title: Neurotoxicity of Methylmercury in Isolated Astrocytes and Neurons: the Cytoskeleton as a Main Target.
abstract: In the present work, we focused on mechanisms of methylmercury (MeHg) toxicity in primary astrocytes and neurons of rats. Cortical astrocytes and neurons exposed to 0.5-5 μM MeHg present a link among morphological alterations, glutathione (GSH) depletion, glutamate dyshomeostasis, and cell death. Disrupted neuronal cytoskeleton was assessed by decreased neurite length and neurite/neuron ratio. Astrocytes presented reorganization of actin and glial fibrillary acidic protein (GFAP) networks and reduced cytoplasmic area. Glutamate uptake and Na+K+ATPase activity in MeHg-treated astrocytes were preserved; however, downregulated EAAC1-mediated glutamate uptake was associated with impaired Na+K+ATPase activity in neurons. Oxidative imbalance was found in astrocytes and neurons through increased 2'7'-dichlorofluorescein (DCF) production and misregulated superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GPX) activities. Glutathione (GSH) levels were downregulated in both astrocytes and neurons. MeHg reduced neuronal viability and induced caspase 3-dependent apoptosis together with downregulated PI3K/Akt pathway. In astrocytes, necrotic death was associated with increased TNF-α and JNK/MAPK activities. Cytoskeletal remodeling and cell death were fully prevented in astrocytes and neurons by GSH, but not melatonin or Trolox supplementation. These findings support a role for depleted GSH in the cytotoxicity of MeHg leading to disruption of the cytoskeleton and cell death. Moreover, in neurons, glutamate antagonists also prevented cytoskeletal disruption and neuronal death. We propose that cytoskeleton is an end point in MeHg cytotoxicity. Oxidative imbalance and glutamate mechanisms mediate MeHg cytoskeletal disruption and apoptosis in neurons. Otherwise, redox imbalance and glutamate-independent mechanisms disrupted the cytoskeleton and induced necrosis in MeHg-exposed astrocyte.
authors.affiliation: Laboratório de Neuroproteção e Doenças Metabólicas, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Paula
authors.initials: P
authors.lastname: Pierozan
authors.affiliation: Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Helena
authors.initials: H
authors.lastname: Biasibetti
authors.affiliation: Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Felipe
authors.initials: F
authors.lastname: Schmitz
authors.affiliation: Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Helena
authors.initials: H
authors.lastname: Ávila
authors.affiliation: Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Carolina Gonçalves
authors.initials: CG
authors.lastname: Fernandes
authors.affiliation: Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.|Laboratório do Citoesqueleto, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Regina
authors.initials: R
authors.lastname: Pessoa-Pureur
authors.affiliation: Laboratório de Neuroproteção e Doenças Metabólicas, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. wyse@ufrgs.br.|Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. wyse@ufrgs.br.|Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP, Porto Alegre, RS, 90035-003, Brazil. wyse@ufrgs.br.
authors.forename: Angela T S
authors.initials: ATS
authors.lastname: Wyse
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D008767:Methylmercury Compounds / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D008767:Methylmercury Compounds; D017382:Reactive Oxygen Species; D019869:Phosphatidylinositol 3-Kinases
keywords: Cell death; Cytoskeleton; Methylmercury; Na+K+ATPase; Oxidative stress