Pergolide protects SH-SY5Y cells against neurodegeneration induced by H(2)O(2)

Randomly methylated β-cyclodextrin improves water - solubility, cellular protection and mucosa permeability of idebenone

Neurodegenerative diseases such as Alzheimer's are very common today. Idebenone (IDE) is a potent antioxidant with good potential for restoring cerebral efficiency in cases of these and other medical conditions, but a serious drawback for the clinical use of IDE in neurological disorders lies in its scarce water solubility, which greatly inhibits its bioavailability. In this work, we prepared the inclusion complex of IDE with randomly methylated β-cyclodextrin (RAMEB), resulting in improved water solubility of the included drug; then its in vitro biological activity and ex vivo permeability was evalutated. The solid complex was characterized through FT-IR spectroscopy, Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). A 78-fold improvement of the solubility of IDE in water resulted, together with a strong 1:1 host-guest interaction (association constant of 12630 M-1), and dissolution of the complex within 15 min, all evidenced during the in-solution studies. Biological in vitro studies were then performed on differentiated human neuroblastoma cells (SH-SY5Y) subjected to oxidative stress. Pretreatment with IDE/RAMEB positively affected cell viability, promoted the nuclear translocation of Nrf2, and increased the levels of GSH as well as those of the endogenous antioxidant enzymes Mn-SOD and HO-1. Lastly, the complexation significantly improved the permeation of IDE through isolated rat nasal mucosa.

In vitro anticholinesterase potential of some spices consumed in Cameroon and their protective effects on hydrogen peroxide-mediated oxidative stress damage in SK-N-SH cells

Background

Many neurodegenerative such as Alzheimer's disease (AD) are characterized by cholinergic dysfunction and oxidative stress which is a key event in neuronal death process. Thus, anticholinesterase and anti-oxidation compounds are two promising strategies in the development of AD drugs. Beyond their culinary use, spices are today studies for health purpose. In this study, some spices consumed in Cameroon were evaluated for their anticholinesterase and neuroprotective effects.

Methods

Colorimetric methods were used to determine total flavonoid and alkaloid content of a combinated extract (hydroethanolic + ethanolic extracts) of different selected spices. Aftermaths, anti-cholinesterase activity of spice extract was carried out using Ellman’s method. Finally, neuroprotective effects performed on human SK-N-SH cells stressed with H₂O₂ by assessing neuronal survival ( resazurin assay) and neuronal death (LDH assay).

Results

Flavonoid content of spices extract were ranged from 22.94 to 32.01 mg EQ/g DM and alkaloid content were ranged from 320 to 896 mg EQu/g DM. Among the spices studied, Xylopia parviflora presented the greatest acetylcholinesterase inhibition with an IC50 = 14 µg/mL. In Cell culture experiments, pre-incubation of SK-N-SH cell with the selected spices at different concentrations were improved neuronal survival and reduced the percentage of neuronal cells dead.

Conclusion

The present results reveal that selected spices consumed in Cameroon have good anticholinesterase activity as well as neuroprotective effect on SK-N-SH which may provide new natural compounds that could help in the management of Alzheimer's disease.

Multi-Target Mechanisms of Phytochemicals in Alzheimer’s Disease: Effects on Oxidative Stress, Neuroinflammation and Protein Aggregation

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by a tangle-shaped accumulation of beta-amyloid peptide fragments and Tau protein in brain neurons. The pathophysiological mechanism involves the presence of Aβ-amyloid peptide, Tau protein, oxidative stress, and an exacerbated neuro-inflammatory response. This review aims to offer an updated compendium of the most recent and promising advances in AD treatment through the administration of phytochemicals. The literature survey was carried out by electronic search in the following specialized databases PubMed/Medline, Embase, TRIP database, Google Scholar, Wiley, and Web of Science regarding published works that included molecular mechanisms and signaling pathways targeted by phytochemicals in various experimental models of Alzheimer’s disease in vitro and in vivo. The results of the studies showed that the use of phytochemicals against AD has gained relevance due to their antioxidant, anti-neuroinflammatory, anti-amyloid, and anti-hyperphosphorylation properties of Tau protein. Some bioactive compounds from plants have been shown to have the ability to prevent and stop the progression of Alzheimer’s.

A Systematic Review of the Protective Actions of Cat's Whiskers (Misai Kucing) on the Central Nervous System

Orthosiphon stamineus (OS) or Orthosiphon aristatus var. aristatus (OAA) is commonly known as cat's whiskers or "misai kucing". It is an herbaceous shrub that is popular in many different traditional and complementary medicinal systems. Its popularity has been justified by the plethora of studies that have shown that the secondary metabolites of the plant has effects that range from anti-inflammatory and gastroprotective to anorexic and antihypertensive. As such, OS could also be a potential treatment for Central Nervous System (CNS) disorders. However, a cohesive synthesis of the protective actions of OS was lacking. This systematic review was therefore commenced to elaborate on the various protective mechanisms of OS in the CNS. The PRISMA model was used and five databases (Google Scholar, SCOPUS, SpringerLink, ScienceDirect, and PubMed) were searched with relevant keywords to finally identify four articles that met the inclusion criteria. The articles described the protective effects of OS extracts on Alzheimer's disease, epilepsy, learning and memory, oxidative stress, and neurotoxicity. All the articles found were experimental or preclinical studies on animal models or in vitro systems. The reported activities demonstrated that OS could be a potential neuroprotective agent and might improve CNS conditions like neurodegeneration, neuroinflammation, and oxidative stress.

