Chrysotoxine, a novel bibenzyl compound selectively antagonizes MPP+, but not rotenone, neurotoxicity in dopaminergic SH-SY5Y cells

Traditional uses, chemical compositions and pharmacological activities of Dendrobium: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Dendrobium is a kind of medicine food homology plant. Dendrobium has long been used to strengthen "Yin" and tonify five viscera.

AIM OF THIS REVIEW

This paper presents a systematic review of the folk usage, chemical composition and pharmacological activity of Dendrobium, aiming to provide a reference for subsequent in-depth understanding and better exploitation of health food, medicine, and natural products.

MATERIALS AND METHODS

Available information about the genus Dendrobium was collected via Web of Science, PubMed, Science Direct, Scopus, APA-Psy Articles, Google Scholar, Connected Papers, Springer Search, and KNCI. The keywords for this article are Dendrobium, traditional use, chemical diversity and pharmacological activity. Use the "Dictionary of Chinese Ethnic Medicine" to provide 23 kinds of Dendrobium with medicinal value, the Latin name of Dendrobium is verified by the Flora of China (www.iplant.cn), and its species distribution and related information are collected.

RESULTS

There are 78 species of Dendrobium in China, 14 of which are endemic to China. At present, 450 compounds including sesquiterpenoids, lignans compounds, phenolic compounds, phenanthrene compounds, bibenzyls, polysaccharides and flavonoids have been isolated and identified from at least 50 species of Dendrobium. Among them, bibenzyls and polysaccharides are the main active components, phenolics and lignans are widely distributed, sesquiterpenes are the most common chemical constituents in genus Dendrobium plants. The most popular research objects are Dendrobium officinale and Dendrobium huoshanense.

CONCLUSIONS

Based on traditional folk uses, chemical composition and pharmacological studies, Dendrobium is considered a promising medicinal and edible plant with multiple pharmacological activities. In addition, a large number of clinical applications and further studies on single chemical components based on the diversity of chemical structures should be conducted, which will lay the foundation for the scientific utilization of genus Dendrobium.

Recent research progress on natural small molecule bibenzyls and its derivatives in Dendrobium species

Orchidaceous plant Dendrobium genus is often used as a tonic, and its phenolic components have attracted attention for its anti-tumor and anti-diabetic complications. Bibenzyls is one of the essential phenolic active ingredients in the Dendrobium genus. At present, 89 bibenzyl derivatives have been extracted and identified from 46 Dendrobium species. The activity studies have shown that 42 compounds have pharmaceutical activity. Among them, 23 compounds showed antitumor activity; 7 compounds showed anti-diabetes and its complications activity; 10 compounds exhibited neuroprotective effects; 18 compounds showed antioxidant effects; 11 compounds had anti-inflammatory activity; 3 compounds had Antiplatelet aggregation effects; 3 compounds had antibacterial and antiviral effects. The Bibenzyls is small-molecular compounds of natural origin and widely sourced. Previous studies showed that the bibenzyls has good anti-tumor, anti-diabetes and its complications, and neuroprotective effects, and it has great potential for treating tumors, diabetes and its complications, Alzheimer's disease (AD) and Parkinson's disease (PD). Additionally, compounds such as moscatilin (1), gigantol (2) and chrysotoxine (3) have been further studied as lead compounds, and compounds exhibited therapeutical effects had been synthesized. Enough pieces of evidences have shown that the Bibenzyls have good development prospects. This article reviews the pharmacological effects of bibenzyls in Dendrobium species and provides an idea for its further development.

In Vitro and In Vivo Neuroprotective Effects of Stellettin B Through Anti-Apoptosis and the Nrf2/HO-1 Pathway

Pharmaceutical agents for halting the progression of Parkinson’s disease (PD) are lacking. The current available medications only relieve clinical symptoms and may cause severe side effects. Therefore, there is an urgent need for novel drug candidates for PD. In this study, we demonstrated the neuroprotective activity of stellettin B (SB), a compound isolated from marine sponges. We showed that SB could significantly protect SH-SY5Y cells against 6-OHDA-induced cellular damage by inhibiting cell apoptosis and oxidative stress through PI3K/Akt, MAPK, caspase cascade modulation and Nrf2/HO-1 cascade modulation, respectively. In addition, an in vivo study showed that SB reversed 6-OHDA-induced a locomotor deficit in a zebrafish model of PD. The potential for developing SB as a candidate drug for PD treatment is discussed.

