Neuroprotective effects of (+/-)-kavain in the MPTP mouse model of Parkinson's disease

Drug repurposing for Alzheimer's disease based on transcriptional profiling of human iPSC-derived cortical neurons

Alzheimer's disease is a complex disorder encompassing multiple pathological features with associated genetic and molecular culprits. However, target-based therapeutic strategies have so far proved ineffective. The aim of this study is to develop a methodology harnessing the transcriptional changes associated with Alzheimer's disease to develop a high content quantitative disease phenotype that can be used to repurpose existing drugs. Firstly, the Alzheimer's disease gene expression landscape covering severe disease stage, early pathology progression, cognitive decline and animal models of the disease has been defined and used to select a set of 153 drugs tending to oppose disease-associated changes in the context of immortalised human cancer cell lines. The selected compounds have then been assayed in the more biologically relevant setting of iPSC-derived cortical neuron cultures. It is shown that 51 of the drugs drive expression changes consistently opposite to those seen in Alzheimer's disease. It is hoped that the iPSC profiles will serve as a useful resource for drug repositioning within the context of neurodegenerative disease and potentially aid in generating novel multi-targeted therapeutic strategies.

The involvement of Kav001 in inhibition of LPS/P. gingivalis-induced

TNF-a is an important cytokine mediator of inflammation which suggests that inhibition of TNF activity may provide potential for clinical application. Recent data indicated that treatment of both human and mouse cells with Kavain significantly modulates P. gingivalis- and LPS-induced TNF-α expression. In order to obtain a selective analog with optimized biological activity and structural physico-chemical properties of Kavain, Kavain analogs were designed and synthesized and found one Kavain analogue (named Kav001) that is similar to Kavain but soluble and does not induce a significant toxicity. Both studies in vitro and in vivo treatment by Kav001 showed stronger biological function as compared to Kavain. Furthermore, most mouse bone marrow macrophages up-regulated Bcl-6 while down-regulating LITAF expression after treatment with Kav001 for 36 h. Consequently, this led to an extension of macrophage pseudopods due to its immune response to P.g. infection/LPS stimulation.

Sorbus alnifolia protects dopaminergic neurodegeneration in Caenorhabditis elegans

CONTEXT

The twigs of Sorbus alnifolia (Sieb. et Zucc.) K. Koch (Rosaceae) have been used to treat neurological disorders as a traditional medicine in Korea. However, there are limited data describing the efficacy of S. alnifolia in Parkinson's disease (PD).

OBJECTIVE

This study was conducted to identify the protective effects of the methanol extracts of S. alnifolia (MESA) on the dopaminergic (DA) neurodegeneration in Caenorhabditis elegans.

MATERIALS AND METHODS

To test the neuroprotective action of MESA, viability assay was performed after 48 h exposure to 1-methyl-4-phenylpyridine (MMP+) in PC12 cells and C. elegans (400 μM and 2 mM of MMP+, respectively). Fluorescence intensity was quantified using transgenic mutants such as BZ555 (Pdat-1::GFP) and and UA57 (Pdat-1::GFP and Pdat-1::CAT-2) to determine MESA's effects on DA neurodegeneration in C. elegans. Aggregation of α-synuclein was observed using NL5901 strain (unc-54p::α-synuclein::YFP). MESA's protective effects on the DA neuronal functions were examined by food-sensing assay. Lifespan assay was conducted to test the effects of MESA on the longevity.

RESULTS

MESA restored MPP+-induced loss of viability in both PC12 cells and C. elegans (85.8% and 54.9%, respectively). In C. elegans, MESA provided protection against chemically and genetically-induced DA neurodegeneration, respectively. Moreover, food-sensing functions were increased 58.4% by MESA in the DA neuron degraded worms. MESA also prolonged the average lifespan by 25.6%. However, MESA failed to alter α-synuclein aggregation.

DISCUSSION AND CONCLUSIONS

These results revealed that MESA protects DA neurodegeneration and recovers diminished DA neuronal functions, thereby can be a valuable candidate for the treatment of PD.

Boesenbergia rotunda: From Ethnomedicine to Drug Discovery

Boesenbergia rotunda is a herb from the Boesenbergia genera under the Zingiberaceae family. B. rotunda is widely found in Asian countries where it is commonly used as a food ingredient and in ethnomedicinal preparations. The popularity of its ethnomedicinal usage has drawn the attention of scientists worldwide to further investigate its medicinal properties. Advancement in drug design and discovery research has led to the development of synthetic drugs from B. rotunda metabolites via bioinformatics and medicinal chemistry studies. Furthermore, with the advent of genomics, transcriptomics, proteomics, and metabolomics, new insights on the biosynthetic pathways of B. rotunda metabolites can be elucidated, enabling researchers to predict the potential bioactive compounds responsible for the medicinal properties of the plant. The vast biological activities exhibited by the compounds obtained from B. rotunda warrant further investigation through studies such as drug discovery, polypharmacology, and drug delivery using nanotechnology.

