The anti-cancer agent SU4312 unexpectedly protects against MPP(+) -induced neurotoxicity via selective and direct inhibition of neuronal NOS

Temperature- and chemical-induced neurotoxicity in zebrafish

Throughout their lives, humans encounter a plethora of substances capable of inducing neurotoxic effects, including drugs, heavy metals and pesticides. Neurotoxicity manifests when exposure to these chemicals disrupts the normal functioning of the nervous system, and some neurotoxic agents have been linked to neurodegenerative pathologies such as Parkinson's and Alzheimer's disease. The growing concern surrounding the neurotoxic impacts of both naturally occurring and man-made toxic substances necessitates the identification of animal models for rapid testing across a wide spectrum of substances and concentrations, and the utilization of tools capable of detecting nervous system alterations spanning from the molecular level up to the behavioural one. Zebrafish (Danio rerio) is gaining prominence in the field of neuroscience due to its versatility. The possibility of analysing all developmental stages (embryo, larva and adult), applying the most common "omics" approaches (transcriptomics, proteomics, lipidomics, etc.) and conducting a wide range of behavioural tests makes zebrafish an excellent model for neurotoxicity studies. This review delves into the main experimental approaches adopted and the main markers analysed in neurotoxicity studies in zebrafish, showing that neurotoxic phenomena can be triggered not only by exposure to chemical substances but also by fluctuations in temperature. The findings presented here serve as a valuable resource for the study of neurotoxicity in zebrafish and define new scenarios in ecotoxicology suggesting that alterations in temperature can synergistically compound the neurotoxic effects of chemical substances, intensifying their detrimental impact on fish populations.

The alleviative effect of Calendula officinalis L. extract against Parkinson's disease-like pathology in zebrafish via the involvement of autophagy activation

Introduction

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder. However, effective preventative or therapeutic agents for PD remain largely limited. Marigold Calendula officinalis L. (CoL) has been reported to possess a wide range of biological activities, but its neuroprotective activity including anti-neurodegenerative diseases is unclear. Here, we aim to investigate whether the extract of CoL (ECoL) has therapeutic activity on PD.

Methods

We identified the chemical composition of flavonoid, an important active ingredient in ECoL, by a targeted HPLC-Q-TOF-MS analysis. Subsequently, we evaluated the anti-PD effect of ECoL by using zebrafish PD model induced by 1-methyl-4-phenyl-1-1,2,3,6-tetrahydropyridine (MPTP). After ECoL+MPTP co-treatments, the changes of dopaminergic neurons, neural vasculature, nervous system, and locomotor activity were examined, respectively. The expressions of genes related to neurodevelopment and autophagy were detected by RT-qPCR. Further, the interaction between autophagy regulators and ECoL flavonoids was predicted using molecular docking method.

Results

As a result, 5 kinds of flavonoid were identified in ECoL, consisting of 121 flavones and flavonols, 32 flavanones, 22 isoflavonoids, 11 chalcones and dihydrochalcones, and 17 anthocyanins. ECoL significantly ameliorated the loss of dopaminergic neurons and neural vasculature, restored the injury of nervous system, and remarkably reversed the abnormal expressions of neurodevelopment-related genes. Besides, ECoL notably inhibited the locomotor impairment in MPTP-induced PD-like zebrafish. The underlying anti-PD effect of ECoL may be implicated in activating autophagy, as ECoL significantly upregulated the expressions of genes related to autophagy, which contributes to the degradation of α-synuclein aggregation and dysfunctional mitochondria. Molecular docking simulation showed the stable interaction between autophagy regulators (Pink, Ulk2, Atg7, and Lc3b) and 10 main compounds of flavonoid in ECoL, further affirming the involvement of autophagy activation by ECoL in anti-PD action.

Conclusion

Our results suggested that ECoL has the anti-PD effect, and ECoL might be a promising therapeutic candidate for PD treatment.

Effects of Apamin on MPP+-Induced Calcium Overload and Neurotoxicity by Targeting CaMKII/ERK/p65/STAT3 Signaling Pathways in Dopaminergic Neuronal Cells

Parkinson's disease (PD), a neurodegenerative disorder, is characterized by the loss of dopaminergic (DA) neurons. The pathogenesis of PD is associated with several factors including oxidative stress, inflammation, and mitochondrial dysfunction. Ca²⁺ signaling plays a vital role in neuronal signaling and altered Ca²⁺ homeostasis has been implicated in many neuronal diseases including PD. Recently, we reported that apamin (APM), a selective antagonist of the small-conductivity Ca²⁺-activated K⁺ (SK) channel, suppresses neuroinflammatory response. However, the mechanism(s) underlying the vulnerability of DA neurons were not fully understood. In this study, we investigated whether APM affected 1-methyl-4-phenyl pyridinium (MPP⁺)-mediated neurotoxicity in SH-SY5Y cells and rat embryo primary mesencephalic neurons. We found that APM decreased Ca²⁺ overload arising from MPP⁺-induced neurotoxicity response through downregulating the level of CaMKII, phosphorylation of ERK, and translocation of nuclear factor NFκB/signal transducer and activator of transcription (STAT)3. Furthermore, we showed that the correlation of MPP⁺-mediated Ca²⁺ overload and ERK/NFκB/STAT3 in the neurotoxicity responses, and dopaminergic neuronal cells loss, was verified through inhibitors. Our findings showed that APM might prevent loss of DA neurons via inhibition of Ca²⁺-overload-mediated signaling pathway and provide insights regarding the potential use of APM in treating neurodegenerative diseases.

N-isopropylbenzylamine, a methamphetamine mimics, produces toxicity via increasing nitric oxide in vitro

N-isopropylbenzylamine, an isomer of methamphetamine, has been used to adulterate methamphetamine, and distributed as fake "Ice" methamphetamine by illicit manufacturers, leading to a world problem of N-isopropylbenzylamine exposure. Though it is unclear whether N-isopropylbenzylamine has addictive potential like methamphetamine, N-isopropylbenzylamine users reported side effects such as headaches and confusion. However, the pharmacological targets and cytotoxicity of this chemical remained unknown. In this study, in vitro toxicity of N-isopropylbenzylamine and its toxicity-related targets were investigated in SN4741, SH-SY5Y or PC12 cell lines that model neurons. The cell viability was analyzed by using MTT assay after incubation with N-isopropylbenzylamine for 24 h in cells. N-isopropylbenzylamine caused cell death with IC₅₀ values at around 1-3 mM in these cell lines. N-isopropylbenzylamine time- and concentration-dependently facilitated the expression of neuronal nitric oxide synthase (nNOS), and increased intracellular nitric oxide (NO) in SN4741 cells. Furthermore, 7-nitroindazole, a specific inhibitor of nNOS, significantly prevented N-isopropylbenzylamine-induced toxicity in vitro. These results suggested that N-isopropylbenzylamine-induced toxicity is at least partially related to the increased intracellular NO levels and the activated nNOS. Considering the circumstances that N-isopropylbenzylamine was used to adulterate and mimic methamphetamine, and the side effects associated with N-isopropylbenzylamine in abusers, our findings sounded an alarm for abuser and warn the dangerousness of N-isopropylbenzylamine for public health.

SU4312 Represses Glioma Progression by Inhibiting YAP and Inducing Sensitization to the Effect of Temozolomide

SU4312, initially designed as a multi-target tyrosine kinase inhibitor, is consequently reported to inhibit tumor angiogenesis by blocking VEGFR. However, although SU4312 can penetrate the brain–blood barrier, its potential to inhibit glioma growth is unknown. In this study, we report that SU4312 inhibited glioma cell proliferation and down-regulated yes-associated protein (YAP), the key effector of the hippo pathway. The exogenous over-expression of YAP partially restored the inhibitory effect of SU4312 on glioma progression. Interestingly, SU4312 sensitized the antitumor effect of temozolomide, both in vitro and in vivo. Moreover, SU4312 decreased the M2tumor-associated macrophages and enhanced anti-tumor immunity by down-regulating the YAP-CCL2 axis. In conclusion, our results suggest that SU4312 represses glioma progression by down-regulating YAP transcription and consequently CCL2 secretion. SU4312 may be synergistic with temozolomide for glioma treatment.

