title: Styrene 7,8-oxide induces caspase activation and regular DNA fragmentation in neuronal cells.
abstract: Neurobehavioral changes have been described in workers occupationally exposed to styrene vapors. Alterations of neurotransmitters and loss of neurons have been observed in brains of styrene-exposed rats. However, the mechanisms of neuronal damage are not yet clearly understood. We have characterized the cellular alterations induced by the main reactive intermediate of styrene metabolism, styrene 7,8-oxide (SO) in the human neuroblastoma SK-N-MC cell line and primary culture of rat cerebellar granule cells (CGC). SK-N-MC cells exposed to SO (0.3-1 mM) displayed apoptotic morphology, together with chromatin condensation and DNA cleavage into high molecular weight fragments of regular size. These features were accompanied by the activation of class II caspases, as detected with the DEVD assay, by following the cleavage of the caspase-substrate poly (ADP-ribose) polymerase (PARP) and by detection of the active fragment of caspase-3. Pre-incubation of the cells with the caspase inhibitor z-VAD-fmk reduced the cellular damage induced by SO, suggesting that caspases play an important role in SO toxicity. Increased proteolysis by class II caspases was detected also in primary culture of CGC exposed to SO. In addition, the presence of the 150-kDa cleavage product of alpha-fodrin suggests a possible activation of calpains in SK-N-MC cells. Moreover, SO did not affect the level of expression of the p53 protein, even though it is known to cause DNA damage. The identified intracellular pathways affected by SO exposure provides end-points that can be used in future studies for the evaluation of the neurotoxic effect of styrene in vivo.
authors.affiliation: The National Institute of Environmental Medicine, Division of Toxicology and Neurotoxicology, Karolinska Institutet, Box 210, S-171 77, Stockholm, Sweden.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Daré
authors.forename: Roshan
authors.initials: R
authors.lastname: Tofighi
authors.forename: Maria Vittoria
authors.initials: MV
authors.lastname: Vettori
authors.forename: Takashi
authors.initials: T
authors.lastname: Momoi
authors.forename: Diana
authors.initials: D
authors.lastname: Poli
authors.forename: Takaomi C
authors.initials: TC
authors.lastname: Saido
authors.forename: Antonio
authors.initials: A
authors.lastname: Mutti
authors.forename: Sandra
authors.initials: S
authors.lastname: Ceccatelli
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry; D020169:Caspases / Q000378:metabolism*; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004396:Coloring Agents; D017077:Culture Media, Conditioned / Q000737:chemistry; D053938:DNA Fragmentation; D004789:Enzyme Activation; D004852:Epoxy Compounds / Q000032:analysis / Q000494:pharmacology*; D006801:Humans; D015151:Immunoblotting; D008840:Microfilament Proteins / Q000737:chemistry; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D009994:Osmolar Concentration; D013194:Staining and Labeling; D014343:Trypan Blue; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D013049:Spectrin
chemical_list: D002352:Carrier Proteins; D020169:Caspases; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D004852:Epoxy Compounds; D008840:Microfilament Proteins; D014343:Trypan Blue; D016159:Tumor Suppressor Protein p53; D013049:Spectrin; C013690:styrene oxide