Inactivation of GAP-43 due to the depletion of cellular calcium by the Pb and amyloid peptide induced toxicity: An in vitro approach

Environmental pollutant, Lead (Pb) is known to induce neurotoxicity in human. The central nervous system is the most vulnerable to the minute levels of Pb induced toxicity. Pb has been linked to Alzheimer's disease (AD) as a probable risk factor, as it shows epigenetic and developmental link associated with Alzheimer's disease-like pathology. Beta amyloid peptides were considered as the crucial factors in the beta amyloid plaque formation in Alzheimer's disease brain. In this context, we investigated the molecular mechanism involved in the development of Pb induced Alzheimer's disease in in vitro. Previous data from our studies have reported that Pb in the presence of beta Amyloid peptide (1-40) and (25-35) induces more apoptosis than individual exposures. Here, to further evaluate the molecular mechanism underlying Pb induced Alzheimer's disease; we focussed on the involvement of calcium signalling in inducing cell death. Our experimental observations suggesting that Pb in the presence of beta amyloid peptide alters intracellular calcium levels, which leads to the increased beta-secretase activity, which further promotes the generation of beta amyloid peptides. It also showed depression in the levels of GAP-43 expression, inhibition of PKC activity and altering synaptic activity further leads to cell death.

The Neuroprotective Effects of Brazilian Green Propolis on Neurodegenerative Damage in Human Neuronal SH-SY5Y Cells

Oxidative stress and synapse dysfunction are the major neurodegenerative damage correlated to cognitive impairment in Alzheimer's disease (AD). We have found that Brazilian green propolis (propolis) improves the cognitive functions of mild cognitive impairment patients living at high altitude; however, mechanism underlying the effects of propolis is unknown. In the present study, we investigated the effects of propolis on oxidative stress, expression of brain-derived neurotrophic factor (BDNF), and activity-regulated cytoskeleton-associated protein (Arc), the critical factors of synapse efficacy, using human neuroblastoma SH-SY5Y cells. Pretreatment with propolis significantly ameliorated the hydrogen peroxide- (H₂O₂-) induced cytotoxicity in SH-SY5Y cells. Furthermore, propolis significantly reduced the H₂O₂-generated reactive oxygen species (ROS) derived from mitochondria and 8-oxo-2'-deoxyguanosine (8-oxo-dG, the DNA oxidative damage marker) but significantly reversed the fibrillar β-amyloid and IL-1β-impaired BDNF-induced Arc expression in SH-SY5Y cells. Furthermore, propolis significantly upregulated BDNF mRNA expression in time- and dose-dependent manners. In addition, propolis induced Arc mRNA and protein expression via phosphoinositide-3 kinase (PI3K). These observations strongly suggest that propolis protects from the neurodegenerative damage in neurons through the properties of various antioxidants. The present study provides a potential molecular mechanism of Brazilian green propolis in prevention of cognitive impairment in AD as well as aging.

Propolis Inhibits Neurite Outgrowth in Differentiating SH-SY5Y Human Neuroblastoma Cells

Propolis is a multicomponent, active, complex resinous substance collected by honeybees from a variety of plant sources. We have studied the effect of propolis on neurite outgrowth of SH-SY5Y human neuroblastoma cells induced to differentiate by all-trans-retinoic acid (RA). Propolis, at a concentration of 3 μg/mL, had no significant effect on the viability of differentiating SH-SY5Y cells. However, the neurite outgrowth of the differentiating SH-SY5Y cells treated with propolis (0.3~3 μg/mL) for 48 hr was significantly inhibited in a dose-dependent manner. Treatment of RA-stimulated differentiating SH-SY5Y cells with 0.3 to 3 μg/mL propolis resulted in decreased level of transglutaminase and 43-kDa growth-associated protein (GAP-43) in a dose-dependent manner. The results indicate that propolis is able to inhibit neurite outgrowth of differentiating SH-SY5Y cells.

Ferulic Acid Regulates the Nrf2/Heme Oxygenase-1 System and Counteracts Trimethyltin-Induced Neuronal Damage in the Human Neuroblastoma Cell Line SH-SY5Y

Over the past years, several lines of evidence have pointed out the efficacy of ferulic acid (FA) in counteracting oxidative stress elicited by β-amyloid or free radical initiators, based on the ability of this natural antioxidant to up-regulate the heme oxygenase-1 (HO-1) and biliverdin reductase (BVR) system. However, scarce results can be found in literature regarding the cytoprotective effects of FA in case of damage caused by neurotoxicants. The aim of this work is to investigate the mechanisms through which FA exerts neuroprotection in SH-SY5Y neuroblastoma cells exposed to the neurotoxin trimethyltin (TMT). FA (1-10 μM for 6 h) dose-dependently increased both basal and TMT (10 μM for 24 h)-induced HO-1 expression in SH-SY5Y cells by fostering the nuclear translocation of the transcriptional activator Nrf2. In particular, the co-treatment of FA (10 μM) with TMT was also responsible for the nuclear translocation of HO-1 in an attempt to further increase cell stress response in SH-SY5Y cells. In addition to HO-1, FA (1-10 μM for 6 h) dose-dependently increased the basal expression of BVR. The antioxidant and neuroprotective features of FA, through the increase of HO activity, were supported by the evidence that FA inhibited TMT (10 μM)-induced lipid peroxidation (evaluated by detecting 4-hydroxy-nonenal) and DNA fragmentation in SH-SY5Y cells and that this antioxidant effect was reversed by the HO inhibitor Zinc-protoporphyrin-IX (5 μM). Among the by-products of the HO/BVR system, carbon monoxide (CORM-2, 50 nM) and bilirubin (BR, 50 nM) significantly inhibited TMT-induced superoxide anion formation in SH-SY5Y cells. All together, these results corroborate the neuroprotective effect of FA through the up-regulation of the HO-1/BVR system, via carbon monoxide and BR formation, and provide the first evidence on the role of HO-1/Nrf2 axis in FA-related enhancement of cell stress response in human neurons.