3-(Naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride attenuates MPP＋-induced cytotoxicity by regulating oxidative stress and mitochondrial dysfunction in SH-SY5Y cells

Parkinson’s disease (PD) is a common chronic neurodegenerative disease mainly caused by the death of dopaminergic neurons. However, no complete pharmacotherapeutic approaches are currently available for PD therapies. 1-methyl-4-phenylpyridinium (MPP⁺)-induced SH-SY5Y neurotoxicity has been broadly utilized to create cellular models and study the mechanisms and critical aspects of PD. In the present study, we examined the role of a novel azetidine derivative, 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride (KHG26792), against MPP⁺-induced neurotoxicity in SH-SY5Y cells. Treatment of KHG26792 significantly attenuated MPP⁺-induced changes in the protein levels of Bcl-2 and Bax together with efficient suppression of MPP⁺-induced activation of caspase-3 activity. KHG26792 also attenuated mitochondrial potential and levels of ROS, Ca²⁺, and ATP in MPP⁺-treated SH-SY5Y cells. Additionally, KHG26792 inhibited the induced production of nitric oxide and malondialdehyde. Moreover, the protective effect of KHG26792 is mediated through regulation of glutathione peroxidase and GDNF levels. Our results suggest a possibility that KHG26792 treatment significantly protects against MPP⁺-induced neurotoxicity in SH-SY5Y cells and KHG26792 may be a valuable therapeutic agent for the treatment of PD induced by an environmental toxin.

Upregulated lncRNA small nucleolar RNA host gene 1 promotes 1-methyl-4-phenylpyridinium ion-induced cytotoxicity and reactive oxygen species production through miR-15b-5p/GSK3β axis in human dopaminergic SH-SY5Y cells

Long noncoding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) has been demonstrated to be upregulated and play a crucial role in the pathology of Parkinson's disease (PD). However, the exact role of SNHG1 and its underlying mechanisms in PD remains elusive. In this study, we found that SNHG1 and glycogen synthase kinase 3 beta (GSK3β) were upregulated, but miR-15b-5p was downregulated in 1-methyl-4-phenylpyridinium ion (MPP⁺ )-treated SH-SY5Y cells. The upregulation of SNHG1 enhanced MPP⁺ -induced cellular toxicity in SH-SY5Y cells, as shown by decreased cell viability, increased ROS production, and increased number of TdT-mediated dUTP Nick-End labeling-positive cells, accompanied with the upregulation of cleaved caspase 3 and elevation of cytochrome C release. Meanwhile, SNHG1 knockdown presented the converse effects. SNHG1 was demonstrated to interact with miR-15b-5p. Moreover, SNHG1 could attenuate the inhibitory effects of miR-15b-5p on MPP⁺ -induced cytotoxicity and production of ROS. Besides, GSK3β was identified as a direct target of miR-15b-5p. The inhibitory effects of SNHG1 knockdown or miR-15b-5p overexpression on MPP⁺ -induced cytotoxicity and reactive oxygen species (ROS) production were abrogated by upregulation of GSK3β. Taken together, these results demonstrate that upregulated lncRNA SNHG1 promotes MPP⁺ -induced cytotoxicity and ROS production through the miR-15b-5p/GSK3β axis in human dopaminergic SH-SY5Y cells, suggesting that SNHG1 may act as a potential therapeutic target for PD treatment in the future.

Rifampicin Prevents SH-SY5Y Cells from Rotenone-Induced Apoptosis via the PI3K/Akt/GSK-3β/CREB Signaling Pathway

In addition to its original application for treating tuberculosis, rifampicin has multiple potential neuroprotective effects in chronic neurodegenerative diseases including Parkinson's disease (PD) and Alzheimer's disease. Inflammatory reactions and the PI3K/Akt pathway are strongly implicated in dopaminergic neuronal death in PD. This study aims to investigate whether rifampicin protects rotenone-lesioned SH-SY5Y cells via regulating PI3K/Akt/GSK-3β/CREB pathway. Rotenone-treated SH-SY5Y cells were used as the cell model to investigate the neuroprotective effects of rifampicin. Cell viability and apoptosis of SH-SY5Y cells were determined by CCK-8 assay and flow cytometry, respectively. The expression of Akt, p-Akt, GSK-3β, p-GSK-3β, CREB and p-CREB were measured by Western blot. Our results showed that the cell viability and level of phospho-CREB significantly decreased in SH-SY5Y cells exposed to rotenone when compared to the control group. Both the cell viability and the expression of phospho-CREB in cells pretreated with rifampicin were higher than those of cells exposed to rotenone alone. Moreover, pretreatment of SH-SY5Y cells with rifampicin enhanced phosphorylation of Akt and suppressed activity of GSK-3β. The addition of LY294002, a PI3K inhibitor, could suppress phosphorylation of Akt and CREB and activate GSK-3β, resulting in abolishment of neuroprotective effects of rifampicin on cells exposed to rotenone. Rifampicin provides neuroprotection against dopaminergic degeneration, partially via the PI3K/Akt/GSK-3β/CREB signaling pathway. These findings suggest that rifampicin could be an effective and promising neuroprotective candidate for treating PD.