Co-treatment with natural HMGB1 inhibitor Glycyrrhizin exerts neuroprotection and reverses Parkinson's disease like pathology in Zebrafish

ETHNOPHARMACOLOGICAL RELEVANCE

Parkinson's disease (PD) is the second most devastating age-related neurodegenerative diseases after Alzheimer diseases (AD) and is characterized by the loss of dopaminergic (DA) neurons in the substantia nigra (SN) and aggregation of α-synuclein (α-syn). The precise etiology of PD is not yet fully understood and lacks the disease-modifying therapeutic strategies that could reverse the ongoing neurodegeneration. In the quest of exploring novel disease modifying therapeutic strategies, natural compounds from plant sources have gained much attention in recent days. Glycyrrhizin (GL) is the main active ingredient of the roots and rhizomes of licorice (Glycyrrhiza glabra L), which are generally used in the treatment of inflammatory diseases or as a tonifying herbal medicine. In Persia, GL is a conventional neuroprotective agent that are used to treat neurological disorders. The traditional use of GL in Japan is to treat chronic hepatitis B. In addition, GL is a natural inhibitor of high mobility group box 1 (HMGB1) which has exerted neuroprotective effect against several HMGB1 mediated pathological conditions.

AIM OF THE STUDY

The study is aimed to evaluate therapeutic effect of GL against PD in zebrafish.

MATERIAL AND METHODS

PD in zebrafish larvae is induced by administration of neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Apoptosis was assessed with TUNEL assay. Gene expression was performed to assess the modulation in genes related to neuroinflammatory and autophagy.

RESULTS

We observed that GL co-treatment increased the length of DA neurons, decreased the number of apoptotic cells in zebrafish brain, and inhibited the loss of vasculature and disorganized vasculature induced by MPTP. GL co-treatment relieved the MPTP-induced locomotor impairment in zebrafish. GL co-treatment suppressed MPTP-induced upregulated mRNA expression of inflammatory markers such as hmgb1a, tlr4b, nfκb, il1β, and il6. GL co-treatment suppressed the autophagy related genes α-syn and atg5 whereas increased the mRNA expression level of parkin and pink1. In addition, molecular docking study reveals that GL has binding interaction with HMGB1, TLR4, and RAGE.

CONCLUSION

Hence, the effect of GL co-treatment on MPTP-induced PD-like condition in zebrafish is to alleviate apoptosis and autophagy, as well as suppress inflammatory responses.

Neuroprotective effect of YIAEDAER peptide against Parkinson's disease like pathology in zebrafish

Parkinson's disease (PD) is characterized by the loss of dopaminergic (DA) neurons in the substantia nigra (SN) and aggregation of α-synuclein (α-syn). Current PD therapies merely provide symptomatic relief, lacking the disease-modifying therapeutic strategies against that could reverse the ongoing neurodegeneration. In the quest of exploring novel disease modifying therapeutic strategies, compounds from natural sources have gained much attention in recent days. YIAEDAER (Tyr-Ile-Ala-Glu-Asp-Ala-Glu-Arg) peptide is a multi-functional peptide isolated and purified from the visceral mass extract of Neptunea arthritica cumingii (NAC) with plethora of pharmacological activities, however its neuroprotective effect against MPTP induced PD model is not yet reported. We found YIAEDAER peptide co-treatment could suppressed the MPTP-induced locomotor impairment in zebrafish, ameliorates the MPTP induced degeneration of DA neurons, inhibited the loss of vasculature and loss of cerebral vessels, suppressed α-syn levels. Moreover, YIAEDAER peptide modulates several genes related to autophagy (α-syn, pink1, parkin, atg5, atg7, beclin1, ulk1b, ulk2, and ambra1a), and oxidative stress (sod1, sod2, gss, gpx4a, gsto2, and cat). Hence, our finding suggests that YIAEDAER peptide might be a potential therapeutic candidate against MPTP-induced PD like condition.

Treatment of Parkinson's disease in Zebrafish model with a berberine derivative capable of crossing blood brain barrier, targeting mitochondria, and convenient for bioimaging experiments

Berberine is a famous alkaloid extracted from Berberis plants and has been widely used as medications and functional food additives. Recent studies reveal that berberine exhibits neuroprotective activity in animal models of Parkinson's disease (PD), the second most prevalent neurodegenerative disorders all over the world. However, the actual site of anti-PD action of berberine remains largely unknown. To this end, we employed a fluorescently labeled berberine derivative BBRP to investigate the subcellular localization and blood brain barrier (BBB) permeability in a cellular model of PD and zebrafish PD model. Biological investigations revealed that BBRP retained the neuroprotective activity of berberine against PD-like symptoms in PC12 cells and zebrafish, such as protecting 6-OHDA induced cell death, relieving MPTP induced PD-like behavior and increasing dopaminergic neuron loss in zebrafish. We also found that BBRP could readily penetrate BBB and function in the brain of zebrafish suffering from PD. Subcellular localization study indicated that BBRP could rapidly and specifically accumulate in mitochondria of PC12 cells when it exerted anti-PD effect. In addition, BBRP could suppress accumulation of Pink1 protein and inhibit the overexpression of LC3 protein in 6-OHDA damaged cells. All these results suggested that the potential site of action of berberine is mitochondria in the brain under the PD condition. Therefore, the findings described herein would be useful for further development of berberine as an anti-PD drug.

Neuroprotection against 1-Methyl-4-phenylpyridinium-induced cytotoxicity by naturally occurring polydatin through activation of transcription factor MEF2D

Polydatin is the major active ingredient of Polygonum cuspidatum Sieb. Et Zucc. A recent study indicated that polydatin could protect against substantia nigra dopaminergic degeneration in rodent models associated with Parkinson's disease. However, mechanisms that underlie the neuroprotection of polydatin have not been fully elucidated. In the current study, the neuroprotective effects and detailed mechanisms of action of polydatin were investigated in Parkinson's disease-related cellular models. Polydatin dose- and time-dependently prevented neurotoxicity caused by 1-methyl-4-phenylpyridinium ion (MPP+) in primary cerebellar granule neurons. Moreover, we found that polydatin enhanced the activity of the transcription factor myocyte enhancer factor 2D (MEF2D) at both basal and pathological conditions using luciferase reporter gene assay. Additionally, western blot analysis revealed that polydatin could downregulate glycogen synthase kinase 3β (GSK3β), which is a negative regulator of MEF2D. Molecular docking simulations finally suggested an interaction between polydatin and a hydrophobic pocket within GSK3β. All these results suggest that polydatin prevents MPP+-induced neurotoxicity via enhancing MEF2D through the inhibition of GSK3β and that treatment with polydatin is worthy of further anti-Parkinson's disease study in future.