Near-infrared light via light-emitting diode treatment is therapeutic against rotenone- and 1-methyl-4-phenylpyridinium ion-induced neurotoxicity

Parkinson's disease is a common progressive neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Mitochondrial dysfunction has been strongly implicated in the pathogenesis of Parkinson's disease. Thus, therapeutic approaches that improve mitochondrial function may prove to be beneficial. Previously, we have documented that near-infrared light via light-emitting diode (LED) treatment was therapeutic to neurons functionally inactivated by tetrodotoxin, potassium cyanide (KCN), or methanol intoxication, and LED pretreatment rescued neurons from KCN-induced apoptotic cell death. The current study tested our hypothesis that LED treatment can protect neurons from both rotenone- and MPP(+)-induced neurotoxicity. Primary cultures of postnatal rat striatal and cortical neurons served as models, and the optimal frequency of LED treatment per day was also determined. Results indicated that LED treatments twice a day significantly increased cellular adenosine triphosphate content, decreased the number of neurons undergoing cell death, and significantly reduced the expressions of reactive oxygen species and reactive nitrogen species in rotenone- or MPP(+)-exposed neurons as compared with untreated ones. These results strongly suggest that LED treatment may be therapeutic to neurons damaged by neurotoxins linked to Parkinson's disease by energizing the cells and increasing their viability.

Brain-derived neurotrophic factor expression in the substantia nigra does not change after lesions of dopaminergic neurons

Progressive and irreversible loss of specific neuronal cell populations is commonly seen in chronic neurodegenerative diseases such as Parkinson's disease (PD). Evidence is accumulating that apoptosis is a crucial cellular event responsible for the dysfunction and death of neurons in this disease. Thus, limiting apoptosis may prevent disease pathogenesis. Key to reducing apoptosis is the discovery of neuroprotective compounds that can be given to patients to minimize neuronal damage. In this manuscript, we reviewed the rationale of using an experimental strategy to provide neurotrophic support to injured neurons. Such rationale includes the increase of endogenous production of brain-derived neurotrophic factor (BDNF). BDNF is a potent inhibitor of apoptosis-mediated cell death and neurotoxin-induced degeneration of dopaminergic neurons. However, availability of BDNF may be reduced when dopaminergic neurons degenerate. Therefore, in this work, we have used several well-established neurotoxins for dopaminergic neurons, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 6-OH-dopamine (6-OHDA), and the HIV protein gp120, to examine whether degeneration of nigrostriatal fibers alters BDNF expression. Our data show that these neurotoxins do not decrease the levels of BDNF in the substantia nigra, suggesting that up-regulation of BDNF synthesis by pharmacological means may be a viable therapy to slow down the progress of PD and other neurodegenerative diseases.

Effect of acute administration of hydroalcohol extract of Ilex paraguariensis St Hilaire (Aquifoliaceae) in animal models of Parkinson's disease

Ilex paraguariensis St Hilaire (Aquifoliaceae) is a plant widely cultivated in South America and with various reputed medicinal properties that can be attributed to phenolic constituents of the leaves: caffeine, theophylline and theobromine, besides the flavonoids, quercetin and rutin. This study examined the antiparkinsonian activity of the hydroalcohol extract of Ilex paraguariensis in models of protection against cerebral injury induced by MPTP and reversal of the catatonia induced by reserpine in mice. The hydroalcohol extract prevented MPTP-induced hypolocomotion at doses of 250 and 500 mg/kg at the all time points observed and also prevented the reserpine-induced catalepsy at the same doses. The extract potentiated the effect of apomorphine in preventing catatonia, suggesting a non-dopaminergic activity, probably through antagonism of adenosine. In biochemical studies the hydroalcohol extract caused a significant decrease in the NO levels, exhibited a DPPH-scavenging ability and was effective in preventing the oxidation of deoxyribose. The results obtained suggest that the hydroalcohol extract of Ilex paraguariensis may have an antiparkinsonian profile in animal models, probably through its antioxidant activity and antagonist action on adenosine A(2A) receptors.