Cancer Stem Cell-Suppressing Activity of Chrysotoxine, a Bibenzyl from Dendrobium pulchellum

Cancer stem cells (CSCs) have been recognized as rare populations driving cancer progression, metastasis, and drug resistance in leading cancers. Attempts have been made toward identifying compounds that specifically target these CSCs. Therefore, investigations of novel therapeutic strategies for CSC targeting are required. The cytotoxic effects of chrysotoxine on human non-small cell lung cancer-derived H460 and H23 cells were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The effects of chrysotoxine suppression of CSC-like phenotypes were determined in CSC-rich populations and primary CSCs in three-dimensional (3D) culture and in an extreme limiting dilution assay. Expression of CSC markers and associated proteins was determined by Western blot analyse and flow cytometry. We have reported herein the CSC-suppressing activity of chrysotoxine, a bibenzyl compound isolated from Dendrobium pulchellum We have shown, to our knowledge for the first time, that chrysotoxine dramatically suppresses CSC-like phenotypes of H460 and H23 cells. Treatment with chrysotoxine significantly reduced the viability of 3D CSC-rich populations and concomitantly decreased known CSC markers. Chrysotoxine suppressed CSC phenotypes through downregulation of Src/protein kinase B (Akt) signaling. Active (phosphorylated Y416) Src was shown to regulate cancer stemness, since ectopic overexpression of Src strongly activated Akt and subsequently enhanced pluripotency transcription factor SRY (sex-determining region Y)-box 2 (Sox2)- mediating CSC phenotypes, whereas the short hairpin RNA of Src and an Src inhibitor (dasatinib) suppressed Akt, Sox2, and CSC properties. Importantly, chrysotoxine was shown to suppress active Src/Akt signaling and in turn depleted Sox2-mediated CSCs. Our findings indicate a novel CSC-targeted role of chrysotoxine and its regulation by Src/Akt and Sox2, which may be exploited for cancer treatment.

Dendrobium: Sources of Active Ingredients to Treat Age-Related Pathologies

Dendrobium represents one of the most important orchid genera, ornamentally and medicinally. Dendrobiums are sympodial epiphytic plants, which is a name they are worthy of, the name coming from Greek origin: "dendros", tree, and "bios", life. Dendrobium species have been used for a thousand years as first-rate herbs in traditional Chinese medicine (TCM). They are source of tonic, astringent, analgesic, antipyretic, and anti-inflammatory substances, and have been traditionally used as medicinal herbs in the treatment of a variety of disorders, such as, nourishing the stomach, enhancing production of body fluids or nourishing Yin. The Chinese consider Dendrobium as one of the fifty fundamental herbs used to treat all kinds of ailments and use Dendrobium tonic for longevity. This review is focused on main research conducted during the last decade (2006-2016) on Dendrobium plants and their constituents, which have been subjected to investigations of their pharmacological effects involving anticancer, anti-diabetic, neuroprotective and immunomodulating activities, to report their undeniable potential for treating age-related pathologies.

Purinergic receptor P2Y6 contributes to 1-methyl-4-phenylpyridinium-induced oxidative stress and cell death in neuronal SH-SY5Y cells