The Neuroprotective Effects of Ratanasampil on Oxidative Stress-Mediated Neuronal Damage in Human Neuronal SH-SY5Y Cells

We previously found that Ratanasampil (RNSP), a traditional Tibetan medicine, improves the cognitive function of mild-to-moderate AD patients living at high altitude, as well as learning and memory in an AD mouse model (Tg2576); however, mechanism underlying the effects of RNSP is unknown. In the present study, we investigated the effects and molecular mechanisms of RNSP on oxidative stress-induced neuronal toxicity using human neuroblastoma SH-SY5Y cells. Pretreatment with RNSP significantly ameliorated the hydrogen peroxide- (H2O2-) induced cytotoxicity of SH-SY5Y cells in a dose-dependent manner (up to 60 μg/mL). Furthermore, RNSP significantly reduced the H2O2-induced upregulation of 8-oxo-2'-deoxyguanosine (8-oxo-dG, the oxidative DNA damage marker) but significantly reversed the expression of repressor element-1 silencing transcription factor (REST) from H2O2 associated (100 μM) downregulation. Moreover, RNSP significantly attenuated the H2O2-induced phosphorylation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase 1/2 (ERK 1/2) in SH-SY5Y cells. These observations strongly suggest that RNSP may protect the oxidative stress-induced neuronal damage that occurs through the properties of various antioxidants and inhibit the activation of MAPKs. We thus provide the principle molecular mechanisms of the effects of RNSP and indicate its role in the prevention and clinical management of AD.

Cadmium Inhibits Neurite Outgrowth in Differentiating Human SH-SY5Y Neuroblastoma Cells

Cadmium, a highly ubiquitous heavy metal, is well known to induce neurotoxicity. However, the underlying mechanism of cadmium-mediated neurotoxicity remains unclear. We have studied cadmium inhibition of neurite outgrowth using human SH-SY5Y neuroblastoma cells induced to differentiate by all- trans-retinoic acid (RA). Cadmium, at a concentration of 3 μmol/L, had no significant effect on the viability of differentiating SH-SY5Y cells. However, the neurite outgrowth of the differentiating SH-SY5Y cells 48 hours after cadmium treatment (1-3 μmol/L cadmium) was significantly inhibited in a dose-dependent manner. Treatment of RA-stimulated differentiating SH-SY5Y cells with 1 to 3 μmol/L cadmium resulted in decreased level of cross-reactivities with 43-kDa growth-associated protein (GAP-43) in a dose-dependent manner. The reactive oxygen species (ROS) scavenger, NAC (N-acetyl-l-cysteine), recovered the expression of GAP-43 in cadmium-treated cells. The results indicate that cadmium is able to inhibit neurite outgrowth of differentiating SH-SY5Y cells and that this effect might result from ROS generation by cadmium.

Protective effect of tomatine against hydrogen peroxide-induced neurotoxicity in neuroblastoma (SH-SY5Y) cells

OBJECTIVES

Reactive oxygen species can induce cell apoptosis, and oxidative stress has been implicated in a variety of neurodegenerative disorders. Tomatine, which is a naturally occurring steroidal glycoalkaloid isolated from Solanum cathayanum, has shown potent anti-oxidant properties.

METHODS

In this study, we used the SH-SY5Y cell line as an in vitro model and investigated the protective effect of tomatine against hydrogen peroxide (H2 O2 )-induced neurotoxicity in SH-SY5Y cells.

KEY FINDINGS

Tomatine might inhibit the release of cellular lactate dehydrogenase, increase anti-oxidant enzyme activity and glutathione content, reverse the downregulated protein expression of the brain-derived neurotrophic factor (BDNF), inhibit expression of Bax and activations of caspase-3 and caspase-9 in H2 O2 -induced SH-SY5Y cells.

CONCLUSIONS

Tomatine exerted beneficially neuroprotective effect on H2 O2 -induced SH-SY5Y cells, mainly enhancing intracellular anti-oxidant enzyme activity and BDNF expression, inhibiting H2 O2 -induced oxidative stress as well as expression of Bax and activations of caspase-3 and caspase-9, alleviating H2 O2 -induced SH-SY5Y cell injury and cell death.

