title: Dopamine exacerbates mutant Huntingtin toxicity via oxidative-mediated inhibition of autophagy in SH-SY5Y neuroblastoma cells: Beneficial effects of anti-oxidant therapeutics.
abstract: Neuronal cell death in Huntington's Disease (HD) is associated with the abnormal expansions of a polyglutamine (polyQ) tract in the huntingtin protein (Htt) at the N-terminus that causes the misfolding and aggregation of the mutated protein (mHtt). Autophagy-lysosomal degradation of Htt aggregates may protect the neurons in HD. HD patients eventually manifest parkinsonian-like symptoms, which underlie defects in the dopaminergic system. We hypothesized that dopamine (DA) exacerbates the toxicity in affected neurons by over-inducing an oxidative stress that negatively impinges on the autophagy clearance of mHtt and thus precipitating neuronal cell death. Here we show that the hyper-expression of mutant (>113/150) polyQ Htt is per se toxic to dopaminergic human neuroblastoma SH-SY5Y cells, and that DA exacerbates this toxicity leading to apoptosis and secondary necrosis. DA toxicity is mediated by ROS production (mainly anion superoxide) that elicits a block in the formation of autophagosomes. We found that the pre-incubation with N-Acetyl-l-Cysteine (a quinone reductase inducer) or Deferoxamine (an iron chelator) prevents the generation of ROS, restores the autophagy degradation of mHtt and preserves the cell viability in SH-SY5Y cells expressing the polyQ Htt and exposed to DA. The present findings suggest that DA-induced impairment of autophagy underlies the parkinsonism in HD patients. Our data provide a mechanistic explanation of the DA toxicity in dopaminergic neurons expressing the mHtt and support the use of anti-oxidative stress therapeutics to restore protective autophagy in order to slow down the neurodegeneration in HD patients.
authors.affiliation: Laboratory of Molecular Pathology, Department of Health Sciences, Università del Piemonte Orientale "A. Avogadro", Novara, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Vidoni
authors.affiliation: Laboratory of Molecular Pathology, Department of Health Sciences, Università del Piemonte Orientale "A. Avogadro", Novara, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Castiglioni
authors.affiliation: Laboratory of Molecular Pathology, Department of Health Sciences, Università del Piemonte Orientale "A. Avogadro", Novara, Italy.
authors.forename: Christian
authors.initials: C
authors.lastname: Seca
authors.affiliation: Laboratory of Molecular Pathology, Department of Health Sciences, Università del Piemonte Orientale "A. Avogadro", Novara, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Secomandi
authors.affiliation: 2° Division of Neurology, Department of Medical Surgical, Neurological, Metabolic Sciences, and Aging, Second University of Naples, Naples, Italy; InterUniversity Center for Research in Neurosciences, Second University of Naples, Naples, Italy. Electronic address: marina.melone@unina2.it.
authors.forename: Mariarosa A B
authors.initials: MA
authors.lastname: Melone
authors.affiliation: Laboratory of Molecular Pathology, Department of Health Sciences, Università del Piemonte Orientale "A. Avogadro", Novara, Italy; InterUniversity Center for Research in Neurosciences, Second University of Naples, Naples, Italy. Electronic address: ciro.isidoro@med.uniupo.it.
authors.forename: Ciro
authors.initials: C
authors.lastname: Isidoro
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D006816:Huntington Disease / Q000188:drug therapy / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*
chemical_list: D000975:Antioxidants; D009419:Nerve Tissue Proteins; D016877:Oxidants; D004298:Dopamine
keywords: Anti-oxidant; Autophagy; Dopaminergic neurons; Huntington; Neurodegeneration; Parkinson