In vivo modulation of the Parkinsonian phenotype by Nrf2

Oxidative stress has been implicated in the etiology of Parkinson's disease (PD) and in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) animal model of PD. In this report we show that Nrf2, a transcription factor that regulates the expression of phase 2 and antioxidative enzymes, modulates MPTP neurotoxicity in rodents. Nrf2 knockout and wild-type mice were administered MPTP doses ranging from 20 to 60mg/kg. Seven days after MPTP administration dopamine transporter (DAT) levels were measured using [(125)I]-RTI-121 quantitative autoradiography as an index of dopamine terminal integrity in the striatum. The results indicate that MPTP administration resulted in a greater loss of DAT levels in the striatum of Nrf2 knockout mice than in wild-type at all MPTP doses tested. Activation of the Nrf2 pathway by oral administration of the Nrf2 inducer 3H-1,2-dithiole-3-thione (D3T) to wild-type mice produced partial protection against MPTP-induced neurotoxicity. The protective effect of D3T was not due to a change in MPTP metabolism since the level of the MPTP metabolite MPP+ was not significantly different in the D3T treated striatum relative to vehicle control. Administration of D3T to Nrf2 knockout mice did not protect against MPTP neurotoxicity suggesting that the Nrf2 pathway is necessary for the D3T-mediated attenuation of MPTP neurotoxicity. This study demonstrates the significance of activating intrinsic antioxidative mechanisms in an in vivo model of neurodegeneration. The in vivo activation of the Nrf2 pathway in the brain may be an important strategy to mitigate the effects of oxidative stress in neurodegenerative disorders and neurological disease.

Viral vector mediated overexpression of human alpha-synuclein in the nigrostriatal dopaminergic neurons: a new model for Parkinson's disease

Parkinson's disease is predominantly a dopamine deficiency syndrome, which is produced in the brain by the loss of cells located in a small area in the ventral midbrain called the substantia nigra. Complete unilateral dopamine lesions, based on the administration of toxic substances (ie, 6-hydroxy-dopamine in rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice and primates) have been extremely useful in testing strategies of replacement. For example, the functional and biochemical impact of the transplanted ventral mesencephalic dopaminergic progenitors has been characterized to a large extent, using the complete lesion model in rats. Over the last decade, however, studies addressing the ability of neurotrophic factors to protect injured dopamine cells prompted researchers to make available partial and progressive lesion models to allow a window of opportunity to interfere the disease progression. Recent findings relating alpha-synuclein with Parkinson's disease pathology have opened new possibilities to develop alternative models based on the overexpression of this protein using recombinant adeno-associated viral vectors, which is valuable not only for helping to better understand its involvement in the disease process, but also to more closely resemble the neurodegeneration found in Parkinson's disease.

Neuroprotective effects of the antiparkinson drugMucuna pruriens

Mucuna pruriens possesses significantly higher antiparkinson activity compared with levodopa in the 6-hydroxydopamine (6-OHDA) lesioned rat model of Parkinson's disease. The present study evaluated the neurorestorative effect of Mucuna pruriens cotyledon powder on the nigrostriatal tract of 6-OHDA lesioned rats. Mucuna pruriens cotyledon powder significantly increased the brain mitochondrial complex-I activity but did not affect the total monoamine oxidase activity (in vitro). Unlike synthetic levodopa treatment, Mucuna pruriens cotyledon powder treatment significantly restored the endogenous levodopa, dopamine, norepinephrine and serotonin content in the substantia nigra. Nicotine adenine dinucleotide (NADH) and coenzyme Q-10, that are shown to have a therapeutic benefit in Parkinson's disease, were present in the Mucuna pruriens cotyledon powder. Earlier studies showed that Mucuna pruriens treatment controls the symptoms of Parkinson's disease. This additional finding of a neurorestorative benefit by Mucuna pruriens cotyledon powder on the degenerating dopaminergic neurons in the substantia nigra may be due to increased complex-I activity and the presence of NADH and coenzyme Q-10.

High-performance liquid chromatography/tandem mass spectrometry assay for the determination of 1-methyl-4-phenyl pyridinium (MPP+) in brain tissue homogenates

A high-throughput liquid chromatography/tandem mass spectrometry method has been developed for the quantitative assessment of 1-methyl-4-phenylpyridinium (MPP+) in brain tissue samples. This separation is based on reversed phase chromatography using formic acid and acetonitrile as the mobile phase. Using gradient separation conditions, MPP+ was resolved within 5 min and detected using tandem mass spectrometry in the positive ion electrospray mode. The limit of detection for MPP+ was found to be 1 fmol on column with a signal to noise ratio of 3:1. The assay has been used routinely in our laboratory for the measurement of MPP+ levels in brain tissue from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice, and can be used to distinguish neuroprotective efficacy and monoamine oxidase inhibition.