Evans Blue Might Produce Pathologically Activated Neuroprotective Effects via the Inhibition of the P2X4R/p38 Signaling Pathway

The main pathological features of ischemic stroke include neuronal damage and blood-brain barrier (BBB) dysfunction. Previous studies have shown that Evans Blue, a dye used to probe BBB integrity, could enter the brain only during the pathological status of ischemic stroke, indicating the potential pathologically activated therapeutic use of this chemical to treat ischemic stroke. In this study, we have reported that Evans Blue could produce in vitro neuroprotective effects against iodoacetic acid (IAA)-induced hypoxia neuronal death in HT22 cells. We further found that P2X purinoreceptor 4 (P2X4R), a subtype of ATP-gated cation channel, was expressed in HT22 cells. Evans Blue could prevent IAA-induced increase of P2X4R mRNA and protein expression. Interestingly, shRNA of P2X4R could protect against IAA-induced activation of p38, and SB203580, a specific inhibitor of p38, could reverse IAA-induced neurotoxicity, indicating that p38 is a downstream signaling molecule of P2X4R. Molecular docking analysis further demonstrated the possible interaction between Evans Blue and the ATP binding site of P2X4R. Most importantly, pre-treatment of Evans Blue could largely reduce neurological and behavioral abnormity, and decrease brain infarct volume in middle cerebral artery occlusion/reperfusion (MCAO) rats. All these results strongly suggested that Evans Blue could exert neuroprotective effects via inhibiting the P2X4R/p38 pathway, possibly by acting on the ATP binding site of P2X4R, indicating that Evans Blue might be further developed as a pathologically activated therapeutic drug against ischemic stroke.

Suppressing Cdk5 Activity by Luteolin Inhibits MPP+-Induced Apoptotic of Neuroblastoma through Erk/Drp1 and Fak/Akt/GSK3β Pathways

Parkinson’s disease (PD) is characterized by the progressive degeneration of dopaminergic neurons. The cause of PD is still unclear. Oxidative stress and mitochondrial dysfunction have been linked to the development of PD. Luteolin, a non-toxic flavonoid, has become interested in an alternative medicine, according to its effects on anti-oxidative stress and anti-apoptosis, although the underlying mechanism of luteolin on PD has not been fully elucidated. This study aims to investigate whether luteolin prevents neurotoxicity induction by 1-methyl-4-phenylpyridinium iodide (MPP⁺), a neurotoxin in neuroblastoma SH-SY5Y cells. The results reveal that luteolin significantly improved cell viability and reduced apoptosis in MPP⁺-treated cells. Increasing lipid peroxidation and superoxide anion (O₂⁻), including mitochondrial membrane potential (Δψm) disruption, is ameliorated by luteolin treatment. In addition, luteolin attenuated MPP⁺-induced neurite damage via GAP43 and synapsin-1. Furthermore, Cdk5 is found to be overactivated and correlated with elevation of cleaved caspase-3 activity in MPP⁺-exposed cells, while phosphorylation of Erk1/2, Drp1, Fak, Akt and GSK3β are inhibited. In contrast, luteolin attenuated Cdk5 overactivation and supported phosphorylated level of Erk1/2, Drp1, Fak, Akt and GSK3β with reducing in cleaved caspase-3 activity. Results indicate that luteolin exerts neuroprotective effects via Cdk5-mediated Erk1/2/Drp1 and Fak/Akt/GSK3β pathways, possibly representing a potential preventive agent for neuronal disorder.

Anti-Parkinson's disease activity of phenolic acids from Eucommia ulmoides Oliver leaf extracts and their autophagy activation mechanism

Although Parkinson's disease (PD) is the second most common neurodegenerative disorder, the preventative or therapeutic agents for the treatment of PD are limited. Eucommia ulmoides Oliver (EuO) is widely used as a traditional herb to treat various diseases. EuO bark extracts have been reported to possess anti-PD activity. Here, we investigated whether extracts of EuO leaves (EEuOL) also have therapeutic effects on PD since similar components and clinical applications have been found between barks and leaves of this tree. We identified the chemical composition of EEuOL by HPLC-Q-TOF-MS and tested the anti-PD effect of EEuOL using the zebrafish PD model. As a result, 28 compounds including 3 phenolic acids, 7 flavonoids, and 9 iridoids were identified. EEuOL significantly reversed the loss of dopaminergic neurons and neural vasculature and reduced the number of apoptotic cells in zebrafish brain in a concentration-dependent manner. Moreover, EEuOL relieved locomotor impairments in MPTP-modeled PD zebrafish. We also investigated the underlying mechanism and found that EEuOL may activate autophagy, contributing to α-synuclein degradation, therefore alleviating PD-like symptoms. Molecular docking simulation implied the interaction between autophagy regulators (Pink1, Beclin1, Ulk2, and Atg5) and phenolic acids of EEuOL, affirming the involvement of autophagy in EEuOL-exerted anti-PD action. The overall results indicated the anti-PD effect of EEuOL, opening the possibility to use the extract in PD treatment.

Ghrelin mitigates MPP+-induced cytotoxicity: Involvement of ERK1/2-mediated Nrf2/HO-1 and endoplasmic reticulum stress PERK signaling pathway

Parkinson's disease (PD) is a common progressive and multifactorial neurodegenerative disease. Current pharmacological therapies for PD are inadequate and often accompanied by serious side effects. In search of neuroprotective agents being considered to be beneficial to PD therapy. Ghrelin confers neuroprotective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned PD model, but the underlying mechanism remains not fully elucidated. Here, we utilized human neuroblastoma SH-SY5Y cells exposed to MPP⁺ as a PD model to investigate the underlying mechanism of Ghrelin. In our present work, cell viability, cell apoptosis, oxidative stress-related indicators, and the level of Nrf2, HO-1, PERK, eIF2α, ATF4, CHOP, and ERK1/2 were examined. The results showed that Ghrelin attenuated MPP⁺-induced change of cell viability, apoptosis, coupled with decreased Cytochrome c, caspase-9, and caspase-3 expressions. Consistently, Ghrelin suppressed MPP⁺-induced oxidative stress. Moreover, Ghrelin markedly enhanced Nrf2 expression and nuclear accumulation as well as HO-1 induction. Further investigations showed that Ghrelin significantly inhibited the endoplasmic reticulum stress PERK-eIF2α-ATF4-CHOP pathway. Interestingly, we then found that Ghrelin promoted phosphorylation of ERK1/2, and pharmacological inhibition of ERK signaling abolished the cytoprotective effect of Ghrelin. Furthermore, we also found promoting the activation of the Nrf2/ HO-1 pathway and suppressing of the PERK pathway were mediated by ERK1/2. These findings provided novel insights into the underlying mechanisms of Ghrelin exerted protective effect, suggesting its potential as a novel therapeutic strategy against PD.

4-Oxatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione Derivatives as NMDA Receptor- and VGCC Blockers with Neuroprotective Potential

The impact of excitotoxicity mediated by N-methyl-D-aspartate (NMDA) receptor overactivation and voltage gated calcium channel (VGCC) depolarization is prominent among the postulated processes involved in the development of neurodegenerative disorders. NGP1-01, a polycyclic amine, has been shown to be neuroprotective through modulation of the NMDA receptor and VGCC, and attenuation of MPP+-induced neurotoxicity. Recently, we reported on the calcium modulating effects of tricycloundecene derivatives, structurally similar to NGP1-01, on the NMDA receptor and VGCC of synaptoneurosomes. In the present study, we investigated novel 4-oxatricyclo[5.2.1.02,6]dec-8-ene-3,5-dione derivatives for their cytotoxicity, neuroprotective effects via attenuation of MPP+-induced neurotoxicity and calcium influx inhibition abilities through the NMDA receptor and VGCC using neuroblastoma SH-SY5Y cells. All compounds, in general, showed low or no toxicity against neuroblastoma cells at 10-50 µM concentrations. At 10 µM, all compounds significantly attenuated MPP+-induced neurotoxicity as evident by the enhancement in cell viability between 23.05 ± 3.45% to 53.56 ± 9.29%. In comparison to known active compounds, the derivatives demonstrated mono or dual calcium modulating effect on the NMDA receptor and/or VGCC. Molecular docking studies using the NMDA receptor protein structure indicated that the compounds are able to bind in a comparable manner to the crystallographic pose of MK-801 inside the NMDA ion channel. The biological characteristics, together with results from in silico studies, suggest that these compounds could act as neuroprotective agents for the purpose of halting or slowing down the degenerative processes in neuronal cells.