Neuroprotective effects of orientin on hydrogen peroxide‑induced apoptosis in SH‑SY5Y cells

Neurodegenerative diseases remain a global issue which affects the ageing population. Efforts towards determining their aetiologies to understand their pathogenic mechanisms are underway in order to identify a pathway through which therapeutic measures can be applied. One such pathogenic mechanism, oxidative stress (OS), is widely considered to be involved in neurodegenerative disease. Antioxidants, most notably flavonoids, have promising potential for therapeutic use as shown in in vitro and in vivo studies. In view of the importance of flavonoids for combating OS, this study investigated the neuroprotective effects of orientin, which has been reported to be capable of crossing the blood‑brain barrier. The maximum non‑toxic dose (MNTD) of orientin against SH‑SY5Y neuroblastoma cells was determined using a 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) assay. The effects of the MNTD and the half MNTD (½MNTD) of orientin on cell cycle progression and intracellular reactive oxygen species (ROS) levels, as well as the activity of caspases 3/7, 8 and 9 after exposure to 150 µM of hydrogen peroxide (H2O2) were also determined using flow cytometry, a 2',7'‑dichlorodihydrofluorescein‑diacetate (DCFH‑DA) assay and caspase assay kits, respectively. The results revealed that orientin at ≤20 µM was not cytotoxic to SH‑SY5Y cells. After treatment with orientin at the MNTD, the percentage of apoptotic cells was significantly reduced compared with that in cells treated with 150 µM H2O2 alone. The results also showed that, although orientin at the MNTD and ½MNTD did not reduce intracellular ROS levels, it significantly inhibited the activity of caspases 3/7. Caspase 9 was significantly inactivated with orientin at the MNTD. Findings from this study suggest that the neuroprotection conferred by orientin was the result of the intracellular mediation of caspase activity.

Pergolide protects CA1 neurons from apoptosis in a gerbil model of global cerebral ischemia

OBJECTIVE

To investigate the effects of dopamine (DA) receptor agonists and antagonists on neuronal apoptosis in hippocampal CA1 region after forebrain ischemia/reperfusion (I/R) injury in gerbils.

METHODS

Gerbil forebrain ischemia was induced by occluding bilateral carotid arteries for 5 minutes. The open field test, hematoxylin-eosin staining and in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) methods were used 1, 3 and 7 days after reperfusion. Western blot was used to examine the phosphorylation of c-Jun.

RESULTS

Pergolide could significantly reduce the habituation impairments of ischemic gerbils, increase the number of normal neurons and reduce the number of apoptotic neurons in hippocampal CA1 region after reperfusion. SKF38393, SCH23390 and spiperone had no effects on these changes in this transient I/R injury model. Furthermore, pergolide can significantly reduce the phosphorylation of c-Jun induced by transient forebrain ischemia.

Dietary zeolite supplementation reduces oxidative damage and plaque generation in the brain of an Alzheimer's disease mouse model

AIM

Oxidative stress is considered one of the main events that lead to aging and neurodegeneration. Antioxidant treatments used to counteract oxidative damage have been associated with a wide variety of side effects or at the utmost to be ineffective. The aim of the present study was to investigate the antioxidant property of a natural mineral, the tribomechanically micronized zeolite (MZ).

MAIN METHODS

Cell death and oxidative stress were assessed in retinoic acid differentiated SH-SY5Y cells, a neuronal-like cell line, after a pro-oxidant stimulus. In vivo evaluation of antioxidant activity and amyloidogenic processing of beta amyloid have been evaluated in a transgenic model of aging related neurodegeneration, the APPswePS1dE9 transgenic mice (tg mice) after a five-month long period of water supplementation with MZ.

KEY FINDINGS

The study showed that 24h of cell pretreatment with MZ (1) protected the cells by radical oxygen species (ROS)-induced cell death and moreover (2) induced a reduction of the mitochondrial ROS production following a pro-oxidant stimulation. Looking for an antioxidant effect of MZ in vivo, we found (3) an increased activity of the endogenous antioxidant enzyme superoxide dismutase (SOD) in the hippocampus of tg mice and (4) a reduction in amyloid levels and plaque load in MZ treated tg mice compared to control tg mice.

SIGNIFICANCE

Our results suggest MZ as a novel potential adjuvant in counteracting oxidative stress and plaque accumulation in the field of neurodegenerative diseases.

Propofol-induced protection of SH-SY5Y cells against hydrogen peroxide is associated with the HO-1 via the ERK pathway

Propofol (2, 6-diisopropylphenol), is an anesthetic and routinely used for the humans sedation during surgery. The potent inducers of phase II detoxifying and antioxidant stress responsive to propofol were investigated. First, a dose of 25-100 µM propofol showed no significant cytotoxicity on SH-SY5Y cells and pre-treatment of SH-SY5Y cells with propofol (25-100 μM) for 8h prevented cell death and maintained cell integrity following exposure to 1 mM hydrogen peroxide by MTT assays. Then, an increase in the generation of ROS following hydrogen peroxide treatment was significantly attenuated by 8 h pre-treatment with propofol. Additionally, the potential roles of ERK, p 38 MAPK and JNK in the regulation of propofol-induced endogenous HO-1 expression in SH-SY5Y cells were estimated by Western blotting assays. Results showed that propofol significantly increased the phosphorylation levels of ERK, p 38 MAPK and JNK and antioxidant stress responsive to propofol was attenuated by the inhibition of ERK signaling biochemical inhibitors. These results suggest that the ERK pathway plays an important role in the regulation of propofol-mediated antioxidant effects in SH-SY5Y cells.