Oxidative stress and neural degeneration have been shown to be involved in the pathogenesis of Parkinson's disease (PD). The P2Y6 purinergic receptor (P2Y6R) has been shown to participate in the activation of microglia and the production of pro-inflammatory factors induced by lipopolysaccharide to cause neuronal loss. However, the function of P2Y6R during oxidative stress in neurons is unclear. In the present study, 1-methyl-4-phenylpyridinium (MPP⁺ ) treatment increased the level of UDP/P2Y6R on neuronal SH-SY5Y cells. Importantly, pharmacological inhibition of P2Y6R or knockdown of P2Y6R using a siRNA exerted an increased protective effect by preventing MPP⁺ -induced increases in the levels of reactive oxygen species (ROS), superoxide anion, inducible nitric oxide synthase (iNOS), and malondialdehyde (MDA) and down-regulation of superoxide dismutase 1 (SOD1) expression. UDP, an agonist of P2Y6R, enhanced the effects of MPP⁺ , which was also inhibited by apyrase or MRS2578. Additionally, P2Y6R knockdown also significantly reversed both the loss of cell viability and the increase in the levels of phosphorylated extracellular signal-regulated protein kinase (p-ERK1/2) and p38 (p-p38) caused by MPP⁺ stimulation. However, the inhibition of the ERK1/2 and p38 kinase signaling pathways had no effect on P2Y6R expression. Taken together, these results support the hypothesis that P2Y6R expressed on neuronal SH-SY5Y cell is associated with the progression of oxidative stress and cell death induced by MPP⁺ , suggesting that P2Y6R may play an important role in the pathogenesis of PD.

Neuroprotective effect of carnosine against salsolinol-induced Parkinson's disease

Carnosine is a dipeptide of β-alanine and histidine amino acids. It is widely present in muscle and brain tissues. Carnosine has been demonstrated to be an antioxidant agent that is beneficial in animals. Reactive oxygen species (ROS) and aldehydes are are generated from membrane fatty acid oxidation. The antioxidant potential and toxicity of salsolinol had been extensively studied in vivo and in vitro. The present study analyzed the protective effect of carnosine against Parkinson's disease in the salsolinol-induced rat brain and rat brain endothelial cells. Antioxidant and biochemical markers were determined in vitro and in vivo. Histopathological examination was completed in order to evaluate the protective effect of carnosine on the cellular architecture of salsolinol-induced brain tissue. In order to confirm the protective effect of carnosine further, it was also investigated at an in vitro level using rat brain endothelial cells. Fluorescence and confocal studies indicated reduced apoptosis in the endothelial cells of the rat brain tissue. Antioxidant enzymes and lipid peroxidation levels were renormalized following treatment with carnosine. In addition, carnosine treatment reduced mitochondria-derived ROS in the rat brain endothelial cells. These findings suggest that carnosine may be a therapeutic agent against salsolinol-induced Parkinson's.

Dose-dependent effect of Curcuma longa for the treatment of Parkinson's disease

Curcuma longa is a plant that belongs to the ginger family, Zingiberaceae. It has been used in Siddha medicine for thousands of years in Asia. Parkinson's disease (PD) is a degenerative disorder of the central nervous system that affects the motor system of the brain. Death of dopamine-producing cells in the substantia nigra leads to PD. Exposure to salsolinol, which is an endogenous neurotoxin, has been associated with damage to dopamine-producing cells. The present study assessed the toxicity of salsolinol in SH-SY5Y human neuroblastoma cells and subsequently investigated the neuroprotective potential of C. longa extract in salsolinol-induced toxic conditions in SH-SY5Y cells. Sulphorhodamine-B assay showed the protective effect of the anti-apoptotic effect of treated SH-SY5Y cells. Fluorescence microscopy and confocal laser scanning microscope analysis indicated the anti-apoptotic impact of the C. longa extract. Mitochondria-derived reactive oxygen species were reduced in C. longa extract-treated SH-SY5Y cells. Downregulated mRNA expression levels of p53, Bcl-2-associated X protein and caspase 3 were observed in the C. longa extract-treated SH-SY5Y cells. Caspase 3 activity was reduced in the C. longa extract-treated SH-SY5Y cells. In conclusion, the present findings demonstrated that solsolinol is neurotoxic to SH-SY5Y cells, and C. longa extract may be useful in the treatment of PD.

The medicinal and pharmaceutical importance of Dendrobium species

Plants of the Dendrobium genus, one of the largest in the Orchidaceae, manifest a diversity of medicinal effects encompassing antiangiogenic, immunomodulating, antidiabetic, cataractogenesis-inhibiting, neuroprotective, hepatoprotective, anti-inflammatory, antiplatelet aggregation, antifungal, antibacterial, antiherpetic, antimalarial, aquaporin-5 stimulating, and hemagglutininating activities and also exert beneficial actions on colonic health and alleviate symptoms of hyperthyroidism. The active principles include a wide range of proteinaceous and non-proteinaceous molecules. This mini-review discusses the latest advances in what is known about the medicinal and pharmaceutical properties of members of the Dendrobium genus and explores how biotechnology can serve as a conduit to mass propagate valuable germplasm for sustainable exploration for the pharmaceutical industry.

