Investigating the therapeutic potential of transcranial direct current stimulation in an experimental Parkinson's model through glutamate pathway.

The principal causative pathology of Parkinson disease is the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta projecting to the striatum in the brain. The information regarding the expression of neuropeptides in parkinsonism is very limited. Here we have elucidated striatal neuropeptide mechanisms in experimental parkinsonism using the unilateral 6-hydroxydopamine model to degenerate dopamine neurons. A thoroughly controlled sample preparation technique together with a peptidomics approach and targeted neuropeptide sequence collections enabled sensitive detection, identification, and relative quantitation of a great number of endogenous neuropeptides. Previously not recognized alterations in neuropeptide levels were identified in the unilateral lesioned mice with or without subchronic 3,4-dihydroxy-L-phenylalanine administration, the conventional treatment of Parkinson disease. Several of these peptides originated from the same precursor such as secretogranin-1, somatostatin, prodynorphin, and cholecystokinin. Disease-related biotransformation of precursors into individual peptides was observed in the experimental model of Parkinson disease. Several previously unreported potentially biologically active peptides were also identified from the striatal samples. This study provides further evidence that neuropeptides take part in mediating the central nervous system failure associated with Parkinson disease.

Docosahexaenoic acid (DHA) has been shown to have beneficial effects on Parkinson's disease (PD). The aim of this study was to investigate if the DHA acts on neurons of substantia nigra (SN) by phosphorylation of neuronal nitric oxide synthase (nNOS) in an experimental mouse model of PD. An experimental model of PD was created by intraperitoneal injections (4 × 20 mg/kg) of the neurotoxin 1-methyl-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). Three-month-old male C57BL/6 mice were randomly divided into four groups as follows: control (C), DHA-treated (DHA), MPTP-injected (MPTP) and DHA-treated and MPTP-injected (DHA + MPTP). DHA (36 mg/kg/day) was administered daily by gavage for four weeks. Motor activity of the mice was evaluated with pole, locomotor activity and rotarod tests. Caspase-3 activity, nitrate/nitrite and 4-hydroxynonenal (4-HNE) levels were determined by spectrophotometric assays. Immunohistochemistry was used to localize and assess the expressions of tyrosine hydroxylase (TH), nNOS and phospho-nNOS (p-nNOS) in SN. An increased return and total down time in the MPTP group was observed in the pole test, while DHA treatment decreased both parameters. The ambulatory activity, total distance and total locomotor activities were decreased in the MPTP group, whereas they were increased by DHA treatment. MPTP-treated animals exhibited shorter time on the rod test which was significantly increased by DHA treatment. DHA administration significantly decreased 4-HNE and nitrate/nitrite levels of SN supernatants and protected the TH (+) dopaminergic neurons of SN in the DHA + MPTP group compared to the MPTP group. DHA treatment significantly decreased nNOS and increased p-nNOS immunoreactivities in the DHA + MPTP group compared to the MPTP group. These results indicate that DHA treatment protects dopaminergic neurons in SN via increasing nNOS serine 852 phosphorylation in the experimental mice model of PD.

The influence and the mechanism of docosahexaenoic acid on a mouse model of Parkinson’s disease

Supersensitization of neurochemical responses by L-DOPA and dopamine receptor agonists in the striatum of experimental Parkinson's disease model rats

Ginsenoside Rd (GSRd), one of the main active monomer compounds from the medical plant Panax ginseng, has been shown to promote neuronal survival in models of ischemic cerebral damage. As an extending study, here we examined whether GSRd could exert a beneficial effect in an experimental Parkinson disease (PD) model in vitro, in which SH-SY5Y cells were injured by 1-methyl-4-phenylpyridinium (MPP+), an active metabolic product of the classical Parkinsonian toxin1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Our results, from the addition of different concentrations of GSRd (1, 10 and 50 μM), showed that GSRd at 1 and 10 μM could significantly attenuate MPP+-induced cell death. This protective effect may be ascribed to its ability to reduce intracellular reactive oxygen species levels, enhance antioxidant enzymatic activities, preserve the activity of respiratory complex I, stabilize the mitochondrial membrane potential and increase intracellular ATP levels. Additionally, the PI3K/Akt survival-signaling pathway was also involved in the protective effect of GSRd. Finally, using a mouse PD model in vivo, we also found that GSRd obviously reversed the loss of tyrosine hydroxylase-positive cells in substanitia nigra induced by MPTP. Thus, our findings demonstrated that GSRd showed a significant neuro-protective effect against experimental PD models, which may involve its antioxidant effects and mitochondrial function preservation.

