Cigarette Smoke Extract Induces Disruption of Structure and Function of Tubulin-Microtubule in Lung Epithelium Cells and in Vitro

In the present study, we have investigated the effect of the aqueous extract of cigarette smoke (AECS) on tubulin-microtubule, a major cytoskeleton protein that maintains cellular morphology and participates in cell division. We found that treatment of AECS results in the loss of both structural and functional properties of tubulin-microtubule. Disruption of the microtubule network was observed in AECS-treated human lung epithelial (A549) cells and noncarcinoma human lung alveolar epithelium (L132) cells, in a dose and time-dependent manner. Tubulin-microtubule mediated important cellular properties, such as proliferation, migration, and maintenance of the cellular morphology, were affected by AECS in A549 cells. The aqueous extract of cigarette smoke (AECS) was also found to interfere the microtubule dynamics inside the cell and induce tubulin degradation. The structure of microtubules was also disrupted by AECS in the presence of protease inhibitors accompanied by a change of morphology of cells and loss of cell viability. In vitro, the functional properties of tubulin, such as the ability of polymerization, was inhibited by AECS in a dose and time-dependent manner, and it was accompanied by the loss of reactive cysteine residues, destabilization of the secondary structure, and quenching of intrinsic tryptophan fluorescence. Carbonyl content of tubulin was increased after treatment with AECS, indicating that one of the pathways of tubulin damage is protein oxidation. The damage of tubulin by AECS thus may be correlated with the pathogenesis of cigarette smoke induced disorders, which result in cellular apoptosis and tissue damage.