Neuroprotective and neurogenic effects of novel tetramethylpyrazine derivative T-006 in Parkinson's disease models through activating the MEF2-PGC1α and BDNF/CREB pathways

T-006, a new derivative of tetramethylpyrazine, has been recently found to protect against 6-hydroxydopamine (6-OHDA)-induced neuronal damage and clear α-synuclein (α-syn) by enhancing proteasome activity in an α-syn transgenic Parkinson’s disease (PD) model. The effect of T-006 on the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced PD model, however, has not been tested and T-006’s neuroprotective mechanisms have not been fully elucidated. In this study, we further investigated the neuroprotective and neurogenic effects of T-006 and explored its underlying mechanism of action in both cellular and animal PD models. T-006 was able to improve locomotor behavior, increase survival of nigra dopaminergic neurons and boost striatal dopamine levels in both MPTP- and 6-OHDA-induced animals. T-006 treatment restored the altered expressions of myocyte enhancer factor 2D (MEF2D), peroxisome proliferator-activated receptor γ (PPARγ) co-activator 1α (PGC1α) and NF-E2-related factor 1/2 (Nrf1/2) via modulation of Akt/GSK3β signaling. T-006 stimulated MEF2, PGC1α and Nrf2 transcriptional activities, inducing Nrf2 nuclear localization. Interestingly, T-006 promoted endogenous adult neurogenesis toward a dopaminergic phenotype by activating brain-derived neurotrophic factor (BDNF) and cAMP responsive element-binding protein (CREB) in 6-OHDA rats. Our work demonstrated that T-006 is a potent neuroprotective and neuroregenerative agent that may have therapeutic potential in the treatment of PD.

Open and rearranged norbornane derived polycyclic cage molecules as potential neuroprotective agents through attenuation of MPP+- and calcium overload-induced excitotoxicity in neuroblastoma SH-SY5Y cells

The neuroprotective effects of closed polycyclic cage molecules such as NGP1-01, memantine and amantadine have been extensively explored. These effects are mostly linked to the antagonism of the N-methyl-d-aspartate (NMDA) receptor- and the blockage of voltage gated calcium channels (VGCC). The synthesis of structurally related open and rearranged cage derivatives has been studied in depth. However, very little is known on their neuroprotective effects. In this study, a series of open and rearranged polycyclic cage molecules containing a norbornane derived scaffold were synthesised and evaluated for cytotoxicity, neuroprotection and calcium blocking effects via the NMDA receptor and VGCC on neuroblastoma cells at a 10 μM concentration. All compounds showed negligible cytotoxicity and were able to significantly attenuate MPP⁺-induced neurotoxicity between 26.07 ± 12.50% to 48.42 ± 0.76%, with compound 14 showing the best neuroprotective effect. In comparison to known NMDA receptor antagonists, all compounds demonstrated moderate to excellent calcium blocking effects of 26.50 ± 2.28 to 72.95 ± 3.38%. Docking studies suggest that these compounds are able to show significant NMDA receptor channel blocking ability since they bind in a comparable manner to the crystallographic pose of MK-801 inside the NMDAR ion channel. Some compounds were also able to attenuate calcium influx through VGCC channels between 21.28 ± 3.69% to 50.34 ± 7.67%. Compound 4 and 15 showed the highest inhibition of calcium influx at the VGCC and NMDA receptor, respectively. The compounds exhibiting good cytotoxicity-, neuroprotective- and calcium blocking profiles could potentially act as neuroprotective agents to clinically benefit people suffering from neurodegenerative disorders.

Neuroprotection Against Parkinson's Disease Through the Activation of Akt/GSK3β Signaling Pathway by Tovophyllin A

Parkinson’s disease (PD) is one of the most prevalent and life-threatening neurodegenerative disease and mainly characterized by lack of sufficient dopaminergic neurons in the substantia nigra pars compacta (SNc). Although current treatments help to alleviate clinical symptoms, effective therapies preventing neuronal loss remain scarce. Tovophyllin A (TA), one of the xanthones extracted from Garcinia mangostana L. (GM), has recently been reported to play a beneficial role in the therapy of neurodegenerative diseases. In our research, we explored whether TA has protective effects on dopaminergic neurons in PD models. We found that TA significantly reduced apoptotic cell death in primary cortical neurons treated with 1-methyl-4-phenyl pyridinium (MPP⁺) or paraquat (PQ) in the in vitro PD model. In an in vivo acute PD model induced by 1-methyl4-phenyl-1,2,3,5-tetrahydropyridine (MPTP) treatment, TA also attenuated the resulting behavioral dysfunctions and dopaminergic neuron loss. In the collected brain tissues, TA increased the phosphorylation of Akt and GSK-3β, which may be related to TA-mediated dopaminergic neuronal protective effects. In summary, our results illustrated that TA is a powerful cytoprotective agent for dopaminergic neurons in the MPTP-induced PD model, suggesting TA as a possible therapeutic candidate for PD.

Transition metal complexes as imaging or therapeutic agents for neurodegenerative diseases

Neurodegenerative diseases are the result of neurodegeneration, which is the process of losing neuronal functions gradually due to the irreversible damage and death of neurons. Metal complexes have attracted intense interest over recent decades as probes or inhibitors of biomolecules.

Photorearrangement of Quinoline-Protected Dialkylanilines and the Photorelease of Aniline-Containing Biological Effectors

The direct release of dialkylanilines was achieved by controlling the outcome of a photorearrangement reaction promoted by the (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ) photoremovable protecting group. The substrate scope was investigated to obtain structure-activity relationships and to propose a reaction mechanism. Introducing a methyl substituent at the 2-methyl position of the CyHQ core enabled the bypass of the photorearrangement and significantly improved the aniline release efficiency. We successfully applied the strategy to the photoactivation of mifepristone (RU-486), an antiprogestin drug that is also used to induce the LexPR gene expression system in zebrafish and the gene-switch regulatory system based on the pGL-VP chimeric regulator in mammals.

Design, synthesis and evaluation of indole derivatives as multifunctional agents against Alzheimer's disease

A series of indole derivatives was designed and synthesised to improve on activity and circumvent pharmacokinetic limitations experienced with the structurally related compound, ladostigil. The compounds consisted of a propargylamine moiety (a known MAO inhibitor and neuroprotector) at the N1 position and a ChE inhibiting diethyl-carbamate/urea moiety at the 5 or 6 position of the indole ring. In order to prevent or slow down the in vivo hydrolysis and deactivation associated with the carbamate function of ladostigil, a urea moeity was incorporated into selected compounds to obtain more metabolically stable structures. The majority of the synthesised compounds showed improved MAO-A inhibitory activity compared to ladostigil. The compounds possessing the propargylamine moiety showed good MAO-B inhibitory activity with 6 and 8 portraying IC₅₀ values between 14-20 fold better than ladostigil. The ChE assay results indicated that the compounds have non-selective inhibitory activities on eeAChE and eqBuChE regardless of the type or position of substitution (IC₅₀: 2-5 μM). MAO-A and MAO-B docking results showed that the propargylamine moiety was positioned in close proximity to the FAD cofactor suggesting that the good inhibitory activity may be attributed to the propargylamine moiety and irreversible inhibition as confirmed in the reversibility studies. Docking results also indicated that the compounds have interactions with important amino acids in the AChE and BuChE catalytic sites. Compound 6 was the most potent multifunctional agent showing better inhibitory activity than ladostigil in vitro on all enzymes tested (hMAO-A IC₅₀ = 4.31 μM, hMAO-B IC₅₀ = 2.62 μM, eeAChE IC₅₀ = 3.70 μM, eqBuChE IC₅₀ = 2.82 μM). Chemical stability tests confirmed the diethyl-urea containing compound 6 to be more stable than its diethyl-carbamate containing counterpart compound 8. Compound 6 also exerted significant neuroprotection (52.62% at 1 μM) against MPP⁺ insult to SH-SY5Y neural cells and has good in silico predicted ADMET properties. The favourable neuronal enzyme inhibitory activity, likely improved pharmacokinetic properties in vivo and the potent neuroprotective ability of compound 6 make it a promising compound for further development.