Stem-leaf saponins from Panax notoginseng (SLSP) comprise numerous PPD-type saponins with diverse pharmacological properties; however, their role in Parkinson's disease (PD), characterized by microglia-mediated neuroinflammation, remains unclear. This study evaluated the effects of SLSP on suppressing microglia-driven neuroinflammation in experimental PD models, including the 1-methyl-4-phenylpyridinium (MPTP)-induced mouse model and lipopolysaccharide (LPS)-stimulated BV-2 microglia. Our findings revealed that SLSP mitigated behavioral impairments and excessive microglial activation in models of PD, including MPTP-treated mice. Additionally, SLSP inhibited the upregulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX2) and attenuated the phosphorylation of PI3K, protein kinase B (AKT), nuclear factor-κB (NFκB), and inhibitor of NFκB protein α (IκBα) both in vivo and in vitro. Moreover, SLSP suppressed the production of inflammatory markers such as interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α) in LPS-stimulated BV-2 cells. Notably, the P2Y2R agonist partially reversed the inhibitory effects of SLSP in LPS-treated BV-2 cells. These results suggest that SLSP inhibit microglia-mediated neuroinflammation in experimental PD models, likely through the P2Y2R/PI3K/AKT/NFκB signaling pathway. These novel findings indicate that SLSP may offer therapeutic potential for PD by attenuating microglia-mediated neuroinflammation.

Parkinson's disease (PD) is one of the most aggressive neurodegenerative diseases and characterized by the loss of dopamine-sensitive neurons in the substantia nigra region of the brain. There is no any definitive treatment to completely cure PD and existing treatments can only ease the symptoms of the disease. Boron nitride nanoparticles have been extensively studied in nano-biological studies and researches showed that it can be a promising candidate for PD treatment with its biologically active unique properties. In the present study, it was aimed to investigate ameliorative effects of hexagonal boron nitride nanoparticles (hBNs) against toxicity of 1-methyl-4-phenylpyridinium (MPP+) in experimental PD model. Experimental PD model was constituted by application of MPP+ to differentiated pluripotent human embryonal carcinoma cell (Ntera-2, NT-2) culture in wide range of concentrations (0.62 to 2mM). Neuroprotective activity of hBNs against MPP+ toxicity was determined by cell viability assays including MTT and LDH release. Oxidative alterations by hBNs application in PD cell culture model were investigated using total antioxidant capacity (TAC) and total oxidant status (TOS) tests. The impacts of hBNs and MPP+ on nuclear integrity were analyzed by Hoechst 33258 fluorescent staining method. Acetylcholinesterase (AChE) enzyme activities were determined by a colorimetric assay towards to hBNs treatment. Cell death mechanisms caused by hBNs and MPP+ exposure was investigated by flow cytometry analysis. Experimental results showed that application of hBNs increased cell viability in PD model against MPP+ application. TAS and TOS analysis were determined that antioxidant capacity elevated after hBNs applications while oxidant levels were reduced. Furthermore, flow cytometric analysis executed that MPP+ induced apoptosis was prevented significantly (p < 0.05) after application with hBNs. In a conclusion, the obtained results indicated that hBNs have a huge potential against MPP+ toxicity and can be used in PD treatment as novel neuroprotective agent and drug delivery system.

Moutan cortex, Angelica Dahurica root, and Bupleurum root are traditional herbal medicines used in Asian countries to treat various diseases caused by oxidative stress or inflammation. Parkinson’s disease (PD) has been associated with mitochondrial dysfunction, but no effective treatment for mitochondrial dysfunction has yet been identified. In this study we investigated the neuroprotective effects of the triple herbal extract DA-9805 in experimental models of PD. DA-9805 was prepared by extracting three dried plant materials (Moutan cortex, Angelica Dahurica root, and Bupleurum root in a 1:1:1 mixture) with 90% ethanol on a stirring plate for 24 h at room temperature and fingerprinted using high-performance liquid chromatography. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its active metabolite 1-methyl-4-phenylpyridinium (MPP+), which both exert neurotoxic effects on dopaminergic neurons by inhibiting mitochondrial oxidative phosphorylation (OXPHOS) complex I, were used to make experimental models of PD. In MPP+-treated SH-SY5Y cells, DA-9805 ameliorated the suppression of tyrosine hydroxylase expression and mitochondrial damage on OXPHOS complex 1 activity, mitochondrial membrane potential, reactive oxygen species (ROS) generation, and oxygen consumption rate. In the MPTP-induced subacute PD model mice, oral administration of DA-9805 recovered dopamine content as well as bradykinesia, as determined by the rotarod test. DA-9805 protected against neuronal damage in the substantia nigra pars compacta (SNpc) and striatum. In both in vitro and in vivo models of PD, DA-9805 normalized the phosphorylation of AKT at S473 and T308 on the insulin signaling pathway and the expression of mitochondria-related genes. These results demonstrate that the triple herbal extract DA-9805 showed neuroprotective effects via alleviating mitochondria damage in experimental models of PD. We propose that DA-9805 may be a suitable candidate for disease-modifying therapeutics for PD.