Protection of Primary Dopaminergic Midbrain Neurons by GPR139 Agonists Supports Different Mechanisms of MPP(+) and Rotenone Toxicity

The G-protein coupled receptor 139 (GPR139) is expressed specifically in the brain in areas of relevance for motor control. GPR139 function and signal transduction pathways are elusive, and results in the literature are even contradictory. Here, we examined the potential neuroprotective effect of GPR139 agonism in primary culture models of dopaminergic (DA) neuronal degeneration. We find that in vitro GPR139 agonists protected primary mesencephalic DA neurons against 1-methyl-4-phenylpyridinium (MPP(+))-mediated degeneration. Protection was concentration-dependent and could be blocked by a GPR139 antagonist. However, the protection of DA neurons was not found against rotenone or 6-hydroxydopamine (6-OHDA) mediated degeneration. Our results support differential mechanisms of toxicity for those substances commonly used in Parkinson's disease (PD) models and potential for GPR139 agonists in neuroprotection.

Dihuang Yinzi, a Classical Chinese Herbal Prescription, for Amyotrophic Lateral Sclerosis: A 12-Year Follow-up Case Report

Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disease with no effective treatment and death within 2 to 5 years after symptom onset. Here, we reported a case of ALS patient using modified Dihuang Yinzi (DHYZ), a classical traditional Chinese medicine (TCM) prescription, who has survived 12 years with significant improvement in bulbar paralysis.A 41-year-old Chinese Han nationality woman was admitted to the hospital with complaints of weakened bilateral grip, slurred speech, stumbling, and muscle twitching for 3 years. The electromyography showed neurogenic injury in bilateral upper limbs and tongue. She was diagnosed with ALS according to the revised El escorial criteria. The patient was orally administrated with Riluzole 100 mg daily for 10 months and then stopped. Subsequently, she resorted to TCM. Based on the TCM theory, the patient was diagnosed with Yinfei syndrome because of kidney deficiency. DHYZ was chosen because it has the function of replenishing kidney essence to treat Yinfei syndrome. Up to now, she has been using modified DHYZ continuously for 12 years. The patient survived with ALS and did not require permanent continuous ventilator. In addition, the symptoms of choking on liquids are improved, and the utility of 30 mL water swallow test was improved with grade 2. The symptoms of muscle fibrillations of limbs are also reduced. However, muscle strength worsened slowly. The repeated electromyography showed motor conduction amplitude reducing gradually and velocity not changing more when compared with the initial electromyography.Our findings suggested that DHYZ can be potentially used in ALS patients because of its multi-targeted neuroprotection and general safety, although ALS does not have a cure. In addition, we identified the area that is worthy of further study and DHYZ as a promising candidate for further clinical application and ALS trials. Rigorous randomized controlled trials are needed in the future.

Synthesis and evaluation of neuroprotective 4-O-substituted chrysotoxine derivatives as potential multifunctional agents for the treatment of Alzheimer's disease

A series of 4-O-substituted chrysotoxine (CTX) derivatives were designed, synthesized and evaluated as multifunctional agents for the treatment of Alzheimer's disease (AD).

Tianma Gouteng Yin, a Traditional Chinese Medicine decoction, exerts neuroprotective effects in animal and cellular models of Parkinson's disease

Tianma Gouteng Yin (TGY) is a traditional Chinese medicine (TCM) decoction widely used to treat symptoms associated with typical Parkinson’s disease (PD). In this study, the neuroprotective effects of water extract of TGY were tested on rotenone-intoxicated and human α-synuclein transgenic Drosophila PD models. In addition, the neuroprotective effect of TGY was also evaluated in the human dopaminergic neuroblastoma SH-SY5Y cell line treated with rotenone and the rotenone intoxicated hemi-parkinsonian rats. In rotenone-induced PD models, TGY improved survival rate, alleviated impaired locomotor function of Drosophila, mitigated the loss of dopaminergic neurons in hemi-parkinsonian rats and alleviated apoptotic cell death in SH-SY5Y cells; in α-synuclein transgenic Drosophila, TGY reduced the level of α-synuclein and prevented degeneration of dopaminergic neurons. Conclusively, TGY is neuroprotective in PD models both in vivo and in vitro.

