alpha-synuclein and sapropterin

Gastrointestinal (GI) motility dysfunction is the most common non-motor symptom of Parkinson's disease (PD). Studies have indicated that GI motility functions are impaired before the onset of PD.. To investigate the underlying mechanism of PD-induced GI dysmotility in MPTP (1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine)-induced animal model.. C57BL/6 mice were administered with or without a selective dopamine neurotoxin, MPTP, to induce parkinsonian symptoms. In addition to in vivo studies, in vitro experiments were also conducted in colon specimens using l-methyl-4-phenylpyridinium (MPP. MPTP-induced PD mice showed decreased expression of nuclear factor erythroid 2-related factor (Nrf2) and its target phase II genes in gastric and colon neuromuscular tissues. Decreased levels of tetrahydrobiopterin (BH

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; 1-Methyl-4-phenylpyridinium; alpha-Synuclein; Animals; Biopterins; Blotting, Western; Colon; Constipation; Disease Models, Animal; Enzyme Inhibitors; Gastric Emptying; Gastrointestinal Motility; Gene Expression Regulation; Heme Oxygenase-1; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; MPTP Poisoning; NF-E2-Related Factor 2; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase Type I; Parkinson Disease; Parkinsonian Disorders; Tyrosine 3-Monooxygenase

Parkinson disease (PD) is a multifactorial disease resulting in preferential death of the dopaminergic neurons in the substantia nigra. Studies of PD-linked genes and toxin-induced models of PD have implicated mitochondrial dysfunction, oxidative stress, and the misfolding and aggregation of α-synuclein (α-syn) as key factors in disease initiation and progression. Many of these features of PD may be modeled in cells or animal models using the neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)). Reducing oxidative stress and nitric oxide synthase (NOS) activity has been shown to be protective in cell or animal models of MPP(+) toxicity. We have previously demonstrated that siRNA-mediated knockdown of α-syn lowers the activity of both dopamine transporter and NOS activity and protects dopaminergic neuron-like cells from MPP(+) toxicity. Here, we demonstrate that α-syn knockdown and modulators of oxidative stress/NOS activation protect cells from MPP(+)-induced toxicity via postmitochondrial mechanisms rather than by a rescue of the decrease in mitochondrial oxidative phosphorylation caused by MPP(+) exposure. We demonstrate that MPP(+) significantly decreases the synthesis of the antioxidant and obligate cofactor of NOS and TH tetrahydrobiopterin (BH4) through decreased cellular GTP/ATP levels. Furthermore, we demonstrate that RNAi knockdown of α-syn results in a nearly twofold increase in GTP cyclohydrolase I activity and a concomitant increase in basal BH4 levels. Together, these results demonstrate that both mitochondrial activity and α-syn play roles in modulating cellular BH4 levels.

Topics: 1-Methyl-4-phenylpyridinium; Adenosine Triphosphate; alpha-Synuclein; Biopterins; Cell Line, Tumor; Dopaminergic Neurons; Gene Expression Regulation; GTP Cyclohydrolase; Guanosine Triphosphate; Humans; Mitochondria; Models, Biological; Oxidative Phosphorylation; Parkinson Disease; RNA, Small Interfering

The neurotoxicity of dopamine (DA) quinones as dopaminergic neuron-specific oxidative stress is considered to play a role in the pathogenesis and/or progression of Parkinson's disease (PD), since DA quinones conjugate with several key PD pathogenic molecules (e.g., tyrosine hydroxylase, alpha-synuclein and parkin) to form protein-bound quinone (quinoprotein) and consequently inhibit their functions. Zonisamide (ZNS) is used as an anti-epileptic agent but also improved the cardinal symptoms of PD in recent clinical trials in Japan. To evaluate the effects of ZNS on excess cytosolic free DA-induced quinone toxicity, we examined changes in DA quinone-related indices after ZNS treatment both in in vitro cell-free system and in cultured cells. Co-incubation of DA and ZNS in a cell-free system caused conversion of DA to stable melanin via formation of DA-semiquinone radicals and DA chrome. Long-term (5 days) treatment with ZNS decreased quinoprotein and increased DA/DOPA chromes in dopaminergic CATH.a cells. ZNS significantly inhibited quinoprotein formation induced by treatment with tetrahydrobiopterin and ketanserin that elevate cytosolic free DA in the cells. Our results suggest that the novel anti-parkinsonian agent ZNS possesses preventing effects against DA quinone formation induced by excess amount of cytosolic DA outside the synaptic vesicles.

Topics: alpha-Synuclein; Animals; Antioxidants; Biopterins; Cell-Free System; Cells, Cultured; Cytosol; Dopamine; Isoxazoles; Ketanserin; Lewy Bodies; Melanins; Mice; Neurons; Oxidative Stress; Parkinson Disease; Quinones; Ubiquitin-Protein Ligases; Zonisamide