The effects of pergolide on memory and oxidative stress in a rat model of Parkinson's disease

One of the most widely used animal models of Parkinson's disease (PD) involves injecting 6-hydroxydopamine (6-OHDA) directly into the substantia nigra (SN). Some recent reports speculated that dopaminergic drugs may exert brain antioxidant activity, which could explain some of their protective actions. In this way, the aim of the present study was to examine the effects of low-dose pergolide on memory deficits and brain oxidative stress in a 6-OHDA-induced rat model of PD. Right-unilateral lesions of the SN were produced with 6-OHDA. Two weeks after neurosurgery, pergolide (0.3 mg/kg/day) was injected intraperitoneally in the 6-OHDA + pergolide and sham-operated + pergolide groups, while sham-operated and 6-OHDA alone groups received saline. Radial-8-arm maze and Y-maze were used for memory assessment. We also determined some enzymatic antioxidant defenses like superoxide dismutase or glutathione peroxidase and a lipid peroxidation marker [malondialdehyde (MDA)], from the temporal lobe. A reduced number of working/reference memory errors was observed in 6-OHDA + pergolide group, compared to sham-operated rats. Additionally, post hoc analysis showed significant differences between 6-OHDA and 6-OHDA + pergolide groups in both Y-maze and radial-arm-maze tasks. We also noted a significant decrease of MDA level in the 6-OHDA + pergolide group, compared to sham-operated rats. Significant correlations were also found between behavioral parameters and MDA levels. Our data suggest that pergolide facilitates spatial memory and improves brain oxidative balance, after a 6-OHDA-induced model of PD. This could be useful for further investigations and clinical applications of pergolide.

Equine pituitary pars intermedia dysfunction

Equine pituitary pars intermedia dysfunction (PPID), also known as equine Cushing's syndrome, is a widely recognized disease of aged horses. Over the past two decades, the aged horse population has expanded significantly and in addition, client awareness of PPID has increased. As a result, there has been an increase in both diagnostic testing and treatment of the disease. This review focuses on the pathophysiology and clinical syndrome, as well as advances in diagnostic testing and treatment of PPID, with an emphasis on those findings that are new since the excellent comprehensive review by Schott in 2002.

Effects of pergolide mesylate on transduction efficiency of PEP-1-catalase protein

The low transduction efficiency of various proteins is an obstacle to their therapeutic application. However, protein transduction domains (PTDs) are well-known for a highly effective tool for exogenous protein delivery to cells. We examined the effects of pergolide mesylate (PM) on the transduction of PEP-1-catalase into HaCaT human keratinocytes and mice skin and on the anti-inflammatory activity of PEP-1-catatase against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation using Western blot and histological analysis. PM enhanced the time- and dose-dependent transduction of PEP-1-catalase into HaCaT cells without affecting the cellular toxicity. In a mouse edema model, PEP-1-catalase inhibited the increased expressions of inflammatory mediators and cytokines such as cyclooxygenase-2, inducible nitric oxide synthase, interleukin-6 and -1β, and tumor necrosis factor-α induced by TPA. On the other hand, PM alone failed to exert any significant anti-inflammatory effects. However, the anti-inflammatory effect of co-treatment with PEP-1-catalase and PM was more potent than that of PEP-1-catalase alone. Our results indicate that PM may enhance the delivery of PTDs fusion therapeutic proteins to target cells and tissues and has potential to increase their therapeutic effects of such drugs against various diseases.

Enhancing the GLP-1 receptor signaling pathway leads to proliferation and neuroprotection in human neuroblastoma cells

Increasing evidence suggests that glucagon-like peptide-1 (GLP-1), an incretin hormone of current interest in type 2 diabetes, is neuroprotective in both cell culture and animal models. To characterize the neuroprotective properties of GLP-1 and associated underlying mechanisms, we over-expressed the GLP-1 receptor (GLP-1R) on human neuroblastoma SH-SY5Y cells to generate a neuronal culture system featuring enhanced GLP-1R signaling. In GLP-1R over-expressing SH-SY5Y (SH-hGLP-1R#9) cells, GLP-1 and the long-acting agonist exendin-4 stimulated cell proliferation and increased cell viability by 2-fold at 24 h at physiologically relevant concentrations. This GLP-1R-dependent action was mediated via the protein kinase A and phosphoinositide 3-kinase signaling pathways, with the MAPK pathway playing a minor role. GLP-1 and exendin-4 pretreatment dose-dependently protected SH-hGLP-1R#9 cells from hydrogen peroxide (H(2)O(2))- and 6-hydroxydopamine-induced cell death. This involved amelioration of elevated caspase 3 activity, down-regulation of pro-apoptotic Bax and up-regulation of anti-apoptotic Bcl-2 protein. In the presence of 6-hydroxydopamine, GLP-1's ability to lower caspase-3 activity was abolished with the phosphoinositide 3-kinase inhibitor, LY2940002, and partly reduced with the protein kinase A inhibitor, H89. Hence, GLP-1R mediated neurotrophic and anti-apoptotic actions co-contribute to the neuroprotective property of GLP-1 in neuronal cell cultures, and reinforce the potential therapeutic value of GLP-1R agonists in neurodegenerative disorders involving oxidative stress.

Morroniside protects human neuroblastoma SH-SY5Y cells against hydrogen peroxide-induced cytotoxicity

Oxidative stress-induced cell damage has been implicated in a variety of neurodegenerative disorders. Morroniside, an iridorid glycoside isolated from Cornus officinalis Sieb. Et Zucc., has shown potent antioxidant properties. The present study investigated the protective actions of morroniside against the cytotoxicity produced by exposure to H(2)O(2) (300-500 microM) in SH-SY5Y cells. Intracellular accumulation of Ca(2+), and decreases in mitochondrial membrane potential (MMP) caused by added H(2)O(2) were reduced by morroniside. Incubation of cells with H(2)O(2) caused a marked decrease in superoxide dismutase (SOD) activity; this decrease was significantly inhibited by morroniside. In addition, the percentage of cells undergoing H(2)O(2)-induced apoptosis was decreased, dose dependently, in the presence of morroniside. These results suggest that morroniside has protective effects against oxidative stress-induced neurotoxic processes.