Sulfuretin Attenuates MPP⁺-Induced Neurotoxicity through Akt/GSK3β and ERK Signaling Pathways

Parkinson's disease (PD) is the second most common neurodegenerative disease. It is caused by the death of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress and mitochondrial dysfunction contribute to the loss of dopaminergic neurons in PD. Sulfuretin is a potent antioxidant that is reported to be beneficial in the treatment of neurodegenerative diseases. In this study, we examined the protective effect of sulfuretin against 1-methyl-4-phenyl pyridinium (MPP⁺)-induced cell model of PD in SH-SY5Y cells and the underlying molecular mechanisms. Sulfuretin significantly decreased MPP⁺-induced apoptotic cell death, accompanied by a reduction in caspase 3 activity and polyADP-ribose polymerase (PARP) cleavage. Furthermore, it attenuated MPP⁺-induced production of intracellular reactive oxygen species (ROS) and disruption of mitochondrial membrane potential (MMP). Consistently, sulfuretin decreased p53 expression and the Bax/Bcl-2 ratio. Moreover, sulfuretin significantly increased the phosphorylation of Akt, GSK3β, and ERK. Pharmacological inhibitors of PI3K/Akt and ERK abolished the cytoprotective effects of sulfuretin against MPP⁺. An inhibitor of GSK3β mimicked sulfuretin-induced protection against MPP⁺. Taken together, these results suggest that sulfuretin significantly attenuates MPP⁺-induced neurotoxicity through Akt/GSK3β and ERK signaling pathways in SH-SY5Y cells. Our findings suggest that sulfuretin might be one of the potential candidates for the treatment of PD.

5-Hydroxycyclopenicillone Inhibits β-Amyloid Oligomerization and Produces Anti-β-Amyloid Neuroprotective Effects In Vitro

The oligomer of β-amyloid (Aβ) is considered the main neurotoxin in Alzheimer’s disease (AD). Therefore, the inhibition of the formation of Aβ oligomer could be a target for AD therapy. In this study, with the help of the dot blotting assay and transmission electronic microscopy, it was have discovered that 5-hydroxycyclopenicillone, a cyclopentenone recently isolated from a sponge-associated fungus, effectively reduced the formation of Aβ oligomer from Aβ peptide in vitro. Molecular dynamics simulations suggested hydrophobic interactions between 5-hydroxycyclopenicillone and Aβ peptide, which might prevent the conformational transition and oligomerization of Aβ peptide. Moreover, Aβ oligomer pre-incubated with 5-hydroxycyclopenicillone was less toxic when added to neuronal SH-SY5Y cells compared to the normal Aβ oligomer. Although 5-hydroxycyclopenicillone is not bioavailable in the brain in its current form, further modification or encapsulation of this chemical might improve the penetration of 5-hydroxycyclopenicillone into the brain. Based on the current findings and the anti-oxidative stress properties of 5-hydroxycyclopenicillone, it is suggested that 5-hydroxycyclopenicillone may have potential therapeutic efficacy in treating AD.

Versatility of 7-Substituted Coumarin Molecules as Antimycobacterial Agents, Neuronal Enzyme Inhibitors and Neuroprotective Agents

A medium-throughput screen using Mycobacterium tuberculosis H37Rv was employed to screen an in-house library of structurally diverse compounds for antimycobacterial activity. In this initial screen, eleven 7-substituted coumarin derivatives with confirmed monoamine oxidase-B and cholinesterase inhibitory activities, demonstrated growth inhibition of more than 50% at 50 µM. This prompted further exploration of all the 7-substituted coumarins in our library. Four compounds showed promising MIC₉₉ values of 8.31–29.70 µM and 44.15–57.17 µM on M. tuberculosis H37Rv in independent assays using GAST-Fe and 7H9+OADC media, respectively. These compounds were found to bind to albumin, which may explain the variations in MIC between the two assays. Preliminary data showed that they were able to maintain their activity in fluoroquinolone resistant mycobacteria. Structure-activity relationships indicated that structural modification on position 4 and/or 7 of the coumarin scaffold could direct the selectivity towards either the inhibition of neuronal enzymes or the antimycobacterial effect. Moderate cytotoxicities were observed for these compounds and slight selectivity towards mycobacteria was indicated. Further neuroprotective assays showed significant neuroprotection for selected compounds irrespective of their neuronal enzyme inhibitory properties. These coumarin molecules are thus interesting lead compounds that may provide insight into the design of new antimicrobacterial and neuroprotective agents.

5-Hydroxycyclopenicillone, a New β-Amyloid Fibrillization Inhibitor from a Sponge-Derived Fungus Trichoderma sp. HPQJ-34

A new cyclopentenone, 5-hydroxycyclopeni cillone (1), was isolated together with three known compounds, ar-turmerone (2), citreoisocoumarin (3), and 6-O-methyl-citreoisocoumarin (4), from a culture of the sponge-derived fungus Trichoderma sp. HPQJ-34. The structures of 1–4 were characterized using comprehensive spectroscopic analyses. The absolute configuration of 1 was determined by comparison of electronic circular dichroism (ECD) spectra with literature values used for the reported analogue, cyclopenicillone (5), which was not isolated in this research. Compound 1 was shown to scavenge 2,2-diphenyl-1-picrylhydrazyl free radicals, and decrease β-amyloid (Aβ) fibrillization in vitro. Moreover, 1 significantly reduced H₂O₂-induced neurotoxicity in SH-SY5Y cells. These findings suggested that compound 1, a newly discovered cyclopentenone, has moderate anti-oxidative, anti-Aβ fibrillization properties and neuroprotective effects, and might be a good free radical scavenger.

Substantial protection against MPTP-associated Parkinson's neurotoxicity in vitro and in vivo by anti-cancer agent SU4312 via activation of MEF2D and inhibition of MAO-B

We have previously demonstrated the unexpected neuroprotection of the anti-cancer agent SU4312 in cellular models associated with Parkinson's disease (PD). However, the precise mechanisms underlying its neuroprotection are still unknown, and the effects of SU4312 on rodent models of PD have not been characterized. In the current study, we found that the protection of SU4312 against 1-methyl-4-phenylpyridinium ion (MPP⁺)-induced neurotoxicity in PC12 cells was achieved through the activation of transcription factor myocyte enhancer factor 2D (MEF2D), as evidenced by the fact that SU4312 stimulated myocyte enhancer factor 2 (MEF2) transcriptional activity and prevented the inhibition of MEF2D protein expression caused by MPP⁺, and that short hairpin RNA (ShRNA)-mediated knockdown of MEF2D significantly abolished the neuroprotection of SU4312. Additionally, Western blotting analysis revealed that SU4312 potentiated pro-survival PI3-K/Akt pathway to down-regulate MEF2D inhibitor glycogen synthase kinase-3beta (GSK3β). Furthermore, using the in vivo PD model of C57BL/6 mice insulted with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), we found that intragastrical administration of SU4312 (0.2 and 1 mg/kg) greatly ameliorated Parkinsonian motor defects, and restored protein levels of MEF2D, phosphorylated-Ser473-Akt and phosphorylated-Ser9-GSK3β. Meanwhile, SU4312 effectively reversed the decrease in protein expression of tyrosine hydroxylase in substantia nigra pars compacta dopaminergic neurons, inhibited oxidative stress, maintained mitochondrial biogenesis and partially prevented the depletion of dopamine and its metabolites. Very encouragingly, SU4312 was able to selectively inhibit monoamine oxidase-B (MAO-B) activity both in vitro and in vivo, with an IC₅₀ value of 0.2 μM. These findings suggest that SU4312 provides therapeutic benefits in cellular and animal models of PD, possibly through multiple mechanisms including enhancement of MEF2D through the activation of PI3-K/Akt pathway, maintenance of mitochondrial biogenesis and inhibition of MAO-B activity. SU4312 thus may be an effective drug candidate for the prevention or even modification of the pathological processes of PD.

