title: Ornithine and Homocitrulline Impair Mitochondrial Function, Decrease Antioxidant Defenses and Induce Cell Death in Menadione-Stressed Rat Cortical Astrocytes: Potential Mechanisms of Neurological Dysfunction in HHH Syndrome.
abstract: Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is caused by deficiency of ornithine translocase leading to predominant tissue accumulation and high urinary excretion of ornithine (Orn), homocitrulline (Hcit) and ammonia. Although affected patients commonly present neurological dysfunction manifested by cognitive deficit, spastic paraplegia, pyramidal and extrapyramidal signs, stroke-like episodes, hypotonia and ataxia, its pathogenesis is still poorly known. Although astrocytes are necessary for neuronal protection. Therefore, in the present study we investigated the effects of Orn and Hcit on cell viability (propidium iodide incorporation), mitochondrial function (thiazolyl blue tetrazolium bromide-MTT-reduction and mitochondrial membrane potential-ΔΨm), antioxidant defenses (GSH) and pro-inflammatory response (NFkB, IL-1β, IL-6 and TNF-α) in unstimulated and menadione-stressed cortical astrocytes that were previously shown to be susceptible to damage by neurotoxins. We first observed that Orn decreased MTT reduction, whereas both amino acids decreased GSH levels, without altering cell viability and the pro-inflammatory factors in unstimulated astrocytes. Furthermore, Orn and Hcit decreased cell viability and ΔΨm in menadione-treated astrocytes. The present data indicate that the major compounds accumulating in HHH syndrome impair mitochondrial function and reduce cell viability and the antioxidant defenses in cultured astrocytes especially when stressed by menadione. It is presumed that these mechanisms may be involved in the neuropathology of this disease.
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos No 2600 - Anexo, Porto Alegre, RS, 90035-003, Brazil.
authors.forename: Ângela
authors.initials: Â
authors.lastname: Zanatta
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos No 2600 - Anexo, Porto Alegre, RS, 90035-003, Brazil.
authors.forename: Marília Danyelle Nunes
authors.initials: MD
authors.lastname: Rodrigues
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos No 2600 - Anexo, Porto Alegre, RS, 90035-003, Brazil.
authors.forename: Alexandre Umpierrez
authors.initials: AU
authors.lastname: Amaral
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos No 2600 - Anexo, Porto Alegre, RS, 90035-003, Brazil.
authors.forename: Débora Guerini
authors.initials: DG
authors.lastname: Souza
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos No 2600 - Anexo, Porto Alegre, RS, 90035-003, Brazil.
authors.forename: André
authors.initials: A
authors.lastname: Quincozes-Santos
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos No 2600 - Anexo, Porto Alegre, RS, 90035-003, Brazil. mwajner@ufrgs.br.|Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil. mwajner@ufrgs.br.
authors.forename: Moacir
authors.initials: M
authors.lastname: Wajner
mesh_terms: D026923:Amino Acid Transport Systems, Basic / Q000187:drug effects; D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002956:Citrulline / Q000031:analogs & derivatives* / Q000494:pharmacology; D022124:Hyperammonemia / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D009952:Ornithine / Q000172:deficiency / Q000378:metabolism / Q000494:pharmacology*; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D056806:Urea Cycle Disorders, Inborn / Q000188:drug therapy / Q000378:metabolism
chemical_list: D026923:Amino Acid Transport Systems, Basic; D000975:Antioxidants; D014409:Tumor Necrosis Factor-alpha; C041356:ornithine transporter; C001352:homocitrulline; D002956:Citrulline; D009952:Ornithine
keywords: Astrocytes; HHH syndrome; Homocitrulline; Mitochondrial function; Ornithine; Oxidative stress