title: Genotoxicity of inorganic lead salts and disturbance of microtubule function.
abstract: Lead compounds are known genotoxicants, principally affecting the integrity of chromosomes. Lead chloride and lead acetate induced concentration-dependent increases in micronucleus frequency in V79 cells, starting at 1.1 microM lead chloride and 0.05 microM lead acetate. The difference between the lead salts, which was expected based on their relative abilities to form complex acetato-cations, was confirmed in an independent experiment. CREST analyses of the micronuclei verified that lead chloride and acetate were predominantly aneugenic (CREST-positive response), which was consistent with the morphology of the micronuclei (larger micronuclei, compared with micronuclei induced by a clastogenic mechanism). The effects of high concentrations of lead salts on the microtubule network of V79 cells were also examined using immunofluorescence staining. The dose effects of these responses were consistent with the cytotoxicity of lead(II), as visualized in the neutral-red uptake assay. In a cell-free system, 20-60 microM lead salts inhibited tubulin assembly dose-dependently. The no-observed-effect concentration of lead(II) in this assay was 10 microM. This inhibitory effect was interpreted as a shift of the assembly/disassembly steady-state toward disassembly, e.g., by reducing the concentration of assembly-competent tubulin dimers. The effects of lead salts on microtubule-associated motor-protein functions were studied using a kinesin-gliding assay that mimics intracellular transport processes in vitro by quantifying the movement of paclitaxel-stabilized microtubules across a kinesin-coated glass surface. There was a dose-dependent effect of lead nitrate on microtubule motility. Lead nitrate affected the gliding velocities of microtubules starting at concentrations above 10 microM and reached half-maximal inhibition of motility at about 50 microM. The processes reported here point to relevant interactions of lead with tubulin and kinesin at low dose levels.
authors.affiliation: Institut für Arbeitsphysiologie an der Universität Dortmund, Dortmund, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Bonacker
authors.forename: Thomas
authors.initials: T
authors.lastname: Stoiber
authors.forename: Konrad J
authors.initials: KJ
authors.lastname: Böhm
authors.forename: Irina
authors.initials: I
authors.lastname: Prots
authors.forename: Minsheng
authors.initials: M
authors.lastname: Wang
authors.forename: Eberhard
authors.initials: E
authors.lastname: Unger
authors.forename: Ricarda
authors.initials: R
authors.lastname: Thier
authors.forename: Hermann M
authors.initials: HM
authors.lastname: Bolt
authors.forename: Gisela H
authors.initials: GH
authors.lastname: Degen
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects* / Q000648:ultrastructure; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D016547:Kinesins / Q000037:antagonists & inhibitors; D007854:Lead / Q000633:toxicity*; D048629:Micronuclei, Chromosome-Defective; D015162:Micronucleus Tests; D046529:Microscopy, Electron, Transmission; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism; D009499:Neutral Red; D009566:Nitrates / Q000633:toxicity*; D009942:Organometallic Compounds / Q000633:toxicity; D017239:Paclitaxel; D014404:Tubulin / Q000378:metabolism; D050257:Tubulin Modulators
chemical_list: D009566:Nitrates; D009942:Organometallic Compounds; D014404:Tubulin; D050257:Tubulin Modulators; D009499:Neutral Red; D007854:Lead; C029891:lead chloride; C017461:lead nitrate; D016547:Kinesins; D017239:Paclitaxel; C008261:lead acetate