title: Involvement of astrocytic CYP1A1 isoform in the metabolism and toxicity of the alkaloid pyrrolizidine monocrotaline.
abstract: Monocrotaline (MCT) and its pyrrole derivative, dehydromonocrotaline (DHMC), interact with molecular targets in cells of the central nervous system. DHMC presents higher toxicity than MCT indicating that its metabolism of MCT is a critical step of this alkaloid toxicity. This study sought to elucidate the metabolism and the toxicity of MCT in C6 astrocyte cell line and primary cultures of rat astrocytes by investigating metabolic enzymatic mechanisms of the cytochrome P450 (CYP) system and conjugation with glutathione. Treatment with omeprazole (OMP) (20 μM), a non-specific inducer of CYP450 induced approximately 10-fold increase in CYP1A1 activity after 2 h of treatment. Similarly, the 7-Ethoxyresorufin-O-deethylase (EROD) activity was induced by treatment with MCT (100-500 μM), indicating that the P450 CYP1A1 isoform was active and involved in the metabolism of MCT. Analysis of conjugation with glutathione showed a significant depletion of GSH after MCT (500 μM) treatment, and this was partially reversed by pretreatment with a P450 inhibitor (cimetidine 100 μM). These results suggest that not only the alkaloid MCT but, also its metabolite may deplete GSH. Rosenfeld staining showed intense vacuolization after MCT treatment, which was partially inhibited in the presence of a P450 activator. MTT test showed that association of MCT with OMP induced a reduction in cell viability in C6 and primary astrocytic cells. These results demonstrate that MCT is metabolized by astrocytic CYP1A1 to generate metabolites that can deplete GSH. Moreover, changes in the activity of the P450 enzymes interfere with the cytotoxic effects induced by the alkaloid.
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil.
authors.forename: Ravena P
authors.initials: RP
authors.lastname: Nascimento
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil.
authors.forename: Joana L
authors.initials: JL
authors.lastname: Oliveira
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil.
authors.forename: José Leilton C
authors.initials: JLC
authors.lastname: Carvalho
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil.
authors.forename: William A
authors.initials: WA
authors.lastname: Santos
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil.
authors.forename: Thyago Rubens C
authors.initials: TRC
authors.lastname: Pires
authors.affiliation: Laboratório de Toxicologia, Hospital de Medicina Veterinária Renato de Medeiros Neto, Universidade Federal da Bahia, Brazil.
authors.forename: Maria José M
authors.initials: MJM
authors.lastname: Batatinha
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil.
authors.forename: Ramon S
authors.initials: RS
authors.lastname: El-Bachá
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil.
authors.forename: Victor Diógenes A
authors.initials: VDA
authors.lastname: Silva
authors.affiliation: Laboratório de Neuroquímica e Biologia Celular, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Brazil. Electronic address: costasl@ufba.br.
authors.forename: Silvia L
authors.initials: SL
authors.lastname: Costa
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D029864:Crotalaria / Q000737:chemistry; D019363:Cytochrome P-450 CYP1A1 / Q000187:drug effects / Q000378:metabolism*; D005978:Glutathione / Q000187:drug effects; D016686:Monocrotaline / Q000031:analogs & derivatives / Q000378:metabolism* / Q000633:toxicity*; D009853:Omeprazole / Q000494:pharmacology; D020033:Protein Isoforms / Q000737:chemistry; D051381:Rats
chemical_list: D020033:Protein Isoforms; C014114:monocrotaline pyrrole; D016686:Monocrotaline; D019363:Cytochrome P-450 CYP1A1; D005978:Glutathione; D009853:Omeprazole
keywords: Astrocytes; C6; CYP1A1 P450; GSH; Monocrotaline; Neurotoxicity