The biogenic trace amine tyramine induces a pronounced hydroxyl radical production via a monoamine oxidase dependent mechanism: an in vivo microdialysis study in mouse striatum

Tyramine is a biogenic trace amine that releases monoamines and is a good substrate for monoamine oxidase (MAO)-A/B. Here we investigated whether tyramine affects hydroxyl radical formation in the intact and lesioned dopaminergic system. Male C57bl/6 mice received systemic and local tyramine administrations. Hydroxyl radical formation and dopamine (DA) overflow were determined in the striatum using in vivo microdialysis in combination with the salicylate hydroxylation assay. Systemic injection of tyramine neither enhanced extracellular dopamine nor induced hydroxyl radical formation. In contrast, when tyramine was incorporated into the dialysate fluid, hydroxyl radical formation and extracellular dopamine levels were significantly enhanced. Systemic pretreatment with the MAO-A/B inhibitor tranylcypromine or with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) significantly diminished the tyramine-induced hydroxyl radical formation by 73.1% and 80.6%, respectively. We conclude that the mechanism of tyramine-induced hydroxyl free radical formation involves MAO metabolism and requires an intact dopaminergic system. Pharmacological intervention on the MAO-mediated formation of hydroxyl free radicals seems to be a promising strategy to prevent oxidative damage in the nigrostriatal dopaminergic system.

Genetic ablation of tumor necrosis factor-alpha (TNF-alpha) and pharmacological inhibition of TNF-synthesis attenuates MPTP toxicity in mouse striatum

The impact of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) in the pathology of Parkinson's disease (PD) and in MPTP neurotoxicity remains unclear. Here, male TNF-alpha (-/-) deficient mice and C57bL/6 mice were treated with MPTP (4 x 15 mg/kg, 24 h intervals) and in one series, thalidomide was administered to inhibit TNF-alpha synthesis. Real-time RT-PCR revealed that the striatal mRNA levels of TNF-alpha, of the astrocytic marker glial fibrillary acidic protein (GFAP) and of the marker for activated microglia, macrophage antigen complex-1 (MAC-1), were significantly enhanced after MPTP administration. Thalidomide (50 mg/kg, p.o.) partly protected against the MPTP-induced dopamine (DA) depletion, and TNF-alpha (-/-) mice showed a significant attenuation of striatal DA and DA metabolite loss as well as striatal tyrosine hydroxylase (TH) fiber density, but no difference in nigral TH and DA transporter immunoreactivity. TNF-alpha deficient mice suffered a lower mortality (10%) compared to the high mortality (75%) seen in wild-type mice after acute MPTP treatment (4 x 20 mg/kg, 2 h interval). HPLC measurement of MPP(+) levels revealed no differences in TNF-alpha (-/-), wild-type and thalidomide treated mice. This study demonstrates that TNF-alpha is involved in MPTP toxicity and that inhibition of TNF-alpha response may be a promising target for extending beyond symptomatic treatment and developing anti-parkinsonian drugs for the treatment of the inflammatory processes in PD.

Attenuation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity by the novel selective dopamine D3-receptor partial agonist FAUC 329 predominantly in the nucleus accumbens of mice

We previously synthesised a novel dopamine (DA) partial agonist FAUC 329 with high affinity and selectivity for the DA D(3) receptor. This is the first in vivo study to investigate the protective effects of FAUC 329 in a MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of Parkinson's disease. Adult male C57bl/6 mice were injected with FAUC 329 (0, 0.1, 0.5, 0.75, or 1 mg/kg) 30 min before MPTP (2 x 30 mg/kg, 4 hr apart). One week later, accumbal and striatal tissue was processed for DA and metabolite HPLC determination as well as immunohistochemical analysis of DA transporter positive neurons in the substantia nigra pars compacta and ventral tegmental area was carried out. FAUC 329 showed a significant attenuation of MPTP-induced DA reduction in the nucleus accumbens (0.5, 0.75 and 1 mg/kg) in a dose-dependent manner. FAUC 329 (0.75 mg/kg) partly protected against DA depletion in the dorsal striatum as well as protected against loss of DA transporter immunoreactivity in the substantia nigra pars compacta. The highest dose of FAUC 329 (1 mg/kg), however, showed a non-significant tendency to augment the MPTP-induced striatal DA reduction. The protective effect of FAUC 329 against MPTP-induced DA depletion was most pronounced in the nucleus accumbens and appears to be linked to the preferential abundance of D(3) receptors in this region. Targeting the mesolimbic DA system may have implications for improvement of impaired motor behaviour and particularly non-motor functions related to the nucleus accumbens.