Inhibition of Protein Ubiquitination by Paraquat and 1-Methyl-4-Phenylpyridinium Impairs Ubiquitin-Dependent Protein Degradation Pathways

Intracytoplasmic inclusions of protein aggregates in dopaminergic cells (Lewy bodies) are the pathological hallmark of Parkinson's disease (PD). Ubiquitin (Ub), alpha (α)-synuclein, p62/sequestosome 1, and oxidized proteins are the major components of Lewy bodies. However, the mechanisms involved in the impairment of misfolded/oxidized protein degradation pathways in PD are still unclear. PD is linked to mitochondrial dysfunction and environmental pesticide exposure. In this work, we evaluated the effects of the pesticide paraquat (PQ) and the mitochondrial toxin 1-methyl-4-phenylpyridinium (MPP(+)) on Ub-dependent protein degradation pathways. No increase in the accumulation of Ub-bound proteins or aggregates was observed in dopaminergic cells (SK-N-SH) treated with PQ or MPP(+), or in mice chronically exposed to PQ. PQ decreased Ub protein content, but not its mRNA transcription. Protein synthesis inhibition with cycloheximide depleted Ub levels and potentiated PQ-induced cell death. The inhibition of proteasomal activity by PQ was found to be a late event in cell death progression and had neither effect on the toxicity of either MPP(+) or PQ, nor on the accumulation of oxidized sulfenylated, sulfonylated (DJ-1/PARK7 and peroxiredoxins), and carbonylated proteins induced by PQ. PQ- and MPP(+)-induced Ub protein depletion prompted the dimerization/inactivation of the Ub-binding protein p62 that regulates the clearance of ubiquitinated proteins by autophagy. We confirmed that PQ and MPP(+) impaired autophagy flux and that the blockage of autophagy by the overexpression of a dominant-negative form of the autophagy protein 5 (dnAtg5) stimulated their toxicity, but there was no additional effect upon inhibition of the proteasome. PQ induced an increase in the accumulation of α-synuclein in dopaminergic cells and membrane-associated foci in yeast cells. Our results demonstrate that the inhibition of protein ubiquitination by PQ and MPP(+) is involved in the dysfunction of Ub-dependent protein degradation pathways.

Agmatine Protects Against 6-OHDA-Induced Apoptosis, and ERK and Akt/GSK Disruption in SH-SY5Y Cells

6-Hydroxydopamine (6-OHDA), a metabolite of dopamine is known to induce dopaminergic cell toxicity which makes that a suitable agent inducing an experimental model of Parkinson's disease (PD). Agmatine has been shown to protect against some cellular and animal PD models. This study was aimed to assess whether agmatine prevents 6-OHDA-induced SH-SY5Y cell death and if yes, then how it affects Akt/glycogen synthesis kinase-3β (GSK-3β) and extracellular signal-regulated kinases (ERK) signals. The cells were treated with different drugs, and their viability was examined via MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay and morphological observation. Western blot studies were done to assess cleaved caspase-3, Akt/GSK-3β, and ERK proteins. 6-OHDA-induced cell death and caspase-3 cleavage, while agmatine prevented those changes. 6-OHDA also decreased the amount of phosphorylated Akt (pAkt)/Akt while increased GSK-3β activity which was prevented by agmatine. Additionally, this toxin increased pERK/ERK ratio which was averted again by agmatine. The PI3/Akt inhibitor, LY294002, impeded the changes induced by agmatine, while ERK inhibitor (PD98059) did not disturb the effects of agmatine, and by itself, it preserved the cells against 6-OHDA toxicity. This study revealed that agmatine is protective in 6-OHDA model of PD and affects Akt/GSK-3β and ERK pathways.

Evaluation of chemical constituents and important mechanism of pharmacological biology in dendrobium plants

Dendrobium species, commonly known as “Shihu” or “Huangcao,” represents the second largest genus of Orchidaceae, which are used commonly as tonic herbs and healthy food in many Asian countries. The aim of this paper is to review the history, chemistry, and pharmacology of different Dendrobium species on the basis of the latest academic literatures found in Google Scholar, PubMed, Sciencedirect, Scopus, and SID.