Fucoxanthin, a Marine Carotenoid, Attenuates β-Amyloid Oligomer-Induced Neurotoxicity Possibly via Regulating the PI3K/Akt and the ERK Pathways in SH-SY5Y Cells

Alzheimer's disease (AD), the most common neurodegenerative disorder, is characterized by neurofibrillary tangles, synaptic impairments, and loss of neurons. Oligomers of β-amyloid (Aβ) are widely accepted as the main neurotoxins to induce oxidative stress and neuronal loss in AD. In this study, we discovered that fucoxanthin, a marine carotenoid with antioxidative stress properties, concentration dependently prevented Aβ oligomer-induced increase of neuronal apoptosis and intracellular reactive oxygen species in SH-SY5Y cells. Aβ oligomers inhibited the prosurvival phosphoinositide 3-kinase (PI3K)/Akt cascade and activated the proapoptotic extracellular signal-regulated kinase (ERK) pathway. Moreover, inhibitors of glycogen synthase kinase 3β (GSK3β) and mitogen-activated protein kinase (MEK) synergistically prevented Aβ oligomer-induced neuronal death, suggesting that the PI3K/Akt and ERK pathways might be involved in Aβ oligomer-induced neurotoxicity. Pretreatment with fucoxanthin significantly prevented Aβ oligomer-induced alteration of the PI3K/Akt and ERK pathways. Furthermore, LY294002 and wortmannin, two PI3K inhibitors, abolished the neuroprotective effects of fucoxanthin against Aβ oligomer-induced neurotoxicity. These results suggested that fucoxanthin might prevent Aβ oligomer-induced neuronal loss and oxidative stress via the activation of the PI3K/Akt cascade as well as inhibition of the ERK pathway, indicating that further studies of fucoxanthin and related compounds might lead to a useful treatment of AD.

Fucoxanthin Inhibits β-Amyloid Assembly and Attenuates β-Amyloid Oligomer-Induced Cognitive Impairments

β-Amyloid (Aβ) can form aggregates through self-assembly and produce neurotoxicity in the early stage of Alzheimer's disease (AD). Therefore, the inhibition of Aβ assembly is considered as the primary target for AD therapy. In this study, we reported that fucoxanthin, a marine carotenoid, potently reduced the formation of Aβ fibrils and oligomers. Moreover, the fucoxanthin-triggered modification significantly reduced the neurotoxicity of Aβ oligomers in vitro. Molecular dynamics simulation analysis further revealed a hydrophobic interaction between fucoxanthin and Aβ peptide, which might prevent the conformational transition and self-assembly of Aβ. Most importantly, fucoxanthin could attenuate cognitive impairments in Aβ oligomer-injected mice. In addition, fucoxanthin significantly inhibited oxidative stress, enhanced the expression of brain-derived neurotrophic factor, and increased ChAT-positive regions in the hippocampus of mice. On the basis of these novel findings, we anticipated that fucoxanthin might ameliorate AD via inhibiting Aβ assembly and attenuating Aβ neurotoxicity.

Assessment of Neuronal Viability Using Fluorescein Diacetate-Propidium Iodide Double Staining in Cerebellar Granule Neuron Culture

Primary cultured Cerebellar Granule Neurons (CGNs) have been widely used as an in vitro model in neuroscience and neuropharmacology research. However, the co-existence of glial cells and neurons in CGN culture might lead to biases in the accurate assessment of neuronal viability. Fluorescein diacetate (FDA) and Propidium Iodide (PI) double staining has been used to measure cell viability by simultaneously evaluating the viable and dead cells. We used FDA-PI double staining to improve the sensitivities of the colorimetric assays and to evaluate neuronal viability in CGNs. Furthermore, we added blue fluorescent DNA stains (e.g., Hoechst) to improve the accuracy. This protocol describes how to improve the accuracy of assessment of neuronal viability by using these methods in CGN culture. Using this protocol, the number of glial cells can be excluded by using fluorescence microscopy. A similar strategy can be applied to distinguish the unwanted glial cells from neurons in various mixed cell cultures, such as primary cortical culture and hippocampal culture.

Fucoxanthin prevents H2O2-induced neuronal apoptosis via concurrently activating the PI3-K/Akt cascade and inhibiting the ERK pathway

Background: As a natural carotenoid abundant in chloroplasts of edible brown algae, fucoxanthin possesses various health benefits, including anti-oxidative activity in particular.

Objective: In the present study, we studied whether fucoxanthin protected against hydrogen peroxide (H₂O₂)-induced neuronal apoptosis.

Design: The neuroprotective effects of fucoxanthin on H₂O₂-induced toxicity were studied in both SH-SY5Y cells and primary cerebellar granule neurons.

Results: Fucoxanthin significantly protected against H₂O₂-induced neuronal apoptosis and intracellular reactive oxygen species. H₂O₂ treatment led to the reduced activity of phosphoinositide 3-kinase (PI3-K)/Akt cascade and the increased activity of extracellular signal-regulated kinase (ERK) pathway in SH-SY5Y cells. Moreover, fucoxanthin significantly restored the altered activities of PI3-K/Akt and ERK pathways induced by H₂O₂. Both specific inhibitors of glycogen synthase kinase 3β (GSK3β) and mitogen-activated protein kinase kinase (MEK) significantly protected against H₂O₂-induced neuronal death. Furthermore, the neuroprotective effects of fucoxanthin against H₂O₂-induced neuronal death were abolished by specific PI3-K inhibitors.

Conclusions: Our data strongly revealed that fucoxanthin protected against H₂O₂-induced neurotoxicity via concurrently activating the PI3-K/Akt cascade and inhibiting the ERK pathway, providing support for the use of fucoxanthin to treat neurodegenerative disorders induced by oxidative stress.

Small-Sized mPEG-PLGA Nanoparticles of Schisantherin A with Sustained Release for Enhanced Brain Uptake and Anti-Parkinsonian Activity

Schisantherin A (SA) is a promising anti-Parkinsonism natural product. However, its poor water solubility and rapid serum clearance impose significant barriers to delivery of SA to the brain. This work aimed to develop SA in a nanoparticle formulation that extended SA circulation in the bloodstream and consequently an increased brain uptake and thus to be potentially efficacious for the treatment of Parkinson's disease (PD). Spherical SA nanoparticles with a mean particle size of 70 nm were prepared by encapsulating SA into methoxy poly(ethylene glycol)-block-poly(d,l)-lactic-co-glycolic acid (mPEG-PLGA) nanoparticles (SA-NPs) with an encapsulation efficiency of ∼91% and drug loading of ∼28%. The in vitro release of the SA-NPs lasted for 48 h with a sustained-release pattern. Using the Madin-Darby canine kidney (MDCK) cell model, the results showed that first intact nanoparticles carrying hydrophobic dyes were internalized into cells, then the dyes were slowly released within the cells, and last both nanoparticles and free dyes were externalized to the basolateral side of the cell monolayer. Fluorescence resonance energy transfer (FRET) imaging in zebrafish suggested that nanoparticles were gradually dissociated in vivo with time, and nanoparticles maintained intact in the intestine and brain at 2 h post-treatment. When SA-NPs were orally administrated to rats, much higher C_max and AUC_0-t were observed in the plasma than those of the SA suspension. Furthermore, brain delivery of SA was much more effective with SA-NPs than with SA suspension. In addition, the SA-NPs exerted strong neuroprotective effects in zebrafish and cell culture models of PD. The protective effect was partially mediated by the activation of the protein kinase B (Akt)/glycogen synthase kinase-3β (Gsk3β) pathway. In summary, this study provides evidence that small-sized mPEG-PLGA nanoparticles may improve cross-barrier transportation, oral bioavailability, brain uptake, and bioactivity of this Biopharmaceutics Classification System (BCS) Class II compound, SA.