Neuroprotective effect of cocoa flavonoids on in vitro oxidative stress

BACKGROUND

Cocoa is a rich source of flavonoids that, among other functions, can act as antioxidants. In living systems, the production of reactive oxygen species (ROS) activate an array of intracellular cascades, including mitogen-activated protein kinases (MAPK), that are closely associated with cell death or survival pathways.

AIM OF THE STUDY

To ascertain the role of a cocoa extract and its main flavonoid, (-)-epicatechin, in an in vitro model of oxidative stress induced in a neuronal cell line.

METHODS

We analyzed ROS production by fluorometry (dichlorofluorescein assay), and activation of MAPK pathways including extracellular signal-regulated kinases 1/2 (ERK 1/2), c-Jun N-terminal kinase (JNK), and p-38, by Western blot analysis.

RESULTS

Cells incubated with cocoa extract or (-)-epicatechin, reduced ROS production in a dose-dependent manner, reaching 35% inhibition. pJNK and p38, involved in apoptosis, were down-modulated by cocoa extract and (-)-epicatechin with p38 inhibition reaching up to 70%.

CONCLUSIONS

Our results show that cocoa extract and (-)-epicatechin may exert a neuroprotective action by reducing ROS production and modulating MAPK activation.

Pramipexole prevents neurotoxicity induced by oligomers of beta-amyloid

Here we demonstrate that pramipexole, an antiparkinsonian dopamine receptor agonist drug, exerts neuroprotective effects against beta-amyloid neurotoxicity. Using a specific protocol to test individually oligomers, fibrils, or unaggregated amyloid beta-peptide, we found pramipexole able to protect cells against oligomers and fibrils. Unaggregated amyloid beta-peptide was found unable to cause cell death. Fibrils and oligomers were also found to produce elevated amount of free radicals, and this effect was prevented by pramipexole. We propose pramipexole may become in the future a coadjuvant in the treatment of neuropathologies, besides Parkinson's disease, where amyloid beta-peptide-mediated oxidative injury exerts a relevant role.

Morroniside prevents peroxide-induced apoptosis by induction of endogenous glutathione in human neuroblastoma cells

(1) Morroniside belongs to an extensive group of natural iridorid glycosides. In the present study, using human neuroblastoma SH-SY5Y cells, we have investigated the protective effects of this compound on modifications in endogenous reduced glutathione (GSH), intracellular oxygen species (ROS) and apoptotic death on H(2)O(2)-mediated cytoxicity. (2) Incubation of cells with morroniside led to a significant dose-dependent elevation of cellular GSH accompanied by a marked protection against H(2)O(2)-mediated toxicity. Morroniside at 1-100 microM inhibited the formation of ROS and the activation of caspase-3 and 9, and the upregulation of Bcl-2, whereas no significant change occurred in Bax levels. (3) The results indicated that the anti-oxidative and anti-apoptotic properties render this natural compound potentially protective against H(2)O(2)-induced cytotoxicity. (4) This study suggested that intracellular GSH appeared to be an important factor in morroniside-mediated cytoprotection against H(2)O(2)-toxicity in SH-SY5Y cells.

Dopaminergic agonists: possible neurorescue drugs endowed with independent and synergistic multisites of action

Dopaminergic agonists have been usually used as adjunctive therapy for the cure of Parkinson's disease (PD). It is generally believed that treatment with these drugs is symptomatic rather then curative and does not stop or delay the progression of neuronal degeneration. However, several DA agonists of the DA D2-receptor family (including D2, D3 and D4-subtypes) have recently been shown to possess neuroprotective properties in different in vitro and in vivo experimental PD models. Here we summarize some recent data from our and other groups underlining the wide pharmacological spectrum of DA agonists currently used for treating PD patients. In particular, the mechanism of action of different DA agonists does not appear to be restricted to the stimulation of selective DA receptor subtypes being these drugs endowed with intrinsic, independent, and peculiar antioxidant effects. This activity may represent an additional pharmacological property contributing to their clinical efficacy in PD.

Dopamine Promotes the Survival of Embryonic Striatal Cells: Involvement of Superoxide and Endogenous NADPH Oxidase

The dopaminergic system appears early in mammalian brain development, and a neurodevelopmental role for dopamine (DA) has been suggested. In the present study, we found that DA markedly promoted the survival of embryonic striatal cells in cultures. The failure of DA receptor antagonists to block this survival-promoting effect and the capability of S-apomorphine, which is devoid of DA receptor agonist activity but possesses antioxidative activity as R-apomorphine and DA, to completely mimic this effect suggested that DA receptor activation was not required in the survival-promoting effect elicited by DA, and its antioxidative activity might be involved. Moreover, it was found that mRNA of NADPH oxidase was expressed in the embryonic striatum. Furthermore, DPI or apocynin, NADPH oxidase inhibitors, promoted the survival of embryonic striatal cells. Addition of either DA or DPI into striatal cell cultures decreased the superoxide level. These results indicate that the mechanisms underlying the neuroprotective effects of DA were likely associated with its antioxidative activity. NADPH oxidase might contribute, at least in part, to ROS generation.

