamine-mediated oxidation of methionine 127 in α-synuclein causes cytotoxicity and oligomerization of α-synuclein

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the selective loss of dopaminergic neurons and the presence of Lewy bodies. Many recent studies focused on the interaction between α-synuclein (α-syn) and dopamine in the pathogenesis of PD, and fluorescent anisotropy suggested that the C-terminal region of α-syn may be a target for modification by dopamine. However, it is not well understood why PD-related pathogenesis occurs selectively in dopaminergic neurons. We investigated the interaction between dopamine and α-syn with regard to cytotoxicity. A soluble oligomer was formed by co-incubating α-syn and dopamine in vitro. To clarify the effect of dopamine on α-syn in cells, we generated PC12 cells expressing human α-syn, as well as the α-syn mutants, M116A, Y125D, M127A, S129A, and M116A/M127A, in a tetracycline-inducible manner (PC12-TetOFF-α-syn). Overexpression of wildtype α-syn in catecholaminergic PC12 cells decreased cell viability in long-term cultures, while a competitive inhibitor of tyrosine hydroxylase blocked this vulnerability, suggesting that α-syn-related cytotoxicity is associated with dopamine metabolism. The vulnerabilities of all mutant cell lines were lower than that of wildtype α-syn-expressing cells. Moreover, α-syn containing dopamine-mediated oxidized methionine (Met(O)) was detected in PC12-TetOFF-α-syn. Met(O) was lower in methionine mutant cells, especially in the M127A or M116A/M127A mutants, but also in the Y125D and S129A mutants. Co-incubation of dopamine and the ₁₂₅YEMPS₁₂₉ peptide enhanced the production of H₂O₂, which may oxidize methionine residues and convert them to Met(O). Y125- or S129-lacking peptides did not enhance the dopamine-related production of H₂O₂. Our results suggest that M127 is the major target for oxidative modification by dopamine, and that Y125 and S129 may act as enhancers of this modification. These results may describe a mechanism of dopaminergic neuron-specific toxicity of α-syn in the pathogenesis of PD.