Sunitinib, a Clinically Used Anticancer Drug, Is a Potent AChE Inhibitor and Attenuates Cognitive Impairments in Mice

Sunitinib, a tyrosine kinase inhibitor, is clinically used for the treatment of cancer. In this study, we found for the first time that sunitinib inhibits acetylcholinesterase (AChE) at submicromolar concentrations in vitro. In addition, sunitinib dramatically decreased the hippocampal and cortical activity of AChE in a time-dependent manner in mice. Molecular docking analysis further demonstrates that sunitinib might interact with both the catalytic anion and peripheral anionic sites within AChE, which is in accordance with enzymatic activity results showing that sunitinib inhibits AChE in a mixed pattern. Most importantly, we evaluated the effects of sunitinib on scopolamine-induced cognitive impairments in mice by using novel object recognition and Morris water maze tests. Surprisingly, sunitinib could attenuate cognitive impairments to a similar extent as donepezil, a marketed AChE inhibitor used for the treatment of Alzheimer's disease. In summary, our results have shown that sunitinib could potently inhibit AChE and attenuate cognitive impairments in mice.

Indirubin-3-Oxime Prevents H2O2-Induced Neuronal Apoptosis via Concurrently Inhibiting GSK3β and the ERK Pathway

Oxidative stress-induced neuronal apoptosis plays an important role in many neurodegenerative disorders. In this study, we have shown that indirubin-3-oxime, a derivative of indirubin originally designed for leukemia therapy, could prevent hydrogen peroxide (H₂O₂)-induced apoptosis in both SH-SY5Y cells and primary cerebellar granule neurons. H₂O₂ exposure led to the increased activities of glycogen synthase kinase 3β (GSK3β) and extracellular signal-regulated kinase (ERK) in SH-SY5Y cells. Indirubin-3-oxime treatment significantly reversed the altered activity of both the PI3-K/Akt/GSK3β cascade and the ERK pathway induced by H₂O₂. In addition, both GSK3β and mitogen-activated protein kinase inhibitors significantly prevented H₂O₂-induced neuronal apoptosis. Moreover, specific inhibitors of the phosphoinositide 3-kinase (PI3-K) abolished the neuroprotective effects of indirubin-3-oxime against H₂O₂-induced neuronal apoptosis. These results strongly suggest that indirubin-3-oxime prevents H₂O₂-induced apoptosis via concurrent inhibiting GSK3β and the ERK pathway in SH-SY5Y cells, providing support for the use of indirubin-3-oxime to treat neurodegenerative disorders caused or exacerbated by oxidative stress.

Multifunction of Chrysin in Parkinson's Model: Anti-Neuronal Apoptosis, Neuroprotection via Activation of MEF2D, and Inhibition of Monoamine Oxidase-B

Chrysin, a flavonoid compound existing in several plants, is applied as a dietary supplement because of its beneficial effects on general human health and alleviation of neurological disorders. However, mechanisms underlying neuroprotection of chrysin has not been fully elucidated, and the effects of chrysin on the Parkinson's disease (PD) model in vivo have not been investigated. It is here shown that chrysin protects primary granular neurons against 1-methyl-4-phenylpyridinium ion insult via antiapoptosis by reversing the dysregulated expression of Bcl-2, Bax, and caspase 3. The mechanisms also involved activating transcriptional factor myocyte enhancer factor 2D (MEF2D) via regulation of AKT-GSK3β signaling. In this in vivo model of PD, chrysin rescued the dopaminergic neurons loss and alleviated the decrease in dopamine level induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice. Moreover, chrysin markedly inhibited monoamine oxidase-B activity in vitro and in vivo. In conclusion, chrysin exerts beneficial effects to PD, possibly through multitarget mechanisms including antineuronal apoptosis, activation of the AKT-GSK3β/MEF2D pathway, and inhibition of the MAO-B activity.

Potent Protection Against MPP+-Induced Neurotoxicity via Activating Transcription Factor MEF2D by a Novel Derivative of Naturally Occurring Danshensu/Tetramethylpyrazine

Danshensu (DSS) and tetramethylpyrazine (TMP) are active ingredients of Salvia miltiorrhiza Bge. and Ligusticum chuanxiong Hort that are widely used in oriental medicine. Structural combination of compounds with known biological activity may lead to the formation of a molecule with multiple properties or new function profile. In the current study, the neuroprotective effects of DT-010, a novel analogue in which TMP was coupled to DSS through an ester bond and two allyl groups at the carboxyl group, were evaluated in a cellular model of Parkinson's disease (PD). As evidenced by the increase in cell survival, as well as the decrease in the number of Hoechst-stained apoptotic nuclei and the level of intracellular accumulation of reactive oxygen species, DT-010 at 3-30 µM substantially protected against MPP⁺-induced neurotoxicity in both PC12 cells and primary cerebellar granule neurons, a protection that was more potent and efficacious than its parent molecules DSS and TMP. Very encouragingly, we found that DT-010, but not DSS or TMP, could enhance myocyte enhancer factor 2D (MEF2D) transcriptional activity using luciferase reporter gene assay. The neuroprotective effects of DT-010 could be blocked by pharmacologic inhibition of PI3K pathways with LY294002, or MEF2D pathway with short hairpin RNA-mediated knockdown of MEF2D. Furthermore, western blot analysis revealed that DT-010 potentiates Akt protein expression against MPP⁺ to down-regulate MEF2D inhibitor GSK3β. Taken together, the results suggest that DT-010 prevents MPP⁺-induced neurotoxicity via enhancing MEF2D through the activation of PI3K/Akt/GSK3β pathway. DT-010 may be a potential candidate for further preclinical study for preventing and treating PD.

Protection against MPP(+)-induced neurotoxicity in SH-SY5Y cells by tormentic acid via the activation of PI3-K/Akt/GSK3β pathway

The cause of Parkinson's disease (PD) could be ascribed to the progressive and selective loss of dopaminergic neurons in the substantia nigra pars compacta, and thus molecules with neuroprotective ability may have therapeutic value against PD. In the current study, the neuroprotective effects and underlying mechanisms of tormentic acid (TA), a naturally occurring triterpene extracted from medicinal plants such as Rosa rugosa and Potentilla chinensis, were evaluated in a widely used cellular PD model in which neurotoxicity was induced by MPP(+) in cultured SH-SY5Y cells. We found that TA at 1-30 μM substantially protected against MPP(+)-induced neurotoxicity, as evidenced by the increase in cell viability, decrease in lactate dehydrogenase release and the reduction in apoptotic nuclei. Moreover, TA effectively inhibited the elevated intracellular accumulation of reactive oxygen species as well as Bax/Bcl-2 ratio caused by MPP(+). Most importantly, TA markedly reversed the inhibition of protein expression of phosphorylated Akt (Ser 473) and phosphorylated GSK3β (Ser 9) caused by MPP(+). LY294002, the specific inhibitor of PI3-K, significantly abrogated the up-regulated phosphorylated Akt and phosphorylated GSK3β offered by TA, suggesting that the neuroprotection of TA was mainly dependent on the activation of PI3-K/Akt/GSK3β signaling pathway. The results taken together indicate that TA may be a potential candidate for further preclinical study aimed at the prevention and treatment of PD.