A dopamine D4 receptor antagonist attenuates ischemia-induced neuronal cell damage via upregulation of neuronal apoptosis inhibitory protein

Neuronal apoptosis inhibitory protein (NAIP/BIRC1), the inhibitor of apoptosis protein (IAP) family member, suppresses neuronal cell death induced by a variety of insults, including cell death from ischemia and stroke. The goal of the present study was to develop an efficient method for identification of compounds with the ability to upregulate endogenous NAIP and to determine the effects on these compounds on the cellular response to ischemia. A novel NAIP-enzyme-linked immunosorbent assay (ELISA)-based in vitro drug-screening system is established. Use of this system identified an antagonist of dopamine D4 receptor, termed L-745,870, with a potent NAIP upregulatory effect. L-745,870-mediated NAIP upregulation in neuronal and nonneuronal cultured cells resulted in decreased vulnerability to oxidative stress-induced apoptosis. Reducing NAIP expression via RNA interference techniques resulted in prevention of L-745,870-mediated protection from oxidative stress. Further, systemic administration of L-745,870 attenuated ischemia-induced damage of the hippocampal CA1 neurons and upregulated NAIP expression in the rescued hippocampal CA1 neurons in a gerbil model. These data suggest that the NAIP upregulating compound, L-745,870, has therapeutic potential in acute ischemic disorders and that our NAIP-ELISA-based drug screening may facilitate the discovery of novel neuroprotective compounds.

Trial of subtherapeutic pergolide in de novo Parkinson's disease

The effect of pergolide 25 mug twice daily on levodopa initiation was assessed in a randomized, placebo-controlled, parallel group, double-blind multicenter trial in 106 untreated early Parkinson's disease patients. The primary endpoint of mean time until levodopa was 520 days (95% confidence interval [CI], 422-618 days) for pergolide versus 434 days (95% CI, 358-609 days) for placebo. However, this increase of 86 days for pergolide was not statistically significant. The wash-in effect of pergolide was significant at 6 weeks (change in mean Unified Parkinson's Disease Rating Scale [UPDRS] 2 and 3 was -0.1 [95% CI, -1.4 to 1.3] for pergolide vs. 2.2 [95% CI, 1.1-3.3] for placebo). At termination, the change from baseline in mean UPDRS 2 and 3 score was 11.4 (95% CI, 8.8-14) for pergolide and 14.6 (95% CI, 12-17.2) for placebo (P=0.08). There was no significant change in UPDRS 2 and 3 for the 83 patients achieving the planned 4-week washout at termination (pergolide 1.2 [95% CI, -0.8 to 3.2] vs. placebo 0.0 [95% CI, -1.6 to 1.6]. Adverse events were infrequent and occurred equally for pergolide and placebo. The study shows no evidence of a neuroprotective effect but indicates a mild symptomatic benefit from pergolide at a dose normally considered subtherapeutic.

Activation of ERK1/2, JNK and PKB by hydrogen peroxide in human SH-SY5Y neuroblastoma cells: role of ERK1/2 in H2O2-induced cell death

Reactive oxygen species including H(2)O(2) activate an array of intracellular signalling cascades that are closely associated with cell death and cell survival pathways. The human neuroblastoma SH-SY5Y cell line is widely used as model cell system for studying neuronal cell death induced by oxidative stress. However, at present very little is known about the signalling pathways activated by H(2)O(2) in SH-SY5Y cells. Therefore, in this study we have investigated the effect of H(2)O(2) on extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38 MAPK) and protein kinase B (PKB) activation in undifferentiated and differentiated SH-SY5Y cells. H(2)O(2) stimulated time and concentration increases in ERK1/2, JNK and PKB phosphorylation in undifferentiated and differentiated SH-SY5Y cells. No increases in p38 MAPK phosphorylation were observed following H(2)O(2) treatment. The phosphatidylinositol 3-kinase (PI-3K) inhibitors wortmannin and LY 294002 ((2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one) inhibited H(2)O(2)-induced increases in ERK1/2 and PKB phosphorylation. Furthermore, H(2)O(2)-mediated increases in ERK1/2 activation were sensitive to the MAPK kinase 1 (MEK1) inhibitor PD 98059 (2'-amino-3'-methoxyflavone), whereas JNK responses were blocked by the JNK inhibitor SP 600125 (anthra[1-9-cd]pyrazol-6(2H)-one). Treatment of SH-SY5Y cells with H(2)O(2) (1 mM; 16 h) significantly increased the release of lactate dehydrogenase (LDH) into the culture medium indicative of a decrease in cell viability. Pre-treatment with wortmannin, SP 600125 or SB 203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole; p38 MAPK inhibitor) had no effect on H(2)O(2)-induced LDH release from undifferentiated or differentiated SH-SY5Y cells. In contrast, PD 98059 and LY 294002 significantly decreased H(2)O(2)-induced cell death in both undifferentiated and differentiated SH-SY5Y cells. In conclusion, we have shown that H(2)O(2) stimulates robust increases in ERK1/2, JNK and PKB in undifferentiated and differentiated SH-SY5Y cells. Furthermore, the data presented clearly suggest that inhibition of the ERK1/2 pathway protects SH-SY5Y cells from H(2)O(2)-induced cell death.