Neurotoxin mechanisms and processes relevant to Parkinson's disease: an update

The molecular mechanism responsible for degenerative process in the nigrostriatal dopaminergic system in Parkinson's disease (PD) remains unknown. One major advance in this field has been the discovery of several genes associated to familial PD, including alpha synuclein, parkin, LRRK2, etc., thereby providing important insight toward basic research approaches. There is an consensus in neurodegenerative research that mitochon dria dysfunction, protein degradation dysfunction, aggregation of alpha synuclein to neurotoxic oligomers, oxidative and endoplasmic reticulum stress, and neuroinflammation are involved in degeneration of the neuromelanin-containing dopaminergic neurons that are lost in the disease. An update of the mechanisms relating to neurotoxins that are used to produce preclinical models of Parkinson´s disease is presented. 6-Hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and rotenone have been the most wisely used neurotoxins to delve into mechanisms involved in the loss of dopaminergic neurons containing neuromelanin. Neurotoxins generated from dopamine oxidation during neuromelanin formation are likewise reviewed, as this pathway replicates neurotoxin-induced cellular oxidative stress, inactivation of key proteins related to mitochondria and protein degradation dysfunction, and formation of neurotoxic aggregates of alpha synuclein. This survey of neurotoxin modeling-highlighting newer technologies and implicating a variety of processes and pathways related to mechanisms attending PD-is focused on research studies from 2012 to 2014.

Protective effects of curcumin against rotenone and salsolinol-induced toxicity: implications for Parkinson's disease

Parkinson's disease (PD) is a debilitating neurodegenerative disorder that results from the loss of or damage to dopaminergic cells in the substantia nigra. Exposure to either the pesticide rotenone or the endogenous neurotoxin salsolinol has been shown to mimic this dopaminergic cell loss. In this study, we first sought to determine whether combination of rotenone and salsolinol would result in an additive or synergistic toxicity. For this purpose we utilized SH-SY5Y cells, a human neuroblastoma cell line that is commonly used to model dopaminergic neurodegeneration. We then tested whether curcumin, a natural plant compound with known health benefits including potential neuroprotective properties, could also protect against rotenone and/or salsolinol-induced toxicity. Moreover, since apoptotic mechanism has been implicated in toxicity of these compounds the anti-apoptotic effect of curcumin was also evaluated. Our results indicate a synergistic toxicity of low concentrations of rotenone (1 and 5 µM) and salsolinol (25 and 50 µM) that was associated with apoptosis as determined by cell flow cytometry. There was also an increase in caspase-3 levels. Pretreatment with curcumin (1-µM) dose-dependently attenuated rotenone and/or salsolinol-induced toxicity and the associated apoptosis. These results suggest that exposure to a combination of rotenone and salsolinol may contribute to the pathology of PD, and that curcumin has a therapeutic potential in this disease.

Determination of chrysotoxine in rat plasma by liquid chromatography-tandem mass spectrometry and its application to a rat pharmacokinetic study

Chrysotoxine (CTX), a naturally occurring bibenzyl compound isolated from Dendrobium species, has been reported to have neuroprotective effects. To evaluate its pharmacokinetics in rats, a rapid, sensitive and specific high performance liquid chromatography-tandem mass spectrometric (HPLC-MS/MS) method has been developed and validated for the quantification of CTX in rat plasma. Samples were pretreated using a simple liquid-liquid extraction with ethyl acetate and the chromatographic separation was performed on a C18 column with acetonitrile-water (90:10, v/v) as the mobile phase. CTX and the internal standard (wogonin) were detected using a tandem mass spectrometer in positive multiple reaction monitoring mode. Method validation revealed excellent linearity over the range 0.5-1000 ng/mL together with satisfactory intra- and inter-day precision, accuracy and recovery. Stability testing showed that CTX spiked into rat plasma was stable for 8 h at room temperature, for up to two weeks at -20 °C, and during three freeze-thaw cycles. Extracted samples were also observed to be stable over 24 h in an auto-sampler. The method was successfully used to investigate the pharmacokinetic profile of CTX after oral (100 mg/kg) and intravenous (25 mg/kg) administration in rats. CTX showed rapid excretion and low bioavailability in rats.

Glia maturation factor deficiency suppresses 1-methyl-4-phenylpyridinium-induced oxidative stress in astrocytes