Sphingosine kinases (Sphk1/2 EC 2.7.1.91) are responsible for synthesis of sphingosine-1-phosphate (S1P) and for regulation of the bioactive sphingolipids homeostasis. Sphingosine-1-phosphate can act as a potent messenger in an autocrine/paracrine manner through five specific G protein-coupled receptors (GPCR) S1P1-5. This sphingolipid is involved in the mechanism of transcription, mitochondrial function, neuronal viability and degeneration. Until now the involvement of Sphk1/2 and sphingolipid alterations in Parkinson's disease (PD) remains unknown. Recent studies have indicated the role of sphingolipids in the regulation of alpha-synuclein (ASN) in the PD brain. Our latest data demonstrated significant inhibition of Sphk1 gene expression and activity in an in vitro PD model, induced by 1-methyl-4-phenylpyridinium (MPP+). The aim of this study was to investigate the role of Sphks inhibition in ASN secretion and in the molecular mechanism of neuronal death in the PD model. Our study was carried out using neuronal dopaminergic SH-SY5Y control cells, transfected with the human gene for ASN or with an empty vector. These cells were treated with MPP+ (1-3 mM), which represents an experimental PD model, or with the Sphks inhibitor (1-5 µM SKI II) for 3-24 h. Our data indicated that MPP+ (3 mM) induced significant alterations of Sphks and S1P lyase (SPL) gene expression. Reduced activity of Sphk1 and Sphk2 in the cytosolic fraction and in the crude nuclear fraction, respectively, was observed. Sphks inhibition evoked enhancement of ASN secretion, suppression of PI3K/Akt phosphorylation and activation of gene expression for the pro-apoptotic Bcl-2 proteins Bax and BH3-only protein Harakiri. Moreover, a lower level of cytochrome c in the mitochondrial fraction and caspase-dependent degradation of DNA-bound enzyme poly(ADP-ribose) polymerase (PARP-1) were observed. The caspase inhibitor (20 µM Z-VAD-FMK) significantly enhanced neuronal cell viability in MPP+ oxidative stress. However, exogenous S1P (1 µM) exerted a more efficient neuroprotective effect as compared to Z-VAD-FMK. In summary, these data indicated that Sphk1 inhibition plays an important role in caspase-dependent apoptotic neuronal death in an experimental PD model.

Depressed contractile function and adrenergic responsiveness of cardiac myocytes in an experimental model of Parkinson disease, the MPTP-treated mouse

l-DOPA inhibits spontaneous acetylcholine release from the striatum of experimental Parkinson's model rats

Testosterone modulates respiratory control but does not exert neuroprotective effects in a Parkinson's disease model.

Parkinson's disease (PD) is one of the most severe socially important neurodegenerative disorders. The loss of dopaminergic neurons of the nigrostriatal sys� tem is considered to be a key aspect of the pathogene� sis of PD. The first clinical symptoms of the disease including motor dysfunction develop many years after the onset of the pathological process, which is believed to be a consequence of the brain plasticity (or com� pensatory mechanisms). However, when 50-70% of dopaminergic neurons in the substantia nigra (SN) are degenerated and the striatal dopamine (DA) is reduced by 80% those compensatory mechanisms lose the ability to mask motor impairments (1-5). Conse� quently, preclinical diagnosis of the masked patholog� ical process is of great importance because it may become the basis for preventive neuroprotective ther� apy. The therapeutic approach in this case can be aimed at slowingdown the process of neuronal loss and thus extending the preclinical stages of the disease or, in other words, the period of patient's comfortable state. Currently, the methods of preclinical diagnosis of PD including positron emission tomography and singlephoton emission computed tomography are very costly and technically challenging, which results in their limited use in mass health screening. The purpose of this study was to experimentally develop a "provocation test" that would allow to diag� nose PD at its preclinical stage. This approach is based on the temporary and reversible "impairment" of dopaminergic nigrostriatal system by pharmacological inhibition of DA synthesis to the threshold level, where the first motor symptoms can be observed. Moreover, it is necessary to use the minimal dose of the DA inhibitor that would cause motor abnormali� ties in an experimental model of presymptomatic PD, but would not affect the behavior of normal animals in the control. Experiments were performed on male C57BL/6JSto mice (2.5� to 3�monthold animals with a body weight of 22-26 g) using the model of PD at a preclinical stage that was developed in our laboratory (6). Accord� ing to this model, the mice (n = 42) were subcutane� ously injected with the neurotoxin 1�methyl�4�phe� nyl�1,2,3,6�tetrahydropyridine (MPTP) at a single dose of 12 mg/kg in 0.9% NaCl. The injection was repeated twice at a 2�h interval. Animals in the control group (n = 42) were administered with 0.9% NaCl in a similar way. The model is characterized by the absence of any motor function impairment, the loss of 26% in dopaminergic neurons SN 59% of axon terminals in the striatum, and a 60% reduction of the striatal level of DA. The locomotor and exploratory activities of the animals were assessed 15 days after MPTP or saline administration during the 6�min period in the "open� field" test using an OptoVarimex�3 system (Columbus Instruments International, United States). Based on the data obtained, all animals were grouped into two subgroups with equal average and variance values; the subgroups were designated as NaCl 1 and NaCl 2 , MPTP 1 and MPTP 2 , respectively.

Pharmacological interactions between adenosine A2A receptor antagonists and different neurotransmitter systems

Nonmotor Symptoms in Experimental Models of Parkinson's Disease.