Peripheral markers of apoptosis in Parkinson's disease: the effect of dopaminergic drugs

In this study, we measured the lymphocyte levels of proteins involved in apoptosis regulation, such as Bcl-2, the peripheral benzodiazepine receptor (PBR), caspase-3, and Cu/Zn superoxide dismutase (Cu/Zn SOD), in patients with Parkinson's disease (PD), either untreated or under therapy with dopaminergic agents (l-Dopa alone or l-dopa + dopamine agonists) and in healthy volunteers. All PD groups showed increased activity of caspase-3, compared to controls, particularly those under treatment only with l-Dopa. In this latter group, the increase in caspase-3 activity was also paralleled by an increase in the concentration of Cu/Zn SOD. In addition, patients taking l-Dopa + dopamine agonists showed marked decrease in Bcl-2 levels and increased PBR expression, which seems in keeping with the hypothesis that PBR may be functionally related to Bcl-2. In conclusion, we found clear modifications in the levels of proteins involved in the control of apoptosis in lymphocytes of PD patients. These changes were disease related but also modulated by the pharmacological treatment, which confirms the potential role of apoptosis in PD pathogenesis and the modulatory influence of dopaminergic agents.

A novel mechanism for pergolide-induced neuroprotection: inhibition of NF-κB nuclear translocation

We previously demonstrated that the dopaminergic agonist pergolide, independently from its DA agonist activity, can exert neuroprotective effects against cell death induced in SH-SY5Y neural cells by H(2)O(2) treatment. Since oxidative stress in SH-SY5Y neural cells is known to activate the NF-kappaB pathway we tested the hypothesis that pergolide may interfere with NF-kappaB activity. Based on Western blot analysis and immunocytochemistry, pergolide was found to prevent H(2)O(2)-induced apoptosis by inhibiting NF-kappaB nuclear translocation and activation of p53 signalling pathway. Similarly, the cell-permeable SN50 peptide, which is known to block NF-kappaB nuclear translocation, prevented both H(2)O(2)-induced p53 expression and apoptosis. The mechanism of action of pergolide responsible for neuroprotection differed from that of antioxidants. In fact, Vitamin E, contrary to pergolide and SN50, rescued neuronal cells from H(2)O(2)-induced apoptosis acting upstream NF-kappaB activation, as demonstrated by the prevention of H(2)O(2)-induced IkappaB degradation. These data suggest a novel site of action of pergolide that may account for additional pharmacological properties of this drug.

Plasma and CSF markers of oxidative stress are increased in Parkinson's disease and influenced by antiparkinsonian medication

We determined systemic oxidative stress in Parkinson's disease (PD) patients, patients with other neurological diseases (OND) and healthy controls by measurement of in vitro lipoprotein oxidation and levels of hydro- and lipophilic antioxidants in plasma and cerebrospinal fluid (CSF). Additionally, we investigated the influence of levodopa (LD) and dopamine agonist therapy (DA) on the oxidative status in PD patients. We found increased oxidative stress, seen as higher levels of lipoprotein oxidation in plasma and CSF, decrease of plasma levels of protein sulfhydryl (SH) groups and lower CSF levels of alpha-tocopherol in PD patients compared to OND patients and controls. Levodopa treatment did not significantly change the plasma lipoprotein oxidation but LD monotherapy tended to result in an increase of autooxidation and in a decrease of plasma antioxidants with significance for ubiquinol-10. DA monotherapy was significantly associated with higher alpha-tocopherol levels. Patients with DA monotherapy or co-medication with DA showed a trend to lower lipoprotein oxidation. These data support the concept of oxidative stress as a factor in the pathogenesis of PD and might be an indicator of a potential prooxidative role of LD and a possible antioxidative effect of DA in PD treatment.

Cabergoline protects SH-SY5Y neuronal cells in an in vitro model of ischemia

Dopamine receptor agonists are protective in different models of neurodegeneration by both receptor-dependent and -independent mechanisms. We used SH-SY5Y cells, differentiated into neuron-like type, to evaluate if cabergoline, a dopamine D2 receptor agonist endowed with anti-oxidant activity, protects the cells against ischemia (oxygen-glucose deprivation model). Cabergoline protected the cells from ischemia-induced cell death in a concentration-dependent manner (EC(50)=1.2 microM), as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) release, and fluorescein diacetate-propidium iodide staining. This effect, observed even when the drug was added after oxygen-glucose deprivation, was not mediated by either dopamine D2 receptor activation or anti-apoptotic Bcl-2 protein over-expression (Western blotting analysis), but was linked to a reduction in cellular free radical loading (2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining) and membrane lipid peroxidation (thiobarbituric acid-reacting test). In conclusion, cabergoline protects in vitro neurons against ischemia-induced cell death, suggesting its possible use in the therapy of other neurodegenerative diseases in addition to Parkinson's disease.

Cabergoline prevents necrotic neuronal death in an in vitro model of oxidative stress

To study if cabergoline, a long-lasting specific dopamine D2 receptor agonist, has neuroprotective effects against oxidative stress, we exposed (3 h) SH-SY5Y human neuroblastoma cells to tert-butylhydroperoxide (t-BOOH; 500 microM). t-BOOH caused a 42+/-4% neuronal death, which was prevented by cabergoline (2 h before) in a concentration-dependent manner (EC(50): 1.24 microM). This effect was not antagonised by haloperidol (concentration up to 10 microM), and was associated with an increased availability of intracellular GSH contents (+30+/-11%) and a decrease in the membrane lipid peroxidation (-23+/-9%). Our data suggest that cabergoline has neuroprotective effects useful for Parkinson's disease therapy.