title: Amelioration strategies fail to prevent tobacco smoke effects on neurodifferentiation: Nicotinic receptor blockade, antioxidants, methyl donors.
abstract: Tobacco smoke exposure is associated with neurodevelopmental disorders. We used neuronotypic PC12 cells to evaluate the mechanisms by which tobacco smoke extract (TSE) affects neurodifferentiation. In undifferentiated cells, TSE impaired DNA synthesis and cell numbers to a much greater extent than nicotine alone; TSE also impaired cell viability to a small extent. In differentiating cells, TSE enhanced cell growth at the expense of cell numbers and promoted emergence of the dopaminergic phenotype. Nicotinic receptor blockade with mecamylamine was ineffective in preventing the adverse effects of TSE and actually enhanced the effect of TSE on the dopamine phenotype. A mixture of antioxidants (vitamin C, vitamin E, N-acetyl-l-cysteine) provided partial protection against cell loss but also promoted loss of the cholinergic phenotype in response to TSE. Notably, the antioxidants themselves altered neurodifferentiation, reducing cell numbers and promoting the cholinergic phenotype at the expense of the dopaminergic phenotype, an effect that was most prominent for N-acetyl-l-cysteine. Treatment with methyl donors (vitamin B12, folic acid, choline) had no protectant effect and actually enhanced the cell loss evoked by TSE; they did have a minor, synergistic interaction with antioxidants protecting against TSE effects on growth. Thus, components of tobacco smoke perturb neurodifferentiation through mechanisms that cannot be attributed to the individual effects of nicotine, oxidative stress or interference with one-carbon metabolism. Consequently, attempted amelioration strategies may be partially effective at best, or, as seen here, can actually aggravate injury by interfering with normal developmental signals and/or by sensitizing cells to TSE effects on neurodifferentiation.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA. Electronic address: t.slotkin@duke.edu.
authors.forename: Theodore A
authors.initials: TA
authors.lastname: Slotkin
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: Skavicus
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Card
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Levin
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Frederic J
authors.initials: FJ
authors.lastname: Seidler
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology* / Q000633:toxicity; D049109:Cell Proliferation / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D059329:Cholinergic Neurons / Q000187:drug effects / Q000473:pathology; D019610:Cytoprotection; D004261:DNA Replication / Q000187:drug effects; D059290:Dopaminergic Neurons / Q000187:drug effects / Q000473:pathology; D004357:Drug Synergism; D055495:Neurogenesis / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects* / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology* / Q000633:toxicity; D009538:Nicotine / Q000633:toxicity; D018733:Nicotinic Antagonists / Q000494:pharmacology* / Q000633:toxicity; D016716:PC12 Cells; D010641:Phenotype; D051381:Rats; D012906:Smoke / Q000009:adverse effects*; D012907:Smoking / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D018696:Neuroprotective Agents; D018733:Nicotinic Antagonists; D012906:Smoke; D009538:Nicotine
keywords: Antioxidants; Methyl donors; Neurodifferentiation; Nicotine; PC12 cells; Tobacco smoke extract