Identification of compounds that modulate retinol signaling using a cell-based qHTS assay

In vertebrates, the retinol (vitamin A) signaling pathway (RSP) controls the biosynthesis and catabolism of all-trans retinoic acid (atRA), which regulates transcription of genes essential for embryonic development. Chemicals that interfere with the RSP to cause abnormal intracellular levels of atRA are potential developmental toxicants. To assess chemicals for the ability to interfere with retinol signaling, we have developed a cell-based RARE (Retinoic Acid Response Element) reporter gene assay to identify RSP disruptors. To validate this assay in a quantitative high-throughput screening (qHTS) platform, we screened the Library of Pharmacologically Active Compounds (LOPAC) in both agonist and antagonist modes. The screens detected known RSP agonists, demonstrating assay reliability, and also identified novel RSP agonists including kenpaullone, niclosamide, PD98059 and SU4312, and RSP antagonists including Bay 11-7085, LY294002, 3,4-Methylenedioxy-β-nitrostyrene, and topoisomerase inhibitors (camptothecin, topotecan, amsacrine hydrochloride, and idarubicin). When evaluated in the P19 pluripotent cell, these compounds were found to affect the expression of the Hoxa1 gene that is essential for embryo body patterning. These results show that the RARE assay is an effective qHTS approach for screening large compound libraries to identify chemicals that have the potential to adversely affect embryonic development through interference with retinol signaling.

Supramolecular Inhibition of Neurodegeneration by a Synthetic Receptor

Cucurbit[7]uril (CB[7]) was found in vitro to sequester the neurotoxins MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and MPP(+) (N-methyl-4-phenylpyridine). The CB[7]/neurotoxin host-guest complexes were studied in detail with (1)H NMR, electrospray ionization mass spectrometry, UV-visible spectroscopic titration, and molecular modeling by density functional theory. The results supported the macrocyclic encapsulation of MPTP and MPP(+), respectively, by CB[7] in aqueous solutions with relatively strong affinities and 1:1 host-guest binding stoichiometries in both cases. More importantly, the progression of MPTP/MPP(+) induced neurodegeneration (often referred to as a Parkinson's disease model) was observed to be strongly inhibited in vivo by the synthetic CB[7] receptor, as shown in zebrafish models. These results show that a supramolecular approach could lead to a new preventive and/or therapeutic strategy for counteracting the deleterious effects of some neurotoxins leading to neurodegeneration.

Indirubin-3-Oxime Effectively Prevents 6OHDA-Induced Neurotoxicity in PC12 Cells via Activating MEF2D Through the Inhibition of GSK3β

Indirubin-3-oxime (I3O), a synthetic derivative of indirubin, was originally designed as potent inhibitors of cyclin-dependent kinases (CDKs) and glycogen synthase kinase 3β (GSK3β) for leukemia therapy. In the current study, we have shown, for the first time, that I3O prevented 6-hydroxydopamine (6OHDA)-induced neuronal apoptosis and intracellular reactive oxygen species accumulation in PC12 cells in a concentration-dependent manner. GSK3β inhibitors but not CDK5 inhibitors reduced the neurotoxicity induced by 6OHDA. Moreover, the activation of GSK3β was observed after 6OHDA treatment. Furthermore, 6OHDA substantially decreased the transcriptional activity of myocyte enhancer factor 2D (MEF2D), a transcription factor that plays an important role in dopaminergic neuron survival, and reduced nuclear localized MEF2D expression. Interestingly, indirubin-3-oxime and GSK3β inhibitors prevented 6OHDA-induced dysregulation of MEF2D. In addition, short hairpin RNA-mediated decrease of MEF2D expression significantly abolished the neuroprotective effects of indirubin-3-oxime. Collectively, our results strongly suggested that indirubin-3-oxime prevented 6OHDA-induced neurotoxicity via activating MEF2D, possibly through the inhibition of GSK3β. In view of the capability of indirubin-3-oxime to cross the blood-brain barrier, our findings further indicated that indirubin-3-oxime might be a novel drug candidate for neurodegenerative disorders, including Parkinson's disease in particular.

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.

In vivo reversal of general anesthesia by cucurbit[7]uril with zebrafish models

We demonstrate for the first time that cucurbit[7]uril effectively reversed general anesthesia induced by tricaine in zebrafish models.

The effect of the aquatic contaminants bisphenol-A and PCB-95 on the zebrafish lateral line

Environmental toxicants such as bisphenol-A (BPA) and polychlorinated biphenyls (PCBs) are prevalent in our water supply, soil, and many food products and can profoundly affect the central nervous system. Both BPA and PCBs can disrupt endocrine signaling, which is important for auditory development and function, but the effect of these toxicants on the auditory periphery is not understood. In this study we investigated the effect of PCB-95 and BPA on lateral line development, function, and regeneration in larval zebrafish. The lateral line is a system of mechanosensory hair cells on the exterior of the fish that are homologous to the hair cells located in the mammalian inner ear. We found that PCB-95 had no effect on lateral line development or hair cell survival. BPA also did not affect lateral line development, but instead had a significant effect on both hair cell survival and regeneration. BPA-induced hair cell loss is both dose- and time-dependent, with concentrations of 1 μM or higher killing lateral line hair cells during a 24h exposure period. Pharmacologic manipulation experiments suggest that BPA kills hair cells via activation of oxidative stress pathways, similar to prior reports of BPA toxicity in other tissues. We also observed that hair cells killed with neomycin, a known ototoxin, failed to regenerate normally when BPA was present, suggesting that BPA in aquatic environments could impede innate regenerative responses in fishes. Collectively, these data demonstrate that BPA can have detrimental effects on sensory systems, both in aquatic life and perhaps in terrestrial organisms, including humans.

Canonical and noncanonical vascular endothelial growth factor pathways: new developments in biology and signal transduction

The past 5 years have witnessed a significant expansion in our understanding of vascular endothelial growth factor (VEGF) signaling. In particular, the process of canonical activation of VEGF receptor tyrosine kinases by homodimeric VEGF molecules has now been broadened by the realization that heterodimeric ligands and receptors are also active participants in the signaling process. Although heterodimer receptors were described 2 decades ago, their impact, along with the effect of additional cell surface partners and novel autocrine VEGF signaling pathways, are only now starting to be clarified. Furthermore, ligand-independent signaling (noncanonical) has been identified through galectin and gremlin binding and upon rise of intracellular levels of reactive oxygen species. Activation of the VEGF receptors in the absence of ligand holds immediate implications for therapeutic approaches that exclusively target VEGF. The present review provides a concise summary of the recent developments in both canonical and noncanonical VEGF signaling and places these findings in perspective to their potential clinical and biological ramifications.

Discovery of a benzofuran derivative (MBPTA) as a novel ROCK inhibitor that protects against MPP⁺-induced oxidative stress and cell death in SH-SY5Y cells

Parkinson disease (PD) is a neurodegenerative disease with multifactorial etiopathogenesis. The discovery of drug candidates that act on new targets of PD is required to address the varied pathological aspects and modify the disease process. In this study, a small compound, 2-(5-methyl-1-benzofuran-3-yl)-N-(5-propylsulfanyl-1,3,4-thiadiazol-2-yl) acetamide (MBPTA) was identified as a novel Rho-associated protein kinase inhibitor with significant protective effects against 1-methyl-4-phenylpyridinium ion (MPP(+))-induced damage in SH-SY5Y neuroblastoma cells. Further investigation showed that pretreatment of SH-SY5Y cells with MBPTA significantly suppressed MPP(+)-induced cell death by restoring abnormal changes in nuclear morphology, mitochondrial membrane potential, and numerous apoptotic regulators. MBPTA was able to inhibit MPP(+)-induced reactive oxygen species (ROS)/NO generation, overexpression of inducible NO synthase, and activation of NF-κB, indicating the critical role of MBPTA in regulating ROS/NO-mediated cell death. Furthermore, MBPTA was shown to activate PI3K/Akt survival signaling, and its cytoprotective effect was abolished by PI3K and Akt inhibitors. The structural comparison of a series of MBPTA analogs revealed that the benzofuran moiety probably plays a crucial role in the anti-oxidative stress action. Taken together, these results suggest that MBPTA protects against MPP(+)-induced apoptosis in a neuronal cell line through inhibition of ROS/NO generation and activation of PI3K/Akt signaling.