title: Smokeless tobacco extract (STE)-induced toxicity in mammalian cells is mediated by the disruption of cellular microtubule network: a key mechanism of cytotoxicity.
abstract: Smokeless tobacco usage is a growing public health problem worldwide. The molecular mechanism(s) underlying smokeless tobacco associated tissue damage remain largely unidentified. In the present study we have tried to explore the effects of aqueous extract of smokeless tobacco (STE) on tubulin-microtubule, the major cytoskeleton protein that maintains cells morphology and participates in cell division. Exposure to STE resulted in dose-dependent cytotoxicity in a variety of mammalian transformed cell lines such as human lung epithelial cells A549, human liver epithelial cells HepG2, and mouse squamous epithelial cells SCC7, [corrected] as well as non-tumorogenic human peripheral blood mononuclear cells PBMC. Cellular morphology of STE-treated cells was altered and the associated disruption of microtubule network indicates that STE targets tubulin-microtubule system in both cell lines. Furthermore it was also observed that STE-treatment resulted in the selective degradation of cellular tubulin, whereas actin remains unaltered. In vitro, polymerization of purified tubulin was inhibited by STE with the IC50 value∼150 µg/ml and this is associated with the loss of reactive cysteine residues of tubulin. Application of thiol-based antioxidant N-acetyl cysteine (NAC) significantly abrogates STE-mediated microtubule damage and associated cytotoxicity in both A549 and HepG2 cells. These results suggest that microtubule damage is one of the key mechanisms of STE-induced cytotoxity in mammalian cells.
authors.affiliation: Department of Biotechnology and Dr. B.C. Guha Centre for Genetic Engineering and Biotechnology, University of Calcutta, WB, India.
authors.forename: Amlan
authors.initials: A
authors.lastname: Das
authors.forename: Abhijit
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Subhendu
authors.initials: S
authors.lastname: Chakrabarty
authors.forename: Arnab
authors.initials: A
authors.lastname: Ganguli
authors.forename: Gopal
authors.initials: G
authors.lastname: Chakrabarti
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003545:Cysteine / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism; D010936:Plant Extracts / Q000633:toxicity; D058105:Polymerization / Q000187:drug effects; D014030:Tobacco, Smokeless / Q000633:toxicity*; D014404:Tubulin / Q000378:metabolism
chemical_list: D010936:Plant Extracts; D014404:Tubulin; D053148:Caspase 3; D003545:Cysteine