Inflammation is closely intertwined with pathogenesis of Parkinson's disease (PD). Increasing evidence suggests that inhibition of glia-mediated inflammation might represent a promising therapeutic target for PD. Glia maturation factor (GMF), an inflammatory protein, predominantly localized in astrocytes is previously isolated, sequenced and cloned in our laboratory. In the present investigation, we demonstrate that GMF-deficiency in astrocytes upregulates the antioxidant status and limit the extent of lipid peroxidation and production of reactive oxygen species (ROS) along with diminished nuclear factor-κB-mediated inflammatory responses in 1-methyl-4-phenylpyridinium (MPP(+))-induced toxicity. Primary astrocytes obtained from wild-type (Wt) and GMF-deficient (GMF-KO) mice were treated with 5, 10, and 20 μM MPP(+) for 24, 48, and 72 h in vitro. Our results show decreased release of ROS and increased level of glutathione in astrocytes obtained from GMF-KO mice when compared to astrocytes derived from Wt mice following MPP(+) treatment. Additionally, we found decreased activity of NF-κB, and reduced levels of proinflammatory tumor necrosis factor- α, interleukin-1β (IL-1β), IL-17, IL-33, and chemokine (C-C motif) ligand 2 (CCL2) in GMF-KO astrocytes when compared to Wt astrocytes. Our overall results suggest that GMF-KO astrocytes are significantly resistant to MPP(+) toxicity when compared to Wt astrocytes.

Impairment of Atg5-dependent autophagic flux promotes paraquat- and MPP⁺-induced apoptosis but not rotenone or 6-hydroxydopamine toxicity

Controversial reports on the role of autophagy as a survival or cell death mechanism in dopaminergic cell death induced by parkinsonian toxins exist. We investigated the alterations in autophagic flux and the role of autophagy protein 5 (Atg5)-dependent autophagy in dopaminergic cell death induced by parkinsonian toxins. Dopaminergic cell death induced by the mitochondrial complex I inhibitors 1-methyl-4-phenylpyridinium (MPP⁺) and rotenone, the pesticide paraquat, and the dopamine analog 6-hydroxydopamine (6-OHDA) was paralleled by increased autophagosome accumulation. However, when compared with basal autophagy levels using chloroquine, autophagosome accumulation was a result of impaired autophagic flux. Only 6-OHDA induced an increase in autophagosome formation. Overexpression of a dominant negative form of Atg5 increased paraquat- and MPP⁺-induced cell death. Stimulation of mammalian target of rapamycin (mTOR)-dependent signaling protected against cell death induced by paraquat, whereas MPP⁺-induced toxicity was enhanced by wortmannin, a phosphoinositide 3-kinase class III inhibitor, rapamycin, and trehalose, an mTOR-independent autophagy activator. Modulation of autophagy by either pharmacological or genetic approaches had no effect on rotenone or 6-OHDA toxicity. Cell death induced by parkinsonian neurotoxins was inhibited by the pan caspase inhibitor (Z-VAD), but only caspase-3 inhibition was able to decrease MPP⁺-induced cell death. Finally, inhibition of the lysosomal hydrolases, cathepsins, increased the toxicity by paraquat and MPP⁺, supporting a protective role of Atg5-dependent autophagy and lysosomes degradation pathways on dopaminegic cell death. These results demonstrate that in dopaminergic cells, Atg5-dependent autophagy acts as a protective mechanism during apoptotic cell death induced by paraquat and MPP⁺ but not during rotenone or 6-OHDA toxicity.

Secalonic acid A protects dopaminergic neurons from 1-methyl-4-phenylpyridinium (MPP⁺)-induced cell death via the mitochondrial apoptotic pathway

Secalonic acid A (SAA) is a natural compound found in marine fungi. We have reported that SAA can attenuate the cytotoxicity of colchicine in rat cortical neurons. Whether SAA can also inhibit the neurotoxicity of 1-methyl-4-phenylpyridinium (MPP(+)) in dopaminergic neurons has not been investigated. Here, we show that pretreatment with 1 μM SAA significantly rescued tyrosine hydroxylase (TH)-positive neurons from MPP(+)-induced neurotoxicity in primary dopaminergic neuron culture. Moreover, SAA at doses of 0.15 mg/kg and 0.75 mg/kg increased the number of dopaminergic neurons and upregulated striatal dopamine in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease mice experiments. We also show that SAA significantly attenuated cytotoxicity induced by 2.5 mM MPP(+) in SH-SY5Y cells. These results indicate that the activation of JNK, p38 mitogen activated protein kinase (MAPK) and caspase-3 during apoptosis triggered by MPP(+) could be suppressed by SAA; on the other hand, an MPP(+)-induced increase in the expression of Bax in SH-SY5Y cells was blocked by SAA. These results indicate that inhibition of the phosphorylation of JNK and p38 MAPK, down-regulation of Bax expression, and suppression of caspase-3 activation are involved in the protective effects of SAA against MPP(+) toxicity in SH-SY5Y cells. SAA may rescue dopaminergic neurons from MPP(+)-induced cell death through the mitochondrial apoptotic pathway.