Kava-kava and anxiety: growing knowledge about the efficacy and safety

Kava-kava (Piper methysticum G. Forster) has been used in social and ceremonial life in the Pacific islands from ancient times for the soporific and narcotic effects. Today several extracts standardized in the biologically active constituents kavalactones are marketed both as herbal medicinal products for anxiety disorders and as dietary supplements to improve stress disorders, nervous tension and restlessness. Unlike other substances used for these purposes, kava-kava has been shown to have minimal negative effects, and possibly positive effects, on reaction time and cognitive processing. Furthermore, it decreases anxiety without the loss of mental acuity. Although kava-kava has been found to be very effective, well tolerated, and non-addictive at therapeutic dosages, potential side effects can occur when very high doses are taken for extended periods. In addition, in the last two years unexpected high liver toxicity has been reported in two patients. Until now no studies support the liver toxicity of kavalactones and it is unknown which compound could have provoked the liver disease. On the other hand, it should be possible that unknown or unexpected constituents are the responsible or contributed to the liver toxicity.

Somatostatin modulates the behavioral effects of dopamine receptor activation in parkinsonian rats

Somatostatin may play a role in several neuropsychiatric disorders, including Parkinson's disease. Although functional interactions between somatostatinergic and dopaminergic transmitter systems have been well documented, no study has been conducted in animals with experimental Parkinsonism to explore the effects of somatostatin on dopamine receptor-mediated behavior. In the present study, rats with unilateral 6-hydroxydopamine-induced destruction of the medial forebrain bundle were assessed following administration of the dopamine(1/2) receptor agonist apomorphine. Ipsilateral intrastriatal infusion of somatostatin produced a dose-related inhibition of apomorphine-induced rotations with maximal effect at a dose of 7.5 microg in 2 microl. This inhibitory effect of somatostatin was antagonized by the somatostatin antagonist cyclo-somatostatin (0.1 microg in 2 microl, intrastriatally). Neither somatostatin (up to 15 microg in 2 microl) nor cyclo-somatostatin on its own induced rotations; similarly, this dose of cyclo-somatostatin did not affect apomorphine-induced rotations. From these results we suggest that exogenous somatostatin, by directly acting on its specific receptors in the striatum, inhibits the effects of dopamine receptor activation in parkinsonian rats. We conclude that therapies based on modulation of somatostatin may be worth exploring in the management of Parkinson's disease and other disorders of the basal ganglia.

Post-insult exposure to (+/-) kavain potentiates N-methyl-D-aspartate toxicity in the developing hippocampus

Kavapyrone extracts of the pepper plant Piper methysticum Forst. have been reported to be pharmacologically active in the brain by modulating the function of several ionotropic receptor systems and voltage-sensitive ion channels. While kavapyrones have previously demonstrated neuroprotective effects against several forms of neurotoxicity, the possibility remains that perturbed function of neuronal ion transport may prove to be neurotoxic in some instances. The present studies were designed to examine the effects of the kavapyrone, (+/-) kavain, on viability of organotypic hippocampal explants exposed to the excitotoxin N-methyl-D-aspartate (NMDA). Exposure to (+/-) kavain (1-600 microM) for 24 h did not alter neuronal viability in the CA1, CA3, or dentate gyrus regions of hippocampal explants. However, higher concentrations of (+/-) kavain (> or =300 microM) produced marked neurotoxicity in the lacunosum moleculare layer of the hippocampus. One hour of exposure to NMDA (20 microM) produced significant neuronal death in both the CA3 and CA1 pyramidal cell regions, effects prevented by co-exposure to MK-801 (30 microM). Co-exposure of explants to (+/-) kavain (1-100 microM) with NMDA did not alter the severity of NMDA-induced neurotoxicity. However, exposure of NMDA-treated explants to (+/-) kavain (> or =10 microM) for 24 h after insult produced significant increases in neurotoxicity in the CA1 and dentate gyrus regions of explants. In conclusion, while the kavapyrone (+/-) kavain is neurotoxic only at high concentrations when exposed alone to the developing hippocampus, it appears to adversely affect neuronal recovery following excitotoxic insults.